無線網路科技在近幾年來蓬勃發展,新興技術也陸續出現在平常的生活周遭並明顯的改變以往人們使用網路的行為模式,這些新的無線通訊科技除了讓工作的環境更加的便利,也大大提升資訊流通的便利性。隨著IC製程日益進步,網路通訊底層的晶片不但能做的越小且越快,因此如何節省功率的損耗也逐步變成一個明顯的問題,在研究無線網路相關知識的過程中,我們去分析了關於MAC (Medium Access Control)層功率的消耗,發現最主要的部分是浪費在傳送封包之前所需等待的一段DIFS (DCF Inter-frame Space)時間,主要工作是偵測頻道是否為閒置或忙碌 (Idle Listening),透過RF天線接受資料,再經過放大器將訊號放大,以及一連串的運算,最後判斷頻道的狀態。隨著PHY層的速度越來越快,實際傳送真正資料封包的時間將越來越短,因此在一樣的傳輸時間內,浪費在聆聽頻道狀態所佔的時間比例卻越來越大,相對的,功率的消耗亦是如此,主要都花費在不必要的DIFS期間內,而真正傳送資料所消耗的功率卻不多。針對這個問題,在不改變標準的架構下,我們提出了一個低功率閒置偵測系統,以期能夠用最小的更動來減少不必要的功率消耗。屏除讓receiver在DIFS期間一直接受資料處理的方式,新系統只會在DIFS的開始及末端的部分去做完整的資料處理,而中間的過程會進入一段淺眠 (Light Sleep Mode)的模式,透過這個方法減少浪費在DIFS期間所消耗的功率。而最後根據我們的實驗結果以及利用NS-2的模擬,我們提出的系統所浪費的功率只有原先標準的17.1%,確實可以大幅減少不必要的功率消耗。最後,我們改良丁國章學長之前提出的GB-DCF+,採用動態調整資料送的編碼方式,並搭配上我們的低功率閒置偵測系統,來節省功率的消耗,形成一個新的Low-Power-GB-DCF+,已說明我們的方法在分群的網路環境中,亦可以有效的節省能量的消耗。
Owe to the success of 802.11, this popular WLAN technology has been embedded in those power sensitive devices such as smart phones and PDA now. However, the power energy efficiency of 802.11 will be very low especially as the number of active stations is large and the data time will be very short while the PHY data rate of next generation WLAN is ultra high. We owe this poor energy efficiency to the fact that it will consume a lot of idle listening energy in the period of DIFS, and the energy consuming in idle listening is no far less than that of receiving real data. In fact, all works in the idle listening period is space checking only. In order to reduce this idle power consumption, we do not need to receive the data from the antenna, clock recovery, amplifier, demodulation, FFT and to decoder. Instead, we can use a very intelligent scheme proposed in this thesis to check space quickly. Amplifier and antenna play a large part in energy consumption, so our proposed system turns on/off the power of these two components so that we can wake up quickly (because of space checking only) from the light sleeping mode defined in later section quickly. According to the results of our analysis and NS-2 simulations, we can reduce the idle listening energy tremendously to 17.1% of legacy DCF if check space time is 1