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

摘要

This paper elucidates the optimum bandwidth per subcarrier in thereverse link for multicarrier (MC)/DS-CDMA using a 10 to 80 MHzbandwidth in a multipath fading channel with numerous resolvedmultipaths, taking into account all major effects, ie, the improvementin the Rake time diversity effect and the degradation in the path searchand the channel estimation due to multipath interference (MPI). Thesimulation results show that the improvement in radio link performanceis almost saturated at a bandwidth of greater than 40 MHz (thecorresponding number of multipaths is 12-48) when the spreading factorof the channel is SF = 32, and the best performance is achieved at thebandwidth of approximately 20 MHz when SF = 4 with two-branch antennadiversity reception. This is generated by the tradeoff between theimprovement in the Rake time diversity effect and the increased MPI inaddition to the degradation in the path search and channel estimationaccuracy associated with a lower average received signal-to-interferenceplus background noise power ratio. Therefore, we conclude thatMC/DS-CDMA, where each carrier has the bandwidth of approximately 20-40MHz, is one of the most promising candidates for broadband packetwireless access in the reverse link