CN117061299A - High-capacity subcarrier number modulation method - Google Patents

High-capacity subcarrier number modulation method Download PDF

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CN117061299A
CN117061299A CN202311114566.2A CN202311114566A CN117061299A CN 117061299 A CN117061299 A CN 117061299A CN 202311114566 A CN202311114566 A CN 202311114566A CN 117061299 A CN117061299 A CN 117061299A
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subcarrier
activated
vector
vectors
subcarriers
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刘光辉
罗湘
柏义阳
施家壮
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University of Electronic Science and Technology of China
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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
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2626—Arrangements specific to the transmitter only
    • H04L27/2627—Modulators
    • 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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  • Digital Transmission Methods That Use Modulated Carrier Waves (AREA)

Abstract

The invention discloses a high-capacity subcarrier quantity modulation method, and belongs to the technical field of communication. The invention improves the capacity of the SNM system by optimizing the modulation order combination and the information bit placement position, namely, the invention optimizes the transmitting symbol constellation point and the subcarrier activation position before the bit mapping of the transmitting end in order to find the modulation order combination and the SAP which optimize the demodulation performance of the system. Compared with the traditional scheme, the system of the invention realizes further improvement of demodulation performance.

Description

High-capacity subcarrier number modulation method
Technical Field
The invention belongs to the technical field of multi-carrier modulation, and particularly relates to a high-capacity subcarrier number modulation method.
Background
In 5G, the explosive growth of data traffic and the popularity of smart devices has led to increasing demands on spectrum and energy efficiency, while also hopefully supporting a wide variety of scenario applications and related requirements. In most applications, higher order modulation is often used to increase spectral efficiency, but is relatively sensitive to interference (e.g., phase noise, channel fading, multipath, etc.), resulting in a system that requires a very large signal-to-noise ratio to ensure good performance.
Unlike conventional information propagation, index modulation activates only a part of resources such as time slots, subcarriers, antennas, etc., and other information is implicitly propagated through an activation mode, thereby improving spectral efficiency and energy efficiency. This is because in addition to the information bits carried by the transmission, which is typically based on amplitude or phase modulation, additional index bit information can be obtained without consuming energy. This allows the index modulation system to achieve the same throughput as a conventional system by using only a portion of the resources, thereby reducing the complexity of the system, greatly reducing the energy consumption, and simultaneously, having an advantage in demodulation performance under multipath channels. Based on the above advantages of index modulation, it is introduced into the field of communication.
Existing IM communication schemes can be distinguished by signal domain: including frequency domain IM (FD-IM), spatial domain IM (SD-IM), and time domain IM (TD-IM), as well as channel domain IM (CD-IM), and the like. In recent years, IM has been applied in various formats in various wireless communication scenarios, including millimeter wave transmission, massive MIMO, network coding, and the like.
Unlike conventional techniques that utilize a fixed number of subcarriers, different active mode (Subcarrier Activation Pattern, SAP) indicators of the time slot to carry the additional information, another modulation scheme is called subcarrier number modulation (Subcarrier Number Modulation, SNM) that utilizes the number of active subcarriers to encode the additional information, the system flow diagram of which is shown in fig. 1.
However, since the SNM technique leaves a part of subcarriers empty, the transmission rate is not very high, in recent years, in order to increase the transmission rate of SNM, an improved OFDM-SNM scheme has been proposed, which uses flexibility of the index bit corresponding position of the OFDM-SNM scheme, adaptively places active subcarriers based on channel instantaneous state information (CSI), dynamically maps incoming information bits onto subcarriers with higher channel power gain, and provides additional coding gain in a high signal-to-noise ratio (SNR) region. OFDM-SNM and OFDM-IM are also combined to provide higher design freedom and spectral efficiency.
However, the gain of the above research on the transmission efficiency of SNM is still limited, and the combination of related codes or techniques also increases the complexity of system detection, and reduces the benefits of the index modulation system.
Disclosure of Invention
The invention aims to solve the problems, and provides a high-capacity subcarrier quantity modulation method which further improves the system capacity of an OFDM-SNM system by optimizing the constellation points of transmitting symbols and the placement positions of information bits.
The invention adopts the technical scheme that:
a high capacity subcarrier number modulation method, before transmitting end bit mapping, carries out the following steps:
a transmitted symbol constellation point optimization step:
step S1-1, setting the number N of subcarriers of each packet, selecting a modulation order set M= { M 1 ,...,M t ,...,M A Calculating the upper limit T of the iterative times of the optimization of the constellation points of the transmitting symbols 1 ＝A N Wherein A is the size of the modulation order set M;
traversing each value K in 1-N, and initializing a carrier activation mode SAP vector based on the number of activated subcarriers corresponding to each K: s (K) = [ S (1), S (2), S (N) ], where S (N) ∈ {0,1}, n=1, 2, ], N, and the number of S (N) = 1 is K, S (N) = 1 indicates that the location subcarrier is in an active state, S (N) = 0 indicates that the location subcarrier is not activated;
step S1-2, changing the corresponding modulation order M for different activated subcarrier numbers t Different constellation point vectors C (K) = [ C (1), C (2),. The, C (K) are generated]Where c (k) represents the state of the subcarrier with index k, and c (k) =1 represents that the subcarrier at that position is activated for carrying data; c (K) =0 indicates not activated, k=1, …, K;
step S1-3, obtaining signal block error rate under different activated subcarrier numbers
Generating different transmission signals X based on the SAP vector S (K) and the constellation point vector C (K) to form a mapping table X map ；
For X map Each of the emission vectors X, calculate X and X map Other vectors in (3)Distance between them, and based on the first R nearest vectors +.>Obtaining a collection W, wherein R is more than or equal to 1;
calculating a function using error ratesAcquiring a transmission vector x and a vector +.>Error Rate at a given signal-to-noise ratio +.>Wherein y represents a received signal;
calculate and recordP (x) represents the probability of transmitting vector x;
step S1-4, when the iterative computation times reach T 1 Then, a plurality of calculated from the transmitted symbol constellation point optimization stepFind the minimum value based on the modulation order combination M corresponding to the minimum value a The optimal modulation combination is obtained; otherwise, returning to the step S1-2;
subcarrier activation position optimization step:
step S2-1, setting the number N of subcarriers in each group;
traversing each value K in 1-N, and setting initial modulation order combination M= { M based on the number of activated subcarriers corresponding to each K 1 ,...,M K ,...,M N }；
Computing a total number of subcarrier activation location optimizationsWherein (1)>Indicating the number of combinations of K selected from N sub-carriers;
step S2-2, for different activated subcarrier numbers, utilizing the corresponding modulation order M K Different constellation point vectors C (K) = [ C (1), C (2),. The, C (K) are generated]Where c (k) represents the state of the subcarrier with index k, and c (k) =1 represents that the subcarrier at that position is activated for carrying data; c (K) =0 indicates not activated, k=1, …, K;
step S2-3, for different numbers of activated subcarriers, changing the positions of the activated subcarriers to obtain different carrier activation patterns SAP vectors S (K) = [ S (1), S (2),. The term "S (N) ], where S (N) ∈ {0,1}, n=1, 2, & the term" N, and the number of S (N) =1 is K, S (N) =1 indicates that the position subcarrier is in an activated state, and S (N) =0 indicates that the position subcarrier is not activated;
s2-4, obtaining signal block error rate under different activated subcarrier numbers
Generating different transmission signals X based on the SAP vector S (K) and the constellation point vector C (K) to form a mapping table X map ；
For X map Each of the emission vectors X, calculate X and X map Other vectors in (3)Distance between them, and based on the first R nearest vectors +.>Obtaining a collection W, wherein R is more than or equal to 1;
calculating a function using error ratesObtain the emission directionQuantity x and vector in set W +.>Error Rate at a given signal-to-noise ratio +.>Wherein y represents a received signal;
calculate and recordP (x) represents the probability of transmitting vector x;
step S2-4, when the iterative computation times reach T 2 Then, a plurality of calculated sub-carrier activation position optimization stepsSearching a minimum value, and obtaining an SAP vector corresponding to the minimum value as a subcarrier activation position optimization result;
wherein different transmission signals X are generated based on the SAP vector S (K) and the constellation point vector C (K) to form a mapping table X map The method comprises the following steps:
x＝[x(1),..,x(n),..,x(N)] T ，n＝1,2,...,N；
where p represents the number of bits per packet;
error rate calculation functionThe method comprises the following steps:
wherein, the Q function is:erfc (·) represents the error complement function, N 0 Representing the noise power spectral density.
The technical scheme provided by the invention has at least the following beneficial effects:
the invention improves the capacity of the SNM system by optimizing the modulation order combination and the information bit placement position. Compared with the traditional scheme, the invention realizes further improvement of demodulation performance.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a flowchart of an OFDM-SNM system.
Fig. 2 is a transmission rate and block error rate image at different modulation order combinations for embodiments of the present invention when the available modulation order is m= {2,4,16}, snr=13 dB.
Fig. 3 is a diagram showing the demodulation performance of the system after the subcarrier locations are optimized using the optimal modulation order combination in fig. 2.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the embodiments of the present invention will be described in further detail with reference to the accompanying drawings.
The embodiment of the invention discloses a high-capacity subcarrier quantity modulation method, which improves the capacity of an SNM system by optimizing modulation order combination and information bit placement positions.
For OFDM-SNM system, first determining the number N of sub-carriers contained in each group, the combination M of modulation order, the total number of bits transmitted, the number G of divided packets, each group containing p=p 1 +p 2 Bit, where p 1 For index bit, p 2 As information bits, in SNM modulation, index bits are different, and active subcarriers are also different, so that the number of active subcarriers is K (G), g=1. Then there is p 1 ＝log 2 (N)，p 2 ＝K(g)log 2 (M); then, according to the corresponding SAP vector S (K) and constellation point vector C (K) obtained by optimizing the positions of the constellation points and the active subcarriers, respectively, an optimal mapping table (i.e. constellation) X is formed map 。
Namely, in the embodiment of the invention, the transmitting end and the receiving end of the OFDM-SNM system respectively execute the following processes:
1) The transmitting end processing step:
bit segmentation: in index modulation, not all subcarriers transmit information, only a part of subcarriers carry information bits, and other subcarriers are empty and implicitly transmit information. The so-called index bits, which determine which subcarriers to activate, are mapped to information bits for transmission on the subcarriers. Fig. 1 is a transmitter flow diagram of OFDM-SNM. In the figure, the total bits transmitted are m, divided into G groups, each group containing p=p 1 +p 2 Bit, where p 1 For index bit, p 2 Is an information bit.
SNM mapping: after bit segmentation, the system maps information bits to activated subcarriers, and the mapping process follows the optimal X map . Let N F For FFT/IFFT points, then the OFDM signal can be represented as x F ＝[x F (1),x F (2),..,x F (N F )] T The method comprises the steps of carrying out a first treatment on the surface of the And then is converted into a time domain signal x through IFFT (Inverse Fast Fourier Transform) t The output after the CP adding operation is x CP ＝[x t (end-N CP +1:end),x t ] T Wherein N is CP For CP length, end represents signal x t Is a length of (c). The signal is then sent to the channel for transmission.
2) The processing step of the receiving end:
taking the Gaussian white noise channel (AWGN) as an example, after passing through the channel, the signal at the receiving end can be expressed as y t ＝x t +n t In which the noise n t ～N(0,N 0,T )，N 0,T Representing the noise power, i.e. the variance. After the CP and FFT conversion, the detection signal of the receiving endIs fed to a maximum likelihood detector (Maximum Likelihood, ML) detection module which discriminates the transmitted signal based on the distance between the transmitted vectors as follows:
wherein,index bit and information bit, respectively, representing the detector output,/->Representing the detector input signal, p 1 ,p 2 Representing all possible forms of index bits and information bits, respectively,/->Representing the transmitted signal.
By the present embodiment, SAP of the G (g=1,.,) th sub-block may be expressed as:
S g (K(g))＝[s(1),s(2),...,s(N)]
where s (N) ∈ {0,1}, n=1, 2,... s (n) =1 represents that the position subcarrier is in an activated state, and s (n) =0 represents that it is not activated. For example, when N=4, K (g) ∈ {1,2,3,4}, then p 1 =2bits, the SAP of the system transmit signal is shown in table 1.
TABLE 1
When S is g After (K (g)) determination, the system will generate K (g) constellation points defined as:
C g (K(g))＝[c(1),c(2),...,K(g)]
wherein c (1), c (2), represents the state of the subcarrier at that location; a 1 indicates that the location subcarrier is activated for carrying data; a 0 indicates not activated.
For these constellation points, the available modulation order combination is defined as m= { M 1 ,...,M a ,...,M A For different K (g) (i.e. different number of active sub-carriers, i.e. different index bits), different modulation modes M can be selected a E.m. Then for each C g As the modulation scheme (K (g)), there are A modulation schemes. By S g (K (g)) and C g (K (g)) the generated constellation symbols may be mapped onto activated subcarriers to obtain a transmit signal x= [ x (1) ], & gt, x (N)] T Wherein
All the different transmitted signals X may form a mapping table, defined as X map Expressed as
Let N F For FFT/IFFT points, then the OFDM signal can be represented as x F ＝[x F (1),x F (2),..,x F (N F )] T The method comprises the steps of carrying out a first treatment on the surface of the And then is converted into a time domain signal x through IFFT (Inverse Fast Fourier Transform) t The output after the CP adding operation is x CP ＝[x t (end-N CP +1:end),x t ] T Wherein N is CP Is CP length.
Based on the above theory, it can be found that: the greater the minimum Euclidean distance between the transmitted signals, the better the system demodulation performance and correspondingly the higher the system capacity. Therefore, the embodiments of the present invention address the following optimization problem, namely maximizing the euclidean distance between the transmitted signals:
wherein max represents maximum value, a 1 And a 2 Two different transmission sequences are represented and, I.I 2 The two norms are represented by the two norms,representing two transmit signals respectively.
As known from the related communication knowledge, under the condition of high signal-to-noise ratio, the block error rate of the signal is highIt can be approximated as:
in the above formula, W is a set of R points closest to the transmitted signal X, and R values can be set artificially; the probability p (X) of different transmitted signals X is often known at the transmitting end, conditional probabilityIndicating that signal X is misjudged as +.>The calculation formula is as follows:
wherein Q (·) is a Q function,erfc (·) is the error compensation function, y represents the received signal.
From the theoretical derivation above, minimizing the system BLER is equivalent to maximizing the euclidean distance between the transmitted signals.
Based on the above theory, to find the modulation order combination and SAP that optimize the demodulation performance of the embodiment of the present invention, the following steps are performed before the transmitting-end bit mapping:
a transmitted symbol constellation point optimization step:
step S101, setting the number of subcarriers N per group, and for each K (k=1 to N), setting an initial SAP vector S (K) = [ S (1), S (2),. S (N)]Selecting a modulation order set M= { M 1 ,...,M a ,...,M A }. Calculating the total number of iterations to be A N A is the size of a modulation order set M;
step S102, initializing the number of calculation a=1;
step S103, for different activated subcarrier numbers K (g), changing the corresponding modulation order M t Different constellation point vectors C (K) = [ C (1), C (2),. The, C (K) are generated]；
Step S104, generating different transmission signals X by using S (K) and C (K) to form a mapping table X map ；
Step S105, for X map Each of the emission vectors X, calculate X and X map Other vectors in (3)Distance between them, and based on the first R nearest vectors +.>Obtaining a collection W, wherein R is more than or equal to 1;
step S106, calculating a function using the error rateCalculate the emission vector x and the vector +.>Error rate at a given signal-to-noise ratio;
step S107, calculate and record
Step S108, the number of times of calculation is increased by 1: a=a+1;
step S109, judging whether a is larger than A at the moment, if a is smaller than or equal to A, returning to step S103; otherwise, step S110 is performed downward;
step S110, a plurality of calculated from the transmitted symbol constellation point optimization stepFind the minimum value in (a) and record as Corresponding modulation order combination M a I.e. the optimal modulation combination that is sought.
Subcarrier activation position optimization step:
step S201, setting each group of subcarrier numbers N, selecting initial modulation order combination m= { M for each k=1 to N 1 ,...,M K ,...,M N -a }; and calculating the total number of SAP iterations to beIndicating the number of combinations of K selected from N sub-carriers, and pi represents the product;
step S202, for different K (g), utilizing its corresponding modulation order M K Different constellation point vectors C (K) = [ C (1), C (2),. The, C (K) are generated]；
Step S203, initializing the number of calculation times a=1;
step S204, for different K (g), changing the activated subcarrier positions thereof, resulting in different S (K) = [ S (1), S (2),. The term, S (N) ];
step S205, generating different transmission signals X by using S (K) and C (K) to form a mapping table X map ；
Step S206, for X map Each of the emission vectors X, calculate X and X map Other vectors in (3)Distance between them, and based on the first R nearest vectors +.>Obtaining a collection W, wherein R is more than or equal to 1;
step S207, calculating a function using the error rateCalculate the emission vector x and the vector +.>Error rate at a given signal-to-noise ratio;
step S208, calculate and record
Step S209, the number of times of calculation is increased by 1: a=a+1;
step S210, judging whether a is larger than A at the moment, if a is smaller than or equal to A, returning to step S204; otherwise, step S211 is performed downward;
step S211, a plurality of calculated from the subcarrier activation position optimizing stepFind the minimum value in (a) and record as The corresponding SAP isThe result is obtained.
Examples
In this embodiment, the capacity improvement of the OFDM-SNM system employing multiple modulation orders according to the present invention as compared with the conventional OFDM-SNM system will be shown. First, the spectrum efficiency calculation formula is:
x of conventional OFDM-SNM map As shown in table 2. Its transmission efficiency is eta conv ＝1.125bit/Hz/s；
TABLE 2
In this embodiment, information bits are transmitted using multiple modulation order combinations, such that m= {2,4,16}, respectively, represents BPSK,4QAM,16QAM. Then the modulation order M is changed by the optimization method K The corresponding relation between the transmission capacity of the system and the BLER of the system under the specific signal-to-noise ratio is shown in figure 2. In fig. 2, the x-axis represents the system transmission rate and the y-axis represents the system BLER, and it can be seen that the further the resulting point is from the origin in the x-direction, the closer the origin is to the y-direction, the higher the overall system capacity and the better the performance. Observations show that when M a = {16,4,2,4}, the OFDM-SNM system capacity of the present embodiment is η conv ＝1.688bit/Hz/s。
X obtained after subcarrier activation position optimization for optimal modulation order combination in FIG. 2 map As shown in table 3.
TABLE 3 Table 3
Other key parameters related to the system are shown in table 4.
Table 4 simulation parameters
Parameters (parameters) Configuration of
Modulation scheme BPSK，4QAM，16QAM
Number of subcarriers per group 4
Number of active subcarriers {1,2,3,4}
Detection mode ML detection
Channel(s) AWGN
Fig. 3 shows the system demodulation performance of the conventional OFDM-SNM system, E-OFDM-SNM, under the above parameter setting. As can be seen from the figure, optimizing the transmitted signal constellation point and subcarrier activation position, when the signal-to-noise ratio is higher than 7dB in the case of increasing the transmission capacity of the system by 0.563bit/Hz/s, the demodulation performance of the E-OFDM-SNM system will be better than that of the conventional OFDM-SNM system, and the bler=10 -2 May be raised by about 0.8dB and the gain will increase with increasing signal to noise ratio.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
What has been described above is merely some embodiments of the present invention. It will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the spirit of the invention.

Claims (1)

1. A method for modulating the number of high capacity subcarriers, characterized in that the following steps are performed before the bit mapping at the transmitting end:
a transmitted symbol constellation point optimization step:
step S1-1, setting the number N of subcarriers of each packet, selecting a modulation order set M= { M 1 ,...,M t ,...,M A Calculating the upper limit T of the iterative times of the optimization of the constellation points of the transmitting symbols 1 ＝A N Wherein A is the size of the modulation order set M;
traversing each value K in 1-N, and initializing a carrier activation mode SAP vector based on the number of activated subcarriers corresponding to each K: s (K) = [ S (1), S (2), S (N) ], where S (N) ∈ {0,1}, n=1, 2, ], N, and the number of S (N) = 1 is K, S (N) = 1 indicates that the location subcarrier is in an active state, S (N) = 0 indicates that the location subcarrier is not activated;
step S1-2, changing the corresponding modulation order M for different activated subcarrier numbers t Different constellation point vectors C (K) = [ C (1), C (2),. The, C (K) are generated]Where c (k) represents the state of the subcarrier with index k, and c (k) =1 represents that the subcarrier at that position is activated for carrying data; c (K) =0 indicates not activated, k=1, …, K;
step S1-3, obtaining signal block error rate under different activated subcarrier numbers
Generating different transmission signals X based on the SAP vector S (K) and the constellation point vector C (K) to form a mapping table X map ；
For X map Each of the emission vectors X, calculate X and X map Other vectors in (3)Distance between them, and based on the first R nearest vectors +.>Obtaining a collection W, wherein R is more than or equal to 1;
calculating a function using error ratesAcquiring a transmission vector x and a vector +.>Error Rate at a given signal-to-noise ratio +.>Wherein y represents a received signal;
calculate and record P (x) represents the probability of transmitting vector x;
step S1-4, when the iterative computation times reach T 1 Then, a plurality of calculated from the transmitted symbol constellation point optimization stepFind the minimum value based on the minimum value pairCorresponding modulation order combination M a The optimal modulation combination is obtained; otherwise, returning to the step S1-2;
subcarrier activation position optimization step:
step S2-1, setting the number N of subcarriers in each group;
traversing each value K in 1-N, and setting initial modulation order combination M= { M based on the number of activated subcarriers corresponding to each K 1 ,...,M K ,...,M N }；
Computing a total number of subcarrier activation location optimizationsWherein (1)>Indicating the number of combinations of K selected from N sub-carriers;
step S2-2, for different activated subcarrier numbers, utilizing the corresponding modulation order M K Different constellation point vectors C (K) = [ C (1), C (2),. The, C (K) are generated]Where c (k) represents the state of the subcarrier with index k, and c (k) =1 represents that the subcarrier at that position is activated for carrying data; c (K) =0 indicates not activated, k=1, …, K;
step S2-3, for different numbers of activated subcarriers, changing the positions of the activated subcarriers to obtain different carrier activation patterns SAP vectors S (K) = [ S (1), S (2),. The term "S (N) ], where S (N) ∈ {0,1}, n=1, 2, & the term" N, and the number of S (N) =1 is K, S (N) =1 indicates that the position subcarrier is in an activated state, and S (N) =0 indicates that the position subcarrier is not activated;
s2-4, obtaining signal block error rate under different activated subcarrier numbers
Generating different transmission signals X based on the SAP vector S (K) and the constellation point vector C (K) to form a mapping table X map ；
For X map Each of (a)The emission vector X, calculate X and X map Other vectors in (3)Distance between them, and based on the first R nearest vectors +.>Obtaining a collection W, wherein R is more than or equal to 1;
calculating a function using error ratesAcquiring a transmission vector x and a vector +.>Error Rate at a given signal-to-noise ratio +.>Wherein y represents a received signal;
calculate and record P (x) represents the probability of transmitting vector x;
step S2-4, when the iterative computation times reach T 2 Then, a plurality of calculated sub-carrier activation position optimization stepsSearching a minimum value, and obtaining an SAP vector corresponding to the minimum value as a subcarrier activation position optimization result;
wherein different transmission signals X are generated based on the SAP vector S (K) and the constellation point vector C (K) to form a mapping table X map The method comprises the following steps:
x＝[x(1),..,x(n),..,x(N)] T ，n＝1,2,...,N；
where p represents the number of bits per packet;
error rate calculation functionThe method comprises the following steps:
wherein, the Q function is:erfc (·) represents the error complement function, N 0 Representing the noise power spectral density.
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