Practical fast scheduling and routing over slotted CSMA for wireless mesh networks

Abstract

Although Wireless Mesh Networks (WMNs) over CSMA and TDMA MAC have been extensively studied, CSMA still suffers from heavy interference due to hidden terminals, while TDMA has a practical difficulty in accurate time synchronization. Slotted CSMA, in which we assume that CSMA runs within relatively large time-divided slots, could be one of the solutions since it works on loosely synchronized time slots and simultaneously avoids major collision under a properly designed feasible schedule. However, if we apply a schedule generally used in TDMA, there are several inconveniences: First, we need heavy overhead of centralized computation or negotiation among nodes in distributed scheduling. Second, end-to-end packet delivery delay grows large since TDMA requires a large number of slots to achieve collision-free scheduling. In this paper, we propose a new scheduling algorithm for slotted CSMA called CATBS (CSMA-Aware Time-Boundable Scheduling) that requires a smaller number of slots for feasible scheduling, and runs within a bounded time. Incorporating the scheduling, we design a routing protocol that enables flexible paths recomputation with small communication overhead. We consequently achieve a new fully distributed and robust network architecture of WMNs that provides practically high throughput and low delivery delay, which can be implemented on the off-the-shelf IEEE802.11 interfaces.