Consideration of Quality of Service is taken into account during the establishment of a sleep cycle in a mobile station providing real-time services. Upon the mobile station's identification of a need for a real-time service to enter into sleep mode, a request conveying that need is sent to the base station. The base station replies with a start frame number and other sleep parameters. Thereafter the mobile station enters sleep mode comprising sleep intervals interleaved with listening intervals. To prevent transmission packets from being buffered at the mobile station for an excessive period of time due to attempts to transmit packets to the base station during a sleep interval, the length of the sleep interval is set so as not to exceed the maximum latency value reflecting the QoS of the real-time service negotiated during establishment of the real-time services.