Title of Invention  MULTIPATH SEARCHING METHOD IN CODEDIVISION MULTIPLE ACCESS COMMUNICATION SYSTEM 

Abstract  A method of multipath search in codedivision multiple access communication system is provided, which comprises the following steps: first, calculating the power delay profile of the received signal, and multiple peaks with comparatively higher energy are selected from the power delay profile, then performing threshold comparison and interpolation for the selected peaks to determine the multipath delay position and energy, finally, determining the multipath delay according to the results of interpolation. Compared with the prior art, the present invention can improve multipath search precision greatly without increasing the complexity of calculation, specifically, the search precision can reach 1/4 chip, 1/8 chip, or even 1/16 chip; at the same time, earlylate gate tracking module are not needed in the method of the present invention, thus complex tracking algorithm are also not needed, which greatly simplify the realization complexity of Rake receiver and the complexity of multipath assignment management; Furthermore, the method of the present invention is applicable for base stations and mobile stations of various of code division multiple access communication system. 
Full Text  TECHNICAL FIELD The present invention relates to the signal receiving technology in CodeDivision Multiple Access (CDMA is used for short) communication system, and particularly, to a method of multipath searching during the period of receiving a signal. The present invention is applicable for any communication system that applies CodeDivision Multiple Access technology. BACKGROUND OF THE INVENTION CodeDivision Multiple Access is a multiple access method based on the spread spectrum technology, which has become another multiple access method applied in communication system in recent years besides frequencydivision multiple access (FDMA) and timedivision multiple access (TDMA). Compared with frequencydivision multiple access and timedivision multiple access technologies, CDMA technology has a lot of advantages, such as high utilization rate of frequency spectra, simple to plan and so on. The communication system which applies CDMA technology includes: narrowband CDMA system, i.e. IS95 system; wideband CDMA system, i.e. WCDMA system; CDMA 2000 system, TDSCDMA system and TDCDMA systematic etc. Abovementioned communication systems all have adopted multicode spread spectrum technology, which is also called twostep spread spectrum code design technology. Thus, the spread spectrum process of the reverse link from a mobile station to a base station can be divided into two steps. The first step comprises making spread spectrum for the signal by using the orthogonal function (such as Walsh function, OVSF code etc) whose crosscorrelation value is zero when the delay is aligned as channel code. The first step is called spreading, and the recovering process occurring at the corresponding receiving side (base station) is called despreading. The second step comprises multiplying pseudorandom code (such as PN sequence, M sequence, Gold sequence etc.) uniquely assigned by each mobile station, which has good performance of both autocorrelation and crosscorrelation, with signal. The second step is called scrambling, and the recovering process occurring at the corresponding receiving side (base station) is called descrambling. And the abovementioned pseudorandom code is called scrambling code .In the second step, the scrambling code is used to distinguish different mobile station. A value in the scrambling code sequence is also called chip. Also, in these systems, the spread spectrum process of the forward link from base station to mobile station is also divided into the same two steps, wherein the only difference is that in the forward link scrambling code is used to distinguish the base station or cell, and different base station or cell has different scrambling code. In a general mobile communication system, signals between a base station and a mobile station propagate along multiple paths between the transmitter and the receiver. This phenomenon of multipath transmission mainly results from the signal reflection caused by the objects' surface around the transmitter and receiver. Because the propagation path is different, the propagation delays of the different multipath components' arriving at the receiver are different, wherein the multipath components are generated by the same signal propagating along different path., which results in multipath interference and signal fading. The receiver in CDMA system is of multibranches structure, wherein each branch is an individual receiver element. The receiver is used to demodulate the component of the desired received signal and combine the signals of different receiver element, which can improve the quality of the received signal. Each branch is synchronized with the multipath that has almost the same propagation delay. This kind of receiver is also called Rake receiver, which can add up the multipath energy of different delay corresponding to the same mobile station according to a certain rule, thus the receiver's performance is improved. The synchronization of the local spread spectrum code and the spread spectrum code in the received signal is a prerequisite for the CDMA system to realize a normal communication. If code synchronization can't be realized, the despreading can't be performed correctly; therefore the original information can't be demodulated correctly. The more accurate the code synchronization is, the better the receiver's demodulation performance is. Multipath searching includes detecting the propagation delay of multipath signal from signals received, and then adjusting local spread spectrum code according to the transmission delay to make it synchronize with the spread spectrum code of each multipath signal of received signals. If the multipath delay can't be searched accurately by multipath searching, then the demodulation performance of the followed Rake receiver will suffer a loss. Multipath searching methods according to the prior art comprise the following steps: first, performing slide correlation integral of the received signal with the scrambling code to obtain the Complex Relation Function (CRF) of the expected user signal; then, the Power Delay Profile (PDP) is obtained by getting the sum of the square of real part and the square of imaginary part of CRF, that is, PDP is the module square of the correlation function of a scrambling code and a received signal; And then, peaks having a comparatively larger profile value (i.e. comparatively larger correlation value, comparatively larger power ) or having a profile value which is larger than a predetermined threshold are picked out from the power delay profile PDP, wherein the position of the peaks are just the positions of the multipath delays. Abovementioned method is the traditional multipath searching method, which has been described in the following books and papers, "Modern Mobile Communication Systems" (People's Post & Telecomm Press, by Qi Yusheng and Shao Shixiang), "CDMA: Principles of Spread Spectrum Communication" (AddisonWeSley Publishing Company, by Andrew J. Viterbi), "Optimal Decision Strategies for Acquisition of SpreadSpectrum Signals in FrequencySelective Fading Channels "(IEEE Transactions on communications Vol. 46. No. 5, by Roland R. Rick and Laurence B. Milstein.). Actually, multipath searching is just equivalent to making descrambling for each different delay of received signal by using scramble code to select real multipath delay. Usually, hundreds of delay positions are needed to be descrambled, while only several of them are the real multipath positions, which is usually less than ten. It's enough for the followed Rake receivers to descramble only the selected real multipath positions. The wireless communication environment changes continuously, so multipath search needs to be carried out continuously in order to reflect the current channel environment in time. To reduce the time of multipath search, a parallel searching method is adopted. Therefore in the receiver, the multipath search takes a great proportion in operation quantity, the realization of which is also complex. If the operation for multipath searching is reduced, the corresponding multipath searching precision will be lowered than usual also, and the gap between two adjacent delay points is usually equal to half of chip period, namely, the precision is only 1/2 chip, while the demodulation needs a precision of 1/4 chip or even 1/8 chip. To improve the precision, a method called earlylate gate tracking method is usually applied, which comprises the following steps of: first, in every branch of Rake receiver, demodulating the energy of the signal at the position of multipath delay (called ontime path) and also demodulating that of the signal which is half chip earlier (called early path) than the multipath delay as well as that of the signal which is half chip later (called late path) than the multipath delay at the same time ; then, comparing these three paths signals, that is, early path signal, late path signal as well as ontime path signal, and sliding 1/8 chip or 1/4 chip of the multipath delay positions of these three channels in the direction of late path if the signal energy of late path exceeds a predetermined threshold; or, sliding 1/8 chip or 1/4 chip of the multipath delay positions of these three channels in the direction of early path if the signal energy of early path exceeds a predetermined threshold; or, considering the current multipath delay position as a relatively correct position and there is no need to slide, if the signal energies of both early path and late path are almost equal. This process is called earlylate gate tracking. This method makes further fine adjustment for the searched result, which functions like a searcher with a smaller searching window (only have three delay positions) substantially. Although the receiver's demodulation performance can be improved greatly by using the earlygate gate tracking method, it makes the complexity of the Rake receiver doubled at the same time. In addition, in multipath assignment method, the multipath search result and earlylate gate tracking result usually need to be synthesized, and the appropriate one of them should be chosen and assigned to the Rake receiver in order to assign a relatively accurate delay position when carrying out the multipath assignment. Also, the method of earlylate gate tracking has increased the complexity of multipath assignment management. The method of earlylate gate tracking has already been described in detail in the following book "CDMA: Principles of Spread Spectrum Communication" (AddisonWeSley Publishing Company, by Andrew J. Viterbi). To sum up, multipath searching method according to the prior art can only offer a search with relatively low precision. To improve the precision, the method of earlylate gate tracking is applied, but it is complicated. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a multipath searching method applied in codedivision multiple access communication system, capable of improving the precision of the result of the multipath searching almost without increasing the complexity of calculation, which overcomes the shortcoming of complicated realization of the earlylate gate searching, and at the same time simplifies the complexity of Rake receiver. A multipath searching method provided in the present invention comprises the following steps: calculating the power delay profile; selecting multiple peaks from said power delay profile which have comparatively higher energy; then, performing threshold comparison and interpolation for the selected peaks to determine multipath delay position as well as energy; finally, determining the multipath delay according to the interpolation result. The multipath searching method, wherein the step of calculating the power delay profile further comprises: performing the matching correlation of a received signal with the local scrambling code to obtain a correlation function; and calculating the module square of the abovementioned correlation function to obtain the power delay profile. The multipath searching method, wherein the step of threshold comparison and interpolation further comprises: calculating the ratio of energy difference between the energy at the delay position earlier than the selected peak and the energy at the delay position later than the selected peak to the energy at the selected peak; comparing the ratio with a threshold to determine a real number section where the ratio is located; then, determining the multipath delay position and multipath energy of this peak value according to the value of the real number section; finally, repeating above steps and completing the threshold comparison and interpolation for all selected peaks. The multipath searching method, wherein the step of determining multipath delay further comprises: selecting multiple paths which have comparatively higher energy from the multi paths obtained by the step of threshold comparison and interpolation, and the corresponding delay is the multipath delay. Compared with multipath searching methods according to the prior art, the multipath searching method described in present invention can guarantee to improve multipath search precision greatly almost without changing the complexity of calculating, wherein the search precision can reach 1/4 chip, 1/8 chip or even 1/16 chip. At the same time, the earlylate gate tracking module is not needed in the present invention, i.e. complicated tracking algorithm is not needed also, which simplifies the complexity of the realization of the Rake receiver and the complexity of multipath assignment management. The method according to the present invention is applicable for base stations and mobile stations in various codedivision multiple access communicate system. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Fig.l is a schematic block diagram of a typical CDMA system; Fig.2 is a schematic block diagram of the CDMA system that applies the multipath searching method according to the present invention; Fig.3 is a flowchart of the multipath searching method according to the present invention; Fig.4 is a graph illustrating the ideal shape of multipath peak value; Fig.5 is a graph showing the relation between the deviation of real peak position to the searched peak position and the ratio of the energy difference between the energy of the sampling point earlier than the searched peak and the energy of the sampling point later than the searched peak to the energy of the searched peak; Fig.6 is a graph showing the relation between the energy deviation factor of the real peak value and the searched peak value and the ratio of the energy difference between the energy of the sampling point earlier than the searched peak and the energy of the sampling point later than the searched peak to the energy of the searched peak. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Accompanying drawings and embodiments are combined to make further description hereinafter, according to which, the present invention can be easily realized for those skilled in the art. Fig.1 is a schematic block diagram of an existing typical CDMA system. Referring to fig.1, the transmitting apparatus includes signal source 101, transmitting filter 102, radio frequency (RF) modulating module and antenna 104. Before being modulated by the radio frequency, the signal first passes through a baseband transmitting filter 102, which is also called pulse shaping filter, which converts the spread spectrum digital signal to a signal that is fit for RF modulating Then the signal fit for RF modulating is modulated by the RF modulating module 103, which is then transmitted into the air by antenna 104. Generally, the characteristic of the transmitting filter 102 is stable, for example, for mobile stations in WCDMA system, the filter is a root raised cosine filter with its rolloff coefficient being 0.22. The receiving apparatus includes antenna 105, RF channel 106, multipath searching module 107, multipath management module 108 and Rake receiver 109. After the antenna 105 receives the signal, this signal passes through RF channel 106 and enters multipath searching module 107, in which the process of multipath search is carried out, signal output through another route from the RF channel 106 enters Rake receiver directly. The multipath searching module applies existing multipath searching method, such as earlylate gate tracking method, and the multipath delay is output to the multipath management module 108, and then the output of the multipath management module 108 enters the Rake receiver. Rake receiver includes multiple relatively independent receiving elements 109. Each receiving element 109 includes delay adjustment module 1091, early path demodulation module 1092, ontime path demodulation module 1093 and late path demodulation module 1094. The signals from multipath management module 108 and RF channel 106 are received by the delay adjustment module 1091, which then adjusts the delay of the signal and transmits the outputs to the early path demodulation module 1092, ontime path demodulation module 1093 and late path demodulation module 1094. The demodulated results of these three early, ontime and late paths need to be fed back to the delay adjustment module 1091, which forms a feedback loop. At the same time, the delay adjustment module 1091 also needs to receive information from the multipath management module 108, and feeds back the information about the delay adjusting to the multipath management module 108, which also forms a feedback loop. While feedback loop will make the muftipath searching method complex. Fig.2 is the schematic block diagram of the CDMA system that applies the multipath searching method according to the present invention. Same as Fig.l, the transmitting apparatus includes signal source 101, transmitting filter 102, RF modulator module 103 and antenna 104. The receiving apparatus includes antenna 105, RF channel 106, multipath searching module 207 and Rake receiver. After the antenna 105 receives the signal, this signal passes RF channel 106 and enters multipath searching module 207, multipath searching module 207 applies the multipath searching method according to the present invention to carry out multipath search. And the searched multipath delay is output to the Rake receiver. Signal output through another route from the RF channel 106 enters Rake receiver directly. Rake receiver includes multiple relatively independent receiving elements 209. Wherein, each receiving element 209 only includes ontime path demodulation module 2091. Compared with Fig.l, the structure of the Rake receiving element has been simplified greatly, the delay adjustment module, the early path demodulation module as well as the late path demodulation module have been omitted, and the ontime path demodulation module 2091 is totally the same as the original ontime path demodulation module 1091. With the present invention, a complex multipath management module is also not needed in the receiving system. Compared with Fig.l, there is no feedback loop in the receiving system, The kernel idea of the multipath searching method of the present invention comprises: calculating the power delay profile PDP without changing the precision of the multipath searching correlative integral, then selecting peak data of PDP with comparatively higher energy to perform interpolation based on the threshold decision, which specifically, i.e. calculating the ratio of the energy difference between the energy of the sampling point earlier than the searched peak and the energy of the sampling point later than the searched peak to the energy of the peak, which is then compared with a predetermined threshold to calculate more accurate multipath delay position and energy . The peak herein and hereinafter is defined to be the position, the energy of which is higher than the energy of the positions on both sides thereof. The flowchart of the present invention is shown as Fig.3. The method of the present invention is an interpolation method based on threshold decision, so it is necessary to set the threshold. The setting of the threshold can be completed during the period of system configuration, as shown in block 301 of Fig.3. The number and value of the thresholds, the corresponding delay position deviation and energy deviation thereof can be determined according to the search precision requirement of the system. According to the requirement of search precision, 2N thresholds Th(n) are determined which are arranged by size, wherein n=+1, ±2,"* +N, wherein N is a natural number , to make a easier description, the number zero is excluded. The smaller the serial number is, the smaller the corresponding threshold value is, i.e. the ranking order of the threshold is Th(N), Th(N+1),....., Th(1), Th(+1),......, Th(N). For instance, if the system needs to interpolate the search precision from 1/2 chip to 1/8 chip, at least four thresholds are needed, so here N is equal to 2. If system needs to interpolate the search precision from 1/2 chip to 1/4 chip, then two thresholds are needed, so here N is equal to 1. 2N thresholds divides the real number into 2N+1 real number sections, with the sequence number for which is defined as following: N, N+1, •••, 0, 1, •••, N. If the calculated ratio R obtained in current peak threshold interpolation locates in the real number section between Th (1) and Th(l), that is, it locates in the NO. 0 real number section , then the current peak position can be considered to be the real multipath delay position and the energy of the current peak is the real multipath energy. For other real number section, if the section number is n, then the position deviation corresponding to the real multipath position is DeltaOffset(n), and the energy deviation factor corresponding to the real peak is AlphaEnergy(n), wherein n=±l,±2,", ±N, n represents the section number of the real number. Generally, the unit of the delay position is 1/2 chip. For example, during the operation of the current peak threshold interpolation, the calculated ratio R locates in the section between threshold Th(1) and Th(2), i.e.real number section 1, then the real peak position is obtained by adding up the current peak position and DeltaOffset(1), the real peak energy is obtained by multiplying the current peak energy by AlphaEnergy(1). Then, the position deviation DeltaOffset(n) and the energy deviation factor AlphaEnergy(n) can be determined according to the ideal shape of peak , wherein the energy deviation factor AlphaEnergy(n) is defined to be the ratio of the real peak energy to the searched peak energy. For example, in the abovementioned embodiment, which has 4 thresholds, the corresponding position deviations are DeltaOffset(2)=0.25 chip, DeltaOffset(1)=0.125 chip, DeltaOffset(1)= +0.125 chip, DeltaOffset(2)=+0.25 chip. While in the embodiment which has 2 thresholds, the corresponding position deviations are DeltaOffset(1)=0.25 chip, DeltaOffset(1)=+0.25 chip. The specific multipath searching method based on the threshold interpolation is carried out during the period of system's operation. First, the power delay profile PDP is calculated (as shown in block 302), which is the basic step for multipath searching. There are many methods to calculate the power delay profile according to the prior art, but the integral length adopted may be of some difference, which has little effect on the method of the present invention. In the present invention, the correlation function is obtained by matching correlating the received signal with the local scrambled code and then the power at different delay can be obtained by calculating the module square of the correlation function, wherein the module square is the sum of the square of real part and the square of imaginary part. Then, the threshold interpolation is carried out (as shown in block 303). First, multiple peaks with comparatively higher energy are selected according to the value of power delay profile PDP. Usually, according to an energy threshold which is defined or calculated by the system itself, the maximum number of selected multipath the energy of which exceeds the energy threshold is less than or equal to Mpath, wherein the value of Mpath can be defined or calculated by each system, typically the value of Mpath is within the range from 4 to 16.Then the ratio of the energy difference between the energy of the delay position earlier than the searched peak and the energy of the delay position later than the selected peak to the energy of the selected peak is calculated. If the energy of selected peak is PDP (k), wherein k is the delay position, then the ratio R is obtained by the following formula: R =[PDP (kl)PDP(k+l)]/PDP(k). Comparing the ratio R with the defined threshold to determine the real number section where the ratio R locates in, then the real multipath delay position and the corresponding multipath energy thereof can be determined according to the value of that real number section. If the real number section where ratio R locates in is p, then the real multipath delay position is the sum of the delay position of the selected peak and the position deviation DeltaOffset(p) of the real number section where the ration R is located, wherein the multipath energy thereof is obtained by multiplying PDP(k) by AlphaEnergy(p). All selected peaks are performed said threshold comparison and interpolation operation according to the above steps to obtain the corresponding real multipath delay position and multipath energy thereof. Finally, the multipath delay is determined (as shown in block 304). After the abovementioned threshold interpolation operation, several real multipath delay positions and multipath energies are obtained. The energy of the real multipath delay are compared and M multipaths, the energy of which are comparatively higher, are selected from above mentioned real multipaths. The specific value of M can be decided by each system independently, typically, M can be any value between 1 and 8. And the delay position tm which is corresponding to the energy is the multipath delay, wherein m= 1, 2,*\ M. By carrying out the abovementioned steps, the entire process of multipath search is completed; therefore, the multipath delay is obtained. Fig.4 is a graph of the ideal shape of the multipath peak value. This ideal peak is obtained by using 256 chips as the correlation integral length and 1/8 chip as the sampling precision, wherein the real peak position is 15 and the real multipath energy is about 4600. If other integral length is adopted, the shape of the obtained peak will be of some difference. In the present embodiment, the coherent integral length with 256 chips will be described as example. Fig.5 is a graph showing the relation between the deviation of real peak position to the searched peak position and the ratio of the energy difference between the energy of the sampling point earlier than the searched peak and the energy of the sampling point later than the searched peak to the energy of the searched peak. Taking 256 chips integral length as example and assuming the multipath search precision is 1/2 chip, then one point for every 4 adjacent points in the curve of Fig.4 should be selected as the sampling point position. If that, the real peak position 15 may not be selected, thus the searched peak may deviate from the real peak position. The position deviation and searched peak have following characteristics: the larger the absolute value of the position deviation is, the larger the absolute value of the ratio R of the energy difference between the early sampling point and the late sampling point around the searched peak to the energy of the searched peak is, and the symbol of the ratio, i.e. positive or negative, corresponds to the direction of the deviation. The specific relation is shown as the curve in Fig.5. For instance, if the position deviation is 0, then the ratio R equals to 0; if the position deviation is 1/8 chip, then the ratio R equals to 0.43; if the position deviation is 1/8 chip, then the ratio R equals to 0.43; if the position deviation is 1/4 chip, then the ratio R equals to 0.94. If the search precision is required to be improved from 1/2 chip to 1/8 chip according to the requirement of the system, then four thresholds can be defined based on the curve in fig.5, which are 0.68, 0.21, 0.21 and 0.68 respectively, and the corresponding four delay position deviations DeltaOffset thereof are 0.25, 0.125, 0.125 and 0.25. Fig.6 is a graph showing the relation between the energy deviation factor of the real peak energy to the searched peak energy and the ratio of the energy difference between the energy of the sampling point earlier than the searched peak and the energy of the sampling point later than the searched peak to the energy of the searched peak. Taking integral length of 256 chips as an example and assuming the multipath search precision is 1/2 chip, and one point for every 4 adjacent points in the curve of Fig.4 should be selected as the sampling point position. If that, the real peak position 15 may not be selected, thus the energy of the searched peak may be lower than the energy of the real peak. And the relation between the size of the energy deviation and the searched peak is of following characteristic: the larger the absolute value of the energy deviation is, the larger the absolute value of the ratio R of the energy difference between the energy of the early sampling point and that of the late sampling point around the searched peak to the energy of the searched peak is. The real relation is shown as the curve in Fig.6. For instance, if the position deviation is 0, then the energy deviation equals to 0 and the ration R equals to 0; and if the position deviation is 1/8 chip, the energy of the real peak is 1.06 times of the energy of the searched peak, and the ratio R equals to 0.43; and if the position deviation is 1/4 chip, the energy of the real peak is 1.28 times of the searched peak energy, and the ratio R equals to 0.94. Supposing that the search precision is required by the system to be improved from 1/2 chip to 1/8 chip, then four thresholds can be defined according to the curve in fig.5, which are 0.68, 0.21, 0.21 and 0.68 respectively, and the corresponding four delay position deviations DeltaOffset are 0.25, 0.125, 0.125 and 0.25, and the ratio of the real energy to the searched energy, i.e.AlphaEnergy is 1.28, 1.06, 1.06 and 1.28. From the abovementioned analysis, in the present embodiment, it is enough only to retain two datas of the energy deviation factor AlphaEnergy, and among the four datas of the delay position deviation DeltaOffset and threshold Th, if the sign is not considered, there are only two different datas, which facilitates the specific realization. To sum up, compared with the CDMA receiving system according to the prior art, the CDMA receiving system applying the multipath searching method according to the present invention can reduce the complexity of the receiving system greatly without reducing the performance of the system, which is easy to realize and is of obvious effect and is applicable for various code division multiple access communication system. It should be understood that the abovedescribed embodiments are used to explain but not to limit the present invention. Although the present invention has been explained in detail by referring to the embodiments, it should be apparent to those skilled in the art that various modifications and variations may be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. WE CLAIM: 1. A method of multipath searching in codedivision multiple access communication system comprising the steps of: calculating power delay profile of a received signal; selecting multiple peaks which have comparatively higher energy from said power delay profile; performing threshold comparison and interpolation for said selected peaks to determine multipath delay position; determining the multipath delay according to the results of said interpolation . 2. The method according to claim 1, wherein said step of performing threshold comparison and interpolation further comprises performing threshold comparison and interpolation to determine multipath energy. 3. The method according to claim 2, wherein said step of calculating power delay profile further comprises: performing a matching correlation of said received signal with local scrambling code to obtain a correlation function; and calculating module square of said correlation function to obtain the power delay profile. 4. The method according to claim 2, wherein said step of selecting multiple peaks which have comparatively higher energy further comprises : selecting no more than Mpath multipaths according to an energy threshold prescribed or calculated by the system, wherein the energy of the selected multipaths exceeds the energy threshold, wherein the maximum number of selected multipath Mpath is prescribed or calculated by the system. 5. The method according to claim 4, wherein said Mpath is within the range between 4 and 16. 6. The method according to claim 2, wherein said step of setting threshold further comprises: determining 2N threshold Th(n) ,which are arranged by size according to the system requirement of the search precision, wherein N is a natural number and n is expressed as: n=± 1,+2,"m, +N, and wherein the smaller the serial number is, the smaller the value of the threshold is; dividing the real number into 2N+1 real number sections by using the 2N thresholds, and the sequence number for the sections are : N, N+1, •••, 0,1, ••, N; considering the peak locating in real number section 0 as the real multipath delay position, for other real number section n, the position deviation corresponding to the real multipath is DeltaOffset(n), and the energy deviation factor corresponding to the real peak is AlphaEnergy(n); determining the value of the position deviation and the energy deviation factor according to an ideal peak shape. 7. The method according to claim 6, wherein said step of performing threshold comparison and interpolation for the selected peaks further comprises : calculating the ratio of the energy difference between the energy at the delay position before the selected peak and the energy at the delay position after the selected peak to the energy of the selected peak; comparing said ratio with said threshold to determine the real number section where said ratio locates; determining the real multipath delay position and the multipath energy thereof corresponding to the selected peak according to the value of the real number section; repeating above steps to complete the threshold comparison and interpolation for all selected peaks. 8. The method according to claim 7, wherein said step of determining the real multipath delay position and the multipath energy thereof corresponding to the selected peak further comprises : adding the position deviation of the real number section where the ratio of the peak locates to the peak to get the real multipath delay position; multiplying the energy of the peak and the energy deviation factor of the real number section where the ratio of the peak locates to get the real multipath energy. 9. The method according to claim 2, wherein said step of determining the multipath delay according to the results of said interpolation further comprises : comparing the energy of the real multipaths obtained by carrying out the step of threshold comparison and interpolation ; selecting M multipaths from said real multipaths, the energy of which are comparatively higher, wherein M is determined by system ; obtaining multipath delays which are the delays corresponding to the M multipaths. 10. The method according to claim 9, wherein said M can be any integer from 1 to 8. A method of multipath search in codedivision multiple access communication system is provided, which comprises the following steps: first, calculating the power delay profile of the received signal, and multiple peaks with comparatively higher energy are selected from the power delay profile, then performing threshold comparison and interpolation for the selected peaks to determine the multipath delay position and energy, finally, determining the multipath delay according to the results of interpolation. Compared with the prior art, the present invention can improve multipath search precision greatly without increasing the complexity of calculation, specifically, the search precision can reach 1/4 chip, 1/8 chip, or even 1/16 chip; at the same time, earlylate gate tracking module are not needed in the method of the present invention, thus complex tracking algorithm are also not needed, which greatly simplify the realization complexity of Rake receiver and the complexity of multipath assignment management; Furthermore, the method of the present invention is applicable for base stations and mobile stations of various of code division multiple access communication system. 

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02075kolnp2006assignment.pdf
02075kolnp2006claims1.1.pdf
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02075kolnp2006international publication.pdf
02075kolnp2006international search authority report.pdf
02075kolnp2006priority document1.1.pdf
02075kolnp2006priority document.pdf
2075KOLNP2006ABSTRACT1.1.pdf
2075KOLNP2006CANCELLED PAGES.pdf
2075KOLNP2006CLAIMS1.1.pdf
2075KOLNP2006CORRESPONDENCE 1.4.pdf
2075KOLNP2006CORRESPONDENCE1.3.pdf
2075KOLNP2006CORRESPONDENCE1.5.pdf
2075kolnp2006correspondence1.2.pdf
2075KOLNP2006DESCRIPTION (COMPLETE)1.1.pdf
2075KOLNP2006DRAWINGS1.1.pdf
2075kolnp2006examination report.pdf
2075KOLNP2006FORM 11.1.pdf
2075KOLNP2006FORM 21.1.pdf
2075kolnp2006grantedabstract.pdf
2075kolnp2006grantedclaims.pdf
2075kolnp2006granteddescription (complete).pdf
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2075kolnp2006grantedform 1.pdf
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2075kolnp2006grantedspecification.pdf
2075KOLNP2006REPLY TO EXAMINATION REPORT.pdf
2075kolnp2006reply to examination report1.2.pdf
2075kolnp2006translated copy of priority document.pdf
Patent Number  245262  

Indian Patent Application Number  2075/KOLNP/2006  
PG Journal Number  02/2011  
Publication Date  14Jan2011  
Grant Date  11Jan2011  
Date of Filing  24Jul2006  
Name of Patentee  ZTE CORPORATION  
Applicant Address  ZTE PLAZA, KEJI ROAD, SOUTH, HITECH INDUSTRIAL PARK, NANSHAN DISTRICT, SHENZHEN, GUANGDONG 518057  
Inventors:


PCT International Classification Number  H04J 13/00  
PCT International Application Number  PCT/CN2003/001129  
PCT International Filing date  20031226  
PCT Conventions:
