CN116319221A - OFDM signal peak-to-average power ratio reducing method based on minimum coverage circle - Google Patents

OFDM signal peak-to-average power ratio reducing method based on minimum coverage circle Download PDF

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CN116319221A
CN116319221A CN202310282726.8A CN202310282726A CN116319221A CN 116319221 A CN116319221 A CN 116319221A CN 202310282726 A CN202310282726 A CN 202310282726A CN 116319221 A CN116319221 A CN 116319221A
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signal
circle
domain signal
frequency domain
subcarriers
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谢映海
李先怀
肖林松
赵海波
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Zhonghui Microelectronics Co ltd
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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
    • H04L27/2614—Peak power aspects
    • H04L27/2623—Reduction thereof by clipping
    • 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
    • H04L5/0001—Arrangements for dividing the transmission path
    • H04L5/0003—Two-dimensional division
    • H04L5/0005—Time-frequency
    • H04L5/0007—Time-frequency the frequencies being orthogonal, e.g. OFDM(A), DMT
    • H04L5/001—Time-frequency the frequencies being orthogonal, e.g. OFDM(A), DMT the frequencies being arranged in component carriers
    • 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

An OFDM signal peak-to-average power ratio reducing method based on a minimum coverage circle method comprises the following signal processing processes at a signal receiving end: after the original frequency domain signal X is obtained, dividing N subcarriers in an OFDM symbol into reserved subcarriers and data subcarriers, wherein the number of the reserved subcarriers is N/Q, and the positions of the reserved subcarriers are distributed at equal intervals; obtaining a time domain signal of a data subcarrier frequency domain signal through IFFT conversion: acquiring a time domain signal of the reserved subcarrier frequency domain signal by adopting a minimum coverage circle method; and adding the time domain signal corresponding to the data subcarrier frequency domain signal and the time domain signal corresponding to the frequency domain subcarrier frequency domain signal to obtain a time domain transmitting signal of the OFDM symbol. The method uses the reserved sub-carrier with special position distribution characteristic, and adopts the minimum coverage circle search method of the limited point set to acquire the time domain signal of the frequency domain signal of the reserved sub-carrier, thereby ensuring the peak-to-average ratio and reducing the complexity of the search calculation process.

Description

OFDM signal peak-to-average power ratio reducing method based on minimum coverage circle
Technical Field
The invention belongs to the technical field of signal processing, and particularly relates to a method for reducing the peak-to-average ratio of an OFDM signal based on a minimum coverage circle.
Background
Orthogonal frequency division multiplexing (Orthogonal Frequency Division Multiplexing, abbreviated as OFDM) is a multi-carrier transmission technology, which can realize high-speed data transmission with higher spectrum utilization rate and can also effectively resist multipath fading, so that the method is widely applied to a plurality of digital broadband communication systems such as 4G, 5G, digital Audio Broadcasting (DAB), digital Video Broadcasting (DVB), high Definition Television (HDTV) and the like. However, the Peak-to-Average Power Ratio (PAPR) problem caused by the multi-carrier system can greatly reduce the power efficiency of the radio frequency amplifier, and put forward higher requirements on the linear range of the existing amplifier, and increase the implementation difficulty and cost of the system, so the Peak-to-average ratio reduction technology is one of the key technologies of the OFDM system.
The basic principle of the method is that a transmitting end reserves a part of special subcarriers for generating peak elimination signals for inhibiting PAPR, a receiver end ignores data on reserved subcarriers for inhibiting PAPR, and recovers useful signals from other normal data subcarriers for transmitting information. The core of the reserved sub-carrier method is how to obtain the data on the reserved sub-carriers so as to reduce the peak value of the original OFDM signal. A solution is proposed, in which, among the K reserved sub-carriers, if each sub-carrier has V values, V can be correspondingly generated K Each alternative peak clipping signal, however, the generation process of each alternative peak clipping signal needs to perform one inverse fast fourier transform (Invert Fast Fourier Transformation, IFFT), and the calculation amount is very large. Another peak clipping-subcarrier reservation method has been proposed, in which an original OFDM signal is first subjected to clipping operation, and then a peak cancellation signal is generated by using clipping noise generated by clipping. However, this method requires many or even infinite iterations to produce a peak cancellation signal that is sufficiently good to be approximately equal to the ideal peak cancellation signal, and is computationally very complex.
Disclosure of Invention
The invention aims to provide a low-complexity method for reducing the peak-to-average ratio of an OFDM signal based on a minimum coverage circle.
In order to achieve the above object, the present invention adopts the following technical solutions:
an OFDM signal peak-to-average power ratio reducing method based on minimum coverage circle comprises the following signal processing process at a signal receiving end: after the original frequency domain signal X is obtained,
s1, dividing N subcarriers in an OFDM symbol into reserved subcarriers and data subcarriers, wherein the number of the reserved subcarriers is N/Q, the positions of the reserved subcarriers are distributed at equal intervals, the reserved subcarriers are fixed to be theta, theta+Q, theta+2Q … … and theta+ (N/Q-1) Q subcarriers in the OFDM symbol, and theta and Q are integers;
in the original frequency domain signal of the OFDM symbol, the data subcarrier frequency domain signal is x1= [ X1 (0), X1 (1),. The term, X1 (N-1)]，
Figure BDA0004138632250000021
Reserved subcarrier frequency domain signal is v= [ V (0), V (1),. The term, V (N-1)]，/>
Figure BDA0004138632250000022
X (n) is an nth element in an original frequency domain signal X of the OFDM symbol;
s2, obtaining a time domain signal X1 of the data subcarrier frequency domain signal X1 through IFFT transformation:
s3, acquiring a time domain signal V of a reserved subcarrier frequency domain signal V by adopting a minimum coverage circle method, wherein the method comprises the following specific steps of:
s301, constructing a first constant vector
Figure BDA0004138632250000023
And a first signal->
Figure BDA0004138632250000024
First constant vector
Figure BDA0004138632250000025
First signal
Figure BDA0004138632250000026
S302, the first signal
Figure BDA0004138632250000027
A matrix Γ converted into N/Q rows, Q columns:
Figure BDA0004138632250000031
s303, for matrix Γ, find the first signal from N/Q row vectors
Figure BDA0004138632250000032
The element with the largest medium amplitude
Figure BDA0004138632250000033
Is of the row vector Γ r The symbol |·| indicates taking absolute value, +.>
Figure BDA0004138632250000034
In the formula->
Figure BDA0004138632250000035
R-th row vector representing matrix Γ, ">
Figure BDA0004138632250000036
The r+N/Q row vector representing matrix Γ, and so on;
s304, constructing a second signal
Figure BDA0004138632250000037
And solving for complex constant delta r So that the second signal +.>
Figure BDA0004138632250000038
The maximum amplitude value of the element in (a) is minimized;
Figure BDA0004138632250000039
solving complex constant delta by adopting minimum covered circle method r The center coordinates of the minimum circle are-delta r ；
S305, order
Figure BDA00041386322500000310
The following calculation process is performed on the remaining N/Q-1 row vectors in the matrix Γ one by one:
for a certain row vector Γ in the matrix Γ q Calculating Γ q Maximum amplitude value max (|Γ) of (a) q |)；
If max (|Γ) q I) is less than or equal to R, the complex constant value corresponding to the row vector is delta q =0, if max (|Γ) q I) R, solving the complex constant Δ using the same method as step S304 q I.e. to construct a third signal
Figure BDA00041386322500000311
And solving complex constant delta by adopting a minimum covered circle method q So that the third signal +>
Figure BDA00041386322500000312
The maximum amplitude value of the element in (1) is minimized if Γ q Radius value of the corresponding minimum circle +.>
Figure BDA00041386322500000313
Then use->
Figure BDA00041386322500000314
R is replaced, and the center coordinates of the minimum circle searched for are-delta q ；
S306, respectively calculating N/Q row vectors of the matrix Γ through the steps to obtain N/Q complex constants, and forming the complex constants into a vector delta, delta= [ delta ] 0 ,Δ 1 ,...,Δ N/Q-1 ]Order-making
Figure BDA00041386322500000315
Constructing a second constant vector P->
Figure BDA00041386322500000316
The time domain signal V corresponding to the reserved subcarrier frequency domain signal V is:
Figure BDA0004138632250000041
and S4, adding the time domain signal X1 corresponding to the data subcarrier frequency domain signal X1 and the time domain signal V corresponding to the frequency domain subcarrier frequency domain signal V to obtain a time domain transmission signal X of the OFDM symbol, wherein x=x1+v.
The method for reducing peak-to-average power ratio of OFDM signal based on minimum coverage circle method as described above, further, in step S304, complex constant delta is solved by minimum coverage circle method r When for point set Γ r The searching steps of the corresponding minimum circle are specifically as follows:
a. from the point set Γ r Finding the two points with the farthest distance and adding the two points into a point set L, and constructing a circle by taking the connecting line of the two points as the diameter
Figure BDA0004138632250000042
b. Judgment circle
Figure BDA0004138632250000043
Whether or not to cover the point set Γ r If yes, the circle is the minimum circle, and the searching process is ended; if not, continuing the next step;
c. from the point set Γ r Find a departure circle
Figure BDA0004138632250000044
Is added into the point set L, and the smallest covered circle of the point set L is calculated by using a random increment method, and then the circle is replaced by the circle>
Figure BDA0004138632250000045
And then returns to step b.
According to the technical scheme, the peak-to-average ratio reducing method based on the subcarrier reservation technology with low calculation complexity is provided for the peak-to-average ratio reducing problem of the OFDM signals.
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In order to more clearly illustrate the embodiments of the present invention, the following description will briefly explain the embodiments or the drawings required for the description of the prior art, it being obvious that the drawings in the following description are only some embodiments of the present invention and that other drawings may be obtained according to these drawings without inventive effort to a person skilled in the art.
Fig. 1 is a signal processing flow chart of a signal transmitting end when OFDM signal peak-to-average power ratio is reduced by a reserved subcarrier method;
fig. 2 is a schematic diagram of a position distribution of data subcarriers and reserved subcarriers;
FIG. 3 is a flow chart of signal processing at the signal transmitting end of the method of the present invention;
FIG. 4 is a graph comparing peak-to-average ratio performance simulation curves using the method of the present invention with peak-to-average ratio simulation curves not using the method of the present invention.
Detailed Description
In describing embodiments of the present invention in detail, the drawings showing the structure of the device are not to scale locally for ease of illustration, and the schematic illustrations are merely examples, which should not limit the scope of the invention. It should be noted that the drawings are in simplified form and are not to scale precisely, but rather are merely intended to facilitate and clearly illustrate the embodiments of the present invention. Meanwhile, in the description of the present application, the terms "first", "second", and the like are used only to distinguish the description, and are not to be construed as indicating or implying relative importance or implying the number of technical features indicated; the terms "forward," "reverse," "bottom," "upper," "lower," and the like are used for convenience in describing and simplifying the description only, and do not denote or imply that the devices or elements being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus should not be construed as limiting the invention.
In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "connected," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; the two components can be directly connected or indirectly connected through an intermediate medium, or can be communicated inside the two components, or can be connected wirelessly or in a wired way. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.
In an OFDM symbol with the number of subcarriers N, a time domain signal corresponding to a frequency domain signal x= [ X (0), X (1),., X (N-1) ] is x= [ X (0), X (1),., X (N-1) ], and the relationship between the two is as follows:
Figure BDA0004138632250000051
IDFT (X) represents the discrete inverse fourier transform result.
Fig. 1 is a signal processing flow chart of a signal transmitting end when OFDM signal peak-to-average power ratio is reduced by a reserved subcarrier method. As shown in fig. 1, in order to reduce the PAPR of the OFDM signal, the reserved subcarrier technology divides N subcarriers into two types, wherein N1 subcarriers carry data symbols to be transmitted, such subcarriers are data subcarriers, the frequency domain signal of the data subcarriers is denoted as X1, and the corresponding time domain signal is denoted as X1; the remaining N-N1 reserved sub-carriers do not carry data symbols and are used for generating peak clipping signals for reducing the peak-to-average value of the transmission signals, the sub-carriers are reserved sub-carriers, the frequency domain signals of the reserved sub-carriers are denoted as V, and the corresponding time domain signals are denoted as V. The essence of the reserved sub-carrier method is that for the time domain signal x1 of the data sub-carrier, the frequency domain signal V matched with the data sub-carrier is found in a certain way, so that the peak-to-average ratio of the final transmitted signal x=x1+v is minimized.
When the signal is subjected to Inverse Fast Fourier Transform (IFFT), the number N of subcarriers satisfies 2 K Frequency domain signal x= [ X (0), X (1),. The term X (N-1),. Gtoreq.2)]It satisfies the following conditions:
Figure BDA0004138632250000061
wherein θ and Q are positive integers, and q=2 q (q≥2)≤N/2，0≤θ≤Q-1；
The corresponding time domain signal x= [ x (0), x (1),. The term, x (N-1) ] has the following properties:
Figure BDA0004138632250000062
wherein P is a constant vector, +.>
Figure BDA0004138632250000063
For the frequency domain signal [ X (θ), X (θ+q), ], X (θ+n-Q)]Corresponding time domain signal,/->
Figure BDA0004138632250000064
(symbol)
Figure BDA0004138632250000065
Representing the dot product operation between two vectors of equal length, time domain signal +.>
Figure BDA0004138632250000066
Figure BDA0004138632250000067
One OFDM symbol has N subcarriers with numbers 0,1,2, … …, N-1. The invention provides a method for carrying out peak-to-average power ratio reduction on an OFDM signal based on a reserved subcarrier technology of a minimum coverage circle theory, which is shown in fig. 3, and comprises the following steps:
at the signal transmitting end, the signal processing process is as follows:
s1, dividing subcarriers in an OFDM symbol into reserved subcarriers and data subcarriers, wherein the reserved subcarriers are used for generating peak elimination signals for reducing peak-to-average ratio of transmitted signals, the data subcarriers are used for bearing data symbols to be transmitted, the number of the reserved subcarriers is N/Q, the positions of the reserved subcarriers are distributed at equal intervals, and the reserved subcarriers are fixed as theta, theta+Q, theta+2Q … … and theta+N/Q-1 in the OFDM symbol, wherein theta and Q are integers, theta is more than or equal to 0 and less than or equal to Q-1, and Q=2 q ，q≤1，Q≤N/2；
For example, assuming that the number of subcarriers of the OFDM symbol is n=16, let q=2, q=4, θ=2, then the reserved subcarriers are the 2 nd, 6 th, 10 th, and 14 th subcarriers in the OFDM symbol, i.e. the 2 nd, 6 th, 10 th, and 14 th subcarriers are reserved subcarriers, respectively;
for an OFDM symbol containing N subcarriers, the original frequency domain signal is
X= [ X (0), X (1), X (N-1) ], of the frequency domain signals of the OFDM symbol, the data subcarrier frequency domain signal is X1, the reserved subcarrier frequency domain signal is V, and the data subcarrier frequency domain signal
X1＝[X1(0),X1(1),...,X1(N-1)]Reserved subcarrier frequency domain signal v= [ V (0), V (1),. The term, V (N-1)]Wherein, the method comprises the steps of, wherein,
Figure BDA0004138632250000071
Figure BDA0004138632250000072
s2, obtaining time domain signals X1, x1= [ X1 (0), X1 (1),. The number, X1 (N-1) ] of the data subcarrier frequency domain signals X1 through IFFT transformation;
s3, acquiring a time domain signal V of a reserved subcarrier frequency domain signal V by adopting a minimum coverage circle method, wherein the method comprises the following specific steps of:
s301 structureBuild a first constant vector
Figure BDA0004138632250000073
And a first signal->
Figure BDA0004138632250000074
First constant vector
Figure BDA0004138632250000075
First signal
Figure BDA0004138632250000076
S302, the first signal
Figure BDA0004138632250000077
A matrix Γ converted into N/Q rows, Q columns:
Figure BDA0004138632250000078
s303, for matrix Γ, find the first signal from N/Q row vectors
Figure BDA00041386322500000817
Element of maximum medium amplitude ∈ ->
Figure BDA0004138632250000081
Is of the row vector Γ r The symbol |·| represents taking the absolute value;
the first signal is provided with
Figure BDA0004138632250000082
Element of maximum medium amplitude ∈ ->
Figure BDA0004138632250000083
Is a row vector of (2)
Figure BDA0004138632250000084
In the formula->
Figure BDA0004138632250000085
An r-th row vector of N/Q row vectors representing matrix Γ,/-th row vector>
Figure BDA0004138632250000086
An (r+N/Q) th row vector among the N/Q row vectors representing matrix Γ, and so on;
s304, constructing a second signal
Figure BDA0004138632250000087
And solving for complex constant delta r So that the second signal +.>
Figure BDA0004138632250000088
The maximum amplitude value of the element in (a) is minimized;
Figure BDA0004138632250000089
vector composed of complex numbers
Figure BDA00041386322500000810
Representing a finite set of points comprising Q points in a two-dimensional plane, wherein the values of the real and imaginary parts represent the abscissa and the ordinate, respectively, the complex constant-delta r Can be regarded as the center coordinates of a circle, and the complex constant delta r Essentially, is the point set Γ r Find the corresponding minimum covered circle, the radius of the minimum covered circle is equal to +.>
Figure BDA00041386322500000811
The invention improves the existing minimum coverage circle method, and aims at point set Γ r The searching steps of the corresponding minimum coverage circle are specifically as follows:
a. from the point set Γ r Finding the two points with the farthest distance and adding the two points into a point set L, and constructing a circle by taking the connecting line of the two points as the diameter
Figure BDA00041386322500000812
b. Judgment circle
Figure BDA00041386322500000813
Whether or not to cover the point set Γ r If yes, the circle is the minimum circle, and the searching process is ended; if not, continuing the next step;
c. from the point set Γ r Find a departure circle
Figure BDA00041386322500000814
Is added into the point set L, and the smallest covered circle of the point set L is calculated by using a random increment method, and then the circle is replaced by the circle>
Figure BDA00041386322500000815
Then returning to the step b;
s305, order
Figure BDA00041386322500000816
The following calculation process is performed on the remaining N/Q-1 row vectors in the matrix Γ one by one:
for a certain row vector Γ in the matrix Γ q Calculating Γ q Maximum amplitude value max (Γ q |)；
If max (|Γ) q I) is less than or equal to R, the complex constant value corresponding to the row vector is delta q =0, if max (|Γ) q I) R, solving the complex constant Δ using the same method as step S304 q I.e. to construct a third signal
Figure BDA0004138632250000091
And solving complex constant delta by using a minimum covered circle method q So that the third signal +>
Figure BDA0004138632250000092
The maximum amplitude value of the element in (letting max (|Γ) q +Δ q I) minimum), if Γ q Radius value of the corresponding minimum circle +.>
Figure BDA0004138632250000093
Then use->
Figure BDA0004138632250000094
R is replaced, and the center coordinates of the minimum circle searched for are-delta q ；
S306, respectively calculating N/Q row vectors of the matrix Γ through the steps to obtain N/Q complex constants, and forming the complex constants into a vector delta, delta= [ delta ] 0 ,Δ 1 ,...,Δ N/Q-1 ]Order-making
Figure BDA0004138632250000095
Constructing a second constant vector P->
Figure BDA0004138632250000096
Reserved subcarrier frequency domain signal v= [ V (0), V (1),. The term, V (N-1)]The corresponding time domain signal v is
Figure BDA0004138632250000097
And S4, adding the time domain signal X1 corresponding to the data subcarrier frequency domain signal X1 and the time domain signal V corresponding to the frequency domain subcarrier frequency domain signal V to obtain a time domain transmission signal X of the OFDM symbol, wherein x=x1+v. After the signal receiving end receives the signal, the received signal is recovered according to the conventional method.
The method adopts a minimum coverage circle method to acquire the time domain signal V of the reserved subcarrier frequency domain signal V. The calculation of the minimum coverage circle is based on some basic properties:
1) The smallest coverage circle is the only one present;
2) A circle can be determined by taking the connecting line between two points as the diameter;
3) The 3 non-collinear points may define a circle, and all three points lie on the circumference of the circle;
4) At least two points of the finite set of points will fall on the circumference of their smallest covered circle, and if there are more than two points, the smallest covered circle is the circumscribing circle of the triangle or polygon formed by these points.
Based on the above properties, one intuitive solution to the minimum coverage circle problem is to traverse the set of points s= { S 1 ,s 2 ,...,s N All 2-point combinations and 3-point combinations in }, but the conventional minimum coverage circle calculation process is still of high complexity, up to O (N 4 ). Even though some existing algorithms make some improvements to the traversal process, such as the random increment method based on the recursive idea, their computational complexity is still at a high level. The specific calculation steps of the random increment method are as follows:
1) Randomly selecting two points from the point set S, and constructing a circle by taking the connecting line of the two points as the diameter
Figure BDA0004138632250000098
2) Randomly selecting a new point from the set of points S if the new point is in a circle
Figure BDA0004138632250000101
In the interior, the circle is not updated>
Figure BDA0004138632250000102
If the new point is in the circle +>
Figure BDA0004138632250000103
In addition, from the position of the circle->
Figure BDA0004138632250000104
The points in the set are traversed to select 2 points, and a circle is formed together with the new points; after all combinations are completed, a circle can be covered simultaneously is selected from>
Figure BDA0004138632250000105
The smallest radius circle of all points and new points in the inner, and then replacing the circle with the circle +.>
Figure BDA0004138632250000106
3) Repeating the above steps until the circle
Figure BDA0004138632250000107
It is possible to cover all points in the set S of points, the circle being the smallest circle.
The invention improves the searching process of the minimum circle based on the following theory:
for any finite point set S, if the corresponding minimum coverage circle is marked as C, there is C e Ω, where the circle set Ω= { C 1 ,....,C 6 The definition of the 6 circles contained in the } is specifically as follows:
1) Circle C 1 : the two points L furthest apart in the point set S 1 And L 2 The determined circle;
2) Circle C i I=2,..6: at the position of
Figure BDA0004138632250000108
In the case of (1), point set { L ] 1 ,...,L i+1 Minimum covered circle corresponding to the point L i+1 Is the point set S and the circle C i-1 One point with the farthest center distance.
From the above, it can be seen that the method can certainly find the minimum covered circle of the point set S, and the theoretical upper limit of the search times is 6 times, so the method of the present invention adopts the improved minimum circle search method in steps S404 and S405, and can have very low calculation amount.
The peak-to-average ratio reduction effect of the method is verified through a simulation experiment. The distribution of the peak-to-average ratio (PAPR) of the signal is described by using a time domain Complementary Cumulative Distribution Function (CCDF) in simulation, wherein the mathematical calculation formula is Pr (PAPR > z) =1-Pr (PAPR < z), and z represents a threshold value. FIG. 4 is a graph of CCDF curves when N/Q is equal to different values, respectively, the TR curve in FIG. 4 shows the CCDF curves after the peak-to-average ratio reduction by the method of the present invention, and the No TR curve shows the CCDF curves without the peak-to-average ratio reduction by the method of the present invention. As can be seen from fig. 4, the method of the present invention can obtain very excellent peak-to-average power ratio performance, such as CCDF reduced by about 2.3dB at 10 "3 when N/q=4, i.e., 4 (the ratio of the total bandwidth is 4/256=1.56%) subcarriers are used as reserved subcarriers, compared with the OFDM signal without the peak-to-average power ratio of the method of the present invention. Simulation results show that the method can obtain very excellent peak-to-average power ratio reducing performance by only a small proportion of reserved subcarriers.
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 (2)

1. An OFDM signal peak-to-average power ratio reducing method based on a minimum coverage circle method is characterized in that:
at the signal receiving end, the signal processing process is as follows: after the original frequency domain signal X is obtained,
s1, dividing N subcarriers in an OFDM symbol into reserved subcarriers and data subcarriers, wherein the number of the reserved subcarriers is N/Q, the positions of the reserved subcarriers are distributed at equal intervals, the reserved subcarriers are fixed to be theta, theta+Q, theta+2Q … … and theta+ (N/Q-1) Q subcarriers in the OFDM symbol, and theta and Q are integers;
in the original frequency domain signal of the OFDM symbol, the data subcarrier frequency domain signal is x1= [ X1 (0), X1 (1),. The term, X1 (N-1)]，
Figure FDA0004138632150000011
Reserved subcarrier frequency domain signal is v= [ V (0), V (1),. The term, V (N-1)]，/>
Figure FDA0004138632150000012
X (n) is an nth element in an original frequency domain signal X of the OFDM symbol;
s2, obtaining a time domain signal X1 of the data subcarrier frequency domain signal X1 through IFFT transformation:
s3, acquiring a time domain signal V of a reserved subcarrier frequency domain signal V by adopting a minimum coverage circle method, wherein the method comprises the following specific steps of:
s301, constructing a first constant vector
Figure FDA0004138632150000013
And a first signal->
Figure FDA0004138632150000014
First constant vector
Figure FDA0004138632150000015
First signal
Figure FDA0004138632150000016
S302, the first signal
Figure FDA0004138632150000017
A matrix Γ converted into N/Q rows, Q columns:
Figure FDA0004138632150000018
s303, for matrix Γ, find the first signal from N/Q row vectors
Figure FDA0004138632150000021
The element with the largest medium amplitude
Figure FDA0004138632150000022
Is of the row vector Γ r The symbol |·| indicates taking absolute value, +.>
Figure FDA0004138632150000023
In the formula->
Figure FDA0004138632150000024
R-th row vector representing matrix Γ, ">
Figure FDA0004138632150000025
The r+N/Q row vector representing matrix Γ, and so on;
s304, constructing a second signal
Figure FDA0004138632150000026
And solving for complex constant delta r So that the second signal +.>
Figure FDA0004138632150000027
The maximum amplitude value of the element in (a) is minimized;
Figure FDA0004138632150000028
solving complex constant delta by adopting minimum covered circle method r The center coordinates of the minimum circle searched for are-delta r ；
S305, order
Figure FDA0004138632150000029
The following calculation process is performed on the remaining N/Q-1 row vectors in the matrix Γ one by one:
for a certain row vector Γ in the matrix Γ q Calculating Γ q Maximum amplitude value max (|Γ) of (a) q |)；
If max (|Γ) q I) is less than or equal to R, the complex constant value corresponding to the row vector is delta q =0, if max (|Γ) q I) R, solving the complex constant Δ using the same method as step S304 q I.e. to construct a third signal
Figure FDA00041386321500000210
Figure FDA00041386321500000211
And solving complex constant delta by adopting a minimum covered circle method q So that the third signal +>
Figure FDA00041386321500000212
The maximum amplitude value of the element in (1) is minimized if Γ q Radius value of the corresponding minimum circle +.>
Figure FDA00041386321500000213
Then use->
Figure FDA00041386321500000214
R is replaced, and the center coordinates of the minimum circle searched for are-delta q ；
S306, respectively calculating N/Q row vectors of the matrix Γ through the steps to obtain N/Q complex constants, and forming the complex constants into a vector delta, delta= [ delta ] 0 ,Δ 1 ,...,Δ N/Q-1 ]Order-making
Figure FDA00041386321500000215
Constructing a second constant vector P->
Figure FDA00041386321500000216
The time domain signal V corresponding to the reserved subcarrier frequency domain signal V is:
Figure FDA00041386321500000217
and S4, adding the time domain signal X1 corresponding to the data subcarrier frequency domain signal X1 and the time domain signal V corresponding to the frequency domain subcarrier frequency domain signal V to obtain a time domain transmission signal X of the OFDM symbol.
2. The minimum coverage circle method-based OFDM signal peak-to-average power ratio method of claim 1, wherein: in the step S304, the complex constant delta is solved by adopting a minimum covered circle method r When for point set Γ r The searching steps of the corresponding minimum circle are specifically as follows:
a. from the point set Γ r Finding the two points with the farthest distance and adding the two points into a point set L, and constructing a circle by taking the connecting line of the two points as the diameter
Figure FDA0004138632150000031
b. Judgment circle
Figure FDA0004138632150000032
Whether or not to cover the point set Γ r If yes, the circle is the minimum circle, and the searching process is ended; if not, continuing the next step;
c. from the point set Γ r Find a departure circle
Figure FDA0004138632150000033
Is added into the point set L, and the smallest covered circle of the point set L is calculated by using a random increment method, and then the circle is replaced by the circle>
Figure FDA0004138632150000034
And then returns to step b.
CN202310282726.8A 2023-03-21 2023-03-21 OFDM signal peak-to-average power ratio reducing method based on minimum coverage circle Pending CN116319221A (en)

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