Broadband Internet Service Choices

Cable is a popular choice for broadband Internet. It's much faster than dial-up, with advertised download speeds of up to 1 Mbps, and its price is usually reasonable when compared to other broadband options that range from $30 to $80 ; per month. The drawback is that cable Internet is not available everywhere, because it is limited to areas serviced by cable companies that have made the necessary upgrades to their networks to support Internet service.

Cable television providers can deliver Internet over the same lines as your cable television signal because of the way they divide the signal. Cable companies broadcast their signals across a very wide-frequency band. The signal trav1els over a Hybrid Fiber Coaxial (HFC) network from the cable company's, "headend" or distribution center to your home.

Cable companies divide the total frequency band into channels by assigning each channel a small portion of the available bandwidth. They assign 6 MHz of the total signal for each television channel. The cable network can carry hundreds of 6 MHz channels. Usually, they assign one or more channels for the downstream data of Internet service.

Cable Internet service providers install a device called a Cable Modem Termination System (CMTS) at the headend of their network. A CMTS interfaces with an Internet Service Provider (ISP) and encodes Internet data into an MPEG video signal carried in the cable company's broadcast stream. The CMTS also separates data received from customers' cable modems from the cable network and passes it on to an ISP.

Each cable channel is assigned a 6 MHz frequency band

At your end of the network sits your cable modem. The cable modem receives the signal transmitted over the cable line and decodes it into data packets recognizable by your computer. The cable modem usually connects to your computer via a standard Ethernet cable, although some modems can connect via a USB port. You may also be able to connect your cable modem to a wireless AP via an Ethernet cable, but some cable modems must be connected directly to a computer. Your modem also translates data traffic from your computer into an MPEG signal for transmission over the cable line on a specific channel. Put simply, the cable modem enables your computer to "talk" to the CMTS over the cable lines.

The major drawback of a broadband cable connection is that all cable customers on a section of the network are sharing the same channel. As more people in your neighborhood sign up for cable Internet service, you will see your connection speed drop, especially at peak usage times. This is because more and more users are dividing the total capacity (often up to 30 Mbps) amongst themselves, which leaves less bandwidth for each individual customer.

Most cable Internet providers also limit the upstream data capacity to an amount significantly less than the advertised downstream rate, which is often less than 256 Kbps. For most users, this isn't an issue, even if they are using internet phone service while watching TV and surfing the net. Web surfing and e-mail require very little upstream bandwidth. When you view a Web page, most of the data travels from the Web server to your computer, not the reverse. Cable providers limit the upstream rate to prevent users from abusing the service by running Web servers from their homes. A Web server uses considerably more upstream bandwidth because it sends data to browsers when it serves Web pages.

Digital Subscriber Line (DSL) Internet services are broadband cable's chief competitors. DSL service operates over the same copper wires that bring phone service into your home. Because service isn't limited to areas where cable is installed, DSL service is potentially available to more households. However, there are limits to the technology that restrict its use to within a predetermined distance from a telephone company office or switch.

There are many types of DSL technology; the most common type available to consumers is Asymmetric DSL (ADSL). The connection is asymmetric because ADSL provides greater capacity for download than for upload. Symmetric versions of DSL do provide high capacity in both directions, but these are expensive and usually reserved for businesses.

Copper telephone wires are capable of carrying a lot more than the signal frequency used for voice phone calls. The DSL signal can share the same line as your telephone service because the phone company transmits the data signal at a much higher frequency than your telephone's analog voice signal.

Phone companies usually give their DSL customers low-pass filters to install on all the phone jacks that they aren't using for DSL service. These filters block all of the high-frequency DSL signals, which allows only the low frequencies used for voice calls to get through. This prevents interference on your voice calls.

Your phone company has to install special equipment at its telephone exchange and in your home to isolate voice and data signals from one another. At the telephone exchange, they install a device called a DSL Access Multiplexer (DSLAM). In your home, they install a DSL modem, which is actually a transceiver that transmits and receives high-frequency DSL signals.

The DSLAM intermixes and separates voice and data signals on your DSL line. The DSLAM also provides a connection point between DSL subscribers and the Internet. Unlike the CMTS on a cable network, the DSLAM provides a dedicated connection for each subscriber. Because of this, DSL subscribers don't experience a slowdown in service when multiple users are online. If the number of subscribers approaches the maximum capacity for a DSLAM unit, the phone company can upgrade or install additional DSLAMs.

In your home, the DSL modem separates the DSL signal from the voice signal on your phone line and converts it to data that your computer can understand. It also does the reverse by converting data into a DSL signal and transmitting it back to the DSLAM.

It may sound like DSL is the perfect broadband solution, and for some customers, it is. Unfortunately, there are limits to DSL technology that exclude millions of potential subscribers from using it. The major factor limiting DSL coverage is distance. DSL service is typically only available to customers less than 18,000 feet from a telephone exchange with a DSLAM. Often, this distance is less than 15,000 feet.

Part of the reason for this is that the telephone system uses Direct Current (DC) electricity to transmit its signals rather than the Alternating Current (AC) electricity that comes out of the outlets in your house. DC power can't travel as far as AC power. This is why the electrical company uses AC, even though it is far more dangerous than DC. If they used DC, they would have to have more power plants and transmission sites to carry the power to all of their customers.

Phone companies use DC to carry their signals because it introduces less signal noise onto the line than alternating current. Using DC also enables the phone company to store power in batteries and supply the phone system with a steady and quiet source of power even during a blackout.

Because DC has a short range, the phone company increases range by using devices called loading coils, as well as amplifiers and bridge taps. A DSL signal cannot travel through these devices so any customers with loading coils between their home and the telephone exchange cannot receive DSL service.

In some cases, DSL can provide a very fast alternative to cable, especially if the customer is close to the telephone exchange. Because the signal strength grows weaker as it gets further from the telephone exchange, customers at the limit of DSL's range experience significantly slower speeds. Depending on your geographic location and the carriers available, DSL service can range in price from $30 per month to over $50.

If you live in an area where you are unable to get cable or DSL Internet service, and dial-up is just too slow for you, you have one alternative. You can sign up with a Satellite ISP. With a satellite dish, you can access the Internet at much higher speeds than with a dial-up modem. There are two types of service: two-way satellite service and one-way (also known as satellite-return). You must have a clear LOS to the southern sky¡ªwhere the satellite orbits¡ªto use either system.

Satellite-return service uses a modem to send upstream data, like page requests, to the satellite ISP's network operation center (NOC) and a satellite dish to receive downstream data. This works out surprisingly well because most of the data flows downstream when you surf the Web. The drawback is that this service isn't an always-on connection because you still have to tie up a phone line and dial-in. The upload speed also is slow because of the dial-up connection.

A two-way satellite connection uses the satellite dish to transmit and receive via a satellite. Because data flows both ways via the satellite connection, the connection is always on, and the upstream speed is much greater than dial-up.

A satellite connection works surprisingly well; the big drawback is in the latency of the connection or how long it takes data to make a round trip. It takes much longer for a signal to travel to and from its destination via a satellite in orbit than it does to travel over a cable or DSL wire. Because of the latency issue, satellite connections do not work for Internet gaming, and you may not see much improvement in Web browsing over dial-up speeds. However, large files download much faster, often in excess of 500 Kbps.

The initial investment for a satellite system can be steep. It sometimes costs almost $800 with installation. The service itself can cost over $70 a month. You can't install a two-way system yourself; it must be precisely aligned with the satellite and properly grounded. If you live in an area where you can't get DSL or cable and want broadband access, consider trying satellite.

Wouldn't it be great to have a high-speed wireless alternative to cable and DSL? It sure would be great if I could recommend a particular service. At this point, any wireless broadband service alternative would be great, but wireless broadband so far remains mostly hype.

Technically, satellite Internet access is wireless broadband, but what I'm referring to here are terrestrial technologies that don't use satellites to broadcast their signals.

A few startups are trying to bring "last mile" wireless broadband connections to residential users, but real solutions are at least a year away. Early attempts by industry leaders, including Sprint and AT&T, were failures: both companies abandoned their wireless broadband services.

Part of the problem was that the first generations of wireless broadband services were line-of-sight (LOS). These LOS services required that all customers have a directional antenna aimed precisely at the ISP's transmission tower. The setup costs were enormous, and many customers simply had no LOS to the tower. Adding to the cost was the problem of scalability. When a tower reached its capacity, ISPs had to install additional towers. When the ISP moved customers to the new tower, they had to have their equipment realigned.

New technologies are non-line-of-sight (NLOS), and they don't require that users have a clear LOS to their ISP. There are several technologies competing to provide this service, but the IEEE 802.16 (WiMax) is starting to gain support from developers and manufacturers.

For now, residential wireless broadband Internet access isn't available in most areas, but you may see reasonably priced wireless ISPs emerge within the next couple of years.