論文提要內容： 隨著無線行動網路的迅速發展，現今使用交通工具作為移動平台的網路通訊系統的車載網路也開始受到重視，要如何有效結合無線基礎建設來提供高品質的傳輸服務已成為重要研究主軸之一。車載網路下的終端設備有較高的移動速度，所以使用者在使用無線網路服務經常會面臨頻繁換手的問題，若每次選取的換手存取點有過長的服務延遲時間將會影響網路服務的品質，對於語音、多媒體等有即時性服務要求的訊務則會大大遭受服務延遲的影響。過去車載換手存取點的挑選往往只依訊號強度指標(RSSI)來選擇則無法將流量有效分散，沒有考慮每次換手存取點本身服務負載量對使用者服務所造成的延遲，而車載網路中有不同的需求的服務類型，在存取點中會有不同程度的負載和不同程度的服務等待延遲，而目前方法無法依不同類型服務的負載來為行動節點選擇合適的存取點。有鑑於此，本篇論文提出服務時延預測的換手機制，使用存取點服務分類的封包排程架構，每個無線服務區域皆由數個存取點事先預建，利用存取點控制器來收集各服務區域的服務情形，本研究依排程機制評估區域內存取點各類服務的負載和服務延遲，能讓有即時性服務需求的行動節點能被分配到等待服務延遲較小的存取點，這樣的負載評估選取到的存取點不僅能減少使用者服務的等待延遲且能讓前方區域負載平衡。 Abstract: With the rapid development of wireless mobile networks, Vehicular Ad hoc Networks (VANET) that uses transportation tools as the mobile platforms has received great attention and how to integrate VANETs with wireless infrastructure to provide high-quality transmission services also has currently become one of the important research topics. The terminal equipment in the VANET has a higher mobile speed, so the mobile node in the network are often face handover frequently. If the handoff AP each selected have long service delay will affect the quality of network service,the voice service,and video service which has real-time request will be influence by the service delay. Previous researches in VANET handoff problem are focus on reduce the latency in scan period, and didn''t consider the service delay cause by the load in the AP and just choose the AP by its RSSI. And not distinguish between different types of services in the VANET, their have different levels of load in each access point will cause different service delay. Currently approach unable choose the appropriate AP for mobile node by the load of each different service. For this reason, this paper uses a packet scheduler for APs'' classified services to present a handover scheme based on service delay prediction. Every wireless service area is pre-established by several APs and the service is monitored and collected by the AP Controller (APC). According to the scheduling mechanism, we can estimate the load and service delay of different service types to the APs in the area. Our mechanism allows the mobile node of real time service needs can be assigned to the smaller access point waiting service delay. Our method can selected access point not only reduce the waiting delay of the network service and make the front area load balancing.
