Adaptive CFAR PN Code Acquisition for DSSS Systems

Wei, Bin

Abstract

The communication between transmitter and receiver in Direct Sequence Spread Spectrum (DSSS) systems starts with synchronisation, which can be carried out in two steps: acquisition and tracking. Acquisition is the coarse searching of the delay of PN code in transmitted signal, and tracking is to find the exact delay of PN code in transmitted signal and maintain the alignment of the two PN codes.

This thesis “Adaptive PN code Acquisition for DSSS Systems” presents research on PN code acquisition in DSSS systems. The research focused on the adapitve threshold optimisation with Constant False Alarm Rate (CFAR) techniques in different noise background. Both homogeneous and non-homogeneous noise background are analysed to check the performance of different CFAR techniques, in the terms of Probability of detection ( Pd), Probability of false alarm (Pja) and Mean Acquisition Time (MAT). The
limitations of general CFAR techniques in non-homogeneous noise background are disclosed in the research, and adaptive censoring technique is applied into general CFAR techniques, showing significant improvement in performance. In the research, MATLAB is used for mathematical simulations, and Monte Carlo simulation is used for independent validation of the theoretical results obtained. ISE, Modelsim, and System generator are used for the hardware implementation in Field Programmable Gate Array (FPGA).

Results show that all the kinds of CFAR techniques perform well in homogeneous noise background, with high Pd and short MAT, however, the general CFAR techniques without automatic censoring suffer serious degradation in non-homogeneous noise background. In this thesis, after disclosing the limilation of general CFAR techniques, Greatest-Of/ Smallest-Of CFAR (GO/SO-CFAR) was introduced to solve the problem in non-homogeneous noise background. The simulation results show that GO/SO-CFAR has much better performance than the general CFAR in non-homogeneous noise background, especially in noise background with high interferences, GO/SO-CFAR can maintain high Pd and short MAT. FPGA is used to analyse the complexity of achievement for GO/SO- CFAR detector, and the results illustrate that GO/SO-CFAR is only slightly more complex and slower than the CA-CFAR and OS-CFAR detectors. Therefore, GO/SO- CFAR is much more suitable than general CFAR techniques in non-homogeneous noise background, when the noise condition is unknown.

Citation

Wei, B. Adaptive CFAR PN Code Acquisition for DSSS Systems. (Thesis). Edinburgh Napier University

• Thesis Type: Thesis
• Deposit Date: Apr 19, 2023
• Publicly Available Date: Apr 19, 2023
• Related Public URLs: https://ethos.bl.uk/OrderDetails.do?did=1&uin=uk.bl.ethos.506342
• Award Date: 2008