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272 Glossary of Terms
Term Definition
AP for proof of identity, which the AP gets from the user and thensends back to the
server to complete the authentication.
ECommerce A business venture between a supplier and its customers using online services (for
example, the Internet). Both parties use online services to conduct business
transactions. Transactions may include generating orders, invoices, and payments, and
submitting inquiries. Also known as Enterprise.
ESS (Extended Service Set) See infrastructure mode.
Ethernet A Local Area Network (LAN) protocol developed by Xerox Corporation in cooperation
with DEC and Intel in 1976. Ethernet uses a bus or star topology and supports data
transfer rates of 10 Mbps. The Ethernet specification served as the basis for the IEEE
802.3 standard, which specifies the physical and lower software layers. Ethernet is one
of the most widely implemented LAN standards. A newer version of Ethernet, called
100Base-T (or Fast Ethernet), supports data transfer rates of 100 Mbps. The latest
version, Gigabit Ethernet, supports data rates of 1 Gigabit (1,000 Mbps) per second. See
also, Mbps.
Fast Ethernet See Ethernet.
FCC (Federal Communications Commission) US wireless regulatory authority. The FCC was
established by the Communications Act of 1934 and is charged with regulating
Interstate and International communications by radio, television, wire, satellite and
cable.
FDM (Frequency Division Multiplexing) A multiplexing technique that uses different
frequencies to combine multiple streams of data for transmission over a
communications medium. FDM assigns a discrete Carrier frequency to each data stream
and then combines many modulated carrier frequencies for transmission. For example,
television transmitters use FDM to broadcast several channels at once.
FHSS (Frequency Hopping Spread Spectrum) One of two types of spread spectrum radio—
the other being Direct-Sequence Spread Spectrum (DSSS). FHSS is a transmission
technology used in WLAN transmissions where the data signal is modulated with a
narrowband carrier signal that “hops” in a random but predictable sequence from
frequency to frequency as a function of time over a wide band of frequencies. The
signal energy is spread in time domain rather than chopping each bit into small pieces
in the frequency domain. This technique reduces interference because a signal from a
narrowband system will only affect the spread spectrum signal if both are transmitting
at the same frequency at the same time. If synchronized properly, a single logical
channel is maintained. The transmission frequencies are determined by a “spreading” or
“hopping” code. The receiver must be set to the same hopping code and must listen to
the incoming signal at the right time and correct frequency in order to properly receive
the signal. Current FCC regulations require manufacturers to use 75 or more frequencies
per transmission channel with a maximum dwell time (the time spent at a particular
frequency during any single hop) of 400 ms.
Flash Memory A special type of EEPROM (Electrically Erasable Programmable Read Only Memory) that
can be erased and reprogrammed in blocks instead of one byte at a time. Many modern
PCs have their BIOS stored on a flash memory chip so that it can easily be updated.
Such a BIOS is sometimes called a flash BIOS. Flash memory is also popular in modems
because it enables the modem manufacturer to support new protocols as they become
standardized.