CED: A Community-Based Event Delivery Protocol in Publish/Subscribe Systems for Delay Tolerant Sensor Network (DTSN)

The basic operation of delay tolerant sensor network (DTSN) is to finish pervasive data gathering in networks with intermittent connectivity, while the publish/subscribe (Pub/Sub for short) paradigm is used to deliver events from a source to interested clients in an asynchronous way. Recently, to extend a Pub/Sub system in DTSN has become a promising topic. However, due to the unique characteristic of frequent partitioning in DTSN, to extend a Pub/Sub system in DTSN is a considerably difficult and challenging problem, and there is no good solution to it in existing works. To adapt Pub/Sub systems to DTSN, we propose CED, a community-based event delivery protocol. In our design, event delivery is based on several unchanged communities, which are formed by sensor nodes in the network according to their connectivity. CED consists of two components: event delivery and queue management. In event delivery, events in a community are delivered to mobile subscribers once a subscriber comes into the community, for improving the data delivery ratio. The queue management employs both the event successful delivery time and the event survival time to decide whether an event should be delivered or dropped for minimizing the transmission overhead. The effectiveness of CED is demonstrated through comprehensive simulation studies.