Patent Description:
The ability to determine current coordinates and motion parameters of movable objects (e.g., moving vehicles) using radio navigation systems is a longstanding problem and there are many well-known solutions representing a variety of techniques for such determination.

In one case, this determination can be accomplished using so-called range-difference location methods which are often used, for example, in different navigation satellite systems, such as the US Global Positioning System (GPS), the Russian GLONASS or European GALILEO, as are well-known. However, indoor GNSS signal reception, for example, within locations having deep mines, canyons or other such impenetrable formations, and/or dense urban high-rise housing developments is limited due to the restricted line-of-sight visibility of satellites in such navigation systems which results in a sharp drop in the effectiveness of such systems with respect to position determination.

Of course, to combat some of these challenges, there are well-known techniques to determine positions of vehicles that use pseudolite signals (i.e., pseudo-satellite signals) to achieve a certain level of navigation accuracy. For example, <CIT>,<CIT>, <CIT>, and <CIT> describe different techniques for using pseudolite signals. Alternatively, there are also a number of well-known techniques (for example, as described in Unites States Patent Nos. <CIT>, and <CIT>) that employ so-called hybrid positioning devices which utilize both GNSS signals and other different signals supplied by ground base stations to achieve position determination. An advantage of such systems is better coverage of the desired territory and improved position accuracy. However, such systems are, as a general matter, very complicated and expensive to deploy, and function as position-determining rather than data-transmitting thereby leading to low communication channel throughput. Further, these potential limitations are compounded in that the task of developing positioning-determining and data-transmitting systems for movable objects is quite critical in delivering certain desired levels of position determination and data communication.

To overcome some of the aforementioned limitations, there are a number of well-known positioning techniques that use Wi-Fi access points (hereinafter "AP") and are based on measuring the strength of the received signal with a further comparison of the measured strength and the known spatial power distribution (e.g., the so-called fingerprinting positioning method). Such a fingerprinting position methodology is described, for example, in <CIT>, <CIT>, and <CIT>. These technical solutions can be used for both position-determination and data transmission/reception of movable subscribers/customers via a Wi-Fi network. Some alternative well-known technical solutions also providing data transmission along with positioning tasks are also described, for example, in Unites States Patent Publication Nos. <CIT>, <CIT>, and <CIT>, respectively, wherein signals are transmitted through information channels of Wi-Fi networks. However, these known methods do not allow for obtaining highly accurate coordinate estimates (i.e., as measured in centimeter increments) and include a number of technical implementation difficulties that make deployment challenging.

Other known technical solutions for position determination (e.g., as described in <CIT>,<CIT>, and <CIT>) employ certain information from ground maps, Wi-Fi AP distribution, and/or coverage zones and received signal intensity to specify a mobile user's position. Further, certain other known positioning devices (e.g., as described in <CIT> and <CIT>) employ the phase difference of signals being received by selected spaced antennas to determine the position of a movable object.

<CIT> is another known positioning technique in which a rover's position is determined using a number of reference transmitters which generate and transmit in-phase navigation signals, which are received by a rover, and determining the delays associated with the received signals for the purpose of calculating the rover's position. However, this technique cannot be directly used for transmitting information between reference transmitters and a mobile receiver/rover due to low communication channel throughput.

Therefore, a need exists for an improved technique for determining the current coordinates and motion parameters of movable objects including when GNSS signal reception is impossible or deficient in providing a desired positioning accuracy.

<CIT> discusses a mobile wireless device configured to provide a location quality of service indicator (QoSI) indicative of the quality of a calculated location estimation for use by a location-based service. The QoSI may be used to represent the predicted location accuracy, availability, latency, precision, and/or yield.

<CIT> discusses a method for localization of a mobile communication device that includes transmitting a data message from the mobile communication device to a first access point, determining the reception times of the data message at the first access point and at second access points, transmitting an acknowledgement message and determining the reception times of the acknowledgement message, and determining the position of the mobile communication device based on the reception times of the data message and the reception times of the acknowledgement message.

<CIT> discusses a method of calibrating a delay within a wireless access point for determining a position of a mobile station, including receiving an initial packet at an eavesdropping device, receiving a response packet, sent by another entity, at the eavesdropping device, and computing a time difference based upon the packet arrival times.

In accordance with the embodiments herein, a position determination is achieved through the modification of certain Wi-Fi access point and station signals, that are radiated by a certain master (i.e., guiding) base station, combined with slave (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 position.

In particular, in accordance with various embodiments, a method and apparatus is provided for determining a mobile station's (e.g., a rover) position by utilizing modified Wi-Fi signals (e.g. in accordance with well-known IEEE <NUM> protocol) and transmitting and receiving Wi-Fi signals by a plurality of base stations, receiving signals transmitted by these base stations (which have known coordinates) and located in some proximity to the mobile station, measuring delay phase differences being received from different pairs of the base stations at the mobile station, and calculating position coordinates of the mobile station (also referred to herein as a mobile object) using the delay and phase differences. The aforementioned position coordinate calculation facilitated by transmitting and receiving of the Wi-Fi signals that are produced by a guiding (i.e., master) base station and a guided (i.e., slave) station(s) which are spatially located in a predetermined manner, and the master base station and slave stations periodically transmit signals in the form of frames with an assigned structure according to a predetermined time sequence, such that the structure of transmitted frames contains a specially generated symbol sequence which is used for the positioning of the moving object, and transmitting service information needed for positioning tasks is implemented in fields of a preamble header and in select/available information fields of such frame.

In an embodiment, the positioning of a mobile user (e.g., a rover-station) by modified Wi-Fi signals (e.g., the IEEE <NUM> protocol) is facilitated by radiating and receiving the Wi-Fi signals by a guiding base station (master station) and guided base stations (slave stations) previously located in space, periodically radiating signals in the form of a pre-set frame, according to a pre-set time sequence, by the master and slave stations. This includes a specially-generated symbol sequence in the structure of radiated frames, in which the sequence is used for positioning mobile users. Further, there is a transmission of service information needed for solving positioning tasks in the header field of the frame preamble and free/available frame information fields.

In accordance with an embodiment, a preamble fragment with a scrambled set of units of the pre-set length expanded by the Barker code is used as a symbol sequence. In accordance with an embodiment, in addition to a preamble fragment with a scrambled set of units of the pre-set length expanded by the Barker code, some other pseudo-random sequences (PRS) situated/located at available frame fields are utilized, excluding fields whose content cannot be previously assigned or determined. Further, the PRS chip duration, agreed upon using Wi-Fi signal parameters, is used as a symbol sequence for positioning tasks.

In accordance an embodiment, a preamble fragment with a scrambled set of units of a preset length is used as a symbol sequence to determine a position of the movable object. In accordance with an embodiment of one or more pseudo-random sequences (PRS) are used in addition to the scrambled set of units of a preset length. These sequences are located at available frame fields excluding fields where the content cannot be previously set or determined.

In a further embodiment, operated according to the well-known IEEE protocol <NUM>. 11b, the master base station generates a QPSK-modulated signal for the entire frame being transmitted , and one of quadrature components of the transmitted signal (for example, designated as "I"), is used to transfer information in a standard mode. Another quadrature component of the transmitted signal (for example, designated as Q) is used to transmit a navigation signal as a PRS, the total duration of which can achieve the frame duration, and PRS symbols in the Q-channel are additionally modulated by the shifted Barker code the length of which coincides with the length of the similar code in the I-channel. In reception of such a signal at a mobile station different reference PRS and shifted Barker codes are applied to quadrature channels of the phase synchronization system.

A further embodiment has the clock and frequency synchronization for the master and slave base stations implemented by a separate communications link, for example, a cable network.

A further embodiment utilizes clock and frequency synchronization of the master and slave base stations with radio signals radiated by the master base station, such that the navigation signal transmitted by the master station is used as the synchronization signal.

In accordance with an embodiment, a standard request to send/clear to send (RTS/CTS) handshake (<<RTX/CTS handshake>>) mechanism is used (in accordance with the <NUM> protocol) to implement time division of base navigation signals, a time interval is allocated to the master station to radiate a broadband message (a Beacon type frame) that is immediately followed by a navigation frame. Further, having received frames from the master station, the slave stations compute time intervals for radiating their signals and at a particular time they initiate the standard «RTS/CTS handshake» mechanism from the master station which provides for the radiating navigation frames from the slave stations. Mobile stations can also initiate data transfer at an allocated time interval by the same mechanism with the described frame exchange implemented periodically in accordance with signals generated by the master base station.

In accordance with an embodiment, interframe intervals are removed to enhance efficiency, and master and slave stations sequentially radiate navigation frames at preset time intervals. A mobile station (e.g., rover) transmits information within an allocated time interval where the aforementioned frame exchange is periodically implemented in accordance with signals generated by the master base station.

In accordance with an embodiment, one of the operation modes of the <NUM> protocol is used by the master base station which can assign time intervals (Contention-Free Period (CFP)), wherein signals can be transmitted by different devices only when such device is enabled by the master station. The time intervals are divided into two parts, namely, a navigation part and communication part. The navigation part is used for radiating navigation frames at pre-set time intervals by the master and slave station, and the communication part is used for sequential requests of data from rovers by the master base station. In reply, each rover transmits a data frame, and once each frame has been received, the master station generates and transmits a corresponding frame such that the described frame exchange is periodically implemented under the control of the master base station.

These and other advantages of the embodiments will be apparent to those of ordinary skill in the art by reference to the following detailed description and the accompanying drawings.

This will be further described in greater detail herein below and the discussion (and associated Figures) will employ the following set of acronyms and abbreviations in.

<FIG> shows diagram <NUM> illustrating a mobile station's position determination when clock and frequency scales of the master and slave base stations are synchronized using a separate communications link to transmit synchronized signals in accordance with an embodiment. In particular, master station <NUM> and a set of slave stations <NUM>, <NUM>, <NUM> will be utilized to determine the current position of mobile station(s) <NUM> (e.g. rover(s)). In accordance with the embodiment, such position determination will be based on signals exchanged between master station <NUM>, slave stations <NUM>, <NUM>, <NUM>, user station <NUM>, and the use of modified Wi-Fi signals (illustratively, Wi-Fi signals in accordance the well-known IEEE <NUM> protocol).

Illustratively, information (i.e., antenna) ports of exchanging data from master station <NUM>, as further described herein below, that use modified Wi-Fi signals through a transmission/access medium are connected with corresponding information (antenna) ports of user station <NUM>, slave stations <NUM>, <NUM>, <NUM>, and mobile station(s) <NUM> and provide data exchange between these objects in accordance with Wi-Fi protocol. As will be appreciated, while only one rover and one user station are shown in <FIG> for illustration purposes, the principles of the embodiment apply to multiple mobile stations and multiple user stations, as well as any number of master base stations and slave base stations. Master base station <NUM> includes a navigation port (not shown) for generating navigation signals <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM> which are exchanged with slave base stations <NUM>, <NUM>, and <NUM>, and for exchanging communication signals <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM> (illustratively, Wi-Fi signals) through the applicable transmission medium with rover(s) <NUM>, user station <NUM>, and slave base stations <NUM>, <NUM>, and <NUM>.

Turning our attention also to <FIG>, the exchange of the aforementioned signals is further illustrated in that synchronization port <NUM> of master base station <NUM> generates synchronization (timing) signals <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM> for receipt by slave base stations <NUM>, <NUM>, <NUM> through synchronization ports <NUM>, <NUM>, and <NUM> of slave base stations <NUM>, <NUM>, <NUM>. Output navigation ports <NUM>, <NUM>, and <NUM>, respectively, of slave base stations <NUM>, <NUM>, <NUM> are connected to corresponding navigation ports <NUM>, <NUM>, and <NUM> of mobile station(s) <NUM> for communication across the transmission medium.

Therefore, to achieve the position determination of mobile station(s) <NUM>, master base station <NUM> (which is acting, in accordance with the embodiment, as a Wi-Fi access point), transmits communication signals <NUM>-<NUM> through <NUM>-<NUM>, such signals being modified signals according to the IEEE <NUM> protocol (also referred to herein as "the <NUM> protocol"). These signals have at least an information component corresponding to the <NUM> protocol and a separate navigation component intended for positioning moving objects. Moreover, master base station <NUM> generates and transmits synchronization signals <NUM>-<NUM> through <NUM>-<NUM> to slave base stations <NUM>, <NUM>, <NUM> using the infrastructure of a separate data transmission network (not shown), for example, a cable communication network in a well-known manner. Slave base stations <NUM>, <NUM>, <NUM> generate and sequentially in time transmit navigation signals <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM> based on the received synchronization signals (i.e., synchronization signals <NUM>-<NUM> through <NUM>-<NUM>). Master station(s) <NUM> receive signals (i.e., communication signal <NUM>-<NUM>, and navigation signals <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM>, respectively) from master station <NUM> and slave base stations <NUM>, <NUM>, and <NUM> and determines its coordinates based on, illustratively, a range-difference method which is a well-known methodology for such purposes.

<FIG> shows diagram <NUM> illustrating a further embodiment in which a mobile station's position determination when clock and frequency scales of master and slave base stations are synchronized using radio signals transmitted by the master base station. In accordance with the embodiment, master base station <NUM> exchanges communication signals <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM> (illustratively, modified Wi-Fi signals conforming with the <NUM> protocol) using information (antenna) ports (not shown) through a transmission medium which are connected with corresponding information (antenna) ports (not shown) of user station <NUM>, slave base stations <NUM>, <NUM>, <NUM>, and mobile station(s) <NUM>, all of the foregoing devices capable of exchanging data in accordance with the <NUM> protocol.

Turning our attention also to <FIG>, the exchange of the aforementioned signals is further illustrated in that navigation port <NUM> of master base station <NUM> generates MSTA navigation signals <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM> for receipt by slave base stations <NUM>, <NUM>, and <NUM> through the transmission medium to navigation ports <NUM>, <NUM>, and <NUM>. Output navigation ports <NUM>, <NUM>, and <NUM>, respectively, of slave base stations <NUM>, <NUM>, and <NUM> generate SSTA navigation signals <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM>. MSTA navigation signals <NUM>-<NUM> through <NUM>-<NUM> and SSTA navigation signals <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM> are transferred together with communications signals <NUM>-<NUM> through <NUM>-<NUM> through the transmission medium, and connected to receiving navigation port <NUM>, <NUM>, and <NUM> of mobile station(s) <NUM>, and to corresponding synchronization ports <NUM>, <NUM>, and <NUM> of slave base stations <NUM>, <NUM>, <NUM>. For clarity, the Figures herein also designate certain ports with certain number designations "<NUM>", "<NUM>", "<NUM>", etc. to show illustrative interconnections between certain ports as shown in corresponding <FIG> herein. Further output navigation ports <NUM>, <NUM>, and <NUM> of slave base stations <NUM>, <NUM>, <NUM>, are connected through the transmission to corresponding navigation ports <NUM>, <NUM>, and <NUM> of mobile station(s) <NUM>. Mobile station(s) <NUM> receive signals (i.e., communications signals <NUM>-<NUM> through <NUM>-<NUM> , and MSTA navigation signals <NUM>-<NUM> through <NUM>-<NUM>, and SSTA navigation signals <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM>, respectively) exchanged by master base station <NUM>, slave base stations <NUM>, <NUM>, and <NUM>, and user stations <NUM> and determines its coordinates based on, illustratively, a range-difference method which is a well-known methodology for such purposes.

In accordance with the embodiment, information (antenna) ports for exchanging data from master base station <NUM> that use modified Wi-Fi signals through a transmission medium are connected with corresponding information (antenna) ports of user stations <NUM>, slave base stations <NUM>, <NUM>, <NUM>, and mobile station(s) <NUM>, as detailed above, and provide data exchange between these objects in accordance with the timing diagrams as shown in <FIG>, <FIG>, and <FIG> herein, thereby forming time division multiple access with dedicated time slots for each STA unlike particular random access in typical operations in accordance with the <NUM> protocol. A navigation port of master base station <NUM> generates navigation and synchronization signals, which are combined with modified Wi-Fi signals through the transmission medium, and is connected to a receiving navigation port of mobile station(s) <NUM>, and to corresponding synchronization ports of slave base stations <NUM>, <NUM>, <NUM>, as detailed above. The output navigation ports of slave base stations <NUM>, <NUM>, <NUM> through the transmission medium are connected to corresponding navigation ports of mobile station(s) <NUM>. Thus, the mobile station(s) receive signals from master base and slave stations and determine their coordinates using a range-difference method.

<FIG> is a functional block diagram of master base station <NUM> shown in <FIG> in accordance with an embodiment. In accordance with the embodiment, master base station <NUM> is configured in the form of sequentially connected blocks via information exchange ports, that is, modified MAC layer generation block <NUM>, standard PHY layer block <NUM>, transceiver <NUM>, as well as navigation signal generator <NUM>. The second data exchange port of modified MAC layer generation block <NUM> is connected to a corresponding port of navigation signal generator <NUM>, the navigation output of which is connected to the corresponding input of transceiver <NUM>. In turn, the synchronized output is the synchronized output of master base station <NUM>, and the information and navigation outputs of which are corresponding logical outputs of transceiver <NUM> combined into a single physical signal.

In this case, a signal transmitted by master base station <NUM> includes both information and navigation components which are combined in transceiver <NUM>. The first component is generated in standard PHY layer block <NUM> with well-known methods relevant to the <NUM> protocol based on the data from modified MAC layer generation block <NUM>. The second component is generated by navigation signal generator <NUM> based on additional parameters entered into modified MAC layer block <NUM>.

<FIG> is a functional block diagram showing a structural scheme of slave base station <NUM> shown in <FIG> in accordance with an embodiment. In accordance with the embodiment, slave base station <NUM> is configured (it will be noted that while <FIG> is focused on slave base station <NUM>, the description thereof is equally applicable to slave base stations <NUM> and <NUM>) as sequentially connected transceiver <NUM>, modified physical layer generation block <NUM> and transmitter <NUM>, as well as modified MAC layer generation block <NUM>. A data exchange port of which is connected to a first data exchange port of modified physical layer generation block <NUM>, and a data exchange port of slave base station <NUM> being an input data exchange port of transceiver <NUM>, an output data exchange port of which is connected to a second modified physical layer generation block <NUM>. A synchronized input of slave base station <NUM> is connected to a corresponding synchronized input of modified physical layer generation block <NUM>, with the output of slave base station <NUM> being the output of transmitter <NUM>.

As shown in <FIG>, slave base station <NUM> functions as follows: a signal transmitted by master base station <NUM> is received by transceiver <NUM> along with a synchronization signal from master base station <NUM> via a separate network (e.g., a cable network). These signals are then demodulated and communicated to modified physical layer generation block <NUM>, where the information signal corresponding to the <NUM> protocol is isolated and transmitted to modified MAC layer generation block <NUM> for further usage. Through this configuration of channel master and slave base stations an exchange of service and control information is enabled. In addition, modified physical layer generation block <NUM> generates navigation signals based on the received synchronization signals and control information, with the navigation signals being transmitted over air by transmitter <NUM> in a well-known fashion.

<FIG> is a functional block diagram showing modified PHY layer block <NUM> shown in <FIG> in accordance with an embodiment. In particular, modified physical layer generation block <NUM> is configured as a sequentially connected transceiver <NUM> having an asynchronous sampling frequency, SSTA control unit <NUM>, and transmitter <NUM>, as well as synchronization block <NUM>. The first data exchange port of transceiver <NUM> being the first data exchange port of modified physical layer signal generation block <NUM>, and the second data exchange port of transceiver <NUM> being the second data exchange port of modified physical layer generation block <NUM>. Further, the input of synchronization block <NUM> is the synchronization input of modified physical layer generation block <NUM>, and the output of transmitter <NUM> is the output of modified physical layer generation block <NUM>.

As shown in <FIG>, modified physical layer generation block <NUM> operates as follows: the <NUM> protocol information signal isolated by transceiver <NUM> and provided to transceiver <NUM> and after necessary standard signal conversions the signal is further transmitted to modified MAC layer generation block <NUM>. Also, signals required to be transmitted to master station <NUM> (serving as an access point) according to the <NUM> protocol can be transmitted back. Moreover, a part of the received data is sent to control block <NUM> together with synchronization signals, and, based on these signals, control block <NUM> generates navigation signals at a required time moment, and these signals are further transmitted (on air) by transmitter <NUM>.

<FIG> is a functional block diagram of master base station shown <NUM> in <FIG> in accordance with an embodiment. In accordance with embodiment, master base station <NUM> is configured in the form of sequentially connected blocks through data exchange ports of modified MAC layer generation block <NUM>, standard physical layer block <NUM>, transceiver <NUM>, and navigation signal generation block <NUM>. The second data exchange port of modified MAC layer generation block <NUM> is connected to a corresponding port of navigation signal generation block <NUM>, the navigation output of which is connected to a corresponding input of transceiver <NUM>, and the synchronization output is the synchronization output of master base station <NUM>. Further, the information and navigation outputs of these blocks are corresponding logical outputs of transceiver <NUM> which are combined into a single physical signal.

In this configuration, the signal transmitted by master base station <NUM> contains information and navigation components combined in transceiver <NUM>. The first component is generated in a standard physical layer block <NUM> by standard methods in accordance with the <NUM> protocol based on data received from modified MAC layer generation block <NUM>, and the second component is generated by navigation signal generation block <NUM> on the basis of additional parameters entered into modified MAC layer generation block <NUM>.

<FIG> is a functional block diagram showing a structural scheme of slave base station <NUM> shown in <FIG> in accordance with an embodiment. In accordance with embodiment, slave base station <NUM> (for ease of illustration only this slave base station is shown but slave base station <NUM> and <NUM> share the same configuration) is made as sequentially connected transceiver <NUM>, modified physical layer generation block <NUM> and transmitter <NUM>. Modified MAC layer generation block <NUM> with a data exchange port of which is connected with a first data exchange port of modified physical layer generation block <NUM>, the data exchange port of slave station <NUM> being an input data exchange port of transceiver <NUM>, and the output data exchange port of which is connected to a second data exchange port of modified physical layer generation block <NUM>. A synchronization input of slave station <NUM> is connected to a corresponding synchronization input of modified physical layer generation block <NUM> and the output of slave station <NUM> is associated with the output of transmitter <NUM>.

In this configuration, slave base station <NUM> operates such that a radio signal transmitted by master base station <NUM> is received by transceiver <NUM> along with a synchronization signal from master base station <NUM> via a separate network (e.g., a cable network). Once these signals are demodulated, and provided to modified physical layer generation block <NUM>, the information signal corresponding to the <NUM> protocol is isolated and transmitted to the modified MAC layer generation block <NUM> for further usage. The master and slave base stations also exchange service and control information in a well-known manner. In addition, modified physical layer generation block <NUM> generates navigation signals based on the received synchronization signals and control information, where the navigation signals are transmitted over air by transmitter <NUM>.

<FIG> is a functional block diagram showing the modified PHY layer block <NUM> of <FIG> in accordance with an embodiment. In accordance with the embodiment, modified physical layer generation block <NUM> is configured as a sequentially connected transceiver <NUM> with asynchronous sampling frequency, SSTA control unit <NUM> and transmitter <NUM>, as well as a tracking channel <NUM>, with the first data exchange port of transceiver <NUM> being a first data exchange port of modified physical layer generation block <NUM>, and the second data exchange port of transceiver <NUM> being a second data exchange port of modified physical layer generation block <NUM>. Further, the input of tracking channel <NUM> is the synchronization input of modified physical layer generation block <NUM>, and the output of transmitter <NUM> is the output of modified physical layer generation block <NUM>.

The operation of modified physical layer generation block <NUM> is such that the <NUM> protocol information signal isolated by transceiver <NUM> and provided to transceiver <NUM> and after necessary and standard conversions the signal is further transmitted to modified MAC layer generation block <NUM>, and signals required to be transmitted to master station <NUM> according to the <NUM> protocol can be transmitted back. Moreover, a part of received data is sent to control block <NUM> together with synchronization signals. Based on these signals, control block <NUM> generates navigation signals at a required time moment, and these signals are further transmitted on air by transmitter <NUM>.

<FIG> is a functional block diagram of mobile station <NUM> shown in <FIG>, in accordance with an embodiment. It will be understood that this discussion will apply equally to mobile station <NUM> shown in <FIG> as well but for brevity only mobile station <NUM> is shown. In accordance with the embodiment, mobile station <NUM> (e.g., a rover) includes modified MAC layer generation block <NUM> and modified physical layer generation block <NUM>, with the data exchange port of modified MAC layer generation block <NUM> connected to a first data exchange port of modified physical layer generation block <NUM>. Further, navigation inputs of mobile station <NUM> are navigation inputs of modified physical layer generation block <NUM>.

Mobile station <NUM> exchanges information signals (e.g., in accordance with the <NUM> protocol) with master base station <NUM>, and receive navigation signals from master base station <NUM> and slave base stations <NUM>, <NUM>, and <NUM>. The signal from master base station <NUM> includes two components: information according to the <NUM> protocol, and a navigation component generated on the basis of certain rules, such rules will be discussed further herein below. Thereafter, the listed signals are provided to ports of modified physical layer generation block <NUM> that interacts with modified MAC layer generation block <NUM>.

<FIG> is a functional block diagram of modified physical layer block <NUM> shown in <FIG> in accordance with an embodiment. In accordance with the embodiment, modified physical layer generation block <NUM> is configured with a standard transceiver <NUM> with asynchronous sampling frequency, tracking channels control and coordinates computation unit <NUM> and a number of tracking channels <NUM>, <NUM>, <NUM> and <NUM>. The first and second data exchange ports of transceiver <NUM> being respectively a first and second data exchange of modified physical layer generation block <NUM>, the third data exchange port of transceiver <NUM> being connected to a similar data exchange port of tracking channels control and coordinates computation unit <NUM> such that certain ports of controlling tracking channels and transmitting navigation data are connected to corresponding ports of tracking channels <NUM>, <NUM>, <NUM> and <NUM>, the inputs of which are corresponding navigation inputs of modified physical layer generation block <NUM>.

The operations of modified physical layer block <NUM> are such that an information signal component transmitted by master base station <NUM> (or master base station <NUM>) is provided to transceiver <NUM> where MAC layer parameters are isolated and further transmitted to modified MAC layer generation block <NUM>, and the MAC layer data can be transmitted back to master base station <NUM> (or master base stations <NUM>).

Navigation signals received from master station <NUM> (or master base station <NUM>) and slave stations <NUM>, <NUM>, and <NUM> (or slave stations <NUM>, <NUM>, and <NUM>) in modified physical layer generation block <NUM> is provided to the corresponding channels tracking in code and phase <NUM>, <NUM>, <NUM>, and <NUM>. These tracking channels are connected to the corresponding ports of tracking channels control and coordinates computation unit <NUM>, where the mobile station's (e.g., mobile station <NUM> and/or <NUM>) current coordinates are computed according to well-known algorithms and the range-difference method. Moreover, certain control commands may also be generated by modified physical layer block <NUM> using current data received via the Wi-Fi information channel from the tracking channels. These control commands can change tracking channel parameters in accordance with current operational conditions.

<FIG> are diagrams showing various structures of different navigation frames and corresponding vector diagrams of modulation methods being used for a frame with long preambles in accordance with an embodiment. In particular, depending on conditions and system configurations one of four (<NUM>) frame structures (also referred to herein as a "type <NUM>, <NUM>, <NUM> or <NUM>") can be selected for the physical layer frame transmitted by the master and slave stations. The basic structure, as shown, corresponds to the IEEE <NUM>. 11b protocol frame wherein SYNC is the long preamble, SFD (start frame delimiter) is the identification of frame start, SIGNAL is the signal format, SERVICE is the reserved field, LENGTH is the duration of the frame, CRC (cyclic redundancy check) is the check sum, MPDU is the field with a frame of MAC layer.

As shown in <FIG>, navigation frame <NUM> of type <NUM> is a standard frame according to the IEEE <NUM>. 11b protocol. In this case, as also illustrated in vector diagram <NUM>-<NUM>, tracking follows preamble SYNC. Any modulation can be used in this frame type (in accordance with the <NUM>. 11b protocol). As shown in <FIG>, navigation frame <NUM> of type <NUM> includes a PNS field containing a pseudorandom sequence for tracking, this field replaces the MPDU field (as shown in <FIG>) with a MAC layer frame. In this case, as also illustrated in vector diagram <NUM>-<NUM>, a binary phase manipulation is used in the signal.

As shown in <FIG>, navigation frame <NUM> of type <NUM>, includes a PNS field which is also used for tracking, but the navigation signal is generated in the quadrature component of the signal, whereas the in-phase component is used for MAC layer frame. The vector diagrams <NUM>-<NUM> and <NUM>-<NUM> show that PLCP-header corresponds to the IEEE <NUM>. 11b protocol and there is binary phase manipulation there, whereas in the main part of the frame there is quadrature phase manipulation.

As shown in <FIG>, navigation frame <NUM> of type <NUM> has a PNS field which is used for tracking and also contains some pseudorandom sequence, the navigation signal being generated at the same time as SYNC preamble but in quadrature component of the signal (as also shown in vector diagrams <NUM>-<NUM> and <NUM>-<NUM>). In the moment of transmitting preamble SYNC quadrature phase manipulation is used in the signal, whereas any other modulation in accordance with the IEEE <NUM>. 11b protocol, including binary phase manipulation, can be used in the rest frame fields.

<FIG> show diagrams of various structures of different navigation frames and corresponding vector diagrams of modulation methods being used for a frame with short preambles in accordance with an embodiment. A short SYNC preamble is used in physical layer frames according to the <NUM> protocol at high signal-to-noise ratios. As shown in <FIG>, navigation frame <NUM> of type <NUM> is a standard frame according to the <NUM>. 11b protocol. In this case tracking follows short SYNC preamble. Any modulation can be used in this frame type (in accordance with protocol). As shown in <FIG>, navigation frame <NUM> of type <NUM> includes a PNS field containing a pseudorandom sequence used for tracking, this field replaces the MPDU field (as shown in <FIG>) with MAC layer frame. In this case, a binary phase manipulation is used in the signal. As shown in <FIG>, navigation frame <NUM> of type <NUM> includes the PNS for tracking purposes, but the navigation signal is generated in the quadrature component of the signal, whereas the in-phase component is used for MAC layer frame.

<FIG> shows a variety timing diagrams <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> illustrating the structure and the order of signal transmission by master and slave stations, and a mobile user when a standard IEEE <NUM> data exchange mechanism is applied in accordance with an embodiment; To implement time-division multiplexing, a standard «RTS/CTS handshake» mechanism provided by the <NUM> protocol can be used, which includes the exchange of service frames RTS, CTS, DATA and ACK between two devices. As shown, these frames are designated respectively as r, c, d (or nav) etc. A time interval TS0 is allocated to the master station when the station transmits frames of type «Beacon» (b), and navigation frame (nav) follows it. Once slave stations (SSTA0, SSTA1, and SSTA N) receive signals from the master station, with time counters they calculate time intervals (TS1, TS2, and TS3), at which signals are to be transmitted, and at the calculated time they initiate the «RTS/CTS-handshake» mechanism at the master station thereby forcing the slave stations to transmit navigation frame as data. Further, rovers also can initiate data transmission by the same mechanism at an allocated time interval (TS N+<NUM>). The exchange of frames described above is periodically performed by a super frame of type <NUM>.

<FIG> shows a variety of time slot diagrams <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> generated by a master and slave base stations, and a mobile user when the first variant of a modified data exchange mechanism is used in accordance with an embodiment. Both service and interframe intervals are present in data exchange in case of using «RTS/CTS-handshake» mechanism. As such, part of the time is spent transmitting service information and waiting for the desired moment of transmission. To minimize such losses, one can employ the remove of interframe intervals. Master base station (MSTA) and slave base station (SSTA0, SSTA1, and SSTA N) stations successively transmit navigation frames at assigned time intervals (TS <NUM> - TS N+<NUM>). If a time interval is allocated to a rover, it is to transmit an information frame. The frame exchange above is a super frame of type <NUM> and implemented periodically in accordance with the time slot diagrams shown in FIGs. <NUM> through <NUM>.

<FIG> shows a variety of time slot diagrams <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> generated by a master and slave base stations, and a mobile user when the second variant of a modified data exchange mechanism is used in accordance with an embodiment. To implement time-division multiplexing, a hybrid coordination function (HCF) can be applied in accordance with the <NUM> protocol. In this case, the master station generates time intervals which are called a Contention-Free Period (CFP) when signal transmission is enabled by the master base station. These intervals, in turn, are divided into two parts: navigation and communication parts. During the navigation part, the master base station (MSTA) and slave base stations (SSTA0, SSTA1, SSTA N) sequentially transmit navigation frames at preset time intervals (TS <NUM> - TS N+<NUM>). During the communication part, the master station polls the rover data using frame POLL (designated as "p" in <FIG>). In reply, the rover transmits a data frame (designated as "d" in <FIG>), and the master station generates frame ACK (designated as "a" in <FIG>). Note that data exchange is to be completed before the CFP end. The frame exchange above is a super frame of type <NUM> and implemented periodically in accordance with the aforementioned time slot diagrams of <FIG>.

<FIG> shows a graph <NUM> of a normalized auto-correlation function for Gold code pseudo-random noise (PRS) sequence with a length of <NUM> chips, typically used in GPS navigation systems, in accordance with an embodiment.

<FIG> shows a graph <NUM> of a normalized auto-correlation function for M-sequence with a length of <NUM> chips, typically used in GLONASS navigation systems, in accordance with an embodiment.

<FIG> shows a graph <NUM> of a normalized auto-correlation function for a long preamble SYNC in accordance with an embodiment. As shown, the level of side-lobes for long preamble SYNC is comparable the level of side-lobes for Gold PRS and M-sequence signals thereby allowing for the use of long preamble SYNC signals for a variety of navigation operations.

<FIG> shows a graph <NUM> of a normalized auto-correlation function for a short preamble SYNC in accordance with an embodiment. As shown, the level of side-lobes for short preamble SYNC signals is higher for the case of long preamble SYNC signals but are comparable to the level of side-lobes for Gold PRS and M-sequence signals thereby allowing for the use of short preamble SYNC signals for navigation operations in which shorter distance navigation is desired.

<FIG> shows a graph <NUM> of a normalized auto-correlation function for Gold code pseudo-random noise (PRS) sequence spread by the Barker codes in accordance with an embodiment. As shown, the level of side-lobes is comparable to the level of side-lobes for Gold PRS and M-sequence signals thereby allowing for the use of spread Gold PRS signals for a variety of navigation operations, and also allowing for users of the <NUM> protocol to detect <NUM>-like signals in the transmission medium through a CCA procedure in accordance with the <NUM> protocol.

<FIG> shows a graph <NUM> of a normalized auto-correlation function for M-sequence signals spread by the Barker codes in accordance with an embodiment. The level of side-lobes is comparable to the level of side-lobes for Gold PRS and M-sequence signals thereby allowing for the use of M-sequence signals for a variety of navigation operations, and also allowing for users of the <NUM> protocol to detect <NUM>-like signals in the transmission medium through a CCA procedure in accordance with the <NUM> protocol.

<FIG> show generating the SYNC and PNS fields in navigation signal frames in accordance with various embodiments. In the of embodiment of <FIG>, the SYNC field of the navigation signal frame is generated when signal bits at rate of <NUM> are provided to the input of scrambler <NUM> configured according to the <NUM> protocol, and then the scrambled signal is expanded by an <NUM>-chip Barker code <NUM> resulting in an output chip frequency of <NUM>. As shown in embodiment of <FIG>, PRS generator <NUM> is used at the output rate of <NUM>, and to decrease mutual correlation of information and navigation components, the bit stream at the generator output is expanded by the <NUM>-chip Barker code <NUM> shifted relative to the information channel, thereby resulting in the output chip rate of <NUM>. As shown in the embodiment of <FIG>, PRS generator <NUM> alone is used with an output chip rate of <NUM>.

<FIG> show certain experimental results associated with determining a mobile station's position in accordance with an embodiment. An estimate of the receiver's two-dimensional (2D) trajectory relative to the starting point (designated by symbol «+») with return to the starting point is shown. This evaluation was done by phase measurements of the rover in the embodiments detailed herein above. Reference measurements were obtained by a RTK GNSS receiver at the same time. As shown in <FIG>, graph <NUM> depicts the results where circles show positions of base stations for the system in consideration. In <FIG>, graph <NUM> depicts the results where 2D position errors are presented based on phase measurements. RTK-obtained positions served as a true trajectory. As will be readily ascertained from <FIG>, the experimental results confirm the operability and efficiency of the herein described embodiments of signal generating and processing as per the prototype configured for such purposes. In particular, a receiver's relative position accuracy based on phase measurements is proved to achieve centimeter-level accuracy when an extra transmitter is added to the local positioning system.

It should be noted that for clarity of explanation, the illustrative embodiments described herein may be presented as comprising individual functional blocks or combinations of functional blocks. The functions these blocks represent may be provided through the use of either dedicated or shared hardware, including, but not limited to, hardware capable of executing software. Illustrative embodiments may comprise digital signal processor ("DSP") hardware and/or software performing the operation described herein. Thus, for example, it will be appreciated by those skilled in the art that the block diagrams herein represent conceptual views of illustrative functions, operations and/or circuitry of the principles described in the various embodiments herein. Similarly, it will be appreciated that any flowcharts, flow diagrams, state transition diagrams, pseudo code, program code and the like represent various processes which may be substantially represented in computer readable medium and so executed by a computer, machine or processor, whether or not such computer, machine or processor is explicitly shown. One skilled in the art will recognize that an implementation of an actual computer or computer system may have other structures and may contain other components as well, and that a high level representation of some of the components of such a computer is for illustrative purposes.

Claim 1:
A method for determining a position of a mobile station comprising:
exchanging a plurality of Wi-Fi signals between the mobile station (<NUM>) and a plurality of base stations, the plurality of base stations comprising a master base station in communication with a set of slave base stations (<NUM>, <NUM>, <NUM>), the master base station (<NUM>) and the set of slave base stations being spatially located in a predefined manner;
exchanging a plurality of communication signals between the mobile station (<NUM>), the master base station (<NUM>) and the set of slave base stations (<NUM>, <NUM>, <NUM>), characterized by particular
ones of the plurality of communication signals configured as a plurality of frames having a predetermined time sequence, particular frames of the plurality of frames having a specified symbol sequence for positioning the mobile station (<NUM>), and at least one frame of the particular frames having a set of service information specific to the positioning of the mobile station (<NUM>);
wherein the position of the mobile station (<NUM>) is determined by calculating the position of the mobile station (<NUM>) using a first set of delay and phase differences and a second set of delay and phase differences, wherein:
the measured first set of delay and phase differences is associated with particular ones of the plurality of Wi-Fi signals and particular ones of the plurality of communication signals exchanged between the mobile station (<NUM>) and a first pair of the plurality of base stations, and
the measured second set of delay and phase differences is associated with particular other ones of the plurality of Wi-Fi signals and particular other ones of the plurality of communication signals exchanged between the mobile station (<NUM>) and a second pair of the plurality of base stations, the first pair of the plurality of base stations and the second pair of the plurality of base stations being different.