- 學位論文
在具網路斷裂之車載隨意行動網路上的IP位址傳遞協定
An IP Address Passing Protocol for Vehicular Ad Hoc Networks with Network Fragmentation
摘要
在車載隨意行動網路(VANET)中，車輛移動管理的目標是有效地減少換手(handoff)延遲的問題，並且維持移動中的車輛能夠持續與網際網路(Internet)連線。在VANETs中，當車輛不能夠透過直接或多重跳躍(multi-hops)中繼方式與同向或對向車輛連接通訊，就會發生網路斷裂(network fragmentation)。當車輛要離開目標基地台的通訊範圍時，因為網絡斷裂發生，車輛沒辦法透過現有IP address passing protocol將IP位址交付到下一台車輛，如此，當車輛進入目標基地台通訊範圍時，車輛就無法獲得前面車輛要交付的 IP地址，所以IP取得時間和network overhead就會增加，造成嚴重換手(handoff)延遲和封包遺失，因此車輛的即時服務就會被中斷，如：VoIP或IPTV。如何延緩IP釋回DHCP的時間是一項非常重要的議題，稱為IP存活時間 (IP lifetime)。當網路發生斷裂時，如果導致handoff latency和封包遺失問題，就會降低網路吞吐量。為了解決這些問題，我們提出了在具網路斷裂之車載隨意行動網路上的IP位址傳遞協定。在高速公路上，每台車輛高速行駛於固定方向下，我們的方法可以延長IP lifetime，並且選擇一個比較快的方式取得它的IP位址。另外，車輛可以透過多重跳躍(multi-hops)中繼方式取得來自同向或對向車輛新的IP位址，就會減少換手(handoff)延遲並且保持網際網路(Internet)的連線。從模擬結果顯示，該提出的方法可以減少IP取得時間、handoff latency、封包遺失率和延長IP存活時間 (IP lifetime)。
並列摘要
The goal of the vehicle mobility management is to effectively reduce handoff delay problem, and keep moving vehicle connecting to the Internet for VANETs. In VANETs, when the vehicles can not continuously communicate with the intended vehicle through directly or multi-hop relays from the vehicle on the lanes of same or opposite direction, network fragmentation occurs. When the vehicle is going to leave the target BS's communication region, the vehicle can not pass IP to next vehicle through existing IP passing protocol because of network fragmentation, so the vehicle can not acquire IP address from the vehicle in front it, when it enters target BS's communication region. In addition, IP acquisition time and network overhead may increase, and create serious handoff delay and packet loss, so the vehicle may break off the real time service, such as VoIP or IPTV. Therefore, how to postpone the time of releasing IP to DHCP server is a very important issue, named IP lifetime. When the network fragmentation occurs, if may cause the handoff latency and packet loss problems, and these problems can lower down the throughput of the network. To overcome these problems, we propose an address passing protocol for VANETs with network fragmentation. In a highway, since each vehicle is moving in a fixed direction at a high speed, our protocol can extend IP lifetime and select a faster way to get its IP address. The vehicle can acquire a new IP address through multi-hop relays from the vehicles on the lanes of the same or opposite direction, and thus reduce handoff delay and maintain the connectivity to the Internet. Simulation results have shown that the proposed scheme is able to reduce IP acquisition time, handoff latency, packet loss rate, and extension of IP lifetime.