in Proc. IEEE International Conference
Space-time block codes (STBC) are powerful techniques to achieve full
spatial diversity in Rayleigh fading channels with low decoding complexity.
When channel state information is available to the transmitter, space-time
block codes can be improved through the use of a transmit precoder chosen based
in part on the current channel state. In this paper, we investigate the
downlink transmission of an Alamouti space-time block coded multiuser wireless
system in which complete channel knowledge is available to the base transceiver
station. A novel unitary precoder is proposed that, with enough antennas, can
effectively precancel co-channel interference at each mobile user thus enabling
simple single user space-time block decoding. It is shown that excess transmit
antennas, beyond the minimum required for precancellation, can be used to
further improve the diversity performance through careful selection of the
precoding matrix. Though the derivation assumes perfect channel state
information, the impact of estimation error is investigated by deriving an
lower bound on the signal to interference plus noise ratio.
This paper is available as a .IEEE Xplore .