CN110519200B - Polarization code auxiliary carrier synchronization system and method under low signal-to-noise ratio environment - Google Patents

Polarization code auxiliary carrier synchronization system and method under low signal-to-noise ratio environment Download PDF

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CN110519200B
CN110519200B CN201910868108.5A CN201910868108A CN110519200B CN 110519200 B CN110519200 B CN 110519200B CN 201910868108 A CN201910868108 A CN 201910868108A CN 110519200 B CN110519200 B CN 110519200B
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frequency offset
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phase
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CN110519200A (en
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陈超凡
郑晨
王帅
王长红
安建平
方金辉
宋哲
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Beijing Institute of Technology BIT
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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
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2655—Synchronisation arrangements
    • H04L27/2657—Carrier synchronisation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2655—Synchronisation arrangements
    • H04L27/2657—Carrier synchronisation
    • H04L27/266—Fine or fractional frequency offset determination and synchronisation

Abstract

The invention discloses a polarization code auxiliary carrier synchronization system and method under a low signal-to-noise ratio environment, and belongs to the field of digital signal processing. The synchronization system comprises a frequency deviation and phase deviation compensation unit, a demodulation unit, a polarization code decoding unit and a frequency deviation and phase deviation calculation unit. The invention realizes the frequency deviation and phase deviation compensation of the system carrier wave through an iteration mechanism among the polarization code decoding unit, the frequency deviation and phase deviation compensation unit and the demodulation unit. In the iteration process, the expected maximum frequency deviation and phase deviation estimation algorithm is adopted to fully utilize the excellent decoding performance of the polar code under the condition of low signal to noise ratio, and the posterior information output by the decoding unit is used for carrying out more accurate frequency deviation and phase deviation calculation, so that the iteration convergence speed and the final estimation precision of the frequency deviation and the phase deviation are improved, and finally, the low signal to noise ratio and high-precision carrier synchronization are realized, thereby improving the condition of communication system performance deterioration caused by the carrier synchronization deviation under the environment of the low signal to noise ratio. The invention has the advantages of low working signal-to-noise ratio and high synchronization precision.

Description

Polarization code auxiliary carrier synchronization system and method under low signal-to-noise ratio environment
Technical Field
The invention relates to a carrier synchronization communication system and method under a low signal-to-noise ratio environment, in particular to a carrier synchronization communication system and method for realizing carrier synchronization in a low signal-to-noise ratio communication system in a polarization code auxiliary mode, and belongs to the field of digital signal processing.
Background
In practical applications, a polar code is a code sensitive to carrier synchronization deviation, and when a certain magnitude of carrier synchronization deviation occurs in a communication system, the decoding performance of the polar code is deteriorated. In order to fully utilize the gain caused by channel coding and realize error-free code decoding, how to realize carrier synchronization and reduce the influence caused by carrier synchronization error to the maximum extent becomes a very important problem in the application of polarization codes. However, for conventional data-aided and non-data-aided carrier synchronization methods, their computational complexity would increase substantially if used in low signal-to-noise ratio (SNR) situations, which is not feasible in practical applications. The decoding performance of the short code of the polarization code is excellent in the low signal-to-noise ratio environment, and the carrier synchronization with higher precision can be realized if the performance of the polarization code can be fully utilized and is linked with the carrier synchronization.
Disclosure of Invention
In order to solve the problem of communication system performance deterioration caused by carrier synchronization deviation in a low signal-to-noise ratio environment, the invention discloses a polarization code auxiliary carrier synchronization system and a method in the low signal-to-noise ratio environment, which aim to solve the technical problems that: the frequency deviation and the phase deviation compensation of the system carrier are realized through an iteration mechanism among the polar code decoding unit, the frequency deviation and phase deviation compensation unit and the demodulation unit, and finally, the carrier synchronization is realized in a communication system with a low signal-to-noise ratio in a polar code assisted mode through setting the maximum iteration times.
The purpose of the invention is realized by the following technical scheme.
The invention realizes the frequency deviation and phase deviation compensation of the system carrier wave through an iteration mechanism among the polarization code decoding unit, the frequency deviation and phase deviation compensation unit and the demodulation unit. In the iteration process, the expected maximum frequency deviation and phase deviation estimation algorithm is adopted to fully utilize the excellent decoding performance of the polar code under the condition of low signal to noise ratio, and the posterior information output by the decoding unit is used for carrying out more accurate frequency deviation and phase deviation calculation, so that the iteration convergence speed and the final estimation precision of the frequency deviation and the phase deviation are improved, and finally, the low signal to noise ratio and high-precision carrier synchronization are realized, thereby improving the condition of communication system performance deterioration caused by the carrier synchronization deviation under the environment of the low signal to noise ratio.
The invention discloses a polarization code auxiliary carrier synchronization system under a low signal-to-noise ratio environment, which comprises a frequency deviation and phase deviation compensation unit, a demodulation unit, a polarization code decoding unit and a frequency deviation and phase deviation calculation unit.
And the frequency deviation and phase deviation compensation unit is used for compensating the difference between the receiving and transmitting carrier frequency and the phase, and the compensated result is used for signal demodulation.
The demodulation unit is used for demodulating the compensated received signal value, obtaining the prior information, and then transmitting the prior information to the polar code decoding unit to participate in decoding.
The polar code decoding unit is used for finishing the polar code decoding function of the receiving system, outputting the final decoding result, namely the estimation signal of the sending signal, and simultaneously outputting the posterior information.
And the frequency offset and phase offset calculating unit is used for estimating the frequency offset and the phase offset of the carrier wave according to the posterior information fed back by the polar code decoding unit.
The invention discloses a working method of a polarization code auxiliary carrier synchronization system under a low signal-to-noise ratio environment, which comprises the following steps:
the method comprises the following steps: and initializing a frequency offset and phase offset compensation value to be 0 during first iteration, and using the value for first calculation of the frequency offset and phase offset compensation unit.
Step two: and in the first iteration, the frequency offset and phase offset compensation unit compensates the channel output information according to the last frequency offset and phase offset calculation value, and outputs the compensated information to the demodulation unit.
The frequency offset and phase offset compensation unit performs compensation according to the following formula:
Figure BDA0002199944090000021
wherein:
Figure BDA0002199944090000022
representing the signal received during the l-th iteration, k representing the k-th signal value,
Figure BDA0002199944090000023
representing the estimated frequency offset, T, during the l-1 st iterationsDenotes the symbol period, θ(l-1)Then the first-1 iteration is indicatedAnd obtaining the phase deviation estimated value in the process.
Step three: the demodulation unit receives the compensated information to perform demodulation processing, and outputs the demodulated information to the polar code decoding unit.
Step four: the polar code decoding unit receives the demodulated information as decoding prior information to decode, and outputs a decoding result and decoding posterior information.
The polar code decoding method of the polar code decoding unit comprises a BP algorithm (G-based BP) based on a generating matrix G and a BP algorithm (H-based BP) based on a check matrix H, and preferably, the polar code decoding unit adopts the H-based BP decoding algorithm for decoding.
Step five: and the frequency offset and phase offset calculation unit receives the decoded posterior information to perform current iteration frequency offset and phase offset value calculation, and outputs the frequency offset and the phase offset value to the frequency offset and phase offset compensation unit. In the calculation process, if the iteration times reach the preset maximum times, the iteration is stopped, and the output result of the current decoding is used as the final decoding output, wherein the final decoding output is the final result meeting the requirement of the carrier synchronization precision. Otherwise, outputting the frequency offset and the phase offset value of the iteration to a frequency offset and phase offset compensation unit, namely returning to the frequency offset and phase offset compensation unit in the second step for the next iteration.
Fifthly, the frequency deviation and phase deviation calculation method of the frequency deviation and phase deviation calculation unit comprises the following steps:
an expectation-maximization algorithm is introduced to estimate the frequency offset and phase offset. The expectation-maximization algorithm is an efficient way to iteratively solve the maximum likelihood estimate. Frequency offset according to an expectation maximization algorithm
Figure BDA0002199944090000024
And phase deviation
Figure BDA0002199944090000025
Is expressed as formula (2) and formula (3):
Figure BDA0002199944090000031
Figure BDA0002199944090000032
wherein the content of the first and second substances,
Figure BDA0002199944090000033
representing the estimated synchronization parameter in the l-1 th iteration, i.e. b(l-1)＝<△f(l-1),θ(l-1)>，
Figure BDA0002199944090000034
Denotes the A posteriori expected value of the k-th symbol, D denotes the number of received symbols, TsWhich is indicative of the period of the symbol,
Figure BDA0002199944090000035
representing the estimated frequency offset value during the ith iteration, and arg {. cndot } represents the angle solving function. The posterior expected value is calculated according to the posterior information of the polar code decoding, and the specific implementation method is as follows:
firstly, the posterior LLR of the kth bit in the l iteration is calculated according to the decoding method of the polarization code and is shown in formula (4)
Figure BDA0002199944090000036
In BPSK modulation systems, the modulation symbols skIs expressed as a conditional probability of
Figure BDA0002199944090000037
And the following equation is established,
Figure BDA0002199944090000038
the material is pushed out of the die,
Figure BDA0002199944090000039
in the same way, sk＝eThe conditional probability of xp (j 1 · pi) is expressed as,
Figure BDA00021999440900000310
from which the expected posterior value is derived
Figure BDA00021999440900000311
The expression (c) of (a),
Figure BDA0002199944090000041
where tanh (x) is a hyperbolic tangent function, which can be written as
Figure BDA0002199944090000042
In the form of (1). In view of the complexity in the hardware implementation,
Figure BDA0002199944090000043
the method is further simplified into the following steps of,
Figure BDA0002199944090000044
th is a set threshold. Therefore, the frequency offset and the estimated value of the phase offset are obtained by iterative calculation according to the equations (2), (3) and (9) (or (10)) until the decoding is correct or the maximum iteration number is reached.
Further comprises the following steps: the polar code auxiliary carrier synchronization system under the low signal-to-noise ratio environment is suitable for a communication system sensitive to carrier frequency deviation and phase deviation synchronization precision, and high-precision carrier synchronization is achieved under the low signal-to-noise ratio through the polar code auxiliary carrier synchronization method under the low signal-to-noise ratio environment in the steps from the first step to the fifth step, and the communication reliability of the system is improved.
Has the advantages that:
1. in the prior art, a communication system realizes carrier synchronization under low signal-to-noise ratio, and has the defects of poor synchronization precision or excessive resource consumption. The invention discloses a system and a method for synchronizing polarization code auxiliary carrier waves in a low signal-to-noise ratio environment, which realize frequency deviation and phase deviation compensation of system carrier waves through an iteration mechanism among a polarization code, a frequency deviation and phase deviation compensation unit and a demodulation unit. In the iteration process, an expectation maximization frequency offset and phase offset estimation algorithm is adopted to fully utilize the excellent decoding performance of the polarization code under the low signal-to-noise ratio, more accurate frequency offset and phase offset calculation is carried out through the posterior information output by the decoding unit, the estimated values of the frequency offset and the phase offset are obtained by utilizing the relatively accurate posterior information of the polarization code under the low signal-to-noise ratio, and finally, the carrier synchronization with the low signal-to-noise ratio and the high precision is realized.
2. The invention discloses a polar code auxiliary carrier synchronization system and method under a low signal-to-noise ratio environment, which are suitable for a communication system sensitive to carrier frequency deviation and phase deviation synchronization precision.
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In order to more clearly illustrate the technical solution of the present invention, the drawings needed to be used in the present invention will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
Fig. 1 is a block diagram of a polar code assisted carrier synchronous communication system.
Fig. 2 is a flow chart of frequency offset and phase offset compensation of a polar code assisted carrier synchronous communication system.
Fig. 3(2048, 1024) is a graph of the error rate of the polarization code under different frequency offsets. Fig. 3(a) is a bit error rate graph of the polarization code under different frequency offsets, and fig. 3(b) is a bit error rate graph of the polarization code under different frequency offsets.
Fig. 4(2048, 1024) shows the mev (mean Estimated value) plots of the polarization codes under different frequency offset and phase offset. Fig. 4(a) is an MEV plot of a polarization code under different frequency offsets, and fig. 4(b) is an MEV plot of a polarization code under different frequency offsets.
Fig. 5 shows MEV plots of (1024, 512) and (512, 256) polarization codes at different frequency offsets. Fig. 5(a) is an MEV plot of a polarization code under different frequency offsets, and fig. 5(b) is an MEV plot of a polarization code under different frequency offsets.
FIG. 6 is a graph of the RMSE (root Mean Square error) plots of the (2048, 1024) polarization code, the (1024, 512) polarization code and the (512, 256) polarization code under specific frequency offset, wherein FIG. 6(a) shows the (2048, 1024) polarization code, the (1024, 512) polarization code and the (512, 256) polarization code at 1.2 × 10 frequency offset respectively-4、2.5×10-4、5×10-4The lower RMSE curve, FIG. 6(b) is the RMSE curve of three polarization codes under the phase offset of 0.2 pi.
Detailed Description
Example 1:
as shown in fig. 1, the polarization code assisted carrier synchronization system in the low snr environment disclosed in this embodiment includes a frequency offset and phase offset compensation unit, a demodulation unit, a polarization code decoding unit, and a frequency offset and phase offset calculation unit.
And the frequency deviation and phase deviation compensation unit is used for compensating the difference between the receiving and transmitting carrier frequency and the phase, and the compensated result is used for signal demodulation.
The demodulation unit is used for demodulating the compensated received signal value, obtaining the prior information, and then transmitting the prior information to the polar code decoding unit to participate in decoding.
The polar code decoding unit is used for finishing the polar code decoding function of the receiving system, outputting the final decoding result, namely the estimation signal of the sending signal, and simultaneously outputting the posterior information.
And the frequency offset and phase offset calculating unit is used for estimating the frequency offset and the phase offset of the carrier wave according to the posterior information fed back by the polar code decoding unit.
As shown in fig. 2, the working method of the polar code assisted carrier synchronization system in the low snr environment disclosed in this embodiment includes the following steps:
the method comprises the following steps: and initializing a frequency offset and phase offset compensation value to be 0 during first iteration, and using the value for first calculation of the frequency offset and phase offset compensation unit.
Step two: and in the first iteration, the frequency offset and phase offset compensation unit compensates the channel output information according to the last frequency offset and phase offset calculation value, and outputs the compensated information to the demodulation unit.
The frequency offset and phase offset compensation unit performs compensation according to the following formula:
Figure BDA0002199944090000061
wherein:
Figure BDA0002199944090000062
representing the signal received during the l-th iteration, k representing the k-th signal value,
Figure BDA0002199944090000063
representing the estimated frequency offset, T, during the l-1 st iterationsDenotes the symbol period, θ(l-1)It represents the phase deviation estimate obtained during the l-1 th iteration.
Step three: the demodulation unit receives the compensated information to perform demodulation processing, and outputs the demodulated information to the polar code decoding unit.
Step four: the polar code decoding unit receives the demodulated information as decoding prior information to decode, and outputs a decoding result and decoding posterior information.
The polar code decoding method of the polar code decoding unit comprises a BP algorithm (G-based BP) based on a generating matrix G and a BP algorithm (H-based BP) based on a check matrix H, and preferably, the polar code decoding unit adopts the H-based BP decoding algorithm for decoding.
Step five: and the frequency offset and phase offset calculation unit receives the decoded posterior information to perform current iteration frequency offset and phase offset value calculation, and outputs the frequency offset and the phase offset value to the frequency offset and phase offset compensation unit. In the calculation process, if the iteration times reach the preset maximum times, the iteration is stopped, and the output result of the current decoding is used as the final decoding output, wherein the final decoding output is the final result meeting the requirement of the carrier synchronization precision. Otherwise, outputting the frequency offset and the phase offset value of the iteration to a frequency offset and phase offset compensation unit, namely returning to the frequency offset and phase offset compensation unit in the second step for the next iteration.
Fifthly, the frequency deviation and phase deviation calculation method of the frequency deviation and phase deviation calculation unit comprises the following steps:
an expectation-maximization algorithm is introduced to estimate the frequency offset and phase offset. The expectation-maximization algorithm is an efficient way to iteratively solve the maximum likelihood estimate. Frequency offset according to an expectation maximization algorithm
Figure BDA0002199944090000064
And phase deviation
Figure BDA0002199944090000065
Is expressed as formula (2) and formula (3):
Figure BDA0002199944090000066
Figure BDA0002199944090000067
wherein the content of the first and second substances,
Figure BDA0002199944090000068
representing the estimated synchronization parameter in the l-1 th iteration, i.e. b(l-1)＝<△f(l-1),θ(l-1)>，
Figure BDA0002199944090000069
Denotes the A posteriori expected value of the k-th symbol, D denotes the number of received symbols, TsWhich is indicative of the period of the symbol,
Figure BDA00021999440900000610
representing the estimated frequency offset value during the ith iteration, and arg {. cndot } represents the angle solving function. The posterior expected value is calculated according to the posterior information of the polar code decoding, and the specific implementation method is as follows:
firstly, the posterior LLR of the kth bit in the l iteration is calculated according to the decoding method of the polarization code and is shown in formula (4)
Figure BDA0002199944090000071
In BPSK modulation systems, the modulation symbols skIs expressed as a conditional probability of
Figure BDA0002199944090000072
And the following equation is established,
Figure BDA0002199944090000073
the material is pushed out of the die,
Figure BDA0002199944090000074
in the same way, skThe conditional probability of exp (j · 1 · pi) is expressed as,
Figure BDA0002199944090000075
from which the expected posterior value is derived
Figure BDA0002199944090000076
The expression (c) of (a),
Figure BDA0002199944090000077
where tanh (x) is a hyperbolic tangent function, which can be written as
Figure BDA0002199944090000078
In the form of (1). In view of the complexity in the hardware implementation,
Figure BDA0002199944090000079
the method is further simplified into the following steps of,
Figure BDA00021999440900000710
th is a set threshold. Therefore, the frequency offset and the estimated value of the phase offset are obtained by iterative calculation according to the equations (2), (3) and (9) (or (10)) until the decoding is correct or the maximum iteration number is reached.
Further comprises the following steps: the polar code auxiliary carrier synchronization system under the low signal-to-noise ratio environment is suitable for a communication system sensitive to carrier frequency deviation and phase deviation synchronization precision, and high-precision carrier synchronization is achieved under the low signal-to-noise ratio through the polar code auxiliary carrier synchronization method under the low signal-to-noise ratio environment in the steps from the first step to the fifth step, and the communication reliability of the system is improved.
In this embodiment, first, a simulation of the bit error rate performance is performed on a communication system that does not carry wave synchronization compensation. In the simulation, an input signal is first encoded (2048, 1024) by a polar code encoding unit, then modulated by a modulation unit, and subjected to different degrees of frequency offset ([ 01.5 e-4 ]]) As shown in FIG. 3(a), and different degrees of phase deviation ([ -0.6 π]) As shown in fig. 3 (b). And demodulating the signal with frequency offset/phase offset after Gaussian noise to obtain a baseband signal, and sending the baseband signal to a polar code decoding unit. The specific bit error rate simulation result obtained by monte carlo simulation is shown in fig. 3. Fig. 3(a) is a graph of error rates under different frequency offsets, and fig. 3(b) is a graph of error rates under different frequency offsets. From FIG. 3(a), it can be seen that when the fluctuation range of the frequency offset is 10-5When the frequency deviation is within the range, the frequency deviation has little influence on the decoding performance of the polarization code, and the frequency deviation continues to increase to 1.2 × 10-4When compared to a system without frequency offset, the system will experience a 0.5dB performance loss, and when the frequency offset again increases to 1.3 × 10-4Sometimes, the decoder may not even work properly. In addition, as can be seen from fig. 3(b), when the fluctuation range of the phase deviation is between-0.5 pi and 0.5 pi, the decoding performance of the polarization code is hardly affected and the decoding performance is excellent. But decoding performance deteriorates drastically when the phase deviation exceeds this range. In summary, when the frequency offset and the phase offset exist at the same time, the decoding performance of the system is worse.
The basis of the above-mentioned communication system with frequency deviation and phase deviationThe frequency offset calculation unit and the frequency offset compensation unit are added, that is, the system structure proposed in this embodiment is adopted (as shown in fig. 1). In the embodiment of the present invention, the polar code-aided carrier synchronization algorithm expressed by formula (9) is referred to as PCAA (polar code-aided algorithm), and the polar code-aided carrier synchronization algorithm expressed by formula (10) is referred to as S-PCAA (simplified polar code-aided algorithm). In fig. 4 and 5, graphs of mean Estimated value mev (mean Estimated value) of frequency and phase synchronization for three code patterns ( code length 2048, 1024, 512, respectively, and code rate 0.5) are listed based on PCAA and S-PCAA algorithms. In this validation, a Monte Carlo simulation of 10000 samples was performed at an Eb/N0 of 2.5 dB. First, it can be seen from fig. 4 that the performance curves of PCAA and S-PCAA almost coincide, so in practical applications, a simpler S-PCAA algorithm is usually used for estimating the frequency offset and the phase offset. As can be seen from fig. 4(a) and (b), when the code pattern is (2048, 1024), the frequency offset estimation accuracy of the PCAA and S-PCAA algorithms reaches 10-4And the reliable synchronization range is [ -1.5 × 10 [ -1.5 [ ]-4,1.5×10-4]And the reliable synchronous range of the simultaneous phase deviation estimation is [ -0.4 pi, 0.4 pi]. Furthermore, as can be seen from fig. 5, as the code length is reduced, the reliable synchronization range of the frequency offset is widened, and the reliable synchronization range of the phase offset remains unchanged.
In consideration of the fact that the MEV curve cannot accurately reflect the fluctuation of the estimated accuracy, in fig. 6, simulation comparison between the rmse (root Mean Square error) and the MCRB (Modified frame-Rao Bound) is performed on the polarization code assisted carrier synchronization estimation algorithm under the environment with the reduced signal-to-noise ratio provided by this embodiment. As shown in FIG. 6, Fitz Estimation and V & V Estimation are traditional frequency offset and phase offset Estimation methods, and compared with the Fitz Estimation and V & V Estimation, S-PCAA curves are closer to MCRB, which shows that compared with the traditional Estimation algorithm, the S-PCAA Estimation precision is higher. The performance of the polar code assisted carrier synchronization algorithm provided by the embodiment is better than that of the traditional synchronization algorithm.
The main content of the polarization code auxiliary carrier synchronization system in the low signal-to-noise ratio environment described above can accurately estimate the carrier frequency offset phase offset through the system structure provided by the embodiment of the present invention, so as to compensate the received signal and finally achieve the purpose of correct decoding. In practical application, some or all of the modules may be selected as needed to achieve the purpose of the solution of the embodiment. The structure of the polar code assisted carrier synchronization system can be clearly understood by those skilled in the art from the above description of the embodiments.

Claims (5)

1. A polar code assisted carrier synchronization system in a low signal-to-noise environment, comprising: the device comprises a frequency offset and phase offset compensation unit, a demodulation unit, a polarization code decoding unit and a frequency offset and phase offset calculation unit;
the frequency deviation and phase deviation compensation unit is used for compensating the difference between the receiving and transmitting carrier frequency and the phase, and the compensated result is used for signal demodulation;
the specific implementation method is as follows,
the frequency offset and phase offset compensation unit performs compensation according to the following formula:
Figure FDA0002515645100000011
wherein:
Figure FDA0002515645100000012
representing the signal received during the l-th iteration, k representing the k-th signal value,
Figure FDA0002515645100000013
representing the estimated frequency offset, T, during the l-1 st iterationsDenotes the symbol period, θ(l-1)Then representing the phase deviation estimated value obtained in the first-1 iteration process;
the demodulation unit is used for demodulating the compensated received signal value, obtaining prior information and then transmitting the prior information to the polar code decoding unit to participate in decoding;
the polar code decoding unit is used for finishing the polar code decoding function of the receiving system, outputting a final decoding result, namely an estimated value signal of a sending signal, and outputting posterior information at the same time;
the frequency offset and phase offset calculation unit is used for estimating the frequency offset and the phase offset of the carrier according to the posterior information fed back by the polar code decoding unit;
the frequency offset and phase offset calculation method of the frequency offset and phase offset calculation unit is as follows,
introducing an expectation maximization algorithm to estimate frequency offset and phase offset; the expectation-maximization algorithm is an effective method for iteratively solving the maximum likelihood estimation; frequency offset according to an expectation maximization algorithm
Figure FDA0002515645100000014
Sum phase deviation estimate
Figure FDA0002515645100000015
Is expressed as formula (2) and formula (3):
Figure FDA0002515645100000016
Figure FDA0002515645100000017
wherein the content of the first and second substances,
Figure FDA0002515645100000018
representing the estimated synchronization parameter in the l-1 th iteration, i.e.
Figure FDA0002515645100000019
Af denotes a sample of the frequency offset search,
Figure FDA00025156451000000110
denotes the A posteriori expected value of the k-th symbol, D denotes the number of received symbols, TsWhich is indicative of the period of the symbol,
Figure FDA00025156451000000111
representing the estimated frequency offset value in the ith iteration process, and representing an angle solving function by arg {. cndot.; wherein the posterior expected value is based on polarizationThe code decoding posterior information is calculated, and the specific implementation method comprises the following steps:
firstly, the kth bit x in the ith iteration is calculated according to a decoding method of a polarization codekThe A posteriori LLR of (2) is shown in equation (4)
Figure FDA0002515645100000021
In BPSK modulation systems, the modulation symbols skIs expressed as a conditional probability of
Figure FDA0002515645100000022
And the following equation is established,
Figure FDA0002515645100000023
the material is pushed out of the die,
Figure FDA0002515645100000024
in the same way, skThe conditional probability of exp (j · 1 · pi) is expressed as,
Figure FDA0002515645100000025
from which the expected posterior value is derived
Figure FDA0002515645100000026
The expression (c) of (a),
Figure FDA0002515645100000027
where tanh (x) is a hyperbolic tangent function, which can be written as
Figure FDA0002515645100000028
In the form of (a); in view of the complexity in the hardware implementation,
Figure FDA0002515645100000029
the method is further simplified into the following steps of,
Figure FDA00025156451000000210
th is a set threshold; therefore, the frequency offset and the estimated value of the phase offset are obtained by iterative calculation according to the formula (2), the formula (3), the formula (9) or the formula (2), the formula (3) and the formula (10) until the correct decoding is carried out or the maximum iteration number is reached.
2. A method for operating a polar code assisted carrier synchronization system in a low snr environment, which is implemented based on the polar code assisted carrier synchronization system in a low snr environment according to claim 1, wherein: comprises the following steps of (a) carrying out,
the method comprises the following steps: during the first iteration, initializing a frequency offset and phase offset compensation value to be 0 for the first calculation of a frequency offset and phase offset compensation unit;
step two: in the first iteration, the frequency offset and phase offset compensation unit compensates the channel output information according to the last frequency offset and phase offset calculation value, and outputs the compensated information to the demodulation unit;
step three: the demodulation unit receives the compensated information to perform demodulation processing and outputs the demodulated information to the polar code decoding unit;
step four: the polar code decoding unit receives the demodulated information as decoding prior information to decode, and outputs a decoding result and decoding posterior information;
step five: the frequency offset and phase offset calculation unit receives the decoded posterior information to perform current iteration frequency offset and phase offset value calculation, and outputs the frequency offset and the phase offset value to the frequency offset and phase offset compensation unit; in the calculation process, if the iteration times reach the preset maximum times, stopping iteration, and taking the output result of the current decoding as the final decoding output, wherein the final decoding output is the final result meeting the requirement of carrier synchronization precision; otherwise, outputting the frequency offset and the phase offset value of the iteration to a frequency offset and phase offset compensation unit, namely returning to the frequency offset and phase offset compensation unit in the second step for the next iteration.
3. The operating method of the polar code assisted carrier synchronization system in low snr environment as claimed in claim 2, wherein: the polar code auxiliary carrier synchronization system under the low signal-to-noise ratio environment is suitable for a communication system sensitive to carrier frequency deviation and phase deviation synchronization precision, and high-precision carrier synchronization is achieved under the low signal-to-noise ratio environment through the polar code auxiliary carrier synchronization method under the low signal-to-noise ratio environment in the steps from the first step to the fifth step, and the communication reliability of the system is improved.
4. The operating method of the polar code assisted carrier synchronization system in low snr environment as claimed in claim 3, wherein: the specific implementation method of the fourth step is as follows, and the polar code decoding method of the polar code decoding unit comprises a BP algorithm based on a generator matrix G and a BP algorithm based on a check matrix H.
5. The operating method of the polar code assisted carrier synchronization system in low snr environment as claimed in claim 4, wherein: the polar code decoding unit adopts an H-based BP decoding algorithm for decoding.
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Publication number Priority date Publication date Assignee Title
CN111030704B (en) * 2019-12-31 2021-07-27 华中科技大学 Polarization code-based synchronization-free communication method, device and system
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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102075476A (en) * 2009-11-25 2011-05-25 电子科技大学 Iteration carrier synchronization method used under condition of extremely low signal to noise ratio
CN102209058A (en) * 2011-06-02 2011-10-05 北京理工大学 Low density parity check (LDPC)-coding-assisted mary phase-shift keying (MPSK) system carrier synchronization method
CN102316062A (en) * 2010-07-07 2012-01-11 电子科技大学 Algorithm for synchronizing carrier wave based on prior probability assistance
US9712317B2 (en) * 2015-02-17 2017-07-18 Avago Technologies General Ip (Singapore) Pte. Ltd. Carrier synchronization appropriate for ALM NFC data transmission
CN107769841A (en) * 2017-10-19 2018-03-06 中国人民解放军陆军工程大学 Satellite communication Turbo code iterative demodulation method under high dynamic Arctic ice area
CN109547156A (en) * 2018-10-18 2019-03-29 北京理工大学 Non-coherent detection methods, device and the electronic equipment of polar short code

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102075476A (en) * 2009-11-25 2011-05-25 电子科技大学 Iteration carrier synchronization method used under condition of extremely low signal to noise ratio
CN102316062A (en) * 2010-07-07 2012-01-11 电子科技大学 Algorithm for synchronizing carrier wave based on prior probability assistance
CN102209058A (en) * 2011-06-02 2011-10-05 北京理工大学 Low density parity check (LDPC)-coding-assisted mary phase-shift keying (MPSK) system carrier synchronization method
US9712317B2 (en) * 2015-02-17 2017-07-18 Avago Technologies General Ip (Singapore) Pte. Ltd. Carrier synchronization appropriate for ALM NFC data transmission
CN107769841A (en) * 2017-10-19 2018-03-06 中国人民解放军陆军工程大学 Satellite communication Turbo code iterative demodulation method under high dynamic Arctic ice area
CN109547156A (en) * 2018-10-18 2019-03-29 北京理工大学 Non-coherent detection methods, device and the electronic equipment of polar short code

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
码辅助迭代载波同步算法的实现;杨光辉,张曙霞,蒋宇中;《舰船电子工程》;20171231;全文 *

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