車輛網路增進吞吐量的傳輸媒介存取控制協定之設計

Abstract

在車輛網路的環境下，車輛可以透過安置在馬路邊的連線設施連接上網際網路。但由於車輛高速的移動性，車輛與連線設施的連線時間相當短。而未來會發展越來越多樣的應用，像是網路電視或是線上遊戲等，都需要足夠的頻寬來滿足使用者的服務品質。因此吞吐量在未來的車輛網路發展裡，會是很重要的一項議題。然而，目前所定義的802.11p協定正有頻道低使用率的問題存在。 在這篇論文中，我們提出了一個可增加系統吞吐量的新網路媒介層協定。這個新協定不僅可以增加頻道使用率，而且可以避免封包傳輸的碰撞。我們也藉由理論分析和模擬來驗證這個協定的效果。由模擬結果可以看出，我們的新協定比過原有的802.11p協定佳。而在安全的議題上，兩個協定都可以滿足延遲時間的限制。

In vehicular network, roadsides units (RSUs) are usually placed along the road for Internet access. However, due to high speed of mobility, vehicles can only connect to RSUs in limited time. Besides, nowadays with quick development of entertainment applications, such as streaming TV and on-line games, these applications would require essential bandwidth to support Quality of Service (QoS). Hence, throughput is an important issue in vehicular networks. However, existing MAC protocol IEEE 802.11p still has a problem with deficiency of bandwidth in urban area, and the main reason lies in low channel utilization. In this thesis, we propose a novel MAC protocol to enhance system throughput. Our proposed MAC not only enhances channel utilization, but also avoids the event of collision. We also evaluate the performance of our protocol via theoretical analysis and simulation. Results show the performance of our proposed MAC is better than IEEE 802.11p. On the other hand, for safety issues, our proposed MAC can also satisfy maximum latency limitation as IEEE 802.11p.