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Prequalifying Your Infrastructure for IPTV

by: Don McCarty

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OSP Magazine OCTOBER 2006

Up until 10 years ago, our service providers went their own separate ways. Dial tone was delivered by the telcos who also provided bandwidth over their high capacity circuits, such as T1 over paired copper conductors. Television was delivered over coaxial cables that delivered analog RF television.

Over the last 10 years, the growth of satellite service, the growth of digital cable, and the beginning of HDTV have all left their signatures on the television outlook. Today, a new delivery technique threatens the TV delivery: Internet Protocol Television (IPTV), and it is rapidly becoming the delivery medium of choice. The traditional ILEC communications industry is now in competition with the cable and satellite providers.

The long-established paired copper conductor distribution plant that is now being used by telcos to deliver Plain Old Telephone Service (POTS) and Internet in the form of ADSL will deliver IPTV.

The set-top box that experienced a stumble is making resurgence in IPTV systems. According to a recent market research report from S2 Data Corporation, more than 66.7 million Advanced Home Networking ports will ship with IPTV Customer Premises Equipment in 2010(1). Advanced Home Networking ports are defined by S2 Data Corporation as both wireless networking and wired technologies transmitting over coaxial, power line and phone line wiring. S2 Data predicts that more than 41 million IPTV CPE units (IP STB, ONT/iNID, and Residential Gateways) will ship in 2010 with Advanced Home Networking technologies. 

In order to provide quality IPTV, a minimum of 25 megabits will have to be available at the side of the house to provide service to 3 standard set-top boxes and 1 HDTV box, plus acceptable Internet bandwidth.

Some telcos have made the decision to provide bandwidth using fiber-to-the-home (FTTH), and I feel that this is the right business plan for new subdivisions that have no other transport vehicles, such as cable or paired copper conductors. In older subdivisions IPTV service is provided over paired copper conductors using a fiber-fed Video Ready Access Device (VRAD) at the cross-connect box fiber to the network (FTTN) and providing the 20+ megabits to the Network Interface. Therefore, in order to benefit from the huge copper subscriber base, it's critical that the telcos maintain a quality, robust copper infrastructure.

The Cable Pair
If you are going to be in the FTTN business, then these concerns must be addressed:

  • The cable pair must be free of DC type faults. That is, any short, ground, cross, battery-cross, or open cable pair must be identified and repaired.
  • The cable pair must show good longitudinal balance. The capacitive balance should be greater than 98 percent and the restive balance should be within 3 ohms. A longitudinal balance or stress test should be greater than 60dB.
  • If IPTV is provided in a 25-pair sub-unit of cable, all other vacant pairs must be free of any DC type fault that would allow interfering signals to corrupt the data stream. For example, a solid tip ground on an adjacent cable pair would allow unwanted AC interference to affect the IPTV service.
  • Any disturbers such as T1 or HDSL must be placed in a separate 25-pair sub-unit. Their high power requirements will knock down IPTV and ADSL.
  • Acceptable bonding and grounding is an absolute must. The shield must have continuity from the VRAD to the Network Interface. The Network Interface must be grounded to the power ground electrode at the residence and must test from 0 to 25 ohms.
  • The distribution plant must be connected to the power company neutral where possible a minimum of 4 times a mile. All pedestal and terminal bonding and grounding connections should be torqued to 40 inch pounds. You cannot effectively do this with a can wrench. T-handle torque wrenches are available in your tool catalog.
  • Good bonding and grounding will not eliminate AC interference, but it will reduce impulse noise, the effect of AM radio, short wave, and ham radio. Solid state protection at the VRAD and the Network Interface can drastically reduce the effect of impulse noise, but will not eliminate it.
  • The only way to effectively eliminate impulse noise and AC interference, especially high frequency AC, is with an Induction Neutralizing Transformer (INT). An INT is a simple, passive device that splices in series with the cable. It is used to mitigate induced AC voltages, currents, or harmonics that may be causing noise or equipment malfunctions or damages.

    Prequalifying Today’s POTS Customers for Tomorrow’s IPTV Service
    Field technicians are dispatched to the customer on a daily basis to install and repair POTS service. A circuit loss test at the Network Interface compared to the loss at the cross- connect box where the VRAD will be placed would instantly qualify the customer for future IPTV.

    If the difference is less than 2.2dB, then that customer is pre-qualified. If the difference is greater than 2.2dB, then that customer is beyond the reach of that VRAD.

    For example, the maximum amount of 26-gauge cable pair that will support IPTV on a VDSL is 4,000 feet of distribution plant. The Circuit Loss at 1004 Hz for 4,000 feet of 26-gauge is 2.2dB. If a field technician measured the loss at 4.8dB and then measured the loss at the cross-box at 3.1 (3.1 subtracted from 4.8dB equals 1.7dB), then that customer is pre-qualified for IPTV if a fiber-fed VRAD is placed at that cross-connect box.

    If you start today with a circuit loss comparison, then you can confidently pre-qualify and deploy IPTV to those customers within the reach.

    Remember: If you’re going to win the game, make sure you have the right equipment. That means the right test sets and your techs must have the right training. Invest in them now and reap the rewards.

    1. June 2006 market research report, “IPTV Customer Premises Equipment - Home Networking Technology Market Analysis and Deployment Forecasts,” S2 Data Corporation.

    Signing Off
    Thanks as always for being such loyal readers. Your letters are all read, and I use the information to make sure I’m addressing the issues that you care about. I want to make your job easier, so let me know what’s on your mind. Contact me at or 831.818.3930.

    About the Author - Don McCarty

    Check out our website ( In addition to providing information about our extensive selection of courses, we are adding an equipment review section and a section on troubleshooting, where we will discuss some interesting cases of trouble. If you have an interesting case, send it along (names withheld by request).

    As always, I appreciate hearing from you with questions or comments on any topics that you think are of general interest to outside plant technicians and managers.

    McCarty Associates
    18281 NE Rainbow Lane
    Newberg, OR 97132
    Telephone: 503.538.2747

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