  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.
