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A new QoS Architecture for IEEE 802.16 and Spec. Instruction

Speaker:93598009 Ming-Chia HsiehDate:2005/05/03

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Outline

Introduction Spec. New Qos Architecture 802.16a brief introduction Conclusion

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Introduction

802.16– Fast Deployment– Cost Savings– Support Quality of Service

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FRAMEWORK

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Outline

Introduction Spec. New Qos Architecture Conclusion

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Spec.

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Spec.

Communicate path – Uplink Channel (SS to BS)—

TDMA UL-MAP

– Downlink Channel (BS to SS) Broadcast

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Spec.

TDMA

mini-slots called Time-Division Multiple Access

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TDD frame structure

Symbol Rate： range 10~32M Baud, increments of 100k Baud

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Spec.

Uplink Channel– Uplink Channel Descriptor

Configuration Change Count– Determine whether the content is changed

Mini-Slot Size– Units of Physical Slot, Allowable n=2m

Uplink Channel ID– Arbitrarily Chosen by the BS– Unique within the MAC-Sublayer domain

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Spec

Uplink Channel (Cont.)– Uplink Map (UL-MAP)

Allocates access to the uplink channel

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Step to enter the network

BS

SSSCAN for a downlink channel

Downlink channel

parameter

DL-MAP

DCD

parameter

Adjust local parameter

Authorize/key exchange

Management msg

SBC-REQ

Control by BSIP

Establish time of day

Configuration information

REG-REQ

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Channel Access

BS

SS

Downlink channel

1 2 3 4 5 6 7

DATA

DL-MAP

Uplink Channel

UL-MAP

Time slot

DATA

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Spec.

Downlink Channel– Downlink Channel Descriptor (DCD)

Transmitted by the BS Define the characteristics of a downlink physical

channel

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Spec.

Downlink Channel– Downlink Map Parameter

PHY Synchronization

DCD Count– Match the DCD

Base Station ID– 48-bit

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Spec.

Qos ( Quality of Service )– Associate a packet with a service flow– Service Flow： unidirectional flow of packets that

provides a particular Qos

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Spec.

Support Quality of Service

Unsolicited Grant Service—UGS

Real-Time Polling Service—rtPS

Non-Real-Time Polling Service—nrtPs

Best Effort—BE

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Spec.

QoS types– UGS

Real-time service flows Periodic, fixed size grants Avoid overhead and latency of frequent SS redundant Meet the continuous need of service flow T1 / E1 / VoIP

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Spec.

Qos Types (Cont.)– rtPS (Real-Time Polling Service)

Real-time service flows Variable size data MPEG

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Spec.

QoS types– nrtPS

Non real-time service flow Variable size data

– BE Best Effort﹝ ﹞ Efficient service to best effort

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Spec.

Bandwidth allocation and request– Each SS is assigned 3 dedicated CID for different

level of QoS

– Incompressible constant bit rate UGS can’t reallocate bandwidth

– DAMA services are given resources on a demand assignment basis

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Spec.

Mode of grant of bandwidth request– GPSS Grant per Subscriber Station Mode﹝ ﹞

Bandwidth request are addressed to SSs Smaller UL maps Allow more intelligent SS

– GPC Grant per Connection﹝ ﹞ Bandwidth request are addressed to CIDs

– 這二個MODE在 802.16a中刪除了

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Outline

Introduction Spec. New Qos Architecture Conclusion

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Qos of IEEE 802.16Admission Control undefined by IEEE 802.16

Uplink BandwidthAllocation Scheduling

Uplink Scheduling for UGS defined by IEEE 802.16

Uplink scheduling for rtPS, nrtPS and BE service undefined

by IEEE 802.16

Traffic

Connection Classifier

UGS rtPS nrtPS BE

scheduler

Connection Request

ConnectionResponse

BW RequestMessage

Data packets

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New Qos Architecture

Admission Control

Uplink BandwidthAllocation Scheduling

Data Packet Packet Module

Traffic Management Table

Packet Allocation Module

Data Packet Analysis Module

Traffic

Connection Classifier

UGS rtPS nrtPS EE

Scheduler

Connection Request

ConnectionResponse

Data packets

BW requestMessage

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New Qos Architecture

Before establish connection SS set connection request to BS Admission control part of the BS decides to

accept or reject BS provide necessary information to SS

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New Qos Architecture

After establish Enforce the traffic on the contract BS update the traffic management table BS generate UL-MAP in downlink subframe SS transmits packets according to the UL-M

AP

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New Qos Architecture

Uplink Scheduler of SS– Transmit data PDU using uplink data slot granted

by BS.– UGS append virtual packet arrival time of rtPS– DPAM ( Data Packet Analysis Module ) receive rt

PS deadline information from SS.– Packet deadline=arrival time + maximum delay re

quirement of the connection

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New Qos Architecture

Uplink Scheduler of SS (Cont.)– nrtPS uses either contention-free or contention m

od.

– BE uses only contention mode

– BS controls contention mini-slot size in frame.

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New Qos Architecture

Uplink Bandwidth Allocation Scheduling– DPAM of BS separates UGS data and virtual pac

kets arrival time of rtPS– Traffic Management Module manages the informa

tion to decide the Poll order of next time

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New Qos Architecture

Backoff Procedure– BS broadcast a common back-off window size “B”

– SSs will randomly choose a reservation slot numbered between 1 and B to transmit its request

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Channel utilization analysis

K Classes Arrival events are mutual independent C denotes the server capacity and channel

utilization for each class I

C=p1+p2+p3+……pi ,C<=1

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Channel utilization analysis

λK： offered load for class K E[τK]： average service time for class K

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Simulation parameters

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Simulationa. no limit bandwidth

Offered Load

Channel

Utilization

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Simulationb. fixed quota

Offered Load

Channel

Utilization

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Simulationc. different data size (100 byte)

Offered Load

Throughp

ut

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Simulation d. different data size (150 byte)

Offered Load

Throughp

ut

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Simulatione. different data size ()

Offered Load

Throughp

ut

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Conclusions

The main target of WiMax is to replace the so called last mile.

It can advance a lot in the future.

Whether it can make it or not is still unable to answer.

But many companies have announced to support it, especially INTEL

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Reference

IEEE 802.16 Standards Performance Analysis of the IEEE 802.16

Wireless Metropolitan Area Network, (DFMA’05)

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END

END

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New Qos Architecture

Example– Backoff window size=B– Probability of choose a given slot=p=1/B– The probability of a given slot is not selected

Pns=(1-p)N

– System throughput is

Pth=Np(1-p)N-1

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Spec.

Provision of Qos– Based on the “Envelopes” – Parameters

ProvisionedQosParamSetA set of external QoS parameters provided to the MAC

AdmittedQosParamSetA set of QoS parameter for which the BS and possibly the SS are reserving resource

ActiveQosParamSetA set of QoS parameters that reflect the actual service being provided to the associated active service flows