Power Saving Feature

1. Sleep Mode: Sleep mode is a state in which the MS effectively turns itself off and becomes unavailable for predetermined periods(sleep window-listen window). The periods of absence are negotiated with the serving BS. WiMAX defines three power-saving classes,

Power saving class-I: in Class-I the sleep window is exponentially increased from a minimum value to a maximum value. This is typically done when the MS is doing best-effort(web browsing HTTP) and non-real-time traffic(FTP)
Power saving class-II: Power Save Class 2 has a fixed-length sleep window and is used for UGS service (VOIP)
Power saving class-III: Power Save Class 3 allows for a one-time sleep window and is typically used for multicast traffic or management traffic when the MS knows when the next traffic is expected

To facilitate handoff while in sleep mode, the MS is allowed to scan other base stations to collect handoff-related information.

2. Idle Mode: Idle mode allows even greater power savings, and support for it is optional in WiMAX. Idle mode allows the MS to completely turn off and to not be registered with any BS and yet receive downlink broadcast traffic.

The MS is assigned to a paging group by the BS before going into idle mode, and the MS periodically wakes up to update its paging group. Idle mode saves more power than sleep mode, since the MS does not even have to register or do handoffs

Note: Active connections will be there during Sleep mode, where as there wont be any active connections during Idle mode