KR20040070847A - Automatic identification system and method using pseudo-satellite - Google Patents

Abstract

PURPOSE: An automatic identification system and a method using a pseudo-satellite are provided to implement the automatic identification function under the bad electromagnetic condition such as a small intensity of the global positioning system(GPS) signal. CONSTITUTION: An automatic identification system using a pseudo-satellite are provided to at least one pseudo-satellite and at least one automatic identification system(AIS). The pseudo-satellite is located at a specific position of the ground around the harbor for generating an identification code, a navigation message including the position of pseudo-satellite and a pseudo-satellite signal including the time information to transmit them. The AIS is installed on the ship for calculating the dynamic information including the position and speed by using GNSS satellite signal and at least one pseudo-satellite signals from the pseudo-satellite. And, the AIS transmits the AIS signals including the calculated navigation information through the TDMA method and receives the AIS signals from the other object to output.

Description

Automatic Identification System and Method using Pseudo-Satellite}

The present invention relates to an automatic identification system using pseudo satellites (Pseudolite or Pseudo-satellite) (AIS) and an automatic identification method, and more particularly to a conventional global navigation satellite (Global Navigation Satellite). System (hereinafter referred to as "GNSS"), by placing a separate terrestrial pseudo-satellite at a certain location of the port and using it in an automatic identification system, the automatic identification function can be performed even when a satellite signal of the GNSS cannot be received. As well as systems and methods that can improve the accuracy of automatic identification.

On the other hand, the Automatic Identification System (AIS) is a wireless transmission / reception system in the VHF (Very High Frequency) band, which continuously broadcasts a signal including the position information of the main ship and broadcasts other ships. It is a ship control system designed to prevent a ship accident by monitoring position, speed and direction. Beginning in the second half of 2002, all ships should be mandated as follows.

-New ships built after July 1, 2002

-International aviation investigation ship built before 1 July 2002

-For passenger ships: before July 1, 2003

For tanker ships: From 1 July 2003 until the first inspection of safety equipment

-For vessels over 50,000 G / T excluding passenger ships and tanker ships: Until July 1, 2004

-In case of 10,000 G / T ~ 50,000 G / T excluding passenger ship and tanker ship: Until July 1, 2005

-3,000 G / T ~ less than 10,000 G / T excluding passenger ships and tanker ships: Until July 1, 2006

-In case of 300 G / T ~ 3,000 G / T excluding passenger and tanker ships: Until July 1, 2007

-For non-international sailing vessels before July 1, 2002: Until July 1, 2008.

AIS uses two channels (87B, 88B) in the maritime mobile frequency band as the basic frequency channel for data communication by TDMA, and transmits up to 4,500 messages by dividing each channel into 2,250 slots per minute at a data rate of 9,600 bps. Do.

The automatic identification device (AIS Transponder, hereinafter referred to as 'automatic identification device') is used for data communication by AIS. This automatic identification device is composed of two independent receivers and one transmitter, which can simultaneously receive information from two channels, and the transmitter alternately transmits two channels. In this regard, the International Maritime Organization (IMO) has undergone many years of review and has a low possibility of disturbance of radio waves and 4S Broadcasting method using Self-Organized Time Division Multiple Access (SOTDMA) technology to maximize the use of the channel. Ship to Ship, Ship to Shore (AIS transponder) is adopted as AIS of Universal Shipborne and Performance Standard for an Universal Automatic Identification System (Resolution MSC.74 (69)) Approved.

In general, the automatic identification process will be described. The automatic identification apparatus performs time synchronization with another apparatus using a clock or UTC information from its own clock or another apparatus and sets a data transmission slot. Next, using the navigation solution calculation means provided inside and outside, it calculates dynamic information such as its current position and speed, and calculates the calculated dynamic information, other static information, safety related information, etc. Broadcast using a communication method. Visual synchronization and navigation solution calculation mainly use GNSS such as Global Positioning System (GPS).

That is, the AIS uses GNSS, such as GPS, to perform time synchronization with other equipment, synchronization of data transmission slots, etc. for TDMA communication, and calculate navigation information such as its location and speed.

The GNSS is a radio navigation system that provides location, speed, and visual information anywhere in the world using satellites. Hereinafter, a description will be given of the GPS representative GNSS.

This GPS is a global positioning system using satellites, which receives and processes radio waves emitted from satellites that know the exact location, and calculates the position and speed of the observation point by observing the time and distance to the observation point. Means system. Specifically, a signal modulated with unique PRN (Pseudo Random Noise) from four or more satellites is received and demodulated to identify the satellite and its precise location. In addition, after calculating the distance (Pseudo Range) between the satellite and the receiver from the progress time of four or more satellite signals, the position of the receiver is calculated by using the principle of triangulation.

GPS consists of three areas: Space Segment, Control Segment, and User Segment. GPS, which is currently operating normally, is designed as follows.

The GPS space sector consists of 24 satellites, 21 of which are used for navigation and three of which are reserved. All satellites are orbiting the earth at an altitude of 20,200 km or 12 hours, and the orbit is at an angle of 55 to the Earth's equator. All six orbits are 60 degrees apart and four satellites are located on one orbit. This arrangement of GPS satellites on Earth's orbit is intended to allow five to eight satellites to be viewed simultaneously at any point on Earth.

The GPS control consists of a Master Control Station (MCS) and five Monitor Stations that operate unattended. In addition to these control stations, there are three terrestrial antennas located at regular intervals along the equator.

Unmanned sub-controllers track the signals of all GPS satellites that can be observed at any given time, store the signals, and transmit them to the main control station. This communication facility is called the DSCS (Defense Satellite Communication System). The data from several sub-controllers are used by the main control station to estimate satellite orbit information, propagation delay correction information and satellite clock-bias, and the results are periodically re-transmitted to the GPS satellites.

The user sector of GPS consists of several devices using GPS receivers. The GPS receiver used requires simultaneous observation of four or more satellites to calculate the position, speed and time of the receiver by processing the signals received from the satellites. This is because three-dimensional coordinates and time must be combined to determine four unknowns. GPS receivers are currently used in various fields such as navigation, position surveying, and time correction.

However, in the conventional automatic identification apparatus using GPS, it cannot be used when four or more visible satellites are not secured due to the geographical or satellite arrangement, and even if four or more satellites are secured, the DOP (Dilution of Precision; visibility) A high measure of the impact on the positioning accuracy of satellite deployments is that the position and velocity measurements become inaccurate.

In addition, the signal used in the GPS system uses a high frequency band of 1.5GHz, the signal strength of the receiver is as small as about -160dBW. High frequency and very small signal strength allows accurate positioning and automatic identification under very good conditions, such as good ambient radio wave conditions or good directivity to satellites, and precise AIS when conditions are even slightly worse. Could not be implemented.

An object of the present invention is to use an automatic identification system capable of performing automatic identification and more accurate automatic identification in an environment where GNSS cannot be used by using one or more pseudo-satellites disposed on the ground around a port in addition to satellites by GNSS. And a method.

It is another object of the present invention to provide an automatic identification system and method capable of performing access and port protection functions for ships or weapons using GNSS which do not have access rights in case of emergency by using one or more pseudo-satellites.

1 schematically shows the overall configuration of a conventional automatic identification system.

Figure 2 shows the overall configuration of the automatic identification system using the false satellite according to the present invention.

Figure 3 shows an example of the internal configuration of each of the pseudo-satellite used in the present invention.

4 is a block diagram schematically showing the configuration of an Automatic Identification System Transponder according to the present invention.

5 shows the configuration of a High Level Data Link Protocol (HDLC) message used by the automatic identification device according to the present invention.

6 is a view for explaining the relationship between a time reference, a slot, and a bit used in the automatic identification device.

7 is a flowchart illustrating the flow of an automatic identification system using a pseudo satellite according to the present invention.

<Description of Symbols for Main Parts of Drawings>

200, 200 ': Pseudosatellite 202: Data message output / code generation control unit

204: positioning unit 205: time determining unit

206: time synchronization unit 208: identification code generation unit

210: frequency synthesizer 214: phase modulator

216: frequency conversion unit 218: power control unit

300: pseudo-satellite signal receiver

400: Automatic Identification Transponder

410: GNSS information receiving unit 420: display unit

430: VHF transceiver 440: communication processing unit

500, 500 ': Ship 600, 600': visible GPS satellite

In order to achieve the above object, the automatic identification system according to the present invention is disposed at a predetermined position on the ground around a port to generate a pseudo-satellite signal including its own identification code, navigation message including its location, and visual information. One or more pseudolites that are sent out,

Calculate dynamic information including position and velocity using GNSS satellite or pseudo-satellite signal from the pseudo-satellite, transmit AIS signal including calculated navigation information by TDMA method, and receive AIS signal from other object And at least one automatic identification device for outputting.

The GNSS is typically GPS, and the pseudo code of the pseudo satellite may be a unique pseudo random noise (PRN) or a PRN of a GPS satellite currently invisible. The pseudo-satellite superimposes this identification code on its own location information and visual information, and generates and transmits a pseudo-satellite signal similar to a general GPS signal. In addition, the time information of the pseudo satellite may be synchronized with UTC time information by the GPS satellite, or may be synchronized using a signal from another pseudo satellite.

In addition, the pseudo-satellite may improve accuracy compared to an automatic identification system using only GPS by including differential GPS (DGPS) information and / or receiver autonomous integrity monitoring (RAIM) information in the pseudo-satellite signal.

The automatic identification device according to the present invention optionally calculates the distance to the satellite by using a satellite signal from a GPS satellite and / or a pseudosatellite signal from a pseudo satellite, and provides dynamic information such as its position and speed from the satellite. It should be equipped with a function to calculate and send the calculated dynamic information (position, speed, etc.) and visual information to the automatic identification device of the surrounding ship.

The automatic identification method using pseudo-satellite according to the present invention uses one or more pseudo-satellite arranged on the ground around the harbor and an automatic identification device mounted on one or more ships. And a second step of receiving a navigation signal of a specific format from three or more GNSS satellites and / or pseudosatellites, and a distance from the navigation signal to each GNSS satellite or pseudosatellite. The third step of calculating the dynamic information and time information, such as the position and speed of the vessel, and converting the calculated dynamic information and time information to meet the AIS standard to generate an AIS signal and VHF band The fourth step of transmitting by TDMA method and the AIS signal received from the automatic identification device of another ship It comprises a fifth step of outputting the dynamic information or time information of the night.

The navigation signal in the second step may include the identification code information of the satellite, and the information about the position of each satellite may be stored in the automatic identification device. Of course, the location information for each satellite may be configured to be calculated directly from the navigation signal from the satellite.

In addition, the pseudo-satellite according to the present invention is not authorized to have only the satellite navigation function by the GNSS without the pseudo-satellite reception function by making the transmission power of the pseudo-satellite signal more than a predetermined threshold or adjusting the signal transmission interruption period only when necessary. By preventing vessels from performing control by GNSS, they can function as jammers that prevent unauthorized vessels from accessing ports. In addition, when a weapon equipped with a positioning system by the GNSS approaches a harbor equipped with a pseudo satellite, the pseudo satellite may transmit the jammer signal described above to prevent the harbor positioning by the GNSS, thereby protecting the harbor. .

Hereinafter, with reference to the accompanying drawings will be described in detail an embodiment of the present invention.

1 schematically shows the overall configuration of a conventional automatic identification system.

Conventional automatic identification system environment is largely one or more ship (Ship 110, 110 ') having four or more visible GPS satellite (Visible GPS Satellite) 100, GPS receiver 111 and automatic identification device (AIS Transponder, 112). And a terrestrial AIS base station 120 including a GPS receiver.

The GPS receiver 111 is largely divided into a hardware part and a software part. The hardware part is divided into RF part, correlator part and central processing part, and the software part can be divided into satellite tracking part, measurement acquisition part and navigation part. The hardware section of a GPS receiver consists of one or more GPS signal antennas, an RF / IF unit for converting high frequency signals to intermediate frequency signals, a correlator unit consisting of a DSP used to identify satellites from the received GPS signal, and a corresponding GPS signal from the converted GPS signal. It is divided into a central processing unit for calculating dynamic information such as position and speed of a receiver and visual information, a memory unit for storing various data, and an input / output unit.

Since the configuration of the GPS satellite 100, the GPS receiver 111, the data format and navigation solution calculation algorithm, etc. are already well known in the related art, a detailed description thereof will be omitted.

The automatic identification device 112 performs slot setting for time synchronization and data transmission for TDMA communication according to AIS standard with other ships based on UTC time information received from the GPS receiver, and also received from the GPS receiver. It performs broadcasting by modulating ship's dynamic information and visual information by GMSK / FM method.

In addition to the transmission function of the vessel identification information, the automatic identification device receives the AIS signal from the automatic identification device mounted on the other vessel, calculates dynamic information and navigation information such as the vessel, its position and speed, and monitors it. It is further provided with a ship identification information receiving function for outputting to an appropriate output means.

When using the conventional AIS, when the number of visible GPS satellites is not secured or sufficient GPS reception strength is not secured by the surrounding radio environment, the AIS could not operate properly. In addition, when the DOP (Dilution of Precision) is increased by satellite arrangement, the accuracy of navigation solution is lowered, so precise AIS is impossible.

Figure 2 shows the overall configuration of the automatic identification system using the weft satellite according to the present invention, one or more pseudosatellite (Pseudolite, 200) disposed on the ground around the harbor and the pseudo-satellite signal receiver 300 according to the present invention ), One or more ships (Ship) 500, 500 'with an automatic identification device (AIS Transponder, 400) and a terrestrial AIS base station 700 including a GPS receiver, of course, one or more visible GPS satellites 600, 600 May include ').

Pseudosatellite 200 used in the present invention generates a navigation message of the same or similar format as the GPS, using a unique PRN (Pseudo Random Noise) or PRN of the GPS satellites currently invisible state Spread out the band. That is, the GPS receiver installed in the ship is designed to have the same signal structure as the GPS signal so that the pseudo-satellite signal can be processed in the same way as the GPS signal processing.

Pseudo-satellite signal receiver 300 to be described later can determine the distance to the pseudo-satellite using ① when the PRN code of the satellite, ② when the receiver receives the PRN code and ③ luminous flux. If the position information of the pseudo satellite and the distance to three or more pseudo satellites are calculated, the exact position of the pseudo satellite signal receiver can be determined by triangulation.

Since the pseudo-satellite installed on the ground does not move, the receiver has an advantage of accurate positioning.

FIG. 3 shows an example of the internal structure of each function of the pseudo-satellite 200 used in the present invention. The message generating unit 202, the message processing unit 203, the positioning unit 204, and the time determining unit ( 205, time synchronizer 206, carrier generator 208, frequency synthesizer 210, BPSK phase modulator 214, frequency converter 216, power controller 218, power amplifier 220 , The transmitting antenna 220 and the code generating unit 300 and the like.

The positioning unit 204 may include a GPS receiver, an inertial navigation system (INS) or other positioning means. However, when the weft satellite is installed in a fixed type, this positioning unit 204 can be omitted.

The message processing unit 203 and the message generating unit 202 process and generate pseudo satellite position information and GPS correction information. According to a preferred embodiment, this may be the 50 Hz message format used by conventional GPS satellites. Since the pseudo-satellite is fixed on the ground, it may include its own location information instead of the orbital information parameter, and exclude ionospheric error correction information. In addition, DGPS (Differential GPS) information can be used to correct errors by GPS satellites, and Receiver Autonomous Integrity Monitoring (RAIM) information can be used to exclude faulty GPS satellites from navigation. The navigation accuracy can be improved compared to the GPS-only automatic identification system.

The time determining unit 205 receives a GPS signal or another pseudo satellite signal to provide an operation reference time of the pseudo satellite. Of course, like GPS satellites, it may be provided with its own time-determining means, such as precise atomic clocks (such as cesium clocks).

The time synchronizer controls the frequency synthesizer so that code or carrier synthesis is synchronized with a reference time provided by the time determiner.

The frequency synthesizer 210 synthesizes various frequencies used in the pseudo satellite. That is, a frequency required for message generation, code generation, carrier generation, and transmission power control is generated.

The code generator 300 may generate a C / A code of 1.023 MHz or a P code of 10.23 MHz through an output. At this time, the C / A code used may be any PRN, but is preferably one of 32 PRNs having excellent correlation characteristics already used in GPS. Therefore, the pseudo-satellite should identify visible GPS satellites in the place where the current pseudo-satellite is present, and use C / A codes of other GPS satellites except the satellites. Of course, a separate unique PRN can be used without using the C / A code of the existing GPS satellites. In the apparatus for receiving the pseudo-satellite signal, that is, the pseudo-satellite signal receiver 300 or the automatic identification device 400, the identification code of the corresponding pseudo-satellite should be defined in advance.

At the synthesis node 212, a 50 Hz data message is combined with the pseudo-satellite C / A code, and the combined signal is provided to the phase modulator 214. The phase modulator 214 phase modulates the output signal of the synthesized node 212 into an intermediate frequency (IF) signal generated by the carrier generator 208. The signal modulated with the intermediate frequency signal is frequency-converted into the L-band via the frequency converter 216 and is transmitted through the power amplifier 220.

The power controller 218 controls the power amplifier to intercept the pseudo satellite signal transmitted according to the signal provided by the frequency synthesizer.

On the other hand, the pseudo-satellite signal receiver 300 used in the present invention may not distinguish the GPS satellite signal and the pseudo-satellite signal. In this case, the data message of the pseudo-satellite signal indicates that the signal is a signal from the pseudo-satellite. It may be included.

However, since the signal transmitted from the pseudo satellite is stronger than the GPS satellite signal, it is necessary to lower the duty cycle by transmitting the signal intermittently. Therefore, in the present invention, it is preferable that the power control unit 218 transmits the phase modulated L-band signal only for 1 to 2 ms of every 20 ms by controlling the power amplifier 220.

According to one embodiment of the present invention, in order to use the pseudo-satellite signal as a kind of port protection jammer, the above-described power control unit increases the signal transmission power or decreases the signal interruption time, that is, signal transmission per unit time. You can increase the time.

In this way, an unauthorized vessel not equipped with the automatic identification device 400 and / or the pseudo-satellite signal receiver 300 according to the present invention cannot use the AIS using GPS satellites due to the interference signal transmitted by the pseudo-satellite, AIS can be performed based on signals received from other ships, etc., but the accuracy is inferior. Therefore, it is possible to prevent unauthorized ship access to the port in case of emergency. In addition, when a weapon equipped with a positioning system by the GNSS approaches a port equipped with a pseudo satellite, the pseudo satellite may transmit a jammer signal to prevent the harbor from being identified by the GNSS.

If the pseudosatellite according to the present invention has a separate GPS receiver, the pseudosatellite serves as a kind of "reference station". Therefore, in this case, the (error) correction data calculated by the pseudo-satellite side can be wirelessly transmitted to the pseudo-satellite signal receiver 300 to correct the error. When the DGPS information is included in the pseudo-satellite signal in this way, the positional error of the vessel is reduced to almost 1 m to 5 m, so that a more accurate position can be obtained.

In order to be used as a navigation device for mobile vehicles, the satellite navigation system has the performance requirements of accuracy, integrity, continuity and availability as set forth by the International Civil Aviation Organization (ICAO). (RNP, Required Navigation Performance) must be satisfied. Among these, integrity is a measure related to the reliability of navigation solution, and it means the ability to alarm the user when there is an error by determining whether the navigation system is operating normally.

Integrity verification can be largely divided into a method of using a ground monitoring station (Ground Monitoring Scheme) and a method of using only information that can be obtained from the user side, and a method of using only user information includes a method of using an auxiliary sensor other than satellite navigation. It can be divided into the method using only the measurement margin of the satellite navigation system (RAIM, Receiver Autonomous Integrity Monitoring).

In the present invention, after verifying the integrity of the GPS signal by the RAIM method in the pseudo-satellite, the method for transmitting the information with the pseudo-satellite signal is used. That is, since the position of the pseudo satellite is already known accurately, when the position of the pseudo satellite is calculated from its GPS signal of the visible satellite received through the GPS receiver of the satellite, and the difference is different from the actual position, the integrity of the GPS signal is in error. It will be proof that there is. In this case, the ship should be informed of the RAIM information that the signal of the current visible GPS satellite is unreliable. Therefore, "RAIM" information in the present invention means information on the integrity of the visible GPS satellite signal determined by the pseudo-satellite.

If the integrity of the visible GPS satellite signal is not verified in this way, the automatic identification device of the ship is notified so that the pseudo satellite signal is used preferentially rather than the GPS satellite.

The pseudo-satellite signal receiver 300 installed in the vessel 500 has a structure similar to a GPS receiver, and is divided into an RF unit, a correlator unit, and a central processing unit in hardware, and in software, a satellite tracking unit, a measurement acquisition unit, Navigation anatomy, etc.

The hardware portion of the pseudo-satellite signal receiver 300 is used to identify one or more pseudo-satellite signal antennas, an RF / IF unit for converting the received high-frequency pseudo-satellite signal into an intermediate frequency signal, and a corresponding pseudo-satellite from the received pseudo-satellite. A correlator comprising a DSP, a central processing unit for calculating dynamic and visual information such as a position and a speed of a corresponding receiver from the converted pseudo-satellite signal, and a memory unit for storing various data. The memory unit may store code information (PRN) of various GPS satellites and / or accurate location information of pseudo satellites.

The pseudosatellite signal receiver 300 according to the present invention has a GPS receiver function for receiving a signal of a general GPS satellite and determining a position or attitude of the receiver therefrom. That is, in a normal environment, the receiver is in a positioning mode using a signal from a visible GPS satellite and only uses a pseudo-satellite signal or a GPS satellite signal together when a pseudo-satellite signal is received as the port approaches. To determine the position of.

The process of determining the exact position of the receiver from the pseudo-satellite signal is similar to determining the position from the GPS signal and can be performed as follows. First, the antenna receives the pseudo-satellite signal and delivers it to the analog signal processor (or RF / IF unit). The analog signal processor filters and amplifies the received phase modulated L-band signal, converts it into an intermediate frequency, and converts it into a digital signal.

In accordance with the control signal from the DSP, the correlator section generates a reference code signal and removes the C / A code from the pseudosatellite signal digitized using the reference code signal. The signal is then converted to baseband.

The navigation solution calculation software installed in the central processing unit identifies the pseudo-satellite from the received pseudo-satellite signal, grasps the time and reception point of the pseudo-satellite signal, and multiplies the elapsed time by the luminous flux. Calculate the pseudo range. When the distance to each satellite is calculated by repeating the above-described process for three or more pseudo-satellites, the position of each pseudo-satellite is already known, and thus, the exact position of the receiver is used.

As described above, the pseudo-satellite signal receiver 300 according to the present invention may also include a navigation solution calculation function by a general GPS in addition to the above-described function. However, it is preferable to apply the navigation solution calculation by GPS and the navigation solution calculation by a pseudo-satellite signal independently or simultaneously according to a predetermined priority.

4 is a block diagram schematically illustrating the configuration of an Automatic Identification Transponder 400 according to the present invention. The automatic identification device includes a physical layer, a link layer, a network layer, a transport layer, and a presentation layer in an OSI (Open System Interconnection) 7 layer structure. It consists only.

The automatic identification device refers to a device that functions to modulate (SKSK / FM) dynamic information such as its own position, speed, and visual information according to the AIS standard, and to transmit the TDMA method in a high frequency band (VHF). do.

The automatic identification device 400 includes information receiving unit 410 from the GNSS, a display unit 420 for indicating own ship and other ship information, a VHF transceiver 430 forming a physical layer, and other higher layers. The processor 440 is configured to connect with other devices. Of course, the above-described pseudo-satellite signal receiver 300 or GPS receiver may be integrated with the automatic identification device.

The display unit 420 of the automatic identification device displays the ship's information at mutual or onshore (shore) AIS base stations by displaying not only magnetic information but also static information, dynamic information, navigation information, and safety related information of other vessels collected through the automatic identification device. It allows you to do this automatically.

The VHF transceiver 430 is equipped with a Gaussian Minimum Shift Keying (GMSK) module 431 and a Frequency Modulation (FM) module 432 to perform VHF band wireless communication, and uses 156.025 MHz to 162.025 MHz as a variable carrier frequency. 2W or 12.5W is used as the variable transmission power.

The communication processor 440 may include a microprocessor 441 that manages an interface with an external device and operation of a self-identifying device, a high-level data link control (HDLC) module 442 for processing an AIS message, and a time for TDMA communication. Automatic identification device controller 443 for synchronization and device control.

The microprocessor 441 is composed of a link layer, a network layer, a transport layer, and a presentation layer and is responsible for automatic identification device operation.

The link layer is divided into three sublayers: medium access control (MAC), data link service (DLS), and link management entity (LME).

The MAC layer, in conjunction with the automatic identification device controller 443, performs slot synchronization and frame synchronization for TDMA communications.

The DLS layer, in conjunction with the HDLC module 442, performs data link activation or release, data transmission, error detection, and control.

The LME layer controls the operation of the DLS, MAC and physical layers, generates or configures a transmission message, determines an operation mode, performs a channel access function appropriate to the operation mode, and initializes a channel. In particular, in the LME layer, the channel access algorithm defined in the AIS standard is used for efficient communication with a large number of other ships.Incremental Time Division Multiple Access (ITDMA), Random Access Time Division Multiple Access (RATDMA), and Fixed Access Time Division Multiple Access Self Organized Time Division Multiple Access (SOTDMA) method. These channel access algorithms minimize transmission collisions and autonomously resolve them when collisions occur, minimizing the intervention of device operators and AIS base stations. The network layer is responsible for channel connection attempts and maintenance, message allocation priority management, distribution of transport packets between channels, and data link congestion resolution.

The transport layer converts data received from the outside into packets of the correct size, controls the order of data packets, and is in charge of interfacing with higher layers. The presentation layer is responsible for interfacing with other navigational devices.

The HDLC module 442 controls data link activation or release, and generates and transmits data according to the AIS standard, and performs error detection / control.

The automatic identification device controller 443 performs time synchronization for TDMA communication, and performs a function of synchronizing bit transmission clocks, frames, and the like with UTC or other automatic identification devices in accordance with the AIS standard.

That is, the automatic identification device controller constituting the automatic identification device performs the time synchronization for TDMA communication with the link layer software, and generates a signal for controlling the operation of the automatic identification device. As shown in FIG. 6, all automatic identification apparatuses use one VHF data channel divided into 2250 slots per minute on the same time reference (for example, UTC), and one slot has a time corresponding to 256 bits.

Meanwhile, in the AIS, it is necessary to synchronize a channel or a slot to the same time reference in order to facilitate TDMA communication between various automatic identification devices, and mainly uses a 1PPS signal synchronized with UTC provided by a GPS satellite. This time synchronization is currently implemented in a variety of ways, preferably using the method described in the applicant's Korean application.

5 shows the configuration of a High Level Data Link Protocol (HDLC) message used by the automatic identification device according to the present invention.

HDLC is a bit-oriented data communication protocol defined by the International Standardization Organization (ISO) for information transmission. In AIS, the HDLC protocol frame format defined in ISO is modified to be used in the format shown in Fig. 5, which includes ramp-up (8-bit), training sequence (24-bit or 32-bit), and start flag (8-bit). It consists of data (maximum 1008 bits), frame error detection information (FCS: Frame Check Sequence, 16bit), and end flag (8bit). That is, the HDLC module uses a bit-based synchronous protocol for data framing and error detection correction.

6 is a view for explaining the relationship between a time reference, a slot, and a bit used in the automatic identification device.

The transmission slot used in the automatic identification device is composed of 37.5 time slots in one second and 2,250 time slots in one minute. One time slot consists of 256 bits (Bit / Slot), and thus has a transmission rate of 9,600 bits (bps) for 1 second.

Hereinafter, the detailed configuration of the automatic identification device is not the core of the present invention, and a detailed description thereof will be omitted since it is currently known to those skilled in the art. In addition, as described above, the pseudo-satellite signal receiver 300 and the automatic identification device 400 used in the present invention may not be physically implemented separately but may be integrated into one.

7 is a flowchart illustrating a flow of an automatic identification method using a pseudo satellite according to the present invention.

First, the pseudo-satellite identifies a visible GPS satellite capable of receiving a signal at its current location (S711), using the C / A code of one of the invisible satellites, and the information about the pseudo-satellite and its exact location information. And modulate and transmit a data message including UTC time information (S712, S713).

The pseudo satellite signal receiver 300 installed in each ship receives a signal from a visible GPS satellite or pseudo satellite. The receiver calculates the distance between the satellite and the receiver from the GPS satellite signal or the pseudo-satellite signal, and calculates and transmits dynamic information such as wishing and speed of the receiver and visual information such as UTC or 1PPS based on the distance to the automatic identification device. (S714).

In the automatic identification device that receives the dynamic information and the time information from the pseudo-satellite signal receiver, a bit transmission clock and a bit transmission slot synchronized to UTC according to the AIS standard are generated (S716), and includes operation information and time information of the corresponding vessel. Create AIS data. GMSK / FM modulation is performed on the generated AIS data according to the AIS standard, and an AIS signal is transmitted in a predetermined transmission slot (S717).

In addition, the automatic identification device receives and demodulates the AIS signal sent by another vessel, calculates dynamic information and time information of the vessel, and outputs it to a predetermined output means such as a monitor (S718).

Since the pseudo satellite according to the present invention is in addition to the existing AIS, the influence of the operation of the pseudo satellite on the AIS operation should be minimized. Thus, for example, when there are four or more visible GPS satellites having a good DOP, it is preferable to operate the AIS based on them, and it is preferable to use the pseudolite according to the present invention only in exceptional circumstances, not in such a radio wave environment. It is. However, even in a normal radio wave environment, the pseudo satellite according to the present invention may be used to improve the efficiency of AIS operation, in particular, the accuracy of providing visual information or location information.

The above description is merely illustrative of the present invention, and those skilled in the art to which the present invention pertains may various modifications without departing from the essential characteristics of the present invention. Accordingly, the embodiments disclosed herein are not intended to limit the present invention but to describe the present invention, and the spirit and scope of the present invention are not limited by these embodiments. It is intended that the scope of the invention be interpreted by the following claims, and that all descriptions within the scope equivalent thereto shall be construed as being included in the scope of the present invention.

As described above, by using the system and method according to the present invention, an automatic identification function of a ship can be implemented even in a radio wave environment in which sufficient GPS visibility is not secured or the strength of the GPS signal is weak.

In addition, since a pseudo-satellite fixed at a specific position on the ground is used as a kind of reference station, a precise automatic identification system can be realized by providing more accurate information about a ship's position and speed.

In addition, even when using a GPS satellite signal, the accuracy of automatic identification can be improved by additionally providing error correction information by DGPS and / or GPS signal integrity information by RAIM in the pseudo satellite.

On the other hand, by using another embodiment of the present invention, by using the pseudo-satellite signal as a kind of jammer or jammer, the vessel or weapon which does not have the automatic identification device according to the present invention prevents access to the harbor. It can perform port protection function.

Claims (13)

One or more pseudo-satellite satellites disposed at a specific location on the ground around the harbor to generate and transmit pseudo-satellite signals including their identification codes, navigation messages and their visual information including their location; Installed in the vessel, using the one or more of the GNSS satellite signal and the pseudo-satellite signal from the pseudo-satellite to calculate the dynamic information including the position, speed, and transmits the AIS signal containing the calculated navigation information by TDMA method At least one automatic identification device for receiving and outputting an AIS signal from another object; Automatic identification system using a pseudo satellite, characterized in that it comprises a. The method of claim 1, The GNSS is GPS, and the pseudo code of the pseudo satellite is one of a C / A code which is a unique PRN (Pseudo Random Noise) or a C / A code which is a PRN of a GPS satellite currently invisible. Automatic identification system using satellites. The method of claim 2, The pseudo satellite generates a pseudo satellite signal by modulating the navigation message in the same or similar format as in GPS using the identification code, and transmits the pseudo satellite signal intermittently every predetermined period. Automatic identification system using. The method of claim 3, wherein The pseudo-satellite increases the power output of the pseudo-satellite signal or changes the signal transmission interruption period, thereby preventing the automatic identification device without the pseudo-satellite receiving function from performing the satellite navigation function by the satellite navigation system. Automatic identification system using a pseudo-satellite, characterized in that to function as a jammer (Jammer) to prevent the vessel or weapons, such as to approach the port. The method of claim 1, The pseudo-satellite is a first method of synchronizing time to UTC using a GNSS satellite signal, a second method of synchronizing time to each other using other pseudo-satellite signals around, and synchronizing the time using its own precise visual device. Automatic identification system using a pseudo-satellite, characterized in that using one or more of the time synchronization method of the third method. The method of claim 1, In order to improve the accuracy of the AIS operation by the GNSS, the pseudo-satellite signal includes at least one of error correction information by the differential GNSS (DGNSS) and GNSS signal integrity information by the RAIM method. Automatic identification system. The method of claim 1, The automatic identification device A doctor that receives at least one of a signal from the pseudo-satellite and a signal from a visible GNSS satellite to calculate a distance to each satellite and generate dynamic and visual information, including the position and velocity of the vessel, based thereon; A satellite signal receiver, Synchronize with UTC or other device time, receive dynamic information and time information of the ship from the pseudo-satellite signal receiver, modulate it to meet AIS standard, and send it to other ship by TDMA method Automatic identification system using a pseudo-satellite, characterized in that made. Using one or more pseudo-satellite satellites placed on the ground around the harbor and automatic identification devices mounted on one or more ships, A first step of intermittently transmitting the pseudo-satellite signal every predetermined period; The automatic identification device includes a second step of receiving a navigation signal of a specific format from three or more GNSS satellites and / or pseudo-satellites; A third step of calculating a distance from each navigation signal to each GNSS satellite or pseudosatellite, and calculating dynamic and visual information such as the position and speed of the corresponding vessel based on the navigation signal; A fourth step of generating the AIS signal by converting the calculated dynamic information and visual information to conform to the AIS standard and transmitting the TIS method in the VHF band; And a fifth step of analyzing the AIS signal received from the automatic identification device of another ship at predetermined intervals and outputting dynamic or visual information of another ship. The method of claim 8, The navigation signal includes identification code information unique to the satellite, and the identification code of the GNSS satellite is a C / A code used for GPS, and the identification code of the pseudo satellite is a PRN (Pseudo Random) unique to each pseudo satellite. Noise) or a C / A code of a GPS satellite in an invisible state at the position of the pseudo satellite. The method of claim 8, The pseudo-satellite signal includes an identification code of a pseudo-satellite, information indicating that the signal is from a pseudo-satellite, and location information of the pseudo-satellite. The method of claim 8, The pseudosatellite does not perform the satellite navigation function by the satellite navigation system by the automatic identification device without the pseudo-satellite reception function by setting the transmission power of the pseudo-satellite signal above a predetermined threshold or adjusting the signal transmission interruption period only when necessary. A method of automatic identification using pseudo-satellite, which prevents unauthorized ships or weapons from accessing the harbor. The method of claim 8, In the first step, the pseudo satellite is a first method of synchronizing time to UTC using a GNSS satellite signal, a second method of synchronizing each other using another pseudo satellite signal of the surroundings, and its own precise visual device. And synchronizing the time by one or more of the third methods of synchronizing the time by using the pseudo- satellite. The method of claim 8, In order to improve the accuracy of the AIS operation by the GNSS, the pseudo-satellite signal includes at least one of error correction information by the differential GNSS (DGNSS) and GNSS signal integrity information by the RAIM method. Automatic identification method using.