BASE STATION TRANSMITTING ANTENNA-ARRAYS FOR MULTIPATH ENVIRONMENTS

Adaptive transmitting antenna arrays can increase the capacity of mobi le radio networks by reusing a channel among several users. To reuse b andwidth, a transmitting antenna array can exploit feedback informatio n from the mobile receivers in order to track changes in the multipath environment. When the mobile is moving rapidly, the required feedback rates can become significant. We present a new method for transmissio n beamforming, which, by exploiting the subspace structure present in the spatial channel, requires much lower feedback data rates than prev ious methods. We consider antenna arrays at the base only, and the mob ile has a single omnidirectional antenna.