CN107911196B - Radar track message transmission method - Google Patents

Abstract

The invention discloses a radar track message transmission method, wherein a sending end encodes a radar track message and then sends the radar track message, and a receiving end decodes a received compressed message. The encoding comprises the following steps: 1, reading a frame of radar track message and generating magic words; 2 judging whether the key field is hit; if not, go to step 3; if hit, defining the current frame as a P frame, adding a frame header identifier of the P frame and magic words retrieved from an I frame file, solving a residual error of the P frame relative to the I frame, carrying out simplified Huffman coding on the residual error, and turning to the step 4; 3 searching whether the magic word has repeated items in the magic word list; if yes, defining the current frame as a non-archive I frame, and constructing a code stream; otherwise, defining the current frame as an I frame, and constructing a code stream; 4, if the next message exists, skipping to the step 1, otherwise ending the coding. By adopting the method to transmit the radar track message, the transmission resource consumption of the same data can be reduced, the message compression ratio is improved, and the integrity and the real-time performance of data transmission are ensured.

Description

Radar track message transmission method

Technical Field

The invention belongs to the technical field of radar data processing, and particularly relates to a lossless compression transmission method for radar track messages.

Background

The radar track message is composed of trace point messages, and the trace point messages are organized according to a certain fixed protocol. Radar track messages are typically data encoded and compressed prior to transmission.

The data compression method can be divided into two types according to whether the information amount before and after compression is lost, namely lossy compression and lossless compression. Lossy compression refers to reconstruction (or restoration and decompression) by using compressed data, and the reconstructed data is different from the original data; lossless compression refers to that after compressed data is used for reconstruction, the data is completely the same as original data, and typical lossless compression methods include run-length coding, huffman coding, arithmetic coding and the like. The basic principle of the Huffman coding is that coding is carried out according to the probability of the source data symbols, short code words are coded for information symbols with high occurrence probability, and long code words are coded for information symbols with low occurrence probability, so that the source data can be represented by using the code symbols as few as possible. Theoretical research shows that the Huffman coding method is a better coding method close to the upper limit of the compression ratio, and meanwhile, the coding method has high efficiency, high operation speed and flexible implementation mode, and is widely applied in the field of data compression from the 20 th century to the present in the 60 th.

The radar track message is directly encoded by the data compression encoding method, information which does not change among continuous trace point data is not utilized, transmission resources are still consumed for the same data among the messages, and when the data volume is large, real-time processing of the data is affected.

Disclosure of Invention

The purpose of the invention is as follows: the invention discloses a radar track message transmission method aiming at the problems in the prior art, which is used for compressing and encoding radar track messages at a sending end and decoding the radar track messages at a receiving end, so that the transmission resource consumption of the same data can be effectively reduced, the compression ratio of the messages is improved, and the integrity, the reliability and the real-time performance of data transmission are ensured.

The technical scheme is as follows: the invention adopts the following technical scheme:

a radar track message transmission method, a sending end sends out a radar track message after encoding, and a receiving end decodes a received radar track compressed message; the encoding of the radar track message comprises the following steps:

(C1) reading a frame of radar track message, and generating magic words according to message data;

the magic word is a check code generated by the message data by adopting a check algorithm; the magic word in the invention is used for generating a unique check code by 16-bit cyclic redundancy check after two fields of message type and message length are removed from message data.

(C2) Judging whether the key field is hit; if not, go to step (C3); if hit, defining the current frame as P frame, adding P frame header mark and magic word searched in magic word list to the message, solving the residual error of P frame relative to I frame, carrying out simplified Huffman coding to the residual error, and turning to step (C4);

the key field is a multi-field set capable of identifying message characteristics, and the key field comprises a message length, an FSPEC field, a data source identifier and a batch number.

(C3) Searching whether the magic word has repeated items in the magic word list; if yes, defining the current frame as a non-archive I frame, and constructing a code stream; otherwise, defining the current frame as an I frame, constructing a code stream, and adding the magic words and the I frame code stream into a magic word list;

(C4) judging whether a next message exists, if so, jumping to the step (C1), otherwise, ending the encoding;

the radar track compressed message decoding comprises the following steps:

(D1) reading a frame of radar track coding message, judging whether the frame is a filing I frame message, if so, generating magic words, analyzing and outputting a code stream, and adding the magic words and the I frame code stream into a magic word list; turning to step (D4);

(D2) judging whether the message is a non-filing I frame message, if so, generating magic words, analyzing and outputting a code stream; turning to step (D4);

(D3) judging whether the message is a P frame message, if so, extracting magic words in the message, searching the same magic word message in a magic word list, restoring a message structure and a key field corresponding to the P frame, decoding simplified Huffman coding content, and constructing and outputting a decoding code stream; turning to step (D4);

decoding simplified Huffman coding content in a P frame message comprises the following steps:

reading in the code stream in sequence, and if the current code element is 0, directly copying the byte content of the corresponding I frame; if the current code element is 1, copying the byte content behind the current code element 1, and combining the decoded byte content into a new code stream for outputting.

(D4) And (D) judging whether a next message exists, if so, turning to the step (D1), otherwise, ending the decoding.

Has the advantages that: compared with the prior art, the radar track message transmission method disclosed by the invention has the following beneficial effects: 1. the idea of intra-frame and inter-frame coding is introduced into radar track message compression, the same information among continuous trace point data is repeatedly utilized, and the compression ratio of the message is greatly improved by removing redundant information among similar messages; 2. generating magic words based on a published reliable verification algorithm, uniquely identifying the filing I frame by the magic words, simplifying the identification into a two-byte check code, and performing special treatment on repeated magic words which may appear, so that the uniqueness of the identification is ensured, and the retrieval of the filing I frame by a decoding end is rapid and effective; 3. by defining various code streams and organization forms thereof, coding messages and non-coding messages are effectively distinguished, and are distinguished through frame header marks, so that good orders are established at the two ends of coding and decoding; 4. residual errors relative to the frame I are calculated for the frame P, simplified Huffman coding is carried out on the residual errors, and transmission of the same data can be effectively reduced; 5. the method disclosed by the invention can effectively reduce the transmission resource consumption of the same data and improve the compression ratio of the message; meanwhile, under the condition of limited channel bandwidth, resources can be effectively saved, the integrity, reliability and real-time performance of data transmission are guaranteed, the transmission efficiency of the message is greatly improved, and the real-time processing and using effects of the message are enhanced.

Drawings

Fig. 1 is a block diagram of an embodiment of a transmission method disclosed in the present invention;

FIG. 2 is a diagram illustrating the variation of P frame reference I frame in an embodiment;

FIG. 3 is a diagram illustrating variations of P frames with reference to I frames in an embodiment;

FIG. 4 is a flow chart of encoding in an embodiment;

fig. 5 is a flowchart of decoding in an embodiment.

Detailed Description

The invention is further elucidated with reference to the drawings and the detailed description.

The embodiment describes the radar track message transmission method disclosed by the invention in detail by constructing a transmission system comprising a sending end and a receiving end, wherein a schematic diagram of the transmission system is shown in fig. 1 and comprises the sending end and the receiving end, wherein the sending end completes the compression and encoding of the radar track message, and the receiving end decodes the compressed message, in the embodiment, the widely adopted part 7 of the European aviation safety organization surveillance Data exchange Standard document is taken as an example, the standard format CAT010 message format of single sensor scene motion Data information is taken as an example to describe the transmission process of the radar track message, the protocol belongs to the radar track message stated in the invention, the format of a protocol frame is shown as "< Cat > < L en > < Fspec > < Data >", each field is separated by < > for distinguishing, and the information represented by each field is as follows:

cat-message type description CAT, one byte;

l EN-Length field L EN, two bytes;

Fspec-FSPEC indicates which fields in the message structure are in length-variable;

Data-Data;

the specific format is described as follows:

<0><1><2><3><4><5><6><7><8><9><10>

field <0 >: 0a, message type description, which indicates that the message is single sensor scene motion data information standard format CAT010 target data, one byte;

field <1 >: length field, two bytes;

field <2 >: FSPEC, which indicates which fields in the message structure are in length-variable;

field <3 >: data source identification, two bytes;

field <4 >: message type, one byte;

field <5 >: describing the target and lengthening;

field <6 >: time, three bytes;

field <7 >: polar coordinates, four bytes;

field <8 >: rectangular coordinates, four bytes;

field <9 >: speed and heading, four bytes;

field <10 >: lot number, two bytes.

The radar track message transmission system constructed in this embodiment is divided into four types of code streams, defined by frame header identifiers, which are transparent transmission, filing I frame, non-filing I frame, and P frame, and corresponds to different types of code streams, and the organization method is specifically as follows:

(1) transparent transmission: transparent transmission identification c2+ original message;

(2) and (3) filing I frame: the identification c3+ of the filing I frame removes the original message of the message type and length field;

(3) no-archive I frame: un-documenting I frame identification c5+ removing the original message of message type and length field;

(4) p frame: p frame id c7+ corresponds to the documenting I frame magic word + huffman coding result.

Assuming that two messages need to be continuously transmitted, the specific contents are as follows:

Q1：0a 00 1b f7 a0 01 00 01 61 00 61 9f 9e 00 52da aa 05 5e 00bb 00 213a 78 00 8a；

Q2：0a 00 1b f7 a0 01 00 01 61 0000 009e 00 52 da aa 05 5e 00bb 0021 3a 78 00 8a。

as shown in fig. 4, Q1 and Q2 are received in sequence, and the work flow of the whole encoding is as follows:

step 1, reading a message;

step 2, judging whether the flight path is a flight path report;

judging whether the message is a flight path message or not according to a message type field, namely a field <0>, if so, jumping to a step 4, and if not, executing a next step 3; the first byte of the message Q1 is 0a, which is judged as a track message,

step 3, transmitting the message in a transparent way;

if the data is not the flight path data, adding a transparent transmission identifier to the message, transmitting the message in a transparent manner, and then jumping to the step 12;

step 4, generating magic words;

the magic word is a 16-bit cyclic redundancy check code (CRC16) generated for the filing I frame message, the CRC16 algorithm is used in the method, but the method is not limited to the method, and the disclosed check algorithm can be applied to the generation of the magic word. In this embodiment, the byte sequence range generated by the magic word is the message content excluding the two fields of the message type and the message length, but is not limited to this range, and can be determined according to the actual situation. Generating a unique check code for the message without the two fields of the message type and the message length by adopting a 16-bit cyclic redundancy check pair, taking the unique check code as a magic character, and then entering the step 5; in this embodiment, the message from which the field <0> and the field <1> are removed participates in the calculation of the magic word (CRC16), so that the magic word generated from the 3 rd byte f7 is 3b 58;

step 5, judging whether the key field is hit;

the key fields are a set of data fields that ensure a message attribute and maximize compression. According to the characteristics of the radar target track message and the data format standard, selecting a plurality of fields which can identify the characteristics of one message and defining the fields as key fields. Any occasions of radar track message compression, such as sharing, storage, transmission and the like, only need to select key fields for message compression according to message characteristics. For radar track messages with different data format standards, information sources, track numbers, message lengths and FSPEC fields are usually selected as key fields in combination with field mandatory option, selectable option and forbidden option provisions formed by the messages. In this embodiment, the key field includes a message length, an FSPEC field, a data source identifier, and a batch number, that is, the fields <1>, <2>, <3>, <10>, and the key field in the Q1 message is an underlined part:

0a00 1bf7 a001 0001 61 00 61 9f 9e 00 52 da aa 05 5e 00bb 00 21 3a7800 8a；

in the encoding process, judging to enter an I frame filing or P frame encoding process according to whether the key field is hit; if yes, jumping to the step 9, otherwise, executing the next step 6;

step 6, searching whether the magic words have repeated items;

searching whether the magic words generated in the step 4 have repeated items in the magic word list, if so, executing a next step 7, otherwise, jumping to the step 8;

step 7, defining as no-file I frame, and constructing a code stream;

when I frames with the same magic words appear, in order to more fully utilize the simplified magic words to realize the association with the I frames, according to the code stream definition of the invention, the I frame mark without filing is added after the message type and length field are removed, and the code stream transmission is generated, so that the decoding end is informed not to file the I frame message, thereby avoiding the problem of decoding disorder; then entering step 12;

step 8, defining as an I frame, and filing the I frame;

according to the code stream type definition of the embodiment, I frame header identification is added to the message, the I frame is formed by the I frame header identification and the message content except the message type and length field, and the document database takes the magic words as the main index and stores the magic words and the I frame; completing the I frame filing and then entering step 12;

when the Q1 is compressed and encoded, if the current filing I frame library is empty, the keyword is not hit, and the magic word is not repeated, the Q1 is an I frame, the field <0> field <1> is removed from the Q1, the message header identifier is added as c3, and the encoded code stream Q1-1 is formed as follows:

Q1-1：c3 f7 a0 01 00 01 61 00 61 9f 9e 00 52 da aa 05 5e 00 bb 00 213a 78 00 8a

the magic word 3b 58 and the code stream Q1-1 are stored in a magic word list.

Step 9, defining as P frame;

under the condition that the key field is hit, according to the code stream definition of the invention, a P frame header mark is added to the message, and then the magic word searched in the magic word list is written, so that the decoding end can determine the decoding process through the P frame mark after receiving, and uniquely searches the associated I frame through the magic word to realize message decoding; then entering step 10;

when reading in Q2, through key field comparison, finding that the hit is hit in < 001 b > < f7 a0> < 0100 > < 008 a >, entering P frame coding, the key field is the same as I frame, namely Q1 message, without coding, directly eliminating, and underlining as a change part:

0a 00 1b f7 a0 01 00 01 61 0000 009e 00 52 da aa 05 5e 00 bb 00 213a 78 00 8a

step 10, solving the residual error of the P frame relative to the I frame;

comparing the read message with hit I frames byte by byte except the message type and key field, and solving the variable quantity between the P frame and the I frame, namely residual error; then entering step 11;

step 11, simplifying Huffman coding and outputting a new code stream;

and carrying out simplified Huffman coding on the residual error, wherein when the same byte content of the P frame and the I frame is the same, the P frame and the I frame are coded into 0, and when the content is different, the 1 is directly added to the highest bit, and the original I frame byte is reserved. When the last 8 bits are not full, directly supplementing 0 at the low bit to complete 8 bits; then entering step 12;

the code stream in the invention comprises an I frame and a P frame, wherein the I frame is an intra-frame coding frame, and the P frame is an inter-frame coding frame. The coding of P-frames requires the use of simplified huffman coding with reference to the I-frame. As shown in fig. 2, the content of the "G", "I", "J" and "K" bytes in the message structure is the same except that the content of the key field is the same between the P-frame message and the I-frame of the reference message, and the same byte is replaced by 0 of one bit during encoding, so that efficient compression encoding transmission is performed, and the amount of transmission data is reduced. As shown in fig. 3, in the case of multiple reference packet I frames and P frames, the key field of a P frame is the same as the corresponding reference packet I frame, and after the reference packet is determined, the variation is calculated for the corresponding P frame and I frame.

According to the simplified Huffman coding method provided by the invention, the binary sequence after the Q2 message is coded is as follows:

0001 00000000 1 0000000000000000 00000；

corresponding to a 16-bit value of 1008000000 (less than 8 bits to complement 0 last).

Where the first three bits 0 represent the same three bytes in the Q1 and Q2 messages: 016100, respectively; the underlined part is a code stream after two variable bytes in Q1 and Q2 messages are coded, the highest bit is 1, and then the original I frame, namely a Q1 message byte, is reserved; the last 13 bits of 0 represent the same 13 bytes in the Q1 and Q2 messages.

According to the code stream rule of this embodiment, the header of the P frame is defined as c7, and at the same time, the magic word 3b 58 corresponding to the filing I frame is attached, and the final P frame encoding code stream Q2-1 is:

Q2-1：c7 3b 58 10 08 00 00 00；

step 12, judging whether a next message exists;

if yes, jumping to the step 1, otherwise, executing the next step 13;

and step 13, ending the coding process.

The original message length of the Q2 message is 27 bytes, only 8 bytes remain after P frame coding, and the compression ratio reaches 3.38.

As shown in fig. 5, the whole decoding work flow is as follows:

step D1, reading a message;

step D2, judging whether the transmission identifier is a transparent transmission identifier;

judging whether the message is a transparent transmission message or not according to the code stream type identifier defined by the invention, if the first byte of the message is c2, executing the next step D3, otherwise, skipping to the step D4;

d3, analyzing the transparent transmission code stream and outputting

According to the definition of the transparent transmission code stream, removing the transparent transmission identifier c2 from the message, namely restoring the original message, and then jumping to the step D13;

step D4, judging whether it is P frame;

judging whether the message is a P frame according to the code stream type identifier defined by the invention, if the first byte of the message is c7, the message is a P frame message, skipping to the step D10, otherwise, if the message is a filing I frame or a non-filing I frame, executing the next step D5;

d5, restoring the message structure corresponding to the I frame;

according to the code stream definitions of the file I frame and the non-file I frame, the frame header mark c5 or c3 is removed, and then the message type and length field contents are written, namely the original message structure is restored; then the next step D6 is performed;

step D6, generating magic words;

generating a unique identifier for the message without the two fields of the message type and the message length by adopting 16-bit cyclic redundancy check, and using the unique identifier as a magic word; then step D7 is entered;

step D7, judging whether it is a filing I frame;

judging whether the message is a filing I frame or not according to the code stream type identifier defined by the invention, if the first byte of the message is c3, executing the next step D8, otherwise, skipping to the step D9; when I frames with the same magic words appear, in order to more fully utilize the simplified magic words to realize the association with the I frames, the I frames are marked as non-filing I frames according to the code stream definition of the invention so as to avoid the problem of decoding disorder;

step D8, the decoding end establishes an I frame and a magic word list;

the magic word list takes the magic words as main indexes, stores the magic words and the I frames, and stores the magic words and the I frames at the two ends of the encoding and decoding respectively; then the next step D9 is performed;

step D9, outputting the decoded message;

outputting the decoded message, and then jumping to the step D13;

step D10, searching for the messages with the same magic words;

the P frame message takes c7 as a message header, carries 2-byte magic words behind the P frame message, extracts the magic words, takes the magic words as a main index, searches an I frame message of the same magic words in a magic word list, and takes the I frame message as a reference message of the P frame to carry out the inverse process of interframe coding; then the next step D11 is performed;

d11, restoring the original message structure and key field corresponding to the P frame;

according to the definition of P frame code stream, removing the frame header mark c7 and magic word content, writing the message type and length field content, and restoring the message content containing Huffman coding result; directly copying the content of the corresponding key field by hitting the I frame; then the next step D12 is performed;

d12, analyzing and outputting the content of the simplified Huffman code;

when decoding, residual content is analyzed according to rules, namely the original message can be restored, if the same byte content is the same and is coded into 0, when decoding, if the same byte content is 0, the corresponding I frame byte content is directly copied; if the number of the bits is 1, directly copying the data after the highest bit 1, and combining the decoded data into a new code stream for outputting; then the next step D13 is performed;

the end conditions for parsing the huffman code are: because the last byte of the encoding end is less than 8 bits and is complemented by 0, the end condition of the residual comparison needs to be limited to the end of comparison of all bytes of the filing I frame, rather than the end of the last 1 bit of the code stream.

Step D13, judging whether there is next message;

if yes, jumping to the step 1, otherwise, executing the next step D14;

and D14, ending the encoding process.

In this embodiment, two encoded messages are received, which are respectively:

Q1-1：c3 f7 a0 01 00 01 61 00 61 9f 9e 00 52 da aa 05 5e 00 bb 00 213a 78 00 8a；

Q2-1：c7 3b 58 10 08 00 00 00。

starting to enter decoding:

(1) reading in Q1-1, judging as a filing I frame through a first byte c3, entering I frame decoding, automatically adding a flight path message header 0a and a length 001 b according to subsequent message combination, and completely decoding the whole message: 0a 001 b f7 a 00100016100619 f 9e 0052 da 055 e 00 bb 00213 a 78008 a;

(2) generating a corresponding magic word aiming at the message, wherein the generation range of the magic word is to remove the field <0> and the field <1> and completely participate in the calculation of the magic word (CRC16), so that the magic word is generated into 3b 58 from the 3 rd byte f7, and a magic word list is established;

(3) reading Q2-1, judging as a P frame through a first byte c7, entering P frame decoding, taking out a magic word corresponding to the P frame as 3b 58 according to a code stream rule, simultaneously inquiring a magic word message comparison table, finding that the last I frame can be matched, supplementing a key field of a filing I frame into the P frame according to the code stream rule, and then performing binary expansion on the content of the P frame Huffman code into the following steps:

0001000000001000000000000000000000000000, and spreading out the I frames corresponding to the magic words 3b 58, comparing one by one, the range of the filing I frame comparison is to eliminate the field<0>And key fields, namely the underlined parts of the following messages: 0a 001 b f7 a 0010001 61 00 61 9f 9e 00 52 da aa 05 5e 00 bb 00 21 3a 7800 8a；

Reading 1 st bit as 0, according to the decoding method of the present invention, it means that the byte is completely the same as the byte of the filing I frame, the byte is directly referenced as 01, then sequentially reading 2 nd bit, 3 rd bit as 0, also directly referenced 6100, 4 th bit as 1, according to the huffman decoding rule, for the changed part, extracting the subsequent 8 th bit, i.e. 5 th bit to 12 th bit as 00, 13 th bit as 1, continuously extracting 14 th bit to 21 st bit as still 00, and then because all the bytes after 22 nd bit are 0, the result of directly referencing the filing I frame is only needed (because the encoding end has the situation of less than 8 bit complement 0, the end condition of comparison needs to be defined as the end of comparison of all the bytes of the filing I frame).

So far, according to the code stream rule, a decoding code stream can be formed as follows:

0a 00 1b f7 a0 01 00 01 61 00 00 00 9e 00 52 da aa 05 5e 00 bb 00 213a 78 00 8a。

this concludes the embodiment. The code stream decoded by the receiving end is consistent with the code stream in the message before being coded by the sending end, and the lossless transmission of the radar track message is realized.

Claims (4)

1. A radar track message transmission method is characterized in that a sending end encodes a radar track message and then sends the radar track message, and a receiving end decodes a received radar track compressed message; the radar track message coding comprises the following steps:

(C1) reading a frame of radar track message, and generating magic words according to message data; the magic words are check codes generated by message data through a check algorithm;

(C2) judging whether the key field is hit; if not, go to step (C3); if hit, defining the current frame as P frame, adding P frame header mark and magic word searched in magic word list to the message, solving the residual error of P frame relative to I frame, carrying out simplified Huffman coding to the residual error, and turning to step (C4); the key field is a multi-field set capable of identifying message characteristics;

the simplified Huffman coding of the residual error comprises the following steps: if the same byte content of the P frame and the I frame is the same, the P frame and the I frame are coded into 0, if the content is different, 1 is directly added at the highest position, and the original I frame byte is reserved; when the last 8 bits are not full, directly supplementing 0 at the low bit to complete 8 bits;

(C3) searching whether the magic word has repeated items in the magic word list; if yes, defining the current frame as a non-archive I frame, and constructing a code stream; otherwise, defining the current frame as an I frame, constructing a code stream, and adding the magic words and the I frame code stream into a magic word list; the magic character list takes the magic character as a main index and stores the magic character and the I frame;

(C4) judging whether a next message exists, if so, jumping to the step (C1), otherwise, ending the encoding;

the radar track compressed message decoding comprises the following steps:

(D1) reading a frame of radar track coding message, judging whether the frame is a filing I frame message, if so, generating magic words, analyzing and outputting a code stream, and adding the magic words and the I frame code stream into a magic word list; turning to step (D4);

(D2) judging whether the message is a non-filing I frame message, if so, generating magic words, analyzing and outputting a code stream; turning to step (D4);

(D3) judging whether the message is a P frame message, if so, extracting magic words in the message, searching the same magic word message in a magic word list, restoring a message structure and a key field corresponding to the P frame, decoding simplified Huffman coding content, and constructing and outputting a decoding code stream; turning to step (D4);

(D4) and (D) judging whether a next message exists, if so, turning to the step (D1), otherwise, ending the decoding.

2. The radar track message transmission method according to claim 1, wherein the magic word is used for generating a unique check code by 16-bit cyclic redundancy check after two fields of message type and message length are removed from the message data.

3. The radar track message transmission method of claim 1, wherein the key fields include message length, FSPEC field, data source identification, batch number.

4. The radar track message transmission method of claim 1, wherein decoding the simplified huffman encoded content in the P-frame message comprises the steps of:

reading in the code stream in sequence, and if the current code element is 0, directly copying the byte content of the corresponding I frame; if the current code element is 1, copying the byte content behind the current code element 1, and combining the decoded byte content into a new code stream for outputting.

Images