Class of collision resolution schemes with multistep distribution for IEEE 802.11

Traditional Medium Access Control (MAC) algorithms for Distributed Co-ordination Function (DCF) in IEEE 802.11 extend window ranges after each packet collision in the next stage. As these window ranges intersect with window ranges of other stages, the system is collision prone. This paper proposes a class of collision resolution schemes for 802.11 contention window control with multistep distribution and called as Overlapped Contention Slots with Multistep Distribution (OCS-MD). It is shown that proper selection of different steps in the distribution of OCS-MD increases the mean value of back-off counter as compared to standard Binary Exponential Back-off (BEB). This reduces probability of window intersection of different stages, resulting in lesser probability of collision. The system model is formulated for the proposed schemes. Analytical results are validated against those obtained from simulation. The performance results show that the proposed algorithm enhances the system performance in terms of throughput and collision probability with comparable mean delay and fairness than existing scheme. Moreover these schemes can be easily incorporated with little modifications in existing 802.11 standard.