A Novel Relay Node Placement and Energy Efficient Routing Method for Heterogeneous Wireless Sensor Networks

In heterogeneous wireless sensor networks (HWSN), sensor nodes may fail due to running out of battery power or sudden damage. This causes HWSN being partitioned to a number of separate networks. Relay node placement is to add new relay nodes to partitioned HWSN such that the network recovers to wireless communication. Energy efficient routing in HWSN is useful for prolonging network lifetime and energy conservation. This paper attempts to solve relay node placement and energy efficient routing problems for HWSN. Both problems have seldom been studied together in the literature. This paper first constructs a mathematical model for both problems. For relay node placement problem, it is assumed that HWSN contains unreachable area, where sensor nodes could not be placed. For energy efficient routing, it is transformed to path length of wireless communication. As the problem is non-deterministic polynomial (NP) hard, a heuristic method called whale optimizer is used. The paper studies the effect of whale optimizer method with three adaptive schemes. Numerical simulations are done to test the proposed method for HWSN. The analysis and discussion show that the proposed method is useful to address NP hard relay node placement and energy saving problems for HWSN.