III.

New Technologies with Larger Bandwidth

By the late 1990s, a variety of other technologies became available that vastly improved bandwidth to 1.5 mbps or more. Cable modems send data back and forth over a cable television network using broadband technology, in which multiple signals, or channels, are sent over a single coaxial cable. Cable television companies allocate one of their cable television channels for sending data to their cable modem users. A second channel is used to send information back. Cable modem technology can send data from the Internet out to its customers at speeds as high as 30 mbps. However, that bandwidth is shared by all the cable modem users in a particular neighborhood, which may range from 500 to 2,000 subscribers. The actual bandwidth that most cable modem users experience when they retrieve, or download, information from the Internet is generally in the range of 200 to 400 kbps.

Digital subscriber lines (DSL) send data over the same telephone lines that carry regular telephone traffic. There are many different types of DSL. The most popular types can share a pair of telephone wires with a regular voice telephone service. This type of DSL uses broadband technology to send a radio-like signal over a telephone line. This signal cannot be heard, so the telephone line can be used simultaneously for both voice calls and computer connections. DSL connections range in speed from 128 kbps to 6 mbps, with the most common speeds ranging from 384 kbps to 1.5 mbps. Newer DSL technologies that use fiber optics can provide download speeds as high as 50 mbps.

Not all technologies with high bandwidth rely on telephone wires or cable. Wireless services use radio waves to transmit information. Cellular telephones have been able to transfer data to compatible modems at speeds of about 9.6 kbps. Wi-fi provides wireless connections between computers and wired connections to the Internet. The data transfer rate can vary depending on the standards used, but 11 mbps to 54 mbps are commonly available, with rates exceeding 100 mbps possible. Multipoint Microwave Distribution Service (MMDS) systems use microwaves to provide computer communications to fixed locations. MMDS provides data speeds similar to those of cable modems and DSL. Satellite dish television companies can also offer two-way wireless Internet access via satellites that orbit Earth over the equator. These services can transfer data from the Internet to a home computer at speeds of 400 kbps or higher.