User adapted position dependent information presenting system in mobile communication, has terminal equipment having client with functionality for data communication, positioning system and display system

(54) (56)

AGENT

NAME

Telia AB, 123 86 Farsta SE

Jonas Christiansson, Luleå SE, Lars-Åke Isaksson,

Gammelstad SE, Roland Kero, Luleå SE, Henrik Melander,

Luleå SE, Amalendu Parasnis, Luleå SE, Peter Rosell, Luleå SE, Andreas Sikström, Luleå SE

Telia Research AB

Method for optimizing accuracy in positioning for mobile terminal (57)

CALLED PUBLICATIONS:

US A 5,563,607 (342/357)

Patent Abstract of Japan, abstract of JP 09-311177 A (SEIKO EPSON CORP), 1997-12-02

SUMMARY:

A method for optimizing accuracy when positioning mobile terminals in a positioning system.

The terminal equipment receives positioning information from the positioning system. The positioning information is adjusted to take into account the geographical position of the terminal and the imperfections of the positioning system. The basis for adjusting positioning information is recorded and updated in at least one database (13). Data for adjusting positioning information is transmitted to the terminal equipment.

Said data for adjustment is affected by the position of the terminal and the status of the positioning system. The adjustment of positioning information is based on the position and direction of movement of the terminal equipment. Data for adjusting positioning information is transmitted to the terminal equipment at a time interval determined from the speed of the terminal equipment.

\ / \ / \ /,. >; GPS salelli! (te) '^X Z \ Z \

<img file="SE522554C2_D0001.tif" />

The numbers in brackets indicate international identification code, INID code. Letters in clamps indicate international document code.

522 554

SUMMARY

A method for optimizing accuracy when positioning mobile terminals in a positioning system. The terminal equipment receives positioning information from the positioning system. The positioning information is adjusted to take into account the geographical position of the terminal and the imperfections of the positioning system. The basis for adjusting positioning information is recorded and updated in at least one database (13). Data for adjusting positioning information is transmitted to the terminal equipment. Said data for adjustment is affected by the position of the terminal and the status of the positioning system. The adjustment of positioning information is based on the position and direction of movement of the terminal equipment. Data for adjusting positioning information is transmitted to the terminal equipment at a time interval determined from the speed of the terminal equipment.

522 554

TECHNICAL FIELD

The present invention describes a method of obtaining improved positioning information with GPS. The invention utilizes differential GPS (DGPS) to improve the positioning information of the GPS system.

The mobile station combines Internet technology, mobile communication and an ordinary laptop with a GPS receiver to utilize the service logic in the network to obtain DGPS data for the position of the mobile station.

The client must be connected to a communication network, eg an IP network, to obtain DGPS data for correction. However, the client does not need a special DGPS receiver but the said DGPS data is transmitted with the IP protocol to the client who extracts and uses this data to determine the position.

BACKGROUND OF THE ART

GPS is a commercial method that uses satellites to obtain position information on the Earth's surface with an accuracy of the order of 100m. It is also known how differential GPS (DGPS) can obtain a more accurate positioning information from the GPS system.

DGPS is based on the fact that from a known location, the reference station (RS), continuously measures the magnitude of the wrong position signals from each GPS satellite.

522 554

Today's DGPS system utilizes radio communications to unilaterally transmit data to the terminals. There is no technology that enables two-way communication between reference stations and terminals in a network-based and bandwidth-saving manner so that the terminals can be provided with current data. The DGPS systems therefore work with autonomous terminals, which have all system information stored locally and receive position information from reference stations.

TECHNICAL PROBLEM

Position assignments can be obtained in different ways with different manual or automated methods, but with the methods used today it can be difficult to get sufficient accuracy on the position statement. With GPS systems, you can get a position assignment with an accuracy of the order of 100m. With DGPS (Differential GPS) system, you can get improved accuracy, but today's existing DGPS system requires the use of a special receiver for correction data.

Today's system, which utilizes unidirectional communication from the central system to the user terminal, does not know where the receiving terminal is. This means that missing DGPS data cannot be replaced by data from other reference station because the system does not know from which other reference station it is to retrieve correction data.

With unidirectional communication there is also no possibility to transfer data for storage in the terminal, which makes renewal of data difficult.

In the absence of communication opportunities, the client in the systems used today has been adapted to take advantage of the bandwidth that can be expected to be available. Consequently, the bandwidth is not utilized optimally.

All required static information and all personal profiles must be stored in the terminal. Thus, the user himself has to make sure that all information, such as

522 554 stored in the terminal is current. In addition to rendering some work for the user, there is also a great risk that the stored data is out of date.

If a reference station fails, the possibility of utilizing DGPS in today's system is lost or lost.

Without utilizing bidirectional communication, it is not possible to distribute DGPS data tailored to the client's position.

TECHNICAL SOLUTION

The invention, described in this patent application, comprises a software and technical solution for distributing DGPS data via the IP protocol over an open data network such as the Internet or other communication network.

The user starts the client program in his terminal where, in a preferred form, a map of the local environment is downloaded to the client. The map shows the user's position, corrected by means of a position correction function, eg DGPS, which is also sent to the client over the data network.

The position correction is based on the continuous measurement of the positioning signals from each GPS satellite from a known location, a reference station (RS). The value measured is the travel time of the signal from each individual GPS satellite to the reference station. By knowing exactly where the reference station is located, it is possible to calculate how long it takes for the signal to reach the reference station from the satellite. The difference between the value measured and the correct value, which is known through knowledge of the position of the reference station, is DGPS data.

The measurements are made for the satellites that the reference station can communicate with, ie those that are above the horizon and not in radio shadow from the reference station. This DGPS data is then transmitted to the GPS receiver, which with the help of the data can correct its position. With that one

522 554 reference station has a limited range, ie DGPS data from an RS cannot be used too far from RS, a number of RS is needed to cover a large area, see Figure 2, which shows the coverage area for a number of reference stations over a geographical area.

The IP protocol is used for user terminal / client communication, which means that 2-way communication is possible. This means that the client has the opportunity to ask intelligent questions with regard to the current position. The client will therefore request, collect and present information based on the mobile user's wishes, position, speed (ie speed and direction of movement).

Unlike conventional DGPS, where RS sends directly to the client, a server handles the communication both with RS and with client. The server can then communicate with several reference stations. Thus, it is possible to supplement the collected data on data from any RS is missing. In the server, correction data from several reference stations is stored, for example, in a correction database.

Because the server communicates with the client, the client's location can be utilized for better accuracy in the correction.

All information is filtered and prioritized so that only relevant data is sent. This means that it is possible to utilize mobile access via a medium with limited bandwidth, eg GSM.

The client contains no stored static information. Instead, personal profiles, map images, information objects, web pages and correction data are retrieved from the service logic of the network if necessary. With this procedure, the service logic operator can be responsible for ensuring that all information presented to the user is accurate and up to date. Therefore, the user does not need to load information, maps etc. to his terminal. All such loading of required information and images can be handled automatically by the client in collaboration with the service logic.

522 554

BENEFITS

A solution according to the invention offers great advantages for both the user and the user who have the information to carry out:

• Only standard components are required for the user equipment: access to the Internet or other communication network, telephone eg mobile phone such as GSM, GPS receiver and simple (eg laptop). No additional receiver for receiving data from differential GPS (DGPS) is needed when said data is distributed over a communication network, eg the Internet.

• With the information service according to the invention, data from differential GPS (DGPS) can be distributed over the Internet and no additional receiver is needed for this.

• All input devices communicate in a preferred embodiment with TCP / IP, which makes it easy to distribute the system, ie send client applications and data to the clients. If the market, use and needs of the invention are changed, the dimensioning of systems and services implementing the invention can be easily changed.

• By utilizing the IP protocol for transmission, 2-way communication can be utilized. The client then has the opportunity to ask intelligent questions with regard to the current position so that the amount of information sent is minimized and available bandwidth is used in the best way. As the client's location can be utilized, the possibility of better accuracy in correction data is obtained.

• A server handles correction data and communication with both client and RS unlike conventional DGPS where RS sends directly to the client. In this way, more reference stations can be used for the position correction (DGPS) and correction data for said stations can be stored in the server, for example in a database.

522 554 • An arrangement according to the invention for generating DGPS data and distributing data over IP can be created, implemented and maintained with simple means utilizing modern technology.

• The client application can be designed so that it does not require large local storage space or large processing resources.

• The invention is described for the use of GPS as a positioning method, but other technologies such as positioning with GSM or with other positioning system, which uses satellites such as GLONASS, can be used. other information stored in its terminal. All required data is transmitted to the user over the data network. Thus, the system operator can be responsible for giving the user access to up-to-date information, current maps, etc.

• Personal settings are stored centrally in the service logic, which means that the user can utilize the positioning system in different locations and with different equipment and still meet the same human-machine interface. The user does not need to use the same client software or hardware to access their profile. Therefore, it is possible to rent equipment according to the invention and the user has access to his personal profile. Rental cars can be equipped with a client according to the invention and the user has access to their personal profile.

• Operation, maintenance and further development are facilitated by upgrading / updating and other changes only in one place. The client systems are automatically updated or recharged when used.

• The information is always fresh and easy to update as it is stored in the network instead of the client.

522 554 • The client function can be developed in Java, which makes it platform independent and that no special requirements are set for the mobile terminal's design.

• The possibility of modular design with well-specified interfaces makes maintenance easy. By utilizing the IP protocol between the incoming blocks, the system becomes scalable and can easily be arranged to handle different number of clients. The described architecture also enables load sharing for distribution of DGPS data to many clients.

• If a reference station falls away or if different circumstances, such as the weather, make it difficult for a particular RS to receive signals from certain satellites, the system solution according to the invention enables DGPS data to be supplemented with data from other nearby reference stations, as the client's position is known.

• In places or situations where GPS coverage is poor, it is especially important that DGPS data can be delivered precisely for the (sometimes few) satellites the receiver sees. With the method described in the invention, the probability of the client having access to good DGPS data increases.

• By means of bidirectional communication, which according to a preferred design is done with the IP protocol, it is possible to send DGPS data tailored to each client, which is adapted to the client's position, which is not possible with the radio systems used today.

• A user of the mobile information service does not need to invest in a separate DGPS receiver but can obtain DGPS data automatically when the client software starts if a GPS receiver is connected to the terminal.

FIGURES

Figure 1 shows an overview of the parts of the system.

522 554

Figure 2 shows an example of the coverage of reference stations.

Figure 3 shows the architecture for the distribution of DGPS data over IP networks.

Figure 4 shows a system overview for the client system.

EXPLANATION

DGPS

GCB

GLONASS

GPS

GSM

IP

Java

multicast

RS

SB

TCP

TEB

Differential GPS; device for obtaining improved positioning information by means of the GPS system.

(GPS Correction Block) Block for GPS correction.

Global Positioning System Positioning system.

(Global System for Mobile Communication)

Cellular cellular telephone system.

(Internet Protocol) Protocol used in the Internet.

An object-oriented, platform-independent programming language.

Broadcast to a group of recipients.

Reference station for position correction in DGPS.

(Server Block) Block for server functions.

Transport Communication Protocol.

(Terminal Equipment Block) Block for user equipment, terminal unit.

522 554

DETAILED DESCRIPTION

The description below refers to the figures in the drawing appendix.

GPS AND DGPS

GPS is a position determination system and works worldwide. With a GPS receiver, anyone can receive satellite signals, which provide information about the receiver's position, speed and direction.

With GPS (Global Positioning System), users get information about the position on land, sea or in the air. Satellites orbiting the Earth transmit radio signals, which are received by GPS receivers. The GPS receiver then uses the information to calculate position, speed and direction.

GPS is made up of three main parts: Satellite part, control part and user part.

GPS satellites circulate around the earth, 21 of which are used and three are reserve satellites, which are available if any of the ordinary ones are to be knocked out. The satellites are located in different orbits at about 20000 km altitude for almost always at least four satellites to be visible from a GPS receiver, wherever it is on the earth. On the satellites are control and radio equipment and atomic clocks, which ensure that the time data transmitted is as accurate as possible.

The control unit comprises six control stations on the ground. These are used to detect errors, disturbances and, above all, to provide a basis for correcting transmitted time data.

The user part consists of a GPS receiver, which can be compared to a regular radio receiver with a computer and a clock.

The GPS satellites transmit radio signals, which contain information on:

• what satellite it is (satellite ID)

522 554 • the state of the satellite (whole / damaged); • information to calculate or otherwise derive the satellite's exact position; • the time when the signal was transmitted.

The signals are captured by the user's receiver, which can calculate the distance to the satellites with the help of data from several different satellites. With three satellites, two possible positions will be obtained, of which only one is on the Earth's surface. Normally three satellites are therefore required for the receiver to be able to give a clear position indication. A fourth satellite is used to allow the receiver to calculate the error in its built-in clock and compensate for it. This is of utmost importance because even very small errors can have fatal consequences for the position determination by including the transmission time of the signals from the satellite in the calculation of the position.

DGPS or differential GPS have been developed to improve accuracy in position determination. This can be achieved by utilizing reference stations with carefully determined positions. The reference stations compare their known position with the position indicated by a GPS receiver at the station to calculate the error in the satellite signals. If the error exceeds a certain tolerance level, a correction signal is used which is used by DGPS receivers in the area.

DESCRIPTION OF THE INVENTION

The server's perspective

The invention describes an arrangement for providing a mobile client (11) with the best possible DGPS data in a wireless communication system. The event is designed as a client server solution. Several clients (11) can be connected to each server (10), which makes the system scalable. The clients join the server and all communication is via this server.

522 554

The server (10) is in turn connected to a database (13) containing current correction data. This correction data is continuously updated by the reference stations (14) that are connected. Correction data is sent to the client via the Internet (15) or other communication network. This means that it is always up-to-date information that is communicated to the user.

The user is equipped with a terminal (client computer, 11) with data communication functionality, eg GSM, positioning system (16), eg GPS, eg a regular laptop, and access to the Internet (15), or other data network, via a telephone , preferably mobile phone, eg GSM.

Required software for the positioning system must be in operation on the client computer. The software can be easily put into operation, for example by charging over the Internet from the service provider's website and subsequent local installation.

The user establishes a connection to the Internet.

The client software reads the position from the GPS receiver (16) and sends the position to the server (10).

The position is received in the server block, SB (Figure 3), which relays the position to position correction, GCB (Figure 3). GCB determines which reference station, RSI, RS2, ... (Figure 3), to be used to correct the user's position. About ten RS is needed to cover Sweden (See Figure 2).

SB (Figure 3) registers for each user which RS is best for the user with regard to the current position and other conditions. If the user moves so that another RS ​​is more suitable, the stored data on best RS is updated.

Correction data is transmitted regularly, for example, every 10 seconds, to the client (11). The time interval for transmitting these transmissions of correction data is determined based on the speed at which the client moves. The client software communicates this to the GPS receiver (16) via a standard protocol (RTCM). The GPS receiver calculates its exact position by itself

522 554 correction data from RS, which means that the error can be reduced to a few meters.

Client's perspective

When a client starts, it connects to a server that handles communication with the client. The position of the client is obtained by means of a receiver (16), which receives a first position assignment from the positioning system (18), for example from the GPS system through GPS satellites. With a regular GPS receiver, the position is indicated by an error which can be 100m. This means that in a city you cannot be sure of the neighborhood you are in. With the help of a correction system such as differential GPS, DGPS, you can achieve better accuracy.

Through a network of reference stations, correction data is collected. This correction data is sent to the clients, who pass it on to their positioning system recipients. In the recipients, the data is used to create a more accurate positioning.

According to the invention, correction data is sent via the Internet, which means that no additional equipment besides the receiver for the positioning system, eg GPS receivers, needs to be connected to manage the correction data, and no special subscription is required for the correction.

Correction data is normally transmitted in a special format,

RTCM, which is a standard protocol used for communication with GPS receivers.

The information service's functions are implemented in a platform-independent program language such as Java. The system therefore works with several different operating systems and hardware and thus it is also easy to change operating systems and hardware for the different parts of the system.

522 554

All communication is done using TCP / IP, which is used on the Internet. This means that the parts do not need to be in the same physical location, and that it is easy to connect to the server.

Technical structure

The server block, SB (Figure 3), is the central unit from which the terminal units, TEB, (Figure 3), update their information. All communication between the function blocks is via SB.

The block for the terminal units, TEB (Figure 3), constitutes the user's Human-Machine system. Inputs and outputs are communicated to and from the user via TEB. Connection to SB takes place, in a preferred form, with the TCP / IP protocol over a mobile communication network, eg GSM. A GPS receiver (16) is connected to the TEB to receive the position of the terminal unit.

The GPS correction block, GCB (Figure 3), collects and provides the system with position correction data from external devices. GCB can handle a number of external units. Each unit receives the position information from a GPS receiver and calculates the position correction with knowledge of the actual position.

PREFERRED EMBODIMENT

The server has access to data for all reference stations. The data can be represented in a matrix with a compilation of which satellites the reference stations can reach and how much runtime error each visible satellite has at this reference station (RS).

522 554

Logically, the table may look like below.

<td></td><td>Satellite 1</td><td>Satellite 2</td><td>Satellite 3</td><td>Satellite n</td><td>Satellite (N + 1)</td>

<td>RS1</td><td>-3ns</td><td>+ 5ns</td><td>-4ns</td><td>-22ns</td><td></td>

<td>RS2</td><td>2ns +</td><td> 0</td><td>-45ns</td><td></td><td></td>

<td>RS3</td><td>+ 12ns</td><td>+23 ns</td><td>-4 ns</td><td>-5 ns</td><td> 0</td>

<td>RSn</td><td>-3ns</td><td>5ns</td><td>etc</td><td>etc</td><td>etc</td>

<td>RS n + 1</td><td>etc</td><td>etc</td><td>etc</td><td>etc</td><td>etc</td>

As the server system has access to the geographical position of the mobile terminal (client), the time errors of the nearest reference station can be retrieved.

If, due to physical obstacles or for any other reason, this RS is unable to contact enough satellites, the next nearest RS is checked and missing values ​​are taken from this RS. This procedure is repeated for each next RS until all time errors for all satellites have been retrieved and recorded, for example, in a data vector.

The data vector contains the time error for each satellite and the position of the reference station (RS) value retrieved from. The values ​​are checked in the client and values ​​that have been retrieved from reference stations located very far from the client can be selected or given less weight.

The reference station position is used in the correction to enable the client to determine which DGPS data is suitable for calculating the exact position. If not all DGPS data is needed for the correction calculations, values ​​from remote RS can be excluded to avoid data from these remote reference stations deteriorating the accuracy of the position indication.

522 554

The client receives DGPS data from the server and transmits this data to the GPS receiver, often in RTCM format. The client may choose to discard certain DGPS data, which does not add precision in position determination. The GPS receiver corrects the position using received DGPS data and then notifies the client computer if the correction was successful or if it cannot calculate the corrected geographical location.

This arrangement guarantees that the best possible and maximum possible number of DGPS data is sent to the client. In this way, the client's GPS receiver is given the optimal opportunity to correct its position. In order for the GPS receiver to be able to correct its position, the received DGPS data must apply to exactly the satellites the client's GPS receiver sees. The method of the invention maximizes the number of DGPS data that correlates to the satellites the GPS receiver sees.

In addition to the position statement, the client's position statement also includes the position statement's accuracy. The accuracy can be presented to the user in three levels:

• the client receives no position from the GPS receiver • the client receives position information from the GPS receiver but DGPS data is not available, which means that the error in the position is usually less than 100 meters • the client receives position information from GPS while DGPS data is available, which means that the error in the position is only 10-20 meters.

System Architecture

The overall architecture for the distribution and generation of DGPS over IP is shown in Figure 3. Communication between the blocks takes place via packet switching eg TCP / IP. On top of TCP, java streams are used to convey the information.

The system consists of a number of reference stations which are connected to the GPS Correction Block (GCB) via an IP network. As a spider in the network there is a Server Block (SB) that handles traffic and

522 554 exchange of messages between GCB and Terminal Equipment Block (TEB).

Reference Station (RS)

The reference stations continuously calculate the time error for each satellite they can communicate with. All reference stations regularly submit data to GCB. Each RS collects DGPS data for a specific geographical region. RS and GCB communicate over IP, which is why GCB may be in an area far from the reference stations.

GPS Correction Block (GCB)

GCB's task is to continuously compile DGPS data from all reference stations and to create a table for each geographical area with the latest DGPS data for each satellite.

There may be several GCBs in the system and all of them hold an updated image of DGPS data for all reference stations. This can easily be done, since the amount of data to be distributed is very small (satellite ID and time error information for normally less than 12 satellites).

Several GCBs can be used to achieve load sharing.

Server Block (SB)

The server block regularly retrieves DGPS data from GCB and then transmits the data to the affected clients. In order for SB to know to which clients different DGPS data will be sent, all clients connected to SB are associated with different geographical regions. The geographical region to which a client is associated is determined by which RS is closest to the client.

The time interval for transmitting DGPS data is also recorded for each client. This time interval can be influenced, among other things, by the wishes of the user by setting the client and by the client's speed.

SB collects DGPS data by geographical region and desired update interval from GCB and sends it to each

522 554 client with java streams over TCP / IP. The amount of data is very small and the consumption of bandwidth becomes negligible. If the client is connected to an IP network that supports multicast, DGPS data with multicast is distributed to all clients within a specific geographical region.

There may be several SBs in the system to achieve load sharing.

Terminal Equipment Block (TEB)

TEB extracts DGPS data from the java stream and converts this data into RTCM format (a standard GPS receiver protocol for receiving DGPS data). This RTCM format data is transmitted to the GPS receiver, which finally calculates the exact position and transmits the position information to the client computer.

CLIENT DESCRIPTION FOR THE CLIENT

The client system can be described in a number of blocks, see Figure 4.

Main blocks (41)

The main block (41) is the major part of the system and the central component. This block handles, among other things, the graphical user interface, communication functions, for example Internet communication, and conversion between the different blocks.

Positioning blocks (42)

The positioning block (42) is the client's position provider. Here, position data is sent from the GPS receiver, as well as correction data (DGPS) from the service logic. This block also ensures that the client is constantly updated with correct position information.

GPS communication (43)

Direct communication with the GPS receiver is via this block (43). By separating the block, it is easy to introduce other positioning technology into the system (eg GSM positioning).

522 554

Information Agent (44)

The information agent (44) is a standalone component that updates the system with current information objects. The information agent thus ensures that the client always has the correct information, based on the user profile and the current position.

User agents

The system can be supplemented with additional standalone components in the form of agents such as a map agent.

The basic function of a map agent may be to provide an updated map to the client. The agent formulates intelligent questions, which are then sent to the service logic. When the answer arrives, the agent ensures that the map objects (map segments) are organized and put together into a complete map image of the area.

The invention is not limited to the above-described embodiments but may in addition be subject to modifications within the scope of the following claims and the inventive idea.

522 554