Multi-Cluster Multi-Parent Wake-Up Scheduling in Delay-Sensitive Wireless Sensor Networks

Immediate notification of urgent but rare events and delivery of time sensitive actuation commands appear in many practical wireless sensor and actuator network applications. Multi-parent wake-up scheduling was presented as a technique which can provide bi-directional end-to-end latency guarantees while optimizing the node battery lifetime. This method takes a cross-layer approach where multiple routes for transfer of messages and wake-up schedules for nodes are crafted in synergy to reduce overall message latencies. In this paper, we generalize the multi-parent method to support a multi-cluster model for the network where we assume that the network has multiple central points called cluster-head (CH) that are in charge of scheduling the nodes in the network. A key step in multi-parent method is to divide the nodes in network into disjoint groups such that each node has at least one link to a node in each group. We formulate this step as a graph coloring problem which is shown to be NP-complete. We propose an algorithm where all the cluster-heads cooperate to find a heuristic solution for the graph coloring optimization problem in a distributed manner. We show that each cluster-head requires less memory and computational power compared to the case where one cluster-head finds the global solution, therefore the solution is very scalable.