IEEE 802.11 Wireless LAN Roaming Based on Channel Quality Estimation

• Main Authors: Yang-Cheng Lai, 賴彥呈
• Other Authors: Jan-Ray Liao
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/05376944869687101732

碩士 === 國立中興大學 === 電機工程學系所 === 94 === 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). APs connect between wireless LAN and wire LAN. Before a station is allowed to send a data message via an AP, it shall first become associated with the AP. Based on the measured SNR from the probe response packets received from each AP, the station will then select the best AP for authentication and association. After a station is associated with an AP, it will wait until the signal of the AP drops to a threshold and start to rescan for new AP’s. In this thesis, we present a new handoff scheme for 802.11. Station estimates the channel quality periodically and piggybacks its channel information with the transmission packet. After AP receives the information, it has a complete picture of the channel utilization. Then AP uses SyncScan mechanism to send the channel quality information to the sataions with the Beacon frame. When a station wants to associate with a new AP, it will use the information it received and choose the AP with low channel utilization.