智慧型運輸系統（Intelligent Transportation System，ITS）利用車載環境無線存取（Wireless Access in Vehicular Environments，WAVE）技術在車對道路系統（Vehicle-to-roadside，V2R) 及車對車（Vehicle-to-vehicle，V2V）的通訊環境下提供即時交通資訊及網路存取服務，而此架構被制定為IEEE 802.11p規格。IEEE 802.16e網路是一個集中式管理控制的系統，主要是為了提供無線寬頻都會網路（Wireless Metropolitan Area Network，WMAN）的服務，且它能使WAVE網路達到最佳化效能。當車載單元（On Broad Unit，OBU）同時擁有IEEE 802.11p及IEEE 802.16e的無線收發器，透過IEEE 802.16e集中式排程的方式可以有效克服IEEE 802.11p的缺點，此集中式排成分為競爭方式的媒體存取控制以及在ad hoc環境下V2R和V2V如何路由的通訊協定。我們提出了一個新穎的方法，名為異質網路排程方法（Heterogeneous Network Scheduling Scheme，HNSS），藉由IEEE 802.16e集中式的管理機制使得不同網路的車載單元可以免競爭地存取其服務頻道且讓它們有較低成本的路由至網際網路存取資源。數值分析及模擬結果都證明我們提出的異質網路排程方法可以增進原本標準的效能。 The wireless access in vehicular environment (WAVE) architecture of intelligent transportation system (ITS) has been standardized in the IEEE 802.11p specification and it is going to be widely deployed in vehicle to roadside (V2R) and vehicle to vehicle (V2V) communication environments in order to provide prompt emergency information and internet services. However, due to the WAVE network employs the IEEE 802.11 contention-based protocol, the obvious drawback of WAVE network is the low channel efficiency. The IEEE 802.16e network, which has been designed as a centralized control system to provide the mobile services in a wireless metropolitan area network (WMAN), is a potential candidate for optimizing the efficiency of WAVE network. As on-board-units (OBUs) equip with IEEE 802.11p and IEEE 802.16e transceivers, the drawbacks of IEEE 802.11p contention-based medium access control protocol and ad-hoc routing protocol for V2R and V2V operations can be resolved by using IEEE 802.16e centralized scheduling scheme. As a solution, we propose an efficient scheme, namely heterogeneous network scheduling scheme (HNSS), which not only allows the OBUs to access service channels in a contention-free manner but also provides OBUs low cost routes to get internet access via IEEE 802.16e centralized scheduler. Numerical and simulation results demonstrate that the proposed HNSS can significantly improve the standard transmission efficiency.
