Presentation on theme: "March 2010Proprietary & Confidential1 Sunrise Telecom Presents: Cable 101 Sales Training – CATV Products By: Jerry Green."— Presentation transcript:
March 2010Proprietary & Confidential1 Sunrise Telecom Presents: Cable 101 Sales Training – CATV Products By: Jerry Green
March 2010Proprietary & Confidential2 Agenda In the beginning…… System Architectures Signal on the Network Channel Allocations Analog Channels Digital Channels System Sweep DOCSIS Future
March 2010Proprietary & Confidential3 It all began… – John Walson of Pennsylvania installs an antenna on the mountain and runs twin-lead wires to his appliance store. TV sales soared. John began to connect customers to his antenna & changes the wire to coaxial cable to improve picture quality Ed Parson, of Astoria, Oregon built a CATV system consisting of twin-lead strung from housetop to house top – Bob Tarlton, of Lansford Pennsylvania used coaxial cable on utility polls under a franchise from the city. Community Antenna Television (CATV) was born.
March 2010Proprietary & Confidential4 First Network Architecture System components: – Preamp installed at antenna – Maybe a ‘booster’ in the tree – 300 ohm ‘Railroad Track’ wire Number of channels: – 1 to 10 Performance: – OK to poor
March 2010Proprietary & Confidential5 Test Equipment of the 1950’s & 60’s Jerrold 704 Developed 1951 Manufactured from 1952 to 1967 Jerrold 727 Developed 1966 Manufactured from 1967 to mid 70’s Portable TV Measure levels with modified unit See distortions
March 2010Proprietary & Confidential6 Tapped Trunk Architecture Headend
March 2010Proprietary & Confidential7 Trunk/Bridger Architecture Typical amplifier cascades: 35+ amplifiers. Antenna Tower TV Transmitter Headend
March 2010Proprietary & Confidential8 Trunk/Bridger Architecture with Return
March 2010Proprietary & Confidential9 Microwave Transport
March 2010Proprietary & Confidential10 Hybrid Fiber Coax (HFC) Architecture Fiber Link reduces the number of amplifiers in cascade Fiber Link
March 2010Proprietary & Confidential12 What is the Forward Path of the System
March 2010Proprietary & Confidential13 Sample Amplifier H L H L Slope Control Response Equalizer AGC / ASC H L Forward Amplifier Return Amplifier Bridger Amplifier T.P. -20 dB T.P. -20 dB T.P. -20 dB Forward Path
March 2010Proprietary & Confidential14 What is the Return Path Return Equip. R H L R Return Signal Path Signal flow in the return path is from the customers home to the headend as shown by the blue arrows. Signal flow in the return path is from the customers home to the headend as shown by the blue arrows. Each amplifier compensates for the loss in the wire after the amplifier under test. Each amplifier compensates for the loss in the wire after the amplifier under test.
March 2010Proprietary & Confidential15 Sample Amplifier H L H L Slope Control Response Equalizer AGC / ASC H L Forward Amplifier Return Amplifier Bridger Amplifier T.P. -20 dB T.P. -20 dB T.P. -20 dB Return Path
March 2010Proprietary & Confidential16 Signals on the Network
March 2010Proprietary & Confidential17 Channel Types & Terms Analog – NTSC, PAL, SECAM Digital – 64QAM, 256QAM, 8VSB – Annex A, Annex B, Annex C – DOCSIS, EuroDOCSIS
March 2010Proprietary & Confidential18 Digital Channel Penetration – Evolution of digital signals penetration in HFC transport architecture % analog TV 10% digital TV % analog TV 40% digital TV % analog TV 75% digital TV % analog TV 100% digital TV
March 2010Proprietary & Confidential19 Why change to Digital? Bandwidth efficiency allows more program channels Picture quality improvement Better conditional access system Supports HDTV Not content dependent
March 2010Proprietary & Confidential20 PAL Cable Frequency Allocation
March 2010Proprietary & Confidential21 Channel Plan
March 2010Proprietary & Confidential22 Analog TV Standard Spectrum
March 2010Proprietary & Confidential23 – High Definition Television (HDTV) 16:9 Format (widescreen) NTSCPALSECAM Lines/Image Images/second3025 Horizontal Frequency kHz kHz Vertical Frequency59.94 Hz50 Hz Analog TV, NTSC / PAL / Secam / HDTV
March 2010Proprietary & Confidential24 Spectrum Analysis Ch. 3 Spectrum Analysis Ch. Allocation 6 MHz V/A 4.5 MHz V/Color 3.58 MHz Lower Band Edge MHz Video Carrier MHz Audio Carrier MHz Lower Band Edge MHz
March 2010Proprietary & Confidential26 Analog Channel in Time
March 2010Proprietary & Confidential27 Analog TV, TV Signal Modulation
March 2010Proprietary & Confidential28 Analog TV, test signal Basic video reference points, - Sync tip amplitude, - Depth of modulation - Color Burst Test signals are added to measure signal quality - Vertical synchronisation - Lines 7 to 21 are part of the non-visible image
March 2010Proprietary & Confidential29 Analog TV Chroma – Chroma (or Color) Subcarrier 3.58MHz Suppressed carrier, AM modulation
March 2010Proprietary & Confidential30 Analog TV audio transmissions – Frequency modulated audio sub-carrier 4.5 MHz to 5.5 MHz, ± 25 kHz – Pre-emphasis Reduces high frequency transmission noise Amplification of high frequencies before modulation An inverse filter is applied after demodulation – Encoding similar to FM stereo receivers L+R base signal L-R differential signal
March 2010Proprietary & Confidential31 Analog Measurements Levels Carrier Frequency Carrier to Noise (CCN) Coherent Disturbances (CCN, CSO & CTB) HUM In-Channel Response Color Measurements
March 2010Proprietary & Confidential32 Analog Measurements Carrier Levels
March 2010Proprietary & Confidential33 Relative Frequency, Hz Relative Amplitude in dB Absolute Frequency, Hz Absolute Amplitude, dBmV l Absolute levels and frequency only on visual carrier l All other amplitudes and frequencies are relative to the visual carrier Absolute and Relative
March 2010Proprietary & Confidential34 CM2000/2800 SLM Mode
March 2010Proprietary & Confidential35 Multi-Channel Modes Mini Scan Scan
March 2010Proprietary & Confidential36 AT2500 Channel Level Display
March 2010Proprietary & Confidential37 CATV Measurements Carrier to Noise (CCN)
March 2010Proprietary & Confidential38 Carrier to Noise Ratio S.A. Noise Floor Overload (TP) Dynamic Range CCN
March 2010Proprietary & Confidential39 CCN Measurement Algorithm Measure Carrier Level Measure Noise in a 30KHz Bandwidth Correct for: – Bandwidth of noise to 4 MHz (add dB) – Log Detection (add 2.5 dB) – Bandpass Filter Shape (subtract.5 dB) Correct for Noise to near Noise Correct for pre-amplifier if used Subtract corrected noise from carrier level
March 2010Proprietary & Confidential40 Out of Band CCN Measurement Carrier Level Noise Measurement NOTE: Noise measurement most be corrected for video bandwidth & instrument measurement errors.
March 2010Proprietary & Confidential41 Setup Out-of-Band CCN Measurement ==> SINGLE ==> COMBINED n Center frequency = Video carrier frequency ==> IN-CH GATED n Press F5 to setup Measurement parameters. Noise Meas set to clear area OR
March 2010Proprietary & Confidential42 Out-of-Band CCN Measurement
March 2010Proprietary & Confidential43 Out-of-Band CCN Measurement CCN Result Measurement Point Noise near Noise Correction
March 2010Proprietary & Confidential44 Out-of-Band CCN Measurement
March 2010Proprietary & Confidential45 Instrument Noise Measurement
March 2010Proprietary & Confidential46 In Band CCN Measurement Measurement Range CNR NOTE: Noise measurement most be corrected for video bandwidth & instrument measurement errors.
March 2010Proprietary & Confidential47 Gated CCN Measurement Quiet Line of Video
March 2010Proprietary & Confidential48 Setup CCN Measurement n Center frequency = Video carrier frequency IN-CH ==> GATED n Press F5 to setup Measurement parameters. ==> SINGLE ==> COMBINED OR Noise Meas set 2 MHz
March 2010Proprietary & Confidential49 CCN Measurement CCN Result Measurement Point Noise near Noise Correction
March 2010Proprietary & Confidential51 Second Order Inter-modulation MHz MHz MHz MHz 2IM = f 1 ± f 2 CSO
March 2010Proprietary & Confidential52 Third Order Inter-modulation MHz MHz MHz MHz MHz CTB 3IM = ± f 1 ± f 2 ± f 3
March 2010Proprietary & Confidential53 CTB 0.75 MHz .25 MHz Visual Carrier Aural Carrier Lower Adjacent Aural CSO Where do the beats fall? Composite Distortions are measured as a ratio in terms of dB down from the carrier.
March 2010Proprietary & Confidential54 Digital Beat Products Add pix of digital channels beating together.
March 2010Proprietary & Confidential55 Manual Measurement Procedures l Measure carrier peak l Turn off carrier l Set 30 kHz resolution bandwidth l Narrow video bandwidth to 10 KHz l Composite level using marker l CSO or CTB = visual carrier - distortion level l Automatic cable analyzers can makes CSO measurement without interrupting the subscriber
March 2010Proprietary & Confidential56 Setup CCN/CTB/CSO SINGLE ==> COMBINED n Center frequency = Video carrier frequency IN-CH ==> GATED n Press F5 to setup Measurement parameters.
March 2010Proprietary & Confidential57 Initiate Measurement n Set Frequency to Video Carrier n Press F6 to MEASURE User is prompted to remove test carrier at the headend once test has been initiated
March 2010Proprietary & Confidential58 CCN/CSO/CTB Results CSO CTB CNR
March 2010Proprietary & Confidential59 CATV Measurements Low Frequency Disturbances or Hum
March 2010Proprietary & Confidential60 Hum Definition Hum is ANY low frequency disturbance of the RF carrier Program modulation sometimes interferes with hum measurements causing the measurement to look worse than it actually is. Hum looks like AM modulation of the carrier HUM problems reduce MER and increase BER
March 2010Proprietary & Confidential61 Demodulated Carrier Voltage Time Peak Peak-to-Peak % Hum = 100 X Peak Peak-to-Peak 0 How is Hum Measured?
March 2010Proprietary & Confidential62 Hum Results
March 2010Proprietary & Confidential63 Digital HUM
March 2010Proprietary & Confidential64 CATV Measurements In Channel Frequency Response
March 2010Proprietary & Confidential65 6 MHz Lower Channel Boundary Upper Channel Boundary 1.25 MHz Visual Carrier 0.75 MHz 1 MHz 4.25 MHz Aural Carrier (Off or Suppressed) 2 dB Measurement Area Response Specification
March 2010Proprietary & Confidential67 Multi-Burst
March 2010Proprietary & Confidential68 Ghost Cancelation Reference
March 2010Proprietary & Confidential69 In-Channel Frequency Response Results Using GCR VITS
March 2010Proprietary & Confidential70 Digital Channels
March 2010Proprietary & Confidential71 Digital Measurements Levels Constellation MER, EVM BER Frequency Response Group Delay
March 2010Proprietary & Confidential72 Basic Components Consistent Wave Carrier (CW Carrier) Content – MPEG stream Multiplexed video/audio streams HD video/audio Audio content Modem traffic VOIP traffic
March 2010Proprietary & Confidential73 CW Carrier Consistent Wave Carrier Sine wave shape At one consistent rate At one frequency Used to carry content over the network
March 2010Proprietary & Confidential74 CW Carrier Frequency Domain Time Time Domain
March 2010Proprietary & Confidential75 Multiple CW Carriers Time Frequency Domain Time Domain F1F2 F1 F2
March 2010Proprietary & Confidential76 Purpose of CW Carrier It’s the BUS Modulation is putting content on the Bus Demodulation is taking content off the Bus
March 2010Proprietary & Confidential77 Describing a sine wave Time Amplitude Phase 90° Ref. Point 0°0° Rate (Frequency): Time to complete a cycle Unit of measure = Hertz 1 cycle/sec = 1Hz
March 2010Proprietary & Confidential78 Putting Content on the BUS AM ASK FM FSK Amplitude Modulation Frequency Modulation PSK MM Phase Modulation
March 2010Proprietary & Confidential79 Phase Relationships 0º0º 90º 180º Time
March 2010Proprietary & Confidential80 Bi-Phase Shift Keying (BPSK) Simplest method of digital transmission. Data transmitted by reversing the phase of the carrier. Carrier amplitude & frequency remains constant. 1 bit transmitted at a time Advantage - Very robust method Disadvantage - Consumes significant bandwidth (1 bit per hertz) 180º0º0º 0 1
March 2010Proprietary & Confidential81 Amplitude and Phase Modulation Higher data rates are achieved by adding amplitude modulation to the carriers By having multiple levels of amplitude and phase more symbols can be transmitted in the same time period. Two Levels of Amplitude Modulation and Bi-Phase Modulation Makes Four Possible Symbols º0º0º
March 2010Proprietary & Confidential82 QPSK Two carriers at the same frequency, 90º out-of-phase, transmitted at the same time One carrier is at 0º or at 180º, called the In Phase carrier – one carrier is at 90º or 270º, called the Quadrature carrier The resultant vector of these two carriers designates the symbol to be transmitted. A symbol is a digital word that is a combination of several bits. In this case the symbol contains two bits Using this method twice as much data can be transmitted in the same amount of bandwidth.
March 2010Proprietary & Confidential83 How QPSK symbols are transmitted The digital receiver analyzes both the phase and the amplitude of the incoming signal and produces a bit stream that corresponds to that signal. 10|11|01|00|
March 2010Proprietary & Confidential84 Symbols, Symbol Rate, Bit Rate The Digital Language – If bits are the letters, then symbols are the words in the language of digital modulation. The bit rate is the number of bits sent per second Symbols transmit one or more bits of digital information. Symbol Rate is the number of symbols sent per second. The transmission bandwidth is the symbol rate. Symbol Rate = Bit Rate / Number of bits per Symbol H
March 2010Proprietary & Confidential85 Describing a sine wave Time Amplitude Phase 90° Ref. Point 0°0° Rate (Frequency): Time to complete a cycle Unit of measure = Hertz 1 cycle/sec = 1Hz
March 2010Proprietary & Confidential86 QPSK Example: I carrier transmitted at 0º, Q carrier transmitted at 90º. Resultant vector at 45º represents a symbol of 11. If we needed to transmit a 01, then the I carrier would be at 0º and the Q carrier would be at 270º º º º º 0º0º180º 270º 90º Q Carrier I Carrier
March 2010Proprietary & Confidential87 Quadrature Amplitude Modulation (QAM) Analog color subcarrier similar to QAM modulation Two signals carried at the same frequency out of phase Two carriers called the I and Q, each carrying one- half of the data. Each I & Q carrier transmits 8 levels of data for 64 QAM Hence 8 2 equals 64 combinations or 64 QAM
March 2010Proprietary & Confidential88 In-Phase and Quadrature I Channel Carrier Phase Q Channel Carrier Phase 90° Shifted + = Carrier Phase Shift over time Carrier Amplitude t t 180 Deg Shift I Q
March 2010Proprietary & Confidential89 Creating a QAM signal Local Osc 8 Level AM Modulator 8 Level AM Modulator Bit Stream Oscillator Shifted 90° Combiner 64 QAM Signal Q Component I Component I & Q carriers, same frequency, but phase shifted by 90° AM modulated Combined make up the QAM signal.
March 2010Proprietary & Confidential90 QAM QAM is Quadrature Amplitude Modulation Two carriers at the same frequency, 90º out-of- phase, transmitted at the same time Uses multiple levels of amplitude & phase modulation Each carrier is a representation of half of the transmitted symbol.
March 2010Proprietary & Confidential91 QAM (Cont.) If each of the I and Q channels transmits 4 levels of data 16 symbols transmitted in one clock cycle Each symbol contains 4 bits Known as 16QAM 8 levels per carrier 64 symbols transmitted Symbol contains 6 bits 64QAM 16 levels per carrier 256 symbols transmitted Symbol contains 8 bits Known as 256QAM
March 2010Proprietary & Confidential92 Vectors and 16 QAM Q 90° I 0° I 180° Q 270° 1011
March 2010Proprietary & Confidential93 Vectors and 16 QAM Q 90° I 0° I 180° Q 270° 1011
March 2010Proprietary & Confidential94 64 QAM Constellation 64 QAM Constellation 6 Bits per Symbol
March 2010Proprietary & Confidential QAM 8 Bits per Symbol
March 2010Proprietary & Confidential96 Digital Measurements Digital Channel Power MER, ENM, and EVM Constellation Impairments Pre and Post FEC BER Adaptive Equalizer QIA Measurements
March 2010Proprietary & Confidential97 Analog vs. Digital Power Measurements 6 MHZ 300 KHz 6 MHZ
March 2010Proprietary & Confidential98 Digital Power Measurement Digital Power Measurement H
March 2010Proprietary & Confidential99 Balancing System Levels
March 2010Proprietary & Confidential100 Modulation Error Ratio MER is used as a single figure of merit for quality for RF digital carriers It includes distortions such as CCN, CSO, CTB, laser compression, etc…. The sum of all evils. A 256 QAM picture tiles at 28dB MER A minimally good MER is 31 dB for 256 QAM at the back of the customer’s set. H
March 2010Proprietary & Confidential101 Vectors and 16 QAM Q 90° I 0° I 180° Q 270° 1011
March 2010Proprietary & Confidential102 MER and a Constellation H
March 2010Proprietary & Confidential103 MER and a Constellation H
March 2010Proprietary & Confidential104 Acceptable MER Output of QAM Modulator – 40 dB Input to Lasers – 39 dB Output of Nodes – 37 dB Output of Subscriber Taps – 35 dB At the input to the subscriber’s receiver – 34 dB The absolute minimum is 31db.
March 2010Proprietary & Confidential105 Constellation Analysis
March 2010Proprietary & Confidential106 Noise Impairments
March 2010Proprietary & Confidential107 Phase Impairments Looks good here in the Headend!
March 2010Proprietary & Confidential108 Coherent Interference Constellation
March 2010Proprietary & Confidential109 Coherent Interference in Freq Spectrum Ingress from UHF off-air channels Headend beats CSO & CTB
March 2010Proprietary & Confidential110 Phase Impairments
March 2010Proprietary & Confidential111 H Gain Compression
March 2010Proprietary & Confidential112 H I/Q Gain Imbalance
March 2010Proprietary & Confidential113 Laser Compression
March 2010Proprietary & Confidential114 CM2000/2800 Constellation
March 2010Proprietary & Confidential115 BER Measurement
March 2010Proprietary & Confidential116 What is BER? BER is defined as the ratio of the number of wrong bits over the number of total bits. Sent Bits Received Bits BER = # of Wrong Bits # of Total Bits = 1 10 = 0.1 error
March 2010Proprietary & Confidential117 BER Display BER is normally displayed in Scientific Notation. The more negative the exponent, the better the BER. Better than 1.0E-6 is needed after the FEC for the system to operate. Lower and Better BER
March 2010Proprietary & Confidential118 Calculated Bit Error Rate Using the amount of FEC overhead required to reproduce a bit string, the bit error rate can be calculated. Using the FEC to determine the BER allows BER to be measured without removing the service which is usually required for most BER testing.
March 2010Proprietary & Confidential119 Forward Error Correction Decoder Forward error correction (FEC) is a digital transmission system that sends redundant information along with the payload, so that the receiver can repair damaged data and eliminate the need to retransmit.
March 2010Proprietary & Confidential120 Pre and Post FEC errors Pre FEC errors – Errors that have occurred before the FEC has had an opportunity to correct any of the errors. Post FEC errors – Errors that could not be corrected A cable modem will tolerate pre-FEC errors and the FEC will continue to correct pre-FEC errors up until 1E-06 or one error in one million bits. After that the FEC can do no more. Post-FEC errors will cause retransmissions requests and slowdowns in a DOCSIS systems.
March 2010Proprietary & Confidential121 Pre and Post FEC BER To get an accurate idea of the BER performance you need to know both the pre and post FEC bit error rate. The FEC decoder needs a BER of better than 1 E-6 in order to operate. Post FEC Bit errors are not acceptable. You should look at both the Pre and Post FEC BER to determine if the FEC is working to correct errors and if so how hard. FEC Decoder Pre FEC BER Post FEC BER
March 2010Proprietary & Confidential122 Parity By adding an additional bit to a group of bits, errors can be detected within the group. This is known as a parity bit. Even parity means that when the parity bit is added the group of bits including the parity always has an even number of ones. Odd parity means the group would have an odd number of ones. If after transmission the number of ones is no longer even (for even parity), then there must be an error Parity Bit Always Even Number of Ones (Even Parity) Error Odd Number of Ones Indicates Error
March 2010Proprietary & Confidential123 How Reed Solomon FEC Works FEC works by addition additional data bits to the data stream to determine if errors exist and to try and correct them Video Data Stream =odd 0=Even Stream With FEC Added
March 2010Proprietary & Confidential124 How Reed Solomon Works Error 1=odd 0=Even Before Transmission After Transmission the Bit in Error is Detected and Corrected Once you know a bit is wrong, correcting it is easy, if you know its wrong and its a zero, then it has to be a one.
March 2010Proprietary & Confidential125 BER and a Constellation H
March 2010Proprietary & Confidential126 CM2000/2800 Constellation
March 2010Proprietary & Confidential127 Statistical Mode
March 2010Proprietary & Confidential128 Statistical Mode
March 2010Proprietary & Confidential129 Adaptive Equalizer Every Digital Receiver has an Adaptive Equalizer It performs 3 functions – Compensates for amplitude imperfections of the digital signal – Compensates for group delay – Rings at the symbol rate to only allow one symbol at a time into the digital receiver
March 2010Proprietary & Confidential130 Equalizer Mode
March 2010Proprietary & Confidential131 Equalizer Mode
March 2010Proprietary & Confidential132 Digital Video – EQ Control Standard EQ – Used in current equipment – More taps – Improved correction Min EQ – Less taps – Mirrors performance of old equipment – Disables Auto Diagnosis
March 2010Proprietary & Confidential133 Frequency Response – Effective span equal to symbol rate – Measurement calculated using Equalizer data
March 2010Proprietary & Confidential134 Amplitude Ripple An in-service spectrum analyzer measurement
March 2010Proprietary & Confidential135 Group Delay Definition: – Group delay is a measure of how long it takes a signal to traverse a network, or its transit time. It is a strong function of the length of the network, and usually a weak function of frequency. It is expressed in units of time, pico-seconds for short distances or nanoseconds for longer distances. Measured in units of time, – Typically nanoseconds (ns) over frequency – Or, Delay per MHz.
March 2010Proprietary & Confidential136 Group Delay (Cont.) In an ideal system all frequencies are transmitted through the system, network or component with equal time delay Frequency response problems cause group delay problems Group delay is worse near band edges and diplex filter roll-off areas
March 2010Proprietary & Confidential137 Group Delay (cont’d) Excessive group delay increases bit error rate due to inter-symbol interference DOCSIS spec. – no greater than 200nSecs per MHZ – Spec should be less than 100 nSecs per MHz
March 2010Proprietary & Confidential138 Group Delay Measurement
March 2010Proprietary & Confidential139 QIA Screen
March 2010Proprietary & Confidential140 QAM Impairment Analysis (QIA) I/Q Gain and Phase – The phase and gain of both the I and Q carrier must be equal in order for the constellation to be correct. – This impairment is caused by the QAM modulators. – The gain difference between the 2 carriers should be less than 1.8% and the phase difference should be less than 1 degree. Echo Margin – A measurement in dB of how far the taps are from the template with the time equalizer measurement. – Caused by impedance mismatches in the system. – Should be at least 6 dB.
March 2010Proprietary & Confidential141 QIA Continued Carrier Offset – Carrier frequency test. – Should be no more than +/- 25KHz Estimated Noise Margin – Difference in dB between MER and the digital cliff – Depends on if the signal is 64 or 256 QAM – Minimum depends on where the measurement is taken – Example if the Minimum MER for 256 QAM is 28 and the measurement is 34, than the ENM is 6 Frequency Response – Frequency response of the digital carrier – Should be less than 3 dB pk-to-pk
March 2010Proprietary & Confidential142 QIA Continued Hum – Low frequency disturbances of the digital carrier – Same as hum on analog carriers, if the level is the same, it’s the system, if higher on the digitals then it’s probably the QAM modulator Symbol Rate Error – Should be less than +/- 5 ppm Phase Noise – Jitter (changes in phase) of the oscillators, most likely the up-converter – The phase shift or jitter should be less than.5 degrees
March 2010Proprietary & Confidential143 QIA Continued Group Delay – Different frequencies travel through the same medium at different speeds. So the lower the lower frequencies of the same carrier arrive at the receiver at different timing than the higher frequencies. – Should be less than 50 nSec pk-to-pk Compression – Caused by overdriving lasers or amplifiers – Shows up as corners pulling in at the outer corners of the constellation – Should less than 1%
March 2010Proprietary & Confidential144 System Sweep
March 2010Proprietary & Confidential145 What does sweep do for the technician? Measures the Frequency Response of the network Confirms Unity Gain View impedance mismatches – Bad connectors & cable – Bad devices Checks both Forward and Return paths Concept: If the system is flat and levels are correct, distortion will be minimal
March 2010Proprietary & Confidential146 Why Sweep? Insures proper headroom Preventative Maintenance Non-obtrusive measurement Look at network with a microscope
March 2010Proprietary & Confidential147 CM2800 Sweep Compatible with 3010H/R Forward Sweep – New 3 Dwell definition – Simultaneous Pilot & Forward Sweep Results Return Sweep – Switch Control (Phase 2) – Return Spectrum (Phase 2)
March 2010Proprietary & Confidential148 Sweep System Facts CM2800 compatible with 3010 version 5.53 firmware only 3010R & 3010H, same measurement hardware 3010H ships fully loaded – Basic unit support Return Path Monitor mode (both R&H) – Option 052 – Forward Sweep TX & Dual Path Mode – Option 061 – Switch control 3010 upgrade to ver – Version 4.x & above included with Calibration – Version 3.x available for an additional charge
March 2010Proprietary & Confidential150 Forward Sweep Forward Sweep Path 3010 Output Combined with Downstream Signals Sweep Level 16dB to 20dB below analog levels Sweep tilt = channel tilt Normalized sweep is a relative meas. Change in response between meas. Point and reference point
March 2010Proprietary & Confidential151 Reverse Sweep Reverse Sweep Path DS Comms Combined with Downstream Signals (Comms only) Test signal inserted in field, measured by 3010H, meas. sent to field instrument on DS Comms Must know your reference points & design levels
March 2010Proprietary & Confidential152 Network basics Unity Gain Concept – Total System Gain equals Total Loss – Gain = Loss or Gain/Loss = 1 – Forward Path: Constant Output Levels Amp compensates for cable before device – Return Path: Constant Input Levels Amp compensates for cable after device Same cable forward amp is compensating for. Sweep Insertion – ~ 17 dB Below Channels – System Level to Sweep Delta will Remain Consistent – Matches Design Level Tilt
March 2010Proprietary & Confidential153 Reality of Frequency Response Output Levels and Slopes are customized to provide the best performance Highest Carrier to noise Ratio (CC/N & MER) Highest Carrier to Distortion Ratio (CSO, CTB, ect.)
March 2010Proprietary & Confidential154 How Sweep Works with no Sweep Table MHz 400 measurement points Transmitter output with a blank sweep table. The sweep frequency resolution is determined by the start and stop frequencies in areas of the spectrum where no frequencies are in the sweep table. Sweep Resolution = (Stop freq... - Start freq...) 400 points = (450MHz - 50MHz) 400 points = 1MHz/point
March 2010Proprietary & Confidential155 Components of the Sweep Table Stop freq... = 450MHzStart freq... = 50MHz 57.20MHz63.20MHz 61.25MHz
March 2010Proprietary & Confidential156 What is the Forward Path of the Cable System
March 2010Proprietary & Confidential157 Lash-Up for Forward Sweep Set Up Forward Combiner RF In RF Out To Forward Lasers
March 2010Proprietary & Confidential158 Forward Sweep Setup Flow Setup Channel plan Connect the input of the 3010 to a port containing all the channels on the network Set Forward Sweep mode to Fast In the Sweep Parameters screen set the following: – Start Freq. to your start frequency – Stop Freq. to your stop frequency – Comm’s Pilot Freq. to a clear area of network spectrum – Scan Type to Phantom – Channel Plan to the Channel Plan you created – Sweep Table to None
March 2010Proprietary & Confidential159 Forward Sweep Parameters Screen Start Frequency Stop Frequency Communications Pilot Frequency Scan Type Frequency Plan Created for system under test Sweep Table (Set to None to create a new table.) 3010H
March 2010Proprietary & Confidential160 Forward Sweep Setup Flow Scan the network and the instrument creates the basic Sweep table for you Add system pilots and edit table Save the table Set the level & slope Your done!!!!
March 2010Proprietary & Confidential161 Table Entries for other type signals Digital Signal – (Places sweep point between Digital Channels) – Frequency = Channel Center Freq.. – Guard band = 1/2 Channel bandwidth – Dwell = 0 Digital Signal – (Measures Digital channel, no sweep point) – Frequency = Channel Center Freq. – Guard band = ½ Channel bandwidth MHz – Dwell = 3 Phantom Carrier Setup – (Sweep point in Vestiges Sideband) – Frequency = Center Freq kHz – Guard band = ½ Channel bandwidth – 0.1 MHz – Dwell = 0 System AGC or Setup Pilot Channels – Frequency = Video carrier frequency – Guard band = 1MHz – Dwell = 0
March 2010Proprietary & Confidential162 Forward Sweep Level Sweep points between Digital Channels – Sweep points must be at least 17dB or greater below analog video level No sweep points around Digital Channels – Sweep points should be at the same level as the measured digital channels
March 2010Proprietary & Confidential163 Sweep Setup Go to SETUP / SWEEP – Enter / Select the Low and High System Pilot – Enter the Forward Sweep Communications Pilot Frequency (per 3010 setting) – Enter the Reverse Sweep Communications Pilot Frequency (per 3010 setting) – Check “Get New Table” to force download of new Forward Sweep – SAVE & EXIT
March 2010Proprietary & Confidential164 Sweep Setup Go to SETUP/LIMITS and SWEEP tab – Select the Location from the Pull Down Menu – Set the Downstream Sweep Limits for Low System Pilot min & max High System Pilot min & max Tilt max (we will add min) Peak-to-valley max – Set the Upstream Sweep Limits for Tilt max (we are adding min) Peak-to-valley max – SAVE & EXIT Sweep Limits Screen
March 2010Proprietary & Confidential165 Sweep Tools View Sweep Table
March 2010Proprietary & Confidential166 Screen Annotations – Forward Sweep Freq. & dB/Div Control View Sweep Table Trace control – (only active when reference is selected) Site File Select Reference Attenuator – Sets Dynamic range System Pilot Freq. & Level P/V freq. range set by Vert. Marker Position Save Ref. File
March 2010Proprietary & Confidential167 Forward Sweep First Connection – Communication Icon (lock symbol) will flash yellow, Markers & start stop will update. – If Comms Icon not flashing - Adjust Attenuation If test point system levels are > 10 dBmV, increase the attenuator setting. If < 0 dBmV, decrease attenuator setting. – Wait for sweep table download (or press F4 on 3010) – Note the sweep trace and the pilot graphs. Pilots should be 10 to 15 dB above sweep. – Note markers Use Touch Screen or Arrows Tilt & Peak-to-valley Calculated on Markers Click on the SAVE icon at top tool bar and enter a name for a reference file. Lock Symbol
March 2010Proprietary & Confidential168 Sweep Reference Sweep File are used as a Reference Select a Reference File – Sweep Display will be the difference between Ref and current results
March 2010Proprietary & Confidential169 Referenced Forward Sweep – Click REFERENCE, select saved file. – RED trace = Live Trace – Reference Trace – Automatically adjusts to 2 dB/Div – Click A, B, A&B, A-B to toggle Trace (Live, Reference, Both or Difference Traces) – Low & High Pilot Frequency & Levels are Displayed – Tilt & Peak to Valley calculations based on Vertical Marker Position
March 2010Proprietary & Confidential170 Return Sweep Configuration Return Equip. R H L R Return Signal Path Signal flow in the return path is from the customers home to the headend as shown by the blue arrows. Signal flow in the return path is from the customers home to the headend as shown by the blue arrows. Each amplifier compensates for the loss in the wire after the amplifier under test. Each amplifier compensates for the loss in the wire after the amplifier under test.
March 2010Proprietary & Confidential171 Alignment Issues & the Return Path The monitor point is some distance from the adjustment point. The communications between the 3010R and 3010H is through the system under test. Interference on the return or forward path can affect the communication between the instruments. The Ingress detection system is used to troubleshoot interference on the return path.
March 2010Proprietary & Confidential172 Reverse Sweep Communications Reverse Sweep Path DS Comms Combined with Downstream Signals (Comms only) Test signal inserted in field, measured by 3010H, meas. sent to field instrument on DS Comms Must know your reference points & design levels
March 2010Proprietary & Confidential H Polling Sequence
March 2010Proprietary & Confidential174 Return Sweep Headend Lash-Up ForwardCombinerForwardCombiner RF out To Forward Lasers RF in Return Receivers To Return Processing Equipment
March 2010Proprietary & Confidential175 Connecting the 3010R to the 3010H back to back 3010H Input Output Input
March 2010Proprietary & Confidential176 Return Sweep Setup Set dynamic range for measurement Full Scale (FS) setting in Spectrum Scan If < 5 return paths connected to 3010 or using AT1600 Switch – Set FS for modem traffic to upper division of display If > 5 return paths – Set FS for noise floor below second division of display Remember the setting!
March 2010Proprietary & Confidential177 Return Sweep Setup (Cont.) Set Switch driver if connected to a switch Set Return Sweep mode to Fast In Return Sweep Parameters screen set the following: – Start Freq. to your start frequency – Stop Freq. to your stop frequency – Forward Pilot to a clear area Forward Path spectrum – Return Pilot to a clear area Return Path spectrum – Ret Swp Table to None (to create new table)
March 2010Proprietary & Confidential178 Return Sweep Setup (Cont.) To Speed up sweep – Enter frequency every 1 MHz – Guard band = 0.5 MHz – Dwell = 0 Save Table Set Forward Pilot level 10 dB below the analog channels You are done!
March 2010Proprietary & Confidential179 Screen Annotations Freq. & dB/Div Control View Sweep Table Trace control – (only active when reference is selected) Site File Select Reference Attenuator – Sets Forward Pilot Dynamic range Source Level/Slope Controls P/V freq. range set by Vert. Marker Position Save Ref. File
March 2010Proprietary & Confidential180 Reverse Sweep – Upstream sweep table is automatically Downloaded – Communication Icon (lock symbol) will flash yellow, Marker Freqs. & start / stop will update – If test point system levels are above 10 dBmV, increase the attenuator setting. If below 0 dBmV, decrease attenuator setting. – – Set the Transmitter Level for the appropriate Injection Level Peak reference level limited by 3010H setting – Note Markers Tilt & P/V Calculated on Vertical Marker Position
March 2010Proprietary & Confidential181 Referenced Return Sweep – Click REFERENCE, select saved file. – RED trace = Live Trace – Reference Trace – Automatically adjusts to 2 dB/Div – Click A, B, A&B, A-B to toggle Trace (Live, Reference, Both or Difference Traces) – Tilt & Peak to Valley calculations based on Vertical Marker Position
March 2010Proprietary & Confidential182 Bi-directional Test Point Typical Amp diagrams How to connect Splitter Set the Test Point Loss to 3 dB to compensate for the Splitter or for the Splitter and Test Point loss.
March 2010Proprietary & Confidential183 Directional Test Points Amp Configurations are Tailored for the Span they serve Diplexers Separate the Upstream & Downstream Path Pads adjust the Flat Gain of Amplifiers Equalizers Compensate for Cable Loss Reverse EQReverse PAD
March 2010Proprietary & Confidential184 Connecting the 3010R to the 3010H in the System 3010H Fiber Node 3010R Forward Path Fiber Laser Return Path Fiber Receiver RF in RF out
March 2010Proprietary & Confidential185 What is Ingress? Ingress refers to interference typically found on the Return Path. Most times it is caused by signals entering the system from the customer drop. When ingress is detected by the 3010H, the it makes a spectrum scan measurement and broadcasts the display data to the field on the forward Pilot. When a 3010R receives the Broadcast Ingress message, it is displayed over F3. Pressing F3 with the message display will allow you to view the spectrum scan measurement from the 3010H Return Path with Ingress Return Path without Ingress 3010R
March 2010Proprietary & Confidential186 When Ingress is a Problem. F3 A flashing Square Indicates loss of Return Communications Indicates Ingress detection at the 3010H A flashing symbol indicate the Forward pilot is received from the 3010H A solid symbol indicates no Forward Pilot communications Pressing F3 will activate the Broadcast Ingress Measurement 3010R
March 2010Proprietary & Confidential187 The Typical Return H L Fiber Node Optical Receiver Optical Receiver Optical Receiver Coax Dist.Network H L Fiber Node H L Fiber Node To CMTS Receive Port Spare Splitter Leg
March 2010Proprietary & Confidential188 The Funnel Noise from every nook & cranny in the system ends up at the CMTS receive port. H L Fiber Node Optical Receiver Optical Receiver Optical Receiver Coax Dist.Network H L Fiber Node H L Fiber Node
March 2010Proprietary & Confidential189 You can’t get there from here H L Optical Receiver Optical Receiver Optical Receiver Coax Dist.Network H L H L Fiber Node To CMTS Receive Port Spare Splitter Leg The actual Call might be here The problem could be here … or here … or the problem could be anywhere in these three nodes.
March 2010Proprietary & Confidential190 Upstream Impairments Common Path Distortion Fast transient noise Ingress
March 2010Proprietary & Confidential191 Upstream Ingress Return Path with Ingress Return Path without Ingress Ingress refers to interference typically found on (but not limited to) the return path. Most ingress comes from the drops. Some sweep systems detect ingress on their return sweep data frequency and broadcast the display data to the field on the forward data carrier for display.
March 2010Proprietary & Confidential192 Corrosion & Diode Effect Crystallization occurs and the corrosion creates thousands of small diodes between the two metals Diodes are non- linear devices that can act as frequency “mixers” in a CATV plant
March 2010Proprietary & Confidential193 Frequency Mixing Mixing two frequencies (F1 & F2) will yield four results: F1 F2 F1 + F2 F2 – F MHz MHz MHz 6.00 MHz
March 2010Proprietary & Confidential194 Common Path Distortion 27 Corroded Connection A corroded connection causes mixing The resulting impedance mismatch also causes reflections The mixing products are reflected right back into the return amplifier. The diplex filter takes out everything above 42 MHz. Downstream Signals Difference frequencies reflected upstream (~6, 12, 18, 24…)
March 2010Proprietary & Confidential195 CPD in 6 MHz Intervals Because the channels in the forward system are 6 MHz apart, the sum & difference frequencies occur at 6 MHz intervals as well.
March 2010Proprietary & Confidential196 Other Non-Linear devices Other non-linear devices can create return path problems Splitters utilizing toroid wound coils can also be non- linear and create mixing problems. A cable modem transmitting at high levels can saturate the toroids forcing them to become non-linear.
March 2010Proprietary & Confidential197 Spectrum Display Limitations Scanning Spectrum Analyzers measure only one band of frequencies at any given instant. Frequency Range Where Measurement is Being Made at That Instant Frequencies Stored From Last Pass of Filter
March 2010Proprietary & Confidential198 Fast Intermittents If the spectrum analyzer is at another frequency when the transient appears it will not be displayed. A transient happening at this time will be missed by the filter unless it is still there when the filter comes by again
March 2010Proprietary & Confidential Switch Control Feature Setup and Operation
March 2010Proprietary & Confidential200 Switch Control Description 3010H – Adds switch driver for AT160x & RPS switches 3010R – Adds remote switch control – Single node return sweep Requirements – Firmware version 5.53 or greater – Option 061 turned on (Shown on opening screen)
March 2010Proprietary & Confidential201 Features Auto node polling Two switch drivers – AT1601 or AT1602 – RPS switch Remote switch control Backwards compatible Single node sweep
March 2010Proprietary & Confidential202 AT160x Configuration
March 2010Proprietary & Confidential203 Cabling & Equipment Cable H to Switch string – Cloning Cable – Male 9-pin to Male 9-pin Null Modem Cable - Switch to Switch – Straight Through cable – Female 9-pin to Male 9-pin Straight Through Combiner – Number of ports equals number of switches
March 2010Proprietary & Confidential204 AT160x Programming the Considerations Each Switch in the string requires a unique address – Switch address is used to identify the ports. If you have multiple 3010H/switch configurations in your system you may want to consider using different addresses for every switch in the system. Use the Short Protocol (P1) Use 38,4k baud rate (b2)
March 2010Proprietary & Confidential205 Programming the AT160x Press Reset then Local/Remote button –S–Status light will turn yellow Set Switch address, then press Local/Remote button Set Protocol to P1 (Short Protocol), then press Local/Remote button Set Band Rate to b2 (38,4k band), then press Local/Remote button Programming Complete –S–Status light will turn green
March 2010Proprietary & Confidential H Programming F3 3010H F3 Switch Driver Port Control
March 2010Proprietary & Confidential208 RPS Limitations Only one switch port in a string can be closed at a time. Special switch lash-up required to minimize connection time.
March 2010Proprietary & Confidential209 RPS Configuration 1
March 2010Proprietary & Confidential210 RPS Configuration 2
March 2010Proprietary & Confidential211 RPS Configuration 3
March 2010Proprietary & Confidential H Programming RPS Driver Set to 4, 7 or 15 AT Driver Set to Last Polled port AT160x Driver Alt SW1 Driver Select switch driver first, then Comm Node
March 2010Proprietary & Confidential H Operation F3 Communication Status
March 2010Proprietary & Confidential214 ADD REALWORX SLIDES
March 2010Proprietary & Confidential215 Troubleshooting DOCSIS Systems
March 2010Proprietary & Confidential216 History of DOCSIS DOCSIS 1.0 – Open standard for high-speed data over cable – Best-effort – 1 st products certified 1999 DOCSIS 1.1 – Quality-of-Service (QoS) service flows – BPI+ with Certificates – Improved privacy with key distribution & encryption processes – SNMP for network management security
March 2010Proprietary & Confidential217 History of DOCSIS (Cont.) DOCSIS 2.0 – Goal: greater throughput & robustness on Return Channel Adds 64 & 128 QAM modulation to Return Channels Higher symbol rate up to 5.12 Msps (BW 6.4) Adds Forward Error correction, Trellis coding & programmable interleaving to Return channel Adds multiple modulation & access schemes DOCSIS 3.0 – Channel bonding (Increase capacity) – Enhanced network security – Expanded addressability (IPv6)
March 2010Proprietary & Confidential218 DOCSIS 1.0, 1.1 & 2.0 Reference Architecture Courtesy of SCTE™
March 2010Proprietary & Confidential219 DOCSIS 3.0 Reference Architecture Courtesy of Cable Labs ®
March 2010Proprietary & Confidential220 Basic DOCSIS Setup Fiber Distribution Coax Dist.Network Drop & Home Wiring H L Fiber Node 10/100 Mb Ethernet DHCP TFTP TOD DNS HTTP ISP C M T S Optical Receiver Up-converter 44 MHz In Out System signals LASER Signal to add’l Laser inputs Combine r Upstream DownstreamNetwork Modem
March 2010Proprietary & Confidential221 Basic DOCSIS Setup Fiber Distribution Coax Dist.Network Drop & Home Wiring H L Fiber Node 10/100 Mb Ethernet DHCP TFTP TOD DNS HTTP ISP C M T S Optical Receiver Up-converter 44 MHz In Out System signals LASER Signal to add’l Laser inputs Combine r Upstream DownstreamIP Network Modem & Cust. Equip.
March 2010Proprietary & Confidential222 Cable Modem Registration Physical layer (RF plant) - signal transport DOCSIS and IP protocol layers - communicate messaging for modems to come online The next slides illustrate the interaction of these layers in the registration process
March 2010Proprietary & Confidential223 DS Freq. Acquisition CMTSCMTS cable modem Wait for UCD Wait for MAP Wait for Sync Yes No Next Frequency Next Frequency Yes No Sync Sync Broadcast (Minimum one per 200 msec) Sync Sync Broadcast (Minimum one per 200 msec) UCD UCD Broadcast (every 2 sec) MAP MAP Broadcast (every 2 ms) Scan DS Scan DS Frequency for a QAM signal Scan DS Scan DS Frequency for a QAM signal
March 2010Proprietary & Confidential224 CMTSCMTS cable modem Adjust Timing Offset and Power Offset Wait for RNG-RSP Wait for RNG-RSP NO YES RNG-RSP Ranging Response Contains: Timing offset Power offset Temp SIDRNG-RSP Ranging Response Contains: Timing offset Power offset Temp SID RNG-REQ Initial Ranging Request Sent in Initial Maintenance time Slot Starting at 8 dBmV Using an initial SID = 0RNG-REQ Initial Ranging Request Sent in Initial Maintenance time Slot Starting at 8 dBmV Using an initial SID = 0 Increment by 3 dB Increment by 3 dB CM Ranging
March 2010Proprietary & Confidential225 DHCP Overview CMTSCMTS DHCP Request Acks Initial lP Address and requests Default GW, ToD Server, TOD offset, TFTP Server Addr and TFTP Boot Config File Name DHCP Request Acks Initial lP Address and requests Default GW, ToD Server, TOD offset, TFTP Server Addr and TFTP Boot Config File Name cable modem MAP MAP Broadcasts ToD Request DHCP Discover DHCP Reply (Offer) DHCP offers an IP address DHCP Reply (Offer) DHCP offers an IP address Bandwidth Request Temp SID Use Temp SID (Service ID) Bandwidth Request Temp SID Use Temp SID (Service ID) ToD Response Contains Time of Day per RFC 868 RFC 868 (Not NTP) ToD Response Contains Time of Day per RFC 868 RFC 868 (Not NTP) DHCP Ack (Response) IP Addr Contains IP Addr, plus additional information DHCP Ack (Response) IP Addr Contains IP Addr, plus additional information
March 2010Proprietary & Confidential226 TFTP & Registration CMTSCMTS cable modem TFTP Boot File Transfer DOCSIS config file which contains Classifiers for QoS and schedule, Baseline Privacy (BPI), etc. TFTP Boot File Transfer DOCSIS config file which contains Classifiers for QoS and schedule, Baseline Privacy (BPI), etc. Registration Request Send QoS Parameters Registration Request Send QoS Parameters Validate file MD5 Checksum Implement Config Validate file MD5 Checksum Implement Config TFTP Boot Request For ‘Boot File name’ TFTP Boot Request For ‘Boot File name’ Registration Response Assigned SID Contains Assigned SID Modem registered Registration Response Assigned SID Contains Assigned SID Modem registered Registration Acknowledge Send QoS Parameters Registration Acknowledge Send QoS Parameters
March 2010Proprietary & Confidential227 BPI+ Added in DOCSIS 1.1 If BPI+ is turned on, the modem will verify it’s authentication Two Certificate types – Factory installed Higher level of security Encrypted Certificate obtained by VeriSign and installed by manufacturer – Self signed MAC address referenced in Certificate server for authentication BPI+ eliminates MAC address spoofing
March 2010Proprietary & Confidential228 CM Registration Summary Downstream channel search Ranging DHCP ToD TFTP Registration Optional BPI Encryption (DOCSIS 1.1 or higher) If modem contains eMTA, the next slide shows a table of the remaining 25 steps in the eMTA registration process
March 2010Proprietary & Confidential229 eMTA Registration CM MTA
March 2010Proprietary & Confidential230 Troubleshooting the Registration Process Downstream Downstream – First step in the process – Make sure you are connected to the correct DOCSIS channel One channel may be fine and another in trouble – Check performance Levels (Remember adjacent channels) MER, BER Linear performance (Freq. response, Group Delay) – If the Downstream is fine, Check the Upstream Downstream
March 2010Proprietary & Confidential231 Troubleshooting the Registration Process Upstream Upstream – Check Transmit Level High or Low could indicate a problem – Check Frequency & Modulation type May work using QPSK & not 16 or 64 QAM – BKER Should be little or no errors Check for Lost or Discarded Packets – Lost Packets indicate ingress – Discarded Packets indicate congestion – May be deceiving Upstream
March 2010Proprietary & Confidential232 Troubleshooting the Registration Process IP Network Network – Check IP addresses A CPE, or Emulator IP address is required to pass data through the network. Cable IP address is not enough Check Bootfile – If default file, you are not provisioned – Test ability to pass data through the network Ping – Test connectivity to another device Tracert (Trace route) – Test IP route with transmit times through the network. Throughput – Test the ability to pass data through the network. Browser – Test the ability to connect to a known site through the modem Network
March 2010Proprietary & Confidential233 Troubleshooting the Registration Process Modem & Customer Equipment Modem – Test ability to pass data through the customer modem Ping – Test connectivity to another device Tracert (Trace route) – Test IP route with transmit times through the network. Throughput – Test the ability to pass data through the network. Browser – Test the ability to connect to a known site – If your test equipment is fine, it is probably the customer equipment Customer Equipment – Connect customer PC to test instrument May have to reboot PC If not working, maybe bad Net card Modem
March 2010Proprietary & Confidential234 CM Network Analyzers Cable Modem Network Analyzer are continually being developed & improved to troubleshoot DOCSIS systems These powerful tools are designed around the premise that if you can quickly determine the source of the problems in a DOCSIS system, you will also save valuable time and un-necessary truck rolls while trying to troubleshoot and repair these problems.
March 2010Proprietary & Confidential235 Digital Network Analyzers Connect to the CMTS Obtain an IP from the DHCP server Provide Downstream QAM information Provide Lost Packets and BKER information in the upstream Can do Ping, Trace Route and Throughput testing from the Cable Modem or PC emulator Provide the ability to emulate another modem and then step you through the connection process using the customer equipment’s MAC address if BPI+ is turned off. Provide special measurements for extended services such as VoIP and IPTV
March 2010Proprietary & Confidential236 Connecting to the Network Select the Downstream DOCSIS channel
March 2010Proprietary & Confidential237 Connecting to the Network Select UCD (upstream channel descriptor)
March 2010Proprietary & Confidential238 Connecting Process Screen updates as the process is completed & displays the status
March 2010Proprietary & Confidential239 Instrument connected Completed Range & Register Process Modem On-line Win CE Emulator IP MTA IP
March 2010Proprietary & Confidential240 Downstream/Upstream Info Analyzer view of Downstream & Upstream parameters.
March 2010Proprietary & Confidential241 Key IP Detail Parameters IP Address Gateway TFTP Server DHCP server TFTP File name & more
March 2010Proprietary & Confidential242 Key Downstream Details Channel Displayed Measurements – MER – Pre & Post FEC BER – Errored Sec Click on a Quadrant to Zoom In
March 2010Proprietary & Confidential243 Upstream Detail Upstream transmit level Lost Packets Upstream Block Error Rate
March 2010Proprietary & Confidential245 The Gateway Fiber Distribution Coax Dist.Network Drop & Home Wiring H L Fiber Node 10/100 Mb Ethernet DHCP TFTP TOD DNS HTTP ISP C M T S Optical Receiver Up-converter 44 MHz In Out System signals LASER Signal to add’l Laser inputs Combiner CMTS converts DOCSIS to Ethernet or some other protocol.
March 2010Proprietary & Confidential246 Network Side of the Gateway 10/100 Mb Ethernet DHCP TFTP TOD DNS HTTP ISP CMTS ISP – Internet Service Provider(s) DHCP – Dynamic Host Control Protocol Server hands out the IP addresses TFTP – Trivial File Transfer Protocol Server sends the tftp file sometimes called bootp file or bootfile. DNS – Domain Name Server Resolves domain names/IP addresses HTTP – Hypertext Transmission Protocol Server used for download testing TOD – Time of Day Server Connection to HFC Network
March 2010Proprietary & Confidential247 Testing the Network Ping Tests Trace Route Tests Throughput Tests Protocol Analysis Digital(DOCSIS) Network Analysis
March 2010Proprietary & Confidential248 How Pings Can Get Lost A CMTS (or any router) will discard any ping packet received in error (upstream errors) A CMTS will discard ping packets when the upstream bandwidth allocation of the originating modem is exceeded DISCARDED PACKETS
March 2010Proprietary & Confidential249 A Simple DOS ping C:\ping Pinging with 32 bytes of data: Reply from : bytes=32 time<10ms TTL=128 Ping statistics for : Packets: Sent = 4, Received = 4, Lost = 0 (0% loss) Approximate round trip times in milli-seconds: Minimum = 0ms, Maximum = 0ms, Average = 0ms (TTL A set maximum amount of time a packet is allowed to propagate through the network before it is discarded.)
March 2010Proprietary & Confidential250 A Simple DOS Tracert C:/tracert Tracing route to SR-INTRA [ ] over a maximum of 30 hops: 1 <10 ms <10 ms <10 ms ms 82 ms 83 ms ms 82 ms 82 ms SR-INTRA [ ] Trace complete.
March 2010Proprietary & Confidential251 Any file Care needs to be taken when making throughput comparisons. Processing time of the servers comes into play as well as the type of networks and routers that are involved. Throughput Testing
March 2010Proprietary & Confidential252 Network Summary Ping – A packet sent to a specific IP address and returned for test purposes. Trace Route – An offshoot of the Ping test, but provides a trace of the packet through the IP network Throughput – Downloading files to a PC to determine how much average data per second is being transferred
March 2010Proprietary & Confidential255 Getting A BKER NE PING#1 PING#2 PING#3 Ping Packets are numbered consecutively and accounted for as they are received.
March 2010Proprietary & Confidential256 Serial Pings & Lost Packets PING #1 Sent PING #1 Received PING #2 Sent PING #2 Received PING #3 Sent PING #3 Received 4 PACKETS LOST (#4, 5, 6 & 7) PING #4 Sent PING #8 Received
March 2010Proprietary & Confidential257 BLOCK ERROR RATE # Lost Packets Block Error Rate = Total # of Transmitted Packets Block Errors (Lost Packets are used to characterize return path performance) It is possible to “Load Test” the Upstream DOCSIS system using BKER
March 2010Proprietary & Confidential258 Why Test Loading ? Confirm that the customer is actually getting the upstream BW he is paying for Confirm that the BW restrictions are working properly
March 2010Proprietary & Confidential259 Loading Calculation Load = (50 Bytes + Bytes in Payload) X (8 bits/Byte) (kb/sec) (delay in msec) X 1000 msec/sec Ping Packet Header & Overhead P A Y L O A D (Packet Size) Bytes50 bytes The upstream “load” is a function of the packet size and the packet delay. Packet size = Header + Payload Packet Delay – How often the packets are transmitted.
March 2010Proprietary & Confidential260 Approximate Loading Delay Size Pkts/min Upstream Load (mSec) (Bytes) (approximate) kb/sec kb/sec kb/sec *Based on a 50 Byte ping packet in addition to the size of the payload.
March 2010Proprietary & Confidential261 Upstream Fly in the Ointment Upstream Downstream Network Modem In three out of the four possible problem areas, the trouble can be solved by the service tech handling the call. The Upstream piece of the puzzle is a different story.
March 2010Proprietary & Confidential262 You can’t get there from here H L Optical Receiver Optical Receiver Optical Receiver Coax Dist.Network H L H L Fiber Node To CMTS Receive Port Spare Splitter Leg The actual Call might be here The problem could be here … or here … or the problem could be anywhere in these three nodes.
March 2010Proprietary & Confidential263 Diplex Filter H L Optical Receiver Optical Receiver Common DOCSIS Network Analyzer C M T S Up-converter 44 MHz In Out LowHigh
March 2010Proprietary & Confidential264 Zero Span/Time Domain Mode Frequency Amplitude TIME In the Spectrum Mode the horizontal access of the analyzer displays frequency. In the Time Domain mode the analyzer remains on one specified frequency and the horizontal access represents TIME.
March 2010Proprietary & Confidential265 Upstream Power Measurement Because upstream Cable Modems transmit in very short bursts, it is difficult to measure their levels. Putting the analyzer in Max Hold will allow you to get an approximation of the CM return levels. Using the Time Domain Mode on the analyzer will allow you to get a very accurate power measurement of your cable modem signals.
March 2010Proprietary & Confidential266 Max Hold Using Max Hold will allow you to get a relative reading on the Cable Modems in the return. This Method is not very accurate, but does provide a good approximation.
March 2010Proprietary & Confidential267 Measuring Power in TDM mode Measuring power of cable modems in the return system is a two step process. Step One – Calculate the half-channel bandwidth of the Upstream signal in order to properly setup the analyzer. Step Two – Measure the power using the analyzer average detector and make a bandwidth correction.
March 2010Proprietary & Confidential268 Calculating Analyzer Center Freq 1. Half Channel Width = Symbol Rate / 2 2. Offset the Center Frequency by 80% of the Half Channel Width: New CF = Original CF - (half Channel Width X 80%) 3. Calculating New CF setting for a 1.6 MHz QPSK signal: Half Channel Width = 1.6MHz (.80)/2 Half Channel Width =.64 MHz = 640 KHz 4. Analyzer CF = MHz – 0.64 MHz 5. Analyzer CF = MHz
March 2010Proprietary & Confidential269 Measuring the Level Set the SPAN to mSec and the Resolution Bandwidth to 1 MHz. Set the trigger level near the top of the signal and adjust to where the preamble is clearly displayed. Use the average detector and place a marker on the preamble Make the bandwidth correction for the measurement. Note: Making the measurement with a noise marker will give you the ability to automatically have the analyzer give you the BW correction. This summary was derived from a detailed Cisco procedure. More detailed information can be found on the Cisco website.
March 2010Proprietary & Confidential270 Measurement at Preamble The Measurement Bandwidth is the symbol rate. In this case 1.6 MHz. Adjust for B/W difference between RBW of 1 MHz and the 1.6 MHz measurement BW. Some analyzers will calculate this automatically. BW adjustment= 10 log BW1/BW2
March 2010Proprietary & Confidential271 Characterizing the Upstream Return Path Verification, Test & Troubleshooting Test signal injected in field & measured on analyzer Measure MER, BER, Constellation, Freq. Response, Group Delay
March 2010Proprietary & Confidential272 Modem & Customer Equip. Testing Upstream Downstream Network Modem Testing the modem, it’s provisioning and the PC connection is the last piece of the troubleshooting puzzle.
March 2010Proprietary & Confidential273 Network Analyzer as a CM Customer PC Digital Network Analyzer CMTS ISP In this case the Network Analyzer is taking the place of the customer’s cable modem. With some units, it is actually possible to “borrow” the MAC address of the customer’s modem and actually emulate that specific modem during the testing process
March 2010Proprietary & Confidential274 PC Emulator Digital Network Analyzer CMTS ISP PC Emulator Using a PC emulation mode, the network analyzer is able to do Ping, Trace Route and Throughput testing from the customer’s premise to any location on the internet. The PC emulation also allows analysis of IP details related to the customers own MAC address
March 2010Proprietary & Confidential275 Key to CM Troubleshooting The key to good DOCSIS troubleshooting is to identify which of the four areas need to be worked on. Then as Kenny Rogers said “know when to hold ‘em and know when to fold ‘em”.
March 2010Proprietary & Confidential276 Architecture of the Future ????????
March 2010Proprietary & Confidential277 Thank You QUESTIONS??
March 2010Proprietary & Confidential278 Group Delay 5 MHz 10 MHz 15 MHz 20 MHz 25 MHz 30 MHz 40 MHz 35 MHz As different frequencies pass through a Cable System, some will move faster than others 5 MHz 10 MHz 15 MHz 20 MHz 25 MHz 30 MHz 40 MHz 35 MHz 5 MHz 10 MHz 15 MHz 20 MHz 25 MHz 30 MHz 40 MHz 35 MHz SYSTEM Filters & Traps SYSTEM Filters & Traps T I M E t
March 2010Proprietary & Confidential279 Equalizer Taps
March 2010Proprietary & Confidential280 What does sweep do? Checks the Frequency response of the network Checks both forward and return paths Confirms unity gain If the system is flat and levels are correct, distortion will be minimal
March 2010Proprietary & Confidential281 Setting the Dynamic Range in the 3010H F1F2F3F4 SCALE ENTER Press to save change 3010H