CN111505584A - Audio signal arrival time correction method based on relative speed and Doppler effect - Google Patents
Audio signal arrival time correction method based on relative speed and Doppler effect Download PDFInfo
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- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
- G01S5/18—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using ultrasonic, sonic, or infrasonic waves
- G01S5/22—Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements
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- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
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Abstract
The invention discloses an audio signal arrival time correction method based on relative speed and Doppler effect, which comprises the following steps: step 1, detecting and acquiring signal arrival time of a current positioning period and a last positioning period; step 2, preliminarily estimating the movement speed of the target relative to the base station by using the arrival time difference of the signals, the system positioning period and the signal propagation speed; and 3, constructing a search interval according to the relative speed and searching for a proper speed in the search interval to accurately estimate the frequency offset caused by the Doppler effect so as to correct the arrival time of the audio signal. The invention does not need extra information and does not depend on historical positions, only utilizes the arrival time difference of signals, the system positioning period and the signal propagation speed to solve the relative motion distance, preliminarily estimates the motion speed of a target relative to a base station, and accurately estimates the frequency offset caused by the Doppler effect, thereby correcting the arrival time of the audio signal. The method has the advantages of no need of introducing redundant information, high precision, good robustness, small calculated amount and the like.
Description
Technical Field
The invention relates to the field of indoor positioning, in particular to a novel audio signal arrival time correction method based on relative velocity and Doppler effect.
Background
Since the advent of positioning technologies represented by the Global Positioning System (GPS), the characteristics of high efficiency, convenience, rapidness, and accuracy have brought tremendous changes to people's lives, driving the rapid development of a range of applications and services. Due to the influence of shielding, positioning technologies such as a GPS cannot meet the positioning and navigation requirements in an indoor scene, and therefore, technical research related to indoor positioning is in the process of being carried out. Currently, common indoor positioning technologies include technologies based on wireless transmission protocols such as WIFI, bluetooth, UWB, and RFID, and technologies based on audio, visual, and PDR. Various technologies have their own features, and among them, audio positioning technologies are receiving increasing attention with low cost, high accuracy, and good compatibility.
The Time of Arrival (TOA) and Time Difference of Arrival (TDOA) of audio signals are two of the most common measurement methods in audio positioning technology, and their accuracy determines the positioning and navigation performance of the system. In an audio positioning system, generally, the time when the audio transmitted by a base station reaches a target, i.e., the signal arrival time, is first detected, and then a TOA or TDOA-based positioning method is performed according to the arrival time. Therefore, accurate detection of signal arrival times is critical to ensure high accuracy audio localization. However, the audio-based indoor positioning is often influenced by various factors such as multipath effect, non-line-of-sight and doppler effect, and the doppler effect has a particularly significant influence on the positioning accuracy for a positioning target in a moving state. Under the influence of the doppler effect, the audio signal received by the target under the condition of motion has a spectrum offset phenomenon, so that a large detection error occurs in the estimation of the audio arrival time, and the positioning and tracking accuracy of the target is further influenced. Therefore, when the target moves, it is necessary to improve the positioning accuracy by correcting the arrival time of the audio signal by estimating the doppler frequency offset.
In the current audio positioning system, there are two main methods for estimating frequency offset caused by doppler effect: the first type is to superimpose one or more single frequency signals on the modulated transmitted audio and estimate the doppler shift by detecting the frequency shift of the single frequency signal in the target received signal. The disadvantages of such methods are the increased computational effort and poor stability; the second method is to estimate the moving speed of the target relative to the base station, and then estimate the frequency offset by using the relationship between the speed and the doppler shift. The performance of the method depends on the acquisition precision of the relative movement speed of the target. A common speed acquisition method is to directly acquire motion information of a user, such as acceleration and angular velocity, by using an inertial sensor. The method not only increases the hardware cost of the system, but also has accumulated errors in the estimated speed, and is difficult to realize the long-time accurate estimation of the target movement speed. Besides, the estimation of the target speed can be realized by means of Kalman filtering, but the performance of the method depends on the position estimation precision of the target, and when the position estimated by a positioning system is abnormal, the estimated target speed has great error.
Disclosure of Invention
In order to solve the above technical problems, the present invention provides a novel audio signal arrival time correction method based on relative velocity and doppler effect, which is different from a method of obtaining velocity by using an inertial sensor and kalman filtering and correcting the arrival time of an audio signal. According to the method, auxiliary equipment is not required to be added, the historical position of the target is not depended on, the relative movement distance is solved by only utilizing the signal arrival time difference, the system positioning period and the signal propagation speed, so that the movement speed of the target relative to the base station is obtained, and finally the correction of the audio signal arrival time is realized by combining the relative speed and the Doppler effect.
The technical scheme of the invention is an audio signal arrival time correction method based on relative velocity and Doppler effect, which comprises the following steps:
step 2, preliminarily estimating the movement speed of the target relative to the base station by using the arrival time difference of the signals, the system positioning period and the signal propagation speed;
and 3, constructing a search interval according to the relative speed and searching for a proper speed in the search interval to accurately estimate the frequency offset caused by the Doppler effect so as to correct the arrival time of the audio signal.
Further, in step 2, the method for acquiring the moving speed of the target relative to the base station is to preliminarily estimate the moving speed of the target relative to the transmitting base station by using the arrival time and the transmission speed of the signal in different positioning periods.
Further, the step 3 constructs a search interval according to the preliminarily estimated relative velocity, and finds a suitable velocity therein to accurately estimate the frequency offset caused by the doppler effect.
Further, the method specifically comprises the following steps:
step 1: detecting and acquiring signal arrival time of a current positioning period and a last positioning period; for a single base station, a positioning period T is a time interval of signal transmission of the base station, and the base station enters a new positioning period every time the base station transmits a signal; suppose that in the kth positioning period, the base station is at time STkStarts to transmit a signal, which propagates and then at time AATkReaching the target; AATkI.e. the signal arrival time of the kth positioning period, the signal arrival time of the last period is AATk-1Can be obtained by a detection algorithm.
Step 2: according to AAT in step 1k-1And AATkThe positioning period of the positioning system and the propagation speed of the emission signal, preliminarily estimating the movement speed of a target relative to a base station in the current positioning period compared with the previous positioning period, and recording the target relative speed of the kth positioning period as vk；
And step 3: according to the relative speed v preliminarily estimated in the step 2kSetting a search interval, and searching a proper speed in the search interval to enable the reconstructed reference signal to be matched with the target received signal so as to estimate the frequency shift caused by the Doppler effect and correct the signal arrival time AATk(ii) a If k is 1, i.e. when it is currently in the first positioning period, let vk0; if k is>1, defining a relative motion speed range [ v ]k-,vk+]Wherein>0, a suitable value is found within this range, denoted v'kIs allowed to stand so that'kThe reconstructed reference signal is matched with the target received signal, and the arrival time of the signal obtained by calculation is recorded as AAT'kThe arrival time AAT'kIs to the AAT in step 1kCorrection of (1), let AATk＝AAT′kAnd finishing the updating.
Has the advantages that:
the method of the invention does not need extra information and does not depend on historical positions, only utilizes the arrival time difference of the signals, the system positioning period and the signal propagation speed to solve the relative motion distance, preliminarily estimates the motion speed of the target relative to the base station, constructs a search interval according to the relative speed and searches for proper speed in the search interval to accurately estimate the frequency offset caused by the Doppler effect, thereby correcting the arrival time of the signals. Compared with methods of acquiring speed and correcting the arrival time of an audio signal by using an inertial sensor and Kalman filtering, the method does not need to introduce redundant information, does not depend on historical positions, and has higher robustness.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
FIG. 1 is a flow chart of an audio signal arrival time correction method according to an embodiment of the present invention;
FIG. 2 is a conceptual diagram of a target relative velocity in an embodiment of the present invention;
FIG. 3 is a model diagram of a method for obtaining relative velocity in positioning according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of audio signal propagation in the time domain in an embodiment of the present invention;
fig. 5 is a schematic diagram of a propagation path of a two-dimensional planar indoor audio signal in an embodiment of the present invention.
Detailed Description
The positioning method in the embodiment of the present invention is clearly and completely described below with reference to the drawings in the embodiment of the present invention, and it is obvious that the described embodiment is only a part of the embodiment of the present invention, and not all embodiments. All other embodiments that can be obtained by a person skilled in the art based on the embodiments of the present invention without any inventive step are within the scope of the present invention.
The definition of the relative movement speed of the target is shown in FIG. 2, assuming that P is the moving target, S is the base station, and V is0P and v is the speed of movement of P relative to S, i.e. the target relative speed of movement, which causes a frequency shift of the audio. Once the relative motion velocity v is estimated, the spectral shift is also determined, so that the correction of the signal arrival time can be achieved. Taking the positioning architecture of the base station transmitting signal and the target receiving signal as an example, the steps for implementing the correction method are as follows, and fig. 1 shows a flow chart of the invention:
step 1: and detecting and acquiring the signal arrival time of the current positioning period and the last positioning period. As shown in fig. 4, for a single base station, the positioning period T is the time interval of the base station transmitting signals, and the base station enters a new positioning period every time it transmits a signal. Suppose that in the kth positioning period, the base station is at time STkStarts to transmit a signal, which propagates at a time AATkAnd the target is reached. AATkI.e. the signal arrival time of the kth positioning period, the signal arrival time of the last period is AATk-1They can all be obtained by a detection algorithm.
Step 2: according to AAT in step 1k-1And AATkThe positioning period T of the positioning system and the propagation speed of the emission signal, preliminarily estimating the movement speed of a target relative to a base station under the current positioning period compared with the previous positioning period, and recording the target phase of the kth positioning periodFor velocity vk。
And step 3: according to the relative speed v preliminarily estimated in the step 2kSetting a search interval, and searching a suitable speed in the search interval to estimate the frequency shift caused by the Doppler effect so as to correct the signal arrival time AATk. If k is 1, i.e. when it is currently in the first positioning period, let vk0; if k is>1, defining a relative motion speed range [ v ]k-,vk+]Wherein>0, a suitable value is found within this range, denoted v'kIs allowed to stand so that'kThe reconstructed reference signal is matched with the target received signal, and the arrival time of the signal obtained by calculation is recorded as AAT'kIt is to AAT in step 1kCorrection of (1), let AATk＝AAT′kAnd finishing the updating.
The embodiment of the invention takes a single base station in an audio positioning system as an example to illustrate a method for acquiring the relative speed of a target, and the method is suitable for any base station in the positioning system. As shown in fig. 3, a base station transmits a modulated audio signal (source signal) at S, and after a target such as a smart phone, a PAD, etc. receives the audio signal at two points a or B through a microphone, first, a signal arrival time is obtained through an audio detection algorithm, then, a relative movement velocity of the target is preliminarily estimated according to the signal arrival time, a search interval is constructed by using the velocity, an appropriate velocity is searched in the search interval to estimate a frequency shift caused by a doppler effect, and finally, the signal arrival time is corrected by using a reference signal constructed by the frequency shift. The specific implementation process is described as follows:
firstly, acquiring signal arrival time through audio detection algorithm
The audio detection algorithm adopts a cross-correlation function-based arrival time detection algorithm, as shown in fig. 5, taking a two-dimensional plane as an example, a source signal S (t) transmitted by a base station S reaches a target P through a direct path and a plurality of reflection paths, and assuming that S (t) only amplitude attenuation and time delay occur in the propagation process, a signal r (t) received by the target can be regarded as linear superposition of the source signal through different path delays:
where L is the total number of paths, αiRepresents the attenuation degree of the source signal to the target through the ith path and satisfies 0 < αi< 1, n (t) is the noise superimposed on the received signal, tiIs the time delay for the source signal to reach the destination through the ith path and assumes that the 1 st path is the shortest path, i.e., the direct path in fig. 5. Calculating the cross-correlation function R of the source signal and the target receiving signal by using the formula (2)r(τ) since the source signal reaches the target first through the direct path, the cross-correlation detection algorithm measures RrAnd (tau) taking the peak time corresponding to the first path as the estimation of the arrival time of the source signal.
Secondly, estimating the relative movement speed of the target according to the arrival time of the signal
The propagation process of the audio signal in the time domain is shown in FIG. 4, assuming that T is the positioning period, STk-1And STkAnd respectively represents the time of the (k-1) th and k-th positioning period base station transmitting signal, the unit is s, then there are:
T＝STk-STk-1k＝2,3,4….. (3)
AAT in FIG. 4k-1And AATkThe source signal arrival time, which is estimated by the audio detection algorithm, of the target in the (k-1) th and k-th positioning periods, respectively, is s. Suppose AATkThe position of the target at the moment is PkIs known to be PkInformation of distance to transmitting base station S1
Satisfies the following conditions:
where c is the speed of sound in m/s. In the same way, AAT can be obtainedk-1The position P of the target at the momentk-1Information of distance to transmitting base station S1
Target slave AATk-1Time to AATkThe distance Δ d traveled by time with respect to S1 is:
the formula (4) and (5) are replaced by the formula (6) which comprises the following components:
Δd＝(AATk-AATk-1+STk-STk-1)*c (7)
at the same time, the slave AAT can be calculatedk-1Time to AATkAt this moment, the movement time Δ t of the object is:
Δt＝(AATk-AATk-1) (8)
from the expressions (3), (7) and (8), the AAT can be calculatedkTime of day, velocity v of target relative to transmitting base stationkComprises the following steps:
vka positive value indicates that the target is moving away from the transmitting base station. v. ofkWhen the value is negative, it indicates that the target is moving closer to the transmitting base station.
Thirdly, correcting the arrival time of the signal according to the relative motion speed and the Doppler effect
Chirp signals (chirp signals) are the audio form often used by source signals in audio positioning systems, and the correction of the arrival time of a signal is described below by taking the transmission of a chirp signal by a base station as an example. A chirp signal is a signal whose instantaneous frequency varies linearly with time, and its expression in the time domain is as shown in equation (10):
wherein f is0Is the initial frequency, f, of the chirp signaleT is the duration of the chirp signal for the cutoff frequency.
As the target moves, the doppler effect causes the frequency of the signal received by the target to change compared to the transmitted source signal, the magnitude of the change being related to the speed of movement. Suppose that the Doppler effect causes the original parameter { f ] of the chirp signal in equation (10)0,feT is changed to { f'0,f′eT', ignoring the influence of the operating frequency of the transmitting base station (i.e. the conversion frequency of the DAC in the hardware device) and the sampling rate of the handset, and the relationship between them is shown in equation (11):
where v is the estimated relative velocity of motion of the object.
Due to AAT in the formula (9)kAnd AATk-1Do not take into account the effect of Doppler, so vkThere may be certain deviations that need to be corrected. V calculated according to equation (9) at the k-th positioning periodkDefining a relative velocity range vk-,vk+]And searching the numerical range for self definition. Search successively within the range to find v'kSo that the following conditions are satisfied: from v'kCalculating a varied chirp signal parameter { f 'in substitution formula (11)'0,f′eAnd T ', substituting the parameters into equation (10) to obtain a reconstructed source signal s ' (T) so that s ' (T) matches the target received signal r (T), i.e. when s (T) in equation (2) is replaced by s ' (T), the peak value corresponding to the direct path of the obtained cross-correlation function is the largest in the velocity range, and the time corresponding to the first peak value in the cross-correlation function at this time is the Doppler-corrected signal arrival time estimate, which is denoted as AAT 'k。
The above description is only one embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.
Claims (4)
1. A method for correcting the arrival time of an audio signal based on relative velocity and Doppler effect is characterized by comprising the following steps:
step 1, detecting and acquiring signal arrival time of a current positioning period and a last positioning period;
step 2, preliminarily estimating the movement speed of the target relative to the base station by using the arrival time difference of the signals, the system positioning period and the signal propagation speed;
and 3, constructing a search interval according to the relative speed and searching for a proper speed in the search interval to accurately estimate the frequency offset caused by the Doppler effect so as to correct the arrival time of the audio signal.
2. The method according to claim 1, wherein the step 2 is implemented by using the arrival time and transmission speed of the signal in different positioning periods to preliminarily estimate the moving speed of the target relative to the transmitting base station.
3. The method for correcting arrival time of audio signal based on relative velocity and Doppler effect according to claim 1, wherein the step 3 constructs a search interval according to the preliminarily estimated relative velocity, and finds a suitable velocity therein for accurately estimating the frequency offset caused by Doppler effect.
4. The method for correcting the arrival time of an audio signal based on the relative velocity and the doppler effect according to claim 1, comprising the steps of:
step 1: detecting and acquiring signals of current positioning period and last positioning periodThe arrival time; for a single base station, a positioning period T is a time interval of signal transmission of the base station, and the base station enters a new positioning period every time the base station transmits a signal; suppose that in the kth positioning period, the base station is at time STkStarts to transmit a signal, which propagates and then at time AATkReaching the target; AATkI.e. the signal arrival time of the kth positioning period, the signal arrival time of the last period is AATk-1All can be obtained by a detection algorithm;
step 2: according to AAT in step 1k-1And AATkThe positioning period of the positioning system and the propagation speed of the emission signal, preliminarily estimating the movement speed of a target relative to a base station in the current positioning period compared with the previous positioning period, and recording the target relative speed of the kth positioning period as vk；
And step 3: according to the relative speed v preliminarily estimated in the step 2kSetting a search interval, and searching a proper speed in the search interval to enable the reconstructed reference signal to be matched with the target received signal so as to estimate the frequency shift caused by the Doppler effect and correct the signal arrival time AATk(ii) a If k is 1, i.e. when it is currently in the first positioning period, let vk0; if k > 1, a relative movement speed range [ v ] is definedk-，vk+]Where > 0, a range of values is searched for by the user, and a suitable value is found within this range, denoted v'kIs allowed to stand so that'kThe reconstructed reference signal is matched with the target received signal, and the arrival time of the signal obtained by calculation is recorded as AAT'kThe arrival time AAT'kIs to the AAT in step 1kCorrection of (1), let AATk＝AAT′kAnd finishing the updating.
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| CN115604817A (en) * | 2022-10-08 | 2023-01-13 | 浙江德清知路导航科技有限公司（Cn） | Wide-area audio indoor positioning method, system and terminal based on radio frequency enhancement |
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