Power Consumption

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Description

Increasing the CPU speed, memory bandwidth etc. could increase the consumption of energy use by the mobile device. Power consumption may thus be the limiting factor for the functionality. Power consumption drives the important mobile device characteristics of stand-by time and operational time. It also has impact on the radius of action through the reach of the transmission and the operating/standby time before the battery needs to be recharged.

Enablers

  • Technology Developments:
    • low voltage semi-conductors. The amount of power reduces with the square of the supply voltage. Thus reducing supply voltage reduces the power consumption of the circuit.
    • asynchronous circuits: high amounts of power are spent in clocking gates on a chip. Asynchronous circuits only spent power when the activity spreads through the chip.
    • dynamic power management (frequency scaling, voltage scaling). In stead of doing away with the clock (as in asynchronous circuits) it is also possible to switch on/off the parts of the chip which are not used.
    • higher integration: Higher intergration of the same functionality on a single chip reduces power as board level currents are much higher than on chip currents.
    • efficient antenna's: large fraction of the power consumed by the mobile device is for transmission. Efficient antenna design can reduce the amount of power spent in the transmission.
    • low power RF protocols. By carefully crafting the protocols for tranmission and reception it is possible to reduce the amount of power needed per information unit.



Inhibitors

  • demand for higher performance CPU. Advanced user interfaces, better compression algorithms, more applications all fight for CPU cycles. Higher performance CPU could be done through higher clock speed.
  • demand for higher bandwidth. Since the performance of the CPU is increasing it is also possible to support moving pictures and higher resolution. This requires higher bandwidth communication.
  • Increasing integration of functionality on the device. Supporting all applications, different communication possibilities needs more functionality on the mobile devise. If these applications and communication possibilities need to operate in parallel they will increase the need for power per unit time.
  • increasing complexity of the user interface (screens, colors, ...)
  • increasing flexibility requires more software solutions which use more energy. Implementation of algorithms in hardware consumes less power than implementing the algorithms in software. However software implementations are much more flexible.
  • increasing pollution of the radio spectrum. If more devices are using the same or adjacent parts of the radio spectrum, then higher power is needed to reach the necessary bandwidths.



Paradigms

The availability of low power electronics has an impact on the level at which the mobile device is experienced as seamless integrated part of your behavior. Every time you need to charge the mobile device reminds you that in fact the mobile device is a piece of electronics which needs special attention.

Timing

  • 1997 foundation of E.INK (http://www.eink.com/company/index.html)
  • 1998 asynchronous implementation of MIPS R3000, dubbed MiniMIPS
  • 2000 low voltage processors (e.g. Low Voltage Mobile Intel® Celeron™ Processor (500 MHz))



Web Resources


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