Polyphase Spreading Sequences for DS - CDMA Wireless Application

Abstract

Abstract In this paper , some of ployphase signature sequences for direct sequence code division multiple access ( DS / CDMA ) system is proposed . The novel sets of polyphase spreading sequences is obtained through the multiplication of the ployphase chirp sequences by some other binary and polyphase sequences such as Barker & Willard binary sequence , generalized chirp - like ( GCL ) and orthogonal polyphase sequences . These sets of polyphase sequences are tested using Matlab version 6.5.The sets shows good correlation properties . GCL - Chirp polyphase sequence show the best performance and a better correlation properties , for the length N - 9 , 16 & 25 which are under test , the normalized peak side - lobe levels of the normalized auto - correlation function are 0.15,0.18 & 0.15 for GCL - Single chirp , and 0.11,0.29 & 0.21 for GCL Double chirp respectively . On the other hand , the peak cross - correlation magnitudes are 0.49,0.32 & 0.55 for GCL - Single chirp , and 0.5,0.38 & 0.45 for GCL - Double chirp , respectively . For the proposed new sets of GCL - Chirp and the Modulatable Chirp - polyphase sequences , there is no limitation in sequence length , but for the Barker - Chirp and Willard - chirp , the length is limited according to the limitation of the Barker and Villard sequences length .