Innovative semi orthogonal revamped walsh hadamard (ISORWH) sequence for asynchronous CDMA application

Abstract

Code Division Multiple Access (CDMA) is the most popular wireless access technology in modern mobile communication. Design of CDMA spreading codes has grown sufficient interest amongst the researchers over the last few decades. CDMA code family is generally categorized into two groups, namely orthogonal and nonorthogonal or near-orthogonal which have established their application in synchronous (downlink) and asynchronous (uplink) CDMA system. Walsh code has been considered to be the most useful spreading code to be used in synchronous link because of its orthogonality property. However, the performance of Walsh code is significantly limited in an asynchronous environment. As a matter of fact, a number of codes have been proposed till date in order to alleviate the drawbacks of Walsh code. This paper makes a novel attempt to enhance the correlation properties of existing Walsh code through one simple yet powerful algorithm. Proposed code of length 'N' has been generated from code sets of length 'N/4' and thus makes the code generation algorithm elegant. Performance of the proposed code has been compared with some relevant orthogonal codes in terms of various metrics and finally the supremacy of our proposition has been established.