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Finite-Horizon Energy Allocation and Routing Scheme in Rechargeable Sensor Networks. Shengbo Chen, Prasun Sinha, Ness Shroff, Changhee Joo Electrical and Computer Engineering & Computer Science and Engineering. Introduction [Rechargeable sensor network]. Environment monitoring
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Finite-Horizon Energy Allocation and Routing Scheme in Rechargeable Sensor Networks Shengbo Chen, Prasun Sinha, Ness Shroff, Changhee Joo Electrical and Computer Engineering & Computer Science and Engineering
Introduction[Rechargeable sensor network] • Environment monitoring • Earthquake, structural, soil, glacial • Unattended Operability for long periods • Battery with renewable energy (like solar or wind) • Challenge: energy allocation • Sensor Network without replenishment: full battery is desirable feature • Sensor Network with replenishment: no opportunity to harvest energy
Introduction(cont’)[Rechargeable sensor network] r(t) B(t) B(t+1) e(t) M M: Battery size B(t): Battery level at time slot t e(t): allocated energy at time slot t r(t): harvested energy at time slot t
Motivation • Rate-power function • Nondecreasing and strictly concave • Data transmission with spending units of energy • How to design
Motivation(cont’) • Example 1: • r(1)=4, r(2)=2, r(3)=0 • e*(1)=2, e*(2)=2, e*(3)=2 r(2) r(1) Average replenishment rate is the best because of Jensen’s inequality
Motivation(cont’) Example 2: r(1)=2, r(2)=0, r(3)=4 r(3) r(2) r(1) Average replenishment rate is infeasible
Problem Statement • Sensor Network with renewal energy • Assumption • No interference from other nodes • Problem: throughput maximization where, is the amount of data from source to the destination at time slot t
Problem Statement (cont’) • Convex optimization problem • Joint energy allocation and routing • Complex due to the “time coupling property” • Concave rate-power function
Related Literatures • Finite horizon • A. Fu, E. Modiano and J. Tsitsiklis, 2003. • Dynamic programming • Infinite horizon • L. Lin, N. B. Shroff, and R. Srikant, 2007 • Asymptotically optimal competitive ratio • M. Gatzianas, L. Georgiadis, and L. Tassiulas, 2010. • Maximize a function of the long-term rate per link • L. Huang, Neely • Asymptotically optimal
Three-step Approach • One node with full knowledge of replenishment profile • One node with estimation of replenishment profile • Multiple-node network
Three-step Approach • One node with full knowledge of replenishment profile • One node with estimation of replenishment profile • Multiple-node network
One node with full knowledge of replenishment profile • Finite time horizon: T time slots • Assumption: replenishment profile is known • Constraints: • Cumulative used no greater than cumulative harvested • Residual no greater than the battery size
Result 1 Shortest path S(t): curve that connects two points (0, 0) and (T,K) in the domain D with least Euclidean length • Theorem 1: The energy allocation scheme , satisfying s(t) = S(t) − S(t − 1), is the optimal energy allocation scheme K R(t) Cumulative Energy D R(t)-M T time
Three-step Approach • One node with full knowledge of replenishment profile • One node with estimation of replenishment profile • Multiple-node network
One node with estimation of replenishment profile • Assumption relaxed • Replenishment profile is unknown • Estimation replenishment rate • Actual replenishment rate
Online algorithm Theorem 2: The throughput U of the online algorithm, achieves fraction of the optimal throughput Calculate e(t) from the lower-bound of the estimated replenishment profile by the shortest-path solution The allocated energy is determined as e(t) = e(t) + r(t) − r(t) K R(t) (1+β2)R(t) Cumulative Energy (1-β1)R(t) T time
Three-step Approach • One node with full knowledge of replenishment profile • One node with estimation of replenishment profile • Multiple-node network
Heuristic scheme: NetOnline • Throughput maximization • Decouple energy allocation and routing: • Energy allocation of each node follows the online algorithm • Routing:
Result 3 • Theorem 3: The heuristic scheme is optimal if all nodes have the same replenishment profile and perfect estimation.
Simulations (cont’) • NRABP: Infinite-horizon based scheme in Gatzianas’s paper
Future work • Considering interference in the model • Replenishment rate is known with some distribution, what is the best strategy? • Infinite horizon but only finite period of estimation
Thank you! 24