Patent Description:
One application known from the prior art (<CIT>) discloses systems, methods, devices and computer-readable storage mediums for device state estimation with body-fixed assumption. In some implementations, a method comprises: determining, by a device, a rotational velocity of a user of the device based on a sensor signal; determining, by the device, user speed; determining, by the device, user acceleration based on the user speed and the rotational velocity of the user; and updating a user state estimator based on the user acceleration.

Another application known from the prior art (<CIT>) relates to a method for determining a target variable, such as speed or altitude, to be measured, in a mobile device (such as a wrist-mounted computer or mobile telephone), and a corresponding mobile system. In the method, a first physical variable is measured with the aid of a first sensor and a second physical variable with the aid of a second sensor. The second physical variable is typically different to the first physical variable, or at least is measured using a different technique. With the aid of the measurements, the value of the target variable is calculated with the aid of the measurement of the first and second physical variables, in such a way that an estimate for the target variable is determined with the aid of at least the measurement of the first physical variable, at least a first error estimate is determined, which depicts the accuracy of the measurement of the first physical variable, and the estimate of the target variable is filtered at a strength that depends on both the first error estimate and the measurement of the said second physical variable.

Techniques are discussed herein for determining a moving body's position and velocity. For example, techniques are discussed for determining a swimmer's position and velocity by compensating for bias that may result from a swimmer's arm swing. The techniques discussed may help avoid over-estimating a swimmer's velocity that results in inaccurate position estimation along the swimmer's path. To compensate for the swimmer's arm swing, resulting in systematic bias errors in velocity determined from measurements of a device on the swimmer's arm, an estimate of translational velocity due to arm rotation may be removed, e.g., from pseudorange rates (PRRs) from satellite positioning system measurements, to reduce the systematic bias errors. A scale factor is applied to an estimated velocity of the swimmer's body to estimate the velocity of a mobile device on the swimmer's wrist, e.g., while above water. These techniques are examples, and other techniques may be used.

Referring to <FIG>, an example of a system <NUM> capable of providing location and communication services includes a mobile wireless communication device <NUM> (also referred to herein as a mobile device), a base station <NUM>, a communication network <NUM>, a server <NUM>, and satellites <NUM>, <NUM>. The system <NUM> is a communication system in that the system <NUM> can at least send and receive communications between components of the system and a wireless communication system in that the system can send at least some communications wirelessly. For example, communications may be sent wirelessly between the mobile device <NUM> and the base station <NUM>, communications may be sent between the base station <NUM> and the network <NUM>, and communications may be sent between the network <NUM> and the server <NUM>. Wired connections are shown between the base station <NUM> and the network <NUM>, and between the network <NUM> and the server <NUM>, although wireless connections may be provided. Positioning signals may be received wirelessly by the mobile device <NUM>. Only one server <NUM> is shown for simplicity, but more than one server <NUM> may be used in the system <NUM>, e.g., in various locations to provide quicker access as the system <NUM> may span large regions, e.g., entire countries or continents, or even the planet. Further, not all components of the system <NUM> are required to implement one or more features discussed herein. For example, the base station <NUM> may be omitted and/or the mobile device <NUM> may not be configured to communicate with the base station <NUM> (e.g., the mobile device <NUM> may not include a cellular modem). As another example, the server <NUM> may be omitted from the system <NUM>, or simply not used, in order to determine compensated speed as discussed herein. Further still, only one base station <NUM> is shown for simplicity, but numerous base stations are provided for communication with the mobile device <NUM> as these devices move. Further, only two satellites are shown for simplicity, but numerous satellites are provided for each satellite positioning system (SPS), and multiple SPSs (e.g., Global Positioning System (GPS), Global Navigation Satellite System (GLONASS), BeiDou Navigation Satellite System (BDS), etc.) may be used by the mobile device <NUM>.

The base station <NUM> is configured to communicate wirelessly with the mobile device <NUM> via an antenna. The base station <NUM> may also be referred to by one or more other names such as a base transceiver station, an access point, an access node (AN), a Node B, an evolved Node B (eNB), etc. The base station <NUM> is configured to communicate wirelessly with the mobile device <NUM> under control of the server <NUM> (via the network <NUM>).

The mobile device <NUM> can be moved to various locations, including into and out of buildings, into and out of water, etc. The mobile device <NUM> may be referred to as access terminals (ATs), mobile devices, user equipment (UE), or subscriber units. The mobile device <NUM> shown in <FIG> is a smart watch, but other implementations of the mobile device <NUM> may be used. For example, other types of wearable mobile devices may be used, or other types of mobile devices that are not configured to be wearable by a user may be used.

Referring also to <FIG>, the mobile device <NUM> comprises a computer system including a processor <NUM>, memory <NUM> including software <NUM>, one or more sensors <NUM>, a transceiver <NUM>, a telecommunication (telecom) antenna <NUM>, a SPS unit <NUM>, a SPS antenna <NUM>, and a user input device <NUM>. The transceiver <NUM> and the telecom antenna <NUM> form a wireless communication system (e.g., a cellular communication system including a telecommunication (e.g., cellular signal) receiver and a telecommunication (e.g., cellular signal) transmitter) that can communicate bi-directionally with the base station <NUM> (e.g., transmitting and receiving cellular signals). Other example mobile devices may have different configurations, e.g., with multiple transceivers and multiple telecom antennas for communicating with base stations of different cellular networks. The SPS antenna <NUM> is configured to receive SPS signals, for example raw SPS signals, from the satellites <NUM>, <NUM> and the SPS unit <NUM> is configured to process the SPS signals to generate SPS measurements (such as, for example, pseudoranges and pseudorange rates, which can be represented in various ways, including, for example, code phase, rate of change of code phase, carrier phase, rate of change of carrier phase, and/or instantaneous Doppler. The SPS unit <NUM> may then transfer the SPS measurements to the processor <NUM>, which can then use such measurements to compute such things as positions and/or velocities (including speeds) of the mobile device <NUM>. As such, the processor <NUM> is configured to receive measurements derived from SPS signals received by the SPS antenna <NUM> of the SPS unit <NUM> and compute SPS-based velocities. The processor <NUM> may determine the SPS-based velocity by assuming a velocity, e.g., zero magnitude velocity, and computing residuals from a Doppler estimate (for the satellite from which the SPS signal was received). The processor <NUM> may compute residuals from Doppler estimates for multiple satellites. The processor <NUM> may apply a technique (e.g., a least squares technique or a Kalman filter) that reduces (or even minimizes) a cost function associated with the residuals to determine an estimate of the velocity. Also or alternatively, the processor <NUM> may determine a speed of the mobile device <NUM> by processing information (e.g., measurements) from signals received by the telecom antenna <NUM>. The processor <NUM> is preferably an intelligent hardware device, e.g., a central processing unit (CPU) such as those made by QUALCOMM®), ARM®), Intel® Corporation, or AMD®, a microcontroller, an application specific integrated circuit (ASIC), etc. The processor <NUM> could comprise multiple separate physical entities that can be distributed in the mobile device <NUM>. For example, the processing performed by the SPS unit <NUM> may be performed wholly or partially by the processor <NUM>. The memory <NUM> is a non-transitory storage medium that includes random access memory (RAM) and read-only memory (ROM). The memory <NUM> stores the software <NUM> which is processor-readable, processor-executable software code containing instructions that are configured to, when executed, instruct the processor <NUM> to perform various functions described herein (although the description may refer only to the processor <NUM>, or the mobile device <NUM>, performing the functions), for example, the stages and methods described below with reference to <FIG> and <FIG>. Alternatively, the software <NUM> may not be directly executable by the processor <NUM> but configured to instruct the processor <NUM>, e.g., when compiled and executed, to perform the functions, for example, the stages and methods described below with reference to <FIG> and <FIG>. The sensor(s) <NUM> and the user input device <NUM> are discussed in more detail below.

Referring also to <FIG>, the base station <NUM> comprises a computer system including a processor <NUM>, memory <NUM> including software <NUM>, a transceiver <NUM>, and an antenna <NUM>. While the base station <NUM> is shown with a single processor <NUM> and a single memory <NUM> (with corresponding software <NUM>), the base station <NUM> may have a processor <NUM> and a memory <NUM> (with corresponding software <NUM>) for each sector served by the base station <NUM>, e.g., each of three sectors. The transceiver <NUM> and the antenna <NUM> form a wireless communication module configured to communicate bi-directionally with the mobile device <NUM>. The processor <NUM> is preferably an intelligent hardware device, e.g., a central processing unit (CPU) such as those made by QUALCOMM®, ARM®, Intel® Corporation, or AMD®, a microcontroller, an application specific integrated circuit (ASIC), etc. The processor <NUM> could comprise multiple separate physical entities that can be distributed in the base station <NUM>. The memory <NUM> is a non-transitory storage medium that includes random access memory (RAM) and read-only memory (ROM). The memory <NUM> stores the software <NUM>, which is processor-readable, processor-executable software code containing instructions that are configured to, when executed, instruct the processor <NUM> to perform various functions described herein (although the description may refer only to the processor <NUM>, or the base station <NUM>, performing the functions). Alternatively, the software <NUM> may not be directly executable by the processor <NUM>, but configured to instruct the processor <NUM>, e.g., when compiled and executed, to perform the functions.

The mobile device <NUM> and the base station <NUM> are configured to communicate with each other. The mobile device <NUM> and the base station <NUM> can send messages to each other that contain a variety of information. For example, the base station <NUM> can collect information from the sensor(s) <NUM> and send the information to the base station <NUM>, e.g., for sending to the server <NUM>.

Referring also to <FIG>, the server <NUM> comprises a computer system including a processor <NUM>, memory <NUM> including software <NUM>, and a transceiver <NUM>, and an antenna <NUM>. The processor <NUM> is preferably an intelligent hardware device, e.g., a central processing unit (CPU) such as those made by QUALCOMM®, ARM®, Intel® Corporation, or AMD®, a microcontroller, an application specific integrated circuit (ASIC), etc. The processor <NUM> could comprise multiple separate physical entities that can be distributed in the server <NUM>. The memory <NUM> is a non-transitory storage medium that includes random access memory (RAM) and read-only memory (ROM). The memory <NUM> stores the software <NUM>, which is processor-readable, processor-executable software code containing instructions that are configured to, when executed, cause the processor <NUM> to perform various functions described herein (although the description may refer only to the processor <NUM>, or the server <NUM>, performing the functions). Alternatively, the software <NUM> may not be directly executable by the processor <NUM>, but configured to cause the processor <NUM>, e.g., when compiled and executed, to perform the functions. The transceiver <NUM> is configured to send communications to and receive communications from the base station <NUM> through wired connections via the network <NUM>.

Referring to <FIG>, with further reference to <FIG>, a swimmer <NUM> is shown swimming a crawl stroke in the presence of at least one of the satellites <NUM>. As shown in <FIG>, during a portion of the stroke, the mobile device <NUM> is above (or below but close enough to) a water line <NUM> and such that the satellite <NUM> is visible to the mobile device <NUM>. That is, the mobile device <NUM> can receive sufficient energy from a signal from the satellite to process the signal for position determination when the mobile device <NUM> is above the water line <NUM> or when the mobile device <NUM> is below the water line <NUM> but receives at least an acquisition threshold amount of energy from the satellite signal. This will generally equate to a threshold depth below the water line <NUM> below which no satellite signal can be acquired or at least reliably used for position determination. As shown in <FIG>, during another portion of the stroke, the mobile device <NUM> is below (or further than the distance from) the water line <NUM> and thus the satellite <NUM> is not visible to the mobile device <NUM>. During times that the satellite <NUM> is visible to the mobile device <NUM>, an arm of the swimmer <NUM> on which the mobile device <NUM> resides is rotating and thus the mobile device <NUM> is typically moving forward, at any instant along and in the direction of a velocity vector <NUM> (Vm), at a speed that is faster than a speed of the swimmer <NUM> overall, e.g., of a torso of the swimmer <NUM>. Herein, reference to speed or velocity of the swimmer <NUM>, unless otherwise noted, is a reference to the torso of the swimmer <NUM>. This differential between the velocity of the mobile device <NUM> and the velocity of the swimmer <NUM>, and the fact that the detected velocity of the mobile device <NUM> is on average similar to the direction of the swimmer <NUM> and faster than the speed of the swimmer <NUM>, will result in a velocity bias being determined for the mobile device <NUM> relative to the swimmer <NUM>. The bias, if a predictive PVT (Position Velocity Time) filter is used (such as a typical Kalman filter), produces a systematic error in the position and velocity determined for the mobile device <NUM>, as discussed below. The determined position may be overshot and the velocity overestimated without adjusting for the bias. The discussion herein focuses on repetitive motion, e.g., of an arm of the swimmer <NUM> relative to a body (e.g., a torso) of the swimmer <NUM>, but the techniques discussed herein may be applicable to non-repetitive motion, and thus techniques discussed herein may be used to compensate for repetitive and/or non-repetitive motion, e.g., to compensate determined velocity.

Referring again to <FIG>, with further reference to <FIG> and <FIG>, the sensor <NUM> may include one or more sensors that may be used to help determine that the mobile device <NUM> is in water, including to help determine whether the mobile device <NUM> is below a threshold depth in the water. For simplicity, the use of the plural "sensors" herein includes the singular "sensor," and vice versa. The sensor <NUM> may obtain and/or produce signals and provide the signals, and/or indications thereof, to the processor <NUM> for determining whether the mobile device <NUM> is in water, out of water, below a threshold depth of water, above a threshold depth of water, etc. If the threshold depth is <NUM> (or inches, etc.), then the threshold is the surface of the water and the determination of being deeper than the threshold becomes a determination of being in the water, and a determination of being above the threshold becomes a determination of being out of the water. The determination of the mobile device <NUM> being below the threshold depth in the water (e.g., below which SPS signals are too weak to be used effectively for ranging/position determination) may be used to trigger operation of the SPS unit <NUM>. Thus, the SPS unit <NUM> may be operated only when sufficient power is received in one or more signals via the SPS antenna <NUM> for processing to determine ranging information.

The sensor <NUM> may include the SPS unit <NUM> and the SPS antenna <NUM> although the SPS unit <NUM> and the SPS antenna <NUM> are shown separate from the sensor <NUM> in <FIG>. The SPS unit <NUM> and the SPS antenna <NUM> are configured to receive SPS signals from the satellites <NUM>, <NUM> (and other satellites not shown). The SPS unit <NUM> is configured to process these signals, e.g., to identify the satellite(s) <NUM>, <NUM> from which the signals originated and/or to determine a range to the source satellite(s). For example, the SPS unit <NUM> may integrate SPS signals over time, perform calculations on the integrated signals, and provide indications of these calculations to the processor <NUM> for further analysis. For example, the SPS unit <NUM> may integrate in phase (I) and quadrature phase (Q) SPS signals, square each of these signals, add the squares, and take a square root of the sum. That is, the SPS unit <NUM> may calculate an I/Q Signal Amplitude according to: <MAT>.

The SPS unit <NUM> is configured to provide the I/Q signal amplitude IQA over time to the processor <NUM>. For example, referring to <FIG>, a plot of IQA <NUM> over time for the mobile device <NUM> while being worn by a user that is swimming. As shown, the IQA <NUM> repeatedly swings between a relatively high amplitude and a relatively low amplitude as the user's arm goes in and out of the water with an amplitude <NUM> being the IQA <NUM> when the mobile device <NUM> is at the surface of the water. As shown, the IQA <NUM> drops significantly with the mobile device <NUM> in the water, with the IQA <NUM> being so low that the SPS signal cannot be acquired or at least reliably used for position determination and is essentially nonexistent once the mobile device <NUM> is less than about <NUM> below the surface of the water. The IQA <NUM> reported by the SPS unit <NUM> to the processor <NUM> may be from one or more of the satellites <NUM>, <NUM>, and/or may be from one satellite constellation from multiple available satellite constellations. For example, the SPS unit <NUM> may provide the IQA <NUM> only for a single one of the satellites <NUM>, <NUM> during a select period of time such as a training period of time. As another example, the SPS unit <NUM> may provide the IQA <NUM> only for one or more satellites from one satellite constellation from multiple available constellations such as GPS (used in the United States), GLONASS (Russia's SPS), BDS (China's SPS), etc. Further discussion of use of the IQA <NUM> by the processor <NUM> is provided below.

The sensor <NUM> may include a telecommunication receiver, e.g., a cellular signal receiver, of the transceiver <NUM>. The cellular signal receiver is configured to produce and provide signals indicative of received cellular signals to the processor <NUM>. These signals are referred to as cellular signals, and the processor <NUM> may analyze these cellular signals for communication purposes and for determining a relationship of the mobile device <NUM> to water, e.g., under water, a depth under water, etc..

The sensor <NUM> may include an accelerometer and/or a pressure sensor. The accelerometer is configured to produce signals indicative of acceleration of the mobile device <NUM> and to provide these signals to the processor <NUM>. The processor <NUM> may compare accelerometer data with accelerometer data characteristic of swimming, e.g., as stored in the memory <NUM> or provided by the server <NUM> or obtained in another manner. If the accelerometer data from the sensor <NUM> correlates well to the accelerometer data characteristic of swimming, then the processor <NUM> can conclude that the mobile device <NUM> is in water (at least during portions of a cycle of the accelerometer data associated with being in water). Similarly, the pressure sensor is configured to measure pressure on the mobile device <NUM> and to produce signals indicative of pressure on the mobile device <NUM> and to provide these signals to the processor <NUM>. The processor <NUM> may be configured to determine that the mobile device is in water based on the measuring of the pressure on the mobile device <NUM>. For example, the processor <NUM> may determine that the mobile device <NUM> is in water if the pressure exceeds a threshold pressure such as <NUM> atmosphere, <NUM> atmospheres, or another pressure threshold.

The user input device <NUM> is configured to provide an interface to a user and to receive information from the user. The user input device <NUM> may include, for example, a touch-sensitive screen, a keyboard, a microphone, and/or a data input jack (e.g., a micro-USB jack). The user input device <NUM> may receive input from the user such as a selection of a smart phone app such as a fitness-tracking app. Further the user input device <NUM> may receive selections within the app such as an indication that the user is swimming (e.g., that the user is starting a swimming workout indicating that the user is or imminently will be swimming), whether the user is swimming indoors or outdoors, how long of a pool the user will be swimming in, that the user is running, etc..

The SPS unit <NUM>, based on signals received by the SPS antenna <NUM>, is configured to determine position and movement of the mobile device <NUM>. For example, the SPS unit <NUM> can determine a Doppler shift of a signal received by the SPS antenna <NUM>, and the Doppler shift along with a known velocity of the satellite <NUM> can be used to determine a velocity of the mobile device <NUM>. If the bias induced by the arm motion of the swimmer <NUM> relative to the torso of the swimmer <NUM> can be (at least partially) accounted for, then a compensated velocity of the mobile device <NUM> will more closely correspond to the velocity of the torso of the swimmer <NUM> (which may be referred to herein as the velocity of the swimmer <NUM>). In the case of GNSS (Global Navigation Satellite System), the satellite positions are determined in an Earth-fixed frame. Assuming no other sources of error, this implies that any error in the estimated Doppler will be the cumulative effect of any velocity of the user, which in this case means the body-to-water velocity and the arm-to-body velocity (ignoring the water current at present). It is desirable to reduce (e.g., remove) the contribution of the arm-to-body velocity from the Doppler for each of the range-rate measurements to the satellites. This can be done by estimating the arm-to-body velocity directly from the estimated body-to-water velocity, or as a separately filtered parameter. As mentioned above, one or more functions described as being performed by the SPS unit <NUM> (e.g., a processor of the SPS unit <NUM>) may be performed by the processor <NUM>, and thus the discussion herein refers to the processor <NUM> performing functions for adjusting for the bias induced by the arm motion of the swimmer <NUM> and determining position and velocity of the swimmer <NUM>.

It may be desirable to determine a position of the swimmer <NUM>, e.g., relative to the Earth, a body-to-Earth velocity of the swimmer <NUM>, and/or a body-to-water velocity of the swimmer <NUM>. Referring to <FIG>, a body-to-Earth velocity Vb|e is shown as a body-to-Earth vector <NUM> and is composed of a body-to-water velocity Vb|w, shown as a body-to-water vector <NUM>, and a water-to-Earth velocity Vw|e shown as a water vector <NUM>. In this example, the water-to-Earth velocity Vw|e is due east. An arm-to-Earth velocity Va|e, shown as an arm-to-Earth vector <NUM> (with the mobile device <NUM> on the arm of the swimmer <NUM>) is composed of the body-to-water velocity Vb| w (represented by the body-to-water vector <NUM>), an arm-to-body velocity Va|b, shown as an arm-to-body vector <NUM>, and the water-to-Earth velocity Vw|e, shown as a water-to-Earth vector <NUM> (that has the same magnitude and direction as the water vector <NUM>). As shown, the arm-to-body velocity <NUM> is not aligned with the body-to-water vector <NUM> (e.g., the arm moves slightly away from the body as the arm moves forward). An arm-to-water velocity Va|w, shown as an arm-to-water vector <NUM>, is composed of the body-to-water velocity Vb|w (represented by the body-to-water vector <NUM>), and the arm-to-body velocity Va|b, shown as the arm-to-body vector <NUM>. The desirable values of the body-to-Earth velocity Vb|e of the swimmer <NUM> and/or the body-to-water velocity Vb|w of the swimmer <NUM> may be determined from the measurable quantities of the position of the swimmer <NUM> and the arm-to-Earth velocity Va|e (represented by the arm-to-Earth vector <NUM>) of the swimmer <NUM> as discussed below. As used herein for velocities and positions, subscripts of a, b, e, w correspond respectively to arm (of the swimmer <NUM>), body (of the swimmer <NUM>, e.g., the torso), Earth, water, a superscript of c indicates that the value corresponds to when a present water speed (current) is non-zero, a character with caret over the character, e.g., V̂, indicated an estimated value, and a character with an inverted caret over the character, e.g., V̌, indicates a measured value. Also, it may be assumed that the position of the swimmer's arm is the same as the position of the swimmer's body.

The processor <NUM> may be configured to determine a compensated velocity, e.g., compensated for velocity bias, of the swimmer <NUM> selectively, e.g., only under one or more conditions. For example, the processor <NUM> may be configured to attempt to determine a velocity of the swimmer <NUM> adjusted for arm motion only if a speed of the swimmer <NUM> exceeds a threshold value, for example, <NUM>/s, <NUM>/s, <NUM>/s, or greater, with an activity of swimming selected by a user of the mobile device <NUM>, e.g., using the user input device <NUM>, and with a last-known position of the mobile device <NUM> being proximate to (e.g., within a threshold distance) of a body of water.

Referring to also <FIG>, if there is no current, e.g., the water-to-Earth vectors <NUM>, <NUM> shown in <FIG> have zero length, and the swimmer's arm swings along a direction of travel of the swimmer <NUM>, then the arm-to-body velocity Va|b, shown as an arm-to-body vector <NUM>, is aligned with (in the same direction as) the body-to-water vector <NUM>. In this case, the body-to-water vector <NUM> is also the body-to-Earth vector, and an arm-to-Earth vector of the arm-to-Earth velocity Va|e will be the sum of the body-to-water vector <NUM> and the arm-to-body vector <NUM>. To determine the body-to-Earth vector, which is equal to the body-to-water vector <NUM> in this case, the arm-to-Earth vector can be scaled by a scalar value as discussed below.

The processor <NUM> is configured to determine a Doppler estimate of a component of relative velocity of the mobile device <NUM> and the satellite <NUM> along a direction from the mobile device <NUM> to the satellite <NUM>. The processor <NUM> is configured to determine the Doppler estimate including an adjustment for the velocity bias due to the arm swing of the swimmer <NUM>. For example, the processor may be configured to determine the Doppler estimate according to <MAT>.

Where V̂ is an estimated velocity of the swimmer <NUM>, α is a scale factor for the arm swing motion (i.e., to scale the velocity of the swimmer <NUM> to the velocity of the mobile device <NUM>), vSV is the satellite vehicle velocity, H is a unit vector <NUM> (<FIG>) in the direction from the mobile device <NUM> to the satellite <NUM>, and ". " is the dot-product matrix operation. The estimated swimmer velocity V̂ may, for example, be a chosen value such as a default value (e.g., zero), or another value such as a most-recently-determined (according to the discussion herein) value of the swimmer's velocity. V̂ α is an estimate of the velocity Vm of the mobile device <NUM>, e.g., as shown in <FIG>. All velocity values and the unit vector H are in an ECEF (Earth-Centered Earth-Fixed) coordinate system, i.e., relative to the center of Earth. Further, the swimmer's velocity is assumed to be horizontal only. The satellite vehicle velocity vSV is a vector of satellite velocity in the ECEF coordinate frame as determined by decoding ephemeris data from the satellite <NUM> and given by <MAT> where vSV[<NUM>] is the x-component of the velocity, vSV[<NUM>] is the y-component of the velocity, and vSV[<NUM>] is the z-component of the velocity, and the estimated velocity V̂ is a vector of swimmer (user) velocity in the ECEF coordinate frame as determined by starting with a velocity assumption (e.g., assuming zero velocity) and computing the residuals from a Doppler estimate. Least squares regression analysis is applied to the residuals to determine an estimate of the velocity. This estimate is then used to determine residuals from a Doppler estimate to determine a revised estimated velocity, with the estimated velocity V̂ given by <MAT>.

The processor <NUM> is configured to use a value of the scale factor α based on a motion model that estimates the amount of velocity of the mobile device <NUM> to remove due to repetitive motion, e.g., arm swing, of the swimmer <NUM>. For example, the processor <NUM> may remove the component of measured velocity (for example, an SPS-based velocity) that is due to velocity of the mobile device <NUM> relative to the body of the swimmer <NUM>. The scale factor α may, for example, be a function of measured acceleration and rotation rate of the arm determined from MEMS (micro electro-mechanical systems) accelerometers and gyroscopes. Also or alternatively, α may be determined based on the speed of the mobile device <NUM>, e.g., as one or more functions of speed of the mobile device <NUM>. For example, the processor <NUM> may be configured to determine α according to the following equations. <MAT> <MAT> where s is the speed of the mobile device <NUM>, e.g., the SPS-based velocity of the mobile device <NUM>, or the speed as determined by another manner (e.g., analysis of telecommunication signals, analysis of sensor (e.g., accelerometer and/or gyroscope) data, etc.). As another example of a technique for determining a value of α, a first-order approximation may be used for the scale factor α such that α = MIN(<NUM> + (Su - Sb), <NUM>), where Su is the speed of the mobile device <NUM> in meters per second as determined from signals from the satellites <NUM>, and Sb is an assumed baseline speed. For example, a default value of Sb may be <NUM> as this is a typical speed of an adult swimmer. Alternatively, the value of α may be set to a predefined value such as <NUM>. The value of Sb may be adjusted, e.g., based on information provided about the swimmer <NUM> such as typical speed, arm length, stroke type, time above water per stroke, etc. One or more of these values may be provided by the swimmer <NUM> (e.g., through the user input device <NUM> and/or learned by the processor <NUM>). Thus, based on the estimated speed of the swimmer <NUM> relative to one or more thresholds, the estimated speed and/or the value of the scale factor may be changed. For example, if the estimated speed is below <NUM>/s, then use of the scale factor may be eliminated, changing the estimated speed. As another example, based on the value of the estimated speed, the value of the scale factor may be changed (e.g., if the value of the scale factor from Equation (<NUM>) is used but results in an estimated speed below <NUM>/s, resulting in the scale factor being determined from Equation (<NUM>)). Changing the value of the scale factor may then change the value of the estimated speed. Or, the new value of the scale factor may be used only for future determinations of estimated speed. Still other techniques for determining values of a variable scale factor may be used, e.g., with thresholds other than those discussed, other scale factor values, no thresholds, other formulas, etc..

Alternatively, the processor <NUM> may be configured to determine a value for the scale factor α using measured velocity, e.g., SPS-based velocity, and position of the mobile device <NUM>. Using the example of <FIG>, at a first epoch, the mobile device <NUM> is observed at an initial position P<NUM>, and at a measured present position P̌<NUM>,b|w (that corresponds to a measured present position P<NUM>,b|e given that there is zero current, with the position of the arm relative to the Earth approximately equal to, and assumed equal to, the position of the body relative to the Earth. The value P<NUM> is not indicated as being measured (inverted caret) or estimated/filtered (caret), as this value may be a prior measured position or a prior estimated/filtered position. The processor <NUM> can compare a distance between these two positions (P̌<NUM>,b|e - P<NUM>) with a distance (P̂<NUM>,a|w - P<NUM>), where P̂<NUM>,a|w is an estimate of a propagated position of the mobile device <NUM>, to the time of the second epoch, based on an uncompensated measured velocity V̌<NUM>,a|e for the first epoch. The uncompensated measured velocity V̌<NUM>,a|e is an SPS-based velocity that comprises a base velocity of a body and a supplemental velocity due to repetitive motion of the mobile device <NUM> relative to the body. The body may be living (e.g., of a user, a swimmer, another person, a non-human animal) or not living (e.g., a robot). Thus, the base velocity may be the velocity of the swimmer <NUM> and the supplemental velocity the velocity due to motion of the swimmer's arm on which the mobile device <NUM> is disposed during a repetitive swim stroke. The scale factor α may be estimated according to <MAT>.

The scale factor â<NUM> may initially come from a model, but eventually be a converged term if the scale factor is a static, or at least stable, term. The (converged) scale factor may be used to reduce position uncertainty resulting from limited accuracy of position fixes, e.g., by incorporating additional, unbiased information from the velocity estimate.

To compensate for a non-zero current, the processor <NUM> can reduce (e.g., remove) a current component and scale the velocity. In this scenario, the processor <NUM> may estimate a value of the scale factor α according to <MAT>.

The processor <NUM> may be configured to determine a velocity of the arm relative to the body V̂<NUM>,a|b. The processor <NUM> may calculate the effective velocity over two sample periods using equation (<NUM>). This calculates the velocity as the quotient of the difference from the measure position P̌<NUM>,b|w to the initial position P<NUM> and the delta time between epochs. This velocity is compared against the measured velocity at the arm V̂<NUM>,a|e, with the difference being attributable to the velocity of the arm relative to the body V̂<NUM>,a|b shown in equation (<NUM>). Equation (<NUM>) is also valid when there is a non-zero, but constant current, as the water velocity will equally affect both the average estimated velocity <MAT>, and the estimated instantaneous velocity V̂<NUM>,a|b. <MAT> <MAT> <MAT>.

With non-zero current and arm swing not aligned with the swimmer's body, a measured position <MAT> (<FIG>) of the swimmer <NUM> relative to the Earth at a second epoch comprises the propagated position of the swimmer's body-to-water velocity V̂<NUM>,b|w indicated by the body-to-water vector <NUM>, from the position P<NUM> at the first epoch, plus the propagated distance of the water current based on the water-to-Earth velocity V̂<NUM>,w|e indicated by the water-to-Earth vector <NUM>. The measured position <MAT> the measured arm-to-Earth velocity <MAT>, and the estimated body-to-Earth velocity V̂<NUM>,b|e can be represented by <MAT> <MAT> <MAT>.

One or more terms in Equations (<NUM>)-(<NUM>) may include one or more error terms (not shown), e.g., to account for imprecision in measurement, approximations in estimates, etc. The estimated arm-to-body velocity V̂<NUM>,a|b may be estimated using one or more of the sensor(s) <NUM>, or the method described in equation (<NUM>). Using this estimated value and the measured arm-to-Earth velocity <MAT> the estimated body-to-Earth velocity V̂o,b|e may be determined. Other techniques may be used to determine body-to-Earth velocity V̂o,b|e, for example, analyzing a change in position for a corresponding change in time using Equation (<NUM>).

The processor <NUM> may be configured to determine the value of the unit vector H. For example, the processor <NUM> may be configured to determine the value of the unit vector H according to <MAT> <MAT><MAT> <MAT> where r is a distance, or geometric range, from the mobile device <NUM> to the satellite <NUM> given by <MAT> where a mobile device position Pb is a vector of mobile device position in the ECEF coordinate frame as determined by decoding ephemeris data from the satellite <NUM> and given by <MAT> where Pb[<NUM>] is the x-component of the position, Pb[<NUM>] is the y-component of the position, and Pb[<NUM>] is the z-component of the position, and where a satellite vehicle position PSV is a vector of satellite position in the ECEF coordinate frame as determined by decoding ephemeris data from the satellite <NUM> and given by <MAT> where PSV[<NUM>] is the x-component of the position, PSV[<NUM>] is the y-component of the position, and PSV[<NUM>] is the z-component of the position.

The processor <NUM> may be configured to obtain an actual, measured Doppler Dmeas from a signal from the satellite and compare this to the Doppler estimate Dest from Equation (<NUM>). The processor <NUM> may receive the measured Doppler Dmeas from the SPS unit <NUM> or may calculate the measured Doppler Dmeas from signal information from the SPS unit <NUM>. The processor <NUM> may, in response to the uncorrected body-to-Earth speed (i.e., magnitude of the velocity) being above a threshold, apply the scale factor to the velocity used in calculating the Doppler estimate Dest. Using the scale factor assumes that the arm-to-body vector and the body-to-Earth vector are aligned (e.g., that misalignment has been removed/reduced). The processor <NUM> may determine a difference between the measured Doppler Dmeas and the Doppler estimate Dest, called a residual, and use the residual to determine a new, revised estimate of the swimmer velocity V̂ using, for example, a Kalman filter. Correction of clock drift of the mobile device <NUM> relative to the satellite <NUM> is performed in accordance with known techniques in determining the measured Doppler Dmeas.

The processor <NUM> may be configured to determine a velocity of the water relative to Earth V̂<NUM>,w|e i.e., a velocity of a current in the water as an approximation (as other factors could influence the estimate, e.g., a change in stroke (e.g., force, direction, frequency, etc.) by the swimmer <NUM>), or a fluctuating current. There are several methods to do this, such as:.

The processor <NUM> may be configured to determine a velocity V̂b|e or speed (i.e., without direction) of the swimmer <NUM> relative to the water. For example, the processor <NUM> may use the determined velocity of the swimmer <NUM> relative to Earth and the determined velocity of the current to determine the velocity of the swimmer <NUM> relative to the water. The processor <NUM> may subtract the velocity of the current (V̂w|e) from the determined body-to-Earth velocity V̂b|e to yield the velocity of the swimmer <NUM> relative to the water (V̂b|w) (e.g., may subtract the water vector <NUM> from the body-to-Earth vector <NUM> to yield the body-to-water vector <NUM>). Also or alternatively, the processor <NUM> may use input from the user as to the swimmer's arm length and swim style, or typical distance per stroke, to determine speed relative to the water. The processor <NUM> may use input from one or more of the sensors <NUM>, e.g., a pressure sensor, one or more accelerometers, and/or one or more gyroscopes, to determine a stroke frequency of the swimmer <NUM>. The processor <NUM> may multiply the stroke frequency by a distance per stroke (e.g., determined from the input arm length and swim stroke (with possibly one or more assumptions, e.g., an open/cupped hand used by the swimmer <NUM>), or a stroke distance input by the user, etc.) to determine speed of the swimmer <NUM> relative to the water. The processor <NUM> may compare the speed estimated by multiplying distance per stroke by stroke frequency with the speed estimated by subtracting the water current velocity from the arm-to-Earth velocity Va|e and may take action if the difference exceeds a threshold. Examples of actions that the processor <NUM> may take include ignoring one or both speed determinations (e.g., not reporting either speed to a user), and adjusting one or more parameters (e.g., the value α and/or the distance per stroke).

Referring to <FIG>, with further reference to <FIG>, a method <NUM> of determining a velocity of a swimmer using a mobile device includes the stages shown. The method <NUM> is, however, an example only and not limiting. The method <NUM> may be altered, e.g., by having stages added, rearranged, combined, performed concurrently, and/or having single stages split into multiple stages.

At stage <NUM>, the method <NUM> includes obtaining a first estimated swimmer velocity. For example, for an initial determination (such as, for example, a first estimation) of the velocity (e.g., after a reset) of the swimmer, the processor <NUM> may use a default estimated velocity of the swimmer (e.g., programmed into the processor, or stored in the memory <NUM>, etc.). The default may be any of a variety of velocities, e.g., any of a variety of speeds (e.g., zero, one, or some other non-zero value) and a default direction, e.g., north. As another example, such as for subsequent (after the initial) determination of the velocity of the swimmer, the processor <NUM> may use a previously-determined velocity of the swimmer, such as the most-recently determined velocity of the swimmer as determined by the method <NUM>. The processor <NUM> may obtain this velocity from, e.g., the memory <NUM> or from the processor <NUM> itself (e.g., being fed back from a determination output as an input). The processor <NUM> may determine a speed of the mobile device <NUM>, e.g., using SPS-based calculations, telecommunication signal calculations, sensor-measurement-based calculations, etc. Means for performing the functionality of stage <NUM> may, but not necessarily, include, for example, the SPS antenna <NUM>, the SPS unit <NUM>, the memory <NUM>, the sensor(s) <NUM>, and/or the processor <NUM> with reference to <FIG>.

At stage <NUM>, the method <NUM> includes determining a compensated velocity by adjusting the first estimated swimmer velocity to account for swimming arm-swing motion. This includes the processor <NUM> determining a scale factor as discussed above and multiplying the estimated velocity of the swimmer by the scale factor to determine the compensated velocity. The processor <NUM> may determine a value of the scale factor based on a speed of the mobile device <NUM> (which may be determined in any of a variety of manners as discussed above). The stage <NUM> may include the processor <NUM> determining whether the speed of the mobile device <NUM> is above a threshold. The processor <NUM> may determine the compensated velocity in response to the speed of the mobile device <NUM> being above the threshold. Means for performing the functionality of stage <NUM> may, but not necessarily, include, for example, the memory <NUM>, the sensor(s) <NUM>, and/or the processor <NUM> with reference to <FIG>.

At stage <NUM>, the method <NUM> includes determining an estimated Doppler value using the compensated velocity and a satellite velocity. For example, the processor <NUM> may determine the estimated Doppler value according to Equation (<NUM>) discussed above. The satellite velocity may be obtained by the processor <NUM> accessing satellite information stored in the memory <NUM>. Means for performing the functionality of stage <NUM> may, but not necessarily, include, for example, the memory <NUM>, and/or the processor <NUM> with reference to <FIG>.

At stage <NUM>, the method <NUM> includes determining a second estimated swimmer velocity based on the estimated Doppler value and a measured Doppler value,wherein the measured Doppler value is received from the SPS unit or is calculated from signal information from the SPS unit. For example, the processor <NUM> may determine a difference between the estimated Doppler value and the measured Doppler value and use this to determine a new, revised estimate of the swimmer velocity using known techniques. Means for performing the functionality of stage <NUM> may, but not necessarily, include, for example, the SPS antenna <NUM>, the SPS unit <NUM>, the memory <NUM>, the sensor(s) <NUM>, and/or the processor <NUM> with reference to <FIG>.

The method <NUM> may include one or more other features. For example, the method <NUM> may include determining, e.g., by the processor <NUM>, a velocity of a water current in which the user is disposed. The processor <NUM> (and/or other device(s)) may, for example, determine the velocity of the water current by comparing an expected travel distance and an expected travel direction with an actual (measured) travel distance and an actual (measured) travel direction. Still other features may be included in the method <NUM>.

Referring to <FIG>, with further reference to <FIG>, a method <NUM> of determining a velocity of a user of a mobile device includes the stages shown. The method <NUM> is, however, an example only and not limiting. The method <NUM> may be altered, e.g., by having stages added, rearranged, combined, performed concurrently, and/or having single stages split into multiple stages.

At stage <NUM>, the method <NUM> includes obtaining a first estimated body velocity. For example, the stage <NUM> may be similar to the stage <NUM> discussed above. Means for performing the functionality of stage <NUM> may, but not necessarily, include, for example, the SPS antenna <NUM>, the SPS unit <NUM>, the memory <NUM>, the sensor(s) <NUM>, and/or the processor <NUM> with reference to <FIG>.

At stage <NUM>, the method <NUM> includes determining a compensated velocity by adjusting the first estimated body velocity to account for a device-to-body motion of a mobile device relative to a body. Device-to-body motion may, for example, be motion of the SPS antenna <NUM> and/or the telecom antenna <NUM> and/or the sensor(s) <NUM> relative to the body (e.g., a torso) of the swimmer <NUM>, with the device-to-body motion being, e.g., due to the swimmer <NUM> wearing the mobile device <NUM> (e.g., a wristwatch) while swimming. Due to swimming, the mobile device <NUM>, and thus the antenna(s) <NUM>, <NUM> and the sensor(s) <NUM> move relative to the body of the swimmer <NUM>, with the antenna-to-body motion possibly including repetitive and non-repetitive motion. The stage <NUM> includes the processor <NUM> determining a scale factor as discussed above and multiplying the first estimated body velocity by the scale factor to determine the compensated velocity. The processor <NUM> may determine a value of the scale factor based on a speed of the mobile device <NUM> (which may be determined in any of a variety of manners as discussed above). The stage <NUM> may include the processor <NUM> determining whether the speed of the mobile device <NUM> is above a threshold. The processor <NUM> may determine the compensated velocity in response to the speed of the mobile device <NUM> being above the threshold. Means for performing the functionality of stage <NUM> may, but not necessarily, include, for example, the memory <NUM>, the sensor(s) <NUM>, and/or the processor <NUM> with reference to <FIG>.

At stage <NUM>, the method <NUM> includes determining a second estimated body velocity based on the estimated Doppler value and a measured Doppler value, wherein the measured Doppler value is received from the SPS unit or is calculated from signal information from the SPS unit. For example, the processor <NUM> may determine a difference between the estimated Doppler value and the measured Doppler value and use this to determine a new, revised estimate of the user velocity using known techniques. Means for performing the functionality of stage <NUM> may, but not necessarily, include, for example, the SPS antenna <NUM>, the SPS unit <NUM>, the memory <NUM>, the sensor(s) <NUM>, and/or the processor <NUM> with reference to <FIG>.

The method <NUM> may include one or more other features. For example, the method <NUM> may include determining, e.g., by the processor <NUM>, an estimated velocity of a water current (i.e., an estimated water current velocity) in which the body is disposed. The processor <NUM> (and/or other device(s)) may, for example, determine the velocity of the water current by comparing an expected travel distance and an expected travel direction with an actual (measured) travel distance and an actual (measured) travel direction. Still other features may be included in the method <NUM>.

Other examples and implementations are within the scope of the appended claims. For example, due to the nature of software and computers, functions described above can be implemented using software executed by a processor, hardware, firmware, hardwiring, or a combination of any of these.

Also, as used herein, "or" as used in a list of items prefaced by "at least one of" or prefaced by "one or more of" indicates a disjunctive list such that, for example, a list of "at least one of A, B, or C," or a list of "one or more of A, B, or C," or "A, B, or C, or a combination thereof" means A or B or C or AB or AC or BC or ABC (i.e., A and B and C), or combinations with more than one feature (e.g., AA, AAB, ABBC, etc.).

As used herein, unless otherwise stated, a statement that a function or operation is "based on" an item or condition means that the function or operation is based on the stated item or condition and may be based on one or more items and/or conditions in addition to the stated item or condition.

Further, an indication that information is sent or transmitted, or a statement of sending or transmitting information, "to" an entity does not require completion of the communication. Such indications or statements include situations where the information is conveyed from a sending entity but does not reach an intended recipient of the information. The intended recipient, even if not actually receiving the information, may still be referred to as a receiving entity, e.g., a receiving execution environment. Further, an entity that is configured to send or transmit information "to" an intended recipient is not required to be configured to complete the delivery of the information to the intended recipient. For example, the entity may provide the information, with an indication of the intended recipient, to another entity that is capable of forwarding the information along with an indication of the intended recipient.

A wireless communication system is one in which communications are conveyed wirelessly, i.e., by electromagnetic and/or acoustic waves propagating through atmospheric space rather than through a wire or other physical connection. A wireless communication network may not have all communications transmitted wirelessly, but is configured to have at least some communications transmitted wirelessly. Further, the term "mobile wireless communication device," or similar term, does not require that the functionality of the device is exclusively, or evenly primarily, for communication, or that the device be a mobile device, but indicates that the device includes wireless communication capability (one-way or two-way), e.g., includes at least one radio (each radio being part of a transmitter, receiver, or transceiver) for wireless communication.

Substantial variations may be made in accordance with specific implementations.

The terms "machine-readable medium" and "computer-readable medium," as used herein, refer to any medium that participates in providing data that causes a machine to operate in a specific fashion. Using a computer system, various computer-readable media might be involved in providing instructions/code to processor(s) for execution and/or might be used to store and/or carry such instructions/code (e.g., as signals). In many implementations, a computer-readable medium is a physical and/or tangible storage medium. Such a medium may take many forms, including but not limited to, non-volatile media and volatile media. Non-volatile media include, for example, optical and/or magnetic disks. Volatile media include, without limitation, dynamic memory.

Common forms of physical and/or tangible computer-readable media include, for example, a floppy disk, a flexible disk, hard disk, magnetic tape, or any other magnetic medium, a CD-ROM, any other optical medium, any other physical medium with patterns of holes, a RAM, a PROM, EPROM, a FLASH-EPROM, any other memory chip or cartridge, a carrier wave as described hereinafter, or any other medium from which a computer can read instructions and/or code.

Various forms of computer-readable media may be involved in carrying one or more sequences of one or more instructions to one or more processors for execution. Merely by way of example, the instructions may initially be carried on a magnetic disk and/or optical disc of a remote computer. A remote computer might load the instructions into its dynamic memory and send the instructions as signals over a transmission medium to be received and/or executed by a computer system.

For instance, in alternative configurations, the methods may be performed in an order different from that described, and that various steps may be added, omitted, or combined.

Specific details are given in the description to provide a thorough understanding of example configurations (including implementations). However, configurations may be practiced without these specific details. For example, well-known circuits, processes, algorithms, structures, and techniques have been shown without unnecessary detail in order to avoid obscuring the configurations. This description provides example configurations only, and does not limit the scope, applicability, or configurations of the claims. Rather, the preceding description of the configurations provides a description for implementing described techniques.

Various changes may be made in the function and arrangement of elements.

Also, configurations may be described as a process which is depicted as a flow diagram or block diagram. Although each may describe the operations as a sequential process, some operations may be performed in parallel or concurrently. In addition, the order of the operations may be rearranged. A process may have additional stages or functions not included in the figure. Furthermore, examples of the methods may be implemented by hardware, software, firmware, middleware, microcode, hardware description languages, or any combination thereof. When implemented in software, firmware, middleware, or microcode, the program code or code segments to perform the tasks may be stored in a non-transitory computer-readable medium such as a storage medium. Processors may perform one or more of the described tasks.

Components, functional or otherwise, shown in the figures and/or discussed herein as being connected or communicating with each other are communicatively coupled. That is, they may be directly or indirectly connected to enable communication between them.

Having described several example configurations, various modifications, alternative constructions, and equivalents may be used.

For example, the above elements may be components of a larger system, wherein other rules may take precedence over or otherwise modify the application of the invention. Also, a number of operations may be undertaken before, during, or after the above elements are considered. Accordingly, the above description does not bound the scope of the claims.

A statement that a value exceeds (or is more than or above) a first threshold value is equivalent to a statement that the value meets or exceeds a second threshold value that is slightly greater than the first threshold value, e.g., the second threshold value being one value higher than the first threshold value in the resolution of a computing system. A statement that a value is less than (or is within or below) a first threshold value is equivalent to a statement that the value is less than or equal to a second threshold value that is slightly lower than the first threshold value, e.g., the second threshold value being one value lower than the first threshold value in the resolution of a computing system.

Various terms as used herein in the plural include the singular, and as used herein in the singular include the plural. The terms "sensors" and "actions" were specifically mentioned above, but this list is not exhaustive and other terms may be used in the singular or plural but include the plural and the singular, respectively.

Claim 1:
A mobile device (<NUM>) on an arm of a swimmer comprising:
a satellite positioning system (SPS) unit (<NUM>) coupled with a SPS antenna (<NUM>);
a memory (<NUM>); and
a processor (<NUM>) communicatively coupled to the memory and configured to:
obtain a first estimated body velocity, wherein the first estimated body velocity is a velocity of the body of the swimmer;
determine a compensated velocity by adjusting the first estimated body velocity to account for a device-to-body motion of the mobile device relative to the body of the swimmer;
determine an estimated Doppler value using the compensated velocity and a satellite velocity; and
determine a second estimated body velocity based on the estimated Doppler value and a measured Doppler value, wherein the measured Doppler value is received from the SPS unit or is calculated from signal information from the SPS unit,
wherein to determine the compensated velocity, the processor is configured to multiply the first estimated body velocity by a scale factor.