Abstract:

Numerous wireless network protocols, including IEEE802.11 and 802.15.4, manage the retransmission of data frames with the binary exponential backoff (BEB) mechanism. In a dynamic distributed environment, the fixed way the BEB adjusts contention window cannot adapt to the ever changing network size. To solve this problem, we propose an improved selfadaptive adjusting backoff algorithm based on contention window diminishment factor. By introducing the concept of contention window diminishment factor, the algorithm adaptively adjusts the waiting time of wireless nodes to realize the network throughput maximization. In addition, in order to track the changing number of competition nodes, we propose a heuristic algorithm when implementing our new backoff scheme. Simulations on the same physical layer parameters of the IEEE 802.11 DCF protocol show that the proposed algorithm can improve the throughput and decrease the frame delay.

Key words: backoff algorithm, contention window, IEEE802.11 DCF, normalized maximum throughput, diminishment factor