Voluntary Energy Harvesting Relays and Selection in Cooperative Wireless Networks

• Published in: IEEE transactions on wireless communications Vol. 9; no. 11; pp. 3543 - 3553
• Main Authors: Medepally, B, Mehta, N B
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01-11-2010; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Access methods and protocols, osi model; amplify-and-forward; Applied sciences; Approximation methods; Asymptotic properties; Batteries; cooperative systems; diversity methods; Energy harvesting; energy storage; Energy transmission; Ergodic processes; Exact sciences and technology; fading channels; Gain; Harvesting; Information, signal and communications theory; modulation; Modulation, demodulation; Networks; Relay; Relays; selection; Services and terminals of telecommunications; Signal and communications theory; Signal to noise ratio; Studies; Symbols; Systems, networks and services of telecommunications; Telecommunications; Telecommunications and information theory; Telemetry. Remote supervision. Telewarning. Remote control; Teleprocessing networks. Isdn; Transmission and modulation (techniques and equipments); Wireless communications; Wireless networks; Wireless sensor networks; Relaying; Relay; Relay network; wireless sensor networks; Wireless telecommunication; relays; Energy harvesting; Remote sensing; diversity methods; energy storage; Modulation; Routing protocols; Symbol error rate; Signal detection; Fading channels; Availability; amplify-and-forward; Space diversity; Transmission protocol; Cooperative systems; Ergodicity; Routing; selection; One way; Wireless network; Sensor array; Signal to noise ratio
• ISSN: 1536-1276; 1558-2248
• DOI: 10.1109/TWC.2010.091510.100447

The use of energy harvesting (EH) nodes as cooperative relays is a promising and emerging solution in wireless systems such as wireless sensor networks. It harnesses the spatial diversity of a multi-relay network and addresses the vexing problem of a relay's batteries getting drained in forwarding information to the destination. We consider a cooperative system in which EH nodes volunteer to serve as amplify-and-forward relays whenever they have sufficient energy for transmission. For a general class of stationary and ergodic EH processes, we introduce the notion of energy constrained and energy unconstrained relays and analytically characterize the symbol error rate of the system. Further insight is gained by an asymptotic analysis that considers the cases where the signal-to-noise-ratio or the number of relays is large. Our analysis quantifies how the energy usage at an EH relay and, consequently, its availability for relaying, depends not only on the relay's energy harvesting process, but also on its transmit power setting and the other relays in the system. The optimal static transmit power setting at the EH relays is also determined. Altogether, our results demonstrate how a system that uses EH relays differs in significant ways from one that uses conventional cooperative relays.