| Summary: | 碩士 === 國立中興大學 === 電機工程學系所 === 95 === The IEEE 802.11 Wireless Local Area Network (WLAN) specification defines two ways to configure a wireless network：infrastructure mode and ad-hoc mode. The infrastructure mode includes an access point (AP) which connects between wireless LAN and wired LAN. Before a station is allowed to send a data message via an AP, it should first become associated with the AP. In conventional IEEE 802.11 protocol, a station associated with the AP that has the strongest SNR. In this thesis, we present a new roaming mechanism based on congestion rate.
First of all, a station estimates the congestion condition periodically and piggybacks its congestion information within the transmission packets. After an AP receives the information, it has a complete picture of the channel utilization. Then it uses SyncScan mechanism to send the congestion information to the stations with the Beacon frame.
In our proposed roaming mechanism, when a station wants to associate with a new AP, it will use the its congestion information and decides whether to roam or not by calculating the congestion rate of every AP. Wireless station can avoid the station that a large number of stations associate with an AP at the same time. Therefore, we can balance the load of each AP.
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