整合多頻道選擇與動態電源控制機制於IEEE 802.11無線隨意網路

Abstract

目前無線區域隨意網路技術是以IEEE 802.11協定為主流，雖然具有簡單、實作成本低廉的優勢，但它基於電源管理的省電模式之效能並不高，且其對電源的使用效率也不佳。在我們所提出的方法中，我們設計了一個高效率的整合機制，E-MCPC，結合了多頻道選擇與動態電源控制，並整合至IEEE 802.11的省電模式中。我們的方法在一個網路密集度高且封包較小的環境下有更佳的效能表現，並且不會因調整傳輸電量而增加碰撞機率。目前的研究主要採用多頻道選擇或電源控制來改善無線隨意網路的存取效能及提升電源使用效率。這些方法皆只能解決單一方面的問題，如減低碰撞機率但電源使用效率不佳，或提升電源使用效率但卻會增加碰撞機率。另外有結合多頻道選擇和電源控制的現有研究，MCPC，其缺點主要是在調整傳輸電量後會增加碰撞機率，且其控制頻道會有嚴重的競爭問題。後者會造成在網路密集度高且封包較小的環境下，其重傳的情形會很頻繁。除此之外，與MCPC相比，我們的機制較易於整合至IEEE 802.11標準。模擬的結果顯示，我們提出的整合機制與IEEE 802.11和MCPC比較， 在無線隨意網路中，在網路流量大且密集度高的環境下，就效能而言，可以分別提高1.2倍和30%，就電量節省而言，可以分別增加2.5倍和2倍的使用效益。

The most popular wireless local area network (WLAN) technology, IEEE 802.11, has advantages of simplicity and low cost, but it has low throughput under power saving mode and low power efficiency as well. In our proposed approach, we design an efficient integrated scheme, E-MCPC, that combines multichannel selection with dynamic power control and is integrated into the IEEE 802.11 power saving mode. Our approach has high throughput when packet size is small in a dense network and will not increase probability of collisions after adjusting the transmit power level. Most existing approaches adopted either multichannel selection or power control to improve throughput or to enhance power conservation in wireless ad hoc networks. These approaches only addressed one single issue, either reducing collisions but with inefficient power consumption or enhancing power conservation but with increased collisions. The main shortcomings of another integrated approach, MCPC, which also combined multichannel selection and power control, are that it increases collisions when adjusting the transmit power level, and will have a serious contention problem on the control channel. The latter would result in frequent retransmission when packet size is small in a dense network. In addition, our scheme is also easier to incorporate into the IEEE 802.11 standard than MCPC. Simulation results have shown that our E-MCPC can achieve 1.2 times and 30% higher throughput, and 2.5 times and 2 times better power conservation compared to the IEEE 802.11 and MCPC, respectively, in a wireless ad hoc dense network with high traffic load.