CN114884792A - High-precision multi-carrier symbol rapid recovery method, device and system - Google Patents

High-precision multi-carrier symbol rapid recovery method, device and system Download PDF

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CN114884792A
CN114884792A CN202210593195.XA CN202210593195A CN114884792A CN 114884792 A CN114884792 A CN 114884792A CN 202210593195 A CN202210593195 A CN 202210593195A CN 114884792 A CN114884792 A CN 114884792A
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symbol
pilot
decision
symbols
carrier
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陈达
徐萌莹
王睿
罗锴
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Huazhong University of Science and Technology
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Huazhong University of Science and Technology
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    • 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
    • H04L27/2649—Demodulators
    • H04L27/26534—Pulse-shaped multi-carrier, i.e. not using rectangular window
    • H04L27/2654—Filtering per subcarrier, e.g. filterbank multicarrier [FBMC]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Abstract

The invention discloses a high-precision multi-carrier symbol rapid recovery method, a device and a system, belonging to the technical field of wireless communication; the method comprises the following steps: s1, after receiving the signal transmitted by the transmitting end, the receiving end carries out OQAM/FBMC demodulation processing on the received signal; the signal transmitted by the transmitting end is a signal obtained by inserting N identical pilot symbols into the data symbols on each transmitting terminal carrier and then carrying out OQAM/FBMC modulation, and the value of each pilot symbol is any real number; s2, after linear fitting is carried out on the pilot demodulation symbols of the sub-carriers, the judgment coefficients corresponding to the sub-carriers are calculated based on the slope and intercept of the fitted linear, and then judgment thresholds and judgment variables are obtained; then, by comparing the relative size of the decision variable and the decision threshold, the decision recovery is directly carried out on the sending symbol corresponding to the demodulation symbol; the invention does not need to isolate the interference on the pilot frequency symbol by means of zero-value pilot frequency, thereby greatly reducing the calculation complexity and simultaneously improving the symbol recovery accuracy.

Description

High-precision multi-carrier symbol rapid recovery method, device and system
Technical Field
The invention belongs to the technical field of wireless communication, and particularly relates to a high-precision multi-carrier symbol rapid recovery method, device and system.
Background
Wireless communication systems need to rely on electromagnetic waves to transmit signals over the air. The channel for wireless transmission is more complex than that for wired transmission due to uncertainty in the positions of both signal transceivers in space. In addition, the transmission of electromagnetic waves has omni-directionality, and signals can be lost to different degrees in the transmission process. For wideband signals, Multi-carrier modulation (MCM) is the dominant technique to overcome the fading effect. The multi-carrier modulation system divides a broadband signal into a plurality of narrow-band signals to be modulated on different subcarriers, and can effectively resist frequency selective fading. As one of MCM schemes applied to a wireless communication system, Orthogonal Frequency Division Multiplexing (OFDM) is robust to multipath fading, but OFDM uses rectangular pulses for shaping, which causes a significant spectrum leakage problem. The Filter Bank Multicarrier with Offset Quadrature Amplitude Modulation (OQAM/FBMC) technology based on interleaved Quadrature Amplitude Modulation utilizes a subcarrier-level Filter with good time-frequency positioning characteristics to shape a transmission signal, and combines with OQAM Modulation. Therefore, more waveform design freedom is provided for the multi-carrier modulation method to better meet the requirements of different transmission scenarios while ensuring high spectral efficiency, and the multi-carrier modulation method is one of the most potential multi-carrier modulation techniques in future communication. However, the OQAM/FBMC system only satisfies orthogonality in the real number domain, and the demodulation symbols at the receiving end thereof will be subject to inherent imaginary interference caused by adjacent symbols, which causes the challenges of high complexity and large pilot overhead for signal recovery of the OQAM/FBMC system. Therefore, some conventional symbol recovery methods for OFDM systems cannot be directly applied to the OQAM/FBMC system, and new methods need to be proposed according to the characteristics of the OQAM/FBMC system.
The accuracy of the data recovery of the receiving end is an important index for judging whether the system performance is excellent or not, and whether the symbol can be accurately recovered can directly influence the application of the system in an actual scene. In the traditional symbol recovery method, channel state information is obtained by channel estimation, channel equalization is carried out by means of the channel state information, and errors in calculation are removed by means of judgment.
Disclosure of Invention
In view of the above defects or improvement requirements of the prior art, the present invention provides a method, an apparatus, and a system for fast recovering a high-precision multi-carrier symbol, so as to solve the technical problems of low symbol recovery accuracy and high complexity due to the influence of the inherent interference in the prior art.
In order to achieve the above object, the present invention provides a high-precision multi-carrier symbol fast recovery method, which comprises the following steps:
s1, after receiving the signal transmitted by the transmitting end, the receiving end carries out OQAM/FBMC demodulation processing on the received signal to obtain a demodulated signal; the signal transmitted by the transmitting end is a signal obtained by inserting N identical pilot symbols into the data symbols on each transmitting terminal carrier and then carrying out OQAM/FBMC modulation; n is more than or equal to 2; the value of the pilot frequency symbol is any real number; data symbols on all subcarriers of a sending end are OQAM modulation symbols with any order; each subcarrier in the demodulation signal comprises a pilot demodulation symbol after demodulating the pilot symbol on the corresponding subcarrier in the signal transmitted by the transmitting end;
s2, respectively carrying out decision operation on each subcarrier in the demodulated signal, thereby recovering the signal transmitted by the transmitting end;
the method for judging the k-th subcarrier in the demodulation signal comprises the following steps: after linear fitting is carried out on the pilot demodulation symbol of the kth subcarrier, a decision coefficient corresponding to the kth subcarrier is obtained through calculation based on the slope and intercept of the fitted linear; calculating to obtain a decision threshold corresponding to the kth subcarrier and a decision variable corresponding to each demodulation symbol on the kth subcarrier according to a decision coefficient corresponding to the kth subcarrier; and obtaining the value of the sending symbol corresponding to each demodulation symbol on the kth subcarrier through the judgment by comparing the relative size of the judgment variable corresponding to each demodulation symbol on the kth subcarrier with the judgment threshold corresponding to the kth subcarrier.
Further preferably, the decision coefficient d corresponding to the k-th subcarrier k And l k Respectively as follows:
d k ＝e k
Figure BDA0003666457560000031
wherein e is k The slope of a fitting straight line corresponding to the pilot demodulation symbol of the kth subcarrier; b k The intercept of a fitting straight line corresponding to a pilot demodulation symbol of the kth subcarrier; p k Is the value of the pilot symbol on the kth subcarrier of the transmitting end.
Further preferably, when N is 2, the slope e of the fitting straight line corresponding to the pilot demodulation symbol of the kth subcarrier is set to 2 k And intercept b k Respectively as follows:
Figure BDA0003666457560000032
Figure BDA0003666457560000033
or
Figure BDA0003666457560000034
Wherein the content of the first and second substances,
Figure BDA0003666457560000035
demodulating symbols p for pilot k (1) An imaginary part of (d);
Figure BDA0003666457560000036
demodulating symbols p for pilot k (1) The real part of (a);
Figure BDA0003666457560000037
demodulating symbols p for pilot k (2) An imaginary part of (d);
Figure BDA0003666457560000038
demodulating symbols p for pilot k (2) The real part of (a); p is a radical of k (1) And p k (2) The symbols are demodulated for the two pilots on the k sub-carrier.
Further preferably, when N ≧ 3, the slope e of the fitting straight line corresponding to the pilot demodulation symbol of the kth subcarrier k And intercept b k Respectively as follows:
Figure BDA0003666457560000041
Figure BDA0003666457560000042
Figure BDA0003666457560000043
Figure BDA0003666457560000044
wherein the content of the first and second substances,
Figure BDA0003666457560000045
demodulating a real part of a symbol for an ith pilot on a kth subcarrier;
Figure BDA0003666457560000046
the imaginary part of the symbol is demodulated for the ith pilot on the kth subcarrier.
Further preferably, the decision threshold f corresponding to the k-th sub-carrier k (x 0 ) The expression of (a) is:
f k (x 0 )＝l k x 0
decision variable b corresponding to mth demodulation symbol on kth subcarrier k The expression of (m) is:
Figure BDA0003666457560000047
wherein x is 0 ＝-(2 r -2),-(2 r -4),...,+(2 r -2) of x 0 (i) I ═ 1,2, …, L; l is x 0 The value number in (1);
Figure BDA0003666457560000048
and
Figure BDA0003666457560000049
respectively the real and imaginary parts of the mth demodulated symbol on the kth subcarrier.
Further preferably, the decision threshold f corresponding to the k-th sub-carrier k (x 0 ) The expression of (a) is:
f k (x 0 )＝l k J k x 0
Figure BDA00036664575600000410
Figure BDA00036664575600000411
decision variable b corresponding to mth demodulation symbol on kth subcarrier k The expression of (m) is:
Figure BDA0003666457560000051
wherein x is 0 ＝-(2 r -2),-(2 r -4),...,+(2 r -2), denoted x 0 (i) I-1, 2, …, L; l is x 0 The value number in (1);
Figure BDA0003666457560000052
and
Figure BDA0003666457560000053
are respectively the firstReal and imaginary parts of the m-th demodulated symbol on k subcarriers; p η Is the noise power in the channel; p x The power of the transmitted signal for the transmitting end.
Further preferably, in step S2, the decision variable corresponding to the demodulation symbol on the k-th subcarrier and a set of decision thresholds f corresponding to the k-th subcarrier are used k (x 0 (i) ) Comparing in sequence;
when the above decision variable is less than f k (x 0 (1) ) When the decision variable is judged to be the value set of the OQAM symbol standard value with the size smaller than x 0 (1) The OQAM symbol standard value;
when the above-mentioned decision variable size is located in [ f k (x 0 (j) )，f k (x 0 (j+1) )]When the decision variable is in the range, the decision variable is decided as that the value concentration of the OQAM symbol standard is positioned in the value range [ x 0 (j) ，x 0 (j+1) ]Taking the value of an inner OQAM symbol standard; j ═ 1,2, …, L-1;
when the above decision variable is larger than f k (x 0 (L) ) When the decision variable is judged to be the value set with the standard value of the OQAM symbol with the size larger than x 0 (L) The OQAM symbol standard value;
wherein, the OQAM symbol standard value-taking set is { - (2) r -1),-(2 r -3),...,+(2 r -1)}。
In a second aspect, the present invention provides a receiving apparatus, configured to perform the method for fast recovering a multicarrier symbol provided in the first aspect of the present invention.
In a third aspect, the present invention provides a method and an apparatus for fast recovering a multicarrier symbol, including: a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to execute the method for fast recovery of multicarrier symbols provided by the first aspect of the present invention.
In a fourth aspect, the present invention provides a multi-carrier system, comprising: a sending end and a receiving end;
the transmitting terminal is used for inserting N identical pilot symbols into the data symbols on each transmitting terminal carrier, then carrying out OQAM/FBMC modulation to obtain transmitting signals and transmitting the transmitting signals to the receiving terminal; n is more than or equal to 2;
the receiving end is configured to perform steps S1-S2 in the method for fast recovery of multi-carrier symbols provided by the first aspect of the present invention.
Generally, by the above technical solution conceived by the present invention, the following beneficial effects can be obtained:
1. the invention provides a method for quickly recovering a multi-carrier symbol, which is based on the discovery that when a plurality of same pilot symbols are inserted into a data symbol on each transmitting terminal carrier by a transmitting terminal, the pilot demodulation symbol demodulated by a receiving terminal presents the same symbol on a complex plane and is approximately distributed along a straight line, after the pilot demodulation symbol of the sub-carrier is subjected to straight line fitting, a judgment coefficient corresponding to the sub-carrier is calculated based on the slope and intercept of the fitted straight line, and then a judgment threshold and a judgment variable are obtained; the invention divides the real number domain into different sections through a decision threshold on the real number domain, and decides the demodulation symbol of the receiving end according to the relative size relation between the decision variable obtained by the calculation of the demodulation symbol of the receiving end and the decision threshold, thereby recovering the symbol; in the process, interference on pilot symbols is isolated without the help of zero-value pilot frequency, and the judgment threshold and the judgment variable are represented by only introducing the judgment coefficient related to the pilot frequency.
2. The multi-carrier symbol rapid recovery method provided by the invention further considers the influence of noise power in a channel when obtaining the decision threshold corresponding to the sub-carrier, introduces the influence degree of channel noise in the decision threshold expression by minimizing symbol waveform distortion, and further improves the accuracy of symbol decision recovery.
Drawings
Fig. 1 is a flowchart of a method for fast recovering a multi-carrier symbol according to embodiment 1 of the present invention;
fig. 2 is a schematic diagram of inserting multiple columns of the same pilot symbols simultaneously before data symbols on all carriers of a transmitting terminal according to embodiment 1 of the present invention; wherein, (a) is a schematic diagram of inserting two columns of the same pilot symbols simultaneously before the data symbols on all the transmit terminal carriers; (b) schematic diagram of inserting three columns of same pilot symbols before data symbols on all transmit terminal carriers at the same time;
fig. 3 is a schematic diagram of comparison decision under 16QAM modulation provided in embodiment 1 of the present invention;
fig. 4 is a graphical representation of a comparison decision under 16QAM modulation provided in embodiment 1 of the present invention;
fig. 5 is a schematic diagram of error rate performance comparison results obtained by respectively adopting the multi-carrier symbol fast recovery method provided by the present invention and the existing method under 16QAM modulation according to embodiment 1 of the present invention;
fig. 6 is a schematic diagram of error rate performance comparison results obtained by respectively adopting the multi-carrier symbol fast recovery method provided by the present invention and the existing method under 256QAM modulation according to embodiment 1 of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
Examples 1,
A method for fast recovery of multi-carrier symbols, as shown in fig. 1, includes the following steps:
s1, after receiving the signal transmitted by the transmitting end, the receiving end carries out OQAM/FBMC demodulation processing on the received signal to obtain a demodulated signal; the signal transmitted by the transmitting end is a signal obtained by inserting N identical pilot symbols into the data symbols on each transmitting terminal carrier and then carrying out OQAM/FBMC modulation; n is more than or equal to 2; the value of the pilot frequency symbol is any real number; specifically, a schematic diagram of simultaneously inserting a plurality of columns of identical pilot symbols before data symbols on all transmission terminal carriers is shown in fig. 2, where (a) is a schematic diagram of simultaneously inserting two columns of identical pilot symbols before data symbols on all transmission terminal carriers; fig. (b) is a diagram showing that three identical pilot symbols are inserted simultaneously before data symbols on all the transmit terminal carriers. Further, each subcarrier in the demodulation signal includes a pilot demodulation symbol obtained by demodulating a pilot symbol on a corresponding subcarrier in a signal transmitted by a transmitting end.
It should be noted that, the data symbols on all subcarriers of the sending end are all the OQAM modulation symbols with any order, and in the present invention, the modulation order of the OQAM is recorded as 4 r R is a positive integer; preferably, the value range of the pilot symbol may be + (2) r -1) or- (2) r -1)；
S2, respectively carrying out decision operation on each subcarrier in the demodulated signal, thereby recovering the signal transmitted by the transmitting end;
the operation method for judging the k-th subcarrier in the demodulation signal comprises the following steps: after linear fitting is carried out on the pilot demodulation symbol of the kth subcarrier, a decision coefficient corresponding to the kth subcarrier is obtained through calculation based on the slope and intercept of the fitted linear; calculating to obtain a decision threshold corresponding to the kth subcarrier and a decision variable corresponding to each demodulation symbol on the kth subcarrier according to a decision coefficient corresponding to the kth subcarrier; and obtaining the value of the sending symbol corresponding to each demodulation symbol on the kth subcarrier through the judgment by comparing the relative size of the judgment variable corresponding to each demodulation symbol on the kth subcarrier with the judgment threshold corresponding to the kth subcarrier.
Specifically, the transmission signal s (n) at the nth time modulated by OQAM/FBMC is represented as:
Figure BDA0003666457560000081
wherein K is a groupNumber of uniform subcarriers, k is subcarrier index, m is symbol index, x k (m) is the real data corresponding to the corresponding subcarrier index and symbol index, g (·) represents the prototype filter function, j is the imaginary unit;
demodulated complex signal y k (m) is represented by:
Figure BDA0003666457560000082
where r (n) denotes a signal after transmission of the transmission signal s (n) through the channel.
In an optional implementation manner, in a fading channel, the influence of gaussian noise is ignored, and after inherent imaginary part interference existing between demodulation symbols is avoided, an estimation expression of a transmission signal is obtained by combining pilot frequency derivation, and is as follows:
Figure BDA0003666457560000091
real part H of channel frequency domain response H (k) corresponding to subcarrier index k R (k) And an imaginary part H I (k) Two real unknowns in the above estimation expression, respectively. The invention obtains the standard corresponding to the quick judgment of the demodulation symbol of the receiving end by means of the pilot frequency, and obtains the standard by inserting at least two pilot frequencies in the transmitting end. The following is an example of inserting two random pilots:
when N is 2, the pilot symbols on the k-th subcarrier of the transmitting end are respectively P k (1) And P k (2) The corresponding pilot demodulation symbols are respectively p k (1) And p k (2) All values of which are P k (ii) a And bringing the pilot frequency symbol into the estimation expression of the sending signal to obtain the following expression:
Figure BDA0003666457560000092
Figure BDA0003666457560000093
wherein the content of the first and second substances,
Figure BDA0003666457560000094
demodulating symbols p for pilot k (1) An imaginary part of (d);
Figure BDA0003666457560000095
demodulating symbols p for pilot k (1) The real part of (a);
Figure BDA0003666457560000096
demodulating symbols p for pilot k (2) An imaginary part of (d);
Figure BDA0003666457560000097
demodulating symbols p for pilot k (2) The real part of (a).
In conjunction with the above expression, the real part H can be represented by a pilot R (k) And an imaginary part H I (k)；
Further, a variant of the estimated expression of the transmitted signal may be obtained:
Figure BDA0003666457560000098
further, the above-mentioned
Figure BDA0003666457560000099
And
Figure BDA00036664575600000910
are respectively marked as the decision coefficient d corresponding to the kth subcarrier k And l k I.e. the decision coefficient d for the k-th sub-carrier k And l k Respectively as follows:
Figure BDA0003666457560000101
Figure BDA0003666457560000102
it can be seen from this that the decision coefficient d k And l k Are associated only with pilot symbols and pilot demodulated symbols. Further, a decision coefficient d is combined k And l k It can be seen that when N is 2, the decision coefficient d is k And l k Exactly as close as the slope and intercept form of a two-point fitted line, d k Is equivalent to the slope expression of a straight line, l k P k Is equivalent to the intercept expression of the corresponding straight line. Specifically, the slope e of the fitting straight line corresponding to the pilot demodulation symbol of the k-th subcarrier k And intercept b k Respectively as follows:
Figure BDA0003666457560000103
Figure BDA0003666457560000104
or
Figure BDA0003666457560000105
Wherein the content of the first and second substances,
Figure BDA0003666457560000106
demodulating symbols p for pilot k (1) An imaginary part of (d);
Figure BDA0003666457560000107
demodulating symbols p for pilot k (1) The real part of (a);
Figure BDA0003666457560000108
demodulating symbols p for pilots k (2) An imaginary part of (a);
Figure BDA0003666457560000109
demodulating symbols p for pilots k (2) The real part of (a); p is a radical of k (1) And p k (2) The symbols are demodulated for the two pilots on the k subcarrier.
According to observation, when a plurality of same pilot symbols are inserted into the data symbols on each transmission terminal carrier by the transmission terminal, the pilot demodulation symbols demodulated by the receiving terminal have the characteristic that the same symbols are approximately distributed along a straight line on a complex plane, so that the pilot demodulation symbols of the sub-carriers can be subjected to straight line fitting firstly, and then the judgment coefficients corresponding to the sub-carriers are calculated based on the slope and the intercept of the fitted straight line. Specifically, the obtained decision coefficient d corresponding to the k-th subcarrier k And l k Respectively as follows: d k ＝e k ，
Figure BDA00036664575600001010
Further, more pilot symbols can be introduced at the transmitting end, so that the straight line fitting is more accurate; in an optional implementation manner, N columns of identical pilot symbols are set at the transmitting end, and the values are all P k (ii) a N is more than or equal to 3. At the receiving end, there are also N columns, i.e. p, to obtain the corresponding pilot demodulation symbols k (i) The ith pilot demodulation symbol corresponding to the kth subcarrier has the corresponding coordinate of the complex plane as
Figure BDA0003666457560000111
And obtaining a regression linear equation by means of linear regression according to the coordinates of pilot demodulation symbols corresponding to the N columns of the same pilot symbols. Specifically, when N is more than or equal to 3, the slope e of the fitting straight line corresponding to the pilot demodulation symbol of the kth subcarrier k And intercept b k Respectively as follows:
Figure BDA0003666457560000112
Figure BDA0003666457560000113
Figure BDA0003666457560000114
Figure BDA0003666457560000115
wherein the content of the first and second substances,
Figure BDA0003666457560000116
demodulating a real part of a symbol for an ith pilot on a kth subcarrier;
Figure BDA0003666457560000117
the imaginary part of the symbol is demodulated for the ith pilot on the kth subcarrier.
Based on the decision coefficient d k And l k Further, the variant of the estimated expression of the transmission signal is converted into:
Figure BDA0003666457560000118
specifically, the channel estimation and channel equalization are performed in the conventional decision mode
Figure BDA0003666457560000119
Then, symbol judgment is carried out on the judgment threshold based on the judgment threshold; wherein the content of the first and second substances,
Figure BDA00036664575600001110
the decision threshold for making symbol decision is x 0 In particular, the modulation order is recorded as 4 r At this time, corresponding x 0 ＝-(2 r -2),-(2 r -4),...,+(2 r -2). These points divide the real number domain into 2 r An interval according to
Figure BDA00036664575600001111
And x 0 Will be decided to the same value in the same interval and will be decided to different symbols in different intervals.
For convenience of calculation, based on the above variant, the decision threshold expression corresponding to the kth subcarrier is obtained as follows:
f k (x 0 )＝l k x 0
the decision variable expression corresponding to the mth demodulation symbol on the kth subcarrier is as follows:
Figure BDA0003666457560000121
wherein x is 0 ＝-(2 r -2),-(2 r -4),...,+(2 r -2), denoted x 0 (i) I ═ 1,2, …, L; l is x 0 The value number in (1);
Figure BDA0003666457560000122
and
Figure BDA0003666457560000123
respectively the real and imaginary parts of the mth demodulated symbol on the kth subcarrier.
It should be noted that the present invention is not to be directly compared
Figure BDA0003666457560000124
And x 0 But rather the original decision threshold x 0 Conversion to f k (x 0 )＝l k x 0 Based on the conversion form of the above estimation expression, the original decision variable is converted
Figure BDA0003666457560000125
Is converted into
Figure BDA0003666457560000126
The comparison is carried out, and the complexity of the judgment calculation of the symbol recovery method is greatly reduced.
It can be seen that the defined decision variables satisfy the relational expression
Figure BDA0003666457560000127
The decision threshold satisfies the relation f k (x 0 )＝l k *x 0 . Therefore, for OQAM modulation of any order, the modulation order is 4 r ，f k (x 0 ) According to x 0 Divide the real number domain into 2 r And (4) each interval. Decision variable b k (m) falls on f k (x 0 ) Probability sum of each real number interval divided in real number domain
Figure BDA0003666457560000128
Fall on x 0 The probability of each real number interval divided is equal. It can be concluded that for the same demodulated symbol, the probability of being decided as the same symbol is the same both at the fast decision and after the symbol decision after channel estimation and channel equalization. Therefore, the method can accurately realize symbol recovery.
The method for rapidly judging and recovering the symbol provided by the invention does not need to carry out channel estimation and channel equalization after obtaining the demodulated symbol, and can directly judge and recover the demodulated symbol to obtain the corresponding symbol only by calculating the judgment variable and the judgment threshold according to the expression.
In another optional embodiment, in order to further improve the accuracy of the above-mentioned decision method, this embodiment further considers the influence of noise in the channel, and derives a method for obtaining a recovery symbol with minimum symbol waveform distortion corresponding to the known noise statistical information, using the minimum mean square error of the estimated symbol as a standard; the improved method is MIAD (Minimum symbol wave distortion-IAD):
the resulting transmit symbol estimate is assumed to be represented as:
Figure BDA0003666457560000131
wherein, g (k) is a channel noise influence factor corresponding to the kth subcarrier;
then, the mean square error between the estimated symbol and the transmitted symbol is expressed as the following expression:
Figure BDA0003666457560000132
if it is desired to minimize the mean square error of the actually transmitted symbols and the estimated symbols, then it is necessary to have
Figure BDA0003666457560000133
Therefore, the above equation is derived and the derivative is 0. The following can be obtained:
Figure BDA0003666457560000134
wherein H * (k)＝H R (k)-jH I (k) Denotes the conjugate of H (k). For convenience of description, let g (k) h (k) J k -1 ，J k Is a real number, we can get:
Figure BDA0003666457560000135
wherein, P η Is the noise power in the channel; p x Transmitting the power of the signal for the transmitting end; h (k) is a channel frequency domain response corresponding to the k-th subcarrier; j. the design is a square k The influence degree of the channel noise is measured based on the signal-to-noise ratio;
wherein | H (k) cells do not 2 Can be assisted by d k And l k Expressed as:
Figure BDA0003666457560000141
to compare the performances of the two symbol decision methods, the difference between the mean square error of the symbol decision method in consideration of noise in the second alternative embodiment and the decision method (denoted as iad (decision based on Interference) in the first alternative embodiment) is as follows:
Figure BDA0003666457560000142
the above equation results show that the mean square error obtained under noise consideration is less than under noise consideration. Moreover, the larger the power of the noise is, the larger the absolute value of the above expression is, and the advantage of the symbol fast recovery method in the second optional embodiment is further obvious.
Based on the decision coefficient d k And l k By minimizing the symbol waveform distortion, the variant of the estimated expression of the transmission signal is further converted into:
Figure BDA0003666457560000143
Figure BDA0003666457560000144
calculation based on pilot frequency, | H (k) & gt luminance 2 Can be expressed as:
Figure BDA0003666457560000145
at this time, the decision threshold expression corresponding to the kth subcarrier obtained based on the minimization of the symbol distortion waveform is:
f k (x 0 )＝l k J k x 0
the decision variable expression corresponding to the mth demodulation symbol on the kth subcarrier is as follows:
Figure BDA0003666457560000151
wherein x is 0 ＝-(2 r -2),-(2 r -4),...,+(2 r -2), denoted x 0 (i) I ═ 1,2, …, L; l is x 0 Number of values in；
Figure BDA0003666457560000152
And
Figure BDA0003666457560000153
respectively the real and imaginary parts of the mth demodulated symbol on the kth subcarrier.
It should be noted that, the related schemes of the second embodiment are the same as those of the first embodiment, and are not described herein again.
The invention divides the real number domain into different sections through the decision threshold on the real number domain, and decides the demodulation symbol of the receiving end according to the relative size relation between the decision variable obtained by the calculation of the demodulation symbol of the receiving end and the decision threshold, thereby recovering the symbol.
Preferably, in step S2, the decision variable corresponding to the demodulation symbol on the k-th subcarrier and a set of decision thresholds f corresponding to the k-th subcarrier are used k (x 0 (i) ) Comparing in sequence;
when the above decision variable is less than f k (x 0 (1) ) When the decision variable is judged to be the value set of the OQAM symbol standard value with the size smaller than x 0 (1) The OQAM symbol standard value;
when the above-mentioned decision variable size is located in [ f k (x 0 (j) )，f k (x 0 (j+1) )]When the decision variable is in the range, the decision variable is decided as that the value concentration of the OQAM symbol standard is positioned in the value range [ x 0 (j) ，x 0 (j+1) ]Taking the value of an inner OQAM symbol standard; j ═ 1,2, …, L-1;
when the above decision variable is larger than f k (x 0 (L) ) When the judgment variable is judged to be that the value set of the OQAM symbol standard is larger than x 0 (L) The OQAM symbol standard value;
wherein, the OQAM symbol standard value-taking set is { - (2) r -1),-(2 r -3),...,+(2 r -1)}。
It should be noted that the OQAM symbol standard values corresponding to the decision variables in each range are all unique values.
In particular, in an alternative embodiment, the decision threshold f is compared k (x 0 ) And a decision variable b k (m), the specific steps of further deciding the corresponding transmission symbol are as follows:
step 1: initialization x 0 ＝-(2 r -2)；
Step 2: if f k (x 0 )≥b k (m), then deciding the demodulated symbol y k (m) the corresponding transmitted symbol value is x 0 -1, the decision is over; otherwise, go to Step 3;
step 3: let x 0 ＝x 0 +2；
Step 4: if x 0 ＝2 r Then, the demodulation symbol y is decided k (m) the corresponding transmitted symbol value is x 0 -1, the decision is over; otherwise, go to Step 2.
Specifically, a schematic diagram of the above comparison decision in the case of 16QAM modulation is shown in fig. 3.
Furthermore, the invention finds that the decision recovery symbols have graphic significance in the complex plane, i.e. the decision thresholds set by the invention correspond to different boundaries on the complex plane, and can be decided as different symbols in different areas. Specifically, will
Figure BDA0003666457560000161
The judgment threshold of the symbol judgment is x 0 After that, it is possible to obtain:
Figure BDA0003666457560000162
x 0 ＝-(2 r -2),-(2 r -4),...,+(2 r -2); the above expression is understood to mean a cluster of straight lines which have mutually different parallel intercepts. Therefore, it can be seen from the figure that the symbol fast recovery method provided by the present invention can be interpreted graphically as well. Is used as a decision criterion k (x 0 ) The receiving end demodulates the intercept corresponding to different straight lines on the complex plane of the symbol. The character provided by the inventionThe quick number judging and recovering method includes substituting the demodulated symbol into the calculated judgment variable b k (m) a re-sum decision threshold f k (x 0 ) A comparison is made. On the complex plane corresponding to the demodulated symbols at the receiving end, these straight lines divide the complex plane into 2 r The mutually disjoint intervals are judged to be the same value when falling in the same interval and are judged to be different symbols when falling in different intervals according to the relative positions of the demodulation symbols and the straight line. In particular, a graphical representation of a comparison decision under 16QAM modulation is shown in fig. 4.
To further illustrate the performance of the multi-carrier symbol fast recovery method provided by the present invention, Bit Error Rate (BER) performances obtained by respectively adopting the multi-carrier symbol fast recovery method provided by the present invention and the existing method under 16QAM and 256QAM modulation are respectively given, and the corresponding comparison results are respectively shown in fig. 5 and fig. 6; the multi-carrier symbol fast recovery method provided by the invention comprises a symbol fast recovery method (marked as LFD) adopting two columns of same pilot frequency and a symbol fast recovery method (marked as LFD (N is equal to 3)) adopting three columns of same pilot frequency; the existing control methods are IAM and POP. It can be seen from fig. 5 that the performance of the multi-carrier symbol fast recovery method under the same pilot structure of three columns is better than that of other methods; in combination with fig. 6, it can be seen that both pilot structures of the proposed method are better than those of the comparison method under 256QAM modulation, which illustrates that the proposed method has better adaptability to high-order QAM modulation.
Further, the number of real number multiplications C required for processing a frame of signal (having K subcarriers and M symbols per subcarrier) is counted RM Number of times of addition of sum real number C RA The complexity of the symbol rapid recovery method provided by the invention is shown, and compared with the traditional symbol recovery method, the method more intuitively shows the advantages of the direct judgment method in the aspect of computational complexity.
The complexity of each step in the multi-carrier symbol fast recovery method provided by the invention is specifically analyzed as follows:
1. calculating a decision variable b k (m): according to b k (m) expressionCan be obtained, in calculating b k (m) before, d is calculated for each subcarrier k To obtain d k Then b corresponding to one demodulation symbol is calculated k (m) requires 1 real multiplication and 1 real addition. For two identical pilot frequency judging method, d is calculated k 1 real multiplication and 2 real additions are required. So that b is calculated for one frame signal k (M) the required real number multiplication (M +1) K times and real number addition (M +2) K times. For the method of N columns of random pilot (N ≧ 3), d is calculated k 2(N +2) real multiplications and 2(N-1) real additions are required. So that b is calculated for one frame signal k (M) the required real number multiplication (M +2N +4) K times and real number addition (M +4N-2) K times.
2. Calculating a decision threshold f k (x 0 ): according to f k (x 0 ) Is calculated by the expression of k (x 0 ) It is necessary to know d k And l k . Since the decision threshold f is calculated k (x 0 ) The multiplication of real numbers which are integer multiples is performed a plurality of times, so that the calculation can be simplified to addition, and the calculation amount can be halved according to the symmetry of the symbols. For modulation order of 4 r OQAM modulation of (2) 0 In total 2 r -1 value. Remove the middle symbol 0 and then calculate l from symmetry k x 0 Need 2 r-1 -1 real addition. At known d k In the case of (2), l corresponding to one subcarrier is calculated k 2 real multiplications and 1 real addition are required. That is, for the symbol decision recovery method, the corresponding l of a frame of demodulation symbols is calculated k 2K real multiplications and 2 are required r-1 K real additions.
3. Calculation of J (k): for the symbol decision method based on the minimum distortion of the symbol waveform, j (k) needs to be calculated for each subcarrier. At known d k And l k In the case of (2), 5 real number multiplications and 2 real number additions are required for one subcarrier. Therefore, for one frame of demodulation symbols, in the case that two columns of the same pilot frequency are used for symbol decision, 5K real multiplication times and 2K real addition times are needed.
Whereas for IAM channel estimation and symbol recovery in the contrast method: channel estimation for one subcarrier IAM method requires 8 real multiplications and 4 real additions. Then, for a frame signal, the IAM method needs 8K real multiplications and 4K real additions for channel estimation. After obtaining the channel state information, 4 real multiplications and 2 real additions are required to recover one symbol. Therefore, for a frame of demodulated symbols, 4MK real multiplications and 2MK real additions are required for the known csi recovery symbols. For POP channel estimation and symbol recovery in the contrast method: channel estimation for one subcarrier POP method requires 6 real multiplications and 2 real additions. Then, for one frame signal, the POP method needs 6K real multiplications and 2K real additions for channel estimation. After obtaining the channel state information, 4 real multiplications and 2 real additions are required to recover one symbol. Therefore, for a frame of demodulated symbols, 4MK real multiplications and 2MK real additions are required for the known csi recovery symbols.
In particular, Table 1 shows the number of real multiplications C required for recovering a frame symbol under two pilot configurations (corresponding to LFD and LFD (N ≧ 3)) and the correlation methods IAM and POP of the proposed method RM Addition of sum and real number C RA The number of times. Wherein, K and M respectively correspond to the number of subcarriers and the number of symbols corresponding to each subcarrier.
TABLE 1
Figure BDA0003666457560000191
As can be seen from table 1, the computation complexity of the fast recovery method for multi-carrier symbols provided by the present invention is much lower than that of the comparison method.
Examples 2,
A receiving apparatus is used to perform the method for fast recovering a multi-carrier symbol provided in embodiment 1 of the present invention.
The related technical scheme is the same as embodiment 1, and is not described herein.
Examples 3,
A fast recovery method device for multi-carrier symbols comprises the following steps: the multi-carrier symbol fast recovery method comprises a memory and a processor, wherein the memory stores a computer program, and the processor executes the multi-carrier symbol fast recovery method provided by the embodiment 1 of the invention when executing the computer program.
The related technical scheme is the same as embodiment 1, and is not described herein.
Examples 4,
A multi-carrier system comprising: a sending terminal and a receiving terminal;
the transmitting terminal is used for inserting N identical pilot symbols into the data symbols on each transmitting terminal carrier, then carrying out OQAM/FBMC modulation to obtain transmitting signals and transmitting the transmitting signals to the receiving terminal; n is more than or equal to 2;
the receiving end is configured to perform steps S1-S2 in the method for fast recovering a multicarrier symbol according to embodiment 1 of the present invention.
The related technical scheme is the same as embodiment 1, and is not described herein.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (10)

1. A high-precision multi-carrier symbol fast recovery method is characterized by comprising the following steps:
s1, after receiving the signal transmitted by the transmitting end, the receiving end carries out OQAM/FBMC demodulation processing on the received signal to obtain a demodulated signal; the signal transmitted by the transmitting end is a signal obtained by inserting N identical pilot symbols into the data symbols on each transmitting terminal carrier and then carrying out OQAM/FBMC modulation; n is more than or equal to 2; the value of the pilot frequency symbol is any real number; the data symbols on all subcarriers of the sending end are OQAM modulation symbols with any order; each subcarrier in the demodulation signal comprises a pilot demodulation symbol after demodulating the pilot symbol on the corresponding subcarrier in the signal transmitted by the transmitting end;
s2, respectively carrying out judgment operation on each subcarrier in the demodulated signal, thereby recovering the signal transmitted by the transmitting end;
the method for judging the k-th subcarrier in the demodulation signal comprises the following steps: after linear fitting is carried out on the pilot demodulation symbol of the kth subcarrier, a decision coefficient corresponding to the kth subcarrier is obtained through calculation based on the slope and intercept of the fitted linear; calculating to obtain a decision threshold corresponding to the kth subcarrier and a decision variable corresponding to each demodulation symbol on the kth subcarrier according to the decision coefficient corresponding to the kth subcarrier; and judging to obtain the value of the sending symbol corresponding to each demodulation symbol on the kth subcarrier by comparing the relative size of the judgment variable corresponding to each demodulation symbol on the kth subcarrier with the judgment threshold corresponding to the kth subcarrier.
2. The method as claimed in claim 1, wherein the decision coefficient d corresponding to the k-th sub-carrier is determined by a decision coefficient d corresponding to the k-th sub-carrier k And l k Respectively as follows:
d k ＝e k
Figure FDA0003666457550000011
wherein e is k The slope of a fitting straight line corresponding to the pilot demodulation symbol of the kth subcarrier; b k The intercept of a fitting straight line corresponding to a pilot demodulation symbol of the kth subcarrier; p k Is the value of the pilot symbol on the kth subcarrier of the transmitting end.
3. The method as claimed in claim 2, wherein when N is 2, the slope e of the straight line corresponding to the pilot demodulation symbol of the kth sub-carrier is the slope of the straight line k And intercept b k Respectively as follows:
Figure FDA0003666457550000021
Figure FDA0003666457550000022
or
Figure FDA0003666457550000023
Wherein the content of the first and second substances,
Figure FDA0003666457550000024
demodulating symbols p for pilot k (1) An imaginary part of (d);
Figure FDA0003666457550000025
demodulating symbols p for pilot k (1) The real part of (a);
Figure FDA0003666457550000026
demodulating symbols p for pilot k (2) An imaginary part of (d);
Figure FDA0003666457550000027
demodulating symbols p for pilot k (2) The real part of (a); p is a radical of k (1) And p k (2) The symbols are demodulated for the two pilots on the k subcarrier.
4. The method as claimed in claim 2, wherein when N is greater than or equal to 3, the slope e of the fitting line corresponding to the pilot demodulation symbol of the kth sub-carrier k And intercept b k Respectively as follows:
Figure FDA0003666457550000028
Figure FDA0003666457550000029
Figure FDA00036664575500000210
Figure FDA00036664575500000211
wherein the content of the first and second substances,
Figure FDA00036664575500000212
demodulating a real part of a symbol for an ith pilot on a kth subcarrier;
Figure FDA00036664575500000213
the imaginary part of the symbol is demodulated for the ith pilot on the kth subcarrier.
5. The method as claimed in claim 2, wherein the decision threshold f corresponding to the k-th sub-carrier is a threshold k (x 0 ) The expression of (a) is:
f k (x 0 )＝l k x 0
decision variable b corresponding to mth demodulation symbol on kth subcarrier k The expression of (m) is:
Figure FDA0003666457550000031
wherein x is 0 ＝-(2 r -2),-(2 r -4),...,+(2 r -2), denoted x 0 (i) I ═ 1,2, …, L; l is x 0 The value number in (1);
Figure FDA0003666457550000032
and
Figure FDA0003666457550000033
of the m-th demodulated symbol on the k-th sub-carrierReal and imaginary parts.
6. The method as claimed in claim 2, wherein the decision threshold f corresponding to the k-th sub-carrier is a threshold k (x 0 ) The expression of (a) is:
f k (x 0 )＝l k J k x 0
Figure FDA0003666457550000034
Figure FDA0003666457550000035
decision variable b corresponding to mth demodulation symbol on kth subcarrier k The expression of (m) is:
Figure FDA0003666457550000036
wherein x is 0 ＝-(2 r -2),-(2 r -4),...,+(2 r -2), denoted x 0 (i) I ═ 1,2, …, L; l is x 0 The value number in (1);
Figure FDA0003666457550000037
and
Figure FDA0003666457550000038
respectively a real part and an imaginary part of an mth demodulation symbol on a kth subcarrier; p η Is the noise power in the channel; p x The power of the transmitted signal for the transmitting end.
7. The method as claimed in claim 5 or 6, wherein in step S2, the decision corresponding to the demodulated symbol on the k-th sub-carrier is determinedA group of decision thresholds f corresponding to the decision variable and the k sub-carrier k (x 0 (i) ) Comparing in sequence;
when the decision variable is less than f k (x 0 (1) ) When the judgment variable is judged to be the value concentration of the OQAM symbol standard value less than x 0 (1) The OQAM symbol standard value;
when the size of the decision variable is in]f k (x 0 (j) )，f k (x 0 (j+1) )]When the judgment variable is in the range, the judgment variable is judged to be that the value concentration of the OQAM symbol standard is positioned in the value range [ x 0 (j) ，x 0 (j+1) ]Taking the value of an inner OQAM symbol standard; j ═ 1,2, …, L-1;
when the decision variable is larger than f k (x 0 (L) ) When the judgment variable is judged to be the value concentration of the OQAM symbol standard value which is larger than x 0 (L) The OQAM symbol standard value;
wherein the OQAM symbol standard value-taking set is { - (2) r -1),-(2 r -3),...,+(2 r -1)}。
8. A receiving apparatus, characterized in that it is configured to perform the multi-carrier symbol fast recovery method of any one of claims 1 to 7.
9. A symbol recovery apparatus for a multi-carrier system, comprising: a memory storing a computer program and a processor executing the computer program to perform the method of fast recovery of multicarrier symbols according to any of claims 1 to 7.
10. A multi-carrier system, comprising: a sending end and a receiving end;
the transmitting terminal is used for inserting N identical pilot symbols into the data symbols on each transmitting terminal carrier, then carrying out OQAM/FBMC modulation to obtain transmitting signals and transmitting the transmitting signals to the receiving terminal; n is more than or equal to 2;
the receiving end is configured to perform steps S1-S2 in the multi-carrier symbol fast recovery method of any one of claims 1-7.
CN202210593195.XA 2022-05-27 2022-05-27 High-precision multi-carrier symbol rapid recovery method, device and system Pending CN114884792A (en)

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