DSL/cable modem update - TvTechnology

DSL/cable modem update

With existing systems in place, it would cost broadcasters about $2 per user to distribute a movie. Cable modems, or Digital Subscriber Lines (DSL) which
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With existing systems in place, it would cost broadcasters about $2 per user to distribute a movie.

Cable modems, or Digital Subscriber Lines (DSL) — which will prove dominant in the broadband market?

The answer seems to be a resounding “neither.” Last year approximately 2.5 million DSL lines and about 3.5 million cable modems were in place. There appears to be little argument they can coexist, and the main question seems to concern how to best use infrastructure already deployed by the telcos and cable companies.

Many in the industry want to know when the technology's growing pains will be worked out and afford users more services, such as video-on-demand and games. Several factors must be analyzed before making any estimate, not the least of which concerns distance: just how far signals can be pumped via copper phone lines, or how far cable can (or will) be laid.

In rural areas, laying cable is very expensive, and phone lines, technically, can only take the DSL signal out about three miles. In major metropolitan areas, however, given the high density, a firm laying ten miles of infrastructure can ensure easy access to many buildings or consumers.

However, according to Robert Beliveau, product marketing manager for Copper Mountain Networks in Palo Alto, CA, cable companies do not always serve businesses. In this case, DSL may be an option for those businesses in need of phone lines and data networking, provided phone companies make DSL service available.

It makes sense economically for them to do so, as businesses often pay a bit more than consumers for basically the same service. It only costs consumers about $50 a month for DSL or a cable modem. For businesses the range is often $200 to $500 a month for DSL.

Beliveau noted that in the early days of DSL, cities like San Jose, Boston, Washington, Chicago and Los Angeles were hot spots, due to the major concentrations of people and businesses in these areas, which meant hundreds of thousands of people were reachable by a central office.

But there are only so many major markets, and smaller markets offer slim returns, if any. Also, after a couple of miles, high speeds dissipate. That's fine for the average Internet user, but businesses need symmetrical lines, since consumers surf to them and employees surf everywhere else.

So, along with the old copper phone lines already in place for DSL users, out come the multiplexers and D-SLAM, a digital subscriber line access multiplexer. While they are costly — approximately $10,000 for the basic platform and $200,000 for an elaborate system — they are not as expensive as laying new copper. Most of the cost is backhaul, at any rate.

Cable also becomes expensive when upgrading old systems or laying out additional infrastructure for small markets. Symmetric vs. asymmetric bandwidth is an issue as well, as much of the cable data runs only one way, from the company to the home. Cable plants, however, are set up for high bandwidth going out and lower returning to the headends.

Now back to DSL, which has two generic classes of symmetrical technologies (S-DSL, H-DSL 2 and the new standard, G.SHDSL) for business services, with equal bandwidth in both directions. There also are two assymmetric versions — ADSL using Discreet Multi-Tone (DMT) modulation and G.lite (lightweight ADSL), which is up to 2Mb downstream and 512Kb back upstream. The lower speed makes it more economical and requires less power to the modem.

But there are other ways and means to distribute the DSL signal. San Jose-based Symmetricom offers a way to maximize bandwidth via copper. It is 8Mb when it leaves the central office, 1Mb on the return. It too attenuates, meaning users cannot tap into the higher frequency. At 9,000 feet it drops from 8- to 1.5Mb, and it is lost altogether at 12,000 to 18,000 feet.

To bridge the gap, Symmetricom markets the telcos with GoLong, an active component allowing users to double reach and triple deliverable bandwidth via split signal amplifications. (See Figure 1.) Ironically, it is similar to cable firms boosting their signal. It works for broadband Internet up to 30,000 feet, which Don Skipwith, vice president of business development for Symmetricom, noted covers more than 97 percent of all copper loops in the United States.

Another concern is what can be done to improve video. The phone companies are investigating providing two TV channels, broadband Internet and voice over a single pair. Unlike cable TV, the channels are video-on-demand. So users can have the TV and computer operating independently, along with phone service. It requires 6Mb which, again, roll off from 3000 to 5000 feet. Normally, 6Mb are needed to send the video signal 12,000 feet with GoLong.

Such technologies boost an already rising market. Projections for DSL and cable modems vary, but they are huge. While the latter got a roughly two-year jump on DSL, many analysts maintain that DSL sales will surpass those of cable modems in five years.

Numbers obtained from Verizon reveal that 70 percent of the mass (consumer and small business) broadband market uses cable modems, with the rest using DSL (28 percent) and some satellite. Fiber optics and wireless also will come into play over time.

Yet there are other kinks to be smoothed over as well. One source noted that data rates of DSL and cable vary dramatically and are almost never reliable. Everything along the path — D-SLAM, DS-3 connection, backhaul — tends to be oversubscribed, resulting in an uncontrolled network that cannot do live video (aside from interview shows) reliably and cuts out on occasion.

Even then, the Internet runs reliably at 200,000- to 300,000Kb, about a third of what is needed for a talking head. Full-screen video calls for at least 750,000Kb, so if the user buys up to 10Mb on cable, or 7Mb DSL, the Internet itself will limit the picture. One possible solution? To deliver video from a server inside each individual network.

Today, full-screen video requires cooperation from the network (except in programming) and servers and will probably be limited to between five and 10 percent of users on the network at once, since networks are not robust enough to deliver megabits to all users simultaneously. This means that broadcasters will need to have a costly arrangement with network operators (AOL, Verizon, Time Warner) to reach users.

Technology will solve the problems via upgrades eventually, but the infrastructure is so large and the business deals so uncertain (worth tens of billions of dollars), it will cost broadcasters about $2 per user to distribute a movie — appropriate for a huge event, but too much for the average show.

Mark R. Smith is a freelance writer and has covered broadcasting and post production for a decade. He resides in Odenton, MD, and can be reached atmsmith1277@aol.com.