WO2003098951A1

WO2003098951A1 - Method for determining the position of a mobile station, and position determination unit

Info

Publication number: WO2003098951A1
Application number: PCT/DE2003/001051
Authority: WO
Inventors: Maik Bienas; Thomas Gottschalk; Frank Kowalewski
Original assignee: Siemens Aktiengesellschaft
Priority date: 2002-05-15
Filing date: 2003-03-31
Publication date: 2003-11-27
Also published as: DE10393057D2; DE10221649A1; AU2003232587A1

Abstract

The invention relates to a method for determining the position of a mobile station (MS1). According to the inventive method, the mobile station (MS1) receives a signal (S3) from a station (BS3) via a transmission station (R3), and the position of the transmission station (R3) is taken into account in order to determine the position of the mobile station (MS1).

Description

description

Method for determining the position of a mobile station and position determining unit

The invention relates to a method for determining the position of a mobile station and a corresponding position determining unit.

In third-generation mobile radio systems, such as systems operating according to the UMTS (Universal Mobile Telecommunications System) mobile radio standard, position determination functions are provided in the mobile terminals.

The UMTS standard provides three modes for transmission over the air interface. These are the FDD (Frequency Division Duplex) mode, the 3.84 Mchip / s TDD (Time Division Duplex) mode and the 1.28 Mchip / s TDD mode. In FDD mode, the transmission in the uplink (UL) and downlink (DL) direction takes place on different frequencies. Uplink means the direction of transmission from a terminal or a mobile station to a network element, which is also referred to as a base station or NodeB. Downlink is accordingly the direction of transmission from a base station to the mobile station. In the TDD mode, only one carrier frequency is used, and the uplink and downlink directions are separated by assigning time slots. The main difference between the two TDD modes is the lower chip rate of the 1.28 Mchip / s TDD mode compared to the 3.84 Mchip / s TDD mode. In all modes, participants are separated using orthogonal codes. This code-based multiple access method is known as Code Division Multiple Access (CDMA). Various methods for determining the position of a mobile station in a radio communication system (UMTS) are known from the technical specification TS 25.305 V5.4.0 of the 3GPP (3rd Generation Partnership Project):

Cell ID method assisted GPS method (GPS: Global Positioning System) OTDOA (Observed Time Difference of Arrival) method - OTDOA-IPDL (Idle Period Downlink)

These methods are intended for both FDD and TDD mode. The two last-mentioned methods are explained in more detail below with reference to figures.

In order to increase the accuracy of the position determination, in particular of the last two methods mentioned, and thus to meet the high requirements of the Mobile Communications Authority of the United States of America (FCC: Federal Communications Commission) for mobile stations in emergency situations, these two methods must be further improved.

The invention is therefore based on the object of specifying an improved method for determining the position of mobile stations.

This object is achieved with the method according to claim 1 and the position determination unit according to the independent claim.

Advantageous further developments of the invention are the subject of the dependent claims. In the method according to the invention for determining the position of a mobile station, the mobile station receives a signal from a station via a forwarding station and at

Position determination of the mobile station, the position of the forwarding station is taken into account.

Since signals that have been forwarded via a forwarding station arrive at the mobile station with a delay compared to a direct transmission by the transmitting station in question, a position determination is incorrect unless it takes this delay into account. By taking the position of the forwarding station into account according to the invention, the transit time of the signal between the forwarding station and the mobile station can be used for position calculation. However, the position of the sending station is not taken into account. The delay times of the signal transmission to the forwarding station are calculated from the total running time for position calculation.

The invention can advantageously be used in any radio system. Radio systems are any systems in which data is transmitted between stations via a radio interface. The data transmission can take place bidirectionally as well as unidirectionally.

Radio systems are, in particular, systems in which GPS is used to determine the position of stations and any mobile radio systems, for example according to the GSM (Global System for Mobile Communications) or UMTS standard.

In a first embodiment of the invention, those forwarding stations for the signal that are in question for forwarding the signal are advantageously determined come. Several positions are calculated for the mobile station, with the position of another forwarding station that is suitable for forwarding being used for each position calculation. The one of the several positions is determined as the actual position of the mobile station for which the position calculations have the smallest error.

The positions of all stations and forwarding stations in the radio communication system are known from network planning. On the basis of this information, those forwarding stations can be determined and taken into account in a position determination that are within the transmission range of the transmitting station whose signal has been forwarded. In this way, the computing effort for a position determination can be minimized, provided the sending station is known, the signal of which was forwarded.

In an advantageous second embodiment of the invention, the mobile station receives a signal from further stations. For each signal, all transmission paths are determined via which the corresponding signal can have been sent to the mobile station. For each combination of the determined transmission paths of the signals, a position is calculated for the mobile station and that of the calculated one

Positions is set as the actual position of the mobile station for which the position calculation has the least error. If the transmitting station, whose signal has been forwarded, is not known to the mobile station, the position of the mobile station can nevertheless be determined with a high degree of accuracy by taking into account all possible transmission paths of all signals. In a preferred third embodiment, the mobile station receives a forwarding signal coded with an individual code of the forwarding station in synchronization with the signal of the station. A position determination unit recognizes on the basis of the forwarding signal without further calculations that the signal has been forwarded and which forwarding station must be taken into account when determining a position.

In a further advantageous embodiment of the invention, the mobile station receives a forwarding signal encoded with a code shared by a number of forwarding stations in synchronism with the station signal. In this way, the mobile station can immediately recognize that the signal has been forwarded. However, the corresponding forwarding station cannot be determined directly on the basis of the forwarding signal. By taking into account all the forwarding stations that are suitable for forwarding the signal (for example, as in the first embodiment of the invention), the position of the mobile station can be determined as accurately as possible.

If the forwarding signal has a time stamp of the forwarding station, the mobile station can directly determine the transit time of the forwarding signal from the forwarding station to the mobile station. A calculation of this runtime from the total runtime of the signal from the sending station to the mobile station can then be omitted.

The code is advantageously a scrambling code or a spreading code. The position determination unit has all the features necessary for carrying out the method according to the invention.

The invention is explained in more detail below with reference to exemplary embodiments shown in the figures. Show it:

Fig. 1 is a schematic representation of a position determination according to the OTDOA and OTDOA-IPDL method and

2 shows a schematic representation of a radio communication system for carrying out a method according to the invention for determining the position of a mobile station.

The same reference symbols in the figures denote the same objects.

In the following, a mobile station is considered to be a mobile station. A mobile station is, for example, a cell phone or a portable device for transmitting image and / or sound data, for sending faxes, short messages, sending SMS and e-mails, and for accessing the Internet. It is therefore a general transmitter and / or receiver unit of a radio communication system.

A known method for position determination is position determination according to the OTDOA method, which is based on measurements of signals transmitted over the air interface between several base stations and the mobile station to be located. According to this method, the mobile station to be located tries to get a known signal from to detect two different, neighboring base stations and to determine the reception times. The times of reception of the known signal from the two different, neighboring base stations are then sent for evaluation to the responsible position calculation function PCF (Position Calculation Function) of the base station which is responsible for the mobile station to be located. In this context, evaluating means that the position calculation function calculates the position from the time difference of the reception times or from the running time difference. The time difference establishes a hyperboloid that indicates the potential location of the mobile station. If base stations and mobile stations are on the surface of the earth, the potential location is a hyperbola on the surface of the earth. By including another base station, the location of the mobile station is then at the intersection of the two hyperbolas.

Figure 1 shows three base stations BS1, BS2 and BS3 and a mobile station MSI. The hyperbola Hy _{3 is} determined by the time difference of the signals from the first base station BS1 and the third base station BS3. Accordingly, the hyperbola Hy _{23 is} determined by the time difference of the signals from the second base station BS2 and the third base station BS3. The mobile station MSI is located at the intersection of the two hyperbolas Hy ₃ , Hy ₂₃ . At least one additional piece of information is required for a more precise position determination. So either

a) a further OTDOA position determination is carried out to a fourth base station, or b) in cells with sectorization, the information about the sector in which the mobile station is located is used for the decision, or

c) an RTT measurement (RTT: Round Trip Time) is carried out. As shown in FIG. 1, a circle K, on which the mobile station MSI is located, is determined on the basis of the round-trip time of known signals transmitted between the third base station BS3 and the mobile station MSI.

The signal to be detected can be the signal of the Common Pilot Channel or CPICH, which is sent continuously by the base stations, but also another pilot signal. In the following, the CPICH is used for simplification. Each base station is assigned a different scrambling code to distinguish the CPICH signals. It is then possible to keep the received CPICH signals apart and to assign them to the corresponding base stations, as well as to calculate the required time differences.

The OTDOA method achieves an accuracy in the position determination of a mobile station of approximately 80 to 100 m. The OTDOA-IPDL method provides an improvement to the OTDOA method. The OTDOA-IPDL method is an extension in the event that signals from a connection base station via which the mobile station is connected to a radio communication network cover signals from other base stations. This makes it difficult or even impossible to detect signals from the other base stations. This applies in particular to signals on the Common Pilot Channel, which all base stations use and which is usually used to determine the time difference. So that detection of signals from other Ba isstations possible, the transmissions of the connection base station are switched off for short periods of time with the OTDOA-IPDL method. The resulting pauses with regard to the transmission of this connection base station can then be used by the mobile station in order to detect the times of reception of the signals of the other, neighboring base stations. This pause can be several symbols long, typically 5 to 10 symbols. The length of a symbol corresponds, for example, to 256 chips in UMTS-FDD mode and a maximum of 16 chips in TDD mode, with one chip being approximately 0.26 μs long at a chip frequency of 3.84 Mchip / s. With the OTDOA-IPDL method, an accuracy in position determination of up to approx. 20 m can be achieved.

In TDMA systems (TDMA: Time Division Multiple Access), the OTDOA method is referred to as E-OTD (Enhanced Observed Time Difference).

The invention is described below using the example of a mobile radio system according to the UMTS standard, but without being restricted thereto.

In a first exemplary embodiment, shown schematically in FIG. 2, the position of a mobile station MSI is determined in accordance with the OTDOA or OTDOA-IPDL method described above. For this purpose, a first base station BS1 sends first signals S1, which are coded with an individual code C1 of the first base station BS1, to the mobile station MSI. In the same way, a second and a third base station BS2, BS3 send second and third signals S2, S3 to the mobile station MSI. The second and third signals S2, S3 are also coded with an individual code C2, C3 of the respective base station BS2, BS3. Using the individual codes Cl, C2, C3 the The base stations BS1, BS2, BS3 can be the mobile station MSI

Differentiate signals S1, S2, S3. Furthermore, a first relay station R1 (English: Repeater), a second relay station R2 and a third relay station R3 are shown, each having an internal signal delay time τ 1, τ2, τ3.

While the first and second signals S1, S2 are sent directly to the mobile station MSI, the third signals S3 cannot be sent directly to the mobile station MSI. The direct path of propagation is blocked by an obstacle H. The third signals S3 are therefore forwarded to the mobile station MSI via the third forwarding station R3. The running time of the first signals S1 is tl, the running time of the second signals S2 is t2 and the total running time of the third signals S3 is made up of the sum of the running time t3 from the third base station to the third forwarding station R3 and the running time tR3 from the third forwarding station R3 Mobile station MSI together.

If a position determination unit PE located in the mobile station MSI now calculates the position of the mobile station MSI, the position determination is incorrect if the position of the third base station BS3 is used together with the total running time t3 + tR3 + τ 3, since this total running time is longer than that actual transit time for a direct transmission from the third base station BS3 to the mobile station MSI. For this reason, the third forwarding station R3 transmits the forwarded third signals S3 in synchronism with a forwarding signal SR3, which is encoded with an individual code CR3 of the third forwarding station R3. The forwarding station R3 sends the forwarded third signal S3 and the forwarding signal SR3 such that the Quotient of the two transmission powers corresponds to a predefined value. Furthermore, the forwarding signal SR3 can

Time stamp Z3 can be provided, which indicates the point in time at which the forwarding signal SR3 is sent from the third forwarding station R3.

The predefined value of the quotient is known to the mobile station MSI and, with the transmission conditions of the signals S3, SR3 sent by the third forwarding station usually being the same, corresponds to the quotient of the corresponding reception powers. In this exemplary embodiment, all forwarding stations R1, R2, R3 use the same predefined value for the quotient. Of course, different predefined values can also be defined.

In FIG. 2, the mobile station MSI receives the second and third signals S2, S3 and the forwarding signal SR3 and, when checking the received signals, determines that it has received the signals synchronously. The mobile station MSI therefore determines a quotient for the two signals S2, S3 from the received power of the respective signal S2, S3 and the received power of the forwarding signal SR3 and compares the calculated values with the predefined value. The quotient only coincides with the predefined value when the receiving power of the third signals S3 is used, so that the mobile station clearly determines that the third signals have been forwarded. The formation of the quotient can of course be omitted if only one signal and one forwarding signal are received synchronously.

It is also necessary to assign the forwarding signal SR3 to a forwarding station R1, R2, R3. Due to the Coding of the forwarding signal SR3 with the individual

Code CR3 of the forwarding signal SR3 of the third

Assign forwarding station R3. It follows from this that the mobile station MSI has also received the third signals S3 from the third relay station R3. To calculate its position, the mobile station now uses MSI in addition to the

Transit times tl, t2 of the first and second signals S1, S2 and the positions of the first and second base stations BS1, BS2, the transit time tR3 of the relayed third signals S3 and the position of the third relay station R3. Because the position of the third relay station R3 is taken into account when determining the position of the mobile station MSI, the position of the mobile station MSI is calculated correctly and with an accuracy that that of a position determination with only signals that were not forwarded (e.g. as in FIG. 1) ) corresponds.

The mobile station MSI calculates the transit time tR3 of the forwarded third signals S3 either on the basis of the time stamp Z3, which indicates the time of transmission of the forwarding signal SR3 and thus also the time of transmission of the third signals S3, or subtracts the known duration from the total duration t3 + tR3 + τ 3 t3 between the third base station BS3 and the third relay station R3 and the likewise known internal signal delay time τ3 of the third relay station R3.

If the transit times tl, t2 of the first and second signals S1, S2 or the total transit time t3 + tR3 + τ 3 of the third signals S3 are not known to the mobile station MSI, they can of course also use the respective reception times of the signals S1, S2, S3 Use position determination. The time of reception of the third signals S3 is then reduced by the Known delay time t3 between the third base station BS3 and the third relay station R3 and the also known internal signal delay time τ 3 of the third relay station R3 corrected, ie these delay times t3, τ3 are subtracted from the time of reception of the third signals S3

An individual code of a base station or a forwarding station consists, for example, of a scrambling code, a spreading code or a product of a scrambling and spreading code. However, it can also be any code, provided that this code enables signals from different stations to be differentiated.

In a second exemplary embodiment, the third forwarding station R3 does not provide the forwarding signal SR3 with an individual code CR3 of the third forwarding station R3 but with a forwarding station code CR used in the same way by a plurality of forwarding stations R1, R2, R3. The mobile station MSI recognizes that it has received the third signals S3 received synchronously with the forwarding signal SR3 from a forwarding station R1, R2, R3, but cannot use the forwarding signal SR3 to determine from which forwarding station R1, R2, R3 forwarded the third signals S3 were. From the forwarding stations R1, R2, R3 known to the mobile station MSI, which are within its range, it determines those forwarding stations R2, R3 via which the third signals S3 may have been forwarded and in each case carries out a position determination taking into account the corresponding forwarding stations R2, R3 through. In this exemplary embodiment, the mobile station MSI calculates positions for two scenarios: a forwarding of the third signals S3 via the second forwarding station R2 and forwarding of the third signals S3 via the third forwarding station R3. Of the positions calculated in this way, the one that has the smallest error is determined as the current position.

If, as in this exemplary embodiment, three stations BS1, BS2, R2 or BS1, BS2, R3 are used for each position determination, there are three hyperbolas, which typically intersect at three points. The reason for this lies in measurement errors that make it unlikely that the three hyperbolas intersect at exactly one point. For example, a possibly weighted mean value is selected from the intersection points of a position determination to determine only one position. To further determine the actual position, the position determination which has the smallest error is used. The smallest error has, for example, the position determination at which the intersection points are closest to each other. In the exemplary embodiment shown, the most precise position thus results taking into account the third forwarding station R3.

An additional increase in the accuracy of the position determination can be achieved by an RTT measurement, for example for the first base station BS1.

A code common to several forwarding stations consists, for example, of a scrambling code, a spreading code or a product of a scrambling and spreading code.

In a third exemplary embodiment of the radio communication system from FIG. 2, the third forwarding station R3 forwards the signals S3 without a forwarding signal. The Mobile station MSI can now not readily recognize on the basis of the received signals S1, S2, S3, in which way the signals S1, S2, S3 were sent to it and whether the signals S1, S2, S3 were forwarded. For each base station BS1, BS2, BS3, it therefore determines all possible ways in which the respective signals S1, S2, S3 can have been sent to it. For the first base station BS1, this is the direct route or a route via the first or third relay station R1, R3. For the second base station BS2 there is the direct route and a route via the first or second relay station R1, R2. For the third base station BS3, the mobile station MSI determines the direct route (the obstacle H is not known to it) and a route via the second or third relay station R2, R3. Using the determined routes, the mobile station calculates its position for all combinations of routes on which the three signals S1, S2, S3 can have been sent to it. In this example, the mobile station determines 3 * 3 * 3 = 27 positions. The mobile station MSI determines the position as the current position, the calculation of which has the smallest error.

The positions of the base stations BS1, BS2, BS3 and the forwarding stations R1, R2, R3 required for the position calculations of the mobile station MSI, the transit times between base stations BS1, BS2, BS3 and forwarding stations R1, R2, R3, the internal signal delay times tl, τ2, τ3 the forwarding stations R1, R2, R3 and the predefined value of the quotient of the reception services are communicated to the mobile station MSI automatically or on request before a position is determined or when the connection is being established by the radio communication system. The mobile station MSI either receives information that only relates to stations that are currently within range of the mobile station or it receives information regarding all stations of the radio communication system.

Of course, the invention can also be carried out when the position determination unit PE is not in the mobile station MSI but in the radio communication system, for example in the RNCl network. All positions of the stations are known to the radio communication system, so that the mobile station MSI only has to send the determined transit times or reception times of the three signals S1, S2, S3, the forwarding signal SR3 and, if appropriate, the calculated quotient of the reception powers to the network RNCl. All of the calculations described above are then carried out in the same way in the position determination unit located in the RNCl network.

In addition to the illustration in FIG. 2, the invention can also be carried out taking into account more than three stations. The more stations are taken into account, the more precise the position determination will be.

Claims

claims

1. Method for determining the position of a mobile station

(MSI), in which - the mobile station (MSI) receives a signal (S3) from a station (BS3) via a forwarding station (R3), and takes the position of the forwarding station (R3) into account when determining the position of the mobile station (MSI) becomes.

2. The method according to claim 1, in which those forwarding stations (R2, R3) are determined for the signal (S3) that are suitable for forwarding the signal (S3), - several positions are calculated for the mobile station (MSI) , the position of another forwarding station (R2, R3) that is suitable for forwarding being used for each position calculation,

- And that of the several positions is determined as the actual position of the mobile station (MSI) for which the position calculations have the smallest error.

3. The method according to claim 1, wherein

- The mobile station (MSI) receives a signal (Sl, S2) from further stations (BSl, BS2), for each signal (Sl, S2, S3) all transmission paths are determined, via which the corresponding signal (Sl, S2, S3) may have been sent to the mobile station (MSI), a position for the mobile station (MSI) is calculated for each combination of the determined transmission paths of the signals (S1, S2, S3), and that of the calculated positions as actual

Position of the mobile station (MSI) is determined for which the position calculation has the least error.

4. The method according to claim 1, wherein the mobile station (MSI) from the forwarding station R3 synchronously with the signal (S3) of the station (BS3) a forwarding signal (SR3) coded with an individual code (CR3) of the forwarding station (R3) ) receives.

5. The method according to claim 1 or 2, wherein the mobile station (MSI) from the forwarding station R3 synchronously with the signal (S3) of the station (BS3) a code used with one of several forwarding stations (Rl, R2, R3) ( CR) coded forwarding signal (SR3) receives.

6. The method according to claim 4 or 5, wherein the forwarding signal (SR3) has a time stamp (Z3) of the forwarding station (R3).

7. The method according to any one of claims 4 to 6, wherein the code (CR3; CR) is a scrambling code.

8. The method according to any one of claims 4 to 6, wherein the code (CR3; CR) is a spreading code.

9. Position determination unit (PE) for determining the position of a mobile station (MSI), with means (P) for determining position using a signal (S3) received by the mobile station (MSI) via a relay station (R3) from a station (BS3), and to take into account the position of the forwarding station (R3) when determining the position of the mobile station (MSI).