A distributed Delay-balancing Slot Allocation algorithm for 802.11s Mesh Coordinated Channel Access under dynamic traffic conditions

摘要

The Mesh Coordinated Channel Access (MCCA) defined by the IEEE 802.11s draft standard implements a TDMA-based Medium Access Control (MAC) protocol by allowing mesh routers to negotiate collision-free transmission opportunities, called MCCAOPs, in a hop-by-hop manner. The procedure to determine the duration, in time slots, and the periodic schedule of MCCAOPs is however left unspecified by the standard. In this paper, we propose a Dynamic Delay-balancing Slot Allocation (D²SA) algorithm to deal with dynamic traffic conditions in the context of IEEE 802.11s MCCA. D²SA is fully distributed and aims at exploiting locally at each node the statistical multiplexing of different traffic flows in order to mitigate temporary congestion or under-utilization of the available capacity due to variable traffic demand. This is accomplished by dynamically balancing over the smallest possible time scale the queuing delays experienced by packets relayed to different neighbors. By means of extensive packet-level simulations under realistic network assumptions, we evaluate the effectiveness of D²SA and show that, by improving both the average and the percentiles of the delay per link at each node, it is able to yield better end-to-end performance than in the static case at basically no additional overhead cost.