1-802

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WLAN QoS : 802.11eWLAN QoS : 802.11e

Merle FrédéricMerle Frédéric

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SummarySummary

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



NoAck

Direct Link Setup

Conclusion

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IntroductionIntroduction

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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

arrive

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Why we need QoS in wireless

LAN nowadays?

Why we need QoS in wireless

LAN nowadays?

Evolution of thecustomer’s needs

Video and audio

streaming Wireless phone

over IP

Real time

applications

Evolution of thecustomer’s needs

Video and audio

streaming Wireless phone

over IP

Real time

applications

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802.11e802.11e

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

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MAC ProtocolMAC Protocol

Enhanced Distributed Channel

Access (EDCA)

Enhanced Distributed Channel

Access (EDCA)

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Main AdvancementsMain Advancements

Introduction of basic traffic priority 4 Types of Traffic

Voice

Video

Best effort

Background application

Creation of a Transmit Opportunity for eachtype of traffic

Introduction of basic traffic priority 4 Types of Traffic

Voice

Video

Best effort

Background application

Creation of a Transmit Opportunity for eachtype of traffic

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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

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When a station wins the access, it can senda 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 senda packet during its Transmit Opportunity

(TXOP)

The TXOP is different for each priority

level

The higher the priority, the longer the TXOP

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MAC ProtocolMAC Protocol

Hybrid Controlled Channel Access

(HCCA)

Hybrid Controlled Channel Access

(HCCA)

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HCCA IntroductionHCCA Introduction

Evolution of the Point CoordinationFunction protocol

Introduces advanced traffic priority

HCCA is the most advanced coordinationfunction

HCCA is not mandatory in 802.11e

There are very few Access Points thatimplement HCCA nowadays

Evolution of the Point CoordinationFunction protocol

Introduces advanced traffic priority

HCCA is the most advanced coordinationfunction

HCCA is not mandatory in 802.11e There are very few Access Points that

implement HCCA nowadays

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Very close to PCF During Contention Period (CP), all stations

work in EDCA

The Access Point can request a ContentionFree 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 ContentionFree Period (CFP) at any time during CP by

sending a Control Contention (CC) frame CFP is called Controlled Access Phase

(CAP) in 802.11e

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Other specificationsOther specifications

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& Block Acknowledgments


& Block Acknowledgments Automatic Power Save Delivery (APSD)

Advanced power management for VoIP phone.

The phone sends and receives data from the AccessPoint at the same time, and enters a sleep state until

more data has to be sent.


Block Acknowledgments allow an entire TXOP to beacknowledged in a single frame.

Automatic Power Save Delivery (APSD)

Advanced power management for VoIP phone.

The phone sends and receives data from the AccessPoint at the same time, and enters a sleep state until

more data has to be sent.


Block Acknowledgments allow an entire TXOP to beacknowledged in a single frame.

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NoAck & Direct Link SetupNoAck & 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 associatedto 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 associatedto the same AP to directly communicate with

each other

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EDCA vs DCFEDCA vs DCF

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WMM CertificationWMM 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

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ReferencesReferences

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


Date:2004

ISBN:1-58053-799-5

Wireless Internet Telecommunications Contributor:Wong, Daniel


Date:2004

ISBN:1-58053-712-X

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


Date:2005

ISBN:1-58053-790-1

OFDM for Wireless Communications Systems Contributor:Prasad, Ramjee


Date:2004

ISBN:1-58053-799-5

Wireless Internet Telecommunications Contributor:Wong, Daniel


Date:2004

ISBN:1-58053-712-X

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