Research On Key Technologies Of Distributed Antenna Communication System

The main challenge of the future wireless system is the conflicting of the scarce frequency resources and requirement of the various high-speed data services. To meet the demand of the high data rate multimedia services and the quality of service (QoS), a higher bandwidth and frequency efficiency is needed, which is stimulating the research on the new wireless transmission technologies and network infrastructure. Currently, the great capacity advantages of the multiple input multiple output (MIMO) system result in the research on the space-time processing technologies. Orthogonal frequency division multiplexing (OFDM) has been accepted as an attractive air interface candidate for the next generation wireless standards due to its capability for combating the frequency selective fading and inter symbol interference (ISI). The distributed antenna system, which is an innovative structure compared with the traditional cellular one for its natural advantages in coverage, frequency efficiency, transmit power etc, become a hot research topic. The National 863 FuTURE Project has carried out a research on the distributed wireless communication system intensively. The dissertation focuses on the key technologies of distributed antenna system. The research topics cover the antenna selection algorithms in distributed MIMO system, the transmit diversity technology of distributed antenna system, multiuser downlink beamforming problems, multiuser sub-carrier, antenna and power allocation algorithm for orthogonal frequency division multiple access (OFDMA) distributed antenna system, and the dynamical system level simulator of distributed antenna system (DAS) etc.We give an overview of current state of the art in DAS. The following are the main contributions of our work on the above topics.In chapter 2, the single cell capacity of the distributed MIMO system is compared with the centralized MIMO system, through which the capacity advantages and characteristics of the distributed MIMO system are given. The instantaneous receive SINR analysis is given under the multicell distributed antenna system scenario, and a phase only maximum ratio transmission is adopted at the transmit side. The closed expressions of the cumulative distribution function (CDF) of the instantaneous SINR and the average SINR are derived, which are verified through simulation.In chapter 3, a norm and correlation based antenna selection algorithm (NCBA) and its modified version (NCBA-M) are proposed for the downlink transmit antenna selection in distributed MIMO systems. The performance of the proposed algorithms is compared with that of norm based antenna selection algorithm (NBA) and large scale fading based antenna selection algorithm (LFBA) respectively. The proposed algorithm NCBA-M has a very low computation complexity and the performance can approach that of the optimal antenna selection algorithm.In chapter 4, the optimum single user transmit weight designing problem is investigated under both sum power constraint (SPC) and antenna power constraint (APC) in distributed antenna system. The weight design problem under SPC and APC is formulated as a nonlinear optimization problem, and an algorithm named Gradient-MRT is proposed to find the optimal solution. A multi-level zero-forcing beamforming method is proposed for the multiuser downlink system with per antenna power constraint (PAPC), and a multi-layer structure is proposed to realize the method. A sub-optimal power allocation algorithm is also proposed to find the power allocation matrix. Simulation result shows that the proposed multi-level zero-forcing method can achieve a higher sum-capacity than that of traditional zero-forcing method with PAPC.In chapter 5, a sub-carrier, antenna and power allocation algorithm is proposed for OFDMA distributed antenna system, which can maximize the effective sum-capacity, and per antenna power constraint. According to the simulation result, the proposed algorithm can fulfill the proportional rate requirement well, and remarkable capacity gain is observed when compared with the centralized antenna system.In chapter 6, the discrete events based dynamical system level simulator of the OFDMA distributed antenna system is described in detail. A cross-layer resource allocation algorithm is proposed and realized in our simulator, and the performance is compared with some normal algorithms.