802.11窄頻實作研究

Abstract

無線網路已經融入生活的一部分，相對於有線網路，無線網路更是提供了可移動的機動性。近幾年，許多身邊的電子用品紛紛加入了無線網路的功能，使得支援無線網路的電子用品越來越多，加上政府與民間機構提供多樣化的網路服務，為生活帶來了許多便利。但是也因為無線產品過多，大部份都使用免申請的工業科學醫學 (Industry, Science, Medical; ISM)頻帶，這當然會有頻道干擾的問題。

多數支援無線網路的電子用品大都支援IEEE802.11g標準，加上微波爐、紅外線、藍芽…等都是定義在2.4G Hz頻帶，這也讓2.4G Hz頻帶的使用變得很擁擠，也就容易造成被干擾的現象，基於這一點，IEEE802.11a標準逐漸的被提高使用率，例如IEEE 802.11a與IEEE 802.11ac 以及車載通訊的IEEE 802.11p都是在5G Hz頻帶開發，但5G Hz頻帶有易衰減的問題存在。

本研究針對5G Hz頻帶傳輸距離較短的部分透過實作縮小頻寬以改善傳輸距離與品質，由原本預設的20MHz頻寬縮小到10MHz及5MHz頻寬做研究，研究結果發現在TxPower為20dB時channel 36分別增加了25%及58%最遠傳輸距離。

Wireless network has become a part of our life. Compare to a wired network, the wireless network provides the mobility convenience. Many 3C products have been integrated with wireless function to provide wireless Internet access capability. However, most of these wireless products, such as microwave、infrared、Bluetooth, etc., are supporting 802.11g standard which using 2.4G Hz band. This will cause the use of 2.4G Hz band becoming crowded, and hence the 2.4G Hz band is very easy to be interfered. That is why the utilization of IEEE 802.11a standard has been increasing recently. For example, both IEEE 802.11ac and IEEE 802.11p are developed on 5G Hz band. The implementation of narrow bandwidth for 5G Hz band is to improve the transmission distance. In this research, we reduced the default 20MHz bandwidth to 10MHz and 5MHz bandwidth for our experiments. The results show that when TxPower is 20dB, the transmission distance on channel 36 increased by 25 % and 58% respectively. Keywords: ISM Band, IEEE, Wireless network, Broad band, Narrow band