Home networks change carriers’ test paradigm

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For the traditional telecom carriers, fiber-to-the-home/node (FTTH/N) opens new territories in installation, testing, and troubleshooting. In the past, the outside of the home provided a clear demarcation point between carrier and customer; the carrier would ensure that the customer had a dial tone, and anything beyond that was the customer’s responsibility. With the advent of triple-play service delivery, those lines have blurred. The demarcation point has moved inside the home and, in some cases, even inside the customer’s LAN, creating a host of new test challenges.

Gone are the days in which a carrier must concern itself with one terminal device, the telephone. Today, carriers are delivering services to awhole host of terminal devices, including PCs, home gateways, set-top boxes, televisions, gaming consoles, and entertainment systems (see Figure 1). Moreover, they now are operating in a multimedia environment. Twisted-pair still is used to deliver traditional POTS, but the carriers now are making use of the existing coaxial cable for video service delivery. They may deliver data services over an Ethernet connection, and they may have to contend with wireless home networks, which are increasingly popular among technology-savvy consumers.

“The home network needs to satisfy requirements that are even more challenging than an office network,” contends Stefan Loeffler, product marketing manager in Agilent Technologies’ Electronics Management Group (www.agilent.com).

The telecom carriers deploying IPTV will be using the home network coaxial cable in a way it hasn’t been used before and at new frequencies, creating new test challenges. According to Bob Heintz, vice president of sales and marketing at Sunrise Telecom (www.sunrisetelecom.com), those carriers adopting an FTTN architecture have “dived into this problem set a little quicker than the fiber-to-the-home folks.”Th 211937

Figure 1. To win triple-play customers, today's carriers must ensure that service is delivered to all the terminal devices in the home, which now include telephones, gateways, TV sets, set-top boxes, whole-home DVRs, gaming consoles, and PCs.

FTTN architectures use a much slimmer pipe to get to the home compared with the unlimited capacity of fiber. As such, they must offer an IPTV service from day one, which requires the use of new components and networking technologies. A residential or home gateway, for example, is required to distribute service throughout the home. The home gateway acts as a router, receiving the VDSL signal from the service provider’s network and then sending the signal via an Ethernet cable or an 802.11 wireless frequency to the customer’s PC. However, the home gateway also must communicate with the set-top boxes inside the home, “and this is where it diverges a little bit from what we’ve seen in FTTH so far,” reports Heintz.Th 211938

Figure 2. A frequency response test is necessary to ensure that the coaxial cable is not crimped, stapled, or punctured by a nail, thereby preventing the cable from transmitting all frequencies equally. This is a particular problem for IPTV transmission.

For FTTN subscribers, the home network requires a high-speed connection to move IPTV traffic between the residential gateway, the set-top boxes, and, as the service evolves, to a whole-home digital video recorder (DVR). Moreover, that high-speed connection must be bidirectional, adds Kevin Oliver, vice president of marketing in JDSU’s Communications Test and Measurement Group (www.jdsu.com). “You have your master gateway, and you have a remote IP box that sits on the TV in your bedroom. That’s an interactive communication. Cable wasn’t really using that wire for two-way communication,” he says, “so not only do [the telecom carriers] have all the challenges that cable traditionally had, but they can’t even assume that just because [the home network] was working for cable or satellite it’s going to work for their service.”

In addition, that high-speed connection carrying video traffic around the house is a coaxial cable, which represents a change for the telecom carrier accustomed to operating in a twisted-pair environment. Today’s carriers are using new protocols as well, primarily developed by the Home Phoneline Networking Alliance (HPNA) and the Multimedia over Coax Alliance (MoCA), to transport IP video traffic over the existing in-home coaxial cable. Heintz compares HPNA and MoCA to the Beta versus VHS discussion in the early days of VCRs. “They both do the same thing, but there are some technical differences between the two,” he explains.

Whether the carrier has opted for an FTTH or an FTTN architecture, the core of the problem is the same, says Oliver. The integrity of the wiring-or, in the case of wireless, the connection-is the carrier’s chief concern. Wiring integrity frequently comes down to shielding. A fundamental shielding integrity problem with a coax cable can manifest itself in numerous ways, notes Oliver. He recalls visiting a home in which the telecom operator had hooked up a video service, and while that service worked fine at installation, the customer called several times to complain about poor video quality on a certain television set. Twice a technician was dispatched to the home, and twice the results were the same: The service was fine.Th 211939

Figure 3. Changes in the home network over time may result in multiple wires serving multiple rooms, some of which may or may not be terminated. Technicians must "map" the home wiring, usually by plugging in numbered taps at each terminal location (in this case, each telephone), then identifying the wires via a handheld test set at the side of the house.

When the customer realized the problem was occurring only between the hours of five and eight o’clock p.m., the carrier dispatched a third technician to test the service at that specific time. “The issue was the shielding integrity of the coax itself, but the source of the ingress was very time-dependent,” recalls Oliver. “It needed people to get home and start using the microwave and the cordless phone. All the activities that you do when you get home generate electrical noise and distortions. In this case, [the electrical noise] happened to be at a similar frequency as [the video traffic] carried over the cable plant.”

Now carriers must worry about not only the terminal devices to which they are providing service but also the everyday appliances in the home. Cordless phones often operate at the same frequency as video. Microwave ovens also can interfere with video transmission-and wreak havoc on a wireless network. “They really blast noise through the wireless spectrum,” notes Oliver. Dave Holly, vice president of JDSU’s Communications Test and Measurement Group, recalls a whole set of cable TV customers whose service was knocked out by a single space heater. “It’s amazing how different devices create different frequencies flying through your home,” he muses.

The most fundamental test for a coaxial cable-from the time it leaves the headend all the way to the home and then inside the home-is a frequency response test. The shielding of a coaxial cable must remain the same distance from the center conductor; if the shielding is crimped, frequency response problems may occur (see Figure 2). Crimping alters the cable’s ability to transmit all frequencies equally. “When you upgrade from an analog video service to an IP video service, you are using different frequencies in different ways,” explains Oliver. A crimped cable “may have worked okay for analog video but not for digital.”

Even before the carrier tests the integrity of the wiring and the impact of service-affecting frequencies, its technicians must first find the wiring, which is no simple task, say the test equipment vendors (see Figure 3). As an example, Oliver cites a home that had been serviced by a cable MSO but now would be serviced by a telecom carrier. The home “had wiring that ran in kind of the homerun to the basement and was hooked up into the different rooms. At one point, the home got a satellite, so you have a wire that ran from the satellite dish from the roof into different rooms. And the homeowners ran their own wire from the satellite,” he explains. “Now the telecom operator comes in and he’s got eight different rooms wired up for TV service, 12 different wires running around the house, and he has to try to figure out which wire he is going to use and which one runs where.”

Because the carriers typically charge additional maintenance fees, “there’s always somebody who figures he is pretty good with this kind of stuff and he decides he’s going to rewire his house himself,” adds Scott Robbins, marketing manager in Fluke Networks’ OSS and Centralized Test Solutions Division (www.flukenetworks.com). “What they typically will do is wire everything even if they don’t connect everything, so you have wires going into rooms with nothing on it. That becomes what we call a bridge tap; the extra capacitance going out actually can affect the bandwidth characteristics coming into the house.”Th 211940

Photo 1. JDSU's handheld Testifier (acquired via the Test-Um acquisition) identifies opens, shorts, miswires, and split pairs in home network wiring, providing the technician simple pass/fail results.

Once you find the wire, you also have to figure out what’s between its end points, says Oliver. Say you have a home that had video service going to two or three TVs originally, but then the homeowners built a bedroom over the garage for which they added a video drop. Maybe the signal is bad, so the homeowners buy an amplifier to amplify the signal. Such a configuration would work fine if the homeowners were getting their video service via RF broadcast from a cable MSO. “But in an IPTV world, they are using home networking standards like MoCA or HPNA to move signals from one master set-top box to these remote TVs,” explains Oliver. “Those don’t go through the amplifier and splitter very well because they need two-way communication, and the amplifiers are one way.” Therefore, the carrier must map the wiring in the home network before it even begins to hook up service.

While the home may represent “the last frontier in testing,” as Robbins puts it, home network testing as a market is still in its infancy. It presents new challenges for carriers, but the kinds of tests required are fairly traditional. For now, technicians are using basic handheld telecom tools-POTS testers, butt sets, and the like. Beyond that, the test equipment companies are adopting various product development strategies.

Recognizing the market potential in home network testing, JDSU acquired Test-Um, whose products would help speed JDSU’s ongoing internal development. “We have been in the middle of deploying video, voice, and data from both [the telecom and cable] operators’ perspectives for years,” reports Holly. “Of course, in the midst of that, you see the battle for the end user intensifying as the cable operators foray into voice and the telecom operators quite publicly and aggressively foray into video. We knew the faster we could get a portfolio-and not just a product or two or three at a time-but a portfolio, that would be advantageous.” The Test-Um acquisition gives JDSU wire-mapping tools and multiwire test instruments, which represent a new class of devices (see Photo 1).

Sunrise Telecom also is developing multiwire test equipment and recently launched the CM750, which integrates “everything from wireless to Ethernet to HPNA to RF video to video-over-IP, physical layer testing, and traditional POTS testing,” says Heintz (see Photo 2). “The product encompasses this whole environment and those six or seven different technologies. The idea is that the technician can go to each point, plug in a test set, and get a red light/green light to determine whether they’re in good shape or not. If they get a red light, it has some diagnostics to steer them in the right direction in terms of troubleshooting that piece of cable or coax,” he adds.Th 211941

Photo 2. Sunrise Telecom's all-in-one CM750 integrates the various tests required for today's home networks, including RF video, wireless, and Ethernet testing, as well as tests for new video transmission protocols like HPNA and MoCA.

Fluke Networks, meanwhile, offers a variety of handheld and wire-mapping devices. However, from “a philosophical perspective in terms of how to test this area, we are looking at all-software solutions so that we can go into a wireless router in a home, for example, and be able to tell various characteristics of what’s going on in that network and then feed that back remotely,” explains Robbins. “Then, at least, when you dispatch [a technician], you’re sure that [the problem] is in the home and not the network. And you’re sure it’s an application and not a network problem.”

Robbins notes that people often talk about the physical layer versus Layer 2 or 3. To test the physical layer, the technician must have access to the media itself, whether it be coax, twisted pair, etc. But “the saving grace here is that because everything is going more and more to IP, if you could test on Layer 2 and 3, that’s pretty much media independent,” he says. “We believe there’s always going to be a physical-layer component that needs to be balanced versus what you find in Layer 2 and Layer 3.”

For its part, Agilent says its primary goal is to follow the path of its service provider customers. “Following this path means providing network test equipment, cable test equipment, laboratory-style equipment that helps simulate and emulate load situations on distribution networks as well as installation and maintenance equipment that goes into the hands of the technician who is debugging a home or distribution network on site. All that is part of our offering,” says Loeffler, who adds that many of Agilent’s customers have talked to him about these new test challenges.

However, despite the challenges, home network testing is absolutely critical-particularly in the case of the telecom carriers who are attempting to wrestle customers away from the cable MSOs. “You’ve got to compel someone to move,” says Holly, “and to compel someone to move, that move has to be smooth.”

And the service has to work, which may be the biggest challenge of all. The early adopters of triple-play services are most likely high-end customers with multiple TVs and multiple service rooms-not to mention high expectations regarding service quality. The more complex the home network gets, the more challenging the carriers’ task. They must provide service, from day one, that is as good as or better than the competition, but under a more complicated set of circumstances. The addition of a home router, for example, “is absolutely akin to a business that puts in a router to do an enterprise-type application,” contends Robbins.

But very few homes have the luxury of an on-site IT manager. “We have a breed of users who are totally unaware of the technology they are using,” agrees Loeffler, “and we have technology that is top-notch to distribute high-definition content into the home.”

All of which requires a shift in thinking on the part of the telecom carriers. The demarcation point has moved from the outside of the house to inside the house, requiring the carriers to take ownership of some of the inner workings of the home network. “And they are willing to do it,” says Loeffler, “because that will be a major barrier for the acceptance of this new technology.”

Meghan Fuller is senior editor at Lightwave.

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