Performance analysis of adaptive receivers for DS/CDMA communication systems

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 call 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. Ill 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 (C) 2008 John Wiley & Sons, Ltd

Performance analyses of adaptive noncoherent receivers for MC‐CDMA communications

“…In addition, MC-CDMA capacity is limited by the intercarrier interference due to the use of multi-carrier modulation. Because the MC-CDMA systems involve the property of DS-CDMA schemes, the single-user detection techniques also need to be performed with some form of adaptation [3][4][5][6][7][8][9][10][11][12][13][14][15]. Besides, coherent receivers require exact knowledge of the channel phase for optimum performance.…”