會(huì)議presentationPPT

1、PN Code Acquisition Method with Enhanced Sensitivity Performance2 22AbstractNon-coherent integration （非相干積分）can enhance the performance of acquisition sensitivity in spread spectrum communication system with high bit rate, but it can not meet the requirements in low SNR environment due to the large

2、loss of SNR. In this paper, a novel method is proposed for PN code（偽碼） acquisition. Since the coherent integration time is extended by pre-judging the data sign, the loss of non-coherent integration is decreased. By pre-processing the coherent integration results before non-coherent integration, thi

3、s method can get an achievable sensitivity gain, i.e. about 2 dB compared with direct non-coherent integration methods. Thus, the proposed method offers an effective way to improve the acquisition sensitivity performance.23 33Contents 2 Methods4 Conclusions 1 Introduction 3 Results1.1 Research scope

4、1.2 Present methods 1.3 My research 2.1 Signal model2.2 Acquire method2.3 Performance analysis 34 441 IntroductionSynchronization of PN code1. Core technology of spread spectrum communication2. Require the receivers to generate a local sequence which is identical with the received signals 3. Two ste

5、ps: acquisition and tracking. Only acquisition technology is considered1.1Research Scope45 551 Introduction5Extend coherent integration time with assistance systemHigh rate of data transmission is not easily implemented Present methods Non-coherent integrationLarge loss of SNR. Differential non-cohe

6、rent integrationOnly be used in low rate condition 1.2 Present methods6 661 IntroductionNovel enhanced method Expand coherent integration time by pre-judging signal sign Enhanced acquisition sensitivity performance compared with direct coherent integration.61.3 My Research7 772 MethodsSpread spectru

7、m communication system with high bit rate, a signal model with one bit period containing one PN code cycle After passing through a band-pass filter with bandwidth( )2cos 2( )iS tPd tC tf tn t ( )2cos( ) cos2.2sin( ) sin2iiqiS tPd tC tn tf tPd tC tn tf t72CT2.1 Signal model8 82 Methods2.2 Acquire met

8、hodFig. 3. Acquisition scheme 12M 9 992 Methods2.3 Performance analysisIn high SNR Chosen combination : corresponds to the real situation Performance : equal to coherent integrationIn low SNR Chosen combination : not always the results supposed to be Performance : weak energy of signal and deteriora

9、ted performance 91010102 MethodsM is set to be 2 for simplicity. The error probability can be computed as: 22222211P IQIQ2222121212122cos( )2sin( )22IIQQIIQQPPPnnnnLnnLnn2121212124422 cos( )() 22 sin( )() 20IIQQIIQQPn nn nLPnnLPnnLP 101111112 MethodsFig. 4. the relationship between probability of er

10、ror and CNR11When CNR is equal to 40 dB, the acquisition performance will be deterioratedAdd a comparing logic 1212122 MethodsProving the assumption that the value distributing of is different between the true and false choosing.Fig. 5. the distributing of when true choosing and error choosing,0/P N

11、equals to 40dB kZkZ1313132 Methods13The true choosing : non-central chi-squared distributionThe false choosing : central chi-squared distributionThe threshold : adaptive and varied kZThkZThadopt the non-coherent integration methodchose combining mode integration1414143 Results14Acquisition times : 1

12、000No residual Doppler（殘余多普勒）No residual code phase errorsConstant false detecting probability : 0.01Total integration time : 12 code cycles Different combinations of M and N ,12MNSimulation conditions1515153 ResultsFig. 6. the performance comparing between the new method and non-coherent integratio

13、n method1616163 Results2 dB better than direct non-coherent integration when SNR is low. Chose M=2, N=6 for the simplicity of implementing 1717174 ConclusionsThe direct non-coherent integration has a disadvantage of SNR loss. So the new method is presented to improve the performance of PN code acqui

14、sition. The coherent integration result is pre-processed before implementing the non-coherent integration. This method can get a sensitivity performance improvement of about 2 dB. And the implementing is simple. So the new method is valuable in real work. 17181818AcknowledgmentWe gratefully acknowle

15、dge the Satellite Navigation Lab in Beijing Institute of Technology for the hardware support and the assistance of data collecting.18191919References1 Deok Won Lim, Sang JeongLee.Design of an Assisted GPS Receiver and its Performance Analysis, IEEE International Symposium on 27-30 May 2007: 1742 174

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17、 (PN) code Acquisition, 2004 IEEE Eighth International Symposium on 30 Aug. - 2 Sep. 2004: 212 217.4 M.H. Zarrabizadeh and E.S. Sousa.A Differentially Coherent PN Code Acquisition Receiver for CDMA Systems. IEEE Transactionson Communications, 45(11):14561465, Nov 1997.5 Vladan M. JovanoviC,Analysis

18、of Non-Coherent Correlation in DS/BPSK Spread Spectrum Acquisition, IEEE TRANSACTIONS ON COMMUNICATIONS, VOL. 43, NO. 2/3/4, FEBRUARY/MARCH/APRIL 1995:565-573.6 O. Shin and K. Lee, “Differentially coherent combining fordouble-dwell code acquisition in DS/CDMA systems,” IEEETrans. Communication, vol. 51, no. 7, pp. 10461050, July 2003.19202020References7 Wang J, Chau-Chin Yang, Sequential detection for code acquisition with and without data modulation on, IEEE Global Telecommunications Conference, 29 Nov.-2 Dec. 1993:1095-1099.8 XU Xiao-yong CHEN Hua-ming