A Study on the Binary Exponential Backoff in Noisy and Heterogeneous Environment

摘要

Recently, some proposals have suggested that maintaining the same contention window (CW), or reducing it, for nodes suffering packet losses, due to channel transmission impairments, is effective in increasing the performance of the IEEE 802.11 in noisy environment. Our study presented inhere will prove analytically and via simulations that this should not be necessarily the case. To facilitate our analysis, we consider two binary exponential backoff (BEB) algorithms in our study: a standard BEB where a host increases its CW upon every packet loss (collision or transmission error) and another access method with a capability to differentiate between the type of losses; here, a host experiencing a loss will increase its CW only after a collision and remain in the same backoff stage otherwise. We show that the second access procedure outperforms the standard BEB when the network is lightly loaded. However, in a congested network, this quick recovery property results in intensifying the collisions among contending nodes and hence yields a poor system performance. We propose a hybrid method that takes advantage of both access methods to achieve better throughput under various network loads.