User`s guide

Appendix

BreezeNET PRO.11

9-35 User’s

Guide

The 802.11 standard does not define how roaming should be performed, but defines

the basic tools. These include active/passive scanning, and a re-association process,

where a station which is roaming from one Access Point to another becomes

associated with the new one

9.5.6 Keeping Synchronization

Stations need to keep synchronization, which is necessary for keeping hopping

synchronized, and other functions like Power Saving. On an infrastructure BSS, this

is achieved by all the stations updating their clocks according to the AP’s clock,

using the following mechanism:

The AP periodically transmits frames called Beacon Frames. These frames contain

the value of the AP’s clock at the moment of transmission (note that this is the

moment when transmission actually occurs, and not when it is put in the queue for

transmission. Since the Beacon Frame is transmitted using CSMA rules,

transmission may be delayed significantly).

The receiving stations check the value of their clocks at the moment the signal is

received, and correct it to keep in synchronization with the AP’s clock. This

prevents clock drifting which could cause loss of synch after a few hours of

operation.

9.5.7 Security

Security is one of the first concerns that people have when deploying a wireless

LAN. The 802.11 committee has addressed the issue by providing what is referred

to as WEP (Wired Equivalent Privacy).

Users are primarily concerned that an intruder should not be able to:

• Access the Network resources by using similar wireless LAN equipment

• Capture wireless LAN traffic (eavesdropping)

The BreezeNET product line provides a patented enhanced roaming mechanism which allows stations to roam at

speeds of 60 Km/h without losing or duplicating packets.