400 points. Two questions asking for a report on wireless positioning.

Wireless positioning service, also known as location-based service (LBS), is a value-added service provided by mobile communication networks. It obtains the location information of mobile stations through a set of positioning technologies ( Such as latitude and longitude coordinate data), provided to mobile users themselves or others and communication systems to implement various location-related services. In a narrow sense, the LBS service is a wireless value-added service that obtains the location information of wireless users through the wireless communication network and provides corresponding services with the support of the geographic information system platform. Broadly speaking, all location-based information services are location services, and some services may have nothing to do with the user's own location, such as weather at a fixed location, bus routes between fixed starting and ending points, etc. However, in mobile communication networks, the most widely used LBS services should be those services that are closely related to the location of the terminal holder.

At present, competition in the telecommunications industry is fierce, and mobile operators are constantly looking for new ways to create new profit points or profit growth points. Among various mobile value-added services, mobile location information service has the greatest market potential. On the other hand, as my country's private car market continues to grow, the demand for automotive mobile communication platforms will also have great development potential. Among them, location services such as navigation and tracking for cars are a market with great development potential in the future.

As far as wireless positioning services are concerned, location services are developed on traditional second-generation wireless communication networks. Due to the low data transmission capabilities of the second-generation system, the types of positioning services that can be provided are also limited. The data transmission capability of the 3G system is greatly improved compared to the 2G system, which guarantees network bandwidth to provide users with richer information, making it possible to implement some positioning services with large amounts of information through wireless networks, such as map display, Real-time navigation, even 3D map services, etc. There are various types of LBS services, which can be divided according to the following different classification methods:

(1) Divided according to service request methods

·PULL type LBS services: mobile terminals use short messages , WAP access, etc. to request LBS;

·PUSH type LBS service: The network actively pushes information to the mobile terminal according to specific conditions.

(2) Divide according to whether it is related to the user's location

·LBS that are related to the user's location need to be positioned;

·LBS that are not related to the user's location , no positioning required.

(3) Divide according to users

·Horizontal market - mass applications;

·Vertical market - industry applications.

(4) Division of positioning service functions in GIS systems

·Map services, including raster maps and vector maps;

·Route search, including Shortest path query, bus route query, etc.;

·Geocoding/reverse geocoding;

·Measurement.

2. Network architecture for realizing LBS application

In the 3G system, the network model for realizing LBS application is shown in Figure 1. As can be seen from Figure 1, implementing LBS services involves multiple entities.

Figure 1 Network architecture for realizing LBS application in 3G system

(1) Positioning operation platform. The location information of the mobile station is obtained through various positioning technologies.

(2)LCS middleware. Provides a location service interface to the SP. The SP accesses the operator's location resources (GIS) through the LCS middleware, and completes functions such as billing and management of LBS services.

(3)GIS system. Provides various geographical information services based on LBS applications, including map services, route search, directory query, etc.

(4)SP. Provide LBS services to end users.

(5)CP. The CP referred to in this article specifically refers to content providers that provide electronic map data and POI (points of interest) information.

(6)Terminal. It is necessary to interact with the network to complete the positioning operation (obtain the terminal's latitude and longitude), and interact with the SP through WAP/Java/BREW/SMS to obtain the final service. For vector map services, the terminal needs to have a built-in vector map browser.

For mobile network operators, in order to better develop LBS services, they first need to build a positioning operation platform. For the GIS system, it can be implemented by SP/CP themselves. However, the development of GIS systems based on LBS in my country has just started, so it is relatively difficult for SP/CP to implement GIS by themselves. Moreover, it is also a waste of resources for SP/CP to establish GIS independently. Therefore, unified construction by operators including LCS middleware and GIS system will play a great role in promoting the promotion of LBS applications.

3. Positioning technology

The positioning operation platform is mainly responsible for obtaining the longitude and latitude information of the terminal through various positioning technologies. Currently, there are various positioning technologies available for mobile networks. The following will take the positioning technology implemented on the cdma2000 system as an example to introduce the implementation methods of various positioning technologies.

1 Network-based positioning technology

In the CDMA system, in order to achieve soft handover, the mobile station needs to constantly search for signals from other base stations while receiving signals from the current serving base station. signal. If the signal from another base station is found to be strong enough, the mobile station needs to determine the time difference between the signals from the different base stations in preparation for merging the two signals. This capability of mobile stations lays the technical foundation for positioning. The positioning operation platform can obtain this information (pilot strength information) of the terminal through the CDMA network for positioning. Some other network-based technologies can provide higher positioning accuracy, such as measuring the mobile station's loop delay, signal arrival angle, etc., but these technologies require adding corresponding measurement equipment to the base station, which is costly.

2 Assisted GPS technology (AGPS)

Assisted GPS technology mainly relies on GPS satellites to complete positioning operations. The mobile station needs to receive signals from at least 4 GPS satellites, complete positioning calculations based on this information, and report the calculation results to the network. For general GPS positioning technology, a GPS receiver is required to search for available GPS satellites in the entire airspace. Usually this kind of search takes a long time, so it cannot meet the needs of fast mobile positioning. In assisted GPS technology, the network can determine the GPS satellites over the cell based on the cell where the mobile station is currently located, and provide this information to the mobile station. Based on this information, the mobile station narrows the search range, shortens the search time, and completes the search process of available satellites faster. After the search is completed, the mobile station needs to transmit the information used to calculate the mobile station's position to the network through interaction with the network, and the network calculates the mobile station's position.

3 Hybrid positioning technology

The hybrid positioning technology used in CDMA systems mainly uses the two mobile station-based technologies mentioned earlier. Generally speaking, GPS technology can provide high positioning accuracy, but in many cases, mobile stations cannot capture enough GPS satellites. At this time, the mobile station can use the base station's signal to supplement the satellite's deficiencies. In this way, availability is improved and indoor positioning is achieved while reducing a certain accuracy.

4 GPS positioning based on mobile stations

For some LBS services that require fast and continuous positioning (such as real-time dynamic car navigation), it may be required to refresh the terminal position every few seconds information. In this case, it is difficult for the AGPS method to meet the time requirements. Therefore, in order to improve the positioning interval time in the case of continuous positioning, GPS positioning based on mobile stations is proposed. Different from AGPS, based on the mobile station positioning method, the location calculation is all completed by the terminal itself, and the terminal is always in GPS tracking state, which reduces the interaction time with the network. However, the time to initial positioning (TTFF) is basically the same as that in AGPS mode. Like AGPS, GPS satellite information needs to be obtained from the network side.

IV. GIS system

The key core of LBS service is location and geographical information. The two complement each other and are indispensable. For normal use, a longitude and latitude position does not mean anything. It must be placed in a geographical information before it can be represented as a certain location, sign, orientation, etc., so that it can be understood by people. Therefore, in addition to obtaining the location of the terminal through the positioning operation platform, the longitude and latitude must be converted into geographical information that users really care about through the GIS system, such as maps, route search results, etc.

For wireless operators, how to develop SPs for end users is the key to the development of any value-added services. For the majority of SPs, they don't know much about the key technology involved in location information services - geographic information systems (GIS). From a technical point of view, it is very difficult for SP to independently provide location information services. Because we need to consider how to interface with the positioning gateways of various manufacturers of wireless operators, what kind of geographic information system to use, what kind of map database to use, how to maintain the map database, how to develop it, and how to promote the market. Development allows more users to join their operating networks, etc. For the above considerations, each CP needs to invest a considerable amount of money to build a platform that provides geographic information services and continuously maintain geographic information data.

In this case, it is very unfavorable to the promotion of mobile location information services and the development of value-added services of the mobile Internet. Therefore, the main task of SP in the entire value-added business value chain is to add its own distinctive services, promote the market, and develop as many end users as possible.

It is not enough for wireless operators to have only one positioning operation platform. They must build a geographical information service platform, the core component of location information services. Let CP reduce investment and focus on its own services.

The geographical information service platform in location information services is a key component. From the perspective of wireless operators managing and activating location information services, it enables wireless operators to provide more comprehensive location information services. At the same time, it also centrally manages and maintains map databases, making it easier for CPs who want to enter the location information service industry to The threshold has been greatly lowered, thus promoting the development of location information services.

1 Development of Geographic Information Systems

Geographic information has now penetrated into information systems in all walks of life. From a demand perspective, whether it is macro-level decision support, comprehensive business analysis, or the positioning of a target and the planning of a route at the specific business level, it is inseparable from the support of geographical information. From a technical perspective, with the development of computer information technology, especially the continuous updating of technology in the field of mobile computing and spatial database in recent years, geographic information technology (GIS) has also incorporated new features in many aspects.

In our country, the construction of geographical information systems has also received more and more attention from the government, especially in some special circumstances, such as the situation like SARS, for tracking some people of concern and moving objects. , as well as analysis and research related to geographical location, which is very important for the government to respond to emergencies.

2 Technology development

(1) From GIS to eb-GIS. Early geographic information systems were highly professional and required the introduction of complex mathematical models. They had higher requirements for end users. The systems were designed independently and did not open interfaces to the outside world. This type of system is more common in professional analysis in geology, meteorology, water conservancy, transportation and other industries. Driven by this demand, most application systems are designed according to the Client/Server model. Its biggest advantage is that the development model is relatively simple and the development cost is low. However, as these C/S model information systems are continuously put into use, their shortcomings are gradually exposed. Due to its professional nature, the application system under the C/S mode can only be used by a small number of professional users, resulting in the existence of a large number of information islands. Moreover, the cost of large-scale deployment and post-maintenance is quite high, which greatly limits the number of users and coverage of the application system, which to a certain extent has seriously restricted the continued development of geographic information systems. On the other hand, since most systems adopt independent designs, data and functions cannot be fully shared between different systems, and the problem of repeated construction of modules with similar functions has become increasingly prominent, resulting in a huge waste of investment.

In recent years, the construction of geographic information systems requires that they be able to meet the needs of more non-professional users. With the gradual popularization of the Internet, the majority of users are increasingly recognizing browsers as a universal client application that does not require training, thus laying the foundation for the development of Web-GIS. In addition, at the technical level, users require geographic information systems to adopt an open design and open callable interfaces to other information systems for integration. Only in this way can the application scope of geographical information systems be expanded from the limited traditional application fields and cover more user groups.

Compared with Client/Server mode, Browser/Server mode has obvious technical advantages in dealing with these problems. Therefore, in some specific fields, the B/S model has replaced the C/S model and become the preferred development model of geographic information systems.

(2) From Web-GIS to network geographic information system. Entering the 21st century, people are no longer satisfied with sitting at the computer desk in the office or at home to obtain information, but have put forward higher requirements for "accessing information anytime, anywhere" (Anytime, Any-where, Anything). Strong demand has promoted the rapid development of technology in the field of mobile computing. The clients of information systems have expanded from traditional desktop devices such as PCs and workstations to mobile terminals such as PDAs, WAP/SMS/kJava/Brew mobile phones. Since all mobile terminals first emphasize the characteristics of being easy to carry, and are limited by size, weight, power consumption and other aspects in hardware design, they adopt an operating system that is completely different from PCs and a communication protocol that is different from IP networks. On the other hand, the bottom layer of geographic information system began to be combined with database technology and developed into a spatial database. Spatial database technology has great advantages over traditional file storage methods in managing massive data, distributed data storage, and solving problems such as consistency of attributes and spatial data, so it has attracted more and more attention.

In recent years, some new geographic information systems have begun to gradually introduce these two technologies. These systems require the application layer to be compatible with various terminal devices, and the data layer to provide good support for heterogeneous or distributed data. We refer to all network-based geographic information systems, including these types, as network geographic information systems.

Since the complexity of the network geographic information system has far exceeded the scope that can be described by the traditional C/S or B/S architecture, and the development workload has become increasingly large, it is necessary to Find a multi-layer model that is different from C/S or B/S to describe the security of these systems. At the same time, we provide product-level solutions on this basis and provide application developers with good underlying support as much as possible to reduce the difficulty of developing systems and improve the quality of the system.

From GIS to Web-GIS, and then to the network geographical information system, the application is developing from traditional fields to all fields, the user group is developing from a small number of professional users to a large number of ordinary users, and technically It is the development from simple architecture to multi-layer model.

3 Application fields

GIS has a wide range of application fields. Some typical examples are given below.

(1) Digital city. Spatial information technology with GIS as the core is the core application technology of digital cities. It is increasingly integrated with wireless communications, broadband networks and wireless networks, providing a three-dimensional, multi-level information service system for urban life and business.

Digital city construction includes four parts, namely infrastructure, e-government, e-commerce and public information services. GIS applications run through the above four parts and at all levels. From urban basic geographic information databases to government spatial data sharing, e-commerce logistics and distribution, and network-based public geographic information services, GIS plays an indispensable role.

In terms of specific applications, GIS has been widely used in many industries that constitute digital cities, such as urban planning, urban underground pipe networks, electricity, telecommunications, public security, firefighting, first aid, etc. The wide application of GIS in various industries has produced unique industry-specific GIS, which is the basis for our construction of digital cities. Digital cities can only be integrated, shared and expanded based on these thematic GIS.

(2)LBS. Through the LBS service, mobile users can easily know their current location, and use the terminal to query or receive information about various nearby places. At the same time, it can also locate specific users or organizations, conduct real-time monitoring and tracking based on the user's location, and combine it with the most shared electronic map to achieve monitoring and scheduling. The LBS business has a very close relationship with Telematics and ITS, which are currently attracting international attention. Due to limited space, we will not describe them again.

(3) Industry application

·Oil fields. The petroleum industry has been applying GIS technology for a long time.

Choosing where to drill a hole, tracking a pipeline for failure analysis, or building a new refinery all rely on an understanding of geography to make informed business decisions. GIS is widely used in the petroleum industry. According to application categories and business scope, GIS applications can be roughly summarized into oil exploration, production development, equipment management, pipeline management, transportation management, sales planning, ground construction, ancillary facilities, etc. .

·Telecommunications. GIS provides telecom operators with the ability to integrate maps and other data for analysis. By analyzing data based on spatial location, we can provide the best solution for telecommunications network planning and construction, mobile signal coverage area analysis, market operation decision-making analysis, management of current user information, and even discovery of new users. Displaying data in a map format is more intuitive than a traditional list format and enables faster decision-making.

·Public Security. The modernization of public security requires the support of geographic information systems (GIS) and computer network technology. GIS technology has many applications in public security, such as fire command system, security command and management system, 110 command and management system, household registration management system, public security traffic command system, emergency public security command and management system, security system, public security situation reporting system, etc. .

·Water conservancy. The application of GIS in water conservancy has expanded to many aspects such as water resources, water environment, soil and water conservation, farmland water conservancy, water conservancy project planning and management, etc. It has a wide range of growth points and good growth potential, and has played a major role in my country's water conservancy construction. .

·Transportation. In terms of transportation, GIS can be applied to highway planning, design and management, transportation scheduling, bus traffic management, railway planning, design and management, port and water transportation management, intelligent transportation system (ITS), etc.

4 Business functions of GIS system in 3G network

Using GIS in mobile networks, the main services that can be provided are as follows:

(1 )Mapping

Mapping is the most basic function provided by the GIS system. The GIS system returns map data according to the client's request (map range, layer, drawing style, etc.). Map data can be a map in raster form or vector data in a specific format. Map rasterization defines multiple image format output support, such as GIF, JPEG, PNG, WMP, BMP, etc. The map image can be returned in the XML document through a BASE-64 encoded document, or only the URL can be returned. "Map drawing" can also "draw" various geometric elements or geographical objects on the "original" map.

Vector maps have greater advantages than raster maps. First of all, for the same map, the vector format file is about 1/7 the size of the raster format file, which greatly saves the resources used in the wireless network. At the same time, the terminal's flexibility in operating vector maps through the vector map browser is very high compared to raster maps. The enlargement and reduction of multiple scales of the map can be completed locally on the terminal, and it also has advantages in navigation applications. However, because the vector map data format is currently not unified among various manufacturers, if there are multiple GIS systems in the network, compatibility issues must be considered. Due to the limited capabilities of the terminal, there is currently no better solution. On the other hand, publishing vector maps externally also requires consideration of map security and encryption issues.

(2) Directory Service (Directory)

Mainly refers to the search for POIs (points of interest), including nearest search, search within a certain range and search based on attributes (such as name, phone number) number, etc.) to search. Search content can include shopping malls, hotels, gas stations, etc.

(3) Route search (Route)

Mainly provide driving routes between two points in various modes (self-driving, bus, walking). The path search service is a very important service in the LBS business. It is also a business that reflects the advantages and characteristics of mobile networks and is the basis for realizing navigation services.

The route search service has higher requirements for map data. For example, the map data provider must provide complete and accurate road network data, including various rules, such as one-way, no left, number of lanes, etc.

The route search service can support the following operations:

·Full route: based on the information specified by the request (self-driving, walking, bus mode, the shortest, fastest, not taking the highway, passing through multiple points, etc. mode) returns information about the entire path.

·Multi-point passing mode: According to the point sequence specified by the request (by default, the first and last points are the starting and ending points), search for a path that passes through all specified points.

·Exclusion conditions: Based on different road types and regional types, you can specify whether to take highways, urban areas, and roads not to take.

·Time and distance information: The service will return multiple time and distance calculations based on the origin, destination, and segmented routes.

(4) Geocoding (GeoCode), encoding a street address or zip code into a geographical location.

(5) Reverse Geocode (Reverse Geocode), reverse encoding a geographical location into a street address or zip code.

(6) Calculation (Cogo), calculation of geometric elements. Currently, the operations supported by this service include calculating the straight-line distance between two points and determining whether the point is within a specified area. The calculation service can complete multiple calculation operations with one request.

(7)Navigation. Navigation service can also be regarded as a type of route search service, but because navigation service has its own characteristics, it is separated in the location business specifications formulated by OGC (Open GIS Consortium). Navigation services can be divided into static navigation and dynamic navigation.

·Static navigation means that the user obtains the best route information of the departure place and destination before departure, and there will no longer be prompt information to the user after departure;

·Dynamic navigation is While the user is driving, the GIS system (network side or user local) dynamically prompts the user in the direction based on the current user's location (such as notifying the user in advance to turn left, dynamically displaying the current user's location on the map, and driving with the destination). The distance on the route, etc.), this kind of service has higher requirements on the system's processing power, positioning accuracy, positioning delay and map accuracy.

5. Standardization work related to LBS services

As mentioned earlier, the implementation of LBS services can be divided into two levels, namely location acquisition and information provision. Correspondingly, standardization work also corresponds to different standards organizations.

(1) The acquisition of location is the standard of positioning technology. Currently, standardization work is mainly carried out in 3GPP and 3GPP2. Relevant standard work on user authentication and authorization, business roaming, and privacy management at the business level is currently mainly carried out in OMA. However, due to differences between 3GPP and 3GPP2 in OMA regarding the LBS process, network structure, etc., Progress on standardization may slow. At the same time, it should also be noted that the same work as OMA is actually done in 3GPP2.

(2) For the standard work at the level of geographical information provision, OGC is currently mainly responsible for formulating it, and has basically completed other businesses except navigation services.

In my country, the industry standard for the Le/L1 interface (the interface between the client and the positioning server) has been completed, as well as the industry standard for positioning technology in WCDMA and cdma2000 systems. Standards related to GIS currently include corporate standards for the GIS interface and SPACCESS interface. The IP-level positioning technology standard corresponding to OMA will also be launched.

6. Application of LBS business in my country

1 Application prospects

LBS business is a characteristic business of mobile networks, especially with the development of 3G systems in the future. Used to provide network bandwidth guarantee for LBS applications. Since the LBS business has just begun to develop in our country, and there are many factors affecting its development, this article only makes a simple analysis of the LBS businesses with development potential that can be encountered at present.

(1) LBS application of handheld terminals

The LBS application range of handheld terminals is very wide, and can be based on voice, SMS, WAP, Java/BREW and multimedia SMS/mail to mass users Provides various services, including information inquiry, map services, handheld terminal navigation, tracking of vulnerable groups and regional warnings (such as the elderly and children), etc.

(2) LBS application in personal cars

Navigation is the main way of LBS application in cars. At present, there are practical applications of car navigation in our country. This application is GPS receiver. + Simplified version of GIS engine + map data model. This model has its own limitations, such as higher cost (higher requirements for vehicle-mounted radios, such as processing power and storage capacity), and map resources cannot be fully shared. (For example, a large amount of map data needs to be stored, and areas that drivers occasionally pass through also need to be stored.) Dynamic map updates cannot be achieved, and the flexibility of business organization is also limited. These problems can be solved by combining with mobile networks. With the continuous growth of the automobile market, the car navigation service is a business growth point that mobile operators need to pay attention to. It can be combined with the existing voice, SMS and other services of the operators to provide users with more diverse LBS services, such as car anti-theft. , tracking, asking for help, etc.

The LBS business has a very close relationship with Telematics, which is currently attracting international attention. The purpose of Telematics is to build an in-car communication platform to provide drivers and passengers with various services through interaction with the network. kind of service. South Korea is more active in this regard and currently has similar applications, mainly providing car navigation and email services.

(3) Industry applications

There are many examples of industry applications, including car dispatching (such as taxi dispatching), logistics management, employee tracking (such as postman tracking), etc. I won’t describe them one by one here.

2 Problems faced in realizing LBS business

LBS business has a broad application market, but compared with other value-added services based on mobile networks, its business implementation involves more aspects. It is more difficult, so if LBS business is to be truly widely used, it still faces some problems that need to be solved.

(1) Positioning accuracy

Currently, the most accurate positioning technology that can be used in LBS applications is GPS positioning technology, but GPS positioning has limitations, such as deep indoor In this environment, GPS positioning will not be possible. If network-based positioning is used, the accuracy is greatly reduced, and there is currently no other better solution. Therefore, a more practical and feasible approach is to divide the services and classify the positioning accuracy requirements of various services. For services with high accuracy requirements, the network side determines whether the requirements can be met and handles them accordingly. Of course, the ultimate solution is to propose a more advanced positioning technology that is less restricted by geographical environment. Research has already begun on technology to achieve high-precision positioning indoors.

(2) Collection and organization of location information

LBS ultimately provides users with location-related content. Location information mainly includes electronic maps and POI information at all levels. In terms of electronic maps, various departments in our country have certain levels of data, but these data are not integrated together. The current status of maps is also uneven in various regions. The solution to this problem lies not with operators and map data providers. What can be accomplished unilaterally requires unified organization by the state to integrate various geographical information resources for use by various industries. For POI information, its richness directly affects user satisfaction with the business, so content providers need to provide rich POI information. However, the workload of information collection is quite large, and it needs to be collected one by one on the spot. Therefore, operators need to integrate the POI information provided by various CPs and provide it to users in a unified manner. This part of the work requires coordination between operators and various content providers.

(3) Vector map browser

Navigation business, especially real-time navigation business, if the map is downloaded in real time through the network, the data cannot be too large, otherwise the user will The cost will be very high, which is not conducive to promotion. Vector maps are a solution to this problem, but vector maps are closely related to the formats of vector data in the systems of various GIS vendors, and currently cannot be unified into the same format.

Therefore, if multiple GIS systems exist, there will be limitations in service coverage. This can be solved by the terminal supporting multiple vector map browsers, but this requires higher processing and storage capabilities of the terminal. Therefore, this issue is also worth noting. Figure 2 is a schematic diagram of how vector maps work.

Figure 2 Schematic diagram of how the vector map service works

7. Conclusion

The LBS business has broad development prospects, and the current commercial LBS industry has also reached Considerable penetration. LBS business involves many fields, and it requires the combination of mobile communications field and GIS field for simultaneous implementation. Our country currently attaches great importance to the development of the GIS field, and there are already quite a few domestic GIS manufacturers with certain strength and development potential. It is believed that with the continuous growth of LBS business demand in the future and the continuous development and improvement of my country's GIS field, LBS business will be more widely used.