An Energy-efficient Multi-candidate Greedy Routing Scheme in Wireless Sensor Networks.

Sleep and wake-up scheduling of sensor nodes is an efficient solution to prolong the network lifetime. However, existing scheduling algorithms may significantly decrease the number of active nodes so that the network may be intermittently-connected. In such networks, traditional geographic routing protocols are inappropriate to obtain low latency routes due to route discovery and data forwarding latency. In this paper, we propose a novel \emph{multi-candidate greedy routing} (MGR) scheme that makes the best effort to find minimum latency routes in the sensor networks. In MGR, each source node sends an RREQ to a set of first wake-up forwarder candidates and selects a route with minimum estimated delivery latency based on their replies. Moreover, to cope with the unreliability of wireless links, we introduce an add-on algorithm for MGR, called \emph{multilevel of link quality requirement-based packet forwarding} (MLRPF), which helps to increase the energy efficiency of MGR while still guaranteeing a low delivery latency. Simulation results demonstrate that MLRPF increases the routing performance of MGR significantly compared with PRRxDistance \cite{7}, DGF \cite{3}, and ODML \cite{2} in terms of packet delivery latency and energy efficiency.