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Testing the Network from Headend to the Home Presented by David Dolnick JDSU Sales Support Engineer.

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Presentation on theme: "Testing the Network from Headend to the Home Presented by David Dolnick JDSU Sales Support Engineer."— Presentation transcript:

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2 Testing the Network from Headend to the Home Presented by David Dolnick JDSU Sales Support Engineer

3 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION2 Agenda What tools are available for testing in the broadcast headend. Where is testing performed within the headend. Testing the HFC plant (Sweeping the Network). Testing signal quality from Tap to the Home. How to Find and Fix problems from Tap to TV.

4 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION3 Web Browsing Digital Music VoIP Digital Photos Video on Demand Video Mail Online Gaming Podcasting Video Blogs High Definition Video on Demand All Video on Demand Unicast per Subscriber Megabits per Second Time Bandwidth Demand is Growing Exponentially!

5 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION4 The HFC Pipe to the Home is Huge! The BAD news is that ingress from one home can potentially kill upstream services for hundreds of your subscribers!!! DOCSIS® 3.0

6 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION5 Testing in the Headend It is important to test the content and timing of digital services at various locations Within the headend. This includes off-air ATSC (8VSB), Satellite delivered signals (QPSK), Gigibit Streams delivered via optical or copper connections, ASI streams within the headend, and QAM RF modulated signals. Even as we move to digital broadcasts, traditional cable providers will still be Delivering a smaller analog package to support limited basic subscribers. This requires the need for continued traditional RF testing to ensure balanced levels and acceptable carrier to noise.

7 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION6 Electronic Program Guide (EPG) Conditional Access keys Service Information (SI) Program Specific Information (PSI) Synchronization Re-multiplexing MPEG-PSI DVB-SI Digital Video Testing Throughout the Network QAM TS (Transport Stream) TS Cable distribution (DVB-C) IP, SDH, ATM, Satellite, DVB- RCS and Terrestrial contribution STB (Set Top Box) SDH Studio A Studio Z IP Router/Gateway CMTS DTS-330/RSAM5800/MVP MPEG Probe Analysis of the feeds and re- multiplexing System management Program management Subscriber management ASI QPSK QAM GbE 8VSB

8 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION7 Testing in the Headend Standalone Spectrum Analyzers have been the test instrument of choice for the last 50 years. They work well when working with traditional RF carriers along with Oscopes For testing Baseband signals. As we transition to all digital broadcast services there are many more parameters that must be verified to ensure reliable delivery of quality services. These digital services must be verified at several stages within broadcast headend. They include testing the content to make certain the program provider is meeting MPEG spec. and that all required MPEG table information is intact. In addition to checking service content we must make certain that there no timing issues within the MPEG stream. Timing is the most common issue preventing Reliable and consistent decoding Timing affects the ability of the MPEG decoder (QAM or 8VSB) to properly read and Reassemble the video frames.

9 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION8 Testing in the Headend Analog services require traditional testing to verify level and separation of Video and Audio sub-carrier as well as measure CNR and SNR. In addition other measurements such as coherent distortion measurements Are required these include CSO, CTB, ICFR, and Hum. The above measurements require a spectrum analyzer. Other measurement such as baseband video and audio require an Oscilloscope. For measuring phase of color carrier to insure proper colors requires the Use of a vectroscope I.e. VM-700

10 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION9 As we enter a world of advance interactive services we have to maintain quality return services. Maintaining clean returns that are free of noise and ingress is a big concern as so many of our advance services require an active return to operate. These include VOD, IPPV, Data 3.0, Voice and Interactive TV (ITV). These advance services make monitoring of each return path a necessity for the modern day service provider Testing in the Headend

11 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION10 HFC Networks Combines fiber optics with coaxial distribution network Return path is more sensitive than the forward path Most of the ingress comes from home wiring on low value taps Wide variety of aging hardware with many connectors Todays HFC networks must be optimized for both forward and reverse performance

12 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION11 Testing Returns in the Headend Return Path Monitoring along with interactive handheld meters has long been the standard to help System operators quickly access issues on the return and very quickly find where issues exist. i.e. (Find and Fix) –Identify Ingress accurately on bad test point or node. –Measurement speed; detects down to 1us burst –Headend equipment detects, alarms, and logs all ingress H L H L H L H L H L NODE 3 Ingress?!? ! System Sweep Receiver Model 3SR LEVEL TILT SCANSWEEP C/NHUMMOD SPECT FILE AUTO SETUP FREQ CHAN ENTER FCNCLEAR help status alpha light abcdefghi jkl mnopqr stuvwx yz space+/ x.

13 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION12 Testing the HFC Plant After the signals leave the headend they are distributed across the HFC plant To make certain that are services remain intact we continue to test services In both the downstream (forward services) and the upstream (reverse services) We look at traditional metrics such as CNR and SNR for analog services And for digital services we also measure MER and BER to determine Signal quality. These same measurements are made on return services that come back from The subscribers STB (VOD and IPPV), Cable modem, and MTA. Sweeping the HFC plant is the quickest way to determine any RF frequency Response issues, as well as allowing for balance of the forward plant and Setting unity gain of the reverse amplifiers.

14 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION13 Less manpower is needed Sweeping can reduce the number of service calls VOD not working VoIP & Internet not working Channel 12 video problems Cracked hardline found with SWEEP WHY SWEEP?

15 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION14 Sweep Verifies Construction Quality Sweep can find craftsmanship or component problems that arent revealed with other tests Damaged cable Poor connectorization Amplifier RF response throughout its frequency range Gain Slope Loose face plates, seizure screws, module hardware……. All of these issues could lead to frequency response problems and major ingress!

16 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION15 A Sweep Finds Problems That Signal Level Measurements Miss Standing Waves Roll off at band edges Misalignment

17 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION16 Testing/Sweeping the HFC Plant Forward Laser Shelf

18 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION17 Testing/Sweeping the HFC Plant Forward sweep and balance of the RF network is the quickest way to determine deficiencies based upon losses within the copper cable as well as determine noise contribution caused by ingress coming from a variety of sources, both electrical and RF. Reverse sweep and balance, setting unity gain and Flatness of the reverse path allows the operator to identify drop noise and balance the return amplifiers so that they all have the same gain factor. Setting unity gain is important to allow all return devices to transmit at similar RF levels.

19 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION18 So how does Sweep work? The idea of forward sweep is to take a reference of all the forward signals in the headend and compare them to what is measured in the field. This means that when viewing forward sweep we are seeing the difference between what was referenced in the headend and what is being measured in the field.

20 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION19 Testing/Sweeping the HFC Plant SDA-5500SDA MHz to 860 MHz. Forward Laser Shelf Reverse Laser Shelf 4WAY4WAY CMTS IPPV VOD Subscriber Dwelling GBGB Forward Sweep Response

21 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION20 Examples of Forward sweep It is important to know which services are digital as opposed to analog services As digital services are carried between 4 and 6 dB below the analog services So when digital QAM services are inserted Within an analog tier they appear to be lower In level than the adjacent carriers creating What may appear to be a response issue. Often numerous digital QAM channels are Bypassed when performing forward sweep There has been a misconceptions that sweep Places pulses within the active QAM channels Creating problems with poor MER and BER. Above you will see an absolutely linier response Between two channels. This is because those Services are not being swept.

22 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION21 Balancing Amplifiers - Forward Sweep Balancing amplifiers using tilt only No Termination Lose Face Plate, or crack cable shield Node Reference Signal Sweep response with a Resonant Frequency Absorption Sweep response with standing waves Headend D = 492*V p /F F

23 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION22 Steps to Successful Forward Sweep 1.Take a Tilt Measurement and make certain desired tilt level is set. 2.Change EQ value to insure tilt requirement is met. 3.Save this measurement into the meters memory, being certain to save under the proper node or amplifier name. 4.Make a forward sweep measurement to view the actual response making certain that there are no major response issues i.e. roll up, roll off, suck outs, ingress. 5.Save raw sweep file to allow view of actual sweep display. 6.Next save the sweep file as a reference sweep file. This will create a flat response which means that any response issues are considered normal for that location. This reference display will be used at the next active downstream so that if both displays are identical then there is no need to perform any other measurements such as tilt. The response will be the same as the previous active.

24 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION23 Steps to Successful Forward Sweep Step 1. change EQ value to meet Required tilt spec 7 to 8 dB at 500 MHz, 10 dB at 750 MHz., 12 dB at 860 MHz, And 14 dB at 1GHz. Save snapshot of tilt display Step 2. checking the actual response Making certain that we run from our Low channel to our highest channel Checking for frequency suck-outs and Any ingress that may appear. Save snapshot of sweep display Step 3. saving the sweep response As a reference. Will auto normalize The trace display creating a flat Response. That will be used as a comparison to next RF active.

25 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION24 Reverse Sweep Balance and Alignment In reverse sweep our goal is to balance the return For flatness and adjust the return gain so that it is the same at every housing (unity gain). Setting the reverse amplifiers at all locations to the same gain allows all return devices to transmit at the same relative RF level i.e. cable modems, MTAs, STBs. You must take into account return band noise as the CMTS will set CMs transmit level to be 29 db c/n or better, therefore high noise floor will cause modems and MTAs to transmit at high RF levels.

26 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION25 Overview Reverse Sweep Balance and Alignment SDA-5500SDA MHz to 860 MHz. Reverse Laser Shelf 4WAY4WAY CMTS IPPV VOD Subscriber Dwelling GBGB Reverse Sweep Response VOD Data Voice 5 MHz to 42 MHz

27 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION26 Steps to Successful Reverse Sweep and Balance When performing reverse sweep it is important to know the desired input level to the reverse chip set. This transmit level is based upon manufacturers spec and the design of the plant. (Typically this will be between 17 and 21 db at the chip set). When we insert we try to adjust for 0 dB telemetry back at the headend. We will use this number to reference our gain at each location. Typical window is -15 to +15 dBmV. We must create an accurate channel plan for the reverse that does not interfere with active return services.

28 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION27 Reverse Sweep The first step for a working reverse sweep is to build a reverse channel plan in the headend unit that does not interfere with active services. This channel plan will be used to tell the meter in the field what frequencies to transmit back on the return. It is important that a technician does not inject carriers at the same frequencies as active services or anyone using these services on that path will be offline.

29 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION28 Creating a Reverse Sweep Plan VOD Data Voice 5 MHz to 42 MHz

30 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION29 Inject correct X level into node test point and then take a sweep reference At next amp reverse sweep displays the effects of the network segment between the last amp and this one Balancing Amplifiers - Reverse Sweep Telemetry level shown below r eturn sweep trace should read around 0 dBmV if the SDA-5510 is padded properly

31 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION30 X dBmV Maintain unity gain with constant inputs X dBmV Optimize the HFC Pipe for Unity Gain X dBmV Telemetry = 0 dBmV Set TP Loss as required Use the DSAM Field View Option to inject a CW test signal into various test points and view remote spectrum

32 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION31 Correct pin length, Properly tightened Pin length too short Typical connector problems that may result in frequency response issues like suck-outs or roll off HFC Network Impairments – Frequency Response

33 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION32 Pin length too long Overtightened seizure screw Damaged pin This may also hamper the seating of the RF module HFC Network Impairments – Frequency Response

34 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION33 Pin tightened before turning connector into housing May result in a broken or twisted pin inside the connector Center Pin/Seizure Screws A more typical result is the pin gets pushed back into the connector instead of pushing past the seizure screw Happens a lot to housing terminators

35 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION34 Back to the Basics Troubleshooting Majority of problems are basic physical layer issues Do a visual inspection of cable, connectors and passives and replace as needed Check for proper grounding Tighten F-connectors per your companys installation policy –Be very careful not to over tighten connectors on CPE (TVs, VCRs, converters etc.) and crack or damage input RFI integrity Check forward and return RF levels, analog and digital Check for reverse ingress coming from home Most of the test strategy remains the same – divide and conquer technique

36 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION35 Back to the Basics Majority of problems are basic physical layer issues Most of the tests remain the same Check AC power Check forward levels, analog and digital Sweep forward & reverse

37 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION36 Back to the Basics Check for leakage sources Check for ingress sources Do a visual inspection of cable / connectors / passives Replace questionable cable / connectors / passives Tighten F-connectors per your companys installation policy –Be very careful not to over tighten connectors on CPE (TVs, VCRs, converters etc.) and crack or damage input RFI integrity

38 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION37 Typical Problem Areas Taps –Most ingress comes from houses off of with low value taps of approximately 17 dB or less Home Wiring –Drop Cable, splitters & F Connectors are approximately ~95% of Problem Amplifiers, hard line cable and the rest of the system are a small percentage of the problem if a proper leakage maintenance program is performed low value taps

39 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION38 NODE Tracking Down Ingress View local spectrum on each return path test point of node to determine which leg has the source of ingress Use divide and conquer technique to identify and repair source of ingress

40 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION39 Kinked or damaged cable (including cracked cable, which causes a reflection and ingress). Defective or damaged actives or passives (water-damaged, water-filled, cold solder joint, corrosion, loose circuit-board screws, etc.). Cable-ready TVs and VCRs connected directly to the drop. (Return loss on most cable-ready devices is poor.) Some traps and filters have been found to have poor return loss in the upstream, especially those used for data-only service. Common problems typically identified in outside plant

41 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION40 Common problems typically identified in outside plant

42 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION41 Electrical Devices Doorbell transformers Toaster Ovens Electric Blankets Ultrasonic pest controls (bug zappers) Fans Refrigerators Heating pads Light dimmers Touch controlled lamps Fluorescent lights Aquarium or waterbed heaters Furnace controls Computers and video games Neon signs Power company electrical equipment Alarm systems Electric fences Loose fuses Sewing machines Hair dryers Electric toys Calculators Cash registers Lightning arresters Electric drills, saws, grinders, and other power tools Air conditioners TV/radio booster amplifiers TV sets Automobile ignition noise Sun lamps Smoke detectors There are Many Possible Sources of Interference Off-Air Broadcast AM Radio Station FM Radio Station TV Station Two-way Radio Transmitters Citizens Band (CB) Amateur (Ham) Taxi Police Business Airport/Aircraft Paging Transmitters FEDERAL COMMUNICATIONS COMMISSION

43 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION42 Damaged or missing end-of-line terminators Damaged or missing chassis terminators on directional coupler, splitter or multiple-output amplifier unused ports Loose tap faceplates and loose center conductor seizure screws Unused tap ports not terminated. This is especially critical on lower value taps Unused drop passive ports not terminated Use of so-called self-terminating taps (4 dB two port; 8 dB four port and 10/11 dB eight port) at feeder ends-of-line. Such taps are splitters, and do not terminate the line unless all F ports are properly terminated Common problems typically identified in outside plant

44 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION43 Intermittent Connections Poor craftsmanship on connectors Loose center seizure screws & fiber connectors Radial cracks in hard-line coaxial cable Cold solder joints Bad accessories

45 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION44 Qualifying the Subscriber Drop and Residence Many tools exist for qualifying both the subscriber drop and in-house wiring. A quick test of service quality across a fair number of channels both analog and digital can reveal issues within the home such as poor craftsmanship. Poor connectorization spun-out F81 connectors in wall plates bad passive devices (splitters and GBs), bad spans of cable, exposed sheath. Can all be causes of ingress that can affect a subscribers quality of service, by creating poor C/N, MER, BERs.

46 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION45 (Gradually poorer C/N) Effect of Noise on Analog Systems Broadcast Quality Required FCC Spec

47 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION46 Incorrect Analog Levels Low analog video level produces noise in the picture High analog video level produces distortion in the picture

48 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION47 Low QAM Digital levels Low QAM average power level causes digital signal to degrade This causes tiling and intermittent or complete loss of high speed Internet access

49 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION48 Home Certification Testing Testing a variety of analog and digital services, including parameters such C/N, MER and BER., can reveal service quality or poor in-house wiring issues. Additionally testing of DOCSIS channel can tell us if we can support data and voice services at the subscribers residence on the drop tested.

50 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION49 Home Certification Testing

51 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION50 Home Certification Testing

52 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION51 eMTA-CABLE MODEM 7 dB TAP Drop Cable High Pass Filter GROUND BLOCK 3-Way Splitter DIGITAL SET-TOP House 2-Way Amplifier Testing the Home for Ingress Contribution VoIP OLDER TV SET Return Equalizer ONLINE GAMING WIRELESS LAPTOP COMPUTOR ETHERNET Disconnect drop from tap and check for ingress coming from customers home wiring INGRESS SPECTRUM MEASUREMENTS If ingress is detected, scan spectrum at ground block for ingress

53 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION52 TAP GBGB 4WAy4WAy TV CM/PC Looking For Forward Ingress in the Subscribers Home DSAM Ingress Free Ingress at MHz

54 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION53 TAP GBGB 4WAy4WAy TV CM/PC Looking For Upstream Ingress from the Subscribers Home DSAM Ingress Free Ingress at 7.25 MHz

55 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION54 How do determine where I need to go to fix problems? TAP GBGB 4WAy4WAy TV DSAM CM/PC

56 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION55 How do determine where I need to go to fix problems? TAP GBGB 4WAy4WAy TV DSAM CM/PC

57 © 2009 JDSU. All rights reserved.JDSU CONFIDENTIAL & PROPRIETARY INFORMATION56 Questions? Thank you for your time! See Digital in a Whole New Light! See digital in a whole new light!


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