Wireless ad-hoc networks are dynamic multi-hop wireless networks established by a group of mobile stations without pre-existing network infrastructure or centralized administration. Several MAC protocols are devised to address the “hidden terminal” problem in wireless ad-hoc networks. Among them, IEEE 802.11 Distributed Foundation Wireless Medium Access Control (DFWMAC) is a proposed standard for wireless ad-hoc and infrastructure LANs. Although DFWMAC achieves reasonable throughput by alleviating “hidden terminal” problem, it still suffers from a severe fairness problem under heavy traffic, because of the multi-hop nature and its channel access scheme....[ Read more ]

Wireless ad-hoc networks are dynamic multi-hop wireless networks established by a group of mobile stations without pre-existing network infrastructure or centralized administration. Several MAC protocols are devised to address the “hidden terminal” problem in wireless ad-hoc networks. Among them, IEEE 802.11 Distributed Foundation Wireless Medium Access Control (DFWMAC) is a proposed standard for wireless ad-hoc and infrastructure LANs. Although DFWMAC achieves reasonable throughput by alleviating “hidden terminal” problem, it still suffers from a severe fairness problem under heavy traffic, because of the multi-hop nature and its channel access scheme.

In this thesis, the architecture with three components is proposed to solve the fairness problem in IEEE 802.11 MAC layer. The deployment of the architecture intends to achieve max-min fairness bandwidth allocation and access among one-hop flows in MAC layer of wireless ad-hoc networks.

A distributed Max-min fairshare assignment algorithm is derived to assign max-min fairshare for one-hop flows in wireless ad-hoc networks only, with local flow information. The fairshare computed by the distributed algorithm can converge to the fairshare computed by a centralized administration with global flow information. A flow information dissemination protocol is proposed and implemented to support the distributed algorithm. With the assigned fairshare, an estimation based channel access scheme is proposed to fairly access the channel for one-hop flows. The channel access scheme modifies the backoff scheme in IEEE 802.11, as well as, estimates the traffic of local flows and non-local flows. The channel access scheme achieves fairness among one-hop flows as well as maintains the overall throughput in original IEEE 802.11.

Simulations are conducted to show the convergence of the distributed max-min fairshare assignment algorithm and the integrity of the channel access scheme. It was shown that max-min fair shares can be assigned with convergence in multihop ad hoc networks and stations can access the channel proportional to the fair shares. The result of the max-min fairness bandwidth allocation and access could be used to support admission control and bandwidth allocation for end to end flows in wireless ad-hoc networks.