QoS Enhancement in IEEE802.11 Wireless Local Area Networks

1. QoS Enhancement in IEEE802.11Wireless Local Area Networks 华中科技大学电子与信息工程系 智能互联网湖北省重点实验室

2. 802.11 Medium Access Mechanisms：DCFand PCF • DCF（distributed coordination function） • Provide best-effort service; • Based on carrier sense multiple access with collision avoidance(CSMA/CA) Introduction

3. Introduction

4. 802.11 Medium Access Mechanisms：DCFand PCF • PCF(Point Coordination Function) • A hybrid coordination, include CFP andCP; • A polling medium access method with the point coordination(PC) performing the role of the polling master; • Only available and usable on infrastructure network • Different delay and bandwidth requirements of applications are not supported. Introduction

5. EDCF : Enhanced DCF Differential distributed access 4 access category(ACs) 8user priorities(UPs) Solutions

6. Solutions • HCF : also include CP and CFP； • The EDCF is the contention-based medium access method for HCF; • HC has higher medium access priority than the EDCF; • HC is a kind of PC, but operates on different rules than a PC.

7. Solutions

8. Simulation Evaluation • Constructed using OPNET, configured in ad hoc mode, four stations; • PHY module with maximum data rate up to 11Mb/s; • Support the EDFC mechanism and don’t consider other traffic parameters such as TXOPs; • Each traffic class has an equal portion of the total data traffic; • The packet has the same size of 1024 bytes; • Cwmin = 31 , Cwmax = 1023 , SlotTime = 20μs;

9. Simulation Evaluation

10. Simulation Evaluation

11. Thanks~