Data-Centric Routing in Sensor Networks: Single-hop Broadcast or Multi-hop Unicast?

Data dissemination strategies and communication protocols that minimize the use of energy can significantly prolong the lifetime of a sensor network. Data-centric dissemination strategies seek energy efficiency by employing short metadata descriptions in advertisements (ADVs) of the availability of data, short requests (REQs) to obtain the data by nodes that are interested in it, and data transmissions (DATA) to deliver data to the requesting nodes. An important decision in this process is whether the DATA transmission should be made at full power in broadcast mode or at low power in multi-hop unicast mode. The determining factor is shown in this paper to be the fraction of nodes that are interested in the DATA, as shown by the number of REQs that are generated. Closed form expressions for this critical fraction of interested nodes is derived when the nodes have no memory or infinite memory for state information and when transmissions are reliable and not reliable. These results can be used during both the design and operation of the network to increase energy efficiency and network longevity