A SVD-Based Location Coding for Cognitive Radio in MIMO Uplink Channels

This letter introduces a transmission technique for cognitive access in M x M Multiple-input multiple-output uplink channels. Based on an appropriate space alignment design, the cognitive channel is decomposed to M orthogonal Gaussian channels that overlap the primary eigenmodes and enable cognitive transmission in two ways: (a) by transmitting cognitive data to the subchannels that overlap unused eigenmodes, (b) by transmitting a codeword of length M using the subchannel activity as a codeword pattern. The investigated technique overcomes limitations of previously reported approaches and guarantees a minimum cognitive data rate equal to the number of antennas.