WLAN QoS : 802.11e
WLAN QoS : 802.11e
Summary
Summary
Introduction
What is QoS?
Why do we need QoS in wireless LAN nowadays? 802.11e
MAC Protocol
Enhanced Distributed Channel Access (EDCA) Presentation
How does it work?
Controlled Channel Access (HCCA) Presentation
How does it work? Other specifications
Automatic Power Save Delivery Block Acknowledgments
NoAck
Direct Link Setup Conclusion
Introduction
What is QoS?
Why do we need QoS in wireless LAN nowadays? 802.11e
MAC Protocol
Enhanced Distributed Channel Access (EDCA) Presentation
How does it work?
Controlled Channel Access (HCCA) Presentation
How does it work? Other specifications
Automatic Power Save Delivery Block Acknowledgments
NoAck
Direct Link Setup Conclusion
What is QoS ?
What is QoS ?
Quality of Service (QoS) This is the capacity of the
network to provide some kind of functionality
Without QoS, when you send some packet on the
network, the packet can arrive in any order or take an undefined time to
arrive
Quality of Service (QoS) This is the capacity of the
network to provide some kind of functionality
Without QoS, when you send some packet on the
network, the packet can arrive in any order or take an undefined time to
Why we need QoS in wireless
LAN nowadays?
Why we need QoS in wireless
LAN nowadays?
Evolution of the customer’s needs Video and audio
streaming Wireless phone over IP Real time applications Evolution of the customer’s needs Video and audio
streaming
Wireless phone over IP
Real time applications
802.11e
802.11e
This is the standard for WLAN QoS Provide essential services for
delay-sensitive applications
Corresponds to the WMM certification of the WiFi Alliance
This is the standard for WLAN QoS Provide essential services for
delay-sensitive applications
Corresponds to the WMM certification of the WiFi Alliance
MAC Protocol
MAC Protocol
Enhanced Distributed Channel Access (EDCA) Enhanced Distributed Channel
EDCA Introduction
EDCA Introduction
Evolution of Distributed Coordination Function (DCF)
Introduces traffic priority Favorite VoIP applications
Every hardware with WMM certification supports at least EDCA
Evolution of Distributed Coordination Function (DCF)
Introduces traffic priority Favorite VoIP applications
Every hardware with WMM certification supports at least EDCA
Main Advancements
Main Advancements
Introduction of basic traffic priority
4 Types of Traffic
Voice Video
Best effort
Background application
Creation of a Transmit Opportunity for each type of traffic
Introduction of basic traffic priority
4 Types of Traffic
Voice Video
Best effort
Background application
Creation of a Transmit Opportunity for each type of traffic
How does it work ?
How does it work ?
There is a FIFO stack for each traffic priority
High priority traffic waits less than low priority
traffic
Each traffic priority has a different backoff value
The higher the priority, the shorter is the Backoff value
There is a FIFO stack for each traffic priority
High priority traffic waits less than low priority
traffic
Each traffic priority has a different backoff value
The higher the priority, the shorter is the Backoff value
How does it work ?
How does it work ?
When a station wins the access, it can send a packet during its Transmit Opportunity (TXOP)
The TXOP is different for each priority level
The higher the priority, the longer the TXOP
When a station wins the access, it can send a packet during its Transmit Opportunity (TXOP)
The TXOP is different for each priority level
MAC Protocol
MAC Protocol
Hybrid Controlled Channel Access (HCCA) Hybrid Controlled Channel Access
HCCA Introduction
HCCA Introduction
Evolution of the Point Coordination Function protocol
Introduces advanced traffic priority
HCCA is the most advanced coordination function
HCCA is not mandatory in 802.11e
There are very few Access Points that implement HCCA nowadays
Evolution of the Point Coordination Function protocol
Introduces advanced traffic priority
HCCA is the most advanced coordination function
HCCA is not mandatory in 802.11e
There are very few Access Points that implement HCCA nowadays
How does it work ?
How does it work ?
Very close to PCF
During Contention Period (CP), all stations work in EDCA
The Access Point can request a Contention Free Period (CFP) at any time during CP by sending a Control Contention (CC) frame
CFP is called Controlled Access Phase (CAP) in 802.11e
Very close to PCF
During Contention Period (CP), all stations work in EDCA
The Access Point can request a Contention Free Period (CFP) at any time during CP by sending a Control Contention (CC) frame
CFP is called Controlled Access Phase (CAP) in 802.11e
How does it work ?
How does it work ?
During CAP, the Access Point, which is
called Hybrid Controller (HC), takes control of the medium
Every station sends a Reservation Request frame to request the medium from the HC The HC give access to the medium to a
service to send packets during a time defined by the HC
During CAP, the Access Point, which is
called Hybrid Controller (HC), takes control of the medium
Every station sends a Reservation Request frame to request the medium from the HC The HC give access to the medium to a
service to send packets during a time defined by the HC
Automatic Power Save Delivery
& Block Acknowledgments
Automatic Power Save Delivery
& Block Acknowledgments
Automatic Power Save Delivery (APSD)
Advanced power management for VoIP phone.
The phone sends and receives data from the Access Point at the same time, and enters a sleep state until more data has to be sent.
Block Acknowledgments
Block Acknowledgments allow an entire TXOP to be acknowledged in a single frame.
Automatic Power Save Delivery (APSD)
Advanced power management for VoIP phone.
The phone sends and receives data from the Access Point at the same time, and enters a sleep state until more data has to be sent.
Block Acknowledgments
Block Acknowledgments allow an entire TXOP to be acknowledged in a single frame.
NoAck & Direct Link Setup
NoAck & Direct Link Setup
NoAck
Asks the receiver not to send an Acknowledgement for that frame. Useful for highly time-critical data
Direct Link Setup
Allow two wireless devices that are associated to the same AP to directly communicate with each other
NoAck
Asks the receiver not to send an Acknowledgement for that frame. Useful for highly time-critical data
Direct Link Setup
Allow two wireless devices that are associated to the same AP to directly communicate with each other
WMM Certification
WMM Certification
Only EDCA and few options like NoAck are mandatory
Two other certifications are needed in order to have the whole HCCA protocol
WiFi Scheduled Multimedia WMM-Admission Control
Only EDCA and few options like NoAck are mandatory
Two other certifications are needed in order to have the whole HCCA protocol
WiFi Scheduled Multimedia WMM-Admission Control
References
References
Power Point by Antoine MERCIER about WiFi Power Point from ICARE research laboratory
about WLAN QoS
Power Point from 3com about WLAN Controller Wikipedia http://en.wikipedia.org/wiki/IEEE_802.11e Web site : http://reseau-wifi.blogspot.com/ http://www.cswl.com/whitepapers/qos-wireless-lan.html http://www.us.design-reuse.com/articles/article11687.html
Power Point by Antoine MERCIER about WiFi Power Point from ICARE research laboratory
about WLAN QoS
Power Point from 3com about WLAN Controller Wikipedia http://en.wikipedia.org/wiki/IEEE_802.11e Web site : http://reseau-wifi.blogspot.com/ http://www.cswl.com/whitepapers/qos-wireless-lan.html http://www.us.design-reuse.com/articles/article11687.html
References
References
802.11 WLANs and IP Networking Contributors:Prasad, Neeli; Prasad, Anand
Publisher:Artech House, Incorporated Date:2005
ISBN:1-58053-790-1
OFDM for Wireless Communications Systems Contributor:Prasad, Ramjee
Publisher:Artech House, Incorporated Date:2004
ISBN:1-58053-799-5
Wireless Internet Telecommunications Contributor:Wong, Daniel
Publisher:Artech House, Incorporated Date:2004
ISBN:1-58053-712-X
802.11 WLANs and IP Networking
Contributors:Prasad, Neeli; Prasad, Anand Publisher:Artech House, Incorporated Date:2005
ISBN:1-58053-790-1
OFDM for Wireless Communications Systems
Contributor:Prasad, Ramjee
Publisher:Artech House, Incorporated Date:2004
ISBN:1-58053-799-5
Wireless Internet Telecommunications
Contributor:Wong, Daniel
Publisher:Artech House, Incorporated Date:2004
