The QoS of WiMAX

Outline

• Introduction

• Connections & Service flows

• Classifier & Scheduler

• Scheduling services

• Handover

Introduction

• QoS supporting is a fundamental part of the WiMAX MAC-layer design.

• How does WiMAX support for QoS?

Connections

• A connection-oriented MAC architecture– all downlink and uplink connections are controlled

by the serving BS

• Each connection is identified by a connection identifier (CID)

• A service flow is a unidirectional flow of packets – with a particular set of QoS parameters– is identified by a service flow identifier (SFID)

• The service flow characteristics of the connection provide the QoS for that packet

Service flows

Operation Object Model

Service Flow Creation

Service Flow Management

• Dynamic Service Change (DSC)

• Dynamic Service Delete (DSD)

• Dynamic Service Activate (DSA)

NULL

OPERATIONAL

DSD

DSA

DSC

Classifier

• A classifier is a set of matching criteria applied to each packet. It consists of – some protocol-specific packet matching criteria

(destination IP address, for example)– a classifier priority– a reference to a CID

• Classifiers can be added by dynamic signaling

Quality of Service Support

1.Associate packets into service flow2.Define QoS parameter for each service flow3.Dynamically establishing QoS-enabled service flows4.Associate QoS service flow with logical connections

Scheduling services

• Four services are supported in 802.16 802.16-2004 – Unsolicited Grant Service (UGS), – Real-time Polling Service (rtPS), – Non-real-time Polling Service (nrtPS), and – Best Effort (BE).

• Five services are supported in 802.16e 802.16e-2005 – UGS (Unsolicited Grant Service)– RT-VR (Real-Time -Variable Rate Service)– NRT-VR (Non-Real Time -Variable Rate service)– BE (Best Efforts)– ERT-VR (Extended Real-Time Variable Rate)

Unsolicited Grant Service (UGS)

• support real-time data streams consisting of fixed-size data packets issued at periodic intervals– Such as T1/E1 and Voice over IP without silence

suppression

INTERNET

VoIP

Real-time Polling Service (rtPS)

• support real-time data streams consisting of variable-sized data packets that are issued at periodic intervals– Such as moving pictures experts group (MPEG)

video.

Non-real-time Polling Service (nrtPS)

• support delay-tolerant data streams consisting of variable-sized data packets for which a minimum data rate is required– such as FTP

Best Effort (BE)

• support data streams for which no minimum service level is required and therefore may be handled on a space-available basis.

Extended Real-Time Variable Rate (ERT-VR) service

• support real-time applications with variable data-rates, which require guaranteed data and delay, for example VoIP with silence suppression.

Handover

• An mobile station (MS) migrates from the air-interface provided by one BS to the air interface provided by another BS

Handover in WiMAX

• Hard Handover• Fast Base Station Switching (FBSS)

– Active Set (Diversity set)– Anchor BS– MS Anchor BS

• Macro Diversity Handover (MDHO)– Active Set (Diversity set)– Anchor BS– MS all BSs in an active set