Wireless based passive bistatic radar.
Doctoral thesis, UCL (University College London).
With the rapid development and deployment of 802.11 wireless network signals over recent years, wireless network transmission has become widely available in many public places. This has given rise to interest from many researchers in application of these systems to detection and tracking. However, the majority of this research is focussed on co-operative detection using base station signal triangulation methods. There has been little research on non-cooperative indoor detection using wireless communication signals. This dissertation offers a comprehensive study of non-cooperative passive bistatic wireless detection methods. This includes a review of the literature, and a detailed theoretical and experimental study to evaluate the performance of the performance of bistatic passive radar (PBR) using wireless signals as an illuminator of opportunity. The characteristics of 802.11 wireless LAN signal were investigated, including the modulation scheme, the effective bandwidth, and the shifting transmission rate, which all influence and contribute to passive radar performance. The bistatic range resolution is 27 m when there is a lower transmission rate (1 Mbps and 2 Mbps) using DSSS PHY (with 11 MHz bandwidth); and the bistatic range resolution is 15 m when there is a higher transmission rate (above 5 Mbps) using OFDM PHY (with 20 MHz bandwidth). The ambiguity functions of typical waveforms of the 802.11 wireless LAN signals were simulated and analyzed from the radar perspective after the investigation of the communication signal characteristics. The echo power performance was then investigated as the initial experiment using the 802.11 beacon signal in an anechoic chamber and real wireless data transmissions in an office environment. The measurements seemed to agree quite closely with the theoretical values in an ideal environment. A comprehensive range of experiments in both indoor and outdoor environments were then conducted to examine the range and Doppler detection performance. These experiments demonstrated the first reported results for non-cooperative detection of human and other targets using wireless transmissions. Performance bounds were determined from these experiments and direct and multipath signal suppression identified as key areas to improve performance. Direct signal interference cancellation methods based on an adaptive filter were therefore developed and verified with effective cancellation results. The adaptive filter method developed in this study improved target SIR by about 30 – 40 dB. This study was finally extended to consider longer range outdoor detection using 802.16 (WiMax) transmissions. Simulations were carried out for real maritime surveillance scenarios and compared with existing active radars. This preliminary study showed that wireless based passive radar has the potential to replace active systems in some scenarios and is the subject of ongoing studies.
|Title:||Wireless based passive bistatic radar|
|Additional information:||Permission for digitisation not received|
|UCL classification:||UCL > School of BEAMS > Faculty of Engineering Science > Electronic and Electrical Engineering|
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