Information Technology Reference
In-Depth Information
and do not have Internet access, can they still
connect?
If you find wireless communication available at a coffee shop or
library, there must be an access point in the area; thank the shop
owner or librarian for providing that computer and connection! But
if no computer in a given area has a cable connection to the
Internet, then wireless computers cannot access that technology. An
Internet connection requires some point of access.
However, several laptop computers still could communicate
with each other—at least if they all have wireless capabilities. A
network between wireless computers is called an
adhoc network
.
In an adhoc network, one of the laptops plays the role of an ac
cess point (but without the Internet access); that is, a laptop could
be set up to establish a beacon for a new and independent net
work. Other computers then could issue association requests, and
communication could proceed. In adhoc networks, the initiating
machine (with the beacon) does not relay communications from
other computers, so all computers must be within transmission
range of each other. This simplifies communications, because all
messages go directly to all parties, but the range of such transmis
sions may be limited.
The simplest way to connect two computers utilizes wires going
from one to the other. A simple circuit requires only two wires.
Multiple pieces of information can be transmitted by sending one
piece at a time, but this serial communication can be slow. To trans
mit data more quickly, parallel communication sends several pieces
of data over parallel wires at the same time.
Although, in principle, many types of wire, plugs, and sockets
might be used for cables, standards provide efficient and reliable
communication at reasonable cost. The simplest standard wiring
cable is called RJ11, and it uses four or six wires. Often only two
of these wires are used for telephone and computer communica
