Max-Min SINR Dependence on Channel Correlation in Line-of-Sight Massive MIMO

Under LoS (line-of-sight) propagation and the assumption of perfect CSI (channel state information), for either MR (maximum-ratio) or ZF (zero-forcing) precoding/decoding, one can readily obtain Massive MIMO (multi-input multi-output) per-user effective SINR for single-cell scenarios. LoS channels are typically less correlated than IID (independent and identically distributed) Rayleigh channels, but the maximum correlation for LoS is typically much greater than for IID Rayleigh. This motivates an investigation of the dependence of max-min SINR on the maximum channel correlation. Perron-Frobenius theory and the classical Fischer inequality are used to establish some rigorous and explicit upper bounds on the effective max-min SINR (signal to interference plus noise ratio) that depend on the maximum channel correlation. These upper bounds provide an accurate description of this dependence relationship, and readily facilitate system performance analyses and scheduler designs without simulations. In high channel correlation environment, ZF can perform substantially better than MR in the downlink but the opposite is true for the uplink.