Spectrum Efficiency in Distributed Antenna Systems

The distributed antenna system (DAS) is a promising system to provide high data rate for future wireless communications, since it can reduce the radio transmission distance. This paper aims to investigate the average spectrum efficiency and the cell edge spectrum efficiency in the downlink transmission of the DAS. Firstly, the approach of antenna unit selection for spatial diversity is presented in the DAS without frequency reuse. Then, to achieve high spectrum efficiency, frequency reuse is exploited in the DAS. In order to show the advantage of frequency reuse, the spectrum efficiency of the DAS with frequency reuse is theoretically compared with the DAS without frequency reuse. Numerical results show that reusing frequency in the DAS can increase the spectrum efficiency significantly. It also shows that when the frequency reuse area increases, the performance gain from the frequency reuse is impaired because of the increase of the co-channel interference.