CN116527459A - Channel equalization method and system of SC-IFDMA system - Google Patents

Channel equalization method and system of SC-IFDMA system Download PDF

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CN116527459A
CN116527459A CN202310220452.XA CN202310220452A CN116527459A CN 116527459 A CN116527459 A CN 116527459A CN 202310220452 A CN202310220452 A CN 202310220452A CN 116527459 A CN116527459 A CN 116527459A
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data
channel
pilot
symbol
signal
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熊海良
张纪伟
王洪君
张玉炎
张文超
郝书吉
杨巨涛
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Shandong University
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Shandong University
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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
    • H04L25/03—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
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0202—Channel estimation
    • 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
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/003—Arrangements for allocating sub-channels of the transmission path
    • H04L5/0048—Allocation of pilot signals, i.e. of signals known to the receiver
    • 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
    • H04L2025/03592—Adaptation methods
    • H04L2025/03598—Algorithms
    • H04L2025/03611—Iterative algorithms
    • 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

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Power Engineering (AREA)
  • Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)

Abstract

The invention discloses a channel equalization method of an SC-IFDMA system, which comprises the following steps: transforming the data of the receiving end of the SC-IFDMA system to a frequency domain, and acquiring pilot frequency symbols and data symbols according to a system frame structure; estimating the current signal-to-noise ratio and the current channel characteristic according to the pilot frequency symbol to obtain an estimated signal-to-noise ratio and a channel estimation parameter; calculating channel equalizer coefficients according to the estimated signal-to-noise ratio and the channel estimation parameters; the data symbols pass through a channel equalizer, the iteration times are set, and the data symbols are subjected to iterative equalization by utilizing the channel equalizer coefficients; transforming the equalized data symbols to a time domain, and judging; judging whether the current iteration times are set times or not, and if the current iteration times are set times, outputting the current data symbol as a final iteration balance result. The method disclosed by the invention improves the equalization performance, simultaneously ensures that most of processing is in the frequency domain, and reduces the complexity of signal processing.

Description

Channel equalization method and system of SC-IFDMA system
Technical Field
The invention relates to the field of wireless communication computation, in particular to a channel equalization method and system of an SC-IFDMA system.
Background
In the existing communication system, the single carrier interleaved frequency division multiple access (SC-IFDMA) communication system has better advantages in some application scenes, combines the advantages of the single carrier frequency domain equalization (SC-FDE) and Orthogonal Frequency Division Multiple Access (OFDMA) communication systems, can overcome frequency selective fading by adopting a frequency domain equalization technology, can divide bandwidths into different subcarriers in an orthogonal frequency division mode, and dynamically distributes the subcarriers to different users, thereby meeting the characteristic of multiple access. In addition, the SC-IFDMA has lower complexity of the system and lower peak-to-average ratio while not reducing the capacity and the multiple access capability of the system, and can reduce the cost of the power amplifier transmitter to a great extent. SC-IFDMA is thus gaining more and more application.
The SC-IFDMA system has more expandability aiming at different application scenes. In order to restrain subcarrier crosstalk and intersymbol interference in transmission, according to the signal characteristics of SC-IDFMA, only a Cyclic Prefix (CP) with a certain length is needed to be added, namely, the data of the subcarriers at the tail part are copied to the forefront of the symbol, so that the orthogonality of the subcarriers can be ensured when multipath effect is generated, and the duration of the CP is larger than the maximum delay spread.
In the SC-IFDMA system, pilot signals may be inserted as needed. The pilot signal is divided into a data preamble and a pilot symbol. And adding a data preamble before the data frame to complete signal synchronization of a receiving end, wherein the signal synchronization is generally a constant envelope sequence with good autocorrelation, and the signal starting position can be considered to be captured when the correlation peak exceeds a synchronization threshold. The pilot symbols function as channel estimation and equalization. The channel characteristics and the channel quality of the current channel can be estimated only by comparing pilot symbols at the receiving and transmitting ends. And then, different equalization algorithms can be adopted to equalize the received data, so as to obtain a soft information sequence of the receiving end.
Channel equalization algorithms are typically applied in fading channels. Linear equalizers, such as zero-forcing equalization, minimum Mean Square Error (MMSE) equalization, are widely used due to their easier implementation. However, in the deep fading channel and low signal-to-noise ratio scenarios, the linear equalizer is greatly affected by noise, and the performance is greatly limited. The nonlinear equalizer can effectively suppress noise influence and has better performance in an ionospheric scattering channel. The block iterative decision feedback equalizer is a nonlinear equalizer, and has better performance by performing equalization in the frequency domain, then converting to time domain decision, and then converting to the frequency domain for iterative equalization. However, there is a greater complexity since the equalizer coefficients need to be recalculated for each iteration.
Disclosure of Invention
In order to solve the technical problems, the invention provides a channel equalization method and a channel equalization system for an SC-IFDMA system, which are used for solving the problems of channel equalization algorithm performance and complexity in the SC-IFDMA system.
In order to achieve the above purpose, the technical scheme of the invention is as follows:
a channel equalization method of an SC-IFDMA system comprises the following steps:
step 1, transforming the data of a receiving end of an SC-IFDMA system to a frequency domain, and acquiring pilot symbols and data symbols according to a frame structure of the SC-IFDMA system;
step 2, estimating the current signal-to-noise ratio and the current channel characteristic according to the pilot frequency symbol to obtain an estimated signal-to-noise ratio and a channel estimation parameter;
step 3, calculating the channel equalizer coefficient according to the estimated signal-to-noise ratio and the channel estimation parameter;
step 4, the data symbols pass through a channel equalizer, the iteration times are set, and the data symbols are subjected to iterative equalization by utilizing the channel equalizer coefficients;
step 5, transforming the equalized data symbol to the time domain, and judging;
and 6, judging whether the current iteration times are set times, if not, returning to the step 4, and if so, outputting the current data symbol as a final iteration balance result.
In the above scheme, the frame structure of the SC-IFDMA system is designed to divide the total subcarriers into all users on average, assuming that the total subcarriers of each symbol are M, the number of subcarriers of each user is N, N is an even number, and m=user×n; for each frame of data, 16 data symbols are total, and for data to be transmitted of each user, a CAZAC sequence with the length of N is inserted into each 4 data symbols at intervals as pilot symbols, 4 identical pilot symbols are inserted, and the pilot symbol with the length of N is generated according to the following formula:
wherein n is the nth data of the pilot symbol, and K is the root value of the pilot symbol;
all the transmitted symbols after pilot symbol insertion are 20 in number, and then all the transmitted symbols are mapped to M subcarriers.
In the above scheme, in step 2, the specific method for estimating the signal-to-noise ratio and the channel estimation parameter is as follows:
assume that a total of 4 pilot symbols with the same length N are inserted at the transmitting end and are marked as P (1) (k)，P (2) (k)，P (3) (k)，P (4) (k) K=1, 2, …, N, k being the kth element of the corresponding pilot symbol; the 4 pilot symbols, denoted Y, are received at the receiving end (1) (k)，Y (2) (k)，Y (3) (k)，Y (4) (k) K=1, 2, …, N; taking the Power average value of the received pilot frequency symbol as the signal Power average value Power_s, taking the Power average value of the pilot frequency symbol difference value of the receiving end as the noise Power Power_n, and estimating the signal-to-noise ratioThe method comprises the following steps:
y is set to (1) (k)，Y (2) (k)，Y (3) (k)，Y (4) (k) The frequency domains are respectively transformed, and the corresponding channel estimation parameters are calculated in the following modes:
H (i) (k)＝FFT(Y (i) (k))/FFT(P (i) (k))，i＝1，2，3，4
taking the average value as a channel estimation parameter:
in a further technical scheme, the calculation formulas of the signal Power average value Power_s and the noise Power Power_n are as follows:
wherein Re represents the real part, im represents the imaginary part, Y (i) (j) Represents the jth value in the ith received pilot symbol, and each pilot symbol has N values.
In the above scheme, in step 3, the channel equalizer parameters include a feedforward filter coefficient C (k) and a feedback filter coefficient B (k), and the calculation method is as follows:
wherein,,for the kth coefficient of the channel estimation parameter, < +.>Is->The corresponding conjugate parameter, alpha is a constant, and is kept unchanged in each iteration process, and the calculation mode is as follows:
in the above scheme, the specific method of step 4 is as follows: after the data is FFT transformed to the frequency domain, the data is IFFT transformed to the time domain after passing through the feedforward filter, the data is FFT transformed to the frequency domain after hard decision is made, and the frequency domain is sent to the feedback filter, so that decision output is performed after iteration for a plurality of times.
In the above scheme, in step 4, the calculation method for performing frequency domain iterative equalization on the received data is as follows:
wherein R is m (k) Is the kth frequency domain data after the mth iteration,is R m (k) Transform to frequency domain after decision is made in time domain, R 0 (k) Is the received kth frequency domain data.
In a further technical scheme, R 0 (k)、The calculation formula of (2) is as follows:
R 0 (k)＝FFT(r 0 (n))
r m (n)＝IFFT(R m (k))
wherein r is 0 (n) is the nth element of the time domain data received by the channel equalizer, R 0 (k) R is 0 The element corresponding to the frequency domain transformation of (n), r m (n) is the nth element of the time domain data after the mth iteration,r is m The nth element of the decision output of (n), if the transmitting end adopts BPSK modulation, the decision mode is hard decision according to signs, namely And demodulating other modulation modes and then carrying out hard decision.
A channel equalization system of an SC-IFDMA system comprises a signal-to-noise ratio estimation module, a channel estimation module and a channel equalization module;
the signal-to-noise ratio estimation module is used for calculating signal power and noise power according to the pilot frequency symbol of the receiving end and calculating an estimated signal-to-noise ratio
The channel estimation module is used for calculating channel estimation parameters in the frequency domain according to the pilot symbols of the receiving end
The channel equalization module is used for calculating channel equalizer parameters according to the estimated signal-to-noise ratio and the channel estimation parameters, and comprises a feedforward filter coefficient C (k) and a feedback filter coefficient B (k), and carrying out iterative equalization on the data of the receiving end.
Through the technical scheme, the channel equalization method and system of the SC-IFDMA system provided by the invention have the following beneficial effects:
(1) The invention adopts the SC-IFDMA system architecture, inserts the pilot frequency symbol into the data symbol, does not occupy the subcarrier resource of the SC-IFDMA system, and improves the utilization ratio of the bandwidth.
(2) The invention adopts the constant envelope autocorrelation sequence as the pilot frequency symbol and the synchronization preamble, realizes the reusability of the sequence, ensures the low peak-to-average power ratio characteristic of the SC-IFDMA system without damaging the frame structure and does not influence the high-power working environment of the system. The pilot frequency symbol of each frame can ensure the real-time performance of signal-to-noise ratio estimation and channel characteristic estimation.
(3) The improved low-complexity frequency domain decision feedback equalizer provided by the invention keeps the coefficients of the feedforward filter and the feedback filter unchanged in the iterative process, improves the equalization performance, simultaneously ensures that most of processing is in the frequency domain, and reduces the complexity of signal processing.
(4) The invention also provides a channel equalization system of the SC-IFDMA system, which gives out a signal processing calculation mode of each processing module, and can call the same module for a plurality of times through modularization, so that the calculation consumed resources of each module are all at minimum requirements.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below.
FIG. 1 is a schematic diagram of an SC-IFDMA system;
FIG. 2 is a frame structure diagram of a designed SC-IFDMA system;
FIG. 3 is a flow chart of a channel equalization method of an SC-IFDMA system disclosed in the present invention;
FIG. 4 is a block diagram of an SC-IFDMA channel equalization system;
FIG. 5 is a block diagram of a received signal for 500k bandwidth SC-IFDMA communications;
FIG. 6 is a block diagram of 500k bandwidth SC-IFDMA data symbols or SC-IFDMA pilot symbols;
fig. 7 is a length 128 pilot symbol constellation;
fig. 8 is a block diagram of a signal-to-noise ratio estimation module.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.
The invention provides a channel equalization method of an SC-IFDMA system, and the SC-IFDMA system is shown in figure 1. The system transmitting end comprises a synchronous preamble generating module, an FFT conversion module, an inserting pilot frequency module, a subcarrier mapping module and an IFFT conversion module; the system receiving end comprises a time domain synchronization module, an FFT conversion module, a subcarrier demapping module, a signal-to-noise ratio estimation module, a channel equalization module and an IFFT conversion module.
SC-IFDMA supports multi-user simultaneous processing, after a system transmitting end inputs information source information of a certain user, a synchronous preamble is firstly generated and added to the information front end to be used for synchronous capturing of a receiving end signal, FFT conversion is carried out to a frequency domain, pilot frequency symbols are inserted in the frequency domain to be used for receiving end signal processing, then frequency domain data is mapped to subcarriers of the user, and single carrier transmitting end processing is completed by IFFT conversion to a time domain.
The receiving end firstly captures the synchronous preamble and then acquires the signal position, then carries out FFT conversion to the frequency domain for signal processing, takes out the pilot frequency symbol according to the same mode of the transmitting end, uses the pilot frequency symbol for signal-to-noise ratio estimation and channel estimation, then sends the result to the equalizer for channel equalization processing, and transforms the data to the time domain through IFFT after equalization, thus obtaining the received soft information.
Specifically, the function of each module is as follows:
and the synchronous preamble generation module is used for: and placing a synchronous leading sequence at the front end of the information to be transmitted at the transmitting end, wherein the synchronous leading sequence is a CAZAC sequence with constant envelope good autocorrelation.
And a time domain synchronization module: the receiving end captures the synchronous lead through a sliding correlation mode, namely the position of the data symbol can be determined according to the frame structure, and the information after receiving.
And an FFT conversion module: and carrying out FFT conversion on the time domain data to a frequency domain according to the characteristics of the SC-IFDMA symbol.
IFFT transformation module: the frequency domain data is transformed to the time domain by IFFT transformation.
Inserting a pilot frequency module: the transmitting end inserts pilot frequency symbols at equal intervals in the data symbols as reference signals, wherein the pilot frequency symbols are CAZAC sequences with corresponding lengths.
Subcarrier mapping module: the SC-IFDMA system supports multi-user transmission, the total sub-carriers are divided into different users, and each user generates the transmission information and then maps the transmission information to all sub-carriers in an interleaving mapping mode.
Subcarrier demapping module: the SC-IFDMA system supports multi-user transmission, divides the total subcarrier number to different users, and obtains the frequency domain data corresponding to the current user through demapping.
A signal-to-noise ratio estimation module: and calculating the estimated signal-to-noise ratio of the current channel environment by using the pilot frequency symbols received by the receiving end.
Channel estimation sequence: the receiving end calculates the channel estimation parameters through the received pilot symbols by taking the pilot symbols inserted in the transmitting end as reference signals.
And a channel equalization module: and carrying out frequency domain equalization through the improved low-complexity block iterative decision feedback equalizer to obtain the SC-IFDMA data symbol soft information.
As shown in fig. 2, the frame structure of the SC-IFDMA system is designed to divide the total subcarriers into all users on average, assuming that the total number of subcarriers of each symbol is M, the number of subcarriers of each user is N, N is an even number, and m=user×n; for each frame of data, 16 data symbols are total, and for data to be transmitted of each user, a CAZAC sequence with the length of N is inserted into each 4 data symbols at intervals as pilot symbols, 4 identical pilot symbols are inserted, and the pilot symbol with the length of N is generated according to the following formula:
wherein n is the nth data of the pilot symbol, and K is the root value of the pilot symbol;
all the transmitted symbols after pilot symbol insertion are 20 in number, and then all the transmitted symbols are mapped to M subcarriers.
The invention discloses a channel equalization method for the SC-IFDMA system, as shown in figure 3, comprising the following steps:
and step 1, transforming the data of the receiving end of the SC-IFDMA system to a frequency domain, and acquiring pilot symbols and data symbols according to the frame structure of the SC-IFDMA system.
The 4 pilot symbols with the same length N are marked as P (1) (k),P (2) (k),P (3) (k),P (4) (k) K=1, 2, …, N, k being the kth element of the corresponding pilot symbol; the 4 pilot symbols, denoted Y, are received at the receiving end (1) (k)，Y (2) (k)，Y (3) (k)，Y (4) (k)，k＝1，2，…，N。
And step 2, estimating the current signal-to-noise ratio and the current channel characteristic according to the pilot frequency symbol to obtain an estimated signal-to-noise ratio and a channel estimation parameter.
Taking the Power average value of the received pilot frequency symbol as the signal Power average value Power_s, taking the Power average value of the pilot frequency symbol difference value of the receiving end as the noise Power Power_n, and estimating the signal-to-noise ratioThe method comprises the following steps:
specifically, the calculation formulas of the signal Power average value power_s and the noise Power power_n are as follows:
wherein Re represents the real part, im represents the imaginary part, Y (i) (j) Represents the jth value in the ith received pilot symbol, and each pilot symbol has N values.
Y is set to (1) (k)，Y (2) (k)，Y (3) (k)，Y (4) (k) The frequency domains are respectively transformed, and the corresponding channel estimation parameters are calculated in the following modes:
H (i) (k)＝FFT(Y (i) (k))/FFT(P (i) (k))，i＝1，2，3，4
taking the average value as a channel estimation parameter:
this results in the fact that,
wherein,,is the kth element of the channel estimation parameter.
Step 3, calculating a channel equalizer coefficient according to the estimated signal-to-noise ratio and the channel estimation parameter, wherein the channel equalizer parameter comprises a feedforward filter coefficient C (k) and a feedback filter coefficient B (k), and the calculation mode is as follows:
wherein,,the kth coefficient of the channel estimation parameter，/>Is->The corresponding conjugate parameter, alpha is a constant, and is kept unchanged in each iteration process, and the calculation mode is as follows:
step 4, the data symbols pass through a channel equalizer, the iteration times are set, and the data symbols are subjected to iterative equalization by utilizing the channel equalizer coefficients;
step 5, transforming the equalized data symbol to the time domain, and judging;
and 6, judging whether the current iteration times are set times, if not, returning to the step 4, and if so, outputting the current data symbol as a final iteration balance result.
The specific method comprises the following steps: after the data is FFT transformed to the frequency domain, the data is IFFT transformed to the time domain after passing through the feedforward filter, the data is FFT transformed to the frequency domain after hard decision is made, and the frequency domain is sent to the feedback filter, so that decision output is performed after iteration for a plurality of times.
The calculation mode for carrying out frequency domain iterative equalization on the received data is as follows:
wherein R is m (k) Is the kth frequency domain data after the mth iteration,is R m (k) Transform to frequency domain after decision is made in time domain, R 0 (k) Is the received kth frequency domain data.
Specifically, R 0 (k)、The calculation formula of (2) is as follows:
R 0 (k)＝FFT(r 0 (n))
r m (n)＝IFFT(R m (k))
wherein r is 0 (n) is the nth element of the time domain data received by the channel equalizer, R 0 (k) R is 0 The element corresponding to the frequency domain transformation of (n), r m (n) is the nth element of the time domain data after the mth iteration,r is m The nth element of the decision output of (n), if the transmitting end adopts BPSK modulation, the decision mode is hard decision according to signs, namely And demodulating other modulation modes and then carrying out hard decision.
The invention discloses a channel equalization system of an SC-IFDMA system, which comprises a signal-to-noise ratio estimation module, a channel estimation module and a channel equalization module as shown in figure 4;
a signal-to-noise ratio estimation module for calculating signal power and noise power according to the pilot frequency symbol of the receiving end and calculating an estimated signal-to-noise ratio
A channel estimation module for calculating channel estimation parameters in the frequency domain according to the pilot symbols of the receiving end
And the channel equalization module is used for calculating channel equalizer parameters according to the estimated signal-to-noise ratio and the channel estimation parameters, including feedforward filter coefficients C (k) and feedback filter coefficients B (k), and carrying out iterative equalization on the data of the receiving end.
After the receiving end of the SC-IFDMA system synchronizes to the received signal, pilot symbols and data symbols are extracted through a frame structure. After FFT is transformed to a frequency domain, pilot symbols are used for channel estimation and signal-to-noise ratio estimation, then a feedforward filter coefficient and a feedback filter coefficient are calculated by using channel estimation parameters and estimated signal-to-noise ratio, the data symbols are subjected to IFFT transformation to a time domain after passing through the feedforward filter to judge, the judgment result is subjected to FFT transformation to the frequency domain, iteration is carried out after passing through the feedback filter, and specific parameters are described below. In actual use, at 250k and 500k bandwidths, two SC-IFDMA system parameters shown in table 1 are provided.
TABLE 1 SC-IFDMA communication System parameters
In order to explain the effect of the present invention in practical use, in this embodiment, the parameters in number 1 are selected for explanation.
The signal received by the receiver is shown in fig. 5, which includes one synchronization preamble sequence, 16 SC-IFDMA data symbols, and 4 SC-IFDMA pilot symbols. The SC-IFDMA data symbols and SC-IFDMA pilot symbols have the same structure, and are each a data block of length 512 as shown in fig. 6. And performing correlation operation on the synchronous preamble sequence and the local sequence, wherein the data symbol and the pilot symbol can be extracted when the correlation peak exceeds the synchronization threshold. Fig. 7 is a pilot symbol constellation of length 128.
Channel equalization may then be performed in accordance with the system shown in fig. 4. Specifically, the signal-to-noise ratio estimation module calculates the signal power and the noise power according to a first formula, and then calculates the signal-to-noise ratio. As shown in fig. 8, the multiplier one performs a square operation in the signal power in the first formula, and adds the real power and the imaginary power through the adder one. The pilot symbol subtraction operation may be registered and output by delaying one pilot symbol by the buffer D. The real part signal and the imaginary part signal after subtraction are respectively sent to a multiplier II to carry out square operation, then the real part power and the imaginary part power of the subtracted data are accumulated through an adder II, and the real part power and the imaginary part power are subtracted through a register and then sent to a divider to carry out division operation.
The first formula includes:
where Power_s, power_n are the estimated signal Power and noise Power, respectively, re represents the real part and Im represents the imaginary part. Y is Y (i) (j) Representing the jth value in the ith received pilot symbol, there are 128 values for each pilot symbol.
The channel estimation module calculates channel estimation parameters according to a second formula:
wherein,,is the kth element of the channel estimation parameter, < +.>And inserting conjugate parameters of the pilot symbols for the transmitting end. The conjugate parameters are obtained by inverting the imaginary part.
The channel equalization module calculates a feedforward filter coefficient C (k) and a feedback filter coefficient B (k) of the channel equalizer according to a third formula:
wherein, C (k) and B (k) are respectively feedforward filter coefficient and feedback filter coefficient,and the conjugate parameter corresponding to the channel estimation parameter.
The channel equalization module performs iterative equalization of the received data according to a fourth formula:
R 0 (k)＝FFT(r 0 (n))
r m (n)＝IFFT(R m (k))
wherein r is 0 (n) is the nth element of the time domain data received by the channel equalization module, R 0 (k) R is 0 The element corresponding to the frequency domain transformation of (n), r m (n) is the nth element of the time domain data after the mth iteration,r is m (n) decision outputThe nth element, if the transmitting end adopts BPSK modulation, the decision mode is hard decision according to signs, namely r m (n) > 0, and performing hard decision after demodulation by other modulation modes.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (9)

1. The channel equalization method of the SC-IFDMA system is characterized by comprising the following steps:
step 1, transforming the data of a receiving end of an SC-IFDMA system to a frequency domain, and acquiring pilot symbols and data symbols according to a frame structure of the SC-IFDMA system;
step 2, estimating the current signal-to-noise ratio and the current channel characteristic according to the pilot frequency symbol to obtain an estimated signal-to-noise ratio and a channel estimation parameter;
step 3, calculating the channel equalizer coefficient according to the estimated signal-to-noise ratio and the channel estimation parameter;
step 4, the data symbols pass through a channel equalizer, the iteration times are set, and the data symbols are subjected to iterative equalization by utilizing the channel equalizer coefficients;
step 5, transforming the equalized data symbol to the time domain, and judging;
and 6, judging whether the current iteration times are set times, if not, returning to the step 4, and if so, outputting the current data symbol as a final iteration balance result.
2. The channel equalization method of SC-IFDMA system of claim 1, wherein the frame structure of the SC-IFDMA system is designed such that, assuming that the total number of subcarriers of each symbol is M, the total number of subcarriers is divided equally to all users, the number of subcarriers of each user is N, N is an even number, and M = user x N; for each frame of data, 16 data symbols are total, and for data to be transmitted of each user, a CAZAC sequence with the length of N is inserted into each 4 data symbols at intervals as pilot symbols, 4 identical pilot symbols are inserted, and the pilot symbol with the length of N is generated according to the following formula:
wherein n is the nth data of the pilot symbol, and K is the root value of the pilot symbol;
all the transmitted symbols after pilot symbol insertion are 20 in number, and then all the transmitted symbols are mapped to M subcarriers.
3. The method for channel equalization in SC-IFDMA system of claim 1, wherein in step 2, the specific method for estimating the signal-to-noise ratio and the channel estimation parameters is as follows:
assume that a total of 4 pilot symbols with the same length N are inserted at the transmitting end and are marked as kP (1) (k)，P (2) (k)，P (3) (k)，P (4) (k) K=1, 2, …, N being the kth element of the corresponding pilot symbol; the 4 pilot symbols, denoted Y, are received at the receiving end (1) (k),Y (2) (k),Y (3) (k),Y (4) (k) K=1, 2, N; taking the Power average value of the received pilot frequency symbol as the signal Power average value Power_s, taking the Power average value of the pilot frequency symbol difference value of the receiving end as the noise Power Power_n, and estimating the signal-to-noise ratioThe method comprises the following steps:
y is set to (1) (k),Y (2) (k),Y (3) (k),Y (4) (k) The frequency domains are respectively transformed, and the corresponding channel estimation parameters are calculated in the following modes:
H (i) (k)＝FFT(Y (i) (k))/FFT(P (i) (k)),i＝1,2,3,4
taking the average value as a channel estimation parameter:
4. a method for channel equalization in an SC-IFDMA system according to claim 3, wherein the signal Power average power_s and the noise Power power_n are calculated as follows:
wherein Re represents the real part, im represents the imaginary part, Y (i) (j) Represents the jth value in the ith received pilot symbol, and each pilot symbol has N values.
5. The method for channel equalization in an SC-IFDMA system of claim 1, wherein in step 3, the channel equalizer parameters include feedforward filter coefficients C (k) and feedback filter coefficients B (k) calculated by:
wherein,,for the kth coefficient of the channel estimation parameter, < +.>Is->The corresponding conjugate parameter, alpha is a constant, and is kept unchanged in each iteration process, and the calculation mode is as follows:
6. the method for channel equalization in SC-IFDMA system according to claim 1, wherein the specific method in step 4 is as follows: after the data is FFT transformed to the frequency domain, the data is IFFT transformed to the time domain after passing through the feedforward filter, the data is FFT transformed to the frequency domain after hard decision is made, and the frequency domain is sent to the feedback filter, so that decision output is performed after iteration for a plurality of times.
7. The method for channel equalization in SC-IFDMA system according to claim 1 or 6, wherein in step 4, the calculation method for performing frequency domain iterative equalization on the received data is as follows:
wherein R is m (k) Is the firstThe kth frequency domain data after m iterations,is R m (k) Transform to frequency domain after decision is made in time domain, R 0 (k) Is the received kth frequency domain data.
8. The method for channel equalization in an SC-IFDMA system of claim 7, wherein R 0 (k)、The calculation formula of (2) is as follows:
R 0 (k)＝FFT(r 0 (n))
r m (n)＝IFFT(R m (k))
wherein r is 0 (n) is the nth element of the time domain data received by the channel equalizer, R 0 (k) R is 0 The element corresponding to the frequency domain transformation of (n), r m (n) is the nth element of the time domain data after the mth iteration,r is m The nth element of the decision output of (n), if the transmitting end adopts BPSK modulation, the decision mode is hard decision according to sign, namely +.> And demodulating other modulation modes and then carrying out hard decision.
9. The channel equalization system of the SC-IFDMA system is characterized by comprising a signal-to-noise ratio estimation module, a channel estimation module and a channel equalization module;
the signal-to-noise ratio estimation module is used for calculating signal power and noise power according to the pilot frequency symbol of the receiving end and calculating an estimated signal-to-noise ratio
The channel estimation module is used for calculating channel estimation parameters in the frequency domain according to the pilot symbols of the receiving end
The channel equalization module is used for calculating channel equalizer parameters according to the estimated signal-to-noise ratio and the channel estimation parameters, and comprises a feedforward filter coefficient C (k) and a feedback filter coefficient B (k), and carrying out iterative equalization on the data of the receiving end.
CN202310220452.XA 2023-03-09 2023-03-09 Channel equalization method and system of SC-IFDMA system Pending CN116527459A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN118200086A (en) * 2024-05-20 2024-06-14 成都泰格微电子研究所有限责任公司 Interference identification method based on frequency domain equalization method

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN118200086A (en) * 2024-05-20 2024-06-14 成都泰格微电子研究所有限责任公司 Interference identification method based on frequency domain equalization method

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