Optimum bandwidth per sub-carrier of multicarrier/DS-CDMA for broadband packet wireless access in reverse link

Abstract

This paper elucidates the optimum bandwidth per subcarrier in the reverse link for multicarrier (MC)/DS-CDMA using a 10 to 80 MHz bandwidth in a multipath fading channel with numerous resolved multipaths, taking into account all major effects, ie, the improvement in the Rake time diversity effect and the degradation in the path search and the channel estimation due to multipath interference (MPI). The simulation results show that the improvement in radio link performance is almost saturated at a bandwidth of greater than 40 MHz (the corresponding number of multipaths is 12-48) when the spreading factor of the channel is SF = 32, and the best performance is achieved at the bandwidth of approximately 20 MHz when SF = 4 with two-branch antenna diversity reception. This is generated by the tradeoff between the improvement in the Rake time diversity effect and the increased MPI in addition to the degradation in the path search and channel estimation accuracy associated with a lower average received signal-to-interference plus background noise power ratio. Therefore, we conclude that MC/DS-CDMA, where each carrier has the bandwidth of approximately 20-40 MHz, is one of the most promising candidates for broadband packet wireless access in the reverse link.