Method and apparatus for improving radio signal reception

Abstract

A method and apparatus for improving radio signal reception includes measuring motion of a radio signal receiver (405), selecting at least one radio signal from received radio signals (406), determining a frequency rate hypothesis for the selected radio signal (408), and for each rate of the hypothesis, generating a complex correlation result (410), motion compensating the complex correlation result, the local signal or the selected at least one radio signal using the measured motion of the receiver to produce a motion compensated complex correlation result (412), and phase compensating the motion compensated complex correlation result to produce a phase compensated, correlation result (414). The method and apparatus further include generating a frequency power profile from the phase compensated correlation results for each rate (415), determining a correlation peak in the frequency power profile (418), determining a correction for a clock of the receiver using the correlation peak, and correcting the clock of the receiver using the determined correction (424).

Description

METHOD AND APPARATUS FOR IMPROVING RADIO SIGNAL RECEPTIONBACKGROUNDField

[0001] Embodiments of the present principles generally relate to radio signal receivers and, in particular, to a method and apparatus for improving radio signal reception.Description of the Related Art

[0002] Positioning signal receivers such as receivers for global navigation satellite systems (GNSS) signals have become ubiquitous in mobile devices. A GNSS receiver (e.g., receivers for GPS, GLONASS, GALILEO, BEIDOU, etc. satellite signals or a combination thereof) receive signals from satellites, process the received signals and determine the position of the receiver from information contained in the received signals. The typical accuracy of a consumer receiver without the assistance of an inertial measurement unit (IMU) can range from 5 to 50m. To provide inertial navigation in a typical mobile device, an IMU typically comprises a magnetometer, a gyroscope and an accelerometer, i.e. , traditional IMU sensors. The signals from these three sensors (typically, MEMS-based sensors) are used to augment the GNSS receiver’s positioning computation such that the receiver accuracy may be improved to about 20cm. However, that additional accuracy comes with a substantial cost of the IMU sensors and additional computational complexity.

[0003] In other forms of radio receivers, it can also be advantageous to signal reception to know the receiver’s motion such that the received signals may be motion compensated (i.e., have the frequency and / or phase error caused by receiver motion removed from the signal correlation process). Compensating for the receiver motion improves receiver signal reception and / or lowers the cost of receiver components.

[0004] Receivers capable of motion compensation can use a signal processing technique known as SUPERCORRELATION™ for improving radio signal reception using receiver motion compensated signal processing. The SUPERCORRELATION™ technique is described in commonly assigned US patent9,780,829, issued 3 October 2017; US patent 10,321 ,430, issued 11 June 2019; US patent 10,816,672, issued 27 October 2020; US patent publication 2020 / 0264317, published 20 August 2020; US patent publication 2020 / 0319347, published 8 October 2020; and US patent publication 2024 / 0045077, published 8 February 2024, which are hereby incorporated herein by reference in their entireties.

[0005] The SUPERCORRELATION™ technique is used for determining a clock offset (error) of a receiver by using motion compensated signal processing of a plurality of received signals (e.g., GNSS signals) and finding a common receiver clock error for all the received signals. When using the SUPERCORRELATION™ technique to process GNSS signals, a substantial amount of computing resources are required.

[0006] Therefore, there is a need in the art for a more efficient way of determining the clock offset using motion compensated signal processing.SUMMARY

[0007] Embodiments of the present principles generally relate to a method and apparatus for improving radio signal reception as shown in and / or described in connection with this disclosure and the associated figures.

[0008] Various features and advantages of the present principles can be appreciated from a review of the following detailed description of the present principles, along with the accompanying figures in which like reference numerals refer to like parts throughout.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] So that the manner in which the above recited features of the present principles can be understood in detail, a more particular description of the present principles, briefly summarized above, can be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of the present principles and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

[0010] FIG. 1 depicts a communication environment in which a receiver with improved signal reception in accordance with at least one embodiment of the present principles can be applied;

[0011] FIG. 2 depicts a functional block diagram of a radio signal receiver in accordance with at least one embodiment of the present principles;

[0012] FIG. 3 depicts a high-level block diagram of a computing device programmed to function as a signal processing module of the receiver of the present principles in accordance with at least one embodiment;

[0013] FIG. 4 depicts a flow diagram of a method for reducing computational resources in a radio signal receiver that uses motion compensated signal processing in accordance with at least one embodiment of the present principles;

[0014] FIG. 5 depicts a graphical diagram of a frequency-frequency rate search space showing stripes of transmitter signal processing in accordance with at least one embodiment of the present principles; and

[0015] FIG. 6 depicts a graphical diagram of a frequency-frequency rate search space showing transmitter correlation power produced through signal processing in accordance with at least one embodiment of the present principles.

[0016] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. The figures are not drawn to scale and may be simplified for clarity. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.DETAILED DESCRIPTION

[0017] While the concepts of the present principles are susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and are described in detail below. It should be understood that there is no intent to limit the concepts of the present principles to the particularforms disclosed. On the contrary, the intent is to cover all modifications, equivalents, and alternatives consistent with the present principles and the appended claims. For example, although embodiments of the present principles will be described primarily with respect to a two-step process, embodiments of the present principles can be implemented as a single or multi-step process including at least some or all of the process steps described herein with respect to different embodiments of the present principles.

[0018] Embodiments of the present principles relate to apparatuses and methods for reducing computational resources in a radio signal receiver that uses motion compensated signal processing. Such receivers include positioning systems (e.g., GNSS receivers) and / or communications receivers (e.g., WiFi, cellular, Bluetooth communications receivers).

[0019] Embodiments of the present principles implement a two-step process to reduce computation resource use. A first step selects preferred signals (i.e., high quality) for processing that are the “best” transmitters (e.g., satellites that are at high elevation that likely have line-of-sight signal paths to the receiver producing a high signal-to-noise ratio (SNR)) and processes those signals using an interlaced SUPERCORRELATION™ technique. The result is an estimate of the receiver’s clock error. This clock error is used to coarsely correct the clock frequency and to repeat processing of the previously received signals or newly received signals using a standard (non-interlaced) SUPERCORRELATION™ technique to produce an accurate joint estimation of the receiver clock error. Once the clock is coarsely corrected, the standard non-interlaced SUPERCORRELATION™ technique is able to utilize a much smaller clock-parameter search space to calculate an accurate clock correction and exploit this clock correction in a navigation solution using both the preferred and lower quality signals (e.g., attenuated signals and / or signals impacted by multipath interference).

[0020] In some embodiments, for completing the first step, the radio signal receiver uses the SUPERCORRELATION™ technique to correlate select received signalsusing select frequency rate values. Rather than test all frequency and frequency rate values in a search space for each received signal, a receiver of the present principles uses a subset of all the values. Specifically, the receiver selects a frequency rate hypothesis for a received signal from a first transmitter, receives the signal, correlates the signal with a local signal, motion compensates the correlation result, the local signal or the received signal using the measured motion of the antenna to produce a motion compensated correlation result; and produces a frequency power profile for the correlation result. One method of creating the profile is to use a Fast Fourier Transform (FFT) on the motion compensated correlation result.

[0021] Alternatively or in addition, in some embodiments, each frequency power profile is calculated explicitly based on a sequence of frequency offset hypotheses. This process is repeated for each available preferred received signal from the various transmitters selecting a different frequency rate hypothesis for each transmitter such that the search space is comprised of stripes of frequency power profiles for each frequency rate and transmitter combination. Analyzing this combined, striped frequency / frequency rate search space to determine a maximum power value provides a coarse estimate of the receiver clock frequency and frequency rate offsets and identifies a much smaller search space in which it is feasible for all frequency and frequency rate hypotheses to be assessed for each received signal in a second stage of processing. The smaller frequency / frequency rate search space may be exploited in a second stage of processing to determine more accurate receiver clock offsets.

[0022] More specifically, satellite-based positioning systems and communications receivers utilize encoded digital signals including a deterministic digital code to facilitate signal acquisition, e.g., Gold codes. Such a digital code is used by a receiver of the present principles and repeatedly broadcast by the transmitter to enable receivers to acquire and process transmitted signals. Using such deterministic codes combined with an accurate motion model of the receiver, embodiments of the present principles are useful to enable a receiver to improve its position computation accuracy and / or signal reception without using traditional IMU data from a full complement of IMU sensors. The technique for improving radio signal reception using receiver motioncompensated signal processing is known as SUPERCORRELATION™ and is described in commonly assigned US patent 9,780,829, issued 3 October 2017; US patent 10,321 ,430, issued 11 June 2019; US patent 10,816,672, issued 27 October 2020; US patent publication 2020 / 0264317, published 20 August 2020; US patent publication 2020 / 0319347, published 8 October 2020; and US patent publication 2024 / 0045077, published 8 February 2024, which are hereby incorporated herein by reference in their entireties. In such techniques, a motion model can be derived using IMU data. In contrast, in some embodiments of the present principles, a motion model can be derived using at least gyroscope data, controller area network (CAN) bus data, visual odometry data, or a combination of data from any of these motion data sources. In one embodiment, the receiver has no motion information except for a position from a GNSS receiver. In addition, motion information determined by the SUPERCORRELATION™ technique can be provided as feedback to a motion module to correct and / or update a motion model.

[0023] In some embodiments, a radio receiver of the present principles can be embedded in a moving platform such as, for example, but not limited to, an automobile, motorcycle, airplane, helicopter, drone, bicycle, person (e.g., a person carrying a smartphone, tablet, computer, internet of things (loT) device, etc.), and the like.

[0024] In some embodiments, at least one received signal is correlated with at least one locally generated signal to produce at least one correlation result. As is described in greater detail below, embodiments of the present principles implement a two-step process to reduce the computational resources needed to perform motion compensated signal processing.

[0025] FIG. 1 depicts a communication environment 100 in which a receiver with improved signal reception in accordance with at least one embodiment of the present principles can be applied. That is, the communication environment of FIG. 1 depicts a scenario for use of the motion compensation signal processing having reduced computational resource requirements in accordance with at least one embodiment ofthe present principles. In the communication environment 100, a person 102 carrying a receiver 104 is walking (arrow 114) along a street 116 near a building 108. The receiver 104 does not have a clear view of the sky and the satellite signals 110 broadcast from a plurality of satellites 112-1 , 112-2, . . . 112-N may be reflected and or attenuated by the building 108. Consequently, the receiver 104 may not be able to accurately know its location when the person 102 is operating in such an “urban canyon.” In such an environment, an embodiment of the reduced computation motion compensated signal processing of the present principles can be used, as described below, to quickly correct for clock error, compensate for receiver motion and determine the location of the receiver.

[0026] In at least some embodiments, the receiver 104 of FIG. 1 can include a component (e.g., a GNSS receiver) within user equipment such as mobile phones, tablets, laptop computers, loT devices, and the like. For simplicity, the device is described herein as a receiver. Those skilled in the art will understand that the receiver can be a standalone receiver or can be a portion or component within user equipment.

[0027] FIG. 2 depicts a functional block diagram of the radio signal receiver 104 of FIG. 1 in accordance with at least one embodiment of the present principles. In the embodiment of FIG. 2, the receiver 104 comprises an antenna 210, a front end 212, a GNSS signal processor 214, motion compensation processor 216, a motion module 218 and a search space generator 224. When carried by a person 102 (or other transport platform such as a vehicle), the receiver 104 and its antenna 210 are an indivisible unit where the antenna 210 moves with the person 102. The SUPERCORRELATION™ technique operates based upon determining a component of motion of the signal receiving antenna that is in the direction of the source (transmitter) of a received signal. Any mention of motion herein refers to the motion of the antenna 210. In most scenarios, the motion of the person 102 is the same as the motion of the antenna 210 and, as such, the following description assumes the motion of the person 102 and the antenna 210 are the same.

[0028] In the embodiment of FIG. 2, the receiver’s front end 212 downconverts, filters, and samples (digitizes) the received signals in a manner that is well-known to those skilled in the art. The output of the receiver front end 212 is a digital signal containing data. The data of interest for performing motion compensation is a deterministic code, e.g., Gold code, used by the GNSS signal processor 214 to synchronize the receiver 104 to the GNSS transmission. For other radio systems, the code may be a deterministic synchronization or initialization code.

[0029] In the embodiment of FIG. 2, the GNSS signal processor 214, in the first step, selects preferred signals of sufficiently high quality (i.e., signals from satellites with high elevation and / or high SNR), extracts the deterministic code, then correlates the received code from each satellite with locally generated codes to produce correlation results. The correlation results are processed as is well-known in the art to generate position information 226, e.g., the correlation results are used to determine pseudoranges for each satellite and the pseudoranges are processed to compute the receiver position. The motion compensation processor 216 of the receiver 104 of FIG. 2 performs the SUPERCORRELATION™ processing to provide signals (phasor sequences) to phase adjust the correlation results such that the coherent integration period used to correlate the signals is extended, e.g., extended to one or more seconds. In some embodiments, the phasor sequence includes a time sequence of phase offsets where each phasor in the sequence adjusts the phase of a signal sample to compensate for the phase evolution (i.e., phase change) caused by receiver motion and / or receiver clock drift. The adjustment can be performed by adjusting the phase of each sample of the received signals, the locally generated signals or the correlation results themselves. In some embodiments, the least computationally intensive adjustment process adjusts the phase of the correlation results.

[0030] In the embodiment of FIG. 2, the motion module 218 generates receiver motion information that is used by the motion compensation processor 216 to generate phasor sequences that are used by the GNSS processor 214 to motion compensate the correlation results as well as adjust for clock error. The phasorsequences comprise a sequence of phase offsets to be made over time, e.g., across a received signal, to compensate for phase changes that occur over time due to movement of the receiver and / or clock drift. In one embodiment, the motion module 218 uses the GNSS signal processor 214 and / or an IMU 222 to generate motion information for the motion compensation processor 216. In some embodiments, motion information can include a prediction of receiver velocity and heading. Alternatively or in addition, in some embodiments, the motion module 218 can include an optional IMU 222 to provide vehicle orientation information for the motion model. In the embodiment of FIG. 2, the motion compensation processor 216 provides motion estimation correction information, along path 220, to the motion module 218. In this manner, the motion compensation processor 216 can provide corrective feedback to the motion module 218.

[0031] In the embodiment of FIG. 2, the search space generator 224 is coupled to the GNSS processor 214 and the motion compensation processor 216. As is described in greater detail below, the search space generator 224 produces a frequency-frequency rate search space to be used by the motion compensation processor 216 to produce corrective phasor hypotheses. Details of the two-step process to rapidly and efficiently perform motion compensation, derive an accurate clock and compute an accurate receiver position in accordance with the present principles are described in greater detail with respect to FIG. 4 below.

[0032] FIG. 3 depicts a block diagram of a computing device capable of performing the functions of the receiver 104 of FIGs. 1 and 2 in accordance with at least one embodiment of the present principles. In some embodiments, some of the functions of the present principles can be performed remotely on a server. In such embodiments, the receiver 104 communicates wirelessly with the server and receiver motion and / or clock hypotheses can be remotely computed. In some embodiments, the functions of a receiver of the present principles are all performed within the receiver 104.

[0033] In the embodiment of FIG. 3, the receiver 104 comprises at least one processor 300, support circuits 302 and memory 304. The at least one processor 300 can be any form of processor or combination of processors including, but not limited to, central processing units, microprocessors, microcontrollers, field programmable gate arrays, graphics processing units, digital signal processors, and the like. The support circuits 302 of FIG. 3 can include well-known circuits and devices facilitating functionality of the processor(s). The support circuits 302 can further include one or more of, or a combination of, power supplies, clock circuits, analog to digital converters, communications circuits, cache, displays, and / or the like. In some embodiments, the support circuits 302 can form an interface between the processor 300 and at least one of the motion compensation processor 216, the search space generator 224 and GNSS signal processor 214. Alternatively or in addition, the functions of the motion compensation processor 216, search space generator 224 and the GNSS signal processor 214 can be performed by processor 300.

[0034] In the embodiment of FIG. 3, the memory 304 can include one or more forms of non-transitory computer readable media including one or more of, or any combination of, read-only memory or random-access memory. The memory 304 stores software and data including, for example, signal processing software 306 and data 308. The data 308 can include at least a receiver position estimate 310, motion and / or clock hypotheses 312, and various additional data used to perform motion compensated signal processing in accordance with the present principles. In some embodiments, the data 308 can include one or more of GNSS signals 316 (or representations of the GNSS signals), GNSS satellite positions 318, building maps 320, and the like. In some embodiments, the signal processing software 316, when executed by the one or more processors 300, can perform a coarse clock correction (first step) and a fine clock correction (second step) of the present principles that leads to improved signal processing. The operation of the signal processing software 306 functions as described with reference to FIG. 4 below.

[0035] FIG. 4 depicts a flow diagram of a method 400 for reducing computational resources in a radio signal receiver that uses motion compensated signal processingin accordance with at least one embodiment of the present principles. The method 400 can be implemented in software, hardware or a combination of both (e.g., using the functions of the GNSS processor 214, the motion compensation processor 216 and the search space generator 224 of FIG. 2).

[0036] The method 400 begins at 402 and proceeds to 404 during which signals are received at a receiver of the present principles from at least one remote source (e.g., transmitters such as the GNSS satellites 112 of FIG. 1 ) in a manner as described with respect to FIG. 1. Each received signal comprises a synchronization or acquisition code, e.g., a Gold code, extracted from the radio frequency (RF) signal received at the antenna. The process of downconverting the RF signal and sampling the digital code is well known in the art and, as such, will not be described herein. The received signals are buffered such that the signals can be repeatedly processed as described below. For example, in some embodiments, in a Global Positioning System (GPS) receiver, the synchronization code is transmitted at 50 Hz; thus, to achieve a one second integration period, enough signal is buffered to generate a vector containing 50 x 20ms complex correlation results. The method 400 can proceed to 405.

[0037] At 405, the motion of the receiver antenna is measured by the IMU (222 FIG. 2) of a receiver of the present principles. The motion module 218 of FIG. 2 produces a motion model of antenna motion in the direction of each signal source (e.g., satellite) from which the receiver is currently receiving signals. This motion information can be subsequently used for motion compensation as described below. The method 400 can proceed to 406.

[0038] At 406, a preferred signal (i.e., high quality) is selected from among the received signals. In some embodiments, the selection can be based on the elevation of the satellite (satellite position) and / or the signal strength of the received signal to attempt to select a source that provides a line-of-sight (LOS) signal. Alternatively or in addition, building maps (three-dimensional city models) can be used to determine the satellites (e.g., signal sources) that are line-of-sight (LOS) to the receiver and thesatellites that may have their signals attenuated (blocked) or reflected. The method 400 can proceed to 408

[0039] At 408, a frequency rate hypothesis is determined for the signal (i.e., an estimate of the change of the receiver’s clock frequency over a given period of time). In some embodiments, the frequency rate hypothesis can be based on historical information regarding at least historical errors in the frequency of a receiver clock based on a given clock and / or receiver, and / or based on signals being received, and / or based on sources of received signals. In some embodiments, the frequency rate hypothesis can be a random estimate large enough to include any possible error / drift parameters of a given receiver clock. The method 400 can proceed to 410.

[0040] At 410, using the frequency rate hypothesis, a complex correlation result is generated by correlating the local code with the received code. In one specific embodiment, the complex correlation result can be a vector containing a number, N, of complex correlation results, for example, N = 50. The method 400 can proceed to 412.

[0041] At 412, a motion compensated correlation process (e.g., the SUPERCORRELATION™ technique) is performed by applying a phasor adjustment to the local signal, the received signal or the correlation result to motion compensate the complex correlation result vector. The method 400 can proceed to 414.

[0042] At 414, a further phasor adjustment can be made with respect to the frequency rate hypothesis, i.e., to compensate for the rate of change of the receiver clock. In some embodiments, the phasor adjustment can be performed for both motion and frequency rate in a single adjustment. In the embodiment of FIG. 4, the adjustment is described as being performed in two steps, for clarity, as described in the following method steps. The method 400 can proceed to 415.

[0043] At 415, a frequency power profile is produced using the compensated complex correlation results. In one embodiment, a Fast Fourier Transform (FFT) can be performed on the compensated complex correlation results. The FFT produces afrequency power profile (i.e., the summed power in each of the frequencies in the correlation result vector). In some embodiments, the FFT results in the summation (i.e., integration) of the correlation results (e.g., N = 50 correlation results) into a 1 second correlation result for each frequency hypothesis. A long (e.g., 1 second) coherent integration for the preferred signals (i.e., unreflected, line of sight (LOS) signals) is achieved when the correct receiver clock frequency and frequency rate hypotheses are selected - hence a peak in the frequency power profile at this coordinate in the search space for all LOS signals.

[0044] In some embodiments, rather than use an FFT to produce the frequency power profile, each frequency power profile can be computed in a discrete manner using a sequence of frequency offset hypotheses at the given frequency rate. In a further alternative embodiment, stripes can be generated for a given frequency versus a sequence of frequency rate hypotheses or an FFT. The method 400 can proceed to 416.

[0045] At 416, it is determined if additional signals are to be processed. If the query is affirmatively answered, the method 400 returns to 406 to select the next preferred signal for processing. With each new signal being processed, the frequency rate is incremented by, for example, 1 Hz / s. In general, the increment is based on the duration of the coherent integration period - the longer the integration period, the smaller the increment. In some embodiments, within the search space, a signal can be reused. For example, if there are 5 satellite signals and the search space is 20 increments of frequency rate wide, a satellite signal can be processed using 4 different frequency rates. If the query at 416 is negatively answered, the method 400 can proceed to 418 (described below with reference to FIG. 6).

[0046] In some embodiments, each frequency profile forms a stripe in a frequencyfrequency rate space. FIG. 5 depicts a frequency-frequency rate space 500 in which 3 satellite signals are correlated using a plurality of frequency rate hypotheses (FR axis 502). For each frequency rate hypothesis and correlation result, the FFT forms phase compensated correlation results having a frequency profile 504 (e.g., a stripe)along frequency axis 506. The magnitude of the FFT extends upward out of the page (not shown in FIG. 5). The size of the search space is defined by the search space generator (224 in FIG. 2) of a receiver of the present principles, such as the receiver 104 of FIG. 2, as a number of frequency rates to use and the number of FFT frequency bins. In one embodiment, the frequency bins of the FFT can be set to a wide value and as the clock frequency becomes more accurately known, the width of the bins can be reduced, and the number of frequency rate hypotheses can be reduced.

[0047] FIG. 6 depicts a three-dimensional view of a search space 600 generated in accordance with at least one embodiment of the present principles. That is, the stripes 504 of FIG. 5 produce a correlation peak 602 in the frequency domain at a particular frequency. In the method 400 of FIG. 4, at 418, the location of the peak (602 in FIG. 6) is determined at a specific frequency and frequency rate. A peak in FIG. 6 represents common power across multiple satellite signals. The method 400 can proceed to 420.

[0048] At 420, it is determined whether the search space should be adjusted. If the space is to be adjusted, the method 400 proceeds to 422 where the search space is adjusted (i.e. , use narrower FFT frequency bins and a smaller number of frequency rate hypotheses, and / or recenter the search space in frequency and frequency rate at the peak location). The method 400 can then return to 406 to repeat the signal processing using the adjusted search space. In some embodiments, this process can repeat until the correlation peak attains a particular threshold value or has a specific relative magnitude larger than the background frequency content. If the query at 420 is negatively answered, the method 400 can proceed to 424.

[0049] At 424, the clock of a receiver of the present principles is corrected using the frequency offset indicated by the frequency and frequency-rate located at the peak correlation within the search space. This is a coarse clock correction based upon the striped search space and concludes the first step of the present principles in correcting the receiver clock. Such a coarse correction can be rapidly computed using very little computing resources. Through use of the striping technique of the present principles,the processing uses less computer resources than using full joint estimation, phase compensated processing. In embodiments of the present principles, computational load is reduced by a factor of M, where M is the number of signals that are interlaced.

[0050] A second step of a clock correction process of the present principles can begin at 426 during which a full, non-interlaced, phase compensated correlation process is performed using the coarse clock correction of the first step as the initial clock correction.

[0051] That is, at 426, in some embodiments, non-interlaced SUPERCORRELATION™ can be performed using the motion hypotheses, the coarse clock correction and the received signals. During this process, the SUPERCORRELATION™ procedure generates a plurality of phasor sequence hypotheses related to the motion information and clock correction information. Each phasor sequence hypothesis comprises a phase estimate that varies with motion parameters of the receiver. The signal processing correlates a local code encoded in a local signal with a code encoded in the received RF signal. The phasor sequence hypotheses are used to adjust, at a sub-wavelength accuracy, the carrier phase of the local code. Such adjustment or compensation can be performed by adjusting a local oscillator signal, the received signal(s), or the correlation result. The signals and / or correlation results comprise complex signal samples having in-phase (I) and quadrature-phase (Q) components. Each phase offset in the phasor sequence can be applied to a corresponding complex sample in the signals and / or correlation results. For each received signal, the process correlates the received signals with a set (plurality) of phasor sequence hypotheses containing estimates of a phase offset necessary to accurately correlate the received signals.

[0052] The motion estimates are typically hypotheses of the motion in a direction of interest such as in the direction of the satellite that transmitted the received signal, for example, along the signal propagation path. At initialization, the direction of interest can be unknown or inaccurately estimated. Consequently, the rapid initialization module is used to identify a limited number of directions of interest. A comparison ofcorrelation results over the direction hypotheses enables the search space to be narrowed when processing subsequently received signals. Consequently, subsequent compensation is performed over a narrow frequency-frequency rate search space.

[0053] In some embodiments, if a signal from a given satellite was received previously, the set of hypotheses for the newly received signal can include a group of phasor sequence hypotheses using the expected Doppler and Doppler rate and / or last Doppler and last Doppler rate used in receiving the prior signal from that particular satellite. The hypotheses values can be centered around the last values used or the last values used additionally offset by a prediction of further offset based on an expected receiver motion. Each received signal can be correlated with that signal’s set of hypotheses. The hypotheses are used as parameters to form the phase- compensated phasors to phase compensate the correlation process. As such, the phase compensation can be applied to the received signals, the local frequency source (e.g., an oscillator), or the correlation result values. The result of the correlation process is a plurality of phase-compensated correlation results - one phase- compensated correlation result value for each hypothesis for each received signal.

[0054] In some embodiments, the correlation results are processed to find the “best” or optimal result for each received signal. In one embodiment, a joint correlation output (referred to as a joint estimation) is produced as a function (e.g., summation) of the plurality of correlation results resulting from all the hypotheses and received transmitter signals. The joint correlation output can be a single value or a plurality of values that represent the parameter hypotheses (preferred hypotheses) that provide an optimal or best correlation output. In some embodiments, a cost function is applied to each set of correlation values for each received signal to find the optimal correlation output corresponding to a preferred hypothesis or hypotheses. The joint correlation result of the present principles provides an accurate clock correction.

[0055] For example, assuming all other receiver parameters are known except receiver motion direction, hypotheses with various phasor sequences thatcompensate for phase changes due to each direction hypothesis are tested. The correct phasor sequence hypothesis that represents the accurate direction estimate will produce the highest correlation result magnitude for a given received signal. By processing the received signals from different satellites, the correlation results will converge upon hypotheses representing the true receiver motion direction. The method 400 can proceed to 428.

[0056] At 428, the compensated correlation results are used in additional signal processing of the received radio signals, such as, but not limited to, a traditional positioning solution (e.g., using range to each satellite transmitter) to generate the position of the receiver, compute a velocity of the receiver, and the like. The method 400 can end at 430.

[0057] In some embodiments, a method for improving radio signal reception in a radio signal receiver includes measuring motion of an antenna of the radio signal receiver, receiving radio signals from a plurality of transmitters, selecting at least one radio signal from the received radio signals, determining a frequency rate hypothesis for the selected at least one radio signal, for each rate of the frequency rate hypothesis of each of the selected at least one radio signal, generating a complex correlation result including correlating each selected at least one radio signal with a local signal, motion compensating the complex correlation result, the local signal or the selected at least one radio signal using the measured motion of the antenna to produce a motion compensated complex correlation result, and phase compensating the motion compensated complex correlation result to produce a phase compensated correlation result. The method further includes generating a frequency power profile from the phase compensated correlation results for each rate of the frequency rate hypothesis for the selected at least one radio signal, determining a correlation peak in the frequency power profile, determining a correction for a clock of the radio signal receiver using the correlation peak, and correcting the clock of the radio signal receiver using the determined correction.

[0058] In some embodiments, the at least one radio signal is selected based on at least one of a quality of a selected radio signal compared to the other received radio signals or by using a building map of an environment in which the radio signals are received.

[0059] In some embodiments, the quality is based on at least one of a signal strength of received radio signals, an elevation of a source of the at least one selected radio signal or a determination that the signal is a line-of-sight signal.

[0060] In some embodiments, the complex correlation result comprises a vector containing a number of complex correlation results corresponding to a required integration time.

[0061] In some embodiments, the frequency power profile is generated using a Fast Fourier Transform (FFT).

[0062] In some embodiments, the method further includes creating a search space, and wherein a frequency power profile of each radio signal of the at selected at least one radio signal comprises a stripe in the search space.

[0063] In some embodiments, the search space is created based on the number of frequency rates of the frequency hypothesis and a selected number of frequency bins.

[0064] In some embodiments, the method is iteratively performed to continuously improve a clock frequency of the clock of the radio signal receiver.

[0065] In some embodiments, an output of the corrected clock of the radio signal receiver clock is used to perform additional signal processing on the received radio signals.

[0066] In some embodiments, the method further includes performing a full, noninterlaced, motion compensated correlation process using the correction determined for the clock of the radio signal receiver.

[0067] In some embodiments, an apparatus for improving radio signal reception in a radio signal receiver includes at least one processor and a memory coupled to the at least one processor, the memory having stored therein at least one of programs or instructions. In such embodiments, the least one of programs or instructions, when executable by the processor, configure the apparatus to measure motion of an antenna of the radio signal receiver, receive radio signals from a plurality of transmitters, select at least one radio signal from the received radio signals, determine a frequency rate hypothesis for the selected at least one radio signal, and for each rate of the frequency rate hypothesis of each of the selected at least one radio signal, generate a complex correlation result including correlating each selected at least one radio signal with a local signal, motion compensate the complex correlation result, the local signal or the selected at least one radio signal using the measured motion of the antenna to produce a motion compensated complex correlation result, and phase compensate the motion compensated complex correlation result to produce a phase compensated correlation result. The apparatus can be further configured to generate a frequency power profile from the phase compensated correlation results for each rate of the frequency rate hypothesis for the selected at least one radio signal, determine a correlation peak in the frequency power profile, determine a correction for a clock of the radio signal receiver using the correlation peak, and correct the clock of the radio signal receiver using the determined correction.

[0068] In some embodiments, rather than using the largest magnitude correlation value, other test criteria can be used. For example, the progression of correlations can be monitored as hypotheses are tested and a cost function can be applied that indicates the best hypotheses when the cost function reaches a minimum (e.g., a small hamming distance amongst peaks in the correlation plots). As such, the joint correlation output can be a joint correlation value or a group of values.

[0069] Here multiple examples have been given to illustrate various features and are not intended to be so limiting. Any one or more of the features may not be limited to the particular examples presented herein, regardless of any order, combination, or connections described. In fact, it should be understood that any combination of thefeatures and / or elements described by way of example above are contemplated, including any variation or modification which is not enumerated, but capable of achieving the same. Unless otherwise stated, any one or more of the features may be combined in any order.

[0070] As above, figures are presented herein for illustrative purposes and are not meant to impose any structural limitations, unless otherwise specified. Various modifications to any of the structures shown in the figures are contemplated to be within the scope of the invention presented herein. The invention is not intended to be limited to any scope of claim language.

[0071] Where “coupling” or “connection” is used, unless otherwise specified, no limitation is implied that the coupling or connection be restricted to a physical coupling or connection and, instead, should be read to include communicative couplings, including wireless transmissions and protocols.

[0072] Any block, step, module, or otherwise described herein may represent one or more instructions which can be stored on a non-transitory computer readable media as software and / or performed by hardware. Any such block, module, step, or otherwise can be performed by various software and / or hardware combinations in a manner which may be automated, including the use of specialized hardware designed to achieve such a purpose. As above, any number of blocks, steps, or modules may be performed in any order or not at all, including substantially simultaneously, i.e., within tolerances of the systems executing the block, step, or module.

[0073] Where conditional language is used, including, but not limited to, “can,” “could,” “may” or “might,” it should be understood that the associated features or elements are not required. As such, where conditional language is used, the elements and / or features should be understood as being optionally present in at least some examples, and not necessarily conditioned upon anything, unless otherwise specified.

[0074] Where lists are enumerated in the alternative or conjunctive (e.g., one or more of A, B, and / or C), unless stated otherwise, it is understood to include one ormore of each element, including any one or more combinations of any number of the enumerated elements (e.g. A, AB, AC, ABC, ABB, etc.). When “and / or” is used, it should be understood that the elements may be joined in the alternative or conjunctive.

[0075] While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

Claims:

1. A method for improving radio signal reception in a radio signal receiver, comprising: measuring motion of an antenna of the radio signal receiver; receiving radio signals from a plurality of transmitters; selecting at least one radio signal from the received radio signals; determining a frequency rate hypothesis for the selected at least one radio signal; for each rate of the frequency rate hypothesis of each of the selected at least one radio signal: generating a complex correlation result including correlating each selected at least one radio signal with a local signal; motion compensating the complex correlation result, the local signal or the selected at least one radio signal using the measured motion of the antenna to produce a motion compensated complex correlation result; and phase compensating the motion compensated complex correlation result to produce a phase compensated correlation result; generating a frequency power profile from the phase compensated correlation results for each rate of the frequency rate hypothesis for the selected at least one radio signal; determining a correlation peak in the frequency power profile; determining a correction for a clock of the radio signal receiver using the correlation peak; and correcting the clock of the radio signal receiver using the determined correction.

2. The method of claim 1 , wherein the at least one radio signal is selected based on at least one of a quality of a selected radio signal compared to the other received radio signals or by using a building map of an environment in which the radio signals are received.

3. The method of claim 2, wherein the quality is based on at least one of a signal strength of received radio signals, an elevation of a source of the at least one selected radio signal or a determination that the signal is a line-of-sight signal.

4. The method of claim 1 , wherein the complex correlation result comprises a vector containing a number of complex correlation results corresponding to a required integration time.

5. The method of claim 1 , wherein the frequency power profile is generated using a Fast Fourier Transform (FFT).

6. The method of claim 5, further comprising creating a search space, and wherein a frequency power profile of each radio signal of the at selected at least one radio signal comprises a stripe in the search space.

7. The method of claim 6, wherein the search space is created based on the number of frequency rates of the frequency hypothesis and a selected number of frequency bins.

8. The method of claim 1 , wherein the method is iteratively performed to continuously improve a clock frequency of the clock of the radio signal receiver.

9. The method of claim 1 , wherein an output of the corrected clock of the radio signal receiver clock is used to perform additional signal processing on the received radio signals.

10. The method of claim 1 further comprising, performing a full, non-interlaced, motion compensated correlation process using the correction determined for the clock of the radio signal receiver.

11. An apparatus for improving radio signal reception in a radio signal receiver, comprising: at least one processor; and a memory coupled to the at least one processor, the memory having stored therein at least one of programs or instructions executable by the processor to configure the apparatus to: measure motion of an antenna of the radio signal receiver; receive radio signals from a plurality of transmitters; select at least one radio signal from the received radio signals; determine a frequency rate hypothesis for the selected at least one radio signal; for each rate of the frequency rate hypothesis of each of the selected at least one radio signal: generate a complex correlation result including correlating each selected at least one radio signal with a local signal; motion compensate the complex correlation result, the local signal or the selected at least one radio signal using the measured motion of the antenna to produce a motion compensated complex correlation result; and phase compensate the motion compensated complex correlation result to produce a phase compensated correlation result; generate a frequency power profile from the phase compensated correlation results for each rate of the frequency rate hypothesis for the selected at least one radio signal; determine a correlation peak in the frequency power profile; determine a correction for a clock of the radio signal receiver using the correlation peak; and correct the clock of the radio signal receiver using the determined correction.

12. The apparatus of claim 11 , wherein the at least one radio signal is selected based on at least one of a quality of a selected radio signal compared to the other received radio signals or by using a building map of an environment in which the radio signals are received.

13. The apparatus of claim 12, , wherein the quality is based on at least one of a signal strength of received radio signals, an elevation of a source of the at least one selected radio signal, or a determination that the signal is a line-of-sight signal.

14. The apparatus of claim 11 , wherein the complex correlation result comprises a vector containing a number of complex correlation results corresponding to a required integration time.

15. The apparatus of claim 11 , wherein the frequency power profile is generated using a Fast Fourier Transform (FFT).

16. The apparatus of claim 15, wherein the apparatus is further configured to create a search space, and wherein a frequency power profile of each radio signal of the at selected at least one radio signal comprises a stripe in the search space.

17. The apparatus of claim 16, wherein the search space is created based on the number of frequency rates of the frequency hypothesis and a selected number of frequency bins.

18. The apparatus of claim 11 , wherein the configuration steps are iteratively performed to continuously improve a clock frequency of the clock of the radio signal receiver.

19. The apparatus of claim 11 , wherein an output of the corrected clock of the radio signal receiver clock is used to perform additional signal processing on the received radio signals.

20. The apparatus of claim 11 , wherein the apparatus is further configured to perform a full, non-interlaced, motion compensated correlation process using the correction determined for the clock of the radio signal receiver.

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