On the Deployment of Antenna Elements in Generalized Multi-User Distributed Antenna Systems

In this paper, we focus on a generalized multi-user distributed antenna system (DAS), where the antenna elements (AEs) are divided into antenna clusters and the antenna clusters are randomly deployed in the coverage area. The mobile terminals equipped with M AEs each are supposed to be uniformly distributed in the coverage area. We are motivated to study the impact of the deployment of antenna elements on the system performance. In the model of consideration, the deployment of antenna elements is characterized by the antenna cluster size V, i.e., the number of AEs within each antenna cluster, and the distribution of the antenna clusters. With the assumption that the antenna clusters are uniformly deployed in the coverage area, the impact of the antenna cluster size V on the uplink sum rate capacity is particularly investigated. The mean square access distance (MSAD), a function of V, is proposed as a reasonable metric instead of the uplink sum rate capacity. From the analysis of the asymptotic behavior of MSAD, we derive an approximate closed-form expression for the expectation of MSAD over system topologies. Then, it is concluded that the ergodic uplink sum rate capacity can be improved due to access distance reduction by scattering AEs further only when V > M. An approximate closed-form expression for the relative variance of MSAD is also derived. And we conclude that the outage uplink sum rate capacity can be improved due to macro-diversity by scattering AEs further only when V a parts per thousand currency signaEuro parts per thousand M. In other words, when V a parts per thousand currency signaEuro parts per thousand M, the ergodic uplink sum rate capacity can not be improved by scattering AEs further, when V > M, the outage uplink sum rate capacity can not be improved by scattering AEs further. Finally, our analysis is well verified by Monte Carlo simulations.