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A method to locate the position of the target vehicle with the aid of infrared signal-direction discrimination for short-range vehicle-to-vehicle communications is proposed in this paper. With the use of two one-dimensional (1-D) signal-direction discriminators mounted on a vehicle with a lateral separation between them to measure the coming directions of the signal emitted from another target vehicle, the position of the target vehicle relative to this detecting vehicle can be located by triangulation. The aforementioned 1-D signal-direction discriminator is composed of two planar receiving modules forming a specific geometric structure, which leads to different responsivities of these individual receiving modules for a signal incident from a definite direction. The coming direction of the signal is determined by comparing the signal strengths received by these individual receiving modules. With a proposed hardware and software implementation, the position of the target vehicle can be accurately determined within a longitudinal range of 50 m. Owing to the restriction of the width of the vehicle, the separation of the signal-direction discriminators mounted on the vehicle cannot exceed 1.8 m. This leads to the consequence that in the remote region any small inaccuracy of the measured signal directions may cause very large position error. However, our measured results reveal a specific characteristic of the distribution of the measured positions for the target vehicle at a definite location. This allows us to design deliberate statistical algorithms to accurately extract the position of the target vehicle in the remote region. Using the simplest statistical algorithm, we are able to locate the position of the target vehicle with acceptable accuracy within a longitudinal range of 80 m. In this paper, we show the feasibility and applicability of this method. Furthermore, improvement is foreseeable with more deliberate design of hardware and software. [ABSTRACT FROM AUTHOR]

In this paper, we propose a reliable method to determine the coming direction of an infrared signal, where the direction of the signal sent by the vehicle relative to the receiver is determined by amplitude comparison. We utilize a simple symmetric structure comprising four identical planar receiving modules, each with a specific tilt angle relative to the receiving plane, to construct the receiver. The coming direction of the signal is extracted by comparing the signal strengths received by these four receiving modules. With the aid of a simple geometric relation, the trajectory of a vehicle is tracked, i.e., its positions are located, from the coming direction of the signal originated from this vehicle when it travels through the communication area of the system. For several vehicles simultaneously appearing in the communication area, the vehicles can be distinguished in the frequency domain from different frequencies sent by different vehicles. Our signal-direction discriminator proposed in this paper is able to locate the position of the vehicle in a communication area of 6 m in width and 20 m in length. In the lateral direction, this area sufficiently covers a typical traffic lane; in the longitudinal direction, it meets the general requirements of shorter than 20 m for common short-range vehicle-to-infrastructure communication systems, such as electronic-toll-collection applications. [ABSTRACT FROM PUBLISHER]

According to our measurements, the radiation pattern of many low-cost commercial light-emitting diodes (LEDs) is not smooth. Some LEDs even have serious irregularities that affect the performance of infrared communication systems. For systems where a definite communication area is required, such as electronic-toll-collection (ETC) applications, this problem is particularly serious. In this paper, we first present our measured results for the radiation pattern of several typical low-cost commercial LEDs, showing that almost all of them are irregular to some extent. We then use the most acceptable model with a suitable half-intensity angle to construct the emitter of an ETC system. The design was calculated with the aid of an optimization algorithm to determine the mounting angle for each LED such that the system has an extended communication area in the longitudinal direction, i.e., in the vehicle traveling direction, and can withstand high signal attenuation. For a typical LED with half-intensity angle \Phi1/2 = 13^{\circ}, a very simple two-group structure for the emitter is obtained, and the analysis results are verified by experimental measurements. [ABSTRACT FROM PUBLISHER]

Based on our previous works in the design of an infrared emitter for electronic-toll-collection (ETC) applications, we use the unidirectional \cosine^n functions to approximate the irregular radiation pattern for typical infrared low-cost commercial light-emitting diodes (LEDs) with a half-intensity angle \Phi1/2 = 10^{\circ}. With the aid of this approximation, the main characteristics of the performance of an infrared ETC system utilizing this type of LED as the emitter can be investigated based on the received signal strength of the system. For on–off keying, a simple model connecting the received signal strength and the bit error rate (BER) of the system is further established. From the calculated or the measured received signal strength of the system, it is not difficult to estimate the system performance in terms of the BER by this simple model. Roughly speaking, for a typical setting of the circuit parameters and a typical uplink and downlink data-transmission protocol, the data transmission can be very successful in terms of a very low BER if the received signal strength is 1.3 times stronger than the signal strength received at the communication boundary. The emitter presented in this paper is able to produce a relatively extended communication area in the vehicle-traveling direction, resulting in longer communication time interval for the data transmission between the onboard unit (OBU) and the roadside unit (RSU) than conventional emitters. Furthermore, the design presented in this paper is validated by experimental measurement to demonstrate its effectiveness. [ABSTRACT FROM PUBLISHER]