Abstract
In an 802.11p (the so-called DSRC) network, the WSMP protocol is used for the communication between OBU and RSU. Unlike a wired network, an 802.11p wireless network is prone to fading, shadowing, and interferences, which might result in high error rates. However, there is no reliability mechanism embedded in the WSMP protocol, which can become an important issue for mission-critical ITS applications such as ETC (Electronic Toll Collection). In this work, we develop a protocol on top of WSMP to build a reliable session for the message exchanges between RSU and OBU. Our protocol uses a timer-based mechanism for the message retransmission in the case of message losses. In this paper, we first describe the design of our session protocol and evaluate its performance for ETC communication in simulations. We then discuss the implementation of our protocol on the ITRI WAVE box and evaluate its effectiveness on real roads.
Highlights
Since the first electronic-toll-collection (ETC) systems appeared around the early 1990s, the number of ETC systems in the world has grown rapidly worldwide, and there are more than 80 important systems in operation in more than 25 countries [1]
Vehicle identification can be further divided into a vehicle positioning system (VPS) and dedicated short-range communication (DSRC)
The implementation of the VPS of an ETC system is typically based on Global Positioning System and mobile communication (e.g., GSM) technologies, in which the onboard units (OBU) receives the vehicle’s positioning information from GPS, automatically calculates the vehicle’s road usage, and sends fee data to the control center through the GSM
Summary
Since the first electronic-toll-collection (ETC) systems appeared around the early 1990s, the number of ETC systems in the world has grown rapidly worldwide, and there are more than 80 important systems in operation in more than 25 countries [1]. Any ETC system must address the following four aspects to functioning properly: vehicle identification, vehicle classification, transaction processing for collecting the toll, and violation handling [2]. Vehicle identification can be further divided into a vehicle positioning system (VPS) and dedicated short-range communication (DSRC). The technologies used in DSRCbased ETC systems can be classified into two categories: infrared and microwave [4]. For communication between roadside units (RSU) and onboard units (OBU) in ETC systems, several different spectrums have been proposed to be utilized for such an application, such as 900 MHz, 2.45 GHz, 5.8 GHz, or 5.9 GHz for microwave-based DSRC, as well as 870 nm for infrared-based DSRC [5, 6]
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