On Using Cooperative Routing for Lifetime Optimization of Multi-Hop Wireless Sensor Networks: Analysis and Guidelines

Theoretically optimal performance and behavior of a routing protocol are very important because they can be used to guide the design of practical protocols. Motivated by the promising lifetime performance of an existing suboptimal cooperative transmission (CT) routing protocol for wireless sensor networks, we formulate the lifetime-optimization problem using linear programming (LP), which requires considerations of CT´s unique characteristics and sophisticated variable definitions. By evaluating LP for various cases, we show the effectiveness of cooperative routing by comparing it with the non-CT case. Also, by analyzing the LP solution, we identify some important factors and behaviors of optimal cooperative routing. More specifically, we conclude that (i) matching the rate of doing CT and matching the candidate pools of cooperators to the LP solution are important factors to achieve near-optimal lifetime performances, and, (ii) for small multi-hop networks, the design of cooperative routing can be simplified because one may use the sink node as a single VMISO receiver and rely on the existing energy-aware routing for the primary routing.