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.