MXPA98002182A - Position determinator system - Google Patents

Abstract

The invention relates to a position determining system for receiving digital telephone signals transmitted by a number of transmission sources (BTS), the system has a pair of receiving stations (CBU and CRU), one at a known position (0), and another in an object R, with no known objective. A position determining processor (CPP), and means for passing a link signal (L1 and L2), from each of the receiver stations to the position determining processor, the link signal information about the signals received at the receiving station from the sources of transmission. Each of the receiving stations is arranged to receive the signals from the respective transmission sources basically simultaneously. The position determining processor is arranged to compare the information received from a first receiving station with the information received from another or the second receiving station, and to determine the time delay between the respective signals received at both receiving stations to determine the position of the object. in motion

Description

DETERMINED SYSTEM-} POSITION DESCRIPTION OF THE INVENTION: The invention relates to a position determining system using radio or other wave transmissions. More particularly, it refers to a system using the System Global for Mobile communications (GSM) or other digital transmission systems. In our European patent EP-B 0 303 371 we describe a navigation and tracking system, now known as CURSOR, which uses the spatial coherence of the signals of several radio transmitters to determine the position in a receiver that moves without knowing its objective. Its principles are explained in the previous patent specification where it is shown as the signals received directly by the receiver in motion and compared with those received by a fixed base station whose location is known to determine its phase difference, and therefore , the distance in reach of the base and the body from each transmitter. Three measurements of this type made in independent transmitters are needed for navigation and tracking in two dimensions to fix the position of the body in motion (rover) with respect to the base station and the network of transmitters. The unknown quantities calculated from each new position are the spatial coordinates x, y, and of the body together with the phase shift between the local oscillators in the equipment of the two receivers. Another patent specification WO 94/28432 shows how the same principle can be applied in tunnels and other armored spaces such as parking lots for underground vehicles. Duffett -Smith and Woan (Journal of Navigation, 45, 157, 1992) describe a particular implementation of the phase measurement system in which signals from three or more public medium-wave AM transmission stations are used to plot the position of a vehicle in and around Cambridge, United Kingdom at speeds of 110 km / h with an accuracy of approximately 5 meters. One of the advantages of such a system lies in the fact that a costly additional infrastructure of coherent radio transmitters is not needed to establish the CURSOR operation. On the contrary, CURSOR is capable of using signals from any independent radio transmitters established for any purpose. EP-B-303 371 also explains how signals of a wider bandwidth of modulated transmissions can be used to measure the time difference between the signals received from each transmitter to the base station and the body in motion. In this case the position of the tip in the cross correlation can be used as an estimate of the time difference between the two signals received, and therefore the difference in distance from the transmitter of the base and the body (rover). As with the phase meter system, the three measurements made on three distanced transmitters are sufficient to calculate the spatial coordinates x, y, and of the moving object with the time shift between the oscillators at the two receiving stations. Mobile phones are increasingly using the GSM and other digital techniques, and it would be an advantage to add the CURSOR time-measuring position technology to provide additional services to users. However, the signals radiated by the digital telephone transmitters are complex and therefore there are problems that must be overcome when attempting to combine the technologies. In accordance with the present invention, a position determining system is provided to receive broadband signals from a number of transmission sources equal to at least the number of dimensions where the movement of a moving object without a known course is to be controlled, the system comprises: a pair of receiving stations, in practice the first of the receiving stations is in a known position and the second located in the moving object; a position determining processor; means for passing a link signal from each of the receiving stations to the position determining processor, the link signal contains information about the signals received at the station from the transmission sources; wherein each of the receiving stations is arranged to receive the signals from the respective transmission sources basically simultaneously, and the position determining processor is prepared to compare the information received from one of the receiving stations about the signals received in that station receiving the transmission sources with the information received from the other receiving station about the signals received at that other station from the transmission sources, and determining the time dilation between the respective signals received at both receiving stations with the object to determine the position of the moving object. The receiving stations can receive signals from the respective transmission sources in sequence and in the same sequence as each other. The invention also includes a method for determining the position of an object that moves without known direction, the method comprising transmitting a transmission signal from a number of transmission sources equal in number to at least the number of dimensions where it has to be transmitted. controlling the movement of the object, receiving the signals in a pair of receiving stations using a first receiving station as a known position and a second one located in the moving object, each of the receiving stations is arranged to receive the signals from the transmission sources respective basically simultaneously; by passing link signals from each of the receiving stations to a position determining processor, the link signals contain information about the signals received at the corresponding receiving station from the transmission sources; comparing the information received in the position determining processor of a receiving station about the signals received at the receiving station from the transmission sources with the information received from the other receiving station about the signals received at the other receiving station from the sources of transmission, and determining the delay or delay in time between the respective signals received at both receiving stations, in order to determine the position of the object in motion without a known direction (roving object). Additionally, the invention includes a method for estimating the displacement in time of the reception of a transmission signal received in two places, where the signal received in one place can be subject to corruption by multiple path effects, the method comprises auto-correlating the signals received in one place (auto correlate the signals received in the other place, cross-correlate the signals received in the one with the other, build a template that includes the portion of the auto-correlation of the signals received in one place corresponding to the negative time axis and that portion of the self-correlation of the signals received in each place corresponding to the positive time axis, and measuring the displacement where the template best fits the cross-correlation of the signals received in one and another of the places as an estimate of the time shift between the signals received in the Two places In some systems each of the receiving stations is also arranged to receive a second signal from one or more of the transmitters, the second signal is used to allow compensation for changes in equipment displacements during the reception of the received signals sequential The position determining processor may be located with one of the receiving stations or it may be located remotely. In a modality, the link signal from one of the receiving stations is passed to the other receiving station and from the other receiving station to the position determining processor. Preferably, for location purposes, a signal that provides information about the position of the moving object can be passed from the processor that determines the position to at least one of the receiving stations. The system can comprise one or more control stations and a signal that provides information about the position of the moving object, can be passed from the processor that determines the position to one or more of the control stations. To provide improved functionality, a database server can be connected to the position determining processor, the server contains data elements relating to a plurality of known positions, and the system comprises means for passing information about the position of the determined moving object. by the position processor to the database server, means for obtaining data elements related to the position determined by the processor, and means for passing the data elements to one of the receiving stations or to more of the control or monitoring stations. monitoring The or each receiving station or the or each monitoring station preferably includes a screen and the position of the moving object is presented on the screen which can be a dot matrix screen. The database server can contain graphic information and is passed to a receiving or control station and is displayed on the screen to indicate the position of the moving object.

The transmission sources and the receiving stations preferably comprise components of a digital cellular telephone network such as a GSM network. It is advantageous if the receiving stations control the strength of the signals of the plural transmission sources and select a plurality of signals strong enough to receive them. The quasi-synchronization, between the signals received from the respective sources, is preferably achieved by the controlled reception of the transmitted signals, but can alternatively be achieved by means independent of the transmitted signals, such as a local clock signal. The system preferably includes a set of fixed receiving stations that are in a national or even international regional network to provide wide coverage and use of the position system. The receiving stations may be able to receive two or more channels simultaneously and it may be advantageous to repeat the signal from plural transmission sources. The description that follows establishes the principles of the CURSOR system, a time meter that can be applied to a digital radio network, such as the GSM telephone system, to allow the position of a receiver, such as a portable telephone manual equipment that is measured with with respect to the transmitting network. The equipment used in such a network already incorporates most of what is required for the position fixing operation, so that its implementation can be achieved with little extra cost. The accuracy of each position measurement is proportional, among other factors, in reverse of the signal bandwidth, for a single SGM channel, with a bandwidth of 200 KHz, the accuracy is approximately 50m. Some improvements in this value can be obtained when more than three CGM transmitters can be received both in the base and in the movement body, all can be used in the position determining process. The principles of the operation of a position determining system, according to the present invention, and a specific application to GSM technology, will be described with reference to the attached drawings and tables wherein: Figure 1 is a diagram of the basic elements of the system; Figure 2 is a diagram used to define the coordinates of the system; Figure 3 illustrates the calculation of cross co-relationship functions; Figure 4 illustrates a GSM network, which incorporates the time measurement technology of the invention and identifies the logical elements thereof; Figure 5 illustrates the basic components of the circuit of a GSM manual equipment; Figure 6 illustrates a particular method of overcoming the multipath propagation effect by measuring the relative time delays; Figure 7, (a, b, c), shows different configurations of the elements in a GSM system, which incorporates the invention; Figure 8 illustrates how the position information can be displayed graphically on a small liquid crystal display; Figure 9 illustrates the arrangement of the elements and test sites in a test conducted in Cambridge, United Kingdom. Table 1 shows how the intrinsic measurement error varies with the signal with respect to the noise power ratio and the number of recorded bits; and table 2 gives some test results of a position determining system carried out in Cambridge, United Kingdom. Principles of operation Suppose that a transmitter A is transmitting modulated radio signals within a band of frequencies of an amplitude band, centered on the frequency 0 0, the signals are received by a fixed base station O, and a Receiver moving R, as shown in Fig. 1. We define the coordinates (x, y), Cartesian, with respect to the centered axes of the base station as shown in Fig. 2, the axes can have any orientation , but it is convenient so that the Y axis is along a north, south direction, marked on the map locally. a = (a-, a?) is a vector that defines a position of the transmitter and R = (x, y), defines the position of the moving object. The vector R - a = (x-a *, y-ay) completes the triangle AOR. The transmitter A, transmits signals continuously, at a pre-arranged time the radio receivers in O and R, begin to receive and record a short length of transmissions. This moment can be indicated by the arrival of a shot transmitted from A, or a signal derived from the normal signal traffic radiated by A, or a locally generated signal. The latter can be achieved, for example, by using a short duration pulse derived from high precision clocks in R, O, which have been previously synchronized. In a digital version of this application, the signals can be converted from? 0, to digital baseband and then recorded in the dynamic memory, although O and R, register simultaneously as close as possible, there will nevertheless be a time shift between two records that is caused both by the difference in distances A, O and A, R, and by the synchronization error between the arrival of shot A, 0, and R, is? r, this travel time, which is give by where e is the synchronization error and? is the speed of radio waves. An estimate of? R can be obtained by the cross-correlation of the records made in o and R. In Fig. 1, the links Ll and L2 are shown, which represent means of transporting representations of the records made at each receiving station to a CPP position determining processor. The nature of the links, whether they convey information in a real time or impose delays, does not matter in the beginning. All that matters is that the duplicates of the records made by each receiving station are assembled together in the processor to be compared with each other. The cross-correlation of the two registers is now performed by the position determining processor using any convenient means. In the case of digital signals, this can best be done by a microprocessor calculating by estimating the function at discrete intervals of time location, t, corresponding to the sample interval tm, as shown by the points in Fig. 3, is It is unlikely that the tip of the function corresponds to a particular sample, so that the micro processor must also adjust an interpolation function shown by the line curve, in order to obtain an optimal estimate of the tip position. The value of t, which corresponds to the tip, is an estimator of? R, (increment of r).

This process of almost simultaneous registration, transmission of one or more links, assembly of copies in one place and estimation of the value of? R, from the cross-correlation, must be carried out in at least two or three different transmitters spatially. If there are means at 0 and R, of sufficiently accurate synchronization, then just two measurements will generally suffice; on the other hand, if e, unknown as is generally the case, at least three measurements are needed. Let A, B and C, three transmitters in the latter case, a vector give as position a = (a ,, ay), b = (b ,, b), and c = (c ,, cy). Then the three measurements of? R, are given by These three nonlinear equations can be solved to evaluate x, y, e, and then the position of the object is determined, in reality the solution of these is generally ambiguous, with two possible pairs of x, and, frequently enough distant so that it is obvious which is the correct result (one could only be inside the triangle formed by the three translators), but if the ambiguity must be resolved automatically then an extra transmitter must be controlled or used. The accuracy of the method depends on the error in the estimator of? R, derived from the cross-correlation and there are three main factors. First the width of the cross correlation affects the accuracy of the result, since a wider function provides a less defined tip exactly. The width is inversely proportional to the bandwidth? , of the transmitted signals, therefore the wide band transmissions provide an intrinsically more accurate position determination. It should be noted, that the bandwidth could cover all the signals radiated from the antenna of a particular radio, and not just a particular channel. For example, if ten adjacent channels of a width of 200 KHz were active within a total band of 2MHz, it may be possible using a wideband receiver or one that can simultaneously receive more than one channel, make use of the 10, at the same time and thus obtain the accuracy corresponding to a bandwidth of 2mHz. If any of the channels were inactive anyway it would be possible to obtain the full accuracy corresponding to the separation of the most separated channels. Secondly, the signal to noise power ratio, r, of the signals is important, say, we are recording one-bit samples of the received signals converted first to the baseband. Each sample is one or zero, depending on whether the signal is greater or less than zero, at the time of sampling, we also assume that the signals are totally contained within a uniform band of frequencies ranging from zero to? , and that are sampled in the Nyquist rate equal to two ?? The error in estimation of the position of the crest or tip, ??, refers to the average number q (r), of consecutive samples that contain just one error by the approximate expression where N is the total number of samples used in the cross-correlation, the minimum value of q is 2, since even when there is no signal, the samples of one bit have the same probability of being correct or false. Here we have assumed that the cross-correlation function is triangular in shape rather than square sync function, expected for noise signals and square bandpass filters. An error of? R, is added quadratically as a position error? X, where? X = ?? r. The relationship between q (r) and r, the following expressions can be obtained assuming that the signals are like noise: with ??, set at 200 KHz, the results shown in table 1 are obtained. Table 1 As it has been noticed the errors in the measurements from each transmitter let's say? X? X2,? X3, they must be added in quadrature with each one and with any other error in the estimation of the object in movement. It is interesting to note that good results can be obtained even in conditions of poor reception. Third, usually the most important thing in practice is the error incurred by not having an exact knowledge of the trajectories or which signals reach the object. Multipath propagation expands the cross-correlation, making it more difficult to estimate the position of the crest, it can also result in a cross-correlation of multiple crests with the desired crest having a lower amplitude than the others. If all the signals arrive by indirect routes, there may be points along the propagation path of the line of sight. It should be noted, however, that multipath propagation always results in a delay in the signals compared to the direct path, provided that the antenna of the base station protrudes over the surrounding environment, so that it receives mostly direct signals only. , then the retracted signals on the moving object appear to be the last side of the crest of the cross correlation. (Under these circumstances it is possible to alleviate the effects of multiple path propagation as explained later). Having adjusted an appropriate interpolation function to the discrete samples it is important to choose the value of t, where there is a significant amount of signal, so that the value of? R, is used in the calculation of the position, rather than the position of the same crest. Application to GSM. The radiated signals or transmitters in a GSM network, are complex, the flexibility and capacity built in their design are such that they become difficult, but impossible to predict precisely how the presented spectrum (about 900 MHz, and 1,800MHz) in Europe will be used in any time, the frequency band is separated into a certain number of radio frequency (RF) channels, 200KHz wide, each of which carries frequency modulated (FM) signals, divided in time into a sequence of frames. The basic unit is what is called multiple time division (TDMA) access, of frame that lasts 4.615ms, and also divided into 8 time slots, each slot, carries 156.25bits, at a rate of 270Kbits, s "1, and it can represent a normal accumulation of data and training bits, an accumulation of fixed frequency frequency correction, an accumulation of data synchronization, and synchronization bits or an accumulation of accesses with a synchronization sequence and data. accumulations also carry head, tail, and guard bits, how many of the time slots are being used at a given time in a given frame, and how many of the RF bearers, are being transmitted from a given transmitter, depends on how the system has been established and the amount of traffic at that time, however, in the minimum case when everything is quiet, one of the RF carriers will always be alive performing the so-called control channel ion (BCCH, a logical channel), calling manual equipment in its cell when transmitting an accumulation or special access signal in each TDMA frame, we can therefore base ourselves on the fact that there will be an FM transmission, from each transmitter mast with a bandwidth of approximately 200KHz, and we can use it for position localization. A regional GSM network incorporates a position system according to the present, and is shown in Fig. 4. Here we see that base sectors mentioned below by the abbreviation CBU, entitled "CBU", CBUb, CBUC, etc. in each GSM transmitter, named A, B, C, capable of receiving not only the signals of its own local transmitters, but also those of at least two other distant transmitters, we also see a group of manual equipment that incorporates object and movement receivers mentioned with the abbreviation CRU, entitled CRUX, CRU2, etc., active in the region. It is important that these equipment receive the signals from the same set of distant transmitters, as well as from the local transmitter. As noted above, it is not necessary to achieve a high signal-to-noise ratio for the reception of distant signals, but nevertheless the need to receive distant transmitters may limit the capacity of this system to be used in rural areas where the cells are very far apart. widely. Also shown in Fig. 4, the position determining processor (CPP), and a database that provides the service (SPD), this is a device that provides specific data related to the position according to the request of the user of the system. position determiner. For example, the user may need directions to find the railway station in an unknown city. The position determining processor will compute the user's position and pass it to the service provider database in conjunction with the user's request. The database will respond with the required list of instructions. The configurations shown here where the position determining processor is a remote unit that is alone, is only one of several possible configurations (see below), for example the CPP, and CRU, can be combined within the manual equipment, so that the Positioning process is carried out by the own computer of the manual equipment. It is necessary to establish a trigger code that is transmitted periodically from each transmitter, probably within the BCCH logical channel. As noted above it could be a special code established within the existing GSM framework, or it could be a repeater element of the same ordinary GSM signals, such as the arrival of a frame number ending in three zeros that occurs every four seconds , the arrival or arrival of the trigger code causes an active object receiver (CRU) to begin the process of registering the signals from at least three transmitters. There may sometimes be a commercial advantage in making a unique trigger code for a particular operator or even for a particular manual equipment, providing a means of charging users for the position determination service, there are many other ways to charge. The trigger code can also activate the registration mechanism in the base unit (CBU), linked to the GSM transmitter. Since most GSM handsets can receive only one RF channel, at a time, the order in which the registration of the remote signals must first be established, for example, using cell transmission or the short message service, we see that it may be necessary to record the local transmitter signals, a second time in order to take into account displacements in the recording period, if 2,048 samples are recorded for each of the two distant transmitters (1,024 of each of the signals of quadrature of phase IYQ), and 4,096 samples for the local transisor (two teams of 2,048), the entire process can be completed within a few hundred MS, including the time taken to switch between the channels and establish each new frequency. The records made by the mobile object receiver (CRU), and the base receiver (CBU), are then sent by any convenient means to the processor (CPP), the movable object receiver could use slots in the GSM signals, or it could establish a data transfer call. The base receiver would probably send its records over a ground line to a remote processor that determines the position. The processor receives and assembles in memory its own copies of the signals received by the base and by receivers of the object for the correlation and position process. You can also use other parameters of the signals recorded by the two receiving stations such as, signal reinforcements. Once the data has been assembled, the processor performs cross-correlation analysis, standard methods can be used, but a preferred one is described later, which reduces the effects of multiple-path propagation, having made estimates of? R «, rb , rc, the processor solves the equations to solve x, and, nevertheless, the need to receive the signals from the three transmitters in sequence introduces a complication because the synchronization error e, is changing all the time and is unlikely to be constant during the registration period. We can model this error in short periods as a displacement plus a linear slope, that is: e = € 0 + e r where e, and e are constants and r, is time. We have another unknown quantity to be evaluated, e, and we can do this by recording the signals from the local transmitter again (both the base and the object). Now we get four values of? R, made in the sequence times rl, r2, r3, r4, and equations (1) become (2) The first and last of the equations can be subtracted by: ? .fl (.,) -? fl (.,) - = £. (/.- ,,) from which it can be found, therefore, with four estimates of the equations? r, (2), can be evaluated to recover x, y. Manual equipment containing multi-channel receivers capable of receiving all three channels simultaneously does not need to repeat the recording of the signals from the transmitter A since the rate of displacement between the clocks (measured by the) has no consequence does not need to be determined, The equipment or manual equipment of a single channel of high quality, may also be able to pass over the repeated high register if the error of displacement of the clock is small enough to ignore it. As noted above, almost all of the hardware elements needed within a GSM manual equipment for the present invention already exist for normal GSM operation. Figure 5 illustrates a typical implementation. RF signals in the region of 900MHz or 1800MHz are received by antenna 1, amplified in RF amplifier 2, and filtered in bandpass filter 3, before mixing at the intermediate frequency, IF, in the mixer 4 with a local oscillator signal LOl, generated by oscillator 5. LO already incorporates the necessary channel switching capacity. It is important for the invention that the frequency be blocked in phase such that a master oscillator MO, usually a crystal oscillator 6. This is also a requirement for normal GSM operation so that it does not impose additional costs. The IF signals are amplified in an amplifier 7, filtered by the bandpass filter 8, and converted to the baseband in the quadrature mixers 9 and 10 using the signal L02, from a second local oscillator 11. As with LOl, this second oscillator also needs to be locked in phase to the master oscillator. However, a good automatic frequency control tuning (AFC) is frequently incorporated into the circuit that must be kept constant during the registration process. The quadrature outputs are filtered in the low pass filters 12 and 13, being digitized in digital analogue converters 14 and 15, and the bit streams labeled I and Q are produced. The position determination then only requires that the microprocessor 16 records the nit currents in the dynamic RAM 17 under the control of the program 18. This may require some additional memory. The main modification to allow position determination is in the firm equipment program running on the microprocessor, and it may be necessary to upgrade the microprocessor to a faster model. Similar equipment is needed at the base receiving station. A commercially limiting element in a system according to the invention is, for example, the means by which the signals recorded in the base and in the object are transferred to the position-determining processor for a cross-correlation. It is therefore important to reduce the number of bits transferred as much as possible. As noted above, sampling of one bit produces adequate results even under conditions of poor signal reception, and although a slightly better accuracy can be obtained by using a two-bit sampling, the increase in link loading is undesirable. , it is probably better to double the number of samples of a bit, and therefore double the length of the raster interval, than to use two-bit samples. It may also be necessary to measure the I and Q channels and perform a complex cross-correlation, since the base and signals of the object are difficult to be in phase with each other, and the crystal oscillators are not locked together, suppose that the Bit quadrature currents in the object (CRU) are represented by I and Q (see Figure 5), where / = V. (t) cos (?) Q = V2 (t) without (? L) where? l is the phase of the signals, and Vl (t), V2 (t) are their amplitudes. The corresponding quantities registered in the base (CBU) are r = V¡ (t) cos (2 The Microprocessor must then compute four cross correlations to go ', QQ', IQ 'and TQ, and then look for the crest in the amount p, where p - * J? r + QQ 'f + (IQ''I'Q f The phase difference? =? 1 -? 2 can also be obtained from i 'Q - ^' i? = tan { - rjr 1 and this can be used to remove the displacement of the small frequency between the local oscillators in the base and the object so that a longer integration is possible. Equations (1) and (2) show how the estimates of the time delays? R can be used to deduce the position (x, y) of the object and the synchronization error, e, between the base and the object. The accuracy with which the estimates of? R can be obtained from the cross-correlations is central to this process. As noted above, the greatest limitation to accuracy appears to be that caused by the multiple path propagation of the GS transmitter signals to the object. It is assumed that the antenna in the base has been installed high enough on the surrounding environment to ensure that the multipath propagation is small enough to be ignored. In these circumstances the propagation of multipath to the object causes the cross-correlation profile to spread towards longer delay times, since the more direct signals arrive first. The preferred method to obtain an estimate of? R is based on using auto-correlations (ACF) of the base and object signals as well as the cross-correlation (CCF) between them. We use the two self-correlations to deduce the probable form of the cross-correlation, and then we adjust that result or pattern to the cross-correlation to obtain the optimal estimate of? R. The two ACF (lower CRU index) and ACF (lower CBU index) autocorrelations along with the CCF correlation, can be obtained by any of the normal means (see for example "Random Data analysis and measurement procedures" by J: S. Bendat and AG Piersol, Wiley Interscience 1971) we prefer methods that include fast Fourier transformations. The ACF (lower CBU index) is a good estimate of the "intrinsic" self-correlation of the transmitted signals (negligible multipath effect) while the ACF (lower CRU index) is easily corrupted by the multipath signals , this is signals delayed by more than approximately 30 m of equivalent trajectory. This is shown in a particular example in Figure 6, where footprint A is ACF (lower CBU index) and B is ACF (ind, inf CRU). We see that the multiple trajectory has given rise to secondary crests in the trace B that appears on both sides of the main crest since the autocorrelation is always symmetric. The pattern is constructed by taking the left hand portion of ACF (ind inf CBU) this is the trace to the left of the central ridge in A corresponding away from the negative time, and joining it to the right hand portion of ACF (ind. Inf CRU) this is the trace to the right of the central peak at B corresponding to the positive time axis. This is shown in figure C with trace C. The measured CCF is shown in trace D, and we see that pattern C reproduces the important characteristics. The time displacement estimate,? R, is then obtained by adjusting the tempering to the CCF, measured using any standard method, allowing the amplitudes of the two halves of the pattern to be free parameters, as well as? R. The adjustment procedure also produces a "goodness of fit" parameter, which can be used as a basis for rejecting or including data. In cases where more than three GSM transmitters can be received both in the base and in the object, it can be an advantage to use them all in the position determining process, especially if one or more of the trajectories is basically indirect. In such a case, the goodness-of-fit parameter can provide a weight factor for each? R, used in evaluating the position. Manual GSM equipment incorporates analog-digital multiple level converters (ADCs) and uses processing techniques adapted to reduce the errors resulting from multiple path propagation. Therefore, it may be possible to use the modulated signals themselves for the cross-correlation function instead of the unpolished data streams Y, Q, of the receivers depending on the design of the equipment. Such extra delay in adaptive processing can be removed, and no amount of processing can allow the extra unknown path length of a totally indirect signal, but, anyway, the demodulated output will be better for estimating time delays than currents of data Y, Q, before processing. In Fig. 5, a discriminator FM19, (FMD) is shown in a striped scheme. The FM discrimination transfers a frequency shift to a continuous displacement (DC) at the output, so that the quadrature signals (Y, Q) are not needed but are replaced by a single signal (J in Fig. 5). This offers two further advantages, because (a) half of the necessary data is transferred over the links and (b) it is not necessary to adjust the frequency offset in the position determining processor, thus reducing the processor expense. As noted above, several different configurations of a position determining system are possible according to the present invention, depending on the relative locations of the GSM transmitters (often called Base Transceiver Stations, BTSs), the object receivers (CRUs). ), the base receivers (CBUs), the position determining processor (CPP), and a service provider database (SPD). Three configurations are illustrated in Figs. 7a, 7b and 7c, designated A, B, C. Each is subdivided into two, Fig. 7a, shows the configuration a, in which the CPP, and the CPD, are co-located at a remote location of both CBU, as of SRU, this could be the case, for example, when a CPP / SPD combination, serves an entire region, in Al, each BTS, has a CBU, co-located with it. In A2, the CBU, which serves the local cell encompassed by three BTS, is shown somewhere within the cell. The configurations Bl, B2 (Fig. 7b), are similar to Al and A2, respectively except that there are now many CPPs. In Bl, each BTS, has a CBU, attached to it, in B2, each triangle of three BTS, has a CPP, inside it, of which only one is shown in Fig. The SPD, regional remains in a remote location . The configurations Cl, C2 (Fig. 7c), are similar to Al, A2, but with the position processing performed within each manual equipment. Other configurations are possible, each having relative advantages that make them suitable for particular commercial applications. In some applications, it may be advantageous to present map information in graphic form, as part of the response of the service provider database to a request related to a position service. An example of this is given in Fig. 8, where it is shown how a map of the local area could be presented on a screen attached to the position determining processor or at the monitoring station. The user has requested addresses in a location marked by a circle and titled Z, and the position-determining processor has computed that the user's position is somewhere within the circle titled W. The user's equipment includes a matrix display of liquid crystal point that can present small portions of the larger map, as well as information based on letters. The first screen presented on the equipment, can be as in the panel marked (a), in Fig. 8. This is, a large scale map of the local area with the circle in a radius of 100m, centered on the calculated position. The tracks are marked 1, 2, 3, etc., corresponding to the names indicated in the second screen, panel (b). The user can go back and advance between the screens according to his will. Panel (c), shows a larger scale map of the local area in conjunction with a pointer K, which indicates the destination direction of target Z. Clearly many other information screens are possible, including one of the destination address of the target , local traffic conditions, approximate distance, etc. In a commercial application, this could be the scope for a limited amount of announcement about the presentation of the equipment. Prototype system tests. A prototype test apparatus using a pair of manually portable standard units and some additional recording equipment, was established in Cambridge, UK, the base station (CBU), was a three-story building near the center of the city (see Fig 9), with the antenna on the ceiling. The receiver of the object in motion (CRU), was transported in a car to several places in the south of the city, as shown by the crosses in Fig. 9. Three GSM transmitters (BTS), were used in the test locating them respectively in the center of the city, in Great Shelford, to the south and in Fulbourn, to the southeast. Table 2 gives the average potential errors in both coordinates, that is, the differences between the averages of approximately 10, independent position determinations and true positions as measured on a map. Simple data analysis techniques were used without any special discrimination against the effects of multipath propagation. The inherent accuracy of the apparatus found with the tests of both the base receiver and the object, side by side in the laboratory, was less than 20m RMS. Test numbers 1 to 6 were performed with the stationary object, tests 7-11, were performed with speeds between 40 and 64 km / h. Table 2: Location number Prom.error this Prompt north error 1 66.5 -59.5 2 -5.5 80.0 3 -68.0 -15.0 4 89.0 90.0 5 -19.0 41.0 6 64.0 79.0 7 -73.0 6.0 8 -62.0 59.0 9 17.0 128.0 10 43.0 31.0 11 95.0 105.0

Claims (19)

1. REVINDIC ACTIONS 1.- A position determining system for receiving broadband signals transmitted by a certain number of transmission sources equal to at least the number of dimensions with which the movement of an object that moves without a known objective must be controlled. , the system comprises: a pair of receiving stations using the first of the receiving stations in a known position and the second located in the moving object; a position determining processor; means for passing a link signal from each of the receiving stations to the position determining processor, the link signal contains information about the signals received at the receiving station from the transmission sources; wherein each of the receiving stations is arranged to receive the signals from the respective sources basically simultaneously, and the position determining processor is arranged to compare the information received from a receiving station about the signals received at the receiving station from the receiving station. the sources of transmission with the information received at the other receiving station about the signals received at the other receiving station from the transmission sources, and for determining the time delay between the respective signals received at the two receiving stations to determine the position of the object that moves without a known objective.
2. 2. A position determining system according to claim 1, wherein the receiving stations can receive the signals from the respective transmission sources in sequence and in the same sequence with each other.
3. 3. A position determining system according to claim 1, wherein each of the receiving stations is arranged to receive a second signal from one or more of the transmission sources.
4. 4. A position determining system according to one of claims 1 to 3, wherein the position determining processor is co-located with one of the receiving stations.
5. 5. A position determining system according to claim 4, wherein the link signal of one of the receiving stations is passed to the other receiving station and from that other station to the position determining processor.
6. 6. A position determining system according to one of the claims 1 to 3, wherein the position determining processor is located remotely from the receiving stations.
7. A position determining system according to one of claims 1 to 6, wherein the signal providing information about the position of the moving object is passed from the position determining processor to at least one of the receiving stations.
8. 8. A position determining system according to one of claims 1 to 7, further comprising an on-site station and wherein a signal providing information about the position of the moving object is passed from the position-determining processor to the monitor station.
9. 9. A position determining system according to one of claims 1 to 8, further comprising: a database server connected to the position determining processor, the base server contains data elements relating to a plurality of positions known; means for passing information about the position of the moving object determined by the position determining processor to the database server; means for obtaining or removing data elements with respect to the position determined by the position determining processor; means for passing the data elements to one of the receiving stations or to the monitoring station.
10. 10. A position determining system according to one of the preceding claims, wherein the or each receiving station or monitoring station includes a screen and the position of the moving object is presented on the screen.
11. 11. A position determining system according to claim 10, wherein the screen comprises a dot matrix screen.
12. 12. A position determining system according to claim 10, 11, dependent on claim 9, wherein the database server contains graphic information, and this information is passed to the receiving or monitoring station and is presented on the screen to indicate the position of the moving object.
13. 13. A position determining system according to any of the preceding claims wherein the sources of transmission and the receiving stations comprise components of a digital cellular telephone network.
14. 14. A position determining system according to claim 13, wherein the digital cellular telephone network is a GSM network.
15. 15. A position determining system according to one of the preceding claims wherein the receiving stations control the strength of the signals from the multiple sources of transmission and select a plurality of signals strong enough for reception.
16. 16. A position determining system according to any of claims 1 to 15, wherein the near synchronization between the signals received from the respective transmission sources is achieved by a controlled reception of a specific portion of the transmitted signals.
17. 17. A position determining system according to claim 15, wherein the near synchronization between the signals received from the respective transmission sources is achieved by means independent of the transmitted signals.
18. 18.- A method to determine the position of an object in motion without a known goal, the method comprises transmitting broadband signals from a number of sources of transmission equal at least to the number of dimensions in which the movement has to be fixed or controlled of the object, receiving the signals in a pair of receiving stations, using the first of the receiving stations in a known position and the second located in the moving object, each of the receiving stations is arranged to receive the signals from the sources of transmission basically simultaneously, link signals are passed from each of the receiving stations to the position determining processor, the link signals contain information about the signals received at the respective receiving station from the transmission sources, compare the received information in the position determining processor of one of the rec stations information about the signals received at that one receiving station from the transmission sources with the information received from another receiving station about the signals received at that other receiving station from the transmission sources; and determining the time delay between the respective signals received at the receiving stations to determine the position of the moving object.
19. 19. A method according to claim 18, wherein the transmitted signal is a digital cellular telephone network transmission signal. 20.- A method to estimate the displacement in time of the reception of a transmitted signal received in two places, where the signal received in one place could have been subject to corruption by effects of multiple trajectories. The method includes the self-correlation of the signals received in one place; auto co-relationship of signals received elsewhere; cross-co-relation of the signals received in the first and second place, construction of a pattern that includes the portion of the self co-relation of the signals received in the other place corresponding to the displacement times before that of the central peak and that portion of the self-co-relation of the signals received in the first place corresponding to the displacement times after that of the central peak; and measure the displacement to which the pattern best fits in relation to the measured cross-co-relation of the signal received in one of the places and another, as an estimate of the time displacement between the signals received in the two places. SUMMARY The invention relates to a position determining system for receiving digital telephone signals transmitted by a number of transmission sources (BTS), the system has a pair of receiving stations (CBU and CRU), one at a known position (O), and another in an object R, with no known objective. A position determining processor (CPP), and means for passing a link signal (Ll and L2), from each of the receiving stations to the position determining processor, the link signal contains information about the signals received at the station receiver from the sources of transmission. Each of the receiving stations is arranged to receive the signals from the respective transmission sources basically simultaneously. The position determining processor is arranged to compare the information received from a first receiving station with the information received from another or second receiving station, and to determine the time delay between the respective signals received at both receiving stations to determine the position of the receiving station. object in motion.