CN110602005A - Method for realizing signal time-frequency domain energy averaging by two time-domain component equipower weighting transformation - Google Patents

Method for realizing signal time-frequency domain energy averaging by two time-domain component equipower weighting transformation Download PDF

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CN110602005A
CN110602005A CN201910562342.5A CN201910562342A CN110602005A CN 110602005 A CN110602005 A CN 110602005A CN 201910562342 A CN201910562342 A CN 201910562342A CN 110602005 A CN110602005 A CN 110602005A
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time
signal
domain
frequency domain
transformation
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房宵杰
李成方
李勇
沙学军
梅林�
李卓明
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Harbin Institute of Technology
CETC 54 Research Institute
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Harbin Institute of Technology
CETC 54 Research Institute
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0202—Channel estimation
    • H04L25/024—Channel estimation channel estimation algorithms
    • H04L25/0256—Channel estimation using minimum mean square error criteria
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
    • H04L25/03006—Arrangements for removing intersymbol interference
    • H04L25/03012—Arrangements for removing intersymbol interference operating in the time domain
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
    • H04L25/03006—Arrangements for removing intersymbol interference
    • H04L25/03159—Arrangements for removing intersymbol interference operating in the frequency domain
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/0014—Carrier regulation
    • 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
    • H04L27/2626—Arrangements specific to the transmitter only
    • H04L27/2627—Modulators
    • H04L27/2628—Inverse Fourier transform modulators, e.g. inverse fast Fourier transform [IFFT] or inverse discrete Fourier transform [IDFT] modulators
    • 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
    • H04L27/265—Fourier transform demodulators, e.g. fast Fourier transform [FFT] or discrete Fourier transform [DFT] demodulators
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/0014—Carrier regulation
    • H04L2027/0024—Carrier regulation at the receiver end
    • H04L2027/0026—Correction of carrier offset

Abstract

A time-frequency domain energy averaging signal transmission method based on two time-domain components equal-power weighted transformation relates to the field of wireless communication and aims to improve transmission performance. The invention provides the method for continuously iterating the frequency domain signal by carrying out two-time component transformation, realizes the frequency domain diversity of the signal, homogenizes the symbol energy of the time domain and the frequency domain by utilizing an iterative algorithm, has low operation complexity and can be applied to a single carrier system and an OFDM system. Changing the weighting coefficients in the transformation process can also be used to improve the security of the information. The signal with uniformly distributed time-frequency domain energy is realized, and the signal has good bit error rate under time selection, frequency selection and double-selection channels.

Description

Method for realizing signal time-frequency domain energy averaging by two time-domain component equipower weighting transformation
Technical Field
The invention belongs to the technical field of wireless communication, and particularly relates to a method for realizing time-frequency domain energy averaging of signals by using an equal-power weighted transformation iteration method of two time-domain components.
Background
Under the frequency selective channel, the traditional single carrier signal has better performance because the energy of the frequency domain is uniformly distributed. Under the time-selective channel, the traditional multi-carrier has better performance because the energy distribution in the time domain is uniform. The classical mixed carrier system is realized based on a four-term weighted fractional Fourier transform theory. The method can realize that the signal time domain energy (the sum of the time domain and the time domain turnover component) is equal to the signal frequency domain energy (the sum of the frequency domain and the frequency domain turnover component), and the signal energy distribution has better error rate performance under the double-selection channel. In order to make the four energies of the time-frequency domain of the signal equal, the clever proposes: the publication number is: CN108833326A, "transmission method of multi-component power-averaged generalized mixed carrier". On the basis, in order to adapt to different channels, the clever proposes the disclosure numbers as follows: CN: 108924077A, the transmission method under the time selective fading channel of the generalized mixed carrier system () and the publication number are: CN: 108737317A entitled generalized Mixed Carrier frequency-Selective channel Transmission method.
The classical four-weighted fractional fourier transform can be represented as follows:
by relaxing the constraint condition of the classical four-item weighted fractional Fourier transform, the transformation reversibility and the energy invariance are only satisfied, and the two-time-domain component equipower weighted transformation is proposed by clever, and the definition form is as follows:
the positive and inverse transformation weighting coefficients are respectively calculated by the following formulas:
[z0 z1 z2 z3]intermediate variables are:
θisatisfies the following conditions:or
It can be seen from the formula that the two time domain components are subjected to equal power weighted transformation, the time domain signal components and the time domain inversion components are subjected to weighted summation, and the squares of the weighted coefficients are allThe original time domain signal component and the time domain inversion component have equal power, the frequency domain component power is 0, because only the time domain component signal is transmitted, the signal energy is uniformly distributed in the frequency domain, the loss of the symbol energy caused by the deep fading of one frequency point of the frequency domain is averagely distributed to each time domain information source symbol, the average signal-to-noise ratio of each symbol of the time domain is higher, and therefore better performance can be obtained under a frequency selection channel. Similarly, for equal power transformation of two frequency domain components, the energy of the time domain component is set to zero, and both the frequency domain component and the frequency domain inversion component are set to zeroWhen only the overloaded signal is transmittedThe wave component signals and the signal energy are uniformly distributed in the time domain, and the energy of deep fading loss of the time domain can be evenly distributed to each frequency domain source symbol, so that the performance is better under a time-selective channel.
The two time domain component transformations introduce self inverse signals to carry out equal power weighted superposition, when the time domain has a little fading, the symbol energy of the time domain component and the time domain turnover component at the same position is lost, although the symbol energy is at the same position, the symbol energy corresponds to two different symbols, and after the inverse transformation, the fading symbol can obtain half of the energy compensation, so that the performance of the signal for selecting channels when resisting the time is improved. And arranging the symbols of the second half length after the conversion in a reverse order to ensure that the symbols with the same length are all spaced equally on the time domain except for the fixed point. All the two time domain components mentioned below are subjected to such post-processing after being subjected to equal power conversion. For simplicity, the two-time component weighted transform is abbreviated below.
The time diversity principle achieved by the two time domain component weighted transform is shown in fig. 1.
To accommodate different channels, many mixed carrier schemes have been proposed. The fractional Fourier transform mixed multi-carrier system based on the four-item weighting can simultaneously transmit time domain components and frequency domain components to resist against double-channel selection, and can match different channels by adjusting the distribution of signal time domain and frequency domain component energy to improve the system performance and realize the conversion of single carrier and multi-carrier transmission. From the above analysis, it can be known that the time domain energy averaging can effectively combat the time-selective channel, and the frequency domain energy averaging can effectively combat the frequency-selective channel, however, it can be observed that no matter how the power ratio of the time domain component and the frequency domain component is designed, it is impossible to simultaneously achieve the high time domain and frequency domain energy averaging in the existing mixed carrier system.
If a signal has the property of uniform distribution in the time-frequency domain, the signal is subjected to frequency selection, time selection and double selection channels, the energy loss of each symbol is the minimum, and the energy loss caused by fading of the time-frequency domain channel is uniformly distributed on each symbol.
Disclosure of Invention
The invention provides a time-frequency domain energy averaging signal transmission method based on two time-domain components equal-power weighted transformation, aiming at realizing a signal with uniformly distributed time-frequency domain energy and ensuring that the signal has good bit error rate performance under time selection, frequency selection and double-selection channels.
The time-frequency domain energy averaging signal transmission method based on the equal power weighted transformation of two time domain components is a time-frequency domain energy averaging signal transmission method based on the equal power weighted transformation of two time domain components under a frequency domain diversity time diversity OFDM system:
the signal transmitting method comprises the following steps:
step one, performing baseband modulation on an original baseband symbol to obtain a modulation signal;
step two, performing serial-to-parallel conversion on the modulation signal obtained in the step one; obtaining a parallel signal;
step three, performing equal-power two-time domain component weighting transformation iterative operation on the parallel converted signal obtained in the step one to obtain an iterative operation signal;
step four, performing N-point IFFT on the signals obtained in the step three after the iterative operation to obtain N-point IFFT converted signals;
step five, performing parallel-serial conversion on the signals obtained in the step four after the N-point IFFT conversion; obtaining a serial signal;
step six, performing CP adding operation on the serial signals obtained in the step five to obtain signals added with CP;
step seven, carrying out time slot expansion on the signal added with the CP obtained in the step six to obtain a signal after time slot expansion operation;
step eight, the signals obtained in the step seven after the time slot expansion operation are subjected to digital/analog conversion and up-conversion processing and then are sent to a channel through an antenna;
the signal receiving method comprises the following steps:
step nine, carrying out down-conversion processing and analog/digital conversion on the received radio frequency signal to obtain a digital baseband signal;
step ten, extracting corresponding time slots from the digital baseband signals obtained in the step nine through two-time component inverse transformation to obtain different time slot channel gains; removing the CP to obtain a signal after the CP is removed;
step eleven, performing MMSE time domain equalization operation on the signal obtained in the step eleven after the CP is removed to obtain a signal after the MMSE time domain equalization operation
Step twelve, performing serial-to-parallel conversion on the signals obtained in the step eleven after the CPMMSE time domain equalization operation is removed to obtain parallel signals;
thirteen, performing FFT processing on the parallel signals obtained in the step twelve to obtain frequency domain signals;
and step fourteen, performing equal-power two-time-domain component weighted transformation quasi-iteration on the frequency domain signal obtained in the step thirteen, recovering an original baseband symbol, and completing one time of time-frequency domain energy-averaged signal transmission based on the equal-power two-time-domain component weighted transformation.
The time-frequency domain energy averaging signal transmission method based on the two-time domain component equipower weighted transformation is a time-frequency domain energy averaging signal transmission method based on the two-time domain component equipower weighted transformation under a single carrier system with time-domain energy averaging time diversity:
the signal transmitting method comprises the following steps:
step one, performing baseband modulation on an original baseband symbol to obtain a modulation signal;
step two, carrying out equal-power two-time domain component weighting transformation iterative operation on the modulation signal obtained in the step one to obtain a signal after the iterative operation;
step three, carrying out equal-power two-time domain component weighting transformation iterative operation on the parallel converted signal obtained in the step one to obtain digital/analog conversion and up-conversion processing, and then sending the processed signal to a channel through an antenna;
step four, carrying out time slot expansion on the signal obtained in the step three after the iterative operation to obtain a signal after the time slot expansion operation;
step five, the signals after the time slot expansion operation obtained in the step four are subjected to digital/analog conversion and up-conversion processing and then are sent to a channel through an antenna;
the signal receiving method comprises the following steps:
step six, performing down-conversion processing and analog/digital conversion on the received radio frequency signal to obtain a digital baseband signal;
step seven, performing MMSE time domain equalization operation on the digital baseband signal obtained in the step six to obtain a signal after the MMSE time domain equalization operation;
step eight, carrying out time slot extraction operation on the signals obtained in the step seven after MMSE time domain equalization operation to obtain signals after time slot extraction;
step nine, performing two-time component weighting transformation inverse iteration operation on the signal obtained after the time slot extraction in the step eight to obtain a signal after the inverse iteration operation;
and step ten, performing baseband demodulation on the signal obtained in the step nine after the inverse iteration operation to recover an original baseband symbol, and completing one time of time-frequency domain energy-averaged signal transmission based on two time-domain components and equal power weighted transformation.
The invention has the following beneficial effects: the invention provides a method for continuously iterating frequency domain signals by carrying out two-time component transformation, realizing frequency domain diversity of the signals, homogenizing time-frequency domain symbol energy by utilizing an iterative algorithm, and provides an effective iterative algorithm, wherein the operation complexity is O (Nlog)2(N)), it is applied to single carrier and OFDM systems. The method is applied to the traditional single carrier, effectively improves the time domain deep fading resistance of the traditional single carrier, effectively improves the frequency domain deep fading resistance of the traditional single carrier when applied to the multi-carrier, and improves the transmission performance of the traditional single carrier and the multi-carrier under the double-selection channel. In essence, the transform iteration technology can be regarded as a coding technology for a source, the coding rate is not changed, excessive complexity is not increased, and effective performance improvement is realized. The scheme has wide application range, and is not only suitable for a single carrier system, but also suitable for a multi-carrier system and a mixed carrier system. In addition, the coefficient in the iterative process can be adjusted at will, so that the safety of the information can be improved.
Drawings
FIG. 1 is a schematic diagram illustrating the time diversity implementation principle of two time domain component weighting transformation according to the background art of the present invention;
FIG. 2 is a schematic diagram of a signal transmission principle of a time-frequency domain energy-averaged signal transmission method based on two time-domain components equal-power weighted transformation in a frequency domain diversity time diversity OFDM system according to the present invention;
FIG. 3 is a schematic diagram of a signal transmission principle of a time-frequency domain energy-averaging signal transmission method based on two time-domain components equal-power weighted transformation in a single carrier system with time-domain energy uniformization and time diversity according to the present invention;
FIG. 4 is a schematic diagram of an iteration flow at a transmitting end of an original symbol;
wherein: blockk，iAn ith iteration module of a kth stage of a sending end;
FIG. 5 is a transmitting end Blockk，iProcessing flow of the module;
wherein: n is the number of subcarriers, k is 1, 22(N)， Represents Blockk，iThe input of the first level is an original signal;represents Blockk，iTo output of (c). W0，k，W1，kFor weighting coefficients, different blocksk，iDifferent weighting coefficients may be employed; the purpose of the half-symbol block inversion is to achieve an averaging of the symbol energy allocation distances.
FIG. 6 is a schematic diagram of an iterative flow of inverse transform at the receiving end of the present invention;
wherein: block _ invk，iA kth level ith path iteration module of a receiving end;
k＝1，2，...，log2(N)，i＝1，2，...，2K-1，[w0，k]-1、[w1，k]-1represents the inverse transform coefficients; input/output and Blockk，iThe modules are opposite;
fig. 7 is a schematic diagram of the distribution change of the signal information after two-stage iteration (taking the length of the input signal as 8 as an example).
FIG. 8 is a schematic diagram showing simulation of BER performance of signals in a pure frequency selective channel (channel 1); (the original signal length is set as 128 points in the following simulation result graphs).
It is composed of
FIG. 9 is a schematic diagram of simulation of BER performance of signals under a single time-selective channel (channel 2);
FIG. 10 is a diagram showing simulation of BER performance of signals under a double channel selection;
fig. 11 is a schematic diagram illustrating the influence of the number of iterations of the OFDM system under channel 4 on the performance; (taking 128 carrier frequencies as an example);
FIG. 12 is a schematic diagram of performance simulation under frequency selective channel for 4 and 6 iterations of single carrier and OFDM;
fig. 13 is a schematic diagram of performance simulation under a time-selective channel for 4 and 6 iterations of single carrier and OFDM;
FIG. 14 is a diagram of performance simulation under dual channel selection for 4 and 6 iterations of single carrier and OFDM;
Detailed Description
In a first embodiment, a time-frequency domain energy-averaged signal transmission method based on two time-domain components and equal power weighted transformation in this embodiment is described with reference to fig. 2, and is a time-frequency domain energy-averaged signal transmission method based on two time-domain components and equal power weighted transformation in a frequency-domain diversity time diversity OFDM system:
the signal transmitting method comprises the following steps:
step one, performing baseband modulation on an original baseband symbol to obtain a modulation signal;
step two, performing serial-to-parallel conversion on the modulation signal obtained in the step one; obtaining a parallel signal;
step three, performing equal-power two-time domain component weighting transformation iterative operation on the parallel converted signal obtained in the step one to obtain an iterative operation signal;
step four, performing N-point IFFT on the signals obtained in the step three after the iterative operation to obtain N-point IFFT converted signals;
step five, performing parallel-serial conversion on the signals obtained in the step three after the N-point IFFT conversion; obtaining a serial signal;
step six, performing CP adding operation on the serial signals obtained in the step five to obtain signals added with CP;
step seven, carrying out time slot expansion on the signal added with the CP obtained in the step six to obtain a signal after time slot expansion operation;
step eight, the signals obtained in the step seven after the time slot expansion operation are subjected to digital/analog conversion and up-conversion processing and then are sent to a channel through an antenna;
the signal transmitting and receiving method comprises the following steps:
step nine, carrying out down-conversion processing and analog/digital conversion on the received radio frequency signal to obtain a digital baseband signal;
step ten, extracting corresponding time slots from the digital baseband signals obtained in the step nine through two-time component inverse transformation to obtain different time slot channel gains; removing the CP to obtain a signal after the CP is removed;
step eleven, performing MMSE time domain equalization operation on the signal obtained in the step eleven after the CP is removed to obtain a signal after the MMSE time domain equalization operation
Step twelve, performing serial-to-parallel conversion on the signals obtained in the step eleven after the CPMMSE time domain equalization operation is removed to obtain parallel signals;
thirteen, performing FFT processing on the parallel signals obtained in the eleventh step to obtain frequency domain signals;
and step fourteen, performing equal-power two-time-domain component weighted transformation quasi-iteration on the frequency domain signal obtained in the step thirteen, recovering an original baseband symbol, and completing one time of time-frequency domain energy-averaged signal transmission based on the equal-power two-time-domain component weighted transformation.
The invention aims to realize a signal with uniformly distributed time-frequency domain energy, so that the signal has good bit error rate performance under time selection, frequency selection and double-selection channels. The technical scheme adopted by the invention for solving the technical problems is as follows: the two-time-domain component equal-power transformation iteration module is used for processing an OFDM frequency domain information source to realize frequency diversity, and the performance of the frequency diversity under a frequency selection channel and a double selection channel is improved; and the two time domain components are utilized to process the SC time domain information source by the equal power transformation iteration module to resist time domain fading, so that the performance of the SC time domain information source under a time selection channel and a double selection channel is improved.
The conventional two-time component transformation is to perform a transformation process on a time domain signal. In most of the actual systems, the signal source symbols are discrete sampling points, so that two time domain component weighted transformation can be performed on the frequency domain signal before the IFFT is performed on the OFDM, diversity is realized on the frequency domain through the transformed discrete points, and the frequency domain diversity degree is continuously improved through repeated iteration, so that the frequency domain symbols are transmitted on subcarriers as many as possible.
The invention takes a classical multi-carrier OFDM system as a frame, realizes frequency diversity by utilizing the equipower transformation of two time domain components, and greatly improves the transmission performance of the system under a frequency selective channel. The transmission system is shown in figure 1. The transmitting end of the transmission system comprises: baseband signal modulation, serial-to-parallel conversion, two time domain component weighting transformation iteration module, N-point IFFT (assuming that the number of subcarriers is N ═ 2)M) The device comprises a parallel-serial conversion module, a CP adding module, a time slot expanding module and a D/A conversion and up-conversion module; the receiving end of the transmission system comprises a down-conversion and A/D conversion module, a time slot extraction module, a CP removal module, an MMSE time domain equalization module, a serial-parallel conversion module, an N-point IFFT module, a two-time domain component weighting inverse conversion iteration module and a parallel-serial conversion module;
at a sending end, a baseband binary code element passes through a modulation module, and an output modulation symbol can be regarded as a frequency domain symbol; converting the high-speed serial data stream into parallel low-speed data stream through an S/P module, mapping one subcarrier by one symbol, and sharing N-2MThe duration of each OFDM symbol of the subcarriers is changed into N times (without considering CP), so that the multipath resistance is improved; performing M-1 times of iteration on the frequency domain signal through a two-time domain component weighting transformation iteration module, and improving the uniformity degree of the frequency domain symbol energy; an IFFT module for mapping the baseband subcarrier, wherein the output signal can be regarded as a time domain signal, the energy of the frequency domain channel is uniformly distributed in the time domain by IFFT conversion, namely each discrete point of the time domain comprises a part of all the discrete points of the frequency domainAn amount; performing serial-to-parallel conversion; CP is added to eliminate ISI and sacrifice spectral efficiency, and the convolution of channel impulse response and signal becomes cyclic convolution, which can simplify the equalization of the receiving end; in order to continuously improve the signal transmission performance, time diversity is realized by performing two-time component transformation after the time domain signal is supplemented with 0 with the same length. And finally, sending signals through the D/A module and the up-conversion module through an antenna.
And adopting a corresponding reverse process at a receiving end. Carrying out down-conversion on the received radio frequency signal, and obtaining a digital baseband signal through A/D conversion; extracting corresponding time slots through two-time component inverse transformation to obtain different time slot channel gains; removing the CP; and compensating channel distortion through an MMSE time domain equalization module to obtain the minimum mean square error estimation of the transmitted signal as a received signal. The energy loss of the received signal relative to the transmitted signal is minimal. At this time, the more average the energy loss distribution, the better the performance obtained; performing FFT (fast Fourier transform) after the S/P module to obtain a frequency domain signal; and performing two time domain component weighted transformation simulation iterations on the signal in the frequency domain to restore the original baseband symbol.
The invention has the beneficial effects that: two-time component transformation is continuously iterated on a frequency domain signal to realize frequency domain diversity of the signal, the time-frequency domain symbol energy is homogenized by utilizing an iterative algorithm, and an effective iterative algorithm is provided, wherein the operation complexity is O (Nlog)2(N)), and applied to single carrier and OFDM systems. The method is applied to the traditional single carrier, effectively improves the time domain deep fading resistance of the traditional single carrier, effectively improves the frequency domain deep fading resistance of the traditional single carrier when applied to the multi-carrier, and improves the transmission performance of the traditional single carrier and the multi-carrier under the double-selection channel. In essence, the transform iteration technology can be regarded as a coding technology for the information source, the coding rate is not changed, excessive complexity is not increased, and effective performance improvement is realized. The scheme has wide application range, and is not only suitable for a single carrier system, but also suitable for a multi-carrier system and a mixed carrier system. In addition, the coefficient in the iterative process can be adjusted at will, so that the safety of the information can be improved.
In the second embodiment, a time-frequency domain energy-averaging signal transmission method based on two time-domain component equal power weighted transformation according to the second embodiment is described with reference to fig. 3, and is a time-frequency domain energy-averaging signal transmission method based on two time-domain component equal power weighted transformation in a single carrier system with time-domain energy uniformization time diversity:
the signal transmitting method comprises the following steps:
step one, performing baseband modulation on an original baseband symbol to obtain a modulation signal;
step two, carrying out equal-power two-time domain component weighting transformation iterative operation on the modulation signal obtained in the step one to obtain a signal after the iterative operation;
step three, carrying out equal-power two-time domain component weighting transformation iterative operation on the parallel converted signal obtained in the step one to obtain digital/analog conversion and up-conversion processing, and then sending the processed signal to a channel through an antenna;
step four, carrying out time slot expansion on the signal obtained in the step three after the iterative operation to obtain a signal after the time slot expansion operation;
step five, the signals after the time slot expansion operation obtained in the step four are subjected to digital/analog conversion and up-conversion processing and then are sent to a channel through an antenna;
the signal receiving method comprises the following steps:
step six, performing down-conversion processing and analog/digital conversion on the received radio frequency signal to obtain a digital baseband signal;
step seven, performing MMSE time domain equalization operation on the digital baseband signal obtained in the step six to obtain a signal after the MMSE time domain equalization operation;
step eight, carrying out time slot extraction operation on the signals obtained in the step seven after MMSE time domain equalization operation to obtain signals after time slot extraction;
step nine, performing two-time component weighting transformation inverse iteration operation on the signal obtained after the time slot extraction in the step eight to obtain a signal after the inverse iteration operation;
and step ten, performing baseband demodulation on the signal obtained in the step nine after the inverse iteration operation to recover an original baseband symbol, and completing one time of time-frequency domain energy-averaged signal transmission based on two time-domain components and equal power weighted transformation.
The technical effects of the invention are verified by specific simulation experiments as follows:
fig. 7 is a schematic diagram of the distribution change of the signal information after two-stage iteration (taking the length of the input signal as 8 as an example).
Wherein: the horizontal axis represents 1-8 subcarrier frequency points or time domain sampling points, and the sampling points are distinguished by different colors; the vertical axis represents Blockk，iAnd (5) processing. And (m, n) indicates that the frequency point contains information of the original m-th and n-th points after conversion, and indicates that information of the 2 nd and 8 th symbols is transmitted in the second subcarrier or the second unit time of the time domain after conversion corresponding to the abscissa 2 as shown in the figure of (2, 8), and the method can be regarded as realizing signal diversity.
FIG. 8 is a schematic diagram showing simulation of BER performance of signals in a pure frequency selective channel (channel 1); (the original signal length is set as 128 points in the following simulation result graphs).
Wherein: the Doppler frequency shift of the channel is 0Hz, and the maximum time delay is 6 mu s. "SC" denotes a legacy single carrier; "OFDM" refers to conventional orthogonal frequency division multiplexing multi-carrier; "SC-2 t 6" represents the signal after adding iteration module to iterate 6 levels at the transmitting and receiving ends of the single carrier system; "OFDM-2 t 6" indicates that signals after iteration module iteration 6 are added at both ends of OFDM system transceiver. "SC-2 slot" represents the signal of traditional single carrier plus two-slot diversity; "OFDM-2 slot" represents the signal of traditional OFDM plus two-slot diversity; "SC-2 t6-2 slot" represents a signal obtained after a traditional single carrier is added into an iteration module (iterated for 6 times) and a slot expansion module, and a system schematic block diagram is shown in fig. 2; "OFDM-2 t6-2 slot" represents a signal obtained by adding an iteration module (iteration six times) and slot expansion to a conventional OFDM, and a system schematic diagram is shown in fig. 2;
and (4) analyzing results: under a pure frequency selection channel, the traditional OFDM performance is poor; the energy distribution of the single carrier in the frequency domain is relatively uniform, and the energy lost by the deep fading of the frequency domain can be uniformly distributed to different time domain symbols, so the transmission performance of the single carrier under a frequency selective channel is good; OFDM transmission (128-point signal, 6 times of iteration and 7 th iteration without frequency diversity gain) added into an iteration module is carried out, a symbol of an original frequency point is transmitted on a plurality of subcarriers, frequency diversity is realized, and the performance of the OFDM transmission under a frequency selective channel is greatly improved and approaches to the performance of a traditional single carrier; the performance of the OFDM and single carrier added time slot expansion module is greatly improved; according to the transmission scheme, the OFDM is added into the iteration module and the time slot expansion module, so that the performance is greatly improved compared with the traditional OFDM; the performance of a single carrier added into an iteration module under the condition of a frequency selection channel with high signal-to-noise ratio is lower than that of a traditional single carrier, which shows that the distortion of the channel to the signal is amplified after the transformation iteration. The number of iterations may in practice be varied depending on the transmission quality. For OFDM, the more the number of iterations in the frequency selective channel, the better, and no iteration is performed on a single carrier.
FIG. 9 is a schematic diagram of simulation of BER performance of signals under a single time-selective channel (channel 2);
wherein: the respective diagrams show the same signals as in fig. 7. And the time selection channel with the Doppler frequency shift of 10KHz and the maximum time delay of 0 mus adopts the power spectrum density of the Jakes frequency shift.
And (4) analyzing results: under a single time selection channel, the traditional single carrier performance is poor; the OFDM has uniform energy distribution in the time domain, and the energy lost by time domain deep fading is distributed to each symbol in the frequency domain, so the transmission performance of the time-selective channel is good; the single carrier transmission (iteration 6 times) of an iteration module is added, the symbol of an original time domain sampling point is transmitted on a plurality of sampling points in the whole single carrier symbol block, and at the moment, the deep fading of a certain point in the time domain is distributed to the symbols which share the transmission of the point, so that the performance of the single carrier transmission is greatly improved compared with that of the traditional single carrier; in order to further improve the transmission performance under the condition of not occupying more time-frequency resources, a time slot expansion module is added. The single carrier plus iteration module and the time slot spreading module are close to the OFDM time slot spreading module. The performance of the OFDM adding iteration module and the time slot module is almost the same as that of the OFDM adding time slot expansion module under the channel, and the frequency diversity can not improve the system performance under the pure time selection channel. By comparing fig. 7, it can be seen that as the doppler shift becomes larger, the channel variation becomes faster, and the performance improvement of slot spreading increases. The performance degradation of the OFDM signal subjected to iteration is reduced by about 1dB as with the single frequency selection channel, and therefore, the more SC iteration times under the time selection channel, the better, the more OFDM signal is not subjected to iteration.
FIG. 10 is a diagram illustrating simulation of BER performance of signals under a double channel selection;
wherein: the respective diagrams show the same signals as in fig. 7. The Doppler frequency shift of the channel is 10KHz, and the maximum time delay is 6 mus, fmaxTsA Jakes frequency-shifted power spectral density is used for the 0.01 double channel.
And (4) analyzing results: under the channel, the traditional multi-carrier and single-carrier performances are poor, and the single-carrier and OFDM signals added into the iterative module have great performance improvement. The multi-carrier and single-carrier performances of the iteration module and the time slot expansion module are further improved, and the performances of the iteration module and the time slot expansion module are almost the same.
Fig. 11 is a schematic diagram illustrating simulation of the influence of the number of iterations of the OFDM system on performance under channel 4; (taking 128 carrier frequencies as an example);
and (4) analyzing results: under this channel condition, we can see that the performance improvement becomes smaller and smaller as the number of iterations increases, and the performance is best when the number of iterations is 4. The reasons are as follows: first, the greater the number of iterations, the less efficient the iteration. Secondly, since the signal is distorted after passing through the channel, the receiving end may have large distortion and too large iteration number after performing the hierarchical iteration as shown in fig. 4, and the frequency diversity effect achieved by the iteration is not enough to compensate for the performance loss. Approximately, in channel four, the maximum delay of the channel is 6 μ s, the coherence bandwidth is about 0.16MHz, and when the available bandwidth is 1MHz, a 128-point IFFT is used for subcarrier mapping. The k-th order subcarrier spacing for achieving frequency diversity isA sub-carrier bandwidth. When the iteration times are more than or equal to 5, the frequency diversity range is less than the coherent bandwidth, and the iteration improves the diversity effect slightly.
Fig. 12 is a schematic diagram of performance simulation under four channels for single carrier and OFDM iterations 4 and 6 times.
Wherein: the legend is the same as before, with the last digit representing the number of iterations. "SC-2 t 4" represents a single carrier level 4 iteration. "OFDM-2 t 4" indicates that the OFDM iteration module has performed 4 levels of iterations.
And (4) analyzing results: as can be seen from fig. 12, the performance of the OFDM4 level iteration is not greatly reduced and is almost unchanged compared with the 6 level iteration under the frequency selective channel. The single-carrier 4-level iteration performance under a large signal-to-noise ratio is improved by 1dB compared with the 6-level iteration performance; fig. 13 can see that, under the condition of a large signal-to-noise ratio of the time-selective channel, the OFDM4 level iteration is improved by about 0.5dB compared with the 6 level iteration, and for a single carrier, the performance of 4 level iteration and 6 level iteration and iteration is almost unchanged; in fig. 14, under the condition of large signal-to-noise ratio of the double channel selection, it can be seen that the single carrier performance and the OFDM performance of 4-level iteration are better than the performance of 6-level iteration by more than 1 dB.
If the relatively proper iteration times can be selected, the performance of the OFDM under the frequency selection channel and the double selection channel can be fully improved, the performance of the single carrier under the time selection channel and the double selection channel can be fully improved, and the performance of the OFDM under the time selection channel and the SC under the frequency selection channel can also be ensured. If the adaptation can be realized according to the statistical characteristics of the channels, different iteration times can be selected according to different channels.

Claims (2)

1. The time-frequency domain energy averaging signal transmission method based on two time-domain components equal-power weighted transformation is characterized in that: the time-frequency domain energy averaging signal transmission method based on two time-domain components equal power weighted transformation under a frequency domain diversity time diversity OFDM system comprises the following steps:
the signal transmitting method comprises the following steps:
step one, performing baseband modulation on an original baseband symbol to obtain a modulation signal;
step two, performing serial-to-parallel conversion on the modulation signal obtained in the step one; obtaining a parallel signal;
step three, performing equal-power two-time domain component weighting transformation iterative operation on the parallel converted signal obtained in the step one to obtain an iterative operation signal;
step four, performing N-point IFFT on the signals obtained in the step three after the iterative operation to obtain N-point IFFT converted signals;
step five, performing parallel-serial conversion on the signals obtained in the step three after the N-point IFFT conversion; obtaining a serial signal;
step six, performing CP adding operation on the serial signals obtained in the step five to obtain signals added with CP;
step seven, carrying out time slot expansion on the signal added with the CP obtained in the step six to obtain a signal after time slot expansion operation;
step eight, the signals obtained in the step seven after the time slot expansion operation are subjected to digital/analog conversion and up-conversion processing and then are sent to a channel through an antenna;
the signal receiving method comprises the following steps:
step nine, carrying out down-conversion processing and analog/digital conversion on the received radio frequency signal to obtain a digital baseband signal;
step ten, extracting corresponding time slots from the digital baseband signals obtained in the step nine through two-time component inverse transformation to obtain different time slot channel gains; removing the CP to obtain a signal after the CP is removed;
step eleven, performing MMSE time domain equalization operation on the signal obtained in the step eleven after the CP is removed to obtain a signal after the MMSE time domain equalization operation
Step twelve, performing serial-to-parallel conversion on the signals obtained in the step eleven after the CPMMSE time domain equalization operation is removed to obtain parallel signals;
thirteen, performing FFT processing on the parallel signals obtained in the eleventh step to obtain frequency domain signals;
and step fourteen, performing equal-power two-time-domain component weighted transformation quasi-iteration on the frequency domain signal obtained in the step thirteen, recovering an original baseband symbol, and completing one time of time-frequency domain energy-averaged signal transmission based on the equal-power two-time-domain component weighted transformation.
2. The time-frequency domain energy averaging signal transmission method based on two time-domain components equal-power weighted transformation is characterized in that: the time-frequency domain energy averaging signal transmission method based on two time-domain components equal-power weighted transformation under a single carrier system with time-domain energy uniformization and time diversity is as follows:
the signal transmitting method comprises the following steps:
step one, performing baseband modulation on an original baseband symbol to obtain a modulation signal;
step two, carrying out equal-power two-time domain component weighting transformation iterative operation on the modulation signal obtained in the step one to obtain a signal after the iterative operation;
step three, carrying out equal-power two-time domain component weighting transformation iterative operation on the parallel converted signal obtained in the step one, obtaining digital/analog conversion and up-conversion processing, and then sending the processed signal to a channel through an antenna;
step four, carrying out time slot expansion on the signal obtained in the step three after the iterative operation to obtain a signal after the time slot expansion operation;
step five, the signals after the time slot expansion operation obtained in the step four are subjected to digital/analog conversion and up-conversion processing and then are sent to a channel through an antenna;
the signal receiving method comprises the following steps:
step six, performing down-conversion processing and analog/digital conversion on the received radio frequency signal to obtain a digital baseband signal;
step seven, MMSE time domain equalization operation is carried out on the digital baseband signals obtained in the step six, and signals after MMSE time domain equalization operation are obtained;
step eight, carrying out time slot extraction operation on the signals obtained in the step seven after MMSE time domain equalization operation to obtain signals after time slot extraction;
step nine, performing two-time component weighting transformation inverse iteration operation on the signal obtained after the time slot extraction in the step eight to obtain a signal after the inverse iteration operation;
and step ten, performing baseband demodulation on the signal obtained in the step nine after the inverse iteration operation to recover an original baseband symbol, and completing one time of time-frequency domain energy-averaged signal transmission based on two time-domain components and equal power weighted transformation.
CN201910562342.5A 2019-06-26 2019-06-26 Method for realizing signal time-frequency domain energy averaging by two time-domain component equipower weighting transformation Pending CN110602005A (en)

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