Greedy Anti-Void Forwarding Strategies for Wireless Sensor Networks

A wireless sensor network (WSN) consists of sensor nodes (SNs) with wireless communication capabilities for specific sensing tasks. Each SN maintains connectivity and exchanges messages between the decentralized nodes in the multi-hop manners. A source node can communicate with its destination via a certain number of relaying nodes, which consequently enlarges the wireless coverage of the source node. In conventional multi-hop routing algorithms, either the proactive or reactive schemes, significant amounts of routing tables and control packets are required for the construction of routing paths. Due to the limited available resources, efficient design of localized multi-hop routing protocols (Estrin et al., 1999) becomes a crucial subject within the WSNs. How to guarantee delivery of packets is considered an important issue for the localized routing algorithms. The wellknown greedy forwarding (GF) algorithm (Finn, 1987) is considered a superior localized scheme with its low routing overheads, which is fit for conducting the routing task of WSNs. However, the void problem (Karp & Kung, 2000) that occurs within the GF technique will fail to guarantee the delivery of data packets. Several routing algorithms are proposed to either resolve or reduce the void problem, which can be classified into non-graph-based and graph-based schemes. In the non-graph-based algorithms, the intuitive schemes as proposed in the research work (Stojmenovi ́c & Lin, 2001) construct a two-hop neighbor table for implementing the GF algorithm. The network flooding mechanism is adopted while the void problem occurs. There also exist routing protocols that adopt the backtracking method at the occurrence of the network holes, such as GEDIR (Stojmenović & Lin, 2001), DFS (Stojmenović et al., 2000), and SPEED (He et al., 2003). The routing schemes as proposed by ARP (Giruka & Singhal, 2005) and LFR (Liu & Feng, 2006) memorize the routing path after the void problem takes place. Moreover, other routing protocols, such as PAGER (Zou & Xiong, 2005), NEAR (Arad & Shavitt, 2006), DUA (Chen et al., 2006), and YAGR (Na et al., 2007), propagate and update the information of the observed void node in order to reduce the probability of encountering the void problem. By exploiting these routing algorithms, however, the void problem can only be either (i) partially alleviated or (ii) resolved with considerable routing overheads and significant converging time. On the other hand, there are research works on the design of graph-based routing algorithms to deal with the void problem. Several routing schemes as surveyed in the literature (Frey & Stojmenović, 2006) adopt the planar graph (West, 2000) as their network O pe n A cc es s D at ab as e w w w .in te ch w eb .o rg