CN113315734A - Carrier synchronization method and device for satellite, electronic equipment and readable medium - Google Patents
Carrier synchronization method and device for satellite, electronic equipment and readable medium Download PDFInfo
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Abstract
The disclosure relates to a carrier synchronization method, device, electronic device and computer readable medium for satellite. The method comprises the following steps: a satellite receiving terminal acquires a carrier input signal; carrying out data separation on the carrier signals to generate a first short training sequence, a second short training sequence and a long training sequence; generating a frequency offset estimation value based on the first short training sequence and the second short training sequence; generating a compensation coefficient based on the frequency offset estimate value, the second short training sequence, and the long training sequence; and integrating based on the compensation coefficient and the long training sequence to complete carrier synchronization and generate a carrier output signal. The carrier synchronization method, the carrier synchronization device, the electronic equipment and the computer readable medium for the satellite can accurately and quickly perform synchronization processing on the communication carrier signals of the satellite, and ensure the communication safety of the satellite.
Description
Technical Field
The present disclosure relates to the field of computer information processing, and in particular, to a carrier synchronization method and apparatus for a satellite, an electronic device, and a computer-readable medium.
Background
Communication systems are an important part of performing satellite flight and various functions. The conventional satellite has a long data acquisition time period, and high-definition images and data signals can be acquired only after the task is finished. Due to the real-time performance of the control command system, high-speed data is required to meet the real-time performance of information transmission. The key for realizing remote control of the satellite is a data flow technology of broadband and big data. If data information can not be communicated and transmitted under the interference of enemies and normal instruction interaction can not be carried out, a command system of the satellite-based intelligent communication system can not operate the satellite, and the functional advantages of the satellite-based intelligent communication system can not be exerted.
The satellite launching and recovery control system, the main control system, the communication system and the satellite form a complete medium and long distance satellite system. The main control system is used for controlling the satellite to arrive at a designated place to complete certain tasks; the launching and recovering system can simultaneously control the rise and fall and communication of a plurality of satellites, is the core of the system and is a platform for completing various tasks. The communication system can transmit and recover various signals and is a bridge for connecting the control system and the satellite, so the development of the communication system directly influences the functional system of the whole satellite.
The above information disclosed in this background section is only for enhancement of understanding of the background of the disclosure and therefore it may contain information that does not constitute prior art that is already known to a person of ordinary skill in the art.
Disclosure of Invention
The present disclosure provides a carrier synchronization method and apparatus for a satellite, an electronic device, and a computer-readable medium, which can perform accurate and fast synchronization processing on a communication carrier signal of the satellite, thereby ensuring the security of satellite communication.
Additional features and advantages of the disclosure will be set forth in the detailed description which follows, or in part will be obvious from the description, or may be learned by practice of the disclosure.
According to an aspect of the present disclosure, a carrier synchronization method for a satellite is provided, the method including: a satellite receiving terminal acquires a carrier input signal; carrying out data separation on the carrier input signal to generate a first short training sequence, a second short training sequence and a long training sequence; generating a frequency offset estimation value based on the first short training sequence and the second short training sequence; generating a compensation coefficient based on the frequency offset estimate value, the second short training sequence, and the long training sequence; and integrating based on the compensation coefficient and the long training sequence to complete carrier synchronization and generate a carrier output signal.
In an exemplary embodiment of the present disclosure, a satellite receiving end acquires a carrier input signal, including: an antenna of a satellite receiving end acquires a signal in a wireless channel; signal processing the signal to generate the carrier input signal.
In an exemplary embodiment of the present disclosure, data separating the carrier input signal to generate a first short training sequence, a second short training sequence, and a long training sequence includes: extracting a first short training sequence, a second short training sequence and a long training sequence in the carrier input signal; and acquiring symbols and data symbols corresponding to the first short training sequence, the second short training sequence and the long training sequence in the carrier input signal based on a counter.
In an exemplary embodiment of the present disclosure, generating a frequency offset estimate value based on the first short training sequence and the second short training sequence includes: generating an integer frequency offset estimator based on the first short training sequence; generating a decimal frequency offset estimator based on the first short training sequence and the second short training sequence; generating the frequency offset estimate value based on the integer frequency offset estimator and the fractional frequency offset estimator.
In an exemplary embodiment of the disclosure, generating an integer multiple frequency offset estimator based on the first short training sequence comprises: obtaining an even number value of an integer frequency offset estimator based on the differential sequence of the first short training sequence; and setting the even number position of the integer frequency offset estimator as 0.
In an exemplary embodiment of the disclosure, generating a fractional frequency offset estimator based on the first short training sequence and the second short training sequence includes: generating a conjugate correlation sequence based on the preamble corresponding to the first short training sequence and the second short training sequence; and after a preset interval, performing conjugate correlation processing on a plurality of short training sequences in the first short training sequence to generate a fractional frequency offset estimator.
In an exemplary embodiment of the disclosure, generating the frequency offset estimate value based on the integer multiple frequency offset estimator and the fractional multiple frequency offset estimator comprises: performing pairwise correlation operation on symbols corresponding to the short training sequences in the first short training sequence to generate a plurality of connection results; generating a plurality of cumulative values based on the concatenation and a plurality of short training sequences of the first short training sequence; determining the integer multiple frequency offset estimator and the fractional multiple frequency offset estimator based on the plurality of accumulated values to generate the frequency offset estimate value.
In an exemplary embodiment of the present disclosure, the first short training sequence includes five short training symbols; determining the frequency offset estimate value based on the plurality of accumulated values, comprising: generating four cumulative values based on the five short training symbols; performing an averaging calculation based on the four accumulated values to generate the frequency offset estimate value.
In an exemplary embodiment of the present disclosure, integrating based on the compensation coefficient and the long training sequence to complete carrier synchronization and generate a carrier output signal includes: determining symbols and data symbols corresponding to the long training sequence; performing frequency offset compensation on the long training sequence based on the compensation coefficient, the symbol corresponding to the long training sequence and the data symbol; and integrating the data after the frequency offset compensation with the carrier input signal to complete carrier synchronization and generate a carrier output signal.
According to an aspect of the present disclosure, a carrier synchronization apparatus for a satellite is provided, the apparatus including: the acquisition module is used for a satellite receiving terminal to acquire a carrier input signal; a separation module, configured to perform data separation on the carrier input signal to generate a first short training sequence, a second short training sequence, and a long training sequence; an estimation module, configured to generate a frequency offset estimation value based on the first short training sequence and the second short training sequence; a compensation module configured to generate a compensation coefficient based on the frequency offset estimate, the second short training sequence, and the long training sequence; and the output module is used for integrating the compensation coefficient and the long training sequence to complete carrier synchronization and generate a carrier output signal.
According to an aspect of the present disclosure, an electronic device is provided, the electronic device including: one or more processors; storage means for storing one or more programs; when executed by one or more processors, cause the one or more processors to implement a method as above.
According to an aspect of the disclosure, a computer-readable medium is proposed, on which a computer program is stored, which program, when being executed by a processor, carries out the method as above.
According to the carrier synchronization method, the carrier synchronization device, the electronic equipment and the computer readable medium for the satellite, a satellite receiving end acquires a carrier input signal; carrying out data separation on the carrier signals to generate a first short training sequence, a second short training sequence and a long training sequence; generating a frequency offset estimation value based on the first short training sequence and the second short training sequence; generating a compensation coefficient based on the frequency offset estimate value, the second short training sequence, and the long training sequence; and based on the mode of integrating the compensation coefficient and the long training sequence to complete carrier synchronization and generate a carrier output signal, the communication carrier signal of the satellite can be accurately and quickly synchronized, and the satellite communication safety is ensured.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.
Drawings
The above and other objects, features and advantages of the present disclosure will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings. The drawings described below are merely some embodiments of the present disclosure, and other drawings may be derived from those drawings by those of ordinary skill in the art without inventive effort.
Fig. 1 is a block diagram illustrating a carrier synchronization system for a satellite according to an example embodiment.
Fig. 2 is a block diagram illustrating a carrier synchronization system for a satellite according to another exemplary embodiment.
Fig. 3 is a flow chart illustrating a method of carrier synchronization for a satellite according to an example embodiment.
Fig. 4 is a diagram illustrating a carrier synchronization method for a satellite according to another exemplary embodiment.
Fig. 5 is a diagram illustrating a carrier synchronization method for a satellite according to another exemplary embodiment.
Fig. 6 is a diagram illustrating a carrier synchronization method for a satellite according to another exemplary embodiment.
Fig. 7 is a diagram illustrating a carrier synchronization method for a satellite according to another exemplary embodiment.
Fig. 8 is a block diagram illustrating a carrier synchronization apparatus for a satellite according to an example embodiment.
FIG. 9 is a block diagram illustrating an electronic device in accordance with an example embodiment.
FIG. 10 is a block diagram illustrating a computer-readable medium in accordance with an example embodiment.
Detailed Description
Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art. The same reference numerals denote the same or similar parts in the drawings, and thus, a repetitive description thereof will be omitted.
Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments of the disclosure. One skilled in the relevant art will recognize, however, that the subject matter of the present disclosure can be practiced without one or more of the specific details, or with other methods, components, devices, steps, and so forth. In other instances, well-known methods, devices, implementations, or operations have not been shown or described in detail to avoid obscuring aspects of the disclosure.
The block diagrams shown in the figures are functional entities only and do not necessarily correspond to physically separate entities. I.e. these functional entities may be implemented in the form of software, or in one or more hardware modules or integrated circuits, or in different networks and/or processor means and/or microcontroller means.
The flow charts shown in the drawings are merely illustrative and do not necessarily include all of the contents and operations/steps, nor do they necessarily have to be performed in the order described. For example, some operations/steps may be decomposed, and some operations/steps may be combined or partially combined, so that the actual execution sequence may be changed according to the actual situation.
It will be understood that, although the terms first, second, third, etc. may be used herein to describe various components, these components should not be limited by these terms. These terms are used to distinguish one element from another. Thus, a first component discussed below may be termed a second component without departing from the teachings of the disclosed concept. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
It is to be understood by those skilled in the art that the drawings are merely schematic representations of exemplary embodiments, and that the blocks or processes shown in the drawings are not necessarily required to practice the present disclosure and are, therefore, not intended to limit the scope of the present disclosure.
The satellite high-speed channel is a multipath propagation channel model, and key characteristics of the channel can be obtained by analyzing the Doppler power spectrum and the time delay power spectrum of the satellite high-speed channel. Considering the normal flight state of the satellite, the environment is wide, the multipath fading is small, and the channel transmission has a main path. The delay power spectrum and the Doppler power spectrum are as follows.
1) Time delay power spectrum:
in a flight scenario, because the environment is relatively wide, we can consider that a transmission channel is composed of two parts, one LOS path and one cluster of reflection paths. Thus, in modeling, we can consider a two-path model to describe the channel. The LOS path is typically described by a constant model and the reflected path is modeled by a rayleigh model. The envelope of the whole channel presents a Rice distribution characteristic, the value range of the Rice factor is 2-20dB, the typical Rice factor of the aviation telemetering channel is 15dB according to the literature, and when the Rice factor is
Time, indicates that the channel is in the worst case.
Since the distance of a satellite from its long range is much greater than its altitude, we can generally consider the difference between the scattering component of the reflected path and the component of the LOS path
And h represents the vertical distance between the satellite and the plane where the ground measurement and control station is located and the high end of the flight.
The average additional delay can be found from:
from this, the root mean square delay spread of
Is 5.69
If the correlation coefficient is at least 0.5, the coherence bandwidth is:
for satellite communication, the transmission rate of data is generally 2Mbps, the signal bandwidth is much larger than the coherent bandwidth, and the channel is a frequency selective fading channel.
Doppler power spectrum:
the velocity of the satellite, which is also an important part of the channel analysis to consider, affects the doppler shift of the channel. In the design, the general situation is considered, the maximum speed of the satellite in daily flight in the air is 70km/s, and the maximum Doppler frequency shift of a channel can be obtained
. The solid line part represents the angle reached by the scattered component and the whole dotted line part represents a non-two-dimensional isotropic scattering doppler power spectrum, proposed by Clark and also known as Jakes distribution.
Assuming that the angle at which the component of the scattering path reaches the ground observation station is
A function that is uniformly distributed in the range,
，
the values of (a) can be in the following three cases:
when in use
The probability density function of the doppler shift can be expressed as:
when in use
The probability density function of the doppler shift can be expressed as:
when the arrival beam angle spans 0 ° or 180 °, the doppler power spectrum of the channel can be regarded as a weighted sum of the two parts above, and the weighting coefficients are determined by the specific case.
The present disclosure assumes that the scattering component is considered on a two-dimensional plane, more closely to the actual three-dimensional scattering quantity distribution, that the angle exhibits a gaussian distribution within the beam range, and that the beam width decreases with increasing distance. In the worst case, the direction of arrival of the LOS component is 0 DEG, at which time the Doppler shift of the LOS component
。
Fig. 1 is a block diagram illustrating a carrier synchronization system for a satellite according to an example embodiment. The carrier synchronization system 10 of the satellite is a transmitting part of the satellite system, and firstly encodes an input signal, then performs interleaving processing on the signal, performs constellation point mapping on information after serial-parallel change on a transmitting end, distributes the coincidence processed in the previous step on each subcarrier, introduces designed corresponding pilot frequency information between the coincidences, obtains time domain coincidence through IFFT parallel-serial change, obtains a complete time domain frame signal by adding a cyclic prefix, and finally transmits the converted analog signal to a wireless channel by using an antenna through a radio frequency module. Thus, the whole transmitting process is finished.
Fig. 2 is a block diagram illustrating a carrier synchronization system for a satellite in accordance with an example embodiment. The carrier synchronization system 20 of the satellite is the receiving part of the satellite system, and the steps of the receiving process are the reverse of those of the transmitting end. It first obtains the signal in the wireless channel through the antenna, then through a series of processing steps opposite to the transmitting system, finally outputs the demodulated result.
The frequency offset estimation of the carrier is a very important part in the synchronization technology, and the frequency offset is also divided into an integer part and a decimal part. The fractional frequency offset can generate intersymbol interference, which is to say, the orthogonality of subcarriers is damaged, and ICI (inter-carrier interference) occurs; the frequency offset of the integer part can cause cyclic shift between data carriers of a receiver, although the orthogonality among the carriers cannot be destroyed. Statistically, the bit error rate of the system is random probability. Frequency offset estimation is often performed using Schmidl and Kim's approach and pilot-based estimation methods, and improvements are made in these methods, such as using only a special preamble. In general, estimating the frequency offset and synchronizing the timing are typically done together.
The signal received by the satellite is mostly frequency-offset in the frequency domain. Therefore, the integer frequency form offset estimation can obtain a receiving sequence by using the cyclic shift condition of the known sequence and the receiving end, record the occurrence condition of the cyclic shift point and the relevant value condition, and search the relevant value to realize the maximum value of the shift point correlation, namely the integer multiple of the frequency offset. The traditional method introduces a schindl algorithm to complete integral multiple in frequency offset estimation. The algorithm uses a difference between the two sequences, but since the odd bits are 0 in this algorithm, the frequency case that yields an integer multiple is estimated to be 2 times. That is, the integer frequency offset value is calculated to be even at this time. When technical frequency deviation occurs, it is no longer accurate, which is detrimental to the system performance. In the present disclosure, carrier synchronization of satellite signals is achieved as follows.
Fig. 3 is a flow chart illustrating a method of carrier synchronization for a satellite according to an example embodiment. The carrier synchronization method 30 for a satellite includes at least steps S302 to S310.
As shown in fig. 3, in S302, the satellite receiving end acquires a carrier input signal. The method comprises the following steps: an antenna of a satellite receiving end acquires a signal in a wireless channel; signal processing the signal to generate the carrier input signal.
In S304, the carrier signal is subjected to data separation to generate a first short training sequence, a second short training sequence, and a long training sequence. The method comprises the following steps: extracting a first short training sequence, a second short training sequence and a long training sequence in the carrier signal; and acquiring symbols and data symbols corresponding to the first short training sequence, the second short training sequence and the long training sequence in the carrier signal based on a counter.
In S306, a frequency offset estimation value is generated based on the first short training sequence and the second short training sequence. The method comprises the following steps: generating an integer frequency offset estimator based on the first short training sequence; generating a decimal frequency offset estimator based on the first short training sequence and the second short training sequence; generating the frequency offset estimate value based on the integer frequency offset estimator and the fractional frequency offset estimator.
The signal obtained by adding the cyclic prefix in the classical carrier synchronization algorithm is as follows:
the signal received through the high white channel contains frequency offset, and the received signal is as follows:
The frequency offset is a part of the phase, and therefore, on the imaginary index, there are two expressions, namely, actual frequency offset and normalized frequency offset (i.e., the ratio of the frequency offset to the subcarrier spacing). Typically, the normalized frequency offset is used more in the simulation in the OFDM system.
The frequency offset correction means that the estimated frequency offset is multiplied by an opposite imaginary exponent to correct the frequency offset.
The fractional frequency offset may be estimated and corrected using the cyclic prefix CP and preamble of the OFDM symbol for correlation, summation, and angle:
the frequency offset estimation of the related integer multiple is to obtain the highest g by the following formula,
is to perform preamble transmission:
where g is a positive integer, the search range of the frequency offset is defined, and the number of bits of the cyclic shift is defined when g1 is the maximum value.
The original sequence TS1 in the SC scheme of the Schmidl & C mode is a random complex number in the corresponding modulation data of even number subcarriers, and the corresponding odd number bits are all 0; conversely, the odd bits are complex numbers, the even bits are 0, and the data sequence obtained by IFFT has the characteristic that the first half is equal to the second half.
Conveniently estimating the integer frequency offset, and defining the frequency domain difference of the two previous and next original sequences TS1 and TS2 as the following relation:
here, the sequence TS1 is an odd number of subcarriers and the data is 0, so the two sequences TS1 and TS2 are only established to distinguish even number positions
At reception, the relative integer frequency offset is determined as:
if the maximum value g is obtained
Then the integer multiple related frequency offset is:
the estimation interval is [ -N/2, N/2]. Here, the
，
The TS1 and TS2 of the sequence are obtained by FFT conversion at the receiving end.
As shown in fig. 4, in the simulation operation performed under the gaussian channel condition, the frequency offset is a definite value, it can be seen that both the schindl algorithm and the Park algorithm can approach the CRB, and the effect of the Park algorithm is less when a low signal-to-noise ratio exists. Because the training sequence is also short, the Minn algorithm gives inaccuracy, but its estimation range is large.
The Minn algorithm is similar to the Park algorithm in structure to finish frequency offset estimation and is obtained by the Schrnidl algorithm, the calculation is a communication system under the high-speed condition, but the frequency offset is processed as a constant value, only frequency offsets with integer and decimal multiplying power appear, the mechanism of the Minn algorithm refers to the S & C algorithm, and the decimal frequency offset estimation is different only due to the difference of training sequences.
The signal received by the satellite is mostly frequency-offset in the frequency domain. Therefore, the integer frequency form offset estimation can obtain a receiving sequence by using the cyclic shift condition of the known sequence and the receiving end, record the occurrence condition of the cyclic shift point and the relevant value condition, and search the relevant value to realize the maximum value of the shift point correlation, namely the integer multiple of the frequency offset.
The traditional method introduces a schindl algorithm to complete integral multiple in frequency offset estimation. The algorithm uses a difference between the two sequences, but since the odd bits are 0 in this algorithm, the frequency case that yields an integer multiple is estimated to be 2 times. That is, the integer frequency offset value is calculated to be even at this time. When technical frequency deviation occurs, it is no longer accurate, which is detrimental to the system performance.
In the present disclosure, if the differential sequence is used to obtain the even-numbered sequence correlation differential, only 0 is needed to be filled in the odd-numbered bits, and the difference sequence is used to obtain the N sequence, so that when the receiving end completes the cyclic shift, the judgment formula for obtaining the integer frequency is:
when the above formula takes a maximum value g of
Then the integer multiple of frequency offset is:
。
as can be seen from fig. 5, since the schirndl algorithm performs twice the final integer part frequency offset value obtained by estimation, when the integer frequency offset is an odd value, it changes randomly; the improved algorithm successfully computes each integer frequency offset.
In the previous section, a decimal frequency offset algorithm is introduced, the classic is that two half-length conjugates are obtained before and after schindl, then improved algorithms such as Minn and Park have very similar structures, and the frequency offset algorithm completed by using a plurality of single training symbols is song and Morell, and at the moment, the estimation interval is small. A plurality of repeated parts are needed for a single training symbol, under the condition of reducing the frequency offset estimation precision, compared with large frequency offset estimation, the used operation complexity is increased, the training symbol is known to realize timing offset estimation, and the error is relatively large. With reference to the fractional frequency offset operation under the cyclic prefix, as long as the precision range is balanced with the length dimension of the cyclic sequence, the length of the cyclic prefix cannot be too large, and the efficiency of the channel is severely reduced, so that careful consideration is required.
The related estimation scheme of communication frequency offset in the case of high-speed movement can use the following fractional order frequency offset. And (3) realizing conjugate correlation according to the preamble of the received information and the locally existing sequence, and after the L-point interval, the conjugate correlation is as follows:
the range of the estimate decreases as the value of L increases, with a consequent increase in the accuracy of the estimate.
The method can be circulated to reach a specific estimation precision, but the estimation precision is related to the sequence length, and the frequency offset estimation precision is limited by the sequence length.
Generating an integer frequency offset estimator based on the first short training sequence, comprising: obtaining an even number value of an integer frequency offset estimator based on the differential sequence of the first short training sequence; and setting the even number position of the integer frequency offset estimator as 0.
Wherein generating a fractional frequency offset estimator based on the first short training sequence and the second short training sequence comprises: generating a conjugate correlation sequence based on the preamble corresponding to the first short training sequence and the second short training sequence; and after a preset interval, performing conjugate correlation processing on a plurality of short training sequences in the first short training sequence to generate a fractional frequency offset estimator.
Wherein generating the frequency offset estimate based on the integer frequency offset estimator and the fractional frequency offset estimator comprises: performing pairwise correlation operation on symbols corresponding to the short training sequences in the first short training sequence to generate a plurality of connection results; generating a plurality of cumulative values based on the concatenation and a plurality of short training sequences of the first short training sequence; determining the integer multiple frequency offset estimator and the fractional multiple frequency offset estimator based on the plurality of accumulated values to generate the frequency offset estimate value.
Short training sequences for acquisition and framing, carrier-synchronized frequency offset estimation of long training sequences, then the frame header of the frame structure is six long sequences, the first five being identical, the same characteristics in the time domain of each sequence, so that there are always ten short sequences in the time domain. Since the ten peaks associated with the received sequence and the local sequence are arranged in descending and ascending order, the starting position of the data can be deduced based on the same concept as before. Since the channel and the frequency offset may affect the actual signal, that is, the actual system is greatly affected by the frequency offset, the probability of packet detection with an increased false alarm rate is reduced. The sequence combination using the SC algorithm is applied in combination with the Minn algorithm to further reduce the error. Although the Minn algorithm is used in the present application, the sequence used in the method is not obtained by the method, and the influence of the frequency offset on the system is reduced by using the corresponding five identical long sequences to take the average value of the sum of the five identical long sequences.
The use of the first five identical long sequences plus averaging makes the correlation peak more sharp, and also avoids the flat top state of the S & C method. Most importantly it is also only the preliminary timing for frame detection, fine synchronization being applied using the locally stored sequence and the received sequence as correlation sequences. Since the accuracy of the timing is then integrated with the results of the previous synchronization detection, the autocorrelation search method can more conveniently find the characteristics of searching for an accurate position, and in the present disclosure, fine synchronization is accomplished by using this algorithm.
This method is affected by too large a frequency offset. Therefore, the integer frequency offset can be estimated by using the detected frame, and then the frequency offset is corrected, so that the influence caused by the frequency offset can be weakened, and the timing accuracy, namely the accuracy in detection can be improved.
In S308, a compensation coefficient is generated based on the frequency offset estimate value, the second short training sequence, and the long training sequence.
On the basis of a wireless communication system, a comb-shaped pilot frequency mechanism is used, only pilot frequency is used for completing auxiliary calculation in channel estimation, a part with the information is placed at a receiving part, and is converted into a frequency domain signal to be extracted, so that proper pilot frequency can be obtained, and the condition of obtaining an input signal can be recovered more accurately. In view of the previous analysis, comb pilots cannot be used continuously in the frequency domain, so a reasonable interpolation can have all the required information, and the relevant interpolation method and theoretical case are as follows.
Combining with interpolation relative channel estimation, selecting fixed position as pilot frequency point, inserting known signal sequence, using channel transmission to obtain pilot information, estimating the information, finding out ideal interpolation method according to the transmission number of pilot channel, and using interpolation relative function to obtain the required effective transfer function of non-pilot channel.
In one embodiment, the channel timing should be fast tracking. The algorithm has low complexity and is easier to implement. The pilot frequency presents time-frequency two-dimensional distribution in the system, so the calculation needs to be completed in two areas.
The implementation steps are as follows:
firstly, calculating the channel frequency response of the pilot frequency point by using an estimation algorithm:
secondly, according to the pilot frequency position and the determined structure degree, a related weight matrix W is obtained through calculation;
thirdly, frequency domain filtering, namely obtaining a channel response matrix related to the data subcarriers by using the weight matrix W and the channel estimation value of the pilot frequency position, wherein the channel response matrix is the only matrix related to the wavelet frequency domain:
fourthly, linear interpolation operation under the condition of time domain is completed, the pilot frequency of the adjacent OFDM symbols is used for completing channel estimation calculation on the intermediate sub-carrier, the pilot frequency carrier number is used, and the calculated channel estimation is filtered;
the channel estimation value generated by the data subcarrier is interpolated by using the adjacent pilot frequency points through the value obtained by the channel transfer function at the pilot frequency point estimation position, the frequency of the data subcarrier is recovered by using the information of the pilot frequency point,
under the condition that the channel estimation value is obtained, the channel information in the data splicing point is obtained in the same way as the interpolation process.
Generating a compensation coefficient of the system based on the frequency offset estimation value calculated by the training sequence and the channel estimation value obtained by the pilot frequency.
In S310, the long training sequence is integrated based on the compensation coefficient to complete carrier synchronization and generate a carrier output signal. The method comprises the following steps: determining symbols and data symbols corresponding to the long training sequence; performing frequency offset compensation on the long training sequence based on the compensation coefficient, the symbol corresponding to the long training sequence and the data symbol; and integrating the data after the frequency offset compensation with the carrier input signal to complete carrier synchronization and generate a carrier output signal.
According to the carrier synchronization method for the satellite, the satellite receiving end acquires a carrier input signal; carrying out data separation on the carrier signals to generate a first short training sequence, a second short training sequence and a long training sequence; generating a frequency offset estimation value based on the first short training sequence and the second short training sequence; generating a compensation coefficient based on the frequency offset estimate value, the second short training sequence, and the long training sequence; and based on the mode of integrating the compensation coefficient and the long training sequence to complete carrier synchronization and generate a carrier output signal, the communication carrier signal of the satellite can be accurately and quickly synchronized, and the satellite communication safety is ensured.
It should be clearly understood that this disclosure describes how to make and use particular examples, but the principles of this disclosure are not limited to any details of these examples. Rather, these principles can be applied to many other embodiments based on the teachings of the present disclosure.
Fig. 6 is a diagram illustrating a carrier synchronization method for a satellite according to another exemplary embodiment. A hardware implementation flow analysis of the carrier frequency dependent synchronization case as shown in fig. 6. The module mainly comprises a data stream part, a data buffer part, a carrier frequency offset estimation part, a frequency offset compensation part and a data output part. The operation process of the data in the module is as follows: firstly, judging the symbol and data symbol conditions respectively used by a short training sequence and a related long training sequence according to input data in a counter, and then completing different operations, which are data stream parts; the carrier frequency offset estimation part uses the obtained short training sequence to complete delay correlation addition and average operation so as to calculate a frequency offset estimation value; then, completing compensation coefficient operation based on the frequency offset estimation value, and then completing frequency offset compensation operation on related symbols and data symbols in the long training sequence by referring to the compensation coefficient; and finally, integrating the values obtained by the compensation operation with the values obtained by the original uncompensated operation, and outputting the expected data frame.
Data distribution module
The module performs an input operation of data and divides it into a short training sequence portion, a long training sequence portion and a data symbol portion. In the hardware implementation, a counter is used for counting, and when the count value is between 1 and 160, the count value is a short training symbol and enters a data cache module; when the counting value is between 1 and 80, the first 5 short symbols are sent to the carrier estimation module to complete the frequency offset estimation; when the count value exceeds 160, the long training sequence symbols and the data symbols which need the compensation operation are sent to the frequency offset compensation module.
Carrier frequency offset estimation submodule
This is the most important part of the whole module, and the estimation of field frequency deviation is completed according to the short training sequence symbol reference formula obtained from the data distribution part. As shown, it is composed of a delay correlation part, a correlation accumulation part, and a compensation calculation part.
Carrier frequency offset compensation submodule
The part is based on the calculation of frequency deviation compensation coefficient, and the frequency deviation compensation is needed
Compensation is performed.
In a hardware implementation, the module is divided into two parts: and calculating a compensation coefficient and compensating data. The compensation factor is delayed in consideration that the compensation factor occurs earlier than the compensation data, and the specific flow is as described in fig. 7.
For compensation factor calculation, when the frequency deviation is estimated
Is realized by complement counter
Taking the inverse, and using an accumulator to complete the phase angle operation
The compensation coefficient is
And
and (c). Compensation factors in the buffer when data is compensated
And outputting and using a complex multiplier to complete corresponding carrier frequency offset calculation.
Data association output submodule
The module is the last sub-module in the carrier synchronization module and is used for integrating and outputting long training sequences and data symbols, short training sequences and data symbols which are not subjected to frequency offset compensation. Because the short training symbols are directly sent to the data output module by the data distribution module, and the long training symbols and the data symbols are transmitted after compensation operation, in order to ensure that the short training symbols and the data symbols continuously complete the output operation, a shift register device is required to realize corresponding delay in hardware implementation.
The frequency offset estimation of the carrier is a very important part in the synchronization technology, and the frequency offset is also divided into an integer part and a decimal part. The fractional frequency offset can generate intersymbol interference, which is to say, the orthogonality of subcarriers is damaged, and ICI (inter-carrier interference) occurs; the frequency offset of the integer part can cause cyclic shift between data carriers of a receiver, although the orthogonality among the carriers cannot be destroyed. Statistically, the bit error rate of the system is random probability. Frequency offset estimation is often performed using Schmidl and Kim's approach and pilot-based estimation methods, and improvements are made in these methods, such as using only a special preamble. In general, estimating the frequency offset and synchronizing the timing are typically done together.
Those skilled in the art will appreciate that all or part of the steps implementing the above embodiments are implemented as computer programs executed by a CPU. When executed by the CPU, performs the functions defined by the above-described methods provided by the present disclosure. The program may be stored in a computer readable storage medium, which may be a read-only memory, a magnetic or optical disk, or the like.
Furthermore, it should be noted that the above-mentioned figures are only schematic illustrations of the processes involved in the methods according to exemplary embodiments of the present disclosure, and are not intended to be limiting. It will be readily understood that the processes shown in the above figures are not intended to indicate or limit the chronological order of the processes. In addition, it is also readily understood that these processes may be performed synchronously or asynchronously, e.g., in multiple modules.
The following are embodiments of the disclosed apparatus that may be used to perform embodiments of the disclosed methods. For details not disclosed in the embodiments of the apparatus of the present disclosure, refer to the embodiments of the method of the present disclosure.
Fig. 8 is a block diagram illustrating a carrier synchronization apparatus for a satellite according to an example embodiment. As shown in fig. 8, the carrier synchronization apparatus 80 for a satellite includes: an obtaining module 802, a separating module 804, an estimating module 806, a compensating module 808, and an outputting module 810.
The obtaining module 802 is used for a satellite receiving terminal to obtain a carrier input signal;
the separation module 804 is configured to perform data separation on the carrier signal to generate a first short training sequence, a second short training sequence, and a long training sequence;
an estimation module 806 is configured to generate a frequency offset estimation value based on the first short training sequence and the second short training sequence;
a compensation module 808 configured to generate a compensation coefficient based on the frequency offset estimate, the second short training sequence, and the long training sequence;
the output module 810 is configured to perform integration based on the compensation coefficient and the long training sequence to complete carrier synchronization and generate a carrier output signal.
According to the carrier synchronization device for the satellite, a satellite receiving end acquires a carrier input signal; carrying out data separation on the carrier signals to generate a first short training sequence, a second short training sequence and a long training sequence; generating a frequency offset estimation value based on the first short training sequence and the second short training sequence; generating a compensation coefficient based on the frequency offset estimate value, the second short training sequence, and the long training sequence; and based on the mode of integrating the compensation coefficient and the long training sequence to complete carrier synchronization and generate a carrier output signal, the communication carrier signal of the satellite can be accurately and quickly synchronized, and the satellite communication safety is ensured.
FIG. 9 is a block diagram illustrating an electronic device in accordance with an example embodiment.
An electronic device 900 according to this embodiment of the disclosure is described below with reference to fig. 9. The electronic device 900 shown in fig. 9 is only an example and should not bring any limitations to the functionality or scope of use of the embodiments of the present disclosure.
As shown in fig. 9, the electronic device 900 is embodied in the form of a general purpose computing device. Components of electronic device 900 may include, but are not limited to: at least one processing unit 910, at least one storage unit 920, a bus 930 connecting different system components (including the storage unit 920 and the processing unit 910), a display unit 940, and the like.
Wherein the storage unit stores program code that can be executed by the processing unit 910 such that the processing unit 910 performs the steps according to various exemplary embodiments of the present disclosure described in this specification. For example, the processing unit 910 may perform the steps as shown in fig. 3.
The storage unit 920 may include a readable medium in the form of a volatile storage unit, such as a random access memory unit (RAM) 9201 and/or a cache memory unit 9202, and may further include a read only memory unit (ROM) 9203.
The memory unit 920 may also include a program/utility 9204 having a set (at least one) of program modules 9205, such program modules 9205 including but not limited to: an operating system, one or more application programs, other program modules, and program data, each of which, or some combination thereof, may comprise an implementation of a network environment.
The electronic device 900 may also communicate with one or more external devices 900' (e.g., keyboard, pointing device, bluetooth device, etc.), such that a user can communicate with devices with which the electronic device 900 interacts, and/or any device (e.g., router, modem, etc.) with which the electronic device 900 can communicate with one or more other computing devices. Such communication may occur via input/output (I/O) interface 950. Also, the electronic device 900 may communicate with one or more networks (e.g., a Local Area Network (LAN), a Wide Area Network (WAN) and/or a public network, such as the Internet) via the network adapter 960. The network adapter 960 may communicate with other modules of the electronic device 900 via the bus 930. It should be appreciated that although not shown, other hardware and/or software modules may be used in conjunction with the electronic device 900, including but not limited to: microcode, device drivers, redundant processing units, external disk drive arrays, RAID systems, tape drives, and data backup storage systems, among others.
Through the above description of the embodiments, those skilled in the art will readily understand that the exemplary embodiments described herein may be implemented by software, or by software in combination with necessary hardware. Therefore, as shown in fig. 10, the technical solution according to the embodiment of the present disclosure may be embodied in the form of a software product, which may be stored in a non-volatile storage medium (which may be a CD-ROM, a usb disk, a removable hard disk, etc.) or on a network, and includes several instructions to enable a computing device (which may be a personal computer, a server, or a network device, etc.) to execute the above method according to the embodiment of the present disclosure.
The software product may employ any combination of one or more readable media. The readable medium may be a readable signal medium or a readable storage medium. A readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination of the foregoing. More specific examples (a non-exhaustive list) of the readable storage medium include: an electrical connection having one or more wires, a portable disk, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.
The computer readable storage medium may include a propagated data signal with readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated data signal may take many forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A readable storage medium may also be any readable medium that is not a readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. Program code embodied on a readable storage medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing.
Program code for carrying out operations for the present disclosure may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, C + + or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The program code may execute entirely on the user's computing device, partly on the user's device, as a stand-alone software package, partly on the user's computing device and partly on a remote computing device, or entirely on the remote computing device or server. In the case of a remote computing device, the remote computing device may be connected to the user computing device through any kind of network, including a Local Area Network (LAN) or a Wide Area Network (WAN), or may be connected to an external computing device (e.g., through the internet using an internet service provider).
The computer readable medium carries one or more programs which, when executed by a device, cause the computer readable medium to perform the functions of: a satellite receiving terminal acquires a carrier input signal; carrying out data separation on the carrier signals to generate a first short training sequence, a second short training sequence and a long training sequence; generating a frequency offset estimation value based on the first short training sequence and the second short training sequence; generating a compensation coefficient based on the frequency offset estimate value, the second short training sequence, and the long training sequence; and integrating based on the compensation coefficient and the long training sequence to complete carrier synchronization and generate a carrier output signal.
Those skilled in the art will appreciate that the modules described above may be distributed in the apparatus according to the description of the embodiments, or may be modified accordingly in one or more apparatuses unique from the embodiments. The modules of the above embodiments may be combined into one module, or further split into multiple sub-modules.
Through the above description of the embodiments, those skilled in the art will readily understand that the exemplary embodiments described herein may be implemented by software, or by software in combination with necessary hardware. Therefore, the technical solution according to the embodiments of the present disclosure may be embodied in the form of a software product, which may be stored in a non-volatile storage medium (which may be a CD-ROM, a usb disk, a removable hard disk, etc.) or on a network, and includes several instructions to enable a computing device (which may be a personal computer, a server, a mobile terminal, or a network device, etc.) to execute the method according to the embodiments of the present disclosure.
Exemplary embodiments of the present disclosure are specifically illustrated and described above. It is to be understood that the present disclosure is not limited to the precise arrangements, instrumentalities, or instrumentalities described herein; on the contrary, the disclosure is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
Claims (12)
1. A carrier synchronization method for a satellite, comprising:
a satellite receiving terminal acquires a carrier input signal;
carrying out data separation on the carrier input signal to generate a first short training sequence, a second short training sequence and a long training sequence;
generating a frequency offset estimation value based on the first short training sequence and the second short training sequence;
generating a compensation coefficient based on the frequency offset estimate value, the second short training sequence, and the long training sequence;
and integrating based on the compensation coefficient and the long training sequence to complete carrier synchronization and generate a carrier output signal.
2. The method of claim 1, wherein the satellite receiver acquiring the carrier input signal comprises:
an antenna of a satellite receiving end acquires a signal in a wireless channel;
signal processing the signal to generate the carrier input signal.
3. The method of claim 1, wherein data separating the carrier input signal to generate a first short training sequence, a second short training sequence, a long training sequence, comprises:
extracting a first short training sequence, a second short training sequence and a long training sequence in the carrier input signal;
and acquiring symbols and data symbols corresponding to the first short training sequence, the second short training sequence and the long training sequence in the carrier input signal based on a counter.
4. The method of claim 1, wherein generating a frequency offset estimate value based on the first short training sequence and the second short training sequence comprises:
generating an integer frequency offset estimator based on the first short training sequence;
generating a decimal frequency offset estimator based on the first short training sequence and the second short training sequence;
generating the frequency offset estimate value based on the integer frequency offset estimator and the fractional frequency offset estimator.
5. The method of claim 4, wherein generating an integer multiple frequency offset estimator based on the first short training sequence comprises:
obtaining an even number value of an integer frequency offset estimator based on the differential sequence of the first short training sequence;
setting even bits of the integer frequency offset estimator to 0.
6. The method of claim 4, wherein generating a fractional frequency offset estimate based on the first short training sequence and the second short training sequence comprises:
determining a conjugate correlation relationship based on the lead code corresponding to the first short training sequence and the second short training sequence;
and after a preset interval, performing conjugate correlation processing on a plurality of short training sequences in the first short training sequence based on the conjugate correlation relationship to generate a fractional frequency offset estimator.
7. The method of claim 4, wherein generating the frequency offset estimate value based on the integer multiple frequency offset estimator and the fractional multiple frequency offset estimator comprises:
performing pairwise correlation operation on symbols corresponding to the short training sequences in the first short training sequence to generate a plurality of connection results;
generating a plurality of cumulative values based on the concatenation and a plurality of short training sequences of the first short training sequence;
determining the integer multiple frequency offset estimator and the fractional multiple frequency offset estimator based on the plurality of accumulated values to generate the frequency offset estimate value.
8. The method of claim 7, wherein the first short training sequence comprises five short training symbols;
determining the frequency offset estimate value based on the plurality of accumulated values, comprising:
generating four cumulative values based on the five short training symbols;
performing an averaging calculation based on the four accumulated values to generate the frequency offset estimate value.
9. The method of claim 1, wherein integrating based on the compensation factor and the long training sequence to complete carrier synchronization and generate a carrier output signal comprises:
determining symbols and data symbols corresponding to the long training sequence;
performing frequency offset compensation on the long training sequence based on the compensation coefficient, the symbol corresponding to the long training sequence and the data symbol;
and integrating the data after the frequency offset compensation with the carrier input signal to complete carrier synchronization and generate a carrier output signal.
10. A carrier synchronization apparatus for a satellite, comprising:
the acquisition module is used for a satellite receiving terminal to acquire a carrier input signal;
a separation module, configured to perform data separation on the carrier input signal to generate a first short training sequence, a second short training sequence, and a long training sequence;
an estimation module, configured to generate a frequency offset estimation value based on the first short training sequence and the second short training sequence;
a compensation module configured to generate a compensation coefficient based on the frequency offset estimate, the second short training sequence, and the long training sequence;
and the output module is used for integrating the compensation coefficient and the long training sequence to complete carrier synchronization and generate a carrier output signal.
11. An electronic device, comprising:
one or more processors;
storage means for storing one or more programs;
when executed by the one or more processors, cause the one or more processors to implement the method of any one of claims 1-9.
12. A computer-readable medium, on which a computer program is stored, which, when being executed by a processor, carries out the method according to any one of claims 1-9.
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