For Everyone Else: Broadband

Broadband is a class of data communications methods. It's also the buzzword of the year in Internet connection circles.

Most computer communications use baseband transmission methods: digital transmission with only one signal per wire. "Most" includes communications between computers and printers, computers and monitors, and so on, and on most types of computer networks.

Newer, faster transmission methods use broadband transmission, where a single wire carries several signals at once. Cable TV, for example, uses broadband transmission, which is why you can use a cable modem and get TV and Internet access at the same time. Your other broadband choices when connecting from home are several varieties of DSL (Digital Subscriber Line), in which both data and regular telephone traffic are carried, simultaneously, over a regular home telephone line. And there are also wireless connections, perhaps the broadest band of all.

If your local TV cable company provides cable modem service, that's probably your best bet, both for speed -- cable modem service is by far the fastest (unless it's vastly oversubscribed) -- and for cost -- it's generally a lot cheaper than other broadband alternatives.

Cable modems are different from normal dialin modems. Cable modems are always external, connected on one side to your TV cable and on the other side to an Ethernet card in your personal computer. The cable company might call the Ethernet card a NIC (Network Interface Card); they will probably provide and/or install it, but they might ask you to do it yourself or have it done.

This all sounds complicated, but your cable company will send a technician, or perhaps two, to your home. They will probably do most of the work of installing and setting up your cable modem and configuring your personal computer to use it.

Cable modem transmission speeds vary. The Home Connections at a Glance table says 1.5 Mbps to 10 Mbps (1,500-10,000 Kbps). You may have seen higher speeds quoted, maybe a lot higher, and here's why. The total downstream (from the Internet to you) data flow rate over cable TV cable is 27-56 Mbps. This is opposed to upstream data flow (you to the Internet), which is always significantly slower over cable TV connections.

That's a lot of throughput, but it's not all yours; you share it with your neighbors. Thus, the number of other connections on your line matters. (It also has security implications. See You've Been Hacked.)

Even if you were the only person on your cable, your actual transmission rate would be limited by the Ethernet/PC transmission rate on your personal computer -- about 10 Mbps -- and/or by the cable operator's Internet connection. For example, mine has a T1 telephone line, which is 1.5 Mbps. Thus the more realistic estimates in the table. But take my word for it, cable modems are still very fast!

DSL (Digital Subscriber Line) is relatively new as a choice for Internet connections in the home. Its speeds are comparable to cable modems and it has some advantages over them, but it also has disadvantages. First, the advantages:

• Assuming that you've got an ordinary telephone line, you've already got the wiring required for DSL in your home -- POTS lines (plain old telephone service). And chances are that your local phone provider offers DSL services.
• Even if your local telephone provider isn't in the DSL business itself, you might have other choices for DSL ISPs. Check out the ACCC's Finding and Selecting a Commercial Internet Service Provider document for links to DSL service-finding sites.
• DSL service isn't shared with your neighbors, so it can offer better peak services and better security than cable modem service.

And then the disadvantages:

• There are strict distance-to-switch limits (the telephony term is "local loop") on all manner of DSL, which can be a problem even in a large metropolitan area like Chicago. (My home in Elmhurst, for example, is OK for G.lite but not for ADSL.)
• DSL service requires a pretty good phone line; it may not work for you if the wiring in your home or neighborhood is deteriorating. The phone company may be able to provide a "clean line" for you, but don't count on it. (Your existing phones may also cause problems, but these problems are easily solved by installing filters at the jack or replacing equipment.)
• DSL service is still in its infancy; its quality varies and I've heard many horror stories about getting it installed. (This is particularly true if you select a DSL provider that doesn't have some connection to your local phone company.)

By far, DSL's best feature is its ability to run over regular telephone lines. It can do this because it uses different frequencies than analog telephones. You can even use your phones for voice or fax at the same time as you're using your DSL Internet connection for data. That's cool!

There are two varieties of DSL listed in the Home Connections at a Glance table. ADSL and G.lite are the varieties most commonly used in homes, but there are many more types of DSL. There are so many, in fact, that we should use xDSL when talking about DSL lines in general. (In the trade, just plain DSL means ADSL.)

ADSL (Asymmetric DSL) is the most common form of DSL. G.lite, a.k.a. DSL-Lite and UADSL (Universal ADSL), is a variation of ADSL that has two advantages for the home market: it has less strict distance requirements, and it's easier to install because it can be turned on remotely. ADSL requires the installation of a splitter in your home, which generally means two service calls to get it going -- one for the phone and another for the computer. G.Lite is also cheaper and slower.

If you can't get cable modem service and are out of range for ADSL and G.lite, you should look into IDSL, which is DSL running on ISDN lines (see below). It supports much longer wires.

ISDN (Integrated Services Digital Network) runs over standard copper telephone wires (like DSL). ISDN was actually a simple innovation. The telephone network is already almost entirely digital, the only exception being the line between the customer and the local exchange. ISDN makes this last segment digital as well. ISDN allows telephone wires to carry two B-channels (bearer channels) of voice or data at the same time at 64 Kbps each, 128 Kbps if both are used for data. Compared to 56 Kbps dialin connections on one hand and the 20 or more times faster cable modems on the other, there's little practical use for ISDN anymore.

And there's also wireless. Don't expect to get it any time soon, but it is on its way. It's competitive in speed, too, in the megabit (Mbps) range. The system to watch for is 3G, the third generation cellular telephone system (the first generation was analog cellular and the second was digital PCS -- Personal Communications Service).

It's hard to say how many homes have broadband Internet connections now, but it's clear that the number is growing fast. In the first quarter of 2000, more than 2.2 million digital modems (both cable and ADSL) were shipped world wide. (That's an increase of around around 38 per cent for cable; 46 per cent for ADSL!)

Comments are welcome; send them top
Judith Grobe Sachs, judygs@uic.edu