Single-cell vs. Multicell MIMO Downlink Signalling Strategies with Imperfect CSI

Cooperative base station (BS) signaling in multiple-input multiple-output (MIMO) multicell networks has been recently shown to achieve significant gains in system throughput and reliability. However, the promised gains of BS cooperation depend on the assumptions of perfect channel state information at the transmitters (CSIT) and ideal backhaul links. By focusing on the effects of imperfect CSIT on cooperative BS systems, this paper considers multi-antenna downlink communication with base stations (BSs) that perform joint transmitter null-space decomposition (JT-decomp) linear precoding strategy. An upper bound for the rate loss of JT-decomp precoding is provided, which demonstrate that the percentage rate loss of JT-decomp cooperative BS system decreases as signal-to-noise ratio (SNR) increases. This shows that JT-decomp precoding, in spite of the imperfect CSIT, preserves its spatial multiplexing gain at high SNR.