Cisco WAP4410N - Small Business Wireless-N Access Point Administration Manual page 78

Troubleshooting and Help
WAP4410N Wireless-N Access Point with Power Over Internet
Q. 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.
Q. What is the ISM band?
The FCC and their counterparts outside of the U.S. have set aside bandwidth for
unlicensed use in the ISM (Industrial, Scientific and Medical) 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.
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