Field Performance Study of a Regional WiMAX Network for Intelligent Transportation System Applications

ent types and numbers of antennas depending on the required coverage range, direction, and throughput. The CPEs are often engineered differently for indoor and outdoor uses and line-of-sight (LOS) and non-line-of-sight (NLOS) conditions. ITS applications rely on a huge amount of real-time traffic information, which needs a fast, reliable, and easily accessible communication network. WiMAX holds much promise of meeting these requirements. First, known as the “last mile” connectivity for delivering broadband access to customers, WiMAX can support a LOS communication range up to 50 km and NLOS range between 6 and 10 km (1). Second, WiMAX supports a large frequency range from 2 to 66 GHz and flexible channel bandwidth in both licensed and unlicensed spectra, which simplifies the spectrum selection and acquisition process. Third, theoretically WiMAX can provide a data rate up to 75 megabits/s (Mbps) (with each 20-MHz channel), which can support all levels of real-time traffic surveillance or video conferencing needs between different traffic agencies. For instance, the emergency management service is able to have real-time images of an accident location or the victims who need immediate care. Furthermore, the WiMAX network configuration provides a possibility of integrating different traffic agencies working in the same region. For example, traffic management centers, emergency management service, police, and other agencies will be able to collaborate with each other by using the same communication network to save time and increase efficiency. Last, mobile WiMAX technologies can be used in emergency situations when wired or other wireless technologies are not available to support the required communication for traffic monitoring and management as well as backhaul service from one site to another. Wireless sensor technology, using spatially distributed sensors connected by a wireless network, is a promising solution for data collection in a large-scale traffic surveillance system. The general idea of using a wireless sensor network for ITS is to deploy a wireless sensor along the roadside to detect traffic information and then send the information to traffic management centers to support further traffic control operations. Within a WiMAX network, each sensor is equipped with a CPE to receive a wireless signal and transmit messages. No extensive and expensive wired communication infrastructure is needed, thus allowing economical system expansion and easier access to remote and rural areas. The large amount of online traffic information from roadside and traffic management centers over the WiMAX network can provide traffic agencies with high-bandwidth streaming to transmit traffic conditions, such as rapid incident and emergency detection. Not many studies have reported the performance of WiMAX networks with respect to requirements for advanced traffic management Field Performance Study of a Regional WiMAX Network for Intelligent Transportation System Applications