Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
  • H04K3/00—Jamming of communication; Counter-measures
  • H04K3/20—Countermeasures against jamming
  • H04K3/22—Countermeasures against jamming including jamming detection and monitoring
  • H04K3/224—Countermeasures against jamming including jamming detection and monitoring with countermeasures at transmission and/or reception of the jammed signal, e.g. stopping operation of transmitter or receiver, nulling or enhancing transmitted power in direction of or at frequency of jammer
  • H04K3/228—Elimination in the received signal of jamming or of data corrupted by jamming
• • 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
  • G01S19/21—Interference related issues ; Issues related to cross-correlation, spoofing or other methods of denial of service
• • 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
  • G01S19/23—Testing, monitoring, correcting or calibrating of receiver elements
• • 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
• • 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
  • G01S19/35—Constructional details or hardware or software details of the signal processing chain
  • G01S19/37—Hardware or software details of the signal processing chain

Definitions

• This invention relates to a method of processing a sampled signal stream containing at least one spread spectrum signal together with a receiver, computer, computer-readable storage medium and computer program for the same.
• GPS receivers conventionally have a single analog to digital converter (ADC) for sampling GPS received GPS signals at a fixed resolution.
• ADC analog to digital converter
• Such ADCs have a 1-bit resolution but as inadvertent narrowband jamming is particularly common, for example, in an indoor environment from mobile phones, PCs and other electrical equipment, some GPS receivers use ADCs having 1.5 or 2 bit resolutions for improved jamming immunity.
• multi-bit sampling can mitigate multipath distortion which can be encountered when attempting to measure GPS pseudorange in a urban environment, i.e. when GPS signals take an indirect route to a GPS receiver having been reflected by nearby buildings.
• a method of processing a sampled signal stream containing at least one spread spectrum signal is provided together with a receiver, computer, computer-readable storage medium and computer program for the same.
• the method comprises the steps of processing samples at a first bit level and, either in parallel or subsequently, processing samples at a second bit level, different from the first bit level.
• the signal stream may be sampled at a higher bit level than at least one of the first or second bit levels wherein the samples are processed at one of either the first or second bit levels by selectively ignoring bits of the signal samples.
• the signal stream may be sampled at a varying bit level of either first or second bit levels corresponding to the bit level at which those samples will be processed.
• the samples may be processed in parallel at first and second bit levels for the purposes of acquiring either respective spread spectrum signals or the same spread spectrum signal. A change from processing the samples at the first bit level to the second bit level may occur upon experiencing difficulty acquiring a spread spectrum signal. If the signal stream contains a GPS spread spectrum signal, the step of processing samples at a first bit level may be used to acquire the GPS signal and the step of processing samples at a second bit level may be used to measure a pseudorange from the GPS signal.
• a GPS receiver is shown in which NAVSTAR GPS SPS signals are received by an antenna 10 and pre- processed in a pre-processor 11 including passive bandpass filtering in order to minimise out-of-band RF interference, preamplification, down converting to an intermediate frequency (IF) and analog to digital conversion.
• the resultant, digitised IF signal remains modulated, still containing all the information from the available satellites, and is fed into each of twelve parallel receiver channels 12 (not all channels shown).
• the satellite signals are acquired and tracked in respective digital receiver channels in co-operation with the receiver processor 13 for the purpose of retrieving the 30 second GPS ephemeris data message and measuring pseudoranges from each satellite.
• the navigation processor 14 uses the GPS pseudoranges, acquired navigation information and the time of arrival of the transmissions to calculate the position of the receiver using conventional algorithms and that position is displayed on a display 15 to the user.
• the pre-processor 11 will be typically implemented in the form of front end analogue circuitry with the digital receiver channels 12, the receiver processor 13 and the navigation processor 14 implemented in the form of a general purpose microprocessor or a microprocessor embedded in a GPS application specific integrated circuit (ASIC).
• ASIC application specific integrated circuit
• the analog to digital conversion and the acquisition and tracked of the digitised signal in the digital receiver channels may be done as described in either of the following example scenarios:
• Example 1 When operating in a urban environment, the GPS receiver uses realtime 1-bit sampling and processing in the digital receiver channels to acquire 3 of the 4 GPS signals necessary to determine a position fix. In order to acquire a 4 th GPS signal, the ADC switches to real-time 2-bit sampling and processing in the digital receiver channels. The improved signal acquisition performance enables a 4 th GPS signal to be acquired. Thereafter, pseudoranges from the 4 acquired GPS signals are measured to determine a position fix.
• Example 2 A snapshot of 1s of GPS signal data is sampled at 2-bit quantization (sign and magnitude bits representing -2, -1 , 1 , 2) and stored. Thereafter, the snapshot is repetitively subjected to 1 bit processing of the sign bit only in the digital receiver to acquired 4 GPS signals. Once the 4 GPS signals are acquired, the snapshot is subjected to 2 bit processing in the digital receiver channels to measure the 4 GPS pseudoranges necessary to determine a position fix.

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• Engineering & Computer Science (AREA)
• Radar, Positioning & Navigation (AREA)
• Remote Sensing (AREA)
• Computer Networks & Wireless Communication (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Signal Processing (AREA)
• Position Fixing By Use Of Radio Waves (AREA)

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Publications (1)

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Family Applications (1)

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Citations (4)

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• 2003
  • 2003-08-06 GB GBGB0318386.0A patent/GB0318386D0/en not_active Ceased
• 2004
  • 2004-07-30 WO PCT/IB2004/002576 patent/WO2005015255A1/en not_active Ceased
  • 2004-07-30 CN CN200480022389A patent/CN100575982C/zh not_active Expired - Fee Related
  • 2004-07-30 US US10/567,208 patent/US7539276B2/en not_active Expired - Lifetime
  • 2004-07-30 EP EP04744215A patent/EP1654555B1/en not_active Expired - Lifetime
  • 2004-07-30 JP JP2006522440A patent/JP4805149B2/ja not_active Expired - Fee Related

Patent Citations (4)

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