1. 1 A Cross-Layer Scheduling Algorithm With QoS Support in Wireless Networks Qingwen Liu, Student Member, IEEE, Xin Wang, Member, IEEE, and Georgios B. Giannakis, Fellow, IEEE IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. 55, NO. 3, MAY 2006 報告者：李宗穎

2. 2 Outline Introduction System Architecture Scheduler Design Simulation Conclusion

3. 3 Introduction 802.11, 802.16, and 802.15 networks support multimedia services with different QoS requirement channel capacity in wireless networks is time varying due to multipath fading Paper define a priority function (PRF) depend on the 1) wireless channel quality, 2) QoS satisfaction, and 3) service priority across layers

4. 4 Network Configuration Star topology is also used to describe the connections between each relay station and multiple SS in mobile ad hoc networks and wireless sensor networks

5. 5 Wireless link from BS to SS A buffer is implemented at the BS for each connection and operates in a FIFO mode The AMC (Adaptive Modulation and Coding) controller follows the buffer at the BS AMC selector is implemented at the SS

6. 6 Transmission modes in the IEEE 802.16 Standard At the MAC, each packet is mapped to a symbol block containing N b /R n symbols At the PHY, each frame is divided into N c + N d time slots

7. 7 Processing units at MAC and PHY

8. 8 QoS Architecture at the MAC Unsolicited grant service (UGS) EX: VoIP… Real-time polling service (rtPS) EX: MPEG video and video stream… Nonreal-time polling service (nrtPS) EX: FTP… Best effort (BE) EX: HTTP 、 Email…

9. 9 AMC Design at the PHY AMC design guarantees that the PER (Packet Error Rate) is less than or equal to P 0 To simplify the AMC design, paper approximate the PER expression in AWGN channels

10. 10 Scheduling UGS Connections The AMC design is not adopted for UGS N r = N d – N UGS N r ： availability time slot N d ： all time slot to transmit data N UGS ： UGS connections time slot

11. 11 Scheduling rtPS Connections F i (t) is the delay satisfaction indicator F i (t) = T i − ΔT i −W i (t) + 1 T i = maximum latency ΔT i = guard time region W i (t) = longest packet waiting time ψ i (t) is the PRF for connection i at time t

12. 12 Scheduling nrtPS Connections F i (t) is the rate satisfaction indicator η i (t) = average rate at time t η i = minimum reserved rate ψ i (t) is the PRF for connection i at time t

13. 13 Scheduling BE Connections ψ i (t) is the PRF for connection i at time t The priority of QoS classes is rtPS > nrtPS > BE β rtPS > β nrtPS > β BE

14. 14 Desirable Features Efficient bandwidth utilization Delay bound T i is provided for rtPS connections Throughput is guaranteed for nrtPS connections Implementation complexity is low Flexibility is provided Scalability is achieved

15. 15 Simulation Parameter Setting MAX delayMIN ThoughputPERSNRβ rtPS-130ms2Mbps0.0115dB1.0 rtPS-250ms1Mbps0.0120dB1.0 nrtPS-1-6Mbps0.00115dB0.8 nrtPS-2-3Mbps0.00120dB0.8 BE-1--0.00116dB0.6 BE-2--0.00118dB0.6 The frame length is T f = 1ms Packet length at the MAC is fixed to N b = 128bytes Simulation time = 60000ms

16. 16 Result N r =3 rtPS nrtPS BE

17. 17 Result N r =2 rtPS nrtPS BE

18. 18 Result N r =1 rtPS nrtPS BE

19. 19 Conclusions Paper developed a cross-layer scheduling algorithm at the MAC layer for multiple connections with diverse QoS requirements Future works, scheduling multiple connections each time may lead to better performance