CN114374447B - Channel detection method, device and medium - Google Patents
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Abstract
The application discloses a method, a device and a medium for channel detection, which are applied to a transmitting end, and comprise the steps of placing an impulse pilot signal in a time delay-Doppler domain at the transmitting end, modulating the impulse pilot signal to obtain an OTFS signal, transmitting the OTFS signal to a channel to be detected so as to be convenient for a receiving end to acquire the OTFS signal, and processing the OTFS signal to determine the time delay and Doppler characteristics of the channel. Therefore, the technical scheme provided by the invention can directly obtain the time delay and Doppler characteristics of the channel by directly placing the impulse pilot signal in the time delay-Doppler domain and modulating the signal by using the OTFS modulation method, and does not need other signal processing in the middle, so that errors caused by the fact that the Doppler domain information of the channel can be obtained only by further processing the detected time domain and frequency domain characteristics when pseudo-random sequence detection or multi-carrier code division multiple access spread spectrum sequence detection is adopted are avoided, and the detection precision of the channel is improved.
Description
Technical Field
The present invention relates to the field of communications, and in particular, to a method, an apparatus, and a medium for channel sounding.
Background
Channel sounding is an important means for a communication system to obtain propagation environment information. The traditional channel detection needs a special detection transmitter and a special detection receiver, a known detection sequence is transmitted on a communication frequency band needing detection, channel characteristics such as channel impulse response, doppler power spectrum and the like are extracted, and a receiving end acquires a return signal for modeling analysis. The traditional channel detection transmitting signals adopt a pseudo-random sequence or a multi-carrier code division multiple access spread spectrum sequence, the two transmitting signals are adopted to be detected in a time domain or a frequency domain, fourier transformation is firstly carried out on the transmitting signals and the receiving signals respectively to obtain frequency domain signals T (omega) and R (omega), and the ratio of the frequency domain signals T (omega) and the frequency domain signals R (omega)/T (omega) is carried out to obtain the channel frequency response H (omega) =R (omega).
The channel frequency response H (omega) is subjected to fast Fourier transform (IFFT) to obtain the impulse response of the channel:
h(τ)＝IFFT{H(ω)} (1)
where τ is the time delay and ω is the angular frequency.
The commonly measured channel response contains a significant multipath component and an insignificant noise component. A fixed value noise threshold is selected, and zero forcing is carried out on multipath taps with multipath powers lower than the noise threshold.
The doppler power spectrum can therefore be calculated from the Fast Fourier Transform (FFT) of the autocorrelation function of the channel impulse response:
wherein W is FFT For the FFT window length, DPSD is the channel doppler power spectrum and m is the sequence shift.
Therefore, with the conventional channel detection method, to obtain the doppler domain information of the channel, the channel frequency response needs to be subjected to fast fourier transform to obtain the channel impulse response, and then the autocorrelation function of the channel impulse response is subjected to Fast Fourier Transform (FFT), which causes errors after the signal processing, and reduces the channel detection precision.
It can be seen that how to improve the channel detection accuracy is a problem to be solved by those skilled in the art.
Disclosure of Invention
The present invention provides a method, an apparatus and a medium for channel detection, which directly modulate an impulse pilot signal in a delay-doppler domain to obtain an OTFS signal, and transmit the OTFS signal to a channel to be detected so as to facilitate a receiving end to obtain the signal, and analyze and determine delay and doppler characteristics of the channel, so as to avoid errors caused by that the acquired time-domain and frequency-domain characteristics of the channel need to be further processed by conventional channel detection to determine the delay and doppler characteristics of the channel.
In order to solve the above technical problems, the present application provides a method for channel sounding, which is applied to a transmitting end, and includes:
placing an impulse pilot signal in a delay-Doppler domain for modulation to obtain an OTFS signal;
the OTFS signal is transmitted to a channel for a receiving end to acquire the OTFS signal and processed to determine delay and doppler characteristics of the channel.
Preferably, the placing the impulse pilot signal in the delay-doppler domain for modulation to obtain the OTFS signal includes:
placing the impulse pilot signal in the delay-Doppler domain to obtain a delay-Doppler domain signal;
transforming the delay-doppler domain signal to a time-frequency domain signal by an inverse-octave fourier transform;
the time-frequency domain signal is modulated by orthogonal frequency division multiplexing.
Preferably, the impulse pilot signal is a plurality of impulse pilot signals.
In order to solve the above technical problem, the present application further provides a method for channel sounding, which is applied to a receiving end, and includes:
acquiring an OTFS signal in a channel, wherein the OTFS signal is a signal which is obtained by a transmitting end by placing an impulse pilot signal in a time delay-Doppler domain for modulation and transmitting the impulse pilot signal into the channel;
the OTFS signal is processed to determine delay and doppler characteristics of the channel.
Preferably, processing the OTFS signal includes:
demodulating the OTFS signal by orthogonal frequency division multiplexing to obtain a time-frequency domain signal;
transforming the time-frequency domain signal to a delay-doppler domain signal by an octave transform;
the delay-doppler domain signal is analyzed to determine delay and doppler characteristics of the channel.
Preferably, the impulse pilot signal is plural, and further includes, after the transforming the time-frequency domain signal into a delay-doppler domain signal by an octave fourier transform:
extracting diversity gain from a plurality of impulse signals obtained by processing a plurality of impulse pilot signals;
determining the time delay and Doppler frequency shift of each path of the channel through a preset threshold;
multiple OTFS frames are analyzed to obtain delay and doppler statistics of the channel.
In order to solve the above technical problem, the present application further provides a device for channel sounding, which is applied to a transmitting end, and includes:
the modulating module is used for placing the impulse pilot signal in a delay-Doppler domain for modulating so as to obtain an OTFS signal;
and the sending module is used for sending the OTFS signal to a channel so that a receiving end can acquire the OTFS signal and process the OTFS signal to determine the time delay and Doppler characteristics of the channel.
In order to solve the above technical problem, the present application further provides a device for channel sounding, which is applied to a receiving end, and includes:
the acquisition module is used for acquiring an OTFS signal in a channel, wherein the OTFS signal is a signal which is obtained by placing an impulse pilot signal in a time delay-Doppler domain by a transmitting end for modulation and transmitting the impulse pilot signal into the channel;
and the processing module is used for processing the OTFS signals to determine the time delay and Doppler characteristics of the channels.
In order to solve the technical problem, the present application further provides an apparatus for channel sounding, including a memory for storing a computer program;
a processor for implementing the steps of the method of channel sounding as described when executing the computer program.
To solve the above technical problem, the present application further provides a computer readable storage medium, on which a computer program is stored, which when being executed by a processor, implements the steps of the method of channel sounding as described.
The method for detecting the channel provided by the invention is applied to a transmitting end, and comprises the steps of placing an impulse pilot signal in a time delay-Doppler domain at the transmitting end, modulating the impulse pilot signal to obtain an OTFS signal, transmitting the OTFS signal to a channel to be detected so as to be convenient for a receiving end to acquire the OTFS signal, and processing the OTFS signal to determine the time delay and Doppler characteristics of the channel. Therefore, the technical scheme provided by the invention can directly obtain the time delay and Doppler characteristics of the channel by directly placing the impulse pilot signal in the time delay-Doppler domain and modulating the signal by using the OTFS modulation method without other signal processing in the middle, thereby avoiding errors caused by further processing the detected time domain and frequency domain characteristics to obtain Doppler domain information of the channel when adopting pseudo-random sequence detection or multi-carrier code division multiple access spread spectrum sequence detection and improving the detection precision of the channel.
In addition, the invention also provides a device and a medium for channel detection, which correspond to the method for channel detection and have the same effects.
Drawings
For a clearer description of the embodiments of the present application, the drawings that are needed in the embodiments will be briefly described, it being apparent that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a flowchart of a method for channel sounding according to an embodiment of the present invention;
fig. 2 is a block diagram of a device for channel sounding based on a transmitting end according to an embodiment of the present invention;
fig. 3 is a diagram of a delay-doppler domain signal grid versus a time-frequency domain signal grid according to an embodiment of the present invention;
fig. 4 is a block diagram of a device for channel sounding based on a receiving end according to an embodiment of the present invention;
fig. 5 is a block diagram of an apparatus for channel sounding according to another embodiment of the present application.
Detailed Description
The following description of the technical solutions in the embodiments of the present application will be made clearly and completely with reference to the drawings in the embodiments of the present application, and it is apparent that the described embodiments are only some embodiments of the present application, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments herein without making any inventive effort are intended to fall within the scope of the present application.
The core of the application is to provide a method, a device and a medium for channel detection, wherein a transmitting end places an impulse pilot signal defined by the transmitting end in a time delay-Doppler domain, modulates the signal by an Orthogonal Time Frequency Space (OTFS) modulation method to obtain an OTFS signal, and transmits the OTFS signal to a channel to be detected, so that a receiving end can conveniently receive the OTFS signal, and processes and determines the time delay and Doppler characteristics of the channel, thereby directly obtaining the time delay and Doppler characteristics of the channel, needing no other processing of the signal, and further improving the detection precision of the channel.
In order to provide a better understanding of the present application, those skilled in the art will now make further details of the present application with reference to the drawings and detailed description.
Channel sounding is an important means for a communication system to acquire propagation environment information, and typically, channel sounding transmits a sounding signal to a channel through a specific channel sounding transmitter, and then a receiver acquires a signal passing through the channel, and the receiver performs signal processing analysis to determine delay and doppler characteristics of the channel. The signal detection transmitter generally selects a pseudo random sequence or a multi-carrier code division multiple access spread spectrum sequence as a transmission signal, and adopts the two signals as the transmission signal, which need to be detected in a time domain or a frequency domain, and the signal obtained in the time domain or the frequency domain needs to be processed as follows when the Doppler domain information of a channel is wanted:
the method comprises the steps of firstly carrying out Fourier transformation on a transmitting signal and a receiving signal to obtain frequency domain signals T (omega) and R (omega), and carrying out ratio on the frequency domain signals T (omega) and R (omega) to obtain channel frequency response H (omega) =R (omega)/T (omega).
The channel frequency response H (ω) is then subjected to an Inverse Fast Fourier Transform (IFFT) to obtain the impulse response H (τ) =ifft { H (ω) }, where τ is the delay and ω is the angular frequency.
The Doppler power spectrum may be calculated from the Fast Fourier Transform (FFT) of the autocorrelation function of the channel impulse responseWherein W is FFT For the FFT window length, DPSD is the channel doppler power spectrum and m is the sequence shift.
Therefore, with the conventional channel detection method, to obtain the doppler domain information of the channel, the channel frequency response needs to be subjected to fast fourier transform to obtain the channel impulse response, and then the autocorrelation function of the channel impulse response is subjected to Fast Fourier Transform (FFT), which causes errors after the signal processing, and reduces the channel detection precision.
In order to improve the accuracy of channel detection, the invention provides a channel detection method, wherein an impulse pilot signal is placed in a time delay-Doppler domain by a transmitting end to be modulated so as to obtain an orthogonal time frequency space modulation (OTFS) signal, and the OTFS signal is transmitted into a channel to be detected, so that a receiver can conveniently receive the signal passing through the channel to be detected, and the acquired signal is processed and analyzed so as to obtain the time delay and Doppler characteristics of the channel.
Fig. 1 is a flowchart of a method for channel sounding according to an embodiment of the present invention, as shown in fig. 1, where the method includes:
s10: the impulse pilot signal is placed in the delay-doppler domain for modulation to obtain an OTFS signal.
S11: the OTFS signal is transmitted to the channel so that the receiving end acquires the OTFS signal and processes to determine the delay and doppler characteristics of the channel.
In step S10, the transmitting end places the impulse pilot signal in the delay-doppler domain for modulation to obtain an OTFS signal, where the impulse pilot signal is generated by emitter customization, and after obtaining the impulse pilot signal, places the signal in the delay-doppler domain to obtain a delay-doppler domain signal, transforms the delay-doppler domain signal into a time-frequency domain signal by inverse-octave fourier transform (ISFFT), and modulates the time-frequency domain signal by Orthogonal Frequency Division Multiplexing (OFDM) to obtain the OTFS signal. The OTFS signal is then transmitted to the channel, via step S11, so that the receiving end receives the signal over the channel and performs processing analysis on the received signal to determine the delay and doppler characteristics of the channel.
It should be noted that performing an ISFFT on a delay-doppler domain signal in a delay-doppler domain and an OFDM modulation are collectively referred to as OTFS modulation, that is, a transmitting end places an impulse pilot signal in the delay-doppler domain and performs OTFS modulation to obtain an OTFS signal, and in addition, in order to obtain delay and doppler characteristics of a channel more comprehensively and accurately, the transmitting end places a plurality of impulse pilot signals in the delay-doppler domain.
In particular implementations, the impulse response of a linear time-varying multipath channel may have different expressions, where the channel varies at a rate of 1/coherence time in the time-frequency domain representation H (t, f) of the channel, resulting in the above-mentioned difficulties of time-frequency domain channel detection in a high-speed moving scenario, whereas the delay-doppler domain representation H (τ, v) is equivalent to H (t, f), and where the parameters under such expressions are multi-path delay and doppler shifts, typically almost unchanged in a minimum of a few milliseconds, so that the delay-doppler domain channel exhibits time invariance over a long detection interval and has sparsity, requiring only a small number of parameters to characterize.
Therefore, the direct channel detection in the delay-Doppler domain has the advantages of conciseness and intuition, compared with an Orthogonal Frequency Division Multiplexing (OFDM) system, the OTFS modulation is equivalent to adding a precoding module on the basis of the OTFS modulation, and can be regarded as the expansion of the OFDM system, and the receiving end can perform inverse process modulation, so that the compatibility with the existing broadband network waveform communication system is realized, and the problem that the OFDM system is incompatible with the existing broadband network waveform communication system is avoided.
The channel detection method provided by the embodiment of the invention is applied to a transmitting end, and comprises the steps of placing an impulse pilot signal in a time delay-Doppler domain at the transmitting end, modulating the impulse pilot signal to obtain an OTFS signal, transmitting the OTFS signal to a channel to be detected so as to be convenient for a receiving end to acquire the OTFS signal, and processing the OTFS signal to determine the time delay and Doppler characteristics of the channel. Therefore, the technical scheme provided by the invention can directly obtain the time delay and Doppler characteristics of the channel by directly placing the impulse pilot signal in the time delay-Doppler domain and modulating the signal by using the OTFS modulation method without other signal processing in the middle, thereby avoiding errors caused by further processing the detected time domain and frequency domain characteristics to obtain Doppler domain information of the channel when adopting pseudo-random sequence detection or multi-carrier code division multiple access spread spectrum sequence detection and improving the detection precision of the channel.
In a specific embodiment, after the transmitting end places the impulse pilot signal in the delay-doppler domain, the symbol X (k, l) in the delay-doppler domain is mapped to X (n, m) in the time-frequency domain using an inverse-octave fourier transform (ISFFT) first using a delay-doppler domain modulator:
where l is the delay domain dimension, k is the doppler domain dimension, n=0, …, N-1, m=0, …, M-1. From the above equation, along the frequency dimension m, a set of Discrete Fourier Transform (DFT) basis functions associate the frequency domain with the delay domain. Along the time dimension n, a set of Inverse Discrete Fourier Transform (IDFT) basis functions correlate the time domain with the doppler domain.
After the time-frequency domain signal is obtained by ISFFT conversion, a certain transmitting pulse waveform g is given to the signal X (n, m) on the time-frequency grid tx (t) converting into a time domain signal s (t) and transmitting to a wireless channel:
the signal s (t) is obtained after performing ISFFT conversion and OFDM modulation in the delay-Doppler domain, the signal s (t) is sent to a channel to be detected, the time-frequency modulation process has a mathematical form of Heisenberg conversion, and can be regarded as a generalized process of pulse shaping OFDM modulation, and the obtained time-domain signal s (t) is transmitted through a time-varying wireless channel.
According to Bello's classical theory, the effect of a channel on the transmitted signal is represented by the delay-doppler domain channel impulse response h (τ, v):
r(t)＝∫∫h(τ,υ)e j2πυ(t-τ) s(t-τ)dτdυ (5)
where h (τ, v) is the channel baseband impulse response, with sparse expression:
wherein, delta (·) is a dirac function, P is the channel diameter number, h i ，τ i And v i Representing the channel coefficient, channel delay and doppler shift of the ith path, respectively.
Therefore, the transmitting end transmits the signal to the channel to be detected, after the OTFS signal passes through the channel to be detected, the receiving end receives the OTFS signal, demodulates the signal through OFDM to obtain a time-frequency domain signal, and then transforms the time-frequency domain signal to a time-delay-Doppler domain signal through an octave Fourier transform so as to determine the time delay and Doppler of the signal. It should be noted that, in order to more fully and accurately determine the delay and doppler characteristics of the channel, the transmitting end places multiple impulse pilot signals in the delay-doppler domain for modulation.
According to the channel detection method provided by the embodiment of the invention, the impulse pilot signal is placed in the time delay-Doppler domain through the transmitting end, the time delay-Doppler domain signal is converted into the time-frequency domain signal through the ISFFT conversion, the time-frequency domain signal is modulated through the OFDM to obtain the OTFS signal, the OTFS signal is transmitted to the channel, so that the receiving end can acquire the signal passing through the channel, and the acquired signal is analyzed to determine the time delay and Doppler characteristics of the channel, so that errors caused by further processing the detected time domain and frequency domain characteristics to obtain the Doppler domain information of the channel when pseudo-random sequence detection or multi-carrier code division multiple access spread spectrum sequence detection is avoided, and the detection precision of the channel is improved.
In the foregoing embodiments, a method for channel sounding based on a transmitting end is described in detail, and the present application further provides corresponding embodiments of an apparatus for channel sounding based on a transmitting end. It should be noted that the present application describes an embodiment of the device portion from two angles, one based on the angle of the functional module and the other based on the angle of the hardware structure.
Fig. 2 is a block diagram of an apparatus for transmitting end-based channel sounding according to an embodiment of the present invention, as shown in fig. 2, where the apparatus includes:
a modulation module 10 is configured to place the impulse pilot signal in the delay-doppler domain for modulation to obtain an OTFS signal.
A transmitting module 11, configured to transmit the OTFS signal to a channel, so that the receiving end obtains the OTFS signal and processes the OTFS signal to determine delay and doppler characteristics of the channel.
Since the embodiments of the apparatus portion and the embodiments of the method portion correspond to each other, the embodiments of the apparatus portion are referred to the description of the embodiments of the method portion, and are not repeated herein.
The device for detecting the channel provided by the embodiment of the invention is applied to a transmitting end, and comprises the steps of placing an impulse pilot signal in a time delay-Doppler domain at the transmitting end, modulating the impulse pilot signal to obtain an OTFS signal, transmitting the OTFS signal to a channel to be detected so as to be convenient for a receiving end to acquire the OTFS signal, and processing the OTFS signal to determine the time delay and Doppler characteristics of the channel. Therefore, the technical scheme provided by the invention can directly obtain the time delay and Doppler characteristics of the channel by directly placing the impulse pilot signal in the time delay-Doppler domain and modulating the signal by using the OTFS modulation method without other signal processing in the middle, thereby avoiding errors caused by further processing the detected time domain and frequency domain characteristics to obtain Doppler domain information of the channel when adopting pseudo-random sequence detection or multi-carrier code division multiple access spread spectrum sequence detection and improving the detection precision of the channel.
In the above embodiments, the method for channel sounding from the transmitting end side angle is described in detail, and the present application also provides corresponding embodiments of the method for channel sounding from the receiving end side angle. And acquiring an OTFS signal in the channel, wherein the OTFS signal is a signal obtained by modulating an impulse pilot signal in a time delay-Doppler domain by a transmitting end, and after the OTFS signal is acquired, the OTFS signal is processed to determine the time delay and Doppler characteristics of the channel.
It is noted that, the transmitting end places the impulse pilot signal in the delay-doppler domain, and performs the ISFFT and OFDM modulation on the signal to obtain the OTFS signal transmitted to the channel to be detected, so after the receiving end obtains the signal in the channel to be detected, the receiving end demodulates the signal through OFDM to obtain the time-frequency domain signal, and then obtains the delay-doppler domain signal through the octave fourier transform (SFFT), and the delay and doppler characteristics of the channel can be determined by the delay-doppler domain signal.
In order to further improve accuracy of the detection channel, the number of impulse pilot signals modulated by the transmitting end is multiple, after the receiving end obtains signals, diversity gains are extracted from a plurality of impulse signals obtained by processing the impulse pilot signals, delay and Doppler frequency shift of each path of the channel are determined through a preset threshold, and finally a plurality of OTFS frames are analyzed to obtain delay and Doppler statistical information of the channel.
The method for detecting the channel provided by the embodiment of the invention is applied to a receiving end and comprises the steps of obtaining an OTFS signal in a channel to be detected, wherein the OTFS signal is a signal obtained by modulating an impulse pilot signal placed in a time delay-Doppler domain by a transmitting end, and after the OTFS signal is obtained, the OTFS signal is processed to determine the time delay and Doppler characteristics of the channel. Therefore, the technical scheme provided by the invention is that the impulse pilot signal is directly placed in the time delay-Doppler domain by the transmitting end to be modulated to obtain the signal in the channel, the time-frequency domain signal is obtained by demodulating the signal by OFDM, and then the time delay-Doppler domain signal is obtained by the Fourier transform (SFFT), so that the time delay and Doppler characteristics of the channel are directly obtained, other signal processing is not needed in the middle, errors caused by the fact that the Doppler domain information of the channel can be obtained only by further processing the detected time domain and frequency domain characteristics when pseudo-random sequence detection or multi-carrier code division multiple access spread spectrum sequence detection is adopted can be avoided, and the detection precision of the channel is improved.
In a specific embodiment, the transmitting end modulates a plurality of impulse pilot signals in a delay-doppler domain to obtain an OTFS signal, and transmits the OTFS signal to a channel to be detected, and after a receiving end obtains a signal in the channel, the receiving end demodulates the OTFS signal by OFDM to obtain a time-frequency domain signal, and then transforms the time-frequency domain signal to the delay-doppler domain signal by SFFT transformation, thereby analyzing the delay-doppler domain signal to determine delay and doppler characteristics of the channel.
The taps of the delay-doppler domain for the ith path can be expressed as:
wherein Δf is the subcarrier spacing, T is the time spacing, and the ith path delay tap isThe ith path Doppler tap is +.>Definition l τ ，k v The maximum delay tap and the maximum doppler tap, respectively.
For example, the receiving end obtains a shaping waveform g rx And (t) carrying out matched filtering on the channel output signal at a receiving end, then sampling Y (t, f) at grid points, and converting the time-frequency domain signal into a time-delay-Doppler domain signal through SFFT conversion. Thus, there is a mathematical relationship between the delay-doppler domain received signal and the transmitted signal and the delay-doppler domain channel impulse response as follows:
where w (k, l) is the varianceIs a complex Gaussian white noise>
Fig. 3 is a diagram illustrating a delay-doppler domain signal grid and a time-frequency domain signal grid conversion according to an embodiment of the present invention, and as shown in fig. 3, the delay-doppler domain signal grid can be converted with the time-frequency domain signal grid by using an ISFFT and SFFT conversion.
In fig. 3, the time-frequency grid time interval is T, and the subcarrier interval is Δf. For a unit signaling frame with a time length NT and a bandwidth mΔf, the signal thereof can be represented by the following grid points:
Λ＝{(nT,mΔf),n＝0,…,N-1,m＝0,…,M-1} (9)
using SFFT transformation, the time-frequency domain grid can be converted to a delay-Doppler domain grid Λ ⊥ ，Λ ⊥ Can be defined as:
Λ ⊥ ＝{(kΔυ,lΔτ),k＝0，…，N-1,l＝0,…,M-1} (10)
where the unit delay length Δτ (i.e., delay resolution) of the delay domain is defined as the inverse of the frequency domain bandwidth in the time-frequency domain:
similarly, the unit Doppler interval Deltav (i.e., doppler resolution) of the Doppler domain is defined as the inverse of the length of time in the time-frequency domain:
it follows that greater resolution in the delay-doppler domain can be obtained if the length and bandwidth of the transmission of a unit signal frame is increased.
For example, when the Doppler grid is [ k ] p ,l p ](0≤k p ≤N-1,0≤l p Placing an impulse pilot x on less than or equal to M-1) p (Pilot variance is) The remaining positions are 0. From equation (8):
wherein b (k-k) p ,l-l p ) E {0,1} is used to indicate whether there is a latency of l-l p Doppler shift of k-k p Is a diameter of (2). The threshold method is adopted: if it is(/>Is positive, according to experienceTaken as 3 sigma p ) Then consider b (k-k p ,l-l p )＝1，On the contrary, let(s)>
Due to the slowly varying nature of the delay-doppler domain, one OTFS frame can be considered as a snapshot of the channel, i.e., a fixed value for each path of power, delay and doppler shift at time t, and multiple OTFS frames are transmitted in succession, thus obtaining statistics of the channel delay and doppler.
According to the channel detection method provided by the embodiment of the invention, a receiving end obtains a signal obtained by modulating an impulse pilot signal in a time delay-Doppler domain by a transmitting end in a channel to be detected, demodulates the obtained signal through OFDM to obtain a time-frequency domain signal, and transforms the time-frequency domain signal into the time delay-Doppler domain signal through SFFT, so that the time delay and Doppler characteristics of the channel are determined. Therefore, by adopting the technical scheme of the invention, the time delay and Doppler characteristics of the channel can be directly obtained without other signal processing in the middle, so that errors caused by the fact that the Doppler domain information of the channel can be obtained only by further processing the detected time domain and frequency domain characteristics when pseudo-random sequence detection or multi-carrier code division multiple access spread spectrum sequence detection is adopted are avoided, and the accuracy of channel detection is improved.
On the basis of the above embodiment, in consideration of that the single-pulse pilot performance is poor under the high noise condition and the time domain signal has higher peak-to-average power ratio, a pilot scheme for extracting diversity gain from a plurality of pulse signals obtained by processing a plurality of impulse pilot signals is further proposed
Let the channel maximum delay tap be l τ The maximum Doppler tap is k v . So long as the distance l between two impulse pilots along the time delay axis is ensured τ 2k apart along the Doppler axis v Can ensure that the receiving end is not aliased, namely N can be inserted at most P ＝MN/(2k v ·l τ ) Individual impulsesPilot frequency:
because the channel is stationary within the OTFS frame, i.e., each symbol experiences the same fading, delay and doppler shift. The diversity gain can be extracted for a plurality of pulses, and the estimated error can be reduced toChannel sounding under very low signal-to-noise conditions is achieved.
In the analysis of the measured data delay-power spectrum, the weibull distribution and the Nakagami distribution show a higher degree of fitting than the rayleigh and rice distributions due to a higher degree of freedom, and thus serve as a distribution model describing taps in the channel model.
Wherein the probability density function of the weibull distribution is:
wherein, beta is a shape parameter, and alpha is a scale parameter.
The probability density function of the Nakagami distribution is:
wherein μ is a shape parameter, ω is a scale parameter, Γ (μ) is a Gamma function.
The channel model is modeled by using two Doppler spectrums below double Gaussian distribution and Laplace distribution, and the type with the minimum Root Mean Square Error (RMSE) is selected from the two fitting functions, and the fitting parameters of the type with the minimum Root Mean Square Error (RMSE) correspond to non-zero parameter values in Doppler parameter tables below.
The double gaussian distribution expression is:
when there is a small number of distinct scatterers at the far and near ends of the receiving end, respectively, the spectral function tends to appear as a superposition of two gaussian functions. Wherein the normalized frequency is f norm ＝f/f max ，a 1 And a 2 As Gaussian function coefficients, μ 1 Sum mu 2 Is the mean value of Gaussian function, sigma 1 Sum sigma 2 Is a gaussian function variance.
The Laplace distribution expression is:
the laplacian spectrum takes into account the mobile station direction and is suitable for fitting to the "upslope" shape spectrum shape. Wherein the normalized frequency f n o rm ＝f/f max ，f max For maximum Doppler shift, a is the amplitude coefficient, σ is the standard deviation of the angular power spectrum (PAS), and φ is the difference between the direction of movement and the direction of arrival.
In the method for detecting the channel, which is provided by the embodiment of the invention, the diversity gain is extracted from the pulse signals obtained by processing the impulse pilot signals, so that the channel detection under the condition of extremely low signal to noise ratio is realized, in addition, the time delay and Doppler frequency shift of each path of the channel are determined through the preset threshold, and finally, a plurality of OTFS frames are analyzed to obtain the time delay and Doppler statistical information of the channel, other signal processing is not needed in the middle, so that errors caused by the fact that the Doppler domain information of the channel can be obtained only by further processing the detected time domain and frequency domain characteristics when pseudo-random sequence detection or multi-carrier code division multiple access spread spectrum sequence detection is adopted are avoided, and the accuracy of the channel detection is improved.
In the foregoing embodiments, a method for channel sounding based on a receiving end is described in detail, and the present application further provides corresponding embodiments of an apparatus for channel sounding based on a receiving end. It should be noted that the present application describes an embodiment of the device portion from two angles, one based on the angle of the functional module and the other based on the angle of the hardware structure.
Fig. 4 is a block diagram of an apparatus for channel sounding based on a receiving end according to an embodiment of the present invention, as shown in fig. 4, where the apparatus includes:
the acquiring module 100 is configured to acquire an OTFS signal in a channel, where the OTFS signal is a signal that a transmitting end places an impulse pilot signal in a delay-doppler domain to modulate and send the impulse pilot signal into the channel.
A processing module 101 for processing the OTFS signal to determine delay and doppler characteristics of the channel.
Since the embodiments of the apparatus portion and the embodiments of the method portion correspond to each other, the embodiments of the apparatus portion are referred to the description of the embodiments of the method portion, and are not repeated herein.
The device for detecting the channel provided by the embodiment of the invention is applied to a receiving end and comprises the steps of obtaining an OTFS signal in a channel to be detected, wherein the OTFS signal is a signal obtained by modulating an impulse pilot signal placed in a time delay-Doppler domain by a transmitting end, and after the OTFS signal is obtained, the OTFS signal is processed to determine the time delay and Doppler characteristics of the channel. Therefore, the technical scheme provided by the invention is that the impulse pilot signal is directly placed in the time delay-Doppler domain by the transmitting end to be modulated to obtain the signal in the channel, the time-frequency domain signal is obtained by demodulating the signal by OFDM, and then the time delay-Doppler domain signal is obtained by the Fourier transform (SFFT), so that the time delay and Doppler characteristics of the channel are directly obtained, other signal processing is not needed in the middle, errors caused by the fact that the Doppler domain information of the channel can be obtained only by further processing the detected time domain and frequency domain characteristics when pseudo-random sequence detection or multi-carrier code division multiple access spread spectrum sequence detection is adopted can be avoided, and the detection precision of the channel is improved.
Fig. 5 is a block diagram of an apparatus for channel sounding according to another embodiment of the present application, and as shown in fig. 5, the apparatus for channel sounding includes: a memory 20 for storing a computer program;
a processor 21 for carrying out the steps of the method of channel sounding as mentioned in the above embodiments when executing a computer program.
The device for channel detection provided in this embodiment may include, but is not limited to, a smart phone, a tablet computer, a notebook computer, a desktop computer, or the like.
Processor 21 may include one or more processing cores, such as a 4-core processor, an 8-core processor, etc. The processor 21 may be implemented in hardware in at least one of a digital signal processor (Digital Signal Processor, abbreviated as DSP), a Field programmable gate array (Field-Programmable Gate Array, abbreviated as FPGA), and a programmable logic array (Programmable Logic Array, abbreviated as PLA). The processor 21 may also include a main processor and a coprocessor, the main processor being a processor for processing data in an awake state, also referred to as a central processor (Central Processing Unit, CPU for short); a coprocessor is a low-power processor for processing data in a standby state. In some embodiments, the processor 21 may integrate with an image processor (Graphics Processing Unit, GPU for short) for rendering and drawing of the content required to be displayed by the display screen. In some embodiments, the processor 21 may also include an artificial intelligence (Artificial Intelligence, AI) processor for processing computing operations related to machine learning.
Memory 20 may include one or more computer-readable storage media, which may be non-transitory. Memory 20 may also include high-speed random access memory, as well as non-volatile memory, such as one or more magnetic disk storage devices, flash memory storage devices. In this embodiment, the memory 20 is at least used for storing a computer program 201, which, when loaded and executed by the processor 21, enables the implementation of the relevant steps of the method for channel sounding disclosed in any of the previous embodiments. In addition, the resources stored in the memory 20 may further include an operating system 202, data 203, and the like, where the storage manner may be transient storage or permanent storage. The operating system 202 may include Windows, unix, linux, among others. The data 203 may include, but is not limited to, data involved in the method of channel sounding, and the like.
In some embodiments, the device for channel detection may further include a display 22, an input/output interface 23, a communication interface 24, a power supply 25, and a communication bus 26.
Those skilled in the art will appreciate that the structure shown in fig. 5 is not limiting of the apparatus for channel sounding and may include more or fewer components than shown.
The device for channel sounding provided in the embodiment of the present application includes a memory and a processor, where the processor can implement the following method when executing a program stored in the memory: a method of channel sounding.
According to the channel detection device provided by the embodiment of the invention, the receiving end is used for acquiring the OTFS signal obtained by modulating the impulse pilot signal in the time delay-Doppler domain by the transmitting end in the channel to be detected, and the acquired OTFS signal is processed to determine the time delay and Doppler characteristics of the channel, so that the time delay and Doppler characteristics of the channel are directly obtained, other signal processing is not needed in the middle, errors caused by the fact that the Doppler domain information of the channel can be obtained only by further processing the detected time domain and frequency domain characteristics when pseudo-random sequence detection or multi-carrier code division multiple access spread spectrum sequence detection is adopted are avoided, and the detection precision of the channel is improved.
Finally, the present application also provides a corresponding embodiment of the computer readable storage medium. The computer-readable storage medium stores a computer program that, when executed by a processor, performs the steps described in the above method embodiments (the method may be a method corresponding to the transmitting side, a method corresponding to the receiving side, or a method corresponding to the transmitting side and the receiving side).
It will be appreciated that the methods of the above embodiments, if implemented in the form of software functional units and sold or used as stand-alone products, may be stored on a computer readable storage medium. With such understanding, the technical solution of the present application, or a part contributing to the prior art or all or part of the technical solution, may be embodied in the form of a software product stored in a storage medium, performing all or part of the steps of the method described in the various embodiments of the present application. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a random access Memory (Random Access Memory, RAM), a magnetic disk, or an optical disk, or other various media capable of storing program codes.
The method, the device and the medium for channel detection provided by the application are described in detail. In the description, each embodiment is described in a progressive manner, and each embodiment is mainly described by the differences from other embodiments, so that the same similar parts among the embodiments are mutually referred. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant points refer to the description of the method section. It should be noted that it would be obvious to those skilled in the art that various improvements and modifications can be made to the present application without departing from the principles of the present application, and such improvements and modifications fall within the scope of the claims of the present application.
It should also be noted that in this specification, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, 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 one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
Claims (6)
1. A method for channel sounding, applied to a transmitting end, comprising:
placing an impulse pilot signal in a delay-Doppler domain for modulation to obtain an OTFS signal; wherein the impulse pilot signals are a plurality of;
transmitting the OTFS signal to a channel so that a receiving end acquires the OTFS signal and processes the OTFS signal to determine delay and doppler characteristics of the channel;
wherein the sending the OTFS signal to a channel so that a receiving end obtains the OTFS signal and processes the OTFS signal to determine delay and doppler characteristics of the channel includes:
the OTFS signals are sent to a channel so that the receiving end can extract diversity gain for a plurality of pulse signals obtained by processing a plurality of impulse pilot signals, the time delay and Doppler frequency shift of each path of the channel are determined through a preset threshold, and a plurality of OTFS frames are analyzed to obtain the time delay and Doppler statistical information of the channel;
the placing the impulse pilot signal in the delay-doppler domain for modulation to obtain the OTFS signal includes:
placing the impulse pilot signal in the delay-Doppler domain to obtain a delay-Doppler domain signal;
transforming the delay-doppler domain signal to a time-frequency domain signal by an inverse-octave fourier transform;
the time-frequency domain signal is modulated by orthogonal frequency division multiplexing.
2. A method for channel sounding, applied to a receiving end, comprising:
acquiring an OTFS signal in a channel, wherein the OTFS signal is a signal which is obtained by a transmitting end by placing an impulse pilot signal in a time delay-Doppler domain for modulation and transmitting the impulse pilot signal into the channel;
processing the OTFS signal to determine delay and doppler characteristics of the channel;
wherein processing the OTFS signal comprises:
demodulating the OTFS signal by orthogonal frequency division multiplexing to obtain a time-frequency domain signal;
transforming the time-frequency domain signal to a delay-doppler domain signal by an octave transform;
analyzing the delay-doppler domain signal to determine delay and doppler characteristics of the channel;
the plurality of impulse pilot signals further comprises, after the transforming the time-frequency domain signal to a delay-doppler domain signal by an octave fourier transform:
extracting diversity gain from a plurality of impulse signals obtained by processing a plurality of impulse pilot signals;
determining the time delay and Doppler frequency shift of each path of the channel through a preset threshold;
multiple OTFS frames are analyzed to obtain delay and doppler statistics of the channel.
3. An apparatus for channel sounding, applied to a transmitting end, comprising:
the modulating module is used for placing the impulse pilot signal in a delay-Doppler domain for modulating so as to obtain an OTFS signal; wherein the impulse pilot signals are a plurality of;
a transmitting module, configured to transmit the OTFS signal to a channel, so that a receiving end obtains the OTFS signal and processes the OTFS signal to determine delay and doppler characteristics of the channel;
the sending module is configured to send the OTFS signal to a channel, so that the receiving end extracts diversity gain from a plurality of pulse signals obtained by processing a plurality of impulse pilot signals, determines delay and doppler shift of each path of the channel through a preset threshold, and analyzes a plurality of OTFS frames to obtain delay and doppler statistical information of the channel;
the modulation module is used for placing the impulse pilot signal in the delay-Doppler domain to obtain a delay-Doppler domain signal; transforming the delay-doppler domain signal to a time-frequency domain signal by an inverse-octave fourier transform; the time-frequency domain signal is modulated by orthogonal frequency division multiplexing.
4. An apparatus for channel sounding, applied to a receiving end, comprising:
the acquisition module is used for acquiring an OTFS signal in a channel, wherein the OTFS signal is a signal which is obtained by placing an impulse pilot signal in a time delay-Doppler domain by a transmitting end for modulation and transmitting the impulse pilot signal into the channel;
a processing module for processing the OTFS signal to determine delay and doppler characteristics of the channel;
the processing module, for processing the OTFS signal, includes:
demodulating the OTFS signal by orthogonal frequency division multiplexing to obtain a time-frequency domain signal;
transforming the time-frequency domain signal to a delay-doppler domain signal by an octave transform;
analyzing the delay-doppler domain signal to determine delay and doppler characteristics of the channel;
and, the plurality of impulse pilot signals further comprises, after the transforming the time-frequency domain signal to a delay-doppler domain signal by an octave fourier transform:
extracting diversity gain from a plurality of impulse signals obtained by processing a plurality of impulse pilot signals;
determining the time delay and Doppler frequency shift of each path of the channel through a preset threshold;
multiple OTFS frames are analyzed to obtain delay and doppler statistics of the channel.
5. An apparatus for channel sounding, comprising a memory for storing a computer program;
processor for implementing the steps of the method of channel sounding according to claim 1 or 2 when executing said computer program.
6. A computer readable storage medium, characterized in that it has stored thereon a computer program which, when executed by a processor, implements the steps of the method of channel sounding according to any of claims 1 or 2.
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