CN107276720A - A kind of Beidou navigation message coding method based on punctured polarization code characteristic - Google Patents
A kind of Beidou navigation message coding method based on punctured polarization code characteristic Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
- H04L1/0009—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the channel coding
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
- H03M13/00—Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes
- H03M13/03—Error detection or forward error correction by redundancy in data representation, i.e. code words containing more digits than the source words
- H03M13/05—Error detection or forward error correction by redundancy in data representation, i.e. code words containing more digits than the source words using block codes, i.e. a predetermined number of check bits joined to a predetermined number of information bits
- H03M13/13—Linear codes
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
- H04L1/0045—Arrangements at the receiver end
- H04L1/0047—Decoding adapted to other signal detection operation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
- H04L1/0056—Systems characterized by the type of code used
- H04L1/0057—Block codes
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Abstract
The invention discloses a kind of Beidou navigation message coding method based on punctured polarization code characteristic, the present invention first obtains Big Dipper D1 navigation message information bits；D1 navigation message information bits are mapped in punctured polarization code；D1 navigation message information bits are encoded using punctured polarization code；BPSK modulation is carried out to the bit stream after coding, and is transmitted in awgn channel, BPSK demodulation is carried out to navigation message in receiving terminal, and carry out SC decodings；D1 navigation message information is obtained by demapping mode, and calculates the corresponding bit error rate.This method employs the thought of unequal error protection; it ensure that the accuracy of the frame swynchronization code of D1 navigation; certain frame loss rate is ensure that, meanwhile, relative to BCH (15; 11; 1) encode, the present invention can obtain 1.6dB gain, effectively raise the accuracy for receiving D1 navigation messages; improve Beidou navigation signal poor anti jamming capability, the problems such as bit error rate is high.
Description
Technical field
The present invention relates to satellite communication, field of satellite navigation, it is related to a kind of Beidou navigation based on punctured polarization code characteristic
Message coding method.
Background technology
Chinese Beidou satellite navigation system (BeiDou Navigation Satellite System, BDS) be China from
The GPS that row is developed.Be after american global positioning system (global positioning system, GPS),
The after Russian Glonass satellite navigation system (global navigation satellite system, GLONASS)
Three ripe satellite navigation systems.BDS, the GPS in the U.S., the GLONASS of Russia and the Galilean satellite of European Union of China
Navigation system (Galileo navigation satellite system, Galileo), is the satellite navigation committee of the United Nations
The supplier assert.China's plan 2012 or so, Beidou system will cover the Asian-Pacific area, and the year two thousand twenty or so covers complete
Ball.
Big-dipper satellite is when being communicated, and its communication distance is far, it is necessary to which the receiving sensitivity and channel that improve system increase
Benefit, wherein channel decoding are one of core technologies in satellite communication, can effectively reduce the bit error rate in satellite communication.Letter
Road coding has already been through the development of more than 50 years, by initial block code widely used Turbo code and low close till now
Spend parity check code (Low Density Parity Check Code, LDPC).The Polar codes that Arikan was proposed in 2009
Encoding scheme, because it can be under binary system discrete memoryless channel(DMC), its symmetrical capacity can reach shannon limit, while it is compiled
The features such as code complexity is relatively low, causes the upsurge of research polarization code both at home and abroad.Polar codes are as a kind of channel coding, mainly
Application be exactly improve communication system having make an uproar interference transmission when reliability.
Big-dipper satellite alignment system uses BCH coding and decoding modes at this stage, and BCH code is a kind of simple linear volume
Code, its coding efficiency is not very high, has been difficult to meet the high-precision requirement of user.Compared to LDPC code and Turbo code,
Polar codes are that a kind of unique channel capacity being proved to can reach the coded system of shannon limit, meanwhile, Polar codes have
Lower encoder complexity, it is often more important that, Polar research history is not long, the text applied on it in satellite communication
Chapter is even more not have, and the patent limitation of correlation technique is also seldom, so, it is one that Polar codes, which are applied in Beidou navigation communication,
Good selection.The preceding 11bit of D1 navigation message subframes information code word is frame swynchronization code, if frame swynchronization code makes a mistake,
Subframe will be dropped, therefore, and frame swynchronization code may be considered most important bit information in subframe.In existing Beidou navigation
In alignment system, D1 navigation messages subframe does not carry out Error Correction of Coding to preceding 15 bit information, and which includes 11bit frame is same
Code is walked, is well imagined, existing navigation signal frame loss rate is very high.In view of Polar after decoding, made a mistake on each position
Probability it is different, this attribute of Polar codes provides possibility for UEP realization, in progress navigation information coding, frame is same
Step code information MAP is to making a mistake on the minimum information position of probability, so as to effectively reduce the frame loss rate of navigation signal.
The content of the invention
In order to improve the antijamming capability of big-dipper satellite, it is punctured that the present invention proposes a kind of dynamic based on decoding reliability
Polarization code is encoded to Beidou navigation textual information, can effectively improve the accuracy of navigation message.
The present invention can be realized by following steps：
Step one：Obtain Big Dipper D1 navigation message information bits；
Step 2：D1 navigation message information bits are mapped in punctured polarization code；
Step 3：D1 navigation message information bits are encoded using punctured polarization code；
Step 4：BPSK modulation is carried out to the bit stream after coding, and is transmitted in awgn channel；
Step 5：BPSK demodulation is carried out to navigation message in receiving terminal, and carries out SC decodings；
Step 6：D1 navigation message information is obtained by demapping mode, and calculates the corresponding bit error rate.
The beneficial effects of the invention are as follows：This method employs the thought of unequal error protection, it is ensured that the frame of D1 navigation is same
Walk the accuracy of code, it is ensured that certain frame loss rate, meanwhile, relative to BCH (15,11,1) codings, the present invention can be obtained
1.6dB gain, so as to effectively raise the accuracy for receiving D1 navigation messages, improves the anti-interference energy of Beidou navigation signal
Power is poor, the problems such as bit error rate is high.
Brief description of the drawings
Fig. 1 is the Beidou navigation message coding method overall flow figure proposed by the present invention based on punctured polarization code characteristic.
Fig. 2 is D1 navigation message frame structure schematic diagrames.
Fig. 3 is punctured polarization code coding/decoding process schematic.
Fig. 4 is to be mapped into the schematic diagram of polarization code to the bit stream of the navigation information of transmission in the present invention.
Fig. 5 is the bit error rate performance contrast schematic diagram of punctured polarization code and BCH (15,11,1) code.
Embodiment
Fig. 1 gives the Beidou navigation message coding method overall flow figure based on punctured polarization code that the present invention is provided,
It is implemented as follows：
(1) what Fig. 2 was provided is D1 navigation message frame structure schematic diagrames, and the subframe of D1 navigation messages is long as seen from Figure 2
Metric is set to 300, and wherein navigation message message length is 224 bits, and redundancy check bit length is 76 bits.Therefore, by with
Machine generating function, obtains the random binary number of 224 bits as Big Dipper D1 navigation message information bits.
(2) subframe lengths of D1 navigation messages are defined as 300, it is necessary to construct length for 300 bits, code check is 224/300
Polarization code navigation message information encoded.The polarization code that Arikan is proposed is to accumulate construction by Kronecker to obtain
, code length is only 2 power.It is, therefore, desirable to provide a kind of compatible punctured polarization available for satellite navigation message of length
Code, while needing to ensure that obtained punctured polarization code has preferable performance.Punctured polarization code can be by conventional polar code
Delete and obtain, it is possible to use the coding and decoding mode of conventional polar code realizes coding and decoding.Assuming that N is the length of conventional polar code
Degree, M is the length of polarization code after punctured, and K is information bit length, then the punctured polarization code of construction can be expressed as (N, M,
K).Fig. 3 is the coding and decoding process of punctured polarization code.It is N's that information sequence with K bit obtains code length through the code coder that polarizes
Code word, code word on correspondence position is left out according to pattern is deleted, and is obtained code word that code length is M and is transmitted in the channel, connects
Receiving end uses likelihood ratio decoder, by delete pattern to receive code word correspondence position on likelihood ratio (Likelihood,
LR) it is set to 1 and enters row decoding, obtains estimating code word.Polarization code is that the subchannel chosen enters row information after channel-polarization code
Bit transfer, so, the performance of polarization code will be directly affected by deleting the selection of pattern.Conventional punctured algorithm has cut-off tree to delete
Remaining, accurate to circulate punctured (quasi-uniform puncturing, QUP) and efficiently punctured scheduling algorithm, these algorithms are all based on
Polarization code structural texture is obtained, i.e., under different channels environment, constructs same punctured polarization code, and obtained pattern of deleting all is
Consistent, above-mentioned algorithm is that the construction based on polarization code proposes that punctured pattern p not is basis as the extra bit that freezes
Error probability selection is obtained, it is possible to is set to freeze position by some good subchannels, is caused the decline of decoding performance.Polarization code
It is to propose that, with the change of environment, the probability that corresponding channel makes a mistake can also be become accordingly based on channel-polarization
Change.Therefore, it is proposed to a kind of dynamic puncturing method based on decoding reliability.Assuming that CiFor i-th of polarisation channelGeneration is wrong
This event, corresponding polarisation channel by mistakeError probability be P (Ci), polarisation channelCorresponding reliability is 1-P
(Ci).The present invention selects the method for Gaussian approximation to calculate the reliability of awgn channel.
Assuming that δ2For the noise variance of original awgn channel, the likelihood ratio of i-th of bitObedience average is 2/ δ2Variance
For 4/ δ2Gaussian Profile.The confidence level of i-th of bit can using approximate representation as
WhereinLR average can be calculated according to following formula
Wherein Initial value be 2/ δ2。
By code length, for the position of 512 standard polarization code, according to decoding, reliability is descending is ranked up, and selection is reliable
Property highest before 224 positions as the position of information bit, the minimum position of 288 reliabilities of selection is used for transmitting transceiver end
It is known to freeze bit, the minimum bit position of 212 reliabilities is selected in bit is freezed as deleting pattern p.
The preceding 11bit of D1 navigation message subframes information code word is frame swynchronization code, if frame swynchronization code makes a mistake, subframe
It will be dropped, therefore, frame swynchronization code may be considered most important bit information in subframe.In the positioning of existing Beidou navigation
In system, D1 navigation messages subframe does not carry out Error Correction of Coding to preceding 15 bit information, and which includes 11bit frame synchronization
Code, is well imagined, existing navigation signal frame loss rate is very high.
As shown in figure 4, by frame swynchronization code information MAP to decoding on reliability highest information position, by remaining information
It is mapped on remaining information position, so as to realize unequal error protection, it is ensured that the reliability of frame swynchronization code, can effectively reduces and lead
The frame loss rate of boat signal.
(3) assume to use channel W:It is symbol X that X { 0,1 } → Y, which represents input, is output as symbol Y, and transmission probability is p (y | x),
X ∈ X, y ∈ Y binary system discrete memoryless channel(DMC) (binary discrete memoryless channel, B-DMC).This
Outside, it is assumed thatIt is the second order nuclear matrix of polarization code, generator matrix isWherein symbolRepresent
Kronecker is accumulated, BNRepresent bit reversal matrix.
From above-mentioned derivation, form can be expressed as by carrying out the process of polarization code coding.
WhereinIt is the bit sequence after coding,It is to contain navigation letter
The bit sequence of breath.
So,Be D1 navigation messages information encodes obtained code word by polarization code, according to deleting
Subtract pattern p and can obtain punctured polarization code and be It is that reality exists
The bit sequence being transmitted in channel.
(4) by punctured polarization codeBPSK modulation is carried out, and is carried out in awgn channel
Transmission.
(5) bit information received in receiving terminalFor
WhereinRepresent AWGN sequence.
When entering row decoding using the SC algorithms of Polar codes, for i-th of subchannel, pass through the estimation of preceding i-1 channel
ValueSequence is received with the channelTo calculate its LR value, and LR values are judged accordingly.For LR solution, need
Recursive thought is used, two subsequences that length is N/2, then root are converted into first for the Polar codes that length is N
Calculated according to following equation：
By punctured pattern p, the LRs on correspondence position is directly set to 1；Because freeze bit be receiving-transmitting sides all
The fixed bit known, it is not necessary to which decoding can directly be set to 0., can be according to following formula for information bit
Judged：
(6) D1 navigation message information is obtained by the demapping mode corresponding with step 2, and counts its bit error rate, with
Beidou navigation signal original Error Correction of Coding BCH (15,11,1) carries out performance comparision.
By Fig. 5 it can be found that reaching 10 in the bit error rate-5When, the Big Dipper proposed by the present invention based on punctured polarization code characteristic
Navigation message coding method can obtain 1.6dB gains relative to BCH (15,11,1), effectively raise Beidou navigation signal
Reliability.
Claims (1)
1. a kind of Beidou navigation message coding method based on punctured polarization code characteristic, it is characterised in that:Method realizes step
It is as follows：
Step one：Obtain Big Dipper D1 navigation message information bits；
Step 2：D1 navigation message information bits are mapped in punctured polarization code；
Step 3：D1 navigation message information bits are encoded using punctured polarization code；
Step 4：BPSK modulation is carried out to the bit stream after coding, and is transmitted in awgn channel；
Step 5：BPSK demodulation is carried out to navigation message in receiving terminal, and carries out SC decodings；
Step 6：D1 navigation message information is obtained by demapping mode, and calculates the corresponding bit error rate.
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| CN111903084A (en) * | 2018-03-29 | 2020-11-06 | 华为技术有限公司 | Apparatus and method for rate matching in polar coding |
| CN115567165A (en) * | 2022-10-18 | 2023-01-03 | 天津津航计算技术研究所 | Coding error correction method, system, terminal equipment and readable storage medium |
| EP4156523A4 (en) * | 2020-06-12 | 2023-10-18 | Huawei Technologies Co., Ltd. | Polar encoding and decoding method and apparatus for satellite communication |
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