Apparatus for own position-fixing, especially for vehicles

The invention relates to a device for determining one's own location, in particular of vehicles, with the aid of an existing, network-synchronous cellular mobile radio network.

On the one hand, methods for determining the location of vehicles are known, which are based on a hyperbolic location method, eg. B. DE-AS 21 37 846, E-PS 0 006 448, DE-OS 36 33 557, "Symposium Land Vehicle Navigation", 1984, the German Society for Location and Navigation in Section 13 and DE-OS 30 29 466. All methods require a considerable infrastructure, and the accuracy depends on the synchronicity of the signals transmitted by the base stations.

A system for determining the vehicle route is also known which is used by a known navigation system, e.g. B. Loran goes out. The location data determined in the Loran receiver are sent to a central station together with the desired destination. This is done via a vehicle transmitter, the z. B. can be part of the mobile station of a cellular radio network. A computer of the central station calculates the vehicle route from the location and the target coordinates, which are sent back from the central station to the receiver of the mobile station. It is essential in the given context that a separate navigation receiver is present next to a mobile radio station and that communication must take place between the vehicle station and the central station (EP 01 23 562).

Also known are methods for cell boundary detection by means of a relative distance measurement according to the hyperbolic method in network-synchronous cellular mobile radio networks (DE-OS 33 35 128, Funktechnik 41 (1986), No. 4, pp. 146-149)).

There, in addition to the location processes, which are insignificant for the object to be considered, and which originate from the fixed stations, a measurement of the transit time difference of a plurality of radio telegrams transmitted by different fixed base stations also takes place in each mobile station in order to assign their respective location to a radio cell.

Based on this prior art, the invention is based on the following finding:

On the one hand, in existing network-synchronous cellular mobile radio networks, the infrastructural prerequisites for the self-location of mobile radio stations are largely present, namely a network of fixed stations and absolute network synchronism for the use of the hyperbole location method.

On the other hand, due to the cost degression of microprocessors, even high computing speeds, there is no longer any reason to link the transit time difference values ​​measured in the mobile station with the known location coordinates of the associated base stations in a central computer arranged at the base station.

For this reason, the invention proposes that the aforementioned data be linked decentrally in a microcomputer assigned to each mobile station.

According to the invention, a device for determining one's own location according to the generic term is characterized by at least the following features:<ul id="ul0001" list-style="none" compact="compact"><li>a) a receiver unit for receiving the network-wide organization channel with demodulator and data processing</li><li>b) a device for measuring the transit time difference between a plurality of data telegrams sent by different base stations to the data telegram sent by a reference base station</li><li>c) a memory in which the different transit time differences, sorted according to base stations, are stored</li><li>d) a permanent memory with the location coordinates of all radio base stations</li><li>e) a computing unit in which the location coordinates of the fixed memory are linked to the content of the main memory and the location coordinates can be calculated by averaging the measurement results determined using the hyperbolic location method.</li></ul>

A device according to the features a to e of the solution specified above clearly represents a passive location receiver, in which participation in the radio telephone service is dispensed with. Nevertheless, its use is an advantage if it is only a matter of locating your own location. Because of the omission of the transmitting part and the voice input and output, such a navigation receiver could also be designed as a portable device after the addition of an LCD display for the location coordinates.

However, if the device is to serve only as an additional device of a mobile radio station that is already equipped for the radio telephone service, according to another embodiment of the inventive concept, only the features d, e and possibly a display unit is additionally required to obtain its own location display as an additional feature for the radio telephone service, because the receiver unit, the device for measuring the time difference and the main memory are already components of the conventional receiving part of a mobile radio station of a cellular mobile radio network.

In the case of a mobile radio station designed for the additional feature: “determining one's own location”, in a further development of the invention there is the possibility of also requesting a fixed (wire or fiber) network by requesting an authorized subscriber by dialing the radio subscriber and retransmitting it via the latter Make stations available.

The location coordinates on a voice channel can expediently be transmitted in digital form via a modem.

Another possibility is to switch on a digital voice output at some point in the transmission path between the mobile station and the calling subscriber. This can advantageously already take place in the mobile station, but can also only take place at the calling subscriber.

Another advantageous possibility of retransmitting the location coordinates would be the native data transmission in the organization channel or voice channel. In addition, the retransmission of the location coordinates on special data channels would be conceivable.

In addition to the already discussed display of the location coordinates on an LCD display, a more convenient display with a graphical display with the display of map sections is also conceivable, which obtain their background information from a suitable database (e.g. topographical database).

For special applications, such as B. the securing of value transports, a mobile station is also conceivable, which, without the need for voice communication and the necessary voice input and output, is only used to report one's own location. In the case of such a version of a mobile station, which is emaciated from a location reporting device, it is also expedient to dispense with a display unit because the location reporting device no longer necessarily has to be accommodated in the driver's cab of a vehicle.

The invention is explained in more detail below on the basis of two diagrams and two block diagrams:

Show it<dl id="dl0001" compact="compact"><dt>Fig. 1</dt><dd>the data telegrams received in each mobile station of a cellular radio network from different base stations and their evaluation with regard to the transit time</dd><dt>Fig. 2</dt><dd>a passive location receiver for determining one's own location</dd><dt>Fig. 3</dt><dd>an additional device to a mobile station for determining one's own location</dd></dl>

The upper diagram of FIG. 1 shows the assignment of the different base stations to one of the 32 time slots of the 2.4 s pulse frame. The reference base station is selected based on its field strength or distance.

The diagram below shows the runtime differences that occur in the data telegrams sent by the various base stations in relation to the selected base base station. The measurements shown only briefly in FIG. 1 run in every mobile station of a network-synchronous cellular mobile radio network. You are e.g. B. in the previously mentioned literature radio technology: 41 (1986), No. 4, pp. 146-149 described in detail. The Fig. 2nd shows a mobile station emaciated to a passive location receiver. The data telegrams of various radio base stations, which are transmitted in a cyclical alternation via a receiving antenna on the network organization channel (e.g. network C of the DBP 465.090 MHz), are received in the receiver unit 1, demodulated and, after processing the data in circuit block 2, the runtime difference in a cyclical sequence to the selected reference radio base station according to FIG. 1 below.

The results of the transit time difference measurement are entered into a working memory 3, which consequently contains a list of all received radio base stations with the associated transit time difference.

On the other hand, the coordinates of the geographical locations of all existing radio base stations are stored in a fixed memory 4. In the arithmetic unit 5, controlled by appropriate software, the runtime differences of the data telegrams of the received base stations are linked to the associated location coordinates. This is done according to an algorithm suitable for the hyperbolic location method. The own location coordinates are shown on a display unit 6, an LCD display.

The dashed-line display with a graphic display 7 is also possible as an alternative with somewhat greater effort. The graphic display 7 is described from a suitable database 8 with a map section as background information.

3 shows a mobile station 11 in which the receiver unit 1, the device for measuring the time difference 2 and the working memory 3 are already contained in the receiving part of the mobile station 11, if the mobile station for a network-synchronous cellular mobile radio network with assignment of its own location to a specific radio cell is designed.

As a result, only the fixed memory 4 and the arithmetic unit 5 are necessary for the more precise determination of the location coordinates if the location coordinates are initially not displayed, which, as already stated, could be useful for certain applications.

The normal case is of course the equipment of the mobile station 11 with a display. 3, two variants for the number are also possible. An LCD display 6 is also provided here as a simple solution. The more complex solution is based on a graphic display 7, which obtains its background information in the form of a map section from a suitable database 8. The more comfortable version has already been implemented in vehicle control systems, e.g. B. the Blaupunkt Travel Pilot traffic control system presented at the Hanover industrial fair in April 1988 and the company brochures displayed there.

3 shows a particularly important application of the device according to the invention, namely the query of the location coordinates by an authorized third party. This third-party subscriber can dial the number of the radio subscriber both from the mobile radio network and from the telephone network and then automatically keeps the location coordinates sent back via the transmitter of the mobile station 11 instead of a conversation. The location coordinates can be transmitted back via the normal voice channel, via the system-specific data transmission of the organizational or voice channel or via a special data channel. The transmission to the normal voice channel does not require any intervention in the existing cellular mobile network.

3 contains two variants for this alternative. On the one hand, the digital location coordinates can be transmitted in the voice channel via a dashed modem 10.

It is also possible to convert the location coordinates in a digital voice output 9 (also shown in dashed lines in FIG. 3) in the mobile station or at the calling third party in the manner of a time announcement.

For voice transport security tasks, all voice communication as well as the display 6 or 7 and 8 can be omitted. What remains would be a location receiver and a transmitter for the transmission of the location coordinates.

The use of the hyperbola locating method is briefly described below with reference to FIG. 4, the relationships of four radio festival detonations S0 to S3 being drawn and explained for the sake of clarity.

4 the coordinates of the 4 base stations from the fixed memory 4 and the resulting distances between the reference base station S0 and the base stations S1 to S3 as well as the associated angular relationships α n are known. The relative distances to the base stations are also known to the reference radio base station from the main memory 4. The location coordinates x sought are unknown_Butt and y_Butt .

Starting from the hyperbola basic equation <maths id="math0001" num=""><math display="inline"><mrow><mfrac><mrow><msup><mrow><mtext>x</mtext></mrow><mrow><mtext>2</mtext></mrow></msup></mrow><mrow><msup><mrow><mtext>a</mtext></mrow><mrow><mtext>2</mtext></mrow></msup></mrow></mfrac></mrow></math><img file="EP0341738B1_D0001.tif" /></maths>-<maths id="math0002" num=""><math display="inline"><mrow><mfrac><mrow><msup><mrow><mtext>y</mtext></mrow><mrow><mtext>2</mtext></mrow></msup></mrow><mrow><msup><mrow><mtext>b</mtext></mrow><mrow><mtext>2</mtext></mrow></msup></mrow></mfrac></mrow></math><img file="EP0341738B1_D0002.tif" /></maths> = 1 are the following basic conditions for calculating x_Butt and y_Butt Fulfills:

a_n (n = number of the radio station) results from half the relative distance to the radio station b_n results from the root of e_n² a_n² , where e_n arises from half the distance between the reference radio base station S0 and the radio base station Sn.

From this, different systems of equations can be derived which lead to the determination of the own location in the computing unit 5.

The software effort required for this is not insignificant and increases with the number of radio base stations included in the location determination, but does not pose an insurmountable difficulty. Of course, the higher computing effort will result in a higher accuracy of the location coordinates.