Cisco Cisco WAP2000 Wireless-G Access Point - PoE Manuale Di Manutenzione

Cisco WAP2000 Wireless-G Access Point with Power Over Ethernet Administration Guide

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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.

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.

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.