Abstract
Both IEEE 802.11 and IEEE 802.15.4 standards adopt the CSMA-CA algorithm to manage contending nodes’ access to the wireless medium. CSMA-CA utilizes the Binary Exponential Backoff (BEB) scheme to reduce the probability of packet collisions over the communication channel. However, BEB suffers from unfairness and degraded channel utilization, as it usually favors the last node that succeeded in capturing the medium to send its packets. Also, BEB updates the size of the contention window in a deterministic fashion, without taking into consideration the level of collisions over the channel. The latter factor has a direct impact on the channel utilization and therefore incorporating it in the computation of the contention window’s size can have positive impacts on the overall performance of the backoff algorithm. In this paper, we propose a new adaptive backoff algorithm that overcomes the shortcomings of BEB and outperforms it in terms of channel utilization, power conservation, and reliability, while preserving the fairness among nodes. We model our algorithm using Markov chain and validate our system through extensive simulations. Our results show a promising performance for an efficient backoff algorithm.
Highlights
The Binary Exponent Backoff (BEB) is an ingenious algorithm employed by both IEEE 802.11 and IEEE 802.15.4 standards to manage the wireless medium access among multiple competing nodes
In this paper we focus on the performance of BEB in IEEE 802.15.4-based wireless sensor networks (WSNs)
1) Channel utilization: We show in Fig. 16 Adaptive Backoff Algorithm (ABA)’s performance in terms of channel utilization, under unacknowledged traffic conditions, compared to BEB and NonOverlapping BEB (NO-BEB)
Summary
The Binary Exponent Backoff (BEB) is an ingenious algorithm employed by both IEEE 802.11 and IEEE 802.15.4 standards to manage the wireless medium access among multiple competing nodes. BEB may have a problem of unfairness under saturation conditions [20][25] This can be seen from noticing that a node that fails to access the medium tends to backoff for longer periods (because BE keeps increasing as mentioned earlier), reducing its opportunity of sending its packets. This way, the node refrains from accessing the medium, which discourages other nodes from using this node as their hop while forwarding packets These functionality issues in BEB are far from being acceptable in WSNs. The section focuses on the efforts proposed in the literature to modify BEB and enhance its performance in IEEE 802.15.4-based WSNs
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