Appendix A
Hayes Commands
Page
33
©
February 2005
Chapter Six
GLOSSARY
ACK
Acknowledgment.
Access point
An access point is the connection that ties wireless communication devices
into a network. Also known as a base station, the access point is usually
connected to a wired network.
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 amount of "transportation" space an Internet user has at any given
time.
Bridge
Collision
avoidance
A network node characteristic for proactively detecting that it can transmit
a signal without risking a collision.
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. Instead of the signals
transferring in parallel paths from one set of plugs to another, the signals
"crossover." If an eight-wire cable was being used, for instance, the signal
would start on pin one at one end of the cable and end up on pin eight at the
other end. They "cross-over" from one side to the other.
CSMA/CA 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
A method of managing traffic and reducing noise on an Ethernet network.