Mobile Mark wap11 - Manual (Page 22)

FHSS (Frequency Hopping Spread Spectrum) - FHSS continuously changes
the center frequency of a conventional carrier several times per second accord-
ing to a pseudo-random set of channels, while chirp spread spectrum changes
the carrier frequency. Because a fixed frequency is not used, illegal monitoring
of spread spectrum signals is extremely difficult, if not downright impossible
depending on the particular method.
Firmware - Programming that is inserted into programmable read-only mem-
ory (programmable read-only memory), thus becoming a permanent part of a
computing device.
Fragmentation - Breaking a packet into smaller units when transmitting over
a network medium that cannot support the original size of the packet.
Gateway - A device that interconnects networks with different, incompatible
communications protocols.
Hardware - Hardware is the physical aspect of computers, telecommunica-
tions, and other information technology devices. The term arose as a way to dis-
tinguish the "box" and the electronic circuitry and components of a computer
from the program you put in it to make it do things. The program came to be
known as the software.
Hub - The device that serves as the central location for attaching wires from
workstations. Can be passive, where there is no amplification of the signals; or
active, where the hubs are used like repeaters to provide an extension of the
cable that connects to a workstation.
IEEE (The Institute of Electrical and Electronics Engineers) - The IEEE
describes itself as "the world's largest technical professional society, promoting
the development and application of electrotechnology and allied sciences for
the benefit of humanity, the advancement of the profession, and the well-being
of our members."
The IEEE fosters the development of standards that often become national and
international standards. The organization publishes a number of journals, has
many local chapters, and several large societies in special areas, such as the
IEEE Computer Society.
Infrastructure - An infrastructure network is a wireless network or other small
network in which the wireless network devices are made a part of the network
through the Access Point which connects them to the rest of the network.
Wireless Network Access Point
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Instant Wireless TM Series
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Download - To receive a file transmitted over a network. In a communications
session, download means receive, upload means transmit.
Driver - A workstation or server software module that provides an interface
between a device and the upper-layer protocol software running in the comput-
er; it is designed for a specific device, and is installed during the initial instal-
lation of a network-compatible client or server operating system.
DSSS (Direct-Sequence Spread-Spectrum) - DSSS generates a redundant bit
pattern for each bit to be transmitted. This bit pattern is called a chip (or chip-
ping code). The longer the chip, the greater the probability that the original data
can be recovered. Even if one or more bits in the chip are damaged during
transmission, statistical techniques embedded in the radio can recover the orig-
inal data without -the need for retransmission. To an unintended receiver, DSSS
appears as low power wideband noise and is rejected (ignored) by most nar-
rowband receivers.
DTIM (Delivery Traffic Indication Message) - A DTIM field is a countdown
field informing clients of the next window for listening to broadcast and mul-
ticast messages. When the AP has buffered broadcast or multicast messages for
associated clients, it sends the next DTIM with a DTIM Interval value. AP
Clients hear the beacons and awaken to receive the broadcast and multicast
messages.
Dynamic IP Address - An IP address that is automatically assigned to a client
station in a TCP/IP network, typically by a DHCP server. Network devices that
serve multiple users, such as servers and printers, are usually assigned static IP
addresses.
Encryption - A security method that applies a specific algorithm to data in
order to alter the data's appearance and prevent other devices from reading the
information.
ESS - More than one BSS in a network.
Ethernet - IEEE standard network protocol that specifies how data is placed
on and retrieved from a common transmission medium. Has a transfer rate of
10 Mbps. Forms the underlying transport vehicle used by several upper-level
protocols, including TCP/IP and XNS.