Chapter 4 Wireless Technology
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Wi-Fi Protected Access
Wireless Application Protocol (WAP) is an open standard developed by
Unwired Planet, Motorola, Nokia, and Ericsson. WAP is used to ensure the safe
exchange of data between a wireless network and a portable Wi-Fi device, such as
a cell phone. WAP technology allows a cell phone to securely exchange data with
the Internet and better protects wireless network systems from hackers, viruses,
worms, and other problems. WAP uses a set of keys to identify a device and to
encrypt the data during the exchange.
Network security and authentication is a very complex subject. There will be
much more about encryption and authentication in Chapter 15—Network Security.
Summary
■ Radio wave and microwave transmissions work on the principle of producing
a carrier wave as the means of communication between two network devices.
■ Modulation is the mixing of two radio signals, typically a carrier wave with a
data signal.
■ Infrared is used in line of sight transmissions and is not susceptible to radio
interference.
■ The FCC regulates the use of the electromagnetic spectrum by assigning
radio frequencies and maximum power ratings to devices.
■ A common source of interference for wireless networks is industrial,
scientifi c, and medical devices that use frequencies in the same range as
wireless networks.
■ Two main classifi cations of antennae based on the shape of the
electromagnetic wave pattern it produces are directional and omni.
■ Radio waves are electromagnetic waves that cover the 10 kHz to 3,000,000 MHz
frequency range.
■ Several transmission techniques are used to communicate between radio
wave-based network devices: single-frequency, spread-spectrum, and
orthogonal frequency-division multiplexing.
■ Spread spectrum is the radio transmission technique that subdivides the
allocated frequency range into smaller units called channels. The two types of
spread spectrum transmission techniques are frequency hopping and direct
sequencing.
■ Frequency hopping avoids interference by changing channels while
transmitting data.
■ Another name for frequency hopping is frequency hopping spread spectrum (FHSS).
■ Direct sequencing consists of 11 overlapping channels of 83 MHz each in
a 2.4-GHz spectrum. Within the 11 channels are three channels with a
22-MHz bandwidth. The three channels do not overlap and can be used
simultaneously.
■ Another name for direct sequencing is direct sequencing spread spectrum (DSSS).
■ Orthogonal frequency division multiplexing (OFDM) is similar to frequency
hopping and direct sequencing and employs multiplexing.
■ A Wireless Access Point (WAP) provides a connection between a wireless
network and a cable-based network. It also serves as the center of communication
in a wireless network.
Wireless
Application
Protocol (WAP)
a protocol that
ensures the safe
exchange of data
between a wire-
less network and
a portable Wi-Fi
device, such as a cell
phone. It uses a set
of keys to identify a
device and to encrypt
the data exchanged.