Nomadix AG 5000, User Manual, Page: 269 / 286

AG 5000
Glossary of Terms 265
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.
Forwarding Rate
The maximum rate at which 64K packets can be delivered to their destination. See also, Packet , Packet
Switching Network , pps , and Throughput .
Fragment Length (Fragmentation)
Breaking a packet into smaller units when transmitting over a network medium that cannot support the
original size of the packet. The fragment length value should remain at its default setting unless you
experience a high packet error rate. Setting the fragment length too low may result in poor performance.
FTP
(File Transfer Protocol) A standard protocol used for copying and moving files quickly, efficiently, and
securely across public and private networks. An FTP site is one where files are available for downloading
and uploading. FTP sites usually require a secure login (name and password) to gain access.
Gateway
Any device that provides a seamless connection between otherwise incompatible systems.
Gopher
A computer program, and an accompanying data transfer protocol, for reading information that has been
made available to the public on the Internet. Gopher is gradually being superseded by HTML.
Home Page
Usually the first page users see when they visit a Web site (if they address the home page’s URL). A well
constructed Web site will normally consist of a home page that provides a clear and concise overview of
the entire Web site, together with the tools for accessing other pages and topics quickly and efficiently. In
this case, the home page is the “portal” to the Web site. See also,
Portal and URL .
Host
Any computer that provides services to other computers that are linked to it by a network. Generally, the
host is the more remote of the computers. For example, if a user in California accesses a computer in New
York, the computer in New York is considered the host.
ag5000_userguide.book Page 265 Friday, March 4, 2005 3:05 PM