seminar hfc networks (may 2005) - tvae - suppliers of ...tvae.co.za/seminar.pdf · seminar hfc...
TRANSCRIPT
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
Seminar HFC networks
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
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
Einga 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
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.
fe 950-2150 M Hzfa 110- 862 MHzPa 95 dBuV
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
fe 950-2150 M Hzfa 110- 862 MHzPa 95 dBuV
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
fe 950-2150 M Hzfa 110- 862 MHzPa 95 dBuV
B
A
C l a ssAKlasse
POWERV mA31 912,5 390
5 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 mA
31 612,5 420
5 620
DEC
PRG
V 4
.08
UFO 38220610048
DVB-S-Transcod.
fe 950-2150 M Hzfa 110- 862 MHzPa 95 dBuV
B
A
C l a ssAKlasse
POWERV mA
31 612,5 4205 620
DEC
PRG
V 4
.08
UFO 38220610048
DVB-S-Transcod.
fe 950-2150 M Hzfa 110- 862 MHzPa 95 dBuV
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.
fe 950-2150 M Hzfa 110- 862 MHzPa 95 dBuV
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
Einga 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
Einga 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
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.
fe 171- 858 MHzfa 110- 862 MHzPa 95 dBuV
PRG
08
UFO 38220610048
DVB-S-Transcod.
fe 950-2150 MHzfa 110- 862 MHzPa 95 dBuV
PRG
.08
UFO 38220610048
DVB-S-Transcod.
fe 950-2150 MHzfa 110- 862 MHzPa 95 dBuV
PRG
08
UFO 38220610048
DVB-S-Transcod.
fe 950-2150 MHzfa 110- 862 MHzPa 95 dBuV
PRG
08
UFO 38220610048
DVB-S-Transcod.
fe 950-2150 MHzfa 110- 862 MHzPa 95 dBuV
PRG
08
UFO 38220610048
DVB-S-Transcod.
fe 950-2150 MHzfa 110- 862 MHzPa 95 dBuV
PRG
08
UFO 38220610048
DVB-S-Transcod.
fe 950-2150 MHzfa 110- 862 MHzPa 95 dBuV
PRG
08
UFO 38220610048
DVB-S-Transcod.
fe 950-2150 MHzfa 110- 862 MHzPa 95 dBuV
PRG
.08
UFO 38220610048
DVB-S-Transcod.
fe 950-2150 MHzfa 110- 862 MHzPa 95 dBuV
PRG
.08
UFO 38220610048
DVB-S-Transcod.
fe 950-2150 MHzfa 110- 862 MHzPa 95 dBuV
PRG
08
UFO 3532 061001 5
DVB-T-Transcod.
fe 171- 858 MHzfa 110- 862 MHzPa 95 dBuV
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
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
CH : .SO TVLEV : 37.2 dBV
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
Cluster 1Cluster 2Cluster 3Cluster 4
Coax
SIMS i.e. 60 dBµV
Cluster 1Cluster 2Cluster 3Cluster 4
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
Seminar HFC networks
Thank you very much for your kindattention!