Coordinated Optimization of underlay network communication for efficient use of spectrum

Underlay communications has the potential to become a valuable tool for increasing the capacity of spectrum provided that the quality of communications is upheld. In this paper, we propose a method for underlay nodes to detect, and coordinate with, other underlay nodes to form a network on preoccupied spectrum. Specifically, we introduce a novel optimization algorithm, called the Coordinated Optimization of EXposure Introduced by a Secondary Transmitter (COEXIST), which selects the best communications channel for all nodes within a network while minimizing interference with the primary user. This algorithm does not require knowledge of spatial location of the primary users or underlay nodes. With the proposed solution, underlay nodes can detect other nodes at power levels far below the power level of the primary user and, once a network is formed, nodes can continue to communicate at very low power levels without causing interference to primary users transmitting at the same time.