الفهرس 
IntroductionOnly 14 pages are availabe for public view
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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
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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.