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IEEE 802.11 MAC Enhancements for Quality of Service

IEEE 802.11 MAC Enhancements for Quality of Service. IEEE Std 802.11e. Characteristics of IEEE 802.11e. The major enhancement of 802.11e Traffic differentiation Enhanced DCF (contention-based) EDCF. MAC Architecture. IEEE 802.11 MAC Architecture. IEEE 802.11e MAC Architecture.

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IEEE 802.11 MAC Enhancements for Quality of Service

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  1. IEEE 802.11 MAC Enhancements for Quality of Service IEEE Std 802.11e

  2. Characteristics of IEEE 802.11e • The major enhancement of 802.11e • Traffic differentiation • Enhanced DCF (contention-based) • EDCF

  3. MAC Architecture IEEE 802.11 MAC Architecture IEEE 802.11e MAC Architecture • DCF : A contention-base access for 802.11. • PCF : An option to support contention-free access in 802.11. • Hybrid Coordination Function (HCF): IEEE 802.11 Task Group E (TGe) proposes HCF to provide QoS for real-time applications.

  4. HCF - Introduction • HCF combines functions from the DCF and PCF with enhanced QoS-specific mechanisms. • HCF consists of • Enhance DCF (EDCF) for contention-based access • Controlled Access (HCCA) for contention-free access

  5. EDCF – Traffic Category • The EDCF provides differentiated access to the WM for 8 priorities, identical to IEEE 802.1D priority tag, for non-AP STAs. • Priorities are numbered from 0 (the lowest priority) to 7 (the highest priority). • The set of MSDUs with the same priority is refer to a Traffic Category (TC).

  6. EDCF – Access Category (1/5) • EDCF defines access category (AC) mechanism to support the priority mechanism at QSTAs. • An AC is an enhanced variant of the DCF which contends for transmission opportunity (TXOP) using the set of parameters such as CWmin[AC], CWmax[AC], AIFS[AC], etc.

  7. EDCF – Access Category (2/5)IFS (Inter Frame Spacing)

  8. EDCA

  9. EDCF – Access Category (3/5) • The parameter set is specified in the “EDCA parameter set element” of beacon frames. • Default QoS parameter set: video voice

  10. EDCF – Access Category (4/5)Queues • An QSTA has four ACs. • Collision between ACs within a QSTA is called internal collision. Collisions will be resolved internally (giving to higher-priority queues).

  11. EDCF – Access Category (5/5) • The mapping from 8 priories to 4 ACs is:

  12. Summary • A new EDCF block • Use of different IFS in traffic categories for QoS support

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