Joint Optimization of the Transmit Antenna Array Geometry and Linear Precoding for MIMO Systems

For a cellular system with a fixed number of transmit antennas at each base station, we investigate how the data rate on the downlink varies as a joint function of the geometry of the transmit array and the linear precoding that precedes the transmit array. The maximum average data rate that can be reliably transmitted over the downlink channel (i.e. the ergodic capacity of the downlink channel) is used in this paper to compare various configurations of transmit antennas at the base stations. Using the 3GPP Spatial Channel Models [4] for a macro-cellular environment, we find the optimum configuration of transmit antennas with a total of 2 or a total of 4 transmit antennas at various SNRs. We offer guidelines for choosing the best transmit antenna geometry for different SNR regions.