1. Adaptive approach for QoS support in IEEE 802.11e WLAN
Joe Naoum-Sawaya, Bissan Ghaddar, Sami Khawam, Haidar Safa, Hassan Artail, and Zaher Dawy
Wireless and Mobile Computing, Networking and Communications (WiMob) 2005

2. Problem
Parameters are depending on traffic category, not network state or network contention level
EDCA technique resets the CW of each station after each successful transmission to CWmin

3. Propose
A new adaptive EDCA technique that adapts CW to channel conditions and adjusts it depending on the network utilization and performance
They estimate channel congestion level start from the fact that CW value ranges in the interval [CWmin, CWmax]

4. Propose
To optimize further ratio, they use a weight that reflects the certainty of the channel estimation
The weight is decreased as time elapses between consecutive transmissions
They fixed weight to 0.9 because video streaming is characterized by transmission occurring at very small time intervals

5. Performance evaluation
Their simulations were implemented using ns-2
They compare three parameters: bit rate, end-to-end packet delay, and packet drop rate
In simulation, 4 source-destination pair with 4 different priorities.
Each source is a CBR over UDP
The levels of priority in EDCA are called access categories (ACs).

6. Performance evaluation
The levels of priority in EDCA are called access categories (ACs).

7. Performance evaluation
The levels of priority in EDCA are called access categories (ACs).

8. Performance evaluation
The levels of priority in EDCA are called access categories (ACs).

9. Design of medical-grade wireless LAN
Sunghwa Son
Adviser: Prof. Kyung-Joon Park

10. Absolute priority Absolute priority mechanism
It can assure the absolute priority of each category with respect to lower-priority ones AC
Length of AIFS
802.11e
Absolute priority
AC0
5.00E-05
5.00E-05(AIFS0)
AC1
(AIFS0+CW0)
AC2
7.00E-05
(AIFS1+CW1)
AC3
1.50E-04
(AIFS2+CW2)

11. My proposal
Absolute priority is so strict that lower priority traffic may not have enough change for channel access
Low priority traffic should wait for a large AIFS, even there is no high priority traffic >> waste of the time and resource
My proposal adaptively changes AIFS with respect to network condition

12. Performance evaluation
Simulate with ns-2
3 alarm nodes and 20 TCP connections
The levels of priority in EDCA are called access categories (ACs).

13. Compare with my simulation
Adaptively change CW vs. AIFS
After successful transmission, does not resets the CW to CWmin vs. reset to CWmin
Sources with only UDP vs. UDP and TCP
4 priorities with video streaming vs. alarm, streaming, and data transmission