Direct sequence spread spectrum uses a carrier that remains fixed to a specific frequency band. The data signal, rather than being transmitted on a narrow band as is done in microwave communications, is spread onto a much larger range of frequencies using a specific encoding scheme. This encoding scheme is known as a Pseudo Noise sequence. The algorithm used by the PN sequence generates a Pseudo Random Number Generator that is then combined, through a binary encoding process, with the binary information from the data stream. In this book, three conventional types of PRNG were implemented. These are linear feed back shift register, nonlinear feed back shift register and Blum Blum Shub generator. A fuzzy system is studied and Fuzzy based Pseudo Random Number Generator had been implemented to generate the frequency hopping sequences for spread spectrum communications system. Thirty sample patterns are the input to FPRNG, while the bandwidth is partitioned into number of frequency bins. Each bin used triangular membership function to analyze the input to fuzzy sets, encoding these as fuzzy rules. The input vector matches if-part of a fuzzy rule and fires that rule's output fuzzy set.

Informazioni sull?autore:

Nagwan A. Al-Karawi,Studied Data Network Security in Al-Nahrian University, Assistant Lecturer in Al-Nahrian University,Baghdad,Iraq.

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