Collision Avoidance in TV White Spaces: A Cross-layer Design Approach   for Cognitive Radio Networks
  One of the most promising applications of cognitive radio networks (CRNs)is the efficient exploitation of TV white spaces (TVWSs) for enhancing the performance of wireless networks. In this paper, we propose a cross-layer design (CLD) of carrier sense multiple access with collision avoidance (CSMA/CA) mechanism at the medium access control (MAC) layer with spectrum sensing (SpSe) at the physical layer, for identifying the occupancy status of TV bands. The proposed CLD relies on a Markov chain model with a state pair containing both the SpSe and the CSMA/CA from which we derive the collision probability and the achievable throughput. Analytical and simulation results are obtained for different collision avoidance and spectrum sensing implementation scenarios by varying the contention window, backoff stage and probability of detection. The obtained results depict the achievable throughput under different collision avoidance and spectrum sensing implementation scenarios indicating thereby the performance of collision avoidance in TVWSs based cognitive radio networks. 
Fotis Foukalas and George Karetsos
cs.NI