Quality of Service Scheduling for 802.16 Broadband Wireless Access Systems

Jonny SUN, Yanling YAO, Hongfei ZHU

IEEE Vehicular Technology Conference, 2006

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Outline Introduction IEEE 802.16 BWA System QoS Scheduling for 802.16 Systems

QoS Scheduling Architecture for 802.16 System Scheduling Algorithm at BS Scheduling Algorithm at SS

Simulation Conclusion

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Introduction

Motivation Providing QoS in BWA systems has become a very

important The rapid growth trend in the use of wireless data service

s and multimedia application IEEE 802.16 specification does not contain an effi

cient schedule to support the heterogeneous traffic

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Introduction

Goal Propose an efficient QoS strategy based on the

hierarchical and distributed architecture Base Station (BS) Scheduler

grant BW to SSs according to the request and reservation Subscriber Station (SS) Scheduler

re-distribute the received transmission opportunities among all of its connection

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IEEE 802.16 BWA Systems

PMP Architecture DL transmission is relatively simple

BS is the unique sender broadcasting to all the SSs without coordination with other stations

UL transmission is relatively hard SSs should coordinate with their neighbor before U

L transmission BS should control the resource allocation of UL acc

ess

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IEEE 802.16 BWA Systems

MAC Operation is connection-oriented Enable end-to-end QoS for different end users

Four types of scheduling services Unsolicited Grant Service (UGS) real-time Polling Service (rtPS) Non-real-time Polling Service (nrtPS) Best Effort (BE)

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Unsolicited Grant Service (UGS)

Traffic attributes Real-time CBR or CBR-like Fixed-sized, periodic

Key Service parameters Maximum sustained traffic rate Maximum latency Tolerated jitter

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real-time Polling Service (rtPS)

Traffic attributes Real-time VBR service flow Variable-sized, periodic

Key Service parameters Maximum sustained traffic rate Minimum reserved traffic rate Maximum latency

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Non-real-time Polling Service (nrtPS)

Traffic attributes Non-real-time VBR service flow Minimum BW grantee Longer delay allowed

Key Service parameters Maximum sustained traffic rate Minimum reserved traffic rate Traffic Priority

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Best Effort (BE)

Traffic attributes The same with nrtPS Depends on traffic load

Key Service parameters Maximum sustained traffic rate Traffic Priority

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SS Scheduler

Traffic

Traffic Classification

BS Scheduler

QoS Scheduling Architecture

BW Request

Type I Queue

Type II Queue

UGS data & dedicated request

opportunities

nrtPS,rtPS and BE

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Scheduling Algorithm at BS

Priority Queue Concept Type I Queue

Used to schedule data grants for UGS Allocate dedicated request opportunities for rtPS an

d nrtPS FIFO discipline

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Scheduling Algorithm at BS

Type II Queue Used to schedule data grants for rtPS, nrtPS, and BS

based on the information contained in the BW request messages

Fair queuing algorithm Minimum reserved BW assurance Excess BW distribution

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Minimum reserved BW assurance

},min{ minminiii BRBb

BW currently demanded by the

connection i

BW actually allocated during the phaseMinimum reserved BW

for connection i

Bbi

i min

Available BW

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Excess BW distribution

i

iEX bBB min

k

kiEXEX

i wwBb /

Remained BW

Pre-assigned connection

weight

The amount of excess BW allocated to connection i

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Scheduling Algorithm at SS

Scheduling Service Priority

Best Effort (BE) 1

Non-real-time Polling Service (nrtPS) 2

real-time Polling Service (rtPS) 3

Unsolicited Grant Service (UGS) 4

The priority of different scheduling services

Select the packet to be transmitted from queue i

Queue (i+1) empty ??

Yes

Transmit

No

Select the packet to be transmitted from queue (i+1)

Priority Queue

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Scheduling Algorithm at SS

Inner Queue Scheduling Scheduling algorithm for rtPS queues Scheduling algorithm for nrtPS queues Scheduling algorithm for BE queues

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Scheduling algorithm for rtPS queues

Goal Tight delay bound should be meet

Solution Each packet entering the rtPS queues should be

marked with a delivery deadline

Schedule all of the packets based on the deadline stamp

delaytoleratedtimearrival __

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Scheduling algorithm for nrtPS queues

Goal Throughput maintenance

Solution Similar to rtPS

1,/),__max(

1,__1

1

krLVtimearrivalPacketV

ktimearrivalPacketV

iki

ki

Ki

i

Virtual Timestamp associated with kth packet of connection i

The length of kth packet

Guaranteed BW share of connection i

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Scheduling algorithm for BS queues

No QoS guarantee required Solution

FIFO mechanism

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Simulation

PHY Configuration Parameters

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Simulation

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Simulation

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Simulation

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Simulation

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Simulation

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Simulation

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Simulation

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Conclusion

This paper proposed a QoS scheduling algorithm based on Hierarchical Distributed

Simulation results prove guarantee the minimum BW for each service fl

ow ensure fairness and QoS in distributing excess

BW among all connections.