Performance of the uplink multicarrier CDMA systems for WPAN indoor applications on MMW band

Abstract

This paper compares the soft-decision decoding based BER performance of two multicarrier CDMA schemes: MC-CMDA and MC-DS-CDMA assuming a 6.4 GHz bandwidth based on 62.5 GHz carrier frequency in order to achieve an optimum wireless access scheme for WPAN (wireless personal area network) applications. In an indoor millimeter wave propagation environment, although the channel is time-invariant for a long time, the requirement of very high data rate makes the system design a hard mission and the severe MAI caused by asynchronous users in the uplink, especially with very low spreading factor, makes it harder. Computer simulation results show that, in the reverse link, MC-CDMA achieves much better performance than MC-DS-CDMA for single user scenario because of the severe ISI in the latter system. However, as the number of users increases, MC-CDMA, which is spread in the frequency domain, cannot hold its BER superiority to that of MC-DS-CDMA, spread in the time domain, since the larger number of subcarriers in MC-CDMA system, requested to reach 1 Gbps data rate, would experience frequency selective degradation in the frequency domain, which results in the loss of orthogonality among subcarriers. Moreover, the low spreading factor would cause more severe MAI.