阅读说明：本技术 基于比例化贪心算法和ace-pts的子载波分配方法 (Subcarrier allocation method based on proportional greedy algorithm and ACE-PTS ) 是由 鲍亚川 蔚保国 易卿武 肖遥 殷本全 卢小峰 于 2021-09-18 设计创作，主要内容包括：本发明公开了一种基于比例化贪心算法和ACE-PTS的子载波分配方法,旨在解决抑制OFDM系统峰均比中损耗系统速率的问题,以及子载波分配过程中复杂度较高的问题。该子载波分配方法的步骤为：1)利用比例化贪心算法预分配子载波；2)正交调制子载波；3)利用ACE-PTS方法对子载波序列分配位置次序；4)优化重组子载波序列。本发明能有效抑制信号峰均比,实现系统吞吐量最大化,降低子载波分配的复杂度,可用于正交频分复用OFDM系统中的子载波分配。(The invention discloses a subcarrier allocation method based on a proportional greedy algorithm and an ACE-PTS (adaptive time warping-space time warping-sequence prediction), and aims to solve the problems of system rate loss in an OFDM (orthogonal frequency division multiplexing) system peak-to-average power ratio and high complexity in a subcarrier allocation process. The subcarrier allocation method comprises the following steps: 1) sub-carriers are pre-distributed by utilizing a proportional greedy algorithm; 2) quadrature modulating the subcarriers; 3) allocating a position order to the subcarrier sequence by using an ACE-PTS method; 4) and optimizing the recombined subcarrier sequences. The invention can effectively inhibit the peak-to-average ratio of signals, realize the maximization of the system throughput and reduce the complexity of subcarrier allocation, and can be used for subcarrier allocation in an Orthogonal Frequency Division Multiplexing (OFDM) system.)

1. A subcarrier allocation method based on a proportional greedy algorithm and an ACE-PTS is characterized in that a subcarrier set corresponding to each user is obtained after subcarrier allocation is performed by the proportional greedy algorithm; allocating a position order to the subcarrier sequence by using an ACE-PTS method; the specific steps of the subcarrier allocation method comprise the following steps:

step 1, pre-allocating subcarriers by using a proportional greedy algorithm:

(1a) selecting an unmarked user from the K users; wherein K represents the total number of users, and K is more than or equal to 8;

(1b) selecting a maximum channel gain value from different channel gain values of all unallocated subcarriers corresponding to the selected user;

(1c) allocating the sub-carrier corresponding to the maximum channel gain value to the selected user, and deleting the sub-carrier from the sub-carrier;

(1d) judging n_k＜N_kIf yes, executing the step (1a), otherwise, marking the selected user as a forbidden user and then executing the step (1 e); wherein n is_kIndicates the total number of sub-carriers, N, allocated to the k-th selected user_kIt is shown that a constant is given,n represents the total number of subcarriers, N is more than or equal to 1024, G_kState value representing transmission channel between k-th selected user and antenna transmitting end；

(1e) Judging whether all the sub-carriers are distributed, if so, executing the step 2, otherwise, executing the step (1 a);

step 2, quadrature modulation of subcarriers:

sequentially carrying out orthogonal modulation on each preassigned subcarrier according to the initial position sequence of the subcarrier to obtain a modulated subcarrier sequence consisting of all subcarriers after completing the orthogonal modulation;

and 3, allocating position order to the subcarrier sequences by using an ACE-PTS method:

(3a) calculating the middle front of subcarrier sequence separatelyLength sequence andpeak-to-average ratio of length sequences; wherein N represents the total length of the subcarrier sequence;

(3b) converting a subcarrier sequence with a large peak-to-average ratio into a time domain by utilizing P-point inverse fast Fourier transform, then carrying out amplitude limiting processing, converting a signal subjected to time domain amplitude limiting into a frequency domain by utilizing Q-point Fourier transform, and carrying out constellation diagram expansion on the signal subjected to frequency domain amplitude limiting; wherein P represents the number of sampling points in inverse fast Fourier transform, Q represents the number of sampling points in Fourier transform, and the values of P and Q are equal to N;

(3c) judging whether the frequency domain amplitude limiting signal after the constellation diagram expansion meets the convergence condition, if so, executing the step (3d), otherwise, executing the step (3 b);

(3d) converting the frequency domain amplitude limiting signal after the constellation diagram expansion into a time domain by utilizing P-point inverse fast Fourier transform to obtain a time domain signal after the constellation diagram expansion;

step 4, optimizing the recombined subcarrier sequence:

(4a) dividing a sub-carrier sequence with a small peak-to-average ratio into V continuous sub-sequences with equal length, and sequentially carrying out P-point inverse fast Fourier transform on each sub-sequence according to a dividing sequence to convert the sub-sequences into a time domain to obtain a time domain signal of the sub-sequences; it is composed ofIn (d), V represents the total number of divided subsequences,

(4b) by usingAndrespectively adjusting the phase of each subsequence time domain signal and the phase of the time domain signal after the constellation diagram is expanded; wherein the content of the first and second substances,i represents the ith subsequence time domain signal after phase adjustment, i represents the serial number of the subsequence time domain signal, i is more than or equal to 1 and less than or equal to V, and X_iRepresenting the i-th subsequence time-domain signal before phase adjustment, e^jφRepresenting a rotating phase factor, e^(·)Denotes exponential operation based on a natural number e, j denotes an imaginary unit symbol, phi denotes an adjustable angle value in the rotating phase factor, the value interval is [0,2 pi ], and the value interval isAnd pi represents a circumferential ratio,representing the constellation diagram expanded time domain signal after phase adjustment, and Y representing the constellation diagram expanded time domain signal before phase adjustment;

(4c) accumulating the phases of all the time domain signals after phase adjustment to obtain a time domain total signal, and storing the time domain total signal into a time domain total signal set;

(4d) judging whether the time domain total signal to be stored is the same as that in the time domain total signal set, if so, executing the step (4e), otherwise, adding the adjustable angle value in the rotation phase factor to the angle valueThen executing the step (4 b);

(4e) converting each time domain total signal in the time domain total signal set into a frequency domain by using Q-point Fourier transform, and calculating the peak-to-average ratio of each subcarrier after changing the position sequence;

(4f) and selecting the subcarrier with the minimum peak-to-average ratio from all the subcarriers with changed position orders as the optimized and recombined subcarrier.

2. The method for allocating sub-carriers based on proportional greedy algorithm and ACE-PTS as claimed in claim 1, wherein the convergence condition in step (3c) is a condition that the following two conditions are satisfied simultaneously:

the method comprises the following steps that 1, the amplitude of a frequency domain amplitude limiting signal is not changed after a constellation diagram is expanded;

and 2, the phase of the frequency domain amplitude limiting signal is not changed after the constellation diagram is expanded.

Technical Field

The invention belongs to the technical field of communication, and further relates to a subcarrier allocation method based on a proportional greedy algorithm and a Constellation diagram Extension-Partial Transmit Sequence (ACE-PTS) in the field of wireless communication systems. The invention can be applied to an Orthogonal Frequency Division Multiplexing (OFDM) system of wireless communication, pre-allocates subcarrier resources, realizes the maximization of system throughput and the suppression of signal Peak-to-Average Power Ratio (PAPR), enables the subcarrier to provide the maximum link rate, ensures the fairness among links, and can avoid signal distortion and system Power efficiency loss caused by the fact that a high Peak-to-Average Ratio signal works in a nonlinear interval when passing through a Power amplifier.

Background

In wireless communication, compared with a single carrier system, an orthogonal frequency division multiplexing OFDM system with multiple carriers has higher transmission efficiency and spectral efficiency, and the OFDM technology is widely used in the field of wireless communication. However, since the OFDM system adopts the multi-carrier modulation technique, when a plurality of sub-carrier signals with the same or similar phases are superimposed on a time domain, a problem of high PAPR of the signal will be caused. Signal peak-to-average ratio imposes higher linearity requirements on the wireless transmitter portion of the communication system, requiring costly power amplifiers to avoid distortion and system spectral and power efficiency losses caused by operating in the non-linear region. Meanwhile, when the subcarriers are modulated, certain rate gaps are generated in the allocation on different links. The allocation scheme of the limited subcarrier resources has a great influence on the performance of the system.

The university of electronic technology disclosed a method for peak-to-average ratio suppression in subcarrier modulation OFDM systems in the patent document "a method for peak-to-average ratio suppression in subcarrier modulation OFDM systems" (patent application No. 201610318530, application publication No. CN 106027444 a). The method comprises the following steps: (1) and carrying out carrier index modulation on the signal to obtain a frequency domain signal, and representing the signal on a time domain through inverse Fourier transform. (2) And carrying out amplitude limiting processing on the time domain signal to obtain a peak value counteracting signal, and converting the peak value counteracting signal to a time domain to complete constellation diagram expansion. (3) And repeating iteration until the peak-to-average ratio of the signal after the constellation diagram expansion reaches the peak-to-average ratio iteration threshold, and outputting the final signal. Finally, the effect of peak-to-average ratio inhibition is achieved. The method has the following defects: because only part of subcarriers are randomly selected to be activated in the carrier index modulation for sending data, the subcarrier resources cannot be utilized fully and efficiently, so that part of rate is lost during system transmission.

A method for Joint peak-to-average ratio suppression and throughput Optimization based on subcarrier Reservation is proposed by Limian Gao et al in the published article "Joint Optimization of Subcarriers Allocation and Tone Reservation PAPR Reduction for OFDMA System" (2012IEEE 14th International Conference on Communication Technology, 2012, 1172-. The method comprises the following steps: (1) and calculating the peak-to-average ratio of the set data at the reserved position by using a traversal method, and finding out the number of reserved subcarriers when the peak-to-average ratio is minimum. (2) And allocating a subcarrier with the maximum channel gain to each user in advance, and calculating the throughput of the system at the moment. (3) And continuously allocating the subcarriers according to a greedy algorithm, and updating the throughput after each allocation until all the subcarriers are allocated. Finally, the purposes of peak-to-average ratio inhibition and throughput optimization are achieved. The method has the following defects: the number of the allocated subcarriers is not set for each user, so that the channel gain of the subcarriers for all users needs to be traversed when the subcarriers are allocated, and the complexity in the subcarrier allocation process is improved.

Disclosure of Invention

The invention aims to provide a subcarrier allocation method based on a proportional greedy algorithm and an ACE-PTS (adaptive time slots-based partial search space) aiming at solving the problems of system rate loss in the peak-to-average power ratio of an OFDM (orthogonal frequency division multiplexing) system and higher complexity in the subcarrier allocation process.

The specific idea of the present invention for achieving the above object is to allocate a subcarrier with the maximum channel gain value to each user in a subcarrier pre-allocation process by using a proportional greedy algorithm, and since the system throughput is in direct proportion to the channel gain value, allocating the subcarrier with the maximum channel gain value to the user can significantly increase the system throughput, and determine whether each user reaches the maximum total number of allocated subcarriers, and if so, the user does not need to be allocated with the subcarrier. Sub-carriers are pre-allocated by utilizing a proportional greedy algorithm, users which can be allocated by the sub-carriers are updated after each judgment, and the sub-carriers are not allocated to the users which reach the maximum total number of the allocated sub-carriers, so that the process of traversing channel gain values of all users in allocation can be reduced, the complexity in the sub-carrier allocation process is reduced, and the system throughput is maximized. The present invention, by using the ACE-PTS method, in the subcarrier allocation position order process, according to the subcarrier arrangement sequence, the subcarriers are divided into two parts, the part with large peak-to-average ratio is processed by amplitude limiting and constellation diagram expansion, because the part has larger peak-to-average ratio, the peak-to-average ratio is reduced by utilizing the amplitude limiting processing and the constellation diagram expanding method before the position sequence is distributed, wherein, the amplitude limiting processing can reduce the occurrence of high amplitude value in the signal, the constellation diagram expanding method can improve the system error rate performance and reduce the negative effect brought by the amplitude limiting processing, therefore, the part with large peak-to-average ratio is subjected to amplitude limiting processing and constellation diagram expansion, and the phase is adjusted for each subcarrier to carry out optimized recombination, in the process of optimizing recombination, adjusting the phase values corresponding to the subcarriers to obtain a plurality of recombined subcarriers, and selecting the subcarrier with the minimum peak-to-average ratio from the recombined subcarriers as the optimized recombined subcarrier. Therefore, the ACE-PTS method is utilized to distribute the position sequence of the subcarriers, and any subcarrier resource can not be lost by recombining the position sequence of the subcarriers and adjusting the phase of each subcarrier, so that the transmission rate of the system is improved, and the peak-to-average ratio of the system is reduced.

The method comprises the following specific steps:

step 1, pre-allocating subcarriers by using a proportional greedy algorithm:

(1a) selecting an unmarked user from the K users; wherein K represents the total number of users, and K is more than or equal to 8;

(1b) selecting a maximum channel gain value from different channel gain values of all unallocated subcarriers corresponding to the selected user;

(1c) allocating the sub-carrier corresponding to the maximum channel gain value to the selected user, and deleting the sub-carrier from the sub-carrier;

(1d) judging n_k＜N_kIf yes, executing the step (1a), otherwise, marking the selected user as a forbidden user and then executing the step (1 e); wherein n is_kIndicates the total number of sub-carriers, N, allocated to the k-th selected user_kIt is shown that a constant is given,n represents the total number of subcarriers, N is more than or equal to 1024, G_kA state value representing a transmission channel between the kth selected user and the antenna transmitting terminal;

(1e) judging whether all the sub-carriers are distributed, if so, executing the step 2, otherwise, executing the step (1 a);

step 2, quadrature modulation of subcarriers:

sequentially carrying out orthogonal modulation on each preassigned subcarrier according to the initial position sequence of the subcarrier to obtain a modulated subcarrier sequence consisting of all subcarriers after completing the orthogonal modulation;

and 3, allocating position order to the subcarrier sequences by using an ACE-PTS method:

(3a) calculating the middle front of subcarrier sequence separatelyLength sequence andpeak-to-average ratio of length sequences; wherein N represents the total length of the subcarrier sequence;

(3b) converting a subcarrier sequence with a large peak-to-average ratio into a time domain by utilizing P-point inverse fast Fourier transform, then carrying out amplitude limiting processing, converting a signal subjected to time domain amplitude limiting into a frequency domain by utilizing Q-point Fourier transform, and carrying out constellation diagram expansion on the signal subjected to frequency domain amplitude limiting; wherein P represents the number of sampling points in inverse fast Fourier transform, Q represents the number of sampling points in Fourier transform, and the values of P and Q are equal to N;

(3c) judging whether the frequency domain amplitude limiting signal after the constellation diagram expansion meets the convergence condition, if so, executing the step (3d), otherwise, executing the step (3 b);

(3d) converting the frequency domain amplitude limiting signal after the constellation diagram expansion into a time domain by utilizing P-point inverse fast Fourier transform to obtain a time domain signal after the constellation diagram expansion;

step 4, optimizing the recombined subcarrier sequence:

(4a) dividing a sub-carrier sequence with a small peak-to-average ratio into V continuous sub-sequences with equal length, and sequentially carrying out P-point inverse fast Fourier transform on each sub-sequence according to a dividing sequence to convert the sub-sequences into a time domain to obtain a time domain signal of the sub-sequences; wherein V represents the total number of divided subsequences,

(4b) by usingAndrespectively adjusting the phase of each subsequence time domain signal and the phase of the time domain signal after the constellation diagram is expanded; wherein the content of the first and second substances,i represents the ith subsequence time domain signal after phase adjustment, i represents the serial number of the subsequence time domain signal, i is more than or equal to 1 and less than or equal to V, and X_iRepresenting the i-th subsequence time-domain signal before phase adjustment, e^jφRepresenting a rotating phase factor, e^(·)Denotes exponential operation based on a natural number e, j denotes an imaginary unit symbol, phi denotes an adjustable angle value in the rotating phase factor, the value interval is [0,2 pi ], and the value interval isAnd pi represents a circumferential ratio,representing the constellation diagram expanded time domain signal after phase adjustment, and Y representing the constellation diagram expanded time domain signal before phase adjustment;

(4c) accumulating the phases of all the time domain signals after phase adjustment to obtain a time domain total signal, and storing the time domain total signal into a time domain total signal set;

(4d) judging whether the time domain total signal to be stored is the same as that in the time domain total signal set, if so, executing the step (4e), otherwise, adding the adjustable angle value in the rotation phase factor to the angle valueThen executing the step (4 b);

(4e) converting each time domain total signal in the time domain total signal set into a frequency domain by using Q-point Fourier transform, and calculating the peak-to-average ratio of each subcarrier after changing the position sequence;

(4f) and selecting the subcarrier with the minimum peak-to-average ratio from all the subcarriers with changed position orders as the optimized and recombined subcarrier.

Compared with the prior art, the invention has the following advantages:

first, the invention pre-allocates the sub-carriers by using a proportional greedy algorithm, allocates each sub-carrier to the user with the maximum gain value, and does not allocate the sub-carriers to the users reaching the maximum sub-carrier allocation total number any more, thereby overcoming the defect of high complexity of the sub-carriers in the prior art, shortening the allocation time of each sub-carrier, improving the allocation efficiency, and reducing the complexity in the allocation process.

Secondly, the invention utilizes the ACE-PTS method to distribute the position order to the subcarrier sequences, adjusts the phase of each subcarrier by recombining the subcarriers, reduces the high-amplitude value of the subcarriers, overcomes the defect that the loss of subcarrier resources reduces the transmission rate of the system in the prior art, and ensures that the invention can utilize the subcarrier resources at full efficiency, improves the transmission rate of the system, maximizes the throughput of the system and reduces the peak-to-average ratio of the system in the OFDM system.

Drawings

FIG. 1 is a flow chart of the present invention;

fig. 2 is an embodiment of a constellation expansion method in the present invention;

FIG. 3 is a simulation diagram of the present invention.

Detailed description of the invention

The invention is further described below with reference to the figures and examples.

The implementation steps of the present invention are further described with reference to fig. 1.

Step 1, subcarrier pre-allocation is carried out by utilizing a proportional greedy algorithm.

Firstly, selecting an unmarked user from K users; wherein K represents the total number of users, and K is more than or equal to 8.

And secondly, selecting the maximum channel gain value from different channel gain values of all the unallocated subcarriers corresponding to the selected user.

And thirdly, distributing the sub-carrier corresponding to the maximum channel gain value to the selected user and deleting the sub-carrier from the sub-carrier.

The throughput of the ith user is calculated as follows:

wherein R is_iRepresenting the throughput of the ith user, B representing the bandwidth of the OFDM system, N representing the total number of sub-carriers, N ≧ 1024, p representing the transmission power of the system, H_i,jRepresenting the channel gain of the ith user to the jth subcarrier;

therefore, the subcarriers corresponding to the maximum channel gain value are allocated to the selected user, so that the throughput of the selected user can be maximized.

The fourth step, judge n_k＜N_kIf yes, executing the first step of the step, otherwise, marking the selected user as a forbidden user and then executing the fifth step of the step; wherein n is_kIndicates the total number of sub-carriers, N, allocated to the k-th selected user_kIt is shown that a constant is given,G_krepresenting the state value of the transmission channel between the k-th selected user and the antenna transmitting end.

The constant N_kRepresenting the maximum subcarrier total number distributed by the kth user;

because each user is in different positions and has different channel state values with a transmission channel between the wireless transmitting end, the total number of the allocated maximum subcarriers is set according to the throughput calculation formula and the channel state value of each user, so that the user under a good channel condition can allocate more subcarriers, the system throughput is greatly improved, the user under a bad channel condition can allocate less subcarriers, and the negative influence of the bad channel condition on the system throughput is reduced as much as possible.

And step five, judging whether all the sub-carriers are distributed, if so, executing the step 2, otherwise, executing the first step of the step.

And 2, quadrature modulating the subcarrier.

And sequentially carrying out orthogonal modulation on each preassigned subcarrier according to the initial position sequence of the subcarrier to obtain a modulated subcarrier sequence consisting of all subcarriers after completing the orthogonal modulation.

And 3, distributing the position sequence to the subcarrier sequence by using an ACE-PTS method.

First, calculating the front of subcarrier sequence separatelyLength sequence andpeak-to-average ratio of length sequences; where N denotes the total length of the subcarrier sequence.

Secondly, converting a subcarrier sequence with a large peak-to-average ratio into a time domain by utilizing P-point inverse fast Fourier transform, then carrying out amplitude limiting processing, converting a signal subjected to time domain amplitude limiting into a frequency domain by utilizing Q-point Fourier transform, and carrying out constellation diagram expansion on the signal subjected to frequency domain amplitude limiting; wherein, P represents the number of sampling points in the inverse fast Fourier transform, Q represents the number of sampling points in the Fourier transform, and the values of P and Q are equal to N.

The constellation diagram expansion method is used for the subcarrier sequences with large peak-to-average ratios because the effect of reducing the peak-to-average ratios is good.

The time domain signal is clipped according to the following formula:

wherein the content of the first and second substances,representing the limited time-domain signal, x_nRepresents the time domain signal without amplitude limiting processing, |, represents the operation of modulus value, A represents the amplitude limiting threshold, A ═ 0.74| x_n|，e^(·)Denotes an exponential operation based on a natural number e, j denotes an imaginary unit symbol, arg [ · [ ]]Representing a phase taking operation;

the amplitude limiting processing is carried out on the time domain signal, so that the occurrence of high amplitude values in the time domain signal can be reduced, and the peak-to-average ratio of the system is reduced.

The constellation diagram extension method in the present invention is further described with reference to the embodiment of fig. 2:

the embodiment of the invention is used for carrying out constellation diagram expansion on frequency domain signals in an OFDM system with a modulation mode of 16 Quadrature Amplitude Modulation (QAM). The black solid circles in fig. 2 represent sixteen constellation points, each constellation point is obtained by mapping a single subcarrier to a vector diagram coordinate system through 16QAM modulation, a single dotted arrow indicates that the constellation point can only be expanded towards the direction, the expanded directional coordinate value is a larger value of an absolute value of a directional coordinate corresponding to the constellation point and an absolute value of a directional coordinate corresponding to the constellation point after amplitude limiting processing, mutually perpendicular dotted arrows indicate that the constellation point can be expanded towards an area indicated by the arrow, and the expanded horizontal and vertical coordinate values are respectively a larger value of an absolute value of a real part and an imaginary part of the constellation point and an absolute value of a real part and an imaginary part of the constellation point after amplitude limiting processing.

The constellation diagram expansion is carried out on the frequency domain signal, the system error rate performance can be improved, and the negative influence brought by amplitude limiting processing is reduced.

And thirdly, judging whether the frequency domain amplitude limiting signal after the constellation diagram expansion meets the convergence condition, if so, executing the fourth step of the step, otherwise, executing the second step of the step.

The convergence condition refers to a condition that the following two conditions are satisfied simultaneously:

the method comprises the following steps that 1, the amplitude of a frequency domain amplitude limiting signal is not changed after a constellation diagram is expanded;

and 2, the phase of the frequency domain amplitude limiting signal is not changed after the constellation diagram is expanded.

And fourthly, converting the frequency domain amplitude limiting signal after the constellation diagram is expanded into a time domain by utilizing P-point inverse fast Fourier transform, and obtaining a time domain signal after the constellation diagram is expanded.

Step 4, optimizing the recombined subcarrier sequence:

the method comprises the steps that firstly, a subcarrier sequence with a small peak-to-average ratio is divided into V continuous subsequences with equal length, P-point inverse fast Fourier transform is sequentially carried out on each subsequence according to the dividing sequence, and then the subsequences are converted into time domains, and time domain signals of the subsequences are obtained; wherein V represents the total number of divided subsequences,

second step, usingAndrespectively adjusting the phase of each subsequence time domain signal and the phase of the time domain signal after the constellation diagram is expanded; wherein the content of the first and second substances,representing the i-th sub-sequence time domain signal after phase adjustment, i representing the sub-sequence time domainThe serial number of the signal, i is more than or equal to 1 and less than or equal to V, X_iRepresenting the i-th subsequence time-domain signal before phase adjustment, e^jφRepresents a rotation phase factor phi represents an adjustable angle value in the rotation phase factor, the value interval is [0,2 pi ], and the value interval isAnd pi represents a circumferential ratio,the time domain signal after the constellation diagram expansion after the phase adjustment is shown, and the time domain signal after the constellation diagram expansion before the phase adjustment is shown by Y.

And thirdly, accumulating the phases of all the time domain signals after phase adjustment to obtain a time domain total signal, and storing the time domain total signal into a time domain total signal set.

The time domain total signal is obtained by accumulating the phases of all the time domain signals after the phase adjustment, and the time domain total signal is formed by recombining all the divided subsequences according to the optimization steps, so that the peak-to-average ratio of the system can be reduced.

The fourth step, judge whether the time domain total signal to be stored is the same as in the time domain total signal set, if yes, then carry out the fifth step of this step, otherwise, add the adjustable angle value in the rotating phase factorThen the second step of this step is performed.

And fifthly, converting each time domain total signal in the time domain total signal set into a frequency domain by using Q-point Fourier transform, and calculating the peak-to-average ratio of each subcarrier after changing the position order.

And sixthly, selecting the subcarrier with the minimum peak-to-average ratio from all the subcarriers with changed position orders as the optimized and recombined subcarrier.

The effect of the present invention is further explained by combining the simulation experiment as follows:

1. simulation experiment conditions are as follows:

the hardware platform of the simulation experiment of the invention is as follows: the processor is an Intel i5-6400 CPU, the main frequency is 2.7GHz, and the memory is 16 GB.

The software platform of the simulation experiment of the invention is as follows: windows 10 operating system and MATLAB R2019 a.

2. Simulation content and result analysis:

the simulation experiment of the invention is to adopt the invention and three prior arts (Root-Finding-mapping method, Constellation expansion-Convex set (ACE-POCS) method and partial sending sequence (PTS) method) to respectively distribute 2048 subcarriers in the orthogonal frequency division multiplexing OFDM system with parameters set in the following table 1, and obtain a system throughput and signal peak-to-average ratio inhibition performance diagram. The simulation experiment parameter settings are shown in table 1:

table 1 summary of experimental parameter settings

Setting item	Value taking
		Total number of subcarriers	2048
Total number of users	[2，4，6，8，10，12，14，16]
		Modulation order	64QAM
System bandwidth	1MHz
		Number of iterations of constellation expansion map	200
Total number of subblocks of partial transmit sequence	8
		Rotating phase factor	[-1，1]

In the simulation experiment, three prior arts are adopted:

the Root-Finding method in the prior art refers to a subcarrier allocation method, called Root-Finding method for short, proposed by Zukang et al in "Optimal power allocation in multiuser OFDM systems, GLOBECOM'03.IEEE Global communications Conference (IEEE Cat. No.03CH37489), San Francisco, CA, USA,2003, pp.337-341 Vol.1".

The prior art constellation expansion-convex set mapping method ACE-POCS refers to a peak-to-average ratio suppression method, which is called constellation expansion-convex set mapping method ACE-POCS for short, proposed by Krongold et al in "PAR reduction in OFDM view active constellation extension,2003IEEE International Conference on optics, Speech, and Signal Processing,2003.Proceedings. (ICASSP'03), Hong Kong, China,2003, pp.IV-525".

The partial transmit sequence PTS method in the prior art is a peak-to-average ratio suppression method, which is called partial transmit sequence PTS method for short, proposed by SeogGeun Kang et al in "A novel sub-block partition scheme for partial transmit sequence OFDM, in IEEE Transactions on Broadcasting, vol.45, No.3, pp.333-338, Sept.1999".

The effect of the present invention will be further described with reference to the simulation diagram of fig. 3.

Fig. 3(a) shows that the method of the present invention and the Root-Finding algorithm in the conventional Root-Finding algorithm obtain the number of subcarriers allocated to each user and the corresponding channel gain value under the condition of increasing the total number of users accessing the OFDM system, and then calculate the system throughput under the condition of different total numbers of users by using the system throughput formula, so as to obtain the throughput performance comparison curve of two different methods.

The system throughput for all users is calculated as follows:

where R represents the system throughput of all users, p_iIndicating the power allocated by the radio transmitter to the ith user, H_iIndicating the total value of the channel gain for the ith user. The system throughput in the case of different total users can be directly calculated by using the system throughput formula, and used as the evaluation index of fig. 3 (a).

The abscissa in fig. 3(a) represents the number of users accessing the system, and the ordinate represents the overall throughput of the system in bits/Hz. The curve marked with "- + -" in fig. 3(a) represents the system throughput performance curve after the sub-carriers are allocated by the method of the present invention and the system is accessed to different numbers of users. The curve labeled "-" in fig. 3(a) represents the system throughput performance curve after the subcarriers are allocated by using the Root-Finding algorithm and under the condition of accessing different numbers of users.

Fig. 3(b) shows a comparison graph of peak-to-average ratio performance obtained by adjusting the position order of subcarriers in an OFDM system to obtain a plurality of optimized and recombined subcarriers, and then calculating complementary cumulative distribution functions of peak-to-average ratios of systems processed by different methods using a peak-to-average ratio calculation formula and a complementary cumulative distribution function, according to the method of the present invention and two prior arts (a conventional partial transmit sequence PTS method and a conventional constellation expansion ACE-POCS method).

The system peak-to-average ratio was calculated as follows:

wherein, PAPR represents the system peak-to-average ratio, max [. cndot.]Representing maximum operation, P (t) representing sub-carriersPower, E [ ·]Indicating taking the mathematical expectation. The complementary cumulative distribution function of the peak-to-average ratio is P { PAPR > PAPR_thAnd the sum of the probabilities that all sampled peak-to-average ratios are greater than a peak-to-average ratio threshold sampling value appears is represented, wherein the value interval of the peak-to-average ratio threshold is [5,13 ]]And (c) taking the complementary cumulative distribution function of the peak-to-average ratio in the value interval as the evaluation index of the figure 3 (b).

The abscissa in fig. 3(b) represents a peak-to-average ratio threshold value of the OFDM system signal, and the ordinate represents a complementary cumulative distribution function. The curve marked with "- - -" in fig. 3(b) represents a peak-to-average ratio performance curve calculated for the subcarrier signal at the transmitting end of the OFDM system without any optimization algorithm processing. The curve labeled "-" in fig. 3(b) represents the peak-to-average ratio performance curve after processing the subcarrier signal at the transmitting end of the OFDM system by using the conventional partial transmit sequence PTS method. The curve marked with "-" in fig. 3(b) represents the peak-to-average ratio performance curve after the subcarrier signal at the transmitting end of the OFDM system is processed by using the conventional constellation diagram extended ACE-POCS method. The curve marked with "- + -" in fig. 3(b) indicates the peak-to-average ratio performance curve after the method of the present invention is used to process the subcarrier signal of the transmitting end of the OFDM system.

As can be seen from the simulation experiment chart of fig. 3(a), when the number of users accessing the system is 2, 4, 6, 8, 10, 12, 14, and 16, respectively, compared with the conventional root-finding algorithm, the minimum value of the system throughput gain is approximately 0.1bits/Hz, and the maximum value of the system throughput gain is approximately 0.2bits/Hz, so that the system throughput can be significantly improved in a large-bandwidth system.

As can be seen from the simulation experiment chart of FIG. 3(b), the invention has a complementary cumulative distribution function value of 10^-3Compared with an orthogonal frequency division multiplexing OFDM system, the method has the peak-to-average ratio gain of nearly 3.7dB, compared with the traditional partial transmit sequence PTS method, the method has the peak-to-average ratio gain of nearly 1.0dB, and compared with the traditional constellation diagram extended ACE method, the method has the peak-to-average ratio gain of nearly 0.9 dB. It can be seen that the invention can significantly reduce the transmission signal of the OFDM systemPeak to average ratio.

The above simulation experiments show that: the method of the invention pre-allocates the sub-carriers by using a proportional greedy algorithm, allocates the position sequence to the sub-carrier sequence by using an ACE-PTS method, can realize the maximization of the system throughput, can inhibit the peak-to-average ratio of the OFDM system, solves the problems of lower system throughput and higher complexity caused by allocating the sub-carriers to users with the maximum channel gain one by one under the conditions of inhibiting the peak-to-average ratio by using partial sub-carriers in the OFDM system and high-order modulation in the prior art, and is a practical sub-carrier allocation method.