Appendix B - Glossary - Weidmuller WI-MOD-E-G User Manual

Weidmuller Wireless Ethernet Modem & Device Server WI-MOD-E-G/A User Manual

APPENDIX B - GLOSSARY

ACK
Acknowledgement
Access Point
An access point connects wireless network stations
(or clients) to other stations within the wireless
network and also can serve as the point of
interconnection between the wireless network and
a wired network. Each access point can serve
multiple users within a defined network area. Also
known as a base station.
Antenna Gain
Antennae don't increase the transmission power,
but focus the signal more. So instead of
transmitting in every direction (including the sky
and ground) antenna focus the signal usually either
more horizontally or in one particular direction. This
gain is measured in decibels
Bandwidth
The maximum data transfer speed available to a
user through a network"".
Bridge
A bridge is used to connect two local area networks
together. Bridges are typically used to connect
wireless networks to wired networks. Typically,
bridges will transfer messages between networks
only when the message destination is on the other
network. Messages that are destined for the same
network as they originated on are not passed to the
other network, therefore reducing traffic on the
entire network.
Collision avoidance
A network node procedure for proactively detecting
that it can transmit a signal without risking a
collision with transmissions from other network
nodes.
Client / Sta / Station
A device on a network that gains access to data,
information, and other devices through a Server
(Access Point).
Crossover cable
A special cable used for networking two computers
without the use of a hub. Crossover cables may
also be required for connecting a cable or DSL
modem to a wireless gateway or access point. The
cable is wired so that the signals "crossover",
Rev. 2.16
connecting transmit signal on one side to receiver
signals on the other.
CSMA/CA
Carrier Sense Multiple Access/Collision Avoidance
is a "listen before talk" method of minimizing (but
not eliminating) collisions caused by simultaneous
transmission by multiple radios. IEEE 802.11 states
collision avoidance method rather than collision
detection must be used, because the standard
employs half duplex radios—radios capable of
transmission or reception—but not both
simultaneously. Unlike conventional wired Ethernet
nodes, a WLAN station cannot detect a collision
while transmitting. If a collision occurs, the
transmitting station will not receive an
ACKnowledge packet from the intended receive
station. For this reason, ACK packets have a higher
priority than all other network traffic. After
completion of a data transmission, the receive
station will begin transmission of the ACK packet
before any other node can begin transmitting a new
data packet. All other stations must wait a longer
pseudo randomized period of time before
transmitting. If an ACK packet is not received, the
transmitting station will wait for a subsequent
opportunity to retry transmission.
CSMA/CD
Carrier Sense Multiple Access/Collision Detection
is the access method used on an Ethernet network.
A network device transmits data after detecting that
a channel is available. However, if two devices
transmit data simultaneously, the sending devices
detect a collision and retransmit after a random
time delay.
DHCP
Dynamic Host Configuration Protocol A utility that
enables a server to dynamically assign IP
addresses from a predefined list and limit their time
of use so that they can be reassigned. Without
DHCP, an IT Manager would have to manually
enter in all the IP addresses of all the computers on
the network. When DHCP is used, whenever a
computer logs onto the network, it automatically
gets an IP address assigned to it.
Dial-up
A communication connection via the standard
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