Bypassing hole scheme using observer packets for geographic routing in WSNs

Greedy forwarding fails due to void area, termed a hole, where no nodes can be deployed in realistic wireless sensor networks. This is known as the local minimum problem. Several schemes have been recently proposed to solve this problem. However, they have the problem that nodes, which are adjacent to the hole, have to maintain hole boundary information and an increase in hop counts due to additional data packet transmission. In this paper, we propose Bypassing Hole Scheme Using Observer Packets for Geographic Routing (BHOP-GR) that selects the optimum bypassing path and also solves the problem to maintain hole boundary information. BHOP-GR obtains the hole boundary information using an observer packet. And the source node uses a time delay when it transmits the data packet. Through this procedure, BHOP-GR can be arranged to decrease the average hop counts and routing path length. Also, using a virtual regular hexagon model, which can exactly cover a hole to be detoured, it solves the problem to maintain hole boundary information. In the simulation, BHOP-GR showed at least 34% of the average hop counts and routing path length compared to SLGF (Safety Information based Limited Geographic greedy Forwarding) and 25% of the average hop counts and routing path length compared to Virtual Circle.