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DE112008001112T5 - Method and device for determining position without sending ephemeris - Google Patents

Method and device for determining position without sending ephemeris Download PDF

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Publication number
DE112008001112T5
DE112008001112T5DE200811001112DE112008001112TDE112008001112T5DE 112008001112 T5DE112008001112 T5DE 112008001112T5DE 200811001112 DE200811001112 DE 200811001112DE 112008001180012800T800 T800 TDE 1120051180012800
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Germany
Prior art keywords
satellite
receiver
satellite information
parameters
information
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Granted
Application number
DE200811001112
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English (en)
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DE112008001112B9 (de
DE112008001112B4 (de
Inventor
Shaowei Palo Alto Han
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
CSR Technology Holdings Inc
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Sirf Technology Holding Inc
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Publication date
Priority to US11 / 741,448 priority Critical
Priority to US11 / 741,448 priority patent / US7869948B2 / en
Application filed by Sirf Technology Holding IncfiledCriticalSirf Technology Holding Inc
Priority to PCT / US2008 / 061665 priority patent / WO2008134579A1 / en
Publication of DE112008001112T5publicationCriticalpatent / DE112008001112T5 / de
Publication of DE112008001112B4publicationCriticalpatent / DE112008001112B4 / de
Application granted granted Critical
Publication of DE112008001112B9publicationCriticalpatent / DE112008001112B9 / de
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Classifications

    • G — PHYSICS
    • G01 - MEASURING; TESTING
    • G01S — RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S19 / 00 — Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19 / 01 — Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19 / 13 — Receivers
    • G01S19 / 24 — Acquisition or tracking or demodulation of signals transmitted by the system
    • G01S19 / 25 — Acquisition or tracking or demodulation of signals transmitted by the system involving aiding data received from a cooperating element, e.g. assisted GPS
    • G — PHYSICS
    • G01 - MEASURING; TESTING
    • G01S — RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S19 / 00 — Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19 / 01 — Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19 / 13 — Receivers
    • G01S19 / 24 — Acquisition or tracking or demodulation of signals transmitted by the system
    • G01S19 / 27 — Acquisition or tracking or demodulation of signals transmitted by the system creating, predicting or correcting ephemeris or almanac data within the receiver

Abstract

Description

  • The present invention relates generally to navigation receivers, and more particularly to systems and methods that assist navigation receivers in determining their position without the immediate need to broadcast ephemeris.
  • Background of the invention
  • With the development of radio and space technologies, various satellite-based navigation systems have already been built, and several will be in use in the near future. One example of such satellite-based navigation systems is the Global Positioning System (GPS), which was built and operated by the US Department of Defense. The system uses 24 or more satellites orbiting the earth at an altitude of approximately 11,000 miles with a time period of approximately 12 hours. These satellites are placed in six different orbits of the earth in such a way that at any point in time at least six satellites are visible anywhere on the earth's surface, except in the polar region. Each satellite sends a time and position signal that is related to an atomic clock. A typical GPS receiver locks onto this signal and extracts the data it contains. Using signals from a sufficient number of satellites, a GPS receiver can calculate its position, speed, altitude and time.
  • A GPS receiver must acquire and lock at least four satellite signals in order to derive the position and the time. Typically, a GPS receiver has many parallel channels, with each channel receiving signals from a visible GPS satellite. The acquisition of the satellite signals comprises a two-dimensional search for a carrier frequency and the pseudo-random number (PRN) code phase. Each satellite broadcasts signals using a unique 1023 chip PRN code that repeats every millisecond. The receiver locally generates a carrier replica to mask out a residual carrier frequency, and a PRN code replica sequence for correlation with the digitized received satellite signal sequence. During the acquisition stage, the code phase search step is half a chip for most navigation satellite signal receivers. Thus, the full code phase search area 2046 contains candidate code phases spaced half a chip interval. The carrier frequency search range depends on the Doppler frequency due to the relative movement between the satellite and the receiver. An additional frequency deviation can result from instability of the local oscillator.
  • Coherent integration and non-coherent integration are two commonly used integration methods for acquiring GPS signals. The coherent integration provides better signal amplification at the expense of a greater computational load for the same integration times.
  • The signals from the navigation satellites are modulated with navigation data at 50 bits / second. This data includes the ephemeris, almanac, time information, clock and other correction coefficients. This data stream is formatted as sub-frames, frames, and super-frames. A sub-frame consists of 300 bits of data and is sent for six seconds. In this sub-frame, a group of 30 bits forms a word, the last six bits being the parity check bits. As a result, one sub-frame consists of 10 words. A frame of data consists of five sub-frames that are sent over 30 seconds. A super frame consists of 25 frames that are sent in sequence over 12.5 minutes.
  • The first word of a sub-frame is always the same and is known as the TLM word, and the first eight bits of this TLM word are preamble bits which are used for frame synchronization. A Barker sequence is used as the preamble because of its excellent correlation properties. The other bits of this first word contain telemetry bits and are not used in the position calculation. The second word of each frame is the HOW (Hand Over Word) word and consists of TOW (Time Of Week), a sub-frame ID, a synchronization flag and a parity, whereby the last two parity bits are always "0". These two "0" s help identify the correct polarity of the navigation data bits. Words 3 to 10 of the first sub-frame contain clock correction coefficients and satellite quality indicators. The 3 to 10 words of sub-frames 2 and 3 contain the ephemeris. These ephemeris are used to precisely determine the position of the GPS satellites. These ephemeris are uploaded every two hours and are valid for four to six hours. The 3 to 10 words of sub-frame 4 contain ionospheric and UTC time corrections and the almanacs of satellites 25 to 32. These almanacs are similar to the ephemeris, but provide a less precise position of the satellites and are valid for six days. The 3 to 10 words of sub-frame 5 only contain the almanacs of different satellites in different frames.
  • The super frame contains 25 consecutive frames. While the contents of sub-frames 1, 2 and 3 repeat in every frame of a super-frame, except for TOW and an occasional change in the ephemeris every two hours. Consequently, the ephemeris of a particular signal from a satellite contains only that satellite's ephemeris, which is repeated in each sub-frame. However, the almanacs of different satellites are sequentially broadcast in different frames of the navigation data signal of a given satellite. Thus, the 25 frames transmit the almanacs of all 24 satellites in sub-frame 5. Any additional spare satellite almanacs are included in sub-frame 4.