Analysis of a multicarrier DS-CDMA code-acquisition system

In this paper, we present two code-acquisition schemes for a multicarrier direct-sequence code-division multiple-access system, one that uses equal gain combining and the other that uses selection combining. The code-acquisition performance of the two multicarrier systems, as well as that of a single-carrier system, are analyzed in both nonfading and Rayleigh fading channels under the assumption that the receiver is chip-synchronized; the effect of partial-band interference (PBI) on the performance is also included. It is demonstrated that in an additive white Gaussian noise channel, the single-carrier system has better code-acquisition performance than both multicarrier systems. However, in a Rayleigh fading channel, the code-acquisition performance of a multicarrier system with equal gain combining is better than that of the single-carrier system, while a multicarrier system with selection combining has the same performance as the single-carrier system. Further, the presence of PBI more severely affects the code-acquisition performance of the single-carrier system than those of both multicarrier systems. Finally, the code-acquisition performance of a multicarrier system with equal gain combining is always better than that of the selection combining system.