DOCSIS 3.1 –Technischer berblick - Fischer RohdeSchwarz Trainingszentrum Mnchen DOCSIS 3.1 –Technischer berblick DOCSIS = Data overCable Service Interface Specification

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  • Walter FischerRohde&Schwarz Trainingszentrum Mnchen

    DOCSIS 3.1 Technischer berblick

    DOCSIS = Data over Cable Service Interface Specification

    Vortrag anlsslich der Cabletech 2017, Spielberg, Mrz 2017

    Cablemodem

    RF

    IP

    Phone

    16.3.2017

  • Referent

    15.03.2017 DOCSIS3.1 - Technischer berblick 2

    Dipl. Ing. (FH) Walter FischerRohde&Schwarz

    Walter.Fischer@rohde-schwarz.com

  • AgendaDOCSIS Intro and Principle

    Single Carrier Modulation Principle

    Time Domain and Spectrum Domain

    QAM and SNR Requirement

    OFDM in CATV

    DOCSIS 3.1 Physical Layer Parameters

    DOCSIS 3.1 Demo Transmission

    15.03.2017 DOCSIS3.1 - Technischer berblick 3

  • DOCSIS Intro and PrincipleDOCSIS Intro and Principle

    Single Carrier Modulation Principle

    Time Domain and Spectrum Domain

    QAM and SNR Requirement

    OFDM in CATV

    DOCSIS 3.1 Physical Layer Parameters

    DOCSIS 3.1 Demo Transmission

    15.03.2017 DOCSIS3.1 - Technischer berblick 4

  • Broadband Internet & Telephone via CATV

    CMTSCable

    modemtermination

    systemIP RF

    RF

    Cablemodem

    RF

    Coax/HFC

    IP

    Phone

    DOCSIS

    Return channel

    Downstream

    Upstream

    DOCSIS Data-over-Cable Service Interface Specification

    15.03.2017 DOCSIS3.1 - Technischer berblick 5

  • DOCSIS Data over Cable Service Interface Specification

    DOCSIS 1.0 1997 Cable Labs, ITU-T spec. ITU-T J.112DOCSIS 1.1 1999 QoS capabilitiesDOCSIS 2.0 2001 enhanced upstream speeds ITU-T J.122DOCSIS 3.0 2006 increase of both up and downstream speed, IPv6 ITU-T J.222DOCSIS 3.1 2013 10Gbit/s downstream, 1Gbit/s upstream, OFDM, 4096QAM

    DOCSIS standard =bidirectional transmission of high-speed data over broadband cable networks using hybrid fiber-coaxial infrastructure

    all DOCSIS standards are backward compatible

    15.03.2017 DOCSIS3.1 - Technischer berblick 6

  • DOCSIS Physical Layer

    DOCSIS 1.0 ... 3.0:Downstream = ITU-T J83B [US] Single Carrier 64QAM/256QAMor ITU-T J83A (DVB-C) [EURO-DOCSIS] Single Carrier 64QAM/256QAM

    Upstream = Single Carrier, QPSK ... 64QAM, TDMA, CDMA

    DOCSIS 3.1:Downstream = OFDM, 4096 (4K) QAM and higher (16K QAM)4K/8K OFDM, 50/25 kHz carrier distance

    Upstream = OFDM, minislots in time and frequency domainup to 4096 (4K) QAM, 2K/4K OFDM, 50/25 kHz carrier distance

    15.03.2017 DOCSIS3.1 - Technischer berblick 7

  • DOCSIS 1.0 ... 3.0 Downstream Data Rates

    Standard Data rate per down stream channel

    DOCSIS, J83B, 64QAM, 6 MHz 26.97 Mbit/s

    DOCSIS, J83B, 256QAM, 6 MHz 38.81 Mbit/s

    EURO-DOCSIS, DVB-C, 64QAM, 8 MHz 38.15 Mbit/s

    EURO-DOCSIS, DVB-C, 256QAM, 8 MHz 51 Mbit/s

    15.03.2017 DOCSIS3.1 - Technischer berblick 8

  • Single Carrier Modulatin PrincipleDOCSIS Intro and Principle

    Single Carrier Modulation Principle

    Time Domain and Spectrum Domain

    QAM and SNR Requirement

    OFDM in CATV

    DOCSIS 3.1 Physical Layer Parameters

    DOCSIS 3.1 Demo Transmission

    15.03.2017 DOCSIS3.1 - Technischer berblick 9

  • IQ Modulator / Single Carrier Modulation

    + iqmod(t)data(t) Mapper

    90

    q(t)

    i(t)

    I

    Q

    Carrier lo(t)

    15.03.2017 DOCSIS3.1 - Technischer berblick 10

  • Single Carrier Modulation very short Symbols

    Example: DVB-C, 6.9 MS/s; Symbol duration = 1/6.9 s = 144 ns

    15.03.2017 DOCSIS3.1 - Technischer berblick 11

  • Constellations QPSK, 16QAM, 64QAM, 256QAM

  • DVB-C FEC

    ScramblerReed-

    Solomonencoder

    Inter-leaver

    MPEG-2TransportStream

    15.03.2017 DOCSIS3.1 - Technischer berblick 13

  • Time Domain and Spectrum DomainDOCSIS Intro and Principle

    Single Carrier Modulation Principle

    Time Domain and Spectrum Domain

    QAM and SNR Requirement

    OFDM in CATV

    DOCSIS 3.1 Physical Layer Parameters

    DOCSIS 3.1 Demo Transmission

    15.03.2017 DOCSIS3.1 - Technischer berblick 14

  • Continuous Streams and Bursted Streams

    Downstream

    Upstream

    15.03.2017 DOCSIS3.1 - Technischer berblick 15

  • Spectral Rolloff Filtering in DVB-C (r=0.15)

    f

    f

    f

    f

    f2BN = BS

    2cos2cos

    2cos 2cos

    r=f/BN

    15.03.2017 DOCSIS3.1 - Technischer berblick 16

  • Spectrum, CATV Network

  • RF Characteristics

    Frequency

    Leve

    l PAL system level-12 dB -6 dB -4-6 dB02 dB

    DVB-C64QAM

    DVB-C256QAM

    DVB-C21024QAM

    DVB-C24096QAM

    ATV

    15.03.2017 DOCSIS3.1 - Technischer berblick 18

  • QAM and SNR RequirementDOCSIS Intro and Principle

    Single Carrier Modulation Principle

    Time Domain and Spectrum Domain

    QAM and SNR Requirement

    OFDM in CATV

    DOCSIS 3.1 Physical Layer Parameters

    DOCSIS 3.1 Demo Transmission

    15.03.2017 DOCSIS3.1 - Technischer berblick 19

  • Required SNR(QAM Order)

    SNR4+6dB SNR16+6dB SNR64+6dB SNR256+6dB

    4QAM, 16QAM, 64QAM, 256QAM, 1024QAM, 4096QAM, ...

  • Mainly used Modulation in Cable: 64QAM, 256QAM

    64QAM 256QAM

    SNR64+6dB = SNR256

    15.03.2017 DOCSIS3.1 - Technischer berblick 21

  • OFDM Basics, OFDM in CATVDOCSIS Intro and Principle

    Single Carrier Modulation Principle

    Time Domain and Spectrum Domain

    QAM and SNR Requirement

    OFDM in CATV

    DOCSIS 3.1 Physical Layer Parameters

    DOCSIS 3.1 Demo Transmission

    15.03.2017 DOCSIS3.1 - Technischer berblick 22

  • Interferences in a CATV Network

    Linear distortions (amplitude response, group delay) Non-linear distortions (... amplifiers ...) Intermodulation (multi-channel load and non-linearity) Short echos (micro-reflections) Noise (AWGN) Noise, frequency selective interferer Ingress noise Leakage (in both directions ...) ...

    15.03.2017 DOCSIS3.1 - Technischer berblick 23

  • Amplitude Response in CATV - Tilt

    A(f)

    f

    15.03.2017 DOCSIS3.1 - Technischer berblick 24

  • Interferer in CATV (Ingress, DVB-T/T2 Interferer, ...)

    A(f)

    f

    15.03.2017 DOCSIS3.1 - Technischer berblick 25

  • Unused, ... Forbidden Frequencies ... in CATV (Notches)

    A(f)

    f

    15.03.2017 DOCSIS3.1 - Technischer berblick 26

  • OFDM Orthogonal Frequency Division Multiplex

    COFDM

    Coded Orthogonal Frequency DivisionMultiplex

    FEC

    Forwarderror

    correction(Channel coding)

    Distribution of data tomany subcarriers

    No crosstalkbetween

    subcarriers

    f = 1/t

    15.03.2017 DOCSIS3.1 - Technischer berblick 27

  • COFDM Principle

    X

    XMap

    per

    +

    X

    XMap

    per

    +

    ..... COFDMsymbol

    Data+

    FEC

    15.03.2017 DOCSIS3.1 - Technischer berblick 28

  • Mapping of OFDM carrier

    Data stream: 0110 1110 0001 1010 1111 0011 0000 1010 0101

    Forming of

    groups of

    4 bit

    at 16QAMcarrer no. 0 1 2 3 4 5 6 7 8

    mapped

    carrier vector

    each carrier is described via a (I,Q) pair

    in the frequency domain

    each carrier corresponds to a narrow-band modulated transmission channel

    ff = 1/t = carrier spacing

    at DVB-T: 6817 or 1705 carriers in a distance of approx. 1kHz or 4kHz

    6817 or 1705 carrier plus guard band = 2 N carrier = 8192 or 2048 carrier

    IFFT = Inverse Fast Fourier Transformation

    OFDM symbol in time domain

    15.03.2017 DOCSIS3.1 - Technischer berblick 29

  • IFFT and I/Q Modulator

    + ofdm(t)

    Re(f)

    Im(f)

    IFFT

    90

    im(t)

    re(t)

    I

    Q

    15.03.2017 DOCSIS3.1 - Technischer berblick 30

  • OFDM Symbols with Guard Interval

    Symbol n Symbol n+1

    Guard interval

    15.03.2017 DOCSIS3.1 - Technischer berblick 31

  • OFDM Symbols with Guard Interval

    Symbol n+1Symbol n

    Guard interval (CP = cyclical prefix)

    15.03.2017 DOCSIS3.1 - Technischer berblick 32

  • Guard Interval Cyclical Prefix

    OFDM Symbol

    Copy of end of symbol Guard Interval

    = protection against intersymbol interference

    in OFDM systems

    Guard interval = quasi-break =

    Mechanism against problems in time domain at multipath reception

    DVB-T

    2K

    f ~ 4kHz

    t~250us

    8K

    f ~ 1kHz

    t~1ms

    t

    Symbol

    duration

    t=1/f

    15.03.2017 DOCSIS3.1 - Technischer berblick 33

  • Intersymbol Interference (ISI)

    Symboln+5

    Symboln+2

    Symboln+3

    Symboln+4

    Symboln

    Symboln+1

    Symboln+5

    Symboln+2

    Symboln+3

    Symboln+4

    Symboln

    Symboln+1

    t

    t = Echo delay timeIntersymbol interference

    +

    =

    Path1

    Path2

    Path1+2

    15.03.2017 DOCSIS3.1 - Technischer berblick 34

  • (Only) Micro Reflections in CATV

    Time Attenuation

    0.5 s -20 dBc

    1.0 s -25 dBc

    1.5s -30 dBc

    >2.0 s -35 dBc

    >3.0 s -40 dBc

    >4.5 s -45 dBc

    >5.0 s -50 dBc

    Micro-reflections in downstream(DOCSIS 3.1)

    Time Attenuation

    0.5 s -16 dBc

    1.0 s -22 dBc

    1.5s -29 dBc

    >2.0 s -35 dBc

    >3.0 s -40 dBc

    >4.5 s -42 dBc

    >5.0 s -51 dBc

    Micro-reflections in upstream(DOCSIS 3.1)

    15.03.2017 DOCSIS3.1 - Technischer berblick 35

  • OFDM Spectrum

    f

    15.03.2017 DOCSIS3.1 - Technischer berblick 36

  • Orthogonality

    t

    f

    tf

    A(f)

    sin(x)/xFouriertransform

    f = 1/t

    15.03.2017 DOCSIS3.1 - Technischer berblick 37

  • OFDM Spectrum

    f

    Shoulder Shoulder

    sin(x)/x functions

    Carriers

    15.03.2017 DOCSIS3.1 - Technischer berblick 38

  • OFDM Spectrum

    15.03.2017 DOCSIS3.1 - Technischer berblick 39

  • OFDM Edge Carriers switched off

    2N carrier, but edge carriers are switched off: guard bandto attenuate the shoulders of the OFDM spectrum

    Shoulders of OFDM spectrum

    Channel M-1 Channel M Channel M+1

    Guard band

    15.03.2017 DOCSIS3.1 - Technischer berblick 40

  • OFDM-Symbol

    OFDMsymbol

    duration t

    modulated OFDM carriers in time domain,discrete carriers ...

    15.03.2017 DOCSIS3.1 - Technischer berblick 41

  • OFDM SymbolOFDM carriers, in time domain, overlayed

    OFDMsymbolduration t

    noise-likesignal with highcrest factor

    15.03.2017 DOCSIS3.1 - Technischer berblick 42

  • Guard Interval / CP before and behind of the Symbol

    OFDM Symbol

    t

    DOCSIS 3.1

    15.03.2017 DOCSIS3.1 - Technischer berblick 43

  • Guard Interval & Windowing

    OFDM Symbol

    t

    DOCSIS 3.1

    15.03.2017 DOCSIS3.1 - Technischer berblick 44

  • Forward Error Correction (FEC)

    Forward Error CorrectionFEC

    15.03.2017 DOCSIS3.1 - Technischer berblick 45

  • Transmission Channel Channel Capacity

    Channel bandwidth [Hz]

    Cha

    nnel

    qua

    lity

    (SN

    R [d

    B])

    Channel capacitydatarate

    Shannon

    CATV 6, 7, 8 MHz

    Coax ... 32 dB .... HFC ... 40 dB ... 43 dB

    15.03.2017 DOCSIS3.1 - Technischer berblick 46

    );1(log 2 N

    SBC +=

    );log(10][

    ;3

    1

    N

    SdBSNR

    SNRBC

    =

    S/N>>1:

    Example: B = 1GHz, SNR = 40 dBC = 13.3 Gbit/s;

  • Channel codingChannel coding

    Block codes

    Convolutional codes

    (1955: Elias,1967: Andrew Viterbi)

    Concatenatedcodes

    (1966: David Forney)

    BCH(1960)

    Reed-Solomon(1963)

    Hamming(1950)

    Turbocodes(1993:concat.convol. codes)

    LDPC(1963: Gallager)

    usinggroup/fieldtheoryof linearalgebra

    Data Code

    ++

    ++ ++

    in

    out1

    out2

    Block code+interleaver+block code

    Block code+interleaver+

    Convol. code

    Cyclicalgroup code

    Generalblock code

    15.03.2017 DOCSIS3.1 - Technischer berblick 47

  • Block Code

    Data

    Algorithm(linear algebra)

    Code

    k lm

    m = k + l

    Example: DVB Reed-Solomon code:k = 188 byte, l = 16 byte, m = 204 byte

    15.03.2017 DOCSIS3.1 - Technischer berblick 48

  • Convolutional Coding

    +

    + +

    in

    out1

    out2

    Shift registers

    code rate =data rate in /data rate out;

    EXOR

    EXOR

    Example: GSM, UMTS, DVB inner coder

    15.03.2017 DOCSIS3.1 - Technischer berblick 49

  • Typical FEC Structure

    Basebandscrambler

    FEC-1 Interleaver FEC-2Data

    inDataout

    FEC-1FEC-2

    ... brakes upones and zerossequences

    ... distributesinformation overtime ...

    ... adds dataoverhead tothe data stream

    ... adds dataoverhead tothe data stream

    code ratecode rate

    data rate in data

    rat

    e ou

    t

    15.03.2017 DOCSIS3.1 - Technischer berblick 50

  • DVB-T FEC Structure

    Basebandscrambler

    Reed-Solomon188, 204

    Forneyinterleaver

    Convol.coder &

    puncturing

    Datain

    Dataout

    FEC-1FEC-2

    ... brakes upones and zerossequences

    ... distributesinformation overtime ...

    ... adds dataoverhead tothe data stream

    ... adds dataoverhead tothe data stream

    188/204code rate

    data rate in data

    rat

    e ou

    t

    squeezepuncturing

    15.03.2017 DOCSIS3.1 - Technischer berblick 51

  • DVB-T2 & DOCSIS3.1 FEC Structure

    Basebandscrambler

    BCHcoder

    LDPCcoder

    Bitinterleaver

    Datain

    Dataout

    FEC-1FEC-2

    ... brakes upones and zerossequences

    ... distributesinformation overtime ...

    ... adds dataoverhead tothe data stream

    ... adds dataoverhead tothe data streamLow Density ParityCheck Coding

    code ratedata rate in da

    ta r

    ate

    out

    BCH=Bose-Chaudhuri-HocquenghemLDPC=Low Density Parity Check Code

    15.03.2017 DOCSIS3.1 - Technischer berblick 52

  • OFDM Subcarriers

    f

    Channel bandwidth

    f

    15.03.2017 DOCSIS3.1 - Technischer berblick 53

  • Orthongonality

    f

    Orthogonality condition: f = 1/t

    15.03.2017 DOCSIS3.1 - Technischer berblick 54

  • OFDM ... Pilots ... (Example: DVB-T)

    TPS=TransmissionParameterSignalling;BPSK modulated;signalling ofDVB-T transmissionparameters

    Scattered pilots =sweep signal(channel estimation andcorrection)

    Continual Pilots,fixed position inspectrum andin constellationdiagram(AFC =AutomaticFrequencyControl)

    Rotating constellationsin the receiver in case of afrequency deviation; frequency correction (AFC)using continual pilots

    15.03.2017 DOCSIS3.1 - Technischer berblick 55

  • Constellations Diagram, showing Pilot Signals

    Example: DVB-T

    15.03.2017 DOCSIS3.1 - Technischer berblick 56

  • Pilot Pattern

    .

    .

    0 i

    Frequency (carrier no.)

    .

    .

    d1

    d2

    d3

    d1 = distance between scattered pilot carrier positionsd2 = distance between scattered pilots in one symbold3 = symbols forming one scattered pilot sequence

    Time

    Edgepilot

    15.03.2017 DOCSIS3.1 - Technischer berblick 57

  • Bulding OFDM Frames ... (1)

    OFDMsymbol

    duration t

    Modulated OFDM carrier signals in time domain,discrete carriers shown ...

    15.03.2017 DOCSIS3.1 - Technischer berblick 58

  • Building OFDM Frames ... (2)OFDM carriers, in time domain, overlayed

    OFDMsymbolduration t

    noise-likesignal with highcrest factor

    15.03.2017 DOCSIS3.1 - Technischer berblick 59

  • Building OFDM Frames ... (3)

    Symbol n+1Symbol n

    Guard intervalcyclical prefix (CP)

    15.03.2017 DOCSIS3.1 - Technischer berblick 60

  • From a OFDM Symbol to a OFDM Frame (4) ...

    ....

    OFDMframe

    S1 SnS2

    S1 ... Sn = OFDM symbols incl. guard interval

    n symbols = 1 frame

    15.03.2017 DOCSIS3.1 - Technischer berblick 61

  • From a OFDM symbol to a OFDM Frame ... (5)

    ....

    DVB-TOFDMframe

    S1 S68S2

    ....

    DABOFDMframe

    S1 S76S2TFPR

    67 TPS bits, scattered pilots ...

    Nullsymbol

    ....

    DVB-T2OFDMframe

    S1 SnS2P1 P2 Payload symbols

    Preamble symbols

    15.03.2017 DOCSIS3.1 - Technischer berblick 62

  • OFDM in Time and Frequency Domain (6)

    Slot

    Time

    Frequency

    n OFDMcarriers

    m OFDM symbols

    15.03.2017 DOCSIS3.1 - Technischer berblick 63

  • DOCSIS 3.1 Upstream

    DOCSIS3.1Upstream

    15.03.2017 DOCSIS3.1 - Technischer berblick 64

  • From DVB-C2 to DOCSIS 3.1DOCSIS Intro and Principle

    Single Carrier Modulation Principle

    Time Domain and Spectrum Domain

    QAM and SNR Requirement

    OFDM Basics, OFDM in CATV

    DOCSIS 3.1 Physical Layer Parameters

    DOCSIS 3.1 Demo Transmission

    15.03.2017 DOCSIS3.1 - Technischer berblick 65

  • From DVB-C2 ... to ... DOCSIS 3.1

    DVB-C2 based on DVB-T2 narrow-band channel design (6, 8 MHz) with wide-band channel-bonding option Long interleaver design for broadcast applications Narrow OFDM subcarrier distance 1.7/2.2 kHz (4K mode in 6, 8 MHz) Only downstream, no upstream defined

    DOCSIS 3.1 design wideband-band channel design (192 MHz) with narrow band option ( ... 24 MHz) Optimized for short response time ... 1 ms Wide OFDM subcarrier distance 25/50 kHz (4K / 8K mode in 192 MHz) Downstream and upstream

    15.03.2017 DOCSIS3.1 - Technischer berblick 66

  • DOCSIS 3.1 Downstream, Upstream

    CMTSCable

    modemtermination

    systemIP RF

    RF

    Cablemodem

    RF

    Coax/HFC

    IP

    Phone

    DOCSIS

    Return channel

    Downstream

    Upstream

    DOCSIS Data-over-Cable Service Interface Specification

    15.03.2017 DOCSIS3.1 - Technischer berblick 67

  • DOCSIS 3.1 Downstream

    Parameter DOCSIS 3.1 DOCSIS 3.0

    Type of modulation OFDM4K and 8 K FFT

    single carrier(J.83/B, DVB-C)

    Frequency range 108 MHz to 1218 MHz(1794 MHz)

    45 MHz to1002 MHz

    Channel bandwidth up to 192 MHz 6 MHz / 8 MHz

    QAM constellations up to 4096, 8k, 16k up to 256

    Cyclic prefix length 0.9375 s to...

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