MXPA00002602A - Method and system for determining position of a cellular mobile terminal - Google Patents

Abstract

A method (500) and system (200) are disclosed by which a round-trip calculation is used to determine the distance between a mobile radio station (MS) (208) and a radio base station (BS) (BS0, BS1, BS2) using the apparent uplink and downlink signal propagation air-times (e.g., T-up and T-down). As such, no absolute time reference is required. The MS and BS report to a service node (203) in the mobile network (200) the local departure and arrival times (308, 328) of the uplink and downlink signals (212-215), and calculate the apparent air-times, T-up and T-down. The distance, D, between the MS and BS can be calculated as D=c(T-up + T-down)/2, where"c"equals the speed of light. The distances, D1, D2 and D3, to at least three base stations whose locations are known, can be used in a triangulation algorithm to determinethe MS's position.

Description

METHOD AND SYSTEM TO DETERMINE THE POSITION OF A CELLULAR MOBILE TERMINAL BACKGROUND OF THE INVENTION Technical Field of the Invention The present invention generally relates to the field of mobile radio communications in particular to an improved method and system for determining the position of a mobile radio terminal. Description of the Related Art In the field of cellular communication, it has become increasingly important to be able to determine the position of mobile radio terminals. As such, the authorities responsible for defining the specifications and standards of mobile radio communication systems are currently involved in the process of specifying the precisions required to perform the mobile terminal position determinations. The most successful methods used to date to determine the position of a mobile terminal are based on measurements of signal propagation times, which in turn are then used to derive distances. These propagation time measurements are performed either on the uplink (base station measurements of transmissions from a mobile terminal) or on the downlink (mobile terminal measurements of transmissions from a base station). For example, the patent application publication of the World Intellectual Property Organization No. WO 96/35958 granted to Ghosh et al. ("Ghosh") describes a method and system for determining the position of a mobile terminal in a communications system. Multiple access with code division (CDMA = Code Multiple Division Access) (for example in accordance with IS-95). The application of Ghosh, illustrates a method by which the measurements of the absolute time of arrival (TOA = Time Of Arrival) of a signal transmitted by a mobile terminal is performed in at least two base stations. TOA measurements are converted remotely. Triangulation is used to determine the position of the mobile terminal. However, a problem with the described TOA position determination method is that it requires the use of an "exact" or highly accurate time reference (eg as provided by the positioning system or global positioning or GPS = Global Positioning System ). In the patent application of the Patent Cooperation Treaty (PCT) Serial No. PCT / SE97 / 00219 (and the related US patent application Serial No. 08 / 799,039) issued to Lundqvist et al., ("Lundqvist ") describes a method and apparatus for determining the position of a mobile terminal in an unsynchronized environment (for example without using an" exact "time reference). In contrast, a plurality of fixed location "reference" radio terminals whose position is known are used to perform downlink propagation time measurements. The relative transmission time offset between base stations is determined and used to derive the position of the mobile terminal. PCT patent application Serial No. PCT / SE96 / 03561-3 (and related US patent application Serial No. 60 / 028,345) issued to B. Bergkvist et al. ("Bergkvis") describes a method and apparatus for determining the position of a mobile terminal in a cellular mobile radio system such as, for example, the global system for mobile communications (GSM = Global System for Mobile Communications). A mobile terminal is ordered to perform a sequence of transfers to several target base stations. As such, the mobile terminal transmits a burst of access to a target base station. However, that target base station does not transmit a confirmation message that the access burst has been received. The mobile terminal then returns to its base service station. That target base station uses in the received access burst to measure the round trip propagation delay (base station-mobile terminal-base station). Consequently, a time reference signal is not required to derive the position of the mobile terminal. A disadvantage of the method described in the Ghosh application described above is that the base stations are required to use a global time reference, such as a GPS signal to precisely determine the position of a mobile terminal. Similarly, although the method described in the Lundqvist application avoids the use of a global time reference, it instead uses a complex system of "reference" fixed position radio terminals whose position is known, in order to derive displacements of Relative base station time. A disadvantage of the Bergkvist request is that it uses round trip prolongation delay measurements ~ to perform an exhausted transfer sequence. This method takes a considerable amount of time to complete and creates substantial disturbances by transmitting individual access bursts to several base stations. However, these access bursts are generated only for the purpose of determining the location of the mobile terminal.

Notably, it is convenient to determine the position of a mobile terminal without the use of complex time references, "mobile reference terminals" and "disturbing" aborted transfers, and conversely to be able to use the basic functions of the cellular mobile radio system. As described above, the present invention successfully provides this capability and solves the problems described above. COMPENDIUM OF THE INVENTION A problem addressed by the present invention is how to measure the distance between a base station and a mobile station, without having to use a global time reference. Another problem addressed by the present invention is how to determine the geographical position of a mobile terminal in a non-synchronized mobile radio system (without a global time reference) while eliminating the need for equipment for additional position determination (e.g. "reference" radio terminals to determine time shifts between base stations). Yet another problem addressed by the present invention is how to determine the geographical position of mobile radio terminals without creating unnecessary "disturbances" (eg, access bursts transmitted for aborted transfers). Therefore, an object of the present invention is to provide a method and system for determining the position of a mobile terminal operating in a conversation mode directly on a digital or analogue traffic channel (but capable of transporting digital information). a mobile radio system. Another object of the present invention is to provide a method and system that meet the above-described purpose, wherein the mobile radio system for example is a CDMA, broadband CDMA (WCDMA) or multiple access system with division of time (TDMA = Time Division Multiple Access). A further objective of the present invention is to provide a method and system that meets the objectives described above, wherein the position determination function is performed by a system that transmits and performs measurements on known patterns of information in advance (ie not they require the transfer of variable information). Still another object of the present invention is to provide a method and system that meets the objectives described above, wherein the relative time shifts of transmissions from radio base stations, can be determined using a mobile terminal, and then applied to determine the position of other mobile terminals. In accordance with the present invention, the foregoing and other objects are achieved by a novel method and system for determining the position of mobile terminals in a cellular mobile radio system. Drawing an analogy to the air traffic field, when consulting a table of air traffic time, it can be seen that the departures and arrivals of aircraft are illustrated with local times. Whereas, an east-west air traffic connection between two cities, (Dallas and Stockholm) local times in these cities may differ up to several hours. Consequently, the apparent air time required to fly from one city to another (for example Dallas to Stockholm) differs from the apparent air time required to fly that route in the opposite direction (for example Stockholm to Dallas), if local times are used to calculate the arrival time in the time table. However, it is relatively easy to calculate the actual air time for a traveler, by adding the apparent air time for the East-to-West trip such as Dallas to Stockholm) to the apparent air time for the return trip, (for example Stockholm to Dallas) and divide the result by two. Essentially, when using this method of "round trip" calculation, the time "lost" when traveling in one direction is time "recovered" when traveling in the other direction., and the result is independent of the local times involved. Finally, in order to determine the distance between the two cities, the calculated real time can be multiplied by the speed of the aircraft making the trip. Similarly, according to the present invention, a round trip calculation method is used to determine the distance between a mobile radio station (MS = Mobile Radio Station) and a radio base station (BS = Radio Base Station) using the uplink and downlink signal propagation air times to (for example, T-up and T-down). As such, no absolute time reference is required. The MS and BS report to a service node in the mobile network the local arrival and departure times of the uplink and downlink signals and calculate the apparent air times T-up and T-down. The distance D, between MS and BS can be calculated as: D = c (T-up + T-down) / 2, (1) where "c" is equal to the speed of light. According to a first embodiment of the present invention, the distance between an MS and a particular radio base station (BS1) can be terminated by the following novel round trip method. A first order of measurement is sent by a network controller (for example, a mobile service switching center or MS = Mobile Service Switching Center) to BS1, which instructs BS1 to measure the local time-of-arrival (L-TOA) -U) of a first signal (eg, a conventional training sequence) that is transmitted (uplink) by the MS within a specified time window. With respect to a downlink transmission, BS1 normally transmits a second signal periodically in the downlink (for example, a pilot signal in a WCDMA system) at local transmission times (L-TOT-D). These second signals can be received by all the MSs, which make it unnecessary for the network controller to order BS1 to send a dedicated downlink signal at a specified time. The network controller sends a second measurement order to the MS through its service BS (BSO) which instructs the MS to transmit the first signal (uplink) with the specified time window and report its local time-of-transmission exact (L-TOT-1). The second measurement order also instructs the MS to measure and report the local time-of-arrival (L-TOA-D) of the second signal (downlink) transmitted by BS1. Additionally, the first and second commands identify the downlink and uplink radio channels to be used for the transmissions and measurements described above. The MS and BS1 report the respective measurements of L-TOA-D and L-TOA-U to the network controller, which sends this information along with the identity of the MS to a processor in the network service node. -Using a form of equation 1 shown above, the processor calculates the distance between MS and BS1. According to a second embodiment of the present invention (for example in a CDMA system or WCDMA), the air time from an MS to a service BS (BSO) can be determined by a novel method that configures a connection (for example a call) between the BSO and MS. The conventional correspondence filter technique can be used to determine the round trip delay for the connection. The value of the resulting round trip delay is divided by two, and the result is multiplied by the speed of light, which gives the distance between MS and BSO. The same method can be used to determine the distance between MS and two neighboring BSs (BS1, BS2). A conventional triangulation algorithm is then used to determine the MS position. According to a third embodiment of the present invention, for example in a system (TDMA), the air time from a service MS to BS (BSO) is determined by a conventional synchronization advance technique (TA = Timing Advance) . As in the second embodiment, a conventional correspondence filtering approach can be used to determine the round trip delay. The distance between MS and BSO is calculated by dividing the round trip delay value by two and multiplying the result by the speed of light. Again, the same method can be used to determine the distance between the MS and two neighboring BSs (BS1, BS2). A conventional triangulation algorithm is then used to determine the position of the MS. According to a fourth embodiment of the present invention, the derived position for an MS (MSI) and the distances derived from MSI to neighboring base stations (e.g. MSI, BS2, etc.) are employed by a network service node to determine the time shifts (transmission) of those neighboring BSs with respect to the BS serving the MSI (BSO) the position of a second MS (MS2) is then determined according to a TOA method either downlink or link conventional descent. It should be noted that as a practical matter, the derivative position for MSI must have been determined recently before the MS2 measurements, since the clocks of the BSs can be derived. The neighboring BSs report the TOA in local time to the service node by means of a network controller (for example MSC). The service node already knows the time shifts of the neighboring BSs. According to a fifth embodiment of the present invention, a radio BS is provided to determine the position of an MS using a round trip position determination approach. The BS includes a control device that has a local clock. The control device in response to receiving a report order reports the uplink arrival time (L-TOA-U) and downlink local time-of-transmission (L-TOT-D) of a sequence downlink and uplink synchronization between BS and MS. The BS also includes a transmitter, which reports to the control device the instant in time a signal is transmitted in the downlink (L-TOT-D). A receiver is also included, which uses a sliding correlator or correspondence filter to determine the instant in time that a signal is received in the uplink (L-TOA-U). The receiver reports this time information to the control device. According to a sixth embodiment of the present invention, a radio MS is provided to determine its own position, using the round trip position termination approach as used for BS in the fifth embodiment. The radio MS includes a control device that has a local clock. The control device in response to receiving a report order reports the uplink local time-of-transmission (L-TOT-U) and the downlink local time-of-arrival (L-TOA-D) of the downlink and uplink synchronization sequence between the MS and the radio BS. The MS also includes a transmitter that reports to the control device the instant in time that a signal is transmitted in the uplink (L-TOT-U). Also included is a receiver that uses a mapping filter or sliding correlator to determine the time at which a signal is received on the downlink (L-TOA-D). The receiver reports this information in time to the control device. An important technical advantage in the present invention is that the method for position determination employed does not require synchronized BSs in time, a time reference or "reference" terminals with known positions. Nor does the present invention generate unnecessary "burst" of access burst. Another important technical advantage in the present invention is that it can be applied to any mobile communication system including, for example CDMA, WCDMA, TDMA, multiple access with frequency division ( FDMA = Frequency Multiple Access Division), or analog system, provided that said system is capable of transporting digital information in the uplink and downlink, and its BSs and MSs are capable of measuring arrival and local transmission times. Yet another important technical advantage in the present invention is that it is still possible to use a time reference (for example GPS reference signal) in BSs which makes it unnecessary to have downlink or uplink measurements taken. Yet another important technical advantage of the present invention is that it makes it possible to use an MS whose position has been determined, as a "reference" terminal for the purpose of terminating the synchronization offsets of neighboring -BSs. Consequently, the present invention advantageously decreases the number of measurements required to determine the position of other MSs. BRIEF DESCRIPTION OF THE DRAWINGS A more complete understanding of the method and apparatus of the present invention can be achieved by reference to the following detailed description when taken in conjunction with the accompanying drawings in which: - = - Figure 1 is a schematic block diagram of a radio system mobile cellular that can be used to implement a method for determining the position of a mobile radio station (without requiring the use of a time reference), in accordance with a preferred embodiment of the present invention; Figure 2 is a schematic block diagram of a radio base station and a radio mobile station, which are structured according to respective embodiments of the present invention; and Figure 3 is a flow chart showing a method for determining the position of a mobile radio station, which can be implemented by the modalities shown in Figures 1 and 2. DETAILED DESCRIPTION OF THE DRAWINGS The preferred embodiment of the present invention and its advantages are better understood by reference to Figures 1 to 3 of the drawings, similar numbers are used for like and corresponding parts in the various drawings. Figure 1 is a schematic block diagram of a cellular mobile radio system 200, which can be used to implement a method for determining the position of a mobile radio station (without requiring the use of a time reference), in accordance with a preferred embodiment of the present invention. The system 200 includes a plurality of radio base stations. For clarity, only three base stations of this plurality of radio base stations are illustrated: BSO (which serves the base station for a mobile radio station whose position is to be determined); and two neighboring base stations BS1 and BS2. Preferably, BS, BS1 and BS2 are located in different sites to define different cells and all are connected to a cable-linked network (for example the public land mobile network or PLM = Public Land Mobile Network) by communications links 201. For In the exemplary embodiment shown, this network includes a network controller such as, for example, a mobile services switching center (MSC = Mobile Services Switching Center) 202 which is connected via a public switched telephone network or PSTN (not shown explicitly) to a service node mobile location center (MPC = Service Node Mobile Positioning Center) 203. MSC 202 includes a memory storage area with a look-up table 204, which relates specific radio channels to specific mobile-radio stations (for example MS 208). The function of the search table (204) allows the MSC 202 to report to the service node MPC 203 times of arrival and transmission of uplink and downlink signals, and relates those times to the mobile station (s) involved (e.g. MS 208). Each MS communicates with a BS by means of a radio air inferium (for example air interface 211 between BSO and MS 208). For this mode, the service node MPC 203 includes a processor 203a, which further includes a receiving unit 203b, storage unit 203c, sending unit 203d and first and second computing units 203e and 203f, respectively. The processor 203a maintains the geographic position information for each of the BSs in the storage unit 203c. Calculation units 203e and 203f are used to calculate the position of the involved MSs (for example MS 208) using the stored BS position information and reported local times of arrival and transmission times (of MSC 202) for the signals of uplink and downlink. For example, the first calculation unit 203e can be used to calculate the round trip distance D, between an MS (for example MS 208) and a BS (for example BS1) as follows: D = c (T-up + T- down) / i, (2) from the reported local transmission times (L-TOT-U, L-TOT-D) and the local arrival times (L-TOA-U, L-TOA-D), where: T-up = (L-TOA-U - L-TOT-U), and ( 3) T-down = (L-TOA-D - L-TOT-D). (4) The second calculation unit 203f can be used to calculate the position of the MS under consideration (for example MS 208) when using the round trip distance information, D between that MS and at least three radio base stations (per example BSO, BS1, BS2). As an option, the second calculation unit 203ÍT can also use any reported arrival information (DOA) address if it is available from the antenna structures to determine the position of the MS. In this case, the position of the MS can be determined simply from the round trip distance D, and DOA information with respect to a BS. As such, the MS is located at a certain azimuth (DOA) and distance from the BS involved. The storage unit 203r * maintains the known positions of the network radio base stations (for example BSO, BS1, BS2). The receiving unit 203b and the sending unit 203d provide means for the MPC of the serving node 203 to communicate with the network controller (MSC 202) and also with subscribers requesting / receiving MS position information (for example using a feature of short message service or SMS).

In operation, considering that the MS 208 is a MS whose position is to be determined, the bi-directional link 211 shown represents a signal connection (for example a call) between the MS 208 and its service BSO. MSC 204 sends a command message through connection 211 to MS 208 which instructs MS 208 to perform the position determination functions. The MS 208 transmits by its connection 211 its reported local signal arrival and transmission times, which are received by BSO and transported to MSC 202. The uplink signal connections 212 and 213 (to BS1 and BS2, respectively) each represent a sequence of position termination transmitted in the uplink and received by BS1 and BS2. For this exemplary embodiment, this position completion sequence information only needs to be a predefined time stamp. Similarly, the downlink signal connections 214 and 215 of BS1 and BS2, respectively) each represent a position determination sequence transmitted in the downlink by BS1 and BS2, and received by MS 208. For this mode, it is Position completion sequence information only needs to be a predefined time stamp. However, for a different embodiment these predefined timestamps can be implemented as pilot signals transmitted by BS1 and BS2 in a CDMA or WCDMA system. The distance of neighboring base stations (BS1, BS2) to MS (208) can be determined with the round trip position determination method described above. The distance from the service base station (BSO) to MS (208) can be determined with a distance measurement method with conventional time advance (for example in a TDMA system) or a distance measurement method with conventional matching filter (for example in a CDMA or WCDMA system). These distances between the MS (208) and the base stations (BSO, BS1, BS2) together with the known location information BS are then used in a triangulation algorithm to determine the position of the MS. Figure 2 is a schematic block diagram of a radio base station and a mobile radio station, which are structured according to the preferred embodiment of the present invention. For this mode, the radio base station BS1 (or BS2, ... BSn) and the mobile station MS 208 are part of a WCDMA system. BS1 includes a transmit antenna 301 and two receive antennas 302. The pair of receive antennas 301 advantageously provides diversity of space for the radio traffic, and also for the uplink measurements of the present invention. BS1 also includes a transmitter section 302, receiver section 304 and a mail filter 305, preferably implemented by a finite impulse-response filter (FIR Finite-Impulse-Response). The FIR filter 305 (connected to the receiver section 304) uses a conventional synchronization technique to determine the time that an uplink signal 309 arrives in BSl, which is to be used by the present method to determine the position of the MS 208. A control unit 306 reads-from a local clock 308, (via connection 307 of the FIR filter 305 at the time reported), the local time-uplink (L-TOA-U) and directs this information together with the radio channel identity information associated with MSC 202. MS 208 is structured to implement the MS position determination method of the invention in a form corresponding to that of BSl. For this embodiment, MS 208 includes a transmit / receive antenna 321, which is connected to a receiving station 324, transmitting section 323 and transmitting / receiving section 323. A matching filter 325 (also implemented as an FIR filter) is connected to a receiver section 324. The FIR filter 325 uses a conventional synchronization technique to determine the instant when a downlink signal 310 arrives at the MSC 208, which will be used for the present method of determining the position of MSC 208. A control unit 326 reads from a local clock 328 (through connection 327 of the FIR filter 325 at the time reported) the time-of-arrival downlink (L-TOA-D) and directs this information _ together with the radio channel identity information associated with the MSC 202 via a signaling path 329, transmitter / receiver section 330, antenna 321, air interface 331 and the base station radio service BSO. The control unit 326 also generates an uplink signal 309 which is transmitted by the MS 208 by a transmitter 323 and antenna 321. The uplink signals 309, which are received by the involved base station (eg BSl) are used. when implementing the present method to determine the position of an MS. As such, the control unit 326 reads on the local clock 328, the local transmission time (L-TOT-U) for the downlink signal 309 and directs this information together with the radio channel identity associated with it. MS 202. MS 202 queries lookup table 204 (Figure 1) to determine the identity of the mobile station whose position is to be determined (eg MS 208). The search table also maintains, in addition to the known BS position information, the associated radio channels that carry the respective signals 211, 212, 213, 214 and 215. These signals are kept in the look-up table when the call is made. set or configured between the service base station BSO and the involved MS (208) and the order message is sent to initiate the present method of determining the MS position. Figure 3 is a flow diagram showing a method 500 for determining the position of a mobile radio station, which can be implemented by the modalities shown in Figures 1 and 2. For these embodiments, the system 200 is a radio system CDMA mobile. In step 501, a request to determine the position of a mobile radio station (e.g. MS 208) is received at the service node MPC 203. For example, this request may arrive at the MPC 203 as a short text message of a subscriber. In response to receiving this request, in step 502, MPC 203 sends an order message by MSC 202 and the service BSO to MS 208, which instructs MS 208 to initiate the position completion function itself. Position determination is performed using the locations of the service BSO and the neighboring base stations BS1 and BS2 as feeds to a conventional triangulation algorithm. In step 508, BSO determines the distance between itself and the MS 208 in calculating the round trip delay (BS0-MS-BS0) using a conventional correspondence / mapping method, and reports that distance information determined by MS 202 to MPC 203. In step 504, MS 208 measures the local arrival times, L-TOA-D1 and L-TOA-D2 of the (pilot) signals transmitted from BS1 and BS2 respectively and reports these local arrival times. by BSO and MSC 202 to MPC 203. In step 505, MPC 203 sends an order message via MSC 202 to BS1 and BS2 which instructs BS1 and BS2 to "listen" for location data to be transmitted in the uplink from MS 208 during a specified interval. In step 506, MPC 203 sends an order message to MS 208 via MSC 202 and BSO which instructs MS 208 to transmit the position data during the specified interval, and report the exact transmission time (L-TOT-U) by BSO and MSC 202 to MPC 203. In step 507, BSl and BS2 measure the respective local arrival times, L-T0A-U1 and L-T0A-U2, of the position data transmitted during the specified interval using a conventional correlation method. In step 508, BSl and BS2 ~ report the respective local base station times for the transmitted signals, L-TOT-D1 and L-T0T-D2 and the local base station arrival times for the received signals L-T0A- U1 and L-TOA-U2, to MPC 203 by MSC 202. In step 509, MPC 203 computes MS 208 position, using the known BS positions and local times reported according to equations 2-4 above. It should be noted that according to the present invention, the uplink signals of the MS 208 can be transmitted at any appropriate time, if the local transmission time is reported from the MS 208. However, in prior art methods, the Uplink signals transmitted from a mobile station whose position is to be determined are transmitted at known absolute time intervals relating to the synchronization of the service base station.; and the distance between the service base station and that mobile station. Consequently, as an alternative to the methods of the prior art, the distance between the service base station and the mobile station can be determined using the present method shown in Figure 3, to determine the distances between BSl and MS 208, and BS2 and MS 208, when performing steps 504-508 instead of what was described above for step 503. Although a preferred embodiment of the method and apparatus of the present invention has been illustrated in the accompanying drawings and described in the above detailed description, it will be understood that the invention is not limited to the described mode, but is capable of numerous arrangements, modifications and substitutions without departing from the spirit of the invention as set forth and defined by the following claims.

Claims (26)

1. CLAIMS 1. - A method for determining the round trip air time between a mobile radio station and a first radio base station, characterized in that it comprises the steps of: the mobile radio station and the first radio base station, each one determining a local transmission time of an uplink signal and a downlink signal respectively; the mobile radio station and the first radio base station each determine a local reception time of the downlink signal and the uplink signal respectively; calculating an apparent uplink air time from one of the local transmission time and one of the local reception time; calculating an apparent downlink air time from one second of the local transmission time and the local reception time; and adding the apparent uplink air time and the apparent downlink air time to obtain the round trip air time. 2. - The method according to claim 1, characterized in that it further comprises the step of determining the distance between the mobile radio station and the first radio base station by multiplying the round trip air time by the speed of light divided by two. 3. - The method according to claim 1, characterized in that it further comprises the step of determining the round trip air time between the mobile radio station and the second radio base station when carrying out the steps of claim 1 for the mobile radio station and the second radio base station. 4. - The method according to claim 3, characterized in that it further comprises the steps of determining the position of the mobile radio station, by: determining a first radial distance between the first radio base station and the mobile radio station, and a second radial distance between the second radio base station and the mobile radio station, by multiplying each round trip air time by the speed of light divided by two; determining a plurality of intersections of the first radial distance and the second radial distance; and selecting the position of the plurality of intersections. 5. - The method according to claim 2, characterized in that it further comprises the steps of determining the position of the mobile radio station, by: determining the distance between the first mobile radio station and the second and third base stations of radius upon re-performing the steps of claims 1 and 2 for the second and third radio base stations; and triangular with the distance between the mobile radio station and the first radio base station the mobile radio station and the second radio Jbase station and the mobile radio station and the third radio base station. 6. - The method according to claim 2, characterized in that it further comprises the steps of determining the position of the mobile radio station by using a time-of-arrival algorithm with more than three radio base stations. 7. - The method according to claim 2, characterized in that it further comprises the steps of: receiving at least one address-d-the arrival signal for the mobile radio station and at least one radio base station; and determining the position of the mobile radio station from the direction of the arrival signal and the distance between the mobile radio station and the first radio base station. 8. - The method according to claim 1 characterized in that the apparent uplink air time is equal to the local time-of-arrival for an uplink signal minus the local time-of-transmission for the uplink signal and the apparent downlink air time is equal to the local time-of-arrival for a downlink signal minus the local time-of-transmission for the downlink signal. 9. - The method according to claim 2, characterized in that the calculation, addition and multiplication steps are performed in a service node of the mobile communications network. 10. - A method for determining the distance between a mobile radio station and a first radio base station, characterized in that it comprises the steps of: the mobile radio station and the first radio base station, each determining a local time of transmission of an uplink signal and a downlink signal respectively; the mobile radio station and the first radio base station each determine a local receive time of the downlink link signal and the uplink signal respectively, calculate an apparent uplink air time from one of local transmission time and one of the local receive time, calculate an apparent downlink air time of one second of the local transmission time and the local reception time, add the apparent uplink air time and the time of apparent downlink air to obtain a round trip air time, and multiply the round trip air time by the speed of light divided by two 11.- A method to determine the distance of a mobile radio station in a mobile communication system, characterized in that it comprises the steps of: configuring a connection between the mobile radio station and at least one radio base station in the mobile communications system; calculating an apparent uplink air time and an apparent downlink time for the connection between the mobile base station and at least one of the radio base stations; add the apparent uplink air time and the apparent downlink air time for the connection, to obtain a round trip air time for the connection; and determine a distance for the connection, by multiplying the round trip air time for the light speed connection divided by two. 12. - The method according to claim 11, characterized in that it further comprises the steps of determining the position of the mobile radio station, when determining a first radio base station and the mobile radio station, and a second radial distance between a second radio base station and the mobile radio station, by multiplying a round trip air time for each radio base station by the speed of light divided by two; determining a plurality of intersections of the first radial distance and the second radial distance; and selecting the position of the plurality of intersections. 13. - The method according to claim 11, characterized in that it further comprises the steps of determining the position of the mobile radio station, by: determining the distance between the mobile radio station and the second and third radio base stations, upon re-performing the steps of claim 12 for the second and third radio base stations; and triangular with the distance between the mobile radio station and the first radio base station, the mobile radio station and the second radio base station and the mobile radio station and the third radio base station. 14. - The method according to claim 11, characterized in that it further comprises the steps of determining the position of the mobile radio station, by using a time-of-arrival algorithm with more than three radio base stations connected to the mobile radio station. 15. - The method according to claim 11, characterized in that the apparent uplink air time for each connection is equal to the local time-of-arrival for a respective uplink signal minus the local transmission time for the respective uplink signal and the apparent uplink air time is equal to the local time-of-arrival for a respective downlink signal minus the local time-of-transmission for the respective downlink signal. 16. The method according to claim 11, further comprising the steps of determining the position of the mobile radio station, using at least the distance for the connection and at least one other distance measurement. 17. - The method according to claim 11, characterized in that the connection comprises a call. 18. The method according to claim 11, characterized in that the connection comprises link communication data. 19. The method according to claim 11, characterized in that it further comprises the steps of determining the position of the mobile radio station, wherein the uplink signals of the mobile radio station are synchronized with the downlink signals of the radio base station at least, and the radio base station at least uses a known round trip time delay for the connection between the radio base station at least and the mobile radio station. 20. Method for determining the position of a mobile radio station, comprising the steps of: measuring a round trip delay between at least one service radio base station and the mobile radio station; service radio base stations report round trip delays to a network processor; the mobile station measures a local arrival time of an O signal from a plurality of radio base stations; report the local arrival times of the signals to the network processor; the mobile radio station transmits a position data signal and reports to the network processor a local transmission time for the position data signal; each of the plurality of radio base stations measures a respective local arrival time for the position data signal and reports to the network processor a local transmission time for the signal from the plurality of radio base stations, and the time respective local arrival measured for the position data signal; and the network processor calculates the position of "the mobile radio station with the local transmission and local arrival times reported. 21. - The method according to claim 20, characterized in that the mobile radio station transmits the position data signal during a specified time interval and each of the plurality of radio base stations measures the respective local arrival time for the position data signal during a time interval, including at least a part of the specified time interval. 22. The method according to claim 20, characterized in that the network processor calculates the position of the mobile radio station using a time-of-arrival estimation algorithm. 23. - A system for determining the distance between a mobile radio station and a first radio base station, characterized in that it comprises: means for the mobile radio station to determine a local transmission time of an uplink signal and the first radio base station, to determine a local transmission time of a downlink signal and the first radio base station, to determine a local reception time of the uplink signal and the mobile radio station, to determine a time of local reception of the downlink signal and processing means for: calculating an apparent uplink air time from the local uplink transmission time and a local uplink reception time; calculating an apparent downlink air time from the local uplink transmission time and the local downlink reception time; add the apparent uplink air time and the apparent downlink air time to obtain a round trip air time; and multiply the round trip air time by the speed of light divided by two. 24. The system according to claim 23, characterized in that the processing means comprise a mobile location center. 25. The system according to claim 23, characterized in that the downlink signal comprises a pilot signal in a CDMA system. 26. The system according to claim 23, characterized in that the means for each mobile radio station and the first radio base station to determine a local transmission time of an uplink signal and a local reception time of a Downlink signal includes a control unit and a local clock.