Scheduling and Dynamic Relocation for IEEE 802.11s Mesh Deterministic Access

Deployment of Wireless Mesh Networks (WMNs) is becoming increasingly popular due to the low-impact and low- cost features of wireless devices. This is especially true for WMNs based on IEEE 802.11 which, however, does not include native support for multi-hop relaying. This gap is being filled by the Task Group ´s´ of the IEEE 802.11 which has recently published an amendment in order to add mesh functions to the popular standard IEEE 802.11. Among the enhancements proposed, Mesh Deterministic Access (MDA) allows mesh routers to negotiate periodic collision-free transmission opportunities, called MDAOPs, to the Medium Access Control (MAC) layer on a hop- by-hop manner. Control messages are exchanged to advertise the reserved MDAOPs in the two-hop neighborhood. MDA lays the foundations for enabling QoS provisioning functions in IEEE 802.11s WMNs, such as end-to-end bandwidth reservation, call admission control, and traffic engineering. In this paper we study the problem of scheduling MDAOPs, which is left unspecified by the standard, and propose two baseline algorithms. Furthermore, we provide evidence that performance under MDA can be significantly degraded by the unknown interference of traffic flows outside the two-hop neighborhood. A dynamic relocation procedure is proposed in order to combat this phenomenon, thus providing traffic flows established in the WMN with stable performance. This procedure does not need any modifications to the standard MDA procedure. To the best of our knowledge, this is the first study that tackles this problem in the context of IEEE 802.11s. The effectiveness of the proposed algorithms is evaluated by means of a packet-level simulation.