Method for Estimating the Over-the-Air Propagation Delay of Direct Wave

Abstract

The invention discloses a method for estimating the air propagation delay of a direct wave, wherein an azimuth, an elevation angle and a total delay of a multipath wave reaching a receiving end are obtained through a receiving device; a departure angle of a reflected wave is obtained using a geometric relationship of wave reflection; a hypothetical point on a direct wave ray is selected as a transmitting end, and hereby the air propagation delay of the direct wave and the position of a reflection point of the reflected wave are calculated; the propagation delay and distance of the reflected wave are calculated according to the total delay of the direct wave and the reflected wave and the position of the hypothetical point. The invention can obtain the air propagation delay of the direct wave, thereby obtaining a propagation distance of the direct wave and fulfilling the requirements of ranging and positioning.

Claims

1. A method for estimating the air propagation delay of a direct wave, comprising 1) obtaining a received signal through a radio wave receiving device, and estimating an azimuth of arrival, an elevation angle and a total delay of each path of a multipath wave arriving at a receiving end; the estimated azimuth of arrival, elevation angle and total delay of each path of the multipath wave arriving at the receiving end comprise the azimuth of arrival, elevation angle of arrival, and total delay of arrival (φ.sub.r,0, θ.sub.r,0, τ.sub.r,0) of the direct wave, and the azimuth of arrival, elevation angle of arrival, and total delay of arrival (φ.sub.r,1, θ.sub.r,1, τ.sub.r,1) of a reflected wave; 2) obtaining a departure angle of the reflected wave according to the geometric principle of wave reflection and an arrival angle of the reflected wave measured by the radio wave receiving device; the arrival angle of the reflected wave refers to the azimuth of arrival and the elevation angle of arrival of the reflected wave, and the departure angle of the reflected wave refers to the azimuth of departure and the elevation angle of departure of the reflected wave; 3) selecting a hypothetical point on a ray where the arrival angle of the direct wave is located as a transmitting end, and calculating the air propagation delay of the direct wave and the position of a reflection point of the reflected wave at the hypothetical point; the position of the reflection point is determined by the midpoint of a common perpendicular line segment between the ray of the departure angle of the reflected wave and the ray of the arrival angle; 4) calculating a propagation distance of the reflected wave according to the total delay of the direct wave, the total delay of the reflected wave and the position of the selected hypothetical point;
l.sub.sc=|r.sub.r−r.sub.sc+|r.sub.sc−r.sub.p| wherein, l.sub.sc means the propagation distance of the reflected wave, r.sub.r means the coordinate of the receiving end, r.sub.sc means the estimated coordinate of the reflection point of the reflected wave, r.sub.p means the coordinate of the hypothetical point, and |⋅| means a modulus value; 5) calculating the sum of the distance between the hypothetical point of the transmitting end and the reflection point and the distance between the reflection point and the receiving end, making a difference between the sum and the propagation distance of the reflected wave, and taking an absolute value; selecting the hypothetical point with the smallest absolute value as the position of the transmitting end; calculating the distance between the transmitting end and the receiving end and dividing the distance by the propagation velocity of the radio wave to obtain the estimated value of the air propagation delay of the direct wave; the path propagation delay when the reflected wave reaches the receiving end is:
τ.sub.p,1=τ.sub.r,1−τ.sub.r,0+τ.sub.p,0 wherein, τ.sub.p,1 means the path propagation delay when the reflected wave reaches the receiving end, τ.sub.r,1 means the measured total delay of the reflected wave, τ.sub.r,0 means the measured total delay of the direct wave, and τ.sub.p,0 means the direct path propagation delay from the hypothetical point P of the transmitting end to the receiving end; the path propagation distance of the reflected wave reaching the receiving end is l′.sub.sc=cτ.sub.p,1, where c is the propagation velocity of an electromagnetic wave in space; choose an appropriate P point position to obtain the smallest cost function:
ƒ(r.sub.p)=|l.sub.sc−l′.sub.sc| wherein, ƒ(r.sub.p) means the cost function, l.sub.sc means the propagation distance of the reflected wave calculated according to the spatial position coordinate, and l′.sub.sc means the propagation distance of the reflected wave calculated according to the calculated path propagation delay when the reflected wave reaches the receiving end; an estimated value {circumflex over (τ)} of the propagation delay of the direct wave is: $\hat{\tau }=\arg \underset{r_p}{\min }f\left(r_p\right)=\arg \underset{\tau }{\min }f\left(c\tau \right)$ wherein, {circumflex over (τ)} means the estimated value of the propagation delay of the direct wave, r.sub.p means the distance from a hypothetical transmitting point to the receiving end, and τ means the propagation delay of the direct wave.

2. The method for estimating the air propagation delay of the direct wave according to claim 1, wherein the azimuth of arrival, the elevation angle and the total delay of each path of the multipath wave arriving at the receiving end are estimated using a joint angle and delay estimation method in step 1).

3. The method for estimating the air propagation delay of the direct wave according to claim 2, wherein the relationship between the arrival angle of the reflected wave and the departure angle of the reflected wave in step 2) is: $\{\begin{array}{c}{\phi }_{r,1}-{\phi }_{t,1}=\pi \\ {\theta }_{r,1}-{\theta }_{t,1}=0\end{array}\mathrm{or}\{\begin{array}{c}{\phi }_{r,1}+{\phi }_{t,1}=\pi ,2\pi ,3\pi \\ {\theta }_{r,1}+{\theta }_{t,1}=\pi \end{array}$ wherein, φ.sub.r,1 means the azimuth of arrival of the reflected wave, φ.sub.t,1 means the azimuth of departure of the reflected wave, θ.sub.r,1 the elevation angle of arrival of the reflected wave, and θ.sub.t,1 means the elevation angle of departure of the reflected wave.

4. The method for estimating the air propagation delay of the direct wave according to claim 3, wherein a hypothetical point on the ray where the arrival angle of the direct wave is located is selected as the transmitting end in step 3; let the hypothetical point be point P; the distance from the hypothetical point to the receiving end is r.sub.P, the receiving end is the origin of coordinates, and the coordinate of the hypothetical point is expressed as:
r.sub.P=r.sub.P[sin θ.sub.r,0 cos φ.sub.r,0 sin θ.sub.r,0 sin φ.sub.r,0 cos θ.sub.r,0] Where, r.sub.P means the coordinate of the hypothetical point, φ.sub.r,0 means the azimuth of departure of the direct wave, and θ.sub.r,0 means the elevation angle of arrival of the direct wave.

5. The method for estimating the air propagation delay of the direct wave according to claim 4, wherein the method for determining the position of the reflection point by the midpoint of the common perpendicular line segment between the ray of the departure angle of the reflected wave and the ray of the arrival angle in step 3 is as follows: obtain the departure angle (φ.sub.t,1, θ.sub.t,1) of the reflected wave and the coordinate r.sub.r of the receiving end according to step 2; then obtain the common perpendicular line segment of the transmitting ray and receiving ray of the reflected wave; finally obtain the midpoint of the common perpendicular line segment, which is recorded as r.sub.sc, and is the estimated reflection point of the reflected wave.

6. The method for estimating the air propagation delay of the direct wave according to claim 5, wherein the positioning of the transmitting end is completed by setting the position coordinate of the receiving end or taking the receiving end as the origin of coordinates according to the finally obtained propagation delay combined with the arrival angle information of the direct wave measured by the device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0058] FIG. 1 The definition of the parameters of the direct wave and reflected wave including the departure angle and the arrival angle.

[0059] FIG. 2 Hypothetical point selection and reflection point position estimation model.

[0060] FIG. 3 Estimated result of the optimal hypothetical point.

DETAILED DESCRIPTION

[0061] According to the drawings and specific embodiments, the invention is further described below. In this specific embodiment, the receiving end is a receiver with a direction finding function, and the transmitting end is a device transmitting a signal with a specific format and a certain bandwidth. In this embodiment, the arrival angle and signal delay of an electromagnetic wave are obtained through a direction-finding antenna array at the receiving end. It should be understood that these embodiments are only used to illustrate the invention instead of limiting the scope of the invention. After reading the invention, various equivalent forms of modifications of the invention by those skilled in the art fall within the scope defined by the claims appended to this application.

[0062] A method for estimating the air propagation delay of a direct wave, wherein the known conditions required to estimate the propagation delay include an arrival angle of the direct wave and the arrival angle of a reflected wave at the receiving end and a total delay experienced by a signal; the information can be obtained by means of a joint angle and delay estimation algorithm, including the following steps.

[0063] Step 1, obtaining a received signal through a radio wave receiving device, and estimating an azimuth angle of arrival, an elevation angle and the total delay of each path of a multipath wave arriving at the receiving end. As shown in FIG. 1, the total delay includes two parts such as the air propagation delay of the radio wave and a system response delay, and the process of estimating the system response delay from the total delay is the main process of the invention.

[0064] The azimuth angle of arrival, the elevation angle and the total delay of each path of the multipath wave arriving at the receiving end are estimated using the joint angle and delay estimation method. The estimated azimuth of arrival, elevation angle and total delay of each path of the multipath wave arriving at the receiving end include the azimuth of arrival, elevation angle of arrival, and total delay of arrival (φ.sub.r,0, θ.sub.r,0, τ.sub.r,0) of the direct wave, and the azimuth of arrival, elevation angle of arrival, and total delay of arrival (φ.sub.r,1, θ.sub.r,1, τ.sub.r,1) of the reflected wave.

[0065] Definition: the azimuth of departure, the elevation angle of departure and the total delay of departure of the reflected wave are expressed as (φ.sub.t,1, θ.sub.t,1, τ.sub.t,1), and the azimuth of departure, the elevation angle of departure and the total delay of departure of the direct wave are expressed as (φ.sub.t,0, θ.sub.t,0, τ.sub.t,0).

[0066] The reflected wave refers to a single reflected wave. In the same coordinate system, when the surface of a wave reflector is secularly reflected, the departure angle of an incident wave and the arrival angle of the reflected wave show a specific algebraic relationship.

[0067] Step 2, obtaining the departure angle of the reflected wave according to the geometric principle of wave reflection and the arrival angle of the reflected wave measured by the radio wave receiving device. The arrival angle of the reflected wave refers to the azimuth of arrival and the elevation angle of arrival of the reflected wave, and the departure angle of the reflected wave refers to the azimuth of departure and the elevation angle of departure of the reflected wave. The departure angle of the reflected wave is obtained according to the relationship between the arrival angle of the reflected wave and the departure angle of the reflected wave:

[00005]$\begin{array}{cc}\{\begin{array}{c}{\phi }_{r,1}-{\phi }_{t,1}=\pi \\ {\theta }_{r,1}-{\theta }_{t,1}=0\end{array}\mathrm{or}\{\begin{array}{c}{\phi }_{r,1}+{\phi }_{t,1}=\pi ,2\pi ,3\pi \\ {\theta }_{r,1}+{\theta }_{t,1}=\pi \end{array}& \left(1\right)\end{array}$

[0068] Where, φ.sub.r,1 means the azimuth of arrival of the reflected wave, φ.sub.t,1 means the azimuth of departure of the reflected wave, θ.sub.r,1 the elevation angle of arrival of the reflected wave, and θ.sub.t,1 means the elevation angle of departure of the reflected wave.

[0069] It can be seen that after the direction-finding device obtains the arrival angle of the reflected wave, the departure angle will also be limited to a certain combination range, so that the possibility of a limited set of departure angles can be obtained. Traverse all the departure angles, and select the departure angle leading to the shortest distance of the common perpendicular line between the ray of the departure angle of the reflected wave and the ray of the arrival angle as the true departure angle of the reflected wave. The ray of the arrival angle of the reflected wave refers to the ray extending in the direction of the arrival angle with the receiving end as the endpoint. The departure angle meeting formula (1) may have no common perpendicular line with the ray of the arrival angle. When the true departure angle is selected, the departure angle corresponding to this case can be directly excluded.

[0070] Step 3, as shown in FIG. 2, selecting a hypothetical point on the ray where the arrival angle of the direct wave is located as the transmitting end, and calculating the air propagation delay of the direct wave and the position of a reflection point of the reflected wave at the hypothetical point. The position of the reflection point is determined by the midpoint of a common perpendicular line segment between the ray of the departure angle of the reflected wave and the ray of the arrival angle.

[0071] The hypothetical point is selected as the transmitting end, and the propagation time from the position of the hypothetical point to the position of the receiving end does not exceed the total delay estimated in the receiving device. Let the hypothetical point be point P; the distance from the hypothetical point to the receiving end is r.sub.P, the receiving end is the origin of coordinates, and the coordinate of the P point is expressed as:

r.sub.P=r.sub.P [sin θ.sub.r,0cos φ.sub.r,0 sin θ.sub.r,0 sin φ.sub.r,0 cos θ.sub.r,0]tm (2)

[0072] Where, r.sub.P means the coordinate of the P point, φ.sub.r,0 means the azimuth of departure of the direct wave, and θ.sub.r,0 means the elevation angle of arrival of the direct wave.

[0073] According to step 2, the departure angle (φ.sub.t,1, θ.sub.t,1) of the reflected wave and the coordinate r.sub.r of the receiving end can be obtained; here, you can define the coordinate of the receiving end as r.sub.r, and then the common perpendicular line segment between the transmitting ray of the reflected wave and the receiving ray can be obtained using the estimated arrival angle (φ.sub.r,1, θ.sub.r,1) and the known coordinate of the receiving end; finally, the midpoint of the common perpendicular line segment is obtained, which is recorded as r.sub.sc, and is the estimated reflection point of the reflected wave.

[0074] The departure angle of the reflected wave can be filtered to a finite set according to the algebraic relationship in formula (2). Then calculate the length of the common perpendicular line segment of the straight line before and after reflection of the reflected wave, and select the angle that can minimize the corresponding common perpendicular line as the departure angle of the reflected wave.

[0075] Step 4, the reflection path is composed of a connecting line of the receiving end, the reflection point and the transmitting end. After selecting the hypothetical point as the transmitting end, the position of the reflection point is obtained. Using the known position of the receiving end, the propagation distance of the reflected wave can be calculated as follows:

l.sub.sc=|r.sub.r−r.sub.sc|+|r.sub.sc−r.sub.p|  (3)

[0076] Where, l.sub.sc means the propagation distance of the reflected wave, and |⋅| means a modulus value.

[0077] Step 5, calculating the sum of the distance between the hypothetical point of the transmitting end and the reflection point and the distance between the reflection point and the receiving end, making a difference between the sum and the propagation distance of the reflected wave, taking an absolute value, and selecting the hypothetical point with the smallest absolute value as the position of the transmitting end; calculating the distance between the transmitting end and the receiving end and dividing the distance by the propagation velocity of the radio wave to obtain the estimated value of the air propagation delay of the direct wave.

[0078] Let the propagation delay of the direct path from the hypothetical point P at the transmitting end to the receiving end be τ.sub.p,0. Based on the principle that the direct wave and the reflected wave start from the transmitting end at the same time and arrive at the receiving end at different times, it is not difficult to calculate the path propagation delay of the reflected wave reaching the receiving end as follows:

τ.sub.p,1=τ.sub.r,1−τ.sub.r,0+τ.sub.p,0   (4)

[0079] Where, τ.sub.p,1 means the path propagation delay when the reflected wave reaches the receiving end, τ.sub.r,1 means the measured total delay of the reflected wave, τ.sub.r,0 means the measured total delay of the direct wave, and τ.sub.p,0 means the direct path propagation delay from the hypothetical point P of the transmitting end to the receiving end.

[0080] The path propagation distance of the reflected wave reaching the receiving end is l′.sub.sc=cτ.sub.p,1, where c is the propagation velocity of an electromagnetic wave in space.

[0081] Choose an appropriate P point position to obtain the smallest cost function:

ƒ(r.sub.p)=|l.sub.sc−l′.sub.sc|  (5)

[0082] Where, ƒ(r.sub.p) means the cost function, l.sub.sc means the propagation distance of the reflected wave calculated according to the spatial position coordinate, and l′.sub.sc means the propagation distance of the reflected wave calculated according to the calculated path propagation delay when the reflected wave reaches the receiving end.

[0083] FIG. 3 shows the estimated result of the optimal hypothetical point.

[0084] The estimated value {circumflex over (τ)} of the propagation delay of the direct wave is:

[00006]$\begin{array}{cc}\hat{\tau }=\arg \underset{r_p}{\min }f\left(r_p\right)=\arg \underset{\tau }{\min }f\left(c\tau \right)& \left(6\right)\end{array}$

[0085] Where, {circumflex over (τ)} means the estimated value of the propagation delay of the direct wave, r.sub.p means the distance from a hypothetical transmitting point to the receiving end, and τ means the propagation delay of the direct wave.

[0086] The invention is not limited to radio waves, and is also applicable to acoustic waves. The invention is used in the fields of positioning and ranging etc.

[0087] The above is only a preferred embodiment of the invention. It should be pointed out that as far as a person of ordinary skill in the art is concerned, the person may implement some improvements and modifications on the premise of following the principle of the invention; however, such improvements and modifications shall be deemed to be within the coverage of protection of the invention.