New Walsh-Like Non-Linear Phase Orthogonal Codes for Direct Sequence CDMA Communication

Abstract

Walsh codes and Gold codes have been used as a spread spectrum codes in Code Division Multiple Access (CDMA) communication because of their ease of generation than the efficiency of these codes. The drawbacks of these codes are that they are limited in number and in their lengths. In this research paper, we relaxed the linear phase requirements of the Walsh code and the new sets of Walsh-like non-linear phase binary orthogonal user codes (transforms) are obtained for the asynchronous and the synchronous spread spectrum multi user communication. We designed the simulink model and performed the algorithm by using MATLAB R 2011 a version in order to obtain this newly proposed Walsh-like code set for the multiuser spread spectrum communication. We compared their performance with the existing codes like the Gold code and the Walsh code families. Our comparisons include their time domain properties like the autocorrelation and the cross correlation along with the bit error rate (BER) performances in the additive white Gaussian noise (AWGN) for the synchronous and asynchronous DS-CDMA communication. We proved that the proposed binary user code family outperforms the Walsh codes significantly and they match in the performance with the popular, nearly orthogonal Gold codes closely for the asynchronous multi user communication in the additive white Gaussian noise (AWGN) channels. We present in this research paper that there are a good number of such desirable code sets which are available in the binary sample space with different transform sizes. These new binary sets with a good performance and flexible code lengths might help us to improve the spread spectrum multiplexing capabilities of future wire line and the wireless CDMA communication systems.