Method and apparatus for OFDM-based local positioning system

Abstract

A method and apparatus are provided for determining the location of a mobile station by transmitting and receiving Wi-Fi signals with modified Wi-Fi signals and by a plurality of base stations, receiving signals transmitted by the base stations (with known coordinates) and located in the vicinity of the mobile station, and transmitting the received signals to the mobile station. And calculating position coordinates of the mobile station (also referred to herein as a moving object) based on the signal.

Description

Technical Field

[0001] The present disclosure relates generally to radio navigation and, more particularly, to determining the position of an object when global positioning satellite system signals are unavailable. Background Art

[0002] The ability to determine the current coordinates and motion parameters of a movable object (eg, a moving vehicle) using a radio navigation system is a long-standing problem, and there are many known solutions representing various techniques for such determination.

[0003] In one case, such determination can be achieved using a range difference positioning method, which is commonly used in, for example, different navigation satellite systems, such as the U.S. Global Positioning System (GPS), the Russian GLONASS, or the European GALILEO. However, indoor GNSS signal reception is limited, for example, in areas such as deep mines, canyons, or other such impenetrable terrain, and / or dense urban high-rise residential areas, which is due to the limited line of sight visibility of satellites in such navigation systems, causing such systems to be drastically reduced in effectiveness in determining position.

[0004] In order to solve these problems, there is a technology that uses pseudo-satellite signals (i.e., pseudo-satellite signals) to determine the position of the vehicle to achieve a certain degree of navigation accuracy. For example, U.S. Patents No. 6,449,558, 7,495,614, 7,859,462 and 8,675,561 describe different technologies for using pseudo-satellite signals. Alternatively, there are also many technologies (e.g., as described in U.S. Patents No. 8,738,035 and 6,449,558) that use hybrid positioning devices, which utilize GNSS signals and other different signals supplied by ground base stations to achieve position determination. The advantage of this system is that it can better cover the required area and improve positioning accuracy. However, this system is very complex and has high deployment costs, and is used as a position determination system rather than a data transmission system, thereby causing the communication channel throughput to be low. In addition, these potential limitations also lie in that the task of developing a position determination and data transmission system for movable objects is quite critical in achieving certain required degrees of position determination and data communication.

[0005] In order to overcome some of the above limitations, there are many positioning technologies using Wi-Fi access points (hereinafter referred to as "AP"), which are based on measuring the strength of the received signal and further comparing the measured strength with the known spatial power distribution (e.g., fingerprint positioning method). For example, such fingerprint positioning methods are described in U.S. Patents Nos. 7,515,578, 8,155,673, and 8,838,151. These technical solutions can be used for location determination and data transmission / reception of mobile subscribers / clients via Wi-Fi networks. For example, some alternative technical solutions are also described in U.S. Patent Publication Nos. 2015 / 0087331, 2015 / 0099536, and 2015 / 0172863, which also provide data transmission and positioning tasks, wherein the signal is transmitted through the information channel of the Wi-Fi network. However, these known methods do not allow high-accuracy coordinate estimates (i.e., measured in centimeter increments), and these known methods include many technical implementation difficulties, which makes deployment challenging.

[0006] Other technical solutions for position determination (e.g., as described in U.S. Patent Nos. 7,515,578, 7,916,661, and 8,155,673) use certain information from ground maps, Wi-Fi AP distribution, and / or coverage areas, and received signal strength to specify the location of a mobile user. In addition, some other known positioning devices (e.g., as described in U.S. Patent Publication Nos. 2012 / 0075145 and 2013 / 0093619) use phase differences of signals received by selected spaced-apart antennas to determine the location of a movable object.

[0007] U.S. Patent No. 7,859,462 is another known positioning technique in which the position of a rover is determined using some reference transmitters that generate and transmit in-phase navigation signals, which are received by the rover and the delays associated with the received signals are determined to calculate the position of the rover. However, due to the low throughput of the communication channel, this technique cannot be used directly to transmit information between the reference transmitters and the mobile receiver / rover.

[0008] Therefore, there is a need for an improved technique involving determining the current coordinates and motion parameters of a movable object when GNSS signal reception is unable to provide or insufficient to provide the required positioning accuracy. Summary of the invention

[0009] A method for determining the position of a mobile station includes exchanging multiple Wi-Fi signals between a mobile station and multiple base stations. The Wi-Fi signals include multiple orthogonal frequency division multiplexing (OFDM) communication signals. The position of the mobile station is determined based on the OFDM communication signals. The Wi-Fi signals can be transmitted via dual polarization antennas or triple polarization antennas. In one embodiment, determining the position of the mobile station based on the OFDM communication signals is also based on the polarization of the OFDM communication signals. The OFDM communication signals can be based on pseudo-noise sequences. A system for determining the position of a mobile station includes a mobile station and multiple base stations. In one embodiment, the system is configured to determine the position of the mobile station using the steps described above. A mobile station is also described, the mobile station having a processor and a memory, the memory storing computer program instructions to determine the position of the mobile station. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In the drawings, like reference numerals describe similar components in different figures. Like reference numerals with different letter suffixes represent different instances of similar components and / or signals.

[0011] Figure 1 A network including a mobile device in communication with one or more of a plurality of wireless access points is shown;

[0012] Figure 2 shows a signal transmission diagram according to an embodiment;

[0013] Figure 3 Components of a master station (MSTA) are shown, which include a transmission antenna with two orthogonal polarizations;

[0014] Figure 4 Components of a slave station (SSTA) are shown, which include a transmit antenna and a receive antenna with two orthogonal polarizations;

[0015] Figure 5 Components of a rover (mobile) station (RSTA) are shown, which includes antennas with two orthogonal polarizations;

[0016] Figure 6 Components of a master station (MSTA) are shown, which include transmission antennas with three orthogonal polarizations;

[0017] Figure 7 Components of a slave station (SSTA) are shown, which include a transmit antenna and a receive antenna with three orthogonal polarizations;

[0018] Figure 8 Components of a rover (mobile) station (RSTA) are shown, which includes antennas with three orthogonal polarizations;

[0019] Fig. 9 Components for generating navigation signals for two antennas using a pseudo noise sequence (PNS) generator and a digital mixer are shown according to one embodiment;

[0020] Fig.10 Components for generating navigation signals for three antennas using a pseudo noise sequence (PNS) generator and a digital mixer are shown according to one embodiment;

[0021] Fig.11 shows 8 tracking channels at the receiver using phase and delay measurements;

[0022] Fig.12 shows the spectrum of an orthogonal frequency division multiplexing (OFDM) signal output according to one embodiment;

[0023] Fig.13 shows a spectrum diagram for a 12.5 MHz signal with 8 subcarriers according to one embodiment;

[0024] Fig.14 shows a spectrum diagram for a 3.125 MHz signal with 8 subcarriers according to one embodiment;

[0025] Fig.15 shows a spectrum diagram for a 3.125 MHz signal with 16 subcarriers according to one embodiment;

[0026] Fig.16 shows a spectrum diagram for a 3.125 MHz signal with 32 subcarriers according to one embodiment;

[0027] Fig.17 shows a spectrum diagram for a 12.5 MHz signal with 8 subcarriers according to one embodiment;

[0028] Fig.18 shows a spectrum diagram for a 12.5 MHz signal with 8 subcarriers according to one embodiment;

[0029] Fig.19 shows a spectrum diagram for a 12.5 MHz signal with 16 subcarriers according to one embodiment;

[0030] Fig. 20 shows a spectrum representation of a signal according to an embodiment;

[0031] Fig.21 is a signal diagram of the difference between phase estimates of subcarriers according to an embodiment;

[0032] Fig. 22shows an estimated position of a rover mobile station according to an embodiment;

[0033] Fig.23 A positioning error graph showing an estimated position of a rover mobile station according to an embodiment;

[0034] Fig.24 shows an estimated position of a rover mobile station according to an embodiment;

[0035] Fig.25 a positioning error graph showing an estimated position of a rover according to an embodiment; and

[0036] Fig.26 A high-level schematic diagram of a computer used to implement the various devices described herein is shown. DETAILED DESCRIPTION

[0037] According to the embodiments of the present invention, location determination is achieved by modifying Wi-Fi access point and station signals radiated by a master base station (i.e., a guide base station), in combination with slave stations (i.e., guided stations) having known coordinates, and processing the signals received from these base stations at a mobile station (or user) to calculate the desired location.

[0038] This will be further described in more detail below, and the discussion (and related figures) will adopt acronyms and abbreviations, which include: Medium Access Control (MAC); Master Station / Master Access Point (MSTA / MAP); Orthogonal Frequency Division Multiplexing (OFDM); Physical Layer (PHY); Pseudo Noise Sequence (PNS); Mobile STA (RSTA); Slave (Fixed STA) (SSTA); User STA (USTA); and Wireless Local Area Network (WLAN).

[0039] In particular, according to various embodiments, methods and apparatus are provided for determining the location of a mobile station (e.g., a rover) by utilizing modified Wi-Fi signals (e.g., according to the IEEE 802.11 protocol) and transmitting and receiving Wi-Fi signals through multiple base stations, receiving signals transmitted by these base stations (having known coordinates and located near the mobile station), measuring delay phase differences received from different base stations at the mobile station, and using the delays and phase differences to calculate the location coordinates of the mobile station (also referred to herein as a mobile object). In one embodiment, the location of the mobile station is determined based on an orthogonal frequency division multiplexing (OFDM) communication signal. In one embodiment, the OFDM communication signal is included in multiple Wi-Fi signals. The location of the mobile station can also be determined based on the polarization of the OFDM communication signal. The OFDM communication signal can be based on the pseudo noise sequence described herein.

[0040] The calculation of position coordinates is facilitated by exchanging (i.e. transmitting and receiving) Wi-Fi signals generated by a guiding (i.e. master) base station and a guided (i.e. slave) station, which are spatially positioned relative to each other in a predetermined manner. The master and slave stations transmit signals in the form of frames with a specified structure periodically according to a predetermined time sequence. The structure of the transmitted frame contains a specially generated sequence of symbols used to locate the mobile object. The service information required for the positioning task is transmitted in the field of the leading terminal and in the selected / available information field of such a frame.

[0041] Figure 1 A master station (MSTA) 12 is shown communicating with a user station (USTA) 11. The MSTA 12 also communicates with a slave station 0 (SSTA0) 14, SSTA 1 15, and SSTA N 16. Figure 1 The devices shown exchange multiple Wi-Fi and OFDM communication signals. It should be noted that there can be any number of slave stations to provide coverage for areas of varying sizes.

[0042] A rover station (RSTA) 13, which is a mobile station, communicates with MSTA 12, SSTA0 14, SSTA 1 15, and SSTA N 16. In one embodiment, MSTA 12 communicates with the SSTA via IEEE 802.11. Figure 1 , which is shown by the double lead between oppositely pointing arrows.

[0043] MSTA 12 transmits navigation signals (e.g., signals used to determine the position of a mobile object (such as RSTA 13)) to SSTA 0 14, SSTA 1 15, SSTA N 16, and RSTA 13, as shown by the solid lines radiating from MSTA 12 to each of SSTA 0 14, SSTA 1 15, SSTA N 16, and RSTA 13 as shown by the arrows at the ends of the solid lines.

[0044] RSTA 13 receives navigation signals from each of SSTA0 14 , SSTA 1 15 , and SSTA N 16 , as shown by the dashed lines where the arrows point to RSTA 13 .

[0045] The navigation signal transmitted from MSTA 12 to each of SSTA0 14, SSTA 1 15, and SSTA N 16 instructs the receiving device to transmit the navigation signal to RSTA 13. In one embodiment, the Wi-Fi signal includes the navigation signal, and the Wi-Fi signal is transmitted in Figure 1 Based on the navigation signals received by the RSTA 13, the device can use the measured phase delays and phase differences to determine its position.

[0046] Figure 2 A signal diagram 200 is shown, which identifies the Figure 1 . The navigation signal is transmitted from the MSTA (MAP) at time interval 0 (TS 0). The navigation signal is then transmitted from SSTA 0, SSTA 1, SSTA N at time intervals TS1, TS2, and TS 3, respectively. It should be noted that there may be "N" slave stations transmitting navigation signals. After the "N" slave stations transmit their navigation signals, the RSTA transmits 802.11 data d at time interval TS N+3. The sequence of navigation signals is then repeated indefinitely.

[0047] The MSTA uses a transmission antenna that uses two polarizations (such as Figure 3 ), or the transmitting antenna uses three orthogonal polarizations (such as Figure 6 Each SSTA uses a transmission antenna and a receiving antenna with two orthogonal polarizations (such as MSTA 12B according to another embodiment). Figure 4 ), or each SSTA uses a transmission antenna and a receiving antenna with three orthogonal polarizations (such as SSTA 14A according to one embodiment). Figure 7 The RSTA uses a receiving antenna with two orthogonal polarizations (such as SSTA 14B according to another embodiment). Figure 5 ), or the RSTA uses a receiving antenna with three orthogonal polarizations (such as RSTA 13A according to one embodiment). Figure 8 The use of different orthogonal polarizations on the transmit antenna and the receive antenna facilitates the realization of a large number of independent receive channels to track the MSTA and SSTA signals. The use of different orthogonal PNS facilitates the determination of which antenna and which subcarrier the MSTA signal and each SSTA signal are transmitted from. The details of these embodiments are described below.

[0048] Figure 3 1 shows an MSTA 12A according to one embodiment, which is configured to transmit via an antenna using two orthogonal polarizations, each of which transmits a different orthogonal pseudo noise sequence (PNS). The medium access control (MAC) and physical layer (PHY) communication module 121 communicates with the Figure 1 11 communications with other devices shown in . The MAC and PHY communication module 121 communicates with the OFDM Nav signal generator 122. Control signals are transmitted and received between the MAC and PHY communication module 121 and the OFDM Nav signal generator 122. In response to the control signal, the OFDM Nav signal generator 122 transmits the OFDM navigation signal to the dual polarization transmission (Tx) antenna 123. The MSTA (MAP) navigation signal is transmitted from the dual polarization transmission (Tx) antenna 123 in response to the OFDM navigation signal.

[0049] Figure 4 An SSTA 0 14A according to one embodiment is shown, which is configured to transmit via an antenna using two orthogonal polarizations, each of which transmits a different orthogonal PNS. The MAC and PHY communication module 141 communicates with the OFDM Nav signal generator 142. Control signals are transmitted and received between the MAC and PHY communication module 141 and the OFDM Nav signal generator 142. In response to the control signal, the OFDM Nav signal generator 142 transmits the OFDM navigation signal to the dual polarization transmission (Tx) antenna 143, which transmits the SSTA navigation signal in response. The MSTA signal tracking channel 144 communicates with the OFDM signal generator 142. The MSTA signal tracking channel 144 and the OFDM signal generator 142 each transmit and receive control signals from each other. The dual polarized RX antenna 145 receives the MSTA (MAP) navigation signal and in response transmits an OFDM navigation signal to the MSTA signal tracking channel 144. It should be noted that although Figure 4 Components are shown for SSTA 0 14A, but the same components may be used for SSTA 1 15 and SSTA N 16, in addition to any number of other SSTAs.

[0050] Figure 5 An RSTA 13A according to one embodiment is shown, which is configured to receive signals using antennas with two orthogonal polarizations. The MAC and PHY communication module 131 communicates with the MSTA and SSTA signal tracking channel 132. The MAC and PHY communication module and the MSTA and SSTA signal tracking channel 132 each transmit and receive control signals from each other. The MSTA and SSTA signal tracking channel 132 receives the SSTA navigation signal from the dual polarization RX antenna 133. It should be noted that the dual polarization RX antenna 133 receives the MSTA (MAP) navigation signal and multiple SSTA navigation signals from multiple SSTAs.

[0051] Figure 6 1 shows an MSTA 12B according to one embodiment, which is configured to transmit via antennas using three orthogonal polarizations, each of which transmits a different orthogonal pseudo noise sequence (PNS). The medium access control (MAC) and physical layer (PHY) communication module 121 communicates with the MSTA 12B via the antennas using three orthogonal polarizations, each of which transmits a different orthogonal pseudo noise sequence (PNS). Figure 1 11 communications with other devices shown in . The MAC and PHY communication module 121 communicates with the OFDM Nav signal generator 122. Control signals are transmitted and received between the MAC and PHY communication module 121 and the OFDM Nav signal generator 122. In response to the control signal, the OFDM Nav signal generator 122 transmits the OFDM navigation signal to the three-polarization transmission (Tx) antenna 123. The MSTA (MAP) navigation signal is transmitted from the dual-polarization transmission (Tx) antenna 123 in response to the OFDM navigation signal.

[0052] Figure 7An SSTA 0 14B according to one embodiment is shown, which is configured to transmit via an antenna using three orthogonal polarizations, each of which transmits a different orthogonal PNS. The MAC and PHY communication module 141 communicates with the OFDM Nav signal generator 142. Control signals are transmitted and received between the MAC and PHY communication module 141 and the OFDM Nav signal generator 142. In response to the control signal, the OFDM Nav signal generator 142 transmits the OFDM navigation signal to the three-polarization transmission (Tx) antenna 143, which transmits the SSTA navigation signal in response. The MSTA signal tracking channel 144 communicates with the OFDM signal generator 142. The MSTA signal tracking channel 144 and the OFDM signal generator 142 each transmit and receive control signals from each other. The dual polarized RX antenna 145 receives the MSTA (MAP) navigation signal and in response transmits an OFDM navigation signal to the MSTA signal tracking channel 144. It should be noted that although Figure 7 Components are shown for SSTA 0 14, but the same components are used for SSTA 1 15 and SSTA N 16, in addition to any number of other SSTAs.

[0053] Figure 8 An RSTA 13B according to one embodiment is shown, which is configured to receive signals using antennas with three orthogonal polarizations. The MAC and PHY communication module 131 communicates with the MSTA and SSTA signal tracking channel 132. The MAC and PHY communication module and the MSTA and SSTA signal tracking channel 132 each transmit and receive control signals from each other. The MSTA and SSTA signal tracking channel 132 receives the SSTA navigation signal from the three-polarization RX antenna 133. It should be noted that the dual-polarization RX antenna 133 receives the MSTA (MAP) navigation signal and multiple SSTA navigation signals from multiple SSTAs.

[0054] Fig. 9 and Fig.10 Additional details of the components used to generate signals to transmit signals via two antennas ( Fig. 9 ) or through three antennas ( Fig.10 ) for transmission.

[0055] Fig. 9Components for generating signals are shown, which are output from two antennas. The timing controller 1421 receives a control signal and generates a control signal in response, which is transmitted to the PNS generator 1422 for antenna 1 and the PNS generator 1424 for antenna 2. In response to the received control signal, the PNS generator 1422 for antenna 1 generates a PNS for multiple subcarriers, which are transmitted to the digital mixer 1423 for orthogonal frequencies. The OFDM navigation signal for the Tx antenna is output from the digital mixer 1423 for orthogonal frequencies. In response to the received control signal, the PNS generator 1424 for antenna 2 generates a PNS for multiple subcarriers. The OFDM navigation signal for the Tx antenna is output from the digital mixer 1425 for orthogonal frequencies.

[0056] Fig.10 Components for generating signals are shown, which are output from three antennas. The timing controller 1421 receives a control signal and generates a control signal in response, which is transmitted to the PNS generator 1422 for antenna 1, the PNS generator 1424 for antenna 2, and the PNS generator 1426 for antenna 3. In response to the received control signal, the PNS generator 1422 for antenna 1 generates a PNS for multiple subcarriers, which are transmitted to the digital mixer 1423 for orthogonal frequencies. The OFDM navigation signal for the Tx antenna is output from the digital mixer 1423 for orthogonal frequencies. In response to the received control signal, the PNS generator 1424 for antenna 2 generates a PNS for multiple subcarriers. The OFDM navigation signal for the Tx antenna is output from the digital mixer 1425 for orthogonal frequencies. The PNS generator 1426 for antenna 3 generates a PNS for multiple subcarriers. The OFDM navigation signal for the Tx antenna is output from the digital mixer 1427 for orthogonal frequencies.

[0057] In one embodiment, using different orthogonal polarizations for the transmit and receive antennas enables a large number of independent receive channels to track MSTA and SSTA signals. Using different orthogonal PNS, it is possible to determine from which antenna and on which subcarrier the MSTA signal and each SSTA is transmitted.

[0058] Fig.11Components configured for use in a receiver having eight tracking channels are shown. For example, when transmitting different orthogonal PNSs on two orthogonal subcarriers from each antenna, under multipath conditions, using antennas with two orthogonal polarizations at the transmitter and the same antennas at the receiver, 2×2×2=8 tracking channels with phase and delay measurements of different multipath effects can be obtained at the receiver. As more antennas and more subcarriers are used, the number of channels with different multipath effects increases depending on the shape of the reflecting objects and the multipath correlation intervals generated in the system operating area. Fig.11 The timing controller 1421 is shown to receive control signals and transmit control signals related to tracking. The timing controller 1421 transmits and receives control signals from the PNS generator 1422 for antenna 1 and the PNS generator 1424 for antenna 2. The PNS generator 1422 for antenna 1 generates PNS for multiple subcarriers and transmits the PNS for multiple subcarriers to the digital mixer 1423 of orthogonal frequency. The PNS generator 1424 for antenna 2 generates PNS for multiple subcarriers and transmits the PNS for multiple subcarriers to the digital mixer 1425 of orthogonal frequency. The digital mixer 1423 of orthogonal frequency transmits PNS1, subcarrier 1 signal and PNS2, subcarrier 2 signal to TX antenna 1 1426. The digital mixer 1425 of orthogonal frequency transmits PNS 3, subcarrier 1 signal and PNS 4, subcarrier 2 signal to TX antenna 2 1428. TX antenna 1 transmits subcarriers to RX antenna 1 and RX antenna 2. TX antenna 2 also transmits subcarriers to RX antenna 1 and RX antenna 2. In response to the received subcarrier signals, RX antenna 1 transmits PNS1, subcarrier 1 signal; PNS2, subcarrier 2 signal; PNS 3, subcarrier 1 signal; and PNS 4, subcarrier 2 signal. In response to the received subcarrier signals, RX antenna 2 transmits PNS1, subcarrier 1 signal; PNS2, subcarrier 2 signal; PNS 3, subcarrier 1 signal; and PNS 4, subcarrier 2 signal.

[0059] Figures 12 to 19 Shows from Fig. 9 , Fig.10 ,and Fig.11 The frequency spectrum of the OFDM signal output by the digital mixers 1423, 1425, and 1427 is shown in FIG. Figures 12 to 19 The signal represented by the solid black line in each figure represents the total signal input to the corresponding Tx antenna.

[0060] Fig.12A spectrum diagram generated using a Gold code 12.5 MHz Type 1 signal with 2 subcarriers and dF=25 MHz is shown according to one embodiment. Signal 1202 is the total signal input to the corresponding Tx antenna.

[0061] Fig.13 A spectrum diagram generated using a Gold code 12.5 MHz type 2 signal with 8 subcarriers and dF = 3.125 MHz is shown. Signal 1302 is the total signal input to the corresponding Tx antenna.

[0062] Fig.14 A spectrum diagram generated using a Gold code 3.125 MHz Type 1 signal with 8 subcarriers and dF = 3.125 MHz is shown. Signal 1402 is the total signal input to the corresponding Tx antenna.

[0063] Fig.15 A spectrum diagram generated using a Gold code 3.125 MHz type 2 signal with 16 subcarriers and dF = 3.125 is shown. Signal 1502 is the total signal input to the corresponding Tx antenna.

[0064] Fig.16 A spectrum diagram generated using a Gold code 3.125 MHz type 3 signal with 32 subcarriers and dF = 1.5625 MHz is shown. Signal 1602 is the total signal input to the corresponding Tx antenna.

[0065] Fig.17 A spectrum diagram generated using the Kasami algorithm with a 12.5 MHz Type 1 signal with 8 subcarriers and dF = 3.125 is shown. Signal 1702 is the total signal input to the corresponding Tx antenna.

[0066] Fig.18 A spectrum diagram generated using the Kasami algorithm with a 12.5 MHz Type 1 signal with 8 subcarriers and dF = 6.25 MHz is shown. Signal 1802 is the total signal input to the corresponding Tx antenna.

[0067] Fig.19 A spectrum diagram generated using the Kasami algorithm with a 12.5 MHz Type 2 signal with 16 subcarriers and dF = 3.125 is shown. Signal 1902 is the total signal input to the corresponding Tx antenna.

[0068] An advantage of the method of position determination using modified Wi-Fi access point and station signals as described herein is that erroneous measurements can be rejected using one of a variety of different algorithms (such as QLL, CQLL, CoOp, vector tracking, etc.) or, for example, the following algorithm.

[0069] In this algorithm, the positioning system uses base stations located at known coordinates. These base stations transmit signals, which are received and processed by the rover. The rover receives signals from multiple base stations and the rover calculates the current coordinates and / or velocity using the range difference method or any other known method.

[0070] In the simplest case, when phase measurements are performed and only relative coordinates are required, the navigation signal can be a pure harmonic signal. More details can be found in the literature, see, for example, Joon Wayn Cheong et al., Characterizing the Signal Structure of Locata's Pseudolite based Positioning System, International Global Navigation Satellite Systems Society IGNSS Symposium 2009 Holiday Inn Surfers Paradise, Qld, Australia 1-3 December, 2009; Barnes J., Rizos C., Wang J., Small D., Voigt G & Gambale N. (2003) Locata: A New Positioning Technology for High Precision Indoor and Outdoor Positioning, Proceedings 2003 International Symposium on GPS\GNSS, 9-18 (Proceedings of the 2003 GPS\GNSS International Symposium, 9-18); and Locata Corporation. Technology Brief (Locata Company Technology Brief), http: / / www.locata.com / wpcontent / uploads / 2014 / 07 / Locata-Technology-Brief-v8-July-2014-Final1.pdf, the entire contents of each of which are incorporated herein by reference.

[0071] The local positioning radio system operates in a strong multipath environment when transmitting signals from a reference (base) station, which is the main background of the present algorithm.

[0072] When multipath signals exist in the radio channel being measured, it will not only cause fading effects on the received signal, but also cause uncontrolled signal phase jumps, which will seriously affect the accuracy of the phase measurement and thus affect the accuracy of the current coordinates of the mobile station.

[0073] Experimental measurements of the overall phase of the signals from two receivers under conditions of multipath reception show visible jumps in the overall phase that increase the error in the current coordinate determination. These jumps represent abnormal behavior of the overall phase and are caused by multipath reception of the signals from the various base stations.

[0074] The core of the algorithm is a method and an apparatus for implementing it, which provide a method for reducing the impact of uncontrolled jumps in the received signal phase on the accuracy of determining the coordinates of the local positioning system and the global positioning system based on the phase measurement method, such uncontrolled jumps occurring in a multipath channel during radio wave propagation.

[0075] The positioning system usually comprises a number of reference (base) stations Tx1 ... TxN with known coordinates, which transmit navigation radio signals of a predetermined structure.

[0076] The movable object (rover) receives navigation signals from the base stations and determines its current coordinates and moving speed after processing these navigation signals. Any known method can be used to solve the navigation task, such as the distance difference method. To determine the coordinates of the movable object in a plane, at least three base stations are required. When determining the coordinates in 3D space, four base stations are required.

[0077] In practice, in many cases, the number of base stations "observable" by a mobile station can substantially exceed the minimum number required to solve the current positioning task of the mobile station.

[0078] Modern navigation and positioning systems use code and phase measurements. Phase measurements allow coordinate estimation methods to be significantly improved and the total positioning error to be substantially less than the carrier wavelength.

[0079] But in practice, especially in local positioning systems, there are multipath signals. In this case, the signal received by the mobile station's receiver is the direct signal as well as

[0080] The sum of a signal / signals reflected from any local objects. The path lengths from local objects to the receiving point are different and therefore the phase delays are also different. Furthermore, they may also differ in amplitude. During the rover motion, the phase difference of these signals changes and at some moments, the signals may become anti-phase signals. If the signal levels are quite close, the sum signal can "fade", i.e. its signal level becomes low or even zero. In this case, the total signal phase can undergo uncontrollable jumps when the signal takes its minimum value.

[0081] For example, to combat multipath effects, two independent antennas with different polarizations can be used to receive the signal. In this case, it is normal to use antennas with a common phase center.

[0082] The multipath propagation of the signals from the two transmitters and their reception by two independent antennas with a common phase center can be used. In this case, the transmitters can operate on different carrier frequencies, allowing for more effective multipath suppression.

[0083] When a signal is reflected from a local object, its polarization changes, so using antennas with different polarizations ensures that signal fades that occur simultaneously in both receiving antennas are cancelled.

[0084] A similar effect is observed when receiving signals from two or more transmitters. The advantage is related to both different antenna polarizations and different transmitter frequencies.

[0085] Therefore, the reception of signals from antennas with different polarizations and transmitters with different carrier frequencies can provide a basis for building a multipath immune positioning system.

[0086] Taking the above into account, the working principle of reducing the multipath effect on the phase measurement of the navigation and positioning radio system is as follows:

[0087] - Transmission of navigation signals with different pseudo-random codes by base stations with known coordinates and located in space in a predetermined manner;

[0088] - receiving a radio signal transmitted by a base station to a multi-channel correlation receiver at a mobile station;

[0089] -Measure the delay and phase differences of signals received from different base station pairs;

[0090] - Calculate the current mobile position based on the measured phase difference and delay difference, where

[0091] - For the transmission of navigation signals, the base stations use radio channels that are differentiated not only by the code used, but also by some other parameters, such as carrier frequency, polarization type, spatial position, etc.;

[0092] - the number of radio channels exceeds the number of channels required to carry out navigation measurements;

[0093] - receiving radio signals from some base stations at the mobile station;

[0094] - generating an estimate of the current full phase of the received signal in each radio channel of the multi-channel correlation receiver;

[0095] - controlling, at the output of each channel of a multi-channel correlation receiver, the rate of change of, for example, the speed or acceleration of changing the current full phase of the received signal;

[0096] -When there is an abnormal change in the full phase of the channel (see Fig.11 ), the result of estimating the current full phase of the signal received in a given channel is eliminated from the raw data when solving the navigation task.

[0097] In an embodiment, when the base station transmits navigation signals with different polarization types, these signals are received at the mobile station on multiple antennas with the same phase center and different polarization types, and the signal from the output of each antenna is fed to the input of the corresponding channel of the multi-channel correlation receiver.

[0098] Furthermore, an abnormal change in the current full phase of the received signal can be detected in each channel based on the square or modulus of the first increment or the second increment of the current full phase exceeding a preset threshold level / value. The required numerical threshold can be determined during the calibration of the phase measurement or based on experimental or simulated measurement results. Since the abnormal full phase change can move both downward and upward, it is reasonable to compare the absolute value characterizing the rate of change of the full phase with a threshold. For example, it can be the modulus or square of the first increment or the second increment of the current full phase.

[0099] The technical implementation of the proposed method can be implemented as a single antenna receiver with full phase estimation redundancy to improve the accuracy of the estimation of the local coordinate.

[0100] The navigation signal from the reference station is received by an antenna and further fed to a typical multi-channel correlation receiver, at the output of which there are generated estimates of the current full phase for each measurement channel, which are fed to the corresponding inputs of the navigation task block / block for solving the navigation task, at the output of which there are generated estimates of the current coordinates of the mobile station (absolute coordinates or relative coordinates, depending on the task solved). In addition, the estimate of the current full phase for each measurement channel from the corresponding output of the multi-channel correlation receiver is fed to the input of the corresponding block of the rate of change estimate of the current full phase for the corresponding channel 1...N, where an over-threshold signal is generated at a threshold value exceeding the rate of change of the full phase. The output of the rate of change estimate block of the corresponding channel 1...N is connected to the corresponding input of the channel selection block, at the output of which there is a generated signal corresponding to the number of the channel in which the threshold has been exceeded. These numbers of the channels measured are fed to the data bus, for example, to the N+1th input of the navigation task block, and according to this information from the solution of the navigation task at the relevant step, the current estimate of the full phase in the indicated channel is eliminated.

[0101] An embodiment of a block for estimating the rate of change of the total phase 1 ... N is shown, comprising a block for calculating a first increment or a second increment of the current total phase, and a block responsible for squaring or modulo the obtained phase increment.

[0102] An abnormal change of the current full phase of the received signal in each radio channel is detected based on the square or modulus of the first increment or the second increment of the current full phase exceeding a given threshold level.

[0103] The operation of the channel selection block is as follows: the values ​​calculated in the rate of change estimation block for each channel 1 ... N are fed to its input. These values ​​are compared with the threshold values ​​in each channel in the threshold units 1 ... N, generating a logic 1 at the output of the threshold unit where the threshold value has been exceeded and a logic 0 at the other outputs. The block generating the channel number generates at its output data on the channel number where the threshold value has been exceeded.

[0104] Embodiments of the proposed method include redundant multi-antenna receivers with full phase estimation to improve the accuracy of the estimation of local coordinates.

[0105] The functionality of a multi-antenna receiver is similar to that of the single-antenna receiver considered above. However, the availability of more independent reception channels ensures a higher level of compensation for multipath effects during the reception of radio signals.

[0106] These rejections of erroneous measurements in complex multipath environments improve RSTA positioning accuracy since measurement redundancy is generated.

[0107] The methods and apparatus described herein were tested in an aircraft hangar.In one embodiment, the methods and apparatus use the detection algorithm and multipath cancellation described above.

[0108] Since there are a lot of cycle slips in estimating the phase of the single signal of the transmitter, which may make this method less useful for positioning with centimeter-level accuracy, redundancy is created in the transmitted signal. In this frequency range, an OFDM signal based on pseudo-random numbers of Gold codes is generated in a band up to 50 MHz with frequency-selective multipath. The spectrum of this signal is shown in Fig. 20 In addition, to further increase redundancy, all available combinations of orthogonal polarizations from the transmitter and receiver are also used. Fig. 20 The spectrum representation of an OFDM signal with GoldPRN is shown. Each subcarrier is modulated by the same Gold code, the result of which corresponds to the sum of the subcarriers 2002.

[0109] The phase estimation for each subcarrier using an OFDM signal with Gold PRN is performed independently. However, when converting the phase estimate into meters, an algorithm for detecting cycle slips in the estimate can be implemented using a capture based on the full phase estimate. To implement the algorithm, it is necessary to calculate the total phase difference between all possible pairs of subcarriers and then, for each point in time, select the estimate of the phase of the subcarrier that is currently not affected by multipath. These operations must be performed independently in the receiver for each transmitter. Thus, an estimate of the delta of the total phase can be obtained, from which most of the cycle slips will be excluded. Fig.21 The difference in phase estimate between the subcarriers is shown. It can be seen that this parameter contains only noise and cycle slips, since the RF part, motion, and other hardware effects affect both subcarriers equally and mutually exclusive.

[0110] The result of applying the algorithm to experimental data from the hangar is that the algorithm achieves a root mean square (RMS) of the 2-D position on the order of 10 cm, as Figure 22 to Figure 25 as shown in .

[0111] Fig. 22 A diagram showing the estimated position of a rover mobile station (RSTA) traveling along a circle according to an embodiment using the algorithm. Circular path 2202 is the actual path traveled, while substantially circular path 2204 is the estimated path of travel as determined by the systems and methods described herein.

[0112] Fig.23 shows that RSTA is Fig. 22 A plot of the estimated position error for the circular progression shown. Fig. 22 and Fig.23 A single run of RSTA along a circular trajectory is shown, and the 2-D RMS is shown to be less than 10 cm.

[0113] Fig.24 A graph showing the estimated position of an RSTA along multiple circular travels according to an embodiment using the algorithm. Circular path 2402 is the actual path traveled, while the other generally circular graphs are estimated paths of travel as determined by the systems and methods described herein.

[0114] Fig.25 shows that RSTA is Fig.24 Plot of the estimated position error for multiple circular runs shown. Fig.24 and Fig.25 It is shown that the tracking errors are only minimally stored / accumulated over multiple runs along the trajectory. The storage / accumulation of errors may be specific to the local positioning system.

[0115] In one embodiment, a computer may be used to implement various devices (ie, a master station, a user station, a slave station, a mobile station, etc.), and the computer may also be used to perform the various methods and operations described herein. Fig.26 A high-level block diagram of such a computer is shown in . Computer 2602 includes a processor 2604, which controls the overall operation of computer 2602 by executing computer program instructions that define such operations. The computer program instructions can be stored in a storage device 2612 or other computer-readable medium (e.g., a disk, CD ROM, etc.), and the computer program instructions are loaded into memory 2610 when the computer program instructions need to be executed. Therefore, the methods and operations described herein can be defined by computer program instructions stored in memory 2610 and / or storage device 2612, and the methods and operations described herein can be controlled by the processor 2604 that executes the computer program instructions. For example, the computer program instructions can be implemented as computer executable code written by a person skilled in the art to perform the algorithms defined by the methods and operations described herein. Therefore, by executing the computer program instructions, the processor 2604 executes the algorithms defined by the methods and operations described herein. Computer 2602 also includes one or more network interfaces 2606, which are used to communicate with other devices via a network. The computer 2602 also includes input / output devices 2608 (e.g., a display, keyboard, mouse, speakers, buttons, etc.) that enable a user to interact with the computer 2602. Those skilled in the art will recognize that the actual computer implementation may also include other components, and Fig.26 is a high-level representation of some of the components of such a computer for purposes of illustration.

[0116] The foregoing detailed description should be understood to be illustrative and exemplary in all respects, rather than restrictive, and the scope of the inventive concept disclosed herein should be interpreted in accordance with the full scope permitted by patent law. It should be understood that the embodiments shown and described herein are only illustrative of the principles of the inventive concept, and that various modifications may be implemented by those skilled in the art without departing from the scope and spirit of the inventive concept. Various other feature combinations may be implemented by those skilled in the art without departing from the scope and spirit of the inventive concept.

Claims

1. A method for determining a position of a mobile station, the method comprising: exchanging a plurality of Wi-Fi signals between the mobile station and a plurality of base stations, the Wi-Fi signals comprising a plurality of orthogonal frequency division multiplexing (OFDM) communication signals; as well as A position of the mobile station is determined based on the OFDM communications signal.

2. The method according to claim 1, wherein: The Wi-Fi signal is transmitted via a dual polarization antenna.

3. The method according to claim 1, wherein: The Wi-Fi signal is transmitted via a three-polarization antenna.

4. The method according to claim 2, wherein: Determining the position of the mobile station based on the OFDM communications signal is also based on polarization of the OFDM communications signal.

5. The method according to claim 3, wherein: Determining the position of the mobile station based on the OFDM communications signal is also based on polarization of the OFDM communications signal.

6. The method according to claim 4, wherein: The OFDM communication signal is based on a pseudo noise sequence.

7. The method according to claim 5, wherein: The OFDM communication signal is based on a pseudo noise sequence.

8. A system, comprising: Mobile station; as well as Multiple base stations, The system is configured to perform the following operations: exchanging a plurality of Wi-Fi signals between the mobile station and the plurality of base stations, the Wi-Fi signals comprising a plurality of orthogonal frequency division multiplexing (OFDM) communication signals; and A position of the mobile station is determined based on the OFDM communications signal.

9. The system according to claim 8, wherein: The Wi-Fi signal is transmitted via a dual polarization antenna.

10. The system according to claim 8, wherein: The Wi-Fi signal is transmitted via a three-polarization antenna.

11. The system according to claim 9, wherein: Determining the position of the mobile station based on the OFDM communications signal is also based on polarization of the OFDM communications signal.

12. The system according to claim 10, wherein: Determining the position of the mobile station based on the OFDM communications signal is also based on polarization of the OFDM communications signal.

13. The system according to claim 11, wherein: The OFDM communication signal is based on a pseudo noise sequence.

14. The system according to claim 12, wherein: The OFDM communication signal is based on a pseudo noise sequence.

15. A mobile station, comprising: processor; as well as A memory storing computer program instructions, wherein the computer program instructions, when executed by the processor, cause the processor to perform operations including: receiving a plurality of Wi-Fi signals from a plurality of base stations, the Wi-Fi signals comprising a plurality of orthogonal frequency division multiplexing (OFDM) communication signals; and A position of the mobile station is determined based on the OFDM communications signal.

16. The mobile station according to claim 15, wherein: The Wi-Fi signal is transmitted via a dual polarization antenna.

17. The mobile station according to claim 15, wherein: The Wi-Fi signal is transmitted via a three-polarization antenna.

18. The mobile station according to claim 16, wherein: Determining the position of the mobile station based on the OFDM communications signal is also based on polarization of the OFDM communications signal.

19. The mobile station according to claim 17, wherein: Determining the position of the mobile station based on the OFDM communications signal is also based on polarization of the OFDM communications signal.

20. The mobile station of claim 18, wherein: The OFDM communication signal is based on a pseudo noise sequence.

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