Distributed energy-delay framework for opportunistic spectrum access

In this paper, we consider the problem of spectrum sharing among one primary and multiple secondary users. Particularly, we study the problem of non-cooperative spectrum sensing and access. Secondary users have to sense the channel before accessing it. There is a tradeoff between large packet delay, partially due to collisions between secondary users, and high energy consumption for sensing. To overcome this problem, we consider an opportunistic spectrum access in cognitive radio taking into account packet delay and energy consumption. Hence, there is an associated spectrum occupancy and packet delay (the time elapsed since the reception) state for each secondary user. Due to partial sensing, a Partial Observable Markov Decision Process (POMDP) is used to determine an equilibrium policy. The equilibrium is obtained by using a linear program. We identify a paradox in this cognitive radio context: when the channel is more occupied by the primary user, this may improve the spectrum utilization by secondary users. We also investigate the impact of transmission cost on the equilibrium and show numerically how this cost can be used to enhance the utilization of the spectrum.