Samsung SWL-2200U User Manual download pdf (Page 10)

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Roaming

Roaming is a service that allows wireless clients to use the network in motion by

automatically changing the connection from an old Access Point to a new Access Point

when the clients enter in a new cell. During roaming the clients may observe the loose

connection or delay in accessing the resources of the network.

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Scanning, Beaconing & ESS ID

When a wireless client is initialized, it is necessary for it to find and communicate with the

correct group of wireless devices, including AP. At this point, it may search for all the

frequency channels and this process is called

scanning

There may be multiple APs and networks operating at the same time. It may be necessary to

ensure that the station joins with the correct network during the scanning process. To

achieve this, each AP is assigned to be part of a logical group called the Extended Service

Set (ESS). The name of this logical group is the ESS ID. When roaming is operating, there

should be several Access Points as part of the same ESS.

After the power on, wireless clients will listen on its default frequency channel. It will be

listening for

beacons

sent by another wireless station or AP. Beacon is a short message

containing the ESS ID that will be broadcast roughly ten times a second. When the wireless

station hears a beacon and the ESS ID in the beacon matches its own, the client knows that

it is on the correct channel and can communicate with its group. If no beacons are seen, or if

the ESS ID does not match, the wireless client may move to the next frequency channel and

repeat this listening procedure.

In case of direct sequence spread spectrum (DSSS) physical layer, this scanning process

occurs at start up and may also occur when the client roams between APs.

1.3 MagicLAN Overview

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The MagicLAN SWL-2200U

(Mini USB Adapter) ar

e wireless LAN adapter that provide

wireless connection between computers.

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The MagicLAN is designed to operate with IEEE 802.11 (wireless LAN International

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Samsung SWL-2200U User Manual Page 10