User`s guide

Appendix
User’s Guide 9-34 BreezeNET PRO.11 Series
• Passive Scanning: In this case the station just waits to receive a Beacon Frame
from the AP, (the beacon frame is a frame sent out periodically by the AP
containing synchronization information), or
• Active Scanning: In this case the station tries to locate an Access Point by
transmitting Probe Request Frames, and waits for Probe Response from the
AP.
Both methods are valid. A method is chosen according to the power
consumption/performance trade-off.
9.5.4.1 The Authentication Process
Once the station has located an Access Point, and decides to join its BSS, it goes
through the Authentication Process. This is the interchange of information between
the AP and the station, where each side proves the knowledge of a given password.
9.5.4.2 The Association Process
Once the station is authenticated, it then starts the Association Process, which is the
exchange of information about the station and BSS capabilities, and which allows
the DSS (the set of APs) to know about the current position of the station). A
station is capable of transmitting and receiving data frames only after the
association process is completed.
9.5.5 Roaming
Roaming is the process of moving from one cell (or BSS) to another without losing
connection. This function is similar to the cellular phones’ handover, with two main
differences:
1. On a packet-based LAN system, the transition from cell to cell may be
performed between packet transmissions, as opposed to telephony where the
transition may occur during a phone conversation, this makes the LAN roaming
a little easier, but
2. On a voice system, a temporary disconnection may not affect the conversation,
while in a packet-based environment it significantly reduces performance
because retransmission is then performed by the upper layer protocols.