Cisco WAP200 Administration Manual page 83

Troubleshooting
Cisco WAP200 Wireless-G Access Point with Power Over Ethernet and Rangebooster
What is roaming?
Roaming is the ability of a portable computer user to communicate continuously
while moving freely throughout an area greater than that covered by a single
access point. Before using the roaming function, the workstation must make sure
that it is set to the same channel number as the access point of the dedicated
coverage area.
To achieve true seamless connectivity, the wireless LAN must incorporate a
number of different functions. Each node and access point, for example, must
always acknowledge receipt of each message. Each node must maintain contact
with the wireless network even when not actually transmitting data.
Achieving these functions simultaneously requires a dynamic RF networking
technology that links access points and nodes. In such a system, the user's end
node undertakes a search for the best possible access to the system.
First, it evaluates such factors as signal strength and quality, as well as the
message load currently being carried by each access point and the distance of
each access point to the wired backbone. Based on that information, the node next
selects the right access point and registers its address. Communications between
end node and host computer can then be transmitted up and down the backbone.
As the user moves on, the end node's RF transmitter regularly checks the system
to determine whether it is in touch with the original access point or whether it
should seek a new one. When a node no longer receives acknowledgment from its
original access point, it undertakes a new search. Upon finding a new access
point, it then re-registers, and the communication process continues.
What is the ISM band?
The FCC and their counterparts outside of the U.S. have set aside bandwidth for
unlicensed use in the Industrial, Scientific, and Medical (ISM) band. Spectrum in the
vicinity of 2.4 GHz, in particular, is being made available worldwide. This presents
a truly revolutionary opportunity to place convenient high speed wireless
capabilities in the hands of users around the globe.
What is Spread Spectrum?
Spread Spectrum technology is a wideband radio frequency technique
developed by the military for use in reliable, secure, mission-critical
communications systems. It is designed to trade off bandwidth efficiency for
reliability, integrity, and security.
A
77