CN104159291A - Passive type TDOA positioning method - Google Patents

Abstract

The invention discloses a passive type TDOA positioning method. The method comprises the following steps: A, installing and positioning anchor nodes, wherein there are at least 2 to 4 anchor nodes in the same positioning area; B, numbering the anchor nodes according to a rule; C, in the same positioning period, the anchor nodes sending positioning signals according to a sequence; D, label nodes, according to the received positioning signals sequentially sent by the multiple anchor nodes, calculating signal arrival time difference between itself and some two anchor nodes; and E, the label nodes, according to the arrival time differences, calculating coordinate positions or sending data to the anchor nodes. By using the method, during a positioning process, the label nodes can finish the positioning process by only receiving the positioning signals without sending the positioning signals, such that no matter how many labels there are in the same area, the positioning process can be finished at a time, thus the system capacity and reliability are greatly improved. The positioning signals are sent through the anchor nodes for multiple times, and positioning results of the multiple times can be obtained, so the positioning precision is substantially improved.

Description

Passive TDOA (time difference of arrival) positioning method

Technical Field

The invention relates to a passive TDOA (time difference of arrival) positioning method.

Background

The indoor wireless positioning system is a system capable of positioning, monitoring and controlling objects such as personnel, mobile production equipment, important assets and the like in real time in an indoor environment or an environment incapable of receiving GPS signals.

Existing indoor wireless positioning systems are generally classified into field strength (RSSI) based positioning systems and time (ranging) based wireless positioning systems. The technology based on the field intensity (RSSI) mainly adopts technical means such as RFID electronic tags (including active and passive types), ZigBee, WiFi and Bluetooth, and the wireless positioning system based on time (ranging) has technical means such as CSS (linear frequency modulation) and UWB (ultra wide band radio).

The present invention is primarily directed to time (ranging) based wireless location systems. It is generally composed of label nodes that need to be located and anchor nodes that are fixed. Since the propagation velocity of radio waves in the air is relatively fixed, the distance between the tag node and the anchor node can be calculated by measuring the propagation time of the radio waves between the tag node and the anchor node, and the two-dimensional and three-dimensional coordinates of the tag can be calculated by using a plurality of anchor nodes.

The above-mentioned time (ranging) -based wireless positioning systems generally employ TOA (time of arrival) or TDOA (time difference of arrival) methods for positioning.

The TOA (time of arrival) location method calculates tag coordinates by measuring the distance of the tag from multiple anchor nodes. To obtain the plane coordinates of a label, at least 3 anchor node distance values are needed, and at least 4 anchor node distance values are needed for the three-dimensional coordinates. Because the labels need to be measured one by one with a plurality of anchor nodes, and a plurality of positioning signals (data packets) need to be sent every time of measurement, the time consumed by each positioning is more, and the problem of collision prevention among a plurality of labels is well solved in the application occasions with dense nodes. Therefore, in a positioning system with dense nodes, the TOA (time of arrival) positioning method can only increase the refresh time interval to increase the system capacity, so that the real-time performance of the system is deteriorated. In short, the method has the defects of small system capacity and poor reliability.

The TDOA (time difference of arrival) location method calculates tag coordinates by measuring the time difference of arrival of radio signals transmitted by tags at a plurality of anchor nodes. Similarly, to obtain the plane coordinates of a label, at least 3 anchor nodes are required, and at least 4 anchor nodes are required for the three-dimensional coordinates.

The general TDOA positioning system is an active TDOA working method, and the working process is as follows:

A. a tag transmits a locating signal.

B. A plurality of anchor nodes record the time of arrival of the positioning signal.

C. And after receiving the positioning signal of the label, the synchronous node sends a synchronous signal.

D. A plurality of anchor nodes record the time of arrival of the synchronization signal.

E. And the multiple anchor nodes calculate the arrival time difference of the signals of the multiple anchor nodes.

F. Coordinates of the tag are calculated from the plurality of arrival time differences.

The time spent on positioning is greatly shortened because the tag only needs to send the positioning signal once, and then the synchronous node sends the synchronous signal once again to generate a plurality of arrival time differences. However, in an application situation with dense nodes, there is a problem of signal collision between tags, and in order to solve the problem, a complex network protocol must be introduced to coordinate the operation of multiple tags, and meanwhile, there is a problem that the tags and anchor nodes in adjacent areas interfere with each other. Therefore, in a node-dense positioning system, the positioning method using active TDOA is improved over the TOA method, and has the disadvantages of smaller system capacity and poor reliability.

In application occasions with dense nodes and more anchor nodes, such as practical application occasions of prisons, coal mines, schools, museums, exhibition halls and the like, how to improve system capacity, positioning accuracy and reliability is a problem to be solved urgently.

In view of the above, the present invention is particularly proposed.

Disclosure of Invention

The technical problem to be solved by the invention is to overcome the defects of the prior art and provide a passive TDOA positioning method with large system capacity, high reliability and high positioning accuracy.

In order to solve the technical problems, the invention adopts the technical scheme that:

a passive TDOA locating method comprises the following steps:

A. installing positioning anchor nodes, wherein at least 2-4 anchor nodes are arranged in the same positioning area;

B. the anchor nodes are numbered according to rules;

C. in a positioning period, each anchor node sends positioning signals in sequence;

D. the tag node calculates the signal arrival time difference between the tag node and a certain two anchor nodes according to the received positioning signals sequentially sent by the plurality of anchor nodes;

E. and the tag node calculates the coordinate position or sends the data to the anchor node according to the arrival time difference.

Preferably, the step B adopts a numbering mode of region numbers plus sequence numbers.

Preferably, in step C, the plurality of anchor nodes sequentially transmit the positioning signal once or several times in each positioning period.

After adopting the technical scheme, compared with the prior art, the invention has the following beneficial effects:

in the positioning process, the label node only receives the positioning signal and can complete the positioning process without sending the positioning signal, and the positioning process can be completed at one time no matter how many labels are in the same area, so that the system capacity and the reliability are greatly improved. The anchor node sends the positioning signal for multiple times, and multiple positioning results can be obtained, so that the positioning precision is obviously improved.

The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.

Drawings

FIG. 1 is a signal flow diagram of the present invention for performing a passive TDOA location method with two anchor nodes and one tag node.

Detailed Description

The invention relates to a passive TDOA (time difference of arrival) positioning method, which can realize that in the positioning process, a label node only receives a positioning signal and can complete the positioning process without sending the positioning signal, and the positioning process can be completed at one time no matter how many labels are in the same area, thereby greatly improving the system capacity and reliability. The anchor node sends the positioning signal for multiple times, and multiple positioning results can be obtained, so that the positioning precision is obviously improved.

The method comprises the following steps:

A. installing and positioning anchor nodes, wherein at least 2 anchor nodes (one-dimensional positioning) or 3 anchor nodes (two-dimensional positioning) or 4 anchor nodes (three-dimensional positioning) are arranged in the same positioning region;

B. the anchor nodes are numbered according to rules (anchor node ID numbers);

C. in a positioning period, each anchor node sends positioning signals in sequence;

D. the tag node calculates the signal arrival time difference between the tag node and a certain two anchor nodes according to the received positioning signals sequentially sent by the plurality of anchor nodes;

E. and the tag node calculates the coordinate position or sends the data to the anchor node according to the arrival time difference.

In the positioning process, the label node only receives the positioning signal and can complete the positioning process without sending the positioning signal, and the positioning process can be completed at one time no matter how many labels are in the same area, so that the system capacity and the reliability are greatly improved. The anchor node sends the positioning signal for multiple times, and multiple positioning results can be obtained, so that the positioning precision is obviously improved.

The number of anchor nodes in the step A is determined according to the positioning dimension requirement. On the premise of meeting the minimum number, the positioning accuracy and the positioning reliability can be improved by increasing the number of anchor nodes.

Preferably, the step B adopts a numbering mode of region numbers plus sequence numbers.

Preferably, in step C, the plurality of anchor nodes sequentially transmit the positioning signal once or several times in each positioning period. The positioning accuracy can be improved by using a plurality of positioning results.

For describing the present invention, two anchor nodes and one tag node are taken as an example, and refer to fig. 1.

In the figure, ANC1 is anchor node number 1, ANC2 is anchor node number 2, ANC3 is anchor node number 3, ANC4 is anchor node number 4, and TAG is a TAG node. The method works according to the following steps:

a. first ANC1 sends a positioning signal.

The TAG node and ANC2, ANC3 receive the positioning signal, and respectively record the arrival time point of the incoming signal, T1TAG, T1ANC2, T1ANC 3.

ANC2 forwards the positioning signal of ANC 1.

The TAG node, ANC1 and ANC3 receive the positioning signal forwarded by ANC2, and respectively record the time point T2TAG, T2ANC1 and T2ANC3 of the arrival of the incoming signal.

e. And calculating the arrival time difference according to the time signals.

T2TAG-T1TAG ═ L12-a)/C + (T2ANC3-T1ANC3- (L13-L12)/C + L23/C) + b/C, namely T2TAG-T1TAG ═ T2ANC3-T1ANC3- (L13-L12+ (L12-a) + L23+ b)/C, then b-a ═ C- (T2ANC3-T1ANC3) - (T2TAG-T1 TAG)). C- (L12+ L23) b-a is the distance difference between the TAG node and ANC1 and ANC 2. Where C is the speed of light in air.

f. By starting with ANC2, ANC3 and ANC4, the above steps are repeated, and the distance difference between the TAG node and ANC2 and ANC3, the distance difference between the TAG node and ANC3 and ANC4, and the distance difference between the TAG node and ANC4 and ANC1 can be obtained.

According to the method, after the distance difference between the TAG node and 4 anchor nodes is obtained, the coordinates of the TAG node can be calculated by using a hyperbolic equation.

Only the two-dimensional assignment of TAG nodes by M anchor nodes is discussed hereinThe problem of bit computation. Setting M anchor nodes on a two-dimensional plane, wherein (X, y) is the position of a TAG node_i，Y_i) Is the known location of the ith anchor node. The distance between the TAG and the ith anchor node is:

$R_i=\sqrt{{(X_i-x)}^2+{(Y_i-y)}^2}$

$R_i^2={(X_i-x)}^2+{(Y_i-y)}^2=K_i-{2X}_{i}x-{2Y}_{i}y+x^2+y^2$

wherein,

$K_i=X_i^2+Y_i^2$

let R_i，1Representing the difference between the actual distance of TAG from the anchor node i (i ≠ 1) and the anchor node 1, then

$R_{i,1}={\mathrm{cd}}_{i,1}=R_i-R_1=\sqrt{{(X_i-x)}^2+{(Y_i-y)}^2}-\sqrt{{(X_1-x)}^2+{(Y_1-y)}^2}$

Where c is the propagation velocity of the electric wave in the air and d_i，1Is a TDOA measurement. The nonlinear system of equations may be solved by first performing a linearization process. Because of the fact that

Then $R_{i,1}^2+{2R}_{i,1}{R}_1+R_i^2=K_i-{2X}_{i}x-{2Y}_{i}y+x^2+y^2$

The following can be obtained: $R_{i,1}^2+{2R}_{i,1}{R}_1=K_i-{2X}_{i,1}x-{2Y}_{i,1}y-K_1$

wherein, X_i，1＝X_i-X₁；Y_i，1＝Y_i-Y₁

X, y, R₁And (4) solving the equation system to obtain the coordinate position of the TAG by considering the unknown number.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims (3)

1. A passive TDOA positioning method is characterized in that: the method comprises the following steps:

A. installing positioning anchor nodes, wherein at least 2-4 anchor nodes are arranged in the same positioning area;

B. the anchor nodes are numbered according to rules;

C. in a positioning period, each anchor node sends positioning signals in sequence;

D. the tag node calculates the signal arrival time difference between the tag node and a certain two anchor nodes according to the received positioning signals sequentially sent by the plurality of anchor nodes;

E. and the tag node calculates the coordinate position or sends the data to the anchor node according to the arrival time difference.

2. The passive TDOA location method of claim 1, wherein: and step B, adopting a numbering mode of adding the area number and the sequence number.

3. The passive TDOA location method of claim 1, wherein: and step C, the plurality of anchor nodes sequentially transmit the positioning signals once or several times in each positioning period.