Chapter 9 – Power Management

Publisher Summary This chapter discusses power management for a Wi-Fi phone from a system perspective. If appropriate power management techniques are not implemented, the radio interface will drain the battery of a Wi-Fi phone very quickly, making it practically unusable. The binary philosophy of power management, where unused components are shut off and components being used remained powered on, can be extrapolated so that components that remain powered on are controlled dynamically such that their power consumption is in proportion to their load. Dynamic power management (DPM) is a power-management framework and it provides the basic infrastructure and hooks inside the operating system to be used for achieving power management. Because the power management of the wireless local area network (WLAN) subsystem must be closely synchronized with the AP timing, as per the standards, low-level aspects of WLAN power-management/control must be localized to the WLAN subsystem itself. However, from an end user's viewpoint, power management is evaluated in terms of “talk time” and “standby time.”