On the Optimality of Single-Carrier Transmission in Large-Scale Antenna Systems

A single carrier transmission scheme is presented for the frequency selective multi-user (MU) multiple-input single-output (MISO) Gaussian Broadcast Channel (GBC) with a base station (BS) having M antennas and K single antenna users. The proposed transmission scheme has low complexity and for M >> K it is shown to achieve near optimal sum-rate performance at low transmit power to receiver noise power ratio. Additionally, the proposed transmission scheme results in an equalization-free receiver and does not require any MU resource allocation and associated control signaling overhead. Also, the sum-rate achieved by the proposed transmission scheme is shown to be independent of the channel power delay profile (PDP). In terms of power efficiency, the proposed transmission scheme also exhibits an O(M) array power gain. Simulations are used to confirm analytical observations.