Complexity considerations in the design of wideband microcellular CDMA receivers

Direct-sequence code division multiple access (DS-CDMA) systems are of interest for wireless access in personal communications systems. Wideband CDMA systems offer potential advantages in capacity and ability to integrate different rate services in wireless access systems. We investigate the receiver design alternatives for wideband CDMA systems in microcellular environments. To implement CDMA systems with a bandwidth larger than 10 MHz, the high chip rate presents a major challenge to achieve a receiver with low complexity and low power consumption. The main objective of this paper is to find ways to minimize the receiver complexity and power consumption without introducing significant performance degradation. We consider the use of a receiver with significantly reduced oversampling for wider bandwidths. Measured channel impulse response estimates are used to estimate the performance of this RAKE receiver. The results indicate that for CDMA systems with bandwidth near 20 MHz, one sample per chip may be adequate for the digital RAKE receiver in the outdoor microcellular environment. Two samples per chip may be enough for the indoor systems and the outdoor 10 MHz system.