Code‐aided simplified receiver design in downlink MC‐CDMA communication system with transmit diversity

Abstract

AbstractIn this paper, we propose a code‐aided optimum receiver and exploit transmit diversity in downlink multicarrier code division multiple access (MC‐CDMA) system to provide a receiving scheme that is robust to fading channel. Our first emphasis is on designing a blind (without knowing the undesired users' signature sequences) MC‐CDMA mobile receiver that can suppress the multiple access interference (MAI) and combine the desired signal stemmed from all the transmitting antennas. The matched filter (MF) receiver, though simple in structure, suffers from the near‐far problem and is severely degraded by MAI. The minimum‐output‐energy (MOE) receiver, though alleviates the problems of the MF receiver, is with computational complexity and suffers from severe performance degradation due to channel estimation error in practical environment. Thereby, we propose a spreading codes selection rule that enables the simple MF receiver to achieve optimum performance regardless of the variation of channel parameters. Moreover, we develop two blind (without requiring training sequences) algorithms to estimate the composite multiple‐inputs‐single‐output (MISO) channel impulse response (IR). Furthermore, we deduce that the complexity of the channel estimator can be extensively reduced for the code‐aided optimum receiver. Simulation results demonstrate significant gain by employing the proposed codes selection rule and transmit diversity. Copyright © 2008 John Wiley & Sons, Ltd.