Mobile Wireless Networking Energy Management

Transcription

1 Mobile Wireless Networking The University of Kansas EECS 882 Energy Management James P.G. Sterbenz Department of Electrical Engineering & Computer Science Information Technology & Telecommunications Research Center The University of Kansas 12 November 2009 rev James P.G. Sterbenz Mobile Wireless Networking Energy Management EM.1 Resource tradeoffs and energy EM.2 Battery management EM.3 Transmission power management EM.4 System power management 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-2 1

2 Energy Management EM.1 Resource Tradeoffs EM.1 Resource tradeoffs and energy EM.2 Battery management EM.3 Transmission power management EM.4 System power management 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-3 Resource Tradeoffs Introduction The network is a complex system of resources what are they? 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-4 2

3 Resource Tradeoffs Introduction The network is a complex system of resources processing memory bandwidth (or channel capacity) latency energy or power cost: $ 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-5 Energy and Power Definitions Difference between energy and power? 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-6 3

4 Energy and Power Definitions: Energy Energy: capacity of a system to do work unit: [J] (Joule named after James Prescott Joule ( ) 1 J = 1 kg m(m/s 2 ) the ability to accelerate 1 kg at 1m/s 2 over 1 m a battery stores energy 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-7 Energy and Power Definitions: Power Energy: capacity of a system to do work unit: [J] (Joule named after James Prescott Joule ( ) 1 J = 1 kg m(m/s 2 ) the ability to accelerate 1 kg at 1m/s 2 over 1 m Power: rate at which energy is transferred P = ΔE/Δt unit: 1W (Watt) = 1 J/s named after James Watt ( ) instantaneous power: P = de/dt a battery provides power 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-8 4

5 Energy and Power Role in Communications and Networks Role in communications and networks? 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-9 Energy and Power Role in Communications Energy is needed to power devices transceivers (radio and wired) intermediate systems (routers and switches) end systems Energy used to transfer information between devices electron movement in a wire photon movement in fiber electromagnetic waves in free space 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-10 5

6 Energy and Power Sources for Computer and Network Systems Sources of energy? 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-11 Energy and Power Sources for Computer and Network Systems Fixed or tethered devices: power grid network infrastructure: routers and switches compute and file servers computing devices desktop computers laptops and PDAs when docked Energy conservation is important ecologically economically 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-12 6

7 Energy and Power Sources for Computer and Network Systems Untethered devices: batteries PDAs mobile telephones laptop computers when not docked sensors Energy conservation important maximise lifetime between battery charge or change difficult or impossible to change in some sensor devices economic and ecological reasons Vast majority of untethered devices battery powered 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-13 Energy and Power Sources for Computer and Network Systems Untethered devices: energy harvesting sensors PDAs mobile telephones and PDAs Power drawn from environment solar wind turbines biomechanical etc. Relatively immature technologies 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-14 7

8 Energy Management EM.2 Battery Management EM.1 Resource tradeoffs and energy EM.2 Battery management EM.3 Transmission power management EM.4 System power management 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-15 Batteries Definitions Battery electrochemical device for storing electric potential energy capacity specified as [V][A hr] = [W hr] = [J] Battery voltage parameters V oc fully charged open circuit voltage under no load V l operating voltage under load V cut cut-off threshold defining discharge state 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-16 8

9 Batteries Technology Battery technology has improved over time Pb acid NiCd NiMH Li ion Li polymer Battery life still a major system constraint fundamental breakthroughs needed for orders-of-magnitude improvements 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-17 Batteries Challenges Problem: maximise time to discharge V cut time to recharge or replace Battery energy discharge is nonlinear over time dependent on current drain dependent on duty cycle (constant vs. pulsed) These effects make battery power management more challenging but can be exploited 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-18 9

10 Batteries Characteristics Affecting Power Management Lower current drain extends battery life communication management scheme? 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-19 Batteries Characteristics Affecting Power Management Lower current drain extends battery life lower data rate: spread communication over time 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-20 10

11 Batteries Characteristics Affecting Power Management Lower current drain extends battery life lower data rate: spread communication over time Batteries recover some charge when idle rebound effect communication management scheme? 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-21 Batteries Characteristics Affecting Power Management Lower current drain extends battery life lower data rate: spread communication over time Batteries recover some charge when idle rebound effect allow batteries to rest pulsed discharge alternate between two batteries 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-22 11

12 Batteries Power Management Strategies Smart battery technologies control drain characteristics Device, component, and system engineering low power circuits energy-aware circuits; selective power efficient algorithms (reduce processing) Communication and network strategies MAC layer link layer network layer transport and application layers 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-23 Batteries Power Management Strategies Smart battery technologies Device, component, and system engineering Communication and network strategies? at each layer? 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-24 12

13 Batteries Power Management Strategies Smart battery technologies Device, component, and system engineering Communication and network strategies MAC: controlling medium access to maximise rebound link layer: packet scheduling to spread over time network layer: traffic shaping to reduce burstiness transport layer: reduce burstiness and chattiness application layer: energy aware applications eliminate unneeded communication data compression 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-25 Battery Management MAC Strategies Battery-aware MAC aware of and exploits discharge characteristics Transceiver-aware MAC schedules medium access to correspond to node wakup 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-26 13

14 Battery Management MAC Strategy Example: BAMAC BAMAC: battery-aware MAC protocol [Jayashree, Mahoj, Murthy 2003] exploits recovery effect of idle batteries BAMAC operation packets contain header field for remaining charge estimate each node has remaining charge estimate of neighbours back-off times are higher for nodes with lower charge 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-27 Battery Management Link Strategy Example: Lazy Scheduling Lazy packet scheduling [Prabhakar, Biyikoglu, El Gamal 2001] minimise energy while satisfying delay constraint 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-28 14

15 Battery Management Network Strategy: Energy-Aware Routing Energy-aware routing protocols remaining node charge is a routing metric nodes with higher charge are favoured Example protocols BEE: battery energy-efficient routing [Chiasserini, Nuggehalli, Srinivasan 2002] many other research proposals some domain specific, e.g. for sensor networks 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-29 Energy Management EM.3 Management EM.1 Resource tradeoffs and energy EM.2 Battery management EM.3 Transmission power management EM.4 System power management 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-30 15

16 Transmitter Characteristics TPO: transmitter power output power [W] of RF energy generated by transmitter ERP: effective radiated power effective power after gains and losses are included e.g. antenna gain 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-31 Transmitter Power Characteristics Higher transmission power effects? 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-32 16

17 Characteristics Higher transmission power longer range faster battery discharge less stealth 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-34 17

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21 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-42 21

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23 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-46 23

24 sufficient connected 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT sufficient connected November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-48 24

25 sufficient connected biconnected 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT sufficient connected biconnected 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT

26 sufficient connected biconnected excessive wasted energy 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT sufficient connected biconnected excessive wasted energy lack of stealth November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-52 26

27 sufficient connected biconnected excessive wasted energy lack of stealth 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT sufficient connected biconnected excessive wasted energy lack of stealth November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-54 27

28 sufficient connected biconnected excessive wasted energy lack of stealth 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT sufficient connected biconnected excessive wasted energy lack of stealth November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-56 28

29 sufficient connected biconnected excessive wasted energy lack of stealth 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT sufficient connected biconnected excessive wasted energy lack of stealth November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-58 29

30 sufficient connected biconnected excessive wasted energy lack of stealth 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT sufficient connected biconnected excessive wasted energy lack of stealth highly connected: self jamming parking lot problem November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-60 30

31 Adaptive Power Control Adaptive transmission power each node adjusts control number of neighbors: degree of connectivity Biconnected graph single link cut avoids partition May be more stealthy in cases of lower transmission power How to adapt? 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-61 Adaptive Link Affinity Link affinity nodes measure signal strength of neighbors Nodes dynamically adjust transmission power minimum power to reach neighbours control degree of connectivity time-varying strength can compensate for mobility Can be adapted to distributed power control loop: add header field CTS returns strength of RTS data packet returns strength of CTS 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-62 31

32 Adaptive Distributed Topology Control Distributed topology control remove links that have lower-power two-hop alternates Distributed topology control for directional antennæ choose lowest power neighbors in each sector 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-63 Energy Management EM.4 System Power Management EM.1 Resource tradeoffs and energy EM.2 Battery management EM.3 Transmission power management EM.4 System power management 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-64 32

33 System Power Management Overview 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-65 Energy Management Further Reading Christine E. Jones, Krishna M. Sivalingam, Prathima Agrawal, and Jyh Cheng Chen, A Survey of Energy Efficient Network Protocols for Wireless Networks, Wireless Networks, vol.7, iss.4, Aug. 2001, pp Giuseppe Anastasia, Marco Conti, Mario Di Francescoa, and Andrea Passarella Energy Conservation in Wireless Sensor Networks: A Survey Ad Hoc Networks, Elsevier, vol.7 iss.3, May 2009, pp November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-66 33

34 Energy Management Acknowledgements Some material in these foils is based on the textbook Murthy and Manoj, Ad Hoc Wireless Networks: Architectures and Protocols 12 November 2009 KU EECS 882 Mobile Wireless Nets Energy Mgt. MWN-MT-67 34