CSE5345_Lecture13

CSE5345_Lecture13 - 1 CSE 5345 Fundamentals of Wireless...

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Unformatted text preview: 1 CSE 5345 Fundamentals of Wireless Networks Yonghe Liu Yonghe@cse.uta.edu 2/23/12 2 Last Class Performance of DCF Markov Chain overview 3 Today Point Coordination Function (PCF) Contention-free access As opposed to contention-based DCF Hybrid Coordination Function (HCF) 4 Enhanced DCF To provide service differentiation among traffic categories Still distributed random access mechanism Based on DCF Backward compatible Leverage existing implementations No guarantee of service 2 5 Service Differentiation in EDCF Using different parameters for various traffic categories CWmin/CWmax Arbitration Inter-frame Space (AIFS) Functioning as DIFS 6 Service Differentiation in EDCF Each station maintains multiple queues For different traffic categories Each queue independently perform DCF Using individual CWmin/CWmas, AIFS Internal collision Low priority assumes collision happened High priority obtains transmission opportunity 7 Bursting Multiple frames can be transmitted once BC=0 Up to announced limit by AP Transmission Opportunity (TXOP) 8 Discussion What is the goal of bursting? 3 9 Discussion on EDCF Can EDCF provide absolute differentiation i.e., one class has strict priority over another? What is the priority for legacy devices How to assign parameters to video/voice What about parameter tuning 10 Contention Free Access Point Coordinator (PC) Residing at an AP Rotates contention-free and contention period Contention free access under PC control Polling based mechanism For uplink No contention transmission For downlink 11 Contention Free Period: Structure and Timing Each CFP begins with a Beacon frame Beacon is a management frame detailed later CFP repeats at fixed interval Announced in beacon Can be delayed by busy medium...
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This note was uploaded on 03/22/2012 for the course CSE 5345 taught by Professor Youngheliu during the Spring '12 term at UT Arlington.

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CSE5345_Lecture13 - 1 CSE 5345 Fundamentals of Wireless...

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