Asymptotic rate analysis for non-orthogonal downlink multi-user systems with co-located and distributed antennas

This paper presents an asymptotic rate analysis for downlink multi-user systems with L base-station (BS) antennas either co-located or uniformly distributed within a circular cell. A representative non-orthogonal linear precoding scheme, maximum ratio transmission (MRT), is considered, based on which the effect of BS antenna layout on the intra-cell interference is characterized. The analysis reveals that the ratio σ of the number of BS antennas L and the number of users K is a key parameter that determines the rate performance of non-orthogonal downlink multi-user systems. Ergodic rates in the colocated antenna (CA) layout and the distributed antenna (DA) layout both logarithmically grow with σ, yet a higher rate is achieved in the DA case thanks to enhanced signal-to-interference ratio.