Realization of Try-Once-Discard in Wireless Multihop Networks

In networked control systems, the Try-Once-Discard (TOD) protocol is of high interest because its properties can be characterized by Lyapunov functions. This feature makes it practical to incorporate TOD into Lyapunov-based design of linear and nonlinear control systems, yielding a self-contained theory for system stabilization. In previous work, candidates for TOD realizations for single-hop (wired and wireless) networks have been proposed. However, it has been a hitherto open question whether TOD can be realized in wireless multihop networks. In fact, it is far from obvious how dynamic value-based competition with deterministically bounded maximum delay, as required by TOD, is achievable in wireless multihop networks. In this paper, we give a positive answer to this question, by presenting a functionally complete realization of TOD in wireless multihop networks. Our solution is based on highly accurate multihop tick synchronization, and applies an algorithm for collision-protected network-wide value arbitration with deterministic delay. We provide experimental evidence for the feasibility of our solution on existing micro controller platforms, and assess our TOD realization in a batch reactor scenario.