Broadband and Broadband ISPs

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 (or to the hub of a home network). The cable company might call the Ethernet card a NIC (Network Interface Card); they might provide and/or install it or they might ask you to do it yourself or have it done. Or better yet, get your computer with ethernet already in it.

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 Securing Your Always-On Internet Connection.)

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) 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. (SBC/Yahoo does: http://www.sbc.com/ )
• Even if your local telephone provider isn't in the DSL business itself, you have other choices for DSL ISPs. See Finding an Internet Service Provider, Web Search Sites 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. (But DSL is still an always-on service, which has its own security implications. See Securing Your Always-On Internet Connection.)

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.
• 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's 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 common varieties of DSL. 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 can 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.

The new are wireless Internet connections. One system is 3G, the third generation cellular telephone system, which is now being used in handheld phone/Internet devices. (You've heard of GSM, TDMA, and CDMA? G3 runs over these wireless interfaces.) It's competitive in speed, too, in the megabit (Mbps) range and those phone/PDA/Internet devices are fun. There are also cellphone modems that use this technology. (The first generation of wireless was analog cellular and the second was digital PCS -- Personal Communications Service).

In the wireless camp, we also have satellite Internet connections. (Click on the links in this paragraph for SearchNetworking.com's article about satellite Internet connections.) Satellite is expensive, but if you're in the country and don't have cable or DSL, it is an option. The broadband search link in Finding an Internet Service Provider, Web Search Sites returns satellite providers.

Fixed wireless, a wireless version of DSL, has been tried and mostly found wanting because it requires line-of-sight connections, but some providers are still working on it, including Sprint, which is currently offering fixed wireless services in a number of cities in the US.