CN114944974A - Frequency offset estimation method and device and electronic equipment - Google Patents
Frequency offset estimation method and device and electronic equipment Download PDFInfo
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Abstract
The application discloses a frequency offset estimation method, a frequency offset estimation device and electronic equipment. The frequency offset estimation method comprises the following steps: acquiring a reference signal through a DTMB signal of an external radiation source, and acquiring a reference signal with synchronous time domain according to the time domain correlation of the reference signal and a standard PN sequence, wherein the reference signal comprises a multi-frame DTMB signal; according to the frequency offset rough estimation of the time domain synchronous reference signal, carrying out frequency offset compensation on each frame of DTMB signal of the reference signal, and demodulating each frame of DTMB signal after frequency offset compensation to obtain a data body of each frame of DTMB signal; framing the data volume obtained by demodulation in a DTMB signal format to obtain a reconstructed reference signal; and obtaining the fine frequency offset estimation of the reference signal according to the time domain correlation of the reference signal and the reconstructed reference signal.
Description
Technical Field
The present application relates to the field of communication signal processing technologies, and in particular, to a frequency offset estimation method and apparatus, and an electronic device.
Background
The external radiation source radar utilizes a third-party non-cooperative illumination source to realize the detection of the target in the coverage area. External radiation source radars have many advantages over conventional radars, such as not requiring bulky transmitters, reducing costs; the working mode of not emitting electromagnetic waves has better anti-interference and hiding capability; the external radiation source radar is essentially a bistatic radar and has a certain anti-stealth capability on a target; the third party radiation source is generally a satellite or television signal, the relative position is generally high, and the available area is wide.
Digital Television Terrestrial Broadcasting (DTMB, abbreviated as DTMB) signals generally cover a large area in a city, and are ideal third-party radiation sources. The emitted energy of the DTMB signal is large, the power is stable, the bandwidth of the DTMB signal is 7.56MHz, and good distance resolution is guaranteed due to the large bandwidth. In an external radiation source system, a reference signal is generally needed for suppressing direct waves and multipath noise on one hand; and on the other hand, the method is used for performing time-frequency two-dimensional correlation calculation with the echo signal.
In order to ensure that the reference signal is not affected by multipath effect, the reference signal is generally obtained by a demodulation reconstruction method, however, the reference signal and the echo signal have a certain degree of frequency offset under the reconstruction condition because the receiver or the transmitter has local oscillation offset and the like. In general, in the related art, the frequency offset is estimated by using autocorrelation of a Pseudo-noise Sequence (abbreviated as PN Sequence) and a cyclic structure characteristic of a frame header, but since the PN Sequence occupies only a small portion of a signal frame, an error is large when the frequency offset is estimated by using the sequences.
Disclosure of Invention
The embodiment of the application provides a frequency offset estimation method, a frequency offset estimation device and electronic equipment, so as to improve the frequency offset estimation precision of a reference signal.
The embodiment of the application adopts the following technical scheme:
in a first aspect, an embodiment of the present application provides a frequency offset estimation method, including:
acquiring a reference signal through a DTMB signal of an external radiation source, and acquiring a reference signal with synchronous time domain according to the time domain correlation of the reference signal and a standard PN sequence, wherein the reference signal comprises a multi-frame DTMB signal;
according to the frequency offset rough estimation of the time domain synchronous reference signal, carrying out frequency offset compensation on each frame of DTMB signal of the reference signal, and demodulating each frame of DTMB signal after frequency offset compensation to obtain a data body of each frame of DTMB signal;
framing the data volume obtained by demodulation in a DTMB signal format to obtain a reconstructed reference signal;
and obtaining the fine frequency offset estimation of the reference signal according to the time domain correlation of the reference signal and the reconstructed reference signal.
Optionally, demodulating each frame of DTMB signal after the frequency offset compensation to obtain a data volume of each frame of DTMB signal, including:
performing channel estimation and equalization on each frame of DTMB signals after frequency offset compensation to obtain a constellation mapping chart of a frame body part of each frame of DTMB signals;
and performing constellation judgment on the constellation mapping chart to obtain the data constellation points of the data volume.
Optionally, performing channel estimation and equalization on each frame of DTMB signal after frequency offset compensation, including:
performing time domain least square channel estimation on each frame of DTMB signals after frequency offset compensation according to the standard PN sequence to obtain channel impact response;
and performing channel equalization on the frame body part of each frame of the DTMB signal by using the channel impact response to obtain a constellation mapping chart of the frame body part of each frame of the DTMB signal.
Optionally, the DTMB signal format includes a frame header part and a frame body part, where the frame body part includes system data and a data body; framing the data volume obtained by demodulation in a DTMB signal format to obtain a reconstructed reference signal, wherein the framing comprises:
the system data and the data body of the frame body part are connected in series in a frequency domain, and the frame body part after the connection is subjected to Fourier transform to obtain a time domain frame body part after the connection is carried out;
and inserting a frame header part consisting of a standard PN sequence in front of a frame body of the time domain frame body part after the serial connection to obtain each frame of the reconstructed DTMB signal.
Optionally, obtaining a frequency offset fine estimate of the reference signal according to the time domain correlation between the reference signal and the reconstructed reference signal, where the obtaining includes:
determining a current frame DTMB signal and an adjacent frame DTMB signal of the reference signal and determining a current frame DTMB signal and an adjacent frame DTMB signal of the reconstructed reference signal according to the one-to-one correspondence relationship between the reference signal and the frame numbers of the reconstructed reference signal;
and obtaining the frequency offset fine estimation of the current frame DTMB signal of the reference signal according to the current frame DTMB signal and the adjacent frame DTMB signal of the reference signal and the current frame DTMB signal and the adjacent frame DTMB signal of the reconstructed reference signal.
Optionally, obtaining a frequency offset fine estimation of the current frame DTMB signal of the reference signal according to the current frame DTMB signal and the adjacent frame DTMB signal of the reference signal and the current frame DTMB signal and the adjacent frame DTMB signal of the reconstructed reference signal, where the frequency offset fine estimation includes:
according to the formula
Obtaining a frequency offset fine estimation of an ith frame DTMB signal of the reference signal;
wherein x (N) is the reference signal, y (N) is the reconstructed reference signal, N is the number of frequency points of the reference signal, i is the frame number, N is the length of the DTMB signal, T s Is a sampling interval, f i And finely estimating the frequency offset of the DTMB signal of the ith frame.
Optionally, the coarse frequency offset estimation of the time domain synchronized reference signal is obtained by:
according to the formula
Obtaining a frequency offset rough estimation of an ith frame DTMB signal of the reference signal;
wherein x (N) is based on reference signal, N is frequency point of reference signal, i is frame number, N is length of DTMB signal, M is length of standard PN sequence, and T is s Is a sampling interval, f i ' is the coarse frequency offset estimate of the i-th frame DTMB signal.
Optionally, performing frequency offset compensation on each frame of the DTMB signal of the reference signal, including:
according to the formula exp (2 π nf) i 'T s ) And performing frequency offset compensation on the DTMB signal of the ith frame.
In a second aspect, an embodiment of the present application further provides a frequency offset estimation apparatus, including:
the device comprises a preprocessing unit, a reference signal acquisition unit and a reference signal processing unit, wherein the preprocessing unit is used for acquiring the reference signal through the DTMB signal of an external radiation source and acquiring a time-domain synchronous reference signal according to the time-domain correlation of the reference signal and a standard PN sequence, and the reference signal comprises a multi-frame DTMB signal;
the demodulation unit is used for carrying out frequency offset compensation on each frame of DTMB signal of the reference signal according to the frequency offset rough estimation of the reference signal of the time domain synchronization and demodulating each frame of DTMB signal after the frequency offset compensation to obtain a data body of each frame of DTMB signal;
the reconstruction unit is used for framing the data volume obtained by demodulation in a DTMB signal format to obtain a reconstructed reference signal;
and the estimation unit is used for obtaining the frequency offset fine estimation of the reference signal according to the time domain correlation between the reference signal and the reconstructed reference signal.
In a third aspect, an embodiment of the present application further provides an electronic device, including:
a processor; and
a memory arranged to store computer executable instructions that, when executed, cause the processor to perform the aforementioned frequency offset estimation method.
In a fourth aspect, embodiments of the present application further provide a computer-readable storage medium storing one or more programs, which when executed by an electronic device including multiple application programs, cause the electronic device to perform the foregoing frequency offset estimation method.
The embodiment of the application adopts at least one technical scheme which can achieve the following beneficial effects: the frequency offset estimation method, the frequency offset estimation device, the electronic device and the computer-readable storage medium of the embodiments of the application obtain a reference signal through a DTMB signal, obtain a coarse frequency offset estimation of each DTMB signal in the reference signal according to an autocorrelation characteristic of each DTMB signal in the reference signal and a standard PN sequence, perform frequency offset compensation on a corresponding DTMB signal frame in the reference signal by using the coarse frequency offset estimation, ensure that the compensated DTMB signal frame can be demodulated, perform framing processing of the DTMB signal on a demodulated data body based on a signal format of the DTMB to obtain a reconstructed reference signal, and obtain a fine frequency offset estimation of each frame of the DTMB signal in the reference signal by using a time domain correlation characteristic between the reconstructed reference signal and the reference signal.
According to the method and the device, the frequency offset with higher precision can be estimated only by demodulating and reconstructing the received reference signal, the problem of large frequency offset estimation error in the existing scheme is solved, and the method is simple and easy to implement and has higher practicability.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the application and not to limit the application. In the drawings:
fig. 1 is a schematic flow chart of a frequency offset estimation method in an embodiment of the present application;
fig. 2 is a flow chart of frequency offset estimation of a DTMB external radiation source radar reference signal in an embodiment of the present application;
fig. 3 is a schematic flow chart illustrating a process of converting a DTMB signal into a digital baseband signal according to an embodiment of the present application;
fig. 4 is a diagram illustrating a DTMB signal format according to an embodiment of the present application;
fig. 5 is a schematic diagram illustrating a correspondence between frame numbers of a reference signal and a reconstructed reference signal in an embodiment of the present application;
fig. 6 is a schematic structural diagram of a frequency offset estimation apparatus in an embodiment of the present application;
fig. 7 is a schematic structural diagram of an electronic device in an embodiment of the present application.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the technical solutions of the present application will be described in detail and completely with reference to the following specific embodiments of the present application and the accompanying drawings. It should be apparent that the described embodiments are only some of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
For the above, the DTMB radiation source is an ideal external radiation source, and when reconstructing the reference signal through the DTMB signal, the prior art estimates the frequency offset of the reference signal by using the autocorrelation of the frame header part of the standard PN sequence and the DTMB signal, but because the standard PN sequence is only a small part of the frame of the DTMB signal, the frequency offset estimation error obtained by using the part of the sequence is large, which causes the subsequent direct wave, multipath clutter suppression and time-frequency two-dimensional correlation result to be deteriorated.
In order to solve the above problem, in the embodiments of the present application, a local standard PN sequence is generated according to a broadcast standard of the DTMB by using a reference signal received through a direct wave channel, and the reference signal and the PN sequence are subjected to time domain correlation to obtain an initial position of a signal frame; further performing frequency offset rough estimation on the reference signal according to the characteristic that each signal frame head is the same, and performing frequency offset compensation on the DTMB signal by using the frequency offset rough estimation so as to demodulate the DTMB signal subjected to frequency offset compensation; and reconstructing the demodulated data frame according to the signal format of the DTMB, and finely estimating the frequency offset according to the time domain correlation between the reconstructed reference signal and the original reference signal.
The technical solutions provided by the embodiments of the present application are described in detail below with reference to the accompanying drawings.
An embodiment of the present application provides a frequency offset estimation method, and as shown in fig. 1, provides a schematic flow chart of the frequency offset estimation method in the embodiment of the present application, where the method at least includes the following steps S110 to S140:
step S110, obtaining a reference signal through the DTMB signal of the external radiation source, and obtaining a time-domain synchronous reference signal according to the time-domain correlation between the reference signal and the standard PN sequence, wherein the reference signal comprises a plurality of DTMB signals.
The standard PN sequence refers to a PN sequence of a multi-core DTMB broadcasting standard, that is, the standard PN sequence of the embodiment of the present application is the same as a signal sequence of a frame header portion of a DTMB signal, so as to implement time domain synchronization of each frame of the DTMB signal in a reference signal by using autocorrelation of the standard PN required by the standard PN and the frame header portion of the DTMB signal.
Step S120, according to the rough frequency offset estimation of the reference signal of the time domain synchronization, performing frequency offset compensation on each frame of DTMB signal of the reference signal, and demodulating each frame of DTMB signal after the frequency offset compensation to obtain a data volume of each frame of DTMB signal.
In the prior art, the coarse frequency offset estimation obtained according to the reference signal of time domain synchronization is used as the final frequency offset estimation result of the reference signal, and because the whole frequency offset estimation process only uses the signal sequence of the frame head part of the DTMB, the frequency offset estimation error of the reference signal related to the DTMB type in the prior art is larger.
Different from the prior art, in the embodiment, the frequency offset coarse estimation is used to perform frequency offset compensation on each frame of DTMB signal in the reference signal, so that the DTMB signal after frequency offset compensation can be demodulated, for example, a data body in a signal frame is demodulated from the DTMB signal by using a channel equalization technology and a constellation judgment technology. Therefore, the demodulated data volume can be framed according to the DTMB signal format, each frame of DTMB signal in the reference signal is subjected to signal reconstruction, the reconstructed complete DTMB signal is used for carrying out fine frequency offset estimation on the original reference signal, and the frequency offset estimation precision is improved.
Compared with the prior art that only the frame header part is used for estimating the frequency offset, the frequency offset is estimated by using the complete DTMB signal, and the accuracy of frequency offset estimation can be remarkably improved.
Step S130, framing the data volume obtained by demodulation in the DTMB signal format to obtain a reconstructed reference signal.
Step S140, obtaining a frequency offset fine estimation of the reference signal according to the time domain correlation of the reference signal and the reconstructed reference signal.
As can be known from the frequency offset estimation method shown in fig. 1, in the embodiment of the present application, a reference signal is obtained through a DTMB signal, coarse frequency offset estimation of each frame of the DTMB signal in the reference signal is obtained according to an autocorrelation characteristic of each frame of the DTMB signal in the reference signal and a standard PN sequence, frequency offset compensation is performed on a corresponding DTMB signal frame in the reference signal by using the coarse frequency offset estimation, it is ensured that the compensated DTMB signal frame can be demodulated, framing processing of the DTMB signal is performed on a demodulated data body based on a signal format of the DTMB, a reconstructed reference signal is obtained, and fine frequency offset estimation of each frame of the DTMB signal in the reference signal is obtained by using a time domain correlation characteristic between the reconstructed reference signal and the reference signal.
According to the frequency offset estimation method of the DTMB external radiation source radar reference signal, the frequency offset with higher precision can be estimated only by demodulating and reconstructing the received reference signal, the problem that the frequency offset estimation error is large in the existing scheme is solved, and the method is simple and easy to implement and has higher practicability.
As shown in fig. 2, the frequency offset estimation process in the embodiment of the present application includes: the four processes of S1 preprocessing, S2 signal demodulation, S3 signal reconstruction and S4 frequency offset estimation are explained in detail by the following embodiments.
S1 pretreatment:
in the external radiation source radar, an antenna of a direct wave channel is aligned with a DTMB transmission tower, an irradiation signal of the DTMB transmission tower is received, and a radio receiver of a communication system samples a radio signal according to a preset sampling frequency and a central frequency, for example, the DTMB signal is sampled according to a preset sampling frequency of 30.24 MHz; the radio frequency signal is converted into an intermediate frequency signal by the receiver, and a digital baseband signal x of the reference signal is obtained according to the intermediate frequency signal, wherein the sampling frequency of the digital baseband signal x is 30.24MHz, for example, and the center frequency is zero.
As shown in fig. 3, the process of obtaining a reference signal by a receiver, that is, a reference signal formed by multi-frame DTMB digital baseband signals in this embodiment, includes:
the method comprises the steps of converting radio signals received by a radio signal receiver at a direct wave channel in real time into electric signals, amplifying the processable electric signals through a low noise amplifier, carrying out frequency mixing filtering on the amplified electric signals through an analog down-conversion module to obtain analog intermediate frequency signals, carrying out high-speed sampling on the analog intermediate frequency signals through an analog-to-digital conversion module to obtain digital intermediate frequency signals, and carrying out frequency mixing filtering on the digital intermediate frequency signals through a digital down-conversion module to obtain DTMB digital baseband signals.
After obtaining the DTMB digital baseband signal, filtering the DTMB digital baseband signal according to a filter adopted by a broadcast signal standard of the DTMB, for example, filtering the DTMB digital baseband signal by using a root-raised cosine filter with a roll-off coefficient of 0.05, and extracting the filtered DTMB digital baseband signal to make a sampling rate meet a demodulation sampling rate of the standard, for example, performing 4 times of down-sampling on the filtered DTMB digital baseband signal to make a sampling rate of the filtered DTMB digital baseband signal change to a standard rate of 7.56 MHz.
And generating a local standard PN sequence according to the broadcasting standard of the DTMB, wherein the standard PN sequence refers to a PN sequence which is the same as the sequence of the frame header part of the DTMB signal. The acquired reference signal comprises a plurality of DTMB signals, and the signal sequence of the frame header part of each DTMB signal is the same as the standard PN sequence, so that the part of the signal has good autocorrelation characteristics, and the time domain synchronization of each DTMB signal in the reference signal can be realized according to the time domain autocorrelation characteristics of the part of the signal. In the process of autocorrelation calculation, time domain sliding correlation peak observation is carried out through a standard PN sequence and a reference signal, and the frame head position of each DTMB signal can be determined according to the correlation peak value.
After the frame header position of each frame of DTMB signal in the reference signal is determined, the frame header parts of two adjacent frame signals may be utilized to perform coarse frequency offset estimation, that is, the frequency offset of the current frame of DTMB signal is determined according to the frame header part of the current frame of DTMB signal and the frame header part of the previous frame of DTMB signal, for example, the coarse frequency offset estimation of the ith frame of DTMB signal of the reference signal is obtained according to the following formula (1):
in formula (1), x (N) is the frequency point according to which is the reference signal, N is the reference signal, i is the frame number, N is the length of the DTMB signal, M is the length of the standard PN sequence, T s Is a sampling interval, f i ' is a coarse frequency offset estimation of the DTMB signal of the i-th frame]And the arg () is an argument operator.
After obtaining the frequency offset rough estimation of each frame DTMB signal of the reference signal, the method can be based on exp (2 π nf) i 'T s ) And performing frequency offset compensation on the ith frame of DTMB signal, wherein each frame of DTMB signal after frequency offset compensation can be demodulated.
S2 signal demodulation:
for the purpose of describing the demodulation and reconstruction process of the DTMB signal according to the embodiment of the present application, the frame format characteristic of the DTMB signal is described with reference to fig. 4.
As shown in fig. 4, each frame of DTMB signal includes a frame header part and a frame body part, where the frame header part is composed of a standard PN sequence and is divided into three modes, i.e., 420, 595 and 945, according to the length of the standard PN sequence; the frame body part includes system data and a data body. Each frame of the DTMB signal includes 4200 symbols, the frame body portion includes 3780 symbols of data, the system data includes 36 symbols, the remaining 3744 symbols are data bodies, and the system data generally includes mode symbols such as frame body mode indication symbols, modulation and code rate.
In an embodiment of the present application, for the DTMB signal with the frame format characteristic, the DTMB signal per frame after frequency offset compensation is demodulated through the following steps:
performing channel estimation and equalization on each frame of DTMB signals after frequency offset compensation to obtain a constellation mapping chart of a frame body part of each frame of DTMB signals; for example, performing time domain least square channel estimation on each frame of DTMB signals after frequency offset compensation according to a standard PN sequence to obtain a channel impact response H, and performing Fourier transform on the channel impact response H to obtain a frequency domain channel response H; in order to eliminate the influence of the frame header part on the signal equalization process, optionally, the frame header part in the DTMB signal is eliminated, and the channel response H is used to perform channel equalization on the frame body part of each frame of the DTMB signal, so as to obtain the constellation mapping diagram of the frame body part of each frame of the DTMB signal.
Generally, the constellation decision is performed on the constellation mapping diagram, so that the data constellation points of the data volume, that is, the data volume of each frame of DTMB signal in the reference signal, can be obtained.
The demodulation processing for each frame of DTMB signal in the reference signal is thus completed by the above-described embodiment.
S3 signal reconstruction:
in an embodiment of the present application, framing the DTMB signal format for the demodulated data volume to obtain a reconstructed reference signal includes:
firstly, system data and a data body of a frame body part are connected in series in a frequency domain, and Fourier transform is carried out on the frame body part after the frame body part is connected in series to obtain a time domain frame body part after the frame body part is connected in series; and then inserting a frame header part consisting of a standard PN sequence in front of a frame body of the time domain frame body part after the serial connection to obtain each frame of the reconstructed DTMB signal.
It should be noted that, during the reconstruction process of the DTMB signal, the average power of the signal of the frame header portion should be ensured to be 2 times of the average power of the signal of the frame body portion.
In practical application, the reconstruction process further includes performing up-sampling and shaping filtering on the DTMB signals obtained by framing, for example, performing 4 times up-sampling on the DTMB signals obtained by framing until the sampling frequency is 30.24MHz, filtering the DTMB signals by using a root-raised cosine filter with a roll-off coefficient of 0.05 to obtain reconstructed DTMB signals, and sequentially reconstructing each frame of the DTMB signals in the reference signal to obtain reconstructed reference signals.
S4 frequency offset estimation:
as shown in fig. 5, the reconstructed reference signal has a one-to-one correspondence with the frame number of the original reference signal. Therefore, in an embodiment of the present application, according to the corresponding relationship, the current frame DTMB signal and the adjacent frame DTMB signal of the reference signal can be determined, and the current frame DTMB signal and the adjacent frame DTMB signal of the reconstructed reference signal can be determined; and obtaining the frequency offset fine estimation of the current frame DTMB signal of the reference signal according to the current frame DTMB signal and the adjacent frame DTMB signal of the reference signal and the current frame DTMB signal and the adjacent frame DTMB signal of the reconstructed reference signal.
Specifically, the fine frequency offset estimation of the i frame DTMB signal of the reference signal is obtained according to the following formula (2):
in the formula (2), x (N) is a reference signal, y (N) is a reconstructed reference signal, N is the number of frequency points of the reference signal, i is the frame number, N is the length of the DTMB signal, and T is the length of the DTMB signal s Is a sampling interval, f i And finely estimating the frequency offset of the DTMB signal of the ith frame.
Compared with the formula (1), the value range of the frequency point of the reference signal in the formula (1) is [0, M ], and the value range of the frequency point of the reference signal and the reconstructed reference signal in the formula (2) is [0, N-1 ]. Namely, in the frequency offset estimation of the prior art, only the frame header part of the DTMB signal is used, and the embodiment of the present application uses the complete DTMB signal in the reference signal, so the frequency offset estimation accuracy of the embodiment of the present application is significantly improved.
An embodiment of the present application further provides a frequency offset estimation apparatus 600, as shown in fig. 6, which provides a schematic structural diagram of a frequency offset apparatus in the embodiment of the present application, where the apparatus 600 includes:
the preprocessing unit 610 is configured to obtain a reference signal through a DTMB signal of an external radiation source, and obtain a reference signal synchronized in a time domain according to a time domain correlation between the reference signal and a standard PN sequence, where the reference signal includes a multi-frame DTMB signal;
a demodulation unit 620, configured to perform frequency offset compensation on each frame of DTMB signal of the reference signal according to the coarse frequency offset estimation of the time domain synchronized reference signal, and demodulate each frame of DTMB signal after frequency offset compensation to obtain a data volume of each frame of DTMB signal;
a reconstructing unit 630, configured to perform framing in a DTMB signal format on the demodulated data volume to obtain a reconstructed reference signal;
an estimating unit 640, configured to obtain a frequency offset fine estimate of the reference signal according to the time domain correlation between the reference signal and the reconstructed reference signal.
In an embodiment of the present application, the demodulating unit 620 is configured to perform channel estimation and equalization on each frame of DTMB signal after frequency offset compensation, so as to obtain a constellation mapping diagram of a frame body portion of each frame of DTMB signal; and obtaining the data constellation points of the data volume by carrying out constellation judgment on the constellation mapping chart.
In an embodiment of the present application, the demodulating unit 620 is specifically configured to perform time-domain least square channel estimation on each frame of DTMB signal after frequency offset compensation according to the standard PN sequence, so as to obtain a channel impulse response; and performing channel equalization on the frame body part of each frame of the DTMB signal by using the channel impact response to obtain a constellation mapping chart of the frame body part of each frame of the DTMB signal.
In one embodiment of the present application, the DTMB signal format includes a frame header part and a frame body part, wherein the frame body part includes system data and a data body; a reconstructing unit 630, configured to concatenate the system data of the frame body part with the data body in the frequency domain, and perform fourier transform on the concatenated frame body part to obtain a concatenated time-domain frame body part; and inserting a frame header part consisting of a standard PN sequence in front of a frame body of the time domain frame body part after the serial connection to obtain each frame of the reconstructed DTMB signal.
In an embodiment of the present application, the estimating unit 640 is configured to determine, according to a one-to-one correspondence relationship between frame numbers of the reference signal and the reconstructed reference signal, a current frame DTMB signal and an adjacent frame DTMB signal of the reference signal, and determine a current frame DTMB signal and an adjacent frame DTMB signal of the reconstructed reference signal; and obtaining the frequency offset fine estimation of the current frame DTMB signal of the reference signal according to the current frame DTMB signal and the adjacent frame DTMB signal of the reference signal and the current frame DTMB signal and the adjacent frame DTMB signal of the reconstructed reference signal.
In an embodiment of the application, the estimation unit 640 is specifically adapted to be based on a formula
Obtaining a frequency offset fine estimation of an ith frame DTMB signal of the reference signal; wherein x (N) is the reference signal, y (N) is the reconstructed reference signal, N is the number of frequency points of the reference signal, i is the frame number, N is the length of the DTMB signal, T s Is a sampling interval, f i And finely estimating the frequency offset of the DTMB signal of the ith frame.
In an embodiment of the present application, the demodulation unit 620 is further configured to calculate a demodulation equation according to the formula
Obtaining a frequency offset rough estimation of an ith frame DTMB signal of the reference signal; wherein x (N) is the reference signal, N is the frequency point of the reference signal, i is the frame number, N is the length of DTMB signal, M is the length of the standard PN sequence, T s For a sampling interval, f i ' is the coarse frequency offset estimate of the i-th frame DTMB signal.
In one embodiment of the present application, the demodulation unit 620 is further configured to demodulate the signal according to the formula exp (2 π nf) i 'T s ) And performing frequency offset compensation on the ith frame DTMB signal.
It can be understood that the above frequency offset estimation apparatus can implement the steps of the frequency offset estimation method provided in the foregoing embodiment, and the related explanations about the frequency offset estimation method are applicable to the frequency offset estimation apparatus, and are not described herein again.
Fig. 7 is a schematic structural diagram of an electronic device according to an embodiment of the present application. Referring to fig. 7, at a hardware level, the electronic device includes a processor, and optionally further includes an internal bus, a network interface, and a memory. The Memory may include a Memory, such as a Random-Access Memory (RAM), and may further include a non-volatile Memory, such as at least 1 disk Memory. Of course, the electronic device may also include hardware required for other services.
The processor, the network interface, and the memory may be connected to each other via an internal bus, which may be an ISA (Industry Standard Architecture) bus, a PCI (Peripheral Component Interconnect) bus, an EISA (Extended Industry Standard Architecture) bus, or the like. The bus may be divided into an address bus, a data bus, a control bus, etc. For ease of illustration, only one double-headed arrow is shown in FIG. 7, but this does not indicate only one bus or one type of bus.
And the memory is used for storing programs. In particular, the program may include program code comprising computer operating instructions. The memory may include both memory and non-volatile storage and provides instructions and data to the processor.
The processor reads the corresponding computer program from the nonvolatile memory into the memory and then runs the computer program to form the frequency offset estimation device on the logic level. The processor is used for executing the program stored in the memory and is specifically used for executing the following operations:
acquiring a reference signal through a DTMB signal of an external radiation source, and acquiring a reference signal with synchronous time domain according to the time domain correlation of the reference signal and a standard PN sequence, wherein the reference signal comprises a multi-frame DTMB signal;
according to the frequency offset rough estimation of the reference signal of the time domain synchronization, carrying out frequency offset compensation on each frame of DTMB signal of the reference signal, and demodulating each frame of DTMB signal after the frequency offset compensation to obtain a data body of each frame of DTMB signal;
framing the data volume obtained by demodulation in a DTMB signal format to obtain a reconstructed reference signal;
and obtaining the fine frequency offset estimation of the reference signal according to the time domain correlation of the reference signal and the reconstructed reference signal.
The method performed by the frequency offset estimation apparatus as disclosed in the embodiment of fig. 1 of the present application may be applied to or implemented by a processor. The processor may be an integrated circuit chip having signal processing capabilities. In implementation, the steps of the above method may be performed by integrated logic circuits of hardware in a processor or instructions in the form of software. The Processor may be a general-purpose Processor, including a Central Processing Unit (CPU), a Network Processor (NP), and the like; but also Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs) or other Programmable logic devices, discrete Gate or transistor logic devices, discrete hardware components. The various methods, steps, and logic blocks disclosed in the embodiments of the present application may be implemented or performed. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like. The steps of the method disclosed in connection with the embodiments of the present application may be directly implemented by a hardware decoding processor, or implemented by a combination of hardware and software modules in the decoding processor. The software module may be located in ram, flash memory, rom, prom, or eprom, registers, etc. storage media as is well known in the art. The storage medium is located in a memory, and a processor reads information in the memory and completes the steps of the method in combination with hardware of the processor.
The electronic device may further execute the method executed by the frequency offset estimation apparatus in fig. 1, and implement the function of the frequency offset estimation apparatus in the embodiment shown in fig. 1, which is not described herein again in this embodiment of the present application.
An embodiment of the present application further provides a computer-readable storage medium storing one or more programs, where the one or more programs include instructions, which, when executed by an electronic device including multiple application programs, enable the electronic device to perform the method performed by the frequency offset estimation apparatus in the embodiment shown in fig. 1, and are specifically configured to perform:
acquiring a reference signal through a DTMB signal of an external radiation source, and acquiring a reference signal with synchronous time domain according to the time domain correlation of the reference signal and a standard PN sequence, wherein the reference signal comprises a multi-frame DTMB signal;
according to the frequency offset rough estimation of the time domain synchronous reference signal, carrying out frequency offset compensation on each frame of DTMB signal of the reference signal, and demodulating each frame of DTMB signal after frequency offset compensation to obtain a data body of each frame of DTMB signal;
framing the data volume obtained by demodulation in a DTMB signal format to obtain a reconstructed reference signal;
and obtaining the fine frequency offset estimation of the reference signal according to the time domain correlation of the reference signal and the reconstructed reference signal.
As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
In a typical configuration, a computing device includes one or more processors (CPUs), input/output interfaces, network interfaces, and memory.
The memory may include forms of volatile memory in a computer readable medium, Random Access Memory (RAM) and/or non-volatile memory, such as Read Only Memory (ROM) or flash memory (flash RAM). Memory is an example of a computer-readable medium.
Computer-readable media, including both permanent and non-permanent, removable and non-removable media, may implement the information storage by any method or technology. The information may be computer readable instructions, data structures, modules of a program, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), Static Random Access Memory (SRAM), Dynamic Random Access Memory (DRAM), other types of Random Access Memory (RAM), Read Only Memory (ROM), Electrically Erasable Programmable Read Only Memory (EEPROM), flash memory or other memory technology, compact disc read only memory (CD-ROM), Digital Versatile Discs (DVD) or other optical storage, magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information that can be accessed by a computing device. As defined herein, a computer readable medium does not include a transitory computer readable medium such as a modulated data signal and a carrier wave.
It should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The above description is only an example of the present application and is not intended to limit the present application. Various modifications and changes may occur to those skilled in the art to which the present application pertains. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.
Claims (10)
1. A method of frequency offset estimation, the method comprising:
acquiring a reference signal through a DTMB signal of an external radiation source, and acquiring a reference signal with synchronous time domain according to the time domain correlation of the reference signal and a standard PN sequence, wherein the reference signal comprises a multi-frame DTMB signal;
according to the frequency offset rough estimation of the time domain synchronous reference signal, carrying out frequency offset compensation on each frame of DTMB signal of the reference signal, and demodulating each frame of DTMB signal after frequency offset compensation to obtain a data body of each frame of DTMB signal;
framing the data volume obtained by demodulation in a DTMB signal format to obtain a reconstructed reference signal;
and obtaining the fine frequency offset estimation of the reference signal according to the time domain correlation of the reference signal and the reconstructed reference signal.
2. The method of claim 1, wherein demodulating the frequency offset compensated DTMB-per-frame signal to obtain a data volume of the DTMB-per-frame signal comprises:
performing channel estimation and equalization on each frame of DTMB signals after frequency offset compensation to obtain a constellation mapping chart of a frame body part of each frame of DTMB signals;
and obtaining the data constellation points of the data volume by carrying out constellation judgment on the constellation mapping chart.
3. The method of claim 2, wherein the channel estimation and equalization of the frequency offset compensated DTMB-per-frame signal comprises:
performing time domain least square channel estimation on each frame of DTMB signals after frequency offset compensation according to the standard PN sequence to obtain channel impact response;
and performing channel equalization on the frame body part of each frame of the DTMB signal by using the channel impact response to obtain a constellation mapping chart of the frame body part of each frame of the DTMB signal.
4. The method of claim 1, wherein the DTMB signal format comprises a frame header part and a frame body part, the frame body part comprising system data and a data body; framing the data volume obtained by demodulation in a DTMB signal format to obtain a reconstructed reference signal, wherein the framing comprises:
the system data and the data body of the frame body part are connected in series in a frequency domain, and the frame body part after the connection is subjected to Fourier transform to obtain a time domain frame body part after the connection is carried out;
and inserting a frame header part consisting of a standard PN sequence in front of a frame body of the time domain frame body part after the serial connection to obtain each frame of the reconstructed DTMB signal.
5. The method of claim 1, wherein obtaining the fine frequency offset estimate of the reference signal based on the time-domain correlation of the reference signal and the reconstructed reference signal comprises:
determining a current frame DTMB signal and an adjacent frame DTMB signal of the reference signal and determining a current frame DTMB signal and an adjacent frame DTMB signal of the reconstructed reference signal according to the one-to-one correspondence relationship between the reference signal and the frame numbers of the reconstructed reference signal;
and obtaining the frequency offset fine estimation of the current frame DTMB signal of the reference signal according to the current frame DTMB signal and the adjacent frame DTMB signal of the reference signal and the current frame DTMB signal and the adjacent frame DTMB signal of the reconstructed reference signal.
6. The method of claim 5, wherein obtaining a fine frequency offset estimate of the current frame DTMB signal of the reference signal based on the current frame DTMB signal and adjacent frame DTMB signal of the reference signal and the current frame DTMB signal and adjacent frame DTMB signal of the reconstructed reference signal comprises:
according to the formula
Obtaining a frequency offset fine estimation of an ith frame DTMB signal of the reference signal;
wherein x (N) is the reference signal, y (N) is the reconstructed reference signal, N is the number of frequency points of the reference signal, i is the frame number, N is the length of the DTMB signal, T s Is a sampling interval, f i And finely estimating the frequency offset of the DTMB signal of the ith frame.
7. The method of claim 1, wherein the coarse frequency offset estimate of the time-domain synchronized reference signal is obtained by:
according to the formula
Obtaining a frequency offset rough estimation of an ith frame DTMB signal of the reference signal;
wherein x (N) is based on reference signal, N is frequency point of reference signal, i is frame number, N is length of DTMB signal, M is length of standard PN sequence, and T is s Is a sampling interval, f i ' is the rough estimation of the frequency offset of the DTMB signal of the ith frame.
8. The method of claim 7, wherein the frequency offset compensation of the DTMB-per-frame signal of the reference signal comprises:
according to the formula exp (2 π nf) i 'T s ) And performing frequency offset compensation on the DTMB signal of the ith frame.
9. An apparatus for frequency offset estimation, the apparatus comprising:
the device comprises a preprocessing unit, a reference signal acquisition unit and a reference signal processing unit, wherein the preprocessing unit is used for acquiring the reference signal through the DTMB signal of an external radiation source and acquiring a time-domain synchronous reference signal according to the time-domain correlation of the reference signal and a standard PN sequence, and the reference signal comprises a multi-frame DTMB signal;
the demodulation unit is used for carrying out frequency offset compensation on each frame of DTMB signal of the reference signal according to the frequency offset rough estimation of the reference signal of the time domain synchronization and demodulating each frame of DTMB signal after the frequency offset compensation to obtain a data body of each frame of DTMB signal;
the reconstruction unit is used for framing the data volume obtained by demodulation in a DTMB signal format to obtain a reconstructed reference signal;
and the estimation unit is used for obtaining the frequency offset fine estimation of the reference signal according to the time domain correlation between the reference signal and the reconstructed reference signal.
10. An electronic device, comprising:
a processor; and
a memory arranged to store computer executable instructions that, when executed, cause the processor to perform the frequency offset estimation method of any of claims 1 to 8.
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