We develop cognitive radio networking methods for a heavy-traffic model in which the channel is always occupied by primary users. This contrasts with the interference-avoidance approach for the non-heavy-traffic model, in which primary users have idle times, and secondary users are allowed to use the channel at those idle times. We use an “underlay” approach to cognitive radio networking by allowing secondary users to share the channel with simultaneously transmitting primary users.

Thus, secondary users can degrade the performance of primary users, and our goal is to ensure that the level of performance degradation is acceptable. This is accomplished by scheduling and coordinating the transmissions among users, as well as providing a safeguard for controlling the level of additional interference caused by transmissions from secondary users. We show that our methods can provide additional throughput for secondary users, while maintaining the performance of primary users at the specified level.

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