Impact of Transmit Antenna Separation on Downlink Cellular OFDM System with PARC Transmission

In this paper, the impact of transmit antenna separations at the base station on the downlink in a cellular OFDM system with per antenna rate control (PARC) is investigated. For the minimum mean square error (MMSE) with successive interference cancellation (SIC) receiver, the highly correlated interference resulting from closely spaced antennas is more easily suppressed than the independent interference resulting from widely separated antenna installations assuming the same number of interfering source(s). In the region where the interference from co-located source is dominating, the larger the transmit antenna separation, the better performances by the MMSE-SIC receiver. But in the region where interference from other cells is dominating, no gain is found when enlarging the transmit antenna separation, since it will only increase the number of uncorrelated interference sources. This means that for cell edge users it is beneficial with base stations with closely separated antenna installation in order to maximize the cancellation of inter-cell interference since the gain by multi-stream transmission for these users are small anyway.