OSP Magazine, July 2007
By Ken Fridley and Yumi Kato, Sunrise Telecom

What You Don’t Know Can Hurt You When It Comes to Home Wiring

Deploying IPTV means dealing with do-it-yourself home owners and the "improvements" they've made to their homes over the years. Chances are, those ingenious homeowners have put in one or two coaxial splitters on their own or made other changes to the original telephone wiring. Unfortunately, these seemingly harmless acts can lead to major headaches for IPTV deployment.

Coax Capers

Do-it-yourselfers can find a variety of coax devices at local hardware stores as well as at major warehouse stores; these can contribute to 4 big mistakes when it comes to IPTV deployment. These coax mistakes usually start with the most common device found in homes and apartments: a splitter. These splitters take 1 cable and divide the signal between 2 cables going in different directions. Often, homeowners will take the original coaxial cable coming into the home for 1 television and use multiple splitters in a cascading fashion: 1-to-2, 2-to-4, and so on. This can lead to these 4 costly mistakes as providers attempt to turn up IPTV in the customers’ homes:

Mistake 1: These unwary homeowners don’t realize that splitters can add to signal loss in the cable. Each port on a splitter is designed to have at least 3.0 dB of loss built into it. This translates into a 50% reduction of signal power. Splitters larger than 2 ports typically have at least 1 port with a 7.0 dB loss characteristic.

Mistake 2: Homeowners may lengthen or extend the cable so it reaches across a room to where the TV is located. Simply purchasing a length of coax cable and fittings from the local hardware store can introduce a number of problems. Even worse, the extension cable may not be of the right quality to support IPTV.

Mistake 3: Typically, the fittings that homeowners choose are inexpensive twist-on ones. The inexpensive twist variety may not support IPTV signals. Better quality compression type fittings require a tool to lock the fitting onto the cable and also may be better suited for IPTV. Homeowners are not aware of that nuance.

Mistake 4: When installing an additional cable, do-it-yourselfers may not use a coax stripper to cleanly expose the center conductor and shielding. In some cases, they may use a simple razor blade or knife. A common result of this action is to "ring", or nick, the center conductor. Even a small nick on the surface of the center conductor may be enough to compromise the quality of the IPTV signal and should be avoided.

Copper Conundrums

Many similar mistakes occur when homeowners make changes to twisted pair wiring. If the homeowner decides to add a second phone line for an office phone or fax machine, he may elect to do the inside wiring. That starts the ball rolling toward two mistakes that can wreak havoc on IPTV service:

Mistake 1: A novice may have knowledge enough to find the twisted pair wiring in the attic, splice into it by twisting the wires with their fingers and securing their work with duct tape. In doing so, the homeowner may use one conductor from one pair and another conductor from another pair, creating a split pair situation with no mutual-inductance twist benefits.

Mistake 2: If a jack is already wired for the new line, the homeowner may purchase a splitter that plugs into the original phone jack allowing two separate phones to work on different numbers. The customer often then purchases a low-cost, non-twisted mounting cord and runs it along the wall or under a carpet to the new phone location.

Why is this a problem? Because low-cost mounting cords and splitters can act like radio antennas, picking up and amplifying signals from cordless phones, radio stations, ham radio operators, microwave, and other appliances. If these signals are in the same frequencies as the services used to provide IPTV to the customer, a service call may likely be the result.

The Realities

If the homeowners documented each and every one of these changes on the original home plan schematics, a technician would have a decent chance of finding the potential problems well before they disrupted IPTV service turn up. However, the sad reality is that schematics don’t usually exist for most homes. Brownfield installations far outnumber greenfield sites, and do-it-yourselfers change, move, and alter their in-home wiring without writing a bit of it down. As such, field techs typically go into a premises fairly blind, having little or no information on the condition or location of existing wiring.

Each of these changes can lead to a host of problems, especially as new digital services are deployed for IPTVs. Older analog video signals were more forgiving to signal impairments. Pictures became snowy as signal strength deteriorated until repairs were made. But because IPTV signals are digital, performance issues are immediate. In general, digital signals work until they can no longer resolve data from background noise. Past this point, the picture may freeze, sounds may disappear, or the image may suffer from pixelization or tiling. The reason this happens is that the data stream coming to the receiver is corrupted or fails to arrive at all.

The result of this is a negative customer experience, especially if it occurs during an important show such as the Super Bowl. And, when the issue is not effectively repaired during the first service visit, multiple repeats can result in a lost customer and harsh critic.

Now, more than ever, physical cable tests are critical - unknown impairments inside the home can degrade the quality of an IPTV signal or cause delays in installation. Whether its single family homes, condos or apartments, there are four simple cable tests that can help shorten installation time, guarantee the quality of the signal, and keep customers happy:

1. Physical Inspection
2. Cable Identification
3. Cable Loss
4. Proof of Performance

Cable Test 1: Physical Inspection

Technicians should view their role as part sleuth and part technician. Oftentimes, obvious problems can be identified simply by looking through the premise and talking with the homeowner. If a tech sees two pieces of coax cable going into the home and three or four televisions connected to coax inside, it’s a sure sign that splitters are being used. The obvious question to ask is if the customer has made any changes himself and if so where was the work performed?

If, for example, the customer mentions that his computer literate nephew was visiting and added another phone jack in the guest bedroom – techs should find out where the jack is located and locate the splice point if the IPTV service will be using the existing twisted pair wiring. If the customer mentions a recent remodel, it should raise a red flag, and may even explain why a suspected splitter isn’t in plain view – it could have been plastered inside a wall.

Talking to customers will generally tell the tech everything he or she needs to know to start identifying any problems or pitfalls. In addition, this conversation gives the tech a unique opportunity to educate homeowners about the special requirements for IPTV, and why the customer may wish to avoid do-it-yourself coax or twisted pair projects once the IPTV installation is completed.

Technicians should know the difference in the types of cabling that are acceptable to IPTV service. There are no shortcuts to doing this correctly. Only a physical inspection will isolate possible problem runs. By talking with the customer, the technician should try to assess whether the customer has any sub-standard wiring. This is important regardless of whether the IPTV service will be fed via twisted pair or coaxial cable:

1. For coax installations, tri- or quad-shield RG-6 or RG-59 cable should be used. Most IPTV recommendations shy away from using cabling of different size and quality. Only compression fittings should be used and all twist-on or crimp style fittings should be replaced.
2. If twisted pair is used to feed the IPTV service, it must be CAT 3 or better rated to eliminate potential cross-talk problems. Depending on the service, a dedicated pair of wires may be required to feed the IPTV signal to the premise equipment. The technician should also replace any corroded jacks that are identified during the inspection.

As a final step, techs should look for visual clues as to the condition of the wiring, especially if it is run on the outside of the building. Has the cable been damaged by weed trimmers? Is it drooping onto the ground, stripped, grounded, and/or rolled over? Is the cable in good condition or has it been chewed by wildlife? Obviously time will not permit a visual inspection of every inch of the cabling, but as much as is practical should be done.

Cable Test 2: Cable Identification

During the visual inspection process, efficient work practice calls for performing cable identification tests to determine which cable run goes where. With any number of connectors and outlets, it’s important for techs to have a clear understanding of where both twisted pair wiring and coax cables go once they leave the gateway or service interface.

There are two tests that can be used for this purpose. Some test platforms include cable identification devices, which plug directly into the outlet, and are numbered for easy identification. Once set up, the tech goes to the main splitter and connects a test set to one individual cable run at a time. The test set will then read out the number and identify the room where each cable terminates. All cables should be clearly tagged or labeled to save time during future service visits.

An alternative technique can be used in place of cable ID devices. If the IPTV service is being provisioned in an apartment or other multiple dwelling unit (MDU), the tech could use a tone generator that attaches at the customer’s living unit and use a receiver wand at the main feed to identify their customer’s cable. All the technician needs to do is wave the receiver wand across the termination point and listen to the set tone to identify which feed belonged to their customer.

Cable Test 3: Cable Loss

Once each cable run has been identified and labeled, it is imperative to conduct a cable loss test to ensure the cable supports the frequency range required by IPTV or any kind of digital signal that may be transmitted. The intent of cable loss testing is to send a set of frequencies from a source transmitter at a known and repeatable level. The test set acts as a receiver and calculates the difference between the power sent from the transmitter and what the test set received. These signals approximate the same high-frequency signal a home networking signal uses.

Cable loss testing is important because, splitters have specific losses designed into each port to equalize the signal on each cable leg attached on the out ports. If there are too many cascades of splitters connected in series to the cable run, the cumulative loss may prevent the signal from reaching the receiver or gateway device. While some loss is acceptable and inevitable, less is always better.

Here are some other general cable testing tips:

• Higher frequencies attenuate (accumulate loss) faster than lower ones. Always follow your local policy guidelines when testing for cable loss.
• The number one cause of cable loss is usually located at the termination points, not the cable itself. Always check for proper compression fittings and check barrel connectors for excessive wear. When in doubt, swap them out.
• If the loss reading is too high, the cable will not reliably support IPTV services, and problems as described previously will result.

For twisted pair installations, technicians need to complete the same comprehensive end-to-end cable loss tests above. Cable loss tests should be performed with all jacks and mounting wires assembled and in place. By doing so, the cable loss test will help identify whether or not any wiring imperfections exist that could potentially cause disruptions.

For xDSL installations, even a phone jack attached too close to the gateway can act as a bridge tap and may degrade the frequency response of the service. xDSL is very sensitive to near end bridge tap situations. If you are on a repair call and the line synchs up fine at the network interface, but fails to synch up at the gateway, check to ensure that your signal is feeding directly to the gateway without any wall jacks attached in between. Without a consistently good signal going into the gateway, reliable IPTV service cannot be assured.

Cable Test 4: Proof of Performance

Once cable loss tests are complete, excess splitters or wall jacks removed or replaced, cabling repaired, and the in-home wiring is correct and complete, technicians should perform a final all-encompassing test to verify that the service performance is of the highest quality. A proof-of-performance test will help ensure that no imperfections exist that can escalate over time and result in multiple service calls. Technicians should complete basic tests, verify the cables, verify the IPTV works, and run standard tests using advanced test sets that sends packets to every node on the home network to verify maximum bit rate, signal to noise ratio, received errors, etc., to check for real-life performance. Cable loss testing verifies that each cable run is in good working order; the final proof-of-performance test stresses the entire home network to verify that weak links do not exist.

Network Testing Your Patience?

As IPTV services evolve, new and improved test systems will make their debut attempting to help reduce or eliminate provisioning and maintenance challenges. Today, companies have a multitude of options in deciding which tools are most important for their technicians to get the job done effectively. However, not all test sets support both coax and twisted pair wiring so it is important for service providers to examine on which platforms they plan to offer their products. With IPTV, it is imperative that whether it is coax or twisted pair, the cable must be tested thoroughly or the results will be sub par. If there is even a thought of providing service on both types of cabling, then a test solution for both should be specified.

Perhaps the most significant decision is whether or not to use a selection of à la carte tools versus an all-in-one solution. Some technicians prefer one brand of test gear over another, but learning and carrying a collection of different test sets may reduce efficiencies offered by equipment that tests all aspects of the IPTV service. The following chart (in print issue) examines the pros and cons of each.

Whether techs use multiple test systems or just one platform that supports all IPTV qualification tests, the important thing is to consistently test for cable performance before turning the new IPTV service over to the customer. If technicians take the time to talk to their customers, clearly identify which cable goes where, test the cable for acceptable loss and perform a final proof-of-performance test, IPTV success can be greatly increased.

Ab out the Author - Ken Fridley and Yumi Kato

Ken Fridley is a sales engineer and Yumi Kato is a product marketing manager with Sunrise Telecom. For more information, please visit www.sunrisetelecom.com.