Minghua Xia

Downlink Capacity of Distributed Antenna Systems in a Multi-Cell Environment

In this paper, the downlink performance of a distributed antenna system (DAS) with random antenna layout is investigated. We address the problem of characterizing the downlink capacity with the generalized assumptions: (a1) per distributed antenna power constraint, (a2) generalized mobile terminals equipped with multiple antennas, (a3) a multi-cell environment. Based on system scale-up, we derive a good approximation of the ergodic downlink capacity by adopting random matrix theory. We also propose an iterative method to calculate the unknown parameter in the approximation. The approximation is illustrated to be quite accurate and the iterative method is verified to be quite efficient by Monte Carlo simulations.

Downlink Power Allocation for Distributed Antenna Systems with Random Antenna Layout

In this paper, the downlink performance of dis- tributed antenna systems (DAS) with random antenna layout is investigated. We consider the composite channel including large-scale fading and small-scale fading. When the large-scale channel state information, which usually varies slowly and is easy to be obtained, is available at the transmitter, the problem of power allocation among distributed antennas with the target of downlink capacity maximization is formulated. Based on system scale-up, we derive a precise approximation of the downlink ergodic capacity by adopting random matrix theory. We also propose an iterative method to calculate the unknown parameter in the approximation. Moreover, the approximation is proved to be concave on the transmit powers of the distributed antennas. Consequently, a simple sub-optimal power allocation scheme is proposed, with which the system capacity is illustrated to be quite close to the optimal one obtained by numerical optimizations. Index Terms—Distributed antenna systems (DAS), downlink capacity, power allocation, iterative method.

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 ≤ M. In other words, when V ≤ 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.

Sum Rate Characterization of Distributed Antenna Systems with Circular Antenna Layout

In this paper, the uplink of a multi-user distributed antenna system (DAS) with antenna elements deployed on a circle is investigated. We address the problem of calculating the sum-rate capacity with per-user power constraints. Based on system scale-up, we derive a good approximation of the sum-rate capacity by adopting random matrix theory. We also propose an iterative method to calculate the unknown parameters in the approximation. The approximation is illustrated to be quite accurate and the iterative method is verified to be quite efficient by Monte Carlo simulations.

On the Optimal Radius to Deploy Antennas in Multi-user Distributed Antenna System with Circular Antenna Layout

In this paper, the uplink of a multi-user distributed antenna system (DAS) with antennas deployed on a circle is investigated. The optimal radius to deploy antennas is studied with the target of sum capacity maximization. Adopting random matrix theory, a good approximation of the per-user sum capacity is derived. We also present a numerical method to calculate the unknown parameters in the approximation. Consequently, as the sum capacity is maximized, we find out the optimal radius of the circle on which the distributed antennas are deployed.

On the size of antenna cluster in multi-user distributed antenna systems

In this paper, multi-user distributed antenna systems (DAS) with antennas deployed in clusters are studied. In order to investigate the impact of the size of antenna cluster on the system performance, the mean square access distance (MSAD), which is a function of the size of antenna cluster, is defined as a metric of the system performance. From the analysis of the asymptotic behavior of the metric, we obtain the approximate closed-form expressions for the expectation and relative variance of the MSAD. Accordingly, we find out the semi-quantitative relationship between the size of antenna cluster and the system performance. Moreover, the benefits of the DAS under different cluster size are discussed. The validity of our analysis is well verified by simulations.

On the Downlink Capacity of Distributed Antenna Systems with Random Antenna Layout

In this paper, the downlink capacity of distributed antenna systems (DAS) with random antenna layout is investigated. When the channel state information is only available at the receiver (CSIR), a good approximation of the downlink capacity is derived by adopting random matrix theory. We also propose an iterative method to calculate the unknown parameters in the approximation. The validity of our analysis is well verified by simulations. The approximation is illustrated to be accurate and the iterative method is verified to be efficient.