TDMH-MAC: Real-Time and Multi-hop in the Same Wireless MAC

Abstract

Supporting real-time communications over Wireless networks (WSNs) is a tough challenge, due to packet collisions and the non-determinism of common channel access schemes like CSMA/CA. Real-time WSN communication is even more problematic in the general case of multi-hop mesh networks. For this reason, many real-time WSN solutions are limited to simple topologies, such as star networks. We propose a real-time multi-hop WSN MAC protocol built atop the IEEE 802.15.4 physical layer. By relying on precise clock synchronization and constructive interference-based flooding, the proposed MAC builds a centralized TDMA schedule, supporting multi-hop mesh networks. The real-time multi-hop communication model is connection-oriented, using guaranteed time slots, ad enables point-to-point communications also with redundant paths. The protocol has been implemented in simulation using OMNeT++, and the performance has been verified in a real-world deployment using Wandstem WSN nodes.

TDMH: a communication stack for real-time wireless mesh networks

“…The initial topology collection implementation [14] only collected a single network graph. However, after an extended experimental evaluation it became evident that certain links could be too weak to be reliably used for data exchange, but at the same time strong enough to cause interference among independent transmissions in the same data slots.…”