会议presentation-PPT.ppt

1、,PN Code Acquisition Method with Enhanced Sensitivity Performance,2,2,Abstract,Non-coherent integration （非相干积分）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 lar

2、ge loss of SNR. In this paper, a novel method is proposed for PN code（伪码） 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,

3、this 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.,2,3,3,Contents,2 Methods,4 Conclusions,1 Introduction,3 Results,1.1 Researc

4、h scope 1.2 Present methods 1.3 My research,2.1 Signal model 2.2 Acquire method 2.3 Performance analysis,3,4,4,1 Introduction,Synchronization of PN code,Core technology of spread spectrum communication Require the receivers to generate a local sequence which is identical with the received signals Tw

5、o steps: acquisition and tracking. Only acquisition technology is considered,1.1Research Scope,4,5,5,1 Introduction,5,1.2 Present methods,6,6,1 Introduction,Novel enhanced method Expand coherent integration time by pre-judging signal sign Enhanced acquisition sensitivity performance compared with di

6、rect coherent integration.,6,1.3 My Research,7,7,2 Methods,Spread spectrum 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,7,2.1 Signal model,8,2 Methods,2.2 Acquire method,Fig. 3. Acquis

7、ition scheme,9,9,2 Methods,2.3 Performance analysis In high SNR Chosen combination : corresponds to the real situation Performance : equal to coherent integration In low SNR Chosen combination : not always the results supposed to be Performance : weak energy of signal and deteriorated performance,9,

8、10,10,2 Methods,M is set to be 2 for simplicity. The error probability can be computed as:,10,11,11,2 Methods,Fig. 4. the relationship between probability of error and CNR,11,When CNR is equal to 40 dB, the acquisition performance will be deteriorated Add a comparing logic,12,12,2 Methods,Proving th

9、e 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,equals to 40dB,13,13,2 Methods,13,The true choosing : non-central chi-squared distribution The false choosing : central chi-squared distribu

10、tion The threshold : adaptive and varied,adopt the non-coherent integration method chose combining mode integration,14,14,3 Results,14,Acquisition times : 1000 No residual Doppler（残余多普勒） No residual code phase errors Constant false detecting probability : 0.01 Total integration time : 12 code cycles

11、 Different combinations of M and N ,Simulation conditions,15,15,3 Results,Fig. 6. the performance comparing between the new method and non-coherent integration method,16,16,3 Results,2 dB better than direct non-coherent integration when SNR is low. Chose M=2, N=6 for the simplicity of implementing,1

12、7,17,4 Conclusions,The direct non-coherent integration has a disadvantage of SNR loss. So the new method is presented to improve the performance of PN code acquisition. The coherent integration result is pre-processed before implementing the non-coherent integration. This method can get a sensitivit

13、y performance improvement of about 2 dB. And the implementing is simple. So the new method is valuable in real work.,17,18,18,Acknowledgment,We gratefully acknowledge the Satellite Navigation Lab in Beijing Institute of Technology for the hardware support and the assistance of data collecting.,18,19

14、,19,References,1 Deok Won Lim, Sang JeongLee.Design of an Assisted GPS Receiver and its Performance Analysis, IEEE International Symposium on 27-30 May 2007: 1742 1745. 2 A. Schmid and A. Neubauer, ”Comparison of the Sensitivity Limits forGPS and GalileoReceivers in Multipath Scenarios,” Proc. IEEE

15、PositionLocation and Navigation, April 2004. 3 RethnakaranPulikkoonattu , Markus Antweiler.Analysis of Differential Non Coherent Detection Scheme for CDMA Pseudo Random (PN) code Acquisition, 2004 IEEE Eighth International Symposium on 30 Aug. - 2 Sep. 2004: 212 217. 4 M.H. Zarrabizadeh and E.S. Sou

16、sa.A Differentially Coherent PN Code Acquisition Receiver for CDMA Systems. IEEE Transactionson Communications, 45(11):14561465, Nov 1997. 5 Vladan M. JovanoviC,Analysis of Non-Coherent Correlation in DS/BPSK Spread Spectrum Acquisition, IEEE TRANSACTIONS ON COMMUNICATIONS, VOL. 43, NO. 2/3/4, FEBRU

17、ARY/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.,19,20,20,References,7 Wang J, Chau-Chin Yang, Sequential detection for code acquisition with

18、 and without data modulation on, IEEE Global Telecommunications Conference, 29 Nov.-2 Dec. 1993:1095-1099. 8 XU Xiao-yong CHEN Hua-ming WANG Fei-xue, Performance analysis of a matched-filter PN code acquisition for direct-sequence spread-spectrum systems, Science of Surveying and Mapping 2008 S1:104-106. 9 Li Hong, LU Mingquan, Feng Zhenming, Direct GPS P-code Acquisition Method Based on FFT, TSINGHUA SCIENCE AND TECHNOLOGY Volume 13 Number 1,Feb 2008:9-16. 10SASCHA M.SPANG