CN1365210A - Multipath searching and channel evaluating method based on digital matched filter - Google Patents
Multipath searching and channel evaluating method based on digital matched filter Download PDFInfo
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Abstract
Digital matched filter is used to complete digital matched filtering of one or several spread spectrum code channel, provide continuously the correlation value of corresponding spread spectrum code channel, complete non-correlative accumulation and judgement of the correlation value of code channel to be captured and thus realize the spread spectrum code capture of the said code channel. Similarly, the correlation value output by the digital matched filter may be used in correlative or non-correlative accumulation and judgement for searching multipath signal in relative higher gain and obtained reliable channel estimation result of every path. To the spread spectrum code channel to be code sheet traced, calculating the leading and lag correlation values of one or several path correlation peaks outupt by the digital match filter can obtain code sheet tracing error signal and thus to complete code sheet tracing.
Description
(1) technical field:
The invention belongs to Direct swquence spread spectrum (DS/SS) communications field, comprise code division multiple access (CDMA) communication and the cellular mobile communication and the wireless access that adopt direct sequence spread spectrum skill.
The present invention relates to follow the tracks of implementation based on the catching of digital matched filter, path search, channel estimating and relevant chip, it is a kind of brand-new cdma communication system receiver implementation, adopt the present invention can reduce the complexity of receiver, and improve the performance of receiver.
(2) background technology:
The receiver of any DSSS wireless communication system all must have spread spectrum code acquisition, how through functions such as search, channel estimating and chip tracking.The object of the present invention is to provide a kind of new implementation, can realize the seizure of spreading code effectively with lower complexity,, and improve the performance of receiver how through functions such as search, channel estimating and chip tracking based on digital matched filter.
(3) summary of the invention:
Basic principle of the present invention is: utilize digital matched filter to finish the digital matched filtering of one or more spread spectrum code channels, the correlation of corresponding spread spectrum code channel is provided continuously, the correlation of the spread spectrum code channel that catch is carried out the spread spectrum code acquisition that noncoherent accumulation and judgement can realize this code channel; Utilize the correlation of digital matched filter output be concerned with equally or noncoherent accumulation and compare judgement, can search multipath signal with higher gain and obtain each reliable channel estimation results directly; Carry out the spread spectrum code channel that chip is followed the tracks of at needs, the lead and lag correlation of the relevant peaks in one or more paths of digital matched filter output is carried out computing can obtain the chip tracking error signal, can finish chip in view of the above and follow the tracks of.
Beneficial effect of the present invention: utilize the present invention can under the situation of low implementation complexity, realize high performance spread spectrum code acquisition neatly, how to follow the tracks of through search, channel estimating and chip.
(4) description of drawings:
Fig. 1 is the inventive method block diagram;
Fig. 2 follows the tracks of and channel estimating realization circuit diagram based on the chip of matched filter.
(5) embodiment:
Further describe embodiment below in conjunction with Fig. 1, Fig. 2:
Digital matched filter is the central module of this invention.Base-band analog signal enters into digital matched filter after the A/D conversion, digital matched filter is finished the sign indicating number filtering to the input digit baseband signal, and the correlation of corresponding spread spectrum code channel is provided continuously.Here, the progression of digital matched filter can be adjusted as required flexibly, the number of spread spectrum code channel can be adjusted as the case may be, different code channels can also utilize to the time-division same matched filtering circuit, as the putative signal sampling rate is 2 times of spreading rates, just can realize the matched filtering of 4 code channels with a digital matched filtering circuit with 8 times of chip clock.Consider the situation of a code channel,, higher correlation peak when local spreading code is consistent with the input signal phase place, occurs, occur low correlation when phase place is inconsistent by the autocorrelation performance of spreading code.These correlations carry the auto-correlation/cross-correlation information of time delay phase information, multipath diffuse information and the spreading code of input signal, catch, path search, channel estimating and chip follow the tracks of and can export these information that correlation carries based on digital matched filter and finish, they extract by demand separately respectively.
Initial acquisition is to finish the first step that spread-spectrum signal receives, and band spread receiver obtains the synchronously thick of spreading code by initial acquisition.Initial acquisition based on digital matched filter is a kind of catching method of classics, can adjudicate as one or many by non-coherent detector usually and finish.Concrete capture circuit and search strategy can be considered flexibly according to the quality of performance requirement of catching and input signal.Specifically, catch and to be divided in limited time and two kinds in unlimited time, its performance index are embodied on the Several Parameters such as mean acquisition time, capture time variance, acquisition probability and the acquisition probability of prescribing a time limit, and concrete capture circuit should be able to satisfy the performance requirement of these indexs.The characteristics of catching based on digital matched filtering are can realize catching fast, because digital matched filtering can provide the correlation of each phase place of spreading code continuously.In addition, can be based on catching of digital matched filter by matched filter output correlation being made the detection performance that relevant or noncoherent accumulation improve capture circuit.It should be noted that characteristics of the present invention do not lie in this, initial acquisition is one of function of realizing of this invention, based on the catching of matched filter, path search, chip is followed the tracks of and channel estimating is a mutual restriction, the integral body that is closely connected.
Enter tracking mode after initial acquisition is finished, can start path search and channel estimation circuit simultaneously.Tracking circuit is realized with delay phase-locked loop (DLL).Usually delay phase-locked loop with late/morning two correlators realize, the correlation of two correlator outputs obtains the phase demodulation error relatively late/early, and the phase demodulation error goes to control the ADC sampling clock phase or adjust the thin tracking that local spreading code phase place realizes spreading code after phase-locked loop filtering.
Figure 2 shows that based on the chip of matched filter and follow the tracks of and channel estimating realization circuit.The present invention adopts the mode of adjusting the sampling ADC clock to realize the accurate tracking of spreading code.As shown in Figure 2, directly from the correlation of matched filter output, extract based on the phase demodulation error of the DLL of matched filter, do not need to do in addition slow/morning correlator.D represents delayer in the accompanying drawing, and 2D is the delay inequality between the correlation late/early, and the time delay size can decide according to the requirement of input correlation speed and phase demodulation.The phase demodulation error is extracted concrete adopt relevant or incoherent can the decision flexibly, if adopt relevant error to extract, then can directly utilize channel estimation results to realize.The correlation length of phase demodulation error can change flexibly by the accumulative frequency of adjusting correlation, and DLL adjusts the frequency of clock and also can adjust flexibly.In addition, because wireless environment and bit rate is different, received signal has the branch of Dan Jing and multipath, and to the reception of single drive signal, the DLL error is extracted the influence that must not consider multipath.The implementation of DLL can determine flexibly under the multipath signal.Because have only an ADC sampling in this structure, i.e. the clock of DLL adjustment has only one, so the phase demodulation error is extracted the form that adopts rake to merge under the multi-path environment, synthetic error signal is adjusted the ADC clock behind loop filtering.The diversity of phase demodulation error can adopt the selecting type diversity, and which kind of mode the diversity mode that also can adopt equal gain combining or high specific to merge specifically adopts to select then flexibly according to demand.DLL adjusts the local clock of ADC sampling, and the result makes the local clock and the clock that transmits reach frequency lock, finely tunes chip timings simultaneously, realizes the accurate tracking of spreading code.It should be noted that DLL adjusts the precision of clock can flexible, and the ADC sampling clock can be that DLL adjusts the directly clock of generation of back, also can be the low rate clock that produces behind its frequency division, and can not influence the tracking accuracy of DLL.
The performance of DLL and tracking accuracy can influence path search and performance for estimating channel, and path search and performance for estimating channel influence performance and precision that DLL follows the tracks of simultaneously conversely.Specifically, the performance of DLL depends under certain signal environment the implementation (as previously mentioned) that adopts, and DLL tracking accuracy height, performance are good, and the detection probability of path search will be high, and false alarm probability will reduce, and channel estimating will be more reliable simultaneously.Conversely, path search provides timing base for DLL and channel estimating, and channel estimating provides the channel response parameter for relevant DLL, so the order of accuarcy of path search and channel estimating affects the tracking performance of DLL again.
Based on the path search of digital matched filtering be determined that signal arrives uncertain interval (by the radio frames of signal regularly and the signal determined of the time delay of wireless channel expansion may due in scope) after, search for the due in of the matched filtering output correlation of this interval correspondence with definite separable path.Different with initial acquisition is, initial acquisition is to determine lock-on signal under the uncertain interval situation that signal arrives.When wireless environment becomes slowly, as perseverance ginseng or slow Change channel circumstances such as satellite channel, line-of-sight transmission, signal arrival path is relatively stable or variation is slow, and this moment, tracking circuit can be caught up with the change slowly of signal, therefore only need initial acquisition and tracking circuit to get final product, the path search circuit can save.When wireless environment presents fast change, under the fast moving environment, the path that arrives receiver acute variation occurs with the quick change of receiver location and (comprises the decline of signal level, the disappearance in old path and the appearance that newly arrives the path), this moment, tracking circuit can't be caught up with this acute variation in path, the path search circuit is the search signal due in real time, and whether decision need to upgrade the address, footpath (signal arrives the position in footpath) of following the tracks of despreading and channel estimating, thereby make receiver keep operate as normal and must not restart capture circuit when following the tracks of failure.
Path search circuit structure based on digital matched filtering is simple, and acquisition speed is fast, reaches uncertain interval correlation because matched filter can ceaselessly provide a signal to, and but can determine flexibly as for the specific strategy of searching for.
Channel estimating refers to the amplitude of arriving signal and phase place are estimated, generally is after the accurate tracking of spreading code, finishes by pilot signal is auxiliary.Pilot signal can be the time-division be carried on the signal that knows that other it is believed that in full, also can be the independent wireless channel parallel with other channels.If be carried on to the time-division on other channels, then can take out matched filter output result from the fixed position and finish channel estimating; If independent wireless channel, then the matched filtering output correlated results at place, address, corresponding footpath all can be used to do channel estimating on this channel.
Shown in Figure 2, channel estimating based on digital matched filter is carried out at each signal arrival path after finishing path search and entering the chip tracking mode, the correlation that only need take out every footpath correspondence position (indication that is produced by the address, footpath among Fig. 2 is represented) this moment respectively is through smoothly adding up or other algorithms are realized, and must additionally not use correlator, thereby simplified circuit.Specific algorithm and parameter can be selected flexibly, can select flexibly according to different environment as the number of times that smoothly adds up, and can also use some aided algorithms such as adaptive algorithm to improve estimated performance in addition.
The receiver structure of realizing based on digital matched filter comes the various algorithms of comprehensive selection with a kind of simple circuit, makes the performance of each parts reach more excellent.
In sum, essential characteristic of the present invention is: the spread spectrum code acquisition in the DSSS communication, how follow the tracks of through search, channel estimating and chip and all realize based on digital matched filter, obtain higher receptivity with lower realization complexity, its outstanding advantage is its flexibility, low complex degree and high-performance.
Protection of the present invention is not subjected to the restriction of Fig. 1 feature that embodiment describes, and comprises other distortion and the change in claims scope.
Claims (10)
1. based on digital matched filter Multipath searching and channel estimation methods, it is characterized in that: utilize digital matched filter to finish the digital matched filtering of one or more spread spectrum code channels, the correlation of corresponding spread spectrum code channel is provided continuously, the correlation of the spread spectrum code channel that catch is carried out the spread spectrum code acquisition that noncoherent accumulation and judgement can realize this code channel; Utilize the correlation of digital matched filter output be concerned with equally or noncoherent accumulation and compare judgement, can search multipath signal with higher gain and obtain each reliable channel estimation results directly; Carry out the spread spectrum code channel that chip is followed the tracks of at needs, the lead and lag correlation of the relevant peaks in one or more paths of digital matched filter output is carried out computing can obtain the chip tracking error signal, can finish chip in view of the above and follow the tracks of.
According to claim 1 based on digital matched filter Multipath searching and channel estimation methods, it is characterized in that: digital matched filter can be one or more.
According to claim 1 based on digital matched filter Multipath searching and channel estimation methods, it is characterized in that: the progression of digital matched filter can make arbitrarily.
According to claim 1 based on digital matched filter Multipath searching and channel estimation methods, it is characterized in that: the search strategy of spread spectrum code acquisition can be arbitrarily.
According to claim 1 based on digital matched filter Multipath searching and channel estimation methods, it is characterized in that: noncoherent accumulation mode during spread spectrum code acquisition and accumulative frequency can be arbitrarily.
According to claim 1 based on digital matched filter Multipath searching and channel estimation methods, it is characterized in that: incoherent or coherent accumulation mode and accumulative frequency during Multipath searching can be arbitrarily.
According to claim 1 based on digital matched filter Multipath searching and channel estimation methods, it is characterized in that: the strategy of Multipath searching can be arbitrarily.
According to claim 1 based on digital matched filter Multipath searching and channel estimation methods, it is characterized in that: the algorithm of channel estimating and implementation method can be arbitrarily.
According to claim 1 based on digital matched filter Multipath searching and channel estimation methods, it is characterized in that: chip is followed the tracks of and can be adopted relevant or incoherent mode.
According to claim 1 based on digital matched filter Multipath searching and channel estimation methods, it is characterized in that: chip Tracking Realization method can be arbitrarily.
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| CNB011367245A CN1152504C (en) | 2001-10-22 | 2001-10-22 | Multipath searching and channel evaluating method based on digital matched filter |
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100342738C (en) * | 2003-02-22 | 2007-10-10 | 艾利森电话股份有限公司 | Arrangements and method for power estimation |
| CN1971304B (en) * | 2006-11-24 | 2010-05-19 | 浙江大学 | Method and device used for processing signal of base band of high dynamic satellite navigation receiver |
| CN101283514B (en) * | 2005-08-15 | 2011-11-23 | 捷讯研究有限公司 | Joint space-time optimum filters (ISTOF) for interference cancellation |
| CN101283512B (en) * | 2005-08-15 | 2011-11-23 | 捷讯研究有限公司 | Joint space-time optimum filter (ISTOF) using QR and eigenvalue decompositions |
| CN101283516B (en) * | 2005-08-15 | 2011-11-23 | 捷讯研究有限公司 | Wireless communications device including a joint space-time optimum filter (ISTOF) using cholesky and eigenvalue decompositions |
| CN105048997A (en) * | 2015-06-08 | 2015-11-11 | 昆腾微电子股份有限公司 | Matched filer multiplexing apparatus and method, and digital communication receiver |
| CN103869339B (en) * | 2014-02-24 | 2016-05-04 | 中国科学院光电研究院 | A kind of catching method of complex carrier navigation signal |
-
2001
- 2001-10-22 CN CNB011367245A patent/CN1152504C/en not_active Expired - Fee Related
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100342738C (en) * | 2003-02-22 | 2007-10-10 | 艾利森电话股份有限公司 | Arrangements and method for power estimation |
| CN101283514B (en) * | 2005-08-15 | 2011-11-23 | 捷讯研究有限公司 | Joint space-time optimum filters (ISTOF) for interference cancellation |
| CN101283512B (en) * | 2005-08-15 | 2011-11-23 | 捷讯研究有限公司 | Joint space-time optimum filter (ISTOF) using QR and eigenvalue decompositions |
| CN101283516B (en) * | 2005-08-15 | 2011-11-23 | 捷讯研究有限公司 | Wireless communications device including a joint space-time optimum filter (ISTOF) using cholesky and eigenvalue decompositions |
| CN1971304B (en) * | 2006-11-24 | 2010-05-19 | 浙江大学 | Method and device used for processing signal of base band of high dynamic satellite navigation receiver |
| CN103869339B (en) * | 2014-02-24 | 2016-05-04 | 中国科学院光电研究院 | A kind of catching method of complex carrier navigation signal |
| CN105048997A (en) * | 2015-06-08 | 2015-11-11 | 昆腾微电子股份有限公司 | Matched filer multiplexing apparatus and method, and digital communication receiver |
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| CN1152504C (en) | 2004-06-02 |
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