I. Project requirements

The environmental monitoring stations and county-level monitoring stations of 16 cities in a certain province have been included in the provincial-level monitoring network. A total of 102 or more environmental monitoring stations above level III have been monitored. The main target of monitoring is the emission and treatment of industrial “three wastes” and the atmospheric environment. , water environment, noise environment, etc. Including: monitoring the current status of air quality in 14 cities, the current status of water quality in 12 major river systems, 7 major lake banks, 7 near-shore harbors, and 16 cities' drinking water sources, noise pollution in 9 cities, and through comprehensive The index and other methods are used for trend analysis, and finally the conclusion of environmental quality is drawn.

Provincial environmental protection data collection system is a pollution source monitoring system composed of pollution source emission monitoring points and monitoring centers. The system can automatically sample the pollution source and conduct on-line monitoring of major pollution factors; master the city pollution source emissions and the total amount of pollution source emissions; the monitoring data is automatically transmitted to the provincial environmental protection monitoring center; data from the monitoring center computer collects, collates and synthesizes data. Analysis; monitoring information is transmitted to the provincial Environmental Protection Bureau, and the provincial Environmental Protection Agency supervises and manages pollution sources.

Pollutant monitoring equipment was installed at each pollution source emission monitoring point to monitor the pollution sources. The monitoring center receives the monitoring information transmitted by the monitoring point; it is responsible for the classification, screening and comprehensive analysis of the monitoring information. As the decision-making center of the system, the Provincial Environmental Protection Bureau analyzes and investigates the monitoring information obtained from the monitoring center station, makes timely management decisions, and increases management efforts.

At present, the data communication between the provincial environmental protection monitoring station and each collection point mainly uses manual transcription or PSTN telephone line transmission. When using a telephone line to transmit data, it takes a long time to wait for dialing, and it is slow and the cost is high. At the same time, because each monitoring point has a wide distribution, a large number, and a long distance, and individual points are still remote, it is necessary to apply for many telephone lines, and some monitoring points have difficulty in reaching the wired lines.

The GPRS data transmission has the characteristics of high speed, wide distribution range and low usage cost. Its transmission speed can theoretically reach up to 171.2 kb/s, and the actual average speed can reach 30 kb/s bytes/sec. Compared with wired communication, using GPRS wireless communication is very flexible. It has the advantages of flexible networking, easy expansion, low operating cost, simple maintenance, and high cost performance. Therefore, GPRS wireless transmission is currently being considered to solve pollution source monitoring. Real-time data transmission problem.

Second, the program advantages

China Mobile GPRS system can provide wide area wireless IP connection. Constructing an environmental protection information collection and transmission system on the mobile communication company's GPRS service platform to realize wireless data transmission of environmental protection information collection points has the advantages of making full use of existing networks, shortening the construction period, and reducing the construction cost, and the equipment is easy to install and maintain. . After a comparative analysis, we chose China Mobile's GPRS system as a data communication platform for environmental information collection and transmission systems.

GPRS wireless environmental pollution source online monitoring system has the following characteristics:

1, high reliability:
Compared with SMS SMS, GPRS DTU adopts connection-oriented TCP protocol to avoid packet loss and ensure reliable data transmission. The center can perform data transmission simultaneously with multiple monitoring points without disturbing each other. The GPRS network itself has a perfect frequency division multiplexing mechanism, and has a strong anti-interference performance, completely avoiding the "collision" phenomenon of multi-frequency band of traditional digital radio stations.

2, real-time strong:
GPRS has the characteristics of real-time online, small data transmission delay, and supports simultaneous transmission of multiple points. Therefore, the GPRS monitoring data center can perform two-way communication between multiple monitoring points in real time and quickly, which satisfies the system's data collection and transmission. Real-time requirements. At present, the actual data transmission rate of GPRS is about 30 Kbps, which fully meets the requirements of system data transmission rate (≥10 Kbps).

3, a wide range of monitoring:
The GPRS network has achieved nationwide coverage, and there is no limitation on capacity expansion. There are no restrictions on access locations and it can meet the access needs of mountainous regions, townships, and regions. Due to the large number of environmental information collection points, which are distributed throughout the province, some environmental protection information collection sites are located in remote areas and geographically dispersed. Therefore using GPRS network is its ideal choice.

4. Low system construction cost:
Due to the adoption of the GPRS public network platform, there is no need to build a network, simply install the equipment, and the construction cost is low; network maintenance costs are also eliminated.

5, the system operating costs are low:
Using GPRS public network communication, all countries are charged at a flat rate, eliminating the need for expensive roaming charges. The GPRS network can be based on actual data traffic accounting data (1 minute - 3 minutes/1 kilobyte), or it can be There is no limit on monthly charges for monthly subscriptions, which enables low-cost communications for the system.

6, can control the monitoring equipment and equipment:
Through the GPRS data monitoring center, remote control of field devices can be realized, such as remote switch control, remote reset control, remote status query, remote parameter configuration, and remote firmware upgrade.

7, the system's transmission capacity, expansion capacity is good:
The environmental protection center station needs real-time connection with every environmental protection information collection point. Due to the large number of environmental information collection points, the system is required to meet the needs of sudden data transmission, and GPRS technology can well meet the needs of transmitting bursty data; because the system adopts a mature TCP/IP communication architecture, it has good With expanded performance, a monitoring center can easily support communication access for thousands of live collection points.

8, GPRS transmission power consumption is small, suitable for field power supply environment:
Although two-way communication with a data center in a thousand miles away, GPRS data transmission equipment only needs to communicate with nearby mobile base stations during operation, and its overall power consumption is equivalent to an ordinary GSM mobile phone, with an average power consumption of only 200 millimeters. Watts around, much smaller than traditional digital radio stations. Therefore, the GPRS transmission method is very suitable for use in the field using solar power or battery power.

Solution introduction Because GPRS communication is a data packet communication network based on IP address, the monitoring center computer needs a fixed IP address or a fixed domain name. Each data acquisition point uses the GPRS module to access the host through an IP address or a domain name. Thereby data communication.

(I) System composition

1, environmental protection information collection point:

The site monitoring point automatically collects the pollution source information through the environmental data collector and connects to the GPRS DTU terminal through RS232 or RS485 interfaces. The data collected by the environmental data collector is processed by the built-in embedded processor of the GPRS DTU terminal and the protocol is encapsulated. Send to GPRS wireless network.

2, monitoring center:

a) Public network access plan

The server uses the public network to access the Internet, such as ADSL dial-up/telecommunications broadband Internet access, etc., to apply for a fixed IP address on the public network; data collection applications with small and medium capacity can be realized.

b) Private network access plan

The server adopts the DDN dedicated line provided by the provincial mobile communications company and applies for the configuration of a fixed IP address, which is connected to the GPRS network. Because the DDN dedicated line can provide higher bandwidth, when the number of environmental protection information collection points increases, the center can meet the demand without expansion, and it can realize large-capacity data acquisition applications.

After receiving the data from the GPRS network, the RADIUS server of the monitoring center first performs AAA authentication, and then transmits it to the host computer of the monitoring center. The data is restored and displayed by the system software, and data processing is performed. This further enhances the data communication security performance of the system.

3, GPRS/GSM mobile data transmission network:

The data collected at the site monitoring point is decoded and processed at the same time via the air interface function module of GPRS/GSM network, converted into the format of data transmission on the public network, transmitted through China Mobile's GPRS wireless data network, and finally transmitted to the IP address of the monitoring center. .

(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 mobile communication company's GPRS ordinary data card or APN special-purpose data card, at the same time the monitoring center registers each point GPRS terminal number, and correlates with the collection point information, in order to identify and maintain the processing. The information collection center runs monitoring system software to collect environmental protection information data in real time.

The system can be used by any information collection point authorized by the Provincial Environmental Protection Agency:
1. The environmental information collection point must use the mobile unified APN card. Users can only use this card for data communication with the environmental protection station.
2. The terminal equipment uses the GPRS mobile data communication terminal provided by Chengdu Zhongshan Technology Co., Ltd.
3, the user registration: in line with the provisions of the provincial Environmental Protection Agency.

(III) Product Features

The system uses ZSD3120 GPRS DTU wireless transparent data transmission terminal. The product is based on China Mobile's GPRS network and features high performance, high reliability and strong anti-interference ability. It provides a standard RS232/RS485 interface. It can be directly connected to PC, SCM system, RTU monitoring and control terminal, PLC, GPS receiver and data concentrator. Such connections, with remote diagnostics, testing, and supervision functions, to meet the data acquisition and control between various industry dispatch or control centers and many remote sites.

1. Built-in TCP/IP protocol stack, optimized for GPRS network
2, provide GPRS wireless data two-way transmission
3, provide RS232/RS485/RS422 interface
4, in line with ETSI GSM Phase 2+ standard
5, support automatic heartbeat, keep online forever
6. Transparent data transmission: Bidirectional 100K large-capacity data buffer is provided for user's data device to support large data packet transmission
7, automatic dial-up connection: DTU power automatically dial-up Internet access, connect to the network, support the user to initiate a command connection or remote wake-up connection
8, to provide SMS channels, built-in Unicode international encoding conversion table
9, support remote SMS / phone wake up
10, real-time monitoring of network connection, dropped automatic redial function
11. The support center is a fixed IP or dynamic domain name
12. Heartbeat report interval can be set by the user
13. Support point-to-point, point-to-multipoint, multipoint-to-multipoint data transmission
14, support for APN data private network business
15, flexible installation, easy to use and reliable
16, support for multiple data centers, automatic switching
17, to adapt to low temperature and high temperature working environment
18, EMC anti-jamming design, suitable for electromagnetic harsh environment applications
19, composite watchdog technology, never crash
20, the whole low-power technology, online standby current <20mA

(four) safety measures

Due to the special nature of the environmental data acquisition 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 be accessed through the public network, or can be accessed by a mobile private network. The cost of adopting the public network access method is relatively low. Enterprises do not need to lease the leased line. When using the data line access, the GPRS data transmission equipment must be authenticated by the Radius server. The entire data transmission process has been protected by encryption, and the security is relatively high, which can fully guarantee the speed and quality of network services.

1. APN data private network mode: The APN server is configured in the internal network of the enterprise, and the APN data private network is used for the mobile terminal. Because the data private network is used, the server is isolated from the public network Internet, and illegal invasion can be effectively avoided.

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 range of users that can access a certain system, only the SIM card mobile phones 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. The DTU ID number and password can be separately configured for each GPRS data transmission device. Application layer authentication is performed when the data center logs in. Other GPRS devices that do not have the DTU ID number and password assigned by the data center cannot log into the system. The security of the system is further enhanced.

4, data encryption: The entire data transmission process can be encrypted protection.

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 data center adopts the wired method. The current cost of renting static IP is about 800~1500 yuan/month. The collection point adopts the GPRS wireless method, and the current cost of the flow rate is monthly and according to the amount of data. According to the flow rate, they are calculated as 0.01-0.03 yuan/KB, while the monthly system is 20 yuan/month with 1024 KB, which can meet the current environmental protection bureau environmental protection requirements. The actual data volume of the data acquisition system is estimated to gradually decrease in the future.

For users such as the Environmental Protection Agency, due to the low cost of communication, they 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 environmental monitoring station and the environmental protection information collection point are relocated, and the original investment of the user can be protected, which is suitable for the characteristics of environmental protection collection work.

Therefore, the use of GPRS to build an environment-friendly data collection system not only satisfies the needs for the collection of environmental information, but also enables the mobile operator, which is a network operator, to obtain a stable group of users. As the number of users increases, The revenue of mobile communications companies also increased, mobilizing the enthusiasm of operators and meeting the requirements for the simultaneous development of network construction and network applications.