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A Framework for Energy-Scalable Communication in High-Density Wireless Networks

A Framework for Energy-Scalable Communication in High-Density Wireless Networks. Telvis Calhoun Wireless Sensor Networks CSC8908-005 Dr. Li 8/27/2008. Background. Overview Power Control API Radio Channel Background Communication Models Summary. API.

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A Framework for Energy-Scalable Communication in High-Density Wireless Networks

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  1. A Framework for Energy-Scalable Communication in High-Density Wireless Networks Telvis Calhoun Wireless Sensor Networks CSC8908-005 Dr. Li 8/27/2008

  2. Background • Overview • Power Control API • Radio Channel Background • Communication Models • Summary

  3. API • Introduce power control API for wireless sensor nodes. • Trade-off communication for energy savings • Latency • Reliability • Range for energy savings. • Goal is to add energy efficient protocol design. • Scalable sensor networks

  4. Energy vs. Performance • Voltage/Freq • Processor effects end-to-end latency scalability in communication • Code[rate] • Provides reliability. • Transmit power • Range scalability.

  5. Knobs • Range • Works with location aware protocol. Set destinations unicast or multicast. • Range number or nearest neighbors or distance in meters.

  6. Other Knobs • Latency – set maximum latency (usecs) • Reliability – set min reliability (ber) • Energy - set max energy(ujoules)

  7. Radio Model • Radio Model Parameters • Amplification • RF and RF Pathloss • Forward Error Correction • Bit-error rate • Receiver thresholds • Noise and Interference

  8. Power Amplification [2, 3] • Increases the power and/or amplitude of a signal. • Also called gain.

  9. RF and RF Pathloss [10] • RF is a frequency or rate of oscillation • Attenuation of an electromagnetic wave as it propagates through space. • Influenced by • terrain contours, • environment (urban or rural, vegetation and foliage), • Propagation medium (dry or moist air), • Distance between the transmitter and the receiver • Height and location of antennas.

  10. Forward Error Correction [5] • Sender adds redundant data to its messages • Allows the receiver to detect and correct errors (within some bound) without the need to ask the sender for additional data. Coderate • k/n for every k bits of useful information • n bits of data, of which n minus k are redundant. [6]

  11. Bit-error rate [7] • Ratio of the number of bits incorrectly received to the total number of bits sent during a specified time interval. • Mitigated by FEC

  12. Receive Thresholds • RF Sensitivity Threshold • Lowest signal strength at which a signal can be detected on the channel. • RF Receive Threshold • Lowest signal strength a which a signal can be received as information.

  13. Noise and Interference [8] • Noise Floor • Measure of the signal created from the sum of all the noise sources and unwanted signals • Includes thermal noise. • Interference • Signals from different users to interfere with one another.[9] • Mitigated by orthogonal channels and MAC algorithms

  14. Communication Energy Models • Radio Transmission Energy – (PIC). Represent the energies at startup and transmission. • Pstart,Tstart represent power and latency or radio at startup • PtxElec is active transmission power • Pamp is dissipated amplifier power • R radio bit rate • Rc is convolutional code rate • N number of bits before FEC (forward error correction)

  15. Decoding and Receive Energy • Energy required to receive a packet • N is energy dissipated by the radio at startup • R received coderate • Edecbit is the decoding energy per information bit

  16. Modeling Communication • Node-to-Base Station • Base station is an energy-unconstrained node • Node-to-Node • Sum of receive and transmit energies. • Minimum energy policy is enforced by choosing least-energy paremeters to satisfy requirements

  17. Point-to-Point Communication • Code (K) Kc=7=max • Power amplifier (V) • Decoding processor voltage (V, MHz) • N is data bits

  18. Multi-hop Data Aggregation • Vary power parameters to achieve least cost multi-hop route

  19. Summary • Paper provides an API used for adaptive power control • Describes theoretical models • Shows performance impact of various parameters • Reviewed radio parameters • Communication Models

  20. References [1] R. Min and A. Chandrakasan, "A framework for energy-scalable communication in high-density wireless networks," in Proceedings of the 2002 international symposium on Low power electronics and design Monterey, California, USA: ACM, 2002. [2] Amplifier, "http://en.wikipedia.org/wiki/Amplifier." [3] Electronic_amplifier, "http://en.wikipedia.org/wiki/Electronic_amplifier." [4] Radio_frequency, "http://en.wikipedia.org/wiki/Radio_frequency." [5] Forward_Error_Correction, "http://en.wikipedia.org/wiki/Forward_error_correction." [6] Code_rate, "http://en.wikipedia.org/wiki/Code_rate." [7] Bit_error_probability, "http://en.wikipedia.org/wiki/Bit_error_probability." [8] Noise_floor, "http://en.wikipedia.org/wiki/Noise_floor." [9] WiMAX, "Wireless Radio Channel," in http://www.wimax.com/commentary/wimax_weekly/1-7-1-wireless-radio-channel. [10] Pathloss, "http://en.wikipedia.org/wiki/Pathloss."

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