Cooperative spectrum sensing with per-user power constraints

In collaborative spectrum sensing, the presence of the primary user is detected at a central entity, known as the fusion center. This center collects the information from the secondary users and decides on the occupancy of the desired frequency band. In the conventional strategy, the secondary users transmit their initial observations toward the fusion center with their maximum transmit powers. In this paper, however, we consider the problem of beamforming among the secondary users with individual power constraints. Correlated shadow fading has been considered in the channel gains between the primary transmitter and the secondary users as well as the channel gains between the secondary users and the fusion center. We consider the problem of maximizing the probability of detection for a required probability of false alarm. Most previous works have considered the total power constraint while in practical scenarios, each secondary user has a limited battery lifetime. An algorithm is developed which efficiently solves the problem via second order cone programming (SOCP) in an iterative manner. An approximation of the original problem is studied which reduces the computational complexity of the iterative procedure. The Monte Carlo simulations confirm the effectiveness of the spectrum sensing framework compared to the conventional strategy.