Signal detection performance in Rayleigh fading environments with a moving antenna

The performances of a single-antenna handheld receiver in detecting a narrowband signal in a Rayleigh fading environment that is temporally static but decorrelates spatially are analysed. Of interest is comparing the detection performance of a static antenna with that of a moving antenna subject to constant processing time. It is shown that the net processing gain resulting from randomly moving the antenna relative to keeping it static can be large, namely over 11 dB in some cases, which is significant for numerous indoor applications. It is further demonstrated that, for a given utilisation scenario, there is an optimum number of spatial samples that maximise the processing gain advantage of the moving antenna. Generally, if the spatial trajectory of the antenna becomes too large, then the loss associated with the signal decorrelation dominates and undermines the gains achieved by the increased spatial diversity. Practical implementation issues including the sensitivity of the proposed method to trajectory estimation are investigated. An extensive set of measurements based on CDMA 2000 signals propagated from outdoor terrestrial base stations and captured in indoor multipath environments using static and moving antennas are utilised to experimentally substantiate these theoretical findings.     

GPS spoofer countermeasure effectiveness based on signal strength,noise power,and C/N0 measurements

Spoofing sources can effectively disrupt a GPS receiver during the acquisition phase by generating multiple false correlation peaks and increasing the noise floor. Such deceptive correlation peaks can mislead the GPS receiver into acquiring the spoofer generated signals rather than the authentic signals. Also, the spoofer can increase the receiver noise floor to bury the authentic signals in the noise and at the same time generate correlation peaks with amplitudes commensurate with reasonable C/N₀ expectations. The main focus of this paper is on assessment of the reduced effectiveness of the GPS spoofer countermeasure during acquisition where the GPS receiver utilizes C/N₀ discrimination. As shown, whereas the C/N₀ discrimination is of limited effectiveness, with a modest circuit modification, the receiver can measure the absolute power of the correlation peaks, which is an effective means of detecting and discriminating spoofer sources. It will be shown that employing absolute power monitoring technique considerably reduces the vulnerability region of the receiver compared with the C/N₀ monitoring techniques. Copyright © 2012 John Wiley & Sons, Ltd.