ON SOME CORRELATION PROPERTIES OF ZCZ AND CONCATENATED ZCZ SEQUENCES

Abstract

Spreading codes play an important role in the design of CDMA systems. The correlation properties of spreading codes can directly affect system's interference resistance capability. It is required to design a set of sequences that eliminate both multi-access and multipath interference for reliable communication. To achieve this, sequences should possess an impulse like auto-correlation and low cross-correlation function. In some situations where time complexity is a major issue, it is required to calculate partial-period correlation, which is the correlation function calculated over a subsequence of a sequence. A number of spreading sequences have been used in the past. Among them are Zero Correlation Zone (ZCZ) sequences. These sequences possess zero correlation zones in their auto and crosscorrelation functions, and hence find applications in QS-CDMA systems. This thesis aims at examining some correlation properties of ZCZ sequences, with special emphasis on partial-period correlation. Concatenated sequences involving ZCZ codes result in good correlation as well