Nomadix AG 5500 User Manual page 323

AG 5500
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
FCC
the incoming signal at the right time and correct frequency in order to properly receive the signal. Current
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 and URL.
"portal" to the Web site. See also,
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.
Glossary of Terms 311