1. LOGO A Cross-Layer Optimization Mechanism for Multimedia Traffic over IEEE 802.16 Networks 指導老師：童曉儒 教授 報告學生：許益晨

2. LOGO Outline  Introduction  Architectural Framework  Information Flow  The Proposed Mechanism  Simulation Model And Results  Conclusion

3. LOGO Introduction

4. LOGO Introduction  A cross-layer optimization mechanism for IEEE 802.16 metropolitan area networks.  Modern communication systems is the parameterized operation at different layers of the protocol stack.  A cross-layer optimization mechanism that interacts with the Physical (PHY), Medium Access Control (MAC), and Application layers.

5. LOGO Architectural Framework

6. LOGO Architectural Framework  IEEE 802.16 又稱為 WiMAX 無線網路技術。  理論傳輸距離超過 100 公里，速度可達 70 Mbps  (IEEE802.16e) 加入 OFDMA 正交分頻多工存取技術， 使頻率可以分配給不同的使用者在同一時間下一起使 用，因此頻寬的使用上能較有效且彈性的分配利用。

7. LOGO Architectural Framework  Physical Layer(PHY)  支援可變動的頻寬和傳輸速率  Medium Access Control Layer(MAC)  定義了 Subscriber station (SS) 與 Base Station (BS) 之間維持 網路運行的 Management 訊息  QoS （ Quality of Service ）  ARQ （ Automatic RepeatRequest ）  Application layers

8. LOGO Architectural Framework The cross-layer optimization which consists of N layers and a cross-layer optimizer. The optimization process is performed in three steps:  Layer abstraction  Optimization  Layer reconfiguration

9. LOGO Architectural Framework In general, the different parameters can be divided in four main types:  Directly Tunable (DT)  Indirectly Tunable (IT)  Descriptive (D)  Abstracted (A)

10. LOGO Information Flow

11. LOGO Information Flow Step 1: Layer Abstraction Step 2: Optimization Step 3: Layer Reconfiguration

12. LOGO Information Flow A.Channel Measurements The BS needs information regarding the quality of the signal received by the SSs.  by each SS on the uplink.  Channel Quality Information Channel (CQICH)

13. LOGO Information Flow

14. LOGO Information Flow B. Traffic Rate Adjustments None of the existing management messages of the standard 802.16 can serve for traffic rate adjustments.

15. LOGO The Proposed Mechanism

16. LOGO The Proposed Mechanism 1)In case most of the losses are due to poor channel conditions (packet errors) the BS part instructs the MAC layer for a degradation of the modulation, in order to achieve higher channel error resilience and increase robustness against interference. 2)In case most of the losses are the result of packet timeouts (unacceptable delays) a. If the loss rate is caused almost exclusively by packet timeouts b. In different case, when a significant percentage of packet losses are caused by errors due to the poor channel conditions

17. LOGO The Proposed Mechanism

18. LOGO The Proposed Mechanism

19. LOGO The Proposed Mechanism 1)If the mean delay is relatively low compared to the delay bound 2)If the mean delay is close to the delay bound

20. LOGO Simulation Model And Results

21. LOGO Simulation Model And Results  Traffic Generator  Scheduler  Channel Modeler  Optimizer

22. LOGO Simulation Model And Results total packet loss rate for AMR traffic should not exceed the value of 7x10-3

23. LOGO Simulation Model And Results

24. LOGO Conclusion

25. LOGO Conclusion With the aid of a detailed simulation model, we showed that the use of the proposed optimization mechanism leads to an efficient exploitation of the adaptation capabilities, resulting in considerably reduced packet loss rates and improved system’s capacity, especially under heavy traffic conditions.