FR3027175A1 - METHOD FOR PROVIDING DATA DATA PACKETS RECEIVED, DEVICE AND COMPUTER PROGRAM THEREFOR - Google Patents

Abstract

The invention relates to a method for providing received AIS data packet data, wherein AIS data packets are received by at least one AIS receiving device (80) and the data of the received AIS data packets are analyzed automatically, such data of an AIS data packet which are erroneous being reconstructed at least in part by means of auxiliary data accessible for the AIS receiving device (80) which do not originate from the AIS data packet whose decoding is in progress . The invention further relates to a device comprising an AIS receiving device (80) and a supplying means (91) for providing AIS data packet data received via the AIS receiving device as well as a computer program.

Description

The present invention relates to a method for providing data of received AIS data packets. The invention further relates to a device comprising an AIS receiving device and a providing means for providing AIS data packet data received via the AIS receiving device, as well as a computer program. More generally, the invention relates to the field of AIS communication in the field of maritime traffic. Today, the world's growing surveillance of maritime traffic relies heavily on radar surveillance, voice radio, and the use of the Automatic Identification System (AIS). In the year 2000, the AIS system was adopted as a binding standard by the International Maritime Organization (IMO) to enhance the safety of international maritime traffic. This local radio system is used for the exchange of navigation data and other vessel data that is intended to enable ships to obtain a comprehensive overview of nearby marine traffic. The main objective is to avoid collisions between ships. The AIS system transmits alternately on two channels of the VHF marine band, namely on the one hand at 168.975 MHz and on the other hand at 162.025 MHz. The transmission of the individual AIS data of a ship takes place at fixed time slots, the occupancy of which is organized autonomously by the participants concerned (so-called SOTDMA: self-organizing time-division multiple access) . Thus, individual participants only have 2250 time slots per minute for data transmission. Because of the VHF frequency band used, the radio range of the AIS system from one ship to another vessel is approximately 40 to 60 km, which is slightly higher than normal visibility on the high seas. elevated position, coast stations may cover a radius of up to 100 km. Because of the limited range and transmission protocol used, ships that can see each other and receive the signals together form an AIS radio cell within which participants can transmit and receive their data without collision. 3027175 In this respect, the AIS system is therefore only a local radio system which provides sufficient data for a vessel on the high seas but without additional provisions is not appropriate for the collection of data at the global maritime traffic, which continues to intensify. For shipowners, shipping organizations or ministries of the environment, the rapid collection of AIS maritime traffic data is of great interest, particularly in order to thwart, inter alia, illegal activities on the high seas. AIS receiving antennas have already been installed on satellites in order to be able to receive AIS signals issued globally by ships at regular intervals. While this allows global collection of maritime traffic data through the AIS system, in practice this presents significant difficulties and disadvantages since initially the AIS system was not developed for reception by the AIS system. satellite. Due to the very high flight height of a satellite, we obtain a reception area which is also called a coverage area or footprint with a diameter of about 5000 km. Since, as a local radio system, the AIS system autonomously organizes into individual radio cells that all transmit on the same frequency bands, a satellite with a footprint of such magnitude is likely to receive the signals of a multitude of radio cells whose transmission frequencies are identical so that the AIS radio signals of the different AIS radio cells can overlap in the reception area of the satellite. List of abbreviations used: AIS Automatic Identification System (SIA) 30 SIC Successive I nterference Cancellation SOTDMA Self-Organizing Time Multiple Access Division (TDMA) CSTDMA Carrier Sense Time Multiple Access Division (time division multiple access and carrier detection) LEO Low Earth Orbit 3027175 Methods for providing received AIS data packet data are for example known from DE 10 2012 110 384 A1 or WO 2008/148188 A1. For many reasons, the limited radio range of the vessels and the relatively large coverage areas of the satellites are likely to cause overlaps of AIS data packets which, due to overlapping transmission in the same range of time, can be altered and thus become erroneous. Below is considered the case where AIS data packets are received in an overlapping manner in the same time interval by an AIS receiving device, for example a satellite or a gateway, from different transmitters which have could not agree with the time of the broadcast or at least who did not. This can occur, for example, when several ships with AIS functionality are present in the footprint of the same AIS satellite and many of these vessels are too far apart for a direct radio link between they are possible. In this case, the overlapping transmission of AIS data packets in the same time interval causes alterations in the AIS receiving device and thus errors in the data transmission.

The purpose of the present invention is to indicate a method, a device and a computer program for improving the reliability of the transmission of AIS data packets in the case of scenarios such as that described above. According to the invention, this object is achieved by a method for providing received AIS data packet data, wherein AIS data packets are received by at least one AIS receiving device and the received AIS data packet data. are analyzed automatically, characterized in that such data of an AIS data packet which are erroneous are reconstructed at least in part by means of auxiliary data accessible for the AIS receiving device, which data do not originate from the data packet AIS whose decoding is in progress. The invention provides a method for providing received AIS data packet data, wherein AIS data packets are received by at least one AIS receiving device and the received AIS packet data is automatically analyzed. Such data of an AIS data packet that are erroneous 3027175 are reconstructed at least in part by means of auxiliary data accessible for the AIS receiving device, which data do not originate from the AIS data packet whose decoding is in progress. . The invention has the advantage that the reliability of correct decoding of the AIS data can be improved in an inexpensive and simple to implement manner. This has the advantage that the overall performance of the AIS data transmission can be significantly improved. This improvement is inexpensively feasible by supplementing the component operating software of an AIS system, for example by completing a computer program of a satellite or gateway of an AIS system. The present invention has the further advantage that it does not need to adapt the AIS standard or the AIS data protocol, either on the transmitter side or on the receiver side.

The present invention may further be advantageously combined with other improvements of AIS receiving devices such as, for example, successive interference canceling (CIS) methods, parallel interference cancellation (PIC) methods. ) or multi-user detectors with one or more receiving antennas (Multi-user detector - MUD). This allows a great variability in the implementation of the invention. In an advantageous embodiment of the invention, it can be provided that such data of an AIS data packet, which data is erroneous, is reconstructed at least in part by means of auxiliary data accessible for the AIS receiving device. which do not originate from AIS data packets. The auxiliary data required for this purpose can be of different natures. They have in common that they do not originate from the AIS data packet being decoded or that they do not originate at all from AIS data packets, so that they are available, so to speak, as a priori information. even if the AIS receiving device has not yet been able to receive data from other AIS participants. In this way, an information source model for improving the reception of AIS data packets is implemented.

If the reception device AIS corresponds for example to a part of a satellite, for example a LEO satellite, then it is for example its position coordinates which can be used as auxiliary data or used for the creation of a satellite. auxiliary data. The auxiliary data may be static data stored permanently and which does not vary. The auxiliary data may also be fully or partially modifiable parameters which are updated for example at defined intervals, which may be regular or irregular.

In the case where an at least partial reconstruction of data is carried out by means of the auxiliary data or by means of other data which will be mentioned later such as certain prior knowledge, this can for example be done in such a way that at least the values of a few data bits of a received AIS data packet can be determined using the auxiliary data or prior knowledge data, or at least estimated with some probability. According to an advantageous embodiment of the invention, the reception device AIS has at least two operating states in which it is used alternatively, the operating states having at least: a) a state of global knowledge in which an analysis of the received AIS data packets is performed without taking into account recorded data from AIS data packets received previously, and b) a prior art state of knowledge, in which an analysis of the received AIS data packets is performed taking into account data recorded, as prior knowledge, of previously received AIS data packets in order to reconstruct at least part of the erroneous data of received AIS data packets with the aid of such prior knowledge.

This has the advantage that when receiving AIS data packets, further enhanced reception security can be achieved using the previously received AIS data packets. In the state of overall knowledge, the auxiliary data can be advantageously used for the reconstruction of erroneous data of an AIS data packet.

According to an advantageous embodiment of the invention, the reception device AIS is automatically switched from the state of knowledge prior to the global knowledge state when no AIS data packet correct or correctly reconstructible is received during a predetermined minimum period.

Thus, an automatic reaction is obtained to existing obsolete data stored as prior knowledge so that the probability of correct data reconstruction is not in turn diminished due to obsolete prior knowledge. The predetermined minimum delay may be a fixed delay or a variable delay set according to different criteria. Thus, the minimum delay can be set for example according to ship data, ie depending on the contents of AIS data packets. The minimum delay may also be set based on a predetermined number of expected AIS data packets during that time interval or on a given number of received incorrect AIS data packets.

According to an advantageous embodiment of the invention, the reception device AIS is used permanently or at least temporarily exclusively in the state of global knowledge. Thus, the reception device AIS can be permanently switched to the state of global knowledge for example by means of an adjustable parameter. This may be desirable for example in the case where no pursuit of ships issuing AIS data packets should take place. According to an advantageous embodiment of the invention, at least one of the following AIS transmission parameters is determined or at least estimated using the auxiliary data: frequency, time synchronization, frame synchronization, channel estimation. In this way, the information source model not only makes it possible to improve the security of detection of the individual data but also an improvement of the other reception properties. Thus, with the information source model by means of which certain data bits of an AIS data packet are to be considered as known, these known bits can for example be used as pilot signals for the purpose of synchronization when receiving AIS messages. According to an advantageous embodiment of the invention, at least AIS data packets received without error are stored, in particular memorized in a specific manner to the transmitter, for connection during subsequent time intervals of time. AIS protocol. AIS data logging can take place in coded or uncoded form, ie directly in the form of the received AIS data packet. According to an advantageous embodiment of the invention, the data reconstruction is carried out packet by packet. This allows a precise association between the data to be reconstructed and the corresponding data from previous time intervals.

According to an advantageous embodiment of the invention, the AIS receiving device is used specifically for the transmitter either in a state of global knowledge or in a state of prior knowledge. Thus, the AIS receiving device can be used not only generally for all transmitters, ie for all ships equipped with AIS, in a state of global knowledge or in a state of prior knowledge. But we can rather implement for each transmitter, namely for each ship, a state of global knowledge and a specific state of prior knowledge of a transmitter. Further improvements in the reception of AIS data packets, especially when they are erroneous, are thus possible.

According to the invention, the purpose mentioned at the beginning is achieved by means of a device comprising an AIS receiving device and a supply means for supplying data of AIS data packets received via the AIS receiving device. means of supply being designed to implement a method of the type described above. This also allows to obtain the advantages mentioned above. The means of supply can be realized in particular in the form of a gateway or be part of a gateway of an AIS system. According to an advantageous embodiment of the invention, the AIS receiving device is a component of an AIS satellite, for example a LEO satellite. The AIS satellite may be designed to transmit, with or without preprocessing, the AIS data received to a common coordination unit, for example a gateway. It is here that further processing and in particular decoding of the data packets can be realized.

According to the invention, the purpose mentioned at the beginning is further achieved by means of a computer program comprising program code means which computer program is designed to implement a method of the type described above when the computer program is running on a computer. The computer program can for example be run on a computer of an AIS receiving device, a supply means or a gateway. In this context, AIS receiving device will be understood to mean any device capable of receiving AIS data packets. These may be pure AIS receivers or AIS transceivers on ships, or AIS communication units inside satellites. Below, the present invention is described in more detail with the aid of exemplary embodiments and drawings.

In the drawings, FIG. 1 illustrates an AIS system and FIG. 2 illustrates a reference topology for receiving AIS data packets in a satellite and FIG. 3 illustrates the frame of reception of the data packets in the satellite for the reference topology of FIG. 2 and FIG. 4 illustrates an AIS information source model based on a Markov chain, and FIG. 5 illustrates an AIS receiving device in the form of a functional diagram of a first one. Embodiment and FIG. 6 illustrates an AIS receiving device in the form of a block diagram of a second embodiment. In the figures, the same reference numbers are used for mutually corresponding elements. Figure 1 illustrates the basic structure of an AIS system involving at least one AIS satellite. Ships 10, 20 communicate with each other or with so-called "base stations". An AIS satellite 80 located for example in low Earth orbit (LEO) listens for AIS data communication as illustrated by the dashed arrows. The AIS satellite 80 communicates with an AIS station 90 3027175 situated for example in the terrestrial atmosphere on the ground, and can be made for example in the form of a bridge. As an improvement in the context of the present invention, the gateway 90 has a provisioning means 91 which performs data reconstruction using the auxiliary data. To this end, the AIS satellite 80 transmits the AIS data packets received from the ships 10, 20 and communicates them to the gateway 90. Where they can be analyzed by the provisioning means 91. FIG. provision of six ships 10, 20, 30, 40, 50, 60 within a footprint 100 of an AIS satellite. The ships 10, 20, 30, 40 form a group of ships which are able, thanks to the sufficiently small distance, to realize between them a SOTDMA access control within the partial zone 101 and thus form a AIS radio cell. Similarly, ships 50, 60 located in partial area 102 can provide SOTDMA access control between them and form another AIS radio cell. No data collision can occur within each partial area 101 and 102. But between the partial areas 101, 102, there is no coordination regarding access to the data channel.

Below, it is assumed that the ship 10 transmits a data packet 1, the ship 20 transmits a data packet 2, the ship 30 transmits a data packet 3, the ship 40 transmits a data packet 4 the vessel 50 transmits a data packet 5 and the ship 60 transmits a data packet 6.

Now, we start from the situation illustrated in FIG. 3 which can be in the case of the topology of FIG. 2. FIG. 3 illustrates a time axis with four frames f1, f2, f3, f4 an AIS data transmission implementing SOTDMA for access control. In the simplified example illustrated here, we see that each frame f1, f2, f3, f4 has ten slots s1, s2, s3, s4, s5, s6, s7, s8, s9, s10 in each from which one of the ships can transmit a packet of data. As already mentioned, six ships 10, 20, 30, 40, 50, 60 using the AIS transmission channel are in the footprint 100 of an AIS satellite. It is further assumed that each ship transmits a packet of data per frame. While the access control is performed by SOTDMA in each partial area 101, 102, there is no access control between the vessels of the different partial areas 101, 102. As a result, it may happen that the The data carriers transmit their data packets during the same time interval so that overlapping and thus altered and erroneous data packets are received by the AIS satellite which scans a larger area.

When considering frame f1, it is understood that data packets 1, 2, 4, 6 can be decoded successfully. An alteration occurs at the level of the data packets 5, 3. In this case, the ship 30 assumes that there is a time slot time interval of four for the transmission of data packets which means that the selected time interval will be retained for the next four frames.

According to the invention, the method for providing data can begin to evaluate the position of the ship 50 using the auxiliary data and to evaluate motion parameters for subsequent frames, the method also being able to eliminate the corresponding data packets. . Once the ship's data packets have been successfully removed, it can be seen that the ship's data packets can be decoded correctly because it is possible to resolve the data collision. As a result, the data packets of all ships can be decoded successfully by the method of the invention. As already mentioned, the present invention implements an information source model for improving the reception of AIS data packets. For this purpose, it is possible firstly to use the auxiliary data which are generally known data and which do not depend on AIS data packets. In addition, the information contained in the received AIS data packets can be used as an additional information source. The AIS messages contain, for example, position indications which contain information about the geographical position (latitude and longitude) of a ship. When an AIS receiving device is on board an aircraft or a satellite and the antenna for example scans a reception area in the Mediterranean region, it is known as generally known information that AIS messages are received must be in the Mediterranean region. When it is also taken into account that longitude and latitude are coded in a two's complement representation, the receiver can assume that the most significant bits (MSBs) of the latitude and longitude fields in the AIS data packet are uniquely known. From this can be deduced auxiliary information that can be used to improve the reception of data in an AIS receiving device as follows: The auxiliary information helps the receiver to obtain a better estimate of the data bits and thus to correct to a large extent the wrong data bits. Auxiliary information helps the receiver detect AIS data packets and evaluate transmission parameters such as frequency, time synchronization, frame timing, and channel estimation. Figure 4 illustrates an AIS information source model based on a Markov chain. The AIS receiving device or its information source model can be used in two operating states 110, 111, namely a global knowledge state 110 and a prior knowledge state 111. The global knowledge state is adopted when no exploitable information from received AIS data packets is yet present, for example because no AIS data packets have yet been received or because they were erroneous. As soon as at least one AIS data packet is received correctly, a state transition 112 occurs causing the switch to prior knowledge state 111. If the AIS data packets fail for a period of time or if are not received with correct data contents or checksums, a state transition 113 again causes switching to the state of global knowledge 110. In the global knowledge state, only the available auxiliary data as a priori information is used for AIS data reconstruction. In the state of prior art, the information that can be retrieved from correctly received AIS data packets is used to improve the reception of AIS data. In view of the state transition 113, it is possible, for example, to check whether N AIS data packets have been received with an erroneous checksum or if no data packet has been received from a ship for a given period of time. For this, the value of N can be chosen freely.

Below, the use of the generally known auxiliary data is explained with some examples. For this purpose, the following table first summarizes the classical structure of an AIS class A (AIS position report) message.

35 3027175 12 Field Number of bits Message ID 6 Repeat indicator 2 User ID 30 Navigational status 4 Rate of turn 8 Speed over Ground SOG 10 Position accuracy 1 Longitude 28 Latitude 27 Course over Ground, COG 12 True heading 9 Time stamp 6 Special maneuver indicator 2 Spare 3 RAIM-flag 1 Communication state 19 In the global knowledge state, for example, a statistical analysis of all the fields of an AIS data packet can be performed to create auxiliary data, while taking into account the fact some values are reserved for later use and are not yet used. The method further takes into account that the occurrence of certain values in some fields is more likely than other values. The statistical distribution is therefore not homogeneous but has heterogeneities that can be used.

When considering for example the Message ID field, it can be seen that this field has 6 bits but only values in the range of 0 to 27 are used. Values from 28 to 63 are reserved for future use. Therefore, the fact that the bit of the Message ID field having the highest value is unambiguously known and always takes the value 0 can be used as prior known information and therefore as auxiliary data. By performing an additional analysis, one can also determine the probability with which the Message ID field takes each available decimal value. A statistical analysis can for example give the following probabilities: 302 71 75 13 Decimal value Probability 0 0 1, 2, 3 1/4 4 to 27 1 / (4'24) 28 to 63 0 The probabilities thus determined make it possible to evaluate the probabilities with which each bit takes the value 1: Bit 1 2 3 4 5 6 Probability for 0 0,1250 0,1250 0,1250 0,5 0,5 the value «1» The probability data can be used moreover as auxiliary data for evaluating the value of data bits of an AIS data packet and for reconstructing erroneous data bits as appropriate. In the present example, a 3.53-bit entropy is obtained for the Message ID field. This means that, as long as there is no redundancy, this field could be compressed to 3.53 bits, or for a 6-bit encoding, 2.47 bits are present as redundancy. Such inherent redundancy in the Message ID field can therefore be used to improve the reception of AIS data packets.

In addition, one can consider the fields in which the longitude and latitude of a ship are memorized. Since the ship must be in the area covered by the AIS receiving device, some ancillary data may also be extracted. Below, this method will be explained using example 20 of the field containing the longitude. The numerical value of longitude in the longitude field is a value of one divided by ten thousand minutes coded as a two's complement representation. The positive values correspond to the longitudes East, the negative values to the longitudes West. The field has 22 bits. Here, the highest value bit determines the sign (east, west), the remaining 21 bits indicate the absolute value of the longitude. Assume that an AIS receiving device is scanning an area whose longitude is between 10 and 20 degrees East. If it is further assumed that the vessels present in these scan areas are homogeneously distributed with respect to the longitude, the probability for each bit to take the value 1 is indicated in the following table. Bit 1 2 3 4 5 6 7 Pr («1») 0 0 0 0 0 0 0 Bit 8 9 10 11 12 13 14 Pr («1») 0 1 0 0 1 0,3792 0,6208 Bit 15 16 17 18 19 20 21 Pr («1») 0.4096 0.5840 0.4880 0.4880 0.4928 0.5008 0.5008 Bit 22 23 24 25 26 27 28 Pr («1») 0.4992 0, 4992 0.5 0.5 0.5 0.5 0.5 5 Pr ("1") here means the probability for the value 1. As can be seen, the value can be unambiguously ascertained for 12 of these bits, namely these bits are known unequivocally in all cases. For four other bits, namely bits 13 to 16, there are probability values that are not very close to 0.5. Here too, there is some redundancy that can be exploited. On the other hand, a probability of 0.5 would mean that the bits take the value 0 or 1 in a totally random way. In this case, the binary entropy of the data coding of the longitude field is 14.8698 bits. Thus, the longitude field has a redundancy of almost 50%.

The information already presented relates to auxiliary information which is always known and therefore already present in the state of global knowledge. The fact of using in addition the state of prior knowledge makes it possible to further increase the probability of reconstruction of the erroneous data bits. It is assumed that the information source model is in the state of prior knowledge for a particular ship 10. Accordingly, the geographical position of the ship 10 at a time T as well as its direction of travel and speed are known. . Thanks to this other information, the position of the ship at a time T + "tau" can be estimated relatively simply. When for example a ship moving at a certain speed is detected at time T at a longitude of 10 degrees east, then assuming that the distribution is homogeneous, it is possible to estimate the position of the ship at time T + "tau" as being of 10.045 degrees +/- 0.05 degrees. Now, therefore, 19 bits of the longitude field are known based on the generally known auxiliary information already presented, and the entropy is then 8.99 bits. In another advantageous improvement, the relationships between the different fields of an AIS data packet can be taken into account for data reconstruction. When a ship at sea is, for example, very far from the coast, it is very likely that it is moving at high speed. Thus, when an AIS data packet is received from a ship at sea and a speed of zero or almost zero is indicated, it is very likely that the AIS data packet is erroneous. In the information source model, this can be taken into account by using a common distribution of the different AIS fields. This distribution can reflect the relationships between the different fields. Example: - Latitude and longitude: this information allows to know if the 15 coordinates of the ship are located on the mainland. - Speed, latitude and longitude: in a port it is very likely that the ship is moving at low speed, in open sea, it is more likely that it moves at high speed.

This can then be achieved with a decoder installed in an AIS receiving device or in a gateway, some examples of which are further presented below.

Example 1: Synchronization Auxiliary data can be used for detection and synchronization. One possibility is to use only the bits whose value is already known accurately. Detection and estimation are performed using the training sequence and the start and end flags of an AIS message which has a total of 40 bits. When only the known bits with the probability 1 are used for this purpose, then the decoder, for example the AIS receiving device, can establish longer training sequences to improve the detection and estimation results. Assuming, on the basis of the indicated information source model, for example that the longitude field data are evenly distributed between 10 degrees and 20 degrees east, 10 bits of the longitude field are known with accuracy and can be used for synchronization for example by extending the drive sequence from 40 bits to 50 bits. This can be done in a similar way with the other fields of an AIS message.

Example 2: Multi-user detection The AIS receiving device may for example be designed as illustrated in Figure 5. It has an input buffer 120, in which the received AIS data packets are stored in raw form. . There is also a detection unit 121 to which the raw data is transmitted by the buffer 120 and in which they are detected. In addition, there is a checksum demodulation and decoding unit 123. The results of the detection unit 121 as well as the raw data of the input buffer 120 are transmitted thereto. The AIS data packets 15 are decoded and checked within the decoding unit 123. Once decoded the AIS data 125 is output through an output. There is also a remodulation unit 124. In addition, the information source model according to the invention is present in the form of block 122. This unit transmits the auxiliary data 126 to the detection unit 121 as well as to the decoding unit 123. AIS data packets are detected in the decoding unit 121 using the auxiliary data 126. As soon as an AIS data packet has been detected, it is decoded by the decoding unit 123. The checksum is also verified.

Here again, the auxiliary data 126 is used. The use of auxiliary data 126 already makes it possible to eliminate certain errors or to reduce them on the basis of probabilities. The data that has first been determined, fully or partially reconstructed are again modulated according to the AIS protocol by the remodulation unit 124 and then sent back to the buffer 120. The interference of the remodulated AIS data packets is then subtracted. by the input buffer 120. The data thus obtained can be detected again by the detection unit 121 and decoded by the decoding unit 123. This eliminates the disturbances in the raw data received. To improve the reception power, it is possible to perform software decoding of the checksum.

In the example illustrated in FIG. 5, a Successive Interference Cancellation (Successive Interference Cancellation) method can be implemented to improve the reconstruction of erroneous data. It is also possible to implement a "Partial Successive Interference 5 Cancellation" method. In this case, it is possible to eliminate at least some of the errors in an AIS data packet, even in the presence of an erroneous checksum. Example 3: Multi-User Detection with Integrity Verification FIG. 6 illustrates another embodiment of an AIS receiving device, in which, compared to the embodiment of FIG. 5, a verification unit of FIG. Integrity 128 has been added on the path between the decoding unit 123 and the remodulation unit 124. Moreover, the embodiment of FIG. 6 is similar to that of FIG. Integrity 128 receives prior knowledge 127 from information source model 122. These are used in integrity check unit 128 to improve the reconstruction of erroneous AIS data. In the end, we will obtain even better performance in correct AIS data 125.

In other examples, another method, such as, for example, a "Parallel Interference Cancellation" method or another suitable method, in particular, may be used in place of the method of successively canceling interference. a method capable of using the auxiliary data and / or prior knowledge.

Claims (12)

CLAIMS: 1. A method for providing received AIS data packet data (1, 2, 3, 4, 5, 6), wherein AIS data packets (1, 2, 3, 4, 5, 6) are received by at least one AIS receiving device (80) and the data of the received AIS data packets (1, 2, 3, 4, 5, 6) are automatically analyzed, characterized in that such data of a packet of AIS data (1, 2, 3, 4, 5, 6) that are erroneous are reconstructed at least in part by means of auxiliary data (126) accessible for the AIS receiving device (80), which data do not originate from the AIS data packet (1, 2, 3, 4, 5, 6) whose decoding is in progress. 2. Method according to claim 1, characterized in that the AIS receiving device (80) has at least two operating states (110, 111), in which it is used alternately, the operating states having at least: a) a global knowledge state (110), wherein an analysis of the received AIS data packets (1, 2, 3, 4, 5, 6) is performed without taking into account recorded data from received AIS data packets previously (1, 2, 3, 4, 5, 6), and b) a state of prior knowledge (111), in which an analysis of received AIS data packets (1, 2, 3, 4, 5, 6) is performed by taking into account recorded data, as prior knowledge, of previously received AIS data packets (1, 2, 3, 4, 5, 6) in order to reconstruct at least partially erroneous data packet data AIS with the help of such prior knowledge (127). 3. Method according to claim 2, characterized in that the AIS receiving device (80) is automatically switched from the state of prior knowledge (111) to the state of global knowledge (110) when no AIS data packet. correct or correctly reconstructible (1, 2, 3, 4, 5, 6) is not received for a predetermined minimum time. Method according to claim 2 or 3, characterized in that in the state of global knowledge (110), the auxiliary data (126) is used for the reconstruction of erroneous data of an AIS data packet (1). , 2, 3, 4, 5, 6). 5. Method according to any one of claims 2 to 4, characterized in that the AIS receiving device (80) is used permanently or at least temporarily exclusively in the state of global knowledge (110). Method according to one of the preceding claims, characterized in that at least one of the following AIS transmission parameters is determined or at least estimated by means of the auxiliary data (126): frequency, time synchronization , frame synchronization, channel estimation. 7. Method according to one of the preceding claims, characterized in that at least received AIS data packets (1, 2, 3, 4, 5, 6) without errors are stored, in particular stored in a specific manner. to the transmitter, for use during subsequent AIS protocol time slots. 20 8. Method according to any one of the preceding claims, characterized in that the AIS receiving device (80) is used in a specific manner to the transmitter either in a state of global knowledge (110) or in a state of prior knowledge. (111). 25 Method according to one of the preceding claims, characterized in that such data of an AIS data packet (1, 2, 3, 4, 5, 6) which are erroneous, are reconstructed at least in part by auxiliary data means (126) accessible for the AIS receiving device (80) which do not originate in the AIS data packet (1, 2, 3, 4, 5, 6). 30 A device comprising an AIS receiving device (80) and a supplying means (91) for providing AIS data packet data (1, 2, 3, 4, 5, 6) received via the device AIS receiver (80), characterized in that the supply means (91) is adapted for carrying out a method according to any one of the preceding claims. 3027175 20 11. Device according to claim 10, characterized in that the supply means (91) is designed as a bridge (90) or part of a bridge (90). 5 A computer program comprising program code means adapted for carrying out a method according to any one of claims 1 to 9, when the computer program is run on a computer.