MrCA: Multi-round collision avoidance for contention-based medium access control

Random access mechanisms play an important role in wireless networks and have been extensively studied in recent years. Although many previous studies have proposed enhanced algorithms, they only considered either throughput or fairness. In this paper we propose an efficient random access mechanism called Multi-round Collision Avoidance (MrCA). The key idea in MrCA is to avoid collisions by performing multiple contentions, each with smaller sized contention window. With this simple modification, we can significantly reduce the collision probability as well as improve the fairness. We analytically find the collision probability, and through simulations demonstrate that MrCA reduces the collision probability and increase the throughput by 25% while improving fairness compared to the IEEE 802.11 DCF with 50 contending stations. When MrCA and 802.11 DCF schemes are used with the auto rate fallback scheme, the performance gain of MrCA over 802.11 DCF increases because MrCA lowers the collision probability, which results in more accurate channel error estimation.