利用拓樸偵測以增進電力線網路路由可靠度

Abstract

電力線網路為一種新興技術，其技術核心為透過一個設備將控制訊號或網路訊號轉換成數位訊號並且在電力線上傳輸。 由於訊號是由電流搭載，因此訊號強度取決於電流強度，不幸的是，使用者時常將同一條電力線分接，導致電流分流，從而使得訊號減弱、傳輸可靠度降低，我們將此電流分流處稱為分支(branch)。 本研究的目的為設計一套演算法，以期達到兩個目的：一為有效率的偵測並正確定位出分支點的位置、二為將分支點轉換為中繼點，以增加網路傳輸的可靠度。

我們針對我們所提出的演算法設計了實驗環境，並且完成實作，證實執行過我們的演算法後，不論有一層或兩層分支，皆能夠正確定位出分支的所在位置。 此外，經由分支點當中繼點轉傳資料的傳輸可靠度，也確實比透過最短路徑傳輸來得高，且網路範圍越廣、分支數越多，進步程度越明顯，從而有效的達到我們的研究目的。

In Power Line Communication (PLC) networks, varying impedance, considerable noise that is not white in nature, and high levels of frequency-dependent attenuation are the main issues. Moreover, multipath effect is another serious problem for PLC because the distribution of power lines is complicated. Multipath is caused by the signal reflection and divergence by the independence mismatching between so many branch lines and different loads. Signal is carried by electric current, and its strength depends on current. The branches of physical power line divides current into multiple streams and makes signal attenuate, which decreases the reliability of data transmission. In this paper, we propose a branch detection algorithm which can detect the location of branches of power lines. We make branch nodes as relays to help our transmission. Our branch detection routing algorithm can dynamically track the state of the power line and the network topology. Cooperating with branch detection algorithm, our branch detection routing can find routing paths with higher reliability and lower end-to-end delays. For the performance evaluation of branch detection algorithm, a test-bed that includes PLC modems with our algorithm are set up. Experimental results show the feasibility of our algorithm.