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  • 专利说明
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    • 专利摘要:
    Summary Method for timing a radio receiver's (320,330,340) receiving a binary coded radio message sent by a transmitter (310), the radio signal being received by the receiver so that an analog electrical signal is provided, which analog signal is sampled and possibly demodulated, the data content of the message determined from the demodulated signal as a stream of data bits, which stream w of data bits contains a predetermined signal element whose reception is timed. The invention is characterized in that a digitally stored, constructed comparison signal is created on the basis of said stream of data, so that the constructed comparison signal is constructed to correspond to the sampled signal, in that a time variable which maximizes a correlation between the constructed comparison signal and the sampled signal is determined, and that the time variable is then used to correct said timing of the reception of the predetermined signal element.
    公开号:SE1351172A1
    申请号:SE1351172
    申请日:2013-10-04
    公开日:2015-04-05
    发明作者:Nils Willart；Bengt Johansson；Anders Bergström
    申请人:True Heading Ab；
    IPC主号:
    专利说明:

    The present invention relates to a method for timing the reception of a radio message, in particular an AIS signal (Automatic Identification System), which is transmitted from a transmitter to a receiver located in the geographical vicinity of the transmitter. In addition, the invention relates to a receiver, especially an AIS receiver, being able to receive such a signal.
    In shipping and aviation, for example, the standardized communication system AIS is largely used for local communication between, for example, conventional vessels or medium-sized vessels and fixed installations, such as a port or a lighthouse. See, for example, "Recommendation ITU-R M.1371-4", published in 2010 by the International Telecommunication Union.
    According to this system, a set of digitally coded, predefined messages of various types can be used by, for example, a vessel to, among other things, communicate its current position and speed to recipients located in the local geographical vicinity of the vessel in question. The system is self-organizing in the sense that the participating probes distribute their respective probes over a predefined periodically repeated time window of a certain length, so that accustomed probes for probing use a certain gap in the time window.
    AIS systems often have legal certainty, in the sense that it is black to verify if the content of the data being sanded, such as the position of the probe, is correct and consistent with the actual situation. This means that senders wishing to participate are expected to follow the AIS standard and send the correct information, and that only simple measures to ensure the security of the information received are built into the system. For example, not too large time errors were allowed for transmitted signals.
    It is your wish to provide an improved control option for a recipient regarding the information a vehicle sends out, as regards the vessel's position, speed and course. In addition, it would be undesirable to be able to detect if a certain AIS signal is transmitted by one and the same transmitter.
    It is possible to use directional antennas to measure the direction of a radio transmitter, so as to verify the position of the transmitter. However, this is costly and provides a relatively clang precision.
    It is also difficult to establish a simple way for a vessel whose local clock has fallen out of sync with other sending vessels to synchronize its local clock. In particular, it will be difficult to achieve a so-called second-party synchronization, which can be used as an alternative to the synchronization process provided for in the AIS standard if this is not available for flagging reasons.
    It is also undesirable to establish a way for two or more transmitters / receivers to jointly agree on a certain, between these transmitters / receivers secret, time definition, without any other recipients also being ridden by information regarding such information.
    These objectives should be met with the help of existing standard AIS equipment, in a cost-effective manner and with a minimum of necessary modifications to existing AIS equipment.
    MsOhiingstext.docx10-04130038EN 3 The present invention solves the problems described above.
    Thus, the invention relates to a method for timing a radio receiver's reception of a binary coded message transmitted by a transmitter in the form of a first signal as a modulated radio signal, the first signal being received by the receiver by means of an antenna so that a second signal in the form of an analog electrical signal is provided, which second signal is sampled and possibly demodulated, which sampling and demodulation can take place in any order, which sampling is performed by means of an AD converter, so that a digitally stored third signal in the form of a sampled and possibly demodulated signal, the data content of the message being determined from the third signal as a stream / 5 of data bits, which stream of data bits contains a predetermined signal element whose receiving time is determined, and the reception of the message is determined based on the timing of the data bits. predetermined signal element, which method is characterized by a digital l agraded, constructed comparison signal is created on the basis of said stream of data bits, so that the constructed comparison signal Or is constructed to correspond to the third signal, in that an optimal value is determined for a time variable, which time variable indicates a location of the constructed comparison signal in time relative to the third signal and for which the optimal value was a correlation between the constructed comparison signal and the third signal Or maximum, and from the fact that the optimum value for the time variable is used to correct said time determination of the reception of the predetermined signal element.
    In addition, the invention relates to a receiving device arranged to receive a binary coded message sent by a transmitter in the form of a first signal which is a modulated radio signal, which receiving device comprises an antenna arranged to receive the first signal. and thereby providing a second signal in the form of an analog electrical signal, an AD converter and an optional demodulation device, which AD converter and any demodulation device are arranged to sample and optionally demodulate said analog signal, which sampling and demodulation can take place in optionally arranged, and clamed to provide a third signal in the form of a digitally stored, optionally demodulated signal, which receiver device also comprises a decoding device arranged to decode the third signal and thereby provide the data content of the message as a stream of data bits, which stream of data bits contains a predetermined signal element whose m and the receiving device Or arranged to time the reception of the message based on the timing of the predetermined signal element, the receiving device being defined by the receiving device comprising a timing device arranged to time the reception of the predetermined signaling element, a digitally stored, constructed comparison signal on the basis of said stream of data bits, so that the constructed comparison signal Or is constructed to correspond to the third signal, in that the timing device Or is arranged to determine an optimum value for a time variable, which time variable indicates a location of the constructed the comparative signal in time relative to said third signal and for which the optimum was a correlation between the constructed comparative signal and the third signal Or maximum, and in that the timing device Or arranged to correct is the said timing of the reception of the predetermined signal element by means of the optimum value for the time variable.
    MsOhiingstext.docx10-04130038EN The invention will now be described in detail, with reference to exemplary embodiments of the invention and the accompanying drawings, in which: Figure 1 shows the structure of a general AIS message; Figure 2 shows a graph representing a Gaussian filtered, digitally encoded, exemplary AIS message; Figure 3 is a schematic diagram illustrating a system according to the invention which may be used in a method according to a first embodiment of the invention; Figure 4 illustrates the transmitter functionality of an AIS equipment according to the invention; Figures 5a and 5b illustrate two different variants of the receiver functionality in an AIS equipment according to the invention; and / Figure 6 is a schematic diagram illustrating a system according to the invention which may be used in a method according to a second embodiment of the invention.
    AIS is an example of a time-distributed messaging system, within the framework of which standardized, bind-coded radio messages can be sent directly between geographically remote connected units, without the need for a common central unit via which messages must be sent. The system is based on AIS-connected transmitters transmitting different types of standardized messages periodically or periodically, and that the various transmitters included in the system themselves distribute the available bandwidth over each transmission period between them.
    Figure 3 shows two onshore equipment 330, 340 for receiving and possibly also sending AIS messages, as well as off a coast 300, on the water, mobile vessels in the form of boats 310, 320 with respective equipment for sending and receiving AIS messages. messages.
    MsOhiingstext.docx10-04130038EN 6 AIS messages in the form of radio signals 311, 321 are schematically illustrated.
    As shown in Figure 3, at least the AIS transmitters 3 and 320 transmit to all AIS receivers located within the reception area of the AIS transmitter in question. Although not all connected units 310, 320, 330, 340 are necessarily of the same standardized type, when brought together geographically, they will establish a self-organizing communication network between them based on time division over a certain sanding period. For this reason, the framework falls within the scope of the AIS standard and Or in itself conventionally.
    It will be appreciated that the fixed and movable units 310, 320, 330, 3 illustrated in Figure 3 may equally be constituted by other types of fixed units, such as a permanently installed transponder at an airport, and other types of moving vehicles, such as aircraft or wheeled vehicles.
    Different types of AIS messages Or intended for different types of information, examples include information regarding current position, speed, yaw rate, destination, draft and so on, for the connected device. Different types of AIS messages are sent according to the AIS standard differently often and with different effect, among other things depending on the type of sender in question.
    These and other aspects of the AIS system are regulated, inter alia, in Recommendation ITU-R M.1371 (above). More information is also available in the documentation provided by the International Maritime Organization (IMO).
    MsOhiingstext.docx10-04130038EN 7 Figure 1 illustrates the general data structure of an AIS message, including the following binary coded flits. A "bit" is a one or a zero.
    Preamble: an initial sequence of 24 bits. Can for example be alternating "0" and "1", with at least one ending "0".
    Start flag and End flag: both include 8 bits and serve as delimiters for the AIS message. Can for example be 8 bits that are all "1".
    Data: 168 bits, in addition to the actual information to be transmitted including the message identifier MSG ID, the sender identifier User ID and the Communication state field.
    The FCS is a 16-bit checksum that is calculated based on the contents of the Data field, and whose purpose is to be able to verify the integrity of the contents of the AIS message.
    Buffer: 24 bits that can be used in predefined ways to communicate information on, for example, sanding distance and signal quality.
    Thus, of the total length of 256 bits, a certain portion of the Data field is used for the actual transfer of the parameter value, while some initial fields, such as Preamble and Start Flag, include predetermined information.
    Figure 4 illustrates the functional structure of sanding having an AIS device 400 according to a preferred embodiment, comprising means for assembling and periodically transmitting AIS messages of at least a certain predetermined type, which AIS messages are readable by a receiving device for AIS messages. It is preferred that the sanding device 400 follow the specifications of a particular AIS type (such as "Class A", "Class B", base stations, AtoN).
    MsOhiingstext.docx10-04130038EN 8 Aids to Navigation, SART (Search and Rescue Transmitter), and so on), and as such is capable of sending a certain set of different types of AIS messages with certain periods.
    The device 400 comprises a sensing means 401, arranged to detect that an AIS message of the certain predetermined type, or possibly other types, is to be transmitted, for example based on the time allotted to the transmitting device 400 in the distributed system or in the CSTDMA.
    Further, the transmitting device 400 comprises a digital message composing means 402, arranged to compile, digitally store and calculate a checksum for an A'S / 5 message of said predetermined and possibly other types. The message composing means 402 receives the information to be transmitted in the AIS message, inter alia or at least from a data line 403, which may contain information such as geographical location, probe identity and so on.
    An example of the message produced and stored by the message composing means 402 is illustrated in Figure 2, as the sequence of binary ones and zeros shown at the bottom of the figure. In Figure 2, the message of clarity is abbreviated.
    The sounding device 400 further comprises, according to a preferred embodiment, a filtering means 404, arranged to produce a filtered signal based on the said digitally stored binary signal. An example of such a filtered signal is shown in Figure 2, as the byre curve. The binary ones and zeros are shown in Figure 2 next to the filtered signal, and it can be seen from Figure 2 that a binary one corresponds to a higher signal value in the curve, and vice versa for a binary zero, which corresponds to a lower signal value. curve. The message illustrated in Figure 2 does not follow the format illustrated in Figure 1 regarding the number of bits in different facts.
    As shown in Figure 2, the filtered curve is not a pure step function, but a filtered version of a step function that corresponds to the number sequence below the curve in the figure. This filtering results in the characteristic appearance of the curve. Examples of preferred filters include filtering using a Gaussian filter, as with conventional GMSK (Gaussian Minimum Shift Keying) modulation. It is preferred that the filter curve produced be analogous, the filter preferably being an analog filter, but it may also be digitally coded, the filter being digitally.
    The filtered curve is fed to a modulator 405, which modulates, preferably modulates frequency, the filtered signal on a gateway, which is then amplified and fed to an antenna 406, which transmits the AIS signal as a radio signal 420.
    It is preferred that all steps 401-406 constitute software and hardware implemented parts of one and the same computer equipment, which then comprises or constitutes the device 400.
    Figure 5a schematically illustrates receiving functionality having an AIS device 500 according to the present invention, to time the AIS device 500 receiving an AIS message sent by a probe similar to that described above. An antenna 501 or arranged to receive an incident radio signal 520 encoding an AIS message so that an analog electrical signal is provided. The radio signal, which is a modulated radio signal, is composed of a bare wave on which a data signal is modulated, preferably frequency modulated. The radio signal constitutes a first signal according to the present invention.
    The received analog signal constitutes a second signal according to the present invention. This second signal is sampled, and possibly demodulated as well. The suede produced, sampled and possibly demodulated signal constitutes a third signal according to the invention. In the event that the signal is both sampled and demodulated, the sampling and demodulation can take place in any order, see below.
    According to the present exemplary embodiment, the second signal is demodulated and sampled, which sampling is performed by means of an AD converter 503, so that a digitally stored, sampled and demodulated signal corresponding to the demodulated analog signal is produced. The AD converter 503 has a sampling frequency of at least 10 kHz, more preferably at least 100 kHz. Alternatively, the sampling frequency is at least 10 times as high as the bit rate per second of the received signal, which bit rate in the case of an AIS message is 9600 Hz.
    Figure 5a shows a demodulating device 502, which is arranged to accept said analog electrical signal and demodulate this signal so that a demodulated analog signal is produced and fed to the AD converter 503. This demodulated analog signal is similar in appearance to the byre curve. in Figure 2, but Oven includes some components in the form of noise as well as any additional filtration effects from sandier saliva as receiver.
    Figure 5b is identical to Figure 5a, but illustrates an alternative design, in which the AD converter 503 Or is arranged to sample the incoming frequency modulated analog signal from the antenna 501, so that a digital version of this signal is provided, and where the demodulation device 502 is digital, and performs the demodulation in the digital domain.
    It is also understood that in case the second signal is sampled directly, either a digital demodulation can take place, alternatively the information can be extracted directly from the sampled signal without any special demodulation.
    The demodulated digital signal is then fed to a decoding device 504, which is arranged to determine the data content of the AIS message from the demodulated signal as a stream of data bits similar to the lower sequence of figures in Figure 2. This decoding takes place in a conventional manner. The decoding device 504 preferably consists of a standard type AIS modem, which modem may also comprise, for example, the demodulation device 502.
    The decoding device 504 is arranged to, after decoding, make the received message accessible via a interface 505, such as a graphic display or a digital communication interface for publishing the message for reading external software modules.
    According to the invention, a predetermined signal element has been defined in advance, which is said to contain said stream of data bits. Preferred examples of such predetermined signal elements are the front or far flank of the field "Start flag", illustrated in Figure 1 and in Figure 2. For example, at the front edge it may be in advance that a zero is followed by a series of eight ones. . At the far flank, it may be a foregone conclusion that a series of eight ones is followed by a zero. A signal element of the latter Msöhiingstext.docx10-04130038EN 12 type is marked with the arrow 201 in Figure 2. It is preferred that the predetermined signal element in a corresponding manner consists of a predetermined number in a number of bits in the AIS message whose data content is in advance, and which preferably consists either of a series of zeros or of a series of ones of predetermined length followed by a change from "0" to "1" or from "1" to "0". This provides a simple and unambiguously identifiable upward or downward edge in the demodulated signal. It is especially preferred in AIS especially that the signal element consists of the last bit in a pre-known series of bits which are all either "0" or "1", and which are followed by a byte to "1" and "respectively". 0 ". Especially the end of, ie. the far flank has, the "Start flag" field in AIS messages / 5 is usable.
    According to the invention, the reception of said signal element is timed, and the reception of the message is then timed based on the timing of the predetermined signal element in that the position of the predetermined signal element within the message is predetermined.
    This is done by first creating a digitally stored, constructed comparison signal, by a timing device 508 and on the basis of the stream of data bits, i.e. the data content of the received AIS message, so that the constructed comparison signal is constructed to correspond to either the received frequency modulated signal before or, preferably, after demodulation. This comparison signal should always correspond to the sampled signal, but in case the AD converter 503 is arranged upstream of the demodulation device 502, it may be the sampled signal before or after demodulation that the comparison signal is to be designed to correspond to. In the case where the signal received by the antenna, for modulation of the transmitter, is filtered by means of a certain filter, it is preferred that the comparison signal is constructed by correspondingly filtering a digital signal representing said data content by means of a filter. with essentially the same properties as the said certain filter, for example a Gaussian filter as above.
    As shown in Figures 5a and 5b, the decoded bind data in the AIS message is fed from the decoder 504 to the timing device 508. In addition, the sampled, alternatively sampled and demodulated, signal is fed as interrupt signals (see below) to the timing device 508.
    That the comparison signal is "constructed to correspond" to the received signal meant in this context that the timing device 508 digitally synthesizes a signal curve by processing the digital content of the received AIS message, as in terms of binary ones and zeros, in a manner which simulates or corresponds to it signal processing which in the transmitter gay gives rise to the transmitted and then received, modulated radio signal 520. In other words, the decoded binary data in the AIS message is used to simulate the sampled and possibly demodulated signal received by the timing device 508, with the aid of of known properties has the transmitter regarding how the transmitter creates the transmitted radio signal.
    In the example illustrated in Figures 4, 5a and 5b, this therefore meant that a Gaussian filtered curve of the type illustrated at the top of Figure 2 was produced, corresponding to the bit sequence in the AIS message analyzed in the decoding device 504. Thus, in this example, the signal received by the antenna 501, before modulating the transmitter, has been filtered using a certain filter which is then also applied to the constructed signal.
    Then, by the timing device 508, an optimal value for a time variable is determined, which time variable indicates a location or displacement of the constructed comparison signal in time relative to said sampled and possibly demodulated signal, and for which optimal value a correlation between the constructed comparison signal and the sampled signal Or maximal. In the following, the sampled and possibly demodulated signal will be simply referred to as the "sampled signal".
    By the term "correlation" is meant a comparison operation which is performed between the two signals time by time, and which constitutes a measure of the signals' total agreement and / or covariation seen over a certain time interval.
    In other words, the constructed comparison signal is oriented with a certain offset in time line 1 relative to the corresponding sampled signal, after which a correlation between the signals is calculated, and the offset that maximizes this correlation Or the optimal value for the time variable.
    The correlation can be calculated, for example, as follows: Ci = k 1 (S (0J (i + j)) i = m dar j = said time constant C = the correlation for time constant = j, k = a constant, MsOhiingstext.docx10-04130038EN {To , = the considered time interval, S (i) = the sampled signal curve in point (i), and J (i) - the constructed comparison signal curve in point (i).
    {To, can thank the entire time overlap of the signal curves, alternatively only a shorter test time interval.
    It will be appreciated that the correlation in the corresponding manner can be calculated over a continuous time interval, rather than for discrete times.
    Thus, the value for j that maximizes C is calculated. According to a preferred embodiment, the optimal value for the time variable is calculated by calculating the correlation for several values of the time variable, and then searching the global maximum for the correlation as a function of the time variable. Numerically, this can be done, for example, by first determining an initial temporal relative orientation for the two signals, which may be based on empirically generated values for delays in the receiver 500. Then the correlation can be calculated for a number of values for the time variable shifted forward and backward, respectively. in relation to the original time orientation, said that a gray approximation to the correlation function C (j) was achieved, by means of which a coarse value for the optimal time variable can be determined. Then the correlation can be calculated for faster intervals if the time variable is in an area around the coarse value, to obtain a more exact value for the maximum. This can be repeated several times, and finally the derivative function of the correlation function can be calculated, and the maximum can be determined to the value of the time variable for which the derivative function intersects 0. This intersection point can be calculated, for example, by means of line interpolation. All of these calculations take place in a microprocessor in the receiver 500 and on behalf of the timing device 508.
    Thereafter, the determined optimal value of the time variable of the suede is used to correct the timing of the reception of the predetermined signal element. Information regarding the corrected timing is then published by the timing device 508 via the interface 505. According to a preferred embodiment, the decoding device 504 is arranged to detect the reception of the predetermined signal element discussed above, and upon such detection, reports the reception to the timing device 50. timing of capping device 504 receiving the predetermined signal element which is corrected by means of the above time variable.
    According to a further preferred embodiment, all relevant delays in the receiver are fed before the AIS message is received, including the delay in the demodulation device 502, the AD converter 503 and the decoder 504. Then the said delays affecting such timing information as the timing depends on the reception of the predetermined signal element, and / or those of said delays that occur before a signal indicating that the predetermined signal element has been received reaches the timing device 508, to adjust the timing of the reception of the predetermined signal element beyond the adjustment. with the help of the optimal time variable. Such delays are generally consistent and predictable, and can therefore be determined in advance. Examples include delays in the AD converter 503 itself.
    In addition to a filtering which is intended to simulate a filter applied by the transmitter for modulation, such as the Gaussian filtering described above, according to a preferred embodiment the constructed comparison signal for calculating said correlations may also be subjected to a filtration with the aid of filters so that deviations have the sampled signal that occurs as a result of the receiver's on-the-spot analog frequency and / or phase response before sampling are simulated with the aid of said filters. Such a filter can, for example, consist of a suitable FIR filter.
    The sampled signal to be correlated with the comparison signal may be fed to the timing device 508 from the decoder 504, but it is preferred that it be fed to the timing device 508 directly from the demodulating device 502 or the AD converter 503. the predetermined signal element is made known to the timing device 508.
    The receiver includes a clock 507 which provides the timing device 508 with current time. According to a preferred embodiment, the AD converter 503 emits at least one interrupt signal to mark a certain sampling time.
    The interrupt signal is detected, directly or via, for example, the decoder 504, by the timing device 508, and the transmission of the interrupt signal is timed by the clock 507. In this case, the timing described above is based on the reception of the predetermined signal element by the timing element. that the output of the interrupt signal is related to a certain lag in time has the sampled signal. It is preferred that the interrupt signal whose output is related to the sampled signal be an interrupt signal that is emitted when or in connection with the predetermined signal element being received. As described above, various predetermined delays may have the demodulating device 502, the converter 503, the decoding device 504 and so on compensated to suitably determine which interrupt signal is emitted when the predetermined signal element is received.
    According to a preferred embodiment, the AD converter 503 outputs a plurality of interrupt signals at predetermined time intervals, preferably one interrupt signal for each sampling point. In this case, the transmission of several such successive interrupt signals is timed with the aid of the clock 507, after which each of the times of receiving these interrupt signals is adjusted by means of said pre-known time intervals to estimate the time of transmission of a certain individual interrupt signal, such as the interrupt signal at which the predetermined signal element was received. The suedes justreamed timings are then averaged, so that an averaged timing of the transmission of the certain single interrupt signal is achieved. Finally, the timing of the reception of the predetermined signal element is based on said averaged timing of the transmission of the certain single interrupt signal, by relating the certain single interrupt signal to a certain layer in time the sample has been sampled.
    For example, the interrupt signal at which the predetermined signal element was received may constitute the particular single interrupt signal, and a sequence of interrupt signals which is then detected by the timing device 508 may be used to calculate a more accurate value for the transmission of the particular interrupt signal. -04130038EN 19 mi 11 Tmed = K + wil (Tax (i) - Ts) i = o (Jar Tmed = the time-averaged value for the reception of the certain single interrupt signal, K = a possible corrective time constant to take into account distortions in the receiver 500, m = the total number of interrupt signals to be used for the mean value calculation, = the time indication for the clock 507 when the interrupt signal number in from the certain interrupt signal is accurately detected by the timing device 508, and F, = the sampling frequency. in the message signal, alternatively at least 100 sam plingar.
    Such a procedure provides a very accurate value for the time before the reception and thus also the transmission of a certain single interrupt signal (in this example the one in which the predetermined signal element was received). Thereby a precisely specified time reference for the sampled signal is obtained, whereby the timing described above with the aid of the constructed signal also in a corresponding manner becomes very accurate.
    It is further preferred that the clock 507 includes a local oscillator which is regularly synchronized with the time information in a received GPS positioning (Global Positioning System) 530, which is received by means of an antenna 506. The extraction of a time signal from the GPS signal 530 Or i sig kant. The present inventors have discovered that if the local oscillator is a per se conventional crystal oscillator which is less expensive than, for example, an atomic clock, provided that the oscillator is regularly synchronized by means of the time signal of the GPS signal. regarding the timing of the received AIS message. It is thus preferred not to use an atomic clock. It is preferred that the oscillator of the clock 507 be regularly synchronized with the aid of the time information of the GPS signal 530, preferably at least the usual minute, preferably at least every tenth second, preferably at least every second. It is preferred that the clock 507 be sufficiently accurate to always have a time conception which is correct as at a maximum of 100 as at such synchronization periods.
    Using a method according to the present invention, the time of receipt of a message comprising a predetermined signal element can be determined with great accuracy. The reception of individual messages can also be accurately timed.
    This is especially true for AIS messages. Since an AIS receiver typically already includes modules 501, 502, 503, 504 and 506, the timing device 508 may be added to the existing equipment by means of a software module, for example in the form of a software module which is arranged to be executed by the same computer already executing software, for example which constitutes the decoding device 504. In this way, the reception of up to 2250 messages per minute can be timed within the framework of the existing AIS system and without significant investments in new hardware.
    MsOhiingstext.docx10-04130038EN 21 In the following, a number of applications are described where such an accurate timing can be used.
    Figure 3 illustrates a first example in which the position of the vessel 310 is determined by triangulation between the reception times of the same message signal by at least three different receivers, such as the AIS receivers 320, 330, 340. The clocks each of these receivers 320, 330, 340 are pre-synchronized to one and the same common time conception, preferably in that all three are of the GPS-synchronized type described above which thus share one and the same time reference.
    All three receivers 320, 330, 340 receive the same AIS radio signal A, B, C from the transmitter 310, but at different times. Each of the receivers 320, 330, 340 times the reception of the same predetermined signal element has the received signal, and a position has the transmitter 310 then determined by triangulation based on the respective position of the three receivers known in advance, in combination with differences in the respective timing of the respective reception of said signal element. The actual triangulation calculations can be performed, for example, by a centrally located computer 350, which is connected to the receivers 320, 330, 340. Any moving participating vehicles 320, such as boats, cars or helicopters, can report their current position via a conventional wireless data connection 322.
    By such a method, the present inventors have been able to establish that accuracies within a fatal hundred meters have been achieved with respect to the position determination of an AIS transmitter 310 at an SNR (Signal to Noise Ratio) of 10 dB, which is sufficient to be able to verify MsOhiingstext in practice. .docx10-04130038EN 22 accuracy has, for example, the position of the transmitter 310 itself reported by the AIS transmitter 310.
    According to a preferred embodiment, at least one AIS message is intercepted by the AIS transmitter 310, so that a specified position of the AIS transmitter can be obtained. In addition, AIS information is preferably intercepted which allows the time of transmission of a certain future AIS message to be predicted, for example by information concerning where in the AIS time window a certain AIS message is periodically transmitted from the AIS transmitter 310 during normal operation. Thereafter, the reception of the certain future AIS message from the AIS transmitter 310 in question is intercepted and timed, and the position of the AIS transmitter 310 is triangulated as above based on the reception of the certain AIS message in question.
    Thereafter, the calculated position of the AIS transmitter 310, and / or a course and / or a speed calculated based on several successive challenges of the position of the AIS transmitter 310 may be compared with a position and / or a course and / or a speed for the AIS transmitter 310 specified in an AIS message transmitted by the AIS transmitter 310. In the event that the two positions and / or the courses and / or speeds differ in pairs that with more than one respective predetermined value is transmitted an alarm signal via an alarm device 351 which is symbolically illustrated in Figure 3.
    Figure 6 illustrates a further example of an application of the above-described procedure for accurately timing an AIS message, including at least two transmitter / receiver equipments 610, 620, such as AIS equipments, which may be installed on fixed and / or movable objects, bath includes a GPS synchronized clock as above, and which bath can transmit radio signals 611, 621 as well as AIS-Allso gsted.clocx 10-04130038EN 23 messages. In this case, the position of a transmitter 610 relative to a receiver 620 is predetermined by the receiver 620, the transmitter 610 transmitting a radio message comprising a predetermined signal element, such as an AIS message, to the receiver 620. Thus, the receiver 620 can accurately time the reception of the transmitted signal, by means of a method according to the invention. After correcting for the delay of the signal between transmitter 610 and receiver 620, based on said relative distance, the receiver 620 thus provides an accurate timing of the transmitter 610 transmitting the message. Thus, a common time can be synchronized between the transmitter 610 and the receiver 620, based on the common known time of the transmitter 610 transmitting the message signal.
    Such a time synchronization between two units 610, 620 can, for example, be used to agree on a common secret time conception, without other nearby units being able to obtain knowledge of such a time conception. The time conception can, for example, be used to agree in advance on the time for changing the bar frequency for secret information exchange or the like.
    In both of the applications described in connection with Figures 3 and 6, there are additional advantages to adding an additional layer of verification based on a fingerprint relating to the transmitter 310, 610.
    In Figure 3, for example, the verification of the position, speed and / or course of the transmitter 310 can be combined with a verification of such a fingerprint, so that the combined verification becomes a lot of things. For example, the fingerprint of an AIS message can be compared with that of a later external AIS message, and verification can be done by examining whether the fingerprints are identical. Alternatively, a detected fingerprint may be compared to a prior known fingerprint based on knowledge of the type of AIS transmitter equipment in question or the like. In addition, it can be verified that it is the same radio signal as the SOM of three receivers 320, 330, 340.
    In Figure 6, a verification of a previous edge fingerprint has the transmitter 610 used to verify that the transmitter 610 is indeed the one expected.
    By a "fingerprint" is meant herein a characteristic having the actual radio signal which depends on properties has the transmitter itself, such as a known deviation from an ideal self-dependence on signal processing in the transmitter. Examples include predictable variations in time inaccuracy seen over an AIS period, characteristic pulse shapes when ramping up or down, and the resulting GMSK signature has the transmitter.
    In the following, an exemplary embodiment will be presented for the purpose of providing an in-depth understanding of the invention, in which example a received AIS signal is simulated and then compared with a constructed signal according to the present invention.
    First, a bitstream is created consisting of the fields "Preamble" and "Start flag", above, and the random bits correspond to the remaining AIS message. In total, the bit stream comprises 250 bits, which are then used as a basis for a simulation of a sanding of an AIS message with a bit rate of 9600 bits / sec.
    The digital bitstream is graphically illustrated in the lower curve of Figure 7. The bitstream then passes through a conventional digital Gaussian filter, resulting in the upper curve of Figure 7a.
    In order to simulate the disturbances, the signal which occurs during normal operating conditions is in fact degraded, the resulting signal then being degraded by means of two consecutive first-order law-pass filters with offset frequencies of about 5 kHz, arranged to simulate the signal processing characteristics of the transmitter. Finally, palOggs a white noise with the same effective value as the signal itself. The resulting curve is illustrated in Figure 7b.
    A simulated sampling, with a sampling rate of 192 kHz, is then performed, whereby a sampled signal according to the invention is obtained.
    A comparison signal is constructed by subjecting the byre curve in Figure 7a to the same pass filter as the simulated signal, but without white noise.
    Then the sampled and the constructed signal for different values are correlated on a time variable which displaces them in time in relation to each other. The calculated correlation as a function of the time variable is illustrated in Figure 7c.
    Figure 7d is an enlargement of the curve 701 shown in Figure 70 near the global maximum of the curve. Figure 7d shows both the curve 701 itself and its derivatives 702. The y-axis indicates the value of the derivative. As Or clearly in Figure 7d, the value 703 that optimizes the correlation 701 is selected as the optimal time variable 700, and is finally calculated by linear interpolation of the derivative function 702.
    MsOhiingstext.docx10-04130038EN 26 Such a simulation of real conditions gives the following repeatability regarding the timing of different relative noise levels: Signal level = Noise level: about 90% ports VAT ± 5.00 ps Signal level - 10 x Noise levels: about 0% ports 50 ps Signal level = 100 x Noise level: approximately 90% ends up at ± ± ps ps The above preferred embodiments have been described. However, it will be apparent to those skilled in the art that many changes may be made to the embodiments described without departing from the spirit of the invention.
    For example, the basic idea of the invention is to apply to other types of radio messages on AIS messages.
    Furthermore, other types of pre-known or detected fingerprints regarding the signal processing characteristics of the transmitter can be used to increase security.
    Thus, the invention should not be limited by the described embodiments, but may be varied within the scope of the appended claims.
    MsOhiingstext.docx10-04130038SE 27
    权利要求:
    Claims (12)
    [1]
    A method for timing a radio receiver's (320,330,340; 500; 620) receiving a bound coded message as an outpost of a transmitter (310; 400; 610) in the form of a first signal or a modulated radio signal (520), wherein the first signal is received by the receiver by means of an antenna (501) so that a second signal in the form of an analog electrical signal is produced, which second signal is sampled and possibly demodulated, which sampling and demodulation can take place in any order, which sampling performed by means of an AD converter (503), so that a digitally stored third signal in the form of a sampled and possibly demodulated signal is produced, the data content of the message being determined from the third signal as a stream of data bits, which stream of data bits contains a predetermined signal element whose reception is timed, and wherein the reception of the message is timed based on the timing of the predetermined signal element, characterized in that a digital degree, constructed comparison signal is created on the basis of said stream of data bits, so that the constructed comparison signal Or is constructed to correspond to the third signal, in that an optimal value is determined for a time variable, which time variable indicates a location of the constructed comparison signal in time relative to the third signal and for which the optimal value was a correlation between the constructed comparison signal and the third signal Or maximum, and in that the optimal value for the time variable any-ands to correct said timing of the reception of the predetermined signal element.
    [2]
    The method of claim 1, wherein the third signal is provided by analog modulation of the second signal followed by sampling of the resulting analog modulated signal.
    [3]
    Method according to claim 1 or 2, characterized in that the first signal for modulating the transmitter (310; 400; 610) is filtered by means of a certain filter, in that the comparison signal is constructed by correspondingly filtering a digital signal representing said data content by means of a filter having essentially the same properties as said certain filter.
    [4]
    A method according to claim 1 or 2, characterized in that the constructed comparison signal for calculating said correlations is filtered by means of a filter so that deviations of the third signal appear as a result of the analog frequency and 320,330,340; 500; 620) / or phase operation before sampling is simulated with the aid of said filters.
    [5]
    A method according to any one of the preceding claims, characterized in that the AD converter (503) emits at least one interrupt signal to mark a certain sampling time, in that the transmission of such an interrupt signal is timed by means of a clock (507) in the receiver, and in that the timing of the reception of said predetermined signal element is based on the timed transmission of said interrupt signal by relating the transmission of the interrupt signal to a certain layer in time, the third signal has.
    [6]
    A method according to claim 4, characterized in that the AD converter (503) emits a plurality of interrupt signals at predetermined time intervals, of which the emission of several such interrupt signals is timed with the aid of said clock (507) and adjusted with the aid of said time interval to estimate the timing of the transmission of the MsOhiingstext.docx10-04130038EN 29 a certain interrupt signal, that these adjusted timings are averaged sh that an averaged timing of the transmission of the certain interrupt signal is achieved, and that the timing of the reception of the signal part is preceded by the of the certain interrupt signal by relating the certain interrupt signal to a certain time lag of the sampled signal.
    [7]
    A method according to claim 4 or 5, characterized in that the clock (507) comprises a local oscillator which is regularly synchronized with the time information in a received GPS signal (530) (Global Positioning System).
    [8]
    Method according to any one of the preceding claims, characterized in that the position of the transmitter (310; 400; 610) is known to the receiver (320,330,340; 500; 620), and in that a common time is synchronized between the transmitter and the receiver by the receiver correcting the timing of the reception of said predetermined signal element for the time it takes for the radio signal (520) to travel between the transmitter and the receiver based on the distance between the positions of the transmitter and the receiver.
    [9]
    A method according to claim 6, characterized in that at least three receivers (320,330,340), whose clocks (507) are pre-synchronized, receive one and the same radio signal (520) from a certain transmitter (310), each of the receivers, the reception of the same predetermined signal element of the received signal determines the time, and of a position of the transmitter being determined by triangulation based on the respective position of the three receivers in combination with differences in the respective time of the respective reception of said signal element. MsOhiingstext.docx10-04130038SE
    [10]
    A method according to claim 8, characterized in that the calculated position of the transmitter (310; 400; 610), and / or a course and / or a speed calculated based on several successive challenges of the position of the transmitter, cf. with a position and / or a course and / or a speed for the transmitter specified in an AIS (Automatic Idenfification System) message transmitted by the transmitter, and that a warning signal is issued if both positions and / or the courses and / or speeds par-vis differs that with more than one respective predetermined value.
    [11]
    A receiver device (320,330,340; 500; 620) arranged to receive a binary coded message as an output of a transmitter (310; 400; 610) in the form of a first signal which Or is a modulated radio signal (520), the receiver device comprising an antenna (501) arranged to receive the first signal and thereby provide a second signal in the form of an analog electrical signal, an AD converter (503) and an optional demodulation device (502), which AD converter and any demodulation device Or arranged sampling and possibly demodulating said analog signal, which sampling and demodulation can take place in any order, and thereby provide a third signal in the form of a digitally stored, possibly demodulated signal, which receiver device Above comprises a decoding device (504) arranged to decoding the third signal and clamed to provide the data content of the message as a stream of data bits, which stream of data bits contains a predetermined signal element whose reception and the receiving device Or is arranged to time the reception of the message based on the time of the predetermined signal element, characterized in that the receiving device comprises a timing device (508) arranged to time the reception of the MsOhiingstext.docx10 31. arranged to provide a digitally stored, constructed comparison signal on the basis of said stream of data bits, so that the constructed comparison signal is constructed to correspond to the third signal, in that the timing device is arranged to determine an optimal value for a time variable, which time variable indicates a location of the constructed comparison signal In time relative to said third signal and for which the optimal value is a correlation between the constructed comparison signal and the third signal is maximum, and of the fact that the timing device is arranged ad correcting said timing of the reception of the predetermined signal element by means of the optimum value for the time variable.
    [12]
    A system for determining the position of a transmitter (310; 400) transmitting a binary coded message in the form of a modulated radio signal (520), characterized in that the system comprises at least three receiver devices (320,330,340) according to claim 10, each comprising a clock (507), which clocks are synchronized, and which receiver devices are arranged to receive one and the same radio signal (520) from the transmitter, in that each of the receiver devices is arranged to time the reception of the same predetermined signal element having the received signal, and in that the system is arranged to determine a position of the transmitter by triangulation based on the respective position of the three receivers in combination with differences in the respective time of the respective reception of said signal element. Msöhiingstext.docx10-04130038SE
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    公开号 | 公开日
    WO2015050492A1|2015-04-09|
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    SE537593C2|2015-07-07|
    US20160259031A1|2016-09-08|
    EP3052956B1|2019-03-13|
    ES2727744T3|2019-10-18|
    EP3517990A1|2019-07-31|
    EP3052956A4|2016-11-02|
    US9804254B2|2017-10-31|
    KR20160065868A|2016-06-09|
    DK3052956T3|2019-06-17|
    EP3517989A1|2019-07-31|
    CN105723234B|2018-10-23|
    KR102295846B1|2021-09-01|
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    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
    SE1351172A|SE537593C2|2013-10-04|2013-10-04|Method and apparatus for determining the timing of receipt of a radio message|SE1351172A| SE537593C2|2013-10-04|2013-10-04|Method and apparatus for determining the timing of receipt of a radio message|
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    CN201480058257.0A| CN105723234B|2013-10-04|2014-09-26|Method for the receiving time for determining radio message|
    DK14850762.7T| DK3052956T3|2013-10-04|2014-09-26|Method for determining the time of receipt of a radio message|
    ES14850762T| ES2727744T3|2013-10-04|2014-09-26|Method for determining the timing of the reception of a radio message|
    EP19157376.5A| EP3517990A1|2013-10-04|2014-09-26|Method for determining the timing of the receipt of a radio message|
    KR1020167009732A| KR102295846B1|2013-10-04|2014-09-26|Method for determining the timing of the receipt of a radio message|
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    EP19157371.6A| EP3517989A1|2013-10-04|2014-09-26|Method for determining the timing of the receipt of a radio message|
    PCT/SE2014/051115| WO2015050492A1|2013-10-04|2014-09-26|Method for determining the timing of the receipt of a radio message|
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