Downlink Transmission of Distributed Antenna Systems in High Building Environments

Over the last few years high data rate wireless transmission has gained considerable attention in hot spot areas, including high buildings. It has been demonstrated that distributed antenna systems (DASs) improve the performance of the indoor environment by covering dead spots. In this paper, the DAS is investigated in high building to provide high data rates for indoor wireless mobile communications by exploiting spatial diversity and reducing radio transmission distance. In the proposed indoor DAS, several neighbouring floors compose a floor-bank and are controlled by one central unit (CU). The spectrum is not reused in a floor-bank, but can be reused among different floor-banks, which causes co-channel interference. In order to analyse the performance of the indoor DAS in high building with the presence of co-channel interference, an accurate propagation model of the interference from other floor is a key requirement. Direct propagation inside the building and reflection from nearby buildings have been considered in the channel model. Based on the theoretical analysis, the impact of several system parameters on the performance is presented in terms of BER. Numerical results indicate that the position of the user in the floor has significant effect on the system performance and the attenuation introduced by the floor separation in high buildings should be taken into consideration during the planning of the number of floor in each floor-bank