EP1454487A1 - Utilisation de signaux de televison numerique permettant d'obtenir des informations d'assistance de gps - Google Patents

Utilisation de signaux de televison numerique permettant d'obtenir des informations d'assistance de gps

Info

Publication number
EP1454487A1
EP1454487A1 EP02795623A EP02795623A EP1454487A1 EP 1454487 A1 EP1454487 A1 EP 1454487A1 EP 02795623 A EP02795623 A EP 02795623A EP 02795623 A EP02795623 A EP 02795623A EP 1454487 A1 EP1454487 A1 EP 1454487A1
Authority
EP
European Patent Office
Prior art keywords
positioning system
satellite positioning
satellite
signal
digital television
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP02795623A
Other languages
German (de)
English (en)
Inventor
Matthew Rabinowitz
James J. Spilker, Jr.
Jimmy K. Omura
Matthew D. Pierce
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.)
Rosum Corp
Original Assignee
Rosum Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US10/003,128 external-priority patent/US7042949B1/en
Application filed by Rosum Corp filed Critical Rosum Corp
Publication of EP1454487A1 publication Critical patent/EP1454487A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N7/00—Television systems
    • H04N7/12—Systems in which the television signal is transmitted via one channel or a plurality of parallel channels, the bandwidth of each channel being less than the bandwidth of the television signal
    • 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
    • G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S5/0009—Transmission of position information to remote stations
    • G01S5/0018—Transmission from mobile station to base station
    • G01S5/0036—Transmission from mobile station to base station of measured values, i.e. measurement on mobile and position calculation on base station
    • 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
    • G01S19/03—Cooperating elements; Interaction or communication between different cooperating elements or between cooperating elements and receivers
    • G01S19/05—Cooperating elements; Interaction or communication between different cooperating elements or between cooperating elements and receivers providing aiding data
    • 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
    • G01S19/38—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system
    • G01S19/39—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/42—Determining position
    • G01S19/45—Determining position by combining measurements of signals from the satellite radio beacon positioning system with a supplementary measurement
    • G01S19/46—Determining position by combining measurements of signals from the satellite radio beacon positioning system with a supplementary measurement the supplementary measurement being of a radio-wave signal type
    • 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
    • G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S5/0009—Transmission of position information to remote stations
    • G01S5/0045—Transmission from base station to mobile station
    • G01S5/0054—Transmission from base station to mobile station of actual mobile position, i.e. position calculation on base station
    • 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
    • G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S5/0009—Transmission of position information to remote stations
    • G01S5/0081—Transmission between base stations
    • 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
    • G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S5/02—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using radio waves
    • G01S5/0205—Details
    • G01S5/021—Calibration, monitoring or correction
    • 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
    • G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S5/02—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using radio waves
    • G01S5/14—Determining absolute distances from a plurality of spaced points of known location
    • 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
    • G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S5/02—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using radio waves
    • G01S5/14—Determining absolute distances from a plurality of spaced points of known location
    • G01S5/145—Using a supplementary range measurement, e.g. based on pseudo-range measurements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/20—Servers specifically adapted for the distribution of content, e.g. VOD servers; Operations thereof
    • H04N21/23—Processing of content or additional data; Elementary server operations; Server middleware
    • H04N21/235—Processing of additional data, e.g. scrambling of additional data or processing content descriptors
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
    • H04N21/43—Processing of content or additional data, e.g. demultiplexing additional data from a digital video stream; Elementary client operations, e.g. monitoring of home network or synchronising decoder's clock; Client middleware
    • H04N21/435—Processing of additional data, e.g. decrypting of additional data, reconstructing software from modules extracted from the transport stream
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/80—Generation or processing of content or additional data by content creator independently of the distribution process; Content per se
    • H04N21/81—Monomedia components thereof
    • H04N21/8126—Monomedia components thereof involving additional data, e.g. news, sports, stocks, weather forecasts
    • 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
    • G01S19/03—Cooperating elements; Interaction or communication between different cooperating elements or between cooperating elements and receivers
    • G01S19/09—Cooperating elements; Interaction or communication between different cooperating elements or between cooperating elements and receivers providing processing capability normally carried out by the receiver
    • 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
    • G01S19/03—Cooperating elements; Interaction or communication between different cooperating elements or between cooperating elements and receivers
    • G01S19/10—Cooperating elements; Interaction or communication between different cooperating elements or between cooperating elements and receivers providing dedicated supplementary positioning signals
    • 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
    • G01S19/254—Acquisition or tracking or demodulation of signals transmitted by the system involving aiding data received from a cooperating element, e.g. assisted GPS relating to Doppler shift of satellite signals
    • 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
    • G01S19/256—Acquisition or tracking or demodulation of signals transmitted by the system involving aiding data received from a cooperating element, e.g. assisted GPS relating to timing, e.g. time of week, code phase, timing offset
    • 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
    • G01S19/258—Acquisition or tracking or demodulation of signals transmitted by the system involving aiding data received from a cooperating element, e.g. assisted GPS relating to the satellite constellation, e.g. almanac, ephemeris data, lists of satellites in view

Definitions

  • This invention relates generally to the transmission of data via broadcast digital television signals, for example digital television signals which follow the American Television Standards Committee (ATSC) format, and more particularly to the transmission of global positioning system (GPS) aiding information by such techniques.
  • ATSC American Television Standards Committee
  • GPS global positioning system
  • ATSC Advanced Television Systems Committee
  • VSB amplitude modulated suppressed-carrier vestigial sideband modulation technique
  • the ATSC standard is geared towards a certain spectral efficiency, meaning that a certain amount of information is to be transmitted over a certain spectral bandwidth.
  • a bit rate which is high enough to support the broadcast of television programming must fit into the bandwidth allocated for a single television channel.
  • a certain signal to noise ratio is required in order to successfully receive the broadcast signal.
  • the 19.2 Mbps ATSC standard broadcast data rate requires the receiver to have a theoretical signal-to-noise ratio of 15 dB.
  • the invention features a method, apparatus, and computer-readable media for providing satellite positioning system aiding information to a satellite positioning system receiver configured to determine the position of the satellite positioning system receiver using the satellite positioning system aiding information and the propagation time of a signal transmitted by a satellite in the satellite positioning system. It comprises providing the satellite positioning system aiding information; providing a digital television signal comprising a plurality of frames, each frame comprising a plurality of data segments; encoding the satellite positioning system aiding information as codewords; replacing data segments within the digital television signal with the codewords; and transmitting the digital television signal; wherein the satellite positioning system receiver receives the digital television signal and recovers the satellite positioning system aiding information.
  • the satellite positioning system is the global positioning system (GPS).
  • the satellite positioning system receiver determines the position of the satellite positioning system receiver based on the signal received from the satellite positioning system satellite and the satellite positioning system aiding information.
  • the satellite positioning system aiding information comprises at least one of the group comprising a position of the satellite positioning system satellite; clock correction information for the satellite positioning system satellite; Doppler information for the signals transmitted by the satellite positioning system satellite; information regarding atmospheric effects on the signal transmitted by the satellite positioning system satellite; and identification of the satellite positioning system satellites that are visible to the satellite positioning system receiver.
  • the digital television signal comprises at least one of the group comprising an American Television Standards Committee (ATSC) digital television signal; a European Telecommunications Standards Institute (ETSI) Digital Video Broadcasting - Terrestrial (DVB-T) signal; and a Japanese Integrated Services Digital Broadcasting-Terrestrial (ISDB-T) signal.
  • ATSC American Television Standards Committee
  • ETSI European Telecommunications Standards Institute
  • DVB-T Digital Video Broadcasting - Terrestrial
  • ISDB-T Japanese Integrated Services Digital Broadcasting-Terrestrial
  • the satellite positioning system is the global positioning system (GPS).
  • GPS global positioning system
  • the satellite positioning system receiver determines the position of the satellite positioning system receiver based on the signal received from the satellite positioning system satellite and the satellite positioning system aiding information.
  • the satellite positioning system aiding information comprises at least one of the group comprising a position of the satellite positioning system satellite; clock correction information for the satellite positioning system satellite; Doppler information for the signals transmitted by the satellite positioning system satellite; information regarding atmospheric effects on the signal transmitted by the satellite positioning system satellite; and identification of the satellite positioning system satellites that are visible to the satellite positioning system receiver.
  • the digital television signal comprises at least one of the group comprising an American Television Standards Committee (ATSC) digital television signal; a European Telecommunications Standards Institute (ETSI) Digital Video Broadcasting - Terrestrial (DVB-T) signal; and a Japanese Integrated Services Digital Broadcasting-Terrestrial (ISDB-T) signal.
  • ATSC American Television Standards Committee
  • ETSI European Telecommunications Standards Institute
  • DVD-T Digital Video Broadcasting - Terrestrial
  • ISDB-T Japanese Integrated Services Digital Broadcasting-Terrestrial
  • the invention features a method, apparatus, and computer-readable media for determining a position of a satellite positioning system receiver using a satellite positioning system. It comprises receiving at the satellite positioning system receiver a signal transmitted by a satellite in the satellite positioning system; receiving at the satellite positioning system receiver a digital television signal comprising a plurality of frames, each frame comprising a plurality of data segments, wherein at least one data segment has been replaced by at least one codeword representing satellite positioning system aiding information; selecting the data segments which have been replaced by codewords; recovering the satellite positioning system aiding information from the selected data segments; and detennining a position of the satellite positioning system receiver based on the signal received from the satellite positioning system satellite and the satellite positioning system aiding information.
  • the satellite positioning system is the global positioning system (GPS).
  • the satellite positioning system aiding information comprises at least one of the group comprising a position of the satellite positioning system satellite; clock correction information for the satellite positioning system satellite; Doppler information for the signals transmitted by the satellite positioning system satellite; information regarding atmospheric effects on the signal transmitted by the satellite positioning system satellite; and identification of the satellite positioning system satellites that are visible to the satellite positioning system receiver.
  • the digital television signal comprises at least one of the group comprising an American Television Standards Committee (ATSC) digital television signal; a European Telecommunications Standards Institute (ETSI) Digital Video Broadcasting - Terrestrial (DVB-T) signal; and a Japanese Integrated Services Digital Broadcasting-Terrestrial (ISDB-T) signal.
  • Implementations comprise determining a pseudo-range between the satellite positioning system receiver and a transmitter of the Atty. Docket No. RSM027W01 -5- digital television signal based on a known component of the digital television signal; and determining a position of the satellite positioning system receiver based on the pseudo- range, the signal received from the satellite positioning system satellite and the satellite positioning system aiding information.
  • digital data is transmitted as part of a digital television (DTV) broadcast signal by encoding the digital data as codewords and replacing some of the data segments in the DTV signal with the codewords.
  • DTV digital television
  • the use of long codewords results in a transmission which is more robust than the portions of the DTV broadcast signal used for television programming and can therefore be received at lower signal to noise ratios.
  • the use of a finite set of codewords allows recovery of the digital data using a simple bank of correlators at the receiver.
  • the invention features an apparatus for providing satellite positioning system aiding information to a satellite positioning system receiver configured to determine the position of the satellite positioning system receiver using the satellite positioning system aiding information and the propagation time of a signal transmitted by a satellite in the satellite positioning system.
  • the satellite positioning system is the global positioning system (GPS).
  • the satellite positioning system receiver determines the position of the satellite positioning system receiver based on the signal received from the satellite positioning system satellite and the satellite positioning system aiding information.
  • the satellite positioning system aiding information comprises at least one of the group comprising a position of the satellite positioning system satellite; clock correction information for the satellite positioning system satellite; Doppler information for the signals transmitted by the satellite positioning system satellite; information regarding atmospheric effects on the signal transmitted by the satellite positioning system satellite; and identification of the satellite positioning system satellites that are visible to the satellite positioning system receiver.
  • the digital television signal comprises at least one of the group comprising an American Television Standards Committee (ATSC) digital television signal; a European Telecommunications Standards Institute (ETSI) Digital Video Broadcasting - Terrestrial (DVB-T) signal; and a Japanese Integrated Services Digital Broadcasting-Terrestrial (ISDB-T) signal.
  • ATSC American Television Standards Committee
  • ETSI European Telecommunications Standards Institute
  • DVD-T Digital Video Broadcasting - Terrestrial
  • ISDB-T Japanese Integrated Services Digital Broadcasting-Terrestrial
  • the invention features an apparatus for recovering satellite positioning system aiding information from a digital television signal. It comprises a front end to receive the digital television signal, the digital television signal comprising a plurality of frames, each frame comprising a plurality of data segments, wherein at least one data segment has been replaced by at least one codeword representing the satellite positioning system aiding information; and a back end to select the data segments which have been replaced by codewords and to recover the satellite positioning system aiding information from the selected data segments.
  • the satellite positioning system is the global positioning system (GPS).
  • the satellite positioning system receiver determines the position of the satellite positioning system receiver based on the signal received from the satellite positioning system satellite and the satellite positioning system aiding information.
  • the satellite positioning system aiding information comprises at least one of the group comprising a position of the satellite positioning system satellite; clock correction information for the satellite positioning system satellite; Doppler information for the signals transmitted by the satellite positioning system satellite; information regarding atmospheric effects on the signal transmitted by the satellite positioning system satellite; and identification of the satellite positioning system satellites that are visible to the satellite positioning system receiver.
  • the digital television signal comprises at least one of the group comprising an American Television Standards Committee (ATSC) digital television signal; a European Telecommunications Standards Institute (ETSI) Digital Video Broadcasting - Terrestrial (DVB-T) signal; and a Japanese Integrated Services Digital Broadcasting-Terrestrial (ISDB-T) signal.
  • ATSC American Television Standards Committee
  • ETSI European Telecommunications Standards Institute
  • DVB-T Digital Video Broadcasting - Terrestrial
  • ISDB-T Japanese Integrated Services Digital Broadcasting-Terrestrial
  • the satellite positioning system is the global positioning system (GPS).
  • the satellite positioning system receiver determines the position of the satellite positioning system receiver based on the signal received from the satellite positioning system satellite and the satellite positioning system aiding information.
  • the satellite positioning system aiding information comprises at least one of the group comprising a position of the satellite positioning system satellite; clock correction information for the satellite positioning system satellite; Doppler information for the signals transmitted by the satellite positioning system satellite; information regarding atmospheric effects on the signal transmitted by the satellite positioning system satellite; and identification of the satellite positioning system satellites that are visible to the satellite positioning system receiver.
  • the digital television signal comprises at least one of the group comprising an American Television Standards Committee (ATSC) digital television signal; a European Telecommunications Standards Institute (ETSI) Digital Video Broadcasting - Terrestrial (DVB-T) signal; and a Japanese Integrated Services Digital Broadcasting-Terrestrial (ISDB-T) signal.
  • the processor determines a pseudo-range between the satellite positioning system receiver and a transmitter of the digital television signal based on a known component of the digital television signal; and determines a position of the satellite positioning system receiver based on the pseudo-range, the signal received from the satellite positioning system satellite and the satellite positioning system aiding information.
  • FIG. 1 is a block diagram of a system according to the present invention.
  • FIG. 2 illustrates the structure of an ATSC frame.
  • FIG. 3 is a flow diagram illustrating a method for transmitting and receiving low data rate data using an ATSC DTV signal.
  • FIGS. 4A-4D illustrate data segments which have been replaced by codewords using various approaches.
  • FIGS. 5A-5B illustrate frames in which various data segments have been replaced by codewords.
  • FIG. 6 is a block diagram of a DTV transmitter.
  • FIG. 7 is a block diagram of a front end for use in a receiver.
  • FIG. 8 is a block diagram of a back end based on a bank of correlators.
  • FIG. 9 is a block diagram of one correlator.
  • FIG. 10 is a block diagram of another correlator.
  • FIG. 11 is a flow diagram illustrating one method of recovering digital data based on establishing framing.
  • FIG. 12 is a block diagram of a back end for establishing framing.
  • FIG. 13 shows a system including a GPS receiver and a plurality of GPS satellites according to one implementation.
  • FIG. 14 shows a process performed by the system of FIG. 13 according to one embodiment.
  • FIG. 15 shows a system including a GPS receiver and only a single GPS satellite according to one implementation.
  • FIG. 16 shows a process performed by system according to one embodiment.
  • client and server generally refer to an electronic device or mechanism
  • messages generally refers to an electronic signal representing a digital message
  • mechanism refers to hardware, software, or any combination thereof.
  • FIG. 1 is a block diagram of an example system 100 according to the present invention.
  • System 100 includes a receiver 102 that receives digital television (DTV) broadcasts from one or more DTV transmitters 106A-N.
  • DTV digital television
  • One example of a DTV transmitter 106 is a transmission tower which broadcasts DTV signals over the air to receiver 102.
  • Another example is the transmitter for a cable television system, in which case the DTV signals arrive at the receiver 102 via a cable link.
  • Satellite TV systems also known as Direct Broadcast Satellites (DBS), are another example of digital TV broadcast systems.
  • EchoStar and DirecTV are the primary DBS services in the U.S. market.
  • the receiver 102 is meant to refer to any object capable of implementing the low data rate channel described below. Receivers 102 may also be capable of receiving the television programming data carried on the DTV signals but this is not required. Receivers 102 may be stationary and/or mobile. Virtually any object which could include a chip or software implementing the robust low data rate channel described below could be a receiver 102. Thus, DTV televisions, pagers, mobile telephones, PDAs, computers, cars and other vehicles would all be examples of receivers 102 if properly equipped.
  • the DTV transmitter 106 transmits digital data to the receiver 102 at a data rate which is significantly less than that of broadcast television programming data.
  • the robust low data rate digital data is inserted into the DTV signal broadcast at the transmitter 106.
  • the DTV signal is received by the receiver 102, which recovers the digital data from the DTV signal.
  • the digital data is local street maps showing places of interest near a cell phone.
  • Other applications include data to allow cell phones to compute their own location without the need for external processing, short messages, applications similar to those on pagers, stock quotes, news headlines, TV programming guide, radio programming guide, bus schedules, short text advertisements for stores in the location of the receiver, and all types of low data rate M-commerce information.
  • most of the digital data for these applications will consist of short text and/or simple graphs, for example representing maps.
  • Many data broadcast applications can have low data rate versions.
  • WAP Wireless Application Protocol
  • An even simpler text only version is an example application for a robust low data rate system using DTV signals.
  • FIG. 2 is a representation of the structure of an ATSC frame from the current ATSC standard.
  • the current ATSC signal is described in "ATSC Digital Television Standard and Amendment No. 1," March 16, 2000, by the Advanced Television Systems Committee, which is incorporated herein by reference in its entirety.
  • the ATSC signal for terrestrial broadcast uses 8-ary vestigial sideband modulation (8-VSB).
  • the symbol rate of the ATSC signal is 10.76 MHz, which is derived from a 27.00 MHz clock.
  • the structure 200 of the ATSC frame is illustrated in FIG. 2.
  • the frame 200 includes a total of 626 segments, each with 828 symbols. Each segment is followed by four symbols that are used for synchronization purposes. These will be referred to as the segment synchronization attachment.
  • FIG. 2 The structure 200 of the ATSC frame is illustrated in FIG. 2.
  • the frame 200 includes a total of 626 segments, each with 828 symbols. Each segment is followed by four symbols that are used for synchronization purposes. These will be referred to as the segment synchronization
  • Each field synchronization segment is one of two fixed, known 828- symbol sequences.
  • the two 828-symbol sequences differ only to the extent that a 63 symbol section is inverted in one sequence relative to the other. Some additional symbols in these field synchronization segments are different for each transmitter.
  • One of these two known field synchronization segments is transmitted every 24.2 milliseconds. These symbol sequences were included as a training sequence to help the ATSC receivers correct for multipath typically found in broadcast channels.
  • the field synchronization segments can be viewed as spread spectrum codewords that are buried in the ATSC data sequence. A spread spectrum codeword is typically detected with correlators (e.g., matched filters).
  • the output of such correlators can provide estimates of the parameters of the multipath signals. Because a field synchronization segment appears once every 24.2 milliseconds, they can be used to provide a periodic snapshot of the multipath signals. For dynamically changing multipath signals, the multipath characteristics during the interim period can be estimated using conventional methods such as blind equalizations or other interpolation schemes.
  • the data segments are where the television programming data is carried.
  • Each data segment corresponds to a 188-byte data packet in the MPEG-2 transport layer.
  • Each 188-byte data packet is expanded into 828 3-bit coded data symbols using a combination of a Reed-Solomon encoder, interleaver, and rate 2/3 trellis encoder.
  • Data segments may also be used to carry other information such as web content from the Internet or may be unused in which case the data segment is said to contain a null packet.
  • the segment synchronization attachment is the same for all segments. It consists of the four symbol sequence (-1, 1, 1, -1) and is typically used for segment synchronization.
  • Implementations of the invention can be extended to use future enhancements to DTV signals.
  • the ATSC signal specification allows for a high rate 16-VSB signal primarily for digital cable television.
  • the 16-VSB signal has the same general frame structure as the 8-VSB signal, using field synchronization segments and data segments. Therefore, it is straightforward to extend the 8-VSB examples shown below to the 16-VSB signal.
  • the 8-VSB signal is constructed by filtering.
  • the in-phase segment of the symbol pulse has a raised-cosine characteristic, as described in J.G. Proakis, Digital Communications, McGraw-Hill, 3 rd edition, 1995.
  • the pulse can be described as [0054]
  • This signal has a frequency characteristic
  • H a (f) is a filter designed to leave a vestigial remainder of the lower sideband.
  • the response U(f)P(f) can be represented as
  • C Fundamental is the 8-level data signal.
  • FIG. 3 is a flow diagram illustrating a method 300 for transmitting digital data using ATSC frames 200.
  • some of the data segments are replaced by codewords representing the digital data to be transmitted.
  • the digital data to be transmitted is encoded 310 as codewords.
  • the codewords replace 320 data segments within the DTV signal.
  • the DTV transmitter 106 broadcasts 330 the DTV signal containing the codewords.
  • the receiver 102 receives 340 the broadcast signal, from which the digital data is recovered 350.
  • each codeword is the same length as a data segment.
  • One codeword represents binary 0 and the other represents binary 1.
  • the two codewords preferably are orthogonal to each other. In this simple example, one bit of data can be transmitted per ATSC frame, for a data rate of approximately 21 bits per second (bps).
  • bps bits per second
  • N 0 is the double sided noise spectral density and E b is the energy per bit.
  • E for the single bit being transmitted is the energy at the receiver for the entire 828-symbol segment. It is equal to the TV transmitter power at the receiver multiplied by the 77.3 microseconds of the segment duration. Thus, E b is 29 dB greater than the energy for each DTV broadcast symbol.
  • the digital data can be recovered from broadcast signals that are much weaker than is acceptable for TV reception. For example, signals which are 30 to 40 dB weaker than needed for the reception of digital TV signals may be suitable for use with these low data rate channels. This, in turn, means that the digital data can be recovered over a much wider range than the typical DTV reception range. In addition, reception of this low data rate channel is possible in many indoor locations where broadcast TV reception is difficult.
  • Another advantage of this approach is that reception of the low data rate signal can be accomplished with receivers that are much simpler than the standard DTV receivers, as will be discussed in further detail below.
  • simple non-coherent energy detection of codewords using correlators at the receiver is appropriate.
  • This type of receiver is simple in design, small in size, and low in energy consumption.
  • Another advantage is that significant expenses are not required to implement the transmitter either, as will be discussed in further detail below. Many DTV transmitters already include standard equipment at the broadcast station for replacing individual segments in the DTV signal.
  • This equipment may be used to replace certain segments with the field synchronization segments or to replace null MPEG packets which arise, for example, because there is no TV programming data to send at the transmission times of these data segments.
  • this equipment need only be modified to replace certain data segments with codewords instead.
  • the simple example given above results in a data rate of approximately 20 bps.
  • the data rate can be increased in a number of ways. For example, more than one bit can be carried by each replaced 828-symbol data segment in a frame. In one approach, more than two codewords are used.
  • the incoming digital data may be divided into bit sequences each of which is three bits long. Each of these bit sequences is encoded as a codeword selected from a set of eight possible 828-symbol codewords. Each of the eight codewords corresponds to one of the eight possible 3-bit sequences.
  • the eight codewords preferably are orthogonal to each other in order to facilitate reception.
  • one of the eight codewords is inserted into the DTV signal, replacing the corresponding data segment in a frame, as shown in FIG. 4A.
  • the data rate is now approximately 62 bps.
  • a codeword is represented by the C n and the notation [Co , . . . C N - I ] represents one codeword selected from the set of N codewords.
  • a lookup table can be used to convert from the 3 -bit sequences to the co ⁇ esponding codewords.
  • 2 ⁇ N codewords can be used to replace bit sequences which are N bits long.
  • the set of codewords should be selected so that they have good correlation properties that minimize reception e ⁇ ors.
  • the codewords preferably should have low time shifted crosscorrelation and small side lobes in their autocorrelation function.
  • codewords based on multi-amplitude symbols will result in better correlation properties than those based on binary amplitude symbols.
  • Such sets of codewords have been studied extensively in various applications, especially in spread spectrum communication systems, with the most popular commercial application being the Code Division Multiple Access (CDMA) system used in the IS-95 cell phone standard in the United States.
  • CDMA Code Division Multiple Access
  • codewords using multi-amplitude symbols may be suitable for this standard. More specifically, 4-level or 8-level symbols can be used instead of binary (2- level) symbols.
  • the digital data is divided into bit sequences of varying lengths, with each bit sequence mapped to a corresponding codeword.
  • the codewords could also be of varying length.
  • all 828 symbols of a data segment could be replaced by codewords.
  • five bits per data segment could be encoded as five 160-symbol codewords, for a total of 800 symbols per data segment, as shown in FIG. 4D.
  • this approach generally is not favored since current technology tends to process DTV signals on a segment by segment basis, so the approach in FIG. 4D effectively wastes the remaining 28 symbols in the data segment.
  • the codewords typically will have a significantly lower data rate than the data segments which they replace.
  • the overall data rate can also be increased by increasing the number of data segments per frame used for the low data rate channel.
  • the resulting DTV signal would have a data rate of approximately 19.2 Mbps.
  • Cu ⁇ ent TV signals typically do not require this much bandwidth.
  • HDTV typically requires about 12-15 Mbps and standard definition TV typically requires about 3-5 Mbps. This leaves anywhere from 20-80% of the overall capacity as unused. If 20% of the overall capacity is used for the low data rate channel, then 125 data segments per data frame will be used for this channel.
  • the overall data rate will be approximately 12.5 Kbps. By doing this, approximately 4 Mbps of television programming is replaced by a 12.5 Kbps low data rate channel, but the low data rate channel is much more robust and can be received over longer ranges using simpler receiver technology.
  • the selection of which and how many data segments are to be replaced can also be implemented in a number of ways.
  • a straightforward approach is to replace preselected data segments.
  • data segments 10-50 of each frame are dedicated to the low data rate channel and these are the data segments which are replaced by codewords.
  • the receiver can be further simplified. The receiver knows a priori that only data segments 10-50 can contain codewords. So it need only test these data segments for codewords. Furthermore, if a codeword is always present in these data segments, then the receiver need only determine which of the possible codewords is the most likely one to have been transmitted.
  • the receiver need only decide which of the eight codewords was transmitted in the received data segment intervals. It need not determine whether a codeword is present.
  • data segments are replaced by codewords on an as-available basis. For example, the transmitter may determine whether a data segment contains a data packet or a null packet. That is, the transmitter determines whether the data segment is used or unused. If it contains data, then that data segment is not used for the low data rate channel. Only unused data segments, typically referred to as "null packets,” are replaced by codewords. In FIG.
  • data segments 600-624 of frame 1 are not being used and are replaced by codewords.
  • data segments 533-597 are not being used and are replaced by codewords.
  • the receiver may not know a priori which data segments contain codewords. Using correlation thresholds, the receiver must first estimate which data segments contain codewords. [0100]
  • FIG. 6 is a block diagram of a DTV transmitter 106.
  • This transmitter 106 includes the following elements, coupled in series: data compression engine 610, data multiplexer 620, channel coder 630, packet multiplexer 640 (for field synchronization segments, segment synchronization attachments, and codewords), 8-VSB modulator and transmitter 650 and transmission tower 660.
  • the transmitter 106 also includes a data encoder 670 coupled to the packet multiplexer 640.
  • the transmitter 106 operates as follows. An analog television signal is compressed by compression engine 610.
  • MPEG 2 is the data compression standard used by the cu ⁇ ent ATSC standard.
  • the data multiplexer 620 combines multiple streams of data into a single ATSC signal. Examples of other types of data include additional TV programming which is already in digital form and program guide information. Since data is packetized over the DTV broadcast signal, any type of digital data can be transmitted over the TV programming channel at the 19.2 Mbps data rate. There have been proposals to sent video rich forms of Internet web traffic over such TV programming channels.
  • Channel coder 630 encodes the resulting data packets in order to co ⁇ ect for channel e ⁇ ors.
  • channel coder 630 implements a combination of Reed-Solomon e ⁇ or co ⁇ ection encoding, interleaving, and trellis encoding.
  • the ATSC standard for te ⁇ estrial broadcast uses 8-VSB modulation with 3- bit symbols in the form of 8 levels of amplitude. After channel coding, the coded data of 8-level symbols is divided into data segments.
  • the packet multiplexer 640 is the device that can replace data on a segment by segment basis.
  • the sequence of 8-level symbols is sent to the 8-VSB modulator and transmitter 650.
  • the modulator 650 applies the 8-VSB modulation.
  • the transmitter 650 then broadcasts the resulting DTV signal via transmitter tower 660.
  • the data encoder 670 For the low data rate channel, the data encoder 670 generates the codewords from the incoming digital data. For example, the data encoder 670 can convert bit sequences to codewords using a lookup table. For applications which are not real-time, both the incoming bit sequences and/or outgoing codewords may be stored and subsequently retrieved from memory.
  • the data encoder 670 divides the incoming digital data into 3-bit sequences and then translates these into the co ⁇ esponding codewords, hi one implementation, this is accomplished by a lookup table that has a 3 -bit input and outputs the co ⁇ esponding codeword.
  • the codewords from data encoder 670 are inserted into the ATSC frames at the transport layer by the packet multiplexer 640. Inserting codewords is very similar to inserting field synchronization segments, except that the actual data to be inserted is different. Since the packet multiplexer 640 almost certainly is already inserting field synchronization segments, it is straightforward to modify the existing packet multiplexer 640 to also insert codewords.
  • blocks 610-640 are implemented as equipment located at the television broadcast station.
  • the modulator and transmitter 650 are located in close proximity to the tower 660, for example at the base of the tower.
  • FIGS. 7-12 illustrate various aspects of receiver 102.
  • the receiver 102 recovers the digital data from the codewords embedded in the broadcast DTV signal.
  • FIG. 7 is a block diagram of a front end 400 for use in the receiver 102.
  • the sampler 400 takes samples of the received DTV signal.
  • the DTV broadcast signal 402 is received by an antenna 404, which is followed by filters and amplifiers 406.
  • the filtered and amplified DTV broadcast signal is then converted into in-phase and quadrature baseband signals by a local oscillator 416, mixers 4081 and 408Q, and low pass filters 4101 and 410Q.
  • the DTV broadcast signal is split into two signals.
  • Each mixer 408L408Q multiplies one of the DTV broadcast signals with the sin or cosine component of the local oscillator 416, respectively.
  • Each multiplied signal is then low pass filtered by filter 4101 or 410Q, respectively, resulting in the baseband I and Q components of the received DTV broadcast signal. This is sampled and quantized by the analog to digital converter (ADC) 412.
  • ADC analog to digital converter
  • FIG. 7 is a typical front end for a receiver.
  • FIG 7 can also be the front end of a conventional DTV receiver that receives TV programming data. Other types of fronts ends will be apparent.
  • FIG. 8 is a block diagram of a back end for use in receiver 102.
  • the back end 800 receives the digital I and Q samples from the front end of the receiver. For convenience, the I and Q samples are shown by a single line in FIG. 8 rather than separate lines for I and Q.
  • the back end 800 includes a bank of co ⁇ elators 805A-805N, with one co ⁇ elator 805 for each of the possible codewords.
  • FIG 8 illustrates the general case where there are N possible codewords and N co ⁇ esponding co ⁇ elators 805.
  • Each co ⁇ elator 805 co ⁇ elates the incoming samples against a template for the co ⁇ esponding codeword.
  • the template is a matched filter for the codeword.
  • the output of co ⁇ elator 805 A provides a measure of the likelihood that the data segment being tested contains codeword Co.
  • the co ⁇ elation produced by co ⁇ elator 805B measures the likelihood of codeword and so on.
  • the bank of co ⁇ elators 805 is coupled to a comparator 810, which determines which of the co ⁇ elations is the largest.
  • the data bits of the selected codeword are then output. For example, if co ⁇ elator 805B produces the strongest co ⁇ elation, then the bit sequence co ⁇ esponding to codeword Ci is recovered by the receiver.
  • Multipath is common in radio channels.
  • multipath signals are multiple copies of the transmitted signal each with a different delay. This results in the co ⁇ elator output having multiple co ⁇ elation peaks of various sizes co ⁇ esponding to the transmitted codeword.
  • a receiver can take advantage of multipath and combine all of the multipath related co ⁇ elation peaks out of each codeword co ⁇ elator and then do the comparison among all such codeword co ⁇ elators. This receiver would perform better than a conventional receiver that would only look at the co ⁇ elator output at a particular instant in time. This type of receiver can be implemented by changing the basis for comparision in comparator 810.
  • FIG. 9 is one example of a co ⁇ elator 900.
  • the I samples from the front end enter the tap delay line 9101 and the Q samples from the front end enter the tap delay line 910Q.
  • the codeword determines which of the samples in the tap delay lines 9101 and 910Q are multiplied and summed in the devices 9201 and 920Q.
  • the tap delay lines 910 are long enough to store the samples for an entire codeword (e.g., an entire data segment if there is a one to one replacement of data segments by codewords).
  • a new I and Q sample from the ADC 412 enters the tap delay lines 9101 and 910Q.
  • FIG. 10 illustrates another type of co ⁇ elator 500 that can be used in FIG. 8.
  • the I and Q samples from the front end are multiplied by mixers 5041 and 504Q, respectively, against the I and Q components of the code generator 502 which are uniquely determined by the codeword.
  • the code generator 502 is synchronized with the a ⁇ ival time of the samples being received by the back end.
  • the multiplied I and Q samples are summed by summers 5061 and 506Q.
  • the sum is taken over the time interval of a codeword (e.g., over one data segment if there is a one to one replacement of data segments by codewords). These sums are squared in square law devices 5071 and 507Q and then added together in the summer 508.
  • Co ⁇ elator 500 produces one output for the entire co ⁇ elation.
  • co ⁇ elator 500 generates the co ⁇ elation function at a specific instant in time (typically, the instant when a co ⁇ elation peak is expected).
  • co ⁇ elator 900 of FIG. 9 generates samples of the co ⁇ elation function at different times.
  • the co ⁇ elator 500 of FIG. 10 is repeated N times, once for each of the correlators 805 in FIG. 8.
  • the templates for the different codewords are generated by varying the code generator 502.
  • the back end of receiver 102 is implemented by a digital signal processor programmed to perform the required co ⁇ elations. [0116] FIG.
  • FIG. 11 is a flow diagram illustrating one method of recovering digital data by establishing framing of the incoming ATSC signal.
  • the receiver 102 establishes framing by identifying 1210 the field synchronization segment within the ATSC frames. This can be accomplished, for example, by using a co ⁇ elator 900 of FIG. 9 where the multiply and sum devices 9201 and 920Q are designed to implement co ⁇ elation against the field synchronization segments.
  • Establishing framing simplifies the subsequent data recovery because individual data segments can then be identified and the temporal location of codewords will be known by the receiver 102. If framing was not established, the receivers would have to detect codewords without knowing the location of the beginning and end of each codeword at the receiver 102. This is more complex, although it could still be achieved, for example by using co ⁇ elation or matched filtering but taking into account the unknown timing as to when codewords are being received by the receiver.
  • FIG. 12 is a block diagram of a device 1200 which removes this ambiguity.
  • This device 1200 includes back end 800, which will recover the digital data once framing is established.
  • the rest of the device 1200 includes the following coupled in series: a co ⁇ elator 900, a bank of counters 1210 and a comparator 1220. These elements are used to identify the field synchronization segment.
  • the counter 1250 is used to synchronize back end 800.
  • the block diagram is functional. Various implementations of the same functionality will be apparent.
  • the framing function of device 1200 operates as follows.
  • the incoming stream of symbols is arbitrarily divided into 24.2 ms blocks, which are further divided into 313 intervals of 77.3 us each.
  • the 24.2 ms blocks co ⁇ espond to ATSC half-frames and the 77.3 us intervals co ⁇ espond to data segments.
  • a field synchronization segment will occur once during each 24.2 ms block and the field synchronization segment will last for one time interval of 77.3 us (although it might span the boundary of two adjacent 77.3 us intervals since the start and end of data segments is not yet known).
  • the co ⁇ elator 900 co ⁇ elates one incoming 77.3 us time interval against a
  • the template is “generic” in the sense that the co ⁇ elator 900 detects the 757 symbols which are common to all field synchronization segments (recall that some symbols vary between different field synchronization segments).
  • the co ⁇ elator 900 has an output for each sample time. That is, it outputs a co ⁇ elation function sampled at many different points in time. This is useful since the exact location of the co ⁇ elation peak is not yet known. [0121] In the bank of counters 1210, one counter is assigned to each of the 313 time intervals. During each of the time intervals, the co ⁇ elator output samples are compared to a threshold.
  • each counter 1210 for that time interval is incremented. This is repeated, cycling through the counters 1210 repeatedly, as each of the 313 intervals appear once every 24.4 milliseconds
  • each counter 1210 counts the number of times each 313th time interval (e.g., the 1st, 314th, 627th, etc. time intervals for counter 1; the 2nd, 315th, 628th, etc. time intervals for counter 2, etc.) exceeds the threshold.
  • the counter 1210 with the largest count will be the one co ⁇ esponding to the field synchronization segment.
  • Comparator 1220 determines which count is the largest, thus identifying the field synchronization segment.
  • the comparator will pin down the location of the field synchronization segment to within 77.3 microseconds.
  • Exact location of the start of the field synchronization segment can be determined based on the fine structure of the output from co ⁇ elator 900.
  • the noise in the front end of the receiver 102 is white Gaussian noise with double-sided spectral density of No.
  • an output sample is the sum of squares of two independent Gaussian random variables each with variance No/2. The probability that this sample X exceeds a threshold T is [0123]
  • [0130] is the probability that this noise sample exceeds the threshold and thus results in the counter being incremented.
  • the co ⁇ elator output can be used to determine the location of the field synchronization segment.
  • the bank of counters 1210 is replaced by a bank of accumulators.
  • the peak co ⁇ elation for each of the 313 intervals is accumulated to produce 313 partial sums. That is, accumulator 1 accumulates the peak co ⁇ elations for the 1st, 314th, 627th, etc. intervals. Over many frames, the largest partial sum will be the one co ⁇ esponding to the field synchronization segment.
  • time-gated delay lock loops can be used to maintain lock onto multipath components of the received broadcast signal's field synchronization segment. Non-coherent combining of these delay lock loop outputs can be done to improve the processing gain.
  • each data segment is processed by a bank of co ⁇ elators, for example as shown in FIG. 8.
  • Comparator 810 selects the most probable codeword based on co ⁇ elation strength, but there is an additional decision as to whether a codeword was sent at all. In one approach, this decision is based on all of the co ⁇ elator outputs.
  • One example is to decide a codeword did not exist if there is no dominant peak co ⁇ elator output among all of the co ⁇ elator outputs.
  • the co ⁇ elator output for the transmitted codeword would, with high probability, have a much larger co ⁇ elator output peak than in the other codeword co ⁇ elator outputs.
  • the largest co ⁇ elator output peak might be required to be at least twice the co ⁇ esponding co ⁇ elator output peaks of the other co ⁇ elator output peak values for a decision to be made that a codeword was transmitted in the particular segment interval.
  • the functionality shown in FIG. 12 is implemented in a DSP processor.
  • a specific frequency such as IF or baseband. This is not meant to limit these examples to these specific frequencies.
  • different implementations can operate at different frequencies.
  • various steps may be implemented either as analog or digital processes.
  • processing of the incoming DTV signal can occur either in real-time, with no storage of the incoming signal, or by retrieving samples of the DTV signal from memory.
  • different types of templates may be used to achieve the co ⁇ elation desired.
  • the field synchronization segments use binary amplitude symbols while in general up to eight levels of amplitude are allowed in the transmitter's 8-VSB modulation signal.
  • the codewords will be selected to use 2 levels, 4 levels, or 8 levels of amplitude in the codeword symbol sequence.
  • more level symbols are used for codewords, there are more choices of codewords with good autoco ⁇ elation and cross co ⁇ elation properties, thus improving the detection of codewords at the receiver 102.
  • More levels make the co ⁇ elators in receiver 102 more complex.
  • DTV signals other than ATSC signals can be used.
  • All DTV signals rely on data segments which are organized into frames. Codewords can replace any of these data segments, resulting in a robust, low data rate transmission, so long as the replacement does not degrade the rest of the DTV signal in an unacceptable way.
  • data segments in a DTV format are independently encoded so that replacing one data segment does not affect the decoding of the other data segments, then data segments can be individually replaced on an as-available basis.
  • the data segments preferably are replaced at the transport layer, although this is not required.
  • GPS global positioning system
  • the GPS system employs a constellation of 24 on-orbit satellites in sub-synchronous 12 hour orbits. Each satellite carries a precision clock and transmits a pseudo-noise signal, which a GPS receiver can precisely track to determine a pseudo-range between the GPS receiver and the GPS satellite. By tracking four or more satellites, the receiver can determine precise position in three dimensions in real time, world-wide. Further details are provided in, for example, B.W. Parkinson and J. J. Spilker, Jr., Global Positioning System-Theory and Applications, Volumes I and II, AIAA, Washington, DC, 1996.
  • GPS has revolutionized the technology of navigation and position location.
  • GPS position determination can be aided by the transmission of data that make GPS more robust to attenuation and multipath. Examples of this type of data include the cu ⁇ ent positions of the GPS satellites and clock co ⁇ ection information based on atomic standards.
  • Additional examples include Doppler information, information about the Earth's atmosphere including Ionospheric effects that may alter or disrupt the satellite signals. Further examples include a list of satellites that should be visible given the location of the user, spatial coordinate data for those selected satellites, and predicted Doppler data for those selected satellites. Examples might also include the data that is modulated onto the C/A GPS code signals. This data might also include information that aids a device in tracking and determining the precise distance to GPS satellites. These types of data are refe ⁇ ed to herein as GPS aiding information. [0145] Devices can use this low-data-rate GPS aiding information to integrate GPS satellite signals more efficiently and/or for longer periods of time according to conventional, well-known techniques.
  • GPS receivers no ⁇ nally determine their position by computing relative times of arrival of signals transmitted simultaneously from a multiplicity of GPS (or NAVSTAR) satellites. These satellites transmit, as part of their message, both satellite positioning data, so-called "ephemeris" data, as well as data on clock timing.
  • This information is sent in a channel that broadcasts at 50 bps.
  • a device it is possible for a device to receive GPS aiding information directly from the GPS satellite itself.
  • the process of searching for and acquiring GPS signals, reading the ephemeris data for a multiplicity of satellites and computing the location of the device from this data is time consuming, often requiring several minutes. In many cases, this lengthy processing time is unacceptable and, furthermore, greatly limits battery life in portable applications.
  • This processing time also makes it very difficult to perform real-time position fixes for applications that require constant position updates, such as real-time electronic street maps used in automobiles.
  • the GPS aiding information is transmitted to the end user device through digital television (DTV) broadcast signals.
  • DTV digital television
  • the GPS aiding information typically requires only a low data rate.
  • the techniques described above are well suited to disseminating the GPS aiding information via the DTV broadcast signals.
  • One advantage of this approach is that this communications channel is fairly robust. Compared to many other types of communications channels, the DTV-based communications channel described above can be recovered at lower signal-to-noise ratios, for example in remote areas or in locations where interference or multipath causes problems.
  • the GPS aiding information allows the GPS receiver to more effectively scan for available GPS signals.
  • the aiding information also makes it easier for GPS receivers to find GPS signals below the noise floor.
  • the DTV signals comprising GPS aiding information are disseminated by other means, both wired and wireless.
  • FIG. 13 shows a system 1300 including a GPS receiver 1302 and a plurality of GPS satellites 1320A, 1320B, and 1320N according to one implementation.
  • FIG. 14 shows a process 1400 performed by system 1300 according to one embodiment.
  • a DTV transmitter 1306 provides GPS aiding information (step 1402).
  • one or more monitor stations 1308 receive the GPS signals transmitted by GPS satellites 1320. Monitor stations 1308 use the received GPS signals to determine the Doppler for those satellites, in addition to ephemeris information, using conventional techniques.
  • DTV transmitter 1306 provides a digital television signal comprising a plurality of frames (step 1404). Each frame comprises a plurality of data segments. DTV transmitter 1306 encodes the GPS aiding information as codewords (step 1406) and replaces the data segments within the digital television signal with the codewords (step 1408) according to the techniques described above. DTV transmitter 1306 then transmits the digital television signal 1310 comprising the GPS aiding information (step 1410).
  • GPS receiver 1302 receives digital television signal 1310 (step 1412) and recovers the GPS aiding information (step 1414) according to the techniques described above. GPS receiver 1302 receives the signals transmitted by GPS satellites 1320 (step 1416) and computes the position of GPS receiver 1302 (step 1418) using the GPS aiding information and the signals transmitted by GPS satellites 1320 according to conventional techniques.
  • the approach described above is used with navigation systems other than GPS that use a constellation of Earth-orbiting satellites having known positions and generating pseudo-random noise type signals to receivers wherein Doppler compensated signal propagation times are measured to calculate user position and velocity.
  • FIG. 15 shows a system 1500 including a GPS receiver 1502 and only a single GPS satellite 1520 according to one implementation.
  • GPS receiver 1502 also employs pseudo-ranges to one or more DTV transmitters 1506 in position determination.
  • FIG. 16 shows a process 1600 performed by system 1500 according to one embodiment.
  • a DTV transmitter 1506 provides GPS aiding information (step 1602).
  • one or more monitor stations 1508 receive the GPS signals transmitted by GPS satellite 1520. Monitor stations 1508 use the received GPS signals to determine the Doppler for the satellite, in addition to ephemeris information, using conventional techniques. This GPS aiding information is transmitted to DTV transmitter 1506 for retransmission to GPS receiver 1502.
  • DTV transmitter 1506 provides a digital television signal comprising a plurality of frames (step 1604). Each frame comprises a plurality of data segments.
  • DTV transmitter 1506 encodes the GPS aiding information as codewords (step 1606) and replaces the data segments within the digital television signal with the codewords (step 1608) according to the techniques described above. DTV transmitter 1506 then transmits the digital television signal 1510 comprising the GPS aiding information (step 1610).
  • GPS receiver 1502 receives digital television signal 1510 (step 1612) and recovers the GPS aiding information (step 1614) according to the techniques described above. GPS receiver 1502 receives the signals transmitted by GPS satellite 1520 (step 1616). GPS receiver 1502 determines a pseudo-range between GPS receiver 1502 and DTV transmitter 1506 based on a known component of the digital television signal transmitted by DTV transmitter 1506 (step 1618).
  • GPS receiver 1502 then computes the position of GPS receiver 1502 (step 1620) using the GPS aiding information, the signals transmitted by GPS satellites 1520, and the pseudo-range between GPS receiver 1502 and DTV transmitter 1506. [0157] Techniques for determining the position of a user terminal using the GPS aiding information, the signals transmitted by GPS satellites 1520, and the pseudo-range between GPS receiver 1502 and DTV transmitter 1506.
  • ISDB-T Japanese Integrated Services Digital Broadcasting-Te ⁇ estrial
  • Each of these television signals includes known components that can be used to obtain a pseudo-range to the transmitter of the television signal.
  • Suitable components within the ATSC digital television signal include synchronization codes such as the Field Synchronization Segment within an ATSC data frame and the Synchronization Segment within a Data Segment within an ATSC data frame.
  • Suitable components within the ETSI DVB-T and ISDB-T digital television signals include scattered pilot carriers.
  • GPS receiver 1502 computes the position of GPS receiver 1502 (step 1620) using the DTV pseudo-range, the GPS aiding information and the signals transmitted by GPS satellite 1520. Techniques for position determination using DTV and GPS signals are disclosed in commonly-owned, copending U.S. Non-provisional Patent Application Serial No.
  • Computation of the position of GPS receiver 1502 can include computations using information describing the phase center (i.e., the location) of each DTV transmitter 1506 provided by a database 1512 and weather information provided by a weather server 1514, and can be performed either by GPS receiver 1502 or by a separate location server 1522. Data can be relayed between GPS receiver 1502 and location server 1504 using a wireless base station 1504 or by other methods.
  • a further signal such as a second GPS signal or a second DTV signal, can be used as a third signal. Further GPS and/or DTV signals can be employed as well.
  • the approach described above is used with navigation systems other than GPS that use a constellation of Earth-orbiting satellites having known positions and generating pseudo-random noise type signals to receivers wherein Doppler compensated signal propagation times are measured to calculate user position and velocity.
  • An identification signal ca ⁇ ies a Kasami code binary sequence that is transmitted repeatedly throughout the period when it is enabled in the transmissions from the particular transmitter with which it is associated. Each Kasami code is uniquely determined by the code sequence generator preloading values that are unique to each transmitter. The bits of the Kasami code are clocked at the symbol rate of the host 8-VSB signal. This identification bit sequence is sent to the equivalent of a 2-VSB modulator for transmission with the 8-VSB host signal. Typically this identification signal will be transmitted at a low enough power level to minimize interference with the normal digital TV reception of the 8-VSB host signal.
  • the start of a transmitter identification signal's Kasami code sequence will be emitted simultaneously with the first symbol of the of the first data segment following the Data Field Sync segment of the host 8-VSB signal. Within a Data Field the Kasami code sequence will occur three and a fraction time where the fourth sequence is truncated upon reaching the data segment sync at the start of the next Data Frame Sync segment. This identification signal is not transmitted during the Data Field Sync segment and restarts on the data segment immediately following the Data Field Sync segment. [0166] This identification signal can be used to transmit a low data rate signal by phase inversion of the code sequence associated with the transmitter. This phase inversion shall occur on a data-field-by-data-field basis.
  • the invention can be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in combinations of them.
  • Apparatus of the invention can be implemented in a computer program product tangibly embodied in a machine-readable storage device for execution by a programmable processor; and method steps of the invention can be performed by a programmable processor executing a program of instructions to perform functions of the invention by operating on input data and generating output.
  • the invention can be implemented advantageously in one or more computer programs that are executable on a programmable system including at least one programmable processor coupled to receive data and instructions from, and to transmit data and instructions to, a data storage system, at least one input device, and at least one output device.
  • Each computer program can be implemented in a high-level procedural or object-oriented programming language, or in assembly or machine language if desired; and in any case, the language can be a compiled or interpreted language.
  • Suitable processors include, by way of example, both general and special purpose microprocessors. Generally, a processor will receive instructions and data from a read- only memory and/or a random access memory.
  • a computer will include one or more mass storage devices for storing data files; such devices include magnetic disks, such as internal hard disks and removable disks; magneto-optical disks; and optical disks.
  • Storage devices suitable for tangibly embodying computer program instructions and data include all forms of non- volatile memory, including by way of example semiconductor memory devices, such as EPROM, EEPROM, and flash memory devices; magnetic disks such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM disks. Any of the foregoing can be supplemented by, or incorporated in, ASICs (application-specific integrated circuits) .
  • ASICs application-specific integrated circuits

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

Abstract

L'invention concerne un procédé, un appareil et un support lisible par ordinateur (fig.15) permettant de fournir des informations d'assistance d'un système de localisation par satellite à un récepteur (1502) du système de localisation par satellite conçu pour déterminer la position dudit récepteur au moyen des informations (1522) d'assistance du système de localisation par satellite et du temps de propagation d'un signal émis par un satellite dans le système de localisation par satellite. Un tel procédé consiste à obtenir lesdites informations (1522); à obtenir un signal de télévision numérique (1506) comprenant une pluralité de trames, chaque trame comprenant une pluralité de segments de données; à coder les informations d'assistance du système de localisation par satellite sous forme de mots codés; à remplacer des segments de données compris dans le signal de télévision numérique par les mots codés; et à émettre le signal de télévision numérique; le récepteur du système de localisation par satellite recevant le signal de télévision numérique et récupérant les informations d'assistance du système de localisation par satellite.
EP02795623A 2001-11-14 2002-11-12 Utilisation de signaux de televison numerique permettant d'obtenir des informations d'assistance de gps Withdrawn EP1454487A1 (fr)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
US10/003,128 US7042949B1 (en) 2001-04-03 2001-11-14 Robust data transmission using broadcast digital television signals
US3128 2001-11-14
US33198201P 2001-11-20 2001-11-20
US331982P 2001-11-20
PCT/US2002/036221 WO2003043323A1 (fr) 2001-11-14 2002-11-12 Utilisation de signaux de televison numerique permettant d'obtenir des informations d'assistance de gps

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EP1454487A1 true EP1454487A1 (fr) 2004-09-08

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EP02795623A Withdrawn EP1454487A1 (fr) 2001-11-14 2002-11-12 Utilisation de signaux de televison numerique permettant d'obtenir des informations d'assistance de gps

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EP (1) EP1454487A1 (fr)
KR (1) KR100941196B1 (fr)
CN (1) CN1586073A (fr)
WO (1) WO2003043323A1 (fr)

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JP4498841B2 (ja) * 2003-07-11 2010-07-07 三星電子株式会社 Ｇｐｓ相関ピーク信号の探索方法及びこれのためのシステム。
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Publication number Publication date
KR20050044390A (ko) 2005-05-12
CN1586073A (zh) 2005-02-23
WO2003043323A1 (fr) 2003-05-22
KR100941196B1 (ko) 2010-02-10

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