Maximizing sum-outage capacity of OFDM-based cognitive radio under primary user queue stability constraint

We consider a cognitive radio system in which primary user stores packets in a queue for transmission. For proper functioning of primary system, the cognitive user must ensure that primary queue remains stable. We show that such a queue stability constraint can be converted to an equivalent interference constraint on cognitive user´s transmission. Under this constraint, we propose a power allocation technique to maximize sum of individual outage capacities achieved on each sub-channel of an OFDM based cognitive user. We present simulation results depicting effect of channel gains of direct links and interference links on primary user´s stable throughput and cognitive user´s sum-outage capacity. The results show that proposed method performs better than only interweave mode of transmission used in literature.