Collaborative Opportunistic Spectrum Access in the Presence of Multiple Transmitters

We present a collaborative algorithm to enable opportunistic spectrum access for cognitive radios in the presence of multiple co-channel transmitters. A spectrum hole detection and estimation technique based on received signal strength observations is developed, which allows the coexistence of both licensed and unlicensed transmitters. We address the issue of how to perform collaborative spectrum sensing in the presence of multiple co-channel transmitters and how to determine the maximum transmit power that can be used for a given frequency channel by a cognitive radio while avoiding harmful interference to the licensed network. We provide some simulation results to validate the feasibility of our approach.