# US 2016/0259031 A1 · Method for determining the timing of the receipt of a radio message

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- Number: US 2016/0259031 A1
- Document ID: US20160259031A1
- Status: Published application
- Kind: A1
- Application number: 15/026,997
- Filed: 2014-09-26
- Published: 2016-09-08
- Earliest claimed: 2013-10-04
- Assignees: True Heading AB
- Applicants: True Heading AB
- Inventors: Nils WILLART; Bengt JOHANSSON; Anders BERGSTRÖM
- Web page: https://patentgrep.com/patent/US20160259031A1

## CPC

- G01S 5/14: Determining absolute distances from a plurality of spaced points of known location
- G01S 5/02216: {Timing or synchronisation of the receivers}
- G01S 11/08: using synchronised clocks
- G08G 3/02: Anti-collision systems
- H04B 1/59: Responders; Transponders
- H04L 9/40: Network security protocols
- H04L 27/06: Demodulator circuits; Receiver circuits
- H04W 4/025: {using location based information parameters}
- G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G08G: TRAFFIC CONTROL SYSTEMS (guiding railway traffic, ensuring the safety of railway traffic B61L; arrangement of road signs or traffic signals E01F9/00; radar or analogous systems, sonar systems, lidar systems specially adapted for traffic control G01S13/91, G01S15/88, G01S17/88; {radar or analogous systems, sonar systems, lidar systems specially adapted for anti-collision purposes G01S13/93, G01S15/93, G01S17/93})
- H04B: TRANSMISSION
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)

## Abstract

Method for determining the time of receipt by a radio receiver (320,330,340) of a binary coded radio message emitted by a sender (310), whereby the radio signal is received by the receiver so that an analogue electrical signal is achieved, which analogue signal is sampled and optionally demodulated, whereby the data content of the message is determined based upon the demodulated signal as a stream of data bits, which stream of data bits comprises a predetermined signal element whose time of receipt is determined. The invention is characterised in that a digitally stored, constructed comparison signal is created based upon the said stream of data bits, 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 in that the time variable is then used to correct the said time determination of the receipt of the predetermined signal element.

## Claims

### Claim 1

Method for determining the time of receipt by a radio receiver of a binary coded AIS (Automatic Identification System) message, sent by a sender in the form of a first signal which is a modulated radio signal, wherein the first signal is received by the receiver using an antenna so that a second signal in the form of an analogue electrical signal is achieved, which second signal is sampled and optionally demodulated, which sampling and demodulation can be performed in any order, which sampling is performed using an AD converter, and a digitally stored third signal in the form of a sampled and optionally demodulated signal is achieved, wherein the data content of the message is determined from the third signal as a stream of data bits, which stream of data bits comprises a predetermined signal element whose time of receipt is determined, and wherein the time of receipt of the message is determined based on the timing of the predetermined signal element, wherein a digitally stored, constructed comparison signal is generated on the basis of said stream of data bits, and the constructed comparison signal is constructed to correspond to the third signal, wherein an optimum value is determined for a time variable, which time variable indicates a time position of the constructed comparison signal relative to the third signal and for which optimum value a correlation between the constructed comparison signal and the third signal is maximal, and wherein the optimum value of the time variable is used to correct the determination of the time of receipt of the predetermined signal element.

### Claim 2 (depends on 1)

Method according to claim 1, wherein the third signal is achieved by analogue modulation of the second signal, followed by sampling of the resulting correspondingly analogously modulated signal.

### Claim 3 (depends on 1)

Method according to claim 1, wherein the first signal, before modulation by the sender, is filtered using a certain filter, and wherein the comparison signal is constructed by, in a corresponding way, filtering a digital signal representing the said data content using a filter with essentially the same properties as the said certain filter.

### Claim 4 (depends on 1)

Method according to claim 1, wherein the constructed comparison signal, before calculation of the said correlations, is filtered using a filter so that deviations of the third signal, arising as a consequence of the analogue frequency and/or phase response of the receiver before sampling is simulated using said filter.

### Claim 5 (depends on 1)

Method according to claim 1, wherein the AD converter sends out at least one interrupt signal for marking a certain sampling time point, wherein the time of emission of such interrupt signal is determined using a clock in the receiver, and wherein the time determination of the receipt of the said predetermined signal element is based upon the timed sending out of the said interrupt signal by relating the sending out of the interrupt signal to a certain time position of the third signal.

### Claim 6 (depends on 5)

Method according to claim 5, wherein the AD converter sends out a number of interrupt signals at predetermined time intervals, whereof the time of the sending out of several such respective interrupt signals is determined using the said clock and are adjusted using the said time interval in order to estimate the point in time of the sending out of a certain interrupt signal, wherein these adjusted timing determinations are averaged so that an averaged timing determination of the sending out of the certain interrupt signal is achieved, wherein the timing determination of the receipt of the said predetermined signal element is based upon the averaged timing determination of the sending out of the certain interrupt signal by relating the certain interrupt signal to a certain time position of the sampled signal.

### Claim 7 (depends on 5)

Method according to claim 5, wherein the clock comprises a local oscillator, which regularly is synchronized to the time information in a received GPS (Global Positioning System) signal.

### Claim 8 (depends on 1)

Method according to claim 1, wherein the location of the sender is known by the receiver, and wherein a common point in time is synchronized between the sender and the receiver by the receiver correcting the timing determination of the receipt of the said predetermined signal element for the time it takes for the radio signal to travel between the sender and the receiver, based upon the distance between the locations of the sender and the receiver, respectively.

### Claim 9 (depends on 7)

Method according to claim 7, wherein at least three receivers, the respective clocks of which have been previously synchronized, receive one and the same radio signal from a certain sender, wherein each of the receivers determine the timing of the receipt of the same predetermined signal element of the received signal, and wherein a location of the sender is determined by triangulation, by a central unit in communication with said at least three receivers, based upon the respective location of the three receivers in combination with differences in the respective point in time for the respective receipt of the said signal element.

### Claim 10 (depends on 9)

Method according to claim 9, wherein the calculated location for the sender, and/or a heading and/or a velocity which has been calculated based upon several consecutive calculations of the location of the sender, is compared to a location and/or a heading and/or a velocity for the sender which is stated in an AIS (Automatic Identification System) message which is sent out from the sender, and wherein a warning signal is emitted in case the two positions and/or headings and/or velocities are pairwise different by more than a respective predetermined value.

### Claim 11

Receiving device arranged to receive a binary coded AIS (Automatic Identification System) 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 achieve a second signal in the form of an analogue electrical signal, an AD converter and an optional demodulation device, which AD converter and optional demodulation device are arranged to sample and possibly demodulate the said analogue signal, which sampling and demodulation can be performed in any order, and achieve a digitally stored third signal in the form of a sampled and optionally demodulated signal, which receiving device furthermore comprises a decoding device, arranged to decode the third signal and achieve the data content of the message as a stream of data bits, which stream of data bits comprises a predetermined signal element whose time of receipt is determined, and wherein the receiving device is arranged to determine the time of receipt of the message based on the timing of the predetermined signal element, and the receiving device comprises a time determination device, arranged to determine the time of receipt of the predetermined signal element, wherein the timing determination device is arranged to generate 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, wherein the timing determination device is arranged to determine an optimum value for a time variable, which time variable indicates a time position of the constructed comparison signal relative to the third signal and for which optimum value a correlation between the constructed comparison signal and the third signal is maximal, and wherein the timing determination device is arranged to correct the said timing determination of the receipt of the predetermined signal element using the optimum value of the time variable.

### Claim 12 (depends on 10)

System for determining the location for a sender emitting a binary coded AIS (Automatic Identification System) message in the form of a modulated radio signal, wherein the system comprises at least three receiving devices according to claim 10, each one comprising a respective clock, which clocks are synchronized, and which receiving devices are arranged to receive one and the same radio signal from the sender, wherein each one of the receiving devices is arranged to determine the time of receipt of the same predetermined signal element of the received signal, and wherein the system is arranged to determine a location of the sender by triangulation based upon the respective location of the three receivers in combination with differences in the respective point in time for the receipt of the said signal element.