Seminar HFC networks (May 2005) - TVAE - Suppliers of ...tvae.co.za/seminar.pdf · Seminar HFC...

1

Schlögl 2005

Seminar

HFC networks

2

Schlögl 2005

Seminar HFC networks

Block diagram of an HFC system (4)The performance of an HFC system (5)Professional reception systems (6)Headend technology for digital and analogue TV and radio signals (7)Headend for network monitoring (KOM/HMS standard) (8)Headend for ingress detection SIMS (9)Headend technology for the Internet (CMTS) (10)Provisioning software for the Internet according to DOCSIS (11)HFC measuring device (12)Forward path and return path matrix (13)Optical star in 1310 nm technology (14)1310 nm transmitters (15)1550 nm analogue transmission; DWDM, CWDM, optical pushpull (16)Passive optical components (17)Optical compact node ORA 820/821 (18)Fibre node for the BK 862 of the KDG (German Postal Telegraph and Telephone PTT) (19)

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Schlögl 2005


CATV / HFC amplifiers (20)Amplifier point BK 862 of the KDG (German PTT) (21)Trunk amplifier and node system GGA 8 (22 and 23)VGF/VGP 90xx trunk and line amplifier system (24)VGF/VGO 938 line amplifier system (25)Broadband return path amplifier (26)The in-building network (27 and 28)KOM / HMS transponder (29)DOCSIS cable modem (30)Technical appendix (31)Downstream broadband interferences CSO and CTB (32)Addition of distortion ratios (33)Upstream broadband composite intermodulation noise CIN (34)C/N and S/N ratios; modulation gain (35)Echo attenuation in the coax part of the HFC system (36)AGC; ALSC; Long Loop AGC (37)

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Schlögl 2005

Block diagram of an HFC system

Headendfor

digital and analogueTV- and Radiosignals

Cable Modem TerminationSystem

with Provisioning Software

VoiceGate

Internet Service ProviderISP

Video- on- demand Status MonitoringSystem

V 5.2 Interface to the TELECOM

Forward Reversemultiplexer multiplexer

Optical transmission:Mono mode standard fibrePoint- to- pointPoint- to- multipoint1310 nm +/- 10 nmDirect intensity modulated

Antenna array

Opt.coupler

HMS Standard

SweepSystem

Transmission and service capability

Way(VoIP)

Videoserver

Billing Ingress controlReverse remote switch

Reverseunity gain

Fast Internet and VoIP

Fast Internet access

Fast Internet, VoIP and video streaming

Residential Gateway: Fast Internet ; VoIPMPEG Decoder; USB; Blue tooth

Status monitoring and ingress control

System Sweeper, in order to aligne forward-and reversepath

BillingStatus monitoring

ISP Reverse pathnecessary

(Options)

Add- on units like switches, routers, PC`s, TV`s etc. not shown

Reversepathreceiver

Forwardtransmitter

CM

EMTA

EMTAIP

streamingbox

Residential gateway

House amplifier

Splitter

House net

Base package: Transmit a number of digitaland analogue TV- and radio channels to thesubscribers (No reversepath necessary)

Data services:

Linetap

Trunkamplifiers

Lineamplifier(s)

Headends

Status monitoring transponder

Trunk

Line

Option: Redundancy

Multimedia sockets

Star distribution

5 - 65 MHZ85 - 862 MHZ

Optical node

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Schlögl 2005

The performance of an HFC system

•An HFC (Hybrid-Fiber-Coax) system, like a return path compatible CATV (Cable Television) system,receives all possible services - including radio, TV, Internet, telephony etc. - at a central point, andtransmits them to various subscribers. The individual ‚traditional‘ transmission blocks can be divided into

- headend(s); channel-selective

- optical transmission network; broadband

- coaxial trunk and line network; broadband

- the in-building networks; broadband

•The physical transmission medium is the coaxial cable (CATV), and for longer distances monomode fibre(HFC). The physical coverage can be 200 km or more, i.e. the number of subscribers can certainly be100,000 or more.

•The forward frequency range is typically set to 80 - 862 MHz, and the return path from 5 - 65 MHz. Thesignals are transparently transmitted using both analogue and digital modulation. In the forward path, up to90 analogue TV channels can be transmitted in a 7/8 MHz pattern or, depending on the data compression,significantly more digital radio/TV channels in conjunction with pure data channels for the Internet.Additional equipment at the headend and at the subscriber facilitates cable telephony, video on demandand much more

•HFC systems are planned on a customer-specific basis, and are mainly realised using products complyingwith a specification.

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Schlögl 2005

Professional reception systems

For terrestrial reception (TV; FM and DVB-T);in acc. with the PFL 3 specification (50 Ohm)of the KDG (German PTT)For terrestrial reception (TV; FM and DVB-T);in acc. with the TL 5820- 3003 (75 Ohm) ofthe KDG (German PTT)Offset dish antennas acc. to KDG 1TS3; withreflector and feed arm heating and multifeedreceptionCentrally fed dish antennas acc. to KDG1TS1Outside temperature control:

- Outside temperature - reflector temperature - Snow cap - soiling

Standard outside temperature control withelectronical two-level controller and settabletemperature controlQuad feeder systems for central / offset dishantennas acc. to the KDG‘s delivery terms

CAS 123 (centrally fed) and CAS 180 (offset) with heating

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Schlögl 2005

Headend technology for digital and analogue TV and radio signals

System-specific designMounted as specified by the customer in thefactory either in 19“ technology or cabinetmountingElectronical tuning using control unit or laptopwith USW 30 software (telephone modem)Optionally controllable via LAN and N-Port IPadapterPhotorealistic on-screen displayAutomatic recognition of the connectedheadendTwin modules for smaller HFC systems;adjacent channel operationSingle modules with increased transmissionparameters and very low linear and non-linear distortions; adjacent channel operationPower supply unit redundancyPassive output couplerHighly constant output spectrumExcellent price-performance ratioPilot generator(s) (MVG 10)Output spectrum optionally KOM monitorable(EoL monitor TLM 30)

1 2 3 4 5 6 7 8 9 10 11 12

PC/M odem

OperationDownlo ad

R emote/D ow nload

Power

1 2 3 4 5 6 7 8 9 10 11 12

PC/M odem

OperationDownlo ad

R emote/D ow nload

Power

Einga ng svert eilerUF S 32026 032 2

BZT

U0111 292 0-2 15 0 M Hz

-1 2 dB -1 2 dB -1 2 dB -12 dB

E inga ng svert eilerUFS 32026 032 2

BZT

U0111292 0-2 15 0 M Hz

-1 2 dB -1 2 dB -1 2 dB -12 dB

E inga ng svert eilerUF S 32026 032 2

BZT

U0111292 0-2 15 0 M Hz

-1 2 dB -1 2 dB -1 2 dB -12 dB


BZT

U0111 292 0-2 15 0 M Hz

-1 2 dB -1 2 dB -1 2 dB -12 dB


BZT

U0111292 0-2 15 0 M Hz

-1 2 dB -1 2 dB -1 2 dB -12 dB

EingangsverteilerUFS 320260322

BZT

U01112 920-2150 MHz

-12 dB -12 dB -12 dB -12 dB

B

A

C l a ssAKlasse

POWERV mA31 912,5 3905 1160

DEC

PRG

V 4

.08

UFO 34020610007

Sat-TV-Converter

fe 950-2150 M Hzfa 110- 862 MHzPa 95 dBuV

B

A

C l a ssAKlasse

POWERV mA31 612,5 4205 620

DEC

PRG

V 4

.08

UFO 38220610048

DVB-S-Transcod.


B

A

C l a ssAKlasse

POWERV mA

31 812,5 500

5 800

PRG

V 4

.08

UFO 39020610008

DVB-S-Transmod.

fe 950-2150 M Hzfa 110- 862 MHzPa 75-85 dBu V

B

A

C l a ssAKlasse

POWERV mA31 912,5 3905 1160

DEC

PRG

V 4

.08

UFO 34020610007

Sat-TV-Converter


B

A

C l a ssAKlasse

POWERV mA

31 912,5 390

5 1160

DEC

PRG

V 4

.08

UFO 34020610007

Sat-TV-C onverter


B

A

C l a ssAKlasse

POWERV mA31 912,5 390

5 1160

DEC

PRG

V 4

.08

UFO 34020610007

Sat-TV-Converter


B

A

C l a ssAKlasse

POWERV mA

31 612,5 420

5 620

DEC

PRG

V 4

.08

UFO 38220610048

DVB-S-Transcod.


B

A

C l a ssAKlasse

POWERV mA

31 612,5 4205 620

DEC

PRG

V 4

.08

UFO 38220610048

DVB-S-Transcod.


B

A

C l a ssAKlasse

POWERV mA

31 712,5 500

5 500

PRG

V 4

.08

UFO 386/TP20610014

DVB-S-Transmod.

fa 920-2150 M Hzfa 110- 862 MHzPa 75-85 dBu V

B

A

C l a ssAKlasse

POWERV mA31 712,5 5005 500

PRG

V 4

.08

UFO 386/TP20610014

DVB-S-Transmod.

fa 920-2150 M Hzfa 110- 862 MHzPa 75-85 dBu V

C l a ssAKlasse

POWERV mA

31 912,5 320

5 800

PRG

V 4

.08

PA

UFO 385206455

fe 950-2150 M Hzfa 302- 806 MHzPa 80-90 dBu V

DVB-S-Transmod.

B

A

C l a ssAKlasse

POWERV mA31 612,5 420

5 620

DEC

PRG

V 4

.08

UFO 38220610048

DVB-S-Transcod.


E inga ng svert eilerUF S 32026 032 2

BZT

U0 111 292 0-2 15 0 M Hz

-1 2 dB -1 2 dB -1 2 dB -12 dB


BZT

U0 111 292 0-2 15 0 M Hz

-1 2 dB -1 2 dB -1 2 dB -12 dB


BZT

U0 111 292 0-2 15 0 M Hz

-1 2 dB -1 2 dB -1 2 dB -12 dB

PRG

08

UFO 3532 0610 015

DVB-T-Transcod.

fe 171- 858 MHzfa 110- 862 MHzPa 95 dBuV

PRG

08

UFO 353206 1001 5

DVB-T-Transcod.


PRG

08

UFO 38220610048

DVB-S-Transcod.

fe 950-2150 MHzfa 110- 862 MHzPa 95 dBuV

PRG

.08

UFO 38220610048

DVB-S-Transcod.


PRG

08

UFO 38220610048

DVB-S-Transcod.


PRG

08

UFO 38220610048

DVB-S-Transcod.


PRG

08

UFO 38220610048

DVB-S-Transcod.


PRG

08

UFO 38220610048

DVB-S-Transcod.


PRG

08

UFO 38220610048

DVB-S-Transcod.


PRG

.08

UFO 38220610048

DVB-S-Transcod.


PRG

.08

UFO 38220610048

DVB-S-Transcod.


PRG

08

UFO 3532 061001 5

DVB-T-Transcod.


For small and medium-sized HFC systems

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Schlögl 2005

Headend for network monitoring (KOM/HMS)Monitors the status and records informationabout an HFC broadband networkConsists of one or more multi-protocol HECcontrollers, one or more ‚view‘- PCs todisplay the collected information on thesynoptic board and a number of monitoringtranspondersMonitors the headend (output level), opticaltransmitters, optical receivers, coax amplifiers(BK 862, GGA 8, compact amplifiers, houseamplifiers) and other peripheral devices if thecorresponding monitoring transponder isusedActivates the 3-stage ‚Ingress-switch‘ in thereturn path componentsOperates conforming with both the KOM andHMS standard and third party equipmentPolling mode; Auto detection of transponders;Contention modeAlarm indications are pre-set, but also user-definable; Allows to automate any task thatcan be manually performedForwards specific alarms to email,pager,SMSSNMP Proxy Agent and SNMP managers

TCU 30

Reset

Power

Power HD

I

O

Keyboard Reset

48x CREATIVEd isccompact

TAM 9700 SeriesHeadend Monitoring System

1 2 3 4 5 6 7 8

OmniProbe

ABCD

FREQ

CCM

HarmonicLigthwaves

HL485

LOCAL

SAM

MCU

PWR

TAM 9700 SeriesHeadend Monitoring System

1 2 3 4 5 6 7 8

OmniProbe

ABCD

FREQ

CCM

HarmonicLigthwaves

HL485

LOCAL

SAM

MCU

PWR

HEC controller TCU 40 with SIMS analyser

Synoptic board

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Schlögl 2005

Headend for Ingress Detection SIMS

SIMS (Scanning Ingress Monitoring System)is an option to KOM; 19 inch rack mountSIMS fully automatically monitors any wantedcarriers as well as unwanted ingress spikesin the return paths (5 to 75 MHz);Spectrum analyser(s) with 4 periodicallyconnected inputs; 60 dB dynamic rangeDisplay on the KOM view monitor2D and 3D spectrum mode; Amplitude-timemode; display plane; normalized modeExtremely high scanning speed of 5600frequencies per second; 50 kHz stepsSpurious <- 50 dBc (2 carriers 75 dBµV)Alarm indications can be set automatically oruser-definedDisplays and activates the ingress switchesduring the spectrum analysisIn case of alarm, the measurement valuesare automatically savedFunctioning at the headendside (RS 485)and in any remote hub via the 2-way HFC netTest port RJ-45 and front panel displays

3-D grahical representation of carriers and ingress spikesAllows hundreds of logged measurements, spot deterioration and alarm

conditionsSignal markers, display lines and digital readout

SIMS analyser backview

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Schlögl 2005

Headend technology for the Internet (CMTS)

The Cable Modem Termination System is theinterface between the data network and theHFC systemFunctions in acc. with the DOCSIS (Dataover Cable Systems Interface Specifications)and/or EuroDOCSIS specifications

1.0 Only for the Internet 1.1 For the Internet and VoIP (Voice over IP) 2.0 For the Internet and VoIP and QoS

(Quality of Service)One or more downstream channelsOne or more upstream channelsRedundancy input on the return pathCluster formation due to frequency multiplexand/or physical network separation toimprove the distortion ratio and increase theamount of data per surferCMTS and Modems function synchronously6,25 µs time slots or a multiple of it indownstream; MPEG-2 transport frame; 64 or256 QAM

CMTSCGW 100

ETHERNET

RESETCONSOLE NETWORK

US IN US MON

DS OUT DS MON

INONET

S1HF01 128.50.1.218

CMTSCGW 100

ETHERNET

RESETCONSOLE NETWORK

US IN US MON

DS OUT DS MON

AcctonCheetah S wi tch Workg roup-3016A

1x 2x 3x 4x

9x 10x 11x 12x

5x 6x 7x 8x

13x 14x 15x 16

M D I-X MD I

P ow er

Lin k/Ac t

10 0M

FDX

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

CMTS CGW 100 with server and switchVoice gateway not shown

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Schlögl 2005

Provisioning Software for the Internet acc. to DOCSIS

Registration of modems and hostsIP administrationDetermining of QoS profilesSetting for the host rangesDetermining the parameters for BPI profiles(data encryption)TFTP, DHCP and TOD serversSQL data bankZOPE managment systemSNMP query of the modem parametersThree user levelsBilling basic packet/Billing outgoinginvoices/Billing traffic assessmentModem monitoring

Transmission/reception level; S/N; packet-errors; micro reflections

ISP additional servicesServer 1 GHz CPU; raid 40 GbyteRedHat Linux 7.2

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Schlögl 2005

HFC measuring device

RF

75Ω

Σmax0.5W

DC

Mains

Vol+

Vol-

Ch- CH+

7 8 9

4 5 6

1 2 3

0 . -

GHzns

MHzµs

KHzms

dB..s

OnOff

Mode

Copy

Help

SAT / TV / FM - TEST -RECEIVER MSK 33

CH : .SO TVLEV : 37.2 dBV

MVG 10

RF

75Ω

V IDE O . SW EE P - G ENE RATO R

On

Off

M enü

S el ect - +

7 8 9

4 5 6

1 2 3

0 .

s- ch


MVG 10

RF

75Ω

V IDE O . SW EE P - G ENE RATO R

On

Off

M enü

S el ect - +

7 8 9

4 5 6

1 2 3

0 .

s- ch


MVG 10

RF

75Ω

V IDE O . SW EE P - G ENE RATOR

On

Off

M enü

S el ect - +

7 8 9

4 5 6

1 2 3

0 .

s- ch

Detailed and accurate analysis in thefrequency, time and constellation domainMeasures satellite IF, terrestrial channels(digital and analogue) telemetry carriers andmodulated data channels

Spectrum mode for any kind of digital andanalogue carriers

Audio / video baseband (line separation) i.efor 2- T pulse; 20 T- pulse; S/N measurement

C/N, MER, BER Baseband input and output DISEqC 2.0 Multi Standard; Multi Norm Downstream sweep Protocol printer

Adjusts upstream unity gain Upstream sweep Battery operation

Remote controllableConsisting of MSK 33 QR / MVG 10 stationary in the headend

MSK 33 QR / MVG 10 / MZK 15 portable

MVG 10 as pilot generators

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Schlögl 2005

Forward path and return path matrix

Matrices connect the signal processing unitsto the network clusters (forward matrix) andthe other way around (return path matrix)The radio and TV headend is splitted to allheadend outputs via the forward path matrix,providing the transmission levelData headends (CMTS, Status Monitoring,Scanning Ingress Monitoring) are connectedto clusters of the entire HFC network only,and the other way around (physicalseparation of the individual clusters and/orfrequency multiplex)The return path matrix provides thecorresponding nominal reception levels forthe data headendsMatrices are system-dependently designedand mounted from discrete components(taps, splitters, amplifiers)

Cluster

Cluster

Cluster

Cluster

1

2

3

4

95 dBµV fromoptical receivers

65 dBµV

Cluster 1Cluster 2Cluster 3Cluster 4

(Redundance)

CMTS nominal

inputlevel i.e. 60 dBµV Cluster 1 to 4 and Coax

Cluster 1 to 4 and CoaxMSK 33 i.e 60 dBµV


Coax

SIMS i.e. 60 dBµV


Coax

KOM i.e. 55 dBµV

Return for other services

Coax line input

Return matrix (Example)

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Schlögl 2005

Optical star in 1310 nm technology

Point-to-point and point-to multi- pointconnection for approximately 30 to 40 km linklength for forward transmissionOptical multi-point to point transmission notfeasible, each receiver can just stand onetransmitterRedundancy operation possible in theforward path and return pathAll essential status parameters can beKOM/HMS monitoredOperating conditions are signalled with LEDsat the front panelSeparate high- launch buffer amplifierHighly linear DFB laser without pre-distortionSettable, constant modulation-index,19“ cabinet or BK housing installationNo moveable parts for coolingActive return path coupler, assists SIMSReturn path transmitter with fibreidentification frequency

„Hot pluggable“230 V or remote poweredTVA 08; OSA 82; TVM 21; ORR 05; ORA 80; TVR 01; TFN 42

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Schlögl 2005

1310 nm transmitters

Direct modulated transmitters (Chirp !) aremostly used in standard single mode fibreG.652 at 1310 nm wave length; 0.35 dB fibre

attenuation/km and zero dispersionDFB laser with cooling (Peltier-element) forthe downstreamMonitor diode for control circuitsDFB laser without cooling for the upstream(Internet and Telephony)Fabry-Perot laser in the upstream only fortelemetry transmissionsRIN(transmitter); thermal and shot noise(receiver); interferometric optical feedbackThe modulation index (driver level)determines the composite-distortions (CSOor CIN). It is calculated, and must be adjustedin the network levellingTransmitters function point-to-point and point-to-multipointThe wave length and optical output levelcannot be setBest transmission quality together with push-pull amplifiers (Laser is CSO limited;amplifier is CTB limited)

LD

B+

R

IL

I

dBm

W

Clipping

Clipping

60 %

(FM, AM, QPSK,QAM)

L

HF

100 %

i.e. 5-65 MHz

Modulationindex

Mono mode fibre

Blockdiagram of a laser transmitter(Directly modulated)

Opt

ical

ligh

t pow

er

Optical operating point

i.e. 6 dBmW

Reserve for ingress(Return data transmission)

Amplitude modulated light

RF modulated carrier (time domain)

i.e. 30 mA DC through the laser diode mA

Laser DC bias; factory adjust

Characteristic line of adirectly modulated laser

Modulation index influences: a) transmission distortions b) outputlevel at the receiver

(simplified)

1310 nm

C

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Schlögl 2005

1550 nm analogue transmission; DWDM; CWDM, optical pushpull(Overview; planned in the factory as a matter of principle)

1550 nm transmission technology fordistances up to appr. 100 kmExternally modulated transmitters (Chirp) foranalogue signal transmission; 2 outputs;180 ° phase-delayed, chromatic dispersion ofthe standard monomode fibre at 1550 nm =17 ps/nm/kmFibre generates CSOStimulated Brillouin (SBS), Raman andRayleigh scatteringPhase noiseSelf-phase modulationWave length selected, direct modulatedtransmitters in DWDM technology (DenseWave Division Multiplex) and wave lengthcouplersCWDM technology (Corse Wave DivisionMultiplex) of 1310 to 1625 nm in connectionwith fibre type G.625.COptical pushpull (single fibre/two fibressystem) to improve the CSO and C/N ratiosOptical 1550 nm EDFA (Erbium doped fibreamplifier), gain flattened

Input40 - 870 MHz

1549,32nm

1550,92nm

1552,52nm

1554,13nm

1555,75nm

1557,36nm

7 dBm

Multiplexer

Gain - Flattened EDFA

Coloured Fibre means different Wavelength only!

Demultiplexer

ITU - Grid200 GHz(1,6 nm) spacing

Targeted Digital ServicesDigital Video, Video on Demand,Internet,Cable Telephony

Input 64 QAM and 256 QAM

DWDM Transmission PrincipleNarrowcasting

Input40 - 870 MHz

Input40 - 870 MHz

Input40 - 870 MHz

Input40 - 870 MHz

Input40 - 870 MHz

(Downstream and upstream)

DWDM- Transmitter

Receiver

Optical amplifier ReceiverLink

extender

0

180 °

0

180 °

Transmitter withexternal modulation

47- 862 MHz 47-862 MHz

Modulation contentof the transmitter is atthe two outputs 180 °

out of phase

Fibre produces CSO

Link extender adds wantedsignals in phase (6 dB higher level)

and eliminates CSO of the fiberC/N increases by 3 dB

(With one or two fibers)Principle of optical push-pull

Link length 100 km and more(Super trunk)

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Schlögl 2005

Passive optical components

E2000HRL connector; SM; 8° angled polish;70 dB RL; 0,2 dB transmission loss; green;locking and anti-dust coverSC/APC plug; SM; 8° angled polish;65 dB RL; 0,2 dB transmission loss; green;lockingPatch cord; Jumper cordOptical couplers; (sym./asym.; to multiplexand de-multiplex)DWDM wave length multiplexers and de-multiplexers according to the ITU channelpatternCWDM wave lenght multiplexers and de-multiplexersWDMC wave length multiplexers and de-multiplexers (1310/1550 nm)Patch fields (mass tailored)Dispersion zero near 1310 nmDispersion 17 ps/nm -km at 1550 nmLoss 0,35 dB (1310 nm); 0,22 dB (1550nm)/kmSplice loss 0,02 dB

20 %10 %

30 %

70 %

1310 nm

1550 nm

WDMC

CWDM1430 nm1450 nm1470 nm

DWDM

/ 1490 nm1510 nm/ 1530 nm

/

1549,32 nm1550,92 nm1552,52 nm

Wave length division multiplex

Coarse wave lengthdivision multiplex

Dense wave lengthdivision multiplex

70 %

CoatingMono mode fibre

Min. bending radius = 30mm

Transmitter Optical coupler

Transmitter Optical coupler

Equivalents to optical passive components:Directional coupler

SplitterBandfilter

Channelfilter

Examples!

Core 9 µmCladding 125 µm

Example of a fibre patchfield

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Schlögl 2005

Optical compact node ORA 820 / 821

Plug-and-play technology due to doublecontrol system

- pluggable pilot control - d.c. light control

GaAs technology, thus extremely lowintermodulation distortionsSeveral different output configurationsPluggable modules for forward and returnpath; redundancyReturn path transmitter(s) in Fabry-Perot,DFB and 1550 nm DWDM technologyFrequency range filters pluggablePluggable module for KOM/HMS networkmonitoringLED signalling; monitor socketE 2000 or SC/APC; PG11Locally fed / remotely fed; 18 - 65 VElectronical ingress return path switch

Node Splice box HF-splitter Earth cable

Recommended inputpower

0 dBm-6 dBm +3dBmW

Maximum input power

-8,5 dBmW

Operation with reduced carrier to noise ratio

-19 dBmW

-15 dBmW -3 dBmW 0 dBmWOSR 30 series OSR 50 series OSR 60 series (DWDM)

LED signalling ORA 820 and 821 nodesOptical receive and transmit power

LED greenLED orangeLED red

+9 dBmW

Receive

Transmit

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Schlögl 2005

Fibre glass amplifier point (GfVrP~Fgap) for BK 862 of KDG

To upgrade the BK 4505 - 65 MHz / 85 - 862 MHzIn the fibre node, the optical signal istransformed into an electrical signal, pilot-controlled and amplified in the forward path10 dB slope (111- 862 MHz) on the A/BoutputSwitchable slope (16 dB; 19 dB; 22 dB) at theC outputElectronical attenuator and slope elements(LED/push buttons), uninterrupted signal flowNon-volatile memoryIn the return path, the signal which iscombined and amplified by all return pathinputs is optically modulated and transmittedback to the headend (bBKVrSt)Remote feeding via the A/B coax line orremote feeding transformerCluster splitting in forward and return pathRemote-Inventory-Data-SystemHMS status monitoringOn-site-controlled by Laptop andCABLEwatch LMT (not HTE 10)

Fsp.1

Ortssp.

Fsp.2

EspFi

Fsp.Vert.

Aan Aab

St.vg

1 2 3 4 5 6 7 8 9 10 11 12

1 2 3 4 5 6 7 8 9 10 11 12

OTR810 TVB812G OTR810 TVB813 TVC810 TVR10 TVR10 TVT10 TFN41 TFN41 SpleissBox

R

V TP

KATHREIN

-30d

B5-

65M

Hz

5-65

MHz

85-8

62M

Hz

WFS865

R

V TP

KATHREIN

-30d

B5-

65M

Hz

5-65

MHz

85-8

62M

Hz

WFS865

R

V TP

KATHREIN

-30d

B5-

65M

Hz

5-65

MHz

85-8

62M

Hz

WFS865

E

A2

KATHREIN

A1

A3 EBC803

E

A2

KATHREIN

A1

A3 EBC803EBC802 EBC802

GEF

AERD

UNG

SG

RAD

1E

N 6

082

5-1

:19

97

OTR 810

Rec eive r

P in

P WR

T ransm.

-20dB

TP

Transmitter

P out

LSN

Receiver

TVB 812G

AGCLimi t

LSN

Pilot

Nominal

TP

-20dB

AB Ausg.

AB / C

AB / C

EMF

Unit

Redunda nt

Unit

-20dB

TVC 810

LSN Pilot

Slope

16 dB

C

19 22

Ret

M

-20dB

GEF

AERD

UNG

SG

RAD

1

EN

60

825

-1:1

997

OTR 810

Rec eive r

P in

PWR

Tran sm .

-20dB

TP

Transmitter

P out

L SN

Receiver

TVB 812G

AGCLimi t

L SN

Pilot

Nomin al

TP

-20dB

AB Ausg.

AB / C

AB / C

EMF

Unit

Redunda nt

Unit

-20dB

TVR 12TR

0,51248

M+-

OMI

R1

R2

R3

R4

R5

0,5124

Slope

LSN1 2

TR

UPS

EMF

Service

TVR 12TR

0,51248

M+-

OMI

R1

R2

R3

R4

R5

0,5124

Slope

LSN1 2

TR

UPS

EMF

Service

TFN 41

- +24 V

TFN 41

- +24 V

Optik an

20

Schlögl 2005

CATV/HFC amplifiers

HFC systems are always designed for specific customers and in line with their particular philosophy. For example, an HFC system canhave short optical transmission links with long downstream amplifier cascades or conversely long optical connections with perhaps justa single amplifier after the node. If no optical connections are used at all and everything is realised using bi-directional cascadedamplifier technology, it is a CATV system. Amplifiers must therefore be designed in different ways depending on whether there is onlyone or whether two or, e.g., forty amplifiers are to be connected in series. Different groups of customers have very differentdesignations for amplifiers with identical applications!

A forward path amplifier that is often cascaded is referred to as a line amplifier, trunk amplifier or, at KDG as an A/B amplifier. Thisamplifier type is always pilot controlled (ALSC, see page 36), has an extremely low amplitude/frequency response, and can be fittedwith a system equaliser (not to be confused with a cable equaliser). Its relatively low nominal gain is also typical. If a second line isbranched from one line amplifier, this is done using a branch amplifier, subtrunk or trunkbridger amplifier. KDG calls this a Bamplifier. The ‚traditional‘ trunk does not include any passive components such as taps or splitters.

A forward path amplifier that is not frequently cascaded, if at all, is referred to as a line amplifier or at KDG as a C amplifier. It hashigher gain, typically no pilot control (C amplifier has AGC), and does not allow installation of a system equaliser. In contrast to thetrunk, passive distribution components are installed in a line.

The HFC system from the KDG has such a specific design that the system technology, equipment and their designations differcompletely from the standard terminology, system philosophy and products in ‚normal‘ HFC systems from other network operators inGermany and other countries. To understand this, one needs to be familiar with the development history of the BK 300, BK 450,BK2K2 and BK862.

All these amplifiers can be remotely fed, and can be installed above or sometimes below ground depending on the degree of protection.

The in-building amplifiers, on the other hand, are locally fed at 230 V and are designed for installation in dry locations. They areintended to allow both a high signal output level and high gain. However, the amplitude/frequency response is higher than with theother type of amplifier, as in-building amplifiers are not normally cascaded.

Return path amplifiers do not have different designations, but their transmission behaviour in terms of cascading is adapted to therelevant forward amplifier types. They are not pilot controlled but, in contrast to the forward path amplifiers, have an electronicallyoperated 3-step swich (see page 25; switch through, 6 dB attenuation; disconnect) in the RF path. This allows the SIMS monitoring (page 9) to beused to identify interference received from so-called ‚man-made noise‘ in the return path channnels, and disconnect the affected lineuntil it is repaired.

21

Schlögl 2005

Amplifier point (KxVrP) BK 862 of the KDG

To upgrade the BK 450Cascadable up to 20 times (NE2.2d or NE 3trunk sections)5 - 65 / 85 - 862 MHzCable-equivalent slope of 6 dBPluggable equalisers in the A/B amplifier;electronical fine equalisationSwitchable slope (16 dB; 19 dB; 22 dB at theC outputElectronical ALSC and attenuator elements(LED displays and push buttons); manual andremotely controlled setting, uninterruptedsignal flowNon-volatile memoryHigh pass filter in the return path (Ingress)2 pilot-controlled A/B amplifier1 pilot-controlled C amplifierRemote-Inventory-Data-SystemHMS status monitoringPower supply unit redundancyOn-site controlled by laptop andCABLEwatch LMT (not HTE 10)

Fsp.1

Ortssp.

Fsp.2

EspFi

Fsp.Vert.

Aan Aab

St.vg

1 2 3 4 5 6 7 8 9 10 11 12

1 2 3 4 5 6 7 8 9 10 11 12

OTR810 TVB812G OTR810 TVB813 TVC810 TVR10 TVR10 TVT10 TFN41 TFN41 SpleissBox

R

V TP

KATHREIN

-30d

B5-6

5MHz

5-65M

Hz85

-862M

Hz

WFS865

R

V TP

KATHREIN

-30d

B5-6

5MHz

5-65M

Hz85

-862M

Hz

WFS865

R

V TP

KATHREIN

-30d

B5-6

5MHz

5-65M

Hz85

-862M

Hz

WFS865

E

A2

KATHREIN

A1

A3 EBC803

E

A2

KATHREIN

A1

A3 EBC803EBC802 EBC802

TVC 810

LSN Pilo t

S lop e

16 dB

C

19 22

Ret

M

-20dB

TVR 12TR

0,51248

M+-

OMI

R1

R2

R3

R4

R5

0,5124

Slope

LSN1 2

TR

UPS

EMF

Service

TVR 12TR

0,51248

M+-

OMI

R1

R2

R3

R4

R5

0,5124

Slope

LSN1 2

TR

UPS

EMF

Service

TFN 41

- +24 V

TFN 41

- +24 V

TVB 812K

PWR

AGCLimi t

L SN

P ilo t

AGCFast

TP

-20dB

AB Ausg.

AB / C

AB / C

EMF

-20dB

TVB 812K

PWR

AGCL imi tLSN

P ilo t

AGCFast

TP

-20dB

AB Ausg.

AB / C

AB / C

EMF

-20dB

22

Schlögl 2005

Trunk amplifier and node system GGA 8 with electronicalparameter setting, KOM/HMS monitorable

Downgradable with GGA 4, GGA 5 and GGA 6 CATV transmission systems

CATV/HFC trunk amplifier and node systemfor high cascadingFrequency range up to 606 MHz or 862 MHzAll parameters can be set electronically viathe manual control unit HTE 10 or optionallyvia the KOM status monitoring system;Inventory Data SystemCloning functionDFB return path transmitter for 1310 nmOperating parameters are remotelymonitorable, ingress control switch isremotely switchableScalable2 Pilot ALSC, frequency agile(CW/PAL/QAM)ICS ingress control switchExtremely high distortion ratios due to GaAstechnologySystem equalisers can be usedInventory-Data-SystemProtection class IP 65 (DIN 40050)GGA 8 being calibrated with HTE 10 hand-held unit

23

Schlögl 2005

Trunk amplifier and node system GGA 8 with electronicalparameter setting; KOM / HMS monitorable

Test

Inter-stage

µPr

µPr

µPr

µPr

Test-30 dB

D

AC

B

Handheld

Handheld

Handheld

Handheld

-20 dB

0-10 dB 5-12 dB

D

EEProm

FSKDemod

FSKMod

C A

µP

UbTemp

X 3External

X 2Rev. Amp

X 3cUAC

X 6RS 485

X 1

WFS 655-65/85-862 MHz

X 15

X 16

X 4

X 3

X 2

X 12

X 11

X 10

X 9

X 8

X 7

X 6

X 5

X 17

X 18

AC

- 30 dB

GMZ 52

ACWFS 65

5-65/85-862 MHz

24 V

Test

HTE 10

LSN

LSN

LSN

LSN

4 fach2 fach

max. 14 mLSN Adr

0-15 dB 1-8 dB

H

0-5 dB 0-10 dB

UPS extern

C

B

F

EDHG

A

B

CA

X 15 - X 18:

br

sw

bl

gb/grgb

VGP 83 (85)

ALSC limit Red alarm

Cable equaliser

Bus

Bus

Bus

Bridger amplifier VGS 40

Return amplifer VGR 09 C

Pilot processor VGP 08

Trunk amplifier; ALSC controlled

Remote powerpatch field

Remote power filter

Status monitoring module(HMS standard) TVM 40 L

ALSC control elements

Bus

Power supply

Busor

programming

to X 2

B

C

E

F G

G2Pilotgenerator

Test

Ingresstest

Ripple equaliser

Bus of the motherboard: Sub- D 9 pinsHandheld: Sub- D Mini DINTestsockets WFS 65: Bi-di; no testprobe ERM 22 !Testsockets are to be terminatedRF- Motherhousing connection:IEC to 3,5/123-stage switches remote controlled by KOM or on- site (X 3) Handheld

3- stage switches

EMR

Lower and upper pilot adjust

Patch

Patch

Optical transceiver for GGA8

24

Schlögl 2005

VGF / VGP 90xx trunk and line amplifier system; electronicalparameter setting, KOM/HMS monitorable

Highly linear GaAs compact amplifierExcellent transmission dataFrequency range 5 - 65...85 - 606/862 MHz2 pilot-ALSC, frequency agile(CW/PAL/QAM)Amplitude frequency response +/- 0.5 dBOperating parameters are electronically andautomatically set using the HTE 10 hand-heldunit, or via the KOM; ‚Cloning‘ function;Inventory DataICS switchRipple equaliserOne output/two outputs (sym./asym.)Directional coupler test sockets:

Input/output; return path test ‚in‘/ ‚Ingress‘(accessible from the outside)Remote feeding current 7 A / 10 A insertionLocally fed/remotely fed (30 - 72 V)Very efficient power supply unitDegree of protection: IP 66

25

Schlögl 2005

VGF/VGO 938 line amplifier system, manual parameter settingwith slide switches; KOM monitorable

State-of-the-art GaAs compact technologyPlug-in filters (5 - 30/65.. 47/85 - 862 MHz)Gain (switchable in interstage)

forward 38/35/32 dB return 30/21 dB

Amplitude/frequency response +/- 0.5 dBLoop-through RF inputDe-emphasis at 450 - 862 MHz switchable in0/4/8 dB steps for active C lines in KDGnetworksOne output/two outputs (sym./asym.)Directional coupler test sockets:

Input; output; ‚Ingress‘; return pathPluggable high pass filter <15 MHz toattenuate the ingress on boardLocally fed/remotely fed (38 - 65 V)Very efficient power supply unitRemote feeding current 5 A / 7 A infeedDegree of protection IP 54PG 11 connectorsVGF 938 with TVM 840/H HMS transponder

26

Schlögl 2005

Broadband return path amplifier

Transports telemetry and digital data burstsPush-pullOperating level is calculated acc. the CINmethod (see page 34)No pilot control; gain is temperaturecompensated (over compensated)3 state switch (ingress detection); set with thehand-held unit or via the remote monitoringsystem (Transponder has to be inserted)Automatic levelling (by approximation) inpilot-controlled VGP 9xxx line amplifiers oninitial operationUnity gain operation (0 dB of the amplifiertogether with its cable section behind)Directional coupler feed in test socket Ingress test jack to connect an ingress testerSettings can be made without shutting downthe operationOne or more inputs combined into one output

Test- 20 dB

5 - 65 MHz out85 - 862 MHz in

5 - 65 MHz in85 - 862 MHz out

Ingress Test

SIMS 3 State Switch0 dB

- 6 dB

LMT

Cable Equalizer Attenuation

Manually operated (Unity gain)Electronically operated (VGF 9000 series)

Status monitoring transponderKOM or HMS standard

TVM 8xx

"off"

Blockdiagram of typical reversepath amplifierinserted in lineamplifiers (i.e. VGF 8xxx)

Automatic levelling (pilotcontrolled VGP 9000 series

Control elementsfor

"unity gain"

from

the

forw

ardp

ath

(Option)

27

Schlögl 2005

The in-building network (network level 4) for bi-directionalservices

Symmetrical star distribution to theapartments in the return pathTree structure inside the apartmentsModem outlet avoids any unwanted ingressvia the subscribers‘ end devices; highdecoupling surpresses any interferencescaused by a transmitting modemTo maximise the signal-to-noise ratio, thetransmission level is applied at 105 dBµV; nosettings are made on the modem itselfCalculated input level on the return pathamplifier plus distribution loss in the returnpath should be 105 dBµV, or be ‚replenished‘on the input using the attenuating element3-stage ‚ingress‘ search switch which isactuated with the monitoringIngress test socketFuture-proof for state-of-the-art data enddevices (e.g. Residential Gateways)

Typ. in-building network for 16 apartments (unmonitored)

House amplifier, monitored

28

Schlögl 2005

The in-building network for bi-directional services

KOM0

-6off

EVK 100TVRdf

DCM 52 i

DCM 52 i

DCM 52 i DCM 52 i DCM 52 i

TV/FM

TV/FM

PC

PC

PC

TV/FM TV/FM TV/FM

PC PC

ESM 30/40

ESM 30/40

ESM31/41/42

10 BaseT Hub

PC

PCTVFM

EST 20

Fax

DECT

EVK 100

Wireless Modem

10 Base T Etherneta/bUSB

ESD 85 ESD 85

TV/Rdf TV/Rdf

Wireless DECT

A

B

C

D

E

(Twisted Pair)

KAZ 11

EMTA

EMTA IP Streaming

Residential Gateway

F

G

H

Wireless Ethernet

A) Flat with one TV-/ Radio set and PC

B) Flat with several sockets and several PC

C)Flat with several sockets and just one modemwith Hub and Ethernet

D) Flat with triple-play-service

E) Flat with several sockets, wireless DECTand wireless Ethernet

HFC- House amplifierSplitter

Overvoltage protector

RF forwardRF return

Line

tap-

off

Cable modem

Cable modem Cable Modem Cable modem

NTU

Cable modem

Cable modem

Telephone

NTU

NTU`s for the very near future:

F) Flat with Embedded MedialTermination Adapter

G) Flat with EMTA and IP- Strea- ming box

H) Flat with Residential Gateway

DCV 10 (E)

for triple play serviceSplitter

Splitter

29

Schlögl 2005

KOM / HMS monitoring transponder

HMS is an international standardKATHREIN compact transponder

TVM 840 (monitoring module)KATHREIN BK transponder TVM 40(L)3rd party transponders (e.g. by AM /Harmonic)Stores the operation and transmissionparameters of HFC devicesActivates the 3-stage switches in the returnpath amplifiersRegistrated and managed by the HECcontrollerAutomatic search for the HEC controllerreception frequencyAssignment of a transmission frequency andtime slotMAC address and IP addressUsing the LMT (Local Monitoring Terminal),the transponder can be operated on site(Software Win-LMT)TVM 40/L and TVM 840 V and H

TVR 12/TR (BK2K2/GGA 8) notshown

30

Schlögl 2005

DOCSIS cable modem (DCM 52 i)

Conforms with the DOCSIS/ EuroDOCSIS 2.0 standard

Automatic registrationTurboDox to significantly increase thedownload speed for TCP applicationsData rate in downstream up to 38 Mbps, inupstream up to 30 Mbps (ED 64 QAM)USB and Ethernet interfacesComprehensive SNMP management support:MIB-II; Ethernet-like MIB; Bridge MIB; CableDevice MIB; Baseline privacy interfaceMIB;RF Interface MIBModulation receiver: 64/256 QAMModulation transmitter with

TDMA: QPSK, 64 QAM S- CDMA: 8 - 128 QAM

Max. output level with S-CDMA: 113 dBµVCable modem (DOCSIS/EuroDOCSIS 2.0 DCM 52 i

Voice Modems (i.e. DCV 10) are being projected

31

Schlögl 2005

Technical appendix

The block diagrams in this seminar show the optical or high frequency signal progression necessaryfor understanding.

Correct installation, earthing, weather protection, lightning protection and power supply hasnot been dealt with!

The technical appendix does not contain comprehensive instructions for calculation of HFCnetworks.

The intention is to provide an overview of how distortion ratios in the forward and return pathsbehave in terms of the relevant operating level and how the distortion ratio sums are determided incascades. This is important because the installation engineer essentially does two things during thecalibration:

- He balances the amplitude/frequency response using cable equalisers, to level out thefrequency progression of the coaxial cable. All channels transmitted then have the samenominal level on the output.

- He sets the appropriate output level on the amplifiers or the drive level for the transmitters:...and therefore influences the distortion ratios (CSO; CTB; C/N and CIN).

If the associated end device does not have the required distortion ratio on the input (and the necessary useful level of course), it will function only poorly or not at all.

We are pleased to provide advice about our HFC products and systems. Please contact us by e-mailat: [email protected]

32

Schlögl 2005

Downstream broadband nonlinear distortions CSO and CTBAMulti-channel measuring station acc. toCENELEC, ANGA/ZVEI or KDG pattern, fedin the test sampleSpectrum analysis on the outputComposite Triple Beat (3 carriers mixing: f1 +/- f2 +/- f3 = f4 (falls below visioncarriers)Composite Second Order (2 carriers mixing: f1 +/- f2 = f3 (falls within channels)Rule 1: If the output levels of all channels arechanged by 1 dB, the CTB ratio will changeby 2 dB (lower outputlevel increases thedistortion ratio, but decreases the C/N ratio)Rule 2: If the output levels of all channels arechanged by 1 dB, the CSO ratio will changeby 1 dB too (lower output; better CSO ratio)Specification of the output level at 60 dBdistortion

Rules 1 and 2 only apply only below the`maximum operating level‘ indicationVisibility limit 55 dB CTB/CSO distortionsratio in analogue TV signals and 43 dB C/NCSO peaks at either end of the spectrum,CTB however in the middleDouble light exposure !!

CTB

CSO

Video carrier

f4

f3

CENELEC plan; 47-606 MHz; 29 unmodulated vision carriers

33

Schlögl 2005

Addition of distortion ratiosThe array of curves allows one to calculatethe distortion sum in two cascaded singledistortion margins (C/N;CSO;CTBA)Example 1:

The output level of one amplifier stage is setin such a way that the result is a calculatedCTB ratio of 70 dB.

Another amplifier stage which shows a CTBratio of 65 dB due to its output level isarranged behind it. How much is thecomposite triple beat sum?Calculation:

First, the difference of the two triple beatdistortions is calculated

70 dB - 65 dB = 5 dB On the x-axis ‚Difference between two ratios‘,

one determines the intersection point of theCTB curve at 5 dB; the result is 3.4 dB on they-axis.

The CTB sum = 65 - 3.4 = 61.6 dB

Example 2:

Two cascaded amplifers with 60 dBC/N each; Alltogether it`s 57 dB

3,4 dB

5 dB

34

Schlögl 2005

Upstream broadband interference CIN

CIN = Composite Intermodulation Noise isthe (data burst) signal to (uncorrelated) noise+ (correlated) intermodulation noise ratioInput level range (based on 1 Hz) specifiedfor a certain minimum compositeintermodulation ratioBandwidth 5 - 65 MHz gives e.g. 30 channelsat 2 MHz.PE=-8 dBµV/Hz + 10 log 2x106; input level 55dBµV ....77 dBµV gives a CIN ratio of => 50dB for each of the 30 channelsThe CIN ratio of an amplifier deteriorates witheach additional return path amplifier (funneleffect)The person planning the system determinesthe signal-to-noise ratio/dynamic range thesystem is to function with

30 dB

40 dB

50 dB

60 dB

S

(N + Intermod)

Inputlevel dBµV/Hz(OMI %)

- 8 dBµV/Hz

22 dB Dynamic

VGR 34

55 dBµV(2 MHz)64 dBµV

10logx40= 16 dB

20logx10=20 dB75

dBµV

55 dBµV

1 Amplifier

Noise generator

Attenuator

Notch filter

White noise

Band limited

Unit under test(reverse amplifier)

(reverse optical link)

S/N CIN

40 Amplifiers

Specification of active return components:Input noise density (dbµV/Hz) results from acertain noise ratio (dB) for a certain dynamicrange (dB)Example: - 8 dBµV/Hz; CIN = 50 dB; Dynamic range 22 dB

Test rack determination:

20 dBdynamic range

EN 50083-3/A1

not correlated noise correlated noise

VGR 34: 5 - 60 MHzCalculation for 30 channels à 2MHzCarrier level = input noise density + 10log B(Hz)

40 amplifiers altogether; (10 cascaded, 4 lines in parallel)

Spectrum analyser

35

Schlögl 2005

C/N and S/N ratios; modulation gain

The C/N (carrier-to-noise) specifies the high-frequency noise ratio (dB) of a carrier signal(dBµV) based on the noise level (dBµV)The noise figure of an active componentspecifies by how many dB the noiseincreases compared to 75 ohm impedanceThe noise level is based on a certainbandwidth; in AM-TV signals with 5 MHzbandwidth, the noise level is 1.8 dBµV +noise figureThe modulation gain is the difference of theinput carrier-to-noise ratio to the outputsignal-to-noise ratio in different analoguemodulations

FMC/N 10 dBDer C/N am Eingang ist ein spezifizierter Mindeswertz. B. 12 dBQPSKTranscoTransmodulAusgangs- C/N hängt nicht Ausgangs- C/N hängt vomModulationsgewinn z. B.

FM AM

C/N 10 dB C/N 42 dB

QPSK PAL

QAM

Transcoder

Demodulation/Remodulation

Input level 70 dBµV

Noise level 6,8 dBµVNoise figure 5 dB

= Noise level (5 MHz) 5+1,8 dBµV

Carrier-to-noise ratio C/N= 63,2 dBS/N= C/N+1,5 dB

Analogue

Conversion gain i.e. 32 dB (data sheet)C/N at the output depends on C/N at the input

Transmodulation

Worst case C/N at the input has to be specified

i.e. 12 dB

C/N at the output is thenoise of the modulator i.e. 61 dB

C/N at the output does not depend on the C/N at the input

Amplifier

36

Schlögl 2005

Echo attenuation in the coax part of the HFC system

Echoes are caused by signal reflexions in thesystemCause: open or shortcicuited cables, faultyassembled RF connectors, componentswhose return losses are too low, etc.The return loss is the logarithmic ratio of theforward path and reflecting energyIncreasing and decreasing levels in thetransmission spectrum depend on the echophasingGhost in TV, timedelayedMeasurement of the 2-T impulse on analogueTV signals using the MSK 33Return loss minimum value for all systemcomponents in the distribution network: 20 dBat 40 MHz - 1.5 dB/ octave (18.5 dB at 80MHz; etc.)Echoes in digital signals are more critical,and depend on the modulation and bit rate(micro-reflexions in modems)Fibre does not show these effects; reflectedoptical power may decrease the the C/N ratioof the link; optical isolator

f

f

dBµ

dBµ

Amplifier Splitter

Level of the entire frequeny spectrum is identical or slopedbecause of the cable length

open or shortcircuitedcable

Forward and reflected waves are superimposedReflection(s) at the TV screenReduced carrier to noise ratio

Modem data traffic might slow down or is cut

The level of the channels is now different

"Critical cable length"

Timedelayed reflection

37

Schlögl 2005

AGC; ALSC; Long Loop AGC

AGC (Automatic Gain Control) controls thelevels frequency-independently

Headend (input level fluctuation) Transmitter (Modulation-index) Optical receivers (plug and play)

ALSC (Automatic Level and Slope Control)frequency-dependently controls the gain ofbroadband amplifiers against the temperatureof the cable in front

1-pilot-control 2-pilots-control

Long Loop AGC; the CMTS controls thetransmission levels of each DOCSIS modemuntil the nominal input level is achieved onthe CMTS

HFC netDownstream

UpstreamNominal inputlevel(Firmware adjusted)

CMTS Cablemodem

forward

returnTransmitting level

Long loop AGC

ALSC

AGC

(Automatic level and slope control)

(Automatic gain control)

Frequency

Cab

le lo

ss

Frequency

- 30 °C

+20°C

+60°C

Cable loss variation0,2 %/°C

Frequency

+60C°

+20°C

-20°C

+/-5 dB+/-2dB

Gai

n va

riatio

n of

the

trun

k am

p

Gai

n

Amber alarm threshold

38

Schlögl 2005


Thank you very much for your kindattention!

Seminar HFC networks (May 2005) - TVAE - Suppliers of ...tvae.co.za/seminar.pdf · Seminar HFC...

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