Energy Conservation in Wireless       Communication Systems with Relays                                Aniruddha Chandra  ...
Outline    Introduction    Energy Conservation    Basics of Relaying    Modelling    Case Study    SummaryA. Chandra - Ene...
Outline    Introduction      - Paradigm shift in wireless system design      - Energy consumption by telecomm industry    ...
Introduction    Paradigm Shift in Wireless System Design     Meteoric growth in wireless usage:       - Demand for covera...
Introduction    Energy Consumption by Telecomm Industry     Some statistics on environmental impact:       - A cellular n...
Introduction    Energy Consumption by Telecomm Industry     Some statistics on cost incurred for power:       - Powering ...
Introduction    Energy Consumption by Telecomm Industry     Cost Components:     Energy Components:       - Top three en...
Outline    Introduction    Energy Conservation      - Various means    Basics of Relaying    Modelling    Case Study    Su...
Energy Conservation    Various Means     Power efficient wireless nodes:       - Low power architecture ~ Clock gating, P...
Outline    Introduction    Energy Conservation    Basics of Relaying      - What is a relay and Why use a relay?      - Mo...
Basics of Relaying    What is a Relay?     A simple repeater: receive, boost, and re-send a signal.     Cellular Network...
Basics of Relaying    Why Use a Relay?                                                                                    ...
Modes of Operation    Direct Path vs. Relayed Path                                                                        ...
Relaying Protocols    Forwarding Strategy     Amplify and Forward (AF)       - Layer #1 relaying: Relays act as analog re...
Relaying Protocols    Protocol Nature     Fixed protocol       - Relays always forward a processed version of their recei...
Outline    Introduction    Energy Conservation    Basics of Relaying    Modelling      - Power consumption at Rx/ Tx      ...
Modelling    Assumptions     Receiver       - Heterodyne, Hartley & Weaver, Zero IF, Low IF.     Baseband Signal Process...
Modelling    Power Consumption at Receiver     Block Diagram                        Band             Image               ...
Modelling    Power Consumption at Transmitter     Block Diagram                               Channel                   I...
Modelling    RF Transmit Power     Friis Free Space Formula                             2              PR  λ           ...
Modelling    Energy Consumed per Bit     Total Circuit Power Consumption             PC = PTx ,total + PRx               ...
Modelling    Energy Consumed per Bit     Consumption per Bit                 PC              E=                 Rb       ...
Modelling    Ensuring a Fixed BER     Consider the Modulation Scheme       - For BPSK modulation, the BER is             ...
Modelling    Effect of Fading     Statistics of Received SNR       - For Rayleigh fading                       1    γ  ...
Modelling    Target SNR Calculation     Ergodic Capacity: Shannon’s Formula       - For reliable communication           ...
Modelling    Energy Consumed per Successful Bit     Effective Data Rate             Rb ,eff = Rb (1 − O )     Energy Con...
Modelling    One More Equation …                           … and you’ll lose rest of your audience!A. Chandra - Energy Con...
Modelling    Research Challenges     Relay: To Use or Not to Use       - Always cooperate, or use relay only when the dir...
Outline    Introduction    Energy Conservation    Basics of Relaying    Modelling    Case Study      - Relay placement: Co...
Modelling for Relay    Statistics of S-R-D Link     Outage Probability                                                   ...
Modelling for Relay    Statistics of S-R-D Link     Energy Consumption per Bit in S-R-D Link       - Outage in S-R path, ...
Relay Placement    Collinear Model     Direct Path vs. Relayed Path                                                      ...
Relay Placement    Non-linear ModelA. Chandra - Energy Conservation with Relays    33/41
Relay Placement    Non-linear Model                                        ?                         Source               ...
Relay Placement    Non-linear Model                              Relay                   Source                       Dest...
Outline    Introduction    Energy Conservation    Basics of Relaying    Modelling    Case Study    SummaryA. Chandra - Ene...
Summary      Energy efficient perspective for wireless systems.      Various means to reduce energy consumption.      U...
Read More About It    Green Communication      •   G. Y. Li et al., “Energy efficient wireless communications: Tutorial, s...
Thank You All    Presenting talks in conferences ensure …                         Hua Hin                                 ...
Acknowledgements     This talk won’t be possible without …      The support of Conference Organizers      Encouragements...
Thank You!                  Questions?                         aniruddha.chandra@ieee.orgA. Chandra - Energy Conservation ...
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Energy conservation in wireless communication systems with relays

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Energy conservation in wireless communication systems with relays

  1. 1. Energy Conservation in Wireless Communication Systems with Relays Aniruddha Chandra Telecommunications, School of Engineering & Technology, Asian Institute of Technology, Bangkok, Thailand. aniruddha.chandra@ieee.orgScience City, 27th December, 2011 Kolkata
  2. 2. Outline Introduction Energy Conservation Basics of Relaying Modelling Case Study SummaryA. Chandra - Energy Conservation with Relays 2/41
  3. 3. Outline Introduction - Paradigm shift in wireless system design - Energy consumption by telecomm industry Energy Conservation Basics of Relaying Modelling Case Study SummaryA. Chandra - Energy Conservation with Relays 3/41
  4. 4. Introduction Paradigm Shift in Wireless System Design  Meteoric growth in wireless usage: - Demand for coverage extension. - Demand for higher capacity. - Demand for better QoS.  Traditional design: - New infrastructure deployment, Complement old ones with Relay. - Femtocell, SDMA, MIMO. - Adaptive modulation, coding, equalization, diversity.  Increase in energy costs and greater awareness of impact on environment: - New energy-efficiency oriented design perspective. - Value power consumption as much as BW, delay, or throughput.A. Chandra - Energy Conservation with Relays 4/41
  5. 5. Introduction Energy Consumption by Telecomm Industry  Some statistics on environmental impact: - A cellular network (medium sized) ~ Energy for 1,70,000 homes. - About 3% of the energy consumption, 2% of CO2 emissions. - The figures are going to double in next 5 years. - Energy from electricity grid, runs on fossil-fuel. - Backup diesel generators for unreliable electric supply. Objects in Mirror are Close than they AppearA. Chandra - Energy Conservation with Relays 5/41
  6. 6. Introduction Energy Consumption by Telecomm Industry  Some statistics on cost incurred for power: - Powering the BSs accounts for half of the total OpEx. - Diesel cost has doubled since 2008. - Even the operators don’t care about environment, they care about ….A. Chandra - Energy Conservation with Relays 6/41
  7. 7. Introduction Energy Consumption by Telecomm Industry  Cost Components:  Energy Components: - Top three energy consuming components, feeder network, RF conversion, and climate control (e.g., air conditioning). Energy consumption at a typical macro BS (normalized)A. Chandra - Energy Conservation with Relays 7/41
  8. 8. Outline Introduction Energy Conservation - Various means Basics of Relaying Modelling Case Study SummaryA. Chandra - Energy Conservation with Relays 8/41
  9. 9. Energy Conservation Various Means  Power efficient wireless nodes: - Low power architecture ~ Clock gating, Power saving modes. - Improved display, Enhanced battery life.  Energy optimized software: - Improved modem software and OS, application driven power management.  Efficient communication strategies: - Energy efficient routing. - Handling idle modes. - Emerging techniques ~ Multi-antenna, Relay, Cognitive radio etc. F. Shearer, Power Management in Mobile Devices, Elsevier, 2008.A. Chandra - Energy Conservation with Relays 9/41
  10. 10. Outline Introduction Energy Conservation Basics of Relaying - What is a relay and Why use a relay? - Modes of operation - Relaying protocols Modelling Case Study SummaryA. Chandra - Energy Conservation with Relays 10/41
  11. 11. Basics of Relaying What is a Relay?  A simple repeater: receive, boost, and re-send a signal.  Cellular Network: different node, carrier owned infrastructure, tree topology. IEEE 802.16j (mobile multihop relay). Sensor Network: identical node, subscriber equipment, mesh topology. IEEE 802.15.5 (WPAN mesh), IEEE 802.11s (WLAN mesh). Relay #1 Relay Station (RS) Source Relay #2 Destination Base Station Mobile Terminal (BS) (MT) Cellular Network Sensor NetworkA. Chandra - Energy Conservation with Relays 11/41
  12. 12. Basics of Relaying Why Use a Relay? RS-MS link  Network performance improvement Cooperative BS-RS MT #1 transmission - Radio range extension link Coverage/ radio range extension - Service for coverage holes RS #1 - Improve QoS RS #2 Traditional direct - Reduce Tx energy requirement MT #2 transmission - Capacity enhancement BS RS #3 - Load balancing between the MT #3 neighbouring cells Capacity enhancement through replacing low rate, unreliable links with multiple high rate, reliable links  Cost benefit Traditional service boundary - Use relays to lower CapEx - Temporary coverage A. Chandra, C. Bose, and M. K. Bose, “Wireless relays for next generation broadband networks,” IEEE Potentials, vol. 30, no. 2, pp. 39-43, Mar.-Apr. 2011.A. Chandra - Energy Conservation with Relays 12/41
  13. 13. Modes of Operation Direct Path vs. Relayed Path 1st time slot × × Relay Relay 2nd time slot Source Destination Source × Destination Co-operative Strategies 1st time slot Relay Relay 2nd time slot Source Destination Source Destination K. J. Ray Liu, A. K. Sadek, W. Su, and A. Kwasinski, Cooperative Communications and Networking, Cambridge University Press, 2009.A. Chandra - Energy Conservation with Relays 13/41
  14. 14. Relaying Protocols Forwarding Strategy  Amplify and Forward (AF) - Layer #1 relaying: Relays act as analog repeaters.  Decode and Forward (DF) - Layer #2 relaying: Relays act as digital regenerative repeaters.  Compress and Forward (CF) - Hybrid solution: Relays quantize and compress (source coding). Relay Relay Relay Source Destination Source Destination Source Destination Amplify and Forward Decode and Forward Compress and ForwardA. Chandra - Energy Conservation with Relays 14/41
  15. 15. Relaying Protocols Protocol Nature  Fixed protocol - Relays always forward a processed version of their received signals.  Adaptive protocol - Relays autonomously decide whether or not to forward.  Feedback protocol - Relays provide redundancy only when explicitly requested by destination. H. Katiyar, A. Rastogi, and R. Agarwal, “Cooperative communication: A review,” IETE Tech. Review, vol. 28, no. 5, pp. 409-417, Sep.-Oct. 2011.A. Chandra - Energy Conservation with Relays 15/41
  16. 16. Outline Introduction Energy Conservation Basics of Relaying Modelling - Power consumption at Rx/ Tx - Energy consumed per bit - Effect of fading Case Study SummaryA. Chandra - Energy Conservation with Relays 16/41
  17. 17. Modelling Assumptions  Receiver - Heterodyne, Hartley & Weaver, Zero IF, Low IF.  Baseband Signal Processing - Source Coding, Pulse Shaping, Digital Modulation blocks are omitted.  Uncoded System - No Error Correction Code (ECC) blocks are included.  Multiple Antennas - Multiple RF processing blocks.A. Chandra - Energy Conservation with Relays 17/41
  18. 18. Modelling Power Consumption at Receiver  Block Diagram Band Image Channel Antenna selection rejection selection ADC filter LNA filter Mixer filter IFA LO  Components PRx = PLNA + Pmix + PIFA + PADC + Pfil + Psyn P. -I. Mak, S. -P. U, and R. P. Martins, Analog-baseband Architectures and Circuits for Multistandard and Low-voltage Wireless Transceivers, Springer, 2007. B. Leung, VLSI for Wireless Communications, 2nd ed., Springer, 2011.A. Chandra - Energy Conservation with Relays 18/41
  19. 19. Modelling Power Consumption at Transmitter  Block Diagram Channel Image DAC selection rejection Antenna filter Mixer filter PA LO  Components ξ PTx = PDAC + Pmix + Pfil + Psyn PPA = PT η PTx ,total = PPA + PTx PT → RF transmit power. ξ → Peak-to-average ratio. η → Drain efficiency.A. Chandra - Energy Conservation with Relays 19/41
  20. 20. Modelling RF Transmit Power  Friis Free Space Formula 2 PR  λ  PR → Received power. =  GT GR PT  4πd  d → Distance between Tx and Rx. 2 λ → Signal wavelength.  4π  d 2 ⇒ PT = PR   G → Combined antenna gain.  λ  G where G = GT GR.  For Terrestrial Transmission 2  4π  d n PT = PR   n → Path loss exponent (2 ≤ n ≤ 4).  λ  G  Considering Link Margin and Noise Figure 2  4π  d n ML → Link margin. PT = PR   M L NF  λ  G NF → Noise figure.A. Chandra - Energy Conservation with Relays 20/41
  21. 21. Modelling Energy Consumed per Bit  Total Circuit Power Consumption PC = PTx ,total + PRx = PPA + PTx + PRx ξ =   PT + PTx + PRx  η   2  ξ   4π  d n =   PR    η M L N F + ( PTx + PRx )    λ  G 2 ξ  4π  d n =   Eb Rb    η M L N F + ( PTx + PRx )    λ  G where, Eb → Received energy per bit, Rb → Bit rate, and PR = Eb Rb.A. Chandra - Energy Conservation with Relays 21/41
  22. 22. Modelling Energy Consumed per Bit  Consumption per Bit PC E= Rb 2  ξ   4π  d n P + PRx =   Eb    η M L N F + Tx    λ  G Rb  Bit Rate (Rb) - When no pulse shaping is used, Rb = 2B, where B = System BW.  Received Energy per Bit (Eb) - This parameter determine the BER floor and QoS.A. Chandra - Energy Conservation with Relays 22/41
  23. 23. Modelling Ensuring a Fixed BER  Consider the Modulation Scheme - For BPSK modulation, the BER is 1  Eb  Pe = erfc  N   2  0   Consider the Target BER - Target BER is application specific, e.g. for voice applications, Pe ≤ 10-3.  Calculate Required Eb 1  Eb  erfc  N   ≤ 10 −3 2  0  [ ⇒ Eb ≥ N 0 erfc 2 ×10 -1 ( −3 )] 2A. Chandra - Energy Conservation with Relays 23/41
  24. 24. Modelling Effect of Fading  Statistics of Received SNR - For Rayleigh fading 1  γ f ( γ ) = exp −   γ γ    Outage Probability - For a target SNR (γo), O = Pr[ γ < γ 0 ] γ0 = ∫ f ( γ ) dγ 0  γ0  = 1 − exp −   γ    - Target SNR is determined by the required data rate.A. Chandra - Energy Conservation with Relays 24/41
  25. 25. Modelling Target SNR Calculation  Ergodic Capacity: Shannon’s Formula - For reliable communication Rb ≤ B log 2 (1 + γ o ) ⇒ γ o ≥ 2 Rb B −1  Outage Probability  γ0  O = 1 − exp −   γ     2 Rb B − 1  = 1 − exp −     γ   3  − = 1 − exp   Eb N 0  A. Chandra - Energy Conservation with Relays 25/41
  26. 26. Modelling Energy Consumed per Successful Bit  Effective Data Rate Rb ,eff = Rb (1 − O )  Energy Consumption per Bit PC Esuc = Rb ,eff PC = Rb (1 − O ) E = 1− OA. Chandra - Energy Conservation with Relays 26/41
  27. 27. Modelling One More Equation … … and you’ll lose rest of your audience!A. Chandra - Energy Conservation with Relays 27/41
  28. 28. Modelling Research Challenges  Relay: To Use or Not to Use - Always cooperate, or use relay only when the direct link fails?  Relay Placement - If relay node is not collinear, is there any boundary region to place it?  Relay Selection - If there are many relay nodes, how many and which ones to select?  Other Issues - Multiple antennas at relay, distributed STC etc.A. Chandra - Energy Conservation with Relays 28/41
  29. 29. Outline Introduction Energy Conservation Basics of Relaying Modelling Case Study - Relay placement: Collinear model - Relay placement: Non-linear model SummaryA. Chandra - Energy Conservation with Relays 29/41
  30. 30. Modelling for Relay Statistics of S-R-D Link  Outage Probability  γ0  OS − R − D = OS − R + (1 − OS − R ) OR − D OS − R = OR − D = 1 − exp −   γ     Energy Consumption per Bit in S-R Link 2 PC , S − R  ξ   4π  d S − R n P + PRx ES − R = =   Eb    η M L N F + Tx Rb    λ  G Rb  Energy Consumption per Bit in R-D Link 2 PC , R − D  ξ   4π  d R − D n PTx + PRx ER − D = =   Eb    η M L NF + Rb    λ  G RbA. Chandra - Energy Conservation with Relays 30/41
  31. 31. Modelling for Relay Statistics of S-R-D Link  Energy Consumption per Bit in S-R-D Link - Outage in S-R path, ES − R − D = ES − R , probability OS − R . - No outage in S-R path, ES − R − D = ES − R + E R − D , probability 1 − OS − R . - Average energy consumption ES − R − D = OS − R ES − R + (1 − OS − R )( ES − R + E R − D )  Effective Data Rate Rb ,eff = Rb (1 − OS − R − D )  Energy Consumption per Successful Bit ES − R − D Esuc = 1 − OS − R − DA. Chandra - Energy Conservation with Relays 31/41
  32. 32. Relay Placement Collinear Model  Direct Path vs. Relayed Path Relayed Path Direct Path (Reference level) 42.2 m (Optimum location) Source Relay DestinationA. Chandra - Energy Conservation with Relays 32/41
  33. 33. Relay Placement Non-linear ModelA. Chandra - Energy Conservation with Relays 33/41
  34. 34. Relay Placement Non-linear Model ? Source Relay DestinationA. Chandra - Energy Conservation with Relays 34/41
  35. 35. Relay Placement Non-linear Model Relay Source DestinationA. Chandra - Energy Conservation with Relays 35/41
  36. 36. Outline Introduction Energy Conservation Basics of Relaying Modelling Case Study SummaryA. Chandra - Energy Conservation with Relays 36/41
  37. 37. Summary  Energy efficient perspective for wireless systems.  Various means to reduce energy consumption.  Use of wireless relays is one of them.  A single collinear relay may save upto 35% energy.  For non-linear setup, an energy efficient region may be found to place the relay.  Many open problems, we need you!A. Chandra - Energy Conservation with Relays 37/41
  38. 38. Read More About It Green Communication • G. Y. Li et al., “Energy efficient wireless communications: Tutorial, survey, and open issues,” to appear in IEEE Wireless Commun. Magz. Modelling Energy Consumption • S. Cui, A. Goldsmith, and A. Bahai, “Energy-efficiency of MIMO and cooperative MIMO techniques in sensor networks,” IEEE J. Sel. Areas Commun., vol. 22, no. 6, pp. 1089-1098, Aug. 2004. • G. G. de Oliveira Brante, M. T. Kakitani, and R. D. Souza, “On the energy efficiency of some cooperative and non-cooperative transmission schemes in WSNs,” Proc. IEEE CISS, Baltimore, MD, Mar. 2011, pp. 1-6.A. Chandra - Energy Conservation with Relays 38/41
  39. 39. Thank You All Presenting talks in conferences ensure … Hua Hin Bangkok Science City … travelling around the Globe!A. Chandra - Energy Conservation with Relays 39/41
  40. 40. Acknowledgements This talk won’t be possible without …  The support of Conference Organizers  Encouragements Prof. Richard D. Souza Prof. Joyanta Kr. Roy Dr. P. Venkateswaran UTFPR - Parana, Principal, NIT Assoc. Prof., ETCE Deptt., Curitiba, Brazil. & Program Chair, ICCIA. & Secretary, IEEE ComSoc.  Permissions  My research group Mr. Biswajit Ghosh Mr. Anirban Ghosh Lecturer, IT, Master’s student, FIEM, Kolkata NIT Durgapur. & Ph.D. student.A. Chandra - Energy Conservation with Relays 40/41
  41. 41. Thank You! Questions? aniruddha.chandra@ieee.orgA. Chandra - Energy Conservation with Relays 41/41
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