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Training Material_Introduction to HSDPA Scheduling Algorithm

Jun 02, 2018

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  • 8/10/2019 Training Material_Introduction to HSDPA Scheduling Algorithm

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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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