An Adaptive Deficit-based Schedulerfor IEEE 802.16e Networks

Nararat RUANGCHAIJATUPON and Yusheng JI

The Graduate University for Advanced StudiesNational Institute of Informatics (NII), Japan

The 24th Asia-Pacific Advanced Network MeetingAugust 27–31, 2007, Xi’an, P.R. China

August 27-31, 2007 24th APAN Meeting 2

IEEE 802.16e TDD mode

Uplink and Downlink share the same frequency but not in the same time

Transmission units are in frames Downlink subframe & Uplink subframe

Subframe is divided into minislots MAP message at the beginning of

each frame DL-MAP & UL-MAP

August 27-31, 2007 24th APAN Meeting 3

WiMAX TDD Frame Structure

August 27-31, 2007 24th APAN Meeting 4

Scheduling services in IEEE 802.16e

Unsolicited Grant Service (UGS) Extended Real-Time Polling Service (ertPS) Real-Time Polling Service (rtPS) Non Real-Time Polling Service (nrtPS) Best Effort Service (BE)

August 27-31, 2007 24th APAN Meeting 5

Scheduling services in IEEE 802.16e (cont.)

Unsolicited Grant Service (UGS) Real-time application with fixed data rate, fixed

size data packet Extended Real-Time Polling Service (ertPS)

Real-time application with fixed data rate, variable size data packet

August 27-31, 2007 24th APAN Meeting 6

Scheduling services in IEEE 802.16e (cont.)

Real-Time Polling Service (rtPS) Real-time application with fixed data rate, varia

ble size data packet Non Real-Time Polling Service (nrtPS)

Delay-tolerant application with variable size data packets, which required minimum data rate

Best Effort Service (BE) Application with no minimum service level

August 27-31, 2007 24th APAN Meeting 7

Request message(s) Dynamic Service Addition (DSA) Dynamic Service Change (DSC) Dynamic Service Delete (DSD)

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QoS parameters Maximum Sustained Traffic Rate (rmax) Minimum Reserved Traffic Rate (rmin) Maximum Latency (tlatency) Minimum Tolerable Traffic Rate (rtol) with tim

e base (ttol) The minimum amount of traffic served (in bits)

during an arbitrary time interval should not be less than (rtol x ttol)

August 27-31, 2007 24th APAN Meeting 9

Admission control

Total bandwidth (BWtotal) A new flow j is accepted if:

BE flows are always accepted as its rmin always equals to zero

0)()( minmin

jrirBWUi

total

August 27-31, 2007 24th APAN Meeting 10

Parameters and states

Connection’s limited queue size

Burst state Connection queue size is more than its

limited queue size Non-burst state

Connection queue size is equal or less than its limited queue size

frametiriq )()( minlimit

August 27-31, 2007 24th APAN Meeting 11

Proposed scheduling scheme

All flows are innon-burst state

A flow is in burst state Tolerable group Guaranteed group Burst group

Schedulerwith EDF

…

DL UGS

Flow 1

Flow 1

Flow n

DL BE RR

Adaptive DRR

Queue size limit

FIFO

FIFOUL UGS

DL ertPS, rtPS, nrtPS

Flow n

Adaptive DRRUL ertPS, rtPS, nrtPS

UL BE RR

……

…available

Ai

Ciq

iqiquantum

)(

)()(

August 27-31, 2007 24th APAN Meeting 12

Adaptive quantum

Tolerable category

])(),(min[)( frametoltol tiriqiquantum

Guaranteed category

)](),(min[)( iqiqiquantumguarantee limit

August 27-31, 2007 24th APAN Meeting 13

Adaptive quantum (cont.)

Burst category

Yi

tolXi

guaranteeUGStotalavailable iquantumiquantumCCC )()(

CavailableZi

iq

)(

)()( iqiquantumburst

If

Else

Employ max-min allocation

August 27-31, 2007 24th APAN Meeting 14

Simulation Setup Single base station Frame duration: 2.5 ms Number of slots per frame: 175,000 Total bandwidth : 75 Mbps

PHY/MAC control message takes 5 Mbps One minislot represents a single physical slot (PS)

with a baud rate of one Traffic utilization is 85.71 %

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Traffic and request generators

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Simulation resultsThroughput of DL ertPS traffic

250

260

270280

290

300

310

320330

340

350

0 1 2 3 4 5

Time (sec)

Thr

ough

put

(kbi

ts)

DL ertPS srcDL ertPS allocated

Throughput of UL ertPS traffic

250

260

270280

290

300

310

320330

340

350

0 1 2 3 4 5

Time (sec)

Thr

ough

put

(kbi

ts)

UL ertPS requestUL ertPS allocated

Throughput of DL rtPS traffic

0

100

200

300

400

500

600

700

800

0 1 2 3 4 5

Time (sec)

Thr

ough

put

(kbi

ts)

DL rtPS srcDL rtPS allocated

Throughput of UL rtPS traffic

0

100

200

300

400

500

600

700

800

0 1 2 3 4 5

Time (sec)

Thr

ough

put

(kbi

ts)

UL rtPS requestUL rtPS allocated

August 27-31, 2007 24th APAN Meeting 17

Simulation results (cont.)

Throughput of DL nrtPS traffic

0

100

200

300

400

500

600

700

800

0 1 2 3 4 5

Time (sec)

Thro

ughp

ut (

kbits

)

DL nrtPS srcDL nrtPS allocated

Throughput of UL nrtPS traffic

0

100

200

300

400

500

600

700

800

0 1 2 3 4 5

Time (sec)

Thro

ughp

ut (

kbits

)

UL nrtPS requestUL nrtPS allocated

Throughput of DL BE traffic

0

100

200

300

400

500

600

700

800

900

1000

0 1 2 3 4 5

Time (sec)

Thro

ughp

ut (

kbits

)

DL BE srcDL BE allocated

Throughput of UL BE traffic

0

100

200

300

400

500

600

700

800

900

1000

0 1 2 3 4 5

Time (sec)

Thro

ughp

ut (

kbits

)

UL BE requestUL BE allocated

August 27-31, 2007 24th APAN Meeting 18

Fairness

j

j

i

i

r

Th

r

ThFairness

Fairness Comparison

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

100 102 104 106 108 110 112 114

Total traffic ( % of maximum kbits/ frame)

Fairne

ss

DFPQ

Adaptive with Max-Min allocation

“A scheduler is considered to be fair if the difference in normalized service received by different flows is bounded.”

August 27-31, 2007 24th APAN Meeting 19

Conclusion An adaptive deficit-based scheduler for

IEEE 802.16e adapts the allocation appropriately to the input traffic and uplink request

The proposed scheme also shows better performance in fairness

Further work must be done on unbalance traffic and cross-layer scheduling

Thank you very much

Questions and Answers