Patent Publication Number: US-2023139193-A1

Title: Indoor direction finding method and system thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of U.S. Patent Application Ser. No. 63/274,484, filed on Nov. 1, 2021, the full disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     Technical Field 
     The present disclosure relates to the technical field of direction finding, particularly to indoor direction finding method and indoor direction finding system. 
     Related Art 
     In the conventional indoor direction finding method, a Bluetooth connection is often established between a Bluetooth tag and a wireless base station. The Bluetooth tag would first transmit a Bluetooth signal to the wireless base station and the wireless base station obtains a relative position between the Bluetooth tag and the wireless base station according to the angle between the wireless base station and the received Bluetooth signal and the distance between the antenna modules received by the wireless base station. Based on the fact that the position of the wireless base station is known, the position of the Bluetooth tag can be obtained for achieving indoor direction finding according to the obtained relative position and the position of the wireless base station. 
     In another indoor direction finding method, it mainly broadcasts the Bluetooth signal to the wireless base station through the Bluetooth tag. The wireless base station obtains the distance between the wireless base station and the Bluetooth tag according to a received signal strength indication (RSSI) of the received Bluetooth signal to obtain the relative position. Since the position of the wireless base station is known, the position of the Bluetooth tag could be obtained according to the obtained relative position and the position of the wireless base station. 
     However, in the conventional indoor direction finding method which is mainly angle based or RSSI based, the angle-based indoor direction finding method could achieve indoor direction finding under the conditions of different angles (e.g. 30° or 45°), and the RSSI-based indoor direction finding method achieves indoor direction finding under the conditions of different received signal strength indications (e.g. −10 dBm or −20 dBm). When the angles or distances are identical (e.g. 30° and 120°, and the RSSI is −10 dB at 30° and −10 dB at 120°), the angle based or RSSI based indoor direction finding method would obtain identical relative position. So, there would be wrongly performed indoor direction finding which affects the accuracy of the indoor direction finding method. 
     Thus, an improved solution for the prior arts is essential. 
     SUMMARY 
     The embodiments of the present disclosure provide an indoor direction finding method and an indoor direction finding system to confirm the azimuth of the transmitter by obtaining a Bluetooth signal that moves in single direction to improve the indoor direction finding accuracy. 
     For achieving the above purpose, the aforementioned indoor direction finding method is applied to an indoor direction finding system. The indoor direction finding system comprises a transmitter and a receiver. A Bluetooth communication link is established between the receiver and the transmitter. Wherein the indoor direction finding method is performed by the receiver with the following steps: obtaining a receiver coordinate information of the receiver; 
     receiving a Bluetooth signal moving in single direction at the receiver coordinate information; and
 
confirming a relative position information of the transmitter according to the receiver coordinate information and the Bluetooth signal moving in single direction.
 
     Preferably, the step of “confirming a relative position information of the transmitter according to the receiver coordinate information and the Bluetooth signal moving in single direction” comprises the following sub-steps: 
     obtaining an angular phase difference information, a distance, and a relative azimuth according to the receiver coordinate information and the Bluetooth signal moving in single direction; and
 
confirming the relative position information of the transmitter according to the angular phase difference information, the distance, and the relative azimuth.
 
     Preferably, the step of “obtaining an angular phase difference information, a distance, and a relative azimuth according to the receiver coordinate information and the Bluetooth signal moving in single direction” comprises the following sub-steps: 
     predetermining an antenna distance; and
 
obtaining the angular phase difference information according to the receiver coordinate information, the Bluetooth signal moving in single direction, and the antenna distance.
 
     Preferably, the step of “obtaining an angular phase difference information, a distance, and a relative azimuth according to the receiver coordinate information and the Bluetooth signal moving in single direction” comprises the following sub-steps: receiving the Bluetooth signal moving in single direction; 
     obtaining a corresponding received signal strength indication (RSSI) according to a transmission power of the Bluetooth signal moving in single direction; and obtaining the distance according to the receiver coordinate information and the received signal strength indication. 
     Preferably, the step of “obtaining an angular phase difference information, a distance, and a relative azimuth according to the receiver coordinate information and the Bluetooth signal moving in single direction” comprises the following sub-steps: obtaining a transmitter frequency signal; 
     obtaining a frequency signal according to the transmitter frequency signal, a speed of sound, a transmitter moving speed of the Bluetooth signal moving in single direction, and a receiver moving speed of the receiver; and
 
comparing the frequency signal according to the transmitter frequency signal to determine whether the frequency signal is greater than the transmitter frequency signal for the obtaining of the relative azimuth;
 
if so, it can be determined that the transmitter is approaching the receiver;
 
if not, it can be determined that the transmitter is moving away from the receiver.
 
     With the above-mentioned methods, the receiver receives the Bluetooth signal moving in single direction transmitted by the transmitter at the receiver coordinate information to confirm a relative position information of the transmitter according to the receiver coordinate information and the Bluetooth signal moving in single direction. So, the transmitter azimuth can be confirmed to improve the indoor direction finding accuracy. 
     For achieving the above purpose, an indoor direction finding system is provided, which comprises: 
     a transmitter transmitting a Bluetooth signal moving in single direction; and
 
a receiver establishing a Bluetooth communication link with the transmitter;
 
wherein, the receiver: obtains a receiver coordinate information of the receiver; receives the Bluetooth signal moving in single direction at the receiver coordinate information; obtains an angular phase difference information, a distance, and a relative azimuth according to the receiver coordinate information and the Bluetooth signal moving in single direction; confirms a relative position information of the transmitter according to the angular phase difference information, the distance, and the relative azimuth.
 
     Preferably, the receiver comprises: an antenna array module receiving the Bluetooth signal moving in single direction; a memory module predetermining an antenna distance; and a processing module connected to the antenna array module and the memory module; wherein, the processing module obtains the angular phase difference information according to the receiver coordinate information, the Bluetooth signal moving in single direction, and the antenna distance. 
     Preferably, the processing module obtains a corresponding received signal strength indication according to a transmission power of the Bluetooth signal moving in single direction, and obtains the distance according to the receiver coordinate information and the received signal strength indication. 
     Preferably, the receiver further comprises: a signal processing module connected to the antenna array module and the processing module; the signal processing module performs a frequency offset demodulation for a frequency offset modulation signal to generate a digital value after obtaining the Bluetooth signal moving in single direction is processed by a Gaussian low-pass filter and modulated by a frequency offset to generate the frequency offset modulation signal. 
     Preferably, the processing module generates a transmitter frequency signal according to the digital value. The processing module obtains a frequency signal according to the transmitter frequency signal, a speed of sound, a transmitter moving speed of the Bluetooth signal moving in single direction, and a receiver moving speed of the receiver, and compares the frequency signal according to the transmitter frequency signal to determine whether the frequency signal is greater than the transmitter frequency signal to obtain the relative azimuth. 
     With the above-mentioned configuration, the receiver could receive the Bluetooth signal moving in single direction transmitted by the transmitter at the receiver coordinate information to confirm a relative position information of the transmitter according to the receiver coordinate information and the Bluetooth signal moving in single direction. In this way, the azimuth of the transmitter can be confirmed, thereby improving the indoor direction finding accuracy. 
     It should be understood, however, that this summary may not contain all aspects and embodiments of the present disclosure, that this summary is not meant to be limiting or restrictive in any manner, and that the disclosure as disclosed herein will be understood by one of ordinary skill in the art to encompass obvious improvements and modifications thereto. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features of the exemplary embodiments believed to be novel and the elements and/or the steps characteristic of the exemplary embodiments are set forth with particularity in the appended claims. The Figures are for illustration purposes only and are not drawn to scale. The exemplary embodiments, both as to organization and method of operation, may best be understood by reference to the detailed description which follows taken in conjunction with the accompanying drawings in which: 
         FIG.  1    is a block diagram of an indoor direction finding system of the present disclosure; 
         FIG.  2    is another block diagram of an indoor direction finding system of the present disclosure; 
         FIG.  3 A  is an application schematic diagram of the indoor direction finding system of the present disclosure; 
         FIG.  3 B  is another application schematic diagram of the indoor direction finding system of the present disclosure; 
         FIG.  4    is a flow chart of an indoor direction finding method of the present disclosure; 
         FIG.  5    is another flow chart of an indoor direction finding method of the present disclosure; 
         FIG.  6 A  is yet another flow chart of an indoor direction finding method of the present disclosure; 
         FIG.  6 B  is yet another flow chart of an indoor direction finding method of the present disclosure; and 
         FIG.  6 C  is yet another flow chart of an indoor direction finding method of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the disclosure are shown. This present disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this present disclosure will be thorough and complete, and will fully convey the scope of the present disclosure to those skilled in the art. 
     Certain terms are used throughout the description and following claims to refer to particular components. As one skilled in the art will appreciate, manufacturers may refer to a component by different names. This document does not intend to distinguish between components that differ in name but function. In the following description and in the claims, the terms “include/including” and “comprise/comprising” are used in an open-ended fashion, and thus should be interpreted as “including but not limited to”. “Substantial/substantially” means, within an acceptable error range, the person skilled in the art may solve the technical problem in a certain error range to achieve the basic technical effect. 
     The following description is of the best-contemplated mode of carrying out the disclosure. This description is made for the purpose of illustration of the general principles of the disclosure and should not be taken in a limiting sense. The scope of the disclosure is best determined by reference to the appended claims. 
     Moreover, the terms “include”, “contain”, and any variation thereof are intended to cover a non-exclusive inclusion. Therefore, a process, method, object, or device that includes a series of elements not only includes these elements, but also includes other elements not specified expressly, or may include inherent elements of the process, method, object, or device. If no more limitations are made, an element limited by “include a/an . . . ” does not exclude other same elements existing in the process, the method, the article, or the device which includes the element. 
     Regarding preferred embodiments of an indoor direction finding system of the present disclosure, as shown in  FIG.  1   , the indoor direction finding system comprises a transmitter  10  and a receiver  20 . A Bluetooth communication link is established between the transmitter  10  and the receiver  20  with a Bluetooth signal. The transmitter  10  transmits a Bluetooth signal moving in single direction. The receiver  20  obtains a receiver coordinate information and receives a Bluetooth signal moving in single direction at the receiver coordinate information. The receiver  20  obtains an angular phase difference information, a distance, and a relative azimuth according to the receiver coordinate information and the Bluetooth signal moving in single direction, and confirms a relative position information of the transmitter  10  according to the angular phase difference information, the distance, and the relative azimuth. In this embodiment, the transmitter  10  could be a Bluetooth tag or a wireless base station, The receiver  20  could be a wireless base station or a Bluetooth tag. 
     In this embodiment, as shown in  FIG.  2   , the receiver  20  comprises an antenna array module  21 , a memory module  22 , and a processing module  23 . The processing module  23  is electrically connected to the antenna array module  21  and the memory module  22 . The antenna array module  21  receives the Bluetooth signal moving in single direction from the transmitter  10 . The memory module  22  predetermines an antenna distance. The processing module  23  obtains the angular phase difference information according to the receiver coordinate information, the Bluetooth signal moving in single direction, and the antenna distance. The receiver  20  obtains the relative position information according to the receiver coordinate information and the angular phase difference information. In this embodiment, the relative position information can be acquired through a signal angle of arrival (AOA) or a signal angle of departure (AOD). The memory module  22  could be a memory, and the processing module  23  could be a processor. 
     In this embodiment, the processing module  23  converts the transmission power into a received signal strength indication (RSSI) according to a transmission power of the Bluetooth signal moving in single direction, and compares with the receiver coordinate information and the received signal strength indication according to a pre-established model in a corresponding distance to the received signal strength indication to obtain a distance between the transmitter  10  and the receiver  20 . The receiver  20  obtains the relative position information according to the receiver coordinate information and the distance. 
     In this embodiment, the receiver  20  further comprises a signal processing module  24 , which is electrically connected to the antenna array module  21  and the processing module  23 . The signal processing module  24  performs a frequency offset demodulation for a frequency offset modulation signal to generate a digital value after obtaining the Bluetooth signal moving in single direction is processed by a Gaussian low-pass filter and modulated by a frequency offset to generate the frequency offset modulation signal. 
     In this embodiment, the processing module  23  generates a transmitter frequency signal according to the digital value. Then, the processing module  23  obtains a frequency signal according to the transmitter frequency signal, a speed of sound, a transmitter moving speed of the Bluetooth signal moving in single direction, and a receiver moving speed of the receiver  20 , and according to the transmitter frequency signal, the frequency signal is compared to determine whether the frequency signal is greater than the transmitter frequency signal to obtain the relative azimuth of the transmitter  10  and the receiver  20 . If so, it can be determined that the transmitter  10  is approaching the receiver  20 . If not, it can be determined that the transmitter  10  is moving away from the receiver  20  to obtain the relative azimuth. 
     For example, as shown in  FIG.  3 A  and  FIG.  3 B , the transmitter  10  is a Bluetooth tag, the receiver  20  is a wireless base station  20 ′. The user possesses a Bluetooth tag, which transmits a Bluetooth signal. The wireless base station  20 ′ predetermines a receiver coordinate information. The wireless base station  20 ′ is relatively set at a coordinate according to the receiver coordinate information, and receives the Bluetooth signal from the Bluetooth tag. Then, the user advances in the direction of the arrow, so that the Bluetooth tag continues to transmit the Bluetooth signal moving in single direction to the wireless base station  20 ′. The antenna array module  21  of the wireless base station  20 ′ comprises two antennas, between which is an antenna distance. The antenna distance is stored in the memory module  22  of the wireless base station  20 ′. The two antennas of the wireless base station  20 ′ respectively receive the Bluetooth signal moving in single direction from the Bluetooth tag. Then, when the two antennas of the antenna array module  21  respectively receive the Bluetooth signal moving in single direction, the angular phase difference information is obtained. The wireless base station  20 ′ then calculates and obtains the relative position information of the Bluetooth tag in the wireless base station  20 ′ according to the received signal strength indication and the angle phase difference information, i.e., the relative angle of the Bluetooth tag to the wireless base station  20 ′. 
     Moreover, according to the transmission power of the Bluetooth signal moving in single direction, the wireless base station  20 ′ converts the transmission power into the received signal strength indication, and compares with the receiver coordinate information and the received signal strength indication according to the pre-established model in a corresponding distance to the received signal strength indication to obtain the distance between the Bluetooth tag and the wireless base station  20 ′. Then, the wireless base station  20 ′ calculates the relative position information between the Bluetooth tag and the wireless base station  20 ′ according to the receiver coordinate information and the distance. 
     The wireless base station  20 ′ performs a frequency offset demodulation for a frequency offset modulation signal to generate a digital value after obtaining the Bluetooth signal moving in single direction is processed by a Gaussian low-pass filter and modulated by a frequency offset to generate the frequency offset modulation signal. The wireless base station  20 ′ then generates the transmitter frequency signal according to the digital value. The frequency signal is calculated according to the transmitter frequency signal, the speed of sound, the transmitter moving speed of the Bluetooth tag of the Bluetooth signal moving in single direction, and the receiver moving speed of the wireless base station  20 ′. The equation is as shown below. 
     
       
         
           
             
               f 
               ′ 
             
             = 
             
               
                 ( 
                 
                   
                     v 
                     ± 
                     
                       v 
                       o 
                     
                   
                   
                     v 
                     ⁢ 
                     ▯ 
                     ⁢ 
                     
                       v 
                       s 
                     
                   
                 
                 ) 
               
               ⁢ 
               f 
             
           
         
       
     
     In the equation: f′ represents frequency signal; f represents the transmitter frequency signal; v represents the speed of sound; v o  represents the receiver moving speed; v s  represents the transmitter moving speed. 
     To make a comparison between the frequency signal and the transmitter frequency signal, when the frequency signal is greater than the transmitter frequency signal, it is determined that the Bluetooth tag is moving in a direction close to the wireless base station  20 ′. When the frequency signal is smaller than the transmitter frequency signal, it is determined that the Bluetooth tag is moving in a direction away from the wireless base station  20 ′. In this way, the relative azimuth between the Bluetooth tag and the wireless base station  20 ′ can be acquired accurately. 
     For example, as shown in  FIG.  3 A  and  FIG.  3 B , the Bluetooth tags possessed by the user is at the positions  10 A and  10 B of the Bluetooth tag. The relative horizontal angles of the Bluetooth tags at the positions  10 A and  10 B of the Bluetooth tag to the wireless base station  20 ′ are 30° and 120°, respectively, and the Bluetooth tags at the positions  10 A and  10 B of the Bluetooth tag move on a circumference of one circle, which implies that the received signal strength indication of the positions  10 A and  10 B where the wireless base station  20 ′ receives the Bluetooth tags are identical so that the distances are also identical. In the aspect of a plane, on which the positions  10 A and  10 B of the Bluetooth tags are positions that are actually different, so when the Bluetooth tags are at the positions  10 A and  10 B of the Bluetooth tag, the frequencies of the Bluetooth signals moving in single direction correspondingly received by the wireless base station  20 ′ are different, so it can be determined that the user is at the position  10 A or the position  10 B of the Bluetooth tag. When at the position  10 A of the Bluetooth tag, the Bluetooth tag at the position  10 A of the Bluetooth tag is moving at a speed close to the wireless base station  20 ′ so that the frequency signal is greater than the transmitter frequency signal, and it can be determined that the Bluetooth tag is approaching the position of the wireless base station  20 ′ when the Bluetooth tag is at the position  10 A. On the contrary, it can be determined that the Bluetooth tag is moving away from the wireless base station  20 ′ at the position  10 B of the Bluetooth tag. In this way, the positions  10 A and  10 B of the Bluetooth tags can be accurately determined. 
     Besides, regarding a preferred embodiment of the indoor direction finding method of the present disclosure, as shown in  FIG.  4   , the indoor direction finding method is applied to an indoor direction finding system, which comprises a transmitter and a receiver. A Bluetooth communication link is established between the receiver and the transmitter. Wherein the indoor direction finding method is performed by the receiver with the following steps: 
     obtaining a receiver coordinate information of the receiver (S 10 );
 
receiving a Bluetooth signal moving in single direction at the receiver coordinate information (S 20 ); and confirming a relative position information of the transmitter according to the receiver coordinate information and the Bluetooth signal moving in single direction (S 30 ).
 
     In this embodiment, as shown in  FIG.  5   , the step of “confirming a relative position information of the transmitter according to the receiver coordinate information and the Bluetooth signal moving in single direction (S 30 )” comprises the following sub-steps: 
     obtaining an angular phase difference information, a distance, and a relative azimuth according to the receiver coordinate information and the Bluetooth signal moving in single direction (S 31 ); and
 
confirming the relative position information of the transmitter according to the angular phase difference information, the distance, and the relative azimuth (S 32 ).
 
     In this embodiment, as shown in  FIG.  6 A , the step of “obtaining an angular phase difference information, a distance, and a relative azimuth according to the receiver coordinate information and the Bluetooth signal moving in single direction (S 31 )” comprises the following sub-steps: 
     predetermining an antenna distance (S 310 A); and
 
obtaining the angular phase difference information according to the receiver coordinate information, the Bluetooth signal moving in single direction, and the antenna distance (S 311 A).
 
     In this embodiment, as shown in  FIG.  6 B , the step of “obtaining an angular phase difference information, a distance, and a relative azimuth according to the receiver coordinate information and the Bluetooth signal moving in single direction (S 31 )” comprises the following sub-steps: 
     receiving the Bluetooth signal moving in single direction (S 310 B);
 
calculating a corresponding received signal strength indication according to a transmission power of the Bluetooth signal moving in single direction (S 311 B); and
 
calculating the distance according to the receiver coordinate information and the received signal strength indication (S 312 B).
 
     In this embodiment, as shown in  FIG.  6 C , the step of “obtaining an angular phase difference information, a distance, and a relative azimuth according to the receiver coordinate information and the Bluetooth signal moving in single direction (S 31 )” comprises the following sub-steps: 
     obtaining a transmitter frequency signal (S 310 C);
 
calculating a frequency signal according to the transmitter frequency signal, a speed of sound, a transmitter moving speed of the Bluetooth signal moving in single direction, and a receiver moving speed of the receiver (S 311 C); and
 
comparing the frequency signal according to the transmitter frequency signal to determine whether the frequency signal is greater than the transmitter frequency signal for the obtaining of the relative azimuth (S 312 C);
 
if so, it can be determined that the transmitter is approaching the receiver (S 313 C);
 
if not, it can be determined that the transmitter is moving away from the receiver (S 314 C).
 
     In summary, the receiver could receive the Bluetooth signal moving in single direction transmitted by the transmitter at the receiver coordinate information to confirm a relative position information of the transmitter according to the receiver coordinate information and the Bluetooth signal moving in single direction. In this way, the azimuth of the transmitter can be confirmed, thereby improving the indoor direction finding accuracy. 
     It is to be understood that the term “comprises”, “comprising”, or any other variants thereof, is intended to encompass a non-exclusive inclusion, such that a process, method, article, or device of a series of elements not only comprise those elements but further comprises other elements that are not explicitly listed, or elements that are inherent to such a process, method, article, or device. An element defined by the phrase “comprising a . . . ” does not exclude the presence of the same element in the process, method, article, or device that comprises the element. 
     Although the present disclosure has been explained in relation to its preferred embodiment, it does not intend to limit the present disclosure. It will be apparent to those skilled in the art having regard to this present disclosure that other modifications of the exemplary embodiments beyond those embodiments specifically described here may be made without departing from the spirit of the disclosure. Accordingly, such modifications are considered within the scope of the disclosure as limited solely by the appended claims.