CN112363152B - Shared waveform design and signal processing method for millimeter wave radar communication system - Google Patents
Shared waveform design and signal processing method for millimeter wave radar communication system Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
- G01S13/06—Systems determining position data of a target
- G01S13/08—Systems for measuring distance only
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
- G01S13/50—Systems of measurement based on relative movement of target
- G01S13/58—Velocity or trajectory determination systems; Sense-of-movement determination systems
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J13/00—Code division multiplex systems
- H04J13/0007—Code type
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- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0202—Channel estimation
- H04L25/0224—Channel estimation using sounding signals
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/003—Arrangements for allocating sub-channels of the transmission path
- H04L5/0048—Allocation of pilot signals, i.e. of signals known to the receiver
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- 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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Abstract
The invention discloses a shared waveform design and signal processing method for a millimeter wave radar communication system, which belongs to the field of millimeter wave radar communication detection, and comprises the following specific processes: firstly, constructing a scene consisting of a radar communication system and single/multiple targets; then, according to the long and short radar signals and the communication frame generated by the actual service, designing a shared waveform and sending out by a radar/communication transmitter; when the shared waveform is transmitted to each target, a communication receiver on the target receives the shared waveform data and demodulates the communication data for communication; meanwhile, after the shared waveform is reflected by a single target, the radar receiving end processes the reflected echo to obtain the distance between the radar and the target and the speed of the target, so that the distance measurement and the speed measurement are realized by using the shared waveform. The invention utilizes the designed shared waveform to process and separate the radar and communication signals, effectively reduces the mutual interference between the signals, improves the detection precision of distance and speed, and achieves the effect of improving the performance of the whole system.
Description
Technical Field
The invention belongs to the field of millimeter wave radar communication detection, is applied to the field of waveform design of radar communication, target ranging and speed measurement, and particularly relates to a shared waveform design and a signal processing method for a millimeter wave radar communication system.
Background
The deep integration of wireless communication and wireless detection systems is one of the main technical features of the Sixth Generation (6G) wireless network. The spectrum resource is an important influencing factor of wireless communication all the time, and along with the gradual decrease of idle frequency bands of low frequency bands (frequency bands below 6 GHz) and the development of phased array antennas and high-speed analog-digital/digital-analog conversion devices, the millimeter wave frequency band becomes an important research object of wireless communication detection.
In order to avoid interference among signals, the conventional radar communication detection fusion method often uses orthogonal resources in different domains, such as time division/frequency division/space division multiplexing and the like, and the method can flexibly design waveforms, but has low resource utilization rate. Although resource utilization may be improved by carrying communication information on the radar waveform or performing object detection using the communication waveform, performance of communication and object detection is not guaranteed.
Compared with a communication detection system in a low frequency band, the millimeter wave communication detection system has the characteristics of large bandwidth, low channel coherence time, narrow beam, high loss, easy shielding and the like, so that specific design is required according to the characteristics of millimeter waves.
The millimeter wave communication and detection research at the present stage is mainly based on two independent systems, so that the waste of spectrum resources can be caused, and mutual interference exists between the millimeter wave communication and detection systems in the signal processing process. Therefore, the millimeter wave communication and detection fusion has important significance, is not only beneficial to reducing interference between the millimeter wave communication and a radar detection system and improving the spectrum utilization rate, but also can realize deep cooperative work of the millimeter wave communication and detection, and has important scientific research significance and application value for the fields of future wireless intelligent networks, unmanned vehicle/unmanned aerial vehicle formation, robot cooperation and the like.
In summary, there is an urgent need to develop a method for processing the waveform design problem and the separation processing problem of communication and radar signals in a radar communication detection fusion system.
Disclosure of Invention
Aiming at the problem that the existing radar communication detection fusion method is limited in function and cannot meet the requirements of waveform design in multiple aspects such as flexibility requirement, high communication speed, high-precision target detection and the like, the invention designs a shared waveform design and signal processing method for a millimeter wave radar communication system, the designed radar sequence has good autocorrelation, radar data and communication data share a preamble code to reduce interference among each other, a communication receiving end can perform channel estimation by utilizing the preamble code, accuracy of communication data transmission is ensured, and short radar signals and long radar signals can be processed simultaneously to improve the effect of ranging and speed measurement, so that the integral performance of the millimeter wave communication detection system is improved.
The shared waveform design and signal processing method for the millimeter wave radar communication system comprises the following specific steps:
step one, constructing a scene consisting of a radar communication system and a target;
the radar communication system includes a radar/communication transmitter and a radar receiver; the targets are single targets or multiple targets, and each target is provided with a communication receiver;
step two, designing a shared waveform according to a short radar signal p (n) and a long radar signal r (n) in a transmitter and a communication frame s (n) generated by actual service;
sharing waveformsThe method comprises the following steps:
where x (n) is a discrete signal sharing a waveform, expressed as:
representing a collection; p is the transmission power, N is the total number of samples in one CPI, n=n c +N p ；N p Is the sampling point number of the short radar signal, N p ＝T p /T s 。T p For short radar signal time period, T s Representing a sampling interval; n (N) c ＝N 1 N 2 Representing the number of samples in a long radar signal, N 1 Is the number of communication frames contained in a CPI, N 2 Is the number of samples per communication frame; g (·) is the baseband pulse shaping function, f c Is the carrier frequency.
The design of the shared waveform is as follows:
firstly, respectively constructing a long radar signal and a short radar signal;
the construction process of the long radar signal is as follows: construction of Length N Using Gray subsequences a and b g Is used as a base sequence, and on the basis of this, a new Gray sequence N is constructed which is much longer than the base sequence c As Long Radar Signals (LRS);
N g is artificially set to a length of N g ＝Q2 J J epsilon {0,1,2, … J, … }, Q is the length of Gray subsequences a and b, N c Is set manually.
The construction process of the short radar signal comprises the following steps: construction of Length N Using Gray subsequences a and b b Is used as a base sequence to construct a new Gray sequence N with a required length s Serving as a Short Radar Signal (SRS);
N b and Ns Is set manually.
Then, gray sequence N of long radar signal c Multiplying the communication frame s (N), starting from the start position of the long radar signal, intercepting N at the same interval 1 A communication preamble CP, the length of which is set manually according to the requirement, N 1 The value of (a) is the same as the number of communication frames s (n).
The subsequent sequence of each communication preamble CP is the product of the data payload in the communication frame s (n) and the long radar signal r (n); the value at the corresponding communication preamble position in the communication frame s (n) is 1.
Step three, the radar/communication transmitter transmits a shared waveform containing communication data and radar data;
step four, when the shared waveform is transmitted to each target, a communication receiver on the target receives the shared waveform data and demodulates the communication data to communicate;
the specific signal processing process is as follows:
step 401, the shared waveform is transmitted to the communication receiving end via the wireless channel, and the baseband signal y is used c (t) represents the received signal, and the baseband signal is sampled and matched filtered to obtain a discrete signal y c (n)：
Is the equivalent channel gain, τ, of the communication channel c Representing the delay of the communication channel, τ c ＝m 1 T s +τ 1 ，m 1 Is an integer, and τ 1 (0＜τ 1 ＜T s ) Is τ c Is a fraction of the number of (a). />Is additive noise after the communication receiving end passes through the matched filter; />Is the estimated starting position of the communication frame; />Is the estimated doppler shift delay.
Step 402, a method of detecting correlation peak is used to process the communication preamble CP, and the maximum peak is the start position of the communication frame.
Step 403, discrete signal y c (n) obtaining a received waveform through time-frequency compensation
wherein ,indicating that the equivalent channel gain is estimated using the preamble of the first communication frame, using the letter +.>And (3) representing. Δf dc Is the frequency offset residual error; n' ∈ {0,1, …, N-N p -1}，/>Is inter-symbol interference->Is additive noise.
Step 404, since the radar signal r (n) is known in advance by the communication receiver, the influence of the channel and the radar signal is removed, and the received communication waveform is:
step 405, demodulating the communication waveform, and starting from the start position of the communication frame, the subsequent demodulation sequence is the communication data.
And fifthly, simultaneously, after the shared waveform is reflected by a single target, the radar receiving end processes the reflected echo to obtain the distance between the radar and the target and the speed of the target, so that the distance measurement and the speed measurement are realized by using the shared waveform.
The specific process is as follows:
step 501, the shared waveform is transmitted via wireless channel to reach radar receiving end, using baseband signal y r (t) represents the received signal, and after sampling and matched filtering, the signal y is obtained r (n)；
wherein ,equivalent channel gain of radar channel, +.>Is additive noise after passing through a matched filter at a radar signal receiving end; τ r Representing the delay of the radar channel, τ r ＝m 2 T s +τ 2 ，m 2 Is an integer τ 2 (0＜τ 2 ＜T s ) Is τ r Is a fraction of the number of (a). f (f) dr Doppler shift caused for the target.
Step 502, receiving signal y by SRS r (n) cross-correlation between the local short radar signal p (n) to achieve coarse time synchronisation;
the cross-correlation output is expressed as:
representing y r Conjugation of (n), m.epsilon. {0 } , 1,…,N - 1}。
Step 503, estimating time delay by detecting peak value of cross correlation output |R (m) |
In particular, the method is shown as follows,
z is an integer set.
Step 504, using the estimated time delaySet length +.>Is a time window of (2);
w is the window length of the time window;
step 505, receiving signal y in the acquired time window r (n) carrying out cross-correlation on the data of the radar receiving end again to obtain accurate time synchronization;
the cross-correlation output is expressed as:
step 506, utilizing cross-correlation outputThe peak value corresponds to +.>Estimating time delay->
Expressed as:
step 507, using accurate time delayTime-synchronized received signal->Estimating a frequency offset;
first, a signal is receivedAnd the long radar signal, the communication frame carries on conjugate multiplication, the calculation formula is as follows:
then, using decimal frequency offset estimation methodDivided into front and rear two containing N d The frequency offset is calculated as follows for the part of the sampling points:
step 508, using the estimated time delayAnd frequency offset->Calculating the distance between the radar and the target and the speed of the target;
the distance calculation formula is:
speed of target
Compared with the prior art, the invention has the following advantages:
the invention designs a frame structure of a shared waveform based on a Gray sequence with good correlation, and compared with a method for processing and separating radar and communication signals by using the shared waveform as mutually independent signals, the invention can effectively reduce the mutual interference between the signals, ensure effective communication, improve the detection precision of distance and speed and achieve the effect of improving the performance of the whole system.
Drawings
FIG. 1 is a flow chart of a shared waveform design and signal processing method for a millimeter wave radar communication system in accordance with the present invention;
FIG. 2 is a diagram of a scenario consisting of a radar communication system and single/multi-target in accordance with the present invention;
FIG. 3 is a schematic diagram of a shared waveform design and signal processing method for a millimeter wave radar communication system in accordance with the present invention;
FIG. 4 is a shared waveform diagram of a radar signal and communication frame design in accordance with the present invention in a transmitter;
FIG. 5 is a schematic diagram of a communication receiver demodulating communication data for communication when a shared waveform is transmitted to a destination in accordance with the present invention;
fig. 6 is a schematic diagram of the radar receiving end of the present invention for processing the reflected echo to achieve ranging and speed measurement.
Detailed Description
The present invention will be further described in detail and in depth with reference to the accompanying drawings, for the purpose of facilitating understanding and practicing the present invention by those of ordinary skill in the art.
The millimeter wave communication and detection research at the present stage is mainly based on two independent systems, so that the waste of spectrum resources can be caused, and mutual interference exists between the millimeter wave communication and detection systems in the signal processing process. The invention designs a radar communication detection shared waveform working in a millimeter wave frequency band, interference in a system is further reduced by researching a separation processing process of radar/communication signals, and the overall working performance of the system is improved; in particular to a shared waveform design and signal processing method for a millimeter wave radar communication system.
As shown in fig. 1, the specific steps are as follows:
step one, constructing a scene consisting of a radar communication system and a target;
the scenario contemplated by the present invention has one single-base radar communication converged (Joint Radar Communication, JRC) transceiver, one communication receiver (Communication Receiver, CR) and a single target (the same applies to multiple targets). The JRC transceiver is implemented by a radar/communication transmitter and a radar receiver, and can operate in full duplex mode. And self-calibration by the transceiver can eliminate self-interference of the transmitter to the Radar Receiver (RR). Further, it is assumed that a single beam can be used for both communication and radar detection.
As shown in fig. 2 and 3, the radar communication detection system sends a shared waveform, the shared waveform includes communication data and radar data, when the shared waveform is transmitted to a single target, a communication receiver on the target receives the waveform and demodulates the communication data, meanwhile, a radar echo reflected by the target is transmitted to the radar communication detection system, and at the moment, the radar receiver receives the detection echo to perform data processing, so as to obtain distance and speed information of the target.
The scene principle of multiple targets is similar to that of a single target, except that a shared waveform is received and reflected by multiple targets simultaneously, while detecting the speed and position of multiple targets.
Step two, designing a shared waveform according to a short radar signal p (n) and a long radar signal r (n) in a transmitter and a communication frame s (n) generated by actual service;
sharing waveformsThe method comprises the following steps:
where x (n) is a discrete signal sharing a waveform, expressed as:
representing a collection; p is the transmission power, N is the total number of samples in one CPI, n=n c +N p ；N p Is the sampling point number of the short radar signal, N p ＝T p /T s 。T p For short radar signal time period, T s Representing a sampling interval; n (N) c ＝N 1 N 2 Representing the number of samples in a long radar signal, N 1 Is the number of communication frames contained in a CPI, N 2 Is the number of samples per communication frame; g (·) is the baseband pulse shaping function, f c Is the carrier frequency.
The design of the shared waveform is as follows:
firstly, respectively constructing a long radar signal and a short radar signal;
the radar signal is distributed over the entire coherent integration time (Coherent Processing Interval, CPI), and the plurality of communication frames is distributed over one CPI. In the invention, the radar signal is composed of Gray complementary sequences with good autocorrelation, wherein a and b are Gray complementary sequences with length Q, a|b represents a cascade of a and b sequences, a|b and a|(-b) are Gray complementary sequences with length 2Q.
The construction process of the long radar signal is as follows: construction of Length N Using Gray subsequences a and b g Is used as a base sequence, and on the basis of this, a new Gray sequence N is constructed which is much longer than the base sequence c As long radar signals (Long Radar Signal, LRS); from N c Selected length of Q2 j Is used as a communication preamble CP (Communication Preamble); the length obtained by the construction is Q2 j Also belonging to the Gray sequence.
N g Is artificially set to a length of N g ＝Q2 J ，J∈{0,1,2,…j,…}，N c Is set manually.
The construction process of the short radar signal comprises the following steps: construction of Length N Using Gray subsequences a and b b Is used as a base sequence to construct a new Gray sequence N with a required length s As short radar signals (Short Radar Signal, SRS);
N b and Ns Is set manually.
Then, gray sequence N of long radar signal c Multiplying the communication frame s (N), starting from the start position of the long radar signal, intercepting N at the same interval 1 Communication preamble CP, N 1 The value of (a) is the same as the number of communication frames s (n).
The subsequent sequence of each preamble CP is the product of the data payload in the communication frame s (n) and the long radar signal r (n);
T c for duration of one communication frame, η c For the proportion of communication preamble, eta c T c For the time of the communication preamble, the length of the communication preamble is N 3 ＝ηT c /T s . Thus, the value at the corresponding communication preamble position in the communication frame s (n) is 1, where n=k' +ln 2 ，k′∈{0,1,…,N 3 -1, l represents the first communication frame in CPI, and l ε {0,1, …, N 1 -1}。
Step three, the radar/communication transmitter transmits a shared waveform containing communication data and radar data;
the discrete form x (n) of the transmission signal is composed of two parts, communication data s (n) and radar data, the radar signal being divided into a short radar signal p (n) and a long radar signal r (n), a part of the long radar signal being used as a communication preamble for channel estimation.
The shared waveform frame structure is shown in fig. 4, that is, the short radar signal p (n) is located in front of the entire long radar signal r (n), the communication preamble CP is a plurality of sequences of the long radar signal which are intercepted at the same intervals from the start position, and the communication data is multiplied by the long radar signal to form a shared waveform together with the short radar signal.
Step four, when the shared waveform is transmitted to each target, a communication receiver on the target receives the shared waveform data and demodulates the communication data to communicate;
as shown in fig. 5, there is no mutual interference between the communication and radar signals in the shared waveform portion, so SRS and CP can be used for time-frequency synchronization and channel estimation of signals. The communication signal receiver may then reconstruct the received radar signal using the known radar sequence and the estimated channel response and extract the communication signal.
The specific signal processing process is as follows:
step 401, the shared waveform is transmitted to the communication receiving end via the wireless channel, and the baseband signal y is used c (t) represents the received signal, and the baseband signal is sampled and matched filtered to obtain a discrete signal y c (n)：
Is the equivalent channel gain, τ, of the communication channel c Representing the delay of the communication channel, τ c ＝m 1 T s +τ 1 ，m 1 Is an integer, and τ 1 (0＜τ 1 ＜T s ) Is τ c Is a fraction of the number of (a). />Is additive noise after the communication receiving end passes through the matched filter; />Is the estimated starting position of the communication frame; />Is the estimated doppler shift delay.
Step 402, a method of detecting correlation peak is used to process the communication preamble CP, and the maximum peak is the start position of the communication frame.
In the invention, a short radar signal and the starting position of a communication frame are detected by using a correlation method based on SRS and CP. Assume that and />Is to estimate the start position and Doppler shift delay of the communication frame, wherein +.>Needs to meet->Otherwise the communication data cannot be correctly recovered.
Step 403, discrete signal y c (n) obtaining a received waveform through time-frequency compensation
Thus, the time-frequency compensated received signal can be expressed as,
wherein the equivalent channel gain is estimated using the preamble of the first communication frameWith letters->And (3) representing. Δf dc Is the frequency offset residual error; n' ∈ {0,1, …, N-N p -1}，/>Is inter-symbol interference->Is additive noise.
Step 404, since the radar signal r (n) is known in advance by the communication receiver, the influence of the channel and the radar signal is removed, and the received communication waveform is:
in the above equation (5), the channel estimation adopts a least square estimation method, and other methods (such as a least mean square error method) can also be adopted to improve the detection performance.
Step 405, demodulating the communication waveform, and starting from the start position of the communication frame, the subsequent demodulation sequence is the communication data.
And fifthly, simultaneously, after the shared waveform is reflected by a single target, the radar receiving end processes the reflected echo to obtain the distance between the radar and the target and the speed of the target, so that the distance measurement and the speed measurement are realized by using the shared waveform.
For radar signals, the shared waveform is processed in two stages. First, coarse time synchronization is performed using SRS. Then, the LRS signal is extracted from the received signal for accurate distance and velocity estimation. In the second step, the communication data needs to be removed from the received signal to reduce the influence of the communication data on the radar signal processing, and the processing process is shown in fig. 6, and the specific process is as follows:
step 501, the shared waveform is transmitted via wireless channel to reach radar receiving end, using baseband signal y r (t) represents the received signal, and after sampling and matched filtering, the signal y is obtained r (n)；
wherein ,equivalent channel gain of radar channel, +.>Is additive noise after passing through a matched filter at a radar signal receiving end; τ r Representing the delay of the radar channel, τ r ＝m 2 T s +τ 2 ，m 2 Is an integer τ 2 (0＜τ 2 ＜T s ) Is τ r Is a fraction of the number of (a). f (f) dr Doppler shift caused for the target.
Step 502, receiving signal y by SRS r (n) cross-correlation between the local short radar signal p (n) to achieve coarse time synchronisation;
the cross-correlation output is expressed as:
representing y r Conjugation of (N), m.epsilon.0, 1, …, N-1.
Step 503, estimating time delay by detecting peak value of cross correlation output |R (m) |
In particular, the method is shown as follows,
z is an integer set.
Step 504, using the estimated time delaySet length +.>Is a time window of (2);
w is the window length of the time window;the accuracy of τ 2 Length N of SRS p And the effect of signal-to-noise ratio, using an oversampling approach to reduce τ in the delay 2 Is a function of (a) and (b). To improve communication efficiency, N is generally p ＜＜N c Therefore, when the signal-to-noise ratio is low, the length N of SRS p Limiting the accuracy of the estimation and also requiring the use of LRS to achieve accurate distance estimation.
Step 505, receiving signal y in the acquired time window r (n) carrying out cross-correlation on the data of the radar receiving end again to obtain accurate time synchronization;
in order to reduce the computational complexity, a length is set asUsing estimated +.>Cross-correlating with data known at RR, the cross-correlation output being expressed as:
step 506, utilizing cross-correlation outputThe peak value corresponds to +.>Estimating time delay->
Expressed as:
step 507, using accurate time delayTime-synchronized received signal->Estimating a frequency offset;
first, a signal is receivedAnd the long radar signal, the communication frame carries on conjugate multiplication, the calculation formula is as follows:
then, using decimal frequency offset estimation methodDivided into front and rear two containing N d The frequency offset is calculated as follows for the part of the sampling points:
step 508, using the estimated time delayAnd frequency offset->Calculating the distance between the radar and the targetAnd the speed of the target;
the distance calculation formula is:
speed of target
Claims (3)
1. A shared waveform design and signal processing method for millimeter wave radar communication system is characterized by comprising the following specific steps:
step one, constructing a scene consisting of a radar communication system and a target;
the radar communication system includes a radar/communication transmitter and a radar receiver; the targets are single targets or multiple targets, and each target is provided with a communication receiver;
step two, designing a shared waveform according to a short radar signal p (n) and a long radar signal r (n) in a transmitter and a communication frame s (n) generated by actual service;
sharing waveformsThe method comprises the following steps:
where x (n) is a discrete signal sharing a waveform, expressed as:
representing a collection; p is the transmission power and N is the total sample in a CPIPoints, n=n c +N p ；N p Is the sampling point number of the short radar signal, N p ＝T p /T s ；T p For short radar signal time period, T s Representing a sampling interval; n (N) c ＝N 1 N 2 Representing the number of samples in a long radar signal, N 1 Is the number of communication frames contained in a CPI, N 2 Is the number of samples per communication frame; g (·) is the baseband pulse shaping function, f c Is the carrier frequency;
the design of the shared waveform is as follows:
firstly, respectively constructing a long radar signal and a short radar signal;
the construction process of the long radar signal is as follows: construction of Length N Using Gray subsequences a and b g Is used as a base sequence, and on the basis of this, a new Gray sequence N is constructed which is much longer than the base sequence c As Long Radar Signals (LRS);
N g is artificially set to a length of N g ＝Q2 J J epsilon {0,1,2, … J, … }, Q is the length of Gray subsequences a and b, N c The length of (2) is set manually;
the construction process of the short radar signal comprises the following steps: construction of Length N Using Gray subsequences a and b b Is used as a base sequence to construct a new Gray sequence N with a required length s Serving as a Short Radar Signal (SRS);
N b and Ns The length of (2) is set manually;
then, gray sequence N of long radar signal c Multiplying the communication frame s (N), starting from the start position of the long radar signal, intercepting N at the same interval 1 A communication preamble CP, the length of which is set manually according to the requirement, N 1 The value of (a) is the same as the number of the communication frames s (n);
the subsequent sequence of each communication preamble CP is the product of the data payload in the communication frame s (n) and the long radar signal r (n); the value at the corresponding communication preamble position in the communication frame s (n) is 1;
step three, the radar/communication transmitter transmits a shared waveform containing communication data and radar data;
step four, when the shared waveform is transmitted to each target, a communication receiver on the target receives the shared waveform data and demodulates the communication data to communicate;
and fifthly, simultaneously, after the shared waveform is reflected by a single target, the radar receiving end processes the reflected echo to obtain the distance between the radar and the target and the speed of the target, so that the distance measurement and the speed measurement are realized by using the shared waveform.
2. The shared waveform design and signal processing method for millimeter wave radar communication system of claim 1, wherein the specific process of demodulating communication data by the communication receiver of the object in the fourth step is as follows:
step 401, the shared waveform is transmitted to the communication receiving end via the wireless channel, and the baseband signal y is used c (t) represents the received signal, and the baseband signal is sampled and matched filtered to obtain a discrete signal y c (n)：
Is the equivalent channel gain, τ, of the communication channel c Representing the delay of the communication channel, τ c ＝m 1 T s +τ 1 ，m 1 Is an integer, and τ 1 (0＜τ 1 ＜T s ) Is τ c Is a fraction of the fraction of (2); />Is additive noise after the communication receiving end passes through the matched filter; />Is the estimated start position of the communication frame；/>Is the estimated doppler shift delay;
step 402, processing a communication preamble CP by using a method of detecting a correlation peak, wherein the maximum peak is the starting position of a communication frame;
step 403, discrete signal y c (n) obtaining a received waveform through time-frequency compensation
wherein ,indicating that the equivalent channel gain is estimated using the preamble of the first communication frame, using the letter +.>A representation; Δf dc Is the frequency offset residual error; n' ∈ {0,1, …, N-N p -1}，/>Is inter-symbol interference->Is additive noise;
step 404, since the radar signal r (n) is known in advance by the communication receiver, the influence of the channel and the radar signal is removed, and the received communication waveform is:
step 405, demodulating the communication waveform, and starting from the start position of the communication frame, the subsequent demodulation sequence is the communication data.
3. The shared waveform design and signal processing method for millimeter wave radar communication system of claim 1, wherein the specific process of ranging and measuring speed by using the shared waveform in the fifth step is:
step 501, the shared waveform is transmitted via wireless channel to reach radar receiving end, using baseband signal y r (t) represents the received signal, and after sampling and matched filtering, the signal y is obtained r (n)；
wherein ,equivalent channel gain of radar channel, +.>Is additive noise after passing through a matched filter at a radar signal receiving end; τ r Representing the delay of the radar channel, τ r ＝m 2 T s +τ 2 ，m 2 Is an integer τ 2 (0＜τ 2 ＜T s ) Is τ r Is a fraction of the fraction of (2); f (f) dr Doppler shift for a target;
step 502, receiving signal y by SRS r (n) cross-correlation between the local short radar signal p (n) to achieve coarse time synchronisation;
the cross-correlation output is expressed as:
representing y r Conjugation of (N), m ε {0,1, …, N-1};
step 503, estimating time delay by detecting peak value of cross correlation output |R (m) |
In particular, the method is shown as follows,
z is a set of integers;
step 504, using the estimated time delaySet length +.>Is a time window of (2);
w is the window length of the time window;
step 505, performing cross correlation again on the received signal yr (n) and the data of the radar receiving end in the acquired time window to obtain accurate time synchronization;
the cross-correlation output is expressed as:
step 506, utilizing cross-correlation outputThe peak value corresponds to +.>Estimating time delay->
Expressed as:
step 507, using accurate time delayTime-synchronized received signal->Estimating a frequency offset;
first, a signal is receivedAnd the long radar signal, the communication frame carries on conjugate multiplication, the calculation formula is as follows:
then, using decimal frequency offset estimation methodThe method is divided into a front part and a rear part which contain Nd sampling points, and frequency offset is calculated as follows:
step 508, using the estimated time delayAnd frequency offset->Calculating the distance between the radar and the target and the speed of the target;
the distance calculation formula is:
speed of target
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