Fairness-oriented spectrum sharing for ODFC-based WRAN

Wireless Regional Area Network (WRAN) is standardized by IEEE 802.22 to improve the spectrum utilization in the TV frequency spectrum. Spectrum sharing or coexistence among unlicensed users, plays a crucial role in the spectrum utilization and hence it has been identified as a critical issue in WRAN. Coexistence between unlicensed users is referred to as self-coexistence for which IEEE 802.22 designs the On Demand Frame Contention (ODFC) as a solution. The traditional 802.22 ODFC selects a contention winner in a random manner where all the contenders have a uniform winning probability distribution, without considering different frame demands from contenders. Consequently, the winner will occupy the channel for a long time if it has a larger frame demand while unsuccessful contenders may suffer from spectrum starvation, thus ODFC does not ensure a fair self-coexistence. In this paper, we investigate the fairness issue and present a novel approach termed Fairness-oriented ODFC (F-ODFC). The proposed approach considers several effects including different frame demands from contenders and previous contention failure rates among multiple users with the same frame demands. In F-ODFC, we employ a probabilistic approach rather than the traditional deterministic solution to attack the fairness problem. Extensive simulations verify that the proposed F-ODFC is able to provide a fair self-coexistence mechanism with varied frame demands and significantly enhance the fairness of ODFC-based WRAN.