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

2. 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.

3. Bandwidth Demand is Growing Exponentially!
All Video on Demand Unicast per Subscriber
100 90
High Definition Video on Demand 80 70
Video Blogs
Podcasting 60
Megabits per Second
Video on Demand 50
Video Mail 40
Online Gaming 30
Digital Photos 20
VoIP
Digital Music 10
Web Browsing
Time

4. The HFC Pipe to the Home is Huge!
DOCSIS® 3.0
The BAD news is that ingress from one home can potentially kill upstream services for hundreds of your subscribers!!!

5. 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.

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

7. 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 Oscope’s
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.

8. 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

9. Testing in the Headend
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

10. 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
Today’s “HFC” networks must be optimized for both forward and reverse performance

11. 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) H L
NODE 3
Ingress?!?!
System Sweep Receiver Model 3SR
LEVEL
TILT
SCAN
SWEEP
C/N
HUM
MOD
SPECT
FILE
AUTO
SETUP
FREQ
CHAN
ENTER
FCN
CLEAR
help
status
alpha
light
abc
def
ghi
jkl
mno
pqr
stu
vwx yz
space
+/- 1 2 3 4 5 6 7 8 9 x .
Identify Ingress accurately on bad test point or node.
Measurement speed; detects down to 1us burst
Headend equipment detects, alarms, and logs all ingress

12. 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.

13. WHY SWEEP? Less manpower is needed
Sweeping can reduce the number of service calls
Cracked hardline found with SWEEP
VoIP & Internet not working
Channel 12 video problems
VOD not working

14. Sweep Verifies Construction Quality
Sweep can find craftsmanship or component problems that aren’t 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!

15. A Sweep Finds Problems That Signal Level Measurements Miss
Misalignment
Standing Waves
Roll off at band edges

16. Testing/Sweeping the HFC Plant
Forward
Laser Shelf
SDA-5500
SDA-5510
50 MHz to 860 MHz.
Reverse
Laser Shelf 4 W A Y
CMTS
IPPV
VOD 23 17 11
Subscriber
Dwelling G B 26
Forward Sweep Response
Reverse Sweep Response

17. 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.

18. 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.

19. Testing/Sweeping the HFC Plant
Forward
Laser Shelf
Forward Sweep Response
50 MHz to 860 MHz.
SDA-5500
Reverse
Laser Shelf 23 17 11
SDA-5510 4 W A Y
CMTS 26
IPPV
VOD 17
Subscriber
Dwelling 11 G B

20. 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.

21. Lose Face Plate, or crack cable shield
Balancing Amplifiers - Forward Sweep Balancing amplifiers using tilt only
Headend
Lose Face Plate, or crack cable shield
No Termination
D = 492*Vp/F F
Node Reference Signal
Sweep response
with a Resonant Frequency
Absorption
Sweep response
with standing waves

22. Steps to Successful Forward Sweep
Take a Tilt Measurement and make certain desired tilt level is set .
Change EQ value to insure tilt requirement is met.
Save this measurement into the meters memory, being certain to save under the proper node or amplifier name.
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.
Save raw sweep file to allow view of actual sweep display.
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.

23. 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.

24. 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, MTA’s, STB’s.
You must take into account return band noise as the CMTS will set CM’s transmit level to be 29 db c/n or better, therefore high noise floor will cause modems and MTA’s to transmit at high RF levels.

25. Reverse Sweep Balance and Alignment
Overview
50 MHz to 860 MHz.
SDA-5500
Reverse
Laser Shelf 23 17 11
SDA-5510 4 W A Y
Reverse Sweep Response
VOD
Data
Voice
5 MHz to MHz
CMTS 26
IPPV
VOD 17
Subscriber
Dwelling 11 G B

26. 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.

27. 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.

28. Creating a Reverse Sweep Plan
VOD
Data
Voice
5 MHz to MHz

29. Balancing Amplifiers - Reverse Sweep
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
Telemetry level shown below return sweep trace should read around 0 dBmV if the SDA-5510 is padded properly

30. Optimize the HFC Pipe for Unity Gain
Maintain unity gain with constant inputs
X dBmV
X dBmV
X dBmV
Telemetry = 0 dBmV
Set TP Loss as required
X dBmV
X dBmV
X dBmV
Use the DSAM Field View Option
to inject a CW test signal into various test points and view remote spectrum

31. HFC Network Impairments – Frequency Response
Typical connector problems that may result in frequency response issues like suck-outs or roll off
Correct pin length,
Properly tightened
Pin length too short

32. HFC Network Impairments – Frequency Response
Pin length too long
This may also hamper the “seating” of the RF module
Overtightened seizure screw
Damaged pin

33. Center Pin/Seizure Screws
Pin tightened before turning
connector into housing
May result in a broken or twisted pin inside the connector
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

34. “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 company’s 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

35. 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

36. 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 company’s installation policy
Be very careful not to over tighten connectors on CPE (TVs, VCRs, converters etc.) and crack or damage input RFI integrity

37. Typical Problem Areas Taps Home Wiring
low value taps
low value taps
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

38. Tracking Down Ingress
View local spectrum on each return path test point of node to determine which leg has the source of ingress
NODE
Use divide and conquer technique to identify and repair source of ingress

39. Common problems typically identified in outside plant
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.

40. Common problems typically identified in outside plant

41. FEDERAL COMMUNICATIONS COMMISSION
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
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
FEDERAL COMMUNICATIONS COMMISSION

42. Common problems typically identified in outside plant
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

43. Intermittent Connections
Poor craftsmanship on connectors
Loose center seizure screws & fiber connectors
Radial cracks in hard-line coaxial cable
Cold solder joints
Bad accessories

44. 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 GB’s), 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, BER’s.

45. Effect of Noise on Analog Systems
(Gradually poorer C/N)
Broadcast Quality Required FCC Spec

46. Incorrect Analog Levels
Low analog video level produces noise in the picture
High analog video level produces distortion in the picture

47. 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

48. 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.

49. Home Certification Testing

50. Home Certification Testing

51. Testing the Home for Ingress Contribution
7 dB TAP
Disconnect drop from tap and check for ingress coming from customer’s home wiring
Return Equalizer
House
Drop Cable
OLDER TV SET
WIRELESS LAPTOP
If ingress is detected, scan spectrum at ground block for ingress
DIGITAL SET-TOP
COMPUTOR
High Pass
Filter
VoIP
GROUND
BLOCK
2-Way
Amplifier
ETHERNET
3-Way
Splitter
ONLINE GAMING
eMTA-CABLE MODEM
INGRESS SPECTRUM MEASUREMENTS

52. Looking For Forward Ingress in the Subscribers Home
TAP
TAP
TAP
Ingress Free
Ingress at MHz TV G B 4 W A y TV TV
CM/PC
DSAM
DSAM

53. Looking For Upstream Ingress from the Subscribers Home
TAP
TAP
TAP
Ingress Free
Ingress at 7.25 MHz TV G B 4 W A y TV TV
CM/PC
DSAM
DSAM

54. How do determine where I need to go to fix problems?
TAP
TAP
TAP TV G B 4 W A y TV TV
CM/PC
DSAM
DSAM

55. How do determine where I need to go to fix problems?
TAP
TAP
TAP TV G B 4 W A y TV TV
CM/PC
DSAM
DSAM

56. See Digital in a Whole New Light!
Questions?
Thank you for your time!