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EP-4113172-B1 - METHOD FOR PERFORMING A PARALLEL SEARCH, RECEIVER, COMPUTER PROGRAM PRODUCT AND NON-VOLATILE STORAGE MEDIUM

EP4113172B1EP 4113172 B1EP4113172 B1EP 4113172B1EP-4113172-B1

Inventors

  • Jin, Boming
  • LEVOLA, Aku

Dates

Publication Date
20260506
Application Date
20210701

Claims (11)

  1. Method (100) for performing a parallel search for a first positioning fix in a Global Navigation Satellite System, GNSS, receiver, and the method (100) comprises the steps of: - determining (102) prepositioning information, wherein the prepositioning information comprises a receiver information and a satellite information for each satellite in a plurality of satellites, - determining (103) a code phase search range (201) and a frequency search range (202), based on the prepositioning information, for each satellite in the plurality of satellites, - determining (104) a search starting point information for each satellite in the plurality of satellites, wherein each respective search starting point information is representative of an offset from a center of a search range of the respective satellite, and - performing (105) the parallel search for all satellites in the plurality of satellites based on the respective code phase search range (201), the respective frequency search range (202) and the respective search starting point information; wherein - the offsets from the centers of the search ranges of the plurality of satellites are uniformly distributed in a common mode search range which is a subset of the respective search range, and - the determining the search starting point information for each satellite in the plurality of satellites comprises determining the search starting point information according to the formula: s k = E ∗ 2 k N + 1 − 1 wherein s k denotes the search starting point information for a satellite k, wherein k is a number between 1 and N N denotes the number of satellites in the plurality of satellites, and [ -E,E ] denotes the common mode search range; or - the offsets from the centers of the search ranges of the plurality of satellites are uniformly distributed in the common mode search range, and - the determining the search starting point information for each satellite in the plurality of satellites comprises determining the search starting point information based on a binary tree; or - the offsets from the centers of the search ranges of the plurality of satellites are uniformly distributed in the common mode search range, and - the determining the search starting point information for each satellite in the plurality of satellites comprises determining the search starting point information based on a pseudo random number generator; or - the offsets from the centers of the search ranges of the plurality of satellites follow a Gaussian distribution of an equal variance, and - the determining the search starting point information for each satellite in the plurality of satellites comprises determining the search starting point information based on the Gaussian distribution.
  2. The method (100) according to claim 1, wherein the determining (102) the prepositioning information comprises: - obtaining a first time information, and - determining at least part of the prepositioning information based on the first time information.
  3. The method (100) according to any of claims 1 or 2, wherein at least part of the prepositioning information is received from a device external to the GNSS receiver.
  4. The method (100) according to any of claims 1 to 3, wherein each search starting point information comprises a first search starting point information, which is representative of an offset from a center of the code phase search range (201) of the respective satellite.
  5. The method (100) according to any of claims 1 to 4, wherein each search starting point information comprises a second search starting point information, which is representative of an offset from a center of the frequency search range (202) of the respective satellite.
  6. The method (100) according to any of claims 1 to 5, wherein the method (100) further comprises: - detecting (106) a first satellite in the plurality of satellites based on the parallel search, and - determining (107) a further prepositioning information based on the detection of the first satellite.
  7. The method (100) according to claim 6, wherein the method (100) further comprises performing (108) a further parallel search for a subset of satellites in the plurality of satellites based on the further prepositioning information.
  8. The method (100) according to any of claims 1 to 7, wherein before determining the prepositioning information, the method (100) further comprises obtaining (101) valid satellite orbit information and an uncertainty window of a position of the GNSS receiver.
  9. A GNSS receiver, comprising a processing unit which is configured to perform the method (100) according to any of claims 1 to 8.
  10. A computer program product comprising instructions which, when executed by a computing device, cause the computing device to carry out the method (100) according to any of claims 1 to 8.
  11. A non-volatile storage medium comprising a computer program product according to claim 10.

Description

TECHNICAL FIELD This disclosure relates to a method performing a parallel search for a first positioning fix in a Global Navigation Satellite System, GNSS, receiver. The disclosure further relates to a GNSS receiver comprising a processing unit. The disclosure also relates to a computer program product and a non-volatile storage medium. BACKGROUND ART A Global Navigation Satellite System, GNSS, receiver can be used for positioning. Therefore, a satellite search process needs to be performed, such as a serial search scheme or a parallel search scheme, in order to obtain a first positioning fix. When a GNSS receiver is powered on, it may use prepositioning information when aiming to obtain a first positioning fix. It is an object of the present disclosure to present a method, a receiver, a computer program product and a non-volatile storage medium, in which a reliable and time efficient parallel search for a first positioning fix is provided. US 2009/0315768 A1 describes a method and an apparatus for processing satellite positioning system signals. Assistance data is received at a mobile receiver from a first wireless network. A time synchronization signal is obtained from a second wireless network at the mobile receiver. A time offset is determined in response to the time synchronization signal. Satellite signals are processed at the mobile receiver using the assistance data and the time offset. SUMMARY OF INVENTION The invention is set out in the appended set of claims. The above-mentioned object is solved by the subject-matter of the attached independent claims. Further embodiments are disclosed in the attached dependent claims. A detection of a satellite is based on time synchronization, which relies on alignment of received and locally generated pseudorandom codes. The GNSS receiver aims to synchronize the received and locally generated identical codes by determining a time shift that results in perfectly time-aligned sequences. The time shift may also be denoted as code phase. In satellite navigation technology, time and position (range) are often interchangeable. A range can be expressed in time units by dividing it by the speed of light. Conversely, time can be expressed in range units when multiplied by the speed of light. Therefore, the code phase search consists of both time and position quantities. When powering on the GNSS receiver, unknown time and range (error) terms obtained by the GNSS receiver may comprise: a local time bias of the GNSS receiver, an approximate location of the GNSS receiver, an information about a position of one or more satellites, atmospheric propagation delays, reflections and/or receiver hardware delays. Similar to time synchronization, the GNSS receiver aims to synchronize to a frequency of a received signal by generating a local copy of it at substantially a same frequency as the received signal. At any relative movement between the signal source, i.e., the respective satellite, and the receiver a Doppler shift is implied. Similarly to time and range, clock drift and velocity may be considered interchangeable. Any deviation in the GNSS receiver's reference oscillator frequency may translate into an apparent Doppler shift in a frequency synchronization process. When powering on the GNSS receiver further unknown (error) terms may comprise a clock drift of the GNSS receiver and a velocity of the GNSS receiver relative to Earth. These (error) terms, which may affect the frequency synchronization are fewer in number and lesser in magnitude than the (error) terms with regard to the code phase synchronization. Therefore, the code synchronization problem may be more complex than frequency synchronization. However, the concepts laid out in the following are applicable to both code phase and frequency search. An advantage of the method according to the first aspect is that a reliable and time efficient parallel search for the first positioning fix may be provided. The method according to the first aspect may be applied, when the GNSS receiver is powered on/started. In this situation, the GNSS receiver needs to obtain the first positioning fix. The GNSS receiver may be an arbitrary GNSS receiver capable of using one or more of the available GNSS constellations when performing the method according to the first aspect. In other words, the GNSS receiver may be a multi GNSS receiver. The parallel search may also be denoted as parallel search scheme. When performing the parallel search, each satellite or signal is searched simultaneously by respective hardware and software resources, i.e., search units, of the GNSS receiver. According to the first aspect, a time for detecting a first satellite in the plurality of satellites, and consequently a time for obtaining the first positioning fix, may be reduced by adding controlled satellite specific offsets in the parallel search. For example, if the plurality of satellites comprises a number of N satellites, such a reduction may be achieved