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Center for Wireless COMMUNICATIONS 5/24/2015 Energy Efficient Networking Ramesh R. Rao University of California, San Diego - NeXtworking’03 - Chania, Crete,

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Presentation on theme: "Center for Wireless COMMUNICATIONS 5/24/2015 Energy Efficient Networking Ramesh R. Rao University of California, San Diego - NeXtworking’03 - Chania, Crete,"— Presentation transcript:

1 Center for Wireless COMMUNICATIONS 5/24/2015 Energy Efficient Networking Ramesh R. Rao University of California, San Diego - NeXtworking’03 - Chania, Crete, Greece, June 23- 25,2003 The First COST-IST(EU)-NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING

2 Center for Wireless COMMUNICATIONS 5/24/2015 Introduction Explosion of wireless devices and applications  Eg. Cellular Networks, Ad Hoc Networks, Sensor Networks Power hungry applications and shrinking form factor Motivates need for energy aware designs

3 Center for Wireless COMMUNICATIONS 5/24/2015 Three Themes Cross-layer optimization Resource ownership Batteries

4 Center for Wireless COMMUNICATIONS 5/24/2015 Cross-layer Optimization Minimum energy/hops routing unsuitable Suppose R2 is chosen as the relay  Lifetime: Relay R2 will die prematurely  Throughput: More interference Need for joint routing and scheduling

5 Center for Wireless COMMUNICATIONS 5/24/2015 The Problem is Hard Joint optimization is an NP-hard problem  Arikan (1984) For small networks, a brute force approach works.  Nuggehalli (2002) Need for scalable and distributed algorithms which can achieve near optimal performance

6 Center for Wireless COMMUNICATIONS 5/24/2015 Lifetime Vs. Throughput Optimal Routes Lifetime Optimal Routes Lifetime=1331.6 Throughput: 1 Throughput Optimal Routes Lifetime=839.2 Throughput=1.33

7 Center for Wireless COMMUNICATIONS 5/24/2015 Resource Ownership Ownership of resources determines protocol design paradigm Ad Hoc Network: Distributed protocols that ensure system resources are used equitably and no user gets cheated BandwidthEnergy Cellular Networks SystemUser Ad Hoc Networks User Sensor Networks System

8 Center for Wireless COMMUNICATIONS 5/24/2015 Cooperation in Ad Hoc Networks Standard Assumption: Nodes always relay messages for other nodes! “What’s in it for me?” No cooperation leads to zero throughput Complete cooperation leads to short active life. S1S1 S2S2 S3S3 D R

9 Center for Wireless COMMUNICATIONS 5/24/2015 Cooperation in Ad Hoc Networks (Contd.) Two Questions:  How Much to relay?  What strategy? (No cheating) Answer: (Srinivasan etal Infocom 2003)  Given complete information –Each node calculates optimal level of cooperation –Implements GTFT strategy (Nash Equilibrium) Challenge: Learn operating point through experience with the system

10 Center for Wireless COMMUNICATIONS 5/24/2015 Battery Management Maximize bits transmitted for a given battery & wireless physical interface (both have serious impairments) Develop MAC protocols for both best battery life & throughput (Tx when channel is best) Optimize Tx time, Rx time, Idle time, Sleep time (high power pulsed Tx time) Coordinate power consumption with battery state (decrease average power towards end of discharge) Operational scenario: Wireless sensor network, solar powered by day, battery powered by night, sends data intermittently

11 Center for Wireless COMMUNICATIONS 5/24/2015 Battery Test Set Up

12 Center for Wireless COMMUNICATIONS 5/24/2015 Battery Test Results E-Tech Li-Ion Polymer Cell, 250mAh, 3.7Vdc Pulsed Discharge, 1 Second Period, 8C=2A

13 Center for Wireless COMMUNICATIONS 5/24/2015 Battery Tests, Summary Li-Ion polymer secondary cell, pulsed discharge, 2x useful energy increase vs continuous discharge (charge recovery) Lithium coin primary cell, pulsed discharge, 8x useful energy increase vs continuous discharge Pulse constraints for charge recovery: min idle time, <max idle current, high pulse current levels possible, 8x to 80x manufacturer’s recommended current Improvement scenario: Same weight, same power, much more energy or Same weight, much more power, same energy


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