On Sum Rate and Power Consumption of Multi-User Distributed Antenna System with Circular Antenna Layout

EURASIP Journal on Wireless Communications and Networking 01/2007; DOI: 10.1155/2007/89780
Source: DBLP

ABSTRACT We investigate the uplink of a power-controlled multi-user distributed antenna system (DAS) with antennas deployed on a circle. Applying results from random matrix theory, we prove that for such a DAS, the per-user sum rate and the total transmit power both converge as user number and antenna number go to infinity with a constant ratio. The relationship between the asymptotic per-user sum rate and the asymptotic total transmit power is revealed for all possible values of the radius of the circle on which antennas are placed. We then use this rate-power relationship to find the optimal radius. With this optimal radius, the circular layout DAS (CL-DAS) is proved to offer a significant gain compared with a traditional colocated antenna system (CAS). Simulation results are provided, which demonstrate the validity of our analysis.

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    ABSTRACT: We investigate the optimal placement of transmit antennas in distributed antenna systems. Our optimization framework imposes no constraints on the location of the an- tennas. Based on stochastic approximation theory, we adopt a formulation that is suitable for node placement optimization in various wireless network scenarios. We show that optimal placement of antennas inside the coverage region can significantly improve the power efficiency of wireless networks. We obtain the optimal placement topologies for different numbers of antennas and illustrate that the circular deployment is not optimum in general. Finally, we show via simulations that the optimal placement solution does not depend on the underlying shadowing model. Next generation cellular systems aim to increase their net- work capacity and coverage, as well as mitigate the adverse effects of interference. One possible strategy to alleviat et he interference, both in the uplink and the downlink of cellular networks, is to reduce the overall transmit power by using distributed antenna systems (DAS). These systems have the additional advantage of improving capacity and coverage (10). Moreover, by reducing the access distance between the transmitter and the receiver, distributed antenna systems have direct impact on the energy efficiency of the cellular network, which may lead to greener architectures for cellular networks in the future. However, the capacity increase (or equivalently the power saving) of DAS is largely influenced by antenna locations.
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    ABSTRACT: 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.
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    ABSTRACT: It has been long believed that the distributed antenna system (DAS) has great potentials for capacity improvement compared to the traditional cellular system with co-located base-station antennas. Intuitively, the distributed characteristic of antennas provides a much more efficient utilization of spatial resources. It, however, also significantly complicates the channel modeling and system analysis. Despite an increasing amount of academic attention and industrial interest, how to characterize the capacity advantages of the DAS in the multiuser scenario remains largely unknown. In this paper, we present a comparative study on the uplink ergodic sum capacity with multiple base-station antennas either co-located or uniformly distributed within a given area. We demonstrate that under the same consumption of transmission power, enormous gains can be achieved by the distributed antenna layout thanks to (1) reduced minimum access distance of each user; and (2) enhanced channel fluctuations which provide a significant boost to the sum capacity when the channel state information is available at both the transmitter and the receiver sides. We further apply the analysis to a cellular system with full cooperation among base stations. The comparison verifies that the DAS yields a much higher sum capacity, and capacity gains increase with the number of base-station antennas per cell.
    IEEE Journal on Selected Areas in Communications 07/2011; · 3.12 Impact Factor


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