都會區車載隨意網路下基於紅綠燈之可靠繞徑技術

Abstract

在本篇論文中，我們簡明的介紹和分析車載隨意網路(VANETs)和行動隨意網路(MANETs)之差別，並且討論車載隨意網路的挑戰。我們比較了現有車載隨意網路的繞俓協定，發現封包傳輸率和端至端延遲時間仍有改善空間。由於車載網路中的車輛在道路上高速移動的特性，如何在車載網路的環境中提供穩定的車輛間資料封包傳輸成了一個很大的挑戰。當我們在討論車載隨意網路的資料封包傳輸時，繞徑協定是一個重要的議題。因此，我們提出了一個基於紅綠燈的可靠遶徑技術(TLR)，它利用十字路口作為資料傳遞的基礎，並善用紅綠燈前車輛等候紅燈的特性來提升封包傳輸率。我們也提出車輛在虛擬細胞內接收到資料封包時的倒數延遲計算機制以減少碰撞。在都會區裡，道路十字路口上有紅綠燈。當車輛在等紅燈時，這些靜止的車輛可被用來傳輸資料封包。透過此方法，我們可以得到更好的封包傳輸率，並減少端至端延遲時間。模擬結果顯示，我們提出的TLR分別提升了CLA及RBVT-P十個百分比和二十個百分比的封包傳輸率，以及減少20毫秒和80毫秒的端至端延遲時間。比起TLR，雖然RBVT-R有好的封包傳輸率，但是其端至端延遲時間非常的高。

In this paper, we briefly introduce and analyze differences between vehicular ad hoc networks (VANETs) and mobile ad hoc networks (MANETs), and discuss some challenges of VANETs. Then, we compare existing routing protocols over VANETs to find ways to further improve the packet delivery ratio and end-to-end delay. Due to the high mobility feature of VANETs, the inter-vehicle communication is a big challenge. Routing is a crucial issue when we discuss about data packet transmissions among vehicles. In the proposed reliable routing protocol, traffic light based routing (TLR), we used road intersections as the basis for data forwarding and leverage vehicles waiting at red traffic lights to improve the packet delivery ratio. We also discussed how to compute the backoff delay for reducing collisions when nodes receive data packets in selected virtual cells. In urban areas, traffic lights are located at road intersections. When vehicles stop at red traffic lights, nodes with no mobility can be used to forward data packets to next nodes. In this way, we can achieve a better packet delivery ratio and have a lower end-to-end delay. Simulation results show that the proposed TLR improves the packet delivery ratio by 10% and 20% and end-to-end delay by 20 ms and 80 ms compared with CLA and RBVT-P, respectively. Although RBVT-R has the better packet deliver ratio than TLR, its end-to-end delay is much higher than that of TLR.