Method and apparatus for event-based processing of radio signals

Abstract

A method and apparatus for providing event-based signal processing in a radio signal receiver (106).

Description

METHOD AND APPARATUS FOR EVENT-BASED PROCESSING OF RADIO SIGNALSBACKGROUNDField

[0001] Embodiments of the present invention generally relate to radio signal receivers and, in particular, to a method and apparatus for processing radio signals upon the occurrence of an event.Description of the Related Art

[0002] Positioning signal receivers such as receivers for global satellite navigation systems (GNSS) signals have become ubiquitous in mobile devices and vehicles. 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] 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 the relative motion between the receiver and transmitter removed from the signal correlation process. Compensating for the receiver motion improves receiver signal reception and / or lowers the cost of receiver components. The improvement in signal reception enables the receiver to determine accurate receiver position when confronted with an urban environment with highsignal multipath and when confronted with an environment containing GNSS signal spoofers.

[0004] Receivers capable of motion compensation may 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 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.

[0005] The SUPERCORRELATION™ technique is used to correct for the effects of reflections and multipath interference on signals received by a receiver. SUPERCORRELATION™ may also be 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, the signal errors are removed such that a very accurate position may be computed.

[0006] GNSS receivers have many applications where very accurate positioning is not required at all times. For example, many passenger vehicles have systems that monitor vehicle acceleration and make automated calls to emergency services when an accident occurs. Upon detecting an accident, the vehicle may automatically send the last position of the vehicle to emergency services. However, if the vehicle is located in a high multipath environment (e.g., urban canyons), the position may be very inaccurate.

[0007] Therefore, there is a need in the art for a method and apparatus for eventbased signal processing of radio signals to improve receiver position when an event occurs that requires an accurate position.SUMMARY

[0008] Embodiments of the present invention generally relate to a method and apparatus for event-based radio signal processing as shown in and / or described in connection with at least one of the figures.

[0009] Various features and advantages of the present disclosure may be appreciated from a review of the following detailed description of the present disclosure, along with the accompanying figures in which like reference numerals refer to like parts throughout.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] So that the manner in which the features of the present invention can be understood in detail, a particular description of the invention, may 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 this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

[0011] FIG. 1 depicts a scenario for use of a method of event-based signal processing in a radio signal receiver in accordance with at least one embodiment of the invention;

[0012] FIG. 2 is a functional block diagram of a radio signal receiver in accordance with at least one embodiment of the invention; and

[0013] FIG. 3 is a flow diagram of a method of performing event-based signal processing in accordance with at least one embodiment of the invention.DETAILED DESCRIPTION

[0014] Embodiments of the present invention comprise apparatus and methods of event-based signal processing in a radio signal receiver that uses motion compensated signal processing. Such receivers include positioning systems (e.g., GNSS receivers).

[0015] In one exemplary embodiment, the radio signal receiver temporarily stores or buffers data related to the received signals or partially processed received signals (collectively, referred to as a representation of the received signals). Such representations may include, but are not limited to, downconverted signals, sampled signals, filtered signals, correlation outputs and the like. In general, the data may be any data from which motion compensated correlation may be performed. The data also includes receiver antenna motion information. The receiver uses the SUPERCORRELATION™ technique (i.e., motion compensated correlation) to process the buffered data only when an event occurs. Events that may trigger such processing include an automobile accident that requires notification of emergency services of the accident and its accurate location. Furthermore, such accident-based processing can provide a highly accurate vehicle position and / or travel path that may be useful in a crash investigation. Rather than have the SUPERCORRELATION technique used at all times and, therefore, continuously use computing resources, the technique is activated only when a high accuracy position is required. This eventbased processing may also be used upon the occurrence of other types of events as described below. In addition, the enhanced signal processing may be applied on a signal-by-signal basis or on all the received signals. As such, signals received directly from a satellite (line of sight (LOS) signals) may be processed in a standard manner and signals that are reflected or attenuated may be processed using enhanced signal processing (e.g., the SUPERCORRELATION™ technique).

[0016] Satellite-based positioning systems utilize encoded digital signals including a deterministic digital code to facilitate signal acquisition, e.g., Gold codes. Such a digital code is determined by the receiver 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 invention are useful to enable a receiver to improve its position computation accuracy and / or signal reception. The technique for improving radio signal reception using receiver motion compensated signal correlation 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; USpatent 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. The motion model is typically derived using inertial measurement unit (IMU) data; however, in embodiments of the invention, the motion model is derived using accelerometer data, gyroscope data, controller area network (CAN) bus data, visual odometry data, or a combination of data from any of these motion data sources.

[0017] In an embodiment, the GNSS receiver is embedded in or carried by 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, wearable device, etc.), and the like.

[0018] In operation, the 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 detail below, embodiments of the invention perform highly accurate position determination only upon detection of an occurrence of an event that requires a highly accurate position. Such an event may be an accident or crash that requires accurate position information for contacting emergency services or an investigation. Other events may include one or more of the following: an automotive breakdown, a person having a tripping or falling incident, a person’s wearable device indicating a medical emergency is occurring (e.g., heart attack, diabetic emergency, and the like), a person calling for emergency services, remote request for position, and the like.FIG. 1 depicts a scenario 100 in which event-based signal processing is used in a radio signal receiver in accordance with at least one embodiment of the invention. In scenario 100, an automobile 104 carrying a GNSS receiver 106 moves along a street (arrow 110). The receiver 106 receives satellite signals 112 broadcast from a plurality of satellites 102A, 102B, and 102C. The receiver 106 buffers (i.e., stores) data related to the received signals 112 or partially processed received signals (collectively, referred to as a representation of the received signals) as well as receiver antenna motion information (e.g., accelerometer and gyroscope measurements, CAN busdata, etc.). Such representations may include, but are not limited to, downconverted signals, sampled signals, filtered signals, correlation outputs and the like. In general, the data may be any data from which motion compensated correlation may be performed. Upon an event occurring, such as an automobile accident (e.g., automobile 104 crashes into automobile 108), the receiver 106 processes the previously stored data to determine an accurate position of the automobile 104 when that accident occurred (e.g., a position within 2 meters of a true position). The intent of using enhanced signal processing is to produce a position accuracy equivalent to the position accuracy computed in an open sky scenario even when the receiver is in a complex environment, e.g., high multipath, electromagnetic interference and / or attenuated signal environments that occur in, for example, urban canyons, spoofing, and / or heavy foliage. As such, the position accuracy found in an open sky scenario is extended to other, more complex scenarios.

[0019] Data over a period of time may be processed to produce a travel path for the automobile. The triggering event may be detected by an accelerometer, airbag deployment sensor, gyroscope, or the like.

[0020] The receiver 106 may be a component (e.g., a GNSS receiver) within user equipment such as mobile phones, tablets, laptop computers, loT devices, wearable devices, and the like. For simplicity, the device is described herein as a receiver. Those skilled in the art will understand that the receiver may be a standalone receiver or may be a portion or component within user equipment.

[0021] Upon the occurrence of an event, in the depicted embodiment, a vehicle accident, a motion compensated signal correlation processing is activated to process the buffered data and provide an accurate position even in an urban environment or in an environment containing one or more GNSS signal spoofers. Although the depicted scenario 100 highlights an automobile accident as the triggering event, for other user devices, the triggering event may include one or more of the following: vehicle breakdown, a person having a tripping or falling incident, a person’s wearable device indicating a medical emergency is occurring (e.g., heart attack, diabetic emergency, and the like), a person calling for emergency services, a bicycle accident,a remote request for a position of the receiver, and the like. The remote request could be initiated by a concerned parent, a fleet manager, police, etc.

[0022] FIG. 2 is a functional block diagram of the radio signal receiver 106 of FIG. 1 in accordance with at least one embodiment of the invention. In one exemplary embodiment, the receiver 106 comprises an antenna 200, a front end 202, support circuits 204, event detector 206, motion module 208, at least one processor 210 and memory 212. When carried by a transport platform such as a vehicle, airplane, bicycle, person, etc., the receiver 106 and its antenna 200 are an indivisible unit where the antenna 200 moves with the platform. The SUPERCORRELATION™ technique operates based upon determining a component of motion of the signal receiving antenna that is in the direction of the source (e.g., GNSS satellite) of a received signal. Any mention of motion herein refers to the motion of the antenna 200. In most scenarios, the motion of the transport platform is the same as the motion of the antenna 200 and, as such, the following description assumes the motion of the platform, the receiver 106 and antenna 200 are the same.

[0023] The receiver’s front end 202 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 202 is a digital signal containing signal data. The signal data of interest for performing motion compensation is a deterministic code, e.g., Gold code, used by the processor 210 to synchronize the receiver 106 to the GNSS transmission.

[0024] The at least one processor 210 may 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 204 may comprise well-known circuits and devices facilitating functionality of the processor(s). The support circuits 204 may comprise one or more of, or a combination of, power supplies, clock circuits, analog to digital converters, communications circuits, cache, displays, filters, and / or the like.

[0025] The memory 212 comprises 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 212 stores software and data including, for example, GNSS signals 214 (and / or representations of those signals), signal processing software 216, a motion model 218 and data 220 (including receiver motion). The data 220 comprises a receiver position 222, motion hypotheses 224, and various additional data used to perform the SUPERCORRELATION™ processing.

[0026] The event detector 206 may be an airbag deployment detector, accelerometer, gyroscope, and / or the like. The event detector 206 is designed to detect an event that requires accurate position information. For example, an event may be a vehicle crash, a vehicle breakdown, a person tripping and falling while carrying their smartphone, an aircraft crash, a person’s wearable device indicating a medical emergency is occurring (e.g., heart attack, diabetic emergency, and the like), a person calling for emergency services, a remote request for position, and / or the like. In each of these examples, stored data may be processed using the SUPERCORRELATION™ technique to determine a position where the event occurred and / or determine a travel path just before the event. The accurate position (within about 2 meters) is computed even when the receiver is operating in an urban environment or an environment containing signal interference from GNSS signal spoofers or other electromagnetic interference sources.

[0027] Upon the event being detected, the at least one processor 210 accesses the stored GNSS signals 214 and the at least one processor 210 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 222, e.g., the correlation results are used to determine pseudoranges for each satellite and the pseudoranges are processed to compute the receiver position. The at least one processor 210 performs the SUPERCORRELATION™ processing to provide signals (phasor sequences) to phase adjust the complex correlation results such that the coherent integration period is extended, e.g., extended to one or more seconds, to improve signal reception. Theenhanced signal processing may be applied on a signal-by-signal basis or on all the received signals. As such, signals received directly from a satellite (line of sight (LOS) signals) may be processed in a standard manner and signals that are reflected or attenuated may be processed using enhanced signal processing (e.g., the SUPERCORRELATION™ technique). The phasor sequence is a time sequence of phase offsets where each phasor in the sequence adjusts the phase of a complex signal sample. The adjustment may be performed by adjusting the phase of each sample of the received signals, the locally generated signals or the correlation results themselves. The least computationally intensive adjustment process adjusts the phase of the complex correlation results.

[0028] In some embodiments, the GNSS signals may have been fully or partially processed before being stored as part of the data. Doing so, saves processing resources and time when an event occurs. For example, the partially processed signals may include downconverted, filtered, and / or sampled GNSS signals. Fully processed signals may include complex correlation results.

[0029] The motion module 208 generates receiver motion information that is buffered in the data 220 and used by the at least one processor 210 to generate phasor sequences that are used to motion compensate the complex correlation results. The buffered data 220 may include motion module inputs, outputs or a combination of both. The phasor sequences 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. In one embodiment, the motion module 208 uses the at least one processor 210 to generate motion information reflecting the motion of the receiver 106. In one embodiment, motion information may comprise a prediction of receiver velocity and heading (i.e., a motion model 218). In one alternative embodiment, the motion module 208 may comprise an inertial measurement unit (IMU) to provide platform (receiver) orientation and velocity information for the motion model.

[0030] FIG. 3 is a flow diagram of a method 300 of operation of the receiver (106 in FIGs. 1 and 2) in accordance with at least one embodiment of the invention. Themethod 300 may be implemented in software, hardware or a combination of both (e.g., using the at least one processor 210, the motion module 208 and the event detector 206 of FIG. 2). The method 300 operates through execution of the signal processing software (216 of FIG. 2) using the at least one processor (210 of FIG. 2) to access and perform instructions of the software.

[0031] The method 300 begins at 302 and proceeds to 304 where signals are received at a receiver from at least one remote source (e.g., transmitters such as the plurality of GNSS satellites 102A, 102B, 102C, . . . 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.

[0032] At 306, the data (e.g., GNSS signals, partially or fully processed signals, motion data, etc.) are stored in memory. The data includes any information from which motion compensated correlation is performed. The data may be stored locally in the receiver or transmitted wirelessly to a server. In some embodiments, the data may be stored on a memory card such that it can be physically moved to a processing location or downloaded to a computer. The server may be a portion of a fleet management system, emergency services provider system, or other user of an accurate position for the platform, that stores the data for subsequent processing when an event occurs that requires investigation or analysis. The signals could be permanently stored or temporarily stored, i.e. , storing a few minutes to a couple of hours of data. If an event is not detected during a predefined period, the signals may be discarded. To facilitate remote processing, in addition to the signal samples, the receiver motion information and the occurrence of an event are also transmitted to the server. Such transmissions may be encrypted.

[0033] At 308, the method queries whether an event has occurred. If an event has not been detected, the query is negatively answered and the method proceeds along path 310 to continue receiving GNSS signals. If an event has occurred, the query is affirmatively answered and method 300 proceeds to 312.

[0034] In a remote processing system, the detection of an event would be sent to the server and the remainder of method 300 would be performed on the server. In a local processing system (i.e., on the receiver), the remainder of method 300 is performed by the receiver’s at least one processor.

[0035] At 312, the data is accessed from memory. At 314, the accessed data is processed using the SUPERCORRELATION™ technique to motion compensate the correlation results. During this process, the SUPERCORRELATION™ procedure generates a plurality of phasor sequence hypotheses related to the motion 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 complex carrier phase of the local signal. Such adjustment or compensation may 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. The method applies each phase offset in the phasor sequence 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. All the hypotheses are tested to find the hypothesis that provides the best or optimal correlation result magnitude.

[0036] 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, e.g., along the signal propagation path. As with all GNSS receivers, the satellite positions are known to the receiver through known ephemeris data. A comparison of correlation results over the direction hypotheses enables the method 300 to narrow the search space when processing subsequently received signals. Consequently, subsequent compensation is performed over a narrow search space.

[0037] In one embodiment, if a signal from a given satellite was received previously, the set of hypotheses for the newly received signal 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 may be centered around the last values used or the last values used additionally offset by a prediction of further offset based on the expected receiver motion. The method 300 correlates each received signal 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 may 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.

[0038] The method 300 processes the correlation results to find the “best” or optimal result for each received signal. In one embodiment, the method 300 produces a joint correlation output 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 may 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 general, 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.

[0039] For example, assuming all other receiver parameters are known except receiver motion direction, the method 300 tests hypotheses with various phasor sequences that compensate for phase changes due to each direction hypothesis. 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.

[0040] If additional receiver parameters (e.g., clock frequency and / or frequency rate) are unknown or not accurately known, those parameter offsets may also be expressed as phasor hypotheses and tested to optimize the correlation output across multiple parameters at once. These parameter offsets are used to correct inaccuracies in, for example, the receiver clock.

[0041] At 316, the compensated correlation results are used by a traditional positioning or navigation solution (e.g., using a pseudorange to each satellite transmitter from which signals were contained in the stored data) to generate the accurate position of the receiver. At 318, the method queries if additional signals are to be processed. By processing a sequence of signals, a path of the receiver prior to the event may be constructed. If the query is affirmatively answered, the method 300 proceeds along path 320 to access additional signals and process them. If the query is negatively answered, the method 300 proceeds to 322 and ends.

[0042] Using the method 300 enables a receiver to collect GNSS signal samples (or representations of the GNSS signals), receiver motion information and event information without the need for processing the GNSS signals in real-time. Thus, computing resources are reserved for use when they are truly needed. Even if the GNSS signal processing is continuously performed and the SUPERCORRELATION™ processing is performed upon event detection, computer resources are used more efficiently.

[0043] 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 the features 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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 or more 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.

[0049] 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 performing event-based signal processing in a radio signal receiver, comprising: receiving radio signals from a plurality of transmitters; storing data related to the received radio signals from which motion compensated correlation can be performed; upon detecting an event, accessing the stored data; performing motion compensated correlation using the accessed data to generate motion compensated correlation results; and generating a receiver position using the motion compensated correlation results.

2. The method of claim 1 , wherein the event includes at least one of a vehicle crash, a vehicle breakdown, a person tripping and falling while carrying a phone, an aircraft crash, a person’s wearable device indicating a medical emergency is occurring, a person calling for emergency services, or a remote request for position.

3. The method of claim 1 , wherein performing motion compensated correlation includes correlating a code encoded in the accessed data with a local code in a local signal to produce correlation results.

4. The method of claim 3, wherein the code encoded in the accessed data is a synchronization or acquisition code extracted from the received radio signals.

5. The method of claim 3, wherein performing motion compensated correlation includes generating a plurality of phasor sequence hypotheses related to accessed data, wherein each phasor sequence hypothesis comprises a phaseestimate that varies with motion parameters of the receiver, and adjusting the phase of the local signal using the phasor sequence hypotheses.

6. The method of claim 5, wherein performing motion compensated correlation includes, for each received signal, correlating the received signal with a set of phasor sequence hypotheses containing estimates of a phase offset necessary to correlate the received signals, and testing the set of phasor sequence hypotheses to determine a phasor sequence hypothesis that provides an optimal correlation result value for the received signal.

7. The method of claim 6, wherein if the received signal was previously received, the set of phasor sequence hypotheses for the received signal include a group of phasor sequence hypotheses using an expected Doppler and Doppler rate and / or last Doppler and last Doppler rate used in receiving the previously received signal.

8. The method of claim 7, wherein hypotheses values are centered around previous hypotheses values used.

9. The method of claim 1 , wherein at least one of performing motion compensated correlation or generating a receiver position is performed remotely.

10. The method of claim 6, wherein performing motion compensated correlation includes producing a joint correlation output as a function of a plurality of correlation results resulting from all the hypotheses and received radio signals.11 . Apparatus for performing event-based signal processing in a radio signal receiver, comprising at least one processor and at least one non-transient computer readable medium for storing instructions that, when executed by the at least one processor, causes the apparatus to perform operations comprising: receiving radio signals from a plurality of transmitters;storing data related to the received radio signals from which motion compensated correlation can be performed; upon detecting an event, accessing the stored data; performing motion compensated correlation using the accessed data to generate motion compensated correlation results; and generating a receiver position using the motion compensated correlation results.

12. The apparatus of claim 11 , wherein the event includes at least one of a vehicle crash, a vehicle breakdown, a person tripping and falling while carrying a phone, an aircraft crash, a person’s wearable device indicating a medical emergency is occurring, a person calling for emergency services, or a remote request for position.

13. The apparatus of claim 11 , wherein performing motion compensated correlation includes correlating a code encoded in the accessed data with a local code in a local signal to produce correlation results.

14. The apparatus of claim 13, wherein the code encoded in the accessed data is a synchronization or acquisition code extracted from the received radio signals.

15. The apparatus of claim 13, wherein performing motion compensated correlation includes generating a plurality of phasor sequence hypotheses related to accessed data, wherein each phasor sequence hypothesis comprises a phase estimate that varies with motion parameters of the receiver, and adjusting the phase of the local signal using the phasor sequence hypotheses.

16. The apparatus of claim 15, wherein performing motion compensated correlation includes, for each received signal, correlating the received signal with a set of phasor sequence hypotheses containing estimates of a phase offsetnecessary to correlate the received signals, and testing the set of phasor sequence hypotheses to determine a phasor sequence hypothesis that provides an optimal correlation result value for the received signal.

17. The apparatus of claim 16, wherein if the received signal was previously received, the set of phasor sequence hypotheses for the received signal include a group of phasor sequence hypotheses using an expected Doppler and Doppler rate and / or last Doppler and last Doppler rate used in receiving the previously received signal.

18. The apparatus of claim 17, wherein hypotheses values are centered around previous hypotheses values used or are centered around previous hypotheses values used offset by a prediction of further offset based on expected motion of the radio signal receiver.

19. The apparatus of claim 16, wherein performing motion compensated correlation includes producing a joint correlation output as a function of a plurality of correlation results resulting from all the hypotheses and received radio signals.

20. At least one non-transient computer readable medium storing instructions that, when executed by at least one processor, causes the at least one processor to perform operations comprising: receiving radio signals from a plurality of transmitters; storing data related to the received radio signals from which motion compensated correlation can be performed; upon detecting an event, accessing the stored data; performing motion compensated correlation using the accessed data to generate motion compensated correlation results; and generating a receiver position using the motion compensated correlation results.

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