Method and apparatus for processing of radio signals using a variable integration period and / or rate

Abstract

A method and apparatus for signal processing in a radio signal receiver using a variable integration period or rate include receiving, at the radio signal receiver, radio signals from at least one transmitter, determining at least one operating characteristic of the environment in which the radio signal receiver is operating, determining at least one of an integration period or an integration rate for processing the received radio signals based on the determined at least one operating characteristic, performing motion compensated correlation on the received radio signals using the determined at least one of the integration period or the integration rate to generate motion compensated correlation results, and determining at least one of a position of the radio signal receiver, a direction of motion of the radio signal receiver, or an error of a clock of the radio signal receiver using the motion compensated correlation results.

Description

METHOD AND APPARATUS FOR PROCESSING OF RADIO SIGNALS USING A VARIABLE INTEGRATION PERIOD AND / OR RATE BACKGROUND Field

[0001] Embodiments of the present principles generally relate to radio signal receivers and, in particular, to a method and apparatus for processing radio signals using a variable integration period and / or rate. 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 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, that is, 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 operating in an urban environment with high signal multipath, attenuated signal reception due to foliage and when operating in an environment containing GNSS signal spoofers / jammers.

[0004] Receivers capable of motion compensation may use a signal processing technique known as SUPERCORRELATIONTMfor improving radio signal reception using receiver motion compensated signal processing. The SUPERCORRELATIONTMtechnique 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 SUPERCORRELATIONTMtechnique is used to correct for the effects of reflections and multipath interference on signals received by a receiver. SUPERCORRELATIONTMcan 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 SUPERCORRELATIONTMtechnique to process GNSS signals, the signal errors are removed such that a very accurate position can be determined.

[0006] GNSS receivers have many applications in which very accurate signal processing is not required at all times. For example, a vehicle carrying a GNSS receiver can be travelling on a straight road through a prairie (no buildings or foliage), with a clear view of the sky such that many satellites with line-of-sight propagation paths are visible to the GNSS receiver. In other instances, the vehicle can be traveling in an urban environment with only limited view of the sky such that buildings block, attenuate or reflect the GNSS signals, or traveling under foliage in which the foliage attenuates the GNSS signals. In all of these communication scenarios, the SUPERCORRELATIONTMtechnique uses a fixed coherent integration period of about 1 second. Such a long integration period may cause the receiver to unnecessarily use computing resources and, in other instances, may not provide position updates quickly enough.

[0007] Therefore, there is a need in the art for a method and apparatus for signal processing of radio signals using a variable integration period depending upon the signal environment. SUMMARY

[0008] Embodiments of the present principles generally relate to a method and apparatus for radio signal processing using a variable integration period and / or integration rate as shown in and / or described in connection with this disclosure and the associated figures.

[0009] Various features and advantages of the present principles can be determined 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

[0010] 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.

[0011] FIG.1 depicts a communication environment in which a receiver performs motion compensated signal processing using a variable integration period and / or integration rate in accordance with at least one embodiment of the present principles can be applied.

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

[0013] FIG. 3 depicts a flow diagram of a method of performing motion compensated signal processing using a variable integration period and / or integration rate an in accordance with at least one embodiment of the present principles.

[0014] FIG. 4 graphically illustrates overlapping signal correlation to facilitate a variable integration rate in accordance with at least one embodiment of the present principles.

[0015] FIG. 5 depicts a block diagram of a radio signal receiver capable of performing motion compensated signal processing using a variable integration period and / or integration rate in a parallel manner in accordance with at least one embodiment of the present principles.

[0016] FIG. 6 depicts a flow diagram of a method 600 of performing motion compensated signal processing using a variable integration period and / or integration rate in a parallel manner in accordance with at least one embodiment of the present principles.

[0017] 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

[0018] 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 particular forms 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 primarilywith respect to specific means for determining operating characteristics / conditions of an environment in which a receiver of the present principles is operating, embodiments of the present principles can be implemented using any means for determining characteristics / conditions of an environment in which a receiver of the present principles is operating.

[0019] Embodiments of the present principles comprise apparatuses and methods of signal processing in a radio signal receiver that implement motion compensated signal processing for determining positioning measurements. Such receivers of the present principles can include positioning systems, such as GNSS receivers. In some embodiments, a GNSS receiver of the present principles can be 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 (IoT) device, wearable device, etc.), and the like.

[0020] In some embodiments, a radio signal receiver of the present principles temporarily stores or buffers data related to received signals or partially processed received signals (collectively, referred to as a representation of the received signals). Such representations can include, but are not limited to, downconverted signals, sampled signals, filtered signals, correlation outputs and the like. In general, the data can include any data from which motion compensated correlation can be performed. In some embodiments of the present principles, the data can also include receiver antenna motion information. In some embodiments, a receiver of the present principles implements the SUPERCORRELATIONTMtechnique (i.e., motion compensated correlation) to process the buffered data using a very long integration period, e.g., about 1 second. Such a long integration period enables a very attenuated signal to be received and used to determine the receiver’s position. The long integration period also enables the receiver to accurately discriminate an angle of arrival of signals such that signals can be received in an urban environment where the receiver is surrounded by tall buildings.

[0021] In accordance with the present principles, rather than applying the SUPERCORRELATION technique using a fixed long integration period at all times and, therefore continuously using computing resources, embodiments of the present principles vary the integration period and / or integration rate depending upon environmental conditions. For example, when a vehicle carrying a receiver of the present principles is traveling along an open road at a high rate of speed, the receiver may shorten the integration period to facilitate generating position updates at a faster rate (e.g., every 0.25 seconds). However, when the same vehicle passes beneath trees that attenuate the GNSS signals, in accordance with the present principles the integration period can be lengthened to improve the received signals’ signal to noise ratio (SNR) caused by, for example, signal attenuation.

[0022] For example, signal attenuation can result from a smartphone being placed in a pocket, handbag, backpack, and the like. In accordance with the present principles, in some embodiments a length of the integration period can be increased to compensate for the signal attenuation. In some embodiments, a length of a selected integration period can be dependent upon the received signals’ SNR or signal strength (i.e., the less attenuated the signal, the shorter the integration period). In another example, when a vehicle enters an urban environment and slows, the integration period can be lengthened to its maximum extent to enable, for example, high accuracy signal angle of arrival discrimination because, at slow vehicle speeds, the faster correlation / position rate is no longer necessary). As such, in some embodiments, signals received directly from a satellite (line of sight (LOS) signals) can be used for position or velocity calculation and signals that are reflected or attenuated (non-LOS signals) can be rejected to avoid corrupting the position or velocity calculations.

[0023] In a further embodiment, integration of the present principles can be performed in parallel threads or parallel processors, where each parallel path produces a different integration period (e.g., 1 second, ½ second, ¼ second) and / or a different integration rate (e.g., 1 Hz, 2 Hz, 4 Hz, etc.). An optimizer generates or analyzes a particular quality metric and selects the integration results having asufficient quality metric value (e.g., an integration result having the largest SNR) to be used for the navigation solution and / or clock correction.

[0024] Satellite-based positioning systems utilize encoded digital signals including a deterministic digital code (e.g., Gold codes) to facilitate signal acquisition. 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 present principles are useful to enable a receiver to improve its position computation accuracy and / or signal reception. A technique for improving radio signal reception using receiver motion compensated signal correlation is known as SUPERCORRELATIONTMand 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. The motion model is typically derived using inertial measurement unit (IMU) data; however, in some embodiments of the present principles, 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.

[0025] In operation, a code in at least one received signal is correlated with at least one locally generated signal / code to produce at least one correlation result. As is described in detail below, embodiments of the present principles perform highly accurate receiver position determination using a variable integration period and / or integration rate. The receiver monitors the surrounding environment for specific environmental conditions that may impact signal reception and alters the integration period and / or the integration rate in response to detecting at least one such specific environmental condition.

[0026] FIG. 1 depicts a communication environment 100 in which a receiver performs motion compensated signal processing using a variable integration period and / or integration rate in accordance with at least one embodiment of the present principles can be applied. In the communication environment 100, an automobile (vehicle) 104 carrying a GNSS receiver 106 moves along a street (arrow 110). The receiver 106 receives at least one satellite signal 112 broadcast from a at least one satellite (illustratively three satellites 102A, 102B, and 102C). In the embodiment of FIG.2, 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 bus data, etc.). Such representations can 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.

[0027] In the embodiment of FIG.1, in position A, the vehicle 104 has an open sky view (e.g., driving on a highway through a prairie). In position B, the vehicle 104 drives beneath trees that attenuate the received signals. In position C, the vehicle 104 slows as it enters an urban environment and the received signals can include a combination of LOS signals (direct), NLOS signals (reflected) and attenuated signals. The intent of using enhanced signal processing, such as SUPERCORRELATIONTM, 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, such as a high multipath environment, an environment having electromagnetic interference and / or attenuated signals, which can occur in, for example, urban canyons, environments including spoofing / jamming, and / or environments having heavy foliage. As such, in embodiments of the present principles, the position accuracy able to be determined by a receiver in an open sky environment can be extended to other, more complex environments.

[0028] A receiver of the present principles, such as the receiver 106 of FIG.1 can comprise a component (e.g., a GNSS receiver) within user equipment such as mobile phones, tablets, laptop computers, IoT devices, wearable devices, and the like. For simplicity, the device of the present principles is described herein as a receiver. In some embodiments of the present principles, the receiver can be a standalone receiver or can include a portion or component within user equipment.

[0029] In the embodiment of FIG. 1, the receiver 106 continuously monitors its environment to anticipate or directly detect when a received signal is being or will be impacted by the environment. For example, in some embodiments, a receiver of the present principles, such as the receiver 106 of FIG. 1, can use onboard sensors to detect characteristics of an environment to determine whether or not objects in the environment exist that can attenuate a signal from a source. For example, in some embodiments, using such detected environmental characteristics, a receiver of the present principles, such as the receiver 106 of FIG.1, can detect whether the receiver 106 is operating in an urban environment having buildings that can attenuate signals from a desired source, whether the receiving 106 is operating in an environment containing foliage (e.g., trees) that can attenuate signals from a desired source, or whether the receiver 106 is operating in open space, in which the receiver 106 can receive LOS signals from a desired source. In accordance with the present principles, a receiver of the present principles, such as the receiver 106, can adjust an integration period based on detected characteristics of the environment in which the receiver 106 is operating.

[0030] Alternatively or in addition, in some embodiments a receiver of the present principles, such as the receiver 106, can monitor the characteristics of received signals to determine an integration period and / or integration rate for the received signals. For example, in some embodiments, the receiver 106 can monitor the signal- to-noise ratio (SNR) of a received signal and, based on the SNR of the received signal(s), determine an integration period / rate for the received signal(s). In such embodiments, the receiver 106 can identify delayed and attenuated signals asreflected signals. Alternatively or in addition, in some embodiments a receiver of the present principles, such as the receiver 106, can use maps or satellite images to determine information (e.g., operating characteristic) about an environment in which a receiver of the present principles is operating, such as when the vehicle 104 is about to or has entered an urban environment, open space, or areas containing foliage.

[0031] In some embodiments, a receiver of present principles and / or a carrier of the receiver, such as the vehicle 104 (e.g., an autonomous or semi-autonomous vehicle) of FIG. 1, can include cameras, LIDAR sensors, RADAR sensors, acoustic sensors, and the like that are capable of monitoring the physical environment to recognize when the vehicle is operating in an open area, under foliage, or in an urban environment and the like. Alternatively or in addition, in some embodiments, a receiver of present principles and / or a carrier of the receiver, such as the vehicle 104 (e.g., an autonomous or semi-autonomous vehicle) of FIG. 1, can include signal processing capabilities (i.e., hardware and / or software) for detecting signal jammers or spoofers to identify when such devices may impact reception of desired signals. It should be noted that many other techniques are available for detecting the signal environment surrounding the receiver 106 and / or the vehicle 106 and any such techniques, individually or in combination, can be used to determine the surrounding signal environment in accordance with embodiments of the present principles.

[0032] In some embodiments, when a receiver of the present principles is part of a personal device, such as a mobile phone or smartphone, an integration period can be varied depending on placement of the device. That is, in some embodiments, an integration period and / or integration rate of a receiver of the present principles can be increased or decreased depending on, for example, whether the device including a receiver of the present principles was being held in the open or being placed in a pocket, handbag, backpack and the like. In some embodiments, a threshold signal- to-noise (SNR) signal strength or noise floor can be used to define when the integration period should be varied.

[0033] FIG.2 depicts a functional block diagram of the radio signal receiver 106 of FIG. 1 in accordance with at least one embodiment of the present principles. In the embodiment of FIG.2, the receiver 106 comprises an antenna 200, a front end 202, support circuits 204, signal environment 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 typically an indivisible unit where the antenna 200 moves with the platform. In the embodiment of FIG.2, the SUPERCORRELATIONTMtechnique 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.

[0034] In FIG. 2, 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 and as such will not be described in detail herein. The output of the receiver front end 202 is a digital signal containing signal data. In the embodiment of FIG. 2, 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.

[0035] The at least one processor 210 of the receiver 106 of FIG. 2 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 204 can comprise well-known circuits and devices facilitating functionality of the processor(s). The support circuits 204 can 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.

[0036] The memory 212 of the receiver 106 of FIG.2 can comprise 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 stored data 220 (including receiver motion). In some embodiments, the stored data 220 can include a receiver position 222, motion hypotheses 224, and various additional data used to perform the SUPERCORRELATIONTMprocessing in accordance with the present principles.

[0037] In the embodiment of FIG. 2, the signal environment detector 206 of the receiver 106 automatically determines characteristics of the signal environment in which the receiver 106 is operating or will be operating. In accordance with the present principles, depending on the detected characteristics of the signal environment, the at least one processor 210 adjusts a length of the integration period used to perform SUPERCORRELATIONTM. Alternatively or in addition, in some embodiments, the detector 206 of the receiver 106 can use a map or satellite images to determine characteristics of a signal environment, such as when the receiver 106 is about to or has entered an urban environment, open space, foliaged areas, other circumstances of attenuated signals, and the like. In some embodiments, the detector 206 of the receiver 106 can continuously or intermittently monitor signal characteristics of received signals to determine if signals have been attenuated by, for example, the existence of an urban environment and / or under foliage, and / or to identify delayed and attenuated signals as reflected signals, monitor signal strength and / or SNR (noise floor, etc.). In embodiments of the present principles, the detector 206 of the receiver 106 can utilize vehicle-mounted cameras, LIDAR sensors, RADAR sensors, acoustic sensors, and the like that monitor the physical environment to recognize when signals received or to be received can be affected by the environment, such as if the vehicle is operating in or about to operate in an open area, under foliage, or in an urban environment. In some embodiments, the detector 206 of the receiver 105 can include a sensor for detecting signal jammers or spoofers to identify when such devices mayimpact reception of a desired signal. Many other techniques exist for detecting characteristics of a signal environment in which a receiver of the present principles is operating, and any such techniques, individually or in combination, can be used to determine the surrounding signal environment and be used to adjust the integration period and / or integration rate in accordance with at least one embodiment of the present principles.

[0038] In some embodiments of the present principles, the at least one processor 210 accesses the buffered 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. That is, the correlation results are used to determine pseudoranges for each satellite and the pseudoranges are processed to compute the receiver position. In embodiments of the present principles, the at least one processor 210 performs the SUPERCORRELATIONTMprocessing to provide signals (phasor sequences) to phase adjust the complex correlation results such that the coherent integration period is extended, for example, extended to one or more seconds, to improve signal reception in accordance with the present principles. The phasor sequence is a time sequence of phase offsets in which each phasor in the sequence adjusts the phase of a complex signal sample. An 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 is implemented to adjust the phase of the complex correlation results.

[0039] In some embodiments, the GNSS signals can have been fully or partially processed before being buffered as part of the data. For example, the partially processed signals can include downconverted, filtered, and / or sampled GNSS signals. In such embodiments, the fully processed signals can include complex correlation results.

[0040] Referring back to FIG.2, the motion module of the receiver 208 generates receiver motion information that is buffered in the stored 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 can 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 some embodiments, the motion module 208 uses the at least one processor 210 to generate motion information reflecting the motion of the receiver 106. Such motion information can comprise a prediction of receiver velocity and heading, in some embodiments as a motion model 218. In some embodiments, to generate motion information, the motion module 208 can comprise an inertial measurement unit (IMU) to provide platform (receiver) orientation and velocity information for the motion model 218.

[0041] FIG. 3 depicts a flow diagram of a method 300 of performing signal processing using a variable integration period and / or integration rate in accordance with at least one embodiment of the present principles. The method 300 can be implemented in software, hardware or a combination of both (e.g., using the at least one processor 210, the memory 212, the motion module 208 and the signal environment detector 206 of FIG.2). In some embodiments, the method 300 operates through execution of the signal processing software (216 of FIG.2) using the at least one processor and memory (210 and 212 of FIG.2) to access and perform instructions of the software.

[0042] The method 300 begins at 302 and proceeds to 304 during which signals (e.g., radio 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 an antenna of the receiver 106. The process ofdownconverting the RF signal and sampling the digital code is well known in the art. The method 300 can proceed to 306.

[0043] At 306, the data (e.g., GNSS signals, partially or fully processed signals, motion data, etc.) are stored (buffered) in a memory, such as the memory 212 of FIG. 2, such that the GNSS signals can be repeatedly processed with various phasor sequences representing various motion hypotheses. The data can include any information from which motion compensated correlation can be performed in accordance with the present principles. The method 300 can proceed to 308.

[0044] At 308, the state of the current or near future signal environment is determined using data / information (e.g., environmental operating characteristic) supplied by, for example, the signal environment detector 206 of FIG. 2, described above. The method 300 can proceed to 310.

[0045] At 310, depending on the determined state of the signal environment, a length for the integration period and / or integration rate can be determined as described above. The integration period can be actively shortened and / or lengthened, and / or the integration rate can be actively increased or decreased, depending on the determined state of the signal environment.

[0046] For example, in some embodiments the integration period can be altered by integrating longer or shorter periods of received signal data. In some embodiments, a plurality of integration periods and / or rates can be used and a receiver of the present principles can select the period / rate to use that generates a sufficient quality metric, such as, but not limited to, a sufficient SNR. In other embodiments, the receiver can adjust the integration period and / or rate until a sufficient quality metric is attained, then use the integration period or rate with the sufficient quality metric to determine clock parameters and / or navigation position for the receiver. Alternatively or in addition, the integration period can be maintained at a fixed length, but the data can be integrated in overlapping periods to increase the integration rate. In further embodiments, parallel signal processing threads or processors can each integrate at different rates and / orperiods and an optimal rate and / or period can be selected in view of the current or future signal environment and / or based on a quality metric (described in greater detail below).

[0047] In various embodiments, the following SUPERCORRELATIONTMtechnique can be performed as part of the signal environment detection process such that the SNR of the correlation results can be used to determine an integration period. For example, a short integration period can be initially selected and the SUPERCORRELATIONTMtechnique performed on the received. buffered signals. The SNR of the resulting correlation results are then compared to a threshold. If the SNR is below the threshold, the integration period can be lengthened, and the threshold test can be repeated. The procedure can be repeated until the threshold is exceeded and / or reached. The integration period / rate that results in a desired SNR can then be used for processing the buffered signals described in 314 below.

[0048] In various embodiments, the iterative thresholding techniques of the present principles can start with the shortest integration period and / or rate or alternatively it can start with a period and / or rate that is selected using other signal environment detection techniques such as, but not limited to, maps, images, RADAR, LIDAR, non-SUPERCORRELATIONTMtechnique-based signal processing to determine SNR, signal strength or noise-floor levels, and the like. In some embodiments, a maximum length of an integration period and / or rate can be based on other signal processing constraints or requirements such as the stability of the receiver clock over the integration period or the required position update rate of the use case. In instances in which a signal environment detector of the present principles finds the signal environment to be so good (i.e., no discernible difference in correlation output between standard correlation-based signal processing and SUPERCORRELATIONTM-based signal processing), the SUPERCORRELATIONTMtechnique can be deactivated or not used at all. The SUPERCORRELATIONTMtechnique can then be reactivated if the signal environment deteriorates. The method 300 can proceed to 314.

[0049] At 314 (and / or combined into the signal environment detection at 308), the buffered data can be processed using the SUPERCORRELATIONTMtechnique to motion compensate the correlation results. During this process, the SUPERCORRELATIONTMprocedure 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. As previously recited, 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 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 is applied to a corresponding complex sample in the signals and / or correlation results. For each received signal, the received signals are correlated with a set (plurality) of phasor sequence hypotheses containing estimates of a phase offset necessary to accurately correlate the received signals. In some embodiments, all the hypotheses are tested to find the hypothesis that provides the best or optimal correlation result magnitude.

[0050] In some embodiments of the present principles, 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 narrower search space.

[0051] In some embodiments, if a signal from a given satellite was received previously, the set of hypotheses for the newly received signal include a group ofphasor 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 the expected receiver motion. Each received signal is 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.

[0052] That is, the correlation results are processed to find the “best” or optimal result for each received signal. In one embodiment, a joint correlation output 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.

[0053] 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.

[0054] If additional receiver parameters (e.g., clock frequency and / or frequency rate) are unknown or not accurately known, in some embodiments those parameter offsets can also be expressed as phasor hypotheses and tested to optimize the correlation output across multiple parameters at once. These parameter offsets can be used to correct inaccuracies in, for example, a clock of a receiver of the present principles.

[0055] For example, in a GNSS receiver of the present principles, the processing can result in a number, N (e.g., N = 50), of correlation results of length 20 ms in a 1 second period. In an urban environment and / or an environment having significant jamming or heavy attenuation, the signal processing would tend to use all N (e.g.,50) correlation results coherently integrated over the 1 second period using SUPERCORRELATIONTM(i.e., a 1 second integration period). However, on an open road at highway speed, the signal processing of the present principles can apply SUPERCORRELATIONTMprocessing to a lesser number of correlation results (e.g., 12 correlations) coherently integrated to produce a correlation output every quarter second (i.e., a quarter second integration period). In a further variation, when some foliage is detected, but not heavy foliage, the signal processing can select a half second integration period or other intermediate length integration period. In some embodiments, the integration period can also be directly variable with SNR or signal strength of the received signal (i.e., the lower the SNR or signal strength, the longer the integration period). The method 300 can proceed to 316.

[0056] At 316, the compensated correlation results are used in 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 an accurate position of the receiver. The method can proceed to 318.

[0057] At 318, it is queried if additional signals are to be processed. In accordance with some embodiments of the present principles, by processing a sequence of signals, a path of the receiver can be constructed. If the query at 318 is affirmatively answered, the method 300 proceeds along a path back to 304 to access additionalsignals and process them. If the query is negatively answered, the method 300 proceeds to 322 and ends.

[0058] In some embodiments, a method for performing signal processing in a radio signal receiver using a variable integration period or rate includes receiving, at the radio signal receiver, radio signals from at least one transmitter, determining at least one operating characteristic of the environment in which the radio signal receiver is operating, determining at least one of an integration period or an integration rate for processing the received radio signals based on the determined at least one operating characteristic, performing motion compensated correlation on the received radio signals using the determined at least one of the integration period or the integration rate to generate motion compensated correlation results, and determining at least one of a position of the radio signal receiver, a direction of motion of the radio signal receiver, or an error of a clock of the radio signal receiver using the motion compensated correlation results.

[0059] In some embodiments, the at least one operating characteristic of the environment includes a signal-to-noise-ratio (SNR) of a received radio signal and the determining of at least one of an integration period or an integration rate for processing the received radio signals includes (a) performing motion compensated correlation of the received radio signal using an initial integration period or an initial integration rate, (b) measuring the SNR of the motion compensated correlation results, (c) comparing the measured SNR of the motion compensated signal with a threshold value, and (d) if the measured SNR is below the threshold value, increasing the initial integration period or decreasing the initial integration rate.

[0060] In some embodiments, the method further includes iteratively repeating (a) – (d) until the measured SNR meets or exceeds the threshold value.

[0061] In some embodiments, the at least one operating characteristic is determined using at least one of a map of the environment or a satellite image of the environment.

[0062] In some embodiments, the method further includes using at least one of the map or the satellite image of the environment to identify sources of attenuation of the radio signals in the environment, such that line-of-sight radio signals and non-line-of- sight radio signals can be identified.

[0063] In some embodiments, the at least one operating characteristic is determined using at least one sensor in communication with the radio signal receiver.

[0064] In some embodiments, the method further includes using data received from the at least one sensor to identify sources of attenuation of the radio signals in the environment, such that line-of-sight radio signals and non-line-of-sight radio signals can be identified.

[0065] In some embodiments, the integration rate is produced using an overlapping signal correlation technique.

[0066] In some embodiments, determining at least one of an integration period or an integration rate comprises determining a plurality of integration periods or integration rate estimates for processing the received radio signals based on the determined at least one operating characteristic.

[0067] In some embodiments, the plurality of integration periods or integration rate estimates are processed in parallel to determine an optimal integration period or integration rate to use in performing the motion compensated correlation on the received radio signals to determine the at least one of a position of the radio signal receiver, a direction of motion of the radio signal receiver, or an error of a clock of the radio signal receiver.

[0068] In some embodiments, an apparatus for performing signal processing in a radio signal receiver using a variable integration period or rate includes at least one processor and at least one memory coupled to the at least one processor, the memory having stored therein at least one of programs or instructions. In some embodiments, when the stored programs or instructions are executed by theprocessor, the apparatus is configured to receive, at the radio signal receiver, radio signals from at least one transmitter, determine at least one operating characteristic of the environment in which the radio signal receiver is operating, determine at least one of an integration period or an integration rate for processing the received radio signals based on the determined at least one operating characteristic, perform motion compensated correlation on the received radio signals using the determined at least one of the integration period or the integration rate to generate motion compensated correlation results, and determine at least one of a position of the radio signal receiver, a direction of motion of the radio signal receiver, or an error of a clock of the radio signal receiver using the motion compensated correlation results.

[0069] FIG. 4 graphically illustrates overlapping signal correlation to facilitate a variable integration rate in accordance with at least one embodiment of the present principles. In some embodiments, to alter the integration rate while maintaining a fixed integration period, a buffered data stream 400 is accessed, a period of data is selected, and the data stream is coherently integrated over a period (e.g., 1 second) to create coherent integration result C1. Subsequently, a new period of data can be selected and is offset in time, but overlapping, the prior segment of data. Processing of this next segment results in coherent integration result C2. Using this manner of overlapped processing, a long integration period (e.g., 1 second) can be used to produce a high integration rate (e.g., 4 Hz). Alternatively or in addition, in some embodiments the integration period can also be varied (increase or decrease from 1 second) in view of the signal environment and / or a signal metric as described above (e.g., with respect to FIG.3). As such, in some embodiments of the present principles, both integration rate and period can both be simultaneously adjusted to optimize signal processing in view of the detected and / or expected signal environment.

[0070] FIG. 5 depicts a block diagram of a radio signal receiver 500 capable of performing motion compensated signal processing in a parallel manner in accordance with at least one embodiment of the present principles. The receiver 500 of FIG. 5 comprises an antenna 502, a front end 504, at least one buffer 506, a plurality ofparallel processors or parallel processing threads 508, an optimizer 510, and a navigation engine 512. The antenna 502 and front end 504 can operate the same as the antenna 200 and front end 202 as described with respect to FIG.2. The received signals can be buffered in the at least one buffer 506 (e.g., memory). Each processor or processing thread 508 performs the SUPERCORRELATIONTMtechnique on the buffered signals. In accordance with the present principles, individual parallel processors can be used or a single processor that instantiates a plurality of parallel processing threads can be used. In such embodiments, each processor or thread can use a different integration period and / or integration rate.

[0071] For example, in the embodiment of FIG.5, processor / thread 1 can use a 1 second integration period (with a 1 Hz rate), processor / thread 2 can use a half second integration period (with a 2 Hz rate), and processor / thread 3 can use a quarter second integration period (with a 4 Hz rate). In accordance with the present principles, any number of processors / threads can be used for processing the signals using various integration periods and rates. In some embodiments, the processors / threads can also use the overlapping method of fixing the integration period while creating a variable integration rate as described with respect to FIG.4 above.

[0072] In the embodiment of FIG. 5, the integration results from each processor / thread are coupled to the optimizer 510. The optimizer 510 selects the integration results that are to be used by the navigation engine 512. The selection process can be performed based upon the determined signal environment or can be determined through analysis of the integration results themselves using a measured and / or determined quality metric such as, but not limited to, signal strength or correlation result SNR. In some embodiments, other selection criteria can be used. For example, in some embodiments, the signal environment can be used to select a longer or shorter integration period as described above (i.e., select a longer period when the signal environment is degraded). Other criteria for selecting an integration rate and / or period in accordance with the present principles can include speed of motion of the receiver (e.g., faster speed, shorter integration periods). Alternatively orin addition, in some embodiments the optimizer 510 can select the integration result from the plurality of processors / threads that has the largest SNR or has an amplitude exceeding a threshold level.

[0073] In accordance with the present principles, the selected integration results can be coupled to the navigation engine 512 to be used to determine the receiver’s position (and / or velocity). By selecting integration results that are optimized in view of the signal environment, the receiver produces an accurate position (and / or velocity) under challenging signal environments.

[0074] In some embodiments, the front end 504 can separate received signals from satellites in different GNSS constellations (e.g., GPS, GLONASS, Galileo, Beidou, etc.) and separately buffer the signals from each constellation. The parallel processors / threads 508 can process the signals from each constellation separately using the SUPERCORRELATIONTMtechnique. The processors / threads 508 can use the techniques described above to apply variable integration periods and / or rates to the signal processing in view of the signal environment.

[0075] FIG. 6 depicts a flow diagram of a method 600 of performing motion compensated signal processing using the variable integration period and / or rate in a parallel manner in accordance with at least one embodiment of the present principles. The method 600 begins at 602 and proceeds to 604 where GNSS signals are received. The method 600 can proceed to 606.

[0076] At 606, information (data) from the signals or the signals themselves are buffered (stored in memory). The method 600 can proceed to 608.

[0077] At 608, the buffered data is accessed. The method 600 can proceed to 610.

[0078] At 610, the accessed data is processed using motion compensated correlation processes (e.g., SUPERCORRELATIONTMtechnique) in each of the processor / threads, 508 of FIG.5. The output of 610 is a plurality of integration resultseach having a different integration period and / or rate. The method 600 can proceed to 612.

[0079] At 612, the parallel set of integration results are processed to select the optimal results for use in the navigation engine. In some embodiments, the integration results can be selected based on a measured or determined quality metric (e.g., characteristic of the operating environment) such as, but not limited to, the signal environment, integration result characteristics (e.g., SNR), received signal strength or other selection criteria. The method 600 can proceed to 614.

[0080] At 614, the selected integration results are used to compute a receiver position (and / or velocity) using navigation computations that are well known in the art. In this manner, receiver position and / or velocity can be calculated when the receiver is faced with challenging signal environments. The method 600 can proceed to 616.

[0081] At 616, it is queried whether additional received signals are to be processed. If the query is affirmatively answered, the method 600 proceeds along path 618 to 604 to receive and process additional GNSS signals. If the query is negatively answered, the method 600 proceeds to 620 and ends.

[0082] 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.

[0083] 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 bewithin the scope of the invention presented herein. The invention is not intended to be limited to any scope of claim language.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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 signal processing in a radio signal receiver using a variable integration period or rate , comprising: receiving, at the radio signal receiver, radio signals from at least one transmitter; determining at least one operating characteristic of the environment in which the radio signal receiver is operating; determining at least one of an integration period or an integration rate for processing the received radio signals based on the determined at least one operating characteristic; performing motion compensated correlation on the received radio signals using the determined at least one of the integration period or the integration rate to generate motion compensated correlation results; and determining at least one of a position of the radio signal receiver, a direction of motion of the radio signal receiver, or an error of a clock of the radio signal receiver using the motion compensated correlation results.

2. The method of claim 1, wherein the at least one operating characteristic of the environment comprises a signal-to-noise-ratio (SNR) of a received radio signal and wherein determining at least one of an integration period or an integration rate for processing the received radio signals comprises: (a) performing motion compensated correlation of the received radio signal using an initial integration period or an initial integration rate; (b) measuring the SNR of the motion compensated correlation results; (c) comparing the measured SNR of the motion compensated signal with a threshold value; and (d) if the measured SNR is below the threshold value, increasing the initial integration period or decreasing the initial integration rate.

3. The method of claim 2, further comprising: iteratively repeating (a) – (d) until the measured SNR meets or exceeds the threshold value.

4. The method of claim 1, wherein the at least one operating characteristic is determined using at least one of a map of the environment or a satellite image of the environment.

5. The method of claim 4, further comprising using at least one of the map or the satellite image of the environment to identify sources of attenuation of the radio signals in the environment, such that line-of-sight radio signals and non line-of-sight radio signals can be identified.

6. The method of claim 1, wherein the at least one operating characteristic is determined using at least one sensor in communication with the radio signal receiver.

7. The method of claim 6, further comprising using data received from the at least one sensor to identify sources of attenuation of the radio signals in the environment, such that line-of-sight radio signals and non line-of-sight radio signals can be identified.

8. The method of claim 1, wherein the integration rate is produced using an overlapping signal correlation technique.

9. The method of claim 1, wherein determining at least one of an integration period or an integration rate comprises determining a plurality of integration periods or integration rate estimates for processing the received radio signals based on the determined at least one operating characteristic.

10. The method of claim 9, wherein the plurality of integration periods or integration rate estimates are processed in parallel to determine an optimal integration period or integration rate to use in performing the motion compensated correlation on the received radio signals to determine the at least one of a position of the radio signal receiver, a direction of motion of the radio signal receiver, or an error of a clock of the radio signal receiver.

11. An apparatus for performing signal processing in a radio signal receiver using a variable integration period or rate, comprising: at least one processor; and at least one 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: receive, at the radio signal receiver, radio signals from at least one transmitter; determine at least one operating characteristic of the environment in which the radio signal receiver is operating; determine at least one of an integration period or an integration rate for processing the received radio signals based on the determined at least one operating characteristic; perform motion compensated correlation on the received radio signals using the determined at least one of the integration period or the integration rate to generate motion compensated correlation results; and determine at least one of a position of the radio signal receiver, a direction of motion of the radio signal receiver, or an error of a clock of the radio signal receiver using the motion compensated correlation results.

12. The apparatus of claim 11, wherein the at least one operating characteristic of the environment comprises a signal-to-noise-ratio (SNR) of a received radio signaland wherein determining at least one of an integration period or an integration rate for processing the received radio signals comprises: (a) performing motion compensated correlation of the received radio signal using an initial integration period or an initial integration rate; (b) measuring the SNR of the motion compensated correlation results; (c) comparing the measured SNR of the motion compensated signal with a threshold value; and (d) if the measured SNR is below the threshold value, increasing the initial integration period or decreasing the initial integration rate.

13. The apparatus of claim 12, wherein the apparatus is further configured to: iteratively repeat (a) – (d) until the measured SNR meets or exceeds the threshold value.

14. The apparatus of claim 11, wherein the at least one operating characteristic is determined using at least one of a map of the environment or a satellite image of the environment.

15. The apparatus of claim 14, wherein the apparatus is further configured to use at least one of the map or the satellite image of the environment to identify sources of attenuation of the radio signals in the environment, such that line-of-sight radio signals and non-line-of-sight radio signals can be identified.

16. The apparatus of claim 11, wherein the at least one operating characteristic is determined using at least one sensor in communication with the radio signal receiver.

17. The apparatus of claim 16, wherein the apparatus is further configured to use data received from the at least one sensor to identify sources of attenuation of theradio signals in the environment, such that line-of-sight radio signals and non-line- of-sight radio signals can be identified.

18. The apparatus of claim 11, wherein the integration rate is produced using an overlapping signal correlation technique.

19. The apparatus of claim 11, wherein determining at least one of an integration period or an integration rate comprises determining a plurality of integration periods or integration rate estimates for processing the received radio signals based on the determined at least one operating characteristic.

20. The apparatus of claim 19, wherein the plurality of integration periods or integration rate estimates are processed in parallel to determine an optimal integration period or integration rate to use in performing the motion compensated correlation on the received radio signals to determine the at least one of a position of the radio signal receiver, a direction of motion of the radio signal receiver, or an error of a clock of the radio signal receiver.

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