CN1061205C - Method for device of carrier exalting and compensating in frequency spreading communication system - Google Patents
Method for device of carrier exalting and compensating in frequency spreading communication system Download PDFInfo
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- CN1061205C CN1061205C CN97115151A CN97115151A CN1061205C CN 1061205 C CN1061205 C CN 1061205C CN 97115151 A CN97115151 A CN 97115151A CN 97115151 A CN97115151 A CN 97115151A CN 1061205 C CN1061205 C CN 1061205C
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Abstract
The present invention relates to a method and a device thereof for determining and tracking carrier deviation in a spread spectrum communication system. The carrier frequency of a received digital spread spectrum signal is removed by a multiplier, and then, a PN code sequence is removed by a despreader. Conjugate multiplication is carried out on two elements with a preset interval of each sample pair of a digital spread spectrum signal by a carrier deviation evaluation device to obtain a series of results comprising phase variation information. Then, the results are averaged and normalized to obtain a carrier deviation evaluation value. Carrier waves are restored, and the carrier frequency of a transmitted signal is regulated, which enables a user terminal to accurately and quickly track the carrier frequency of the base station. The device is realized by software on a DSP platform, and precise carrier deviation evaluation is obtained by a simplified algorithm and fewer storage units.
Description
The present invention relates in a kind of wireless communication system that adopts digital modulation mode on the analog carrier frequency, carrier wave recovers and the technology of compensation.
In the direct sequence spread spectrum wireless communication system, each digital information symbols all uses the known pseudo-random code sequence of receiving-transmitting sides to expand to polynary chip, use digital modulation mode (as phase shift keying PSK or QAM) to be modulated on the analog carrier then, the radiofrequency signal that is converted to after the modulation by upconverter is launched at last.At receiving terminal, the rf modulated signal that receives is converted to modulated intermediate frequency signal by low-converter, separates to be in harmonious proportion again and uses known pseudo-random code sequence despreading, in the hope of the recovering information symbol.
Ideally, thereby receiver can utilize identical pseudo-random code sequence that the down-conversion received signal is carried out despreading recovers the information symbol of transmission with the pseudo-random code sequence that removes wherein, but in real system, because transmitter and receiver use fully independently master clock, certainly exist a difference on the frequency, cause when despreading, can not realizing that carrier wave recovers accurately, its concrete manifestation is to do to remain with the residual carrier component in the baseband signal after treatment in the first step of digital demodulation with analog multiplier.Because the collection of letters is independent variation with the master clock at the two ends of posting a letter, so the residual carrier component also changes, equals the difference on the frequency of transceiver carrier wave.
Be head it off, in digital demodulator, must carry out carrier wave and recover.Traditional carrier recovering method adopts the analog phase-locked look circuit.Its advantage is a technology maturation, and shortcoming is that performance and pullin banwidth are difficult to take into account, and is relatively more responsive to the shake of carrier wave, also has the problem of the complicated aspect of hardware circuit in addition.
U.S. Pat 5303257 (carrier wave in the DSSS communication system is proofreaied and correct, in April, 1994) has proposed a kind of digital carrier frequency bearing calibration, thereby this method obtains the rough valuation of carrier shift by the energy that calculates many class frequencys received signal.Because its carrier estimation precision depends on the number of the frequency that participates in calculating, therefore,, can not guarantee best carrier wave compensation even under the situation that does not have noise and interference.
The objective of the invention is to propose to realize in a kind of spread spectrum communication system that carrier wave recovers and method that compensates and the device of designing its realization, in the hope of under the prerequisite that does not reduce the spread spectrum communication system performance, use simple algorithm and obtain accurate carrier frequency offset, the realization carrier wave recovers, and the carrier frequency that transmits is compensated.
The object of the present invention is achieved like this: the method that carrier wave recovers and compensates in the spread spectrum communication system, the wireless base station sends the training sequence of the steering signal that contains useful pseudo noise code modulation to each user terminal, each receiver carries out demodulation sampling and grouping to the steering signal that receives, form the digital spread spectrum signal of spreading rate, this digital spread spectrum signal comprises wanted carrier and residual carrier, it is characterized in that comprising the following steps:
1 with in the first digital spread spectrum signal incoming carrier skew valuation device that contains known carrier wave of receiving terminal and the last carrier shift of knowing after the demodulation;
2 carrier shift valuation devices utilize first multiplier to remove required known carrier frequency in the first digital spread spectrum signal;
3 carrier shift valuation devices utilize despreader/second multiplier to remove pseudo-random code sequence in the first digital spread spectrum signal, obtain the second digital spread spectrum signal;
4 carrier shift valuation devices utilize the carrier shift estimator that carrier shift is estimated to obtain the carrier shift valuation;
5 carrier shift valuation devices utilize the validity detector that the validity of carrier shift valuation is made detection;
6 if the carrier shift valuation is effective, and carrier shift valuation device utilizes the carrier wave adjuster further to adjust required known carrier frequency.
The described carrier shift estimator that utilizes is estimated may further comprise the steps to carrier shift:
Second digital signal after 1 pair one group demodulation is by selected sample length sampling and divide rightly, and each sample centering is contained two elements, and each element is the value of getting the second digital spread spectrum signal of different variate-values;
2 calculate each sample respectively to the contained phase change result of information of element, obtain the result of a series of valuations;
3 calculate the mean value of resulting a series of valuations;
The mean value of 4 pairs of a series of valuations is made normalized, obtains the carrier shift valuation.
The device that carrier wave recovers and compensates in the spread spectrum communication system of the present invention, be connected between the input of the digital spread spectrum signal output part of radio frequency reception channel in the spread spectrum communication system and extended frequency demodulator, and, it is characterized in that to total carrier frequency that timing recovers module outgoing carrier skew estimated value and the frequency mixer conveying of transmission channel comprises required carrier frequency and carrier shift valuation in spread spectrum communication system:
Described carrier wave recovers and the device of compensation comprises first multiplier that is used to remove known carrier frequency, be used to remove despreader/second multiplier of pseudo-random code sequence, the carrier shift estimator that the carrier deviation of cycle of training is made an estimate, the validity detector of detected carrier skew valuation validity, carrier frequency adjuster that required carrier frequency is upgraded and digital oscillator from required carrier frequency to first multiplier that carry;
Described first a digital spread spectrum signal of input termination of first multiplier, another input termination digital oscillator output of first multiplier, the output of first multiplier connects an input of despreader/second multiplier, pseudo-noise code generator output connects another input of despreader/second multiplier, despreader/second multiplier is exported the second digital spread spectrum signal and is connect described extended frequency demodulator and carry ripple skew estimator input, carrier shift estimator output connects validity detector input, the validity detector output end is carried adjuster input frequently, carrier frequency adjuster output termination digital oscillator control end, described digital oscillator is also exported the total carrier frequency that comprises the carrier shift estimated value.
Described carrier shift estimator comprises the switch that the second digital spread spectrum signal after the demodulation of serial is distributed, first register of first element variable value of digital signal samples centering after the storage demodulation, second register of second the element variable value of digital signal samples centering after the storage demodulation, to first, thereby the element in second register is made division arithmetic and is produced the divider that comprises the phase change information result, the right phase change result of information of each sample of divider is averaged the equalizer of computing and average is made the normalized device of normalized, the valuation of normalized device output carrier shift.
The present invention utilizes a limited number of sample (the first digital spread spectrum signal x (k))
X (k), k=1,2 ..., K carries out valuation to carrier shift.In the receiver of user terminal, after the local frequency compensation with its local clock generation, carry out spread spectrum demodulation again, remove pseudo-random code sequence, the baseband signal that obtains is the second digital spread spectrum signal y (k)
y(k)=e
jk(δω0)，k=1，2，…，K
Signal after this demodulation is input in the carrier shift estimator, with the carrier shift of determining that the end is known.It is right that the present invention divides this baseband signal earlier, calculates every pair of phase information that is comprised respectively, averages then to obtain accurate carrier shift valuation.Above-mentioned every pair contains two elements, and each element is the value of getting the y (k) of different variable K values, calculates two of every centerings
Y (k), k=1,2 ..., the method for the phase change between the K element is the conjugate number that respectively first element of every centering be multiply by second element.Like this, by calculate in the demodulated received signal might form right subclass signal, thereby obtain phase change information.
In a device, calculate the phase change information that adjacent y (k) antithetical phrase is concentrated, be calculated to be the phase change information that comprises among the right restituted signal y (k) in another device, wherein in pairs element comprises element in the one or more L that appoints in advance chip or L the sampling interval.System averages the result of at least one subclass of obtaining, then mean value is carried out normalization, to obtain the valuation of carrier shift.Normalization adopts one or more L chips or L sampling interval to carry out.After finishing the carrier shift valuation, system adjusts required carrier frequency according to this carrier shift valuation, and adjusted required carrier frequency is used for the digital spread spectrum signal that arrives through demodulated received is removed residual carrier.
Before adjusting required carrier frequency with the carrier shift valuation, must check at first whether the carrier shift valuation is correct, only guaranteeing just to carry out the carrier frequency adjustment under the correct condition.This inspection method comprises checks the variable quantity of present carrier shift valuation with respect to other a plurality of carrier shift valuations, and whether this variable quantity surpasses predetermined thresholding; Perhaps use the carrier shift that demodulated received signal is carried out obtaining behind the fourier transform to obtain the reference value of carrier shift valuation, again the carrier shift valuation that will obtain with this method therewith reference value compare, determine that its deviation is whether in predetermined scope.Also to check the signal to noise ratio (snr) of demodulated received signal at last, judge that this SNR is whether below predefined thresholding.
The present invention compares with existent method not having can to obtain carrier shift valuation accurately under the situation of noise, and the advantage of the inventive method is:
Utilizes the structural information of the received signal after the demodulation to obtain of carrier deviation and effectively estimate, and existent method is to realize high-precisionly to increase amount of calculation that the amount of calculation of this method is fixed, the restriction of no precision or estimation range;
Adopt validity test to guarantee reliability, only adopt effective carrier shift to estimate required carrier frequency is carried out adaptive adjustment, thereby eliminated the possibility of pernicious mistake;
No memory requirement, existent method must determine that time enough and memory space construct the sample with the sinusoidal single-tone of memory gap, this will become very difficult along with the increase of required precision, and valuation scheme of the present invention is all minimum to the requirement of memory space and computing time.
Therefore, algorithm is simple, to use less memory cell, reliability height be characteristics of the present invention.
Fig. 1. typical spread spectrum communication system structured flowchart
Fig. 2. the structured flowchart of carrier shift valuation device among the present invention
Fig. 3. the flow chart that a carrier wave recovers the valuation process is described among the present invention
Fig. 4. the flow chart of carrier shift valuation process among Fig. 2 is described
Fig. 5. the block diagram of carrier shift estimator device among the present invention
Further specify technology of the present invention below in conjunction with embodiment and accompanying drawing
Referring to Fig. 1, a typical spread spectrum communication system structure that comprises carrier shift valuation device 6 is shown.Mainly comprise and be used to launch or receive the antenna 10 that is modulated at the rf modulated signal (RF) on the simulation carrier frequency, by spread spectrum modulator (SS) 26, shaping pulse module 22, frequency mixer 64, regularly adjuster 18, and the transmission channel formed of upconverter 14 and recover the receive path that module 28 and spread spectrum (SS) demodulator 24 are formed by low-converter 12, sampler 16, carrier shift valuation device 6, timing.
Time division duplex (TDD) mode that the emission of spread spectrum communication system has received The data, i.e. emission (TX) is carried out in different time frames with reception (RX).
During reception, the rf modulated signal of antenna 10 outputs is given low-converter 12, and low-converter becomes rf modulated signal into baseband signal, promptly removes carrier frequency, and information demodulation from the simulation carrier frequency is come out and sent sampler 16.Sampler 16 is finished the work of two aspects, the one, the baseband signal of receiving is carried out analog to digital conversion produce the spread spectrum digital signal, the 2nd, the baseband signal of receiving is carried out over-sampling, then sample is extracted, produce chip rate signal (chip rate signal), so sampler 16 comprises digital spread spectrum signal and chip rate signal to the signal 40 that carrier shift valuation device 6 provides.Sampler 16 is used for sample is extracted from the timing signal that regularly recovers module 28 acquisitions, so that can correctly produce chip rate signal.
As previously mentioned, though the effect of low-converter is that the simulation carrier frequency is removed from received signal, but because emission, receive the inaccurate of frequency difference between two oscillators and radiating portion modulator, make and also include the base band carrier frequency of knowing at the end in the baseband signal 40, carrier shift valuation device 6 be exactly to the carrier frequency in the baseband signal estimate (the carrier frequency difference in the baseband signal is time dependent, generally can think to change around a fixing point, this fixing point is called valuation again, refer to required carrier frequency value, therefore the base band carrier frequency can be regarded required known carrier frequency value and the last carrier deviation value sum of knowing as, must estimate and compensate carrier deviation, could realize that carrier wave recovers accurately).
Carrier shift valuation device 6 has been removed the required known carrier frequency and the signal of carrier deviation to extended frequency demodulator 24 outputs, make demodulation process by extended frequency demodulator 24 by conventional method, the message recovery that is about to the remote terminal transmission comes out, and carrier shift valuation device 6 also recovers the total carrier frequency estimated value of frequency mixer 64 conveyings of module 28 and transmission channel simultaneously to timing.
Regularly recover module 28 and receive the carrier frequency estimated value from carrier shift valuation device 6, receive the output signal 40 of sampler 16 simultaneously, regularly recover module 28 according to carrier shift valuation decision timing signal, when collecting mail, provide timing signal to timing adjuster 18 to sampler 16 with when posting a letter.
Spread spectrum modulator 26 is modulated the message data that is sent to far-end by current current techique, is about to message data and modulates mutually with a pseudo noise signal or spread-spectrum signal.Modulation back signal send shaping pulse module 22, and signal energy is limited among the bandwidth.Signal send frequency mixer 64 after the shaping, signal after 64 pairs of shapings of frequency mixer and total carrier frequency estimated value (required carrier frequency value and carrier shift estimated value sum) are carried out mixing, signal is modulated on the carrier frequency that is obtained by carrier shift valuation device 6, carries out precompensation to transmitting so that use with the difference of oscillator.
Frequency mixer 64 outputs connect regularly adjuster 18, regularly adjuster 18 is regularly regulated emission according to the timing signal that regularly recovers module 28 and provide, obtain baseband signal and serve frequency converter 14, upconverter 14 usefulness simulation carrier frequency is modulated baseband signal, 10 emissions of modulation signal antennas.In technical scheme shown in Figure 1, by the modulation that frequency mixer 64 is realized information, the signal after the band spectrum modulation just has required carrier frequency and carrier deviation, and upconverter 14 is further baseband message information and the modulation of simulation carrier frequency, to launch.
In sum, image duration when the first initial reception, antenna 10 received signals, low-converter 12 is down-converted to baseband signal with the signal that receives from radio frequency, sampler 16 produces the digital spread spectrum signal with the base band data digitlization, because baseband signal is still modulated by the carrier deviation that known required carrier frequency and end are known after the down-conversion, therefore to estimate by 6 pairs of carrier deviations of carrier shift valuation device, recover module 28 and frequency mixer 64 provides required carrier frequency value to timing then.
Image duration when second emission, message data to be sent is modulated the horizontal pulse shaping of going forward side by side by spread spectrum modulator 26, signal send frequency mixer 64 after the shaping, realize mixing with carrier shift valuation device 6 output carrier frequency, signal after the mixing send regularly adjuster 18, the baseband signal of its output is served frequency converter 14, and upconverter 14 is modulated to baseband signal on the simulation carrier frequency, forms the emission of radiofrequency signal antennas.
Usually, a spread spectrum communication system all comprises wireless base station and a plurality of user terminals of communicating by letter with it.The communication of Any user is at first all since a cycle of training, and actual speech or message data are following closely.In the wireless base station, emission to training series of each user terminal transmission, provides the carrier wave reference value for the user terminal receiver with the steering signal of each user's PN sequence (pseudo noise code) modulation.(grouping) sampled, extracted to the receiver of user terminal to the steering signal that receives, and forms the digital spread spectrum signal of spreading rate.Because the timing differential of receiving-transmitting sides contains the residual carrier component in this digital spread spectrum signal, carrier wave can be decomposed into required carrier wave and residual carrier two parts in other words, and available mathematical formulae with this digital spread spectrum signal representation is:
X (k)=p (k) e
Jk (ω 0+ δ ω 0)In the formula, p (k) expression PN sign indicating number sequence, ω
0Represent required carrier frequency value, δ ω
0Represent that end to be estimated knows the carrier shift estimated value.Carrier shift valuation device 6 is exactly will be according to the data sample x (k) of limited quantity, k=1 ..., K carries out valuation and compensation to undesirable carrier deviation.Carrier shift valuation device 6 needs to remove PN sign indicating number sequence earlier from the digital spread spectrum signal, then the required carrier frequency that the local digital oscillator provides is compensated.Received signal y (k)=e after the demodulation soon
Jk (δ ω 0), k=1 ..., K is input in the carrier shift estimator, to obtain the carrier deviation that the end is known.
Before the present invention, to δ ω
0The conventional method of estimating is that method of the present invention is to calculate y (k) with y (k) and the compact arranged sinusoidal single-tone sample mixing that prestores, k=1 ..., the phase change information of K is with accurate estimation carrier deviation.
Carrier shift valuation device 6 of the present invention can be applicable to comprise in the various communication systems of spread spectrum and non-spread spectrum, no matter information is to be modulated on simulation carrier frequency or other other signals, all can know that the baseband signal of carrier frequency analyzes, the end is known that carrier frequency compensates comprising the end.
Carrier shift valuation device 6 can have multiple implementation, comprise and adopt one or more programmable cpus, the logical devices that microcontroller or other programming devices separate etc. also can adopt one or more digital signal processors (DSP) and one or more pieces memories.
Referring to Fig. 2, the enforcement structure of a carrier shift valuation device 6 is shown.Comprise first order multiplier (or claiming frequency mixer) 33, digital oscillator 34, PN code generator 30, carrier shift estimator 38, validity detector 46 and carrier frequency adjuster 36.
Remove the analog radio frequency carrier frequency among digital spread spectrum (or non-spread spectrum) signal 40 x (k) of input, but still included required known carrier frequency and the last carrier deviation of knowing.The x (k) of input is as an input signal of first order multiplier 33, digital oscillator 34 required carrier frequency of output and as another input signal of first order multiplier 33, first order multiplier 33 has been finished the work of removing required carrier frequency from the x (k) of input with two signal mixings.
The output signal of multiplier 33 is sent second level multiplier 32 (or claiming despreader), multiplier 32 with input signal with multiply each other from one of PN code generator 30 identical with it PN sign indicating number sequence, further remove PN sign indicating number sequence, so first, second grade multiplier 33,32 has realized removing the purpose (can omit second level multiplier 32 and PN code generator in the non-spread spectrum scheme) of required carrier frequency and PN sign indicating number sequence from the x (k) of input.
Received signal y after the demodulation (k) is sent to extended frequency demodulator 24 and send carrier shift estimator 38, in cycle of training carrier deviation is made an estimate, and the demodulated received signal after cycle of training then send extended frequency demodulator 24, recovers the message data of emission.Carrier deviation among the received signal y (k) after 38 pairs of demodulation of carrier shift estimator is made carrier deviation estimation accurately and is exported estimated signal 44 to validity detector 46, validity to valuation is tested, this validity test is optionally, also can omit and not do.
Whether valuation reaches the requirement of upgrading required carrier frequency can multiple verification scheme, uses δ ω
0(n) be illustrated in carrier deviation that n received frame obtain estimate can with current carrier deviation estimate with before carrier shift estimated value relatively because the variation of actual carrier frequency is slowly, so this relative variation, i.e. [δ ω
0(n)-δ ω
0(n-k)], k=1 ..., K, any valuation that surpasses thresholding all will be excluded.Can also allow the carrier shift estimated sequence by low pass finite impulse response (FIR) filter, carry out smoothly changing big valuation.Also can in frequency domain, carry out fourier transform (FFT), obtain the reference valuation of carrier deviation earlier, if the reference valuation of carrier deviation not in the preset range of carrier shift valuation, judges that then the carrier deviation value is invalid the received signal after the demodulation.Can also carry out signal to noise ratio (snr) to the received signal after the demodulation earlier and detect,, just judge that the carrier frequency valuation is invalid if SNR is lower than predetermined threshold value.
Referring to Fig. 3 and in conjunction with referring to Fig. 1, the carrier shift valuation process of the valuation of carrier shift shown in figure device 6.
Step 102 is communication system receiving digital signals (in spread spectrum communication system, the digital signal of reception comprises the digital spread spectrum signal), with conventional method, adopts the low-converter sampler to obtain the digital spread spectrum signal.Step 104 is to remove required carrier frequency from received signal, in order to recover the carrier deviation that the end is known in digital signal, utilizes the at first demodulation or remove required carrier frequency of first order multiplier.Step 106 is removed PN sign indicating number sequence from the spread spectrum digital signal, finished by second level multiplier.For the carrier deviation of recovering to know at the end from the digital spread spectrum signal that receives at first wants demodulation to remove PN sign indicating number sequence and required carrier frequency.After the step 106, the demodulated received signal that is obtained is expressed as y (k)=e
Jk (δ ω 0), k=1 ..., K.These values are delivered to carrier shift estimator 38, and with the carrier deviation that determines that the end is known, if the no-load frequency deviation is poor, signal y (k) will only comprise DC component.Owing to have carrier deviation, so signal y (k) contains a sinusoidal signal.
Step 108 is the carrier shift valuation, a kind of preferred scheme is that to obtain a lot of demodulated received signals earlier right, carries out division arithmetic again, thereby produces a series of phase change result of information that comprise, at last selectively to the result average, normalized, obtain the carrier shift valuation.
The validity that step 110 is finished the carrier shift valuation detects, the assessment estimated value.
Referring to Fig. 4, Fig. 4 illustrates the carrier shift valuation process of Fig. 3 step 108, the operating process of carrier shift estimator 38 among also middle Fig. 2.
Received signal y (k)=e behind carrier shift estimator 38 receiving demodulations
Jk (δ ω 0), k=1 ... K by first element and the second element conjugate multiplication wherein, realizes division arithmetic.
Step 122, estimator 38 is divided into paired signal with the received signal after the demodulation, calculates phase change more in pairs.Specifically, each is formed the y (k) by two different value of K, and promptly every pair contains two elements, and each element is the y (k) that is formed by different value of K.Being divided by just of every pair of element of demodulated received signal, comprise the phase change result of information thereby calculate each centering divided by different y (k) value.This method will may be done to be divided by at least to total to two elements of the demodulated received signal centering of a subclass concentrating.
The technical scheme of being divided by can have multiple, wherein first kind of scheme is: division is to carry out in neighbor at least one subclass to formation of y (k), promptly is made of the adjacent value of y (k), as { y (1), y (2)], { y (2), y (3) }, { y (3), y (4) } or the like, promptly described sample centering, the k value of each centering is adjacent, and certain is a pair of to be adjacent right k value and to repeat.
Second kind of scheme is: division is to carry out at least one subclass centering of demodulated received signal, wherein has predetermined L sheet between each right element at interval.An example of this scheme be such one to series, i.e. { y (1), y (4) }, { y (2), y (5) }, { y (3), y (6) } or the like, promptly described sample centering, two k values of each sample centering all have predetermined L sheet at interval, and the k value of each sample centering two element is adjacent respectively.
The third scheme is: division arithmetic is concentrated at such son of demodulated received signal at least and is carried out, and wherein each is spaced apart the predetermined L chip-spaced that two or more do not wait to element.One of this scheme is right
Series as { y (1), y (2) }, { y (2), y (3) }, { y (3), y (6) }, { y (4), y (7) } or the like, promptly described sample centering, the k value of each centering has unequal interval, each minute the k value of centering first element adjacent, in this scheme, require at interval each of the pre-stator of this difference carried out normalization to the group.
After step 122 was finished division arithmetic, step 124 was calculated the mean value of at least one subclass that comprises the phase change information result, thereby calculates the carrier deviation estimated value.The result that wherein a kind of preferred scheme will use all to calculate, another kind of scheme then use these results' a subclass, and for example, high and minimum one or more results are dropped, and remaining result is used for average treatment.
In step 126, if desired, can carry out normalization to mean value, thereby calculate carrier deviation.Adopt L chip-spaced to carry out normalization with a plurality of uses in division is handled.First kind of scheme is that division is handled the vicinity that only adopts y (k) to carrying out, and the L chip-spaced is 1, does not at this moment just need normalization.Second kind of scheme is that the y (k) that has only single predetermined L chip-spaced is handled carrying out division, use L compensation factors L chip-spaced, carries out normalized.
As mentioned above, in division arithmetic to y (k) have of unequal interval (one or more predetermined L chip-spaced) when subclass is handled, normalized will adopt the group of different predetermined spaces (one or more L chip-spaced) to handle at each.And this normalized will be carried out before average treatment.On the other hand, system can be earlier to adopting different pre-stators each group at interval to calculate one or more mean values.And then, by each accordingly predetermined chip-spaced each mean value is carried out normalization.This normalized produces one or more normalized mean values.System averages one or more normalization average value more then, calculates the carrier deviation estimated value.
In non-spread spectrum scheme, division arithmetic comprises the received signal after the demodulation is carried out at least one subclass of concentrating, and wherein the distance between the every pair of element is one or more predetermined time intervals that do not wait.Also can adopt and above description similar methods, the L chip-spaced that wherein one or more do not wait can substitute with one or more time intervals of not waiting.
In Fig. 4 flow chart, required carrier frequency initial value is made as 0, first carrier shift is estimated to round a base band carrier frequency, and in the computing second time, initial carrier frequency offset is estimated just to be used as required carrier frequency value, and determines new deviation based on this required carrier frequency value.In the computing afterwards, the required carrier frequency of combination and carrier shift estimate to be used as required carrier frequency value next time.Flow process order is like this carried out, and promptly estimates required carrier frequency is adjusted based on new skew, so that frequency is compensated in handling in reception, emission after this.
Referring to Fig. 5, embodiment for carrier frequency offset estimator 38, signal 42 after the demodulation (y (k)) given switch 50 serially, and be assigned to first register 52 and second register 54, storage has the right element of demodulated received signal of L chip at interval respectively, register 52 storage first element variable y (k1) values, register 54 second element variable y of storage (k2) values.
To the time interval be the buffering of the sample of L chip, only need the register of L length.Can adopt equalizer 58 as required, thereby store with regard to not needing.Distinctive feature of the present invention is to obtain high-precision carrier deviation with minimum sampling storage and least amount calculation to estimate.
Ideally, the received signal after the demodulation is simple tone signal, hints that promptly any one sample centering includes enough carrier deviation information.Yet in actual use,, thereby to adopt the sample that a lot of L chips or the time interval may not wait right because that noise and other disturb is inevitable.Use a large amount of samples to and subsequently average, normalization, purpose is to eliminate noise and interference.
In sum, valuation process comprises:
Great amount of samples with predetermined time interval L to making division or making conjugate multiplication, is obtained comprising the series of results of phase change information, and wherein n (k) represents distracter,
Calculate the average of resulting a series of valuations;
The valuation of the normalization average phase that adopts factor L as carrier deviation.
In the scheme that has, L can elect 1 as simply, promptly only uses adjacent element in calculating, and the estimation of carrier deviation does not need normalization just can finish.In another program, have received signal after the demodulation at interval of one or more pre-stators, produce a series of phase change result of information that comprise at first being divided by.Every kind of result uses with its corresponding intervals and carries out normalization, produces a series of normalization result, at last these normalization result is averaged, and promptly obtains carrier deviation and estimates.In the scheme that also has, has received signal after the demodulation at interval of one or more pre-stators at first being divided by, produce a series of phase change result of information that comprise, each that has same intervals then as a result subclass by average respectively, adopt with their corresponding intervals again and carry out normalization, obtain a series of normalized value, the result averages to these normalization, promptly obtains carrier deviation and estimates.
Obviously, in every kind of scheme, the calculating of estimating is changeless, so the precision that carrier deviation is estimated without limits.But comparing with existent method, its accuracy, cost obviously have advantage.L does not select 1 in the preferred scheme, and its reason is: phase difference from δ ω
0Be increased to L δ ω
0, make easier the detecting of phase place of z, thus can be to real carrier deviation δ ω
0Estimate more accurately; In addition, the increase of phase place has also increased antijamming capability, thereby estimates more reliable.
Claims (15)
1. carrier wave recovers and the method for compensation in the spread spectrum communication system, the wireless base station sends the training sequence of the steering signal that contains useful pseudo noise code modulation to each user terminal, each receiver carries out demodulation sampling and grouping to the steering signal that receives, form the digital spread spectrum signal of spreading rate, this digital spread spectrum signal comprises wanted carrier and residual carrier, it is characterized in that comprising the following steps:
1.1 in the first digital spread spectrum signal incoming carrier skew valuation device that contains known carrier wave of receiving terminal and the last carrier shift of knowing after the demodulation;
1.2 carrier shift valuation device utilizes first multiplier to remove required known carrier frequency in the first digital spread spectrum signal;
1.3 carrier shift valuation device utilizes despreader/second multiplier to remove pseudo-random code sequence in the first digital spread spectrum signal, obtains the second digital spread spectrum signal;
1.4 carrier shift valuation device utilizes the carrier shift estimator that carrier shift is estimated to obtain the carrier shift valuation;
1.5 carrier shift valuation device utilizes the validity detector that the validity of carrier shift valuation is made detection;
1.6 if the carrier shift valuation is effective, carrier shift valuation device utilizes the carrier wave adjuster further to adjust required known carrier frequency.
2. carrier wave recovers and the method for compensation in a kind of spread spectrum communication system according to claim 1, it is characterized in that the described carrier shift estimator that utilizes estimates to comprise to carrier shift:
2.1 by selected sample length sampling and divide rightly, each sample centering is contained two elements to second digital signal after the group demodulation, each element is the value of getting the second digital spread spectrum signal of different variate-values;
2.2 calculate each sample respectively to the contained phase change result of information of element, obtain the result of a series of valuations;
2.3 calculate the mean value of resulting a series of valuations;
2.4 the mean value to a series of valuations is made normalized, obtains the carrier shift valuation.
3. the method that carrier wave recovers and compensates in a kind of spread spectrum communication system according to claim 2 is characterized in that:
Described sample centering, the variate-value of each sample centering is adjacent, certain is a pair of to be adjacent right variate-value and to repeat.
4. the method that carrier wave recovers and compensates in a kind of spread spectrum communication system according to claim 2 is characterized in that:
Described sample centering, two variate-values of each sample centering all have predetermined chip-spaced, and the variate-value of each sample centering two element is adjacent respectively.
5. the method that carrier wave recovers and compensates in a kind of spread spectrum communication system according to claim 2 is characterized in that:
Described sample centering, the variate-value of each sample centering has the chip-spaced that does not wait, and the variate-value of each sample centering first element is adjacent.
6. the method that carrier wave recovers and compensates in a kind of spread spectrum communication system according to claim 2 is characterized in that:
Described normalized is the second digital spread spectrum signal with predetermined chip-spaced or sampling interval to be made division by selected sample length handle.
7. the method that carrier wave recovers and compensates in a kind of spread spectrum communication system according to claim 1 is characterized in that:
Described validity to the carrier shift valuation is made and being detected is that current carrier shift valuation and former carrier shift valuation are compared, and gets rid of the valuation that changes relatively above thresholding, and first carrier shift valuation is the base band carrier frequency after the whole demodulation.
8. the method that carrier wave recovers and compensates in a kind of spread spectrum communication system according to claim 1 is characterized in that:
Described validity to the carrier shift valuation is made and being detected is that carrier shift valuation sequence is passed through the low pass finite impulse response filter, carries out smoothing processing to changing big valuation.
9. the method that carrier wave recovers and compensates in a kind of spread spectrum communication system according to claim 1 is characterized in that:
Described validity to the carrier shift valuation is made and being detected is earlier the second digital spread spectrum signal after the demodulation to be carried out fourier transform in frequency domain, obtain the reference valuation of carrier deviation, will not remove with reference to the carrier shift valuation in the valuation scope in predetermined carrier deviation.
10. the method that carrier wave recovers and compensates in a kind of spread spectrum communication system according to claim 1 is characterized in that:
Described validity to the carrier shift valuation is made and being detected is earlier the second digital spread spectrum signal after the demodulation to be carried out signal to noise ratio to detect, and removes the carrier shift valuation that signal to noise ratio is lower than predetermined threshold.
11. the method that carrier wave recovers and compensates in a kind of spread spectrum communication system according to claim 1 is characterized in that:
The required known carrier frequency of described adjustment is the additive value that required carrier frequency value is revised as former required carrier frequency value and carrier shift valuation.
12. the method that carrier wave recovers and compensates in a kind of spread spectrum communication system according to claim 1 is characterized in that:
The required known carrier frequency of described adjustment is to calculate the confidence level that carrier deviation is estimated.
13. carrier wave recovers and the device of compensation in the spread spectrum communication system, be connected between the input of the digital spread spectrum signal output part of radio frequency reception channel in the spread spectrum communication system and extended frequency demodulator, and, it is characterized in that to total carrier frequency that timing recovers module outgoing carrier skew estimated value and the frequency mixer conveying of transmission channel comprises required carrier frequency and carrier shift valuation in spread spectrum communication system:
Described carrier wave recovers and the device of compensation comprises first multiplier that is used to remove known carrier frequency, be used to remove despreader/second multiplier of pseudo-random code sequence, the carrier shift estimator that the carrier deviation of cycle of training is made an estimate, the validity detector of detected carrier skew valuation validity, carrier frequency adjuster that required carrier frequency is upgraded and digital oscillator from required carrier frequency to first multiplier that carry;
Described first a digital spread spectrum signal of input termination of first multiplier, another input termination digital oscillator output of first multiplier, the output of first multiplier connects an input of despreader/second multiplier, pseudo-noise code generator output connects another input of despreader/second multiplier, despreader/second multiplier is exported the second digital spread spectrum signal and is connect described extended frequency demodulator and carry ripple skew estimator input, carrier shift estimator output connects validity detector input, the validity detector output end is carried adjuster input frequently, carrier frequency adjuster output termination digital oscillator control end, described digital oscillator is also exported the total carrier frequency that comprises the carrier shift estimated value.
14. the device that carrier wave recovers and compensates in a kind of spread spectrum communication system according to claim 13 is characterized in that:
Described carrier shift estimator comprises the switch that the second digital spread spectrum signal after the demodulation of serial is distributed, first register of first element variable value of digital signal samples centering after the storage demodulation, second register of second the element variable value of digital signal samples centering after the storage demodulation, to first, thereby the element in second register is made division arithmetic and is produced the divider that comprises the phase change information result, the right phase change result of information of each sample of divider is averaged the equalizer of computing and average is made the normalized device of normalized, the valuation of normalized device output carrier shift.
15. the device that carrier wave recovers and compensates in a kind of spread spectrum communication system according to claim 13 is characterized in that:
Described carrier shift estimator is by one or more data signal processor and one or more respective memory, and programmable cpu microcontroller or programmable logic device are formed.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| CN97115151A CN1061205C (en) | 1997-07-24 | 1997-07-24 | Method for device of carrier exalting and compensating in frequency spreading communication system |
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| Application Number | Priority Date | Filing Date | Title |
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| CN97115151A CN1061205C (en) | 1997-07-24 | 1997-07-24 | Method for device of carrier exalting and compensating in frequency spreading communication system |
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| CN1175171A CN1175171A (en) | 1998-03-04 |
| CN1061205C true CN1061205C (en) | 2001-01-24 |
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| CN97115151A Expired - Lifetime CN1061205C (en) | 1997-07-24 | 1997-07-24 | Method for device of carrier exalting and compensating in frequency spreading communication system |
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Families Citing this family (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3418981B2 (en) | 2000-02-16 | 2003-06-23 | 日本電気株式会社 | Spread spectrum communication synchronization acquisition circuit |
| CN1131653C (en) * | 2000-03-27 | 2003-12-17 | 信息产业部电信科学技术研究院 | Small-region initial search method for CDMA digital mobile communication system |
| US6532251B1 (en) * | 2001-08-16 | 2003-03-11 | Motorola, Inc. | Data message bit synchronization and local time correction methods and architectures |
| CN1259785C (en) * | 2003-08-04 | 2006-06-14 | 大唐移动通信设备有限公司 | Method for obtaining carrier frequency departure of time division synchronous CDMA (TD-SCDMA) user terminal and equipment |
| US8438026B2 (en) * | 2004-02-18 | 2013-05-07 | Nuance Communications, Inc. | Method and system for generating training data for an automatic speech recognizer |
| CN100356704C (en) * | 2004-06-02 | 2007-12-19 | 大唐移动通信设备有限公司 | Method for compensating frequency offset in wireless mobile communication system |
| CN101237436B (en) * | 2007-01-31 | 2011-03-23 | 扬智科技股份有限公司 | A method and circuit for detecting carrier frequency deviation and sampling frequency deviation |
| CN103634255B (en) * | 2012-08-20 | 2017-04-05 | 中国电子科技集团公司第十研究所 | The method of quick estimation MSK signal carrier |
| JP6165888B2 (en) | 2013-02-21 | 2017-07-19 | クゥアルコム・インコーポレイテッドＱｕａｌｃｏｍｍ Ｉｎｃｏｒｐｏｒａｔｅｄ | Method and apparatus for data assisted timing recovery in 10GBASE-T system |
| CN103973622B (en) * | 2014-05-26 | 2017-03-01 | 许昌学院 | One kind efficiently MSK communication check demodulation method |
| CN106656386B (en) * | 2015-10-30 | 2019-08-27 | 南京中兴新软件有限责任公司 | A kind of local clock method of adjustment, time service method and device |
| CN107094042B (en) * | 2016-02-18 | 2020-09-25 | 中国移动通信集团公司 | Channel information indication method, system and receiving terminal equipment |
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| US4630283A (en) * | 1985-07-17 | 1986-12-16 | Rca Corporation | Fast acquisition burst mode spread spectrum communications system with pilot carrier |
| US5303257A (en) * | 1992-12-31 | 1994-04-12 | Gte Government Systems Corporation | Carrier frequency correction for a DSSS communication system |
| WO1995024086A2 (en) * | 1994-02-25 | 1995-09-08 | Philips Electronics N.V. | A multiple access digital transmission system and a radio base station and a receiver for use in such a system |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US4630283A (en) * | 1985-07-17 | 1986-12-16 | Rca Corporation | Fast acquisition burst mode spread spectrum communications system with pilot carrier |
| US5303257A (en) * | 1992-12-31 | 1994-04-12 | Gte Government Systems Corporation | Carrier frequency correction for a DSSS communication system |
| WO1995024086A2 (en) * | 1994-02-25 | 1995-09-08 | Philips Electronics N.V. | A multiple access digital transmission system and a radio base station and a receiver for use in such a system |
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| CN1175171A (en) | 1998-03-04 |
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