Antenna placement for downlink distributed antenna systems with selection transmission

In this paper we propose new algorithms to determine the antenna location for downlink distributed antenna systems (DAS) with selection transmission (ST). ST has some advantages for DAS since the feedback overhead is quite small and other-cell interference can be reduced compared to other transmission schemes. For the single-cell case, we consider a circular antenna layout with or without a center antenna and divide a cell into regions with the same physical area. Then, we formulate the optimization problem of distributed antenna (DA) port locations which maximizes the lower bound of the expected signal to noise ratio in each region. Also, for the two-cell DAS, we maximize the lower bound of the expected signal to leakage ratio to identify the optimum da positions. In order to solve the problem, we propose an iterative method by deriving the gradient of the cost function for a gradient ascent algorithm. The da locations obtained from our proposed method are compared with conventional solutions. Simulation results show that the proposed algorithms offer a large capacity gain over the centralized antenna systems in single-cell and two-cell environments.