Employing Coordinated Transmit and Receive Beamforming in Clustering Double-Directional Radio Channel

A novel beamforming (BF) system that employs two switched beam antennas (SBAs) at both ends of the wireless link in an indoor double-directional radio channel (DDRC) is proposed. The distributed directivity gain (DDG) and beam pattern correlation in DDRC are calculated. The channel capacity of the BF system is obtained from an analytical model. Using the channel capacity and outage capacity as performance measures, we show that the DDG of the BF system directly increases the average signalto-noise ratio (SNR) of the wireless link, thus achieving a direct increase of the ergodic channel capacity. By jointly switching between different pairs of transmit (Tx) and receive (Rx) directional beam patterns towards different wave clusters, the system provides diversity gain to combat against multipath fading, thus reducing the outage probability of the random channel capacity. Furthermore, the performance of the BF system is compared with that of a multiple-input multiple-output (MIMO) system that is set up using linear antenna arrays. Results show that in a low-SNR environment, the BF system outperforms the MIMO system in the same clustering DDRC.