Multi-mode precoding using linear receivers for limited feedback MIMO systems

Multiple-input multiple-output (MIMO) wireless systems obtain large diversity and capacity gains by employing multi-element antenna arrays at both transmitter and receiver. The theoretical performance benefits, however, are irrelevant unless low error rate, high spectral efficiency spatio-temporal signaling techniques are found. Most work in space-time coding concentrates on either designing low error rate codes or high data-rate codes but not both simultaneously. This paper proposes a new method for designing high data-rate spatio-temporal signals with low error rates. The basic idea is to use transmitter channel information in the form of limited feedback to adaptively vary the transmission scheme for a fixed data-rate. This adaptation is done by varying the number of substreams and the rate of each substream in a precoded spatial multiplexing system. We show how this method can be implemented in a limited feedback scenario where only finite sets, or codebooks, of possible precoding configurations are known to both the transmitter and receiver. Monte Carlo simulations show substantial performance gains over beamforming and spatial multiplexing.