Relay Selection with Channel Probing in Sleep-Wake Cycling Wireless Sensor Networks

TL;DR

This paper addresses relay selection in sleep-wake cycling wireless sensor networks by formulating a sequential decision problem as an MDP, aiming to optimize relay choice based on rewards, delay, and probing costs.

Contribution

It introduces a novel relay selection framework with a sequential probing strategy modeled as an MDP, providing structural insights into optimal policies for energy-efficient forwarding.

Findings

Optimal relay selection policies have threshold and stage-independence properties.

Simulation results demonstrate the effectiveness of the proposed relay selection approach.

The framework balances delay, reward, and probing costs effectively.

Abstract

In geographical forwarding of packets in a large wireless sensor network (WSN) with sleep-wake cycling nodes, we are interested in the local decision problem faced by a node that has custody of a packet and has to choose one among a set of next-hop relay nodes to forward the packet towards the sink. Each relay is associated with a reward that summarizes the benefit of forwarding the packet through that relay. We seek a solution to this local problem, the idea being that such a solution, if adopted by every node, could provide a reasonable heuristic for the end-to-end forwarding problem. Towards this end, we propose a relay selection problem comprising a forwarding node and a collection of relay nodes, with the relays waking up sequentially at random times. At each relay wake-up instant the forwarder can choose to probe a relay to learn its reward value, based on which the forwarder can then decide whether to stop (and forward its packet to the chosen relay) or to continue to wait for further relays to wake-up. The forwarder's objective is to select a relay so as to minimize a combination of waiting-delay, reward and probing cost. Our problem can be considered as a variant of the asset selling problem studied in the operations research literature. We formulate our relay selection problem as a Markov decision process (MDP) and obtain some interesting structural results on the optimal policy (namely, the threshold and the stage-independence properties). We also conduct simulation experiments and gain valuable insights into the performance of our local forwarding-solution.