adjusted based on traffic availability or control signaling in the MS or BS. The listening window can be extended through explicit signaling. The listening window cannot be extended beyond the end of the current sleep cycle. The MS or BS can initiate the Sleep Mode termination/deactivation procedure. The BS signals the termination of the MS Sleep Mode using MAC management messages. The traffic indication signal is sent for a single MS or a group of mobile stations using the AAI_TRF-IND message. The AAI_TRF-IND message is transmitted at the first frame in the listening window of each MS. If the traffic indication is enabled for an MS with Sleep Identifier (SLPID) assigned (i.e., a unique identifier for a mobile station or a group of mobile stations in the Sleep Mode), the MS should expect a traffic indication message at predetermined intervals. The set of SLPID values range from 0 to 1023 and are divided into 32 SLPID Groups. The SLPID Groups are defined as follows: SLPID-Group#0 corresponding to SLPID values 0 31; SLPID-Group #1 corresponding SLPID values SLPID-Group#31 corresponding to SLPID values 992 1023. The SLPID-Group Indication Bitmap is a 32-bit field where each bit is assigned to a particular SLPID-Group. In other words, the MSB in the field is assigned to SLPID-Group#0 and subsequent bits correspond to SLPID-Group #1, 2, 31. Therefore, the Sleep Mode MS associated with SLPID- Group #n may return to sleep mode if the nth bit in the SLPID-Group Indication Bitmap is not set. If the corresponding bit were set, the MS would read its own Traffic Indication Bit-map in the AAI_TRF- IND message. On receiving the traffic indication message, the MS checks whether there is a positive traffic indication (e.g., through SLPID-Group Indication Bit-map and Traffic Indication Bit-map or the SLPID assigned to it). If the MS receives a negative traffic indication, then it ends the listening window and proceeds with sleep window operation for the remainder of the sleep cycle, unless the MS has UL signaling or pending traff