An integrated waveform design method for radar communication based on NC-CE-OFDM

Abstract

The present invention discloses a radar communication integrated waveform design method of NC-CE-OFDM, including: setting signal parameters and initializing the target state; determining the subcarrier position and PAPR of the unoccupied frequency band through dynamic spectrum sensing and channel estimation technology; using phase technology to reduce PAPR, and modulating communication information on the subcarrier of the unoccupied bandwidth for transmission; solving the bit error rate of the non-continuous constant envelope integrated signal in the additive white Gaussian noise channel; solving the fuzzy function in the radar communication integrated signal; solving the distance resolution, Doppler resolution and Doppler tolerance characteristics of the integrated signal waveform according to the fuzzy function. The present invention combines non-continuous OFDM signals with phase modulation technology, which can alleviate the problem of tight spectrum resources and achieve the maximum utilization of the spectrum of non-continuous OFDM signals.

Description

Technical Field

[0001] The present invention belongs to the field of radar communication integration, and relates to a phase modulation technology of a non-continuous OFDM system, specifically a NC-CE-OFDM radar communication integration waveform design method, which can be used for waveform design to reduce PAPR in radar communication integration of non-continuous OFDM signals. Background Art

[0002] With the rapid development of electronic information technology, the integrated combat platform mainly supported by non-continuous OFDM signals has become the backbone of radar communication integration, which has greatly improved the spectrum utilization efficiency while maximally alleviating the shortage of spectrum resources. However, the development of non-continuous OFDM integration mainly depends on the suppression of PAPR by non-continuous OFDM signals. Phase modulation technology, as the preferred method to suppress the PAPR of OFDM signals, is of great significance in modern radar communication integration. Radar communication integration requires non-continuous OFDM signals to have higher spectrum utilization efficiency, more accurate target recognition capability, and stronger anti-interference capability.

[0003] Within a given system bandwidth, non-continuous OFDM systems dynamically identify available spectrum by real-time spectrum detection, generate spectrum utility sequences, and realize non-continuous spectrum communication functions. However, there are two major defects in non-continuous OFDM systems: high PAPR and large sidelobe power, which seriously affect the bit error rate performance and are difficult to eliminate using traditional methods. Phase modulation technology is an important method to suppress the PAPR of OFDM signals, that is, to reduce the PAPR of the signal to 0dB by using phase modulation, thereby achieving the purpose of improving the efficiency of the power amplifier. In recent years, phase modulation technology has been widely used in continuous OFDM signals, but rarely in non-continuous OFDM signals. Therefore, phase modulation technology needs to respond to these challenges in non-continuous OFDM systems in a robust and efficient working mode.

[0004] Phase modulation technology uses interference technology and has high detection sensitivity and a large dynamic measurement range, and has strong anti-interference ability. In order to alleviate the shortage of spectrum resources, the transmission of communication information has transitioned from continuous frequency bands to non-continuous frequency bands. Non-continuous frequency bands use cognitive radio technology as the core to sense and utilize idle spectrum resources in the electromagnetic environment, and limit and reduce the occurrence of conflicts. At present, a more effective method published in international journals is that scholars such as Hao Minzhong use the idea of ​​precoding and propose a systematic method to generate a PAPR reduction matrix with a minimum error rate. The algorithm establishes a precoding matrix based on the selected pulse shape and uses singular value decomposition and reconstruction processes to reduce the PAPR value. However, this algorithm largely only considers the active subcarriers at regular intervals, that is, in order to improve the PAPR performance of the system, the distribution of active subcarriers of non-continuous OFDM signals is simplified.

[0005] PAPR reduction techniques proposed in OFDM systems need to be adapted to NC-OFDM systems. In spectrum systems, active subcarriers are co-located with occupied subcarriers. Therefore, both inter-symbol interference (ISI) and inter-carrier interference (ICI) may cause distortion in primary user transmissions. Time domain or distortion-based techniques, such as clipping and filtering, increase interference to active subcarriers; frequency domain adjacent subcarrier-based techniques, such as coding, cannot sense the location of active subcarriers, resulting in inter-symbol interference; techniques such as interleaving, selective mapping (SLM) and partial transmission sequence (PTS) require knowledge of the location of active subcarriers. In dynamic spectrum access networks, the total number of active subcarriers and their locations may change continuously, and most PAPR reduction techniques have difficulty adapting to these changes. Therefore, these techniques are difficult to directly apply to reduce the PAPR of NC-OFDM signals. Summary of the invention

[0006] Purpose of the invention: In order to overcome the deficiencies in the prior art, a NC-CE-OFDM radar communication integrated waveform design method is provided, which is based on non-continuous OFDM signals and achieves maximum utilization of the non-continuous OFDM signal spectrum through phase modulation technology.

[0007] Technical solution: To achieve the above purpose, the present invention provides a NC-CE-OFDM radar communication integrated waveform design method, comprising the following steps:

[0008] S1: Set signal parameters and initialize the target state;

[0009] S2: Determine the subcarrier position and PAPR of unoccupied frequency bands through dynamic spectrum sensing and channel estimation technology;

[0010] S3: Use phase technology to reduce PAPR and modulate communication information on subcarriers in unoccupied bandwidth for transmission;

[0011] S4: Solve the bit error rate of the discontinuous constant envelope integrated signal in the additive white Gaussian noise (AWGN) channel;

[0012] S5: Solving the ambiguity function in radar communication integrated signal;

[0013] S6: Determine the range resolution, Doppler resolution and Doppler tolerance characteristics of the integrated signal waveform based on the fuzzy function.

[0014] Furthermore, the step S1 is specifically as follows:

[0015] In each Ts module time, an N DFTThe IDFT of the point calculates a time sampling value module {x[n]}, with a sampling rate F0 = N DFT / T; The input of IDFT is a conjugate symmetric data vector after zero padding: In the formula, is the QAM data symbol, N zp A row vector of zero elements.

[0016] Furthermore, the PAPR in step S2 includes the PAPR of active subcarriers in a continuous interval case, a regular interval case and a random interval case.

[0017] Furthermore, the method for determining the PAPR situation in step S2 is: performing PAPR analysis on the active subcarriers distributed at three different positions of the non-continuous OFDM system:

[0018] Continuously spaced active subcarriers:

[0019] When the active subcarrier and the inactive subcarrier are continuously spaced, the data on the active subcarrier is:

[0020]

[0021] Among them, x k Represents data symbol;

[0022] The inactive subcarrier is equivalent to zero padding, which improves the time resolution of the original OFDM signal. Due to the position of the zero point, the NC-OFDM subcarrier will be equivalent to the frequency shift of the original OFDM subcarrier, thereby generating a phase-shifted NC-OFDM signal in the time domain. The NC-OFDM signal is just a phase shift of the original OFDM signal with better time resolution. Therefore, the PAPR of the NC-OFDM signal is exactly the same as the original OFDM signal.

[0023] Regularly spaced active subcarriers:

[0024] When the active subcarriers are regularly spaced from the inactive subcarriers, the data on the active subcarriers is:

[0025]

[0026] Wherein, m is the subcarrier spacing;

[0027] When there are m-1 inactive subcarriers between any two consecutive active subcarriers, the time domain NC-OFDM signal contains m signals of the original OFDM time domain signal. Therefore, only a part of the time domain signal, namely N / m, is needed to estimate the PAPR of the signal. In this case, the NC-OFDM signal consists of the original OFDM signal, so the PAPR of the NC-OFDM signal remains the same as the PAPR of the adjacent OFDM signal.

[0028] Randomly distributed active subcarriers:

[0029] When the active subcarriers are randomly spaced, the phase factors of the active subcarriers are difficult to exist in a regularly spaced form after IFFT during transmission. In this case, the NC-OFDM signal will be different from the equivalent continuous OFDM signal, resulting in the PAPR value of the NC-OFDM signal being different from the PAPR value of the original OFDM signal.

[0030] Analysis of the PAPR in the three cases shows that the PAPR distribution of the NC-OFDM signal with continuously spaced active subcarriers and regularly spaced active subcarriers is equivalent to the PAPR distribution of the continuous OFDM signal; among them, the NC-OFDM signal with randomly spaced active subcarriers produces different IFFT output signals due to different phase factors, resulting in its PAPR distribution being different from that of the continuous OFDM signal.

[0031] Furthermore, the transmission of communication information on the subcarriers of the unoccupied frequency band in step S3 is performed based on continuously spaced active subcarriers and regularly spaced active subcarriers.

[0032] Since the non-continuous CE-OFDM system is equivalent to the CE-OFDM system in the case of continuously spaced active subcarriers and regularly spaced active subcarriers, it is difficult to suppress PAPR using phase modulation technology for randomly spaced active subcarriers due to their different phase factors. Therefore, the transmission of communication information on subcarriers in unoccupied frequency bands is based on continuously spaced active subcarriers and regularly spaced active subcarriers.

[0033] Furthermore, the method for transmitting communication information to subcarriers in unoccupied frequency bands based on continuously spaced active subcarriers and regularly spaced active subcarriers in step S3 includes the following steps:

[0034] The complex envelope of the baseband NC-OFDM signal composed of all non-adjacent subcarriers in a [0,T] time interval is:

[0035]

[0036] Among them, A k is the kth subcarrier of the signal, T is the OFDM symbol duration, The symbol on the kth unoccupied subcarrier is A k =0, then PAPR is defined as the ratio of the maximum instantaneous power to the average power of the OFDM signal, that is:

[0037]

[0038] Where E{·} represents the expectation; the continuous-time peak-to-average ratio PAPR (s(t)) can be approximated by the discrete-time peak-to-average ratio PAPR (s(n)), which is obtained by sampling the OFDM signal s(n);

[0039] The real and imaginary parts of the NC-OFDM signal will obey the Gaussian distribution, its amplitude will obey the Rayleigh distribution, and the power distribution will obey the chi-square distribution with two degrees of freedom, so the cumulative probability density function (CDF) of each sampling point is:

[0040]

[0041] Among them, σ 2 It is expressed as the variance of the input sequence. It is usually not described by CDF, but by the complementary cumulative distribution function (CCDF). The CCDF of the peak-to-average ratio represents the probability that the peak-to-average ratio of the OFDM signal exceeds a given threshold. It is the most commonly used parameter to characterize PAPR and is also a performance indicator of the PAPR reduction technology. The probability formula for each sample point being greater than the threshold PAPR0 is:

[0042]

[0043] Wherein, αK (α>1) represents the number of oversampled subcarriers in the NC-OFDM system;

[0044] Through phase modulation technology, NC-CE-OFDM signal is obtained:

[0045] The high PAPR sequence signal {x[n]} is converted into a sequence with a PAPR of 0dB through a phase modulator:

[0046] {s[n]=exp(jCx[n])} <7>

[0047] Where C is the measurement constant;

[0048] The low-pass equivalent expression of the NC-CE-OFDM signal is:

[0049] s(t)=Aexp{j[2πhm(t)+θ]} <8>

[0050] Among them, -T cp ≤t≤T; A is the signal amplitude, θ is any phase deviation;

[0051] The message symbol m(t) carrying information is a real-valued OFDM waveform, which is equivalently expressed as:

[0052]

[0053] Among them, -T cp ≤t≤T, C0 is a constant;

[0054] Perform frequency domain equalization on the received signal:

[0055] The received signal is first passed through an A / D converter to obtain the sampled value r[n], then the cyclic prefix is ​​removed, and finally the distortion caused by the channel is corrected using a frequency domain equalizer, and the inverse process of information transmission is performed;

[0056] Among them, after the NC-CE-OFDM signal passes through the multipath fading channel, the baseband of its received signal can be expressed as:

[0057]

[0058] Among them, h(τ,t) is the maximum transmission delay, τ max is the impulse response of the channel; ω(t) is the energy spectral density over the effective bandwidth of s(t) ωω (f) = complex Gaussian noise of N0.

[0059] Furthermore, the process of solving the bit error rate in step S4 is as follows:

[0060] Phase demodulation is achieved through an inverse tangent calculator and phase unwrapping;

[0061] Assuming simple AWGN, the received signal is:

[0062]

[0063] The output of the phase modulator is:

[0064]

[0065] Among them, φ0 is the phase deviation caused by the channel; is the nonlinear noise term; A ω (t)≡|ω(t)|and φ ω (t)≡arctan[ω(t)] are the envelope and phase of ω(t) respectively;

[0066] Therefore, the BER of the NC-CE-OFDM system is:

[0067]

[0068] Where k = 1, 2, ..., N; is the Gaussian Q function; ε b =A 2 T / (2Nlog2 M ) is the energy per bit of NC-CE-OFDM signal transmission.

[0069] Furthermore, the process of solving the ambiguity function in the radar communication integrated signal in step S5 is as follows:

[0070] The integrated signal fuzzy function is:

[0071]

[0072] Where τ is the time delay; f d is the Doppler frequency shift; s * (t) represents the conjugate of s(t).

[0073] Furthermore, the solution process of step S6 is specifically as follows:

[0074] Under the same pulse width conditions, the Doppler frequency shift when the pulse pressure gain of the echo signal drops to the minimum allowable level is called the Doppler tolerance characteristic. The Doppler tolerance detection function is:

[0075]

[0076] Where B is the signal bandwidth;

[0077] T on both sides of the equation s (1 / f s ) is the sampling interval, let t = nT s ,have

[0078]

[0079] The discrete Doppler tolerance detection function r(m) can be obtained:

[0080]

[0081] The present invention first determines the position distribution and PAPR of active subcarriers through spectrum sensing, and uses phase modulation technology to minimize the PAPR of OFDM signals; then analyzes the ambiguity function of the signal in AWGN and radar communication integration signal to better improve the spectrum utilization efficiency. It mainly solves the problem of high peak-to-average power ratio (PAPR) of non-continuous OFDM signals, that is, PAPR is suppressed by phase modulation of active subcarriers distributed at three different positions of the NC-OFDM system.

[0082] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0083] 1. The present invention proposes a technology for suppressing the PAPR of non-continuous OFDM signals - phase modulation technology. In non-continuous OFDM signals, this technology can not only meet the requirement that the signal has the lowest PAPR (0dB), but also maximize the efficiency of the power amplifier.

[0084] 2. The present invention combines non-continuous OFDM signals with phase modulation technology, which can alleviate the problem of tight spectrum resources and improve spectrum utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0085] Figure 1 is a flow chart of the present invention;

[0086] Figure 2 It is a distribution diagram of unoccupied subcarriers of the present invention. DETAILED DESCRIPTION

[0087] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, various equivalent forms of modifications to the present invention by those skilled in the art all fall within the scope defined by the claims attached to this application.

[0088] The present invention provides a radar communication integrated waveform design method of NC-CE-OFDM, such as Figure 1 As shown, it includes the following steps:

[0089] S1: Set signal parameters and initialize the target state:

[0090] In each Ts module time, an N DFT The IDFT of the point calculates a time sampling value module {x[n]}, with a sampling rate F0 = N DFT / T; The input of IDFT is a conjugate symmetric data vector after zero padding: In the formula, is the QAM data symbol, N zp A row vector of zero elements.

[0091] S2: Determine the subcarrier position and PAPR of unoccupied frequency bands through dynamic spectrum sensing and channel estimation technology:

[0092] The specific implementation process of this step is as follows:

[0093] Reference Figure 2 ,Through spectrum sensing, the active subcarriers of the NC-OFDM system have three different ,distributions, i.e., continuous interval, regular interval and random interval.,The PAPR in the three cases is analyzed respectively:

[0094] PAPR analysis is performed on the non-continuous OFDM system with active subcarriers distributed at three different locations:

[0095] (2a) Continuously spaced active subcarriers

[0096] When the active subcarrier and the inactive subcarrier are continuously spaced, the data on the active subcarrier is:

[0097]

[0098] Among them, x k Indicates data symbol.

[0099] The inactive subcarriers are equivalent to zero padding, which improves the time resolution of the original OFDM signal. Due to the location of the zeros, the NC-OFDM subcarriers will appear as frequency-shifted versions of the original OFDM subcarriers, resulting in a phase-shifted NC-OFDM signal in the time domain. The NC-OFDM signal is just a phase-shifted version of the original OFDM signal with better time resolution. Therefore, the PAPR of the NC-OFDM signal is exactly the same as the original OFDM signal.

[0100] (2b) Regularly spaced active subcarriers

[0101] When the active subcarriers are regularly spaced from the inactive subcarriers, the data on the active subcarriers is:

[0102]

[0103] Wherein, m is the subcarrier spacing.

[0104] When there are m-1 inactive subcarriers between any two consecutive active subcarriers, then the time domain NC-OFDM signal contains m of the original OFDM time domain signal. Therefore, only a portion of the time domain signal, i.e., N / m, is needed to estimate the PAPR of the signal. In this case, the NC-OFDM signal consists of the original OFDM signal, so the PAPR of the NC-OFDM signal remains the same as the PAPR of the adjacent OFDM signal.

[0105] (3c) Randomly distributed active subcarriers

[0106] When the active subcarriers are randomly spaced, the phase factors of the active subcarriers are calculated by IFFT during transmission and it is difficult for them to exist in a regularly spaced form. In this case, the NC-OFDM signal will be different from the equivalent continuous OFDM signal, resulting in the PAPR value of the NC-OFDM signal being different from the PAPR value of the original OFDM signal.

[0107] Analysis of the PAPR in the three cases shows that the PAPR distribution of the NC-OFDM signal with continuously spaced active subcarriers and regularly spaced active subcarriers is equivalent to the PAPR distribution of the continuous OFDM signal; among them, the NC-OFDM signal with randomly spaced active subcarriers produces different IFFT output signals due to different phase factors, resulting in its PAPR distribution being different from that of the continuous OFDM signal.

[0108] S3: Use phase technology to reduce PAPR and modulate communication information on subcarriers in unoccupied bandwidth for transmission:

[0109] Since the non-continuous CE-OFDM system is equivalent to the CE-OFDM system in the case of continuously spaced active subcarriers and regularly spaced active subcarriers, it is difficult to suppress PAPR using phase modulation technology for randomly spaced active subcarriers due to their different phase factors. Therefore, the transmission of communication information on subcarriers in unoccupied frequency bands is based on continuously spaced active subcarriers and regularly spaced active subcarriers.

[0110] The method for transmitting communication information to subcarriers in unoccupied frequency bands based on continuously spaced active subcarriers and regularly spaced active subcarriers comprises the following steps:

[0111] The complex envelope of the baseband NC-OFDM signal composed of all non-adjacent subcarriers in a [0,T] time interval is:

[0112]

[0113] Among them, A k is the kth subcarrier of the signal, T is the OFDM symbol duration, The symbol on the kth unoccupied subcarrier is Ak =0, then PAPR is defined as the ratio of the maximum instantaneous power to the average power of the OFDM signal, that is:

[0114]

[0115] Where E{·} represents the expectation; the continuous-time peak-to-average ratio PAPR (s(t)) can be approximated by the discrete-time peak-to-average ratio PAPR (s(n)), which is obtained by sampling the OFDM signal s(n);

[0116] The real and imaginary parts of the NC-OFDM signal will obey the Gaussian distribution, its amplitude will obey the Rayleigh distribution, and the power distribution will obey the chi-square distribution with two degrees of freedom, so the cumulative probability density function (CDF) of each sampling point is:

[0117]

[0118] Among them, σ 2 It is expressed as the variance of the input sequence. It is usually not described by CDF, but by the complementary cumulative distribution function (CCDF). The CCDF of the peak-to-average ratio represents the probability that the peak-to-average ratio of the OFDM signal exceeds a given threshold. It is the most commonly used parameter to characterize PAPR and is also a performance indicator of the PAPR reduction technology. The probability formula for each sample point being greater than the threshold PAPR0 is:

[0119]

[0120] Wherein, αK (α>1) represents the number of oversampled subcarriers in the NC-OFDM system;

[0121] Through phase modulation technology, NC-CE-OFDM signal is obtained:

[0122] The high PAPR sequence signal {x[n]} is converted into a sequence with a PAPR of 0dB through a phase modulator:

[0123] {s[n]=exp(jCx[n])} <7>

[0124] Where C is the measurement constant;

[0125] The low-pass equivalent expression of the NC-CE-OFDM signal is:

[0126] s(t)=Aexp{j[2πhm(t)+θ]} <8>

[0127] Among them, -T cp ≤t≤T; A is the signal amplitude, θ is any phase deviation;

[0128] The message symbol m(t) carrying information is a real-valued OFDM waveform, which is equivalently expressed as:

[0129]

[0130] Among them, -T cp ≤t≤T, C0 is a constant;

[0131] Frequency domain equalization and phase demodulation process of the received signal:

[0132] The received signal is first passed through an A / D converter to obtain the sampled value r[n], then the cyclic prefix is ​​removed, and finally the distortion caused by the channel is corrected using a frequency domain equalizer, and the inverse process of information transmission is performed;

[0133] Among them, after the NC-CE-OFDM signal passes through the multipath fading channel, the baseband of its received signal can be expressed as:

[0134]

[0135] Among them, h(τ,t) is the maximum transmission delay, τ max is the impulse response of the channel; ω(t) is the energy spectral density over the effective bandwidth of s(t) ωω (f) = complex Gaussian noise of N0.

[0136] The received signal first passes through the A / D converter to obtain the sample value r[n], then removes the cyclic prefix, and finally uses the frequency domain equalizer to correct the distortion caused by the channel, and performs the inverse process of information transmission: phase demodulation is achieved through the inverse tangent calculator and phase unwrapping.

[0137] S4: Solve the bit error rate of the discontinuous constant envelope integrated signal in the additive white Gaussian noise channel:

[0138] Phase demodulation is achieved through an inverse tangent calculator and phase unwrapping;

[0139] Assuming simple AWGN, the received signal is:

[0140]

[0141] The output of the phase modulator is:

[0142]

[0143] Where φ0 is the phase deviation caused by the channel;

[0144] The nonlinear noise term is, and the envelope and phase of ω(t) are:

[0145]

[0146] A ω (t)≡|ω(t)| <14>

[0147] φ ω (t)≡arctan[ω(t)] <15>

[0148] Therefore, the BER of the NC-CE-OFDM system is:

[0149]

[0150] Where k = 1, 2, ..., N; is the Gaussian Q function; ε b =A 2 T / (2Nlog2 M ) is the energy per bit of NC-CE-OFDM signal transmission.

[0151] S5: Solving the ambiguity function in radar communication integrated signal:

[0152] The integrated signal fuzzy function is:

[0153]

[0154] Where τ is the time delay; f d is the Doppler frequency shift; s * (t) represents the conjugate of s(t).

[0155] S6: Based on the fuzzy function, the range resolution, Doppler resolution and Doppler tolerance characteristics of the integrated signal waveform are obtained:

[0156] Under the same pulse width conditions, the Doppler frequency shift when the pulse pressure gain of the echo signal drops to the minimum allowable level is called the Doppler tolerance characteristic. The Doppler tolerance detection function is:

[0157]

[0158] Where B is the signal bandwidth;

[0159] T on both sides of the equation s (1 / f s ) is the sampling interval, let t = nT s ,have

[0160]

[0161] The discrete Doppler tolerance detection function r(m) can be obtained:

[0162]

Claims

1. A radar communication integrated waveform design method for NC-CE-OFDM, characterized in that: The steps include: S1: Set signal parameters and initialize the target state; S2: Determine the subcarrier position and PAPR of unoccupied frequency bands through dynamic spectrum sensing and channel estimation technology; S3: Use phase modulation technology to minimize the PAPR of OFDM signals and modulate communication information on subcarriers that do not occupy bandwidth for transmission; S4: Solve the bit error rate of the discontinuous constant envelope integrated signal in the additive white Gaussian noise channel; S5: Solving the ambiguity function in radar communication integrated signal; S6: Determine the range resolution, Doppler resolution and Doppler tolerance characteristics of the integrated signal waveform based on the fuzzy function.

2. According to claim 1, the NC-CE-OFDM radar communication integrated waveform design method is characterized in that: The step S1 is specifically as follows: In each Ts module time, an N DFT The IDFT of the point calculates a time sampling value module {x[n]}, with a sampling rate F0 = N DFT / T; The input of IDFT is a conjugate symmetric data vector after zero padding: In the formula, is the QAM data symbol, N zp A row vector of zero elements.

3. The radar communication integrated waveform design method of NC-CE-OFDM according to claim 1 is characterized in that: The PAPR in step S2 includes the PAPR of active subcarriers in the case of continuous interval, regular interval and random interval.

4. The radar communication integrated waveform design method of NC-CE-OFDM according to claim 3 is characterized in that: The method for determining the PAPR situation in step S2 is: performing PAPR analysis on the active subcarriers distributed at three different positions of the non-continuous OFDM system: Continuously spaced active subcarriers: When the active subcarrier and the inactive subcarrier are continuously spaced, the data on the active subcarrier is: Among them, x k Represents data symbol; The inactive subcarrier is equivalent to zero padding. Due to the position of the zero point, the NC-OFDM subcarrier will be equivalent to the frequency shift of the original OFDM subcarrier, thereby generating a phase-shifted NC-OFDM signal in the time domain. The NC-OFDM signal is just a phase shift of the original OFDM signal, so the PAPR of the NC-OFDM signal is exactly the same as the original OFDM signal. Regularly spaced active subcarriers: When the active subcarriers are regularly spaced from the inactive subcarriers, the data on the active subcarriers is: Wherein, m is the subcarrier spacing; When there are m-1 inactive subcarriers between any two consecutive active subcarriers, the time domain NC-OFDM signal contains m signals of the original OFDM time domain signal. Therefore, only a part of the time domain signal, namely N / m, is needed to estimate the PAPR of the signal. In this case, the NC-OFDM signal consists of the original OFDM signal, so the PAPR of the NC-OFDM signal remains the same as the PAPR of the adjacent OFDM signal. Randomly distributed active subcarriers: When the active subcarriers are randomly spaced, the phase factors of the active subcarriers undergo IFFT during transmission. In this case, the NC-OFDM signal will be different from the equivalent continuous OFDM signal, resulting in the PAPR value of the NC-OFDM signal being different from the PAPR value of the original OFDM signal.

5. The radar communication integrated waveform design method of NC-CE-OFDM according to claim 3 is characterized in that: The transmission of communication information on the subcarriers of the unoccupied frequency band in step S3 is performed based on continuously spaced active subcarriers and regularly spaced active subcarriers.

6. The radar communication integrated waveform design method of NC-CE-OFDM according to claim 5 is characterized in that: The method for transmitting communication information to subcarriers in unoccupied frequency bands based on continuously spaced active subcarriers and regularly spaced active subcarriers in step S3 comprises the following steps: The complex envelope of the baseband NC-OFDM signal composed of all non-adjacent subcarriers in a [0,T] time interval is: Among them, A k is the kth subcarrier of the signal, T is the OFDM symbol duration, The symbol on the kth unoccupied subcarrier is A k =0, then PAPR is defined as the ratio of the maximum instantaneous power to the average power of the OFDM signal, that is: Where E{·} represents the expectation; the continuous-time peak-to-average ratio PAPR (s(t)) can be approximated by the discrete-time peak-to-average ratio PAPR (s(n)), which is obtained by sampling the OFDM signal s(n); The real and imaginary parts of the NC-OFDM signal will obey Gaussian distribution, its amplitude will obey Rayleigh distribution, and the power distribution will obey chi-square distribution with two degrees of freedom, so the cumulative probability density function of each sampling point is: Among them, σ 2 It is expressed as the variance of the input sequence and described by the complementary cumulative distribution function. The CCDF of the peak-to-average ratio indicates the probability that the peak-to-average ratio of the OFDM signal exceeds a given threshold. It is a parameter that characterizes the PAPR and is also a performance indicator of the PAPR reduction technology. The probability formula for each sample point being greater than the threshold PAPR0 is: Wherein, αK represents the number of oversampled subcarriers in the NC-OFDM system, α>1; Through phase modulation technology, NC-CE-OFDM signal is obtained: The high PAPR sequence signal {x[n]} is converted into a sequence with a PAPR of 0dB through a phase modulator: {s[n]=exp(jCx[n])} <7> Where C is the measurement constant; The low-pass equivalent expression of the NC-CE-OFDM signal is: s(t)=Aexp{j[2πhm(t)+θ]} <8> Among them, -T cp ≤t≤T; A is the signal amplitude, θ is any phase deviation; The message symbol m(t) carrying information is a real-valued OFDM waveform, which is equivalently expressed as: Among them, -T cp ≤t≤T, C0 is a constant; Perform frequency domain equalization on the received signal: The received signal is first passed through an A / D converter to obtain the sampled value r[n], then the cyclic prefix is ​​removed, and finally the distortion caused by the channel is corrected using a frequency domain equalizer, and the inverse process of information transmission is performed; Among them, after the NC-CE-OFDM signal passes through the multipath fading channel, the baseband of its received signal can be expressed as: Among them, h(τ,t) is the maximum transmission delay, τ max is the impulse response of the channel; ω(t) is the energy spectral density over the effective bandwidth of s(t) ωω (f) = complex Gaussian noise of N0.

7. The radar communication integrated waveform design method of NC-CE-OFDM according to claim 1 is characterized in that: The process of solving the bit error rate in step S4 is as follows: Phase demodulation is achieved through an inverse tangent calculator and phase unwrapping; Assuming simple AWGN, the received signal is: The output of the phase modulator is: Among them, φ0 is the phase deviation caused by the channel; is the nonlinear noise term; A ω (t)≡|ω(t)|and φ ω (t)≡arctan[ω(t)] are the envelope and phase of ω(t) respectively; Therefore, the BER of the NC-CE-OFDM system is: Where k = 1, 2, ..., N; is the Gaussian Q function; ε b =A 2 T / (2Nlog2 M ) is the energy per bit of NC-CE-OFDM signal transmission.

8. The radar communication integrated waveform design method of NC-CE-OFDM according to claim 1 is characterized in that: The process of solving the fuzzy function in the radar communication integrated signal in step S5 is as follows: The integrated signal fuzzy function is: Where τ is the time delay; f d is the Doppler frequency shift; s * (t) represents the conjugate of s(t).

9. The radar communication integrated waveform design method of NC-CE-OFDM according to claim 1, characterized in that: The solution process of step S6 is specifically as follows: Under the same pulse width conditions, the Doppler frequency shift when the pulse pressure gain of the echo signal drops to the minimum allowable level is called the Doppler tolerance characteristic. The Doppler tolerance detection function is: Where B is the signal bandwidth; T on both sides of the equation s (1 / f s ) is the sampling interval, let t = nT s ,have The discrete Doppler tolerance detection function r(m) can be obtained:

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