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Introduction to HSDPA Scheduler

-UMTS Radio Network Planning & Optimization Dept

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HSDPA Schedulers Structure

HSDPA Scheduling Algorithm

HS-SCCH Power Control Algorithm AMC Algorithm

HARQ Algorithm

HSDPA power allocation methods

HSDPA code allocation methods

The Features of HSDPA scheduler

Q&A

Contents

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HSDPA Schedulers Structure

Wireless Resource calculation

HSDPA power

calculation module

HSDPA code

calculation module

HS-SCCH power

reservation

module

Priority Calculation Module

HS-SCCH Power Control Module

CQI Adjusment Module

TFRC Module

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Scheduling Algorithm 2/8

PFit always schedules the UE which has the biggestinstantaneous throughput/mean throughput. The fairness

and throughput could be adjusted according to operators

requirement.

RRit always schedules the UE which lies in the head ofqueue, then move this scheduled UE to the last.

MAX-C/Iit always

schedules the UE which

has the largest C/I or CQI.

W1W2W3 denote

respectively the

different fairness PF

algorithm

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Scheduling Algorithm 3/8

PFRRMAX-C/I field trial result:Alog ThroughputKbpsUE1far UE2far UE3near UE4near CELLtotal

RR 361 369 841.6 836.4 2408

PF1 421.4 411.7 939.3 937.4 2709.8

PF2 308.7 322.3 1150 1120 2901

PF3 213.8 240.8 1290 1250 2994.6

PF4 164.8 184 1380 1360 3088.8

PF5 111.1 132 1490 1460 3193.1

PF6 74 90 1510 1550 3224

MaxC/I 0 0 1670 1680 3350

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Scheduling Algorithm 4/8

The figure of above data:

Throughput vs Algorithm

0

500

1000

1500

20002500

3000

3500

4000

RR

PF1

PF2

PF3

PF4

PF5

PF6

MaxC/I

Algorithm

Throughput[

kbps]

UE1

UE2UE3

UE4

CELL

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Scheduling Algorithm 5/8

GBR algorithmthis algorithm is designed to schedule I/B/S

mixture trafficit combines M-LWDF algorithm and Tokenalgorithm, it considers two QoS parameters, i.e.,GBR andDiscardTimer . The priority formula is below:

, , _ ,j j

( ) / 2Priority (n)=f(SPI )

( )j n j n Token HOL j

j

w TB TB d

r n DiscardTime jf(SPI ) : denots the j users weight of different

Scheduling Priority Indicator.

,( )j nw TB :adjusts the fairness and throughput through it.

,j nTB :denotes the instantaneous throughput.

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Scheduling Algorithm 6/8

( )j

r n

:denotes the mean

throughput of j user.

_ ,Token HOL nd

:denotes the delay of j users virtual token.Its input and output is described as figure

below.

Token barrel

GBR

UE data

rate

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Scheduling Algorithm 7/8

Simulation result of GBR algorithm: in case of below 5%

unsatisfied user probability, cell throughput is about1.3Mbps, about 10~11 UE with 128kbps GBR service.

1200 1400 1600 1800 2000 2200 2400 2600

0

5

10

15

20

25

30

35

40

45

50

HS-DSCH throughput [kbps]

Unsatisfied

userprobability[%]

cell layout:19cell,57sector;3km velocity,UE uniform distribution,14codes and 65% HSDPA power

GBR=128Kbps;DiscardTimer=4 second

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Scheduling Algorithm 8/8

The characteristic of GBR algorithm:

Soft priority adjustment: when UE data rate decreases to

below GBR, scheduler increases gradually the UEs

priority, it can obtain more bigger multiuser diversity gain,

i.e., support more streaming user.

Relative scheduling priority: SPI is used for indicating UEscheduling priority, first we may map SPI to a weight,

then, multiply priority formula by the weight.

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HS-SCCH Power Control Algorithm 2/6

Outer loop Inner loop

Target BLER

HSDPA UE

HS-SCCH

Node B

ACK/NACK/DTX

CQI

MPO

HS-SCCH Power control Based on CQI

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HS-SCCH Power Control Algorithm 3/6

0

4.5 CQIs

HS DSCH

E

N

0 0

MPO 8s sHSSCCH CPICH

HS SCCH HS DSCH

E EP P

N N

Inner loop power calculation:

0

= 1.2dbs

HS SCCH

E

N

HS-SCCH Power control Based on CQI

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HS-SCCH Power Control Algorithm 5/6

HS-SCCH Power control associated with DPCCH PILOT

Outer loop Inner loop

Target BLER

HSDPA UE

HS-SCCH

Node B

ACK/NACK/DTXTPC

P_HS-SCCH = P_DL-DPCCH + delta

Delta is controled by outer loop.

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The method based on CQI have a great deal ofadvantage, i.e., because CQI always denotes channel

quality, whether UE is Non-SHO or SHO (Soft HandOver) ,while DPCCH is not like that.

So HS-SCCH power control based on CQI is stronglyrecommended. The figure below is got from field trial,target mean value is 3%.

HS-SCCH Power Control Algorithm 6/6

0

2

4

6

8

10

12

1 17 33 49 65 81 97 113 129 145 161 177 193 209 225 241 257 273 289 305 321 337 353 369 385 401 417 433 449 465 481 497

1

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AMC Algorithm 1/4

AMC theory:

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AMC Algorithm 2/4

AMC(Adaptive Modulation Coding): According to

CQIMPOUE capacityavailable power andcodesdata buffer size and BLER, HSDPA

scheduler smartly selects transmission format and

allocates power/codes resources.

CQI Adjustment

Module

HS-DSCHBLER

Transmmsion

Format Selction

Aailable HS-DSCH power

Aailable HS-DSCH codes

Adjusted CQI

Power/Codes

Allocation

Data Buffer Size

MPO

AMC

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AMC Algorithm 3/4

AMC algorithms basic link level results:

Simulation condition: RAKE receiver,AWGN channel.

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AMC Algorithm 4/4

AMC Algorithms characteristic:

Steady BLER

Higher throughput and power/codes efficiency,

especially for unbalanced power and codes case,because expanded TB tables has been included.

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HARQ Algorithm 1/7

HARQ types:

HARQ type 1: the same block is retransmitted andoptimum combining at the bit level is performed. This is

Chase Combining (CC).

2.TX

P2 P1

Systematic Bits Parity Bits

1.TX

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HARQ Algorithm 2/7

HARQ types:

HARQ type 2: Full IR (FIR) with non self-decodableretransmissions allowed. Optimum combining is

performed for bits already transmitted.

2.TX

P2 P1

Systematic Bits Parity Bits

1.TX

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HARQ Algorithm 3/7

HARQ types:

HARQ type 3: Partial IR (PIR) with self-decodableretransmissions only. Optimum combining is performed for

bits already transmitted (for instance systematic bits).

2.TX

P2 P1

Systematic Bits Parity Bits

1.TX

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HARQ Algorithm 4/7

HARQ types:

For 16QAM, constellationrearrangment may be availableto balance the bit reliability.

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HARQ Algorithm 5/7

HARQ combination program:

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HARQ Algorithm 6/7

CC/PIR/FIR performance

In case of higher code rate, FIR is better than

PIR, and PIR is better than CC.

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