A comparison of data transmission methods
The GPS application system has the functions of positioning, timing, etc. If it is installed on a moving target and acquires the position information of the moving target in real time, the real-time monitoring of the moving target can be realized. In the past, due to the obstacles in data communication, the application of GPS technology has been limited. With the development and progress of science and technology, this system bottleneck has found a solution through the use of the relevant service functions of the mobile communication network. The system can be used. A variety of communication methods, such as clusters, analog networks, satellite communications, and GSM, consider the advantages of the GSM network in terms of cost, investment, coverage, and reliability.
Establishing a smooth, low-cost communication link is a prerequisite for the successful application of the GPS system. On the surface, there seem to be many alternative ways of communication, such as conventional communications, trunked communications, satellite communications, analog cellular communications, and GSM communications. However, considering practical applications such as capacity, response speed, coverage, and cost performance ratio, currently there are few available communication methods.
At present, the cluster communication method is a relatively common communication platform for departments such as the *, firefighting, and transportation departments. However, this communication platform is not suitable for the establishment of large-scale systems because it is limited by the coverage of the communication network (usually the working radius is about 10 kilometers). With the decline of mobile communication costs and mobile phone costs, systems based on the GSM platform have greatly increased the object and scope of monitoring, will be applied in all aspects of social life, and provide services for more people. This is inevitable for mobile target services. development trend.
The communication tasks undertaken by the GSM network service in the GPS technology are mainly completed by the short message service and the virtual network service.
Short Message Service (SMS) A value-added service for transmitting user packet information over the control channel of the GSM network. It is especially suitable for business data with a small amount of information. It uses the public control channel of the GSM network and does not affect the transmission of short messages during the call. The advantage of the short message service is that the transmission speed is fast, and the single data transmission is cheap and does not occupy the voice communication channel.
Virtual Private Mobile Network Service (VPMN) Set up a dedicated private network for voice sessions on existing mobile communications networks. Through the use of abbreviated dialing and dedicated numbering plans, the company and group users can communicate with each other. The VPMN service allows VPMN users to make in-network calls and private numbers, and gives the group and the enterprise a certain degree of in-network call discount.
Second, GPS/GSM system
The GPS/GSM system is a comprehensive set of positioning, monitoring, and dispatching command system that combines a global positioning system and a GSM short message service system. With the development of GSM in China, the transmission of GPS signals is gradually shifted from radio and private networks to transmission using the GSM public network. The GPS/GSM system uses the combination of GPS technology and wireless mobile communication technologies to achieve all-weather monitoring of mobile targets. , Alarm, command, anti-theft and scheduling functions, it uses the short message function of the GSM system for data transmission, with the characteristics of timely response.
1. system structure
After processing the received GPS information, the system calculates the longitude, latitude, speed, and direction of the moving target, and uses the existing GSM network as the medium for communication transmission to achieve the positioning information transmission.
The overall structure of the system can be divided into the following parts: location information acquisition and transmission (GPS intelligent vehicle-mounted terminal), mutual information transfer (mobile communication system GSM), information analysis and processing (dispatch monitoring center).
The GPS intelligent vehicle-mounted terminal can provide the control center with the latest position data, target status and alarm information for each moving target in real time, and automatically records these information for later analysis. The dispatch monitoring center processes the received location information through the short message service center, and displays the current monitored geographical location of the moving target on the large-screen display with the electronic map as a background.
Short Message Service Center (SMSC) equipment is generally placed in the GSM switching center (the same room as the mobile switch). If you add GPS-related equipment based on this, you can form a differential DGPS system. And the dispatch monitoring center can be connected via DDN (the extraction and collection of GPS data can be realized and displayed on the command platform of the monitoring center).
The dispatch monitoring center consists of a number of on-duty seats and is a networked structure. Each on-duty seat consists of relevant GIS and GPS application management software as a software platform and a graphics workstation as hardware support. The use of large-screen display management, due to the use of network architecture design, can easily expand the number of on-duty seats to accommodate the increasing number of users.
Among them, the communication management agency is responsible for the receipt of short message service center messages and the transmission of control instructions to the short message service center. It also has the function of information flow statistics and self-regulation, so that the information flow on the DDN line can be safely managed and controlled. And has the function of traffic statistics and the role of network security firewall.
2. System functions
â— Location search finds the position of each networked vehicle in real time.
â— Command dispatching can dispatch command dispatching commands to the access vehicles at any time according to their needs.
â— Special service and related service network connection, providing related services to networked vehicles to facilitate better self-protection of networked vehicles (such as connection with 110 alarm system) and more benefits to humans (such as connecting with 120 rescue systems ), while also extending more services and areas of service (such as connecting with the tax system).
â— The plan management implements various quantitative management and report statistics for the networked vehicles, and grasps the running status of each vehicle in time to provide relevant decision-making basis for the development of the transportation industry, especially the urban transportation industry.
â— Information dissemination can be achieved through the connection between the center and other information systems to obtain a wide range of information and disseminate it to every user to maximize the development and use of limited investment.
3. working principle
Car GPS receivers receive positioning data from positioning satellites, and calculate the plane coordinates of their geographical location based on data from three or more different satellites. The coordinate data is transmitted to the GSM public network using the wireless modem that conforms to the GSM standard and uses the form of a short message to input the vehicle's position, status, alarm, and sensor status. GSM public network will receive the vehicle positioning information through the DDN special line or communication receiving and sending equipment to the dispatch monitoring center, after processing by the computer and the electronic map on the computer system to match, and display the correct position of the coordinates on the map, then control The center can clearly and intuitively grasp the dynamic position information of the vehicle. In the event of an emergency, the vehicle's own equipment can be used to use automatic or manual alarms to send the data such as the location of the vehicle and the type of alarm to the control center. After processing by the computer, the exact location of the vehicle in question is displayed in electronic form. On the map. At the same time, the user database can be opened, the original file of the accident user can be inquired and reported to law enforcement agencies such as *, transportation, etc. for timely processing.
4. application
â— The communication server software completes the data transmission and communication between the vehicle terminal and the dispatch monitoring center, and implements data transmission and reception, encoding/decoding, data storage and authentication.
â— Voice server software completes telephony relay services, such as call acceptance services, automatic agent assignment, automatic dialing, and voice communications, providing conditions for vehicle dispatch systems and vehicle security systems.
â— Business workstation software implements functions such as customer management, vehicle management, driver management, vehicle terminal management, billing/payment management, and statistical reporting.
â— Management workstation software provides scheduling monitoring center management for each workstation, employee management and database management.
â— The display workstation software mainly implements GIS functions, stores, displays, queries, and analyzes spatial data and draws conclusions to support decision systems.
other apps
1. Cell Broadcast Service
In the vehicle dispatching system, the dispatcher must first understand the location of the vehicles that can be dispatched. If short messages and voice communications are used to query the location of each vehicle, it will inevitably increase the overhead of the wireless channel. If there is support for cell broadcast services, problems will be solved. The system can broadcast scheduling messages within a certain area and the vehicle can choose whether to answer according to its own situation (such as location and whether it is busy).
2. WAP business
In the location-based information service system, mobile users need to know information related to their location, such as the gas station nearest to them, the nearest tourist attractions, etc., and also need to access Internet resources. Such information is often displayed in the form of pictures, and The amount of data is large. If the short message service is used, it cannot meet the requirements. WAP services have unparalleled advantages in this regard.
The GPS application system has the functions of positioning, timing, etc. If it is installed on a moving target and acquires the position information of the moving target in real time, the real-time monitoring of the moving target can be realized. In the past, due to the obstacles in data communication, the application of GPS technology has been limited. With the development and progress of science and technology, this system bottleneck has found a solution through the use of the relevant service functions of the mobile communication network. The system can be used. A variety of communication methods, such as clusters, analog networks, satellite communications, and GSM, consider the advantages of the GSM network in terms of cost, investment, coverage, and reliability.
Establishing a smooth, low-cost communication link is a prerequisite for the successful application of the GPS system. On the surface, there seem to be many alternative ways of communication, such as conventional communications, trunked communications, satellite communications, analog cellular communications, and GSM communications. However, considering practical applications such as capacity, response speed, coverage, and cost performance ratio, currently there are few available communication methods.
At present, the cluster communication method is a relatively common communication platform for departments such as the *, firefighting, and transportation departments. However, this communication platform is not suitable for the establishment of large-scale systems because it is limited by the coverage of the communication network (usually the working radius is about 10 kilometers). With the decline of mobile communication costs and mobile phone costs, systems based on the GSM platform have greatly increased the object and scope of monitoring, will be applied in all aspects of social life, and provide services for more people. This is inevitable for mobile target services. development trend.
The communication tasks undertaken by the GSM network service in the GPS technology are mainly completed by the short message service and the virtual network service.
Short Message Service (SMS) A value-added service for transmitting user packet information over the control channel of the GSM network. It is especially suitable for business data with a small amount of information. It uses the public control channel of the GSM network and does not affect the transmission of short messages during the call. The advantage of the short message service is that the transmission speed is fast, and the single data transmission is cheap and does not occupy the voice communication channel.
Virtual Private Mobile Network Service (VPMN) Set up a dedicated private network for voice sessions on existing mobile communications networks. Through the use of abbreviated dialing and dedicated numbering plans, the company and group users can communicate with each other. The VPMN service allows VPMN users to make in-network calls and private numbers, and gives the group and the enterprise a certain degree of in-network call discount.
Second, GPS/GSM system
The GPS/GSM system is a comprehensive set of positioning, monitoring, and dispatching command system that combines a global positioning system and a GSM short message service system. With the development of GSM in China, the transmission of GPS signals is gradually shifted from radio and private networks to transmission using the GSM public network. The GPS/GSM system uses the combination of GPS technology and wireless mobile communication technologies to achieve all-weather monitoring of mobile targets. , Alarm, command, anti-theft and scheduling functions, it uses the short message function of the GSM system for data transmission, with the characteristics of timely response.
1. system structure
After processing the received GPS information, the system calculates the longitude, latitude, speed, and direction of the moving target, and uses the existing GSM network as the medium for communication transmission to achieve the positioning information transmission.
The overall structure of the system can be divided into the following parts: location information acquisition and transmission (GPS intelligent vehicle-mounted terminal), mutual information transfer (mobile communication system GSM), information analysis and processing (dispatch monitoring center).
The GPS intelligent vehicle-mounted terminal can provide the control center with the latest position data, target status and alarm information for each moving target in real time, and automatically records these information for later analysis. The dispatch monitoring center processes the received location information through the short message service center, and displays the current monitored geographical location of the moving target on the large-screen display with the electronic map as a background.
Short Message Service Center (SMSC) equipment is generally placed in the GSM switching center (the same room as the mobile switch). If you add GPS-related equipment based on this, you can form a differential DGPS system. And the dispatch monitoring center can be connected via DDN (the extraction and collection of GPS data can be realized and displayed on the command platform of the monitoring center).
The dispatch monitoring center consists of a number of on-duty seats and is a networked structure. Each on-duty seat consists of relevant GIS and GPS application management software as a software platform and a graphics workstation as hardware support. The use of large-screen display management, due to the use of network architecture design, can easily expand the number of on-duty seats to accommodate the increasing number of users.
Among them, the communication management agency is responsible for the receipt of short message service center messages and the transmission of control instructions to the short message service center. It also has the function of information flow statistics and self-regulation, so that the information flow on the DDN line can be safely managed and controlled. And has the function of traffic statistics and the role of network security firewall.
2. System functions
â— Location search finds the position of each networked vehicle in real time.
â— Command dispatching can dispatch command dispatching commands to the access vehicles at any time according to their needs.
â— Special service and related service network connection, providing related services to networked vehicles to facilitate better self-protection of networked vehicles (such as connection with 110 alarm system) and more benefits to humans (such as connecting with 120 rescue systems ), while also extending more services and areas of service (such as connecting with the tax system).
â— The plan management implements various quantitative management and report statistics for the networked vehicles, and grasps the running status of each vehicle in time to provide relevant decision-making basis for the development of the transportation industry, especially the urban transportation industry.
â— Information dissemination can be achieved through the connection between the center and other information systems to obtain a wide range of information and disseminate it to every user to maximize the development and use of limited investment.
3. working principle
Car GPS receivers receive positioning data from positioning satellites, and calculate the plane coordinates of their geographical location based on data from three or more different satellites. The coordinate data is transmitted to the GSM public network using the wireless modem that conforms to the GSM standard and uses the form of a short message to input the vehicle's position, status, alarm, and sensor status. GSM public network will receive the vehicle positioning information through the DDN special line or communication receiving and sending equipment to the dispatch monitoring center, after processing by the computer and the electronic map on the computer system to match, and display the correct position of the coordinates on the map, then control The center can clearly and intuitively grasp the dynamic position information of the vehicle. In the event of an emergency, the vehicle's own equipment can be used to use automatic or manual alarms to send the data such as the location of the vehicle and the type of alarm to the control center. After processing by the computer, the exact location of the vehicle in question is displayed in electronic form. On the map. At the same time, the user database can be opened, the original file of the accident user can be inquired and reported to law enforcement agencies such as *, transportation, etc. for timely processing.
4. application
â— The communication server software completes the data transmission and communication between the vehicle terminal and the dispatch monitoring center, and implements data transmission and reception, encoding/decoding, data storage and authentication.
â— Voice server software completes telephony relay services, such as call acceptance services, automatic agent assignment, automatic dialing, and voice communications, providing conditions for vehicle dispatch systems and vehicle security systems.
â— Business workstation software implements functions such as customer management, vehicle management, driver management, vehicle terminal management, billing/payment management, and statistical reporting.
â— Management workstation software provides scheduling monitoring center management for each workstation, employee management and database management.
â— The display workstation software mainly implements GIS functions, stores, displays, queries, and analyzes spatial data and draws conclusions to support decision systems.
other apps
1. Cell Broadcast Service
In the vehicle dispatching system, the dispatcher must first understand the location of the vehicles that can be dispatched. If short messages and voice communications are used to query the location of each vehicle, it will inevitably increase the overhead of the wireless channel. If there is support for cell broadcast services, problems will be solved. The system can broadcast scheduling messages within a certain area and the vehicle can choose whether to answer according to its own situation (such as location and whether it is busy).
2. WAP business
In the location-based information service system, mobile users need to know information related to their location, such as the gas station nearest to them, the nearest tourist attractions, etc., and also need to access Internet resources. Such information is often displayed in the form of pictures, and The amount of data is large. If the short message service is used, it cannot meet the requirements. WAP services have unparalleled advantages in this regard.
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