Traffic pattern-based opportunistic spectrum access of cognitive femto base stations for decentralized cross-tier interference management

We propose opportunistic spectrum access methods of cognitive femto base station (BS) for time slot level operation after self-configuration and self-optimization processes. When a femto BS shares frequency channels with a macro BS, it performs spectrum sensing and accesses available frequency channels opportunistically. Partially observable Markov decision process (POMDP) and its suboptimal strategy are proposed as opportunistic spectrum access methods of the femto BS. In the strategy, change of channel state after channel sensing and resource collision between femto and macro BSs are considered for short-term operation. Performance results show that the proposed methods contribute the spectral efficiency to the system when the channels are occupied by macro users with bursty internet traffic.