On Renewable Sensor Networks with

WirelessEnergy Transfer

IEEE INFOCOM 2011

Yi Shi, Liguang Xie, Y. Thomas Hou, Hanif D. Sherali

OUTLINE

IntroductionGoalNetwork ModelOverviewProblem DescriptionAlgorithmSimulationConclusions

Introduction

Wireless sensor networks (WSNs) today are mainly powered by batteries.

limited battery energy WSN can only remain operational for a limited amount of time.

To prolong the network lifetime, there have been a flourish of research efforts in the last decade. energy-harvesting techniques

Introduction

Wireless energy transfer technology exploiting a novel technique called magnetic resonance

[11] A. Kurs, A. Karalis, R. Moffatt, J.D. Joannopoulos, P. Fisher, and M. Soljacic, “Wireless power transfer via trongly coupled magnetic resonances,” Science, vol. 317, no. 5834, pp. 83–86, 2007.

◎ wireless energy transfer : the ability to transfer electric energy from one storage device to another without any plugs or wires

Goal

Employing a mobile vehicle carrying a battery charging station periodically visit each sensor node and charge it wirelessly

can remove the lifetime performance bottleneck from a battery-powered WSN

Network Model

sensor node distributed over a two-dimensional area has a battery capacity of Emax and is fully charged initially

minimum energy Emin

mobile wireless charging vehicle(WCM) base station(B)service stationmulti-hop data routing

Overview

Service station

Base station

Sensor node

Mobile WCM

i

Overview

Service station

Base station

Sensor node

Mobile WCM

vac

resting period vacation time

Problem Description

multi-hop data routing flow balance constraint at each sensor node i

• fij : the flow rate from sensor node i to sensor node j• fiB : the flow rate from sensor node i to the base station B

• Each sensor node i generates sensing data with a rate Ri of (in b/s)

Problem Description

Each sensor node consumes energy for data transmission and reception.

the rate of energy consumption for receiving a unitof data rate

Cij (or CiB) is the rate of energy consumption for transmitting a unit of data rate from node i to node j (or the base station B).

N nodesensor at raten consumptioenergy the i

Problem Formulation

maximize the percentage of time in a cycle that the WCV can take vacation.

max

s.t.

RENEWABLE CYCLE CONSTRUCTION

RENEWABLE CYCLE CONSTRUCTION

RENEWABLE CYCLE CONSTRUCTION

CONSTRUCTION OF INITIAL TRANSIENT CYCLE

Initial transient cycle must meet the following criterion :

] [0, for )( (ii)

)( and (0) (i)

min

max

t Ete

EeEe

i

iii

CONSTRUCTION OF INITIAL TRANSIENT CYCLE

ˆai is the arrival time of the WCV at node i in the initial transient cycle.

Simulation

Number of nodes : 50Data rate from each node : randomly generated within [1,10]kbps Base station location : (500, 500) (m)V=5 (m/s)Emax=10.8KJ

Emin=540JU=5W

Simulation

Simulation

An optimal traveling path for the 50-node sensor network. Only counter clockwise traveling direction is shown.

[18] Concorde TSP Solver, http://www.tsp.gatech.edu/concorde/.

Simulation

Simulation

Property 1: In an optimal solution, there exists at least one node in the network with its battery energy dropping to Emin when the WCV arrives at this node.

Conclusions

This paper exploits recent breakthrough in wireless energy transfer technology for a WSN.

Exploiting a mobile charging vehicle periodically travels inside the network and charges each sensor node wirelessly without any plugs or wires.

we showed that a sensor network operating under our solution can indeed remain operational with unlimited lifetime.