DE10308005A1 - Position determination method for communications network terminal e.g. cellular mobile telephone using observed time differences between signals exchanged with different transmission and/or reception stations - Google Patents

Abstract

The position determination method calculates the position of the terminal from the observed time differences of signals transmitted between the terminal and at least 2 transmission and/or reception stations. An estimation of the relative synchronization interval between 2 transmission and/or reception stations is determined electronically via a computer, without requiring the synchronization of the transmission and/or reception stations.

Description

The present extension concerns a Method for determining the position of a terminal in a communication network according to the generic term of claim 1.

In particular, the Terminal device to act as a mobile phone while the communication network as a cellular communication network, for example as a GSM network (Global Systems For Mobile Communication). In such a Communication network is a geographical area in a number of cells with one transmitting and / or receiving station each (also base station called) divided. Even if the invention is first in the following Line explained using the GSM network is, it is not limited to this particular network. Also can which are advantageously designed as mobile telephones in another configuration, for example as laptops, notebooks, digital organizer or the like.

Knowing the coordinates A cell phone subscriber can add new ones based on the location of each Services adapted to users, so-called location-based services (LBS) (location-based services), offer within mobile radio systems. These provide information Transactions or the like in a spatial Relation to the current position of the participant. The new services offer opportunities that both the mobile phone users, the telecommunications companies, but also application service providers (service providers respectively Company that provides platforms or software to the network operator introduction of services) and content providers (companies that provide databases offer to set up services in the case of location based Services for example road maps, Position databases and the like) can use.

For the network operator who strives to create new value to achieve, the location-specific mobile services provide a useful and attractive expansion of the offer portfolio. A position determination therefore offers the possibility to offer a number of new service ideas within the mobile radio systems by means of that the network operators could achieve the aforementioned goals. Because on the one hand allow location-specific Services the development of customized, personalized services, on the other hand, that means the necessary Equipment but also that the participant who has an appropriate terminal has acquired itself stronger binds to the network operator.

A division of the different Areas of application for location-based services are, for example in the categories information, navigation, security, marketing, Entertainment and the like possible.

Regarding security demanded the US regulator Federal Communication Commission (FCC) back in 1996 Localization of participants with mobile devices in an emergency using the so-called E-911 service. This E-911 localization, for example in the event of a car breakdown, a traffic accident or a robbery enable rapid assistance, even if the mobile subscriber does not find his current location knows or this may be is no longer accessible.

Are under the security aspect still different tracking systems imaginable with which the Position of a mobile device can be located continuously, for example identification and allows you to find stolen vehicles.

Provide information within the Location-based services are a significant field of application especially since almost everyone is location-dependent Service based on retrieval of location-based information. Here are, for example, services such as industry information or points of interest applications conceivable, which is not alphabetical but distance dependent in Sorted according to the current location of the service user, with the help of which the mobile subscriber can quickly find, for example, the next bank, the next Workshop, the next Restaurant or the sights nearby along with a short online travel guide Can be found. These information services are already partially open SMS or WAP basis realized.

The navigation is also one important category that is very closely related to the previous concept of Information related because the user may not just want to know where to find an offer, but also how to get there. A solution therefor would be a Combined information and navigation service that the participant not just the phone numbers of the municipal theaters, restaurants or Petrol stations indicates, but also those of these facilities calls the one closest to you and leads him there straight away. Here is from simple directions to a concrete one Navigation that takes into account the current traffic situation and construction sites, everything conceivable. Useful for Location based services are also approaches for navigation systems that are not tied to a vehicle and therefore also a pedestrian in can help a city to orientate yourself to prominent points in the area.

Another important aspect is telematics, which focuses on tracking a mobile device. Services such as fleet management or complex tracking systems are conceivable here, by means of which a company can always determine where a vehicle of its fleet is currently located. Consequently it is possible to use vehicles more effectively or to avoid detours and unnecessary empty runs.

One can already in the present Measurement of traffic to data for an adaptive traffic management system to be realized by the density of mobile phones, and no longer exclusively through measuring devices as before at the edge of the road, as the majority of road users a mobile phone or a telematics device is in the vehicle. So it is possible, using this traffic density information, individual To guide road users past congestion sections using offboard navigation.

Marketing will also be in the future an important part of location based services take as the targeted presentation of location dependent Advertising, for example special offers of a supermarket in direct Near the Location of the user, promises a much higher efficiency than Conventional advertising Sense. Event notices such as concerts are also conceivable or sporting events that focus on the immediate local Relate to the environment.

In addition to the event information mentioned above the entertainment category includes a variety of others Possibilities, that may interest the mobile user. You can do this include communications services that you use to connect with other people who are in the immediate vicinity stop and use the same service. Furthermore, in so-called "friend finder" applications the position of a member of a precisely defined group of people be determined that this service in its profile for the seeker unlocked. Areas of application of that service are for example determining the whereabouts of the child, the concerned parents want to get but also quickly finding friends for appointments. In this There are still numerous areas of possible areas Applications conceivable, for example location based games, in which participants in a closer local Environment can play against or with each other.

But there are also reasons for determining a position the mobile subscriber, of which primarily the network operator can benefit. These consist, for example, of radio network optimization. The radio cells can through macroscopic and long-term monitoring and identification individual hot spots better geared to real occupancy what increases spectral efficiency. Furthermore, one is localizable Error detection, for example the detection of areas on them heaped Calls are canceled, and therefore an additional one quality assurance possible within the network.

Another application for the mobile operator, the location dependent Tariff structure is already in use. Based on the location of the customer it is possible cheaper in a home area Tariffs as outside to offer it. The price structure of the talks about the mobile network operator consequently remains comparable to that of the fixed network. Under the Condition of location dependent Tariff structures can the telecommunications companies discount their subscribers Get offers to make calls at the places where this is Business management related to the network infrastructure or future network planning is advantageous.

By knowing the whereabouts of the mobile phone user is also more effective resource management possible. This means that the selection of the transmission channel over which the connection to the subscriber is established depending on the position of the user is hit.

Could continue through surveillance the participant movement handover decisions (handover = Performance feature of cellular mobile radio networks, which an automated Forwarding an existing user data connection to another Channel of the same or a different radio cell) more effectively be taken by unnecessary Handovers caused by localized fading are not carried out, which causes the so-called ping-pong effect every now and then withdrawn handovers can be avoided.

For the network-wide introduction of previously mentioned services in the mass market, it is necessary to be as resource-efficient as possible Use positioning procedures. Future realized in the GSM network Positioning procedures should be in addition to a location calculation a location determination by the network infrastructure Handset (the mobile device, for example, the mobile phone or the like).

There are already different procedures known how the position of a mobile device, such as a cell phone, in a cellular communication network, for example the GSM network can be determined.

These differ in relation on the location accuracy, the technical effort and thus related investments for terminals and network infrastructure. The procedure can be based on certain criteria be divided.

A property for classification of these localization techniques is whether the position is unilateral, this means that the position of the object by receiving signals from several reference points whose position is known, estimated or is determined multilaterally, the object to be positioned sends a signal that is received by several reference locations.

Furthermore, the techniques in the cellular communication network could be grouped into the “handset-as sisted "or in the" handset-based "positioning techniques. In this context, handset-assisted means that the mobile station (MS) or the mobile terminal device carries out any necessary measurements and forwards these measured values to the network infrastructure. However, the actual position calculation is carried out in the network. The latter type of positioning primarily uses multilateral positioning techniques. In contrast to this, the mobile station itself uses handset-based positioning techniques to carry out all measurements or calculations that are necessary for determining the position. If it is not possible for the mobile station to measure certain parameters independently, the transmission of these variables from the network infrastructure to the mobile station can enable them to carry out handset-based positioning techniques.

For example, it is possible to use a Determine the location by determining the direction. Here are Directions to calculate the position of the desired Object. Direction finders measure the reception angle a signal sent by this object. This is ideal Fall along a straight line in the received direction. Puts If you enter several DF stations, you get different directional determinations and there are several straight lines at their intersection the object is located. When determining the location by determining the direction it is a multilateral procedure.

In the cellular communication network, For example the GSM network, this basic technique of determining the direction through the so-called “Angle of arrival "procedures can be implemented. The DF stations realized by antenna arrays at the location of the base stations. These antennas consist of several (usually 4 to 12) individual antennas, their distances Multiples of half the wavelength be. The disadvantage of this positioning method is because the replacement of existing antennas with complex antenna arrays requires high investment costs. Adaptive antennas can the capacity on the air interface can be increased by reducing the interference, for the exact localization of mobile participants is however one difficult to carry out exact alignment and calibration of the arrays necessary while the achievable capacity increase of misalignment is not affected.

In mobile radio systems, it is through Multipath or as a result of shadowing (Non Line of Sight (NIoS) spread) possible, that the antenna array is pointing in the wrong direction. Based this fact leaves this method is sensitive to those Establish propagation conditions. This sensitivity is however due to the changing Scatterer characteristics from the distance of the mobile station with respect to the Base station dependent.

Located on a macro cell model a circular one Area of so-called scatterers around the mobile station, the base station however, is far outside of this ring. In contrast, the base station is in a microcell model often surrounded by local scatterers in their vicinity. Using these scatterer configurations shows that when using macrocell scenarios the signals under one received small error of the reception angle at the base station in the microcell model by targeting local spreaders nearby the base station potentially large Errors in the reception angle and thus in the position result.

With another basic positioning technique, the group of location determination by distance calculation, are geometric Distances used to determine the location of the property. The category of these distance techniques can still be divided into two Classify basic techniques: position determination by geometric Distance between object and reference point (spherical location), and Difference between two geometrical distances between object and reference point (Hyperbolic location).

The basic technique of spherical Position determination directly uses the geometric distance between the object and a reference position. In two-dimensional application results for the possible Position of the object a circular line with the measured distance around the reference location. Using a multiple lateration, the Position of the object determined. First, two measurements are different Combined reference locations, this results in a maximum of two positions as the potential location of the object, the intersection respectively the point of contact of the two circular lines. Further distance measurements with further reference points are carried out until this ambiguity is eliminated. A disadvantage of the basic technique of spherical Location is dependence the dissolution of the system geometry, that is, the position of the reference locations across from the positioning object. This state of affairs is called “Dilution of Precision (DOP) "Problem. Dilution of Precision means in this context the reinforcement an error in the input values of the position determination for the Location error.

In a cellular communication network, for example in the GSM network, the basic method of spherical location determination can also be implemented by the so-called "time of arrival" method, at least three measuring stations in the base stations determining the propagation times of a signal sent by the mobile station Known position of the base stations, which serve as reference positions, and the measured propagation times, which are proportional to the distance, can be the position the mobile station can be determined multilaterally.

Since the GSM specification, however a non-synchronized network is provided by the individual Base stations their bursts at different times or the base stations expect the burst reception at unequal moments, this time offset referred to as the offset in the time bases becomes. Knowing these offsets between those at the positioning Base stations involved is a prerequisite for the determination the propagation times and thus the location of the mobile station.

There is an approach to measurement the propagation time from the mobile station to the base station without the explicit awareness of the offsets in the time bases, but proves this approach turns out to be impractical. There the round trip Delay, hence the time delay a request sent from the base station to the mobile station until the answer of the mobile station arrives. The processing delays, the processing times within the mobile station and the base station, are different depending on the manufacturer, therefore do not estimate the propagation time as necessary.

Therefore the challenge lies in this method in the synchronization of the individual base stations, or in the determination of these offsets in the time bases, which in the asynchronous GSM network basically through a GPS receiver can be reached in every base station, but this increases the infrastructure costs arise. The "Time of arrival "method can be done with all handsets, one Modification is therefore not necessary.

The accuracy of the position determination using "Time of arrival "procedure depends the number of measuring stations involved and the local ones Circumstances. In rural The method typically achieves accuracy in areas of 50 meters, in difficult urban Areas is the uncertainty around 150 meters.

Another example of a spherical position determination is the GPS satellite navigation system. For a position determination radio contact to at least four satellites is required serve as reference positions and the geometric distance with respect to that for execution spherical Positioning techniques is determined. The main problem besides one additional Hardware extension in the mobile terminal device in the form of a special GPS receiver, its increased power consumption and increased hardware expenditure, which too rising device prices leads, are the weak signals from the satellites. Inside closed building if these are not to be received, consequently GPS receivers are "standing alone "solution for the Use in urban conurbations severely limited in their usability. In addition, the so-called “urban canyon "problem plays an important role, because in house gorges let yourself a clear view of four satellites that are in a low Move earth orbit relative to the viewer, difficult to ensure. Still need conventional GPS receiver after switching on between ten and 60 seconds to use the received satellite data to determine their own location (Time to first fix). This period is for most areas of application a position determination of mobile terminals too large.

The multitude of the problems mentioned when using a GPS reception structure in handsets can take consideration the so-called A-GPS procedure can be reduced, but for what an additional Hardware expenditure in the cellular network is required. Here will some of the position parameters sent by the satellites are already over fixed installed GPS receivers in the GSM network infrastructure, and over Cell broadcast channels transmitted to the mobile terminals. This simplifies the calculation in individual cases and shortens one Positioning process down to a few seconds while the Accuracy in the range of 10 to 50 meters is increased at the same time. At the same time there is only one GPS receiver with limited Range of functions required in the handset, its costs and energy requirements compared to full recipients is significantly reduced. Regardless, it is also in use the A-GPS procedure does not locate inside buildings possible. Therefore, to complete Coverage of the cellular network a combination with other technologies to a hybrid positioning system required.

When using the hyperbolic Positioning procedure, another basic technique of the group the location by distance determination, the location is by means of the difference of the distances with respect to two Reference positions calculated. The stand line, the set of all possible Positions of the object, each corresponds to a hyperbola, the by the difference in distance the reference position pair and the two reference points is.

A two-dimensional coordinate system is then considered again. The position of the object is determined by first combining two measurements with different reference throw pairs. There are a maximum of two positions as potential object locations that correspond to the two possible intersections of the two hyperbolas. Measurements of distance differences with further reference points are carried out until this uncertainty as to which of these two locations corresponds to the position of the object has been eliminated. In order to obtain a reliable determination of the position, at least two hyperbolas are required, which corresponds to at least three reference positions. This is exemplified in 1 shown.

wobei die Koordinaten (Xk, Yk) die Position der k.ten Referenzposition und (x, y) die Position des Objektes repräsentieren.The distance difference of the objects with respect to the i.th and j.th reference positions is

where the coordinates (Xk, Yk) represent the position of the kth reference position and (x, y) the position of the object.

The hyperbola is the set of all points for which the difference between the distances with respect to two fixed points is a constant quantum. This is exemplified in 2 shown.

The hyperbolic position determination is advantageously used in the described below E-OTD process.

It is also possible to use a to carry out direct location determination in cellular networks.

Cellular networks offer due to their Building another way a basic positioning technique. The location of associated end devices is used knowledge of cell information and the respective coverage areas of the individual cells.

Such a method is for example the so-called "Cell-ID" Method. Cover like a mosaic Radio cells, in the center of which there is a base station Radio antenna is located, the entire area of expansion of the mobile network. When using direct location in cellular networks, such as it is implemented, for example, in the GSM mobile radio network the determination of the position data on the basis of the "cell identifier" (cell ID) which identifies the radio cell, in which the terminal is located, clearly identified. This provides the easiest location determination of terminal equipment to be realized in the GSM network, because their position is described by the location of the serving cell becomes. With this localization method, the position of everyone can be Determine the terminal equipment because changes to the mobile stations are not required. Only a slight modification is required the network infrastructure to transform the "Cell Identifier" in coordinates.

In metropolitan areas, localizations via micro-cells allow Already an exact position specification to about 300 m, however, can a radio cell in thin theoretically populated and low-traffic areas cover about 35 kilometers, which results in a smaller one Accuracy of position determination leads.

To resolve the Cell ID positioning method in large Cells to increase can two additional Parameters are consulted, the value of timing advance (TA) and the reception field strength the signals from the neighboring cells. The result under the use The timing advance is that the mobile station is somewhere within a circular ring at least 550 meters wide around the position of the Base station is located. This value of the uncertainty of the distance from the Base Trancieving Station (BTS) corresponds to the quantization resolution of the Timing Advance parameters. The exact match Distance from the base station with the one converted into a distance In addition to quantization, the TA value is essentially based on the distance the terminal equipment from the base station and the propagation conditions ((non) line of Sight, multipath propagation) dependent.

Another method for determining position is the so-called E-OTD method, (Enhanced-Observed Time Difference), which is a specified positioning method for a cellular Communication network, for example for the GSM network that based on measured time differences enables the terminal to be positioned. This localization technique Fulfills the stated claim to future Positioning procedure and offers the mobile station as an alternative for one conventional "stand alone "GPS receiver. However, there are new ones for using this positioning method Functional units in the network infrastructure, so-called location Measurement Units (LMUs), for measuring different ones for positioning necessary parameters in relation to every third to fifth Base station required. To an existing network infrastructure, for example one It is therefore necessary to equip the GSM infrastructure with the E-OTD process a big Number of additional locations Measurement units necessary, the location of which is complex Task is. Doing so possible Network expansions due to required capacity increases in sufficient measure be considered. The infrastructure costs to be paid using these LMUs is one of the main disadvantages of the previous one System design of the E-OTD process, because of the financial effort for every this location measurement units is very high.

Below is the basic one How the E-OTD process works is described.

The E-OTD procedure is a positioning procedure for a cellular communication network, which enables both handset-based and handset-supported position determination based on measured time differences. The location of the mobile station can advantageously be calculated on the basis of a spherical or hyperbolic location determination. E-OTD positioning does not require any changes to the antenna or RF hardware, but it does require software expansion of the Terminals. This requirement of new terminal capabilities means that this process can only be established to the extent that the terminal fleet is renewed.

As a result, two system designs become Implementation of the E-OTD method explained, which is used to measure various for the Positioning necessary parameters in the network infrastructure Location Measurement Units (LMUs) are required. The geographic position the LMU or the propagation delays to the associated base Transcieving Stations (BTS) or Base Station Controller (BSC) assumed to be known. To support the E-OTD localization method must for at least three to five Radio cell locations an LMU can be provided, which, depending on System design, radio measurements or for synchronization the base stations is used.

To connect the LMU with the rest Communication network network can if possible lines be used in place of the air interface because those connections turn out to be far less prone to failure and the propagation delay is not falsified by multipath propagation.

The solution of positioning by means of of the spherical type solution needed unlike that later presented hyperbolic solution no determination of time intervals with respect to the reception of different signals at the location of the mobile station respectively an LMU, because the propagation times of the signals are taken into account calculated separately for each base station.

When using the type of hyperbolic solution in principle, only relative signal delays are required. The exact time of transmission or a synchronization between the terminal device, the base stations and the LMUs are therefore based on the measurement not claimed by time differences. However, since in the GSM network, as already mentioned, a There is no synchronization between the individual base stations is additional the offset in the time bases of the base stations involved in the positioning participate, be determined.

The following three basic ones are relatively measured time quantities with the E-OTD positioning method according to the hyperbolic type connected.

The first of these time variables, the Observed Time Difference (OTD), describes the time interval between the reception of the signals from two different base transceiver stations. If the signal of the first base station is received at time t1 and t2 corresponds to the moment at which the signal of the second base station arrives, then the OTD value is calculated OTD = t2 - t1 (3-2)

The second time variable associated with this position method is the relative synchronization interval between two base stations, the so-called Real Time Difference (RTD). Previously, this was referred to as the offset in the time bases of the corresponding base stations. If the first base station sends a burst at a time t3 and t4 corresponds to this moment with respect to the second base station, the value of the RTD is determined from the difference between these times RTD = t4 - t3 (3-3)

From a synchronized network can be spoken if for each base station pair that has RTD = 0.

The last relative time variable that characterizes the E-OTD method according to the hyperbolic type is the Geometric Time Difference (GTD). This denotes the time interval at a certain position, which is caused by different signal delays. If d1 corresponds to the length of the propagation path between the first base station and d2 corresponds to the length of the propagation path between the second base station and the position under consideration, the GTD value is determined in accordance with GTD = d2 - d1 / c (3-4) calculated, where c represents the speed of light.

The individual, relatively measured time variables are through OTD = RTD - GTD (3-5) connected.

The determination of the observed time difference (OTDMS) parameter at the location of the mobile station can be carried out by means of the analysis of the training sequences both in idle and in dedicated mode by the terminal itself, whereby normal and dummy bursts can be used. The opportunity to realize this observation of the observed time difference in idle mode does not result in any additional Network load generated, and furthermore, a large number of measured values of this parameter can be obtained, which allows the use of advanced filter algorithms to this value.

The real time difference between the individual base stations is determined in the previous system designs of the E-OTD method according to the hyperbolic type by means of the location measurement units. Similar to the process in the mobile stations, these measure the observed time difference (OTDLMU) at the location of the LMU. Since the location of the LMU was assumed to be known, contrary to the position of the mobile station, the value of the Geometric Time Difference (GTDLMU) can also be calculated at its position. The real time difference can then be determined using equation (3-5). RTD = OTDLMU - GTDLMU (3-6) Again using equation (3-5), the geometric time difference (GTDMS) at the location of the terminal can be calculated based on the measured values of the observed time difference (GTDMS) at the position of the mobile station and the real time difference determined by the LMUs. GTDMS = OTDMS - RTD (3-7)

After converting this time interval in distance differences and including the positions of the Base stations are defined hyperbolas, by means of which the determination the position of the terminal using the hyperbolic approach Position determination takes place.

Despite the restrictions mentioned in the form of a necessary extension of the terminal equipment and the Financial and logistical effort for new network infrastructure units the E-OTD process offers numerous advantages. Because this requires compared to other positioning methods, no increased capacity in the network and therefore offers the possibility of individual and continuous Process position requests without increasing network loads cause. In the case of using the handset-based architecture are all for the positioning of necessary data from the network infrastructure transmitted to the terminal. As a result, no uplink connection is used for position calculation needed and this handset-based architecture is therefore for continuous position requirements particularly suitable. additionally is only a low signaling effort in comparison to other methods necessary in the network, even if the position determines end device-supported becomes. Still behaves the handset corresponds to a measuring device that increases the measuring effort Determining some parameters different from other positioning methods. This in turn has a positive effect on capacity requirements. Therefore are not extraordinary increases the system capacity at the introduction this procedure is necessary.

The specified specified system designs the E-OTD process, as already noted, for determining the position in addition to the base stations Location measurement units.

However, the hyperbolic stands out Type compared to spherical Type by several advantages. For one thing, this guy has one less complexity, since relative time differences are sufficient to determine the position and therefore no real-time coordination between the individual signals must be achieved. On the other hand, the system design in the case one feasible Determination of the real time difference without the use of location Measurement units are used to implement the task, with the spherical However, this type cannot succeed.

Based on the state of the art Technology, the present invention is based on the object To further develop methods of the type mentioned in the introduction such that the disadvantages described in connection with the prior art can be avoided. In particular, an alternative system proposal is to be provided be the one with no or limited use of location Measurement units can be used and therefore lower infrastructure costs in terms of of the general approach.

The present invention lies based on the knowledge that a possibility is created the real time difference between the individual Base stations when using the E-OTD method, in particular by means of the type of hyperbolic solution without the use of Location measurement units in the network infrastructure in sufficient To estimate accuracy.

The object is achieved by the method with the features according to claim 1. Further Advantages arise from the subclaims, the description and the drawings.

The invention basically relates to a method for determining the position of a terminal, in particular a mobile telephone, in a communication network, in particular in a GSM network, which is characterized in that the position of the terminal is determined on the basis of determined time difference values of Signals between the terminal device and at least two transmitting and / or receiving stations is determined.

According to the invention, a method for determining the position a terminal, in particular a mobile phone, in one cellular communication network, in particular in a GSM network, proposed the position of the terminal device using an E-OTD method of determined time difference values of signals between the terminal and at least two transmitters and / or receiving stations is determined, characterized in that that the relative synchronization interval between two transmission and / or receiving stations (Real Time Difterence) without the need for Synchronization of different sending and / or receiving stations electronically is determined by electronically estimating the relative synchronization interval is calculated.

The determination of the Synchronization intervals electronically in a computer unit. However, the invention is not limited to specific embodiments the computing unit limited. The computing unit can, for example, one or more computers, a computer network, at least one server device or the like exhibit. The design of the computer unit results from where it is trained, either as a central unit in the communication network or as a unit that is assigned to the mobile terminal.

The electronic determination of the estimate takes place via suitable means, which are, for example, the computer unit, Parts of the computer unit, circuit arrangements of electronic components, Computer programs or software in the computer unit is / are implemented or the like can act. Due to the Signals between the transmitting and / or receiving stations and the mobile devices then becomes electronic and in particular automatic in the computer unit the estimate for the relative synchronization interval calculated or determined.

Additional hardware components, such as the LMUs described above are not more needed. The synchronization previously required can omitted.

The relative synchronization interval is preferred in the computing unit using a hyperbolic location method determined.

The computer unit is advantageous assigned to the terminal device, for example provided in this, wherein the location is handset-based in the terminal becomes.

In a further embodiment, the Computer unit as the central computer unit in the communication network be provided, the location determination supported by handset in the central computer unit is made.

The relative synchronization interval is advantageously electronically by means of a pseudo-synchronized handover method determined, which is explained in detail below.

It turns out that the estimate of Real time difference when location measurement is not integrated Units in the network infrastructure can be used.

The method according to the invention makes it clear like a mobile station during a handover directly in synchronization with their new base station by giving them the timing advance value in terms of of the new base station. However, this is an estimate of the Real time difference necessary in the case of a completed handover is renewed.

In the application of the E-OTD according to the invention Positioning procedure is the one presented in this specification Pseudo-synchronized handover as an alternative to location measurement Units used to determine the value of the real time difference, since that as a product also provides an estimate of the RTD.

The invention is now based on embodiments explained in more detail with reference to the accompanying drawings.

This particular pseudo-synchronized handover is first explained in more detail. To use this pseudo-synchronization scheme, new requirements are placed on both the base station and the mobile station, which are explained below. It is therefore necessary that both base stations involved in the handover and the mobile station, for example a mobile phone, explicitly support this special handover and that this was requested in the handover request. The newly required extensions of the base stations consist in the calculation and storage of an estimate of the real time difference with respect to each of their logical neighboring base stations. This is in 3 shown.

A handover of one in the coverage area the current base station (referred to as old base station) Handsets should go to one of their neighboring base stations (new base station) be carried out. Here, t-new (or t-old) puts through the time delay the signal propagation between the mobile station and base station new (or base station old).

Analogous to the explanations above, the real time difference is described by the value of the offset of the local system time in base station old minus that of base station new, while the observed time difference is described by the difference in the reception times between the signals from base station old and Base station new at the location of the mobile station with the same sign condition as for the Be calculation of the RTD is determined.

When using the pseudo-synchonized Handovers are part of the handover procedure from the current serving cell to the terminal the previous one stored in the old base station estimated value the real time difference (RTD-BTSaIt, BTSnew) between her and the Base station newly transmitted (1).

Under normal propagation conditions the propagation time t0 should be close to the last one, from the base station-old Timing Advance value (TA-old) sent to the mobile station. By moving the mobile station and drifting apart the oscillators of the base stations, all the values mentioned are slowly time-variant. However, regardless of this, they are defined immediately before the execution of the handover.

Among the required new terminal capabilities, it should be mentioned that the mobile station must meet the condition to measure the observed time difference immediately before the handover is carried out (2). This defines itself as:

Based on the received estimate of the real time difference (RTD-BTSaIt, BTSneu} by the current base station, the measurement of the observed time difference and the old timing advance value, the mobile station can determine the timing advance value for the future base station itself, without being transmitted to the mobile station (3). TA (new) ≈ OTD - RTD (BTSalt, BTSneu) + TA (old) (3-9)

After the handover has been completed, according to the specification, the mobile station should transmit the value of the observed time difference it has added together with the last time advance value relating to the old base station (TA-old) in the handover complete message (4). This allows the base station-new to calculate an estimate of the real time difference again from the transmitted OTD + TA (old) and the estimate of the propagation delay t1 (TA-new) determined by itself (5). (RTD BTSold, BTSnew ) new estimate = OTD + TA (old) - TA (new) (3-10) transmitted with OTD + TA (old) from the mobile station (MS).

In practice, an additional, So far unspecified processing is necessary to get the effects of estimation error and reduce quantization.

With regard to the complexity of the end device proves turned out to be particularly positive that through the use of the pseudo-synchonized Handover regarding of the E-OTD positioning procedure no additional needs of advanced device capabilities for the Mobile station arise. Because the determination of the observed time difference, the only modification required by this special handover procedure the mobile station, is ultimately used for this handover as well for the Positioning needed.

To carry out the handset-based E-OTD Positioning technology needed the mobile station, as already indicated, additional data for independent determination the own position transmitted by the network infrastructure Need to become. This so-called E-OTD Broadcast Assistance data, all the information needed with regard to the neighboring cells include, by a Point-to-multipoint transmission from the serving cell to those in their service area Mobile stations using a special cell broadcast Channel transmitted. This is broadcast by the mobile phones in idle state Control Channel (BCCH) received.

In this cell broadcast channel however only data regarding of the neighboring cells of the serving cell, which are transmitted in the so-called System Information Neighbor List are listed. Therefore there is none possibility Assistance data regarding other base stations because of possible overreaches are received and are therefore not included in that list.

The following table shows the content the transmitted via the E-OTD Broadcast Assistance Message Data. Various information elements are potential fields, this means, you can, have to but not transmitted become.

information element Message structure definition GOT TO Reference time GOT TO Ciphering Seriai Number CAN Time slot scheme GOT TO Neighbor Bitmap Definition CAN Sectored channels definition CAN Sectored channels BTS ID definition CAN Sectored BTS Sync / Async definition CAN

51 Multiframe offset values GOT TO BCC definition GOT TO RTD drift factor values CAN Channel RTD values CAN Serving cell location GOT TO Relative Neighborhood Location Values GOT TO

The element of the message structure Definition defines the content of the remaining cell broadcast message by identifying which of the potential information items is being transmitted become. Furthermore, this element determines the number of in the System Information Neighbor List registered neighboring base stations specified and it communicates whether that list of sectorized base station locations includes.

Likewise, through this information element the maximum range of values and the quantization of those transmitted later Real time difference values and the accuracy of the position information of the neighboring base stations.

As a result, the others Information elements only described in their basic features. The information element the Neighbor Bitmap Definition determines which neighboring cells the further assistance from the System Information Neighbor List Data is transmitted in this cell broadcast message. Also marks the information element of the sectored channels definition, which this selected Neighbors, assigned to a sectorized base station location become.

Through that through the information element The Sectored Channels BTS ID Definition is where the concentration happens of these sectorized channels to the exact same base station location. Furthermore, Sectored BTS sync / async definition information element determines whether the individual sectorized base station locations synchronous or asynchronous channels contain, that is, the individual sectors of those base stations synchronously or broadcast asynchronously.

To estimate the observed time difference through the mobile station to be able it is necessary that this information is provided by the individual neighboring base stations training sequences used. The information element the BCC definition describes the so-called base station color Code (BCC) that indicates which of the eight potential training sequences from each of the selected ones Neighbor base stations are currently being used.

The E-OTD also includes broadcast Assistance Message the information elements RTD Factor Values IE and RTD Drift Factor Values, which the, through the LMUs or the pseudo-synchronization Handover determined, real time difference values by the Neighbor Bitmap definition selected Neighboring base stations relative to the serving cell and the respective one Drift factors of these RTD values include. These drift factors correspond of strength of change the real time difference values above currently. The value of the RTD can be up to the duration of a quantity or up to eight time slot periods under the resolution of Accept 1 / 16-1 / 128 bit.

Furthermore, in the context of Position calculation of the exact location of the Serving Gell and the Neighbor base stations needed. The serving gell location information element therefore gives the latitude or Longitude fields the position of the serving gell, especially under the use of the WGS84 coordinate system. In contrast, the relative neighbor transmits Location information element the positions of the neighboring base stations by means of a relative distance specification in the two spatial directions with respect to the Serving cell. With the help of this transmitted The mobile station can independently transmit data through the network infrastructure Determine your own position.

The conventional way to measure time delays is to use correlation methods that compare the time pattern of a received signal with a reference pattern. Assuming a distorting channel with additive noise on the transmission path, the signals of two base stations at the location of the mobile station can be represented as follows: r1 (t) = A1s (t - r1) + n1 (t) (3-11) r2 (t) = A2s (t - r2) + n2 (t) (3-11)

In the following, A = A2 / A1 and D = t2-t1, where (t1 <t2). The time average of s (t), n1 (t) and n2 (t) is zero and the send function s (t) is over the time of n1 (t) and n2 (t) is statistically independent. According to the matched filter the transmission channel, that the effects of interference and noise on the transmission channel degraded, preserved the equalized received signal x1 and x2. For an insight into the associated To obtain signal theory, let us introduce cyclic cross-correlation.

Assuming the factor a = 0, which represents the so-called cycle frequency, gives the equation (3-121 to the conventional cross correlation.

Since a limited observation period T must be assumed, an estimate of the cross correlation is obtained by:

Following the matched filter, there is the possibility of filtering the equalized received signal x1 and x2 again in order to increase the resolution of the delay determination. This illustrates 4 , the equalization of the received signal r1 and r2 is not shown by the matched filtering.

The two filter functions N 1 (f) and H2 (f) to enlarge the resolution the delay determination have to, a falsification the time lag to avoid having the same phase characteristics.

The filter functions can be selected in order to obtain a larger peak in the cross-correlation of x1 and x2, which results in a higher resolution of the time differences, but also in a narrower spectrum. Due to this narrow spectrum, the peaks can be significantly disturbed by a limited observation time, especially in the case of a low signal-to-noise ratio. Therefore, when choosing the appropriate filter function, a compromise between a good resolution and the robustness against interference and noise of the delay estimate must be found. There are various filter functions ψ (f) = H1 (f) · H2 (f) ^* with advantages or their impairments. With a filter function of Y (f) = 1, the conventional cross-correlation is obtained.

die Impulsantwort des Übertragungskanals repräsentiert.Assuming multipath propagation, the cross correlation can be represented by

represents the impulse response of the transmission channel.

Conventional delay estimates based on the correlator principle are influenced by multipath propagation. These cannot separate different delay components that overlap one another due to the small bandwidth available in the GSM system. Therefore, the conventional channel estimation alone is not sufficient to determine the correlation exactly. Various methods have therefore been developed to reduce the influence of multipath propagation on the delay estimate. Examples include high-resolution delay detector algorithms such as Root MU To name SIC and TLS-Esprit.

A position determination using using the hyperbolic location approach the E-OTD procedure is generally carried out by executing two Steps. The first step is to calculate the Geometric Time difference values according to equation (3-5). Due to the transmission of the Real time differences through the network infrastructure to the Mobile station and the estimate the Observed Time Difterences by themselves, this is in the Able to calculate those geometric time difference values yourself.

In a second step, these are GTDs converted into distance differences. by means of which a non-linear System of equations is generated using equation (2-5). It should be noted that values of the Geometric Time Difference as a result of the definition of the transmitted RTD throws only in terms of the serving cell can be determined. Possible geometric time differences in relation to two neighboring base stations can therefore not be considered become.

Below is a general in the method according to the invention usable, geometric model for position determination under using N base stations. the different Approaches to the hyperbolic equations used in the following sections becomes.

Without restricting generality one assumes that the base station with the index i = 1 is the one that corresponds to the serving cell of the mobile station.

wobei Δτi der Ausbreitungszeit eines Signals zwischen der Basisstation i und der Mobilstation entspricht, die geometrische Abstandsdifferenz,

und der relative Abstand der i. ten Basisstation in Bezug auf die Serving Cell in x-beziehungsweise in y-Richtung

definiert.For further calculations, the geometric time difference Δτi, 1 between the base station i and the serving cell,

where Δτi corresponds to the propagation time of a signal between the base station i and the mobile station, the geometric distance difference,

and the relative distance of the i. base station in relation to the serving cell in the x or y direction

Are defined.

about the accuracy of the positioning or the calculation effort decides after setting up the nonlinear system of equations only the algorithm used to solve this system. by virtue of the limited computing capacity mobile phones use the most efficient algorithms, for a solution to obtain this nonlinear system of equations, which is the estimated value of the Position of the mobile station corresponds.

There is a selection of algorithms which the nonlinear system of equations under different complexity respectively solve different restrictions. To the for the application most suitable to choose a decision must therefore be made under different criteria. These characteristics include the requirements of the algorithm, its accuracy, the computational effort and the ability advantages from overdetermined To draw systems of equations.

The case of an overdetermined system of equations corresponds to a participation of a larger number of equations to determine the position, as necessary to determine the unknown is. In the 2-D case, the hyperbolic system design explained an overdetermined System of equations through the use of more than 3 base stations (Serving cell and more than 2 neighboring base stations) that more than 2 nonlinear equations according to equation Define (2-5). Restrictions of the individual algorithms can be found under other a necessary a priori position estimate or one certain reference location constellation.

On the one hand there are a number of simple algorithms that the nonlinear system of equations under the Solve the requirement that the reference positions are arranged in a linear manner. Since this configuration does not correspond to the basic infrastructure of a cellular network, these algorithms cannot be used in the application of determining the position of a mobile station, for example a mobile telephone in the mobile radio network. For completeness, these algorithms, which presuppose linear reference locations, should be mentioned: Carter's Beamforming, Hahn, Abel and Smith.

For fortuitously distributed locations of the base stations are therefore only more complex To use algorithms for determining the position of the mobile station. Therefore, then the investigated algorithms for solving the nonlinear system of equations assuming random distributed reference positions explained. The used Algorithms divided into the following classes.

The group of approaches that are explicit and closed form of solution are shown below by the so-called solution method represented by Chan. Another solution scheme this class is the solution method after catch.

The second fraction of algorithms results from iterative approaches that when using overdetermined Systems of equations based on least squares criteria advantages in the position determination can pull. These are through the Taylor series method respectively represented the procedure according to Levenberg-Marquardt.

Furthermore, as in the calculation method Error analysis applied through logical and geometric considerations and using the maximum error bound of the geometric time difference the position of the terminal can be determined.

Solution method according to Chan

This solution is an algorithm that in a closed form only the two possible Intersections of two hyperbolas determined. Therefore this algorithm cannot Benefits from over-determined Draw systems of equations.

setzt man nun x = f1 (R1) und y = f2 (R1) in die folgende Gleichung ein,

so erhält man eine Funktion ausschließlich in der Unbekannten R1: a·R1 2 + b·R1 + c = 0. (3-21) Mathematical procedure of the algorithm under the described geometric model: x and y can be described by transforming the system of equations formed by equation (2-5) depending on the unknown distance R1 to

now put x = f1 (R1) and y = f2 (R1) into the following equation,

so you get a function only in the unknown R1: a · R 1 2 + bR 1 + c = 0. (3-21)

As solutions to this quadratic Equation you have two possible distances R1 of the mobile station to the serving cell. The two intersections of the Hyperbolas that the possible Represent locations of the terminal, result from the respective insertion of the two solutions of Quadratic equation in equation (3-19).

The ambiguity of this potentially two intersections can be eliminated in the majority of all cases by the apriori information about the maximum cell size (R1 <35 km) was evaluated becomes. Because it turns out that usually a solution for R1 one Distance that is greater than is the maximum cell size, and thus as a solution excretes. In practice, they intersect due to estimation errors in solving over-determined Systems of equations not all curves at exactly one point. To one solution to get their errors regarding the one with estimation errors has the smallest amount, it is necessary the position of the mobile station using a least squares solution determine. The basics of the least squares solutions used are explained below.

erfüllt, wobei ||ê|| minimal ist. Es wird folglich jene Lösung gesucht, die den minimalen geometrischen Fehler zu den Messwerten aufweist.The equation is given y = fx) (3-22) in which x and y can be vectors with different dimensions and a vector Y of measured values. We are looking for a vector x that meets the equation

met, where || ê || is minimal. The solution that has the minimal geometric error to the measured values is therefore sought.

For the use case of hyperbolic position determination is by Transforming the equation introduced the following mathematical model.

This results in the so-called Design matrix A

The individual measured values, the distance deviations Rj, 1, from the difference in the distance of the mobile station to Base statian j and the distance to base station 1, the serving Cell, calculated. Because of this difference, the individual Measured values can no longer be regarded as incorrect. This means that the covariance matrix does not correspond to a unit matrix.

der sich in einen Vektor ΔT, der die Ausbreitungszeiten bezüglich den einzelnen Basisstationen enthält, und eine Verknüpfungsmatrix N dieser Ausbreitungszeiten zerlegen lässt. Dabei entspricht N einer N × N –1 Matrix. Daraus ergibt sich die unnormierte Kovarianzmatrix der Messwerte des beschriebenen mathematischen Modells

In order to calculate the correlation of the different distance differences, the vector of the geometric time difference values is introduced

which can be broken down into a vector ΔT, which contains the propagation times with respect to the individual base stations, and a linkage matrix N of these propagation times. N corresponds to an N × N -1 matrix. The non-normalized covariance matrix of the measured values of the described mathematical model results from this

Taylor series

A first approach to over-determined Solving hyperbolic systems of equations is the so-called Taylor series Method. This is an iterative algorithm that uses the nonlinear System of equations near one necessary a priori estimate of the terminal location linearized. The position estimate will step for Step improved by local least squares in each iteration (LS) solution is calculated.

wobei in jedem Schritt die folgenden Vektoren und Matrizen neu berechnet werden: Fehlervektor der gemessenen gegenüber der aktuellen iterativen Abstandsdifferenz

Abstand der aktuellen iterativen Lösung bezüglich den Referenzorten

die unnormierte Designmatrix unter der Verwendung der aktuellen iterativen Lösung

Iteration rule of the solution with a Taylor series

the following vectors and matrices are recalculated in each step: error vector of the measured versus the current iterative distance difference

Distance of the current iterative solution with respect to the reference locations

the non-standardized design matrix using the current iterative solution

Levenberg-Marquardt process

The Levenberg-Marquardt method is based on the well-known Gauss-Newton method and is generally used for non-linear approximation. A function f (x) for measured values y ^ is searched so that it is the sum of the squares of errors || F (x) || ² becomes minimal: F (x) = f (x) - y ^ (3-32)

berechnet werden.The solution can be calculated iteratively, starting with a starting value x0, gradually following the following values

be calculated.

wobei J(x(ⁿ⁾) der Jacobi-Matrix von F(x(ⁿ⁾) der Stelle x⁽ⁿ⁾ und I einer Diagonalmatrix entspricht.Δ ^{(n) is} the solution to a linear compensation task which results from the expansion of the equation J ^T (x ⁽ⁿ⁾ ) · J (x ⁽ⁿ⁾ ) · Δ ⁽ⁿ⁾ = –J (x ⁽ⁿ⁾ ) · F (x ⁽ⁿ⁾ ) of the Newton method for the Levenberg-Marquardt method results

where J (x ( ⁿ⁾ ) of the Jacobi matrix of F (x ( ⁿ⁾ ) corresponds to the position x ⁽ⁿ⁾ and I to a diagonal matrix.

The value λ ⁽⁰⁾ is initialized with a very small value. If the error decreases with Δ ⁽ⁿ⁾ , then λ ^{(n + 1) is} reduced for the next iteration step by division by a factor. However, if the error increases, λ ^{(n + 1)} is increased again by multiplying by the corresponding factor. For small amounts of the factor λ ⁽ⁿ⁾ , the Levenberg-Marquardt method approximates the Newton method, whereby the Levenberg-Marquardt method has increased robustness in comparison, while for increasing values of λ ⁽ⁿ⁾ the method of the method of the steepest Descent almost corresponds.

error analysis

The calculation method of error analysis uses systematic and geometric considerations to position of the terminal. Due to errors in the measurement the observed time difference or in the estimated value of the Real time difference value corresponds to the measured distance difference not the exact distance deviation at the location of the mobile station.

The inner hyperbolas - as in 5 represented - are defi by the respective distance difference nated, which is represented by the calculated geometry time difference at the location of the mobile station. The two outer hyperbolas limit the area of inaccuracy that is described by the maximum achievable error in the GTD value.

In the intersection of old hyperbolic areas the location of the mobile station is accordingly. In the Positioning by means of error analysis is done with the help of maximum GTD error the position of the terminal as the geometric Center point of this intersection obtained.

To the performance of the location technology to be able to measure objectively and to enable comparison with previous references, are the following standards for measurement the resolution accuracy localization introduced.

(Root) Mean Square Error ((R) MSE)

A frequently used method of measurement the accuracy of the position determination is the comparison of the measured Mean square error with the theoretically achievable mean square Mistake after the Cramer Rao border.

berechnet.The measured mean square error is determined by: MSE = E {(x - x ^) 2 + (y - y ^) 2 } (3-35) where x, y represent the coordinates of the exact and x ^, y ^ the coordinates of the calculated position of the mobile station. Furthermore, the root mean square error can be used to measure the performance of location determination techniques. who through

calculated.

Dilution of Precision (DOP)

As already mentioned, there is one that should not be neglected Influence of the geometry of the reference locations compared to the one to be positioned Object on the accuracy of location. The strength of this Represented influence the factor of dilution of precision.

When developing a positioning system, it is therefore necessary to minimize this factor by selecting the locations of the reference points. However, when planning a cellular network, the focus is on the availability of communication services and the accessibility of the mobile subscriber, whereby the locations for base stations are selected based on these criteria, which, however, cannot be reconciled primarily with a low DOP value. σ p = DOP · σ m (3-37) where σ _p or σ _m correspond to the standard deviations of the position estimates or the distance estimates.

In the case of hyperbolic positioning the factor of dilution of precision must be in a way other than how described above, since here, according to the derivation the least squares solution, Incorrect measurement errors can no longer be assumed.

However, the dilution of precision factor can be calculated using design matrix A:

wobei σ_s ² dem Mean Square Fehler der Abstandsdifferenz und σ_x ² beziehungsweise σ_Y ² dem Mean Square Fehler der Positionsschätzung in der jeweiligen Richtung entsprechen.The horizontal dilution of precision (HDOP) is a measure of the geometric strength in both directions. It can be calculated by:

where σ _s ² corresponds to the mean square error of the distance difference and σ _x ² or σ _Y ^{2 to} the mean square error of the position estimate in the respective direction.

coordinate systems

The positions of the serving gell are as mentioned above, transmitted to the mobile station in coordinates according to the so-called WGS84 system. However, to the transmitted evaluate relative information of the neighboring base station locations and easy to do Enable position calculations in a two-dimensional case have to these WGS84 coordinates are converted into other, flat coordinate systems become. Therefor the xy representation of the Gauss-Krüger coordinate system is useful. Both coordinate systems are presented below.

WGS84 coordinate system

The World Geodetic System (WGs), released in 1984 by the US Department of Defense has been used as the most common coordinate system in recent years used. This consists of orthogonal three-dimensional coordinate axes, whose origin is in the earth mass center. The z axis runs through the geographic North Pole while the x-axis through the intersection of the equator with the prime meridian runs. The y axis finally extends at right angles to the aforementioned axes.

The origin of the coordinate system described again lies in the geometric center of the WGS84 ellipsoid, the by the rotation of an ellipse around the minor axis, which is in the north-south direction is oriented, is formed. The dimensions of this ellipse are: size Axis a = 6378137 m and minor axis b = 6356752.314 m. The coordinates of a point on the surface of this ellipsoid are given by values of longitude and latitude. longitudes can Values from -180 ° to Assume + 180 °, while Latitude in the range of -90 ° to + 90 ° can be selected.

Gauss-Krüger coordinate system

The position specification according to Gauss and Krüger works according to the principle of the transverse projection projection, in which the Earth globe by means of a cylindrical-transverse image on a Cylinder jacket is projected.

The position is indicated with the help of 3 ° wide strips around a so-called main meridian, the Gauss-Krüger coordinate system 120 this streak includes. Each of these zones has an extension of 1 ° 40 minutes on both sides, so that two neighboring zones overlap by 20 minutes. The individual meridian strips are numbered starting from zero, starting with the prime meridian in Greenwich. The position is indicated by a right-angled indication of a legal and a high value. The distance of a point from the equator, measured in meters, is called the high value. In contrast, the distance from the main meridian to the east, again measured in meters, represents the legal value. In order to avoid negative values for positions west of the main meridian, each main meridian is assigned the value 500,000. In order to define the position exactly, the main meridian to which the position refers must be part of the coordinate. For this reason, the longitude number of the main meridian divided by 3 is placed in front of both figures. In the case of an xy representation, the legal value corresponds to the x coordinate, while the y coordinate is described by the high value.

To the current in a GSM communication network available To clarify the degree of position accuracy were in one Test series in the Munich area initially carried out various measurement runs. As As a result of these measurement runs, the accuracy of the Gell ID method, without the use of additional Parameters, such as the value of the timing advance and signal strength considerations, be inferred. It also shows that according to the distributions of the received, geometrically different neighboring base stations in about 99% of cases at least two of these are available and consequently that E-OTD procedure is applicable.

They were then pseudo-synchronized Handover modified E-OTD positioning procedure simulations carried out, to make assessments about the gain achievable positioning accuracy.

The basic conditions of these simulations are to be clarified below.

To system behavior in certain To get configurations of how it could arise in reality from the classic and theoretical model of the arrangement of the radio cells apart from honeycomb structure. As two extreme configurations of the arrangement and accumulation of the base stations, two scenarios were selected, one as possible typical geometric distribution and density of base stations in urban and rural Represent population areas should. When modeling these scenarios was based on real locations used by base stations in a GSM communication network. Logical neighboring cells become these in the simulation environment base locations used in the model, i.e. those radio cells to which a handover from the network operator allows, or at all possible is the real time by means of a pseudo-synchronized handover Estimating difference between these two cells. Since not every neighboring cell, in the geometric sense, a handover provided by the network operator and umbrella cells cover individual micro or pico cells, the locations of all logical neighboring cells were determined using a special database of the communication network location directory, which contains all cells for each radio cell, to which a direct one Feasible handover is.

Urban scenario

This scenario that the distribution and density of base stations in a big city 111 base station locations in downtown Munich. The mean distance two neighboring cell locations in this is urban Scenario about 900 meters.

Rural scenario

The rural scenario included 176 base station locations in a rural area of Bavaria, with their neighboring cell locations on average 10 .700 m away.

Modeling multipath propagation

There is a multipath propagation by reflection, scattering or dispersion on objects in the Propagation environment of the signal. This causes the signal to both in time (delay spread), in space (angle spread) but also if the object moves, spread in frequency (Doppler spread) becomes. The received signal results from multiple time and frequency shifted and steamed differently Replicas of the broadcast signal coming from different directions at the place of the recipient arrive. An object can be called a scatterer if its dimensions larger than the wavelength of the Are transmission frequency.

Macrocell Model

The modeling of the scatterter configuration of a macrocell scenario initially assumes that a direct line of sight is not available in the majority of all cases, since the mobile station is surrounded by a large number of local scatterers in its environment. In this scenario, the base station is in an elevated position, which means that its immediate vicinity is relatively free of local spreaders. Jakes and Gans have summarized these in a geometric situation in a scattering model, which is also referred to in the literature as a Geometrically Based Single-Bounce Circluar Model. There is - as in 6 is shown - a circular region of scatterers around the position of the mobile station in which the scatterers are uniformly distributed. The radius of this area is 30 m <R <200 m, and the base station is placed far outside of this ring (R << D, D = distance (mobile station base station)).

Microcell Model

The scattering model of the microcell model is based on the assumption that base stations are at the height of house roofs. As a result, in contrast to the previously explained model, these are also surrounded by local scatterers nearby. To 7 the region of the possible spreaders can be modeled as an ellipse with the base station and the mobile station at the location of the respective foken and is referred to there as a geometrically based single-bounce elliptical model.

This configuration of the scatterer region shows that the signals are scattered near the base station with the same probability as near the terminal. Due to the geometric property of the ellipse, only signals with the maximum propagation delay τ _{max are} possible.

The main axes of the ellipse result from this:

The simulations were carried out using the solution methods explained above. In order to obtain an a priori estimate of the terminal location for the algorithms of the Taylor series and the Levenberg-Marquardt method, the position was first calculated using the Chan solution method. According to its own considerations, this was modified in such a way that a position determination using four base stations ( 3 Neighboring cells + senving cell) while increasing the accuracy was possible.

Now with overdetermined systems of equations using the solution method according to Chan, if possible best position estimate to get those two (for the Chan method presented above) or three (for the modified Chan method) selected hyperbolas, the particularly cheap appeared, for this were initially all constants of the hyperbones are calculated based on the reference positions the received neighboring cells and the serving cell and the measured Distance differences can be defined. The criteria for selection The corresponding lines of life are primarily whether the hyperbola is defined and the respective slope of the hyperbola symptoms. Because it was already in earlier Investigations have shown that it is positive for the error in the Position determination has an effect if the radius difference is small compared to b, that means the slope of the hyper loads of the amount is large.

With the means described so far of the pseudo-synchronized handover modified E-OTD positioning method simulations were carried out the achievable positioning accuracy when using different To investigate boundary conditions.

The accuracy of the E-OTD method the modification examined depends on the one hand on the one used solution process of the nonlinear system of equations. The Chan algorithm offers for fortuitously distributed base stations of the number three the optimal performance, as well as distant as well as near base stations because is the estimation error of the GTD values is small, so the solution is according to this algorithm an approximation of the so-called maximum likelihood estimator.

Furthermore, more than three received Base stations used to increase position accuracy become. According to the literature, however, it turns out to be using of the Taylor series approach as disadvantageous that neglect the higher Terms especially in situations with large DOP values for large errors lead in position determination can. Furthermore needed this method is a good estimate the solution as an initial value to guarantee convergence of what is achieved by means of the simulation results have been verified. This could continue be analyzed from which average cell spacing the a priori reckoning according to the solution process according to Chan or the BTS location of the serving cell, the more correct one Position determination delivers.

The Levenberg-Marquardt method considers the gradients of the function, whereby it can happen that the determined minimum value represents a local, but not the global minimum. It can also happen that the algorithm does not converge at all, which could be confirmed under the precondition of the inner city scenario. The result of the iteration is strongly dependent on the choice of the a priori position estimate and the selected scaling factor λ ^(o) .

The algorithm of error analysis can by means of overdetermined Systems of equations increase the accuracy of the position determination but in comparison a lower resolution.

In the case of these overdetermined systems of equations The method is therefore available within the algorithms examined the Taylor series as a recommendation in both scenarios: Because of that Calculation effort is only slightly greater than that of the solution scheme According to Chan, this can benefit from least squares criteria in determining the position of over-determined ones Draw systems of equations and there is no error behavior of the Iteration algorithm, as happened with Levenberg-Marquardt can. on.

To compare the positional accuracy achieved, reference is made to the location resolution using the defined scenarios and the Cell-ID procedure: If the position of the mobile station were determined in such a way that it corresponds to the location of the closest base station, the Location resolution in the case of the rural scenario about 3790 m (67% quantiles) and 2895 m (RMSE (90%)). The accuracy achieved under the individual algorithms in the case of the rural environment therefore represents a significant improvement in the position accuracy compared to the previously available degree of location by using the cell identifier.

It works in an inner-city environment this modified E-OTD process, at least the same resolution as with Cell-ID method (67% quantile: 285m and RMSE (90%): 210 m) to achieve.

According to the present invention a modified system design of the E-OTD method is provided been made without or with limited use of location Measurement units can be used. The analysis of the presented modified E-OTD The design shows that in particular increases the positioning accuracy in relation to the only positioning method currently used, the Cell-ID procedure, in rural Areas possible are. This modified E-OTD process, in contrast to the other positioning methods mentioned, after the introduction of the Pseudo-synchronized handovers quickly, with less logistic Effort and without increased Infrastructure costs are implemented. It is also an advantage to mention that the end devices following the E-OTD procedure support the general system design and in a short time available on the market will be compatible with the modified system design according to the invention are because all the changes described refer only to the network infrastructure.

Claims (5)

Method for determining the position of a terminal device, in particular a mobile telephone, in a cellular communication network, in particular in a GSM network, the position of the terminal device using an E-OTD method on the basis of determined time difference values (observed time differences) of signals between the terminal device and at least two Transmitting and / or receiving stations is determined, characterized in that the relative synchronization interval between two transmitting and / or receiving stations (real time difference) is determined electronically in a computer unit without the need for synchronization of different transmitting and / or receiving stations, in the computer unit an estimate of the relative synchronization interval is calculated electronically. A method according to claim 1, characterized in that the relative Synchronization interval in the computing unit using a hyperbolic location determination method is determined. Method according to claim 1 or 2, characterized in that the computer unit is assigned to the terminal and that the location is handset-based is carried out in the terminal. Method according to one of claims 1 to 3, characterized in that that the Computer unit as the central computer unit in the communication network is provided and that the Location determination supported by handset the central computer unit is made. Method according to one of claims 1 to 4, characterized in that that this Relative synchronization interval electronically using a pseudo-synchronized Handover process is determined.