A STUDY OF SEQUENCES FOR DIRECT SEQUENCE SPREAD SPECTRUM MULTIPLE ACCESS SYSTEMS

Abstract

Spread Spectrum (SS) techniques are finding increa-. sing applications in modern day communication. When used in multiple access environment, SS-systems offer features hitherto unavailable in multiple access systems. In this dissertation, various SS and spread spectrum multiple access (SSMA) systems have been briefly reviewed and the necessity of 'good' sequences for proper SSMA performance has been established with specific reference to Direct sequence (DS) systems. Two families of sequences viz, Gold and bent, of various lengths, have been generated and their properties have been verified. A search for sequences with good correlation and large linear span has been under-taken. Concatenated sequences obtained from Barker, relaxed Barker, Gold and bent sequences have been examined for their properties. The linear spans for concatenated sequences are observed to be larger than those of the comparable length Gold or bent sequences. The cross-correlation and out-of-phase auto correlation values are found to be sufficiently low. Emprical relationships satisfied by correlation values of one class of concatenated sequences are also established in this dissertation.