The Internet has grabbed on to the world and it isnt letting go. Nearly 36 million U. S. homes currently have PCs and everyone is dying to jump on the information superhighway. The Internet, which started as a group of government agencies and universities, has grown to include almost anyone, from home users to large companies and everyone in between. It makes sense then that providing Internet service is big business.
The service which used to be dominated by groups of nerdy computer whizzes using equipment in someones basement is now being provided by many telephone companies, large on-line services and may oon be available from you local cable company. Computer users are an impatient group. They are starving for a faster way of connecting to the net. Until now home users have had to suffer with the slow connections available with analog modems or spend a relatively large amount on having a digital line, such as ISDN, installed and then continue paying a lot for the monthly charges associated with such lines.
Standard analog modems have always been hindered by the bandwidth they are allowed to use. Standard voice grade phone lines use the frequency spectrum between 0khz and 4khz to transmit their signal. 33. kbps modems packed nearly 11 bits of data per hertz, a remarkable feat, which is very near the theoretical limit. To allow faster connections modems must use a wider bandwidth. Two new competing technologies are now being developed which use this broadband idea to give computer users the speed they crave.
Telephone companies are working on developing a way to use the standard twisted pair copper wires that now connect nearly every home in America to transmit data at high speeds. These technologies, collectively called DSL, come in two main flavors. ADSL, this is an acronym for asymmetric digital subscriber line, is the most common. This name was coined by Bellcore in 1989. The other main type of digital subscriber line is called HDSL. It stands for high-bit-rate digital subscriber line.
These two technologies are essentially the same, except they apportion a different bandwidth to upstream (user to network) and downstream (network to user) data transmission. Concurrently, cable television providers are working on technologies to allow them to connect computers to their network and allow users to connect to the Internet at speeds just as high. Such equipment is being called a cable modem. Cable modems offer the possibility of transferring data t rates up to ten megabits per second, a speed nearly ten times faster than that of ISDN and about twenty times faster than todays fastest analog modems.
This number is somewhat misleading however. The truth is that in order to actually achieve that speed you must be the only user on the network. The reason for this is that this throughput is shared by everyone connected to a given line. Typical cable systems serve 500 to 2500 homes on one line. Therefore the actual throughput will depend upon how many other people in your neighborhood are also trying to access the net. Actual speeds vary greatly. Cable modems are already being used in several limited areas, mostly large metropolitan areas, especially in Southern California.
According to research by The Yankee Group there are approximately 25,000 people already using cable modems. They expect this number to grow to around 275,000 by the end of 1998 (Tedesco). The reason cable modems are not already widespread is that they present a bigger technical challenge to cable operators than anything theyve ever faced. Cable companies do not have a very good track record. Theyve given us lots of unfilled promises 500 channels of television, nteractive television and low priced telephone service. Before cable operators can offer service to cable modems they must upgrade their network.
Only about fifteen to twenty percent of existing cable networks are modem-ready. The rest will need to spend a great deal of money upgrading connectors, transmitters and sometimes wires. The biggest problem is that most cable networks were not designed to handle two-way communication. The amplifiers that strengthen the signal on its way to homes only operate in one direction. These amplifiers must be upgraded to work in both directions before cable modems will work. Cable modems are a box that is xternal to your computer.
They are currently being produced by manufacturers of TV top cable boxes, such as Scientific Atlanta and General Instrument, as well as manufacturers of computer components, such as 3Com, Intel and Motorola. To connect to a computer, cable modems require an Ethernet network interface card because the standard ports on a computer are too slow to handle data at these speeds. So, from the computers point of view it is on an Ethernet LAN. This makes configuring the computer quite easy. The network interface card will send Ethernet packets to the cable modem.
The modem will then modulate the data and send t out over the coaxial cable as an RF signal, just as cable TV signals are transmitted. One small problem with this scheme is that typically this data is carried via a low-frequency band that hasnt previously carried a TV channel. These low frequencies are very susceptible to noise from common household electrical devices. Cable modems will be somewhat expensive when compared to the analog modems being used by most computer users today. According to Bruce Leichtman, broadband technologies analyst for The Yankee Group Its a Lexus product and its priced accordingly. Tedesco) Generally, there will be an nstallation fee of about $150 which will pay for the network interface card and the installation by the cable operator. Users will then pay $34. 95 to $59. 95 per month for the service, which will include the use of a modem provided by the cable operator. This charge is sometimes cheaper when coupled with cable television service, in some cases as low as $19. 95. One of the biggest differences between cable modems and digital subscriber lines is the number of lines available to each.
There are over 600 million telephone lines installed in the U. S. today. No more than 12 million homes today can handle cable modems. Although this number is growing steadily, it is not expected to catch up with telephone lines for many years. Digital subscriber lines currently are not available anywhere except in a very few test markets. Bell Atlantic has been testing ADSL in Northern Virginia for the last few months. Users have been paying sixty dollars per month, this includes the use of an ADSL modem running at 1. 5 mbps.
They plan on rolling out ADSL across their six-state mid-Atlantic region in mid-1998, at which point the data rate should be increased to 6 mbps. Customers will have to provide their own modem. The price for this service has not et been determined. Pacific Bell is also about to launch ADSL service in San Francisco and Los Angeles. They have been testing the service in East San Francisco and Palo Alto. U. S. West plans to debut HDSL in fourteen cities across its service area very soon, reportedly during the fourth quarter of 1997.
It will be priced at $75 to $150; depending on the amount of throughput the user requires. The user will be required to supply the modem. Telephone companies will also have to upgrade their networks before digital subscriber lines can become widespread. The first thing they must do is remove all loading coils from their lines. Loading coils are electronic devices that cut off all frequencies above 4khz. They were installed years ago as a way of reducing noise during voice calls. These higher frequencies are required by digital modems. There are also several other problems with telephone lines which must be resolved.
These include overlong loops which attenuate signals, bridged taps which are essentially unterminated pairs and cross coupled interference which is crosstalk between wires in feeder cables that run into neighborhood distribution nodes. XDSL modems will work much like cable modems, commonly requiring a network interface card is installed in the PC. Some vendors however, are developing modems that are installed inside the PC and will not require the Ethernet card. The modems work by adding two additional channels to a phone line, giving a total of three channels.
These channels are divided by frequency. The first channel is used for telephone service (POTS). It uses the spectrum between 0khz and 4khz, as is common with telephones. The other two channels are for upstream data and downstream data. They use the spectrum from 4khz to 2. 2mhz; The allocation of frequencies to each channel helps determine the throughput for the upstream channel and the downstream channel. Several other factors will also play a role in determining speed, such as the line length and loop conditions. Therefore, the actual speed will vary greatly.
Generally speeds will range from 192 kbps to 9 mbps, with downstream speeds being greater than upstream speeds because more of the bandwidth is allocated to it. Downstream speeds of about 1. 5 mbps and upstream speeds of about 500 kbps seem quite common. However, speeds as high as 55 mbps have been reported using short loop distances. Pricing for digital subscriber lines is expected to be higher than for cable modems. Prices ranging from $75 to $150 will probably be common. These prices will depend on the throughput of the line and who supplies the modem.
It is expected that most telephone companies will require the user to supply the modem. Modems are in the $300 to $400 price range. Many people are questioning whether the Internets backbone will be able to handle the traffic increase it will see as a result of users having such high speed on ramps to the information superhighway. These technologies will allow users to transmit a lot of data to the Internet but once it hits the net it is subject to the same traffic problems that affect data from standard modems. The fact is that if hese technologies were widely available today the Internet would not be able to handle it.
However it is expected that; by the time they become widely available the net will have undergone sufficient upgrades so that it will not become saturated by this increase in data. There is currently a great deal of work being done to upgrade the Internets backbone. Work currently being done includes increasing server access speeds, improving the backbone and NAP bandwidth, increasing router speeds and introducing ATM into the backbone for much lower latency. Also the size of the Internet is constantly increasing. Telephone companies nstalled an estimated 10 million kilometers of fiber in the 1980s.
Only a fraction of the potential bandwidth has been utilized (Digital Horizon). Both of these technologies appear to be just what many PC users are looking for a way for them to surf the web at increased speeds. Who is going to win the battle between the cable operators and the telephone companies is yet to be seen. Overall when comparing price and performance the cable companies appear to have an advantage but whether they can actually implement the technology is questionable. I definitely wish them luck and hope that they implement the necessary upgrades in my area soon.
