Optimal spread spectrum sequences-constructed from Gold codes
C.-C. Chen, K. Yao, E. Biglieri · 2002
This paper derives general results on the partial auto-correlation function of the optimal spreading sequences for asynchronous CDMA systems with respect to the minimization of the average error probability under the standard Gaussian approximation (SGA) condition without the assumption of stationary random processes on the spreading sequences. We construct a family of optimal spreading sequences from the existing Gold codes, which have the same number of codes as a set of Gold codes. An asynchronous CDMA system using such optimal spreading sequences allows 15% more users than when purely random binary sequences or Gold codes are employed. Moreover, the acquisition time performance of the proposed optimal spreading sequences is also shown to be better than that of Gold codes.