A short-term fair MAC protocol for WLANs

Abstract

Designing a medium access control (MAC) protocol that simultaneously provides high throughput and allows individual users to share limited spectrum resources fairly, especially in the short-term time horizon, is a challenging problem for wireless LANs. In this paper, we propose an efficient cooperative MAC protocol with very simple state information that considers only collisions, like the standard IEEE 802.11 MAC protocol. However, contrary to the IEEE 802.11 MAC, the cooperative MAC gives collided users priority to access the channel by assigning them shorter backoff counters and interframe-spaces than users who did not participate in the collision event. In other words, collided users are the only ones allowed to transmit in the following contention period. For the cooperative MAC protocol, we utilize an analytical throughput model to obtain the optimal parameter settings. Simulation results show that the cooperative MAC provides significant improvement in short-term fairness and access delay, while still providing high network throughput.

Achieving per Node Throughput Fairness in a Single-Branch of Mesh Networks

“…In this section, we first briefly review the underlying MAC protocol, Cooperative MAC (C-MAC) [21]. Then, we describe the proposed mesh fairness algorithm.…”

“…The Cooperative-MAC (C-MAC) [21] protocol provides short-term fair access to all users in wireless LANs via a contention-based MAC protocol with minimum computational complexity and memory requirements, and high network throughput. In this section, we briefly explain the C-MAC protocol and more detailed information about the C-MAC can be obtained from Reference [21].…”

“…If a successful transmission occurs, then the sender chooses a new backoff counter uniformly from the discrete range [Ws,2Ws -1]. As shown in Reference [21], the C-MAC requires a successful user to choose a large value for its backoff counter so that the new value is larger than other users' backoff counters. Hence, the successful user will not transmit before the other existing users.…”

“…Therefore, we need an additional mechanism to allow multi-hop nodes to access channel more. In Reference [21], we show that transmission probability of any node is…”