Demonstration of a Visible Light Communication System for Underground Mining Applications Gang Wu a, Jian Zhang b

Transcription

1 2016 International Conference on Information Engineering and Communications Technology (IECT 2016) ISBN: Demonstration of a Visible Light Communication System for Underground Mining Applications Gang Wu a, Jian Zhang b National Digital Switching System Engineering and Technological Research Center, Zhengzhou , China; a xdwugang@126.com, b swordrawn@163.com Keywords: visible light communication, underground mining environment, LED Abstract: In this paper, a visible light communication system for underground mining environment is demonstrated. The system structure and corresponding experiment demonstration are presented. Our results indicate that proposed system can provide a useful insight into the future applications for underground mining environment. Introduction With the development of economy, coal is playing an important role in our daily life. And many wireless communication technologies such as WLAN, IrDA, Bluetooth and ZigBee and so on have been widely applied to underground mining environment over the past few decades. But these technologies are inadequacy in the underground applications, for instance WLAN is easily affected by electromagnetism, and needs higher electronic energy [1]; IrDA will be harmful to miners eyes with too high power; Bluetooth is more expensive and also needs high electronic storage; although ZigBee is very flexible and can be used easily, however it has some unstable problems [2]. To enhance the availability of the communication system about the underground coal mine applications, visible light communication (VLC) technology has been considered to apply to the underground mining environment [3]. Due to the characteristics with short response time and high speed on-off keying of light-emitting diode(led), VLC technology based on the fast switch of LEDs can achieve communication at the same time of lighting [4-7]. The environment of underground mine coal without natural light is fully covered by LEDs, and the cough wall have provided incomparable advantages for VLC. In this paper, we proposed a LED-based communication system integrated with power line communication (PLC), IrDA and VLC technologies for underground mining environment. This paper is organized as follows: the structure of communication system is proposed, and then the channel model of the proposed communication system was analyze. Utilizing our proposed system, the demonstration and result could be obtained and the experimental results have proved the communication system is available. The structure of communication system In Fig. 1, we present a block diagram of the communication system that consists of ground part and underground part in the underground environment. The ground part mainly contains workstation which can contact with LED lighting underground mine coal by PLC and ETH, and the

2 underground part includes LEDs and miner s lamps. These two parts communicate with each other through VLC and IrDA technologies. In the downlink, the beacon frame is sent from STM32 to miner s lamp 50 times per second through VLC by STM32 itself. If the workstation wants to send some warning signal to miner, firstly the signal is transmitted to LED through PLC from the workstation, and then it is transformed into the warning frame by ARM9 and STM32, lastly it is sent from VLC transmitter to VLC receiver of miner s lamp through optical signal. In the uplink, the Infrared transmitter transfers different data in different condition. When the VLC receiver receives beacon frame, Infrared transmitter returns positioning frame. And the alarm in miner s lamp sounds, then VLC receiver obtains the warning frame. Infrared also could send the alarm frame if the miner encounters danger, then the work station can get the signal. Figure 1. The block diagram of the communication system. Analysis of system channel In this section we analyze the communication system in theory to confirm whether the project is available. There are two points need to discuss, the horizontal illumination of underground coal mine and the received power of miner s lamp. The model of lane in underground coal mine is shown as Fig. 2. Due to the unique environment, the LEDs are ranked in line. And when the miner walks down the lane, he will pass underneath the LEDs.

3 Figure 2. Architecture of the lane. Next, we will discuss the possible application of the communication system. The width of lane is about 3~5 m, but the scope of the activity of the miner is just about 1 m. The distance between the adjacent LEDs is about 10 m, and the LEDs are installed at a height of 2.8 m from the ground. Each LED is consisted of 4 light chips. The specific parameters are summarized in Table 1. Table 1. Parameters. Number Project Name Value 1 Center luminous intensity/(cd) Number of light chips 4 3 Transmitted optical power/(w) 9 4 Chip interval/(mm) 17 5 Semi-angle at half power/( o ) 70 It is assumed a LED chip has a Lambertian radiation pattern. The luminous intensity of LED is given by m I( ) I(0) cos ( ) (1) The horizontal illumination of the underground coal mine is given by E I(0) cos m ( )cos( ) / D 2 (2) The distribution of horizontal illumination at the ground of lane is shown in Fig. 3 [8]. According to the lighting standard of industrial enterprise, 10 lx is required at least in the general observational production. From the figure, we can see this LED lighting has a function as lighting.

4 Figure 3. The distribution of horizontal illumination. Then we established the channel model of visible light for the proposed communication system. The optical link has been divided into Line of sight (LOS) and Non line of sight(nlos). In the paper, we only consider the effect of direct light. According to the real environment of the underground coal mine, the channel DC gain is given by ( m 1) A m cos ( ) T ( ) g( )cos( ) T 0 2 H(0) a, 2Dd 0, (3) where light transmittance Ta can be given as T a exp( 0.201C) (4) where C denotes dust concentration. The received optical power of miner s lamp is given by P H (0) r P t (5) where P t means the transmitted optical power. Table 2. Parameters. Number Project Name Value 1 Detector s area/cm Refractive index of a lens Gain of an optical filter FOV at a receiver/( o ) 60 5 Dust concentration/(mg/m 3 ) Miner s height/(m) 1.75

5 According to these analyses and the parameters given in Table 2, we can obtain the distribution of received power of the miner s lamp shown in figure 4. From this figure, the received power is 1 dbm at the edge of activity area. When the miner stands underneath the LED, the received power could meet the demand of communication. Figure 4. The distribution of received power. The demonstration and results In the underground mining environment, a demonstration system is built as shown in Fig. 5. The system mainly consists of LEDs and miner lamps. When the miner stands underneath the LED, he can communicate with the station. The communication could implement two main functions, alarm and positioning. Figure 5. The demonstration of the communication in the underground mining environment. To test the communication system, a series of experiments has been done. Through buzzer of miner s lamp, we can make sure whether the miner s lamps receive the warning signal. Through the station we can measure the accuracy of the alarm and positioning, as shown in figure 6 (a) (b).

6 Figure 6. The figure of testing interface. Summary In this paper we proposed a new LED-based communication system for underground mining environment. The system is composed of PLC, IrDA and VLC technologies. And the system provides communication and illumination simultaneously. We have shown the frame of the communication system, and the experimental results have proved the communication system can obtain the performance of the practicability and effectiveness. References [1] Song J., Ding W., Yang F., et al. Indoor hospital communication systems: An integrated solution based on power line and visible light communication [C]// Faible Tension Faible Consommation (FTFC), 2014 IEEE. IEEE, 2014: 1-6. [2] Iturralde, Daniel, et al. A new location system for an underground mining environment using visible light communications [C]// Networks & Digital Signal Processing (CSNDSP), th International Symposium on. IEEE, [3] Wang Y., Chi N., Wang Y., et al. Network Architecture of a High-Speed Visible Light Communication Local Area Network [J]. Photonics Technology Letters IEEE, 2015, 27(2): [4] Honglei L., Xiongbin C., Junqing G., et al. A 550 Mbit/s real-time visible light communication system based on phosphorescent white light LED for practical high-speed low-complexity application. [J]. Optics Express, 2014, 22(22): [5] Haigh P.A., Ghassemlooy Z., Rajbhandari S., et al. Visible light communications using organic light emitting diodes[j]. Communications Magazine IEEE, 2013, 51(8):

7 [6] Sertthin C., Tsuji E., Nakagawa M., et al. A Switching Estimated Receiver Position Scheme For Visible Light Based Indoor Positioning System [C]// Wireless Pervasive Computing, ISWPC th International Symposium on. IEEE, 2009: 1-5. [7] Li P. Optical Interference Cancellation in Visible Light Identification System Based on Wireless Mesh Network Topology [J]. Proceedings of SPIE - The International Society for Optical Engineering, 2013, [8] Komine T., Nakagawa M. Fundamental analysis for visible-light communication system using LED lights [J]. IEEE Transactions on Consumer Electronics, 2004, 50(1):