CN115442197B - Integrated signal design and processing method adopting cyclic prefix-free OFDM (orthogonal frequency division multiplexing) - Google Patents
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Abstract
The invention discloses an integrated signal design and processing method adopting cyclic prefix-free OFDM, which generates CP-free OFDM radar communication integrated signals on the basis of constructing CP-free OFDM signals when designing signals. When the receiving end processes signals, echo signals carrying communication information and radar information are processed respectively. The invention adopts a blank guard interval to construct an OFDM radar communication integrated signal without cyclic prefix, and adopts frequency compensation and channel equalization when processing echo signals. The method solves the problems that the CP occupies communication system resources and the OFDM signal has sensitivity to Doppler frequency offset in the prior art. The accuracy and the resolution of the signal detection target are improved, and the error rate is reduced.
Description
Technical Field
The invention belongs to the technical field of communication, and further relates to a radar communication integrated signal design and processing method adopting cyclic prefix-free Orthogonal Frequency Division Multiplexing (OFDM) Frequency Division Multiplexing in the technical field of radar communication. The invention can be used for radar communication integrated systems in low-speed multipath scenes, and the radar can transmit communication information after sending designed radar communication integrated signals, and can acquire radar information according to echoes.
Background
In order to make the radar communication integrated system work efficiently, it is necessary to design an integrated fusion signal that makes full use of spectrum resources, so as to realize simultaneous radar and communication functions. A typical integrated fusion signal is generated by using a communication signal to realize a radar function, and an OFDM signal is commonly used. OFDM is a multi-carrier parallel transmission technology, has a large bandwidth, has significant advantages In resisting frequency selective fading and narrowband interference, frequency agility, doppler tolerance, and the like, and is easy to combine with a Multiple-In Multiple-Out (MIMO) radar, as compared with a conventional radar signal, and is an effective radar signal.
The university of electronic technology discloses a design method of an OFDM carrier joint optimization communication radar integrated signal in the patent literature of the university of electronic technology, namely an orthogonal frequency division multiplexing-based radar communication integrated signal design method (application No. 201910025384.5 and application publication No. CN 108512797A). The method is that based on the traditional OFDM signal, a transmitting end firstly modulates a bit stream to be transmitted into a data symbol, then carries out partial reserved waveform design according to the data bandwidth ratio by utilizing the data symbol and a random phase sequence to obtain a RadCom frequency domain signal, then maps the RadCom frequency domain signal to a time domain through IFFT, and transmits the RadCom frequency domain signal to a channel through a radio frequency front end after adding a cyclic prefix. At the receiving end, the received signal is mapped to the frequency domain through FFT after the cyclic prefix is removed, the frequency domain is equalized to compensate the channel distortion, then the equalized signal is extracted into symbols according to the data bandwidth ratio, and finally the bit information is obtained through symbol demodulation. Meanwhile, the frequency domain signals of the transmitting end and the receiving end are used for radar processing. The invention introduces a partial reservation circulation algorithm, can flexibly allocate bandwidth on the premise of keeping the advantages of the communication system, effectively reduce the peak average power ratio and improve the spectrum utilization rate. However, the method still has the defects that, due to the fact that the cyclic prefix is reserved in the transmitted signal, resources of a communication system are occupied by the cyclic prefix, and in a scene with larger time delay in a complex environment, the length of the cyclic prefix is often insufficient to counteract the influence of multipath, so that subcarriers are not orthogonal any more, a receiving end is difficult to accurately demodulate the communication signal, and a higher error rate is caused.
The western electronic technology university discloses a signal processing method of an OFDM radar communication integrated fixed platform system in the patent literature (application No. 201811218839.7, application publication No. CN 109085574B) applied thereto. Firstly, setting echo signal conditions, then carrying out down-conversion processing and sampling processing on the echo signals to obtain processed baseband signals, removing cyclic prefixes of the signals, carrying out Fourier transformation on the signals with the cyclic prefixes removed, decoding and judging the signals with the Fourier transformation to obtain communication information, and finally carrying out pulse compression processing on the signals with the cyclic prefixes removed by utilizing reference signals. However, the method still has the defects that the OFDM signal is sensitive to Doppler frequency shift, the OFDM signal containing the cyclic prefix resists multipath effect by using the cyclic prefix, radar and communication capability are limited when facing complex scenes with more targets and dispersion, the introduction of the cyclic prefix can reduce communication rate, and symmetrical pseudo peaks can be introduced into a fuzzy function of the radar, so that the distance and speed resolution of the radar are reduced.
Disclosure of Invention
The invention aims to provide a radar communication integrated signal design and processing method adopting OFDM without cyclic prefix in a complex scene, aiming at the defects of the prior art, which is used for solving the problems that resources of a communication system are occupied by the cyclic prefix, sub-carriers are not orthogonal, a receiving end is difficult to accurately demodulate a communication signal and high error rate is caused, and symmetric false peaks are introduced into a fuzzy function of a radar when the cyclic prefix is introduced to reduce the communication rate.
The method has the specific idea that the blank guard interval is utilized to replace the cyclic prefix to construct the OFDM signal without the cyclic prefix, thereby completing the functions of radar detection and communication and avoiding the problem that the cyclic prefix occupies resources in an OFDM communication system in the prior art. In the signal transmission process, the invention periodically transmits the known OFDM training symbols as pilot frequency to carry out channel estimation, and the pilot frequency estimation mode is suitable for frequency selective channels because all subcarriers have known signals, improves indexes such as Peak Side Lobe Ratio (PSLR), integral Side Lobe Ratio (ISLR), communication error rate (BER) and the like, and solves the problem of higher communication error rate of the traditional CP-OFDM signal. The invention selects proper receiving window length and executes reasonable sampling at the communication signal receiving end, can resist multipath effect and can solve the problem that the length of the cyclic prefix is continuously increased due to multipath delay under complex scene. According to the method, the radar signal receiving end carries out downsampling processing on the multi-scattering-point echo signals, and the OFDM echo signals with Doppler sensitivity are subjected to frequency offset correction according to the speed of known target information, so that the frequency spectrum efficiency can be ensured while the radar performance and the communication performance are realized, the problem that a false peak exists in a radar fuzzy function is solved, and the radar resolution is improved.
The method for designing the integrated signal by adopting the OFDM without the cyclic prefix comprises the following specific steps:
step 1, constructing an OFDM signal without a cyclic prefix:
step 1.1, calculating the amplitude of the baseband signal of each OFDM transmission pulse in each transmission path at each sampling time according to the following formula:
wherein s is pL (t) represents the amplitude of the baseband signal of the L-th OFDM transmit pulse in the p-th transmit path at the t-th sampling instant, p=0, 1, …, m-1, m represents the total number of paths, l=0, 1, …, N L -1, each OFDM transmission pulse is obtained by adding N sub-carriers, N representing the total number of sub-carriers of one OFDM transmission pulse determined according to the amount of data to be transmitted, k representing the sequence number of sub-carriers, N L Representing the total number of pulses of the L-th OFDM subcarrier, S L [k]Representing data carried by the L-th OFDM pulse on the k-th subcarrier, exp (·) represents an exponential operation based on a natural constant e, j represents an imaginary unit, pi represents a circumference ratio, f k Represents the center frequency, T, of the kth subcarrier r Representing the repetition period of OFDM transmission pulse, rect [. Cndot.]Representing a rectangular window function, T represents one OFDM symbol period when a blank guard interval is adopted, and T is equal to or greater than 0 and equal to or less than T,in other cases, the value is 0;
step 1.2, calculating the integration window length T according to the following formula L The amplitude of the baseband signal of the OFDM transmitting pulse after all the transmission path receiving signals are overlapped at each sampling moment:
wherein y is L (T) represents that all paths are superimposed over the integration window length T L Superimposed L-th OFDM transmission pulseAmplitude of baseband signal at t-th sampling time, τ p Indicating the time delay of the p-th path, rect [. Cndot. ]]Representing a rectangular window function, T L Represents any integer multiple of T, when T is more than or equal to 0 and less than or equal to T L In the time-course of which the first and second contact surfaces,in other cases, the value is 0, τ 0 Representing the time delay of the direct path received signal;
step 2, generating an OFDM radar communication integrated signal without a cyclic prefix:
step 2.1, modulating OFDM transmitting pulse signals without cyclic prefix by using training pulse parameters commonly confirmed by communication sending and receiving parties to obtain integrated signals carrying training pulse, modulating OFDM transmitting pulse signals without cyclic prefix by using communication information to be transmitted to obtain integrated signals carrying data pulse;
step 2.2, respectively calculating the amplitude of the OFDM radar communication integrated signal without cyclic prefix carrying training pulse or carrying data pulse in each pulse repetition period according to the following formula:
wherein s (t, eta) 2n ) Expressed in the eta 2n In the pulse repetition period, the amplitude of the OFDM radar communication integrated signal without the cyclic prefix carrying the training pulse at the t sampling time, s (t, eta 2n-1 ) Expressed in the eta 2n-1 In the pulse repetition period, the amplitude of the cyclic prefix-free OFDM radar communication integrated signal carrying the data pulse at the t sampling moment, S L [k 1 ]Representing symbol data carried by all training pulses; s is S L [k 2 ]Representing the symbol data carried by all data pulses, Δf representing no cyclic prefixSubcarrier spacing of OFDM radar communication integration signal, Δf=1/T.
The method for processing the integrated signal by adopting the OFDM without the cyclic prefix comprises the following steps:
step 1, processing communication information in echo signals:
step 1.1, selecting a sampling interval of 1/T L The communication information carried by the baseband receiving signal sub-carrier after symbol synchronization is sampled at a radar receiving end, and a sampled communication signal is obtained;
step 1.2, correcting the sampled communication signal through a carrier to obtain carrier frequency deviation CFO, and then carrying out frequency domain compensation on the carrier frequency deviation CFO to obtain a corrected signal after the frequency domain compensation;
step 1.3, correcting the channel at the corresponding time of the data pulse by using the channel response at the time of the equalization required by the training pulse, and finishing the channel equalization;
step 1.4, adopting quadrature phase shift keying QPSK algorithm to demap the corrected signal after frequency domain compensation, and then carrying out channel decoding on the demapped signal to obtain original communication data;
step 2, carrying out frequency compensation on echo signals carrying radar information:
step 2.1, calculating the amplitude of the Doppler compensation filter at each sampling moment according to the following formula:
h 1 (t)＝exp{-j2πf d 't}
wherein h is 1 (t) represents the amplitude of the doppler compensation filter at the t-th sampling instant,v p the relative speed between the detection target and the signal transmitting end is represented, and lambda represents the wavelength of the transmitted signal;
step 2.2, calculating the amplitude of the echo signal after the Doppler frequency offset compensation of the receiving end at each sampling moment according to the following steps:
where u (t, eta) represents the amplitude, g, of the echo signal at the t-th sampling instant after Doppler shift compensation at the eta-th pulse repetition period m Represents a backscattering coefficient, ε, of 1 a (. Cndot.) represents the azimuth beam function, R m (. Cndot.) represents a distance function, f d Represents Doppler frequency offset, c represents light velocity, f c Representing a center frequency of the transmitted OFDM integrated signal;
and step 3, performing pulse compression processing on the echo signals after frequency compensation by adopting a pulse compression algorithm to obtain radar information of the detected target.
Compared with the prior art, the invention has the following advantages:
firstly, in the invention, in designing an integrated signal without a cyclic prefix OFDM, a blank guard interval is adopted to construct an OFDM radar communication integrated signal without a cyclic prefix, so that the communication system resource is prevented from being occupied by the cyclic prefix, and meanwhile, in the transmission process of the signal, the periodical transmission of a known OFDM training symbol is used as a pilot frequency to carry out channel estimation, so that the performances of peak sidelobe ratio, integral sidelobe ratio, communication error rate and the like are improved, and the defects that the cyclic prefix occupies the communication system resource and the error rate is higher in the communication transmission process in the prior art are overcome, so that the invention has higher transmission efficiency and accuracy in the communication transmission process.
Second, because the invention adopts frequency compensation and channel equalization when processing the communication information of echo signals when processing the designed integrated signals adopting OFDM without cyclic prefix, the invention overcomes the defect of demodulation errors caused by phase change in the prior OFDM signal transmission process, so that the invention has higher demodulation capability, reduces the error rate of signal transmission and improves the resolution of signals.
Thirdly, when the designed integrated signal without the cyclic prefix OFDM is processed, frequency compensation is adopted when radar information of echo signals is processed, the problem of sensitivity of the OFDM signals to Doppler frequency offset is solved, the defect that pseudo peaks appear after pulse pressure of the OFDM signals containing the cyclic prefix in a radar system is overcome, and finally echo information of a detection target is obtained through pulse compression, so that the method has better performance in radar signal processing and higher accuracy.
Drawings
FIG. 1 is a flow chart of the present invention;
FIG. 2 is a QPSK-OFDM fuzzy function diagram with cyclic prefix of the radar subsystem in the simulation experiment of the invention;
FIG. 3 is a QPSK-OFDM fuzzy function diagram without cyclic prefix of the radar subsystem in the simulation experiment of the present invention
Fig. 4 is a comparison chart of error rates of multipath channels with communication signal to noise ratios between-5 dB and 15dB in the communication subsystem in the simulation experiment of the present invention.
Detailed Description
The invention is further described below with reference to the drawings and examples.
Implementation steps of the present invention will be further described with reference to fig. 1 and the embodiment.
And 1, constructing an OFDM signal without a cyclic prefix.
When the OFDM signal adopts the cyclic prefix as the guard interval, the cyclic prefix occupies the pulse width, but in the case of adopting the blank guard interval, the cyclic prefix does not occupy the pulse width any more, and the pulse width is the same as the OFDM symbol period.
Step 1.1, calculating the amplitude of the baseband signal of each OFDM transmission pulse of each path at each sampling time according to the following formula:
wherein s is pL (t) represents the amplitude of the baseband signal of the L-th OFDM transmit pulse in the p-th path at the t-th sampling instant, p=0, 1, …, m-1, m represents the total number of paths determined by the multipath parameter, l=0, 1, …, N L -1, each OFDM transmission pulse being obtained by summing N sub-carriers, N representing the sub-carrier of one OFDM transmission pulse determined according to the amount of data to be transmittedEach subcarrier is composed of a different number of pulses, N L Representing the total number of pulses of the L-th OFDM subcarrier, S L [k]Representing data carried by the L-th OFDM pulse on the k-th subcarrier, exp (·) represents an exponential operation based on a natural constant e, j represents an imaginary unit, pi represents a circumference ratio, f k Represents the center frequency of the kth subcarrier, f k Represents the center frequency, T, of the kth subcarrier r Representing the repetition period of OFDM transmission pulse, rect [. Cndot.]Representing a rectangular window function, T represents one OFDM symbol period when a blank guard interval is adopted, and T is equal to or greater than 0 and equal to or less than T,in other cases, the value is 0, and when cyclic prefix is employed, the period of one OFDM transmission pulse is T+T g ，T g Representing the length of the cyclic prefix.
Step 1.2, calculating the length T of the integration window of all the transmission path received signals according to the following L Amplitude of the baseband signal of the superimposed OFDM transmit pulse at each sampling instant:
wherein y is L (T) represents the length T of the integration window of all paths L Amplitude, tau, of baseband signal of the L-th OFDM transmission pulse after being superimposed at t-th sampling moment p Indicating the time delay of the p-th path, rect [. Cndot. ]]Representing a rectangular window function, T L Represents any integer multiple of T, when T is more than or equal to 0 and less than or equal to T L In the time-course of which the first and second contact surfaces,in other cases, the value is 0, τ 0 Representing the time delay of the direct path received signal.
And 2, generating an OFDM radar communication integrated signal without a cyclic prefix.
Step 2.1, according to training pulse parameters commonly confirmed by communication sending and receiving parties, modulating OFDM transmitting pulse signals without cyclic prefix by using the training pulse parameters to obtain training pulses, wherein the training pulses are used for communication frequency offset estimation, channel estimation and assisting radar signal processing; modulating OFDM transmitting pulse signals without cyclic prefix as data pulses according to the communication information to be transmitted, wherein the data pulses are used for communication information transmission and radar signal processing.
Step 2.2, calculating the amplitude of the OFDM radar communication integrated signal without the cyclic prefix at each sampling time according to the following steps:
wherein s (t, eta) 2n ) Representing the amplitude of an OFDM radar communication integrated signal without a cyclic prefix carrying a training pulse at the t-th sampling moment, wherein eta represents a slow time index and eta represents a slow time index 2n Representing the pulse repetition period of the training pulse S L [k 1 ]Representing symbol data carried by the training pulses; s (t, eta) 2n-1 ) Representing the amplitude, eta, of an OFDM radar communication integrated signal carrying a data pulse without a cyclic prefix at the t-th sampling time 2n-1 Representing the pulse repetition period in which the data pulse is located, S L [k 2 ]Representing symbol data carried by the data pulse, Δf represents the subcarrier spacing, Δf=1/T.
And step 3, processing communication information in the echo signals.
Step 3.1, the receiving window length of the OFDM baseband receiving signal is T L At the condition of meeting T L ＜T r Under the condition of T L =nt, n is a positive integer.
And 3.2, performing symbol synchronization on the baseband receiving signal, extracting a clock from the echo signal by adopting a periodic pulse sequence, and synchronizing the clock with the symbol rate of the echo signal so as to determine the positions of the training symbol information and the communication symbol information.
Step 3.3, selecting a sampling interval of 1/T L Sampling the communication symbol information of all subcarriers to obtain a sampled communication signal:
the data carried by each pulse on each subcarrier obtained by sampling the echo signal is calculated according to the following steps:
wherein Y is L' [k]Representing data carried on a kth subcarrier by an L' th pulse corresponding to an L pulse of a transmission signal after sampling an echo signal, the sampling interval being 1/T L ，S' L [i]Representing the amplitude of the transmission data carried by the L-th pulse of the transmission signal on the ith subcarrier after the path superposition.
Calculating f according to the following i ＝f k When the echo signals are sampled, the data carried by each pulse on each subcarrier is obtained:
wherein Y is L' [k]Representing the data carried by the L' th pulse corresponding to the L th pulse of the transmitting signal on the k sub-carrier after the echo signal is sampled.
And 3.4, the sampled communication signal passes through a carrier correction module to obtain carrier frequency deviation CFO (Carrier Frequency Offset), and frequency domain compensation is performed to obtain a frequency domain compensated correction signal.
Step 3.5, correcting the channel at the corresponding time of the data pulse by using the channel response at the equalization time of the training pulse, wherein the channel at the time of the training pulse is consistent with the channel at the time of the data pulse, namely H 2η-1 (f)＝H 2η (f) Wherein H is 2η-1 (f) Indicating the channel response at the instant of the data pulse H 2η (f) Representing training pulse stationsChannel equalization is accomplished by the channel response at time instant.
And 3.6, performing quadrature phase shift keying QPSK (Quadrature Phase Shift Keying) demapping on the correction signal passing through the equalization channel, and then performing channel decoding processing to obtain the original communication information.
And 4, performing frequency compensation on the echo signal carrying the radar information.
And 4.1, constructing a Doppler compensation filter.
The amplitude of the Doppler compensation filter at each sampling instant is calculated as follows:
h 1 (t)＝exp{-j2πf' d t}
wherein h is 1 (t) represents the amplitude of the doppler compensation filter at the t-th sampling instant,v p the relative speed between the detection target and the signal transmitting end is represented, and lambda represents the wavelength of the transmitted signal.
Step 4.2, calculating the amplitude of the echo signal after the Doppler frequency offset compensation of the receiving end at each sampling moment by using the Doppler compensation filter according to the following steps:
wherein u (t, eta) represents the amplitude of the echo signal after Doppler frequency offset compensation at the t sampling moment, eta represents the repetition period of the pulse of the echo signal after Doppler frequency offset compensation, and g m Represents a backscattering coefficient, ε, of 1 a (. Cndot.) represents the azimuth beam function, R m (. Cndot.) represents a distance function, f d Represents Doppler frequency offset, c represents light velocity, f c Representing the center frequency of the transmitted OFDM integrated signal.
And step 5, performing pulse compression processing on the corrected echo signals by adopting a pulse compression algorithm to obtain radar information of the target.
The invention is further described in connection with simulation experiments.
1. And (5) simulating experimental conditions.
The hardware platform of the simulation experiment of the invention: CPU is Intel Core i7-7700, RAM is 8GB.
The software platform of the simulation experiment of the invention: windows 10 operating system and Matlab R2019a.
In order to ensure that the channel response of training pulse estimation and the frequency offset estimation can balance and offset the channel corresponding to the data pulse, the pulse width and the pulse repetition period are not excessively large, the length of one OFDM symbol is 66.67us, and the traditional cyclic prefix-OFDM signal comprises 7 OFDM symbols in one frame of signal, so that the size of the pulse repetition period can ensure that the better channel equalization capability can be maintained around one frame of time. Meanwhile, in order to ensure that the received signal undergoes slow fading, the Doppler spread is ensured to be much smaller than the bandwidth of a sub-channel of the baseband transmitting OFDM signal, and the bandwidth of the sub-channel is generally set to be 10 times of the Doppler spread, so that the integrated system can be ensured to have better communication performance. And according to constraint conditions among the parameters, the simulation parameters of the integrated signal and the target are given. The carrier frequency is 10GHz, the pulse repetition period is 40us, the pulse width is 4us, the signal width is 1024MHz, the basic sampling rate is 1024MHz, the up-sampling multiple is 16, the number of subcarriers is 4096, the mapping mode is QPSK, the detection offset relative to the radar platform speed is 75m/s, the cooperative target relative to the radar platform speed is 75m/s, the detection target height is 2km, the detection target scene center distance is 50km, the radar system signal-to-noise ratio is-5 dB, the communication system signal-to-noise ratio is-5 dB to 15dB, and the multipath signal delay is [ 01 us ].
2. And (5) analyzing simulation content and results.
The simulation experiment of the invention adopts the method provided by the invention and a prior art (cyclic prefix-OFDM method) to generate two integrated waveform signals, and then carries out communication performance analysis and radar performance analysis on the generated two integrated waveform signals. And respectively drawing three-dimensional graphs of fuzzy functions of the QPSK-OFDM signal with the cyclic prefix and the QPSK-OFDM signal without the cyclic prefix by adopting simulation software Matlab R2019a, as shown in figures 2 and 3. And drawing an OFDM signal with a cyclic prefix, an OFDM signal without the cyclic prefix, an OFDM signal with frequency offset compensation, an error rate of the OFDM signal without the frequency offset compensation and a theoretical error rate curve of a Rayleigh channel by adopting simulation software Matlab R2019a, wherein the error rate curve corresponds to an inverted triangle curve, a hexagram curve, a rice-shaped curve, a cross curve and a five-pointed star curve shown in figure 4 respectively.
The x-axis in fig. 2 and 3 represents normalized frequency in hertz, the y-axis represents normalized time in seconds, and the z-axis represents normalized blur function magnitude. Fig. 2 is a fuzzy function diagram of an OFDM signal with cyclic prefix, when the OFDM signal has cyclic prefix, signal correlation will deteriorate, symmetrical side lobes appear in the radar fuzzy function, imaging quality will be affected, and if the influence of false targets is avoided, the maximum time delay needs to be limited within the length of the cyclic prefix, and mapping bandwidth of the synthetic aperture radar SAR (Synthetic Aperture Radar) system is seriously affected.
Fig. 3 is a graph of a vague function of an OFDM signal without cyclic prefix, the vague function being a pin type and having a steep and unique peak, in contrast to a vague function with cyclic prefix, in which energy outside the peak is not distributed as abrupt in the plane of delay and doppler. The steep peak means that a higher distance and speed resolution can be achieved, the unique peak means that there is no ambiguity in distance or speed, and no abrupt energy distribution indicates that there is no strong interference to mask weak targets. These above features are very beneficial for achieving high radar detection performance, reflecting the superior range and speed resolution performance of the signal.
The x-axis in fig. 4 represents the signal-to-noise ratio in db, and the y-axis represents the bit error rate, which is highest and remains unchanged in the case of an increase in signal-to-noise ratio when the transmission signal is a cyclic prefix-free QPSK-OFDM signal, and which is substantially the same as the cyclic prefix-free OFDM signal in terms of the trend and magnitude of the change in signal-to-noise ratio when the transmission signal is a cyclic prefix-free QPSK-OFDM signal. When the echo signal of the receiving end is subjected to frequency offset compensation, the signal error rate is greatly reduced, under the condition of cyclic prefix, the error rate is only slightly reduced along with the increase of the signal to noise ratio, and under the condition of no cyclic prefix, the error rate is in a descending trend along with the increase of the signal to noise ratio, and the lowest curve is the theoretical error rate of the set Rayleigh channel.
As can be seen from fig. 4, under the multipath channel, the error rate of the signal directly demodulated without compensating the frequency offset caused by the speed is very high, and after the frequency offset compensation is performed, the error rate performance is effectively improved. For the OFDM signal with the cyclic prefix, when the length of the cyclic prefix is smaller than the maximum time delay of the multipath, the frequency offset caused by the speed is compensated or the increase of the signal to noise ratio is limited to improve the error rate, because in the case, the cyclic prefix length is insufficient to resist the inter-carrier interference caused by the multipath, all sub-carriers in the integral interval are not orthogonal, so that the corresponding weight cannot be extracted correctly, for the OFDM signal without the cyclic prefix, the integral interval is increased, all carrier periods are received back, the orthogonality among the sub-carriers can be maintained through extracting sampling points, so that the influence caused by the multipath can be eliminated, and the simulation result shows that under the condition of higher signal to noise ratio, the designed QPSK-OFDM signal without the cyclic prefix has very low error rate, and the communication integrated system keeps higher precision.
Claims (4)
1. An integrated signal design method adopting OFDM without cyclic prefix is characterized in that an OFDM radar communication integrated signal is generated on the basis of constructing an OFDM signal without cyclic prefix; the design method comprises the following steps:
step 1, constructing an OFDM signal without a cyclic prefix:
step 1.1, calculating the amplitude of the baseband signal of each OFDM transmission pulse in each transmission path at each sampling time according to the following formula:
wherein s is pL (t) represents the p-th transmission pathThe amplitude of the baseband signal of the L-th OFDM transmit pulse in the path at the t-th sampling instant, p=0, 1, …, m-1, m represents the total number of paths, l=0, 1, …, N L -1, each OFDM transmission pulse is obtained by adding N sub-carriers, N representing the total number of sub-carriers of one OFDM transmission pulse determined according to the amount of data to be transmitted, k representing the sequence number of sub-carriers, N L Representing the total number of pulses of the L-th OFDM subcarrier, S L [k]Representing data carried by the L-th OFDM pulse on the k-th subcarrier, exp (·) represents an exponential operation based on a natural constant e, j represents an imaginary unit, pi represents a circumference ratio, f k Represents the center frequency, T, of the kth subcarrier r Representing the repetition period of OFDM transmission pulse, rect [. Cndot.]Representing a rectangular window function, T represents one OFDM symbol period when a blank guard interval is adopted, and T is equal to or greater than 0 and equal to or less than T,otherwise, the value is 0, =1;
step 1.2, calculating the integration window length T according to the following formula L The amplitude of the baseband signal of the OFDM transmitting pulse after all the transmission path receiving signals are overlapped at each sampling moment:
wherein y is L (T) represents that all paths are superimposed over the integration window length T L Amplitude, tau, of baseband signal of the L-th OFDM transmission pulse after being superimposed at t-th sampling moment p Indicating the time delay of the p-th path, rect [. Cndot. ]]Representing a rectangular window function, T L Represents any integer multiple of T, when T is more than or equal to 0 and less than or equal to T L In the time-course of which the first and second contact surfaces,in other cases, the value is 0, τ 0 Representing the time delay of the direct path received signal;
step 2, generating an OFDM radar communication integrated signal without a cyclic prefix:
step 2.1, modulating OFDM transmitting pulse signals without cyclic prefix by using training pulse parameters commonly confirmed by communication sending and receiving parties to obtain integrated signals carrying training pulse, modulating OFDM transmitting pulse signals without cyclic prefix by using communication information to be transmitted to obtain integrated signals carrying data pulse;
step 2.2, respectively calculating the amplitude of the OFDM radar communication integrated signal without cyclic prefix carrying training pulse or carrying data pulse in each pulse repetition period according to the following formula:
wherein s (t, eta) 2n ) Expressed in the eta 2n In the pulse repetition period, the amplitude of the OFDM radar communication integrated signal without the cyclic prefix carrying the training pulse at the t sampling time, s (t, eta 2n-1 ) Expressed in the eta 2n-1 In the pulse repetition period, the amplitude of the cyclic prefix-free OFDM radar communication integrated signal carrying the data pulse at the t sampling moment, S L [k 1 ]Representing symbol data carried by all training pulses; s is S L [k 2 ]Representing symbol data carried by all data pulses, Δf represents a subcarrier spacing of the OFDM radar communication integrated signal without cyclic prefix, Δf=1/T.
2. An integrated signal processing method adopting the cyclic prefix-free OFDM based on the integrated signal adopting the cyclic prefix-free OFDM design as claimed in claim 1 is characterized in that the communication information and the radar information of the designed transmitting signal in the echo signal of the radar receiving end are respectively processed; the processing method comprises the following steps:
step 1, processing communication information in echo signals:
step 1.1, selecting a sampling interval of 1/T L The communication information carried by the baseband receiving signal sub-carrier after symbol synchronization is sampled at a radar receiving end, and a sampled communication signal is obtained;
step 1.2, correcting the sampled communication signal through a carrier to obtain carrier frequency deviation CFO, and then carrying out frequency domain compensation on the carrier frequency deviation CFO to obtain a corrected signal after the frequency domain compensation;
step 1.3, correcting the channel at the corresponding time of the data pulse by using the channel response at the time of the equalization required by the training pulse, and finishing the channel equalization;
step 1.4, adopting quadrature phase shift keying QPSK algorithm to demap the corrected signal after frequency domain compensation, and then carrying out channel decoding on the demapped signal to obtain original communication data;
step 2, carrying out frequency compensation on echo signals carrying radar information:
step 2.1, calculating the amplitude of the Doppler compensation filter at each sampling moment according to the following formula:
h 1 (t)＝exp{-j2πf' d t}
wherein h is 1 (t) represents the amplitude of the doppler compensation filter at the t-th sampling instant,v p the relative speed between the detection target and the signal transmitting end is represented, and lambda represents the wavelength of the transmitted signal;
step 2.2, calculating the amplitude of the echo signal after the Doppler frequency offset compensation of the receiving end at each sampling moment according to the following steps:
where u (t, eta) represents the amplitude, g, of the echo signal at the t-th sampling instant after Doppler shift compensation at the eta-th pulse repetition period m Represents a backscattering coefficient, ε, of 1 a (. Cndot.) represents the azimuth beam function, R m (. Cndot.) represents a distance function, f d Represents Doppler frequency offset, c represents light velocity, f c Representing a center frequency of the transmitted OFDM integrated signal;
and step 3, performing pulse compression processing on the echo signals after frequency compensation by adopting a pulse compression algorithm to obtain radar information of the detected target.
3. The integrated signal processing method according to claim 2, wherein the specific steps of sampling, at the radar receiving end, the communication information carried by the sub-carriers of the baseband received signal after symbol synchronization in step 1.1 are as follows:
the first step, the communication information carried by each pulse on each subcarrier obtained by sampling the echo signal is calculated according to the following formula:
wherein Y is L' [k]Representing communication information carried by an L' th pulse corresponding to an L-th pulse of a transmission signal on a k-th subcarrier after sampling an echo signal, wherein the sampling interval is 1/T L ，S' L [i]Representing the amplitude of the communication data carried by the L-th pulse of the transmitting signal on the ith subcarrier after path superposition;
second, calculating f according to the following formula i ＝f k When the echo signals are sampled, the communication information carried by each pulse on each subcarrier is obtained:
wherein Y is L' [k]And the communication information carried by the L' pulse corresponding to the L pulse of the transmission signal on the kth subcarrier after the echo signal is sampled is represented.
4. The integrated signal processing method using cyclic prefix-free OFDM according to claim 2, wherein the specific steps of the pulse compression algorithm in step 3 are as follows:
firstly, inputting an echo signal subjected to Doppler frequency offset compensation at a receiving end into a matched filter to obtain an amplitude value of an output signal at each time sampling point, and drawing a time-amplitude diagram corresponding to each sampling time and amplitude value on a time-amplitude plane;
second, retrieving the time-dimensional coordinate value t of the amplitude peak point on the time-amplitude graph 1 From the coordinate transformation formula r=ct 1 And 2, obtaining the distance between the radar detection target, wherein R represents the distance between the radar receiving end and the detection target.
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Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2006191686A (en) * | 2006-03-28 | 2006-07-20 | Victor Co Of Japan Ltd | Orthogonal frequency division multiplex signal receiver and receiving method of orthogonal frequency division multiplex signal |
| CN109061634A (en) * | 2018-10-19 | 2018-12-21 | 西安电子科技大学 | The Design of Signal method of OFDM radar-communication integration Mini-Unmanned Aerial Vehicles |
| CN109085574A (en) * | 2018-10-19 | 2018-12-25 | 西安电子科技大学 | The signal processing method of OFDM radar-communication integration fixed platform system |
| CN109617847A (en) * | 2018-11-26 | 2019-04-12 | 东南大学 | A kind of non-cycle prefix OFDM method of reseptance based on model-driven deep learning |
| CN109688082A (en) * | 2019-01-11 | 2019-04-26 | 电子科技大学 | A kind of Radar-Communication Integrated system based on OFDM carrier wave combined optimization |
| CN112068081A (en) * | 2020-09-10 | 2020-12-11 | 西安电子科技大学 | OFDM frequency agile transmitting signal design method based on cyclic prefix |
| CN113676431A (en) * | 2021-07-08 | 2021-11-19 | 东南大学 | Model-driven MIMO-OFDM receiving method without cyclic prefix |
| CN114844753A (en) * | 2022-04-15 | 2022-08-02 | 中国电子科技集团公司第五十四研究所 | Scene-adaptive conductance integrated signal design method |
| CN114895251A (en) * | 2021-07-31 | 2022-08-12 | 西安电子科技大学 | Multivariable optimization-based OFDM radar communication integrated signal design method |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9178737B2 (en) * | 2012-11-20 | 2015-11-03 | Intel Deutschland Gmbh | Method for generating an OFDM data signal |
| US9444595B2 (en) * | 2014-04-01 | 2016-09-13 | Qualcomm Incorporated | Hybrid waveform design combining OFDM and cyclic prefix based single carrier for millimeter-wave wireless communication |
-
2022
- 2022-08-30 CN CN202211045287.0A patent/CN115442197B/en active Active
Patent Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2006191686A (en) * | 2006-03-28 | 2006-07-20 | Victor Co Of Japan Ltd | Orthogonal frequency division multiplex signal receiver and receiving method of orthogonal frequency division multiplex signal |
| CN109061634A (en) * | 2018-10-19 | 2018-12-21 | 西安电子科技大学 | The Design of Signal method of OFDM radar-communication integration Mini-Unmanned Aerial Vehicles |
| CN109085574A (en) * | 2018-10-19 | 2018-12-25 | 西安电子科技大学 | The signal processing method of OFDM radar-communication integration fixed platform system |
| CN109617847A (en) * | 2018-11-26 | 2019-04-12 | 东南大学 | A kind of non-cycle prefix OFDM method of reseptance based on model-driven deep learning |
| CN109688082A (en) * | 2019-01-11 | 2019-04-26 | 电子科技大学 | A kind of Radar-Communication Integrated system based on OFDM carrier wave combined optimization |
| CN112068081A (en) * | 2020-09-10 | 2020-12-11 | 西安电子科技大学 | OFDM frequency agile transmitting signal design method based on cyclic prefix |
| CN113676431A (en) * | 2021-07-08 | 2021-11-19 | 东南大学 | Model-driven MIMO-OFDM receiving method without cyclic prefix |
| CN114895251A (en) * | 2021-07-31 | 2022-08-12 | 西安电子科技大学 | Multivariable optimization-based OFDM radar communication integrated signal design method |
| CN114844753A (en) * | 2022-04-15 | 2022-08-02 | 中国电子科技集团公司第五十四研究所 | Scene-adaptive conductance integrated signal design method |
Non-Patent Citations (5)
| Title |
|---|
| Gaogao Liu ; Youming Wang ; Wenbo Yang.Radar Sensor and Data Communication System Based on OFDM Without Cyclic Prefix.《IEEE Sensors Journal》.2022,全文. * |
| Xiang Lan ; Min Zhang ; Le-tian Wang.OFDM Chirp Waveform Design Based on Imitating the Time–Frequency Structure of NLFM for Low Correlation Interference in MIMO Radar.《IEEE Geoscience and Remote Sensing Letters》.2021,全文. * |
| 吴振南 ; 姚瑶 ; 张文旭 ; 代雪飞 ; 张发洋.一种OFDM雷达通信共享信号优化设计方法.《制导与引信》.2022,全文. * |
| 基于L频段数字航空通信系统1的F-OFDM波形设计;任子毅;马召;张涛;陈俊杰;;电讯技术;20170628(06);全文 * |
| 梁晶 ; 李鹏. 超宽带雷达信号产生器的设计.《 舰船电子对抗》.2012,全文. * |
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