Maximise success probability for real-time sensor networks using contention-based protocols

We study real-time data aggregation problem for wireless sensor net-works that use CSMA/CA MAC layer protocols. The problem is, for a given sink, a set of sensor nodes and a delay bound, to maximise the average transmission success probability of all sensor nodes within the delay bound. In CSMA/CA protocols, the success probability and the expected transmission delay are highly sensitive to node interference. We divide the system time into time-frames with fixed size and schedule the transmission of nodes into time-frames. The transmissions of all child nodes under the same parent are scheduled in the same time-frame. Therefore, the construction of data aggregation trees becomes very important in maximising the success probability of data collection. We solve the joint routing and scheduling problem by first constructing an aggregation tree that minimises the node interference. Then, we propose an efficient greedy scheduling method to assign time-frames to sensor nodes.