How To Understand Wireless Network Quality Of Service (Qos) In E

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WLAN QoS : 802.11e

WLAN QoS : 802.11e

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Summary

Summary

ƒ Introduction

ƒ What is QoS?

ƒ Why do we need QoS in wireless LAN nowadays? ƒ 802.11e

ƒ MAC Protocol

ƒ Enhanced Distributed Channel Access (EDCA) ƒ Presentation

ƒ How does it work?

ƒ Controlled Channel Access (HCCA) ƒ Presentation

ƒ How does it work? ƒ Other specifications

ƒ Automatic Power Save Delivery ƒ Block Acknowledgments

ƒ NoAck

ƒ Direct Link Setup ƒ Conclusion

ƒ Introduction

ƒ What is QoS?

ƒ Why do we need QoS in wireless LAN nowadays? ƒ 802.11e

ƒ MAC Protocol

ƒ Enhanced Distributed Channel Access (EDCA) ƒ Presentation

ƒ How does it work?

ƒ Controlled Channel Access (HCCA) ƒ Presentation

ƒ How does it work? ƒ Other specifications

ƒ Automatic Power Save Delivery ƒ Block Acknowledgments

ƒ NoAck

ƒ Direct Link Setup ƒ Conclusion

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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

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Why we need QoS in wireless

LAN nowadays?

Why we need QoS in wireless

LAN nowadays?

Evolution of the customer’s needs ƒ Video and audio

streaming ƒ Wireless phone over IP ƒ Real time applications Evolution of the customer’s needs ƒ Video and audio

streaming

ƒ Wireless phone over IP

ƒ Real time applications

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802.11e

802.11e

ƒ This is the standard for WLAN QoS ƒ Provide essential services for

delay-sensitive applications

ƒ Corresponds to the WMM certification of the WiFi Alliance

ƒ This is the standard for WLAN QoS ƒ Provide essential services for

delay-sensitive applications

ƒ Corresponds to the WMM certification of the WiFi Alliance

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MAC Protocol

MAC Protocol

Enhanced Distributed Channel Access (EDCA) Enhanced Distributed Channel

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EDCA Introduction

EDCA Introduction

ƒ Evolution of Distributed Coordination Function (DCF)

ƒ Introduces traffic priority ƒ Favorite VoIP applications

ƒ Every hardware with WMM certification supports at least EDCA

ƒ Evolution of Distributed Coordination Function (DCF)

ƒ Introduces traffic priority ƒ Favorite VoIP applications

ƒ Every hardware with WMM certification supports at least EDCA

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Main Advancements

Main Advancements

ƒ Introduction of basic traffic priority

ƒ 4 Types of Traffic

ƒ Voice ƒ Video

ƒ Best effort

ƒ Background application

ƒ Creation of a Transmit Opportunity for each type of traffic

ƒ Introduction of basic traffic priority

ƒ 4 Types of Traffic

ƒ Voice ƒ Video

ƒ Best effort

ƒ Background application

ƒ Creation of a Transmit Opportunity for each type of traffic

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How does it work ?

How does it work ?

ƒ There is a FIFO stack for each traffic priority

ƒ High priority traffic waits less than low priority

traffic

ƒ Each traffic priority has a different backoff value

ƒ The higher the priority, the shorter is the Backoff value

ƒ There is a FIFO stack for each traffic priority

ƒ High priority traffic waits less than low priority

traffic

ƒ Each traffic priority has a different backoff value

ƒ The higher the priority, the shorter is the Backoff value

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How does it work ?

How does it work ?

ƒ When a station wins the access, it can send a packet during its Transmit Opportunity (TXOP)

ƒ The TXOP is different for each priority level

ƒ The higher the priority, the longer the TXOP

ƒ When a station wins the access, it can send a packet during its Transmit Opportunity (TXOP)

ƒ The TXOP is different for each priority level

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MAC Protocol

MAC Protocol

Hybrid Controlled Channel Access (HCCA) Hybrid Controlled Channel Access

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HCCA Introduction

HCCA Introduction

ƒ Evolution of the Point Coordination Function protocol

ƒ Introduces advanced traffic priority

ƒ HCCA is the most advanced coordination function

ƒ HCCA is not mandatory in 802.11e

ƒ There are very few Access Points that implement HCCA nowadays

ƒ Evolution of the Point Coordination Function protocol

ƒ Introduces advanced traffic priority

ƒ HCCA is the most advanced coordination function

ƒ HCCA is not mandatory in 802.11e

ƒ There are very few Access Points that implement HCCA nowadays

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How does it work ?

How does it work ?

ƒ Very close to PCF

ƒ During Contention Period (CP), all stations work in EDCA

ƒ The Access Point can request a Contention Free Period (CFP) at any time during CP by sending a Control Contention (CC) frame

ƒ CFP is called Controlled Access Phase (CAP) in 802.11e

ƒ Very close to PCF

ƒ During Contention Period (CP), all stations work in EDCA

ƒ The Access Point can request a Contention Free Period (CFP) at any time during CP by sending a Control Contention (CC) frame

ƒ CFP is called Controlled Access Phase (CAP) in 802.11e

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How does it work ?

How does it work ?

ƒ During CAP, the Access Point, which is

called Hybrid Controller (HC), takes control of the medium

ƒ Every station sends a Reservation Request frame to request the medium from the HC ƒ The HC give access to the medium to a

service to send packets during a time defined by the HC

ƒ During CAP, the Access Point, which is

called Hybrid Controller (HC), takes control of the medium

ƒ Every station sends a Reservation Request frame to request the medium from the HC ƒ The HC give access to the medium to a

service to send packets during a time defined by the HC

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Automatic Power Save Delivery

& Block Acknowledgments

Automatic Power Save Delivery

& Block Acknowledgments

ƒ Automatic Power Save Delivery (APSD)

ƒ Advanced power management for VoIP phone.

ƒ 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.

ƒ Block Acknowledgments

ƒ Block Acknowledgments allow an entire TXOP to be acknowledged in a single frame.

ƒ Automatic Power Save Delivery (APSD)

ƒ Advanced power management for VoIP phone.

ƒ 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.

ƒ Block Acknowledgments

ƒ Block Acknowledgments allow an entire TXOP to be acknowledged in a single frame.

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NoAck & Direct Link Setup

NoAck & Direct Link Setup

ƒ NoAck

ƒ Asks the receiver not to send an Acknowledgement for that frame. ƒ Useful for highly time-critical data

ƒ Direct Link Setup

ƒ Allow two wireless devices that are associated to the same AP to directly communicate with each other

ƒ NoAck

ƒ Asks the receiver not to send an Acknowledgement for that frame. ƒ Useful for highly time-critical data

ƒ Direct Link Setup

ƒ Allow two wireless devices that are associated to the same AP to directly communicate with each other

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WMM Certification

WMM Certification

ƒ Only EDCA and few options like NoAck are mandatory

ƒ Two other certifications are needed in order to have the whole HCCA protocol

ƒ WiFi Scheduled Multimedia ƒ WMM-Admission Control

ƒ Only EDCA and few options like NoAck are mandatory

ƒ Two other certifications are needed in order to have the whole HCCA protocol

ƒ WiFi Scheduled Multimedia ƒ WMM-Admission Control

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References

References

ƒ Power Point by Antoine MERCIER about WiFi ƒ Power Point from ICARE research laboratory

about WLAN QoS

ƒ Power Point from 3com about WLAN Controller ƒ Wikipedia http://en.wikipedia.org/wiki/IEEE_802.11e ƒ Web site : ƒ http://reseau-wifi.blogspot.com/ ƒ http://www.cswl.com/whitepapers/qos-wireless-lan.html ƒ http://www.us.design-reuse.com/articles/article11687.html

ƒ Power Point by Antoine MERCIER about WiFi ƒ Power Point from ICARE research laboratory

about WLAN QoS

ƒ Power Point from 3com about WLAN Controller ƒ Wikipedia http://en.wikipedia.org/wiki/IEEE_802.11e ƒ Web site : ƒ http://reseau-wifi.blogspot.com/ ƒ http://www.cswl.com/whitepapers/qos-wireless-lan.html ƒ http://www.us.design-reuse.com/articles/article11687.html

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References

References

ƒ 802.11 WLANs and IP Networking ƒ Contributors:Prasad, Neeli; Prasad, Anand

ƒ Publisher:Artech House, Incorporated ƒ Date:2005

ƒ ISBN:1-58053-790-1

ƒ OFDM for Wireless Communications Systems ƒ Contributor:Prasad, Ramjee

ƒ Publisher:Artech House, Incorporated ƒ Date:2004

ƒ ISBN:1-58053-799-5

ƒ Wireless Internet Telecommunications ƒ Contributor:Wong, Daniel

ƒ Publisher:Artech House, Incorporated ƒ Date:2004

ƒ ISBN:1-58053-712-X

ƒ 802.11 WLANs and IP Networking

ƒ Contributors:Prasad, Neeli; Prasad, Anand ƒ Publisher:Artech House, Incorporated ƒ Date:2005

ƒ ISBN:1-58053-790-1

ƒ OFDM for Wireless Communications Systems

ƒ Contributor:Prasad, Ramjee

ƒ Publisher:Artech House, Incorporated ƒ Date:2004

ƒ ISBN:1-58053-799-5

ƒ Wireless Internet Telecommunications

ƒ Contributor:Wong, Daniel

ƒ Publisher:Artech House, Incorporated ƒ Date:2004

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