Diversity reception for CDMA based mobile communication systems

Abstract

Multiple access schemes are used to allow many mobile users to share simultaneously a finite amount of radio spectrum. For high quality communications, this must be done without severe degradation in the performance of the system. Code Division Multiple Access (CDMA) is one of the major multiple access techniques used now days to share the available bandwidth in a wireless communication system. CDMA systems are characterised by multipath interference. Rake receivers are commonly used in CDMA systems to restrict the multipath fading and provide efficient reception. These receivers collect the time-shifted versions of the transmitted signal, combine them and produce the strongest estimate of the original signal. This paper discusses the various structures of Rake receivers such as multiple antennas single Rake finger, single antenna multiple Rake fingers, multiple antennas multiple Rake fingers and performs the bit error rate (BER) comparison. BPSK modulation and code modulation are considered for spreading the original signal. Space diversity (Antenna diversity) technique is employed at the receiver.