**4. Conclusion**

52 Mobile Networks

(c)

(d) Fig. 12. The average energy efficiency of an MSS with two schemes and four connection types with a varied number of connections under jitter constraints: (a) connection type *A*',

(b) connection type *A*'+*B*', (c) connection type *A*'+*B*'+*C*', and (d) connection type

*A*'+*B*'+*C*'+*D*'.

An energy-efficient scheduling scheme to improve the energy efficiency and guarantee Quality of Service in IEEE 802.16e was proposed. The previous literature only considers the delay constraint of QoS requirement in one MSS. We first consider both the jitter and delay constraints of QoS requirement to schedulethe real-time connections in one MSS. Our proposed algorithmis to schedule the packet transmission in successively fashion with the minimal interval of listen periods and maximal interval of sleep periods without violating the QoS of all connections in an MSS. Additionally, the successive scheduling of time slots would reduce the number of status transitions between the sleep periods and listen periods. The proposed approach can be adapted to the power-saving class of type III where the length of sleep and listen periods arevariable. Simulation results show that, incomparison with the AS and Naïve schemes, the proposed SSS scheduling algorithm can result in a significant overall energy saving and can guarantee the delay and jitter QoS.
