1. Introduction
Driven by the national informatization strategy, many industry groups have recognized the importance of informatization. At present, the finance, education, medical care, transportation, electric power, tobacco, logistics and other industries have established their own information systems according to the characteristics and needs of the industry. In order to promote the development of industry informatization, China Mobile gives full play to its own business advantages and closely integrates Mobile Data businesses with voice and fixed data businesses. It has launched an overall mobile informatization solution for the industry, while meeting the customer's needs, it also creates new values for the customer and achieves a win-win situation between the mobile operator and the industry customer.
Wireless DDN (Digital Data Network) is one of the key applications of the overall mobile information solution. It is mainly used by the Mobile GSM/uplsgeneral Packet Radio Service, universal grouping wireless business) network, using GPRS, SMSShort Message Service, short Message Service), USSDUnstructured Supplementary Service Data, Unstructured Supplementary Data Service), CSDCircuit Switched Data, circuit exchange Data) and other bearer methods, machine-to-machine wireless data transmission services provided to industrial customers, it can provide wireless real-time data transmission and collection services for users in the water conservancy, electric power, oil production, mining, environmental protection, meteorology, transportation, taxation, medical care, public security, education, finance, tobacco, customs, and other industries.
2. features and advantages of wireless DDN
Compared with traditional transmission methods such as circuit dialing and fixed data leased lines, wireless DDN is flexible and convenient, saving investment and other advantages. In addition, wireless DDN has the following main features:
(1) diverse data transmission methods: the main bearer methods of wireless DDN include GPRS, CSD, SMS, and USSD. Based on the needs of customers in the industry and their equipment configurations, you can select one or more methods for data transmission and interaction.
(2) relatively suitable for small-traffic and high-frequency data transmission: The peripheral terminals of industrial customers who use wireless DDN for data transmission are basically scattered, data collected or transmitted from these terminals is generally small-traffic data, and the transmission frequency is high. For example, the positioning data transmitted in the GPS Vehicle Monitoring System is mainly the basic information such as the vehicle longitude/latitude, speed, direction, and time, the data transmitted by the wireless POS machine includes the user account, password, and transaction amount.
(3) mainly used for industrial customers and special industry terminals: the main function of wireless DDN is to help industrial customers collect or transmit scattered data using various bearer methods, this greatly improves the efficiency of industry customers and reduces investment costs. According to the characteristics of various industries, the appearance and capacity of Industrial terminals vary greatly, including ordinary mobile phone terminals, on-board terminals, ATM machines, street lamp monitors, and so on are all industry customers' data collection equipment.
(4) data transmission and communication between peripheral devices and internal data centers in the industry: Due to the dispersion, mobility, and danger of peripheral devices, the wireless DDN can be used to transmit the data collected by peripheral devices to internal data centers of the industry for processing and implement corresponding functions.
According to the features of the wireless DDN terminal, the wireless DDN can be divided into two categories. The first type is mobile applications, which are suitable for applications that require real-time communication with the central node due to unfixed device locations and strong mobility, such as transportation, public security, customs, taxation, medical care, logistics and other industry practitioners handheld terminals or onboard terminals. The other type is fixed application, which is suitable for applications with fixed terminal device locations but widely distributed, difficult to deploy in Wired Access Mode, or costly. You can use machines to perform unattended operations, such as electric power, water conservancy, oil production, mining, environmental protection, meteorology, tobacco, finance and other industry information collection or trading systems.
3. Bearer mode of wireless DDN
There are four main bearer methods for wireless DDN: GPRS, SMS, USSD, and CSD. These four methods have their own characteristics. The specific analysis is as follows.
1) GPRS
GPRS, a universal grouping wireless service, has the advantages of always online, pay-as-you-go, fast logon, and easy switch. It is the most important bearer method in wireless DDN. GPRS provides a traffic-based billing method, and the billing plan is flexible. Compared with SMS and USSD, although the cost is high, it is characterized by its speed and security, there are mature solutions for industrial applications. At present, most industry customers use GPRS as the main bearer method. For example, the wireless POS application of the banking system and the data collection and monitoring application of the oil wells.
2) SMS
SMS can transmit 160 bytes of information, which is about 70 Chinese characters, and the communication cost is relatively low. At the same time, because of its storage and forwarding, it is suitable for mass communication, and is very popular among users. In wireless DDN, the SMS bearer mode is often the most important supplement of GPRS. In the absence of GPRS signals, SMS can be used to send information to the data center of industrial customers, such as GPS for vehicle satellite positioning.
3) USSD
USSD is a connection-oriented, real-time online interactive session data service based on the GSM network. There are many similarities between USSD and SMS, but compared with SMS, USSD has strong interactivity, connection orientation, fast response, interactive menu operations, and other advantages, however, there is still a big gap between USSD and GPRS, SMS and CSD in terms of the penetration rate and interconnection of USSD systems in various provinces. However, with its powerful wireless transmission and information interaction capabilities, once the USSD system construction and interconnection problems are solved, USSD will certainly have a broad application in the industry. The USSD mode is especially suitable for data transmission services with high interaction requirements, small data volumes, and frequent transmission. Such as wireless transactions in the banking industry, Wireless Meter Reading in the power industry, hydrological monitoring in the water conservancy industry, and traffic condition monitoring in the transportation industry.
4). CSD
CSD is short for the Circuit Switching Data Service, and the transfer rate can reach 9.6kb/s. Currently, CSD technology is used for voice communication. voice calls and other data transmission cannot be performed simultaneously. For example, you cannot access the Internet by phone, and you cannot make a phone call when you access the internet. CSD is mainly billed on time and on time. It is suitable for a small number of slow data transmission services. There are few CSD applications in the industry.
For more information about the bearer modes of wireless DDN, see the following table.
Table 1: Comparison of DDN bearer Modes
4. Network Structure of wireless DDN
In several bearer modes of wireless DDN, Although GPRS charges are relatively high, due to its always-on-line, pay-as-you-go, fast login, and other features, industry customers generally choose GPRS as the main transmission mode, supplemented by SMS, CSD, or USSD to implement reminder, interaction, or backup functions. The following uses GPRS as an example to describe the network structure of the wireless DDN.
Figure 1: network structure of a gprs-based wireless DDN Application
: The GPRS-based wireless DDN system consists of terminals in special industries, GPRS networks of mobile operators, and industry data centers. Special Industry terminals collect and send and receive data. Mobile Carrier GPRS network mainly refers to the GPRS core network, including GGSNGateway GPRS Support Node, GPRS Gateway Support Node), SGSNServing GPRS Support Node, GPRS Service Support Node), PCU (Packet Control Units, group Control Unit) and CGCharging Gateway, billing Gateway). On the one hand, it is responsible for receiving data sent by users, verifying user identities, and then transmitting data to industry data centers through a leased line, on the other hand, it receives instructions or data from the industry data center and sends it to the industry terminal. The industry data center is connected to the GGSN in the GPRS Core network through a leased line. It is responsible for receiving data transmitted from the GPRS network. After Authentication, it processes and stores the data according to the actual characteristics of its own industry; you can also send various information or instructions to industrial terminals for transmission through a leased line or GPRS network.
The GPRS wireless access method provides a better solution for the completeness issues that industry customers are concerned about.
1) wireless part: GPRS is a group exchange service developed on the GSM system. The service inherits the security characteristics of the GSM system, and the data transmitted in the air is encrypted. This effectively prevents unauthorized interception of user data in wireless networks.
2) wired part: As we can see, because industry customers' intranets are connected to the GPRS Core network through a leased line, it can fundamentally prevent malicious intruders from intercepting industry customers' data from the Internet.
3) user identity authentication:
Due to the characteristics of GPRS industry applications, mobile operators will provide a specific Access code (APN, Access Point Name) for each GPRS industry application ), end users or devices can only access the industry's intranet through GPRS through this access code. The mobile operator can bind the mobile phone number of the end user/device to the access code through the HLR Location Register Home Location Register, that is, only mobile phone numbers recognized by the industry can access the industry's internal network through the GPRS network. When mobile phone numbers not recognized by the industry attempt to access the industry's internal network, data of the phone number will be truncated in the wireless part, effectively preventing trial attacks by illegal users against internal systems in the industry.
Because internal systems in the industry can also manage user identities, including user names and passwords, through self-managed Radius servers, that is, they have the user authentication function, therefore, it further guarantees the security of internal systems of industry customers.
Through the above security mechanisms, the security of wireless DDN applications based on GPRS can be effectively guaranteed.
5. Typical application of wireless DDN
The biggest advantage of the GPRS bearer method is its fast speed, secure and reliable, and mature solutions. Currently, industries with high traffic and security requirements adopt this access method. The following uses street lamp monitoring and wireless POS in industrial applications as an example to briefly introduce the GPRS-based wireless DDN application.
1) street lamp Monitoring System
The system integrates GPRS-based wireless DDN applications and power line carrier communication technology to provide the city street lamp monitoring center with a view to the working status and fault of the street lamp at any time, you can turn on or off the street lamp as you like.
Figure 2: street lamp Monitoring System
The main purpose of the street lamp monitoring system is to configure the GPRS transmission module on the line terminal. The installation position of the GPRS module varies according to the actual situation. Solution 1: a gprs communication module connects multiple monitors in the Unified Distribution Transformer network through low-voltage power line management, a gprs communication module is responsible for monitoring and managing data transmission of multiple street lights or lighting devices. solution 2: Each street lamp is equipped with a monitor and a GPRS module, monitor and manage every street lamp. Through the monitor, the system can automatically detect trips, open circuit, voltage exceptions, power supply faults, switch lamp control exceptions and other emergencies, and upload the alarm data to the monitoring center through the GPRS communication module in a timely manner, for the monitoring center personnel on duty to know the situation and handle the situation in a timely manner.
For the street lamp Management Department, based on the wireless DDNGPRS load-carrying method), the street lamp monitoring system only needs to add the GPRS module on the original street lamp line. The GPRS module sends the real-time information of the street lamp to the monitoring center, and receive scheduling commands from the monitoring center), and add the GPRS interface function in the monitoring center, and connect the monitoring center to the GPRS Core network through a leased line. The system has the following features:
A. Economic: the construction cost is low. The connection between the street lamp monitoring center and the street lamp is through the GPRS network, which can greatly save the wiring cost, with less investment and quick effect in the early stage, later upgrades and maintenance costs are low and easy to plan.
B. Real-time: Because GPRS is always online, it can transmit the street lamp change information to the monitoring center in real time, so that the staff can monitor the street lamp status and schedule it in time.
C. Flexibility: due to the reduction of fixed transmission lines, the positioning of street lamps is flexible. On the other hand, due to the different installation positions of the GPRS transmission module, the GPRS module can be used to transmit data from one, several, or one street lamp. The overall arrangement is flexible.
2) wireless POS machine
Currently, POS Card swiping machines are everywhere on the market. Most of them communicate over the telephone line. They have poor mobility and are not flexible, which limits business development. The wireless POS machine is free from the limitations of telephone lines. Using the GPRS module installed on the POS machine, the collected data is transmitted to the bank or related center in real time.
Wireless POS machines use GPRS-based wireless DDN technology as a means of communication between POS machines and bank databases. Its advantages are obvious, such as strong mobility, short average transaction time, portable carrying, and low investment.
A. Flexible: you do not need to apply for A telephone line or other lines to avoid wiring troubles. It is equipped with A battery and can be carried with you for take-out, home delivery, and other services. Retailers can choose places without communication lines, such as stadiums, trade fairs, concerts, and temporary commercial activities.
B. Quick: after testing, the bill is printed from the magnetic card to the POS machine after receiving the confirmation data. The entire process is only 4 ~ 8 seconds, far less than the transaction time of the POS machine through the telephone line.
C. Security: It is very secure and reliable. Using GPRS network to transmit data is protected by multiple security policies, and data confidentiality is effectively guaranteed.
D. Economic: You can choose the billing method based on traffic, plan, or monthly subscription. The communication cost is low, and the cable line application and wiring costs are saved.
In addition to street lamp monitoring and real-time monitoring and maintenance systems for urban utilities, wireless POS and other e-commerce applications, wireless DDN is also widely used in mobile data query system, Mobile Vehicle Monitoring and scheduling system, data center monitoring and remote maintenance management system.
6. Conclusion
To sum up, the biggest feature of the wireless DDN business is to create a channel between the industrial application system and the China Mobile Network System by adding a wireless communication module to the peripheral device to transmit information. It is particularly suitable for industries where peripheral devices are scattered, dangerous, and mobile and require real-time communication.
With the further development of information technology in the industry, as China Mobile and other communication operators further strengthen their cooperation in the industry, they can achieve win-win wireless DDN Services for communication operators, industries, and end customers, it will surely be widely used.
