Efficient Link Scheduling and Channel Hopping for Convergecast in WirelessHART Networks

Fast convergecast is a critical functionality for data collection in wireless networks deployed for industrial monitoring and control. We address the joint link scheduling and channel hopping problem for convergecast in networks operating according to the recent WirelessHART standard. We first demonstrate that the minimum time to complete convergecast in networks with multi-line/tree routing topology is max{2n1 − 1, N} time-slots where N is the number of field devices in the network and n1 is the maximum number of field devices in a line/subtree. Then we present time-optimal scheduling policies which complete convergecast using at most h(the maximum hopcount from a field device to the gateway) channels and require each device to buffer at most one packet at any time slot. We also establish lower bounds on the number of channels for time-optimal convergecast with single-packet buffering capability, and present a heuristic algorithm which can generate near-optimal schedule for timeand channel-optimal convergecast. We further demonstrate that, with our heuristic algorithm, the success rate that both the lower bound on convergecast time and the lower bound on the number of channels can be achieved goes up to 99.8%. Simulation and experimental results show that our scheme can provide very fast convergecast in WirelessHART networks.