Investigating the relation between optimum guard interval and channel delay spread for a MC-CDMA system

Abstract

This paper demonstrates a novel approach to determining the optimum guard interval for a multicarrier code division multiple access (MC-CDMA) system. Analytical expressions for useful and interference power are derived as a basis for comparison. From these, an expression for the signal-to-noise ratio of a detected bit is derived and used to determine the optimum guard interval for a given channel profile and system parameters. In contrast to other works, we use channel models based on actual measurements and we highlight important differences from theoretical models to support our approach. From our results, we propose an empirical rule for optimum guard intervals given prevailing channel parameters. We show that the optimum guard interval can be selected as the delay window that includes 95% and 99% multipath power for E-s/N-o = 10 dB and E-s/N-o = 20 dB, respectively. In our case, the optimum guard interval was between 2 tau(rms) and 4 tau(rms) for E-s/N-o = 10 dB and between 3 tau(rms) and 6.4 tau(rms) for E-s/N-o = 20 dB.