On relay node placement and locally optimal traffic allocation in heterogeneous wireless sensor networks

In this paper, we explore the relay node (RN) placement problem in a heterogeneous wireless sensor network (WSN). The objective of the RN placement is to use a minimum number of additional RNs to enable the relaying of given traffic on existing nodes to the base station (BS) under the energy constraints. We assume RNs can adjust their transmission power according to the distance to the intended destination. To make best use of power adaptivity of RN, we propose two heuristic solutions, namely, independent placement with direct allocation (IPDA) and collaborative placement with locally optimal allocation decision (CPLOAD). Furthermore, a lower bound on the minimum number of additional RNs is provided. The effectiveness of our proposals is investigated through simulation using numerical examples