RU2527189C1 - Method for multichannel reception and transmission of navigation safety information - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: existing single-channel method of receiving navigation safety information through narrow-band direct printing in the short-wave range with an allowable error threshold thereof of 4% can be replaced with extended verbal instructions of message symbols by a digital selective call, wherein a shipborne receiver may collect symbol-by-symbol even a message that is received distorted on all transmission channels thereof.

EFFECT: high reliability of receiving navigation safety information, shorter time for multichannel transmission of messages owing to compression of text, compatibility of the disclosed method with the existing level of usage of shipborne digital selective call receivers/controllers.

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Description

The invention relates to communication technology and can be used in the maritime mobile service to ensure reliable automatic reception of information on the safety of navigation in the short-wave range on board ships that are located in any region of the oceans.

The well-known "Multichannel system for transmitting and receiving discrete information" (see RF patent No. 2207729 H04J 3/00, published June 27, 2003), in which the distribution of a different number of low-speed communication channels at the input of the multiplexer between discrete message sources operating at different speeds in the process messaging is carried out using a transmitting switch and a control unit and the inverse transformation of M low-speed channels into N channels of information reception.

Also known is the "System and method for transmitting and receiving data" (see RF patent No. 2338324 H04J 3/00, bull. 31 dated 10.11.2008), in which the basis is a two-dimensional data array for a digital television broadcast network.

A common disadvantage of analogues is the requirement for increased stability of synchronization of transmitted messages. In the short wavelength range, the implementation of such a requirement is rather problematic. Multipath reflection from the ionosphere, and then from the earth, then again from the ionosphere, etc. does not allow the use of analogs in the short wavelength range.

The closest to the achieved technical result is the transmission of information on the safety of navigation through narrow-band letter printing. The transmission is carried out by the method of correction of received errors (Collective B-mode operation) [1] by a network of coastal radio stations of various countries according to a schedule simultaneously from one radio station at frequencies of 4210 kHz, 6314 kHz, 8416.5 kHz, 12579 kHz, 16806.5 kHz, 19680.5 kHz, 22376 kHz and 26100.5 kHz [2]. Sending and receiving text is in English. To receive the transmitted message on the safety of navigation, you should successfully select one of the eight channels of short-wave communication. Features of the message transmission method Collective B-mode operation allow the result in which the message is considered successfully received if the number of distorted characters does not exceed 4% [3]. In this case, the message identifier is stored in the receiver's memory so as not to receive the same message again in the next transmission period from the coastal radio station [3].

The disadvantage of the prototype is the likelihood of an emergency at sea, if the number of acceptable errors includes important information for the safety of navigation.

The aim of the invention is to increase the reliability of the reception of information on the safety of navigation transmitted in the short wavelength range. This will allow you to be from 4% of permissible errors in the text, which is a potential danger of accidents at sea.

To achieve this goal in the method of receiving and transmitting information on safety of navigation, which consists in introducing a new interpretation of the seven information bits in the ten-bit volume of each of the characters in the set of characters and the interconnection of characters in the modernized digital selective call, which allows you to compress the transmitted message text by using letter digrams , and trigrams, and digital groups by introducing paired specialized labels in the text, which after its simultaneous re-writing Achi on several channels of the shortwave range, even if there are errors on all reception channels, the message assembly is restored using one to four levels of operation, printed automatically on paper in English and recorded in the memory of the ship receiver in the form of text and a mark for the depth of the assembly level of a successfully received message while the number of operation levels of the message assembly is determined by calculating the reference checksum of the message and comparing it with the actually received checksum source of fragments or the newly obtained corrected message fragments by replacing the distorted characters undistorted symbols defined in the set of six pieces of the received message with the least amount of distortion characters - three in the main time slot and three in the spare time position.

The technical result achieved is an increase in the reliability of reception of information on navigation safety, a decrease in the time of multi-channel message transmission due to text compression, the compatibility of the proposed method with the existing level of use of ship receivers-controllers of digital selective calling.

The essence of the invention lies in the fact that the proposed method of multichannel reception and transmission of information on the safety of navigation significantly increases the reliability of reception in the short-wave range. This will make it possible to avoid 4% of permissible errors in the text, that is, eliminate the potential danger of an accident at sea by eliminating the uncertainties of the information received.

New features of the method of multichannel reception and transmission of information on the safety of navigation are the possibility of transmitting semantic text in a digital selective call by compressing the transmitted text without loss of information, assembling the received message, even if the message is received with errors on all channels of its transmission. As for the compression of the text, the counting of the number of characters of the source text of the message, which is presented in figure 2, when presented by means of narrow-band letter printing, it will be possible to get a value equal to 362. This value also takes into account the characters of alphabetic and digital registers, spaces between words, line breaks and carriage translations [1]. Each of the characters of the source text is transmitted twice through narrow-band letterpress, and the beginning (32 characters with minimal synchronization) and the end of the transmission of such text have their own characteristics. Therefore, the transmission time of the source text on the safety of navigation by means of standard narrow-band letter printing (in Collective B-mode operation with a minimum time of use) [1] will be equal to

(32 characters + 2 · 362 characters) · 0.07 s / character + 2 s = 54.92 s.

For the transmission of this source text, presented in figure 2, through the extended digital selective call (figure 3, figure 4) it will take a time equal to 418 characters · 0.1 s / character + 0.2 s (transmission of B / Y pairs) = 42.0 s. Which is almost 24% faster than transmitting the source text using narrow-band letterpress.

The analysis of the prior art made it possible to establish that analogues that are characterized by a combination of features that are identical to all the features of the claimed method are absent, which indicates the compliance of the claimed invention with the condition of patentability "novelty".

Search results for known solutions in this and related fields of technology in order to identify features that match the distinctive features of the claimed object from the prototype showed that they do not follow explicitly from the prior art. The prior art also did not reveal the popularity of the impact provided by the essential features of the claimed invention, the transformations on the achievement of the specified technical result.

The inventive method is illustrated by drawings, in which:

figure 1 shows the interpretation of the characters for the pointer (101) format of the text message on the safety of navigation;

figure 2 is the text of a typical source message on the safety of navigation;

figure 3 is a fragment of the presentation of the original message through an upgraded digital selective call from the beginning to the middle;

figure 4 is a fragment of the presentation of the original message through an upgraded digital selective call from the middle to the end;

figure 5 is a method of assembling a previously received error message on communication channels;

6 is an example of a fragment of a message received with errors on all channels;

Fig.7 - selected messages with fewer errors for both time positions;

on Fig - execution of the operation "Assembly 2" in a previously received message;

Fig.9 - the operation "Assembly 3" in a previously received message.

Each of the characters used in a conventional digital selective call consists of 10 bits of two types - B and Y [4]. The first seven bits are information bits, and the last three bits are bits that allow you to determine the presence of an error in a group of the first seven information bits. In the text below, a record of the form (99), (100), etc. corresponds to the conversion of the first seven information bits to their decimal representation. A typical (pre-existing) digital selective call uses 128 characters, of which a variety of (00) to (99) are used to transmit digital information about the position of the ship, the time it takes to determine the position of the ship, the channel number or the frequency of subsequent communication via other communication systems (radiotelephony or narrow-band typography). Many characters from (100) to (127) are used as command characters, the same character being interpreted depending on the type of message format [4].

The use of an unused resource by introducing a new format indicator, for example, in the form of a symbol (101), allows you to indicate the subsequent transfer of navigation safety information. This allows you to enter a different interpretation of the transmitted characters. In any of the languages, when using alphabetic writing of a text or a substitute for hieroglyphic text, there are stable combinations of two letters (alphabetic bigrams) and three letters (alphabetic trigrams). Using the proposed new message format - the transmission of text on the safety of navigation allows you to enter a different new display of letters, numbers, letter bigrams and letter trigrams on a set of 125 characters (figure 1). This is three characters less than 128, because the characters (117), (122), (127) are used only as types of message endings in the same way as in a regular digital selective call.

The proposed symbol (10) (in a new mapping to a set of 125 characters) will allow you to easily go to the symbol table of a (other) national language (default), which can be constructed similarly to the one described below. When transmitting information on the safety of navigation, groups of numbers are often used to indicate time intervals. To speed up the process of transmitting numbers in this format (101), it is proposed to use the @ mark. Its use, for example, will mean that the symbol (32) should not be taken as the letter V, but as two 32 digits. This condition becomes invalid after the repeated appearance of the @ mark. With a different format pointer, the @ mark can also be used for other purposes. The designation of the hemispheres N, S, E, W and the way of representing the coordinates of the sea areas remain the same as in a regular digital selective call when transmitting coordinates. But for this we introduce the label #, which, when used twice, should indicate the beginning and end of the transfer of coordinates of some positions according to the principle that coincides with the usual digital selective calling.

The use of alphabetic bigrams and trigrams, as well as the introduction of the use of the @ mark before and after a group of four or more digits in a row, the use of a pair of # marks in the text with a pointer symbol of the proposed format (101) allow you to compress the transmitted message without loss of information. In this case, the source text (FIG. 2) transmitted by the upgraded digital selective calling will look like that shown in FIG. 3. and figure 4.

For compatibility with the existing experience of using digital selective calling, the beginning (bitwise - B / Y and character-by-symbol DX / RX-i synchronization of the transmitted message) and the end of any of the digital selective calling formats are saved without change. Two temporary transmission positions of each of the symbols and a method for determining the checksum, illustrated by the designation ⊕2, are also stored. The method of transmitting two types of bits (B / Y) used to represent characters as analogs of a logical zero and a logical unit in a radio channel remains unchanged. The end type of the message format, expressed as a character (127), also means that the reception of this message should not be confirmed using digital selective calling [4]. The explanatory labels in FIG. 3 and FIG. 4, which are underlined, are identical to a conventional (pre-existing) digital selective calling. The underlined explanatory labels of the symbols in FIG. 3 and FIG. 4 correspond to the new in the proposed upgraded digital selective calling.

It is proposed to transmit textual information on navigation safety using multiple channels (from three or more) in the short-wave range using an upgraded digital selective call simultaneously on all channels from the coastal radio station. The above-described possibility of transmitting textual information on the safety of navigation allows us to propose a multi-channel algorithm for receiving messages on the safety of navigation, shown in Fig.5. Functional relationships in the receiver's memory are shown by dashed arrows. In this algorithm, in each channel, for both time positions, a label is assigned that indicates the number of errors (QO) in the received message fragment. This opportunity arises through the use of the last three check bits of each of the ten bit characters.

As a result, three message fragments in the main temporary position DX and three message fragments in the standby temporary position RX with the lowest values of the number of errors (QO) will be selected. In each of the temporary positions, these fragments are assigned a queue tag (label) in a possible subsequent message assembly procedure. The queue tag will be considered the sequence in the possible subsequent assembly of the message from the received message fragments on different channels. The smaller the number of errors in the message fragment, the lower its number in the queue, that is, the lower the tag number. Tag numbering is separate for each of the temporary positions.

The constancy of the location of the symbol of the transmitted checksum of the message (relative to the end of the message) in both temporary positions allows us to evaluate the presence or absence of errors in each of these best six message fragments by comparing the transmitted and actually calculated checksum. The principle of calculating the checksum in the proposed modernized and in the usual (existing) digital selective call remains the same - even vertical parity for the first seven bits of the characters in the group. Such a group of characters for calculating the checksum includes all characters from the second format pointer (101) to the first character of the ending type (127) inclusive for each of the temporary positions of the message format [4]. It is proposed to verify the transmitted checksum at the receiving site by determining the majority of the same values in the standard positions of its placement in these six fragments with the lowest values of QoS. If it can be determined, then its value is called the reference checksum (ACS). Now, the method compares with the reference checksum the actually obtained checksums on all channels in both time positions. If they coincide, at least one of the channels prints the received text and registers it in the device’s memory as successfully received on one of the eight channels.

If the ACS does not coincide with the accepted checksum at both temporary positions or at least at one of the temporary positions on all receive channels, the method selects one of the three message fragments with the lowest queue number (queue tag) for the DX temporary position and one of the three message fragments with the smallest queue tag for the RX temporary position. The newly received checksum in both positions is compared with the ACS. If the comparison is successful, the received text is printed out and registered in the device’s memory with the mark “assembly 1”.

If the ACS does not coincide with the newly received checksum in both temporary positions or at least in one of the temporary positions, the method tries to collect a message from fragments. At the same time, from the message fragment with the tag of the 2nd queue correctly received characters replace erroneously received characters in the message fragment with the tag of the 1st queue. Such actions are performed separately for both the temporary position DX and the temporary position RX. The newly received checksum in both positions is compared with the ACS. If the comparison is successful, the printed text is printed and registered in the device’s memory with the mark "assembly 2".

If the ACS does not coincide with the newly received checksum in both temporary positions or at least in one of the temporary positions, the method attempts to reassemble the message from fragments. In this case, correctly received characters from the message fragment with the tag of the 3rd queue replace erroneously received symbols in the previously received message fragments of the previous assembly. The newly received checksum in both positions is compared with the ACS. If the comparison is successful, the printed text is printed and registered in the device’s memory with the mark “assembly 3”.

If the ACS does not coincide with the newly received checksum at both temporary positions or at least at one of the temporary positions, the method tries to collect a message from two message fragments, which are presented from what ultimately happened. Now the method is guided by the mutual substitution of distorted characters from DX and RX temporary positions. In this case, it is necessary to take into account that mutually substituting characters are exactly four characters behind in the temporary position RX with respect to the temporary position DX. The newly received checksum in both positions is compared with the ACS. If the comparison is successful, the printed text is printed and registered in the device’s memory with the mark "assembly 4". In case of discrepancy between the ACS and the newly received checksum in both temporary positions, the message is considered unacceptable (Fig. 5). After successfully printing the message or the missed message, the receiver's memory is alerted to the next message.

A multi-channel method of receiving and transmitting information on the safety of navigation works as follows. Figure 6 shows the final fragment of the message, which was fully presented above in figure 3 and figure 4. The message is received simultaneously on eight channels. At the same time, we believe that bitwise and character-by-character synchronization on these channels was quite successful as well as in the existing ordinary digital selective calling. That is, two consecutive RX-n characters and one DX character between them were correctly recognized, either one of the RX-n characters and two neighboring DX characters was successfully received, or three consecutive RX-n characters were correctly recognized [4]. We assume that the symbol of the message format indicator (101), which is devoted to the transmission of information on the safety of navigation, has also been successfully adopted in at least one of four attempts (two symbols of the format indicator are located in two temporary positions). The location of format pointers is strictly fixed in digital selective calling formats. Symbols with seven information bits are not confirmed by three check bits (information or check bits are distorted), are indicated by an asterisk (*). The ship receiver analyzes the recorded message on eight channels in eight entries in its memory. The number of errors in the received message is determined, which is expressed in FIG. 5 as QoS values separately for the main temporary position DX and for the backup temporary position RX. The upper part of the message record of each channel corresponds to the main time position DX, and the lower part of the message record of each channel corresponds to the standby time position RX. Since not the whole message format is shown, the value of the number of errors (QO) for each channel was conditionally determined by the product of the error repetition rate in the message fragment (Fig. 6) by the entire message volume. The reference checksum is determined by the method of most identical values in the standard positions of its placement in these six fragments with the lowest values of QoS. This value is symbol (59). This is a character that is located in the third from the end position of the message format for the temporary position DX and the first from the end position of the message format for the temporary position RX (Fig.6). Symbol (59) was obtained by estimating the majority of matching values in the position of the checksum. When calculating the checksum on each of the eight channels, its result does not coincide with the reference checksum on either channel or in any of the temporary positions. In this case, two fragments with the lowest value of the number of errors (QO) from different time positions are selected. Such fragments will be a message fragment from the DX position with KO 28 (1st stage tag) and a message fragment from the RX position with KO 29 (1st stage tag). The checksum calculation at both temporary positions will not coincide with the reference checksum. Then, the distorted characters in the message fragment with KO 28 are replaced from the message fragment with KO 48 (tag of the 2nd queue) for the temporary position DX. At the same time, the distorted characters in the message fragment with KO 29 are replaced from the message fragment with KO 47 (2nd queue tag) for the temporary position RX (Fig. 8). Again, the method performs a checksum calculation and its comparison with the reference checksum. The value of the reference checksum matches only for the temporary position DX. Therefore, the assembly of the message fragment at the RX position continues. In this case, the distorted symbol in the obtained intermediate result is replaced by a message fragment from the RX position with KO 58 (3rd queue tag) (Fig. 9). When comparing with the reference checksum, the resulting checksum is completely identical in both temporary positions. In this case, the message is printed on the printer and the AA25 message marker is stored with the “Assembly-3” label added when printing on the printer and in the receiver's memory. In the future, the memory of the ship receiver is prepared to receive the next message.

Literature

1. Recommendation ITU-R M.625-4 (03/2012). Direct-printing telegraph equipment employing automatic identification in · the maritime mobile service. http://www.itu.int/rec/R-REC-M.625-4-201203-I/en.

2. International Telecommunication Union CCIR Recommendation 688 (1990). Annex 3-5-6. Technical characteristics for a high frequency direct-printing telegraph system for promulgation of high seas and navtex-type maritime safety information.

http://www.itu.int/dms_pubrec/itu-r/rec/rn/R-REC-M.688-0-199006-I!!PDF-E.pdf

3. International Maritime Organization Resolution A.700 (17) (Adopted 6 November 1991). Performance standards for narrow-band direct printing telegraph equipment for the reception of navigational and meteorological warnings and urgent information to ships (MSI) by HF. http://www.imo.org/blast/blastData.asp7doc_id=10859&filename=A700(17).pdf.

4. International Telecommunication Union Recommendation ITU-R M.493-12 (2007). Digital selective-calling system for use in the maritime mobile service. http: //http.7/www.itu.int/rec/R-REC-M.493-12-200703-S/en.

Claims (1)

The method of receiving and transmitting navigation safety information consists in introducing the interpretation of seven information bits in a ten-bit volume of each of the symbols in a plurality of symbols and the interconnection of symbols in a digital selective call expanded by explanatory lettering of symbols of a message, which allows compressing the transmitted message text by using alphabetic digrams and trigrams , and digital groups by introducing paired labels in the text, which after its simultaneous transmission on several channels the shortwave range, even if there are errors on all reception channels, the message assembly is restored using one to four levels of operation, printed automatically on paper in English and recorded in the memory of the ship receiver in the form of text and a mark for the depth of the assembly level of the successfully received message, while the number the levels of the operation, the message assembly is determined by calculating the reference checksum of the message and comparing it with the actually received checksum of the original received fragments or in the newly received corrected message fragments by replacing distorted characters with undistorted characters defined in the set of six fragments of the received message with the least amount of distorted characters - three in the main temporary position and three in the standby time position.

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