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

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

3. MAC Architecture DCF : A contention-base access for 802.11.
IEEE MAC Architecture
IEEE e MAC Architecture
DCF : A contention-base access for
PCF : An option to support contention-free access in
Hybrid Coordination Function (HCF): IEEE 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
aCWmin 15, aCWMax 1023

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