I. Project Background
The main purpose of the urban water supply dispatch monitoring system is to solve the data collection and monitoring of the water supply company's monitoring points in each link of water supply. The system is composed of a monitoring center and various water source monitoring points. The data collection terminals (RTU or PLC) of each water source monitoring point can monitor and collect various data such as water level, pressure, flow rate, turbidity, residual chlorine, and pump frequency for control. The center and related departments analyze and make decisions, increase work efficiency, ensure the quality of water supply, and meet the demand for increasing water consumption.
The urban water supply dispatch monitoring system can monitor and control the remote on-site operating equipment to realize the data transmission of pipeline pressure and water flow and the automatic control of the valve switch, which reduces the failure rate and improves the reaction time to the system. Facilitate timely and prompt understanding and control of remote pipes and valves, low failure rate and overhaul time, reducing the number of water stops. The data collection terminal of each water source monitoring point can automatically collect data such as pipeline pressure, water flow real-time data and switch status, and the information is transmitted to the water company's monitoring center. The monitoring center can analyze the data transmitted back to find the fault. Location, so that when a remote end fails, it can solve the problem in the shortest time, restore water supply, improve the overall level of service, thus achieving the city's water supply information and modernization.
In urban water supply dispatch monitoring systems, because of the wide distribution, large number, and long distance of individual pipe network monitoring points, individual points are still remote, so it is difficult and unrealistic to set up optical cables and cables, and lease dedicated telephones to the telecommunications sector. The line has to apply for many telephone lines, and some monitoring point lines are difficult to reach, in addition to the use of telephone lines need to wait for a long telephone dialing process, slow speed, high operating costs, in short, the monitoring system uses wired communication to build a long cycle, work difficulty Larger and higher operating costs make it inconvenient for large-scale use. In contrast, wireless communication is very flexible. It has the advantages of less investment, short construction period, simple operation and maintenance, and high cost performance. In the monitoring system, wireless communication methods mainly include: GSM short messages, GPRS, CDMA systems, and the like.
Second, the program choice
After a comparative analysis, China Mobile's GPRS system was selected as the data communication platform for the urban water supply dispatch monitoring system. At present, the GSM network has been built by the telecommunications sector for many years, and its coverage has been continuously expanded. It has become a mature, stable and reliable communication network, especially the newly launched GPRS data service of China Mobile. The GSM/GPRS system provides a wide area wireless IP connection. Constructing tap water supply dispatch monitoring system on mobile communication company's GPRS service platform to realize wireless data transmission of pipe network monitoring point has the advantages of making full use of existing network, shortening construction period and reducing construction cost, and convenient installation and maintenance of equipment. .
GPRS wireless monitoring system has the following characteristics:
1, good real-time response and processing capabilities. Compared with short message service, since GPRS has real-time online characteristics, the system has no time delay, and the system can simultaneously receive and process various data of multiple/all monitoring points in real time. The clocks of the monitoring points can be synchronized without patrolling. Meet the system's requirements for real-time data collection and transmission.
2. Remote instrument and equipment control: Due to adopting GPRS two-way transmission system, the monitoring center can realize the functions of time correction, status report, switch and other monitoring and control of the instrument and equipment in reverse;
3, low construction cost: can make full use of the existing GSM network, equipment installation that is connected, and the use of ultra-short wave communications need to fully consider the on-site environment, but also need to be equipped with ancillary equipment and other ancillary equipment.
4, simple installation and commissioning, short construction period: the use of existing mature GSM network, the system put into operation basically do not need to debug, simple installation. When using ultra-short wave communication, the workload of installation and debugging is large. It is necessary to conduct on-site signal testing, erection of antenna iron frame, and adjustment of the antenna direction angle.
System Features
1. Wide coverage. The construction of a water supply dispatch monitoring system requires a wide range of data communications, unlimited expansion, and unlimited access points to meet the access needs of mountainous regions, townships and regions.
Due to the large number of pipe network monitoring points, which are distributed throughout the city, some pipe network monitoring sites are located in remote areas and geographically dispersed. The use of ultra-shortwave communication means that the coverage area is only over 30 kilometers. With GPRS, it is theoretically possible to achieve monitoring within the coverage of wireless GSM/GPRS networks.
2, the data transmission rate is high. The GPRS network transmission rate can theoretically reach 171.2 kbit/s. In practical applications, the data transmission rate is about 40 Kbps, while the current general UHF transmission radio transmission rate is mostly 2.4 kbit/s or lower.
3, the system's transmission capacity. The monitoring center station must implement real-time connection with each pipe network monitoring point. Due to the large number of monitoring points in the pipeline network, the system is required to meet the need for sudden data transmission, and the GPRS technology can well meet the needs of transmitting bursty data.
4, communication costs are low. Because GPRS adopts the monthly billing method and the operation and maintenance cost is low, the monthly communication fee will be within 200 yuan.
Third, solution introduction
Since GPRS communication is a data packet communication network based on IP address, the host computer of the monitoring center configures a fixed IP address, and the GPRS module of each end station communicates with the host.
(I) System composition
1, pipe network monitoring point:
Pipe network monitoring point: Each monitoring point collects data such as pressure and flow through data acquisition module, connects to GPRS transparent data transmission terminal through RS232 interface, and processes data and protocol encapsulation through GPRS transparent data transmission terminal's built-in embedded processor. After sending to the GSM network.
2, monitoring center:
The server applies to configure a fixed IP address and uses the DDN dedicated line provided by the provincial mobile communications company to connect to the GPRS network. Because the DDN dedicated line can provide higher bandwidth, when the number of monitoring points in the pipe network increases, the center can meet the demand without expanding.
After receiving the data from the GPRS network, the RADIUS server of the monitoring center performs AAA authentication first and then transmits it to the host computer of the monitoring center. The system software then restores and displays the data and performs data processing.
3, GPRS/GSM mobile data transmission network:
The data collected by the site monitoring point is decoded and processed by the GSM network air interface function module, converted into a data transmission format in the public network, and transmitted through the China Mobile GPRS wireless data network, and finally transmitted to the monitoring center IP address.
(two) system plan
Each monitoring point uses a GPRS transparent data transmission terminal and is connected to a monitoring center through a mobile GPRS network.
Each pollution source data collection point uses the unified STK card of the mobile communication company, at the same time the monitoring center carries on the registration to each spot, preserves the correlation data for the recognition and the maintenance treatment. The information acquisition point running monitoring system software, support 24 hours real-time online, to achieve the information collection point 24 hours to transmit the collected information and data.
All systems that are authorized by the Water Company can use this system:
1. The pipe network monitoring point must use the mobile unified STK card. Users can only use this card for data communication with the monitoring center.
2. The terminal equipment uses the GPRS mobile data communication terminal provided by Macro Electronics.
3, user registration: in line with the provisions of the water company.
(III) Product Features
The system uses H7000 series GPRS wireless transparent data transmission terminals. Products based on China Mobile's GPRS network, with high-performance, high reliability and strong anti-jamming capabilities, providing a standard 232 data port can be directly connected to computers, RTU, PLC, GPS receivers, digital cameras, data terminals, etc., transmission rate Up to 171Kbps, with remote diagnostics, testing, and supervision capabilities, to meet the data acquisition and control between various industry dispatch or control centers and many remote stations.
1, support 900/1800/1900MHz tri-band GSM/GPRS.
2. Interface: RS232, RS485, RS422.
3, the system theoretical transmission rate of 171Kbps, the actual transmission rate of 40Kbps.
4, support for Windows95/98/200/XP, LINUX operating system.
5, support transparent data transmission and protocol conversion.
6, support VPN security features.
7, flexible installation, easy to use and reliable.
(four) safety measures
Due to the particularity of the water supply dispatch monitoring system, this system requires extremely high system security and stability. Security protection is mainly to prevent intentional and unintentional damage from inside and outside the system. Network security protection measures include channel encryption, source encryption, login protection, access protection, access protection, and firewall. Stability means that the system can operate continuously for 7×24 hours. Even if there are hardware and software failures, the system cannot be interrupted.
The data center can use the VPN to access the mobile GPRS network through the public network. The cost of adopting the VPN method is relatively low. The enterprise does not need to lease the leased line, it can also use the old VPN equipment, and the mobile terminal needs to install the VPN virtual dial function. Software. Through the VPN method, before the client connects to the application server, the entire data transmission process through the authentication of the Radius server is encrypted, and the security is relatively high, which can fully guarantee the speed and the quality of the network service. In addition, the data center can also use the APN access method to lease leased lines to the mobile company's GGSN equipment. This high cost, high security, stability and reliability.
For a system with a very high security requirement, a hybrid access method using a VPN access method may be considered on the basis of the dedicated APN access, and the security of the system may be further improved.
1. VPN virtual private network mode: The VPN server is configured in the internal network of the enterprise, and the mobile terminal loads the client software with the function of VPN secondary virtual dialing. Using VPN security technology, users are isolated from the Internet by accessing the company's internal virtual private network, which can encrypt and protect the entire data transmission process, effectively avoiding illegal intrusions.
2. Using the uniqueness of the SIM card to authenticate and authorize the user's SIM card mobile phone number, bind the SIM card number and the APN at the network side, demarcate the user's range that can access a certain system, only the SIM card mobile phone belonging to the specified industry No. can access the dedicated APN. The mobile terminal and the data center use the special APN assigned by China Mobile to access the wireless network. The SIM card number of the ordinary mobile phone cannot call the dedicated APN.
3. For a specific user, a specific user ID and password can be assigned through the data center. Users without other user IDs and passwords assigned by the data center cannot log in to the system and the security of the system is further enhanced.
4. Data encryption: Encrypt the entire data transmission process through VPN.
5, network access security authentication mechanism: the use of firewall software, set up network authentication and security features to protect system security.
Fourth, the conclusion
The use of GPRS to build water supply dispatch monitoring system, for users, because of the lower communication costs, enjoy the benefits. In addition, since the access equipment can be moved, the equipment can be migrated and can continue to be used when the monitoring points of the pipeline network are relocated, which can protect the original investment of users, and is suitable for the characteristics of water supply dispatch monitoring work, and can well meet the requirements of water supply regulation and monitoring. Demand, and as a mobile operator of a network operator, it will also obtain stable group users. With the increase in the number of users, the revenue of mobile communication companies will also increase, mobilizing the enthusiasm of operators. The requirements for the simultaneous development of network construction and network applications.