Space alignment based on primary transmission-outage for cognitive transmission

A space-alignment scheme based on primary transmission-outage (TO) for cognitive transmission in a multiple-input multiple-output uplink system is proposed. The main idea is that a secondary transmitter aligns its transmit directions by precoding to unused primary channel eigenmodes where the TO event happened, which is denoted by bit error rate (BER) over a target BER which is the typical minimum value required for acceptable system performance. The proposed scheme achieves a higher performance in comparison with the SA scheme of zero outage.