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在 IEEE802.16 系統上提供 QoS機制之研究

Student:Hsin-Hsien LiuAdvisor:Ho-Ting WuDate:2007.7.24

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Outline

Background Motivation Call Admission Control & Bandwidth

Allocation Algorithm Simulation result Conclusion Future Work

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Background

IEEE 802.16 specifies the air interface of fixed and mobile BWA systems

WiMAX (Worldwide Interoperability for Microwave Access) Support QoS High transmission rate Easy and less expensive to deploy

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The IEEE 802.16 family of standardsName 802.16 802.16a 802.16d 802.16e

Completed 2001/12 2003/01 2004/06 2005/12

Mobility Fixed Fixed Fixed Portable

Mobility

Spectrum(GHz)

10~66LOS

2~11NLOS

2~11NLOS

2~6NLOS

Bit Rate(Mbps)

32~134 75 75 15

Cell Radius(KM)

2~5 7~10 7~10 2~5

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IEEE 802.16-2004

Topology PMP (Point-to-Multipoint) Mesh

Communication path direction Downlink (BS to SS) Uplink (SS to BS )

Multiplex TDD FDD

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Service type in IEEE 802.16

Unsolicited Grant Service (UGS) Real-time, Constant bit rate, ex VoIP T1

Real-time Polling Service (rtPS) Real-time, Variable bit rate, ex MPEG

Non-real-time Polling Service (nrtPS) Delay-tolerant, require min rate, ex FTP

Best Effort (BE) No QoS guarantees are promised, ex HTTP

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QoS Architecture of IEEE 802.16

ServiceAddition / Change /

Delete

Bandwidth Request

MAP Parsing

Uplink Processing

Call Admission Control

Classification

BWA & Packet Scheduling

UGS

rtPSnrtPS

BE

DSADSCDSD

BS

BW_REQ

UL_MAP

SS

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Motivation

IEEE 802.16 defines four service flows with different QoS requirement

Except for UGS, the bandwidth allocation mechanism for the other three service flows are left undefined

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Call Admission Control Decides whether to accept or reject the

connection base on network state A simple admission control is adopted by

using the Minimum Reserved traffic rate [2]

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min0 0

,iJI

a totali j

C C r i j

0aC

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Proposed CAC

QoS-Considered CAC Considers each service flow with

different QoS requirement rtPS: Average traffic transmission rate nrtPS: Minimum reserved traffic rate BE: always accept

_ _ mina total rtPS avg nrtPSC C r r

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Bandwidth Allocation Algorithm Strict Priority BWA

Simple Starvation problem

Deficit Fair Priority Queue (DFPQ) BWA[2] Provides more fairness Refers DWRR Scheduler uses variable deficit counter to

visit each non-empty queue

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DFPQ Procedure

1. Update the parameters ,

2. Service the connections in the service flow with the first priority queue

a. DeficitCounter[i] ≤ 0b. Waiting queue is emptyc. No available bandwidth leftd. It is time sending MAP message

a totalL L

[ ] [ ]DeficitCounter i Quantum i

max0

,iJ

j

Quantum i r i j

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DFPQ Procedure (cont.)

3. If Cond. a or Cond. b stands, service other lower priority queues as in Step 2. If there is no lower priority queue, go to Step 2 for anther scheduling round

4. If Cond. c or Cond. d stands, send the MAP message out . Go to Step 1 for next TDD frame

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Proposed BWA

Fairness-based BWA (FBWA) First, fundamental QoS bandwidth

allocation Second, fairness bandwidth allocation

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FBWA Procedure

1. Satisfies rtPS fundamental QoS requirement

2. Satisfies nrtPS fundamental QoS requirement

_ *QoS rtPS rtPS rtPSBW N AVG

_ *QoS nrtPS nrtPS nrtPSBW N MIN

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FBWA Procedure (cont.)

3. Allocates fair for each service flow

_ _Avaiable Total QoS rtPS QoS nrtPSBW BW BW BW

_ * rtPSFair rtPS Available

Total

NBW BW

N

_ * nrtPSFair nrtPS Available

Total

NBW BW

N

_ * BEFair BE Available

Total

NBW BW

N

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FBWA Procedure (cont.)

4. Each service flow finally gain bandwidth :

_ _rtPS QoS rtPS Fair rtPSBW BW BW

_ _nrtPS QoS nrtPS Fair nrtPSBW BW BW

_BE Fair BEBW BW

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Simulation parameters setting Total Bandwidth:10Mbps Frame Size:10ms Packet Size:40, 552, 1200bytes rtPS, nrtPS, BE Data Rate:387, 64, 64Kbits/sec rtPS, nrtPS, BE Call Duration:240, 120, 60s rtPS, nrtPS, BE Max. Delay:40, 100, 200ms rtPS, nrtPS, BE Max. Sustained Traffic Rate:

464.4, 76.8, 76.8Kbits/sec rtPS, nrtPS Min. Reserved Traffic Rate:309.6,

51.2Kbits/sec

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Simulation result – CAC Blocking Probability

0

5

10

15

20

25

30

35

0.2 0.4 0.6 0.8 1 1.2 1.4

Blo

ck

ing P

rob

. (%

)

Mean Connection Arrival Rate (connection/sec)

QoS_CAC_rtPS QoS_CAC_nrtPS

R_min_CAC_rtPS R_min_CAC_nrtPS

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Simulation result – CAC Accepts Connection

0

10

20

30

40

50

60

70

0.2 0.4 0.6 0.8 1 1.2 1.4

Nu

mb

er

of

co

nnecti

on

Mean Connection Arrival Rate (connection/sec)

QoS_CAC_rtPS QoS_CAC_nrtPS QoS_CAC_BE

R_min_CAC_rtPS R_min_CAC_nrtPS R_min_CAC_BE

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Simulation result – CAC generates system loading

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0.2 0.4 0.6 0.8 1 1.2 1.4

Nor

mal

ized

Loa

d

Mean Connection Arrival Rate (connection/sec)

QoS_CAC

R_min_CAC

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Simulation result – QoS Performance Analysis

1. Different CAC with FBWA 2. Different CAC with DFPQ3. QoS_CAC with different BWA 4. Rmin_CAC with different BWA5. QoS_CAC with FBWA vs. Rmin_CAC

with DFPQ

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Different CAC with FBWA - Packet Delay

0

20

40

60

80

100

120

140

160

0.2 0.4 0.6 0.8 1 1.2 1.4

Dela

y (

ms)

Mean Connection Arrival Rate (connection/sec)

QoS_FBWA_rtPS QoS_FBWA_nrtPS QoS_FBWA_BE

Rmin_FBWA_rtPS Rmin_FBWA_nrtPS Rmin_FBWA_BE

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Different CAC with FBWA - Packet Drop Rate

0

10

20

30

40

50

60

70

80

90

100

0.2 0.4 0.6 0.8 1 1.2 1.4

Dro

p R

ate

(%

)

Mean Connection Arrival Rate (connection/sec)

QoS_FBWA_rtPS QoS_FBWA_nrtPS QoS_FBWA_BE

Rmin_FBWA_rtPS Rmin_FBWA_nrtPS Rmin_FBWA_BE

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Different CAC with DFPQ - Packet Delay

0

20

40

60

80

100

120

140

160

180

0.2 0.4 0.6 0.8 1 1.2 1.4

Del

ay (

ms)

Mean Connection Arrival Rate (connection/sec)

QoS_DFPQ_rtPS QoS_DFPQ_nrtPS QoS_DFPQ_BE

Rmin_DFPQ_rtPS Rmin_DFPQ_nrtPS Rmin_DFPQ_BE

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Different CAC with DFPQ - Packet Drop Rate

0102030405060708090

100

0.2 0.4 0.6 0.8 1 1.2 1.4

Dro

p R

ate

(%)

Mean Connection Arrival Rate (connection/sec)

QoS_DFPQ_rtPS QoS_DFPQ_nrtPS QoS_DFPQ_BE

Rmin_DFPQ_rtPS Rmin_DFPQ_nrtPS Rmin_DFPQ_BE

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QoS_CAC with different BWA – Packet Delay

0

20

40

60

80

100

120

140

160

180

0.2 0.4 0.6 0.8 1 1.2 1.4

Del

ay (

ms)

Mean Connection Arrival Rate (connection/sec)

QoS_FBWA_rtPS QoS_FBWA_nrtPS QoS_FBWA_BE

QoS_DFPQ_rtPS QoS_DFPQ_nrtPS QoS_DFPQ_BE

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QoS_CAC with different BWA – Packet Drop Rate

0

10

20

30

40

50

60

70

80

90

100

0.2 0.4 0.6 0.8 1 1.2 1.4

Dro

p R

ate

(%

)

Mean Connection Arrival Rate (connection/sec)

QoS_FBWA_rtPS QoS_FBWA_nrtPS QoS_FBWA_BE

QoS_DFPQ_rtPS QoS_DFPQ_nrtPS QoS_DFPQ_BE

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Rmin_CAC with different BWA – Packet Delay

0

20

40

60

80

100

120

140

160

180

0.2 0.4 0.6 0.8 1 1.2 1.4

Del

ay (

ms)

Mean Connection Arrival Rate (connection/sec)

Rmin_FBWA_rtPS Rmin_FBWA_nrtPS Rmin_FBWA_BE

Rmin_DFPQ_rtPS Rmin_DFPQ_nrtPS Rmin_DFPQ_BE

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Rmin_CAC with different BWA – Packet Drop Rate

0

10

20

30

40

50

60

70

80

90

100

0.2 0.4 0.6 0.8 1 1.2 1.4

Dro

p R

ate

(%

)

Mean Connection Arrival Rate (connection/sec)

Rmin_FBWA_rtPS Rmin_FBWA_nrtPS Rmin_FBWA_BE

Rmin_DFPQ_rtPS Rmin_DFPQ_nrtPS Rmin_DFPQ_BE

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QoS_CAC with FBWA vs. Rmin_CAC with DFPQ – Packet Delay

0

20

40

60

80

100

120

140

160

180

0.2 0.4 0.6 0.8 1 1.2 1.4

Dela

y (

ms)

Mean Connection Arrival Rate (connection/sec)

QoS_FBWA_rtPS QoS_FBWA_nrtPS QoS_FBWA_BE

Rmin_DFPQ_rtPS Rmin_DFPQ_nrtPS Rmin_DFPQ_BE

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QoS_CAC with FBWA vs. Rmin_CAC with DFPQ – Packet Drop Rate

0102030405060708090

100

0.2 0.4 0.6 0.8 1 1.2 1.4

Dro

p R

ate

(%)

Mean Connection Arrival Rate (connection/sec)

QoS_FBWA_rtPS QoS_FBWA_nrtPS QoS_FBWA_BE

Rmin_DFPQ_rtPS Rmin_DFPQ_nrtPS Rmin_DFPQ_BE

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Conclusion

Proposed QoS CAC provides QoS guarantee under system overload

Proposed Fairness-based BWA improves fairness

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Future Work

Downlink and Uplink dynamic bandwidth allocation

Consider real performance of each service flow in time

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Reference

[1]IEEE 802.16-2004:Air Interface for Fixed Broadband Wireless Access System. Standard, 2004. IEEE standard for local and metropolitan area network

[2]Jianfeng Chen, Wenhua Jiao and Hongxi Wang, “A Service Flow Management Strategy for IEEE 802.16 Broadband Wireless Access System,” Lucent Technologies, Bell Labs Research China

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Q&A