02. 16m System Operation and State Diagrams Negative Positive Traffic Traffic Data Traffic Indication Indication W0: Initial Sleep Cycle W: ith Sleep Cycle Sleep Cycle Update: WL: Final Sleep Cycle For best effort traffic W = min(2 * Wi-1, WL) LW: Listening Window For real-time traffic W = Wo LWE: Listening Window Extension SW: Sleep Window FIGURE 4-6 An illustration of sleep mode operation [27] 20 ms) prior to its listening window to verify whether the Superframe Number and System Config- uration Description Change Count parameters are as expected. Upon wakeup, if the synchronization with the serving BS is lost or the MS detects base stations other than the serving BS, then the MS exits the Sleep Mode and performs (handover and) network re-entry procedures with the target BS, as described earlier. The length of successive sleep cycles may remain constant or may be adaptive based on traffic conditions. The sleep and listening windows may also be dynamically adjusted for the purpose of data transmission and MAC control signaling. The MS and BS may keep up to 16 previously used sleep cycle patterns and associated sleep cycle identifiers. The sleep cycle pattern can be changed by sending a sleep request management message to the serving BS. The BS responds using a sleep response management message either approving the request or suggesting another sleep pattern. A single sleep cycle setting, identified by a sleep cycle identifier, is applied per MS across all the active connections of the MS. The Sleep Mode entry can be initiated either by the MS or the BS. When the MS is in Active Mode, the Sleep Mode parameters are negotiated between the MS and the serving BS. The sleep cycle is measured in units of frames. The start of the listening window is aligned at the frame boundary. The MS must ensure that it has the latest system information for proper operation. If the system information is not up-to-date, the MS will not transmit in the listening window until it receives the current system information. The BS transmissi