TRACKING PERFORMANCE OF AN ADAPTIVE TRANSMIT BEAMSPACE BEAMFORMER IN DYNAMIC MISO WIRELESS CHANNELS

This paper presents the performance of an Adaptive Transmit Beamspace Beamformer (ATBBF) in a dynamic channel for Multiple Input Single Output (MISO) per user wireless system. An ATBBF consists of several transmit beamformers on the Transmit Antenna Array (TAA). The antenna weights of each Transmit Beamformer (TB) are held constant while its input is weighted by an adaptive beamspace weight. A Beamspace Gradient Sign Feedback (BGSF) algorithm updates these beamspace weights. The performance metric of an ATBBF is derived and analyzed in a dynamic channel undergoing Rayleigh fading independently at the antennas. A performance comparison between an ATBBF and a TB having adaptive antenna weights is made in terms of convergence and tracking of various slow and fast fading channels by simulations. Both Full Dimension (FD) and Reduced Dimension (RD) ATBBFs are considered. Comparisons show that the FD ATBBF gives a performance equivalent to that of a TB and outperforms the RD ATBBF. Thus the FD ATBBF can provide beamforming gain and fading diversity similar to that of a TB. Furthermore, the performance of the FD ATBBF improves on increasing the number of antenna elements of the TAA.