Wi-Fi裝置在5GHz頻段頻道配置機制之探討

Investigation of channel allocation mechanism for Wi-Fi devices at 5GHz band

何錦淮(Ching-Huai Ho)

指導教授 ： 林信標

國立臺北科技大學/電資學院/電腦與通訊研究所/碩士(2014年)

https://doi.org/10.6841/NTUT.2014.00909

摘要

本論文主要探討無線保真(Wireless Fidelity；Wi-Fi)裝置在5GHz頻段的干擾問題與頻道配置機制，802.11ac標準在80 MHz的工作頻寬下與802.11a/n標準的20/40MHz頻寬通道重疊的情況會經常發生。本論文想藉由實際802.11a/n與802.11ac干擾的量測實驗，來探討802.11ac產品普及後所即將面臨的問題。
在本論文中分別使用無線網路晶片大廠Atheros平台的無線網卡與Broadcom平台的無線基地台，在四種基礎建設模式(Infrastructure mode)架構下的設置，用來模擬實際開放空間多個使用者使用相同頻道通訊時，所產生的干擾現象。在5GHz頻段802.11a/n分別對802.11n/ac的六種連線干擾情境下，量測出實際的無線網路卡效能，利用量測吞吐量的大小作為實驗的效能評估依據。
實驗結果顯示當802.11n使用者互相重疊頻道時，效能皆會大幅下降30%~70%。當802.11n使用者與802.11ac使用者次要頻道重疊時效能會大幅下降92%~97%。另外本論文建立一種用於802.11n的頻道配置機制，並藉由第三方韌體打開無線基地台軟體環境執行演算法程式，並且根據量測實驗結果做為程式判斷依據，除了在面對相同頻道有其他使用者時能夠去選擇其他空閒的頻道，還能夠優先選出對802.11n衝擊較小的802.11a頻道來使用，使吞吐量效能提升將近36%。

關鍵字

Wi-Fi ； 干擾 ； 頻道配置 ； 802.11ac ； 802.11n

並列摘要

This thesis focuses on investigating Wi-Fi devices interference and channel allocation mechanism at the 5GHz band. The overlap with the 802.11a/n standards 20/40MHz bandwidth channel occurs frequently when set to 80 MHz bandwidth on 802.11ac standard. This thesis would like to discuss the interference problems between 802.11a/n and 802.11ac by measurement experiments for the upcoming 802.11ac products.
In this thesis, we use the Wi-Fi card with chipset maker Atheros platforms and wireless base station with Broadcom platform respectively. We use four kinds of infrastructure mode settings to simulate the interference phenomenon rising from actual communication condition in open space with multiple users using the same frequency channel. When set to 5GHz band on 802.11a/n and 802.11n/ac respectively, we use six kind of connection interference scenario to evaluate the Wi-Fi card performance by measuring throughput.
The experimental results show that when the 802.11n users overlapping channels to each other, the performance will be substantially decreased around 30% to 70%. When 802.11n device working on 802.11ac secondary channel, 802.11ac device performance will be significantly decreased around 92% to 97%. In this thesis we also use third-party firmware to enter the wireless base station software environment and run a shell script for 802.11n channel selection. When users use the same channel with another user, the shell script will choose to use other free channels automatically. This could improve throughput performance near 36%.

並列關鍵字

Wi-Fi ； interference ； channel allocation ； 802.11ac ； 802.11n

參考文獻

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