Dissertation > Excellent graduate degree dissertation topics show

Performance Analysis of Anti-Multipath Capability in DSSS System and Study on the Compensation Methods

Author: GuanLei
Tutor: ZhangZhongZhao
School: Harbin Institute of Technology
Course: Information and Communication Engineering
Keywords: DSSS system multipath double-threshold bidirectionally sliding narrow correlator FPGA
CLC: TN914.42
Type: Master's thesis
Year: 2008
Downloads: 109
Quote: 0
Read: Download Dissertation


Spread-spectrum technology, especially direct-sequence spread-spectrum (DSSS) modulation, is extensively used in modern military and commercial communication systems. One reason for its popularity is the ability of interferece suppression, in particular for multipath components which are intractable in common systems. DSSS technology is applied to both data links of the researched Wireless Image and Command Transmission System for anti-multipath. However, experimental results with long-distance communication in the channel of ground-air or sea surface showed that both the sensitivity and bit error rate (BER) of the command data link were worse than theoretical values apparently. Thus, it is meaningful to systematically study the performance of the DSSS system under various channels and with different parameters. Through this way, proper compensation methods will be proposed for improving the anti-multipath capability of the command data link in the system.Firstly,The channel of ground-air or sea surface is modeled as a time-nonselective Rician channel based on analyzing the general characteristics of multipath channels. Rician factor K is used to differentiate the communication distance which induces the unexpected errors. A simulate thought which can be fulfilled by FPGA is proposed .Then a two-path model and a DSSS-DQPSK system based on Matlab/Simulink Communication Toolkits are established for simulations in the next Chapters.Secondly, the performance of DSSS system under multipath channels and its influential parameters are systematically analyzed. This study is conducted in two aspects. For a theoretical sytem with ideal chip synchronization, effects of multipaths with time delay longer or shorter than one chip interval on DSSS system are mathematically and experimentally researched in a typical Rician channel, and the influences of different chip rate and different code are also simulated. Then the impact of Rician factor K is also studied. The researches above illustrate that in the presence of multipaths with time delay shorter than one chip interval, or in a channel with small Rician factor K, the DSSS system has a poor anti-multipath performance which will lead to unexpected BERs. For a practical sytem without ideal chip synchronization, the effects of multipaths on the acquisition as well as the tracking loop are studied, which indicate that it’s essential to choose a proper threshold in acquisition algorithm, and that the correlation width or early-late spacing has important impact on the tracking error caused by multipaths.Finally, compesation methods are broungt forward in three ways, which are respectively the optimization of system parameters, the acquisition algorithm and the tracking algorithm. Employing the proposed method of high sample rate, the algorithms of double-threshold multiple-dwell acquisition as well as the bidirectionally sliding acquisition, the probability of unlocking in acquisition loop will decrease apparently; and using the method of increasing the chip rate and the technique of narrow correlator, the BER performance will moderately ameliorate. At last some methods which maybe bring the gain to the system under the multipath channel are discussed.

Related Dissertations

  1. Research on Electromagnetic Acoustic Transducer Detection System Based on FPGA,TH878.2
  2. Study on Drive and Control System of Five-Phase PMSM Based on FPGA,TM341
  3. Development of LXI Arbitrary Waveform Generator,TM935
  4. Design of Digital Predistorter for RF Power Amplifier Based on FPGA,TN722.75
  5. Synchronization and Channel Estimation Algorithm in Bursted OFDM System and Its Implementation on FPGA,TN919.3
  6. Optimizing and Realising Research on Vedio Compression in TV Guidance System,TN919.81
  7. Research and Hardware Simulation of Multiuser Spread Spectrum Code Acquisition Based on FPGA,TN914.42
  8. Research on Basic Algorithms of Digital Image Processing and Implementation with FPGA,TP391.41
  9. Research of High Speed Image Pre-processing System Based on FPGA,TP391.41
  10. Design of High-Speed Digital Image Acquisition and Interface Based on FPGA,TP274.2
  11. Development of Inductance Sensor Data Acquisition System Based on FPGA,TP274.2
  12. Development of Serial Bus Analyzer Based on Nios,TP274
  13. Development of PMC High-speed Data Transmission Board Design Based on FPGA-RocketIO_X,TP274.2
  14. Development of Pxibus High Performance Digital I/O Module,TP274
  15. Development of LXI Counter,TP274
  16. A High-Speed and Real-Time Data Acquisition System Based on FPGA,TP274.2
  17. Design of GPS Information Receiving System Based on Nios Ⅱ,TN967.1
  18. Temperature and pressure explosives temperature field memory test technology,TQ560.7
  19. Erbium-doped fiber amplifier pump laser drive source research applications,TN248
  20. Remote FPGA system design and implementation of security upgrades,TP309

CLC: > Industrial Technology > Radio electronics, telecommunications technology > Communicate > Communication systems ( transmission system) > Frequency hopping spread spectrum communication system > Spread spectrum communication
© 2012 www.DissertationTopic.Net  Mobile