On the design of spectrally overlaid CDMA systems under a practical interference environment

Abstract

This paper studies the capacity of a multiple chip rate (MCR) system under a practical environment. In our analysis, the use of non-orthogonality spreading codes, differences in carrier frequencies and power spectrum density of signals for different users, are taken into consideration. Capacities of two MCR systems with different subsystem configurations are obtained. Comparison between the capacity of a MCR system and a multiple processing gain (MPG) system is also given. From the numerical results obtained, it can be concluded that for MCR systems, the full assignment configuration (a) can provide higher system capacity than configuration (b), and configuration (b) with Δω=0 achieves the same capacity as that of MPG systems. Hence with good control of the spectrally overlaid structure, MCR systems can achieve higher capacity than MPG systems. © 2003 IEEE.