To improve battery life on mobile wireless devices including phones, voice badges, and handheld scanners, increase the WLAN DTIM period to the client vendor recommended values. Each vendor typically provides optimal recommendations for DTIM settings with their devices. Examples include DTIM settings of between 2 - 10 beacon intervals.
The DTIM period controls how often the client device must wake out of power-save mode to receive the beacon indicating if any data is buffered for it at the access point. Higher DTIM periods allow the devices to stay in power-save mode longer and increase battery life.
Also, in QoS enabled networks U-APSD (unscheduled automatic power save delivery) and in 802.11n networks PSMP (power-save multi-poll) provide better power-save performance than legacy DTIM operation and are usually enabled by default.