Resolving Collision and Delay Deterioration by a Novel Channel Collision Based Adaptive Backoff (CCBAB) Scheme in Wireless LANs

IEEE 802.11e standard has defined EDCA to guarantee prioritized QoS by service differentiation. However, it induces significant performance deterioration in both delay performance and collision probability at heavy load due to inherent drawbacks of binary exponential backoff (BEB) scheme. In this paper we proposed a novel backoff scheme, channel collision based adaptive backoff (CCBAB)1 scheme which compels each station to react to channel collisions irrespective of whether or not it is involved in, to combat the deterioration problem. CCBAB selectively forces some uncollided traffics to reduce their transmission probability and grants collided real time traffics larger transmission probability to ensure them be successfully transmitted in a shorter time. Simulations demonstrate that CCBAB scheme achieves more stable channel collision probabilities, smaller delay and jitter for real time traffics than EDCA and its enhanced variation AEDCF schemes and proves to be more resistant towards collisions and delay deterioration at high congestion level.