Joint interference avoidance and spectrum sharing for unlicensed wireless systems

One of the Interference Avoidance (IA) approaches is waveform adaptation in which transmitters adapt their waveforms and powers to avoid the multiple access interference in their corresponding receiver. In this paper, the uplink scenario of a multi carrier code division multiple access (MC-CDMA) cognitive radio system is considered under slow fading. In this set-up, a number of licensed (fixed) and unlicensed (agile) users share some orthogonal carriers to send data to a common receiver (or colocated independent receivers). Then, an iterative distributed algorithm is presented based on greedy interference avoidance as well as power control for this system which results in an ensemble of optimal waveforms. The proposed algorithm will be confirmed by the numerical examples and we look at properties of optimal solution.