Downlink Sum-Rates of SC-FDP and OFDM Massive MIMO Systems in Doubly Dispersive Channels

Abstract

We investigate channel double dispersiveness in downlink of a massive multiple input multiple output system which operates in time division duplex (TDD) mode. We examine single carrier frequency domain processing (SC-FDP) and orthogonal frequency division multiple access (OFDM). In four scenarios. In the first scenario, which is the comprehensive scenario, we consider both the channel aging and channel estimation error effect due to Doppler Frequency. Therefore, we assume to have knowledge of the estimated channel in the previous block which was estimated in presense of Doppler shifts and noise. The other three scenarios are special cases of the first scenario which are studied to have a better insight on the Doppler effects on massive MIMO systems. In the second scenario the system is subject to both channel aging and channel estimation errors, but the channel estimation error is model with Gaussian noise. In the second scenario, we focus only on channel aging effect. In the fourth scenario, to investigate only the impact of channel time variation within the block duration, we assume perfect channel state information (CSI) with no channel aging. The results indicate that in all the scenarios, SC-FDP achieves higher sum-rate than OFDM. For the first scenario the sum-rate of both systems get bounded as the number of BS antennas tends to infinity. However, for the other three cases the sum-rate of SC-FDP, unlike OFDM, increases unboundedly as we increase the number of BS antennas. The results from the block error rate (BLER) studies validate the sum-rate results.