Download
energy models n.
Skip this Video
Loading SlideShow in 5 Seconds..
Energy Models PowerPoint Presentation
Download Presentation
Energy Models

Energy Models

166 Views Download Presentation
Download Presentation

Energy Models

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. Energy Models David Holmer dholmer@jhu.edu

  2. Energy Model • Captures the effect of the limited energy reserves of mobile devices (i.e. batteries) • Models the power levels of the device during operation so that total energy consumption can be calculated • A number of different models are used in the literature • Transmission Power Model • Transmission & Reception Model • Power State Model

  3. Transmission Power Model • Assumes energy consumption is directly related to wireless output power • Output power in typical cards range from 1mW to 200mW • Output power is related to the square of range • Cutting transmission range in half cuts output power requirement by ¼ • In some environments related by greater exponent (depends on path loss constant = 1.8 to 6) • This means by choosing shorter hops, the total output power can be reduced (¼ + ¼ < 1) • Used by many papers (particularly theory papers) • Minimum energy routing • Minimum energy broadcast • Topology control • Flawed model ignores MANY sources of energy consumption • Fixed transmission consumption overhead • Consumption by receiver • Consumption by idle nodes

  4. Transmission & Reception Model • Energy consumption depends on the number of packets sent & received • Energy consumption of a packet is calculated using several constants • Not very commonly used • Increased accuracy but still missing a significant contribution to energy consumption (idle power)

  5. Power State Model • Uses different power levels depending on state of wireless card • Transmit (1.33 Watts) • Receive (0.97 Watts) • Idle (0.84 Watts) • Sleep (.07 Watts) • Based on measurements of a real wireless card on lab equipment • Captures the majority of card power consumption effects (most accurate model in general use) • Measured values only apply for the exact model of card • Does not take into account transient consumption from mode switches • Does not take into account power consumption of host(i.e. from packet processing) • Usually assumes fixed output power(not normally used with transmission power control)

  6. Sending Power Example Receiving Sending

  7. Receiving Power Example

  8. Different Transmit Options

  9. Sleep Mode • High consumption while active • High transmit power constant • High idle & receive power • Sleep mode allows much of the electronics to be turned off • Radio cannot send or receive packets • Can be activated again by host in a small amount of time • SIGNIFICANTLY lower power levels (.07 Watts) • Only protocols that make extensive use of sleep mode can save a large fraction (>50%) of the card power consumption • Sleep mode limit = <90% savings • Transmit power control limit = <<35% savings

  10. PRISM Sleep Power Ramp Up