Performance analysis of adaptive receivers for DS/CDMA communication systems
Fang‐Biau Ueng, Jun‐Da Chen, Jia‐Yu Yang · International Journal of Communication Systems · 2008
Abstract Both intersymbol interference (ISI) and multiple‐access interference (MAI) are the important issues in code division multiple access (CDMA) multiuser communication systems. The step size of the traditional least‐mean‐square (LMS) adaptive receivers must be substantially adjusted to overcome the effect due to different channel responses or different numbers of active users. The normalized‐LMS (NLMS) algorithm can automatically manipulate the adjustment to avoid the problem just discussed. This paper proposes the symbol‐based interference rejection filter with NLMS algorithm and derives both finite impulse response (FIR)‐ and infinite impulse response (IIR)‐type algorithms. We also derive the optimal step sizes and minimum mean‐square errors (MSEs) for both the FIR and IIR symbol‐based receivers. The complexity of our proposed FIR receiver is lower than that of the conventional chip‐based receivers. In addition, it is shown that the bit error rate performance of our proposed symbol‐based receivers is superior to conventional one in the simulations. Simulations also show the correctness of our theoretical analysis of minimum MSE. Copyright © 2008 John Wiley & Sons, Ltd.