RU2431866C2 - System and/or method for detecting global navigation satellite system signals - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: first code phase is detected in a first periodically recurring pseudorandom encoded signal received from a first space vehicle (SV) in a reference location; and the search range of the code phase is determined for detecting the phase of a second code in a second periodically recurring pseudorandom encoded signal received from a second SV in said reference location based at least partly on said detected code phase of said first received signal, estimated azimuthal angle for said first SV from said reference location and estimated azimuthal angle for said second SV from said reference location.

EFFECT: low consumption of power and processing resources in mobile telephones and other devices when detecting one or more attributes in one navigation signal received in a reference location.

26 cl, 7 dwg

Description

State of the art

Related Applications

This application claims priority according to co-pending provisional application US No. 60/825,656, entitled "Reducing the search ranges for satellites in other GNSS systems", filed September 14, 2006; and US Provisional Application No. 60 / 870,075, entitled “System and / or Method for the Detection of GNSS Signals,” filed December 14, 2006; and US Provisional Application No. 11 / 682,692, entitled “System and / or Method for Detecting GNSS Signals,” filed March 6, 2007, and the rights of which are assigned to the copyright holder of this application, and which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to positioning based on signals received from geostationary satellites.

Information

A satellite positioning system (SPS) typically comprises a system of satellites moving in orbit around the Earth, enabling objects to determine their location on Earth, based at least in part on signals received from satellites. Such an SPS satellite typically transmits a signal marked with a repeating pseudo-random noise (PN) code with a fixed number of chips. For example, a satellite in a Global Navigation Satellite System (GNSS) constellation, such as GPS or Galileo, may transmit a signal marked with a PN code that is distinguishable from PN codes transmitted by other satellites in the constellation.

To estimate the location of the receiver, the navigation system can measure pseudorange to satellites that are “in the field of view” of the receiver using well-known methods based, at least in part, on the detection of PN codes in signals received from satellites. Such pseudorange to satellites can be determined based at least in part on the phase of the code detected in the received signal marked with the PN code associated with the satellite during the process of detecting the received signal at the receiver. To detect a received signal, the navigation system typically correlates the received signal with a locally generated PN code associated with the satellite. For example, such a navigation system typically correlates such a received signal with a multiple code and / or time-shift versions of such a locally generated PN code. Detecting a specific time and / or version of a time-shifted code, giving a correlation result with the highest signal strength, may indicate the phase of the code associated with the detected signal for use in pseudorange measurement, as described above.

To detect the phase of a code in a signal received from a satellite in GNSS, the navigation system can correlate a signal received from a satellite with a multiple code and / or time-shifted versions of a locally generated PN code sequence associated with “code phase hypotheses”, encompassing the entire period of a periodically repeating sequence of PN code. In a specific example of a GPS signal, the PN code sequence contains 1,023 chips (chips) and is repeated every millisecond. Accordingly, in order to detect the phase of the signal code code received from the GPS satellite, the navigation system can correlate the received signal with 1,023 versions of the locally generated PN code sequence associated with the GPS satellite, phase-shifted in increments of one chip.

Figure 1 shows the application of the SPS system, according to which the subscriber terminal 100 in wireless communication systems receives transmissions from satellites 102a, 102b, 102c, 102d in the visibility range of the subscriber terminal 100 and extracts time measurements from four or more transmissions. Subscriber terminal 100 may provide such measurements to a location determination object (PDE) 104, which determines the location of the terminal from these measurements. Alternatively, the subscriber terminal 100 may determine its own location from this information.

Subscriber terminal 100 may seek transmission from a particular satellite by correlating the PN code for the satellite with the received signal. The received signal typically comprises a set of transmissions from one or more satellites within the field of view of the receiver of terminal 100 in the presence of noise. Correlation can be performed in the range of code phase hypotheses known as the W _CP code phase search window, and within the Doppler frequency hypotheses known as the W _DOPP Doppler search window. As indicated above, such code phase hypotheses are usually displayed as a range of PN code shifts. In addition, hypotheses about the Doppler frequency are usually presented as elements of the resolution of the Doppler frequency.

Correlation is usually performed during the integration time “I”, which can be expressed as the product of Nc and M, where Nc is the time of coherent integration and M is the number of coherent integrations that are incoherently combined. For a particular PN code, correlation values are usually associated with the corresponding PN code shifts and Doppler frequency resolution elements to determine a two-dimensional correlation function. The peaks of the correlation function are located and compared with a given noise threshold. The threshold is usually chosen so that the probability of false alarm, the probability of false detection of satellite transmission would be close to or lower than the set value. The time measurement for the satellite is usually derived from the location of the first non-off-peak lobe peak by measuring the phase of the code that is equal to or exceeds the threshold. The Doppler measurement for the subscriber station can be obtained from the location of the first non-off-peak lobe peak by measuring the Doppler frequency, which is equal to the threshold or exceeds it.

Correlation of the received signal with multiple versions of the PN code sequence, in the hypothesis range of the code phase for detecting the received signal, consumes power and processing resources. This expenditure of power and processing resources usually creates critical design constraints in portable products, such as mobile phones and other devices.

Disclosure of invention

A system and / or a method of reducing the range for detecting one or more attributes in one navigation signal received at a reference location, based at least in part on information obtained from a previous detection of another navigation signal at a reference location, is disclosed. It should be understood, however, that this is only an example of the specific embodiment described herein, and that the claimed subject matter is not limited to this. By reducing the range for detecting one or more attributes in a navigation signal, the detection of one or more attributes can be achieved faster and / or using less resources.

Brief Description of the Drawings

Non-limiting and non-exhaustive options for implementation are considered with reference to the following drawings, in which like numerals refer to similar parts among the various drawings.

1A is a schematic diagram of a satellite positioning system (SPS) in accordance with an embodiment.

1B is a schematic diagram of a system suitable for determining the location of a receiver by measuring pseudorange to spacecraft (SV) in accordance with an embodiment.

2 is a flowchart illustrating a process for detecting a signal from an SV encoded with a periodically repeated PN code in accordance with an embodiment.

Figure 3 is a schematic diagram of a two-dimensional region for searching for detecting a signal transmitted from a spacecraft in accordance with an embodiment.

FIG. 4 illustrates the overlapping of a predetermined number of chips in a search window to avoid skipping peaks that appear within a segment in accordance with an embodiment.

5 is a schematic diagram of a system for processing signals for determining location in accordance with an embodiment.

6 is a schematic diagram of a subscriber station in accordance with an embodiment.

The implementation of the invention

A reference in this description to “one embodiment” or “embodiment” means that a particular feature, structure or characteristic described in connection with an embodiment is included in at least one embodiment of the claimed subject matter. Thus, the occurrence of the phrase “in one embodiment” or “embodiment” in various places throughout the description is not necessarily all referring to the same embodiment. In addition, specific features, structures, or characteristics may be combined in one or more embodiments.

The methods described herein can be implemented by various means depending on the application in accordance with specific options for implementation. For example, such methods may be implemented in hardware, hardware-software, software, and / or combinations thereof. When implemented in hardware, for example, the processing unit can be implemented in one or more special integrated circuits (ASIC), digital signal processors (DSP), digital signal processing devices (DSPD), programmable logic devices (PLD), programmable gate arrays ( FPGA), processors, controllers, microcontrollers, microprocessors, electronic devices, other special modules designed to perform the functions described here, and / or combinations thereof.

"Instructions" in this case refer to expressions that represent one or more logical operations. For example, instructions may be “machine-readable” and interpreted by a machine to perform one or more operations on one or more data objects. However, this is only an example of instructions, and the claimed subject matter is not limited in this regard. In another example, the instructions referenced herein may relate to encoded instructions that are executed by a processing circuit having a set of instructions that includes encoded instructions. Such an instruction may be encoded in the form of a machine language understood by a processing circuit. And this is also only examples of instructions, and the claimed subject matter is not limited in this regard.

"Storage medium" in this case refers to media capable of supporting expressions that are perceived by one or more machines. For example, the storage medium may comprise one or more storage devices for storing machine-readable instructions and / or information. Such storage devices may comprise any of several types of media, including, for example, magnetic, optical, or semiconductor storage media. Such storage devices may also comprise any type of long-term, short-term, volatile or non-volatile memory device. However, these are only examples of the storage device, and the subject matter is not limited in this regard.

Unless expressly stated otherwise, or it is obvious from the following consideration, the terms used in the description, such as "processing", "calculation", "calculation", "choice", "formation", "provision", "prohibition", "location "," end "," identification "," initialization "," detection "," receipt "," hosting "," maintenance "," presentation "," rating "," reception "," transmission "," definition "and / or the like relate to actions and / or processes that may be performed by a computing platform, for example, a computer or the like, electronic a computing device that controls and / or converts data represented as physical electronic and / or magnetic quantities and / or other physical quantities within the processors of the computing platform, memory units, registers and / or other devices for storing, transmitting, receiving and / or display. Such actions and / or processes can be performed by a computing platform under the control of computer-readable instructions stored in a storage medium, for example. Such machine-readable instructions may include, for example, software or firmware stored in a storage medium included as part of a computing platform (for example, included as part of a processing circuit or external to such a processing circuit). Furthermore, unless expressly stated otherwise, the processes described herein in connection with flowcharts or otherwise may also be performed and / or controlled, in whole or in part, by such a computing platform.

A “spacecraft” (SV) in this case refers to an object that is suitable for transmitting signals to receivers on the surface of the Earth. In one particular embodiment, such an SV may comprise a geostationary satellite. Alternatively, the SV may comprise a satellite in orbit and moving relative to the stationary position of the Earth. However, these are only examples of SV, and the claimed subject matter is not limited in this regard.

"Location" in this case refers to information related to the location of an object or item in accordance with a reference point. Here, for example, such a location can be represented as geographical coordinates, for example, latitude and longitude. In another example, such a location can be represented as the coordinates of XYZ with the Earth at the origin. In yet another example, such a location may be represented as a street address, a municipality or other government territory, a zip code and / or the like. However, these are only examples of how a location can be represented in accordance with specific embodiments, and the claimed subject matter is not limited in this regard.

The location techniques described here can be used for various wireless networks, such as wireless wide area network (WWAN), wireless local area network (WLAN), personal wireless network (WPAN), etc. The terms “network” and “system” may be used interchangeably herein. The WWAN may be a code division multiple access (CDMA) network, a time division multiple access network (TDMA), a frequency division multiple access network (FDMA), an orthogonal frequency division multiple access network (OFDMA), a frequency division multiple access network single-carrier frequency (SC-FDMA), etc. A CDMA network can implement one or more radio access technologies (RATs), for example, cdma2000, broadband CDMA (W-CDMA), and these are just a few radio technologies. Here, cdma2000 may include technologies implemented in accordance with IS-95, IS-2000 and IS-856 standards. A TDMA network may implement a Global System for Mobile Communications (GSM), Advanced Digital Mobile Telephone System (D-AMPS), or some other RAT. The GSM and W-CDMA standards are described in documents from a consortium called the 3rd Generation Partnership Project (3GPP). The Cdma2000 standard is described in documents from a consortium called the 3rd Generation 2 Partnership Project (3GPP2). 3GPP and 3GPP2 documents are publicly available. A WLAN may comprise an IEEE 802.11x network, and a WPAN may comprise a Bluetooth network, IEEE 802.15x, for example. These location methods can also be used with any combination of WWAN, WLAN and / or WPAN.

According to an embodiment, the device and / or system can estimate its location based at least in part on signals received from the SV. In particular, such a device and / or system can obtain pseudorange measurements containing approximations of the distances between the associated SVs and the navigation satellite receiver. In a specific embodiment, such a pseudorange can be determined at a receiver that is suitable for processing signals from one or more SVs as part of a Satellite Positioning System (SPS). Such an SPS may include, for example, Global Positioning System (GPS), Galileo, Glonass, or any SPS developed in the future. To determine its location, the satellite navigation receiver can receive pseudorange measurements for three or more satellites, as well as their position during transmission. Knowing the SV orbital parameters, these positions can be calculated in advance for any point. The pseudorange measurement can then be performed based at least in part on the time taken for the signal to propagate from the SV to the receiver times the speed of light. Although the methods described herein may be provided as performing GPS and / or SPS location determination of the Galileo type, as certain illustrations in accordance with a particular embodiment, it should be understood that these methods may also apply to other types of SPS, and that the claimed subject matter is not limited in this regard.

A “Global Navigation Satellite System” (GNSS) in this case refers to an SPS containing SV transmitting synchronized navigation signals in accordance with a conventional signal format. Such GNSS may comprise, for example, an SV constellation in synchronized orbits for transmitting navigation signals for locations on a large portion of the Earth’s surface simultaneously from multiple SVs in the constellation. That SV, which is an element of a particular GNSS constellation, usually transmits navigation signals in a format that is unique to a particular GNSS format. Accordingly, techniques for detecting a navigation signal transmitted by SV in the first GNSS can be modified to detect a navigation signal transmitted by SV in the second GNSS. In a specific example, although the claimed subject matter is not limited in this regard, it should be understood that GPS, Galileo and Glonass, each represents GNSS, which is different from the other two named SPS. However, these are only examples of SPS associated with different GNSS, and the claimed subject matter is not limited in this regard.

According to an embodiment, the navigation receiver may obtain a pseudorange measurement for a particular SV based at least in part on detecting a signal from a particular SV that is encoded by periodically repeating a PN code sequence. Detection of such a signal may comprise detecting a “code phase” that is time-related and associated with a point in the PN code sequence. In one specific embodiment, for example, such a phase of the code may be mapped to the state of the locally generated clock signal and to a particular chip in the PN code sequence. However, this is only an example of how the phase of the code can be represented, and the claimed subject matter is not limited in this regard.

In accordance with an embodiment, code phase detection can provide several ambiguous pseudorange options or pseudorange hypotheses for PN code intervals. Accordingly, the navigation receiver can obtain a pseudorange measurement for SV, based at least in part on the detected phase of the code and ambiguity resolution to select one of the pseudorange hypotheses as a pseudorange measurement for SV. As indicated above, the navigation receiver can estimate its location based, at least in part, on pseudorange measurements received from multiple SVs.

As shown below, in accordance with a specific embodiment, the navigation receiver may detect a first signal from a first SV to detect a code phase of a first signal. When a second signal is detected from the second SV, the navigation receiver can detect the code phase in a limited range of the code phase search in the second signal, based at least in part on the code phase of the detected first signal. Accordingly, the code phase of the detected first signal allows such a navigation receiver to detect the second signal faster and / or using fewer processing resources.

FIG. 1B is a schematic diagram of a system suitable for positioning in a receiver by measuring pseudorange to SV. A receiver at a reference location 116 on earth 118 may receive signals from SV1 and SV2 while in direct line of sight with them. Location 116 may be known to be within the region 114 defined, for example, by a circle with a radius of approximately 10 km. It should be understood that this is only an example of how the uncertainty of the estimated location can be represented in accordance with a specific embodiment, and the claimed invention is not limited in this regard. In one embodiment, region 114 may comprise a coverage area of a particular cell of a cellular wireless network at a known location.

According to an embodiment, the receiver at the reference location 116 may communicate with other devices, for example, a server (not shown) via a terrestrial wireless network. In one particular embodiment, such a server may transmit detection support (AA) messages to the receiver containing information used by the receiver to process signals received from the SV and / or obtain pseudorange measurements. Alternatively, such AA messages may be provided from information locally stored in the receiver. In this case, such locally stored information can be stored in local memory from a removable memory device and / or obtained from a previous AA message received from the server, which is mentioned only as examples. In a particular embodiment, the AA messages may contain information such as, for example, information showing the positions of SV1 and SV2, an estimate of the reference location 116, uncertainty associated with the estimated location, and / or the like. Such information indicates the provisions of SV1 and SV2, may contain ephemeris information and / or calendar information. As indicated below, in accordance with specific embodiments, the receiver may evaluate the positions of SV1 and SV2 based at least in part on such an ephemeris and / or calendar and a rough estimate of the time. Such an estimated SV position may comprise, for example, an estimated azimuthal angle from the reference direction and an elevation angle from the Earth's horizon at reference location 116, and / or XYZ coordinates in the Earth's coordinate system. As shown in FIG. 1B, SV1 has an estimated position characterized by an estimated azimuthal angle A1 between the north and the projection of the line of sight for SV1 from the reference location 116 onto the Earth’s horizon at the reference location 116. The estimated position SV1 is also shown as being characterized by the estimated elevation angle E1 from Earth's horizon at reference location 116. The estimated position of SV2 can be similarly characterized by the estimated azimuthal angle A2 and elevation angle E2.

2 is a flowchart of a process 200 for detecting signals from an SV in accordance with an embodiment. According to an embodiment, the receiver may receive a first signal encoded with a first periodically repeating PN code from a first SV (e.g., SV1), and receive a second signal encoded with a second periodically repeating PN code from a second SV (e.g., SV2). To detect the first signal in block 202, such a receiver can detect the Doppler frequency in the received signal by correlating the code and / or time-shifted versions of the locally generated code sequence with the received first signal. In a specific example, where the first SV transmits a GPS signal encoded with a periodically repeating PN code of 1023 chips in length, the received signal can be correlated with 1023 versions of the corresponding locally generated code sequence, code and / or time-shifted increment of one chip. However, this is only an example of how a signal from an SV of a particular GNSS can be detected, and the claimed subject matter is not limited in this regard. Such a correlation operation can be expressed in accordance with the following relation (1):

where m is the number of chips in a periodically repeating sequence of PN code of the signal received from SV1;

CP1 is the phase of the code detected in the signal received from SV1 at the reference moment;

Chipl _i is the i-th chip in the locally generated PN code sequence for SV1, 0≤i <m;

RSl _i is the i-th segment in the signal received from SV1, 0≤i <m;

As can be seen from the above relation (1), the value of h is in the search range from 0 to m-1, specifying the execution of the number m of correlation operations on the signal received from SV1 to exhaustively search for hypotheses for the code phase in the entire PN code detection interval result of maximum correlation. As shown below, the receiver can estimate the phase of the signal code received from the second SV based, at least in part, on the estimates of the positions of the first SV, the second SV, and the location of the receiver. At block 204, the receiver may obtain information describing the positions of the first and second SV from any of several sources, for example, from calendar or ephemeris information locally stored and / or received in an AA message. Such an AA message may also provide a time estimate. Using such a time estimate, information describing the positions of the first and second SV, and an estimate of the position of the receiver, block 204 can estimate the elevation angle of the first and second SV, E1 and E2 and the azimuths of the first and second SV, A1 and A2, related to the estimated position of the receiver.

At block 206, the receiver can estimate the code phase of the received signal from the second SV based at least in part on the code phase detected at block 202 and the estimates A1, A2, E1, and E2. According to an embodiment, block 206 may calculate the difference between the estimated distance from the reference location 116 to SV1 ("R _SV1 ") and the estimated distance from the reference location 116 to _SV1 ("R _SV2 "). In this case, block 206 may receive AA information from one or more AA messages, indicating, for example, estimates of the locations SV1 and SV2 in the XYZ coordinates of the Earth coordinate system, in addition to estimating the XYZ coordinates of the Earth coordinate system for location 116. Using such XYZ Earth coordinates coordinate system, block 206 can calculate Euclidean distances for R _SV1 and R _SV2 .

In a specific embodiment, where SV1 and SV2 belong to the same GNSS system (for example, both SV1 and SV2 are part of either GPS or Galileo constellations), the phase of the code in the signal from SV2 CP ₂ can be estimated in accordance with the following relation (2 ):

0E [CP ₂ ] = [(T ₁ -T ₂ ) + CP ₁ ] modPNI, for (T ₂ -T ₁ ) + CP ₁

0

0 (2)E [CP ₂ ] = {(N * PNI) + [(T ₂ -T ₁ ) + CP ₁ ]} mod PNI, for (T ₂ -T ₁ ) + CP ₁ <0, where N is a positive integer, such that (N * PNI) + [(T ₂ -T ₁ ) + CP ₁ ]

0 (2)

Where:

T1 is the propagation delay of the signal from SV1 measured by the receiver;

T2 is the propagation delay of the signal from SV2 measured by the receiver;

PNI - periodically repeating code interval of signals received from SV1

and SV2; and

CP ₁ is the detected phase of the signal code received from SV1 (for example, as determined in accordance with relation (1)).

According to an embodiment, the values for T1 and T2 can be expressed as follows:

Where:

c is the speed of light;

τ is the systematic error of the receiver synchronizer;

R _SV1 is an estimate of the range to SV1 from the reference location; and

R _SV2 is an estimate of the range to SV2 from the reference location.

In a specific embodiment, where the system error of the receiver synchronizer is common and identical for T1 and T2, the estimated phase of the code in the signal from SV2, as expressed in relation (2), can be reduced. Here, the expression for T2-T1 can be provided as follows:

T ₂ -T ₁ = [(R _SV2 / c) -τ] - [(R _SV1 / c) -τ] = (R _SV2 / c) - (R _SV1 / 1)

Accordingly, expression (2) can then be represented as follows:

0;E [CP ₂ ] = {[(R _SV2 / c) - (R _SV1 / c)] + CP ₁ } mod PNI, for [(R _SV2 / c) - (R _SV1 / c)] + CP ₁

0;

and

0.E [CP ₂ ] = {(N * PNI) + [(R _SV2 / c) - (R _SV1 / c)] + CP ₁ } mod PNI, for [(R _SV2 / c) - (R _SV1 / c) ] + CP ₁ <0, where N is a positive integer such that (N * PNI) + [(R _SV2 / c) - (R _SV1 / c)] + CP ₁

0.

In an alternative embodiment, SV1 and SV2 may be elements of various GNSS constellations. In a specific example, by way of illustration, SV1 may be a GPS constellation element, while SV2 may be a Galileo constellation element. In this particular embodiment, it should be noted that the transmitted SV1 signal can be encoded with a PN code sequence that repeats with 1.0 ms periods, while SV2 is encoded with a PN code sequence that repeats with 4.0 ms periods. Alternatively, SV1 may be a Galileo constellation element, while SV2 may be a GPS constellation element. In this particular embodiment, it should be noted that the transmitted SV1 signal can be encoded with a PN code sequence that repeats with 4.0 ms periods, while SV2 is encoded with a PN code sequence that repeats with 1.0 ms periods. However, these are only examples of how SV1 and SV2 can belong to different GNSS groups that transmit signals encoded with PN code sequences repeating with different periods, and the claimed subject matter is not limited in this regard.

In a specific embodiment, where SV1 is an element of the Galileo constellation and SV2 is an element of the GPS constellation, the phase of the code in the signal from SV2 can be estimated in accordance with the following relation (3):

0;E [CP ₂ ] = {[(R _SV2 / c) - (R _SV1 / c)] + CP ₁ } mod PNI _GPS , for [(R _SV2 / c) - (R _SV1 / c)] + CP ₁

0;

and

0

(3)E [CP ₂ ] = {(N * PNI _GPS ) + [(R _SV2 / c) - (R _SV1 / c)] + CP ₁ } mod PNI _GPS , for [(R _SV2 / c) - (R _SV1 / c)] + CP ₁ <0, where N is a positive integer such that (N * PNI _GPS ) + [(R _SV2 / c) - (R _SV1 / c)] + CP ₁

0

(3)

Where:

c is the speed of light;

PNI _GPS - periodically repeating code interval of signals received from SV2;

CP1 is the detected phase of the signal code received from SV1 (for example, as determined in accordance with relation (1));

R _SV1 is an estimate of the range to SV1 from the reference location; and

R _SV2 is an estimate of the range to SV2 from the reference location.

It should be noted here that relation (3) in its abbreviated form removes the systematic error of the receiver synchronizer, as shown above.

According to an embodiment, although the claimed subject matter is not limited in this regard, block 208 may determine a code phase search range for detecting a code phase in a signal received from SV2 as E [CP2] +/- ε _CP2 , where ε _CP2 displays one-sided phase ambiguity of the code in the received signal near E [CP2]. In accordance with an embodiment, block 208 may determine such a one-sided uncertainty ε _CP2 in accordance with the following relation (4):

Where:

c is the speed of light;

A1 is the estimated azimuthal angle for SV1 from the reference location;

A2 is the estimated azimuthal angle for SV2 from the reference location;

E1 is the estimated elevation angle for SV1 from the reference location;

E2 is the estimated elevation angle for SV2 from the reference location; and

Punc - One-sided uncertainty in a reference location in units of length.

According to an embodiment, although the claimed subject matter is not limited in this regard, the values for A1, A2, E1, E2 and Punc can be obtained from one or more AA messages, as described above, or locally, as stored in the receiver itself. The code phase search range, defined as E [CP2] +/- ε _CP2 in accordance with a particular embodiment, can be used by the receiver to limit the code phase search range near which it searches for the code phase upon detection of a signal received from SV2. In a specific embodiment, although the claimed subject matter is not limited in this regard, the receiver may try to correlate the signal received from SV2 in block 210 with a limited number of code versions and / or a time-shifted PN code sequence in accordance with the following relation (5 ):

Where:

n is the number of chips in a periodically repeating interval of the PN code of the signal received from SV2;

CP2 is the code phase detected in the signal received from SV2;

Chip2 _i is the i-th chip in the locally generated sequence of PN code for SV2, 0≤i <n;

RS2 _i is the i-th segment in the signal received from SV2, 0≤i <n;

θ is the index associated with the center of the code phase search range associated with the expected code phase of the signal received from SV2; and

ρ is a one-sided offset to θ, which determines the search range.

Here, as can be seen from relation (5), the correlation operation is performed in a limited range for h, θ-ρ≤h≤θ-ρ, and not for the entire range 0≤h≤n-1, as is done in the correlation operation in the above relation (1). In accordance with a specific embodiment, although the claimed subject matter is not limited in this regard, the center θ of the code phase search range may be based, at least in part, on an estimate of the code phase of the signal received from SV2 determined in accordance with relation (2) or (3). Here, for example, E [CP2] and θ can be connected by means of permanently connected chips in a PN code sequence with time. Similarly, the one-way offset ρ can be determined, at least in part, from the one-way uncertainty ε _CP2 defined above in accordance with relation (4), where ρ and ε _CP2 are connected by a constant associating the chips in the PN code sequence with time, for example.

In a specific embodiment, where SV1 is a GPS constellation element, while SV2 is a Galileo constellation element, E [CP2] in accordance with relation (3) is ambiguous within 4.0 ms of a periodically repeating code interval. In this particular embodiment, CP1 can be used to determine four hypotheses for the expected phase of the code in the signal from SV2, separated by 1.0 ms intervals. In this case, the first assumption (i) can be defined as E [CP2], as shown above. Accordingly, four assumptions (i), (ii), (iii) and (iv) can be defined as follows:

Where:

PNI _GPS - period duration for a periodically repeating sequence of PN signal code received from SV1; and

PNI _Gal - period duration for a periodically repeating sequence of PN signal code received from SV2.

According to a specific embodiment, although the claimed subject matter is not limited in this regard, block 206 may formulate a plurality of code phase search ranges associated with a plurality of code phase hypotheses. Continuing again with the example shown above, where SV1 is a GPS grouping element, while SV2 is a Galileo grouping element, such code phase search ranges can be defined as follows:

where ε _CP2 represents the one-sided phase ambiguity of the code in the received signal determined in accordance with relation (4), as shown above. After determining the multiple search ranges associated with the multiple assumptions, block 210 may then attempt to correlate the locally generated PN code sequences over the limited search ranges of the code phase, as shown above in relation to relation (5), and select a code phase from the search ranges providing the result maximum correlation, for example.

As indicated above, in addition to detecting the phase of the code, detecting the signal from the GNSS SV may also include detecting and / or measuring the Doppler frequency of the detected signal. According to an alternative embodiment, although the claimed subject matter is not limited in this regard, the reference location estimate 116 may also be used to shorten the detection range of the Doppler frequency of the signal from SV2 in block 210 when a signal is detected after detecting and / or measuring the Doppler frequency of the signal from SV1 in block 202. In accordance with an embodiment, the Doppler frequencies of signals from SV1 and SV2 measured and / or detected at the receiver at a reference location 116 can be expressed as follows:

Where:

ξ is the frequency error of the receiver synchronizer;

TrueDopp _SV1 - the true Doppler frequency of the signal received from SV1 at the reference location;

TrueDopp _SV2 - the true Doppler frequency of the signal received from SV2 at the reference location;

Dopp _SV1 - detected and / or measured Doppler frequency of a signal detected from SV1; and

Dopp _SV2 is the detected and / or measured Doppler frequency of a signal detected from SV2.

In this case, it should be noted that the detected and / or measured Doppler frequency in the signal received from SV2 can be estimated based at least in part on the Doppler frequency detected in the signal from SV1 in accordance with the following relation (6 ):

In this case, it should be noted that relation (6) removes the error component in the frequency of the receiver clock signal. As shown above, the value for Dopp _SV1 can be obtained from detecting a signal from SV1. According to a specific embodiment, values associated with TrueDopp _SV1 and TrueDopp _SV2 can be obtained as estimates of the true Doppler frequency in an AA message provided, for example, as the corresponding centers of the Doppler search windows for SV1 and SV2.

According to an embodiment, the range for finding the Doppler frequency in detecting a signal received from SV2 can be defined as E [Dopp _SV2 ] +/- ε _DoppSV2 , where ε _DoppSV2 contains the one-sided uncertainty of the Doppler frequency of the signal received from SV2 near E [ Dopp _SV2 ]. In accordance with a specific embodiment, although the claimed subject matter is not limited in this regard, ε _DoppSV2 can be determined based at least in part on the uncertainty associated with the accuracy of the reference position of the receiver in accordance with the following relation (7):

Where:

k is a constant linking the position uncertainty along the length to the uncertainty in frequency units (for example, Hz);

A1 is the estimated azimuthal angle for SV1 from the reference location;

A2 is the estimated azimuthal angle for SV2 from the reference location;

E1 is the estimated elevation angle for SV1 from the reference location;

E2 is the estimated elevation angle for SV2 from the reference location; and

Punc - One-sided uncertainty in a reference location in units of length.

In this case, the value for k can be determined using experimental and / or empirical methods. In one particular embodiment, although the claimed subject matter is not limited in this regard, k may presumably have a value of 1.0 Hz per km of uncertainty, for example. However, this is only an example of how the uncertainty in the location can quantitatively affect the uncertainty in the field of Doppler search, and the claimed subject matter is not limited in this regard.

It should be noted that the value of ε _DoppSV2 , as determined in accordance with relation (7), can lead to the Doppler search window, which is larger than the Doppler search window determined in accordance with the information in the AA message. Accordingly, in an alternative embodiment, ε _DoppSV2 can be selected as a minimum:

(i) one-way Doppler search windows provided by information in an AA message; and

(ii) one-way Doppler uncertainty based at least in part on location uncertainty, as shown above in relation (7).

According to an embodiment, the SV visible to the receiver (for example, as indicated in the AA message) may be associated with a specific set of search box parameters defining a two-dimensional region of the code phase and Doppler frequency hypotheses intended to search for SV. In one embodiment shown in FIG. 3, the search window parameters for SV comprise the code phase search window size, WIN_SIZE _CP , the center of the code phase window, WIN_CENT _CP , the size of the Doppler search window, WIN_SIZE _DOPP and the center of the Doppler window, WIN_CENT _DOPP . In the case where the object whose position is sought for determination is a subscriber station in a wireless communication system conforming to the IS-801 standard, these parameters can be indicated by an AA message provided to the subscriber station via PDE.

A two-dimensional search space for SV is shown in FIG. 3 with the phase axis of the code along the horizontal axis and the axis of the Doppler frequency along the vertical axis, but this designation is arbitrary and can be reversed. The center of the code phase search window is designated as WIN_CENT _CP , and the size of the code phase search window is indicated as WIN_SIZE _CP . The center of the Doppler frequency search window is indicated as WIN_CENT _DOPP , and the size of the Doppler frequency search window is indicated as WIN_SIZE _DOPP .

Following the detection of the first signal from the first SV, in accordance with an embodiment, WIN_CENT _CP and WIN_SIZE _CP for detecting the second signal from the second SV can be determined based at least in part on the code phase detected in the first detected signal, the estimate receiver locations and location information for the first and second SV. In this case, the search space for detecting the second signal can be divided into a plurality of segments 1202a, 1202b, 1202c, each of which is characterized by the limits of Doppler frequencies and the limits of code time shifts.

According to an embodiment, when detecting a signal from the second SV, after detecting the first signals from the first SV, it should be understood that WIN_CENT _DOPP can be determined at least partially from E [Dopp _SV2 ] in accordance with the relation (6 ) Similarly, it should be understood that WIN_SIZE _DOPP can be determined, at least in part, from ε _DoppSV2 in accordance with the uncertainty associated with the reference location, as shown above.

According to a specific embodiment, when a single search range is set to detect a phase of a code in a signal received from SV2, it should be understood that WIN_CENT _CP can be determined at least partially in accordance with E [CP ₂ ] defined in accordance with with the ratio (2) or (3), as shown above. Similarly, it should be understood that WIN_SIZE _CP can be determined, at least in part, in accordance with ε _CP2 in accordance with relation (4). In a particular embodiment with a plurality of code hypotheses, as shown above, a plurality of code phase search windows may be defined from a plurality of centers of a code phase window limited by WIN_SIZE _CP . In this case, such code phase search windows can be similarly specified by the WIN_CENT _CP and WIN_SIZE _CP parameters, as shown above.

According to an embodiment, the phase range of the code characterizing the segment may be equal to the channel capacity of the correlator for searching for the segment by passing through one channel. In one specific example, where the channel throughput is thirty-two chips, for example, the phase range of the code characterizing the segment may similarly be thirty-two chips, but keep in mind that other examples are also possible.

Segments can be made overlapping by a predetermined number of chips to avoid skipping peaks that appear at the boundaries of the segment, as shown in FIG. In this case, the end of the segment 1202a is superimposed on the front of the segment 1202b by Δ chips, and the end of segment 1202b is similarly superimposed on the front of segment 1202c by Δ chips. Due to the overlap due to this overlap, the effective code phase range represented by the segment may be less than the channel capacity. In the case where the overlap is four chips, for example, the effective code phase range represented by the segment can be twenty-eight chips.

A system for detecting periodically repeating signals from an SV is shown in FIG. 5 in accordance with a particular embodiment. However, this is only an example of a system that is suitable for detecting such signals in accordance with a specific embodiment, and other systems can be used without deviating from the essence of the invention. As shown in FIG. 5, in accordance with a specific embodiment, such a system may comprise a computing platform including a processor 1302, a memory device 1304, and a correlator 1306. The correlator 1306 may be adapted to generate correlation functions from signals provided by the receiver (not shown), for processing by a processor 1302, either directly or through a memory device 1304. The correlator 1306 may be implemented in hardware, software, or a combination of hardware and rogrammnogo software. However, these are only examples of how the correlator can be implemented in accordance with specific embodiments, and the claimed invention is not limited in this regard.

According to an embodiment, the memory device 1304 may store machine-readable instructions that are accessible and executable by the processor 1302 to provide at least a portion of the computing platform. In this case, the processor 1302 in combination with such computer-readable instructions may be adapted to execute the entire process or parts of the process 200 illustrated above with reference to FIG. 2. In a specific embodiment, although the claimed invention is not limited in this regard, processor 1302 may direct the correlator 1306 to search for position signals, as shown above, and obtain measurements from the correlation functions created by the correlator 1306.

6, the radio transceiver 1406 may be adapted to modulate an RF carrier signal with baseband information, for example, modulate an RF carrier with voice or data, and demodulate a modulated RF carrier to obtain such baseband information. Antenna 1410 may be adapted to transmit a modulated RF carrier over a wireless channel and receive a modulated RF carrier over a wireless channel.

A baseband signal processor 1408 may be adapted to provide baseband information from a CPU 1402 to a transceiver 1406 for transmission over a wireless channel. In this case, the CPU 1402 may receive such baseband information from the data input device within the user interface 1416. The baseband signal processor 1408 may also be adapted to provide baseband information from the transceiver 1406 to the CPU 1402 for transmission through the output device within the user interface 1416.

User interface 1416 may comprise a plurality of devices for inputting or outputting user information, such as voice or data. Such devices may include, for example, a keyboard, a display screen, a microphone, and a speaker.

The receiver 1412 can be adapted to receive and demodulate transmissions from the SV and provide demodulated information to the correlator 1418. The correlator 1418 can be adapted to extract the correlation functions, as shown in relations (1) and (2) above, from the information provided by the receiver 1412. For a given PN code, for example, correlator 1418 can generate a correlation function defined in the code phase range to establish a code phase search window and in the range of Doppler frequency hypotheses, as shown above. Similarly, individual correlation can be performed in accordance with certain parameters of coherent and incoherent integration. The correlator 1418 may also be adapted to extract pilot correlation functions from information related to the pilot signals provided by the transceiver 1406. This information may be used by a subscriber terminal to detect wireless services. The channel decoder 1420 may be adapted to decode channel symbols received from the baseband processor 1408 into the main source bits. In one example, where channel symbols comprise convolutional encoded symbols, such a channel decoder may comprise a Viterbi decoder. In a second example, where the channel symbols comprise sequential or parallel concatenations of the convolutional codes, the channel decoder 1420 may comprise a turbo decoder.

The memory 1404 may be adapted to store machine-readable instructions that are executed to perform one or more of the processes, embodiments, embodiments, or examples thereof that have been described or proposed. A central processing unit, CPU 1402, may be adapted to access and execute such machine-readable instructions. By following these machine-readable instructions, the CPU 1402 can instruct the correlator 1418 to stop executing specific search modes in blocks 204 and 220, analyze the GPS correlation functions provided by the correlator 1418, extract measurements from their peaks, and determine if the location estimate is sufficiently accurate. However, these are only examples of tasks that can be performed by the central processor in a particular embodiment, and the claimed subject matter is not limited in these respects.

In a specific embodiment, the CPU 1402 at the subscriber station may estimate the location of the subscriber station based at least in part on the signals received from the SV, as shown above. The central processor 1402 may also be adapted to determine a code search range for detecting a second received signal, based at least in part on the code phase detected in the first received signals, as shown above in accordance with particular embodiments. It should be understood, however, that these are only examples of position estimation systems based at least in part on pseudorange measurements, quantifying such pseudorange measurements and completing the process to improve the accuracy of pseudorange measurements in accordance with particular embodiments, and what is claimed the invention is not limited in these respects.

Although what constitutes exemplary embodiments has been shown and described, it will be apparent to those skilled in the art that various modifications and equivalent replacements are possible without departing from the spirit of the claimed invention. In addition, many modifications can be made to adapt a particular situation to the principles of the claimed invention, without deviating from the central concept described here. Therefore, it is assumed that the claimed invention is not limited to the specific embodiments disclosed, and may also include all embodiments falling within the scope of the attached claims and their equivalents.

Claims (26)

1. A method of reducing the range for detecting one or more attributes in a satellite system, comprising:
detecting the phase of the first code in the first periodically repeating pseudo-random encoded signal received from the first spacecraft (SV) at a reference location; and
determining a code phase search range for detecting a phase of the second code in a second periodically repeating pseudo-random encoded signal received from the second SV at said reference location based on at least partially said detected code phase of said first received signal, an orbital parameter of said first SV, and the orbital parameter of said second SV, in which the determination of the code phase search range includes:
determining an estimated phase of the code code of the signal received from the second SV based at least in part on the phase of the first code, and
determining the phase ambiguity of the code based at least in part on the orbital parameter of said first SV and the orbital parameter of said second SV. 2. The method according to claim 1, wherein said code phase search range is based at least in part on an estimated elevation angle for said first SV from said reference location and an estimated elevation angle for said second SV from said reference location. 3. The method according to claim 1, wherein said first SV relates to a GPS constellation, and said second SV relates to a Galileo constellation. 4. The method according to claim 1, wherein said detection of said phase of the first code comprises correlating said first signal with a locally generated pseudo-random code sequence associated with said first SV. 5. The method according to claim 1, wherein said reference location comprises estimating a location of a receiver adapted to receive said first and second signals. 6. The method according to claim 5, wherein said code phase search range comprises a predetermined number of chips for the period of said second periodically repeating pseudorandom encoded signal. 7. A method of reducing the range for detecting one or more attributes in a satellite system, comprising:
detecting a phase of a first code of a first periodically repeating pseudorandom encoded signal received from a first spacecraft (SV) at a reference location, said first SV being in an SV constellation in a first Global Navigation Satellite System (GNSS); and
determining a code phase search range for detecting a phase of a second code of a second periodically repeating pseudo-random encoded signal received from the second SV at said reference location based at least in part on said detected phase of the first code, said second SV being in the SV grouping in the second GNSS other than the first GNSS mentioned,
wherein determining the code phase search range includes an estimate of the code phase of the second SV based on the at least partially detected phase of the first code and the difference between the estimated ranges from the reference location for the first and second SV. 8. The method according to claim 7, wherein determining said code search range further comprises determining said code search range based at least in part on the estimated azimuth angle for said first SV from said reference location and the estimated azimuth angle for said second SV from mentioned reference location. 9. The method according to claim 7, wherein said first GNSS comprises GPS, and said second GNSS comprises Galileo GNSS. 10. The method according to claim 7, wherein said first GNSS comprises Galileo, and said second GNSS comprises GPS. 11. The method according to claim 7, wherein said first GNSS comprises Galileo, and said second GNSS comprises Glonass. 12. The method according to claim 7, wherein said first GNSS comprises Glonass, and said second GNSS comprises GPS. 13. The method according to claim 7, wherein said first GNSS comprises GPS, and said second GNSS comprises Glonass. 14. The method according to claim 7, wherein said first GNSS comprises Glonass, and said second GNSS comprises Galileo. 15. The method according to claim 7, wherein said first periodically repeating pseudorandom encoded signal comprises a period shorter than the period of said second periodically repeating pseudorandom signal. 16. A product containing:
a storage medium, said storage medium containing machine-readable instructions for reducing the range for detecting one or more attributes in a satellite system stored on it, and which, when executed by a computing platform, are adapted to induce said computing platform:
determine the phase of the first code in the first periodically repeating pseudo-random encoded signal received from the first spacecraft (SV) at a reference location; and
determine a code phase search range for detecting a second code phase in a second periodically repeating pseudo-random encoded signal received from the second SV at said reference location based on at least partially said detected code phase of said first received signal, orbital parameter of said first SV and orbital a parameter of said second SV, wherein determining the range of the code phase search range includes:
determining an estimated phase of the code code of the signal received from the second SV based at least in part on the phase of the first code, and
determining a phase ambiguity of the code based on at least partially an orbital parameter of said first SV and an orbital parameter of said second SV. 17. The product according to clause 16, wherein said computer-readable instructions, when executed by said computing platform, are further adapted to cause said computing platform to determine said code phase search range based on at least a partially estimated elevation angle for said first SV from said reference location and estimated elevation for said second SV from said reference location. 18. A product containing:
a storage medium, wherein said storage medium contains computer-readable instructions stored thereon to reduce the range for detecting one or more attributes in a satellite system, which, when executed by a computing platform, are adapted to induce said computing platform:
determine the phase of the first code of the first periodically repeating pseudo-random encoded signal received from the first spacecraft (SV) at a reference location, said first SV being in the SV constellation in the first Global Navigation Satellite System (GNSS); and
determine a code phase search range for detecting a phase of a second code of a second periodically repeating pseudo-random encoded signal received from the second SV at said reference location based on at least partially said phase of the first code, said second SV being in the SV grouping in the second GNSS different from said first GNSS, wherein said instructions are adapted to encourage said computing platform to determine a code phase search range by evaluating the phase of and a second SV based at least in part on the sum of the phase of the first code and the difference between the estimated ranges from the reference location for the first and second SV. 19. A subscriber module for reducing the range for detecting one or more attributes in a satellite system, comprising:
a receiver for receiving a discovery support message (AA) containing information showing an orbital parameter of a first spacecraft (SV) and an orbital parameter of a second SV, said subscriber module being adapted to:
detecting the phase of the first code in a first periodically repeating pseudo-random encoded signal received from said first spacecraft (SV) at said reference location; and
determining a code phase search range for detecting a phase of a second code in a second periodically repeating pseudo-random encoded signal received from said second SV at said reference location, based at least in part on said detected phase of the code of said first received signal, said orbital parameter of said first SV and said orbital parameter of said second SV, wherein determining a phase range of a code phase includes:
determining an estimated phase of the code code of the signal received from the second SV based at least in part on the phase of the first code, and
determining a phase ambiguity of the code based on at least partially an orbital parameter of said first SV and an orbital parameter of said second SV. 20. The subscriber module according to claim 19, wherein said subscriber module is further adapted to determine said code phase search range based at least in part on the estimated elevation angle for said first SV from said reference location and the estimated elevation angle for said second SV from said reference location. 21. The subscriber module according to claim 19, wherein said subscriber module is further adapted to receive said AA message over a wireless communication channel. 22. A subscriber module for reducing the range for detecting one or more attributes in a satellite system, comprising:
a receiver for receiving a discovery support message (AA) containing information showing the locations of spacecraft (SV) in two or more Global Navigation Satellite Systems (GNSS), said subscriber unit being adapted to:
detecting a phase of a first code of a first periodically repeating pseudorandom encoded signal received from a first spacecraft (SV) at a reference location, said first SV being in an SV constellation in the first of said GNSSs; and
determining a phase search range of a code for detecting a phase of a second code of a second periodically repeating pseudo-random encoded signal received from the second SV at said reference location based at least in part on said detected phase of the first code, said second SV being in the SV grouping in the second of said GNSS other than said first GNSS, wherein said subscriber unit determines a code phase search range by evaluating a code phase of a second SV based on ve, at least in part of the detected phase of the first code and the difference between the estimated ranges from the reference locations for the first and second SV. 23. The subscriber module of claim 22, wherein said subscriber module is further adapted to receive said AA message over a wireless communication channel. 24. A system for reducing the range for detecting one or more attributes in a satellite system, comprising:
position determination object (PDE) and
a subscriber module, wherein the subscriber module is adapted to:
receiving a discovery support message (AA) from said PDE over a wireless communication channel, said AA message containing information showing an orbital parameter of a first spacecraft (SV) and an orbital parameter of a second SV;
detecting the phase of the first code in a first periodically repeating pseudo-random encoded signal received from said first spacecraft (SV) at said reference location; and
determining a code phase search range for detecting a phase of a second code in a second periodically repeating pseudo-random encoded signal received from said second SV at said reference location, based at least in part on said detected phase of the code of said first received signal, said orbital parameter of said first SV and said orbital parameter of said second SV, wherein determining a phase range of a code phase includes:
determining an estimated phase of the code code of the signal received from the second SV based at least in part on the phase of the first code, and
determining a phase ambiguity of the code based on at least partially an orbital parameter of said first SV and an orbital parameter of said second SV. 25. The system of claim 24, wherein said subscriber unit is further adapted to determine said code phase search range based at least in part on an estimated elevation angle for said first SV from said reference location and an estimated elevation angle for said second SV from mentioned reference location. 26. A system for reducing the range for detecting one or more attributes in a satellite system, comprising:
position determination object (PDE) and
a subscriber module, wherein the subscriber module is adapted to:
receiving a discovery support message (AA) from said PDE over a wireless communication channel, said AA message containing information showing locations of spacecraft (SV) in two or more Global Navigation Satellite Systems (GNSS);
detecting a phase of a first code of a first periodically repeating pseudorandom encoded signal received from a first spacecraft (SV) at a reference location, said first SV being in an SV constellation in the first of said GNSSs; and
determining a phase search range of a code for detecting a phase of a second code of a second periodically repeating pseudo-random encoded signal received from the second SV at said reference location based at least in part on said detected phase of the first code, said second SV being in the SV grouping in the second of said GNSS, which is different from said first GNSS, wherein said subscriber unit is adapted to determine a code phase search range by evaluating a code phase and a second SV based on at least a partially detected phase of the first code and the difference between the estimated ranges from the reference location for the first and second SV.

Images