車輛網路研究已經是越來越普及的一環了。有越來越多的車輛大廠 [23] 目前都有研究如何在行車中能夠更加有安全的防護、或者是像利用衛星導航來協助停車等等。雖然有很多學者都有詳細探討相關的問題，但我們所關心的仍然是將所需要的訊息及資料越快的散佈在整個車輛網路中越好。資料的傳播主要是由Routing Protocol來決定，例如像是AODV，需要先知道由來源端至終點端的路徑才能將訊息傳送出去，另外如NOAH，需先將車子傳送的路徑寫好在檔案中，但在車輛網路系統中，有很多不確定的因素，例如車子行進的方向，行進的速度等等。故若使用先將路徑規畫好的方式則不適用在我們的環境中。我們這篇論文主要是來探討透過車輛與車輛之間的互動來傳遞訊息。像是在有線網路中有名的BitTorrent。每台車子之間假設都有儲存訊息的裝置，這樣一來若在車子的密度小的情況下則可以先將資料存放在裝置中，等到有機會遇到其他車子時再將資料傳送。至於傳送的準則我們利用網路編碼的方式，將原始資料切割成數十個或數百個片段，編碼則是每次將這些片段搭配隨機產生的系數整合起來再傳送出去，這樣一來，每次所產生的編碼封包都會有不一樣的結果，即使遇到網路塞車的情況下，其中一個片段被丟棄了也無所謂，只需要再透過其他的車輛再產生不同的網路編碼封包即可。而對此原始資料有興趣的車子則可以將所收到完整的片段解碼即可。至於我們使用的Routing Protocol則是DumbAgent，也就是不需要先規畫好路徑，只需要將收到的封包往Transport Layer或是Mac Layer送即可。最後我們透過不同的車輛分佈來詳細探討其效能結果。

Vehicular network system has been a hot topic recently. There are more and more vehicle companies [23] like Mercedes-Benz focusing on how to safely drive or using GPS to assist parking. A lot of researchers have also researched many issues in this field. What we care about is that how to disseminate messages as soon as possible throughout the entire network. Routing protocols are used to achieve that. AODV is a pre-defined protocol which means that we have to set up at least one route from the sender to a destination, the message is then sent. Noah also needs to establish routes in the file which is loaded while running the transcript script in NS2. In VANET, uncertain things such as directions, or speeds change constantly. Hence, pre-defined routes are not suitable for us to focus on. In this thesis, we concentrate on how to interact between cars to transmit messages. The famous software in wired network is BitTorrent. We suppose that there is a storage in each car, when the car density is low, it stores received messages in it until it encounters other cars then forwards the messages in the storage to them. Network coding is another way for us to use. We cut the file into smaller pieces which are encoded with randomly chose coefficients and then are sent out. According to network coding, the encoded packets are usually different, thus, if an encoded packet is lost, the car can still receiver other encoded packet to decode as long as it receives the full pieces to recover the original file. The least but not the last, the routing protocol we use is DumbAgent. Basically, it doesn’t do anything, just simply forward the received packets to upper or lower layer.

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