Delta modulation for channel feedback in transmit diversity systems

In a wireless communication system with multiple transmit antennas, knowledge of the channel at the transmitter can be used to increase link and system capacity. In a frequency division duplex system, the channel may be estimated by the receiver and communicated back to the transmitter for use in future transmissions. Efficient schemes that achieve channel feedback in this manner are of interest. We present a channel feedback scheme that uses delta modulation to encode channel information efficiently by exploiting the temporal correlation of the wireless channel. A system with multiple transmit antennas and a single receive antenna is used to evaluate the performance of the channel feedback scheme. The effect of feedback channel errors on system performance is shown. The presented method is found to be advantageous for channels with low to moderate Doppler frequencies.