Abstract : This article introduces a new type of wireless automatic rainfall monitoring network. The network breaks through the weaknesses of traditional automatic weather network information collection and transmission, and uses GPRS data terminals in combination with mobile wireless transmission and Internet technology to realize the automation and wirelessness of rainfall monitoring. VC ++ programming is used to establish a database and process the data information, and finally achieve the purpose of sharing meteorological data on the Internet and serving users.
The development of mobile communication and Internet technology is bringing profound changes to the society, and the maturity of GPRS wireless data transmission technology makes it applicable in many industries, which also provides a new method for data transmission of measurement and control systems [1 ]. The GPRS wireless rainfall monitoring network developed by Henan was developed based on this purpose.
1. Overview of automatic rainfall monitoring network
An automatic weather station is a weather station controlled by electronic equipment or a computer that automatically collects and transmits meteorological observations and data. There are usually two forms in terms of data transmission methods: automatic weather stations that send information through wired networks and automatic weather stations that send information directly through GPRS wireless. The data information of multiple automatic weather stations is connected to the data center processing system by wired or wireless means to form an automatic weather monitoring network. Generally, the data it collects is multi-element weather information. What we introduced here is that the rainfall monitoring network collects single-element rainfall information, and multi-element information collection can be realized by expanding the sensor system of the automatic station.
The automatic rainfall monitoring network is an automatic meteorological data collection system composed of an automatic rainfall station, a data communication network (both wired and wireless), a data center workstation and its local computer network [2]. Figure 1:
The automatic rainfall station is installed at each observation point as the end station of the system. The wireless automatic rainfall station is mainly composed of sensor unit, single chip system and GPRS data terminal unit (using H711x series GPRS DTU). The wired automatic rainfall station is composed of a sensor unit and a single-chip system, and is equipped with a local microcomputer system. [2]
The wireless automatic rainfall station directly sends the information through the GPRS data terminal in a wireless transmission mode, transfers it to the Internet through the wireless network provider, and finally enters the data processing center via the Internet; the wired automatic rainfall station uses the local computer system to collect the meteorological information Process it and transfer it directly to the data processing center via the Internet. The communication cost of the wireless automatic rainfall station is calculated by the data flow, the cost is low, and the automatic station has a stronger geographical adaptation space, as long as the mobile phone network signal coverage can communicate.
The data processing center workstation is the main control part of the entire network system, which is composed of a main server and three data processing servers. The main server has a fixed IP address on the public network, and the three data servers are connected to the main server through a hub. SQL SERVER2000 is installed on the main server for receiving and processing rainfall data. The three data processors are respectively responsible for receiving rain station information from GPRS wireless transmission, receiving rain station information from wired transmission, and providing rain data services to government departments ( (Such as web browsing, information services, etc.). The meteorological data returned from each station are sorted and stored in the SQL Server database, and provided to government decision-making departments and other users through web browsing.
2. GPRS overview
GPRS (General Packet Radio Service) is short for General Packet Radio Service. GPRS is one of the contents of the GSM Phase2.1 specification. It is a new type of mobile packet data bearing service based on GSM, which can provide a higher data rate than the existing GSM network 9.6kbit / s [3] [4]. GPRS uses the same frequency band, bandwidth, burst structure, wireless modulation standard, frequency hopping rules, and the same TDMA frame structure as GSM. It breaks through the GSM network can only provide a circuit-switching thinking, only by adding the corresponding functional entities and part of the existing base station system transformation to achieve packet switching, this transformation investment is relatively small, but the The user data rate is quite impressive. [5]
The GPRS network is implemented by adding GGSN and SGSN to the existing GSM network, so that users can send and receive data in an end-to-end packet mode. [4]
GPRS is a new mobile data communication service that provides a connection between mobile users and data networks to provide high-speed wireless IP or X.25 services to mobile users. Compared with the original GSM dial-up circuit-switched data transmission method, GPRS is a packet-switched technology. Each user can occupy multiple wireless channels at the same time, and the same wireless channel can be shared by multiple users, and resources are effectively used [6], Has the advantages of "high speed" and "always online".
1) Speedy transmission, moving Shinkansen
Circuit switched data service (CSD for short), the rate is 9.6kbps, the highest rate of GPRS can reach 115.2kbps.
2) Always online, low cost, doing what you want
In addition to the speed advantage, GPRS also has the "always-on" feature, that is, users keep in touch with the network at any time. GPRS data service can be charged according to flow or time or monthly fixed fee. For operators, the cost of providing data services is basically based on traffic. China Mobile has adopted a segmented billing (traffic) pricing model, which greatly reduces the cost of data transmission for users using GPRS, especially in data. In the collection and monitoring system. For example, when a user clicks on a hyperlink when accessing the Internet, the mobile phone sends and receives data on the wireless channel. After the home page is downloaded to the local, there is no data transmission, the mobile phone enters a "quasi-sleep" state, the mobile phone releases the The wireless channel is used by other users. At this time, a logical connection is maintained between the network and the user. When the user clicks again, the mobile phone immediately requests the wireless channel for data transmission from the network, instead of disconnecting like ordinary dial-up Internet access. You have to redial to surf the Internet. [5]
3. Overall system configuration
3.1 Data terminal and data transmission network
1) Rain station that directly sends information via GPRS wireless
The GPRS wireless data terminal (DTU) in the system uses the H711x series GPRS wireless DDN data terminal. Each module needs to be installed with a SIM card, which has a unique ID in the mobile network like a mobile phone. The terminal supports dual-band GSM / GPRS, conforms to the ETSI GSM Phase 2+ standard, uses a real-time clock, supports A5 / 1 & A5 / 5 encryption algorithms, and provides users with a high-speed, always-on, transparent data transmission virtual private data communication network.
The H711x GPRS DTU series module has a 20Pin user data interface to facilitate power supply and data exchange for the module. The connection and data exchange of external data lines are similar to RS-232. At the same time, most models of this series support + 4.5 ~ + 26VDC power supply, which is convenient for installation and use in more occasions. After all connections of the terminal are completed, the GPRS data terminal is managed through the terminal's built-in setting, management and debugging tools, which is convenient for users to configure related parameters before use and flexibly change related parameters during the debugging process, as well as software upgrades and simple tests. [6]
The wireless data transmission part of the automatic rainfall monitoring network adopts the center point ~ multipoint method, as shown in Figure 3
There are multiple automatic rainfall collection devices. They use their respective GPRS data terminals to pack the data into IP packets, access the wireless GPRS network through the GPRS air interface, and then transfer to the Internet by the mobile service provider, and finally reach the unified through various gateways and routes. Data processing center workstation. It should be pointed out that the data sent by the GPRS terminal to the data service center is sent intermittently, and the frequency of sending data can be adjusted as needed, which also reduces the cost of wireless information transmission to a certain extent. The key issues to be solved in the entire wireless network design process are: how to connect the meteorological information collection unit and the GPRS terminal, how to set it up reasonably according to the specific wireless network situation, how to package the data and send it to the data center workstation to receive.
2) Rainfall station that sends information via wired network
The AT89C52 single-chip microcomputer in the wired rainfall station sends the rainfall information obtained by the sensor to the local microcomputer through serial communication. The computer first processes and encodes the data, and then sends the data information to the data service central station with a fixed IP through the Internet. In this process, it is necessary to develop local computer data processing and sending software for data transmission, and at the same time, the data service center station must have corresponding server-side data receiving software to achieve data reception and storage.
3.2 Data center workstation
The main server is installed with Windows Server 2003 operating system and SQL Server 2000 database management software. All data from the terminal's automatic rainfall station first enters the main server with a fixed IP address through the network. However, considering the stable operation of the server, it is generally not allowed to install other application software on the server. In order to reduce the load on the main server, three additional servers need to be added to the system to share the data processing tasks of the main server. These four servers together constitute a data center workstation (DSC) similar to the internal LAN. Although there are multiple servers in the data center station, it only provides one IP address to the external public network. Therefore, a network address translation (NAT) technology is used in the installation process. The NAT port mapping function maps a false IP address of a host to a true IP address. When a user accesses a port of the host that provides the mapped port, the server transfers the request to the host that provides this specific service internally. You can let a machine in the internal network provide WWW services to the outside instead of directly transferring the true IP address to the host that provides WWW services internally.
The three processing servers process the information from different ports, and the information from the wireless automatic rainfall monitoring station is mapped to the wireless data receiving and processing server through the port of the main server, and then sent back to the main server to save in the SQL database; The task is completed by the wired receiving and processing server. Finally, the WWW server calls the SQL database from the main server to dynamically update and display the rainfall information on the Web page for external users to access through the Internet.
3.3 Software design
Software design mainly refers to the use of computer high-level language to develop data receiving and processing software on the data center station. For the wired data transmission method, the client (local computer) data sending software and the server (wired data receiving and processing server) data receiving software were developed using VC ++ 6.0. The data transmission in the software adopts Winsock mode.
For the software development of wireless data transmission, the development kit provided by GPRS manufacturers was used. After collecting information from a rainfall station on the network, the data is stored in a SQL database after a series of processing. [8]
Finally, ASP (AcTIve Sever Pages) was used to develop Web pages on the WWW server for external users to access.
4 Conclusion
The maturity of GPRS wireless data transmission technology has promoted its application in a wider field. In the field of meteorology, foreign countries introduced an automatic weather station based on GPRS in the first half of 2003. The rain monitoring network introduced in this article has been completed. This kind of small and medium-scale meteorological monitoring network will greatly enhance the ability of early warning of severe weather and reduce the property loss of the country and people.
[1] Han Bing, Li Fenhua. Application of GPRS technology in data collection and monitoring system. Electronic Technology, 2003 (8): 26 ~ 29.
[2] Bao Ruoyu, Luo Xiaofen, etc. Zhuhai Automatic Weather Station Network Project. Journal of Sun Yat-sen University (Natural Science Edition), 1996 (35): 182 ~ 188.
[3] Zhao Zhiwei. Summary of GPRS technology and network construction. Mobile Communications, 2002 (6), 23 ~ 28.
[4] http: //
[5] What is GPRS? , Http: //
[6] Instructions for H711x GPRS wireless DDN data terminal.
[7] 900 / 1800MHz TDMA digital cellular mobile communication network general packet radio service (GPRS) equipment technical requirements mobile station
[8] H711x GPRS wireless DDN data terminal DSC DEVELOP handbook
[9] http: //
Abstract:
This paper describes a new kind network for wireless autonomous rain-fall detecTIng. It gets over the weakness of tradiTIonal autonomous meteorological systems concerning informaTIon acquisition and transmission. And it also makesrainfall detection autonomous and wireless, which adopts GPRS data terminal modular based on wireless mobile communication and Internet technology. By means of VC ++ database programming for data processing, the aim has been achieved that the meteorological information is displayed dynamically on web via Internet.
Keywords:
Autonomous Weather Station GPRS data acquisition
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