CN1529440A - CDMA system multi-path search interpolation method - Google Patents
CDMA system multi-path search interpolation method Download PDFInfo
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Abstract
The method includes following steps: (1) calculating complex valued correlation function CRF(k); matching correlation operation is carried out between local scrambling code and received signal so as to obtain complex value of correlation in different values of time delay; (2) interpolation in time domain is carried out for complex correlation function obtained at step (1); (3) calculating power time delay function PDPri; (4) determining multipaths time delay. M pieces of larger functional values are searched out from power time delay function obtained in step (3). The time delayed locations tm m=1,2..., M, which are corresponding to the said functional values, are multipaths time delays. The invented method avoids using present complex early or late gates tracking algorithm so as to simplify complexity for realizing Rake receiver.
Description
Technical field
The present invention relates to mobile communcations system, relate in particular to the Multipath searching interpolation method of code division multiple access (CDMA:Code-Division Multiple-Access) communication system.
Background technology
Code division multiple access (CDMA) is a kind of multiple access method, it is based on spread spectrum and become and remove existing frequency division multiple access (FDMA, Frequency-Divisoin Multiple-Access) and be applied to another multi-address method of communication system outside time division multiple access (TDMA, the Time-Division Multiple-Access) method.Compare with existing method, CDMA has many advantages, and for example availability of frequency spectrum height, planning are simple etc.Adopt the system of CDMA method to mainly contain now: narrowband CDMA (IS-95, Interim Standard 95) system, wideband CDMA (WCDMA, Wideband CDMA) system, CDMA2000 system, TD-SCDMA (TimeDivision Synchronous Code Division Multiple Access) system, TD-CDMA (Time Division-Code Division Multiple Access) system etc.Many yards spread spectrums (or claiming double-deck spreading code distribution technology) have been adopted in these systems, in these cdma systems, the spread spectrum mode of the reverse link from mobile subscriber to the base station can be divided into for two steps, the first step is that cross-correlation is zero orthogonal function (Walsh function when aliging with time delay, ovsf code) as the channel code spread spectrum, be called and add expansion, the recovery process of corresponding receiving terminal is called despreading; Second step was used auto-correlation and all reasonable pseudo noise code of cross-correlation performance (PN sequence, M sequence, Gold sequence) and the signal multiplication of the unique distribution of each user, was called scrambling, and the recovery process of corresponding receiving terminal is called descrambling.Above-mentioned pseudo noise code is called scrambler, distinguishes different mobile subscribers with scrambler.A numerical value also is chip (chip) in the scrambler sequence.Equally, the spread spectrum mode of the forward link in these systems from the base station to mobile subscriber is also divided the two same steps, and unique difference is that the scrambler in the forward link is used for distinguishing base station or sub-district, the scrambler difference of different base stations or sub-district.
In general mobile communication environment, the signal between base station and the travelling carriage is propagated along the some paths between the Receiver And Transmitter, and this multipath transmisstion phenomenon mainly is to be caused by the reflection of signal at transmitter and receiver body surface on every side.Because the difference of different propagation path, it is also different that the different multipath compositions that arrive the same signal of receivers along different paths arrive the propagation delay of receivers, thereby cause multipath to disturb and signal fadeout.The receiver that uses in cdma system is a kind of receiver of multiple-branching construction, wherein the essentially identical multipath of each branch and propagation delay is synchronous, each branch is an independent receiver element, its function is a demodulation expectation received signal component, merge the different receivers element signal, can improve received signal quality.This receiver also is Rake (Rake) receiver, can be superimposed the multipath energy of same user's different delay by certain rule, thereby improve receptivity.
Spreading code is the prerequisite of proper communication in the cdma system synchronously in local spreading code and the received signal.If can not obtain sign indicating number synchronously, just correctly despreading can't correctly solve raw information.Sign indicating number is accurate more synchronously, and demodulation performance is just good more.Multipath searching is exactly to detect the multipath signal propagation delay from received signal, with adjust local spreading code make it with received signal in the spreading code of each multipath information keep synchronously.If Multipath searching can not accurately search multidiameter delay, the Rake receiver demodulation performance of back will have loss.
In the existing Multipath searching algorithm, with scrambler and the received signal correlation intergal of sliding, obtain the plural correlation function CRF (Complex RelationFunction) of desired user signal, the quadratic sum of step and imaginary part when getting plural correlation function then, obtain power time delay function (PDP:Power Delay Profile), the power time delay function is exactly the mould value square of the correlation function of scrambler and received signal in fact.Then, find out functional value big (be correlation is big, power bigger) or just think the position of multidiameter delay greater than the peak of certain thresholding from the power time delay function, this is the multipath searching method that uses at present.In " modern mobile communcations system " (People's Telecon Publishing House, Qi Yusheng, Shao Shixiang writes), " CDMA:Principles of Spread Spectrum Commucication " (Addison-WeSleyPublishing Company, by Andrew J.Viterbi), in " Optimal DecisionStrategies for Acquisition of Spread-Spectrum Signals inFrequency-Selective Fading Channels " scientific and technical literatures such as (IEEE Transactions oncommucications Vol.46.No.5., by Roland R.Rick and LaurenceB.Milstein.) this all there is narration.
Multipath searching is equivalent to each different time delay is carried out descrambling with scrambler, usually to carry out descrambling to hundreds of delay positions, and real multi-path location has only wherein several (generally being less than 10) position, follow-up Rake receiver only need carry out demodulation to a few position and get final product.In addition, wireless communications environment will constantly carry out Multipath searching in continuous variation, in time reflects current channel circumstance, in order to reduce the Multipath searching time, even adopts the method for parallel search.So in receiver, the operand accounting of Multipath searching is heavy very big, realizes also more complicated.In order to reduce the operand of Multipath searching, the precision of Multipath searching is general more coarse, and its adjacent time delay point is generally equal to one half chip period, that is to say that its precision has only 1/2 chip.And the precision that demodulation needs often needs 1/4 even 1/8 chip.In order to improve precision, a kind of way of routine is to adopt door tracking sooner or later, this method has more detailed description in " CDMA:Principlesof Spread Spectrum Commucication " (Addison-WeSley PublishingCompany, by Andrew J.Viterbi).In the method, in each Rake receiver branch, in the time of demodulation multidiameter delay place (road in the title) signal energy (this is that receiver must be finished), demodulation is than the signal energy of Zao half-chip of multidiameter delay (claiming Zao road) and slow half-chip (claiming slow road or late road), signal to the morning, noon and afternoon three tunnel compares then, if the signal energy on late road is greatly to a certain degree, just past late road, the position of morning, noon and afternoon three tunnel direction slip 1/8 or 1/4 chip; If morning, the signal energy on road arrived to a certain degree greatly, just the position of morning, noon and afternoon three tunnel past road direction early slip 1/8 or 1/4 chip; If the two-way energy is more or less the same sooner or later, just think that current position is more accurately, needn't slide.This process has been carried out further meticulous adjustment door tracking sooner or later to Search Results, and its essence is similar to the searcher of a search window less (having only three delay positions).Adopt door tracking sooner or later, can make demodulation performance obtain the raising of big performance, but simultaneously Rake receiver complexity be increased greatly.In addition, in order to divide timing just to distribute delay positions more accurately at multipath, the multipath allocation algorithm usually needs comprehensive multi-path searching results and a tracking results sooner or later, selects suitable multipath and distribute to the Rake receiver from both, and this has also increased the complexity of multipath allocation manager algorithm.
Summary of the invention
The operand that the objective of the invention is prior art and cause because adopt door track algorithm sooner or later is big, realize complicated shortcoming, in the hope of proposing a kind of code division multiple access system Multipath searching interpolation method that improves the multi-path searching results precision under the prerequisite that does not improve computation complexity substantially, simplify Rake receiver complexity.
Core algorithm of the present invention is: do not change Multipath searching correlation intergal precision, after calculating plural correlation function CRF, a part of data that energy is bigger among the plural correlation function CRF are carried out interpolation based on finite pulse response FIR (Finite Impulse Response) filtering.
For achieving the above object, the present invention proposes a kind of code division multiple access system multipath searching method, it is characterized in that, may further comprise the steps:
The first step, calculated complex correlation function CRF (k): mate related operation with local scrambler and received signal, the plural correlation when obtaining different delay;
In second step, the plural correlation function that the first step is obtained carries out time domain interpolation: this step can be divided into following each small step again:
1. select the interpolation zone: from CRF (k), select the bigger function segment CRF of one or more snippets mould value
i(n) as the interpolation zone, subscript i=1 wherein, 2 ..., I; If operational capability is fully arranged in the system design, this step also can omit, and directly uses whole section CRF (k) as the interpolation zone.
2. carry out the time domain zero insertion: suppose that precision will improve r doubly, the CRFi that the 1st small step is obtained carries out the time domain zero insertion, obtains ICRFri (p), p=0, and 1 ..., Ni*r-1, Ni are the length of i section interpolation area segments CRFi; Concrete interpolation method is:
3. carry out FIR filtering: the FIR filtering that the ICRFri (p) that the 2nd small step is obtained carries out time domain obtains CRFri (p); But the balance for amount of calculation and performance considers that the exponent number of filter can be different.
The 3rd step, rated output time delay function PDP ri: to second step to the CRFri quadratic sum of carrying out imaginary part and real part obtain power time delay function PDP ri;
In the 4th step, determine multidiameter delay: go on foot the 3rd and find out M bigger functional value, the delay positions t that these values are corresponding in the power time delay function that obtains
m, m=1,2 ..., M is exactly a multidiameter delay.
Based on same design, the present invention also proposes another kind of code division multiple access system multipath searching method, it is characterized in that, may further comprise the steps:
The first step, calculated complex correlation function CRF (k): mate related operation with local scrambler and received signal, the plural correlation when obtaining different delay;
Second step, rated output time delay function PDP: ask the real part of CRF (k) and imaginary part quadratic sum can obtain PDP;
In the 3rd step, the PDP that the first step is obtained carries out time domain interpolation; This step can be divided into following each small step again:
1. select the interpolation zone: from PDP, select the bigger function segment PDP of one or more snippets mould value
i(n) as the interpolation zone, subscript i=1 wherein, 2 ..., I; If operational capability is fully arranged in the system design, this step also can omit, and directly uses whole section PDP as the interpolation zone.
2. carry out the time domain zero insertion: suppose that precision will improve r doubly, the PDPi that the 1st small step is obtained carries out the time domain zero insertion, obtains IPDPri (p), p=0, and 1 ..., Ni*r-1, Ni are i section interpolation area segments CRF
iLength; Concrete interpolation method is:
3. carry out FIR filtering: the IPDPri (p) that the 2nd small step is obtained carries out time domain FIR filtering and obtains PDPri (p); But the balance for amount of calculation and performance considers that the exponent number of filter can be different.
In the 4th step, determine multidiameter delay: go on foot the 3rd and find out M bigger functional value, the delay positions t that these values are corresponding in the power time delay function that obtains
m, m=1,2 ..., M is exactly a multidiameter delay.
Multipath searching filtering interpolation method of the present invention is by carrying out the interpolation based on FFT to plural correlation function, compare with existing Multipath searching, can under amount of calculation increase situation seldom, increase substantially the Multipath searching precision, avoid adopting the complicated track algorithm of door sooner or later, simplified the implementation complexity of Rake receiver greatly.And multipath allocation manager algorithm also only needs to handle Search Results, do not need to handle the result of trace demodulation, implements very simple.The Multipath searching precision can reach 1/4,1/8 chip precision, even can reach 1/16 chip precision.
Description of drawings
Fig. 1 is the typical code-dividing multiple-access receiving system structure chart that generally adopts.
Fig. 2 is the code-dividing multiple-access receiving system structure chart that adopts the method for the invention.
Fig. 3 is a kind of code division multiple access system Multipath searching interpolation method flow chart of the present invention.
Fig. 4 is an another kind of code division multiple access system Multipath searching interpolation method flow chart of the present invention.
Fig. 5 is two kinds of method median filter coefficient schematic diagrames of the present invention.
Fig. 6 is the interpolation effect schematic diagram as a kind of filtering interpolation method of the specific embodiment of the invention.
Fig. 7 is the interpolation effect schematic diagram as the another kind of filtering interpolation method of the specific embodiment of the invention.
Embodiment
Be described in further detail below in conjunction with the enforcement of accompanying drawing technical scheme.
Core algorithm of the present invention is: do not change Multipath searching correlation intergal precision (just can guarantee that the computation complexity of Multipath searching algorithm is constant substantially like this), after calculating plural correlation function CRF, a part of data that energy is bigger among the plural correlation function CRF are carried out interpolation based on finite pulse response FIR (Finite Impulse Response) filtering, briefly, earlier this partial data is carried out zero insertion on the time domain exactly, be inserted into the r double precision, again the data behind the zero insertion are passed through a FIR filter, the emission filter Performance Match of this filter and transmitting station.The result that filtering obtains is exactly the correlation function CRFr of r double precision.Then the real part and the imaginary part of the plural correlation function after the interpolation are asked quadratic sum, obtain power time delay function PDP r.The delay positions of finding out bigger value correspondence at last from the power time delay function is exactly the multidiameter delay position.
The invention is characterized in: 1, plural correlation function is carried out interpolation based on FIR filtering; 2, the Multipath searching precision can reach 1/4,1/8 chip precision, even can reach 1/16 chip precision (but not having this necessity in the general communication system).In fact, also can obtain the power time delay function PDP, then PDP be carried out zero insertion filtering by plural correlation function CRF real part imaginary part quadratic sum.This algorithm can be called the filtering interpolation method.
Fig. 1 is a kind of typical C DMA receiving system structure chart.Signal source 101, emission filtration module 102, rf modulations module 103, antenna 104 have been formed transmitting station.Here it should be noted that before rf modulations signal also can be called pulse shaping filter (Pulse Shaping Filter) through the emission filter 102 of a base band.The effect of this filter is that the digital signal after the spread spectrum is converted to the signal that is fit to rf modulations.The characteristic of this filter is generally fixed, such as travelling carriage, stipulate in the standard that this filter is that rolloff-factor (roll-off factor) is 0.22 root raised cosine filter (RRC:root-raised cosine filter) for the WCDMA system.At receiving terminal, form by antenna 105, radio-frequency channel 106, Multipath searching module 107, multipath administration module 108 and Rake receiver.The Rake receiver is made up of a plurality of relatively independent receiver elements 109,110,111 etc. again.Each rake receiver element comprises time delay adjusting module 109.1 again, early road demodulation module 109.2, middle road demodulation module 109.3, late road demodulation module 109.4 are formed.As can be seen from the figure, morning, noon and afternoon three tunnel demodulation result need feed back to time delay adjusting module 109.1, constitutes a feedback loop here.Time delay adjusting module 109.1 also needs the information of multipath administration module 108, and gives multipath administration module 108 feedback information that time delay is adjusted, and also constitutes a feedback loop here.These feedback loops all make algorithm design become complicated.
Fig. 2 is the CDMA receiving system structure chart that adopts interpolation method.Same as in figure 1, signal source 201, emission filtration module 202, rf modulations module 203, antenna 204 have been formed transmitting station.At receiving terminal, form by antenna 205, radio-frequency channel 206, Multipath searching module 207 and Rake receiver.The Rake receiver is made up of a plurality of relatively independent receiver elements 209,210,211 etc. again.Visibly differently with Fig. 1 be: road demodulation module 209.1 during each rake receiver element only comprises, prolong modules such as adjustments, road demodulation morning, the demodulation of late road when not required.Middle road demodulation module 209.1 and the middle road demodulation module 109.3 among Fig. 1 among this figure are identical.Do not need complicated multipath administration module 109.1 in the receiving system of employing interpolation method yet, but need in Multipath searching module 207, carry out interpolation algorithm.Contrast as can be known by Fig. 1 and Fig. 2, adopt the system of interpolation method much succinct.
Fig. 3 is the flow chart of one of filtering interpolation method.Square frame 301 is corresponding to the first step of method, calculated complex correlation function CRF.In second step of square frame 302 corresponding method, plural correlation function is carried out interpolation.This step is divided 3 small steps again.Square frame 302.1,302.2 and 302.3 corresponds respectively to 3 small steps in the method.Select the interpolation zone earlier, again the time domain zero insertion is carried out in the interpolation zone and obtain ICRFr, then ICRFr is carried out FIR filtering and obtain plural correlation function CRFr.Square frame 303 is corresponding to the 3rd step of method, and the quadratic sum of calculated complex correlation function real part imaginary part promptly obtains the power time delay function.Square frame 304 is found out multi-path location corresponding to the 4th step of method from the power time delay function.Particularly, may further comprise the steps:
The first step, calculated complex correlation function CRF (k).Mate related operation with local scrambler and received signal, the plural correlation when obtaining different delay.The calculated complex correlation function is a basic step in the Multipath searching, and a lot of method rated output time delay function C RF (k) are arranged in the prior art.
In second step, the plural correlation function that the first step is obtained carries out time domain interpolation.This step can be divided into following each small step again:
1, selects the interpolation zone.From CRF (k), select the function segment CRF of big (it is bigger to be equivalent to energy) of one or more snippets (such as the I section) mould value
i(n) as the interpolation zone, subscript i=1 wherein, 2 ..., I.The place that the mould value is bigger is that the bigger place of possibility appears in true multipath.The less function segment of mould value is general unlikely true multipath.This step mainly is in order to reduce amount of calculation, to avoid some unnecessary interpolation arithmetics.If operational capability is fully arranged in the system design, this step also can omit, and directly uses whole section CRF (k) as the interpolation zone.
2, go the time domain zero insertion.Suppose that precision will improve r doubly, the CRFi that the 1st small step is obtained carries out the time domain zero insertion, obtains ICRFri (p), p=0, and 1 ..., Ni*r-1, Ni are i section interpolation area segments CRF
iLength.Concrete interpolation method is:
3, carry out FIR filtering.The FIR filtering that the ICRFri (p) that the 2nd small step is obtained carries out time domain obtains CRFri (p).Filter characteristic is consistent with the transmit filter characteristics of transmitting station, has same bandwidth.But the balance for amount of calculation and performance considers that the exponent number of filter can be different.
The 3rd step, rated output time delay function PDP ri.To second step to the CRFri quadratic sum of carrying out imaginary part and real part obtain power time delay function PDP ri.
In the 4th step, determine multidiameter delay.In the 3rd power time delay function that obtain of step, find out M bigger functional value, the delay positions t that these values are corresponding
m, m=1,2 ..., M is exactly a multidiameter delay.
Fig. 4 is two a flow chart of filtering interpolation method.Square frame 401 is corresponding to the first step of method, calculated complex correlation function CRF.In second step of square frame 402 corresponding method, the quadratic sum of calculated complex correlation function real part imaginary part obtains the not power time delay function PDP of interpolation.In the 3rd step of square frame 403 corresponding method, the power time delay function PDP is carried out interpolation.This step is divided 3 small steps again.Square frame 403.1,403.2 and 403.3 corresponds respectively to 3 small steps in the method.Select the interpolation zone earlier, again the time domain zero insertion is carried out in the interpolation zone and obtain IPDPr, then ICRFr is carried out FIR filtering and obtain power time delay function PDP r.Square frame 404 is found out multi-path location corresponding to the 4th step of method from power time delay function PDP r.Particularly, may further comprise the steps:
The first step, calculated complex correlation function CRF (k).Mate related operation with local scrambler and received signal, the plural correlation when obtaining different delay.The calculated complex correlation function is a basic step in the Multipath searching, and a lot of method rated output time delay function C RF (k) are arranged in the prior art.
Second step, the rated output time delay function PDP.Ask the real part of CRF (k) and imaginary part quadratic sum can obtain PDP.
In the 3rd step, the PDP that the first step is obtained carries out time domain interpolation.This step can be divided into following each small step again:
1, selects the interpolation zone.From PDP, select the function segment PDP of big (it is bigger to be equivalent to energy) of one or more snippets (such as the I section) mould value
i(n) as the interpolation zone, subscript i=1 wherein, 2 ..., I.The place that the PDP value is bigger is that the bigger place of possibility appears in true multipath.The less function segment of PDP value is general unlikely true multipath.This step mainly is in order to reduce amount of calculation, to avoid some unnecessary interpolation arithmetics.If operational capability is fully arranged in the system design, this step also can omit, and directly uses whole section PDP as the interpolation zone.
2, go the time domain zero insertion.Suppose that precision will improve r doubly, the PDPi that the 1st small step is obtained carries out the time domain zero insertion, obtains IPDPri (p), p=0, and 1 ..., Ni*r-1, Ni are i section interpolation area segments CRF
iLength.Concrete interpolation method is:
3, carry out FIR filtering.The IPDPri (p) that the 2nd small step is obtained carries out time domain FIR filtering and obtains PDPri (p).Filter characteristic is consistent with the transmit filter characteristics of transmitting station, has same bandwidth.But the balance for amount of calculation and performance considers that the exponent number of filter can be different.
In the 4th step, determine multidiameter delay.In the 3rd power time delay function that obtain of step, find out M bigger functional value, the delay positions t that these values are corresponding
m, m=1,2 ..., M is exactly a multidiameter delay.
Fig. 5 is the filter coefficient schematic diagram.Shown in the figure is 83 rank root raised cosine filters, and 83 filter factors are arranged, and filter factor is the center left-right symmetric with the 42nd number.The unit of abscissa is 1/8 chip among the figure.What the baseband transmission filtering of transmitting station was adopted is exactly this filter.In the filtering interpolation method, if be interpolated into 1/8 chip precision, can directly adopt this median filter coefficient, perhaps only adopting with the 42nd number is that one section coefficient at center is to reduce amount of calculation, such as adopting the 28th to the 56th number to form 29 rank FIR filters as coefficient.If be interpolated into 1/4 chip precision, can get the coefficient of the number of even number sequence number in the coefficient shown in Figure 6 as filter, such as the 2nd, 4 ..., 82 these 41 numbers form 41 rank FIR filters.Equally, if in order to reduce amount of calculation, also can adopt with the 42nd number is one section less filter of even number sequence number coefficient formation exponent number at center.Such as adopt the 28th, 30,32 ..., 54,56 these 15 numbers form 15 rank FIR filters.
Fig. 6 is the interpolation effect schematic diagram of one of filtering interpolation method.Abscissa is a multidiameter delay, is unit with 1/8 chip, and the position in true footpath is 2050.Ordinate is a performance number.Curve among the figure is exactly the power time delay function.This figure signal is interpolated into PDP18, PDP28, PDP38 and the PDP48 of 8 sampling precision respectively never with PDP1, PDP2, PDP3 and the PDP4 of the 2 sampling precision (sampling rate is 2 times of spreading rate, i.e. 1/2 chip precision) of time delay skew.If also drawn the real 8 double precision power time delay function PDP 8 that the search of adopting 8 samplings obtains simultaneously among the figure.Such as the data of PDP4 in values of having located such as delay positions 2040,2044,2048,2052,2056, shown in square frame point among the figure, if do not take interpolation, judge that then the multidiameter delay position is the position 2048 or 2052 of energy larger part, differ 1/4 chip with true multi-path location 2050, this error has had a strong impact on the performance of communication system, in order to reach performance, come further estimation time delay position by door tracking sooner or later, or just carry out interpolation by interpolation method of the present invention.If the 29 rank filters that the 28th to the 56th number forms among employing Fig. 6 carry out the filtering interpolation to PDP1, PDP2, PDP3 and PDP4 by one of filtering interpolation method, the curve that obtains is respectively shown in PDP18, PDP28, PDP38 and PDP48.Though these curves do not have and the PDP8 of true 8 samplings overlaps (mainly being because filter order falls short of) fully, but the shape of these curves is all similar with PDP8, and the peak of these curves all is in 2050 delay positions, so from these interpolation results, can judge the actual position of multipath accurately.
Fig. 7 is two an interpolation effect schematic diagram of filtering interpolation method.Abscissa is a multidiameter delay, is unit with 1/8 chip, and the position in true footpath is 2050.Ordinate is a performance number.Curve among the figure is exactly the power time delay function.This figure signal is interpolated into PDP18, PDP28, PDP38 and the PDP48 of 8 sampling precision respectively never with PDP1, PDP2, PDP3 and the PDP4 of the 2 sampling precision (sampling rate is 2 times of spreading rate, i.e. 1/2 chip precision) of time delay skew.If also drawn the real 8 double precision power time delay function PDP 8 that the search of adopting 8 samplings obtains simultaneously among the figure.Such as the data of PDP4 in values of having located such as delay positions 2040,2044,2048,2052,2056, shown in square frame point among the figure, if do not take interpolation, judge that then the multidiameter delay position is the position 2048 or 2052 of energy larger part, differ 1/4 chip with true multi-path location 2050, this error has had a strong impact on the performance of communication system, in order to reach performance, come further estimation time delay position by door tracking sooner or later, or just carry out interpolation by interpolation method of the present invention.If the 29 rank filters that the 28th to the 56th number forms among employing Fig. 6 carry out the filtering interpolation to PDP1, PDP2, PDP3 and PDP4 by two of filtering interpolation method, the curve that obtains is respectively shown in PDP18, PDP28, PDP38 and PDP48.Though these curves do not have and the PDP8 of true 8 samplings overlaps (mainly be because filter order falls short of, and energy is carried out filtering) fully, these curve multi-path locations are the same with PDP8.The peak of these curves all is in 2050 delay positions, so from these interpolation results, also can judge the actual position of multipath accurately.In addition, influenced by multipath energy, to differ the energy at the position 2039 of about 1.5 chips and 2061 places also relatively large with multipath actual position 2050 in PDP8, thereby might also be considered to true multipath greatly than the energy of noise position, and this also can cause adverse effect to systematic function.And by two of filtering interpolation method, this local value can drop to less than zero.So, can also improve systematic function aspect this by this filtering method.
To sum up, adopt the CDMA receiving system of Multipath searching interpolation method of the present invention, compare, reduce the receiving system complexity significantly under the situation about can guaranteed performance not reducing with existing C DMA receiving system.The inventive method realizes simple, and effect is obvious, and very high practical value is arranged in various code division multiple address communication systems.
Claims (8)
1, a kind of code division multiple access system multipath searching method is characterized in that, may further comprise the steps:
The first step, calculated complex correlation function CRF (k): mate related operation with local scrambler and received signal, the plural correlation when obtaining different delay;
In second step, the plural correlation function that the first step is obtained carries out time domain interpolation:
The 3rd step, rated output time delay function PDP ri: to second step to the CRFri quadratic sum of carrying out imaginary part and real part obtain power time delay function PDP ri;
In the 4th step, determine multidiameter delay: go on foot the 3rd and find out M bigger functional value, the delay positions t that these values are corresponding in the power time delay function that obtains
m, m=1,2 ..., M is exactly a multidiameter delay.
2, code division multiple access system multipath searching method according to claim 1 is characterized in that, the described first step further comprises:
(1) selects the interpolation zone: from CRF (k), select the bigger function segment CRF of one or more snippets mould value
i(n) as the interpolation zone, subscript i=1 wherein, 2 ..., I;
(2) carry out the time domain zero insertion: suppose that precision will improve r doubly, the CRFi that the 1st small step is obtained carries out the time domain zero insertion, obtains ICRFri (p), p=0, and 1 ..., Ni*r-1, Ni are i section interpolation area segments CRF
iLength; Concrete interpolation method is:
(3) carry out FIR filtering: the FIR filtering that the ICRFri (p) that (2) small step is obtained carries out time domain obtains CRFri (p).
3, code division multiple access system multipath searching method according to claim 2 is characterized in that, omits wherein said step (1), directly uses whole section CRF (k) as the interpolation zone.
4, code division multiple access system multipath searching method according to claim 2 is characterized in that, the filtering exponent number can be different in the described step (3).
5, a kind of code division multiple access system multipath searching method is characterized in that, may further comprise the steps:
The first step, calculated complex correlation function CRF (k): mate related operation with local scrambler and received signal, the plural correlation when obtaining different delay;
Second step, rated output time delay function PDP: ask the real part of CRF (k) and imaginary part quadratic sum can obtain PDP;
In the 3rd step, the PDP that the first step is obtained carries out time domain interpolation;
In the 4th step, determine multidiameter delay: go on foot the 3rd and find out M bigger functional value, the delay positions t that these values are corresponding in the power time delay function that obtains
m, m=1,2 ..., M is exactly a multidiameter delay.
6, code division multiple access system multipath searching method according to claim 5 is characterized in that, the described first step further comprises:
(1) selects the interpolation zone: from CRF (k), select the bigger function segment CRF of one or more snippets mould value
i(n) as the interpolation zone, subscript i=1 wherein, 2 ..., I;
(2) carry out the time domain zero insertion: suppose that precision will improve r doubly, the CRFi that the 1st small step is obtained carries out the time domain zero insertion, obtains ICRFri (p), p=0, and 1 ..., Ni*r-1, Ni are i section interpolation area segments CRF
iLength; Concrete interpolation method is:
(3) carry out FIR filtering: the FIR filtering that the ICRFri (p) that (2) small step is obtained carries out time domain obtains CRFri (p).
7, code division multiple access system multipath searching method according to claim 5 is characterized in that, omits wherein said step (1), directly uses whole section CRF (k) as the interpolation zone.
8, code division multiple access system multipath searching method according to claim 5 is characterized in that, the filtering exponent number can be different in the described step (3).
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| CN104052555A (en) * | 2014-06-19 | 2014-09-17 | 北京交通大学 | Method for estimating wireless channel multipath parameters in OFDM system |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN104052555A (en) * | 2014-06-19 | 2014-09-17 | 北京交通大学 | Method for estimating wireless channel multipath parameters in OFDM system |
| CN104052555B (en) * | 2014-06-19 | 2016-04-27 | 北京交通大学 | A kind of method of radio channel multi-path parameter Estimation under ofdm system |
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| CN100512073C (en) | 2009-07-08 |
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