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

This paper considers multi-antenna downlink communication with base stations (BSs) that perform joint transmitter null-space decomposition (JT-decomp) and conventional single-cell linear precoding strategies under imperfect channel state information (CSI). Upper bounds for the rate loss of JT-decomp precoding and conventional cellular systems are first provided, which demonstrate that unlike conventional systems, the percentage rate loss of JT-decomp cooperative base station (BS) system decreases as signal-to-noise ratio (SNR) increases. This shows that JT-decomp precoding, in spite of the imperfect CSI, preserves its spatial multiplexing gain at high SNR. Accurate closed-form analytical expressions for the net ergodic achievable rate and the rate loss under erroneous CSI of the JT-decomp cooperative BS system are also derived.