An initial acquisition scheme for Walsh-Hadamard code division multiplexing

This paper addresses the problem of initial acquisition in code division multiplexing employing Walsh-Hadamard code (WHCDM). Unlike pseudo-noise codes used in direct-sequence spread spectrum communications, Walsh-Hadamard code has many side lobes in its autocorrelation function. Well-known initial acquisition schemes for direct-sequence spread spectrum communications, therefore, cannot be applied to WHCDM. In order to solve this problem, we propose an initial acquisition scheme for WHCDM with a novel approach. It detects the symbol timing on the basis of not the autocorrelation function of Walsh-Hadamard code but the energy variance of the signal after demultiplexing. The results of computer simulation confirm that the proposed scheme provides rapid acquisition.