GNSS RECEIVER AND OPERATING METHOD

• US 20120188124A1
• Filed: 06/29/2009
• Published: 07/26/2012
• Est. Priority Date: 06/29/2009
• Status: Abandoned Application

• Current Assignee: Qualcomm technologies international, ltd. (Qualcomm, Inc.)
• Original Assignee: Qualcomm technologies international, ltd. (Qualcomm, Inc.)
• Inventors: Mitelman, Alexander Michael, Reidevall, Martin Borjesson, Hakanson, Mats Robin
• Application Number:
  US13/322,865
• Publication Number:
  US 20120188124A1
• Time in Patent Office: Days
• US Class Current: 342/357.67
• CPC Class Codes: G01S 19/22 Multipath-related issues
• CPC Class Codes: G01S 19/258 relating to the satellite constellation, e.g. almanac, ephemeris data, lists of satellites in view
• CPC Class Codes: G01S 19/28 Satellite selection

Abstract

A GNSS receiver (100) receives radio signals (S(SV)) transmitted from an active set of signal sources (SV1, SV2, SV3, SV5) and based thereon produces position/time related data (D_PT). The receiver (100) has a tracking channel resource for each signal source (SV1, SV2, SV3, SV5) in the active set, and the tracking channel resources process the radio signals (S(SV)) in parallel with respect to a real-time signal data rate of the signals. The receiver (100) also includes a signal-source database (140), a signal-masking database (150) and a control unit (130). The signal-source database (140) describes the movements of the signal sources (SV1, SV2, SV3, SV4, SV5) over time relative to a given reference frame, and the signal-masking database (150) reflects, for positions (P) within a predefined geographic area, visibility/blockage to the sky with respect to a direct line of sight in terms of spatial sectors (M₁(P), M₂(P) M₃(P)). The control unit (130) derives data describing a current position/time (PT_R(t)) and a current velocity vector (V_R(t)) for the receiver (100) based on the position/time related data (D_PT); and derives an estimated visibility of the signal sources (SV1, SV2, SV3, SV5) in the active set at a second position/time (PT_R(t+Δt)) representing an expected future position/time for the receiver (100) based on the signal-source and signal-masking databases (140; 150). If at least one signal source (SV1) in the active set is estimated not to be visible at the second position/time (PT_R(t+Δt)), the control unit (130) initiates a modification of the active set aiming at replacing the at least one non-visible signal source (SV1) with at least one signal source (SV4) which, based on the signal-source and signal-masking databases (140; 150), is estimated to be visible at the second position/time (PT_R(t+Δt)).

Claims

1. A GNSS receiver adapted to process radio signals transmitted from an active set of signal sources and based thereon produce position/time related data, the receiver comprising a tracking channel resource for each signal source in the active set, the tracking channel resources being configured to process the radio signals in parallel with respect to a real-time signal data rate of the signals, the receiver comprising a signal-source database describing the movements of the signal sources over time relative to a given reference frame, the active set of signal sources being a subset of the signal sources described in the signal-source database,

wherein the receiver further comprises:

a signal-masking database reflecting, for positions within a predefined geographic area, visibility/blockage to the sky with respect to a direct line of sight in terms of spatial sectors, and

a control unit configured to;

derive data describing a current position/time and a current velocity vector for the receiver based on the position/time related data,

derive an estimated visibility of the signal sources in the active set at a second position/time representing an expected future position/time for the receiver based on the signal-source and signal-masking databases, and if at least one signal source in the active set is estimated not to be visible at the second position/time

initiate a modification of the active set aiming at replacing the at least one non-visible signal source with at least one signal source which, based on the signal-source and signal-masking databases, is estimated to be visible at the second position/time.

2. The receiver according to claim 1, wherein the control unit is configured to initiate the modification of the active set before the receiver reaches the second position/time.

3. The receiver according to claim 1, wherein the control unit is configured to repeatedly update the signal-source database based on received orbital data describing the movements of the signal sources.

4. The receiver according to claim 3, wherein the orbital data comprises at least one of ephemeris data and almanac data.

5. The receiver according to claim 1, wherein the control unit is configured to implement a ray-tracing algorithm in conjunction with information from the signal-source and signal-masking databases to estimate whether or not a signal source is visible at a given position/time.

6. The receiver according to claim 1, comprising a signal processing unit is which configured to implement the control unit.

7. The receiver according to claim 1, comprising a signal processing unit which is at least partly implemented in software running on a processor.

8. The receiver according to claim 1, comprising a calculator module configured to derive a first part of the signal-masking database based on an altimetric database describing in three dimensions respective positions and extensions of stationary objects on Earth which objects may potentially intersect a signal transmission path between a signal source in the GNSS and the receiver.

9. The receiver according to claim 8, wherein the calculator module is configured to derive at least one second part of the signal-masking database based on measurements in respect of signal sources in the GNSS from which signals have been received in at least one geographic position.

10. A method of operating a GNSS receiver, the method comprising processing radio signals transmitted from an active set of signal sources and based thereon producing position/time related data, the receiver comprising a tracking channel resource for each signal source in the active set, and the tracking channel resources being configured to process the radio signals in parallel with respect to a real-time signal data rate of the signals, the method further comprising:

deriving data describing a current position/time and a current velocity vector for the receiver based on the position/time related data,

deriving an estimated visibility of the signal sources in the active set at a second position/time representing an expected future position/time for the receiver by consulting a signal-source database a signal-masking database reflecting, for positions within a predefined geographic area, visibility/blockage to the sky with respect to a direct line of sight in terms of spatial sectors, and if at least one signal source in the active set is estimated not to be visible at the second position/time

initiating a modification of the active set to replace the at least one signal source that is expected not to be visible at the second position/time with at least one signal source which, based on the signal-source and signal-masking databases, is estimated to be visible at the future position/time.

11. The method according to claim 10, comprising initiating the modification of the active set before the receiver reaches the second position/time.

12. The method according to claim 10, comprising updating repeatedly the signal-source database based on received orbital data describing the movements of the signal sources.

13. The method according to claim 12, wherein the orbital data comprises at least one of ephemeris data and almanac data.

14. The method according to claim 10, comprising estimating whether or not a signal source is visible at a given position/time based on a ray-tracing algorithm ray-tracing algorithm in conjunction with information from the signal-source and signal-masking databases.

15. The method according to claim 10, comprising deriving a first part of the signal-masking database based on a topographic database describing in three dimensions respective positions and extensions of stationary objects on Earth which objects may potentially intersect a signal transmission path between a signal source in the GNSS and the receiver.

16. The method according to claim 15, comprising deriving at least one second part of the signal-masking database based on measurements in respect of signal sources in the GNSS from which signals have been received in at least one geographic position.

17. A computer program loadable into the memory of a computer, comprising software for controlling the steps of the method of claim 10 when said program is run on the computer.

18. A computer readable medium, having a program recorded thereon, where the program is to make a computer control the steps of the method of claim 10 when the program is loaded into the computer.