الفهرس 
Spread Spectrum OverviewOnly 14 pages are availabe for public view
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Abstract
ABSTRACT
Spread spectrum communication and navigation systems employ a wideband code to spread the message signal over the communication channel. The estimation of the spreading code and information sequence is of great importance in the security of spread spectrum system, which remains a hot research problem in the wireless communication. There are different types of spreading codes depending on the application. This study discusses the higher-order statistics (HOS) specified in terms of triple correlation (TC) of spreading codes. For the maximal-length sequence, each code has a specific unique triple correlation function pattern of peaks which can be used to detect the original message signal. The Gold code constitutes of a pair of m-sequences, each of them having its own triple correlation peaks, so, also TC can be used in detection of complete or truncated Gold code as demonstrated by simulations.
Conventional receivers are generally ineffective in detecting direct-sequence spread spectrum (DSSS) signals if the spreading sequences are unavailable. A higher-order statistics based efficient receivers for the detection of Gold code spread spectrum signal in the presence of noise is proposed. These receivers take advantage of the TC and use it for code self-synchronization. We study two types of Gold code TC receivers; one-stage receiver which is used with divisible by three code length and two-stage receiver which can be used with any code length. A comparison between the performances of both receivers in Additive White Gaussian Noise (AWGN) channel is performed using Matlab simulations to prove the efficiency of the suggested receivers’ structure.Also, a TC Gold code channelized receiver has been developed and analyzed. The effect of changing the number of channels on the performance of triple correlation TC receiver in AWGN channel is performed to prove the immunity of the receiver against noise.
The output from the proposed receivers depends on the used threshold. Two threshold techniques were investigated. The fixed and adaptive threshold techniques were tested. The adaptive threshold is more effective in decreasing the noise influence in Gold code detection but works only for offline computation.