Research on Urban Pipeline Network Monitoring System Based on GPRS Technology

      The urban municipal pipe network system undertakes tasks such as water supply, electricity supply, gas supply, heating supply, and drainage supply, and maintains and guarantees the normal operation of urban production and life. However, many urban municipal pipelines have many problems such as incomplete and non-standard pipelines, poor operational reliability and safety, and high operating costs. The monitoring and maintenance of urban pipe networks are still at the stage of regular or fixed-point manual inspections and on-site inspections, lacking effective monitoring, early warning, and scientific monitoring and maintenance.

　　Therefore, a monitoring system for urban municipal pipe networks is developed to achieve real-time monitoring of the operation status of the pipe networks, and on this basis, dynamic monitoring and analysis are implemented to provide a basis for handling pipe network emergencies, comprehensive disaster warning and defense, relevant information analysis, and reasonable planning and design of pipe networks; at the same time, scientific and effective management of pipe network map data and other information is carried out to provide accurate information and decision-making support for accurately judging the disaster and damage in the pipe network, and to solve the many problems that have long existed in my country, such as the low safety guarantee rate and information management level of the municipal pipe network system. Based on GPRS, the urban municipal pipe network monitoring system has changed the current situation of backward equipment, single function, and imperfect monitoring methods. It links the monitoring system with the early warning system, improves the security of the system, strengthens the information management level of the system, and can prevent disasters before they happen.

1 GPRS Technology

　　GPRS is the abbreviation of general packet radio service. It adds functional entities such as SGSN and GGSN to the original GSM network based on circuit switching to provide packet switching data services for GSM users. GPRS makes full use of the resources of the original GSM network, allowing users to send and receive data in end-to-end packet transfer mode, providing an efficient and low-cost wireless packet data service.

　　1.1 Main features of GPRS technology

　　1) GPRS uses packet switching technology to efficiently transmit high-speed or low-speed data and signaling, optimizing the use of network resources and wireless resources. 2) It supports medium and high-speed data transmission and can provide a data transmission rate of 9.05 to 171.2 kbit/s. 3) GPRS network access speed is fast, providing seamless connection with the existing data network, and it is always online, and users are always connected or online. 4) GPRS supports communication protocols such as TCP and UDP, and can be interconnected with IP networks and X.25 networks. 5) The design of GPRS enables it to support both intermittent burst data transmission and occasional large amounts of data transmission. 6) GPRS can realize real-time data transmission, effective data flow collection, and realize pipe network monitoring based on data information.

　　The pipe network terminal needs to collect field data in real time and transmit it to the monitoring center quickly and efficiently. If the transmission is delayed, the monitoring center cannot efficiently use the collected data to monitor the heat exchange station, so the transmission network must be fast. GPRS communication technology is just suitable for this transmission requirement and can provide a cost-effective communication method for data collection of the pipe network monitoring system.

　　1.2 Components of GPRS wireless data transmission system

　　The GPRS wireless data transmission system is divided into three parts: monitoring terminal equipment, GPRS data transmission terminal, and monitoring center master station.

　　1) Monitoring terminal equipment. It mainly completes the collection of digital and analog quantities. The monitoring point DTU uses a SIM card with a fixed IP address. After the GPRS data transmission terminal is powered on, it will actively access the central GPRS DTU server according to the IP address preset inside it, and establish a TCP/IP link with the monitoring center. The monitoring center server establishes PPP (Point to Point Protocol) dial-up, enters the GPRS APN intranet, and obtains a fixed IP address. When the main station wants to make a data request to a certain monitoring terminal, it will find the corresponding terminal based on the IP address and ID number, and send the command to the terminal. After the terminal responds, it sends the data to the network proxy server port through the GRPS data transmission terminal, and forwards it to the monitoring center main station through port mapping, completing a responsive communication process.

　　2) GPRS data transmission terminal. The GPRS data transmission terminal realizes the communication between the monitoring center master station and the monitoring terminal. The field data is output through the data acquisition module in the form of RS232 interface, directly connected to the RS232 interface of the DTU for data transmission, and completes the upload and download of information.

　　3) Monitoring center main station. Mainly completes human-computer interaction work. The central server is mainly responsible for the establishment of network data links and the transparent transfer of data reception and transmission. The innermost layer of the system is the operating system and system software; the second layer is the system support software layer, which is mainly for data collection and transmission, that is, to collect various data from different terminals according to various communication protocols, and then distribute them to the systems that need these data through the network; the third layer is the basic application layer, which processes the collected data in various ways and displays it to the monitoring personnel through the GUI (Graphieal User Interface); the fourth layer is the advanced application layer, and the data generated is used for further management and decision-making of the pipe network dispatching system.

2 System Hardware Structure

　　The GPRS-based pipe network data measurement and control system mainly consists of a monitoring host, a GSM/GPRS network, and a GPRS data transmission unit (GPRS DTU). From a macro perspective, the system is divided into two parts: the hardware platform and the software platform.

　　2.1 Hardware Platform Structure

　　The hardware platform is divided into two parts: the monitoring center and the detection terminal. The detection terminal collects sensor data, then packs the data into IP packets, connects to the GPRS network through the SM card of the GPRS module, sends it to the external Internet network, and then sends the data to the monitoring center through the GPRS server. The PC in the monitoring center receives and processes the data. The hardware composition diagram of the pipeline network hardware data measurement and control system is shown in Figure 1:

      The monitoring terminal equipment uses a data acquisition system based on a single-chip microcomputer. The data collected by the sensor is processed and connected to the GPRS communication module through RS232, thereby realizing GPRS network communication. The data terminal encapsulates the data through UDP/IP and PPP protocols and sends it to the GPRS network, and transmits the data to the monitoring center through the GPRS data network.

  2.2 Software Platform Structure

　　The software platform is divided into two parts: terminal software and monitoring center software.

　　The terminal software is responsible for monitoring the operating status of the terminal hardware and uploading data. The main tasks of the terminal software are to read the collected data regularly, send data via GPRS, and receive and execute commands from the remote PC. The task of reading collected data does not require high real-time performance, so it is implemented using time-sharing operations, while the other two tasks are implemented through user processes.

　　The monitoring center software is mainly responsible for data reception, storage, query and presentation. The monitoring center software system adopts object-oriented concept and modular design method, and encapsulates various functions into several independent functional modules according to needs, such as real-time data display, pipe network information query, alarm processing, statistical reports, etc.

　　The system makes full use of advanced technologies such as computers, virtual instruments, single-chip microcomputers, and GIS, and establishes a corresponding GIS spatial database management system to organically integrate urban municipal pipeline management such as operation control, billing management, pipeline maintenance, and user management, thereby realizing the integration of urban pipeline management and operation control.

　　2.3 Working process of monitoring system

　　1) On-site measurement and control equipment collects network operation data in real time, processes and analyzes the data, and adjusts the operation status of on-site equipment based on the analysis results; 2) Responds to the data transmission request of the GPRS communication terminal and uploads the collected and processed data to the communication terminal. The communication terminal packs the data into IP packets and sends them to the dispatch center via the GPRS network and the Internet; 3) The dispatch center software unpacks the IP packets, restores the data, and realizes remote monitoring based on the overall operation of the network.

3 Field data and wireless data transmission system

　　3.1 Field instrument data collection

　　The field data is transmitted to the microcontroller through the A/D conversion module, and then processed by MAX232 and transmitted to the wireless communication module. It is connected to the GPRS transparent data transmission terminal in the RS232 interface mode and transmitted to the data center through the GPRS network, realizing the real-time online connection between the field data collection and the data center system. The structure of the field data collection and wireless data transmission system is shown in Figure 2:

　　3.2 Data Center

　　1) The data center server applies for a fixed IP address and uses the DDN dedicated line provided by the mobile communication company to connect to the GPRS network. Since the DDN dedicated line can provide a higher bandwidth, when the number of on-site instrument data collection points increases, the center can meet the demand without expanding capacity.

　　2) After the data center server receives the data from the GPRS network, it transmits it to the data center computer host, restores and displays the data through the system software, and processes the data.

　　3) The computer host in the data center can perform business management, verify, calculate, store, analyze and manage the data of field instruments, issue alarms for abnormal situations and monitor the use of the pipeline network in real time.

　　3.3 GPRS/GSM mobile data transmission network

　　The data collected by the field instruments are decoded and processed by the GSM network air interface function module, converted into a format for public network data transmission, transmitted through the GPRS wireless data network, and finally transmitted to the data center IP address. Since GPRS communication is a data packet communication network based on IP addresses, the computer host in the data center is configured with a fixed IP address, and each field instrument data collection point uses a GPRS module to communicate with the host.

　　Through GPRS wireless communication, a serial communication connection can be established between a remote data device and a local data device. The data sent by the remote data device through GPRS DTU can be forwarded to the local data device connected to the specified serial port; or the data sent by the local data device connected to the specified serial port can be forwarded to the remote data device through GPRS RTU.

　　The functions of the GPRS wireless data service program are: to establish a one-to-one correspondence between DTU and serial port; to receive data sent by DTU and forward it to the corresponding serial port; to receive data from the specified serial port and forward it to the corresponding DTU; to manage and monitor DTU, serial port and data transmission.

4 Conclusion

　　The monitoring system of the urban municipal pipe network based on GPRS makes full use of the characteristics of GPRS network transmission data, such as high reliability, real-time online, low latency, and the ability to simultaneously collect and process various data from multiple/all monitoring points in real time. It well meets the system's requirements for real-time data collection and transmission, and has great advantages in construction cost and maintenance cost. It can improve work efficiency and management level, and ensure the safe and stable operation of the pipe network. With the further improvement of the GPRS network, and the integration of virtual instruments and GIS and other advanced technologies, the establishment of a complete GIS spatial database management system has great practical significance and extensive practical value for improving the management level of my country's urban municipal pipe network, accelerating the construction of the dynamic management of the urban municipal pipe network information system, and realizing the integration of urban pipe network management and operation control.