Environmental Engineering Reference
In-Depth Information
for the individual components to be connected physically via wires. Wireless
data communications have found widespread application in water and
wastewater systems, but they also have limitations. First, wireless data con-
nections are limited by the distance between components (radiowaves scat-
ter over a long distance and cannot be received efficiently, unless directional
antennas are used). Second, these devices only function if the individual
components are in direct line of sight with each other, because radiowaves
are affected by interference from physical obstructions. In some cases, how-
ever, repeater units can be used to amplify and retransmit wireless signals
to circumvent these problems. The two components of wireless devices are
discussed in more detail below.
The wireless access point (WAP) provides the wireless data communi-
cation service. It usually consists of a housing (constructed from plastic or
metal, depending on the environment in which it will be used) that contains
a circuit board, as well as flash memory that holds the necessary software,
one of two external ports to connect to existing wired networks, a wireless
radio transmitter/receiver, and one or more antenna connections. Typically,
the WAP requires a one-time user configuration to allow the device to inter-
act with the local area network (LAN). This configuration is usually accom-
plished using web-driven software accessed via a computer.
The wireless network interface card or client is a piece of hardware that
is plugged into a computer and enables that computer to make a wireless
network connection. The card consists of a transmitter, functional circuitry,
and a receiver for the wireless signal, all of which work together to enable
communication between the computer, its wireless transmitter/receiver, and
its antenna connection. Wireless cards are installed in a computer through a
variety of connections, including USB adapters or laptop PCMCIA Cardbus
or desktop PCI peripheral cards. As for the WAP, software is loaded onto the
user's computer, allowing configuration of the card so it may operate over
the wireless network
Two of the primary applications for wireless data communications systems
are to enable mobile or remote connections to a LAN and to establish wire-
less communications links between SCADA remote terminal units (RTUs)
and sensors in the field. Wireless card connections are usually used for LAN
access from mobile computers. Wireless cards can also be incorporated into
RTUs to allow them to communicate with sensing devices that are located
remotely.
Cyber Protection Devices
Various cyber protection devices are currently available for use in protect-
ing utility computer systems. These protection devices include antivirus and
pest eradication software, firewalls, and network intrusion hardware/soft-
ware. These products are discussed in this section.
