Research and implementation of GPRS Remote Monitoring System

　　1. Introduction

　　With the rapid development of communication technology and information processing technology, the combination of the two - remote monitoring system has become a hot spot in the current research field. Remote monitoring system refers to the system that can know the working condition of the controlled object in time when it is far away from the controlled object, and send instructions to remotely control it when necessary. With the emergence of remote monitoring system, the staff do not need to arrive at the scene. As long as they are in the monitoring center, they can grasp the overall situation, get the details of the controlled object in time, make decisions quickly and implement them effectively. It not only greatly improves the work efficiency, saves human and material resources, but also improves the response ability of the system to emergencies. It is the development trend of monitoring system in various industries. The remote monitoring system is widely used, and has been widely used in transportation, electric power, industry and agriculture, water conservancy remote monitoring, environmental protection, construction and other industries.

　　With the popularization of Internet technology and the development of GPRS communication technology, remote monitoring system is more closely combined with modern communication technology and more applied in industrial enterprises.

　　2. Functions and characteristics of GPRS Technology

　　GPRS is the English abbreviation of general packet radio service. It is a new packet data bearer service developed from the existing GSM system. GPRS adds some hardware equipment and software upgrades to the existing GSM network to form a new network logical entity. Based on packet switching technology and adopting IP data network protocol, it improves the data service transmission rate of the existing GSM network, up to 170kb / s. GPRS introduces packet switching technology into the existing GSM system, which combines mobile communication and data network. It has the characteristics of "fast transmission", "always online", "low price" and so on.

　　GPRS is a wireless network technology based on GSM. It superimposes a wireless interface based on packet switching on the existing GSM network and introduces three new logical network entities: Service GPRS support node (SGSN), gateway GPRS support node (GGSN) and packet control unit (PCU). At the same time, with software upgrade, it aims to provide high-speed packet data service. Using packet switching to supplement circuit switching is an important upgrade of GSM technology. One of the advantages of packet switching is that it can flexibly allocate network resources and use the wireless channel only during data transmission. In this way, multiple users can share a wireless channel and greatly improve the resource utilization. GPRS data transmission uses service channels with a rate of 9kbps ~ 21.4kbps. If a user monopolizes 8 channels, the total rate will exceed 170kbps. In practice, a single user can use 1 to 3 channels at the same time, with a rate of tens of Kbps.

　　3. System design scheme

　　3.1 overall design idea

　　The system integrates GPRS wireless communication technology, computer monitoring technology, data acquisition technology and database technology, and constructs a computer remote monitoring system platform based on GPRS technology.

　　The system is divided into two parts: monitoring center station and remote monitoring sub station: the monitoring center station is mainly composed of monitoring center station server, intranet, database server, display and other peripheral equipment; The remote monitoring substation is mainly composed of MSP430F149 single chip microcomputer, peripheral circuits (LCD, keyboard function, RS232 communication, a / D conversion) and GPRS wireless communication module.

　　The GPRS module adopts wismo2d module of wavecom company in France. This module is a dual band GSM module (GSM900 / 1800mh or GSM900 / 199mhz), which is suitable for handheld cellular mobile phones and other wireless communication products. Its design and development comply with ETSI GSM Phase2 + standard. The monitoring center adopts APN mode to connect with GPRS network. The communication operator allocates internal fixed IP address to the monitoring center. As the APN dedicated line can provide high bandwidth, when the number of monitoring points increases, the monitoring center can meet the demand without expanding the capacity. The wireless remote communication between the monitoring center station and the remote monitoring substation is realized through GPRS network, and the remote monitoring based on GPRS network is realized. The system structure diagram is shown in Figure 1.

　　3.2 hardware design of monitoring center station

　　The main hardware equipment of the monitoring center station includes: an industrial computer as the server of the monitoring center station, intranet, database server, display, printer and other peripheral equipment.

　　3.3 hardware design of remote monitoring substation

　　The main hardware of remote monitoring substation includes MCU and its peripheral circuit and GPRS wireless communication block wismo2d. The MCU adopts MSP430F149 series produced by American TI company. According to the needs of the system, several power units such as LCD, keyboard function, RS232 communication and a / D conversion are designed. The A / D conversion part is completely realized by MSP430F149 on-chip integration module.

　　4. System development

　　4.1 system software design

　　In the system, the GPRS wireless communication module wismo2d is used to realize the data communication between the two. The GPRS wireless communication module wismo2d is controlled by at command. The data transmission adopts remote transmission through Internet network and compatible short message transmission. At command, Microsoft VC + + 6.0 advanced programming language and IAR's workbench development environment are the basis of system software design.

　　4.2 software design of monitoring center station

　　The program design of monitoring center station adopts VC + + 6.0 as the development tool. Its software includes monitoring center control interface and initialization program, data packet sending and receiving program, data processing and storage program. The most important one is the wireless communication between the monitoring center server and the GPRS wireless communication module wismo2d, which is the key to realize the reception and transmission of data packets. VC + + 6.0 provides the network port communication control Winsock, which can easily realize the scanning and listening of computer network ports. By setting a fixed port not occupied by the computer as the communication port, and then constantly listening to the state of this port, once it is found that there is a packet acceptance in the port, it starts to put the data into the data buffer, then receive it, and call the relevant interrupt handler to process the corresponding data. The program flow chart is shown in Figure 2.

　　4.3 software design of remote monitoring substation

　　Main tasks of remote monitoring substation: convert through a / D and process the data collected by peripheral sensors; Trigger and send real-time data to the monitoring center or management personnel through keyboard keys; Control the GPRS wireless communication module wismo2d to receive and send data packets or short messages. The software design adopts modular programming, and each functional module appears in the form of sub module, which shortens the software development time and is easy to modify and transplant the program.

　　5. Conclusion

　　The computer remote monitoring system based on GPRS technology proposed in this paper makes comprehensive use of computer technology, wireless communication, graphics processing, database, software development and other technologies to realize the computer remote monitoring and management system based on GPRS wireless communication technology. The practical application shows that the system runs stably and reliably, achieves the expected design goal, and has good practical value.