Networks that trans-mit signals through the atmosphere via radio frequency (RF) waves
continuum of the electromagnetic waves used for data and voice communication.
collection of frequencies available for communication
describes the relative strength over a three dimensional area of all the electromagnetic energy the antenna sends or receives.
antenna’s radiation pattern
issues wireless signals along a single direction
issues and receives wireless signals with
equal strength and clarity in all directions
uses the leastamount of energy and results in the reception of the clearest possible signal
in wireless signaling is no different from reflection of other electromagnetic waves,such as light.
a wireless signal splits into secondary waves when it encounters an obstruction.
the diffusion, or the reflection in multiple different directions, of a signal. Scattering occurs when a wireless signal encounters an object that has small dimensions compared to the signal’s wavelength.
multiple number of differentpaths to their destination
paths wireless signals take, they are bound to run into obstacles
a transmitter concentrates the signal energy at a singlefrequency or in a very small range of frequencies
uses a relatively wide band of the wireless spectrum
The use of multiple frequencies to transmit a signa
a signal jumps between several different frequencies within a band in a synchronization pattern known only to the channel’s receiver and transmitter.
frequency hopping spread spectrum
a signals bits are distributed over an entire frequency band at once.
direct-sequence spread spectrum
wireless communication falls into one of two categories:
wireless systems, the locations of the transmitter and receiver do not move.
the receiver can be located anywhere within the
a device that accepts wireless signals from multiple nodes and retransmits them to the rest of the network
access point (AP)
In active scanning, the station transmits a special frame
In passive scanning, a wireless station listens on all channels within its frequency range for aspecial signa
a unique character string used to identify an access point.