Ultrasonic Communication by Applying Binary Frequency Shift Keying to Piezoelectric Transducers
Date Issued
2015
Date
2015
Author(s)
Kao, Yu-Han
Abstract
In recent years, security, comfort and convenience driving experience have become increasingly important. This trend as well as issues of energy saving and environmental protection, result in the popularity of intelligent vehicles with vehicular ad-hoc network. The vehicle manufacturers install transducers, radars and cameras on intelligent vehicles, which operate many functions such as safety system, auto-driving system, and instantaneous navigation. Vehicular ad-hoc network includes several different ways of communication. For example, parking sensors apply ultrasonic communication. The advantage of acoustic communication system is low cost, high system compatibility, less influence on human health compared to radio waves. As a result, such system has increasing importance in the technique of short-distance data transmission. If we combine the acoustic communication system with other wireless communication systems via radio waves, the problem of narrow band can be solved, and a good communication quality can be achieved. The purpose of this research is to establish a communication system that not only detects the signals but also has the ability to transmit information. The system applies binary frequency shift keying to piezoelectric transducers. In the future, we can integrate it in vehicular ad-hoc network system. Once the distance between two adjacent vehicles becomes too short such as getting stuck in a traffic jam or waiting in the queue, vehicles will automatically share the relevant information. For example, vehicles will notify one another when car accidents or breakdowns happened. This research will, first, measure the basic characteristics of ultrasonic piezoelectric transducers and construct the model based on them. In addition, we compare different methods of encoding and decoding so as to ensure the lowest error rate during transmission. Last, we analyze the data error rate of different distances. According to the experiment results, the lower the quality factor of the piezoelectric transducer, the shorter the response time of alternating frequency. Under the circumstance of high bits transmission rate, NRZ-L and filter-type FSK demodulators deliver better performance in the bit error rate. Due to the damping effect of transducers, the bit error rate of first bit and last bit is much higher than that of other bits. Therefore, the data should be encoded via an adequate method to avoid damping effect during transmission. When the distance between two transducers is 30cm, we can achieve 0.19% bit error rate of Chinese characters and 0% of the rate of English words by setting bit duration as 0.15msec. When the distance between two transducers is 45cm, 0% bit error rate of both Chinese characters and English words can be achieved by setting bit duration as 0.2msec. However, if the distance between two transducers is 60cm, we have to set bit duration as 0.43msec to attain 0% bit error rate of both Chinese characters and English words.
Subjects
VANET
Ultrasonic Communication
BFSK
Signal Encoding
Signal Decoding
Piezoelectric Transducer
SDGs
Type
thesis