US20110080923A1 - Interference Suppression for CDMA Systems - Google Patents

Interference Suppression for CDMA Systems Download PDF

Info

Publication number
US20110080923A1
US20110080923A1 US12/966,953 US96695310A US2011080923A1 US 20110080923 A1 US20110080923 A1 US 20110080923A1 US 96695310 A US96695310 A US 96695310A US 2011080923 A1 US2011080923 A1 US 2011080923A1
Authority
US
United States
Prior art keywords
sinr
receiver
interference
recited
estimates
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
US12/966,953
Inventor
Michael L. McCloud
Vijay Nagarajan
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
III Holdings 1 LLC
Original Assignee
Rambus Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US10/247,836 external-priority patent/US7158559B2/en
Priority claimed from US10/294,834 external-priority patent/US7200183B2/en
Priority claimed from US10/686,829 external-priority patent/US7580448B2/en
Priority claimed from US10/686,359 external-priority patent/US7068706B2/en
Priority claimed from US10/773,777 external-priority patent/US7394879B2/en
Priority claimed from US11/100,935 external-priority patent/US20050180364A1/en
Priority claimed from US11/233,636 external-priority patent/US8761321B2/en
Priority to US12/966,953 priority Critical patent/US20110080923A1/en
Application filed by Rambus Inc filed Critical Rambus Inc
Publication of US20110080923A1 publication Critical patent/US20110080923A1/en
Assigned to III HOLDINGS 1, LLC reassignment III HOLDINGS 1, LLC ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: RAMBUS INC.
Priority to US14/713,740 priority patent/US9735816B2/en
Abandoned legal-status Critical Current

Links

Images

Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B1/00Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/06Receivers
    • H04B1/10Means associated with receiver for limiting or suppressing noise or interference
    • H04B1/1027Means associated with receiver for limiting or suppressing noise or interference assessing signal quality or detecting noise/interference for the received signal
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B1/00Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69Spread spectrum techniques
    • H04B1/707Spread spectrum techniques using direct sequence modulation
    • H04B1/7097Interference-related aspects
    • H04B1/7103Interference-related aspects the interference being multiple access interference
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B1/00Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69Spread spectrum techniques
    • H04B1/707Spread spectrum techniques using direct sequence modulation
    • H04B1/7097Interference-related aspects
    • H04B1/7103Interference-related aspects the interference being multiple access interference
    • H04B1/7107Subtractive interference cancellation
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B1/00Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69Spread spectrum techniques
    • H04B1/707Spread spectrum techniques using direct sequence modulation
    • H04B1/7097Interference-related aspects
    • H04B1/711Interference-related aspects the interference being multi-path interference
    • H04B1/7115Constructive combining of multi-path signals, i.e. RAKE receivers
    • H04B1/712Weighting of fingers for combining, e.g. amplitude control or phase rotation using an inner loop

Definitions

  • Patent Application Publication Number 2005-0180364 A1 which is a Continuation-in-Part of (a) U.S. patent application Ser. No. 11/773,777, entitled “Systems and Methods for Parallel Signal Cancellation,” and filed on Feb. 6, 2004, now U.S. Pat. No. 7,394,879; (b) U.S. patent application Ser. No. 10/686,359, entitled “Systems and Methods for Adjusting Phase,” and filed Oct. 15, 2003, now U.S. Pat. No. 7,068,706; (c) U.S. patent application Ser. No. 10/686,829, entitled “Method and Apparatus for Channel Amplitude Estimation and Interference Vector Construction,” and filed on Oct. 15, 2003, now U.S.
  • the present invention relates generally to interference cancellation in received wireless communication signals and, more particularly, to forming a composite interference signal for interference cancellation.
  • a communication resource is divided into subchannels and allocated to different users.
  • subchannels may include time slots, frequency slots, multiple-access codes, spatio-temporal subchannels, or any combination thereof
  • a plurality of subchannel signals received by a wireless terminal may correspond to different users and/or different subchannels allocated to a particular user.
  • a plurality of subchannels may be allocated to at least one user such that the number of users is less than the number of subchannels.
  • a single transmitter broadcasts different messages to different receivers, such as a base station in a wireless communication system broadcasting to a plurality of mobile terminals
  • the channel resource is subdivided in order to distinguish between messages intended for each mobile.
  • each mobile terminal by knowing its allocated subchannel(s), may decode messages intended for it from the superposition of received signals.
  • a base station typically separates signals it receives into PN-coded subchannels in order to differentiate between users.
  • received signals are superpositions of time delayed (and complex scaled) versions of the transmitted signals.
  • Multipath can cause co-channel and cross-channel interference that correlates, the allocated subchannels.
  • co-channel interference may occur when time-delayed reflections of transmitted signals interfere with a line-of-sight signal from the same source.
  • Cross-channel interference occurs when signals in a subchannel leak into and, thus, impair acquisition and tracking of other subchannels.
  • Co-channel and cross-channel interference can degrade communications by causing a receiver to incorrectly decode received transmissions, thus increasing a receiver's error floor.
  • Interference may also have other degrading effects on communications. For example, interference may diminish the capacity of a communication system, decrease the region of coverage, and/or decrease maximum data rates. For these reasons, a reduction in interference can improve reception of selected signals by addressing the aforementioned limitations due to interference.
  • embodiments of the present invention may provide for identifying interference components for the purpose of forming a composite interference signal for use in any subtractive or projective interference canceller.
  • the identification of interference components and the cancellation of such components may be implemented using a parallel, serial, iterative, or one-shot mode of operation.
  • Embodiments of the invention may be employed in any receiver configured to support one or more CDMA standards, such as (1) the “TIA/EIA-95-B Mobile Station-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System” (the IS-95 standard), (2) the “TIA/EIA-98-C Recommended Minimum Standard for Dual-Mode Wideband Spread Spectrum Cellular Mobile Station” (the IS-98 standard), (3) the standard offered by a consortium named “3rd Generation Partnership Project” (3GPP) and embodied in a set of documents including Document Nos.
  • CDMA Code Division Multiple Access
  • 3G TS 25.211, 3G TS 25.212, 3G TS 25.213, and 3G TS 25.214 (the WCDMA standard), (4) the standard offered by a consortium named “3rd Generation Partnership Project 2” (3GPP2) and embodied in a set of documents including “TR-45.5 Physical Layer Standard for cdma2000 Spread Spectrum Systems,” the “C.S0005-A Upper Layer (Layer 3 ) Signaling Standard for cdma2000 Spread Spectrum Systems,” and the “C.S0024 CDMA2000 High Rate Packet Data Air Interface Specification” (the CDMA2000 standard), and (5) other CDMA standards.
  • 3GPP2 3rd Generation Partnership Project 2
  • Embodiments of the invention may provide for analytically characterizing the received signal-to-interference-and-noise ratio (SINR), estimating it in a composite signal or in an interfering user subchannel, and choosing feedback terms (e.g., adaptive weights from a companding function) to construct an interference-cancelled signal that maximizes this quantity.
  • a means for determining an SINR estimate in each subchannel uses an estimated SINR for each estimated symbol.
  • each estimated symbol may be generated by a means for producing symbol estimates from a received baseband signal.
  • symbol estimates may include resolutions of the baseband signal into multiple antenna copies, multipath components, or the like.
  • a means for determining whether to use weighted soft decisions or hard decisions for each subchannel compares each subchannel's SINR estimate to a predetermined threshold.
  • a means for generating hard decisions and/or weighted soft decisions for each symbol estimate produces either a hard estimate or a weighted soft estimate for each symbol estimate based on how the corresponding SINR estimate compares to the threshold.
  • a means for producing a synthesized interference signal may synthesize a composite interference vector from the hard or soft-weighted symbol estimates.
  • a means for emulating channel distortions in the synthesized interference signal may simulate channel effects corresponding to paths other than a predetermined path of interest.
  • a means for producing an interference-cancelled signal combines a received baseband signal with the synthesized interference signal in order to subtract or project out interference in the received baseband signal, or in one or more rake-resolved components of the baseband signal.
  • the means for producing symbol estimates corresponding to a received baseband signal may include, by way of example, a rake receiver, a plurality of rake receivers coupled to a rake combiner, an equalizer, and/or any CDMA receiver employing antenna diversity, equalizers, and/or other elements of an advanced receiver.
  • the means for determining an SINR estimate in each subchannel may include, by way of example, an apparatus or method configured for filtering complex amplitudes and estimated variances of the complex amplitudes for each subchannel.
  • the means for determining an SINR estimate may include an apparatus or process configured for calculating a mean-squared error due to noise plus interference or a component or method for computing a broadband noise plus interference floor.
  • the means for determining whether to use weighted soft decisions or hard decisions for each subchannel may include, by way of example, any apparatus or method configured for comparing estimated SINRs to at least one predetermined threshold.
  • the means for generating hard decisions and/or weighted soft decisions for each pre-processed symbol estimate may include, by way of example, an apparatus or method for generating hard decisions, an apparatus or method for generating weights on soft estimates, and/or an apparatus or method for discarding soft estimates with a low estimated SINR.
  • the means for producing a synthesized interference signal may include, by way of example, a CDMA signal generator configured for performing an inverse fast Walsh transform (IFWT), PN covering, pulse shaping, and channel emulation.
  • INFWT inverse fast Walsh transform
  • PN covering PN covering
  • pulse shaping pulse shaping
  • channel emulation channel emulation
  • the means for emulating channel distortions may include, by way of example, an apparatus or method configured for convolving the synthesized interference signal with a channel profile, which in some cases, excludes channel effects corresponding to one or more predetermined paths or rake fingers of interest.
  • the means for producing an interference-cancelled signal may include, by way of example, a subtractive canceller, a weighted subtractive canceller, a projective canceller, and/or a weighted projective canceller.
  • Receivers and cancellation systems described herein may be employed in subscriber-side devices (e.g., cellular handsets, wireless modems, and consumer premises equipment) and/or server-side devices (e.g., cellular base stations, wireless access points, wireless routers, wireless relays, and repeaters). Chipsets for subscriber-side and/or server-side devices may be configured to perform at least some of the receiver and/or cancellation functionality of the embodiments described herein.
  • subscriber-side devices e.g., cellular handsets, wireless modems, and consumer premises equipment
  • server-side devices e.g., cellular base stations, wireless access points, wireless routers, wireless relays, and repeaters.
  • Chipsets for subscriber-side and/or server-side devices may be configured to perform at least some of the receiver and/or cancellation functionality of the embodiments described herein.
  • FIG. 1 Various functional elements, separately or in combination, depicted in the figures may take the form of a microprocessor, digital signal processor, application specific integrated circuit, field programmable gate array, or other logic circuitry programmed or otherwise configured to operate as described herein. Accordingly, embodiments may take the form of programmable features executed by a common processor or discrete hardware unit.
  • Embodiments according to the present invention are understood with reference to the schematic block diagrams of FIGS. 1 , 2 A, and 2 B, and the flow diagrams of FIGS. 3 , 4 A, and 4 B.
  • Various functional units depicted in the figures may take the form of a microprocessor, digital signal processor, application specific integrated circuit, field programmable gate array, or other logic circuitry programmed or otherwise configured to operate as described herein. Accordingly, embodiments shown herein may take the form of programmable features executed by a common processor or a discrete hardware unit.
  • FIG. 1 is a system diagram illustrating a communication system configuration in which embodiments of the present invention may be configured to operate.
  • FIG. 2A is a block diagram of an interference-cancelling circuit, which may be configured for removing interference from a predetermined multipath component.
  • FIG. 2B is a block diagram showing an embodiment of an interference-cancelling circuit configured to cancel interference in a receiver employing antenna diversity.
  • FIG. 3 is a flow chart that illustrates a cancellation method in accordance with an embodiment of the invention.
  • FIG. 4A illustrates a method for estimating subchannel symbols as part of an interference-cancellation technique.
  • FIG. 4B illustrates a method for estimating subchannel symbols for a system (e.g., an HSDPA system) that employs different signal constellations and spreading codes for different data rates.
  • a system e.g., an HSDPA system
  • FIG. 4B illustrates a method for estimating subchannel symbols for a system (e.g., an HSDPA system) that employs different signal constellations and spreading codes for different data rates.
  • FIG. 1 shows an exemplary CDMA system configuration for the purpose of illustrating embodiments of the invention configured to perform soft-weighted subtractive cancellation.
  • a k th user terminal 100 receives communications from sources (e.g., base stations) 101 and 102 via signal paths 111 and 112 , respectively.
  • the sources 101 and 102 may correspond to two propagation paths from one base station.
  • the orthogonalizing codes spread the symbol transmission by a factor of N.
  • a data symbol for a k th user of a j th base-station may be represented by a jk .
  • a received signal r[n] at the k th user terminal 100 for an n th chip and a symbol duration that spans N chips is expressed by
  • W jk [n] denotes the n th chip of the k th user from the j th source
  • u [n] is additive white Gaussian noise of variance ⁇ u 2 .
  • the values c j are complex channel gains corresponding to the signal from the j th base station to the receiver.
  • transmissions from the second base station 102 may comprise interference.
  • Interference cancellation such as subtractive and/or projective cancellation may be employed.
  • a receiver may synthesize interference from a combination of soft-weighted and hard-coded pre-processed symbol estimates.
  • a synthesized interference signal s 2 [n] corresponding to the second base station 102 may be expressed by
  • ⁇ 2k [l] is a pre-processed soft estimate of a k th user's symbol on symbol period l
  • ⁇ 2k ( ⁇ 2k [l]) is a companding function acting on the estimated symbol ⁇ 2k [l].
  • the expression for the synthesized interference s 2 [n] may assume perfect channel estimates c 2 , uncertainty in the channel estimates may be factored into the functions ⁇ 2k ( ⁇ 2k [l]).
  • the receiver may subtract the synthesized interference s 2 [n] from the received signal r [n].
  • An interference-cancelled version of the first path 111 ⁇ circumflex over (r) ⁇ 1 , is given by
  • ⁇ mk is the correlation between the m th code of the first base station 101 and the k th code of the second base station 102 that includes the effects of the PN covers:
  • the post-processed SINR for user m is given by
  • E 1m is the expected value of
  • the post-processed SINR is maximized by minimizing the expectation terms per subchannel (e.g. Walsh channel). This is accomplished by decomposing the function ⁇ 2k ( ⁇ 2k ) into its real and imaginary components and differentiating with respect to each component.
  • the minimizing function is the real scalar weighting ⁇ 2k ⁇ 2k .
  • the symbol estimates ⁇ 2k may be assumed to be uncorrelated symbol estimates, which have mean a 2k and variance ⁇ k .
  • the post-processed SINR m for a particular subchannel m may be maximized by selecting weights for the other subchannels as
  • E 2k E
  • 2 is the average energy of subchannel k for source 2
  • 2 E 2k + ⁇ 2k 2
  • SINR 2 ⁇ ⁇ k ( 1 ) E 2 ⁇ ⁇ k ⁇ 2 ⁇ ⁇ k 2
  • the soft weight ⁇ 2k may be estimated as
  • avg(.) denotes an average of the variable (.) over a sequence of symbol transmissions. This average may be quite general, and it may be based on prior knowledge or probability models for E 2k and/or ⁇ 2k 2 .
  • ⁇ ⁇ 2 ⁇ ⁇ k max ⁇ ( 0 , avg ⁇ ( ⁇ a ⁇ 2 ⁇ ⁇ k ⁇ 2 ) - ⁇ 2 ⁇ ⁇ k 2 avg ⁇ ( ⁇ a ⁇ 2 ⁇ ⁇ k ⁇ 2 ) ) .
  • ⁇ circumflex over ( ⁇ ) ⁇ 2k is quantized to zero or one, such as for selecting active subchannels. If ⁇ circumflex over ( ⁇ ) ⁇ 2k is quantized to zero or one, such as for selecting active subchannels, then ⁇ circumflex over ( ⁇ ) ⁇ 2k is quantized to zero or one, such as for selecting active subchannels.
  • ⁇ ⁇ 2 ⁇ ⁇ k ⁇ 1 , avg ⁇ ( ⁇ a ⁇ 2 ⁇ ⁇ k ⁇ 2 ) ⁇ 2 ⁇ ⁇ k 2 > z 0 , otherwise
  • z is a predetermined threshold value.
  • ⁇ ⁇ 2 ⁇ ⁇ k max ⁇ ( 0 , avg ⁇ ( ⁇ a ⁇ 2 ⁇ ⁇ k ⁇ 2 ) - avg ⁇ ( ⁇ ⁇ 2 ⁇ ⁇ k 2 ) avg ⁇ ( ⁇ a ⁇ 2 ⁇ ⁇ k ⁇ 2 ) )
  • other channels having known values of a 2m and ⁇ square root over (E 2m ) ⁇ may be used.
  • ⁇ circumflex over ( ⁇ ) ⁇ 2k E[ ⁇ 2k ⁇ 2k
  • 2 [l],l 1, 2, . . . , L]
  • hard decisions may be made for the pre-processed symbol estimates when ⁇ 2k exceeds a predetermined threshold.
  • the derivation for the SINR in such embodiments is described in the co-pending application, entitled “Soft-weighted subtractive interference cancellation systems,” which is hereby incorporated by reference.
  • Some embodiments may employ weighted soft decisions on some subchannels and hard decisions on others.
  • all subchannels having a preprocessed SINR (1) between two predetermined thresholds employ soft weighted (e.g., companded) estimates for interference synthesis.
  • Subchannels having values of SINR (1) below the lower threshold may be zeroed.
  • Subchannels having values of SINR (1) above the upper threshold may be hard-coded to a nearest constellation point (i.e., hard decisions are used).
  • a CDMA2000 system in which symbols are drawn from a single QPSK constellation may use a combination of soft and hard decisions based on predetermined thresholds.
  • constellations for various users may differ.
  • the constellations of interfering users are typically unknown at the receiver, making hard decisions impractical, unless constellation classification is performed per user.
  • the estimation of E 2k + ⁇ 2k 2 remains unchanged.
  • Other embodiments may quantize the weighting of soft estimates.
  • FIG. 2A is a block diagram that shows a receiver embodiment of the invention that may be employed in a CDMA system.
  • the receiver includes a baseband receiver 201 coupled to an SINR-estimation module 202 and a companding module 204 .
  • a thresholding module 203 is coupled between the SINR-estimation module 202 and the companding module 204 .
  • the companding module 204 is coupled to an interference synthesizer 205 , followed by a channel emulator 206 , and a canceller 207 .
  • the baseband receiver 201 provides pre-processed symbol estimates for subchannels of a received baseband signal.
  • a rake receiver may be employed for producing pre-processed estimates for all of the received CDMA subchannels.
  • symbol estimates may be chosen per rake finger.
  • the baseband receiver 201 may comprise an equalizer receiver.
  • the pre-processed estimates are coupled into the SINR-estimation module 202 , which estimates a pre-processed SINR (1) for each subchannel.
  • SINR estimates may be extracted from EVMs.
  • the noise-plus-interference variance may be measured on a representative subchannel (e.g., a pilot channel) and used for all subchannels.
  • 2 ) may be used to estimate E 2k + ⁇ 2k 2 directly without resolving onto a constellation.
  • the thresholding module 203 compares estimated SINR to a predetermined threshold for determining whether soft or hard decisions are to be used for generating interference-symbol estimates for each subchannel.
  • the companding module 204 generates the hard decisions and/or weighted soft decisions for each pre-processed symbol estimate.
  • the companding module 204 may employ filtering for each subchannel to estimate user amplitudes, and amplitude scaling may be employed prior to hard decisions.
  • the estimated SINR may be used to generate weights used to soft weight symbol estimates for each subchannel.
  • the interference synthesizer 205 performs source-specific operations on the symbol estimates (which may be soft and/or hard symbol estimates) to produce a synthesized interference signal. For example the interference synthesizer 205 may perform an Inverse Fast Walsh Transform (IFWT) to respread user symbol estimates, followed by a PN covering that provides for PN/Scrambling cover codes.
  • IFWT Inverse Fast Walsh Transform
  • a transmitter pulse-shaping filter may be used to shape the scrambled, code-multiplexed signal.
  • the channel emulator 206 which may optionally be part of the interference synthesizer 205 , adds channel distortions to the synthesized interference signal.
  • a path of interest is selected from a multipath signal.
  • the first signal path 111 from base station 101 corresponding to a first finger of a rake receiver may be denoted as the path of interest.
  • the channel emulator 206 may convolve the synthesized interference with a channel profile that excludes the channel effects corresponding to the first finger (i.e., the first signal path 111 ). This enables a canceller (e.g., canceller 207 ) to remove effects of other multipath components from the path of interest (i.e., signal path 111 ).
  • Receiver embodiments of the invention may be configured to remove any number of multipath components from a path of interest. Furthermore, when multiple transmit sources are present, signals from sources other than the source corresponding to the path of interest may be removed.
  • the canceller 207 may include a subtractive canceller or a projective canceller configured to remove interference from the received baseband signal, which may be obtained from a receiver pulse-shaping filter (not shown).
  • the interference synthesizer 205 or the channel emulator 206 may optionally emulate the effects of receiver pulse-shaping for the synthesized interference.
  • the canceller 207 may provide for a scale factor ⁇ to adjust the amount of interference that is removed.
  • the received signal and the synthesized interference are not to scale.
  • Walsh Codes and PN codes typically are not normalized. Walsh stripping and Walsh insertion together introduce a scale equal to the code length N, and PN code stripping and insertion together introduce an additional factor of 2.
  • MRC combining for M paths results in a scaling factor given by
  • b i is a weighting factor employed for an i th finger.
  • 2
  • 2
  • the normalizing factor in this case is
  • may also represent a projective cancellation factor that accounts for path correlations, An example of ⁇ for such a case is given by
  • Interference-cancelled signals output by the canceller 207 may be coupled to one or more rake fingers.
  • interference-cancelled signals in which the effects of a third and a fourth path are removed may be coupled to fingers configured for processing first and second multipath components.
  • a comparator (not shown) may optionally be employed for selecting one of the interference-cancelled signal and the uncancelled signal for processing by a rake receiver,
  • Embodiments of the invention may be configured for receivers having more than one receive antenna.
  • each of a plurality N of rake receivers 201 . 1 - 201 .N corresponding to a different receive antenna may include an interference canceller 207 . 1 - 207 .N, respectively.
  • a generalized combiner may be used to combine paths that are common to two or more receive antennas.
  • a combiner 211 may perform maximal ratio combining across the rake 201 . 1 - 201 .N fingers. Alternative types of combining may be performed.
  • Pre-processed soft estimates are output by the combiner 211 and used to produce synthesized interference, such as described previously.
  • the synthesized interference is coupled to a plurality of channel emulators 206 . 1 - 206 .N, wherein each channel emulator 206 . 1 - 206 .N has an associated rake receiver 201 . 1 - 201 .N.
  • a first channel emulator produces two interference signals corresponding to the two paths received by the first antenna.
  • a second channel emulator produces two interference signals corresponding to the two paths received by the second antenna.
  • the receiver may include four rake fingers, each matched to one of the four paths.
  • the first finger may be assigned to the signal received by the first antenna, wherein interference due to the second path is removed via subtractive or projective cancellation.
  • the second finger may be assigned to the signal received by the first antenna wherein the interference due to the first path is removed.
  • the third and fourth fingers may be matched to the multipath components received by the second receive antenna.
  • CDMA Coded Physical Broadcast
  • multiple subchannels transmitting high data rates have the same frequency-selective fade and each of these coded subchannels has the same transmission amplitude.
  • These subchannels coexist with voice channels, which have a lower data rate.
  • these low-rate channels may have different amplitudes.
  • only one weight may be calculated for each of the K subchannels carrying high data rates.
  • Signal amplitudes may be averaged over time and/or across subchannels, and the noise power may also be averaged over subchannels to obtain a single SINR estimate.
  • an SINR estimate may be compared to a predetermined threshold for determining whether to perform hard decisions, weighted soft decisions, or zeroing for all of the high data rate subchannels.
  • FIG. 3 is a flow chart that illustrates a cancellation method in accordance with an embodiment of the invention.
  • Rake synthesis 301 . 1 processes a received baseband signal to produce soft symbol estimates for data symbols modulated on subchannels by a first source (e.g., a first base station).
  • rake synthesis 301 .N produces soft symbol estimates for data symbols modulated on subchannels by an N th source.
  • the rake synthesis steps 301 . 1 - 301 .N may optionally be cross-coupled if source diversity is present for at least some of the subchannels, such as may typically occur during a soft hand over.
  • an SINR estimate or a vector magnitude is made from the soft symbol estimates 302 .
  • This companding process 303 . 1 - 303 .N may implement subchannel selection, such as by discarding subchannels that have a signal energy that falls below a predetermined threshold.
  • Interference synthesis (such as providing for PN covering, Walsh covering, pulse shaping, and channel emulation) 304 . 1 - 304 .N is performed to synthesize interference received from each source (i.e. each base station and/or multipath).
  • Interference for a particular rake finger is synthesized 305 using synthesized multipath signals from each of the first source to the N th source.
  • Scaling 306 may optionally be used to scale interference received from the different sources.
  • Some form of interference cancellation 307 (such as subtractive cancellation, weighted subtractive cancellation, projective cancellation, or weighted projective cancellation) is provided for cancelling interference from a predetermined path of interest.
  • Rake finger input selection 308 is performed to select between an interference-cancelled signal and the original received baseband signal (depending on which signal has the highest value of estimated SINR or an alternative figure of merit) prior to coupling the resulting selected signal into a rake finger.
  • Rake synthesis 309 produces soft estimates for each subchannel.
  • Signal and noise powers are measured 310 , followed by another selection process 311 configured to select either soft estimates produced by some combination of rake synthesis 301 . 1 to 301 .N or soft estimates produced by rake synthesis 309 , The selected signals may be output for further processing.
  • ASICs Application Specific Integrated Circuits
  • FPGAs Field Programmable Gate Arrays
  • DSPs Digital Signal Processors
  • Software and/or firmware implementations of the invention may be implemented via any combination of programming languages, including Java, C, C++, MatlabTM, Verilog, VHDL, and/or processor specific machine and assembly languages.
  • Computer programs i.e., software and/or firmware implementing the method of this invention may be distributed to users on a distribution medium such as a SIM card, a USB memory interface, or other computer-readable memory adapted for interfacing with a consumer wireless terminal.
  • computer programs may be distributed to users via wired or wireless network interfaces. From there, they will often be copied to a hard disk or a similar intermediate storage medium.
  • the programs When the programs are to be run, they may be loaded either from their distribution medium or their intermediate storage medium into the execution memory of a wireless terminal, configuring an onboard digital computer system (e.g. a microprocessor) to act in accordance with the method of this invention. All these operations are well known to those skilled in the art of computer systems.
  • FIG. 4A illustrates a method for estimating subchannel symbols as part of an interference-cancellation technique.
  • hard decisions are employed if the SINR is higher than a first predetermined threshold 401 .
  • Weighted soft decisions may be employed for an intermediate range of SINRs defined by an upper bound (e.g., the first predetermined threshold) and a lower bound 402 (e.g., a second predetermined threshold).
  • Subchannel symbol values may be discarded (e.g., set to zero) if the pre-processed SINR falls below the second predetermined threshold 403 .
  • an interference cancellation circuit may be turned off if the measured SINR falls below a predetermined threshold, since, in some embodiments of the invention, it is known that interference cancellation may not be as useful as power conservation at lower pre-processed SINRs.
  • FIG. 4B illustrates a method for estimating subchannel symbols for a given system that employs different signal constellations corresponding to different data rates.
  • a system identification 400 is performed for each subchannel. For example, system identification 400 may distinguish between HSDPA subchannels and non-HSDPA subchannels, which have a lower data rate. For subchannels (e.g., HSDPA subchannels) having a higher data rate, some predetermined strategy may be used to estimate subchannel symbols based on whether the symbol constellation for those subchannels is known or unknown. Weighted soft estimates may be employed or cancellation may be bypassed for HSDPA subchannels in which the constellation is unknown. If the constellation is known, hard decisions 411 , weighted soft decisions 412 , and/or no cancellation 413 may be performed. For non-HSDPA (e.g., WCDMA) subchannels, it is assumed that the constellation is known. Thus, hard decisions 421 , weighted soft decisions 422 , and/or no cancellation 423 may be performed.
  • modules may be provided through the use of dedicated hardware, as well as hardware capable of executing software in association with appropriate software.
  • the functions may be performed by a single dedicated processor, by a shared processor, or by a plurality of individual processors, some of which may be shared.
  • explicit use of the term “processor” or “module” should not be construed to refer exclusively to hardware capable of executing software, and may implicitly include, without limitation, digital signal processor DSP hardware, read-only memory (ROM) for storing software, random access memory (RAM), and non-volatile storage. Other hardware, conventional and/or custom, may also be included.
  • the function of any component or device described herein may be carried out through the operation of program logic, through dedicated logic, through the interaction of program control and dedicated logic, or even manually, the particular technique being selectable by the implementer as more specifically understood from the context.

Abstract

Interference is cancelled from a baseband signal by synthesizing interference from estimated symbols in interfering subchannels. The estimated symbols are hard-coded, soft weighted, or zeroed, depending on the value of an estimated pre-processed signal-to-interference-and-noise ratio (SINR) in each subchannel in order to maximize a postprocessed SINR. The estimated pre-processed SINR is obtained from averages of estimated symbol energies and estimated noise variances, or from related statistical procedures.

Description

    CROSS-REFERENCE TO RELATED APPLICATIONS
  • This application is a continuation of U.S. patent application Ser. No. 11/266,928, entitled “Soft Weighted Interference Cancellation for CDMA Systems,” filed Nov. 4, 2005, and published as U.S. Patent Application Publication Number 2006-0227854 A1; which is a Continuation-in-Part of (1) U.S. patent application Ser. No. 11/233,636, entitled “Optimal Feedback Weighting for Soft-Decision Cancellers,” filed Sep. 23, 2005, and published as U.S. Patent Application Publication Number 2006-0227909 A1; and (2) U.S. patent application Ser. No. 11/100,935, entitled “Construction of Projection Operators for Interference Cancellation,” filed Apr. 7, 2005, and published as U.S. Patent Application Publication Number 2005-0180364 A1, which is a Continuation-in-Part of (a) U.S. patent application Ser. No. 11/773,777, entitled “Systems and Methods for Parallel Signal Cancellation,” and filed on Feb. 6, 2004, now U.S. Pat. No. 7,394,879; (b) U.S. patent application Ser. No. 10/686,359, entitled “Systems and Methods for Adjusting Phase,” and filed Oct. 15, 2003, now U.S. Pat. No. 7,068,706; (c) U.S. patent application Ser. No. 10/686,829, entitled “Method and Apparatus for Channel Amplitude Estimation and Interference Vector Construction,” and filed on Oct. 15, 2003, now U.S. Pat. No. 7,580,448; (d) U.S. patent application Ser. No. 10/294,834, entitled “Construction of an Interference Matrix for a Coded Signal Processing Engine,” and filed on Nov. 15, 2002, now U.S. Pat. No. 7,200,183; and (e) U.S. patent application Ser. No. 10/247,836, entitled “Serial Cancellation Receiver Design for a Coded Signal Processing Engine,” and filed on Sep. 20, 2002, now U.S. Pat. No. 7,158,559. The entirety of each of the foregoing patents, patent applications, and patent application publications is incorporated by reference herein.
  • BACKGROUND
  • 1. Field of the Invention
  • The present invention relates generally to interference cancellation in received wireless communication signals and, more particularly, to forming a composite interference signal for interference cancellation.
  • 2. Discussion of the Related Art
  • In an exemplary wireless multiple-access system, a communication resource is divided into subchannels and allocated to different users. For example, subchannels may include time slots, frequency slots, multiple-access codes, spatio-temporal subchannels, or any combination thereof A plurality of subchannel signals received by a wireless terminal (e.g., a subscriber unit or a base station) may correspond to different users and/or different subchannels allocated to a particular user. In some systems, a plurality of subchannels may be allocated to at least one user such that the number of users is less than the number of subchannels.
  • If a single transmitter broadcasts different messages to different receivers, such as a base station in a wireless communication system broadcasting to a plurality of mobile terminals, the channel resource is subdivided in order to distinguish between messages intended for each mobile. Thus, each mobile terminal, by knowing its allocated subchannel(s), may decode messages intended for it from the superposition of received signals. Similarly, a base station typically separates signals it receives into PN-coded subchannels in order to differentiate between users.
  • In a multipath environment, received signals are superpositions of time delayed (and complex scaled) versions of the transmitted signals. Multipath can cause co-channel and cross-channel interference that correlates, the allocated subchannels. For example, co-channel interference may occur when time-delayed reflections of transmitted signals interfere with a line-of-sight signal from the same source. Cross-channel interference occurs when signals in a subchannel leak into and, thus, impair acquisition and tracking of other subchannels.
  • Co-channel and cross-channel interference can degrade communications by causing a receiver to incorrectly decode received transmissions, thus increasing a receiver's error floor. Interference may also have other degrading effects on communications. For example, interference may diminish the capacity of a communication system, decrease the region of coverage, and/or decrease maximum data rates. For these reasons, a reduction in interference can improve reception of selected signals by addressing the aforementioned limitations due to interference.
  • SUMMARY OF THE INVENTION
  • In view of the foregoing background, embodiments of the present invention may provide for identifying interference components for the purpose of forming a composite interference signal for use in any subtractive or projective interference canceller. The identification of interference components and the cancellation of such components may be implemented using a parallel, serial, iterative, or one-shot mode of operation.
  • Embodiments of the invention may be employed in any receiver configured to support one or more CDMA standards, such as (1) the “TIA/EIA-95-B Mobile Station-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System” (the IS-95 standard), (2) the “TIA/EIA-98-C Recommended Minimum Standard for Dual-Mode Wideband Spread Spectrum Cellular Mobile Station” (the IS-98 standard), (3) the standard offered by a consortium named “3rd Generation Partnership Project” (3GPP) and embodied in a set of documents including Document Nos. 3G TS 25.211, 3G TS 25.212, 3G TS 25.213, and 3G TS 25.214 (the WCDMA standard), (4) the standard offered by a consortium named “3rd Generation Partnership Project 2” (3GPP2) and embodied in a set of documents including “TR-45.5 Physical Layer Standard for cdma2000 Spread Spectrum Systems,” the “C.S0005-A Upper Layer (Layer 3) Signaling Standard for cdma2000 Spread Spectrum Systems,” and the “C.S0024 CDMA2000 High Rate Packet Data Air Interface Specification” (the CDMA2000 standard), and (5) other CDMA standards.
  • Embodiments of the invention may provide for analytically characterizing the received signal-to-interference-and-noise ratio (SINR), estimating it in a composite signal or in an interfering user subchannel, and choosing feedback terms (e.g., adaptive weights from a companding function) to construct an interference-cancelled signal that maximizes this quantity. In one embodiment of the invention, a means for determining an SINR estimate in each subchannel uses an estimated SINR for each estimated symbol. In this case, each estimated symbol may be generated by a means for producing symbol estimates from a received baseband signal. Alternatively, symbol estimates may include resolutions of the baseband signal into multiple antenna copies, multipath components, or the like. A means for determining whether to use weighted soft decisions or hard decisions for each subchannel compares each subchannel's SINR estimate to a predetermined threshold. A means for generating hard decisions and/or weighted soft decisions for each symbol estimate produces either a hard estimate or a weighted soft estimate for each symbol estimate based on how the corresponding SINR estimate compares to the threshold. A means for producing a synthesized interference signal may synthesize a composite interference vector from the hard or soft-weighted symbol estimates. A means for emulating channel distortions in the synthesized interference signal may simulate channel effects corresponding to paths other than a predetermined path of interest. A means for producing an interference-cancelled signal combines a received baseband signal with the synthesized interference signal in order to subtract or project out interference in the received baseband signal, or in one or more rake-resolved components of the baseband signal.
  • The means for producing symbol estimates corresponding to a received baseband signal may include, by way of example, a rake receiver, a plurality of rake receivers coupled to a rake combiner, an equalizer, and/or any CDMA receiver employing antenna diversity, equalizers, and/or other elements of an advanced receiver.
  • The means for determining an SINR estimate in each subchannel may include, by way of example, an apparatus or method configured for filtering complex amplitudes and estimated variances of the complex amplitudes for each subchannel. The means for determining an SINR estimate may include an apparatus or process configured for calculating a mean-squared error due to noise plus interference or a component or method for computing a broadband noise plus interference floor.
  • The means for determining whether to use weighted soft decisions or hard decisions for each subchannel may include, by way of example, any apparatus or method configured for comparing estimated SINRs to at least one predetermined threshold.
  • The means for generating hard decisions and/or weighted soft decisions for each pre-processed symbol estimate may include, by way of example, an apparatus or method for generating hard decisions, an apparatus or method for generating weights on soft estimates, and/or an apparatus or method for discarding soft estimates with a low estimated SINR.
  • The means for producing a synthesized interference signal may include, by way of example, a CDMA signal generator configured for performing an inverse fast Walsh transform (IFWT), PN covering, pulse shaping, and channel emulation.
  • The means for emulating channel distortions may include, by way of example, an apparatus or method configured for convolving the synthesized interference signal with a channel profile, which in some cases, excludes channel effects corresponding to one or more predetermined paths or rake fingers of interest.
  • The means for producing an interference-cancelled signal may include, by way of example, a subtractive canceller, a weighted subtractive canceller, a projective canceller, and/or a weighted projective canceller.
  • Receivers and cancellation systems described herein may be employed in subscriber-side devices (e.g., cellular handsets, wireless modems, and consumer premises equipment) and/or server-side devices (e.g., cellular base stations, wireless access points, wireless routers, wireless relays, and repeaters). Chipsets for subscriber-side and/or server-side devices may be configured to perform at least some of the receiver and/or cancellation functionality of the embodiments described herein.
  • Various functional elements, separately or in combination, depicted in the figures may take the form of a microprocessor, digital signal processor, application specific integrated circuit, field programmable gate array, or other logic circuitry programmed or otherwise configured to operate as described herein. Accordingly, embodiments may take the form of programmable features executed by a common processor or discrete hardware unit.
  • These and other embodiments of the invention are described with respect to the figures and the following description of the preferred embodiments.
  • BRIEF DESCRIPTION OF THE DRAWINGS
  • Embodiments according to the present invention are understood with reference to the schematic block diagrams of FIGS. 1, 2A, and 2B, and the flow diagrams of FIGS. 3, 4A, and 4B. Various functional units depicted in the figures may take the form of a microprocessor, digital signal processor, application specific integrated circuit, field programmable gate array, or other logic circuitry programmed or otherwise configured to operate as described herein. Accordingly, embodiments shown herein may take the form of programmable features executed by a common processor or a discrete hardware unit.
  • FIG. 1 is a system diagram illustrating a communication system configuration in which embodiments of the present invention may be configured to operate.
  • FIG. 2A is a block diagram of an interference-cancelling circuit, which may be configured for removing interference from a predetermined multipath component.
  • FIG. 2B is a block diagram showing an embodiment of an interference-cancelling circuit configured to cancel interference in a receiver employing antenna diversity.
  • FIG. 3 is a flow chart that illustrates a cancellation method in accordance with an embodiment of the invention.
  • FIG. 4A illustrates a method for estimating subchannel symbols as part of an interference-cancellation technique.
  • FIG. 4B illustrates a method for estimating subchannel symbols for a system (e.g., an HSDPA system) that employs different signal constellations and spreading codes for different data rates.
  • DESCRIPTION OF THE PREFERRED EMBODIMENTS
  • The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
  • FIG. 1 shows an exemplary CDMA system configuration for the purpose of illustrating embodiments of the invention configured to perform soft-weighted subtractive cancellation. In the present example, a kth user terminal 100 receives communications from sources (e.g., base stations) 101 and 102 via signal paths 111 and 112, respectively. In an alternative embodiment not shown, the sources 101 and 102 may correspond to two propagation paths from one base station. The sources 101 and 102 employ orthogonalizing (e.g., Walsh) codes Wj with PN/Scrambling code covers P where j=1 or 2. The orthogonalizing codes spread the symbol transmission by a factor of N.
  • A data symbol for a kth user of a jth base-station may be represented by ajk. A received signal r[n] at the kth user terminal 100 for an nth chip and a symbol duration that spans N chips is expressed by
  • r [ n ] = c 1 P 1 [ n ] k = 1 K 1 W 1 k [ n ] a 1 k [ l ] + c 2 P 2 [ n ] k = 1 K 2 W 2 k [ n ] a 2 k [ l ] + u [ n ] , lN n ( l + 1 ) N - 1
  • where Wjk [n] denotes the nth chip of the kth user from the jth source, and u [n] is additive white Gaussian noise of variance σu 2. Although this exemplary embodiment excludes pulseshape filtering effects, alternative embodiments that consider pulse shaping may be provided. The variables K1 and K2 denote the number of user channels multiplexed by the 1st and 2nd transmit sources, respectively. If both sources correspond to the same base station, then K1=K2. The values cj are complex channel gains corresponding to the signal from the jth base station to the receiver. Although a single path per base station is described, embodiments of the invention may be configured to account for multiple paths from each base station.
  • If the first base station 101 transmits a signal of interest, then transmissions from the second base station 102 may comprise interference. Interference cancellation, such as subtractive and/or projective cancellation may be employed. According to one aspect of the present invention, a receiver may synthesize interference from a combination of soft-weighted and hard-coded pre-processed symbol estimates. A synthesized interference signal s2 [n] corresponding to the second base station 102 may be expressed by
  • s 2 [ n ] = c 2 P 2 [ n ] k = 1 K 2 W 2 k [ n ] λ 2 k ( a ~ 2 k [ l ] ) a ~ 2 k [ l ] , lN n ( l + 1 ) N - 1
  • where ã2k[l] is a pre-processed soft estimate of a kth user's symbol on symbol period l, and λ2k2k[l]) is a companding function acting on the estimated symbol ã2k[l]. Although the expression for the synthesized interference s2 [n] may assume perfect channel estimates c2, uncertainty in the channel estimates may be factored into the functions λ2k2k[l]). The receiver may subtract the synthesized interference s2 [n] from the received signal r [n]. An interference-cancelled version of the first path 111, {circumflex over (r)}1, is given by
  • r ^ 1 [ n ] = r [ n ] - s 2 [ n ] = c 1 P 1 [ n ] k = 1 K 1 W 1 k [ n ] a 1 k [ l ] + c 2 P 2 [ n ] k = 1 K 2 W 2 k [ n ] ( a 2 k [ l ] - λ 2 k ( a ~ 2 k [ l ] ) a ~ 2 k [ l ] ) + u [ n ]
  • Each chip of a corresponding PN-stripped output x1 [n] is given by
  • x 1 [ n ] = P 1 * [ n ] r ^ 1 [ n ] = c 1 k = 1 K 1 W 1 k [ n ] a 1 k [ l ] + c 2 P 1 * [ n ] P 2 [ n ] k = 1 K 2 W 2 k [ n ] ( a 2 k [ l ] - λ 2 k ( a ~ 2 k [ l ] ) a ~ 2 k [ l ] ) + P 1 * [ n ] u [ n ]
  • where * denotes a complex conjugate and the identity P1*[n]P1[n]=1 is enforced. This step is followed by matching to an mth code for a user of interest. The result of this operation, â1m, is
  • a ^ 1 m [ l ] = n = 1 N W 1 m * [ n ] x 1 [ n ] = c 1 a 1 m [ l ] + c 2 k = 1 K 2 ρ mk ( a 2 k [ l ] - λ 2 k ( a ~ 2 k [ l ] ) a ~ 2 k [ l ] ) + n = 1 N W 1 m * [ n ] P 1 * [ n ] u [ n ]
  • where the orthogonality
  • n = 1 N W 1 m * [ n ] W 1 k [ n ] = δ mk
  • has been enforced, and ρmk is the correlation between the mth code of the first base station 101 and the kth code of the second base station 102 that includes the effects of the PN covers:
  • ρ mk = n = 1 N W 1 m * [ n ] P 1 * [ n ] P 2 [ n ] W 2 k [ n ]
  • Symbol estimates ã1m[l] for the mth user signal from the first base station 101 are
  • a ~ 1 m [ l ] = c 1 * a ^ 1 m [ l ] = c 1 2 a 1 m [ l ] + c 1 * c 2 k = 1 K 2 ρ mk ( a 2 k [ l ] - λ 2 k ( a ~ 2 k [ l ] ) a ~ 2 k [ l ] ) + c 1 * n = 1 N W 1 m * [ n ] P 1 * [ n ] u [ n ]
  • The post-processed SINR for user m is given by
  • SINR m = E 1 m c 1 4 c 1 * c 2 2 k = 1 K 2 E ρ mk 2 E a 2 k - λ 2 k ( a ~ 2 k ) a ~ 2 k 2 + c 1 2 σ w 2
  • where the noise
  • w [ l ] = n = 1 N W 1 m * [ n ] P 1 * [ n ] u [ n ]
  • is modeled as a complex random variable with zero mean and variance σw 2, and E1m is the expected value of |a1m|2.
  • The post-processed SINR is maximized by minimizing the expectation terms per subchannel (e.g. Walsh channel). This is accomplished by decomposing the function λ2k 2k) into its real and imaginary components and differentiating with respect to each component. The minimizing function is the real scalar weighting λ2kã2k.
  • The symbol estimates ã2k may be assumed to be uncorrelated symbol estimates, which have mean a2k and variance σk. The post-processed SINRm for a particular subchannel m may be maximized by selecting weights for the other subchannels as
  • λ 2 k = E 2 k E 2 k + σ 2 k 2 = E 2 k E a ~ 2 k 2 = E a ~ 2 k 2 - σ 2 k 2 E a ~ 2 k 2 = SINR 2 k ( 1 ) SINR 2 k ( 1 ) + 1
  • where E2k=E|a2k|2 is the average energy of subchannel k for source 2, E|ã2k|2=E2k2k 2, and
  • SINR 2 k ( 1 ) = E 2 k σ 2 k 2
  • is the pre-processed SINR. If E2k is known, the soft weight λ2k may be estimated as
  • λ 2 k = E 2 k avg ( a ~ 2 k 2 )
  • where avg(.) denotes an average of the variable (.) over a sequence of symbol transmissions. This average may be quite general, and it may be based on prior knowledge or probability models for E2k and/or σ2k 2.
  • If E2k is unknown and σ2k 2 is known, then λ2k may be estimated as
  • λ ^ 2 k = max ( 0 , avg ( a ~ 2 k 2 ) - σ 2 k 2 avg ( a ~ 2 k 2 ) ) .
  • If {circumflex over (λ)}2k is quantized to zero or one, such as for selecting active subchannels, then {circumflex over (λ)}2k is
  • λ ^ 2 k = { 1 , avg ( a ~ 2 k 2 ) σ 2 k 2 > z 0 , otherwise
  • where z is a predetermined threshold value. In one embodiment of the invention, the threshold value z=2 may be used.
  • If neither E2k nor σ2k 2 is known, then σ2k 2 may be estimated from another subchannel having a common value σ2m 22k 2 known E2m, and known symbols. Then λ2k may be estimated as
  • λ ^ 2 k = max ( 0 , avg ( a ~ 2 k 2 ) - avg ( σ ~ 2 k 2 ) avg ( a ~ 2 k 2 ) )
  • or with a corresponding quantized version. In some cases, avg(σ2k 2) can be obtained from avg({tilde over (σ)}2k 2) as an estimate of σ2m 2=E|ã2m−√{square root over (E2m)}a2m|2, where a2m is a known symbol on a pilot channel. Similarly, other channels having known values of a2m and √{square root over (E2m)} may be used.
  • If there is prior information about the distribution of E2k, then λ2k may be estimated as the posterior mean, given a sequence of symbol estimates {ã2k[l], l=1, 2, . . . , L}:

  • {circumflex over (λ)}2k =E[λ 2k ∥ã 2k|2 [l],l=1, 2, . . . , L]
  • The expectation is over the posterior distribution of E2k, given the sequence {ã2k[l]}. When the posterior mean is intractable to compute, it may be numerically approximated to produce estimates of λ2k=E|ã2k|2/(E|ã2k|22k 2) that are companded versions of |ã2k|2/(|ã2k|22k 2) or companded versions of (|ã2k|2−σ2k 2)/|ã2k|2.
  • In some embodiments, hard decisions may be made for the pre-processed symbol estimates when λ2k exceeds a predetermined threshold. The derivation for the SINR in such embodiments is described in the co-pending application, entitled “Soft-weighted subtractive interference cancellation systems,” which is hereby incorporated by reference.
  • Some embodiments may employ weighted soft decisions on some subchannels and hard decisions on others. In one such embodiment, all subchannels having a preprocessed SINR(1) between two predetermined thresholds employ soft weighted (e.g., companded) estimates for interference synthesis. Subchannels having values of SINR(1) below the lower threshold may be zeroed. Subchannels having values of SINR(1) above the upper threshold may be hard-coded to a nearest constellation point (i.e., hard decisions are used). A CDMA2000 system in which symbols are drawn from a single QPSK constellation may use a combination of soft and hard decisions based on predetermined thresholds. However, in a system where W-CDMA and HSDPA coexist, constellations for various users may differ. Thus, the constellations of interfering users are typically unknown at the receiver, making hard decisions impractical, unless constellation classification is performed per user. However, the estimation of E2k2k 2 remains unchanged. Other embodiments may quantize the weighting of soft estimates.
  • FIG. 2A is a block diagram that shows a receiver embodiment of the invention that may be employed in a CDMA system. The receiver includes a baseband receiver 201 coupled to an SINR-estimation module 202 and a companding module 204. A thresholding module 203 is coupled between the SINR-estimation module 202 and the companding module 204. The companding module 204 is coupled to an interference synthesizer 205, followed by a channel emulator 206, and a canceller 207.
  • The baseband receiver 201 provides pre-processed symbol estimates for subchannels of a received baseband signal. For example, a rake receiver may be employed for producing pre-processed estimates for all of the received CDMA subchannels. In another embodiment, symbol estimates may be chosen per rake finger. In some embodiments, the baseband receiver 201 may comprise an equalizer receiver.
  • The pre-processed estimates are coupled into the SINR-estimation module 202, which estimates a pre-processed SINR(1) for each subchannel. SINR estimates may be extracted from EVMs. Alternatively, the noise-plus-interference variance may be measured on a representative subchannel (e.g., a pilot channel) and used for all subchannels. The value avg(|ã2k|2) may be used to estimate E2k2k 2 directly without resolving onto a constellation.
  • The thresholding module 203 compares estimated SINR to a predetermined threshold for determining whether soft or hard decisions are to be used for generating interference-symbol estimates for each subchannel. The companding module 204 generates the hard decisions and/or weighted soft decisions for each pre-processed symbol estimate. The companding module 204 may employ filtering for each subchannel to estimate user amplitudes, and amplitude scaling may be employed prior to hard decisions. The estimated SINR may be used to generate weights used to soft weight symbol estimates for each subchannel.
  • The interference synthesizer 205 performs source-specific operations on the symbol estimates (which may be soft and/or hard symbol estimates) to produce a synthesized interference signal. For example the interference synthesizer 205 may perform an Inverse Fast Walsh Transform (IFWT) to respread user symbol estimates, followed by a PN covering that provides for PN/Scrambling cover codes. A transmitter pulse-shaping filter may be used to shape the scrambled, code-multiplexed signal.
  • The channel emulator 206, which may optionally be part of the interference synthesizer 205, adds channel distortions to the synthesized interference signal. In one embodiment, a path of interest is selected from a multipath signal. For example, the first signal path 111 from base station 101 corresponding to a first finger of a rake receiver may be denoted as the path of interest. In this case, the channel emulator 206 may convolve the synthesized interference with a channel profile that excludes the channel effects corresponding to the first finger (i.e., the first signal path 111). This enables a canceller (e.g., canceller 207) to remove effects of other multipath components from the path of interest (i.e., signal path 111). Receiver embodiments of the invention may be configured to remove any number of multipath components from a path of interest. Furthermore, when multiple transmit sources are present, signals from sources other than the source corresponding to the path of interest may be removed.
  • The canceller 207 may include a subtractive canceller or a projective canceller configured to remove interference from the received baseband signal, which may be obtained from a receiver pulse-shaping filter (not shown). Thus, the interference synthesizer 205 or the channel emulator 206 may optionally emulate the effects of receiver pulse-shaping for the synthesized interference.
  • In some embodiments of the invention, the canceller 207 may provide for a scale factor α to adjust the amount of interference that is removed. In some cases, the received signal and the synthesized interference are not to scale. For example, Walsh Codes and PN codes typically are not normalized. Walsh stripping and Walsh insertion together introduce a scale equal to the code length N, and PN code stripping and insertion together introduce an additional factor of 2. Furthermore, MRC combining for M paths results in a scaling factor given by
  • η = i = 1 M b i 2
  • where bi is a weighting factor employed for an ith finger. For example, |bi|2=|ci|2 or |bi|2=|ci|22. The normalizing factor in this case is
  • α = 1 2 N η ,
  • and the interference-cancelled signal is given by

  • r c =r−αs
  • The term α may also represent a projective cancellation factor that accounts for path correlations, An example of α for such a case is given by
  • α s = P s r , α = s H r s H s
  • Where Ps is a projection operator Ps=ssH/sHs.
  • Interference-cancelled signals output by the canceller 207 may be coupled to one or more rake fingers. In an exemplary rake receiver configured to process four multipath components, interference-cancelled signals in which the effects of a third and a fourth path are removed may be coupled to fingers configured for processing first and second multipath components. A comparator (not shown) may optionally be employed for selecting one of the interference-cancelled signal and the uncancelled signal for processing by a rake receiver,
  • Embodiments of the invention may be configured for receivers having more than one receive antenna. For example, in FIG. 2B, each of a plurality N of rake receivers 201.1-201.N corresponding to a different receive antenna (not shown) may include an interference canceller 207.1-207.N, respectively. A generalized combiner may be used to combine paths that are common to two or more receive antennas. A combiner 211 may perform maximal ratio combining across the rake 201.1-201.N fingers. Alternative types of combining may be performed. Pre-processed soft estimates are output by the combiner 211 and used to produce synthesized interference, such as described previously. The synthesized interference is coupled to a plurality of channel emulators 206.1-206.N, wherein each channel emulator 206.1-206.N has an associated rake receiver 201.1-201.N.
  • In an exemplary two-antenna system configured for receiving two multipath components from a single transmit source, a first channel emulator produces two interference signals corresponding to the two paths received by the first antenna. Similarly, a second channel emulator produces two interference signals corresponding to the two paths received by the second antenna. In this case, the receiver may include four rake fingers, each matched to one of the four paths. The first finger may be assigned to the signal received by the first antenna, wherein interference due to the second path is removed via subtractive or projective cancellation. The second finger may be assigned to the signal received by the first antenna wherein the interference due to the first path is removed. Similarly, the third and fourth fingers may be matched to the multipath components received by the second receive antenna.
  • In “data optimized” CDMA, such as High-Speed Downlink Packet Access (HSDPA), multiple subchannels transmitting high data rates have the same frequency-selective fade and each of these coded subchannels has the same transmission amplitude. These subchannels coexist with voice channels, which have a lower data rate. Unlike the high-rate subchannels, these low-rate channels may have different amplitudes. In such systems, only one weight may be calculated for each of the K subchannels carrying high data rates. Signal amplitudes may be averaged over time and/or across subchannels, and the noise power may also be averaged over subchannels to obtain a single SINR estimate. In one embodiment of the invention, an SINR estimate may be compared to a predetermined threshold for determining whether to perform hard decisions, weighted soft decisions, or zeroing for all of the high data rate subchannels.
  • FIG. 3 is a flow chart that illustrates a cancellation method in accordance with an embodiment of the invention. Rake synthesis 301.1 processes a received baseband signal to produce soft symbol estimates for data symbols modulated on subchannels by a first source (e.g., a first base station). Similarly, rake synthesis 301.N produces soft symbol estimates for data symbols modulated on subchannels by an Nth source. The rake synthesis steps 301.1-301.N may optionally be cross-coupled if source diversity is present for at least some of the subchannels, such as may typically occur during a soft hand over. For each source, an SINR estimate or a vector magnitude is made from the soft symbol estimates 302.1-302.N. These measurements are used to determine the reliability of the soft symbol estimates. Based on this reliability determination, either a hard decision or a weighted soft-decision is produced for each soft symbol estimate 303.1-303.N. This companding process 303.1-303.N may implement subchannel selection, such as by discarding subchannels that have a signal energy that falls below a predetermined threshold. Interference synthesis (such as providing for PN covering, Walsh covering, pulse shaping, and channel emulation) 304.1-304.N is performed to synthesize interference received from each source (i.e. each base station and/or multipath).
  • Interference for a particular rake finger is synthesized 305 using synthesized multipath signals from each of the first source to the Nth source. Scaling 306 may optionally be used to scale interference received from the different sources. Some form of interference cancellation 307 (such as subtractive cancellation, weighted subtractive cancellation, projective cancellation, or weighted projective cancellation) is provided for cancelling interference from a predetermined path of interest. Rake finger input selection 308 is performed to select between an interference-cancelled signal and the original received baseband signal (depending on which signal has the highest value of estimated SINR or an alternative figure of merit) prior to coupling the resulting selected signal into a rake finger. Rake synthesis 309 produces soft estimates for each subchannel. Signal and noise powers are measured 310, followed by another selection process 311 configured to select either soft estimates produced by some combination of rake synthesis 301.1 to 301.N or soft estimates produced by rake synthesis 309, The selected signals may be output for further processing.
  • Those skilled in the art should recognize that method and apparatus embodiments described herein may be implemented in a variety of ways, including implementations in hardware, software, firmware, or various combinations thereof. Examples of such hardware may include Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), general-purpose processors, Digital Signal Processors (DSPs), and/or other circuitry. Software and/or firmware implementations of the invention may be implemented via any combination of programming languages, including Java, C, C++, Matlab™, Verilog, VHDL, and/or processor specific machine and assembly languages.
  • Computer programs (i.e., software and/or firmware) implementing the method of this invention may be distributed to users on a distribution medium such as a SIM card, a USB memory interface, or other computer-readable memory adapted for interfacing with a consumer wireless terminal. Similarly, computer programs may be distributed to users via wired or wireless network interfaces. From there, they will often be copied to a hard disk or a similar intermediate storage medium. When the programs are to be run, they may be loaded either from their distribution medium or their intermediate storage medium into the execution memory of a wireless terminal, configuring an onboard digital computer system (e.g. a microprocessor) to act in accordance with the method of this invention. All these operations are well known to those skilled in the art of computer systems.
  • FIG. 4A illustrates a method for estimating subchannel symbols as part of an interference-cancellation technique. For a given pre-processed SINR, hard decisions are employed if the SINR is higher than a first predetermined threshold 401. Weighted soft decisions may be employed for an intermediate range of SINRs defined by an upper bound (e.g., the first predetermined threshold) and a lower bound 402 (e.g., a second predetermined threshold). Subchannel symbol values may be discarded (e.g., set to zero) if the pre-processed SINR falls below the second predetermined threshold 403. In a related embodiment, an interference cancellation circuit may be turned off if the measured SINR falls below a predetermined threshold, since, in some embodiments of the invention, it is known that interference cancellation may not be as useful as power conservation at lower pre-processed SINRs.
  • FIG. 4B illustrates a method for estimating subchannel symbols for a given system that employs different signal constellations corresponding to different data rates. A system identification 400 is performed for each subchannel. For example, system identification 400 may distinguish between HSDPA subchannels and non-HSDPA subchannels, which have a lower data rate. For subchannels (e.g., HSDPA subchannels) having a higher data rate, some predetermined strategy may be used to estimate subchannel symbols based on whether the symbol constellation for those subchannels is known or unknown. Weighted soft estimates may be employed or cancellation may be bypassed for HSDPA subchannels in which the constellation is unknown. If the constellation is known, hard decisions 411, weighted soft decisions 412, and/or no cancellation 413 may be performed. For non-HSDPA (e.g., WCDMA) subchannels, it is assumed that the constellation is known. Thus, hard decisions 421, weighted soft decisions 422, and/or no cancellation 423 may be performed.
  • The functions of the various elements shown in the drawings, including functional blocks labeled as “modules” may be provided through the use of dedicated hardware, as well as hardware capable of executing software in association with appropriate software. When provided by a processor, the functions may be performed by a single dedicated processor, by a shared processor, or by a plurality of individual processors, some of which may be shared. Moreover, explicit use of the term “processor” or “module” should not be construed to refer exclusively to hardware capable of executing software, and may implicitly include, without limitation, digital signal processor DSP hardware, read-only memory (ROM) for storing software, random access memory (RAM), and non-volatile storage. Other hardware, conventional and/or custom, may also be included. Similarly, the function of any component or device described herein may be carried out through the operation of program logic, through dedicated logic, through the interaction of program control and dedicated logic, or even manually, the particular technique being selectable by the implementer as more specifically understood from the context.
  • The method and system embodiments described herein merely illustrate particular embodiments of the invention. It should be appreciated that those skilled in the art will be able to devise various arrangements, which, although not explicitly described or shown herein, embody the principles of the invention and are included within its spirit and scope. Furthermore, all examples and conditional language recited herein are intended to be only for pedagogical purposes to aid the reader in understanding the principles of the invention. This disclosure and its associated references are to be construed as applying without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure.

Claims (56)

1. A CDMA receiver, comprising:
a signal-to-interference-and-noise ratio (SINR)-estimation module in a receiver, the SINR estimation module configured for producing one or more SINR estimates corresponding to one or more subchannels of a received multipath signal;
a thresholding module configured for comparing each of the one or more SINR estimates to a threshold to determine whether to employ a weighted soft decision or a hard decision;
a companding module configured for generating the weighted soft decision or the hard decision determined by the thresholding module for each of the one or more SINR estimates; and
a suppressor configured for producing at least one interference-suppressed signal from one or more of the soft decisions or hard decisions generated by the companding module.
2. The receiver recited in claim 1, wherein the SINR-estimation module is configured for producing the one or more SINR estimates by averaging symbol amplitudes over at least one of a set of parameters, the set of parameters including time and a plurality of subchannels.
3. The receiver recited in claim 1, wherein the thresholding module is further configured for determining an estimated SINR below which weighted soft decisions provide better performance than hard decisions, and above which hard decisions provide better performance than weighted soft decisions.
4. The receiver recited in claim 1, wherein the companding module generates a weighted soft decision for each of the one or more SINR estimates that is below the threshold and generates a hard decision for each of the one or more SINR estimates that is above the threshold.
5. The receiver recited in claim 1, wherein the thresholding module is further configured for determining a cutoff SINR, below which corresponding symbol estimates are set to zero.
6. The receiver recited in claim 1, wherein the thresholding module is configured for determining an estimation strategy based on whether subchannel constellations are known.
7. The receiver recited in claim 1, further comprising a baseband receiver configured for producing one or more symbol estimates for one or more subchannels of the received multipath signal.
8. The receiver recited in claim 7, wherein the thresholding module is further configured for determining a cutoff SINR, below which corresponding symbol estimates are set to zero.
9. The receiver recited in claim 7, wherein the baseband receiver comprises a rake receiver.
10. The receiver recited in claim 1, wherein the companding module is configured for producing at least one weight expressed by an estimate of
SINR k ( 1 ) SINR k ( 1 ) + 1 ,
where SINRk (1) is a signal-to-interference-and-noise ratio for a user or subchannel k.
11. The receiver recited in claim 7, wherein one or more of the SINR estimates are estimated via a function of the one or more symbol estimates.
12. The receiver recited in claim 1, further comprising a synthesizer configured for producing a synthesized interference signal.
13. The receiver recited in claim 12, wherein the synthesizer comprises a channel emulator configured for providing channel distortions to the synthesized interference signal.
14. The receiver recited in claim 1, further comprising a channel emulator configured to perform channel emulation.
15. The receiver recited in claim 1, wherein the suppressor is configured to perform scaling.
16. The receiver recited in claim 1, wherein the suppressor is configured to perform at least one of subtractive suppression, weighted subtractive suppression, projective suppression, and weighted projective suppression.
17. The receiver recited in claim 1, further comprising a rake combiner configured to perform maximal ratio combining across a plurality of rake fingers.
18. The receiver recited in claim 17, wherein the SINR-estimation module is coupled to the Rake combiner.
19. The receiver recited in claim 1 configured to operate in at least one of a handset and a base station.
20. A method of receiving a CDMA signal, comprising:
producing in a receiver one or more SINR estimates corresponding to one or more subchannels of a received multipath signal;
comparing each of the one or more SINR estimates to a predetermined threshold for determining whether to employ a weighted soft decision or a hard decision;
generating the weighted soft decision or the hard decision determined for each of the one or more SINR estimates to produce at least one interference-symbol estimate; and
producing at least one interference-suppressed signal from a received baseband signal and the at least one interference-symbol estimate.
21. The method recited in claim 20, wherein producing one or more SINR estimates comprises averaging symbol amplitudes over at least one of a set of parameters, the set of parameters including time and a plurality of subchannels.
22. The method recited in claim 20, wherein comparing comprises determining an SINR below which weighted soft decisions provide better performance than hard decisions, and above which hard decisions provide better performance than weighted soft decisions.
23. The method recited in claim 20, wherein comparing comprises determining a cutoff SINR, below which corresponding symbol estimates are set to zero.
24. The method recited in claim 20, wherein comparing comprises determining an estimation strategy based on whether subchannel constellations are known.
25. The method recited in claim 20, further comprising producing one or more symbol estimates for one or more subchannels of the received multipath signal.
26. The method recited in claim 20, wherein generating comprises generating a weighted soft decision for each of the one or more SINR estimates that is below the threshold and generating a hard decision for each of the one or more SINR estimates that is above the threshold.
27. The method recited in claim 20, wherein generating the weighted soft decision or the hard decision comprises producing at least one weight expressed by an estimate of
SINR k ( 1 ) SINR k ( 1 ) + 1 ,
where SINRk (1) is a signal-to-interference-and-noise ratio for a user or subchannel k.
28. The method recited in claim 25, wherein SINRk (1) is estimated via a function of one or more of the symbol estimates.
29. The method recited in claim 20, further comprising producing a synthesized interference signal.
30. The method recited in claim 29, further comprising emulating channel distortions in the synthesized interference signal.
31. The method recited in claim 20, further comprising performing channel emulation.
32. The method recited in claim 20, wherein producing at least one interference-suppressed signal includes scaling.
33. The method recited in claim 20, wherein producing at least one interference-suppressed signal comprises performing at least one of subtractive suppression, weighted subtractive suppression, projective suppression, and weighted projective suppression.
34. The method recited in claim 20, further comprising performing maximal ratio combining across a plurality of rake fingers.
35. The method recited in claim 25, wherein producing one or more SINR estimates includes receiving the one or more symbol estimates from a Rake combiner.
36. A chipset configured to perform the method recited in claim 20.
37. A digital computer system programmed to perform the method recited in claim 20.
38. A computer-readable medium storing a computer program implementing the method of claim 20.
39. A base station configured to perform the method of claim 20.
40. A handset configured to perform the method of claim 20.
41. A CDMA receiver, comprising:
a means for determining an SINR estimate for each of one or more subchannels of a received signal;
a means for determining whether to use weighted soft decisions or hard decisions for each of the one or more subchannel;
a means for generating the weighted soft decisions or hard decisions determined for each of the one or more SINR estimates; and
a means for producing an interference-suppressed signal from a received baseband signal and at least one interference-symbol estimate, wherein each of the at least one interference-symbol estimate comprises a hard decision or a weighted soft decision of a corresponding symbol estimate.
42. The receiver recited in claim 41, further comprising a means for determining at least one SINR threshold.
43. The receiver recited in claim 42, wherein the means for determining at least one SINR threshold is configured for determining an SINR below which weighted soft decisions provide better performance than hard decisions, and above which hard decisions provide better performance than weighted soft decisions.
44. The receiver recited in claim 43, where the means for generating is configured for generating a weighted soft decision for each of the one or more SINR estimates that is below the SINR threshold and generating a hard decision for each of the one or more SINR estimates that is above the SINR threshold
45. The receiver recited in claim 42, wherein the means for determining at least one SINR threshold includes a means for determining a cutoff SINR, below which the processed symbol estimates are set to zero.
46. The receiver recited in claim 41, further comprising a means for generating at least one weight for weighting at least one of the plurality of soft symbol estimates.
47. The receiver recited in claim 46 wherein the at least one weight is expressed by an estimate of
SINR k ( 1 ) SINR k ( 1 ) + 1 ,
where SINRk (1) is a signal-to-interference-and-noise ratio for a user or subchannel k.
48. The receiver recited in claim 41, wherein the means for producing an interference-suppressed signal comprises a means for producing a synthesized interference signal from the at least one interference-symbol estimate.
49. The receiver recited in claim 48, wherein the means for producing a synthesized interference signal includes a means for emulating channel distortions in the synthesized interference signal.
50. The receiver recited in claim 41, wherein the means for determining an SINR estimate is configured for estimating an SINR in each of the one or more subchannels.
51. The receiver recited in claim 41, wherein the means for producing an interference-suppressed signal is configured for performing scaling.
52. The receiver recited in claim 41, wherein the means for producing an interference-suppressed signal is configured to perform at least one of subtractive suppression, weighted subtractive suppression, projective suppression, and weighted projective suppression.
53. The receiver recited in claim 41, wherein the means for determining the SINR estimate is coupled to a means for producing one or more symbol estimates corresponding to a received baseband signal.
54. The receiver recited in claim 53, wherein the means for determining the SINR estimate is configured for averaging amplitudes of the one or more symbol estimates over at least one of a set of parameters, the set of parameters including time and a plurality of subchannels.
55. The receiver recited in claim 41, wherein the means for determining whether to use weighted soft decisions or hard decisions is further configured for determining an estimation strategy based on whether subchannel constellations are known.
56. A CDMA receiver, comprising:
a signal-to-interference-and-noise ratio (SINR)-estimation module in a receiver, the SINR estimation module configured for producing one or more SINR estimates corresponding to one or more subchannels of a received multipath signal;
a thresholding module configured for comparing each of the one or more SINR estimates to a threshold to determine whether to employ a weighted soft decision or a hard decision; and
a companding module configured for generating the weighted soft decision or the hard decision determined by the thresholding module for each of the one or more SINR estimates.
US12/966,953 2002-09-20 2010-12-13 Interference Suppression for CDMA Systems Abandoned US20110080923A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
US12/966,953 US20110080923A1 (en) 2002-09-20 2010-12-13 Interference Suppression for CDMA Systems
US14/713,740 US9735816B2 (en) 2002-09-20 2015-05-15 Interference suppression for CDMA systems

Applications Claiming Priority (9)

Application Number Priority Date Filing Date Title
US10/247,836 US7158559B2 (en) 2002-01-15 2002-09-20 Serial cancellation receiver design for a coded signal processing engine
US10/294,834 US7200183B2 (en) 2001-11-16 2002-11-15 Construction of an interference matrix for a coded signal processing engine
US10/686,359 US7068706B2 (en) 2002-10-15 2003-10-15 System and method for adjusting phase
US10/686,829 US7580448B2 (en) 2002-10-15 2003-10-15 Method and apparatus for channel amplitude estimation and interference vector construction
US10/773,777 US7394879B2 (en) 2001-11-19 2004-02-06 Systems and methods for parallel signal cancellation
US11/100,935 US20050180364A1 (en) 2002-09-20 2005-04-07 Construction of projection operators for interference cancellation
US11/233,636 US8761321B2 (en) 2005-04-07 2005-09-23 Optimal feedback weighting for soft-decision cancellers
US11/266,928 US7876810B2 (en) 2005-04-07 2005-11-04 Soft weighted interference cancellation for CDMA systems
US12/966,953 US20110080923A1 (en) 2002-09-20 2010-12-13 Interference Suppression for CDMA Systems

Related Parent Applications (1)

Application Number Title Priority Date Filing Date
US11/266,928 Continuation US7876810B2 (en) 2002-09-20 2005-11-04 Soft weighted interference cancellation for CDMA systems

Related Child Applications (1)

Application Number Title Priority Date Filing Date
US14/713,740 Continuation US9735816B2 (en) 2002-09-20 2015-05-15 Interference suppression for CDMA systems

Publications (1)

Publication Number Publication Date
US20110080923A1 true US20110080923A1 (en) 2011-04-07

Family

ID=37900244

Family Applications (3)

Application Number Title Priority Date Filing Date
US11/266,928 Active 2027-06-23 US7876810B2 (en) 2002-09-20 2005-11-04 Soft weighted interference cancellation for CDMA systems
US12/966,953 Abandoned US20110080923A1 (en) 2002-09-20 2010-12-13 Interference Suppression for CDMA Systems
US14/713,740 Expired - Lifetime US9735816B2 (en) 2002-09-20 2015-05-15 Interference suppression for CDMA systems

Family Applications Before (1)

Application Number Title Priority Date Filing Date
US11/266,928 Active 2027-06-23 US7876810B2 (en) 2002-09-20 2005-11-04 Soft weighted interference cancellation for CDMA systems

Family Applications After (1)

Application Number Title Priority Date Filing Date
US14/713,740 Expired - Lifetime US9735816B2 (en) 2002-09-20 2015-05-15 Interference suppression for CDMA systems

Country Status (2)

Country Link
US (3) US7876810B2 (en)
WO (1) WO2007038039A2 (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20060089102A1 (en) * 2002-12-26 2006-04-27 Akihiko Nishio Radio communication apparatus and radio communication method
US20090067355A1 (en) * 2007-09-12 2009-03-12 Jacobus Cornelis Haartsen Power-Aware Link Adaptation in a Wideband CDMA System
US20100054373A1 (en) * 2008-08-29 2010-03-04 Andres Reial Method and Apparatus for Low-Complexity Interference Cancellation in Communication Signal Processing
US20110019656A1 (en) * 2002-09-20 2011-01-27 Rambus Inc. Advanced signal processors for Interference Cancellation in baseband receivers
US9723496B2 (en) 2011-11-04 2017-08-01 Qualcomm Incorporated Method and apparatus for interference cancellation by a user equipment using blind detection

Families Citing this family (45)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8761321B2 (en) 2005-04-07 2014-06-24 Iii Holdings 1, Llc Optimal feedback weighting for soft-decision cancellers
US7697595B2 (en) * 2006-05-11 2010-04-13 Tensorcomm Incorporated Interference cancellation in variable codelength systems for multi-access communication
US8179946B2 (en) 2003-09-23 2012-05-15 Rambus Inc. Systems and methods for control of advanced receivers
US7826516B2 (en) 2005-11-15 2010-11-02 Rambus Inc. Iterative interference canceller for wireless multiple-access systems with multiple receive antennas
CN101132389B (en) * 2007-09-26 2010-06-02 中兴通讯股份有限公司 Compensation method for estimation of signal to interference ratio
TWI354454B (en) * 2008-04-17 2011-12-11 Sunplus Mmobile Inc Method for mitigating interference
US8842785B2 (en) * 2008-07-01 2014-09-23 Telefonaktiebolaget Lm Ericsson (Publ) Soft scaling method and apparatus
US8315342B2 (en) * 2008-10-16 2012-11-20 Telefonaktiebolaget Lm Ericsson (Publ) Method and apparatus for simplified expected symbol value computation and interference cancellation in communication signal processing
US8743854B1 (en) * 2010-09-27 2014-06-03 Rockwell Collins, Inc. Signal separation and SINR enhancement
US8811522B2 (en) 2012-05-29 2014-08-19 Magnolia Broadband Inc. Mitigating interferences for a multi-layer MIMO system augmented by radio distribution network
US8971452B2 (en) 2012-05-29 2015-03-03 Magnolia Broadband Inc. Using 3G/4G baseband signals for tuning beamformers in hybrid MIMO RDN systems
US8619927B2 (en) 2012-05-29 2013-12-31 Magnolia Broadband Inc. System and method for discrete gain control in hybrid MIMO/RF beamforming
US8644413B2 (en) 2012-05-29 2014-02-04 Magnolia Broadband Inc. Implementing blind tuning in hybrid MIMO RF beamforming systems
US8861635B2 (en) 2012-05-29 2014-10-14 Magnolia Broadband Inc. Setting radio frequency (RF) beamformer antenna weights per data-stream in a multiple-input-multiple-output (MIMO) system
US8837650B2 (en) 2012-05-29 2014-09-16 Magnolia Broadband Inc. System and method for discrete gain control in hybrid MIMO RF beamforming for multi layer MIMO base station
US8842765B2 (en) 2012-05-29 2014-09-23 Magnolia Broadband Inc. Beamformer configurable for connecting a variable number of antennas and radio circuits
US8767862B2 (en) 2012-05-29 2014-07-01 Magnolia Broadband Inc. Beamformer phase optimization for a multi-layer MIMO system augmented by radio distribution network
US9154204B2 (en) 2012-06-11 2015-10-06 Magnolia Broadband Inc. Implementing transmit RDN architectures in uplink MIMO systems
US9343808B2 (en) 2013-02-08 2016-05-17 Magnotod Llc Multi-beam MIMO time division duplex base station using subset of radios
US8797969B1 (en) 2013-02-08 2014-08-05 Magnolia Broadband Inc. Implementing multi user multiple input multiple output (MU MIMO) base station using single-user (SU) MIMO co-located base stations
US9155110B2 (en) 2013-03-27 2015-10-06 Magnolia Broadband Inc. System and method for co-located and co-channel Wi-Fi access points
US8989103B2 (en) 2013-02-13 2015-03-24 Magnolia Broadband Inc. Method and system for selective attenuation of preamble reception in co-located WI FI access points
US20140226740A1 (en) 2013-02-13 2014-08-14 Magnolia Broadband Inc. Multi-beam co-channel wi-fi access point
US8774150B1 (en) 2013-02-13 2014-07-08 Magnolia Broadband Inc. System and method for reducing side-lobe contamination effects in Wi-Fi access points
US9100968B2 (en) 2013-05-09 2015-08-04 Magnolia Broadband Inc. Method and system for digital cancellation scheme with multi-beam
US9425882B2 (en) 2013-06-28 2016-08-23 Magnolia Broadband Inc. Wi-Fi radio distribution network stations and method of operating Wi-Fi RDN stations
US8995416B2 (en) 2013-07-10 2015-03-31 Magnolia Broadband Inc. System and method for simultaneous co-channel access of neighboring access points
US8824596B1 (en) 2013-07-31 2014-09-02 Magnolia Broadband Inc. System and method for uplink transmissions in time division MIMO RDN architecture
US9497781B2 (en) 2013-08-13 2016-11-15 Magnolia Broadband Inc. System and method for co-located and co-channel Wi-Fi access points
US9088898B2 (en) 2013-09-12 2015-07-21 Magnolia Broadband Inc. System and method for cooperative scheduling for co-located access points
US9060362B2 (en) 2013-09-12 2015-06-16 Magnolia Broadband Inc. Method and system for accessing an occupied Wi-Fi channel by a client using a nulling scheme
US9172454B2 (en) 2013-11-01 2015-10-27 Magnolia Broadband Inc. Method and system for calibrating a transceiver array
US8891598B1 (en) 2013-11-19 2014-11-18 Magnolia Broadband Inc. Transmitter and receiver calibration for obtaining the channel reciprocity for time division duplex MIMO systems
US8929322B1 (en) * 2013-11-20 2015-01-06 Magnolia Broadband Inc. System and method for side lobe suppression using controlled signal cancellation
US8942134B1 (en) 2013-11-20 2015-01-27 Magnolia Broadband Inc. System and method for selective registration in a multi-beam system
US9014066B1 (en) 2013-11-26 2015-04-21 Magnolia Broadband Inc. System and method for transmit and receive antenna patterns calibration for time division duplex (TDD) systems
US9294177B2 (en) 2013-11-26 2016-03-22 Magnolia Broadband Inc. System and method for transmit and receive antenna patterns calibration for time division duplex (TDD) systems
US9042276B1 (en) 2013-12-05 2015-05-26 Magnolia Broadband Inc. Multiple co-located multi-user-MIMO access points
US9172446B2 (en) 2014-03-19 2015-10-27 Magnolia Broadband Inc. Method and system for supporting sparse explicit sounding by implicit data
US9100154B1 (en) 2014-03-19 2015-08-04 Magnolia Broadband Inc. Method and system for explicit AP-to-AP sounding in an 802.11 network
DE102014103853B4 (en) * 2014-03-20 2016-02-18 Intel IP Corporation A method and apparatus for noise source timing detection and estimation of noise and noise parameters
US9271176B2 (en) 2014-03-28 2016-02-23 Magnolia Broadband Inc. System and method for backhaul based sounding feedback
DE102014111735A1 (en) * 2014-08-18 2016-02-18 Intel IP Corporation Radio communication devices and methods for controlling a radio communication device
WO2016194519A1 (en) * 2015-05-29 2016-12-08 株式会社日立国際電気 Noise canceler
US10666337B2 (en) * 2016-11-11 2020-05-26 Nippon Telegraph And Telephone Corporation Radio apparatus and radio communication method

Citations (95)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3742201A (en) * 1971-02-22 1973-06-26 Raytheon Co Transformer system for orthogonal digital waveforms
US4088955A (en) * 1975-04-07 1978-05-09 Baghdady Elie J Interference rejection technique
US4309769A (en) * 1980-02-25 1982-01-05 Harris Corporation Method and apparatus for processing spread spectrum signals
US4665401A (en) * 1980-10-10 1987-05-12 Sperry Corporation Millimeter wave length guidance system
US4670885A (en) * 1985-02-26 1987-06-02 Signatron, Inc. Spread spectrum adaptive antenna interference canceller
US4893316A (en) * 1985-04-04 1990-01-09 Motorola, Inc. Digital radio frequency receiver
US4922506A (en) * 1988-01-11 1990-05-01 Sicom Corporation Compensating for distortion in a communication channel
US4933639A (en) * 1989-02-13 1990-06-12 The Board Of Regents, The University Of Texas System Axis translator for magnetic resonance imaging
US5017929A (en) * 1989-09-06 1991-05-21 Hughes Aircraft Company Angle of arrival measuring technique
US5099493A (en) * 1990-08-27 1992-03-24 Zeger-Abrams Incorporated Multiple signal receiver for direct sequence, code division multiple access, spread spectrum signals
US5105435A (en) * 1990-12-21 1992-04-14 Motorola, Inc. Method and apparatus for cancelling spread-spectrum noise
US5109390A (en) * 1989-11-07 1992-04-28 Qualcomm Incorporated Diversity receiver in a cdma cellular telephone system
US5119401A (en) * 1989-11-17 1992-06-02 Nec Corporation Decision feedback equalizer including forward part whose signal reference point is shiftable depending on channel response
US5218359A (en) * 1991-08-06 1993-06-08 Kokusai Denshin Denwa Co., Ltd. Adaptive array antenna system
US5218619A (en) * 1990-12-17 1993-06-08 Ericsson Ge Mobile Communications Holding, Inc. CDMA subtractive demodulation
US5220687A (en) * 1990-05-30 1993-06-15 Pioneer Electronic Corporation Radio receiver having switch for switching between a wide filter and a narrow filter
US5224122A (en) * 1992-06-29 1993-06-29 Motorola, Inc. Method and apparatus for canceling spread-spectrum noise
US5280472A (en) * 1990-12-07 1994-01-18 Qualcomm Incorporated CDMA microcellular telephone system and distributed antenna system therefor
US5305349A (en) * 1993-04-29 1994-04-19 Ericsson Ge Mobile Communications Inc. Quantized coherent rake receiver
US5386202A (en) * 1993-11-03 1995-01-31 Sicom, Inc. Data communication modulation with managed intersymbol interference
US5390207A (en) * 1990-11-28 1995-02-14 Novatel Communications Ltd. Pseudorandom noise ranging receiver which compensates for multipath distortion by dynamically adjusting the time delay spacing between early and late correlators
US5394110A (en) * 1993-02-02 1995-02-28 Nec Corporation Demodulation system having adaptive matched filter and decision feedback equalizer
US5396256A (en) * 1992-10-28 1995-03-07 Atr Optical & Radio Communications Research Laboratories Apparatus for controlling array antenna comprising a plurality of antenna elements and method therefor
US5481570A (en) * 1993-10-20 1996-01-02 At&T Corp. Block radio and adaptive arrays for wireless systems
US5506865A (en) * 1992-11-24 1996-04-09 Qualcomm Incorporated Pilot carrier dot product circuit
US5513176A (en) * 1990-12-07 1996-04-30 Qualcomm Incorporated Dual distributed antenna system
US5602833A (en) * 1994-12-19 1997-02-11 Qualcomm Incorporated Method and apparatus for using Walsh shift keying in a spread spectrum communication system
US5736964A (en) * 1995-05-08 1998-04-07 Motorola, Inc. Method and apparatus for location finding in a CDMA system
US5859613A (en) * 1996-08-30 1999-01-12 Harris Corporation System and method for geolocating plural remote transmitters
US5872540A (en) * 1997-06-26 1999-02-16 Electro-Radiation Incorporated Digital interference suppression system for radio frequency interference cancellation
US5872776A (en) * 1995-11-22 1999-02-16 Yang; Lin-Lang Signal detection and interference cancellation based on simplified matrix inversion for CDMA applications
US5894500A (en) * 1997-06-13 1999-04-13 Motorola, Inc. Method and apparatus for canceling signals in a spread-spectrum communication system
US6014373A (en) * 1993-04-22 2000-01-11 Interdigital Technology Corporation Spread spectrum CDMA subtractive interference canceler system
US6018317A (en) * 1995-06-02 2000-01-25 Trw Inc. Cochannel signal processing system
US6032056A (en) * 1996-05-20 2000-02-29 Metawave Communications Corporation Cellular system signal conditioner
US6078611A (en) * 1997-09-16 2000-06-20 Motorola, Inc. Rake receiver and finger management method for spread spectrum communication
US6173008B1 (en) * 1997-04-26 2001-01-09 Samsung Electronics Co., Ltd. Rake receiver for reducing hardware consumption and improving search performance
US6172969B1 (en) * 1997-01-31 2001-01-09 Oki Electric Industry Co., Ltd. CDMA receiver employing successive cancellation of training-signal interference
US6175588B1 (en) * 1997-12-30 2001-01-16 Motorola, Inc. Communication device and method for interference suppression using adaptive equalization in a spread spectrum communication system
US6175587B1 (en) * 1997-12-30 2001-01-16 Motorola, Inc. Communication device and method for interference suppression in a DS-CDMA system
US6177906B1 (en) * 1999-04-01 2001-01-23 Arraycomm, Inc. Multimode iterative adaptive smart antenna processing method and apparatus
US6185716B1 (en) * 1998-01-30 2001-02-06 Maxtor Corporation Dual detector read channel with semi-soft detection
US6192067B1 (en) * 1996-12-20 2001-02-20 Fujitsu Limited Multistage interference canceller
US6201799B1 (en) * 1997-05-01 2001-03-13 Lucent Technologies, Inc Partial decorrelation for a coherent multicode code division multiple access receiver
US6215812B1 (en) * 1999-01-28 2001-04-10 Bae Systems Canada Inc. Interference canceller for the protection of direct-sequence spread-spectrum communications from high-power narrowband interference
US6219376B1 (en) * 1998-02-21 2001-04-17 Topcon Positioning Systems, Inc. Apparatuses and methods of suppressing a narrow-band interference with a compensator and adjustment loops
US6222828B1 (en) * 1996-10-30 2001-04-24 Trw, Inc. Orthogonal code division multiple access waveform format for use in satellite based cellular telecommunications
US6230180B1 (en) * 1998-10-14 2001-05-08 Conexant Systems, Inc. Digital signal processor configuration including multiplying units coupled to plural accumlators for enhanced parallel mac processing
US6233229B1 (en) * 1994-11-28 2001-05-15 Nokia Telecommunications Oy Method of allocating frequency bands to different cells, and TDMA cellular radio system
US6233459B1 (en) * 1997-04-10 2001-05-15 The Atlantis Company, Limited, Japan System for providing Geolocation of a mobile transceiver
US6240124B1 (en) * 1995-06-06 2001-05-29 Globalstar L.P. Closed loop power control for low earth orbit satellite communications system
US20010003443A1 (en) * 1996-10-10 2001-06-14 Scott R. Velazquez Communication system using geographic position data
US6252535B1 (en) * 1997-08-21 2001-06-26 Data Fusion Corporation Method and apparatus for acquiring wide-band pseudorandom noise encoded waveforms
US20020001299A1 (en) * 1996-11-14 2002-01-03 Petch Byran K. Methods and apparatus for synchronization in a wireless network
US6351642B1 (en) * 1998-12-22 2002-02-26 Telefonaktiebolaget Lm Ericsson (Publ) CDMA soft hand-off
US6351235B1 (en) * 1999-01-08 2002-02-26 Trueposition, Inc. Method and system for synchronizing receiver systems of a wireless location system
US6359874B1 (en) * 1998-05-21 2002-03-19 Ericsson Inc. Partially block-interleaved CDMA coding and decoding
US6363104B1 (en) * 1998-10-02 2002-03-26 Ericsson Inc. Method and apparatus for interference cancellation in a rake receiver
US6363103B1 (en) * 1998-04-09 2002-03-26 Lucent Technologies Inc. Multistage interference cancellation for CDMA applications using M-ary orthogonal moduation
US6377607B1 (en) * 1999-05-13 2002-04-23 Qualcomm Incorporated System and method for performing accurate demodulation of turbo-encoded signals via pilot assisted coherent demodulation
US6377636B1 (en) * 1999-11-02 2002-04-23 Iospan Wirless, Inc. Method and wireless communications system using coordinated transmission and training for interference mitigation
US20020051433A1 (en) * 1999-12-23 2002-05-02 Institut National De La Recherche Scientifique Interference suppression in CDMA systems
US6385264B1 (en) * 1999-06-08 2002-05-07 Qualcomm Incorporated Method and apparatus for mitigating interference between base stations in a wideband CDMA system
US20020060999A1 (en) * 2000-10-10 2002-05-23 Yugang Ma Multiple-user CDMA wireless communication system
US6396804B2 (en) * 1996-05-28 2002-05-28 Qualcomm Incorporated High data rate CDMA wireless communication system
US6404760B1 (en) * 1999-07-19 2002-06-11 Qualcomm Incorporated CDMA multiple access interference cancellation using signal estimation
US20030005009A1 (en) * 2001-04-17 2003-01-02 Mohammad Usman Least-mean square system with adaptive step size
US20030012264A1 (en) * 2001-06-20 2003-01-16 Aris Papasakellariou Interference cancellation system and method
US6515980B1 (en) * 1999-09-22 2003-02-04 Ericsson Inc. Methods and apparatus for interference cancellation using complex interference orthogonalization techniques
US6522683B1 (en) * 2000-08-10 2003-02-18 Qualcomm, Incorporated Method and apparatus for adaptive linear equalization for walsh covered modulation
US20030053524A1 (en) * 2001-08-31 2003-03-20 Dent Paul W. Interference cancellation in a CDMA receiving system
US20030053526A1 (en) * 1999-10-19 2003-03-20 Interdigital Technology Corporation Parallel interference cancellation receiver for multiuser detection of CDMA signals
US20030092456A1 (en) * 2001-07-26 2003-05-15 Dent Paul Wilkinson Communication system employing transmit macro-diversity
US20030095590A1 (en) * 2001-11-16 2003-05-22 Fuller Arthur T. G. Symbol-directed weighting in parallel interference cancellation
US6570909B1 (en) * 1999-07-09 2003-05-27 Nokia Mobile Phones Interference suppression in a CDMA receiver
US6570919B1 (en) * 1999-07-30 2003-05-27 Agere Systems Inc. Iterative decoding of data packets employing decision feedback equalization
US6574270B1 (en) * 1999-07-30 2003-06-03 Ericsson Inc. Baseband interference canceling spread spectrum communications methods and apparatus
US6580771B2 (en) * 2001-03-30 2003-06-17 Nokia Corporation Successive user data multipath interference cancellation
US6584115B1 (en) * 1998-06-25 2003-06-24 Nec Corporation Multiuser interference canceler for DS-CDMA system
US20040008765A1 (en) * 2001-12-18 2004-01-15 Wonzoo Chung Joint adaptive optimization of soft decision device and feedback equalizer
US6680727B2 (en) * 2000-10-17 2004-01-20 Qualcomm Incorporated Method and apparatus for canceling pilot interference in a CDMA communication system
US20040013190A1 (en) * 2002-07-18 2004-01-22 Srikant Jayaraman Method and apparatus for hybrid decision feedback equalization
US6687723B1 (en) * 2000-11-24 2004-02-03 Nortel Networks Limited Tri-mode adaptive filter and method
US6690723B1 (en) * 1999-07-02 2004-02-10 Motorola, Inc. Decision-aided equalizer
US6714585B1 (en) * 1999-06-25 2004-03-30 Ericsson Inc. Rake combining methods and apparatus using weighting factors derived from knowledge of spreading spectrum signal characteristics
US20040076224A1 (en) * 2002-10-15 2004-04-22 Onggosanusi Eko N. Multipath interference-resistant receivers for closed-loop transmit diversity (CLTD) in code-division multiple access (CDMA) systems
US6839390B2 (en) * 2002-01-23 2005-01-04 Bae Systems Information And Electronic Systems Integration Inc. Voting system for improving the performance of single-user decoders within an iterative multi-user detection system
US6882678B2 (en) * 2000-12-01 2005-04-19 Ning Kong Method and system for canceling multiple access interference in CDMA wireless communication system
US20050084045A1 (en) * 2003-10-17 2005-04-21 Stewart Kenneth A. Multi-pass interference reduction in a GSM communication system
US20050111566A1 (en) * 2003-08-23 2005-05-26 Samsung Electronics Co., Ltd. Wireless communication apparatus and method for multiple transmit and receive antenna system using multiple codes
US6985516B1 (en) * 2000-11-27 2006-01-10 Qualcomm Incorporated Method and apparatus for processing a received signal in a communications system
US20060007895A1 (en) * 2001-06-06 2006-01-12 Coralli Alessandro V Method and apparatus for canceling pilot interference in a wireless communication system
US20060013289A1 (en) * 2002-07-16 2006-01-19 In Kwan Hwang Multistage adaptive parallel interference canceller
US7010073B2 (en) * 2001-01-19 2006-03-07 Qualcomm, Incorporated Delay lock loops for wireless communication systems
US7027533B2 (en) * 2001-02-20 2006-04-11 Ntt Docomo, Inc. Turbo-reception method and turbo-receiver

Family Cites Families (121)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4359738A (en) 1974-11-25 1982-11-16 The United States Of America As Represented By The Secretary Of The Navy Clutter and multipath suppressing sidelobe canceller antenna system
US4713794A (en) 1978-12-22 1987-12-15 Raytheon Company Digital memory system
IL67379A (en) 1982-12-01 1985-11-29 Tadiran Israel Elect Ind Ltd Real-time frequency management system for hf communication networks
US4601046A (en) 1984-05-15 1986-07-15 Halpern Peter H System for transmitting data through a troposcatter medium
US4965732A (en) 1985-11-06 1990-10-23 The Board Of Trustees Of The Leland Stanford Junior University Methods and arrangements for signal reception and parameter estimation
DE3687748T2 (en) 1985-12-26 1993-05-27 Matsushita Electric Ind Co Ltd TRANSMISSION METHOD OF A DIGITAL SIGNAL WITH IMPROVED ERROR RATE PROPERTIES FOR MULTIPLE-WAY TRANSMISSION.
DE69023324T2 (en) 1990-01-02 1996-06-27 Max Planck Gesellschaft Method and system for measuring atmospheric wind fields using spatially offset, diagonally radiating antennas.
US5157671A (en) * 1990-05-29 1992-10-20 Space Systems/Loral, Inc. Semi-systolic architecture for decoding error-correcting codes
US5140615A (en) 1990-06-12 1992-08-18 Motorola, Inc. Maximal ratio diversity combining technique
US5151919A (en) 1990-12-17 1992-09-29 Ericsson-Ge Mobile Communications Holding Inc. Cdma subtractive demodulation
US5263191A (en) 1991-12-11 1993-11-16 Westinghouse Electric Corp. Method and circuit for processing and filtering signals
US5515378A (en) 1991-12-12 1996-05-07 Arraycomm, Inc. Spatial division multiple access wireless communication systems
DE4201439A1 (en) 1992-01-21 1993-07-22 Daimler Benz Ag High-rate data transmission procedure via digital radio channel - providing multipath propagation compensation by decision feedback equaliser of correctly phased and weighted antenna signal combination
DE4206476A1 (en) 1992-03-02 1993-09-09 Blaupunkt Werke Gmbh CIRCUIT ARRANGEMENT FOR ELIMINATING INTERFERENCE WITH STEREO BROADCAST SIGNALS
JPH05268128A (en) 1992-03-18 1993-10-15 Kokusai Denshin Denwa Co Ltd <Kdd> Cdma communication system
US5237586A (en) 1992-03-25 1993-08-17 Ericsson-Ge Mobile Communications Holding, Inc. Rake receiver with selective ray combining
TW214620B (en) 1992-04-13 1993-10-11 Ericsson Ge Mobile Communicat Calling channel in CDMA communications system
US5423045A (en) * 1992-04-15 1995-06-06 International Business Machines Corporation System for distributed power management in portable computers
US5353302A (en) 1993-02-03 1994-10-04 At&T Bell Laboratories Signal despreader for CDMA systems
DE4303355A1 (en) 1993-02-05 1994-08-11 Philips Patentverwaltung Radio system
US5343493A (en) 1993-03-16 1994-08-30 Hughes Aircraft Company Personal assistance system and method for use with a cellular communication system
US5437055A (en) 1993-06-03 1995-07-25 Qualcomm Incorporated Antenna system for multipath diversity in an indoor microcellular communication system
GB9315845D0 (en) 1993-07-30 1993-09-15 Roke Manor Research Apparatus for use in equipment providing a digital radio link between a fixed and a mobile radio unit
DE4326843C2 (en) 1993-08-10 1997-11-20 Hirschmann Richard Gmbh Co Receiving method and receiving antenna system for eliminating reusable interference or control device for performing this method
FR2709028B1 (en) 1993-08-13 1995-10-20 Matra Communication Method for selecting the propagation paths used to receive messages transmitted by CDMA radiocommunication.
US5343496A (en) 1993-09-24 1994-08-30 Bell Communications Research, Inc. Interference suppression in CDMA systems
DE4343959C2 (en) 1993-12-22 1996-04-25 Hirschmann Richard Gmbh Co Receiving method and receiving antenna system for eliminating reusable interference or control device for performing this method
US5553098A (en) 1994-04-12 1996-09-03 Sicom, Inc. Demodulator with selectable coherent and differential data
US5440265A (en) 1994-09-14 1995-08-08 Sicom, Inc. Differential/coherent digital demodulator operating at multiple symbol points
US5606560A (en) * 1994-09-23 1997-02-25 Motorola, Inc. Between a base station and a portable device
FI102797B1 (en) 1994-10-07 1999-02-15 Nokia Telecommunications Oy A signal detection method in a receiver for a TDMA mobile radio system and a receiver for performing the method
US5644592A (en) 1995-04-24 1997-07-01 California Institute Of Technology Parallel interference cancellation for CDMA applications
DE69633219T2 (en) 1995-06-13 2005-08-25 Ntt Docomo, Inc. CDMA demodulator
US6487190B1 (en) * 1996-06-27 2002-11-26 Interdigital Technology Corporation Efficient multichannel filtering for CDMA modems
US6307868B1 (en) 1995-08-25 2001-10-23 Terayon Communication Systems, Inc. Apparatus and method for SCDMA digital data transmission using orthogonal codes and a head end modem with no tracking loops
US5978413A (en) 1995-08-28 1999-11-02 Bender; Paul E. Method and system for processing a plurality of multiple access transmissions
JP3272940B2 (en) 1996-03-07 2002-04-08 ケイディーディーアイ株式会社 Spread spectrum signal demodulator
US6127973A (en) 1996-04-18 2000-10-03 Korea Telecom Freetel Co., Ltd. Signal processing apparatus and method for reducing the effects of interference and noise in wireless communication systems
US6308072B1 (en) 1996-04-26 2001-10-23 Motorola, Inc. Method and apparatus for controlling a wireless communication system
JP2743912B2 (en) 1996-05-30 1998-04-28 日本電気株式会社 CDMA interference canceller
JP2746261B2 (en) 1996-06-10 1998-05-06 日本電気株式会社 DS-CDMA interference cancellation device
US5926761A (en) 1996-06-11 1999-07-20 Motorola, Inc. Method and apparatus for mitigating the effects of interference in a wireless communication system
DE19623667C2 (en) 1996-06-13 2003-02-13 Siemens Ag Method and device for the detection of information transmitted according to the DS-CDMA principle in a receiving device
US5812086A (en) 1996-06-27 1998-09-22 Motorola, Inc. Method and apparatus for providing duplex communication service in geographical areas where conventional services are obstructed
US6430216B1 (en) 1997-08-22 2002-08-06 Data Fusion Corporation Rake receiver for spread spectrum signal demodulation
JP3311943B2 (en) 1996-10-18 2002-08-05 松下電器産業株式会社 Interference signal canceller
US5844521A (en) 1996-12-02 1998-12-01 Trw Inc. Geolocation method and apparatus for satellite based telecommunications system
US5787130A (en) 1996-12-10 1998-07-28 Motorola Inc. Method and apparatus for canceling interference in a spread-spectrum communication system
JPH10190495A (en) 1996-12-20 1998-07-21 Fujitsu Ltd Interference canceler
US6163696A (en) 1996-12-31 2000-12-19 Lucent Technologies Inc. Mobile location estimation in a wireless communication system
US5943331A (en) 1997-02-28 1999-08-24 Interdigital Technology Corporation Orthogonal code synchronization system and method for spread spectrum CDMA communications
US6049564A (en) 1997-04-28 2000-04-11 Northern Telecom Limited Method and apparatus for configuring PN-offsets for a non-uniform CDMA cellular network
US6101385A (en) 1997-10-09 2000-08-08 Globalstar L.P. Satellite communication service with non-congruent sub-beam coverage
US6131031A (en) * 1997-10-10 2000-10-10 Watkins- Johnson Company System and method for an underlay cellular system
US6157842A (en) 1997-10-16 2000-12-05 Telefonaktiebolaget Lm Ericsson System and method for positioning a mobile station in a CDMA cellular system
US6295311B1 (en) 1997-11-07 2001-09-25 Hughes Electronics Corporation Method and apparatus for compensating for phase differences in received signals
US6269075B1 (en) 1998-01-26 2001-07-31 Nokia Mobile Phones Limited Finger assignment in a CDMA rake receiver
US6131013A (en) 1998-01-30 2000-10-10 Motorola, Inc. Method and apparatus for performing targeted interference suppression
US6327471B1 (en) 1998-02-19 2001-12-04 Conexant Systems, Inc. Method and an apparatus for positioning system assisted cellular radiotelephone handoff and dropoff
JP2937994B1 (en) 1998-03-04 1999-08-23 日本電気移動通信株式会社 Cellular system, mobile portable device, base station device, and optimal path detection method and device
FR2776869B1 (en) * 1998-03-24 2000-05-05 Commissariat Energie Atomique CDMA RECEIVER WITH PARALLEL INTERFERENCE SUPPRESSION AND WEIGHTING
JP2965202B1 (en) 1998-04-07 1999-10-18 日本電気株式会社 Multi-user receiving apparatus and CDMA communication system
US6324159B1 (en) 1998-05-06 2001-11-27 Sirius Communications N.V. Method and apparatus for code division multiple access communication with increased capacity through self-noise reduction
US6266529B1 (en) 1998-05-13 2001-07-24 Nortel Networks Limited Method for CDMA handoff in the vicinity of highly sectorized cells
KR100318959B1 (en) 1998-07-07 2002-04-22 윤종용 Apparatus and method for eliminating interference between different codes in a CDMA communication system
US6154443A (en) 1998-08-11 2000-11-28 Industrial Technology Research Institute FFT-based CDMA RAKE receiver system and method
US6304618B1 (en) 1998-08-31 2001-10-16 Ericsson Inc. Methods and systems for reducing co-channel interference using multiple timings for a received signal
EP1142153A1 (en) * 1998-10-26 2001-10-10 Nokia Corporation Channel estimation in a cellular communication system
US6321090B1 (en) 1998-11-06 2001-11-20 Samir S. Soliman Mobile communication system with position detection to facilitate hard handoff
US6333947B1 (en) 1998-11-25 2001-12-25 Nortel Networks Limited Interference cancellation system and method and CDMA receiver including an interference cancellation circuit
KR100378124B1 (en) 1998-12-10 2003-06-19 삼성전자주식회사 Device and method for estimating the position of terminal in mobile communication system
US6668011B1 (en) 1998-12-21 2003-12-23 Nortel Networks Limited Block detection receiver
US6754340B1 (en) * 1998-12-22 2004-06-22 Nortel Networks Limited Stable adaptive filter and method
US6501788B1 (en) 1999-01-22 2002-12-31 Ericsson Inc. Apparatus and methods for intereference cancellation in spread spectrum communications systems
US6104712A (en) 1999-02-22 2000-08-15 Robert; Bruno G. Wireless communication network including plural migratory access nodes
EP1039662A1 (en) 1999-03-25 2000-09-27 Alcatel Improvements to a telecommunication system using code division multiple access (CDMA)
US6661832B1 (en) * 1999-05-11 2003-12-09 Qualcomm Incorporated System and method for providing an accurate estimation of received signal interference for use in wireless communications systems
US6263208B1 (en) 1999-05-28 2001-07-17 Lucent Technologies Inc. Geolocation estimation method for CDMA terminals based on pilot strength measurements
US6285861B1 (en) 1999-06-14 2001-09-04 Qualcomm Incorporated Receiving station with interference signal suppression
US6115409A (en) 1999-06-21 2000-09-05 Envoy Networks, Inc. Integrated adaptive spatial-temporal system for controlling narrowband and wideband sources of interferences in spread spectrum CDMA receivers
US6801565B1 (en) 1999-06-25 2004-10-05 Ericsson Inc. Multi-stage rake combining methods and apparatus
KR100343773B1 (en) * 1999-06-28 2002-07-19 한국전자통신연구원 Apparatus and method of partial parallel interference cancellation system for CDMA
US6157847A (en) 1999-06-29 2000-12-05 Lucent Technologies Inc. Base station system including parallel interference cancellation processor
US6166690A (en) 1999-07-02 2000-12-26 Sensor Systems, Inc. Adaptive nulling methods for GPS reception in multiple-interference environments
US7415061B2 (en) 1999-08-31 2008-08-19 Broadcom Corporation Cancellation of burst noise in a communication system with application to S-CDMA
US6278726B1 (en) 1999-09-10 2001-08-21 Interdigital Technology Corporation Interference cancellation in a spread spectrum communication system
US6633614B1 (en) * 1999-09-15 2003-10-14 Telcordia Technologies, Inc. Multicarrier personal access communication system
US6798737B1 (en) 1999-10-06 2004-09-28 Texas Instruments Incorporated Use of Walsh-Hadamard transform for forward link multiuser detection in CDMA systems
US6922434B2 (en) 1999-10-19 2005-07-26 Ericsson Inc. Apparatus and methods for finger delay selection in RAKE receivers
US6282231B1 (en) 1999-12-14 2001-08-28 Sirf Technology, Inc. Strong signal cancellation to enhance processing of weak spread spectrum signal
US6285316B1 (en) 2000-06-02 2001-09-04 Cellguide Ltd. Locating a mobile unit using signals from both mobile beacons and stationary beacons
US6285319B1 (en) 2000-01-27 2001-09-04 Litton Systems, Inc. Method for reducing geometrical dilution of precision in geolocation of emitters using phase circles
JP4292442B2 (en) 2000-01-31 2009-07-08 ソニー株式会社 Global positioning system receiver and portable radio terminal
US6415018B1 (en) 2000-02-08 2002-07-02 Lucent Technologies Inc. Telecommunication system and method for handling special number calls having geographic sensitivity
US6963546B2 (en) * 2000-03-15 2005-11-08 Interdigital Technology Corp. Multi-user detection using an adaptive combination of joint detection and successive interface cancellation
DE10026615B4 (en) 2000-05-19 2004-12-23 Systemonic Ag Method and arrangement for receiving CDMA signals
US6546043B1 (en) 2000-06-29 2003-04-08 Trw Inc. Method and apparatus for cancellation of multiple access interference in a code division multiple access (CDMA) communication system
US6829313B1 (en) * 2000-07-17 2004-12-07 Motorola, Inc. Sliding window turbo decoder
US6330460B1 (en) 2000-08-21 2001-12-11 Metawave Communications Corporation Simultaneous forward link beam forming and learning method for mobile high rate data traffic
DE10060610B4 (en) * 2000-12-05 2005-09-22 Webasto Ag Vehicle roof with integrated fan
JP2002217871A (en) * 2000-12-19 2002-08-02 Telefon Ab Lm Ericsson Publ Method for setting weighting coefficient in subtractive interference canceller, interference canceller unit using weighting coefficient and the interference canceller
US20020131534A1 (en) 2001-02-07 2002-09-19 Masayuki Ariyoshi System and method for multistage interference cancellation
US6466611B1 (en) * 2001-02-07 2002-10-15 Motorola, Inc. Multi-user detection using a finite-impulse-response matrix filter
US20020191676A1 (en) 2001-02-16 2002-12-19 Kenneth O?Apos;Hagan Parallel spread spectrum communication system and method
US6785341B2 (en) 2001-05-11 2004-08-31 Qualcomm Incorporated Method and apparatus for processing data in a multiple-input multiple-output (MIMO) communication system utilizing channel state information
US7170924B2 (en) * 2001-05-17 2007-01-30 Qualcomm, Inc. System and method for adjusting combiner weights using an adaptive algorithm in wireless communications system
US7106792B2 (en) * 2001-06-04 2006-09-12 Qualcomm, Inc. Method and apparatus for estimating the signal to interference-plus-noise ratio of a wireless channel
US6956893B2 (en) * 2001-08-20 2005-10-18 Motorola, Inc. Linear minimum mean square error equalization with interference cancellation for mobile communication forward links utilizing orthogonal codes covered by long pseudorandom spreading codes
US7154959B2 (en) * 2001-08-29 2006-12-26 Intel Corporation System and method for emulating a multiple input, multiple output transmission channel
US7430253B2 (en) 2002-10-15 2008-09-30 Tensorcomm, Inc Method and apparatus for interference suppression with efficient matrix inversion in a DS-CDMA system
US20030219085A1 (en) * 2001-12-18 2003-11-27 Endres Thomas J. Self-initializing decision feedback equalizer with automatic gain control
FI20021554A (en) * 2001-12-28 2003-06-29 Nokia Corp Method for channel estimation and radio system
US7280585B2 (en) * 2002-02-11 2007-10-09 Texas Instruments Incorporated Parallel interference cancellation device for multi-user CDMA systems
US7110449B2 (en) * 2002-04-16 2006-09-19 Thomson Licensing Decision feedback equalizer
BRPI0309179B1 (en) * 2002-04-17 2016-05-31 Thomson Licensing Sa selector device and method for automatic selection
US20050180364A1 (en) 2002-09-20 2005-08-18 Vijay Nagarajan Construction of projection operators for interference cancellation
US7187736B2 (en) * 2003-02-13 2007-03-06 Motorola Inc. Reducing interference in a GSM communication system
US7313168B2 (en) * 2003-03-06 2007-12-25 Nokia Corporation Method and apparatus for receiving a CDMA signal
US7342952B2 (en) * 2003-06-24 2008-03-11 Qualcomm Incorporated Slicer input and feedback filter contents for block coded digital communications
US7397842B2 (en) 2003-09-26 2008-07-08 Telefonaktiebolaget Lm Ericsson (Publ) Method and apparatus for combining weight computation in a DS-CDMA RAKE receiver
US7502412B2 (en) * 2004-05-20 2009-03-10 Qisda Corporation Adaptive channel estimation using decision feedback

Patent Citations (99)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3742201A (en) * 1971-02-22 1973-06-26 Raytheon Co Transformer system for orthogonal digital waveforms
US4088955A (en) * 1975-04-07 1978-05-09 Baghdady Elie J Interference rejection technique
US4309769A (en) * 1980-02-25 1982-01-05 Harris Corporation Method and apparatus for processing spread spectrum signals
US4665401A (en) * 1980-10-10 1987-05-12 Sperry Corporation Millimeter wave length guidance system
US4670885A (en) * 1985-02-26 1987-06-02 Signatron, Inc. Spread spectrum adaptive antenna interference canceller
US4893316A (en) * 1985-04-04 1990-01-09 Motorola, Inc. Digital radio frequency receiver
US4922506A (en) * 1988-01-11 1990-05-01 Sicom Corporation Compensating for distortion in a communication channel
US4933639A (en) * 1989-02-13 1990-06-12 The Board Of Regents, The University Of Texas System Axis translator for magnetic resonance imaging
US5017929A (en) * 1989-09-06 1991-05-21 Hughes Aircraft Company Angle of arrival measuring technique
US5109390A (en) * 1989-11-07 1992-04-28 Qualcomm Incorporated Diversity receiver in a cdma cellular telephone system
US5119401A (en) * 1989-11-17 1992-06-02 Nec Corporation Decision feedback equalizer including forward part whose signal reference point is shiftable depending on channel response
US5220687A (en) * 1990-05-30 1993-06-15 Pioneer Electronic Corporation Radio receiver having switch for switching between a wide filter and a narrow filter
US5099493A (en) * 1990-08-27 1992-03-24 Zeger-Abrams Incorporated Multiple signal receiver for direct sequence, code division multiple access, spread spectrum signals
US5390207A (en) * 1990-11-28 1995-02-14 Novatel Communications Ltd. Pseudorandom noise ranging receiver which compensates for multipath distortion by dynamically adjusting the time delay spacing between early and late correlators
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
US5218619A (en) * 1990-12-17 1993-06-08 Ericsson Ge Mobile Communications Holding, Inc. CDMA subtractive demodulation
US5105435A (en) * 1990-12-21 1992-04-14 Motorola, Inc. Method and apparatus for cancelling spread-spectrum noise
US5218359A (en) * 1991-08-06 1993-06-08 Kokusai Denshin Denwa Co., Ltd. Adaptive array antenna system
US5224122A (en) * 1992-06-29 1993-06-29 Motorola, Inc. Method and apparatus for canceling spread-spectrum noise
US5325394A (en) * 1992-06-29 1994-06-28 Motorola, Inc. Method and apparatus for canceling spread-spectrum noise
US5396256A (en) * 1992-10-28 1995-03-07 Atr Optical & Radio Communications Research Laboratories Apparatus for controlling array antenna comprising a plurality of antenna elements and method therefor
US5506865A (en) * 1992-11-24 1996-04-09 Qualcomm Incorporated Pilot carrier dot product circuit
US5394110A (en) * 1993-02-02 1995-02-28 Nec Corporation Demodulation system having adaptive matched filter and decision feedback equalizer
US6014373A (en) * 1993-04-22 2000-01-11 Interdigital Technology Corporation Spread spectrum CDMA subtractive interference canceler system
US5305349A (en) * 1993-04-29 1994-04-19 Ericsson Ge Mobile Communications Inc. Quantized coherent rake receiver
US5481570A (en) * 1993-10-20 1996-01-02 At&T Corp. Block radio and adaptive arrays for wireless systems
US5386202A (en) * 1993-11-03 1995-01-31 Sicom, Inc. Data communication modulation with managed intersymbol interference
US6233229B1 (en) * 1994-11-28 2001-05-15 Nokia Telecommunications Oy Method of allocating frequency bands to different cells, and TDMA cellular radio system
US5602833A (en) * 1994-12-19 1997-02-11 Qualcomm Incorporated Method and apparatus for using Walsh shift keying in a spread spectrum communication system
US5736964A (en) * 1995-05-08 1998-04-07 Motorola, Inc. Method and apparatus for location finding in a CDMA system
US6018317A (en) * 1995-06-02 2000-01-25 Trw Inc. Cochannel signal processing system
US6240124B1 (en) * 1995-06-06 2001-05-29 Globalstar L.P. Closed loop power control for low earth orbit satellite communications system
US5872776A (en) * 1995-11-22 1999-02-16 Yang; Lin-Lang Signal detection and interference cancellation based on simplified matrix inversion for CDMA applications
US6032056A (en) * 1996-05-20 2000-02-29 Metawave Communications Corporation Cellular system signal conditioner
US6396804B2 (en) * 1996-05-28 2002-05-28 Qualcomm Incorporated High data rate CDMA wireless communication system
US5859613A (en) * 1996-08-30 1999-01-12 Harris Corporation System and method for geolocating plural remote transmitters
US20010003443A1 (en) * 1996-10-10 2001-06-14 Scott R. Velazquez Communication system using geographic position data
US6222828B1 (en) * 1996-10-30 2001-04-24 Trw, Inc. Orthogonal code division multiple access waveform format for use in satellite based cellular telecommunications
US20020001299A1 (en) * 1996-11-14 2002-01-03 Petch Byran K. Methods and apparatus for synchronization in a wireless network
US6192067B1 (en) * 1996-12-20 2001-02-20 Fujitsu Limited Multistage interference canceller
US6172969B1 (en) * 1997-01-31 2001-01-09 Oki Electric Industry Co., Ltd. CDMA receiver employing successive cancellation of training-signal interference
US6233459B1 (en) * 1997-04-10 2001-05-15 The Atlantis Company, Limited, Japan System for providing Geolocation of a mobile transceiver
US6173008B1 (en) * 1997-04-26 2001-01-09 Samsung Electronics Co., Ltd. Rake receiver for reducing hardware consumption and improving search performance
US6201799B1 (en) * 1997-05-01 2001-03-13 Lucent Technologies, Inc Partial decorrelation for a coherent multicode code division multiple access receiver
US5894500A (en) * 1997-06-13 1999-04-13 Motorola, Inc. Method and apparatus for canceling signals in a spread-spectrum communication system
US5872540A (en) * 1997-06-26 1999-02-16 Electro-Radiation Incorporated Digital interference suppression system for radio frequency interference cancellation
US6362760B2 (en) * 1997-08-21 2002-03-26 Data Fusion Corporation Method and apparatus for acquiring wide-band pseudorandom noise encoded waveforms
US6380879B2 (en) * 1997-08-21 2002-04-30 Data Fusion Corporation Method and apparatus for acquiring wide-band pseudorandom noise encoded waveforms
US6252535B1 (en) * 1997-08-21 2001-06-26 Data Fusion Corporation Method and apparatus for acquiring wide-band pseudorandom noise encoded waveforms
US6078611A (en) * 1997-09-16 2000-06-20 Motorola, Inc. Rake receiver and finger management method for spread spectrum communication
US6175587B1 (en) * 1997-12-30 2001-01-16 Motorola, Inc. Communication device and method for interference suppression in a DS-CDMA system
US6175588B1 (en) * 1997-12-30 2001-01-16 Motorola, Inc. Communication device and method for interference suppression using adaptive equalization in a spread spectrum communication system
US6185716B1 (en) * 1998-01-30 2001-02-06 Maxtor Corporation Dual detector read channel with semi-soft detection
US6219376B1 (en) * 1998-02-21 2001-04-17 Topcon Positioning Systems, Inc. Apparatuses and methods of suppressing a narrow-band interference with a compensator and adjustment loops
US6363103B1 (en) * 1998-04-09 2002-03-26 Lucent Technologies Inc. Multistage interference cancellation for CDMA applications using M-ary orthogonal moduation
US6359874B1 (en) * 1998-05-21 2002-03-19 Ericsson Inc. Partially block-interleaved CDMA coding and decoding
US6584115B1 (en) * 1998-06-25 2003-06-24 Nec Corporation Multiuser interference canceler for DS-CDMA system
US6363104B1 (en) * 1998-10-02 2002-03-26 Ericsson Inc. Method and apparatus for interference cancellation in a rake receiver
US6230180B1 (en) * 1998-10-14 2001-05-08 Conexant Systems, Inc. Digital signal processor configuration including multiplying units coupled to plural accumlators for enhanced parallel mac processing
US6351642B1 (en) * 1998-12-22 2002-02-26 Telefonaktiebolaget Lm Ericsson (Publ) CDMA soft hand-off
US6351235B1 (en) * 1999-01-08 2002-02-26 Trueposition, Inc. Method and system for synchronizing receiver systems of a wireless location system
US6215812B1 (en) * 1999-01-28 2001-04-10 Bae Systems Canada Inc. Interference canceller for the protection of direct-sequence spread-spectrum communications from high-power narrowband interference
US6177906B1 (en) * 1999-04-01 2001-01-23 Arraycomm, Inc. Multimode iterative adaptive smart antenna processing method and apparatus
US6377607B1 (en) * 1999-05-13 2002-04-23 Qualcomm Incorporated System and method for performing accurate demodulation of turbo-encoded signals via pilot assisted coherent demodulation
US6385264B1 (en) * 1999-06-08 2002-05-07 Qualcomm Incorporated Method and apparatus for mitigating interference between base stations in a wideband CDMA system
US6714585B1 (en) * 1999-06-25 2004-03-30 Ericsson Inc. Rake combining methods and apparatus using weighting factors derived from knowledge of spreading spectrum signal characteristics
US6690723B1 (en) * 1999-07-02 2004-02-10 Motorola, Inc. Decision-aided equalizer
US6570909B1 (en) * 1999-07-09 2003-05-27 Nokia Mobile Phones Interference suppression in a CDMA receiver
US6404760B1 (en) * 1999-07-19 2002-06-11 Qualcomm Incorporated CDMA multiple access interference cancellation using signal estimation
US6574270B1 (en) * 1999-07-30 2003-06-03 Ericsson Inc. Baseband interference canceling spread spectrum communications methods and apparatus
US6570919B1 (en) * 1999-07-30 2003-05-27 Agere Systems Inc. Iterative decoding of data packets employing decision feedback equalization
US6515980B1 (en) * 1999-09-22 2003-02-04 Ericsson Inc. Methods and apparatus for interference cancellation using complex interference orthogonalization techniques
US6724809B2 (en) * 1999-10-19 2004-04-20 Interdigital Technology Corporation Parallel interference cancellation receiver for multiuser detection of CDMA signals
US20030053526A1 (en) * 1999-10-19 2003-03-20 Interdigital Technology Corporation Parallel interference cancellation receiver for multiuser detection of CDMA signals
US6377636B1 (en) * 1999-11-02 2002-04-23 Iospan Wirless, Inc. Method and wireless communications system using coordinated transmission and training for interference mitigation
US20020051433A1 (en) * 1999-12-23 2002-05-02 Institut National De La Recherche Scientifique Interference suppression in CDMA systems
US6522683B1 (en) * 2000-08-10 2003-02-18 Qualcomm, Incorporated Method and apparatus for adaptive linear equalization for walsh covered modulation
US20020060999A1 (en) * 2000-10-10 2002-05-23 Yugang Ma Multiple-user CDMA wireless communication system
US6680727B2 (en) * 2000-10-17 2004-01-20 Qualcomm Incorporated Method and apparatus for canceling pilot interference in a CDMA communication system
US6687723B1 (en) * 2000-11-24 2004-02-03 Nortel Networks Limited Tri-mode adaptive filter and method
US6985516B1 (en) * 2000-11-27 2006-01-10 Qualcomm Incorporated Method and apparatus for processing a received signal in a communications system
US6882678B2 (en) * 2000-12-01 2005-04-19 Ning Kong Method and system for canceling multiple access interference in CDMA wireless communication system
US7010073B2 (en) * 2001-01-19 2006-03-07 Qualcomm, Incorporated Delay lock loops for wireless communication systems
US7027533B2 (en) * 2001-02-20 2006-04-11 Ntt Docomo, Inc. Turbo-reception method and turbo-receiver
US6580771B2 (en) * 2001-03-30 2003-06-17 Nokia Corporation Successive user data multipath interference cancellation
US20030005009A1 (en) * 2001-04-17 2003-01-02 Mohammad Usman Least-mean square system with adaptive step size
US20060007895A1 (en) * 2001-06-06 2006-01-12 Coralli Alessandro V Method and apparatus for canceling pilot interference in a wireless communication system
US20030012264A1 (en) * 2001-06-20 2003-01-16 Aris Papasakellariou Interference cancellation system and method
US20030092456A1 (en) * 2001-07-26 2003-05-15 Dent Paul Wilkinson Communication system employing transmit macro-diversity
US20030053524A1 (en) * 2001-08-31 2003-03-20 Dent Paul W. Interference cancellation in a CDMA receiving system
US20030095590A1 (en) * 2001-11-16 2003-05-22 Fuller Arthur T. G. Symbol-directed weighting in parallel interference cancellation
US20040008765A1 (en) * 2001-12-18 2004-01-15 Wonzoo Chung Joint adaptive optimization of soft decision device and feedback equalizer
US6839390B2 (en) * 2002-01-23 2005-01-04 Bae Systems Information And Electronic Systems Integration Inc. Voting system for improving the performance of single-user decoders within an iterative multi-user detection system
US20060013289A1 (en) * 2002-07-16 2006-01-19 In Kwan Hwang Multistage adaptive parallel interference canceller
US20040013190A1 (en) * 2002-07-18 2004-01-22 Srikant Jayaraman Method and apparatus for hybrid decision feedback equalization
US20040076224A1 (en) * 2002-10-15 2004-04-22 Onggosanusi Eko N. Multipath interference-resistant receivers for closed-loop transmit diversity (CLTD) in code-division multiple access (CDMA) systems
US20050111566A1 (en) * 2003-08-23 2005-05-26 Samsung Electronics Co., Ltd. Wireless communication apparatus and method for multiple transmit and receive antenna system using multiple codes
US20050084045A1 (en) * 2003-10-17 2005-04-21 Stewart Kenneth A. Multi-pass interference reduction in a GSM communication system

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9172411B2 (en) 2002-09-20 2015-10-27 Iii Holdings 1, Llc Advanced signal processors for interference cancellation in baseband receivers
US8654689B2 (en) * 2002-09-20 2014-02-18 Rambus Inc. Advanced signal processors for interference cancellation in baseband receivers
US20110019656A1 (en) * 2002-09-20 2011-01-27 Rambus Inc. Advanced signal processors for Interference Cancellation in baseband receivers
US20060089102A1 (en) * 2002-12-26 2006-04-27 Akihiko Nishio Radio communication apparatus and radio communication method
US8369285B2 (en) * 2002-12-26 2013-02-05 Panasonic Corporation Radio communication apparatus and radio communication method
US20130121202A1 (en) * 2002-12-26 2013-05-16 Panasonic Corporation Radio communication apparatus and radio communication method
US20090104877A1 (en) * 2002-12-26 2009-04-23 Panasonic Corporation Radio communication apparatus and radio communication method
US8254335B2 (en) * 2002-12-26 2012-08-28 Panasonic Corporation Radio communication apparatus and radio communication method
US8670776B2 (en) * 2002-12-26 2014-03-11 Panasonic Corporation Radio communication apparatus and radio communication method
US11296808B2 (en) 2005-09-23 2022-04-05 Iii Holdings 1, Llc Advanced signal processors for interference cancellation in baseband receivers
US10666373B2 (en) 2005-09-23 2020-05-26 Iii Holdings 1, L.L.C. Advanced signal processors for interference cancellation in baseband receivers
US10050733B2 (en) 2005-09-23 2018-08-14 Iii Holdings 1, Llc Advanced signal processors for interference cancellation in baseband receivers
US8055291B2 (en) * 2007-09-12 2011-11-08 Telefonaktiebolaget Lm Ericsson (Publ) Power-aware link adaptation in a wideband CDMA system
US20090067355A1 (en) * 2007-09-12 2009-03-12 Jacobus Cornelis Haartsen Power-Aware Link Adaptation in a Wideband CDMA System
US8238499B2 (en) * 2008-08-29 2012-08-07 Telefonaktiebolaget Lm Ericsson (Publ) Method and apparatus for low-complexity interference cancellation in communication signal processing
US20100054373A1 (en) * 2008-08-29 2010-03-04 Andres Reial Method and Apparatus for Low-Complexity Interference Cancellation in Communication Signal Processing
US9723496B2 (en) 2011-11-04 2017-08-01 Qualcomm Incorporated Method and apparatus for interference cancellation by a user equipment using blind detection

Also Published As

Publication number Publication date
US20150318883A1 (en) 2015-11-05
US9735816B2 (en) 2017-08-15
WO2007038039A3 (en) 2007-06-07
US20060227854A1 (en) 2006-10-12
US7876810B2 (en) 2011-01-25
WO2007038039A2 (en) 2007-04-05

Similar Documents

Publication Publication Date Title
US9735816B2 (en) Interference suppression for CDMA systems
US8953723B2 (en) Iterative interference suppression using mixed feedback weights and stabilizing step sizes
US7711075B2 (en) Iterative interference cancellation using mixed feedback weights and stabilizing step sizes
US9036748B2 (en) Interference cancellation in variable codelength systems for multi-access communication
US7702048B2 (en) Iterative interference cancellation using mixed feedback weights and stabilizing step sizes
US11296808B2 (en) Advanced signal processors for interference cancellation in baseband receivers
US9172456B2 (en) Iterative interference suppressor for wireless multiple-access systems with multiple receive antennas
US8761321B2 (en) Optimal feedback weighting for soft-decision cancellers
US9270325B2 (en) Iterative interference suppression using mixed feedback weights and stabilizing step sizes
US7733941B2 (en) Inter-symbol interference cancellation for wireless multiple access

Legal Events

Date Code Title Description
AS Assignment

Owner name: III HOLDINGS 1, LLC, DELAWARE

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:RAMBUS INC.;REEL/FRAME:032642/0115

Effective date: 20140317

STCB Information on status: application discontinuation

Free format text: ABANDONED -- AFTER EXAMINER'S ANSWER OR BOARD OF APPEALS DECISION