USRE36079E - Handover method for mobile radio system - Google Patents

Handover method for mobile radio system Download PDF

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Publication number
USRE36079E
USRE36079E US08/938,840 US93884097A USRE36079E US RE36079 E USRE36079 E US RE36079E US 93884097 A US93884097 A US 93884097A US RE36079 E USRE36079 E US RE36079E
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Prior art keywords
base station
mobile
station transmitter
message information
base
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US08/938,840
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Jan E. Uddenfeldt
Alex K. Raith
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Telefonaktiebolaget LM Ericsson AB
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Telefonaktiebolaget LM Ericsson AB
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Priority to US08/938,840 priority Critical patent/USRE36079E/en
Priority to US09/235,456 priority patent/USRE37787E1/en
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    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W36/00Hand-off or reselection arrangements
    • H04W36/0005Control or signalling for completing the hand-off
    • H04W36/0083Determination of parameters used for hand-off, e.g. generation or modification of neighbour cell lists
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04MTELEPHONIC COMMUNICATION
    • H04M15/00Arrangements for metering, time-control or time indication ; Metering, charging or billing arrangements for voice wireline or wireless communications, e.g. VoIP
    • H04M15/82Criteria or parameters used for performing billing operations
    • H04M15/825Criteria or parameters used for performing billing operations based on the number of used channels, e.g. bundling channels, frequencies or CDMA codes
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W36/00Hand-off or reselection arrangements
    • H04W36/08Reselecting an access point
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W36/00Hand-off or reselection arrangements
    • H04W36/16Performing reselection for specific purposes
    • H04W36/18Performing reselection for specific purposes for allowing seamless reselection, e.g. soft reselection
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04MTELEPHONIC COMMUNICATION
    • H04M2215/00Metering arrangements; Time controlling arrangements; Time indicating arrangements
    • H04M2215/32Involving wireless systems
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04MTELEPHONIC COMMUNICATION
    • H04M2215/00Metering arrangements; Time controlling arrangements; Time indicating arrangements
    • H04M2215/78Metric aspects
    • H04M2215/7853Based on the number of used channels, e.g. bundling channels or frequencies or CDMA codes

Definitions

  • the present invention relates to a mobile radio system which has a plurality of radio channels for transmitting control information and message information between base stations and mobile stations. More specifically, the invention relates to a method in which the responsibility for transmitting message information to a mobile station is handed over from at least a first base station transmitter to at least a second base station transmitter.
  • a mobile radio system has high traffic handling capacity and a high degree of coverage.
  • the traffic handling capacity of a mobile radio system is dependent, inter alia, upon the number of available radio channels and how effectively these channels may be utilised. It is known to arrange several base stations with small covering areas close to each other in a mobile radio system. Available radio channels can then be utilised in a more efficient way for handling peak traffic within a limited geographical area than if base stations with large covering areas are arranged far away from each other in the mobile radio system. Arranging several base stations close to each other can also increase the accessibility in a mobile radio system, particularly if the covering areas of the base stations are mutually overlapping. Two base station with such overlapping covering areas cannot, however, normally use the same radio channel for communication with different mobile stations.
  • Handover can be a critical function in known traditional mobile radio systems. There is a risk of the established connection being temporarily interrupted or completely lost in conjunction with the handover. There is usually required comparatively extensive signalling in the mobile radio system in conjunction with changing of radio channel at handover.
  • the degree of coverage of a mobile radio system depends, inter alia, on the presence of radio shadows and how the covering areas of the individual base stations overlap each other.
  • the possibility of establishing new connections and maintaining established connections to/from mobiles also depends on the presence of reflections and interference.
  • U.S. patent application Ser. No. 07/315,361 describes a mobile radio system and a method of transmitting message information where at least two bases at least partially simultaneously transmit substantially the same message information to a mobile.
  • the object with this is, inter alia, to enable the degree of coverage to be made greater without the cells in a mobile radio system needing to be reduced, which gives greater freedom in the selection of cell pattern, and fewer handovers.
  • the intention is that the mobile radio system shall be given better possibilities of establishing new connections and maintaining already established connections.
  • these objects are achieved by certain relationships between modulation of radio signals and parameters of adaptive equalisers in the mobiles and the distance between base transmitters which transmit the same message information.
  • channels may be allocated to cells and mobiles in various ways.
  • a base for a particular cell may only use certain predetermined channels.
  • Bases in adjacent cells use different channels.
  • Bases in different cells sufficiently distant from each other may use same channels according to a channel re-use or allocation plan.
  • some or all channels are a common resource to all base stations, which means that some or all channels may be used by any base as long as the radio transmission conditions permit, i.e. certain carrier to interference or noise level.
  • One object of the present invention is to achieve a handover where the risk of temporary interruption or lost connections can be sufficiently small.
  • Another object of the present invention is to achieve a handover where the need of signalling via radio signals in the mobile radio system may be comparatively small.
  • Yet another object of the invention is to achieve a handover which is particularly suitable for mobile radio systems with a high degree of coverage and large overlapping between the covering areas of different base transmitters.
  • the responsibility of transferring message information to a mobile station is handed over from at least one first base transmitter to at least a second base transmitter. Distinguishing for a method in accordance with the invention, and particularly preferred embodiments thereof will be seen from the independent and the dependent claims. Somewhat simplified, it may be said that in a method in accordance with the invention, the same radio channel is preferably used for transmitting message information to the mobile before and after the handover.
  • the handover preferably takes place without the mobile being informed beforehand that the handover is going to take place.
  • the radio transmission of message information from a second base station transmitter to the mobile station is started before transmission of message information to the mobile from a first base station transmitter is terminated. Essentially the same message information is thus transmitted during a transition time to the mobile both from a first and a second base station transmitter.
  • the transmission of message information to the mobile is then preferably started from one of the second base transmitters before initiating transmission of message information from another of the second base transmitters.
  • the transmission of message information to the mobile from one of the first base transmitters is preferably terminated before the transmission of such information is terminated from another of the first base transmitters. Initiation and termination of the transmission from the base transmitters preferably takes place in an order such that at least two base transmitters transmit essentially the same message information to the mobiles the whole time.
  • the radio channels are selected such that during the transition time the mobile station can receive the transmissions from the different base transmitters essentially without interference from each other. Designing the handover of responsibility for transmitting message information to a mobile in accordance with the invention means several advantages, which are accentuated in preferred embodiments.
  • the need for handover signaling via radio signals can be made particularly small. If the mobile sends and receives on the same channels before, during and after the handover, it does not really need to know whether the responsibility for communication has been handed over. In an extreme case, there is thus no need of handover signalling at all via radio signals in conjunction with handover, and all handover signalling could take place in the stationary part of the mobile radio system.
  • Another important advantage is that the risk of temporary interruption in an established connection call to a mobile or that the connection is lost can be made small.
  • a method in accordance with the invention is particularly suitable for a mobile radio system where at least two base station transmitters are simultaneously responsible for transmitting message information to at least certain mobile stations. It seems therefore to be suitable to describe an embodiment of a method in accordance with the invention in connection with such a system.
  • a cellular mobile radio system illustrated in FIG. 1 has mobile and base stations with transmitters and receivers for radio signals. Message information is transmitted digitally to and from the mobiles by transmission and reception of radio signals with digital modulation corresponding to the message information.
  • the radio signals are sent on one of a plurality of radio channels. Several radio channels can share in time multiplex the same radio frequency, and radio signals can be transmitted to and from several mobiles in different time slots on the radio frequency, these slots being associated with the radio channels.
  • the mobiles may move within and between the cells of the system.
  • the base transmitters are assigned to the cells so that there is at least one base transmitter for each cell, for transmitting signals to the mobiles of the cell.
  • the channel allocation in the system is some kind of dynamic or adaptive channel allocation meaning that at least some channels are a common resource to at least some neighbour bases/cells.
  • FIG. 1 Somewhat simplified, there is illustrated in FIG. 1 the division of an area into cells and the assignation of base station transmitters to the cells in a mobile telephone system.
  • all cells C1 to C24 are illustrated as regular hexagons with sides L. In practice the cells will probably have different sizes and shapes. In addition, depending on traffic conditions, it will often be suitable with overlapping in the boundary areas between the cells.
  • the base transmitters then off-load each other by handling transmissions to mobiles where such transmission should from a purely geographically point of view, be performed by the base transmitters of a contiguous cell.
  • each cell C1-C24 there is an ordinary base transmitter BS1-BS24.
  • these transmitters are conventionally co-located in groups of three.
  • the base transmitter BS1 for the cell C1 is co-located with the base transmitter BS3 for the cell C3 and with the base transmitter BS5 for the cell C5.
  • the base transmitter BS14 for the cell C14 is co-located with the base transmitter BS16 for the cell C16 and with the base transmitter BS18 for the cell C18.
  • These co-located ordinary base station transmitters are situated in the boundary regions between the cells to which they are assigned.
  • the ordinary base transmitters BS2, BS4 and BS6 are colocated in the boundary areas between the cells C2, C4 and C6.
  • the system includes a number of extra base transmitters for certain of the cells.
  • Cells C6, C7, C10, C11, C13, C14, C19 and C20 each has one extra base station transmitter.
  • XS6, XS7, XS10, XS11, XS13, XS15A, XS15B, XS18A, XS18B, XS19, XS20 and XS22A are co-located in groups with three extra base transmitters in each group in a similar manner as the ordinary base transmitters.
  • the extra base transmitter or transmitters for a given cell transmit radio signals which are substantially the same as those sent by the ordinary base transmitter of the cell.
  • the signals are digitally modulated with selective digital message information to the individual mobiles in the cell.
  • the radio signals may also be digitally modulated with general control information common to all mobiles concerned.
  • a mobile in a cell for which three is one or more extra base transmitter can therefore receive, at least in certain cases, corresponding radio signals from more than one base transmitter approximately simultaneously within the same frequency range.
  • corresponding signals from different base transmitters can be received without, or with a given time shift at the mobile.
  • the distance between two base transmitters for the same cell varies between L and 2L, i.e. between the side and diameter of the regular hexagons. If, for the sake of simplicity, reflections are ignored and the assumption made that the base transmitters transmit without mutual time shifting, the time reception shift at the mobile station could then attain a maximum of 2L/c, where c is the propagation rate of the radio signals.
  • FIG. 2 there are illustrated parts of a mobile radio system in accordance with FIG. 1.
  • a mobile radio exchange MSC is connected via cables L 1 , L 2 , . . . L m , L n to a plurality of bases of which two, B m and B n are illustrated in FIG. 2.
  • the base B m has a central unit connected via cables L ma and L mb to two transceiver units B ma and B mb situated at a distance from the central unit.
  • the central unit of the base B m includes a central line and control unit 1, transmission time shifting means 2A and 2B, one for each of the transceivers, reception time shifting means 3A and 3B, one for each of the transceivers and line units 4A and 4B, one for each of the transceivers.
  • transceivers in the base B m are alike. Each such transceiver contains a line and control unit 5A or 5B, transmitter means 6A or 6B, receiver means 7A or 7B, a transmission-reception filter 8A or 8B and an antenna 9A or 9B.
  • the base B n differs partly from base B m , primarily due to its central line and control unit 10 being situated in juxtaposition with one of its transceivers B na . Accordingly, no cable with associated line units corresponding to L m , L mb 4A-5B is needed for the transceiver B na , but only for the other transceiver B nb . In addition, no transmission or reception time shifting means is included in any central unit in B n , but the corresponding means 2A, 2B, 3A and 3B are respectively included in transceivers B na and B nb .
  • the mobiles MS 1 and MS 2 are mutually alike. Each mobile includes sound sensing means 11, encoding means 12, transmitting means 13, transmit-receive switch 14, reception means 15, equaliser and decoding means 16, sound reproducing means 17, control means 18 and means 19 for feeding in and out or presentation of digital information.
  • the mobile radio system in FIG. 2 functions in most respects in a way well-known in mobile radio systems. No complete description of how the system functions in different respects should therefore be necessary for one skilled in the art, and it should only be necessary to describe what is unique or unusual in the mobile radio system according to FIG. 2.
  • One not skilled in the art of mobile radio systems is referred to the technical literature.
  • Message information e.g. speech or data that the mobile radio exchange forwards towards a mobile in the cell C m , e.g. the MS 1 , is transmitted from the mobile radio exchange via the cable L m to the line and control unit 1. From here the information is transferred via the transmission time shifting means 2A, line unit 4A, cable L ma and line and control unit 5A to the transmitting means 6A.
  • the transmitting means 6A transmits, via the transmission-reception filter 8A and antenna 9A, radio signals with digital modulation in correspondance with the message information from the mobile radio exchange.
  • the message information from the mobile radio exchange is also transferred from the line and control unit 1 via the transmission time shifting means 2B, line unit 4B, cable L mb and line and control unit 5B to the transmission means 6B in the transceiver B mb .
  • the transmission means 6B transmits, via the transmission reception filter 8B and antenna 9B, radio signals with digital modulation in correspondance with the information from the mobile radio exchange.
  • the radio signals can be transmitted from the antenna 9A of the transceiver unit B ma substantially without time shifting, or time shifted in relation to the transmission of corresponding radio signals from the antenna 9B of the other transceiver B mb .
  • the radio signals from the antenna 9A i B ma arrive at a given mobile in the cell C m , e.g. the mobile MS 1 , with or without time shift in relation to corresponding radio signals from the antenna 9B in B mb .
  • the possible time shift on arrival at the mobile depends partly on possible time shifting at transmission from the antennas and partly on possible difference in propagation time for the radio waves from the antennas.
  • the transmission time shifting means 2A and 2B have a variable delay and can be controlled by the line and control unit 1, such that the signals are transmitted from the antenna 9A in B ma time-shifted more or less before or after corresponding signals from the antenna 9B in B mb .
  • FIG. 1 In the preferred embodiment according to FIG.
  • the line and control unit 1 controls the variable delays in the transmission time shifting means 2A and 2B so that the differences in delay in the cables L ma and L mb as well as the differences in the radio signal propagation times are counteracted.
  • This may also be expressed by saying that the line and control unit controls the variable delays in the transmission time shifting means 2A and 2B, such that the time shift of the radio waves on arrival at the mobile is decreased compared with the situation where the means 2A and 2B have the same fixed delay. It could be thought that the ideal case were that the line and control unit controlled the delays in the time shifting means 2A and 2B so that the digitally modulated signals transmitted from the antenna in B ma arrived at the antenna in MS 1 , exactly simultaneously and in phase with corresponding signals transmitted from the antenna in B mb .
  • this method can be applied in practice such that the delays in the reception time shifting means 3A and 3B are adjusted so that information received from the mobile MS 1 at B ma arrives at the line and control unit 1 simultaneously as corresponding information received at B mb from the mobile station MS 1 arrives at the line and control unit 1.
  • the delays in the transmission time shifting means 2A and 2B are subsequently adjusted in correspondence with the optimum delays in the reception time shifting means 3A and 3B.
  • the other method is to estimate in the mobile the difference in arrival time or time shift between the digitally modulated radio signals from one transceiver B ma and the corresponding digital signals from the other transceiver B mb .
  • TDMA Time Division Multiple Access
  • special synchronising words can be transmitted from the base station transmitters solely to enable the mobile to estimate the differences in arrival times or time shifts.
  • the mobile transmits information about the estimated arrival time difference or time shift via radio signals to the fixed part of the system, where it is utilised for controlling the transmission time shifting means 2A and 2B.
  • the line and control unit 1 then receives, via the respective line units 5A, 4A and 5B, 4B, information about estimated arrival time difference from the mobile in the same way as the line and control unit obtains message information from the mobile.
  • Measuring the difference in arrival time or time shifting for corresponding radio signals can be performed in a conventional way, e.g. with the aid of correlation.
  • the radio signals conventionally contain predetermined synchronising patterns (words)
  • the time difference between the appearance of these in different signals can be measured using conventional methods.
  • a mobile control means 18 and/or a base line and control unit 1 or 10 possible in combination with the transceiver's line units 5A and 5B can then include time measurement means for estimating reception time shifting, or arrival time comparison means for comparing arrival times.
  • a base preferably conventionally utilises the same transmitter means and antenna for transmitting, in time multiplex within the same frequency range, radio signals digitally modulated with message information to different mobiles associated with the same cell. Radio signals with message information to a given mobile are then transmitted from different base transmitters with a possible transmission time shift which is specially adjusted with regard to the position of this particular mobile.
  • a base in a mobile radio system needs to transmit a radio signal with information other than message information intended for reception by several or all of the mobiles in the cell, e.g. information as to the identity of the base/cell.
  • Such signals are preferably transmitted simultaneously without mutual time shifting, from the transceivers B ma , B mb and B na , B nb of the base in a mobile radio system according to FIG. 2.
  • the transmission time shifting means are then controlled to a balancing state where the delay of information from the line and control unit 1 to the antenna in one transceiver B ma is equally as great as the delay of information from the line and control unit 1 to the antenna in the other transceiver B mb .
  • the corresponding situation can apply when a base "listens" in unoccupied combinations of time slot and frequency range for set up calls from mobiles in unknown positions relative to the transceivers of the base.
  • the reception time shifting means 3A and 3B can then be controlled to a balancing state where the delay of the message information from the antenna in one transceiver B na to the line and control unit 9 is equally as great as the delay of information from the antenna in the other transceiver B nb to the line and control unit 9.
  • the mobiles MS 1 and MS 2 have adaptive equalisers, whereby the digital modulation during a modulation time interval in the radio signals transmitted from a base transmitter can be reconstructed from signals received during a reception time interval.
  • the reception time interval of the equalisers is dimensioned according as the dispersion on the radio channel, i.e. expected time shifts between corresponding signals from a single base transmitter due to reflections. Because of the equaliser, not only the radio signal having the greatest amplitude or arriving first to the mobile station is utilised for reconstructing the digital modulation, but also other corresponding radio signals arriving with a time shift within the extent of the equaliser's reception time interval can be utilised.
  • the mobiles in a system according to FIGS. 1 and 2 preferably have equalisers which are dimensioned such that the reception time interval of the mobile in reconstruction of the digital modulation is greater than the time it takes for signals to propagate a distance as long as the greatest distance between two base transmitters associated with the same cell within a restricted geographical area.
  • the mobile equalisers would thus be dimensioned for a reception interval in reconstruction which is greater than 2L/c.
  • the reception time interval of the mobiles is therefore preferably substantially greater than the time it takes for radio signals to propagate a distance which is just as great as the greatest distance between two base transmitters associated with the same cell within the geographical area in question.
  • the modulation time interval of the digital modulation of the signals can be of the same order of magnitude as the time it takes for radio signals to propagate a distance just as long as the greatest transmitting distance between two base station transmitters serving the same cell within a limited area.
  • the modulation time interval will be the time during which a single symbol is decisive for the digital modulation. For example, if a sequence of binary symbols individually and one at a time determines the modulation, the modulation time interval will be the time during which one symbol determines the modulation. This can also be expressed by saying that the modulation time interval will be the inverted value of the transmission rate in bits.
  • the modulation interval can be the time when a preceeding, but not the nearest subsequent symbol affects the modulation.
  • a symbol affects the phase of a carrier wave during a time interval 3T.
  • the nearest preceding symbol also affects the phase change of the carrier wave during a first part 2T of the time interval 3T.
  • the nearest subsequent symbol also affects the change of phase of the carrier wave during a last part of 2T of the time interval 3T.
  • modulation time interval will be T, which agrees with what is called the symbol time interval in SE 8102802-9.
  • the modulation time interval is to be interpreted as the interval in time between two successive changes in the transmitted digital modulation.
  • the position of the latter can be estimated by comparison of the radio propagation times. The estimation can be improved if more than three bases are used.
  • Knowledge of the position of the mobile can be used by the stationary part of the mobile radio system for selecting what bases are suitable for use as new bases when handing over the responsibility.
  • the mobile radio exchange or other stationary part of the system assigns new bases the responsibility in a manner such that communication can be maintained with good quality as the mobile travels through the cell structure.
  • Knowledge of the position of the mobile can also be used as a criterion for performing the handing over of responsibility. For example, if the mobile moves out of the cell which is serving it as the moment, this is an indication that a handover of responsibility should soon take place, irrespective of whether the communication quality is still good.
  • the decision for handing over can take place in more or less different ways. Different criteria have been proposed for the decision as to if and where handover is to take place. Collection of the basis for the handover decision can take place in different ways. The distribution of tasks and the signalling in connection with handover between mobiles and the stationary part of the mobile radio system can differ from system to system. All this is well known to one skilled in the art. One not skilled in the art can obtain necessary information from the technical literature or United States patents in the field of cellular mobile radio.
  • the traffic conditions in different parts of the mobile radio system can be given attention, substantially conventionally, e.g. if certain bases tend to have too high traffic while adjacent bases have unoccupied capacity for further traffic.
  • the mobile is in the position of MS 1 within the coverage area of the base station B m , but outside the coverage area of the base station B n , i.e. the radio transmission conditions for radio signals between the mobile station and B ma or B mb are sufficiently good, but the radio transmission conditions for radio signals between the mobile and B na and B nb are too poor.
  • the mobile is in the position of MS 2 within the coverage area for the base B n , but outside the coverage area for the base B m , i.e. the radio transmission conditions for radio signals between the mobile and B na and B nb are sufficiently good, but the radio transmission conditions for radio signals between the mobile and B ma and B mb are too poor.
  • a handover decision is made, and this decision may be based on facts such as the radio transmission conditions and traffic within the coverage areas of the base stations.
  • the decision is made by the mobile radio exchange or possible some other stationary part of the mobile radio system.
  • the stationary part of the mobile radio system Before handing over the responsibility for communication with the mobile, it is tested in the stationary part of the mobile radio system whether the second base transmitter can use the same radio channel after handover for transmitting message information to the mobile as the radio channel the first base transmitter used before handover. This may also be expressed by saying that the stationary part tests whether a change of radio channel can be avoided on handover.
  • This testing takes place according to predetermined rules based on predetermined parameters. For example, if the base to which the responsibility is to be handed over already utilises the radio channel in question for communication with another mobile having higher priority, a change of a radio channel must take place on handover. On the other hand, if the base to which responsibility is to be handed over does not utilise the radio channel in question, and possible transmission on this radio channel would not interfere with other traffic, there is no need for changing channels on handover. Another reason for having to change channels is that the channel in question has too much interference in the cell served by the base to which responsibility is to be handed over. Other rules or reasons for, and against, changing channels will be understood by one skilled in this art.
  • one of the base transmitters B na or B nb begins to transmit the same message information to the mobile as the base transmitters B ma and B mb .
  • This base transmitter is preferably transmitting on the same channel as the base transmitters B ma and B mb .
  • the transmission times at B na and B nb of the radio signals is preferably adjusted to corresponding transmission times for the signals at B ma and B mb in accordance with what has been described above.
  • the transmission of corresponding message information to the mobiles from one of the base transmitters B ma and B mb is terminated.
  • One of the base transmitters B ma or B mb then transmits the same message information, e.g. speech or data, to the mobile as one of the base transmitters B na and B nb .
  • Neither one of the two other base transmitters in FIG. 2 then transmit corresponding information to the mobile.
  • the one of the base transmitters B ma and B mb which has the best radio transmission conditions and the one of base transmitters B na and B nb which has the best radio transmission conditions preferably transmit to the mobile.
  • B na and B nb are then transmitting the same message information to the mobile.
  • All three transmitters preferably transmit on the same radio channel, and in a TDMA mobile radio system this means the same radio frequency and same time slot.
  • the transmission times of B na and B nb and at the third base transmitter of the radio signals are preferably adjusted to each other in agreement with what has been described above.
  • both B na and B nb have begun to transmit the same message information to the mobile as the remaining base transmitter of B ma and B mb , the transmission of message information to the mobile is terminated from this remaining base transmitter. Both B na and B nb are then transmitting message information to the mobile, whereas none of the base transmitters B ma and B mb is transmitting such information to the mobile.
  • the responsibility for communication between the mobile has been handed over from the base transmitters B ma and B mb to the base transmitters B na and B nb . This may also be expressed by saying that responsibility for the communication has been handed over from the base B m to the base B n , i.e. an execution of handover is completed.
  • the base transmitters send the same message information to the mobile.
  • all base transmitters of the affected stations never send the same information to the mobile.
  • the risk of accidental interruption in the transmission of message information between the mobile and the fixed part of the mobile radio system will thus be small.
  • the receiving time shift at the mobile will be less than if all base transmitters were to send the same message information to the mobile.
  • re-use of radio channels if facilitated in the mobile radio system when all affected base transmitters never send simultaneously on the same radio channel.
  • the channel which is to be used after handover is selected such that during a transition time the mobile can receive the same message information on both channels.
  • a base transmitter e.g. B na
  • the base transmitter B nb When the base transmitter B nb begins to transmit message information to the mobile, it transmits in the same time slot as B na . Due to B na and B nb transmitting message information in a time slot than the one used by B ma and B nb , the mobile can receive, by modifying its radio receiver tuning, both the message information transmitted by B na and/or B nb and the message information transmitted by B ma and B mb . In this case, however, the mobile must be given advance information as to the handover.
  • a mobile radio system where at least two base transmitters are simultaneously responsible for transmitting message information to a mobile does not need to be formed according to the above, but can differ to a greater or lesser extent from the system described above.
  • base transmitter shall be accordingly understood at least a transmitter antenna for radio signals and preferably more or less of the remaining means required in a base.
  • base transmitter there are preferably included at least means corresponding to the means included in a transceiver unit B ma or B mb in FIG. 2.
  • the base transmitters B na and B nb can be controlled directly by the mobile radio exchange MSC and independently of how the exchange controls the base transmitters B ma and B mb .
  • a method in accordance with the invention is of course not restricted to a given implementation of base transmitter, even if it is assumed in the example above that base transmitters can start and terminate transmission at different times.
  • a method in accordance with the invention is not restricted to mobile radio systems with two or more base transmitters per cell, and it is conceivable to apply embodiments of a method in accordance with the invention in a mobile system, the method involves, summarily explained, that the same radio channel is used both before and after handover, if possible, for transmitting message information to the mobile.
  • a decision on handover is preferably made in the mobile radio exchange or other stationary part of the system, and the handover takes place without the mobile being formed beforehand.
  • the mobiles have equalizers and the system transmits message information digitally by digital modulation of radio signals, it is also preferably in this case as well that the transmission of message information is started from the base transmitter to which responsibility is to be handed over, before transmission of the same information is terminated from the base transmitter from which responsibility is to be handed over.
  • the same message information is transmitted during a transition period to the mobile from two base transmitters. If it is not possible to utilise the same radio channel for some reason, it is then preferable in such a system to select the different channels such that during a transition period the mobile can receive the transmissions from the different base transmitters essentially without their mutually obstructing each other. In a TDMA system with mobiles according to FIG. 2, this means that the base transmitters transmit in different time slots.
  • a method in accordance with the invention is not limited to described embodiments or mobile radio systems according to FIGS. 1 and 2, but can be applied and varied within the scope of the claims.

Abstract

The invention relates to a method in mobile radio systems in which the responsibility for transmitting message information to a mobile station is handed over from a first base station transmitter to a second base station transmitter. In this method, the same radio channel is used, if possible, before and after the handover for transmitting message information to the mobile station. If the same radio channel can be utilized, the handover takes place without the mobile station being informed beforehand of the handover by a special signal or order or the like. In digital mobile ratio systems with digital transmission of message information by digital modulation of the radio signals, the transmission is preferably started from a second base station transmitter before the transmission is terminated from a first base station transmitter. During a certain transmission time substantially the same message information is transmitted to the mobile station from both the first and second base station transmitters.

Description

TECHNICAL FIELD
The present invention relates to a mobile radio system which has a plurality of radio channels for transmitting control information and message information between base stations and mobile stations. More specifically, the invention relates to a method in which the responsibility for transmitting message information to a mobile station is handed over from at least a first base station transmitter to at least a second base station transmitter.
BACKGROUND ART
It is desirable that a mobile radio system has high traffic handling capacity and a high degree of coverage. The traffic handling capacity of a mobile radio system is dependent, inter alia, upon the number of available radio channels and how effectively these channels may be utilised. It is known to arrange several base stations with small covering areas close to each other in a mobile radio system. Available radio channels can then be utilised in a more efficient way for handling peak traffic within a limited geographical area than if base stations with large covering areas are arranged far away from each other in the mobile radio system. Arranging several base stations close to each other can also increase the accessibility in a mobile radio system, particularly if the covering areas of the base stations are mutually overlapping. Two base station with such overlapping covering areas cannot, however, normally use the same radio channel for communication with different mobile stations.
When a mobil station moves from the area covered by one base station to the area covered by another base station in a mobile radio system, the responsibility for communication with the mobile must be transferred from one base station to another. Such transfer in conjuction with an established connection to the mobile station is usually called "handover".
Handover can be a critical function in known traditional mobile radio systems. There is a risk of the established connection being temporarily interrupted or completely lost in conjunction with the handover. There is usually required comparatively extensive signalling in the mobile radio system in conjunction with changing of radio channel at handover. The degree of coverage of a mobile radio system depends, inter alia, on the presence of radio shadows and how the covering areas of the individual base stations overlap each other. The possibility of establishing new connections and maintaining established connections to/from mobiles also depends on the presence of reflections and interference.
For increasing the degree of coverage in a mobile radio system, it is known to transmit substantially the same information to a mobile from two or more base transmitters and to receive information from a mobile at two or more base receivers. The publication "RF PERFORMANCE OF MACROSCOPIC DIVERSITY IN UNIVERSAL PORTABLE RADIO COMMUNICATIONS: FREQUENCY REUSE CONSIDERATIONS" by Richard C: Bernhardt, from IEEE International Conference on Communications, Jun. 22-25, 1986, Toronto, Canada describes different types of cells and placing of transmitters and the result of simulations of such a system. The publication "USER ACCESS IN PORTABLE RADIO SYSTEMS IN THE NOISE LIMITED ENVIRONMENT" by Richard C. Bernhardt, from ICC'97, Jun. 1987, Seattle. Wash, U.S.A., describes different types of cell and placing of transmitters as well as comparsions between different criteria and algorithms for the selection of base transmitter.
U.S. patent application Ser. No. 07/315,361 describes a mobile radio system and a method of transmitting message information where at least two bases at least partially simultaneously transmit substantially the same message information to a mobile. The object with this is, inter alia, to enable the degree of coverage to be made greater without the cells in a mobile radio system needing to be reduced, which gives greater freedom in the selection of cell pattern, and fewer handovers. The intention is that the mobile radio system shall be given better possibilities of establishing new connections and maintaining already established connections. According to the patent application, these objects are achieved by certain relationships between modulation of radio signals and parameters of adaptive equalisers in the mobiles and the distance between base transmitters which transmit the same message information.
in cellular mobile radio systems available channels may be allocated to cells and mobiles in various ways. In systems with fixed channel allocation a base for a particular cell may only use certain predetermined channels. Bases in adjacent cells use different channels. Bases in different cells sufficiently distant from each other may use same channels according to a channel re-use or allocation plan. In systems with adaptive channel allocation some or all channels are a common resource to all base stations, which means that some or all channels may be used by any base as long as the radio transmission conditions permit, i.e. certain carrier to interference or noise level.
SUMMARY OF THE INVENTION
At least in certain mobile radio systems, it is a problem to make the handover so that the risk of temporary interruption in a connection or that the connection is lost in conjunction with handover is sufficiently small. This problem is particularly great with peak traffic. Another problem in connection with handover is the comparatively large need for signalling in the mobile radio system. The object of the invention is, inter alia, to ameliorate these problems.
One object of the present invention is to achieve a handover where the risk of temporary interruption or lost connections can be sufficiently small.
Another object of the present invention is to achieve a handover where the need of signalling via radio signals in the mobile radio system may be comparatively small.
A still further object of the present invention is to achieve a handover which is particularly suitable for mobile radio systems where two or more base transmitters spaced from each other transmit essentially similar message information to a mobile.
Yet another object of the invention is to achieve a handover which is particularly suitable for mobile radio systems with a high degree of coverage and large overlapping between the covering areas of different base transmitters.
In a method in accordance with the invention the responsibility of transferring message information to a mobile station, is handed over from at least one first base transmitter to at least a second base transmitter. Distinguishing for a method in accordance with the invention, and particularly preferred embodiments thereof will be seen from the independent and the dependent claims. Somewhat simplified, it may be said that in a method in accordance with the invention, the same radio channel is preferably used for transmitting message information to the mobile before and after the handover.
The handover preferably takes place without the mobile being informed beforehand that the handover is going to take place. According to a further preferred embodiment of the invention, the radio transmission of message information from a second base station transmitter to the mobile station is started before transmission of message information to the mobile from a first base station transmitter is terminated. Essentially the same message information is thus transmitted during a transition time to the mobile both from a first and a second base station transmitter.
In mobile radio systems where at least two base station transmitters are simultaneously responsible for transmitting message information to at least certain mobiles, it may be preferred not to start or interrupt the transmission from several base transmitters simultaneously in conjunction with the handover. The transmission of message information to the mobile is then preferably started from one of the second base transmitters before initiating transmission of message information from another of the second base transmitters. In such a case, the transmission of message information to the mobile from one of the first base transmitters is preferably terminated before the transmission of such information is terminated from another of the first base transmitters. Initiation and termination of the transmission from the base transmitters preferably takes place in an order such that at least two base transmitters transmit essentially the same message information to the mobiles the whole time.
In the cases where transmission from a second base transmitter must take place on another radio channel than the transmission from a first base transmitter, it is preferable that the radio channels are selected such that during the transition time the mobile station can receive the transmissions from the different base transmitters essentially without interference from each other. Designing the handover of responsibility for transmitting message information to a mobile in accordance with the invention means several advantages, which are accentuated in preferred embodiments.
Perhaps the most important advantage is that in the cases where the same radio channel is utilised by the bases before, during and after the handover, the need for handover signaling via radio signals can be made particularly small. If the mobile sends and receives on the same channels before, during and after the handover, it does not really need to know whether the responsibility for communication has been handed over. In an extreme case, there is thus no need of handover signalling at all via radio signals in conjunction with handover, and all handover signalling could take place in the stationary part of the mobile radio system. Another important advantage is that the risk of temporary interruption in an established connection call to a mobile or that the connection is lost can be made small.
Another advantage is great flexibility with regard to distributing tasks between the mobile and base in conjunction with the handover. Preparations for and initiative to the handover can take place to a greater or lesser extent in the mobile. It will then be possible to form and distribute tasks in conjunction with preparation for, initiation and execution of the handover such that the need of signalling with respect to the handover will be comparatively small.
A still further important advantage with the method in accordance with the invention is that it is particularly suitable in a mobile radio system where at least two base station transmitters are simultaneously responsible for transmitting message information to at least certain mobiles. In such a system the increasing degree of coverage can be utilised to the full in handing over the responsibility in accordance with the invention.
Further advantages ought to be understood by one skilled in the art after having studied the description of preferred embodiments.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 illustrates cells and location of base station transmitters in a mobile radio system where in certain areas two or three base station transmitters simultaneously transmit message information to at least certain mobiles.
FIG. 2 illustrates two mobiles and some stationary parts of a mobile radio system according to FIG. 1.
BEST MODES FOR CARRYING OUT THE INVENTION
A method in accordance with the invention is particularly suitable for a mobile radio system where at least two base station transmitters are simultaneously responsible for transmitting message information to at least certain mobile stations. It seems therefore to be suitable to describe an embodiment of a method in accordance with the invention in connection with such a system.
A cellular mobile radio system illustrated in FIG. 1 has mobile and base stations with transmitters and receivers for radio signals. Message information is transmitted digitally to and from the mobiles by transmission and reception of radio signals with digital modulation corresponding to the message information. The radio signals are sent on one of a plurality of radio channels. Several radio channels can share in time multiplex the same radio frequency, and radio signals can be transmitted to and from several mobiles in different time slots on the radio frequency, these slots being associated with the radio channels.
The mobiles may move within and between the cells of the system. The base transmitters are assigned to the cells so that there is at least one base transmitter for each cell, for transmitting signals to the mobiles of the cell.
There is no completely Fixed channel allocation for all cells and base stations in the entire system. At least for some base stations and cells there is allowed some freedom in the selection of radio channels. Thus the channel allocation in the system is some kind of dynamic or adaptive channel allocation meaning that at least some channels are a common resource to at least some neighbour bases/cells. Somewhat simplified, there is illustrated in FIG. 1 the division of an area into cells and the assignation of base station transmitters to the cells in a mobile telephone system. For the sake of simplicity in FIG. 1, all cells C1 to C24 are illustrated as regular hexagons with sides L. In practice the cells will probably have different sizes and shapes. In addition, depending on traffic conditions, it will often be suitable with overlapping in the boundary areas between the cells. To a certain extent, the base transmitters then off-load each other by handling transmissions to mobiles where such transmission should from a purely geographically point of view, be performed by the base transmitters of a contiguous cell.
For each cell C1-C24 there is an ordinary base transmitter BS1-BS24. For contiguous cells these transmitters are conventionally co-located in groups of three. For example, the base transmitter BS1 for the cell C1 is co-located with the base transmitter BS3 for the cell C3 and with the base transmitter BS5 for the cell C5. Correspondingly, the base transmitter BS14 for the cell C14 is co-located with the base transmitter BS16 for the cell C16 and with the base transmitter BS18 for the cell C18. These co-located ordinary base station transmitters are situated in the boundary regions between the cells to which they are assigned. For example, the ordinary base transmitters BS2, BS4 and BS6 are colocated in the boundary areas between the cells C2, C4 and C6.
Further to the ordinary base transmitters BS1-BS24 the system includes a number of extra base transmitters for certain of the cells. Cells C6, C7, C10, C11, C13, C14, C19 and C20 each has one extra base station transmitter. For each of the cells C15, C18 and C22 there are two extra base transmitters. Of the extra base transmitters XS6, XS7, XS10, XS11, XS13, XS15A, XS15B, XS18A, XS18B, XS19, XS20 and XS22A are co-located in groups with three extra base transmitters in each group in a similar manner as the ordinary base transmitters. Accordingly, for example, the extra base transmitter XS15B for the cell C15 is co-located with the extra base transmitter XS19 for the cell C19 and the extra base transmitter XS18A for the cell C18. On the other hand, neither the extra base transmitter XS14 for the cell C14 nor the extra base transmitter XS22B for the cell C22 are co-located with any other base transmitter, but are situated approximately at the centre of the cell with which they are associated. An extra base transmitter does not need to differ technically from an ordinary base transmitter. For a given cell an extra base transmitter can thus have technical equipment of the same type as an ordinary base transmitter for the same cell. In principle, it can also function in the same way as the ordinary one. If there are two identical base station transmitters for a given cell, either of them may be respectively regarded as ordinary or extra in certain cases.
The extra base transmitter or transmitters for a given cell transmit radio signals which are substantially the same as those sent by the ordinary base transmitter of the cell. The signals are digitally modulated with selective digital message information to the individual mobiles in the cell. The radio signals may also be digitally modulated with general control information common to all mobiles concerned. A mobile in a cell for which three is one or more extra base transmitter can therefore receive, at least in certain cases, corresponding radio signals from more than one base transmitter approximately simultaneously within the same frequency range. Depending on the mutual, relative positions in the cell of the mobiles and bases as well as the transmission times and propagation paths of the radio signals from the base transmitters to the mobile stations, corresponding signals from different base transmitters can be received without, or with a given time shift at the mobile. The greater the distance between the base transmitters associated with the cell, the greater in general can be the time shift. When the ordinary base station transmitters and the extra base station transmitters are situated according to FIG. 1, the distance between two base transmitters for the same cell varies between L and 2L, i.e. between the side and diameter of the regular hexagons. If, for the sake of simplicity, reflections are ignored and the assumption made that the base transmitters transmit without mutual time shifting, the time reception shift at the mobile station could then attain a maximum of 2L/c, where c is the propagation rate of the radio signals.
In FIG. 2 there are illustrated parts of a mobile radio system in accordance with FIG. 1. A mobile radio exchange MSC is connected via cables L1, L2, . . . Lm, Ln to a plurality of bases of which two, Bm and Bn are illustrated in FIG. 2. The base Bm has a central unit connected via cables Lma and Lmb to two transceiver units Bma and Bmb situated at a distance from the central unit. The central unit of the base Bm includes a central line and control unit 1, transmission time shifting means 2A and 2B, one for each of the transceivers, reception time shifting means 3A and 3B, one for each of the transceivers and line units 4A and 4B, one for each of the transceivers.
Both transceivers in the base Bm are alike. Each such transceiver contains a line and control unit 5A or 5B, transmitter means 6A or 6B, receiver means 7A or 7B, a transmission- reception filter 8A or 8B and an antenna 9A or 9B.
The base Bn differs partly from base Bm, primarily due to its central line and control unit 10 being situated in juxtaposition with one of its transceivers Bna. Accordingly, no cable with associated line units corresponding to Lm, L mb 4A-5B is needed for the transceiver Bna, but only for the other transceiver Bnb. In addition, no transmission or reception time shifting means is included in any central unit in Bn, but the corresponding means 2A, 2B, 3A and 3B are respectively included in transceivers Bna and Bnb.
The mobiles MS1 and MS2 are mutually alike. Each mobile includes sound sensing means 11, encoding means 12, transmitting means 13, transmit-receive switch 14, reception means 15, equaliser and decoding means 16, sound reproducing means 17, control means 18 and means 19 for feeding in and out or presentation of digital information.
Apart from the bases having two transceiver units at a distance from each other, and having controllable transmission and reception time shifting means, the mobile radio system in FIG. 2 functions in most respects in a way well-known in mobile radio systems. No complete description of how the system functions in different respects should therefore be necessary for one skilled in the art, and it should only be necessary to describe what is unique or unusual in the mobile radio system according to FIG. 2. One not skilled in the art of mobile radio systems is referred to the technical literature.
Message information e.g. speech or data that the mobile radio exchange forwards towards a mobile in the cell Cm, e.g. the MS1, is transmitted from the mobile radio exchange via the cable Lm to the line and control unit 1. From here the information is transferred via the transmission time shifting means 2A, line unit 4A, cable Lma and line and control unit 5A to the transmitting means 6A. The transmitting means 6A transmits, via the transmission-reception filter 8A and antenna 9A, radio signals with digital modulation in correspondance with the message information from the mobile radio exchange.
The message information from the mobile radio exchange is also transferred from the line and control unit 1 via the transmission time shifting means 2B, line unit 4B, cable Lmb and line and control unit 5B to the transmission means 6B in the transceiver Bmb. The transmission means 6B transmits, via the transmission reception filter 8B and antenna 9B, radio signals with digital modulation in correspondance with the information from the mobile radio exchange.
Depending on the delay in transferring the message information to the transmission means 6A and the corresponding delay in transferring to the transmission means 6B the radio signals can be transmitted from the antenna 9A of the transceiver unit Bma substantially without time shifting, or time shifted in relation to the transmission of corresponding radio signals from the antenna 9B of the other transceiver Bmb.
The radio signals from the antenna 9A i Bma arrive at a given mobile in the cell Cm, e.g. the mobile MS1, with or without time shift in relation to corresponding radio signals from the antenna 9B in Bmb. The possible time shift on arrival at the mobile depends partly on possible time shifting at transmission from the antennas and partly on possible difference in propagation time for the radio waves from the antennas. The transmission time shifting means 2A and 2B have a variable delay and can be controlled by the line and control unit 1, such that the signals are transmitted from the antenna 9A in Bma time-shifted more or less before or after corresponding signals from the antenna 9B in Bmb. In the preferred embodiment according to FIG. 2, the line and control unit 1 controls the variable delays in the transmission time shifting means 2A and 2B so that the differences in delay in the cables Lma and Lmb as well as the differences in the radio signal propagation times are counteracted. This may also be expressed by saying that the line and control unit controls the variable delays in the transmission time shifting means 2A and 2B, such that the time shift of the radio waves on arrival at the mobile is decreased compared with the situation where the means 2A and 2B have the same fixed delay. It could be thought that the ideal case were that the line and control unit controlled the delays in the time shifting means 2A and 2B so that the digitally modulated signals transmitted from the antenna in Bma arrived at the antenna in MS1, exactly simultaneously and in phase with corresponding signals transmitted from the antenna in Bmb. In practice, this is neither striven for nor normally achieved. Reflections occur as the radio signals are propagated between the antenna, and the mobile has an adaptive equaliser. It is therefore not necessary for the signals from the different transceiver units to arrive exactly simultaneously to the mobile. On the contrary, there is preferably sought a small time shift to achieve diversity against Rayleigh fading. One not skilled in this art and who is desirious of obtaining further information can find it in the technical literature and in publications such as: "Radio Test Performance of a Narrow-band TDMA System-DMS 90", J-E Stjernvall, B. Hedberg, K. Raith, T. Backstrom and R. Lofdahl.
In principle, there are at least two conceivable methods of determining how the line and control unit 1 shall control the delay in the transmission time shifting means 2A and 2B. One method is to estimate in the fixed part of the mobile radio system the time shift between the mobiles radio signals at one of the mobile radio system the time shift between the mobiles radio signals at one of the transceivers Bma and corresponding radio signals at the other transceiver Bmb. There is thus obtained an estimation of the differences in propagation time to the mobile, these differences depending on the position of the mobile. Remaining differences in delay are related to the fixed part of the mobile radio system, e.g. differences in length of the cables Lma and Lmb and are not dependent on the position of the mobile. In the embodiment according to FIG. 2, this method can be applied in practice such that the delays in the reception time shifting means 3A and 3B are adjusted so that information received from the mobile MS1 at Bma arrives at the line and control unit 1 simultaneously as corresponding information received at Bmb from the mobile station MS1 arrives at the line and control unit 1. The delays in the transmission time shifting means 2A and 2B are subsequently adjusted in correspondence with the optimum delays in the reception time shifting means 3A and 3B. The other method is to estimate in the mobile the difference in arrival time or time shift between the digitally modulated radio signals from one transceiver Bma and the corresponding digital signals from the other transceiver Bmb. Some kind of encoding of the radio signals is required for this, which indicates from which transceiver they are transmitted. In TDMA systems it is known to transmit special synchronising words. These can be utilised if they are formed or supplemented with additional individual wards so that two base transmitters for the same cell do not only have identical synchronising words. Alternatively, special synchronising words can be transmitted from the base station transmitters solely to enable the mobile to estimate the differences in arrival times or time shifts. The mobile transmits information about the estimated arrival time difference or time shift via radio signals to the fixed part of the system, where it is utilised for controlling the transmission time shifting means 2A and 2B. The line and control unit 1 then receives, via the respective line units 5A, 4A and 5B, 4B, information about estimated arrival time difference from the mobile in the same way as the line and control unit obtains message information from the mobile.
It is conceivable per se, but hardly to be preferred, to combine both methods for controlling the transmission time shift in a mobile radio system according to FIG. 2.
Measuring the difference in arrival time or time shifting for corresponding radio signals can be performed in a conventional way, e.g. with the aid of correlation. In the cases where the radio signals conventionally contain predetermined synchronising patterns (words), the time difference between the appearance of these in different signals can be measured using conventional methods. A mobile control means 18 and/or a base line and control unit 1 or 10, possible in combination with the transceiver's line units 5A and 5B can then include time measurement means for estimating reception time shifting, or arrival time comparison means for comparing arrival times.
When so required, a base preferably conventionally utilises the same transmitter means and antenna for transmitting, in time multiplex within the same frequency range, radio signals digitally modulated with message information to different mobiles associated with the same cell. Radio signals with message information to a given mobile are then transmitted from different base transmitters with a possible transmission time shift which is specially adjusted with regard to the position of this particular mobile. The case can arise where a base in a mobile radio system needs to transmit a radio signal with information other than message information intended for reception by several or all of the mobiles in the cell, e.g. information as to the identity of the base/cell. Such signals are preferably transmitted simultaneously without mutual time shifting, from the transceivers Bma, Bmb and Bna, Bnb of the base in a mobile radio system according to FIG. 2. The transmission time shifting means are then controlled to a balancing state where the delay of information from the line and control unit 1 to the antenna in one transceiver Bma is equally as great as the delay of information from the line and control unit 1 to the antenna in the other transceiver Bmb. The corresponding situation can apply when a base "listens" in unoccupied combinations of time slot and frequency range for set up calls from mobiles in unknown positions relative to the transceivers of the base. The reception time shifting means 3A and 3B can then be controlled to a balancing state where the delay of the message information from the antenna in one transceiver Bna to the line and control unit 9 is equally as great as the delay of information from the antenna in the other transceiver Bnb to the line and control unit 9.
The mobiles MS1 and MS2 have adaptive equalisers, whereby the digital modulation during a modulation time interval in the radio signals transmitted from a base transmitter can be reconstructed from signals received during a reception time interval. In known cellular, digital, mobile radio systems with only one base transmitter per cell, the reception time interval of the equalisers is dimensioned according as the dispersion on the radio channel, i.e. expected time shifts between corresponding signals from a single base transmitter due to reflections. Because of the equaliser, not only the radio signal having the greatest amplitude or arriving first to the mobile station is utilised for reconstructing the digital modulation, but also other corresponding radio signals arriving with a time shift within the extent of the equaliser's reception time interval can be utilised. The mobiles in a system according to FIGS. 1 and 2 preferably have equalisers which are dimensioned such that the reception time interval of the mobile in reconstruction of the digital modulation is greater than the time it takes for signals to propagate a distance as long as the greatest distance between two base transmitters associated with the same cell within a restricted geographical area. With the base transmitters placed according to FIG. 1, the mobile equalisers would thus be dimensioned for a reception interval in reconstruction which is greater than 2L/c. However, there can be dispersion, and reflections can extend the propagation time from a base transmitter to a mobile more than the extension of the propagation time from another base transmitter for the same cell. The reception time interval of the mobiles is therefore preferably substantially greater than the time it takes for radio signals to propagate a distance which is just as great as the greatest distance between two base transmitters associated with the same cell within the geographical area in question.
In mobile radio systems according to FIGS. 1 and 2, the modulation time interval of the digital modulation of the signals can be of the same order of magnitude as the time it takes for radio signals to propagate a distance just as long as the greatest transmitting distance between two base station transmitters serving the same cell within a limited area. Although the use of extra base transmitters in combination with equalizers described affords greater advantages the smaller the modulation time interval is in relation to this propagation time, and the described combined use maybe has its greatest importance when the modulation time interval has the same size as or is less than the mentioned propagation time, the combined use of equalizers and extra base transmitters can mean substantial advantages even when the modulation time interval is some few times greater than the mentioned propagation time.
It is conceivable to use different kinds of digital modulation in a mobile radio system, whereby somewhat different relationships can exist between information transmission rate and modulation time interval. In digital modulation of the radio signals involving transmission of one symbol at a time of a sequence of uncorrelated symbols, the modulation time interval will be the time during which a single symbol is decisive for the digital modulation. For example, if a sequence of binary symbols individually and one at a time determines the modulation, the modulation time interval will be the time during which one symbol determines the modulation. This can also be expressed by saying that the modulation time interval will be the inverted value of the transmission rate in bits. In digital modulation of the signals involving two or more at a time of a sequence of digital symbols being decisive for the modulation during wholely or partly overlapping times, the modulation interval can be the time when a preceeding, but not the nearest subsequent symbol affects the modulation. For example, in digital modulation according to SE 8102802-9, FIGS. 1-2, a symbol affects the phase of a carrier wave during a time interval 3T. The nearest preceding symbol also affects the phase change of the carrier wave during a first part 2T of the time interval 3T. The nearest subsequent symbol also affects the change of phase of the carrier wave during a last part of 2T of the time interval 3T. In this case modulation time interval will be T, which agrees with what is called the symbol time interval in SE 8102802-9. In general, it can be said that the modulation time interval is to be interpreted as the interval in time between two successive changes in the transmitted digital modulation.
Perhaps the most usual reason for bandover in conventional mobile radio systems is that a mobile moves from one area which is best served by one base to another area which is best served by another base. Of course, there may be other reasons, e.g. changed traffic conditions or changed radio reception conditions.
When three or more bases can receive radio signals from a mobile, the position of the latter can be estimated by comparison of the radio propagation times. The estimation can be improved if more than three bases are used. Knowledge of the position of the mobile can be used by the stationary part of the mobile radio system for selecting what bases are suitable for use as new bases when handing over the responsibility. The mobile radio exchange or other stationary part of the system assigns new bases the responsibility in a manner such that communication can be maintained with good quality as the mobile travels through the cell structure.
Knowledge of the position of the mobile can also be used as a criterion for performing the handing over of responsibility. For example, if the mobile moves out of the cell which is serving it as the moment, this is an indication that a handover of responsibility should soon take place, irrespective of whether the communication quality is still good.
In different known mobile radio systems, the decision for handing over can take place in more or less different ways. Different criteria have been proposed for the decision as to if and where handover is to take place. Collection of the basis for the handover decision can take place in different ways. The distribution of tasks and the signalling in connection with handover between mobiles and the stationary part of the mobile radio system can differ from system to system. All this is well known to one skilled in the art. One not skilled in the art can obtain necessary information from the technical literature or United States patents in the field of cellular mobile radio.
What is distinguishing for handing over the responsibility in accordance with the present invention is primarily the actual execution of handover. For the handover decision, at least in certain cases, known parameters can be used such as the signal-noise ratio for transmitting signals to and from the mobiles. The signal-noise ratio or other parameters can be measured, either solely in the stationary part of the mobile radio system e.g. by the base central or control units or solely in the mobiles by the reception and control means or in both mobiles and the stationary part. In the handover decision, the traffic conditions in different parts of the mobile radio system can be given attention, substantially conventionally, e.g. if certain bases tend to have too high traffic while adjacent bases have unoccupied capacity for further traffic.
An embodiment of the execution of handing over responsibility for the communication in accordance with the invention will now be described in connection with FIG. 2. For the sake of simplicity, it is assumed that handing over the responsibility will take place in conjunction with a mobile moving from the position of MS1 in FIG. 2 to the position of MS2 in FIG. 2.
Sometime before the bandover, the mobile is in the position of MS1 within the coverage area of the base station Bm, but outside the coverage area of the base station Bn, i.e. the radio transmission conditions for radio signals between the mobile station and Bma or Bmb are sufficiently good, but the radio transmission conditions for radio signals between the mobile and Bna and Bnb are too poor.
Sometime after the handover, the mobile is in the position of MS2 within the coverage area for the base Bn, but outside the coverage area for the base Bm, i.e. the radio transmission conditions for radio signals between the mobile and Bna and Bnb are sufficiently good, but the radio transmission conditions for radio signals between the mobile and Bma and Bmb are too poor.
When the mobile has moved to position somewhere between the positions of MS1 and MS2, a handover decision is made, and this decision may be based on facts such as the radio transmission conditions and traffic within the coverage areas of the base stations. The decision is made by the mobile radio exchange or possible some other stationary part of the mobile radio system.
Before handing over the responsibility for communication with the mobile, it is tested in the stationary part of the mobile radio system whether the second base transmitter can use the same radio channel after handover for transmitting message information to the mobile as the radio channel the first base transmitter used before handover. This may also be expressed by saying that the stationary part tests whether a change of radio channel can be avoided on handover.
This testing takes place according to predetermined rules based on predetermined parameters. For example, if the base to which the responsibility is to be handed over already utilises the radio channel in question for communication with another mobile having higher priority, a change of a radio channel must take place on handover. On the other hand, if the base to which responsibility is to be handed over does not utilise the radio channel in question, and possible transmission on this radio channel would not interfere with other traffic, there is no need for changing channels on handover. Another reason for having to change channels is that the channel in question has too much interference in the cell served by the base to which responsibility is to be handed over. Other rules or reasons for, and against, changing channels will be understood by one skilled in this art.
After a decision as to handover and radio channel has been made, one of the base transmitters Bna or Bnb begins to transmit the same message information to the mobile as the base transmitters Bma and Bmb. This base transmitter is preferably transmitting on the same channel as the base transmitters Bma and Bmb. In a TDMA mobile radio system, this means that Bna or Bnb begin to transmit the same message information as Bma and Bmb on the same radio frequency and in the same time slot as Bma and Bmb. The transmission times at Bna and Bnb of the radio signals is preferably adjusted to corresponding transmission times for the signals at Bma and Bmb in accordance with what has been described above. After transmission of the message information to the mobile has been started from Bna and Bnb, the transmission of corresponding message information to the mobiles from one of the base transmitters Bma and Bmb is terminated. One of the base transmitters Bma or Bmb then transmits the same message information, e.g. speech or data, to the mobile as one of the base transmitters Bna and Bnb. Neither one of the two other base transmitters in FIG. 2 then transmit corresponding information to the mobile. The one of the base transmitters Bma and Bmb which has the best radio transmission conditions and the one of base transmitters Bna and Bnb which has the best radio transmission conditions preferably transmit to the mobile.
After of the base transmitters Bma or Bmb has ceased to transmit message information to the mobile, a further one of the base transmitters Bna or Bnb beings to send message information to the mobile. Both Bna and bnb as well as one of the other base transmitters Bma and Bmb are then transmitting the same message information to the mobile. All three transmitters preferably transmit on the same radio channel, and in a TDMA mobile radio system this means the same radio frequency and same time slot. The transmission times of Bna and Bnb and at the third base transmitter of the radio signals are preferably adjusted to each other in agreement with what has been described above.
After both Bna and Bnb have begun to transmit the same message information to the mobile as the remaining base transmitter of Bma and Bmb, the transmission of message information to the mobile is terminated from this remaining base transmitter. Both Bna and Bnb are then transmitting message information to the mobile, whereas none of the base transmitters Bma and Bmb is transmitting such information to the mobile. At this, the responsibility for communication between the mobile has been handed over from the base transmitters Bma and Bmb to the base transmitters Bna and Bnb. This may also be expressed by saying that responsibility for the communication has been handed over from the base Bm to the base Bn, i.e. an execution of handover is completed.
During the whole of the above described handover, at least two of the base transmitters send the same message information to the mobile. During certain times there are three base transmitters sending the same message information. On the other hand, all base transmitters of the affected stations never send the same information to the mobile. The risk of accidental interruption in the transmission of message information between the mobile and the fixed part of the mobile radio system will thus be small. Simultaneously, the receiving time shift at the mobile will be less than if all base transmitters were to send the same message information to the mobile. In addition, re-use of radio channels if facilitated in the mobile radio system when all affected base transmitters never send simultaneously on the same radio channel.
If, for some reason, it is necessary to change radio channels in conjunction with handing over the responsibility for communication from the base Bm to the base Bn, it is to be preferred that the channel which is to be used after handover is selected such that during a transition time the mobile can receive the same message information on both channels. In a TDMA system according to FIG. 2, this means that a base transmitter, e.g. Bna, begins to transmit the same message information as the base transmitters Bma and Bmb, but in another times slot, so that the radio signals from Bna arrive at the mobile during other times other than the radio signals from Bma and Bmb. When the base transmitter Bnb begins to transmit message information to the mobile, it transmits in the same time slot as Bna. Due to Bna and Bnb transmitting message information in a time slot than the one used by Bma and Bnb, the mobile can receive, by modifying its radio receiver tuning, both the message information transmitted by Bna and/or Bnb and the message information transmitted by Bma and Bmb. In this case, however, the mobile must be given advance information as to the handover.
If handing over the responsibility for communication is to take place from three or more base transmitters to more than two base transmitters, its execution will naturally be somewhat different than what has been described in connection with FIG. 2, since the transmission form three or more base transmitters is to be terminated or started. Different orders for starting and terminating transmission are then conceivable. Common for these varients is, however, that at least two base transmitters always transmit the same message information to the mobile. In addition, the transmission of message information is always started from at least one base, to which responsibility shall be handed over before transmission of message information is terminated from all base transmitters, from which the responsibility shall be handed over. The order is preferably such that never all base transmitters simultaneously transmit the same message information to the mobile in conjunction with the handover.
A mobile radio system where at least two base transmitters are simultaneously responsible for transmitting message information to a mobile does not need to be formed according to the above, but can differ to a greater or lesser extent from the system described above. For example, it is conceivable to co-localise at least parts of the equipment in an ordinary base transmitter with parts of the equipment in the extra base transmitter for the same cell, providing that the antennas are spaced from each other. In an extreme case, it is conceivable, in principle, for all equipment excepting the antennas to be co-localised to one place, i.e. in the vicinity of one of the antennas, and that the antennas are fed by signals at radio frequency via a cable from this place. By "base transmitter" shall be accordingly understood at least a transmitter antenna for radio signals and preferably more or less of the remaining means required in a base. In a base transmitter there are preferably included at least means corresponding to the means included in a transceiver unit Bma or Bmb in FIG. 2.
To avoid misunderstanding, it is pointed out that none of the base transmitters to which responsibility shall be handed over is a slave transmitter to any base transmitter from which the responsibility shall be handed over. From FIG. 2 it will be seen, for example, that the base transmitters Bna and Bnb can be controlled directly by the mobile radio exchange MSC and independently of how the exchange controls the base transmitters Bma and Bmb.
A method in accordance with the invention is of course not restricted to a given implementation of base transmitter, even if it is assumed in the example above that base transmitters can start and terminate transmission at different times.
In actual fact, a method in accordance with the invention is not restricted to mobile radio systems with two or more base transmitters per cell, and it is conceivable to apply embodiments of a method in accordance with the invention in a mobile system, the method involves, summarily explained, that the same radio channel is used both before and after handover, if possible, for transmitting message information to the mobile. A decision on handover is preferably made in the mobile radio exchange or other stationary part of the system, and the handover takes place without the mobile being formed beforehand. If the mobiles have equalizers and the system transmits message information digitally by digital modulation of radio signals, it is also preferably in this case as well that the transmission of message information is started from the base transmitter to which responsibility is to be handed over, before transmission of the same information is terminated from the base transmitter from which responsibility is to be handed over. In this case also, the same message information is transmitted during a transition period to the mobile from two base transmitters. If it is not possible to utilise the same radio channel for some reason, it is then preferable in such a system to select the different channels such that during a transition period the mobile can receive the transmissions from the different base transmitters essentially without their mutually obstructing each other. In a TDMA system with mobiles according to FIG. 2, this means that the base transmitters transmit in different time slots. The advantages with a method in accordance with the invention will then be substantially less, however, than in a system according to FIGS. 1 and 2, where the same radio channel can be utilised.
A method in accordance with the invention is not limited to described embodiments or mobile radio systems according to FIGS. 1 and 2, but can be applied and varied within the scope of the claims.

Claims (10)

I claim:
1. In a mobile radio communication system comprising base stations and mobile stations and a plurality of radio channels for transmitting control information and message information between base stations and mobile stations, said base stations and mobile stations including radio transmitters and radio receivers for a plurality of radio channels, a method for handing over the responsibility for transmitting message information to a mobile station from at least one first base station transmitter to at least one second base station transmitter, comprising the steps of:
before handing over the responsibility carrying out a test in the stationary part of the system to see whether after the handover the second base station transmitter can use the same radio channel for transmitting message information to the mobile as the radio channel used by the first base station transmitter before handover; and
if the test result is positive then using the same radio channel after the handover as before for transmitting message information to the mobile.
2. A method according to claim 1 comprising the further step of:
executing handover without first informing the mobile of the handover.
3. A method according to claim 1 comprising the further steps of:
starting the transmission of message information to the mobile station from the second base station transmitter before terminating the transmission of message information to the mobile station from the first base station transmitter; and
transmitting substantially the same message information during a transition period from both the first base station transmitter and the second base station transmitter.
4. In a mobile radio communication system comprising base stations and mobile stations having radio transmitters and radio receivers for transmitting control information and message information therebetween, a method for handing over the responsibility for transmitting message information to a mobile station from at least one first base station transmitter to at least one second base station transmitter comprising the steps of:
starting the transmission of message information to the mobile station from the second base station transmitter before terminating the transmission of message information to the mobile station from the first base station transmitter; . .and.!.
transmitting substantially the same message information during a transition period from both the first base station transmitter and the second base station transmitter.Iadd.; and
combining, in said mobile station, information transmitted by said first base station transmitter and information transmitted by said second base station transmitter to reconstruct said message information.Iaddend..
5. A method according to claim 4 comprising the further steps of:
before handing over the responsibility, carrying out a test in the stationary part of the system to see whether after the handover the second base station transmitter can use the same radio channel for transmitting message information to the mobile as the radio channel used by the first base station transmitter before handover; and
when the radio transmission conditions and remaining radio communication in the system permit, then using the same radio channel after the handover as before for transmitting message information to the mobile.
6. A method according to claim 5 comprising the further steps of:
executing the handover without first informing the mobile station of the handover. .Iadd.7. The method according to claim 4, further comprising the step of:
receiving, at said mobile station signals transmitted by said first base station transmitter and signals transmitted by said second base station
transmitter with a time shift therebetween. .Iaddend.8. .Iadd.The method according to claim 7, further comprising the step of:
introducing a delay in transmission of either said signals transmitted by said first base station transmitter or said signals transmitted by said second base station transmitter, said delay at least in part causing said time shift. .Iaddend..Iadd.9. The method according to claim 7, wherein said step of combining further comprises the step of:
combining said information received within a reception time interval, said reception time interval being greater than said time shift. .Iaddend..Iadd.10. The method according to claim 4, further comprising the step of:
selecting said second base station transmitter based on a position of said mobile station. .Iaddend..Iadd.11. The method according to claim 4, wherein said first and second base station transmitters are co-located and share transmitting circuitry. .Iaddend..Iadd.12. In a mobile radio communication system comprising base stations and mobile stations having radio transmitters and radio receivers for transmitting control information and message information therebetween, a method for handing over the responsibility for transmitting message information to a mobile station from at least one first base station transmitter to at least one second base station transmitter comprising the steps of:
starting the transmission of message information to the mobile station from the second base station transmitter before terminating the transmission of message information to the mobile station from the first base station transmitter;
transmitting substantially the same message information during a transition period from both the first base station transmitter and the second base station transmitter, wherein a fixed delay is introduced between said transmission of a symbol of said message information from said first base station transmitter and said transmission of said same symbol of said message information from said second base station transmitter; and
combining, in said mobile station, information transmitted by said first base station transmitter and information transmitted by said second base station transmitter, to reconstruct said message information.
.Iaddend..Iadd.13. The method according to claim 12, further comprising the step of:
receiving, at said mobile station, signals transmitted by said first base station transmitter and signals transmitted by said second base station transmitter with a time shift therebetween. .Iaddend..Iadd.14. The method according to claim 13, wherein said step of combining further comprises:
combining said information received within a reception time interval said reception time interval being greater than said time shift. .Iaddend..Iadd.15. The method according to claim 12, further comprising the step of:
selecting said second base station transmitter based on a position of said mobile station. .Iaddend..Iadd.16. The method according to claim 12, wherein said first and second base station transmitters are co-located and share transmitting circuitry. .Iaddend..Iadd.17. In a mobile radio communication system comprising base stations and mobile stations having radio transmitters and radio receivers for transmitting control information and message information therebetween, said base stations and said mobile stations operating within a geographic area divided into a plurality of communication cells, a method for handing over the responsibility for transmitting message information to a mobile station from at least one first base station transmitter to at least one second base station transmitter when said mobile station moves from a first one of said plurality of cells serviced by said at least one first base station transmitter to a second one of said plurality of cells serviced by said at least one second base station transmitter, comprising the steps of:
starting the transmission of message information to the mobile station from the second base station transmitter before terminating the transmission of message information to the mobile station from the first base station transmitter;
transmitting substantially the same message information during a transition period from both the first base station transmitter and the second base station transmitter, said transition period being that time required for the mobile station to move from said first cell to said second cell;
combining, in said mobile station, information transmitted by said first base station transmitter and information transmitted by said second base station transmitter to reconstruct said message information; and
terminating the transmission of message information to the mobile station from said first base station transmitter when the mobile station has moved
from said first to said second cell. .Iaddend..Iadd.18. The method according to claim 17, further comprising the step of:
receiving, at said mobile station, signals transmitted by said first base station transmitter and signals transmitted by said second base station transmitter with a time shift therebetween. .Iaddend..Iadd.19. The method according to claim 18, further comprising the step of:
introducing a delay in transmission of either said signals transmitted by said first base station transmitter or said signals transmitted by said second base station transmitter, said delay at least in part causing said time shift. .Iaddend..Iadd.20. The method according to claim 18, wherein said step of combining further comprises the step of:
combining said information received within a reception time interval, said reception time interval being greater than said time shift. .Iaddend..Iadd.21. The method according to claim 17, further comprising the step of:
selecting said second base station transmitter based on a position of said
mobile station. .Iaddend..Iadd.22. The method according to claim 17, wherein said first and second base station transmitters are co-located and share transmitting circuitry. .Iaddend.
US08/938,840 1988-06-14 1997-09-26 Handover method for mobile radio system Expired - Lifetime USRE36079E (en)

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US07/365,432 US5109528A (en) 1988-06-14 1989-06-13 Handover method for mobile radio system
US08/938,840 USRE36079E (en) 1988-06-14 1997-09-26 Handover method for mobile radio system
US09/235,456 USRE37787E1 (en) 1988-06-14 1999-01-21 Handover method for mobile radio system

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US08/938,840 Expired - Lifetime USRE36079E (en) 1988-06-14 1997-09-26 Handover method for mobile radio system
US09/228,279 Expired - Fee Related USRE37685E1 (en) 1988-06-14 1999-01-11 Handover method for mobile radio system
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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6216003B1 (en) * 1997-06-03 2001-04-10 Ntt Mobile Communications Network Inc. Method of handover control in mobile radio communication realizing reduced control load
US20030211849A1 (en) * 2002-05-08 2003-11-13 Paul Robinson Handover of a call connection in a cellular telecommunications network
US20140115139A1 (en) * 2012-10-19 2014-04-24 International Business Machines Corporation Service Placement on Hosts for a Consumer Based on Their Geographic Location

Families Citing this family (168)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4675863A (en) 1985-03-20 1987-06-23 International Mobile Machines Corp. Subscriber RF telephone system for providing multiple speech and/or data signals simultaneously over either a single or a plurality of RF channels
US5930297A (en) * 1989-11-20 1999-07-27 Interdigital Technology Corporation Base station emulator
US7106819B1 (en) 1987-11-20 2006-09-12 Interdigital Technology Corporation Plural subscriber system utilizing synchronized timeslots on a single frequency
US5495508A (en) * 1987-11-20 1996-02-27 Interdigital Technology Corporation Base station emulator
SE8802229D0 (en) * 1988-06-14 1988-06-14 Ericsson Telefon Ab L M MOBILE RADIO STATION PROCEDURE
US5327577A (en) * 1988-06-14 1994-07-05 Telefonaktiebolaget L M Ericsson Handover method for mobile radio system
FR2657211A1 (en) * 1990-01-18 1991-07-19 Cit Alcatel METHOD FOR TRANSFERRING COMMUNICATION IN A RADIOTELEPHONY NETWORK
GB2242805B (en) * 1990-04-06 1994-08-03 Stc Plc Handover techniques
US5230082A (en) * 1990-08-16 1993-07-20 Telefonaktiebolaget L M Ericsson Method and apparatus for enhancing signalling reliability in a cellular mobile radio telephone system
US5140627A (en) * 1990-10-09 1992-08-18 Telefonaktiebolaget L M Ericsson Handoff procedure that minimizes disturbances to dtmf signalling in a cellular radio system
JP2841900B2 (en) * 1991-02-27 1998-12-24 日本電気株式会社 Handoff method
US5303289A (en) * 1991-08-12 1994-04-12 Motorola, Inc. Communication transfer in a cellular radiotelephone system
US5309503A (en) * 1991-12-06 1994-05-03 Motorola, Inc. Dynamic channel assignment in a communication system
DE4141398C2 (en) * 1991-12-16 1994-01-20 Detecon Gmbh Method for improving the radio cell illumination in a cellular mobile radio system and device for carrying out the method
US5267261A (en) * 1992-03-05 1993-11-30 Qualcomm Incorporated Mobile station assisted soft handoff in a CDMA cellular communications system
SE9200915D0 (en) * 1992-03-24 1992-03-24 Ericsson Telefon Ab L M METHODS IN A CELLULAR MOBILE RADIO COMMUNINCATION SYSTEM
US5390234A (en) * 1992-04-20 1995-02-14 International Business Machines Corporation Dynamic tracking of mobile stations in wireless networks
GB9210971D0 (en) * 1992-05-22 1992-07-08 Philips Electronics Uk Ltd Telecommunications system
GB2269726B (en) * 1992-06-22 1996-08-28 Motorola Inc Alternate base-site transmission of a handoff command in a communication syste m
DE4225582C2 (en) 1992-08-04 2001-05-23 Detecon Gmbh Method for improving the radio coverage of a traffic route structure by a cellular mobile radio system and device for carrying out the method
EP0657077A4 (en) * 1992-08-25 1999-02-24 Motorola Inc Method and apparatus for performing a hand-off in a wireless communication system.
JP3372612B2 (en) * 1992-11-09 2003-02-04 キヤノン株式会社 Digital cordless telephone system
TW306102B (en) * 1993-06-14 1997-05-21 Ericsson Telefon Ab L M
US5740208A (en) * 1993-06-25 1998-04-14 Roke Manor Research Limited Interference cancellation apparatus for mitigating the effects of poor affiliation between a base station and a mobile unit
US5854808A (en) * 1993-09-14 1998-12-29 Pacific Communication Sciences Methods and apparatus for detecting the presence of a prescribed signal in a channel of a communications system
US5574750A (en) * 1993-09-14 1996-11-12 Pacific Communication Sciences, Inc. Methods and apparatus for detecting a cellular digital packet data (CDPD) carrier
US5668837A (en) * 1993-10-14 1997-09-16 Ericsson Inc. Dual-mode radio receiver for receiving narrowband and wideband signals
DE4497810B4 (en) * 1993-10-14 2009-10-08 Ericsson - Ge Mobile Communications Inc. Radio receiver and method for demodulating both wideband frequency modulated signals and narrowband frequency modulated signals
ZA948134B (en) * 1993-10-28 1995-06-13 Quaqlcomm Inc Method and apparatus for performing handoff between sectors of a common base station
FR2711867B1 (en) * 1993-10-28 1995-12-01 Alcatel Radiotelephone Method of handover in a cellular mobile radio system and device for implementing this method.
US5577047A (en) * 1993-11-10 1996-11-19 Telefonaktiebolaget Lm Ericsson System and method for providing macrodiversity TDMA radio communications
FI97671C (en) * 1994-02-14 1997-01-27 Nokia Telecommunications Oy A method for processing signaling messages in a mobile communication system and a mobile communication system
US5491837A (en) * 1994-03-07 1996-02-13 Ericsson Inc. Method and system for channel allocation using power control and mobile-assisted handover measurements
WO1995032591A1 (en) * 1994-05-19 1995-11-30 Airnet Communications Corp. System for dynamically allocating channels among base stations in a wireless communication system
GB2321831B (en) * 1994-07-22 1999-02-17 Int Mobile Satellite Org Satellite communication method and apparatus
US5586170A (en) * 1994-08-19 1996-12-17 Georgia Tech Research Corporation Cellular devices, systems and methods using intercell macro-diversity and dynamic channel allocation
DE4430553A1 (en) * 1994-08-27 1996-02-29 Sel Alcatel Ag Mobile radio system and handover procedure of a portable subscriber
US6914965B1 (en) 1994-09-30 2005-07-05 Qualcomm Incorporated Method and apparatus of providing a single state mobile unit in a modem connection comprising a wireless link
FR2726424B1 (en) * 1994-10-26 1996-12-20 Alcatel Mobile Comm France METHOD FOR CHANGING CELLS IN A CELLULAR RADIO COMMUNICATION NETWORK WITH MOBILES AND INFRASTRUCTURE EQUIPMENT FOR IMPLEMENTING THE METHOD
AU3893695A (en) * 1994-10-31 1996-05-23 Airnet Communications Corporation Cellular telephone system maintaining channel frequency at hand-off
SE516723C2 (en) * 1994-12-08 2002-02-19 Ericsson Telefon Ab L M Method and device for uplink macro diversity in a digital mobile radio communication system
JP2986145B2 (en) * 1995-02-06 1999-12-06 キヤノン株式会社 Wireless communication device
US5933787A (en) * 1995-03-13 1999-08-03 Qualcomm Incorporated Method and apparatus for performing handoff between sectors of a common base station
US5732353A (en) * 1995-04-07 1998-03-24 Ericsson Inc. Automatic control channel planning in adaptive channel allocation systems
US6047187A (en) * 1995-04-07 2000-04-04 Ericsson, Inc. Stabilized control channel planning using loosely coupled dedicated traffic channels
US5828948A (en) * 1995-04-07 1998-10-27 Telefonaktiebolaget Lm Ericsson Dynamic allocation of channels in a cellular telephone system
US5883899A (en) * 1995-05-01 1999-03-16 Telefonaktiebolaget Lm Ericsson Code-rate increased compressed mode DS-CDMA systems and methods
US5896368A (en) * 1995-05-01 1999-04-20 Telefonaktiebolaget Lm Ericsson Multi-code compressed mode DS-CDMA systems and methods
US6418324B1 (en) * 1995-06-01 2002-07-09 Padcom, Incorporated Apparatus and method for transparent wireless communication between a remote device and host system
US20040264402A9 (en) * 1995-06-01 2004-12-30 Padcom. Inc. Port routing functionality
US5732351A (en) * 1995-08-31 1998-03-24 Motorola, Inc. Communication system and method for single channel hand-offs
ATE263469T1 (en) * 1995-08-31 2004-04-15 Nokia Corp HANDOVER RANGE METHOD AND CELLULAR RADIO SYSTEM
US5903834A (en) * 1995-10-06 1999-05-11 Telefonaktiebolaget L/M Ericsson Distributed indoor digital multiple-access cellular telephone system
US5884177A (en) * 1995-10-25 1999-03-16 Northern Telecom Limited Cellular communication system and method providing improved handoff capability
US5907813A (en) * 1995-11-30 1999-05-25 Qualcomm Incorporated Signal acquisition in a wireless communication system by transmitting repeated access probes from a terminal to a hub
JPH09163431A (en) * 1995-12-12 1997-06-20 Fujitsu Ltd Radio channel allocating method
FI102447B (en) * 1996-02-06 1998-11-30 Nokia Telecommunications Oy Method of establishing connection, subscriber terminal and radio system
JP3392630B2 (en) * 1996-03-22 2003-03-31 松下電器産業株式会社 Spread spectrum communication equipment
US5784695A (en) * 1996-05-14 1998-07-21 Trw Inc. Method and apparatus for handover control in a satellite based telecommunications system
US6021122A (en) 1996-06-07 2000-02-01 Qualcomm Incorporated Method and apparatus for performing idle handoff in a multiple access communication system
US5890067A (en) * 1996-06-26 1999-03-30 Bnr Inc. Multi-beam antenna arrays for base stations in which the channel follows the mobile unit
US5884145A (en) * 1996-08-28 1999-03-16 Telefon Akmebolget Lm Ericsson Method and system for autonomously allocating a cellular communications channel for communication between a cellular terminal and a telephone base station
US5794157A (en) * 1996-08-28 1998-08-11 Telefonaktiebolaget Lm Ericsson Method and system for autonomously allocating transmit power levels for communication between a cellular terminal and a telephone base station
US6405048B1 (en) 1996-08-28 2002-06-11 Telefonaktiebolaget L M Ericsson Method and system for autonomously allocating frequencies to a radio system sharing frequencies with an overlapping macro radio system
US6009332A (en) * 1996-08-28 1999-12-28 Telefonaktiebolaget Lm Ericsson Method and system for autonomously allocating a frequency hopping traffic channel in a private radio system
US5870673A (en) * 1996-08-30 1999-02-09 Telefonaktiebolaget Lm Ericsson Methods and systems for concurrent receipt of incoming calls from a wide area cellular network and a private radio communications network
US5898929A (en) * 1996-08-30 1999-04-27 Telefonaktiebolaget L/M Ericsson (Publ) Method and apparatus for synchronizing private radio systems
US5909433A (en) * 1996-08-30 1999-06-01 Telefonaktiebolaget L M Ericsson (Publ) Method and apparatus for acquiring low duty-cycle reference signals in a mobile communications environment
US5940765A (en) * 1996-08-30 1999-08-17 Telefonaktiebolaget Lm Ericsson Radio communications systems and methods for jittered beacon transmission
US5778075A (en) * 1996-08-30 1998-07-07 Telefonaktiebolaget, L.M. Ericsson Methods and systems for mobile terminal assisted handover in an private radio communications network
US6112088A (en) * 1996-08-30 2000-08-29 Telefonaktiebolaget, L.M. Ericsson Radio communications system and method for mobile assisted handover between a private network and a public mobile network
US5953323A (en) * 1996-08-30 1999-09-14 Telefonaktiebolaget L M Ericsson (Publ) Method and apparatus for adapting non-cellular private radio systems to be compatible with cellular mobile phones
FI103855B1 (en) * 1996-10-30 1999-09-30 Nokia Telecommunications Oy Transmission method and cellular radio network
US5978366A (en) * 1996-12-20 1999-11-02 Ericsson Inc. Methods and systems for reduced power operation of cellular mobile terminals
US6999766B1 (en) 1997-05-19 2006-02-14 Qualcomm Incorporated Method and apparatus for optimization of a cellular network
US6259927B1 (en) 1997-06-06 2001-07-10 Telefonaktiebolaget Lm Ericsson Transmit power control in a radio communication system
US6085108A (en) * 1997-12-15 2000-07-04 Telefonaktiebolaget Lm Ericsson Modified downlink power control during macrodiversity
US5953320A (en) * 1997-08-08 1999-09-14 Qualcomm Incorporated Method and apparatus for constructing a temporary list of neighboring base stations in a wireless communication device
KR100259846B1 (en) * 1997-08-22 2000-06-15 윤종용 Semi-soft handoff
FR2768289B1 (en) * 1997-09-08 1999-10-15 Alsthom Cge Alcatel METHOD FOR TRANSFERRING COMMUNICATION BETWEEN TWO CELLS OF A DIGITAL CELL RADIO COMMUNICATION NETWORK
US6215777B1 (en) 1997-09-15 2001-04-10 Qualcomm Inc. Method and apparatus for transmitting and receiving data multiplexed onto multiple code channels, frequencies and base stations
SE515862C2 (en) * 1997-10-20 2001-10-22 Radio Design Innovation Tj Ab Matchless lobe handover
CN1161894C (en) * 1997-12-16 2004-08-11 三菱电机株式会社 Method for allocating radio channel for radio communication
US6339585B1 (en) * 1998-05-05 2002-01-15 Philips Electronics North America Corp. Error-recovery mechanism using a temporary forwarder in a wireless-ATM network
KR100308900B1 (en) * 1998-05-13 2001-11-15 윤종용 Hand-off apparatus and method of mobile communication system having time switched transmission deversity
US5999815A (en) * 1998-07-08 1999-12-07 Motorola, Inc. Method and apparatus for implementing diversity for a dual-mode communication unit
US6519248B1 (en) 1998-07-24 2003-02-11 Telefonaktiebolaget Lm Ericsson (Publ) Packet data network having distributed database
US6272345B1 (en) 1998-07-31 2001-08-07 Motorola, Inc. Method and apparatus for region based hand-offs in a satellite communication system
US6618363B1 (en) 1998-10-09 2003-09-09 Microsoft Corporation Method for adapting video packet generation and transmission rates to available resources in a communications network
US6385454B1 (en) * 1998-10-09 2002-05-07 Microsoft Corporation Apparatus and method for management of resources in cellular networks
US8078727B2 (en) * 1998-10-09 2011-12-13 Netmotion Wireless, Inc. Method and apparatus for providing mobile and other intermittent connectivity in a computing environment
US6289297B1 (en) 1998-10-09 2001-09-11 Microsoft Corporation Method for reconstructing a video frame received from a video source over a communication channel
US6507587B1 (en) 1998-10-09 2003-01-14 Microsoft Corporation Method of specifying the amount of bandwidth to reserve for use in network communications
US7136645B2 (en) 1998-10-09 2006-11-14 Netmotion Wireless, Inc. Method and apparatus for providing mobile and other intermittent connectivity in a computing environment
US8060656B2 (en) 1998-10-09 2011-11-15 Netmotion Wireless, Inc. Method and apparatus for providing mobile and other intermittent connectivity in a computing environment
US7293107B1 (en) 1998-10-09 2007-11-06 Netmotion Wireless, Inc. Method and apparatus for providing mobile and other intermittent connectivity in a computing environment
US6546425B1 (en) * 1998-10-09 2003-04-08 Netmotion Wireless, Inc. Method and apparatus for providing mobile and other intermittent connectivity in a computing environment
US6438136B1 (en) 1998-10-09 2002-08-20 Microsoft Corporation Method for scheduling time slots in a communications network channel to support on-going video transmissions
US6519004B1 (en) 1998-10-09 2003-02-11 Microsoft Corporation Method for transmitting video information over a communication channel
US6754266B2 (en) 1998-10-09 2004-06-22 Microsoft Corporation Method and apparatus for use in transmitting video information over a communication network
US7778260B2 (en) * 1998-10-09 2010-08-17 Netmotion Wireless, Inc. Method and apparatus for providing mobile and other intermittent connectivity in a computing environment
US6445701B1 (en) * 1998-10-09 2002-09-03 Microsoft Corporation Channel access scheme for use in network communications
GB2343330A (en) * 1998-10-29 2000-05-03 Fujitsu Ltd Soft handoff method using a backup link
US7882247B2 (en) * 1999-06-11 2011-02-01 Netmotion Wireless, Inc. Method and apparatus for providing secure connectivity in mobile and other intermittent computing environments
JP4231593B2 (en) 1999-07-21 2009-03-04 株式会社日立コミュニケーションテクノロジー Communication system and communication method thereof
US7206580B2 (en) * 1999-11-04 2007-04-17 Qualcomm Incorporated Method and apparatus for performing handoff in a high speed communication system
JP4478340B2 (en) * 2000-01-24 2010-06-09 株式会社日立国際電気 Receiving machine
US6970708B1 (en) 2000-02-05 2005-11-29 Ericsson Inc. System and method for improving channel monitoring in a cellular system
CA2420907A1 (en) * 2000-08-31 2002-03-07 Padcom, Inc. Method and apparatus for routing data over multiple wireless networks
US6922559B2 (en) * 2001-02-26 2005-07-26 Kineto Wireless, Inc. Unlicensed wireless communications base station to facilitate unlicensed and licensed wireless communications with a subscriber device, and method of operation
US7308263B2 (en) * 2001-02-26 2007-12-11 Kineto Wireless, Inc. Apparatus for supporting the handover of a telecommunication session between a licensed wireless system and an unlicensed wireless system
US7644171B2 (en) * 2001-09-12 2010-01-05 Netmotion Wireless, Inc. Mobile networking system and method using IPv4 and IPv6
US7095987B2 (en) * 2001-11-15 2006-08-22 Texas Instruments Incorporated Method and apparatus for received uplinked-signal based adaptive downlink diversity within a communication system
GB0207129D0 (en) * 2002-03-26 2002-05-08 Nokia Corp Positioning-triggered handover
US6681112B1 (en) * 2002-04-29 2004-01-20 Nokia Corporation Handovers of user equipment connections in wireless communications systems
US7853260B2 (en) * 2002-04-29 2010-12-14 Nokia Corporation Method and apparatus for cell identification for uplink interference avoidance using inter-frequency measurements
US7424296B2 (en) * 2002-04-29 2008-09-09 Nokia Corporation Method and apparatus for soft handover area detection for uplink interference avoidance
US20040047312A1 (en) * 2002-04-29 2004-03-11 Peter Muszynski Method and apparatus for UL interference avoidance by DL measurements and IFHO
US7525948B2 (en) * 2002-04-29 2009-04-28 Nokia Corporation Method and apparatus for utilizing synchronization information
US20040022217A1 (en) * 2002-04-29 2004-02-05 Sari Korpela Method and apparatus for soft handover area detection using inter-band measurements
US20030224730A1 (en) * 2002-04-29 2003-12-04 Peter Muszynski Method and apparatus for selection of downlink carriers in a cellular system using multiple downlink carriers
US20030224733A1 (en) * 2002-04-29 2003-12-04 Uwe Schwarz Method and apparatus for estimating signal quality for uplink interference avoidance
US7787572B2 (en) 2005-04-07 2010-08-31 Rambus Inc. Advanced signal processors for interference cancellation in baseband receivers
US7885644B2 (en) 2002-10-18 2011-02-08 Kineto Wireless, Inc. Method and system of providing landline equivalent location information over an integrated communication system
US7606190B2 (en) 2002-10-18 2009-10-20 Kineto Wireless, Inc. Apparatus and messages for interworking between unlicensed access network and GPRS network for data services
US7369859B2 (en) * 2003-10-17 2008-05-06 Kineto Wireless, Inc. Method and system for determining the location of an unlicensed mobile access subscriber
EP2334136A3 (en) * 2002-10-18 2012-07-18 Kineto Wireless, Inc. Method and apparatuses for channel activation for a telecommunication device
US7565145B2 (en) 2002-10-18 2009-07-21 Kineto Wireless, Inc. Handover messaging in an unlicensed mobile access telecommunications system
US7640008B2 (en) * 2002-10-18 2009-12-29 Kineto Wireless, Inc. Apparatus and method for extending the coverage area of a licensed wireless communication system using an unlicensed wireless communication system
US7873015B2 (en) 2002-10-18 2011-01-18 Kineto Wireless, Inc. Method and system for registering an unlicensed mobile access subscriber with a network controller
US7953423B2 (en) * 2002-10-18 2011-05-31 Kineto Wireless, Inc. Messaging in an unlicensed mobile access telecommunications system
US7349698B2 (en) * 2002-10-18 2008-03-25 Kineto Wireless, Inc. Registration messaging in an unlicensed mobile access telecommunications system
US7634269B2 (en) * 2002-10-18 2009-12-15 Kineto Wireless, Inc. Apparatus and method for extending the coverage area of a licensed wireless communication system using an unlicensed wireless communication system
US7471655B2 (en) * 2003-10-17 2008-12-30 Kineto Wireless, Inc. Channel activation messaging in an unlicensed mobile access telecommunications system
US20040170181A1 (en) * 2003-02-27 2004-09-02 Padcom, Inc. Prioritized alternate port routing
JP2006525739A (en) * 2003-05-07 2006-11-09 コーニンクレッカ フィリップス エレクトロニクス エヌ ヴィ Data communication system
US7283822B2 (en) * 2003-10-17 2007-10-16 Kineto Wireless, Inc. Service access control interface for an unlicensed wireless communication system
US7272397B2 (en) * 2003-10-17 2007-09-18 Kineto Wireless, Inc. Service access control interface for an unlicensed wireless communication system
US20080132207A1 (en) * 2003-10-17 2008-06-05 Gallagher Michael D Service access control interface for an unlicensed wireless communication system
US7957348B1 (en) 2004-04-21 2011-06-07 Kineto Wireless, Inc. Method and system for signaling traffic and media types within a communications network switching system
US20050243857A1 (en) * 2004-04-30 2005-11-03 Padcom, Inc. Simultaneously routing data over multiple wireless networks
US8041385B2 (en) 2004-05-14 2011-10-18 Kineto Wireless, Inc. Power management mechanism for unlicensed wireless communication systems
KR100965694B1 (en) * 2004-06-15 2010-06-24 삼성전자주식회사 System and method for supporting soft handover in a broadband wireless access communication system
US7940746B2 (en) 2004-08-24 2011-05-10 Comcast Cable Holdings, Llc Method and system for locating a voice over internet protocol (VoIP) device connected to a network
US20060239277A1 (en) * 2004-11-10 2006-10-26 Michael Gallagher Transmitting messages across telephony protocols
WO2006072811A1 (en) * 2005-01-04 2006-07-13 Nokia Corporation Handover of user equipment
WO2006086756A2 (en) * 2005-02-09 2006-08-17 Kineto Wireless Inc. Unlicensed mobile access network (uman) system and method
US7933598B1 (en) 2005-03-14 2011-04-26 Kineto Wireless, Inc. Methods and apparatuses for effecting handover in integrated wireless systems
US7756546B1 (en) 2005-03-30 2010-07-13 Kineto Wireless, Inc. Methods and apparatuses to indicate fixed terminal capabilities
US7843900B2 (en) 2005-08-10 2010-11-30 Kineto Wireless, Inc. Mechanisms to extend UMA or GAN to inter-work with UMTS core network
US7515575B1 (en) 2005-08-26 2009-04-07 Kineto Wireless, Inc. Intelligent access point scanning with self-learning capability
US8165086B2 (en) 2006-04-18 2012-04-24 Kineto Wireless, Inc. Method of providing improved integrated communication system data service
US20090059848A1 (en) * 2006-07-14 2009-03-05 Amit Khetawat Method and System for Supporting Large Number of Data Paths in an Integrated Communication System
US7852817B2 (en) * 2006-07-14 2010-12-14 Kineto Wireless, Inc. Generic access to the Iu interface
US7912004B2 (en) * 2006-07-14 2011-03-22 Kineto Wireless, Inc. Generic access to the Iu interface
US20080076425A1 (en) * 2006-09-22 2008-03-27 Amit Khetawat Method and apparatus for resource management
US20080039086A1 (en) * 2006-07-14 2008-02-14 Gallagher Michael D Generic Access to the Iu Interface
US8036664B2 (en) * 2006-09-22 2011-10-11 Kineto Wireless, Inc. Method and apparatus for determining rove-out
US20080076392A1 (en) * 2006-09-22 2008-03-27 Amit Khetawat Method and apparatus for securing a wireless air interface
US8204502B2 (en) 2006-09-22 2012-06-19 Kineto Wireless, Inc. Method and apparatus for user equipment registration
US7995994B2 (en) * 2006-09-22 2011-08-09 Kineto Wireless, Inc. Method and apparatus for preventing theft of service in a communication system
US8073428B2 (en) 2006-09-22 2011-12-06 Kineto Wireless, Inc. Method and apparatus for securing communication between an access point and a network controller
US8019331B2 (en) * 2007-02-26 2011-09-13 Kineto Wireless, Inc. Femtocell integration into the macro network
US20090265543A1 (en) * 2008-04-18 2009-10-22 Amit Khetawat Home Node B System Architecture with Support for RANAP User Adaptation Protocol
US20100041387A1 (en) * 2008-08-15 2010-02-18 Amit Khetawat Method and Apparatus for Inter Home Node B Cell Update Handling
CN102378214B (en) * 2010-08-23 2014-05-07 大唐移动通信设备有限公司 Switching testing method and system and evolved Node B (eNB)
US9100886B2 (en) * 2010-11-23 2015-08-04 Telefonaktiebolaget L M Ericsson (Publ) Pico cell error recovery in HetNet
FR3046473B1 (en) * 2015-12-30 2018-02-16 Starbreeze Paris METHOD AND DEVICE FOR EXTENSION OF DETECTION SURFACES INTERFACING A PLURALITY OF MOBILE ELEMENTS WITH A COMPUTER SYSTEM

Citations (87)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2745953A (en) * 1951-12-27 1956-05-15 Bell Telephone Labor Inc Radiant energy signaling systems
JPS45882Y1 (en) * 1966-08-12 1970-01-16
DE2022425A1 (en) * 1970-05-08 1971-11-25 Kalin Feinbau Gmbh Hand ignition for gas street lights with electronic pulse ignition
US3819872A (en) * 1972-07-10 1974-06-25 Bell Telephone Labor Inc Mobile telephone cellular switching system
US4057758A (en) * 1974-10-21 1977-11-08 Nippon Telegraph And Telephone Public Corporation Mobile diversity radio communication system
US4097804A (en) * 1975-10-30 1978-06-27 Kokusai Denshin Denwa Kabushiki Kaisha Transmitting and receiving diversity system
US4112257A (en) * 1977-03-24 1978-09-05 Frost Edward G Comprehensive automatic mobile radio telephone system
US4152647A (en) * 1978-02-23 1979-05-01 The United States Of America As Represented By The United States Department Of Energy Rapidly deployable emergency communication system
US4211894A (en) * 1977-10-14 1980-07-08 Nippon Telegraph And Telephone Public Corporation Transmitter multiplexing system for a land mobile communication system
US4222115A (en) * 1978-03-13 1980-09-09 Purdue Research Foundation Spread spectrum apparatus for cellular mobile communication systems
US4255814A (en) * 1977-07-15 1981-03-10 Motorola, Inc. Simulcast transmission system
DE3012141A1 (en) * 1980-03-28 1981-10-01 Siemens AG, 1000 Berlin und 8000 München MOBILE RADIO SYSTEM
EP0040731A1 (en) * 1980-05-28 1981-12-02 Licentia Patent-Verwaltungs-GmbH Method and arrangement for the simultaneous transmission of information by several common-wave transmitters
US4308429A (en) * 1978-08-25 1981-12-29 Nippon Electric Co., Ltd. Mobile telephone channel exchange system
JPS5773539A (en) * 1980-10-25 1982-05-08 Hitachi Denshi Ltd Mobile radio communication system
EP0072479A2 (en) * 1981-08-13 1983-02-23 Licentia Patent-Verwaltungs-GmbH Apparatus for compensating amplitude and phase distortions in a common-wave radio system
EP0072984A1 (en) * 1981-08-21 1983-03-02 Licentia Patent-Verwaltungs-GmbH Method of automatically determining a time delay compensation in a common-wave radio network
US4383332A (en) * 1980-11-21 1983-05-10 Bell Telephone Laboratories, Incorporated High capacity digital mobile radio system
JPS58111443A (en) * 1981-12-25 1983-07-02 Nec Corp Mobile radio communication system
US4398063A (en) * 1980-10-24 1983-08-09 Hass Ronald J Mobile telephone interoffice handoff limiting method and apparatus
JPS58159083A (en) * 1982-03-17 1983-09-21 Toshiba Corp Sampling pulse generating circuit
US4475246A (en) * 1982-12-21 1984-10-02 Motorola, Inc. Simulcast same frequency repeater system
JPS59176935A (en) * 1983-03-28 1984-10-06 Hitachi Denshi Ltd Multichannel access system radiotelephone system
JPS59212041A (en) * 1983-05-18 1984-11-30 Hitachi Ltd Continuity test system of mobile radio communication
US4490830A (en) * 1981-07-22 1984-12-25 Nippon Electric Co., Ltd. Radio signal transmission system including a plurality of transmitters for transmitting a common signal
JPS6042950A (en) * 1983-08-19 1985-03-07 Nec Corp Dynamic zone designation type mobile communication system
JPS6052131A (en) * 1983-09-01 1985-03-25 Nippon Telegr & Teleph Corp <Ntt> Switching system of mobile communication system
US4516269A (en) * 1982-12-10 1985-05-07 Michigan Consolidated Gas Company Automatic equalization for a simulcast communication system
US4596042A (en) * 1982-12-21 1986-06-17 Bbc Brown, Boveri & Co., Limited Radio transmission method for a mobile radio system
JPS61171269A (en) * 1985-01-25 1986-08-01 Fujitsu Ltd Channel switching system
US4633519A (en) * 1983-03-31 1986-12-30 Tokyo Shibaura Denki Kabushiki Kaisha Diversity reception system in a portable radio apparatus
US4642633A (en) * 1983-08-05 1987-02-10 Motorola, Inc. Individual simulcast station control system
US4644560A (en) * 1982-08-13 1987-02-17 Hazeltine Corporation Intranetwork code division multiple access communication system
WO1987001897A1 (en) * 1985-09-13 1987-03-26 Comvik Ab Cellular mobile telephone system and method of controlling a cellular mobile telephone system
US4667202A (en) * 1983-09-28 1987-05-19 Siemens Aktiengesellschaft Mobile radio network
US4670899A (en) * 1985-05-31 1987-06-02 Northern Telecom Limited Load balancing for cellular radiotelephone system
JPS62132444A (en) * 1985-12-04 1987-06-15 Nec Corp Radio communication system provided with centralized control function
US4675863A (en) * 1985-03-20 1987-06-23 International Mobile Machines Corp. Subscriber RF telephone system for providing multiple speech and/or data signals simultaneously over either a single or a plurality of RF channels
US4696052A (en) * 1985-12-31 1987-09-22 Motorola Inc. Simulcast transmitter apparatus having automatic synchronization capability
US4696051A (en) * 1985-12-31 1987-09-22 Motorola Inc. Simulcast transmission system having automtic synchronization
US4697260A (en) * 1984-12-22 1987-09-29 U.S. Philips Corporation Method of and arrangement for transmitting messages in a digital radio transmission system
US4698839A (en) * 1986-06-03 1987-10-06 Devaney David B Mobile telephone switching office
US4715048A (en) * 1986-05-02 1987-12-22 Canadian Patents And Development Limited Frequency offset diversity receiving system
US4718081A (en) * 1986-11-13 1988-01-05 General Electric Company Method and apparatus for reducing handoff errors in a cellular radio telephone communications system
US4718109A (en) * 1986-03-06 1988-01-05 Motorola, Inc. Automatic synchronization system
US4723266A (en) * 1987-01-21 1988-02-02 General Electric Company Cellular communication system sharing control channels between cells to reduce number of control channels
US4737978A (en) * 1986-10-31 1988-04-12 Motorola, Inc. Networked cellular radiotelephone systems
US4759051A (en) * 1987-03-16 1988-07-19 A. A. Hopeman, III Communications system
US4765753A (en) * 1986-03-08 1988-08-23 U.S. Philips Corporation Method and apparatus for handing-over a radio connection from one radio cell to another radio cell of a digital radio transmission system
US4771448A (en) * 1986-11-18 1988-09-13 Northern Telecom Limited Private cellular system
US4811380A (en) * 1988-01-29 1989-03-07 Motorola, Inc. Cellular radiotelephone system with dropped call protection
US4850032A (en) * 1987-11-18 1989-07-18 Motorola, Inc. Simulcast data communications system
US4852090A (en) * 1987-02-02 1989-07-25 Motorola, Inc. TDMA communications system with adaptive equalization
US4856048A (en) * 1987-03-02 1989-08-08 Nippon Telegraph And Telephone Corporation Mobile communication system
US4901307A (en) * 1986-10-17 1990-02-13 Qualcomm, Inc. Spread spectrum multiple access communication system using satellite or terrestrial repeaters
US4930140A (en) * 1989-01-13 1990-05-29 Agilis Corporation Code division multiplex system using selectable length spreading code sequences
US4955082A (en) * 1988-01-14 1990-09-04 The Tokyo Electric Power Company Ltd. Mobile communication system
WO1990013187A1 (en) * 1989-04-17 1990-11-01 Telefonaktiebolaget Lm Ericsson Method of maintaining an established connection in a mobile radio system comprising both analog and digital radio channels
US4984247A (en) * 1988-09-29 1991-01-08 Ascom Zelcom Ag Digital radio transmission system for a cellular network, using the spread spectrum method
WO1991007020A1 (en) * 1989-11-07 1991-05-16 Qualcomm Incorporated Soft handoff in a cdma cellular telephone system
US5022049A (en) * 1989-11-21 1991-06-04 Unisys Corp. Multiple access code acquisition system
US5048059A (en) * 1988-09-19 1991-09-10 Telefonaktiebolaget Lm Ericsson Log-polar signal processing
US5056109A (en) * 1989-11-07 1991-10-08 Qualcomm, Inc. Method and apparatus for controlling transmission power in a cdma cellular mobile telephone system
US5091942A (en) * 1990-07-23 1992-02-25 Ericsson Ge Mobile Communications Holding, Inc. Authentication system for digital cellular communications
US5095531A (en) * 1987-08-28 1992-03-10 Iwatsu Electric Co., Ltd. Mobile communication position registering method and system therefor
US5103459A (en) * 1990-06-25 1992-04-07 Qualcomm Incorporated System and method for generating signal waveforms in a cdma cellular telephone system
US5109390A (en) * 1989-11-07 1992-04-28 Qualcomm Incorporated Diversity receiver in a cdma cellular telephone system
US5124698A (en) * 1985-04-10 1992-06-23 Tecnomen Oy Method and apparatus for synchronizing radio transmitters in a paging network
US5126748A (en) * 1989-12-05 1992-06-30 Qualcomm Incorporated Dual satellite navigation system and method
US5128959A (en) * 1991-02-22 1992-07-07 Motorola, Inc. Variable bandwidth CDMA radio system
US5179571A (en) * 1991-07-10 1993-01-12 Scs Mobilecom, Inc. Spread spectrum cellular handoff apparatus and method
US5257283A (en) * 1989-11-07 1993-10-26 Qualcomm Incorporated Spread spectrum transmitter power control method and system
US5265119A (en) * 1989-11-07 1993-11-23 Qualcomm Incorporated Method and apparatus for controlling transmission power in a CDMA cellular mobile telephone system
US5267262A (en) * 1989-11-07 1993-11-30 Qualcomm Incorporated Transmitter power control system
US5267261A (en) * 1992-03-05 1993-11-30 Qualcomm Incorporated Mobile station assisted soft handoff in a CDMA cellular communications system
US5280472A (en) * 1990-12-07 1994-01-18 Qualcomm Incorporated CDMA microcellular telephone system and distributed antenna system therefor
EP0274857B1 (en) * 1986-12-05 1994-01-19 BRITISH TELECOMMUNICATIONS public limited company Mobile radio systems
US5383219A (en) * 1993-11-22 1995-01-17 Qualcomm Incorporated Fast forward link power control in a code division multiple access system
US5437055A (en) * 1993-06-03 1995-07-25 Qualcomm Incorporated Antenna system for multipath diversity in an indoor microcellular communication system
US5452473A (en) * 1994-02-28 1995-09-19 Qualcomm Incorporated Reverse link, transmit power correction and limitation in a radiotelephone system
US5475870A (en) * 1994-09-12 1995-12-12 Qualcomm Incorporated Apparatus and method for adding and removing a base station from a cellular communications system
US5485486A (en) * 1989-11-07 1996-01-16 Qualcomm Incorporated Method and apparatus for controlling transmission power in a CDMA cellular mobile telephone system
US5490165A (en) * 1993-10-28 1996-02-06 Qualcomm Incorporated Demodulation element assignment in a system capable of receiving multiple signals
US5509035A (en) * 1993-04-14 1996-04-16 Qualcomm Incorporated Mobile station operating in an analog mode and for subsequent handoff to another system
US5513176A (en) * 1990-12-07 1996-04-30 Qualcomm Incorporated Dual distributed antenna system
US5519761A (en) * 1994-07-08 1996-05-21 Qualcomm Incorporated Airborne radiotelephone communications system
US5528593A (en) * 1994-09-30 1996-06-18 Qualcomm Incorporated Method and apparatus for controlling power in a variable rate communication system

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE8802229D0 (en) * 1988-06-14 1988-06-14 Ericsson Telefon Ab L M MOBILE RADIO STATION PROCEDURE

Patent Citations (90)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2745953A (en) * 1951-12-27 1956-05-15 Bell Telephone Labor Inc Radiant energy signaling systems
JPS45882Y1 (en) * 1966-08-12 1970-01-16
DE2022425A1 (en) * 1970-05-08 1971-11-25 Kalin Feinbau Gmbh Hand ignition for gas street lights with electronic pulse ignition
US3819872A (en) * 1972-07-10 1974-06-25 Bell Telephone Labor Inc Mobile telephone cellular switching system
US4057758A (en) * 1974-10-21 1977-11-08 Nippon Telegraph And Telephone Public Corporation Mobile diversity radio communication system
US4097804A (en) * 1975-10-30 1978-06-27 Kokusai Denshin Denwa Kabushiki Kaisha Transmitting and receiving diversity system
US4112257A (en) * 1977-03-24 1978-09-05 Frost Edward G Comprehensive automatic mobile radio telephone system
US4255814A (en) * 1977-07-15 1981-03-10 Motorola, Inc. Simulcast transmission system
US4211894A (en) * 1977-10-14 1980-07-08 Nippon Telegraph And Telephone Public Corporation Transmitter multiplexing system for a land mobile communication system
US4152647A (en) * 1978-02-23 1979-05-01 The United States Of America As Represented By The United States Department Of Energy Rapidly deployable emergency communication system
US4222115A (en) * 1978-03-13 1980-09-09 Purdue Research Foundation Spread spectrum apparatus for cellular mobile communication systems
US4308429A (en) * 1978-08-25 1981-12-29 Nippon Electric Co., Ltd. Mobile telephone channel exchange system
DE3012141A1 (en) * 1980-03-28 1981-10-01 Siemens AG, 1000 Berlin und 8000 München MOBILE RADIO SYSTEM
EP0040731A1 (en) * 1980-05-28 1981-12-02 Licentia Patent-Verwaltungs-GmbH Method and arrangement for the simultaneous transmission of information by several common-wave transmitters
US4398063A (en) * 1980-10-24 1983-08-09 Hass Ronald J Mobile telephone interoffice handoff limiting method and apparatus
JPS5773539A (en) * 1980-10-25 1982-05-08 Hitachi Denshi Ltd Mobile radio communication system
US4383332A (en) * 1980-11-21 1983-05-10 Bell Telephone Laboratories, Incorporated High capacity digital mobile radio system
US4490830A (en) * 1981-07-22 1984-12-25 Nippon Electric Co., Ltd. Radio signal transmission system including a plurality of transmitters for transmitting a common signal
EP0072479A2 (en) * 1981-08-13 1983-02-23 Licentia Patent-Verwaltungs-GmbH Apparatus for compensating amplitude and phase distortions in a common-wave radio system
EP0072984A1 (en) * 1981-08-21 1983-03-02 Licentia Patent-Verwaltungs-GmbH Method of automatically determining a time delay compensation in a common-wave radio network
JPS58111443A (en) * 1981-12-25 1983-07-02 Nec Corp Mobile radio communication system
JPS58159083A (en) * 1982-03-17 1983-09-21 Toshiba Corp Sampling pulse generating circuit
US4644560A (en) * 1982-08-13 1987-02-17 Hazeltine Corporation Intranetwork code division multiple access communication system
US4516269A (en) * 1982-12-10 1985-05-07 Michigan Consolidated Gas Company Automatic equalization for a simulcast communication system
US4475246A (en) * 1982-12-21 1984-10-02 Motorola, Inc. Simulcast same frequency repeater system
US4596042A (en) * 1982-12-21 1986-06-17 Bbc Brown, Boveri & Co., Limited Radio transmission method for a mobile radio system
JPS59176935A (en) * 1983-03-28 1984-10-06 Hitachi Denshi Ltd Multichannel access system radiotelephone system
US4633519A (en) * 1983-03-31 1986-12-30 Tokyo Shibaura Denki Kabushiki Kaisha Diversity reception system in a portable radio apparatus
JPS59212041A (en) * 1983-05-18 1984-11-30 Hitachi Ltd Continuity test system of mobile radio communication
US4642633A (en) * 1983-08-05 1987-02-10 Motorola, Inc. Individual simulcast station control system
JPS6042950A (en) * 1983-08-19 1985-03-07 Nec Corp Dynamic zone designation type mobile communication system
JPS6052131A (en) * 1983-09-01 1985-03-25 Nippon Telegr & Teleph Corp <Ntt> Switching system of mobile communication system
US4667202A (en) * 1983-09-28 1987-05-19 Siemens Aktiengesellschaft Mobile radio network
US4697260A (en) * 1984-12-22 1987-09-29 U.S. Philips Corporation Method of and arrangement for transmitting messages in a digital radio transmission system
JPS61171269A (en) * 1985-01-25 1986-08-01 Fujitsu Ltd Channel switching system
US4675863A (en) * 1985-03-20 1987-06-23 International Mobile Machines Corp. Subscriber RF telephone system for providing multiple speech and/or data signals simultaneously over either a single or a plurality of RF channels
US5124698A (en) * 1985-04-10 1992-06-23 Tecnomen Oy Method and apparatus for synchronizing radio transmitters in a paging network
US4670899A (en) * 1985-05-31 1987-06-02 Northern Telecom Limited Load balancing for cellular radiotelephone system
WO1987001897A1 (en) * 1985-09-13 1987-03-26 Comvik Ab Cellular mobile telephone system and method of controlling a cellular mobile telephone system
JPS62132444A (en) * 1985-12-04 1987-06-15 Nec Corp Radio communication system provided with centralized control function
US4696051A (en) * 1985-12-31 1987-09-22 Motorola Inc. Simulcast transmission system having automtic synchronization
US4696052A (en) * 1985-12-31 1987-09-22 Motorola Inc. Simulcast transmitter apparatus having automatic synchronization capability
US4718109A (en) * 1986-03-06 1988-01-05 Motorola, Inc. Automatic synchronization system
US4765753A (en) * 1986-03-08 1988-08-23 U.S. Philips Corporation Method and apparatus for handing-over a radio connection from one radio cell to another radio cell of a digital radio transmission system
US4715048A (en) * 1986-05-02 1987-12-22 Canadian Patents And Development Limited Frequency offset diversity receiving system
US4698839A (en) * 1986-06-03 1987-10-06 Devaney David B Mobile telephone switching office
US4901307A (en) * 1986-10-17 1990-02-13 Qualcomm, Inc. Spread spectrum multiple access communication system using satellite or terrestrial repeaters
US4737978A (en) * 1986-10-31 1988-04-12 Motorola, Inc. Networked cellular radiotelephone systems
US4718081A (en) * 1986-11-13 1988-01-05 General Electric Company Method and apparatus for reducing handoff errors in a cellular radio telephone communications system
US4771448A (en) * 1986-11-18 1988-09-13 Northern Telecom Limited Private cellular system
EP0274857B1 (en) * 1986-12-05 1994-01-19 BRITISH TELECOMMUNICATIONS public limited company Mobile radio systems
US4723266A (en) * 1987-01-21 1988-02-02 General Electric Company Cellular communication system sharing control channels between cells to reduce number of control channels
US4852090A (en) * 1987-02-02 1989-07-25 Motorola, Inc. TDMA communications system with adaptive equalization
US4856048A (en) * 1987-03-02 1989-08-08 Nippon Telegraph And Telephone Corporation Mobile communication system
US4759051A (en) * 1987-03-16 1988-07-19 A. A. Hopeman, III Communications system
US5095531A (en) * 1987-08-28 1992-03-10 Iwatsu Electric Co., Ltd. Mobile communication position registering method and system therefor
US4850032A (en) * 1987-11-18 1989-07-18 Motorola, Inc. Simulcast data communications system
US4955082A (en) * 1988-01-14 1990-09-04 The Tokyo Electric Power Company Ltd. Mobile communication system
US4811380A (en) * 1988-01-29 1989-03-07 Motorola, Inc. Cellular radiotelephone system with dropped call protection
US5048059A (en) * 1988-09-19 1991-09-10 Telefonaktiebolaget Lm Ericsson Log-polar signal processing
US4984247A (en) * 1988-09-29 1991-01-08 Ascom Zelcom Ag Digital radio transmission system for a cellular network, using the spread spectrum method
US4930140A (en) * 1989-01-13 1990-05-29 Agilis Corporation Code division multiplex system using selectable length spreading code sequences
WO1990013187A1 (en) * 1989-04-17 1990-11-01 Telefonaktiebolaget Lm Ericsson Method of maintaining an established connection in a mobile radio system comprising both analog and digital radio channels
US5257283A (en) * 1989-11-07 1993-10-26 Qualcomm Incorporated Spread spectrum transmitter power control method and system
US5485486A (en) * 1989-11-07 1996-01-16 Qualcomm Incorporated Method and apparatus for controlling transmission power in a CDMA cellular mobile telephone system
US5101501A (en) * 1989-11-07 1992-03-31 Qualcomm Incorporated Method and system for providing a soft handoff in communications in a cdma cellular telephone system
US5056109A (en) * 1989-11-07 1991-10-08 Qualcomm, Inc. Method and apparatus for controlling transmission power in a cdma cellular mobile telephone system
US5109390A (en) * 1989-11-07 1992-04-28 Qualcomm Incorporated Diversity receiver in a cdma cellular telephone system
WO1991007020A1 (en) * 1989-11-07 1991-05-16 Qualcomm Incorporated Soft handoff in a cdma cellular telephone system
US5267262A (en) * 1989-11-07 1993-11-30 Qualcomm Incorporated Transmitter power control system
US5265119A (en) * 1989-11-07 1993-11-23 Qualcomm Incorporated Method and apparatus for controlling transmission power in a CDMA cellular mobile telephone system
US5022049A (en) * 1989-11-21 1991-06-04 Unisys Corp. Multiple access code acquisition system
US5126748A (en) * 1989-12-05 1992-06-30 Qualcomm Incorporated Dual satellite navigation system and method
US5103459A (en) * 1990-06-25 1992-04-07 Qualcomm Incorporated System and method for generating signal waveforms in a cdma cellular telephone system
US5103459B1 (en) * 1990-06-25 1999-07-06 Qualcomm Inc System and method for generating signal waveforms in a cdma cellular telephone system
US5091942A (en) * 1990-07-23 1992-02-25 Ericsson Ge Mobile Communications Holding, Inc. Authentication system for digital cellular communications
US5280472A (en) * 1990-12-07 1994-01-18 Qualcomm Incorporated CDMA microcellular telephone system and distributed antenna system therefor
US5513176A (en) * 1990-12-07 1996-04-30 Qualcomm Incorporated Dual distributed antenna system
US5128959A (en) * 1991-02-22 1992-07-07 Motorola, Inc. Variable bandwidth CDMA radio system
US5179571A (en) * 1991-07-10 1993-01-12 Scs Mobilecom, Inc. Spread spectrum cellular handoff apparatus and method
US5267261A (en) * 1992-03-05 1993-11-30 Qualcomm Incorporated Mobile station assisted soft handoff in a CDMA cellular communications system
US5509035A (en) * 1993-04-14 1996-04-16 Qualcomm Incorporated Mobile station operating in an analog mode and for subsequent handoff to another system
US5437055A (en) * 1993-06-03 1995-07-25 Qualcomm Incorporated Antenna system for multipath diversity in an indoor microcellular communication system
US5490165A (en) * 1993-10-28 1996-02-06 Qualcomm Incorporated Demodulation element assignment in a system capable of receiving multiple signals
US5461639A (en) * 1993-11-22 1995-10-24 Qualcomm Incorporated Fast forward link power control in a code division multiple access system
US5383219A (en) * 1993-11-22 1995-01-17 Qualcomm Incorporated Fast forward link power control in a code division multiple access system
US5452473A (en) * 1994-02-28 1995-09-19 Qualcomm Incorporated Reverse link, transmit power correction and limitation in a radiotelephone system
US5519761A (en) * 1994-07-08 1996-05-21 Qualcomm Incorporated Airborne radiotelephone communications system
US5475870A (en) * 1994-09-12 1995-12-12 Qualcomm Incorporated Apparatus and method for adding and removing a base station from a cellular communications system
US5528593A (en) * 1994-09-30 1996-06-18 Qualcomm Incorporated Method and apparatus for controlling power in a variable rate communication system

Non-Patent Citations (54)

* Cited by examiner, † Cited by third party
Title
Benndorf, V. et al., Quasissynchroner Gleichwellenfunk ein Gleichkanalfunk Verfahren zur Erhohung der Erriech barkiet in Mobilfunknetzen , Elektrizitatswirtschaft, Jg. 80, Heft 6, pp. 187 198. (1981). *
Benndorf, V. et al., Quasissynchroner Gleichwellenfunk-ein Gleichkanalfunk-Verfahren zur Erhohung der Erriech-barkiet in Mobilfunknetzen, Elektrizitatswirtschaft, Jg. 80, Heft 6, pp. 187-198. (1981).
Bennett, M. et al., A Hand Off Algorithm for Cellular Radio Based on Reed Solomon Coding , Dialog Abstract from IEEE Colloquium on Mobile Radio Networks (1988). *
Bennett, M. et al., A Hand-Off Algorithm for Cellular Radio Based on Reed-Solomon Coding, Dialog Abstract from IEEE Colloquium on `Mobile Radio Networks` (1988).
Bernhardt, R., RF Performance of Macroscopic Diversity in Universal Digital Portable Radio Communications: Frequency Reuse Considerations , IEEE International Conference on Communications, pp. 65 71 (1986). *
Bernhardt, R., RF Performance of Macroscopic Diversity in Universal Digital Portable Radio Communications: Frequency Reuse Considerations, IEEE International Conference on Communications, pp. 65-71 (1986).
Bernhardt, R., User Access in Portable Radio Systems in the Noise Limited Environment , IEEE International Conference on Communications 87, pp. 1 8 (1987). *
Bernhardt, R., User Access in Portable Radio Systems in the Noise Limited Environment, IEEE International Conference on Communications '87, pp. 1-8 (1987).
Figel, W., et al., Vehicle Location by a Signal Attenuation Method , IEEE Transactions VT 18, pp. 105 109 (1969). *
Figel, W., et al., Vehicle Location by a Signal Attenuation Method, IEEE Transactions VT-18, pp. 105-109 (1969).
Frenkiel, R., A High Capacity Mobile Radiotelephone System Model Using a Coordinated Small Zone Approach , IEEE Transaction on Vehicular Technology, vol. VT 19, No. 2, pp. 173 177 (1970). *
Frenkiel, R., A High-Capacity Mobile Radiotelephone System Model Using a Coordinated Small-Zone Approach, IEEE Transaction on Vehicular Technology, vol. VT-19, No. 2, pp. 173-177 (1970).
Herold, W., A Small Zone Radio Telephone System with Code Division Multiple Access , Proc. Internat. Zurich Seminar, F6 1 4 (1974). *
Herold, W., A Small-Zone Radio Telephone System with Code Division Multiple Access, Proc. Internat. Zurich Seminar, F6 1-4 (1974).
Herold, W., Changing Radio Zones of Fixed Stations by Mobile Subscribers , Communication form AEG Telefunken Wireless Communications Research Institute, Ulm (Germany), pp. 173 179. *
Herold, W., Changing Radio Zones of Fixed Stations by Mobile Subscribers, Communication form AEG-Telefunken Wireless Communications Research Institute, Ulm (Germany), pp. 173-179.
Herold, W., et al., Aufbau und Eigenschaften von Quasiorthogonalen Codekollektiven , AEU 27, pp. 463 470 (1973). *
Herold, W., et al., Aufbau und Eigenschaften von Quasiorthogonalen Codekollektiven, AEU 27, pp. 463-470 (1973).
Herold, W., Fangverhalten einer Phasenregelschleife mit S a gezahn Komparator , AEU 25, pp. 226 230 (1971). *
Herold, W., Fangverhalten einer Phasenregelschleife mit Sagezahn-Komparator, AEU 25, pp. 226-230 (1971).
Herold, W., Nachrichtentechnische Zeitschrift , NTZ, 27, pp. 253 259 (1974). *
Herold, W., Nachrichtentechnische Zeitschrift, NTZ, 27, pp. 253-259 (1974).
Heynisch, B., NTG Gleichkanalfunksysteme fur die Frequenzokonomische Versorgung Grosser Gebiete , NTG Fachbereich Sprech und Datenfunk, AEG, Ulm, pp. 41 46 (1985). *
Heynisch, B., NTG Gleichkanalfunksysteme fur die Frequenzokonomische Versorgung Grosser Gebiete, NTG-Fachbereich Sprech--und Datenfunk, AEG, Ulm, pp. 41-46 (1985).
Kerdock, A., A Class of Low Rate Nonlinear Binary Codes , Information and Control, vol. 20, pp. 182 187 (1972). *
Kerdock, A., A Class of Low-Rate Nonlinear Binary Codes, Information and Control, vol. 20, pp. 182-187 (1972).
MacWilliams, F., et al., The Theory of Error Correcting Codes , Part I, pp. 93 124 (1977). *
Macwilliams, F., et al., The Theory of Error Correcting Codes , Part II, pp. 451 465 (1977). *
MacWilliams, F., et al., The Theory of Error-Correcting Codes, Part I, pp. 93-124 (1977).
Macwilliams, F., et al., The Theory of Error-Correcting Codes, Part II, pp. 451-465 (1977).
Monsen, P., Digital Transmission Performance on Fading Dispersive Diversity Channels , IEEE Transactions on Communications, vol. COM 21, No. 1 (1973). *
Monsen, P., Digital Transmission Performance on Fading Dispersive Diversity Channels, IEEE Transactions on Communications, vol. COM-21, No. 1 (1973).
Morinaga, T., et al., Automatic Selection of Fixed Receiving Stations in Mobile Radio Systems , Review of the Electrical Communication Laboratory, vol. 16, Nos. 5 6, pp. 374 384 (May Jun. 1968). *
Morinaga, T., et al., Automatic Selection of Fixed Receiving Stations in Mobile Radio Systems, Review of the Electrical Communication Laboratory, vol. 16, Nos. 5-6, pp. 374-384 (May-Jun. 1968).
Nakajima, A., Advanced Mobile Communication Network Based on Signaling System No. 7 , International Switching Symposium (1987). *
Nakajima, A., Advanced Mobile Communication Network Based on Signaling System No. 7, International Switching Symposium (1987).
Okumura, Y., et al., Field Strength and its Variability in VHF and UHF Land Mobile Radio Service , Ref. Electr. Commun. Lab. (Japan) 15, pp. 825 873 (1968). *
Okumura, Y., et al., Field Strength and its Variability in VHF and UHF Land-Mobile Radio Service, Ref. Electr. Commun. Lab. (Japan) 15, pp. 825-873 (1968).
Raith, K. et al., Multi Path Equalization For Digital Cellular Radio Operating at 300 KBIT/S , Proceedings of the 36 th IEEE Vehicular Technology Conference (1986). *
Raith, K. et al., Multi-Path Equalization For Digital Cellular Radio Operating at 300 KBIT/S, Proceedings of the 36th IEEE Vehicular Technology Conference (1986).
Schenkel, K., Entwurf Eines Integrierten Digitalen Nachrichtensystems mit Vielfachzugriff fur ein Beliebig Verzweigtes Breitbandnetz , AEU 27, pp. 168 176 (1973). *
Schenkel, K., Entwurf Eines Integrierten Digitalen Nachrichtensystems mit Vielfachzugriff fur ein Beliebig Verzweigtes Breitbandnetz, AEU 27, pp. 168-176 (1973).
Sergo, J., et al., Analysis and Simulation of a PN Synchronization System , IEEE Transactions Com 18, pp. 676 679 (1970). *
Sergo, J., et al., Analysis and Simulation of a PN Synchronization System, IEEE Transactions Com-18, pp. 676-679 (1970).
Shefer, J. et al., An X Band Vehicle Location System , IEEE Transaction on Vehicular Technology, vol. VT 21, No. 4, pp. 117 120 (Nov., 1972). *
Shefer, J. et al., An X-Band Vehicle-Location System, IEEE Transaction on Vehicular Technology, vol. VT-21, No. 4, pp. 117-120 (Nov., 1972).
Spilker, J. Jr., et al., The Delay Lock Discriminator An Optimum Tracking Device , Proc. Inst. Radio Engrs. 43, pp. 1403 1416 (1961). *
Spilker, J. Jr., et al., The Delay-Lock Discriminator-An Optimum Tracking Device, Proc. Inst. Radio Engrs. 43, pp. 1403-1416 (1961).
Stjernall, J E et al., Radio Test Performance of a Narrowband TDMA System , Ericsson Radio Systems AB, S 163 80 pp. 293 299 (1987). *
Stjernall, J-E et al., Radio Test Performance of a Narrowband TDMA System, Ericsson Radio Systems AB, S-163 80 pp. 293-299 (1987).
Turin, G., Introduction to Spread Spectrum Antimultipath Techniques and Their Application to Urban digial Radio , Proceedings of the IEE, vol. 68, No. 3 (1980). *
Turin, G., Introduction to Spread-Spectrum Antimultipath Techniques and Their Application to Urban digial Radio, Proceedings of the IEE, vol. 68, No. 3 (1980).
Viterbi, A., Very Low Rate Convolutional Codes for Maximum Theoretical Performance of Spread Spectrum Multiple Access Channels , IEEE Journal on Selected Areas in Communications, vol. 8, No. 4, pp. 641 649 (1990). *
Viterbi, A., Very Low Rate Convolutional Codes for Maximum Theoretical Performance of Spread-Spectrum Multiple-Access Channels, IEEE Journal on Selected Areas in Communications, vol. 8, No. 4, pp. 641-649 (1990).

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6216003B1 (en) * 1997-06-03 2001-04-10 Ntt Mobile Communications Network Inc. Method of handover control in mobile radio communication realizing reduced control load
US20030211849A1 (en) * 2002-05-08 2003-11-13 Paul Robinson Handover of a call connection in a cellular telecommunications network
US20140115139A1 (en) * 2012-10-19 2014-04-24 International Business Machines Corporation Service Placement on Hosts for a Consumer Based on Their Geographic Location
US10015061B2 (en) * 2012-10-19 2018-07-03 International Business Machines Corporation Service placement on hosts for a consumer based on their geographic location
US10469335B2 (en) 2012-10-19 2019-11-05 International Business Machines Corporation Service placement on hosts for a consumer based on their geographic location

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