USOO7126536B2
`
`(12) United States Patent
`Rabinowitz et al.
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 7,126,536 B2
`*Oct. 24, 2006
`
`(54)
`
`(75)
`
`(73)
`
`(*)
`
`(21)
`(22)
`(65)
`
`(63)
`
`(60)
`
`POSITION LOCATION USING
`TERRESTRAL DIGITAL VIDEO
`BROADCAST TELEVISION SIGNALS
`
`Inventors: Matthew Rabinowitz, Palo Alto, CA
`(US); James J Spilker, Jr., Woodside,
`CA (US)
`Assignee: Rosum Corporation, Mountain View,
`CA (US)
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 1280 days.
`This patent is Subject to a terminal dis
`claimer.
`
`Notice:
`
`Appl. No.: 09/932,010
`Filed:
`Aug. 17, 2001
`
`Prior Publication Data
`US 2002/014.4294 A1
`Oct. 3, 2002
`
`Related U.S. Application Data
`Continuation-in-part of application No. 09/887,158,
`filed on Jun. 21, 2001, now abandoned.
`Provisional application No. 60/265,675, filed on Feb.
`2, 2001, provisional application No. 60/281,270, filed
`on Apr. 3, 2001, provisional application No. 60/281,
`269, filed on Apr. 3, 2001, provisional application No.
`60/293.812, filed on May 25, 2001, provisional appli
`cation No. 60/293,813, filed on May 25, 2001, pro
`visional application No. 60/293,646, filed on May 25,
`2001.
`
`(51)
`
`(52)
`(58)
`
`Int. C.
`(2006.01)
`GOIS3/02
`U.S. Cl. ...................................................... 342/.464
`Field of Classification Search ........... 342/357.01,
`342/357.06, 453, 463,464
`See application file for complete search history.
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`4,555,707 A 11/1985 Connelly
`
`(Continued)
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`
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`(Continued)
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`Li, X., et al., “Indoor Geolocation Using OFDM Signals. In
`HIPERLAN/2 Wireless LANS,' 11" IEEE International Sympo
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`PIMRC 2000, Proceedings (Cat. No. 00TH8525), Proceedings of
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`XPO 10520871, 2000, Piscatawat, NJ, USA, IEEE, USA, ISBN:
`9-7803-6463-5, Chapter I and III.
`(Continued)
`Primary Examiner Dao L. Phan
`(74) Attorney, Agent, or Firm—Richard A. Dunning, Jr.
`
`(57)
`
`ABSTRACT
`
`A method and computer program product for determining
`the position of a user terminal includes receiving at the user
`terminal a plurality of digital television (DTV) broadcast
`signals from a plurality of DTV transmitters, wherein each
`of the DTV signals is a European Telecommunications
`Standards Institute (ETSI) Digital Video Broadcasting-Ter
`restrial (DVB-T) signal; determining a pseudo-range
`between the user terminal and each DTV transmitter based
`on the DTV broadcast signals based on a known component
`in the DTV signals; and determining a position of the user
`terminal based on the pseudo-ranges and a location of each
`of the DTV transmitters.
`
`87 Claims, 17 Drawing Sheets
`
`Receive a plurality of digital television broadcast signals at
`the user terminal.
`
`
`
`
`
`
`
`
`
`Determine a pseudorange between the user terminal and
`the transmitter of each of the digital television broadcast
`signals.
`
`Determine a position of the user terminal based on the
`pseudoranges and a location of each of the transmitters.
`
`204
`
`206
`
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`US 7,126,536 B2
`Page 2
`
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`5,504,492
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`5,648,982
`5,774,829
`5,920,284
`5,952,958
`5,953,311
`6,016,119
`6,078,284
`6,094,168
`6,107,959
`6,137,441
`6,215,778
`6,317,452
`6,317,500
`6,373,432
`6,374,177
`6,433,740
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`
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`T/2000
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`
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`
`- - - - - - - - - - - - - 342/457
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`Cisneros et al.
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`Levanon ..................... 342.357
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`Durrant et al.
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`Lee et al.
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`
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`
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`2003/O122711 A1
`7/2003 Panasik et al.
`2003.0156063 A1
`8/2003 Spilker et al.
`FOREIGN PATENT DOCUMENTS
`2254 508 A 10, 1992
`OTHER PUBLICATIONS
`Rabinowitz, M., et al., “Positioning Using the ATSC Digital Tele
`vision Signal.” Rosum whitepaper. Online 2001, XP002235053,
`Retrieved from the Internet on Mar. 13, 2003 at URL www.rosum.
`com/whitepaper 8-7-01.pdf.
`EP Abstract/Zusammenfassung/Abrege, 02102666.1.
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`A (Nihon Musen KK) Aug. 2, 1983.
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`Combining GPS with Low Earth Orbit Satellites for Rapid Reso
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`Electrical Engineering, Stanford University (Dec. 2000), pp. 59-73.
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`* cited by examiner
`
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`

`

`U.S. Patent
`
`Oct. 24, 2006
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`US 7,126,536 B2
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`U.S. Patent
`
`Oct. 24, 2006
`
`Sheet 2 of 17
`
`US 7,126,536 B2
`
`Receive a plurality of digital television broadcast signals at
`the user terminal.
`
`Determine a pseudorange between the user terminal and
`the transmitter of each of the digital television broadcast
`signals.
`
`2O2
`
`204
`
`Determine a position of the user terminal based on the
`pseudoranges and a location of each of the transmitters.
`
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`Oct. 24, 2006
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`US 7,126,536 B2
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`U.S. Patent
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`Oct. 24, 2006
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`US 7,126,536 B2
`
`1.
`POSITION LOCATION USING
`TERRESTRAL DIGITAL VIDEO
`BROADCAST TELEVISION SIGNALS
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`
`10
`
`15
`
`This application is a continuation-in-part of U.S. patent
`application Ser. No. 09/887/158, “Position Location Using
`Broadcast Digital Television Signals.” by James J. Spilker,
`Jr. and Matthew Rabinowitz, filed Jun. 21.2001, now aban
`doned.
`This application also claims the benefit of U.S. Provi
`sional Patent Applications Ser. No. 60/265,675, "System and
`Method for Navigation and/or Data Communication Using
`Satellite and/or Terrestrial Infrastructure.” by Matthew
`Rabinowitz and James J. Spilker, filed Feb. 2, 2001; Ser. No.
`60/281,270, “Use of the ETSI DVB Terrestrial Digital TV
`Broadcast Signals For High Accuracy Position Location in
`Mobile Radio Links.” by James J. Spilker, filed Apr. 3, 2001;
`Ser. No. 60/281.269, “An ATSC Standard DTV Channel For
`Low Data Rate Broadcast to Mobile Receivers.” by James J.
`Spilker and Matthew Rabinowitz, filed Apr. 3, 2001; Ser.
`No. 60/293.812, “DTV Monitor System Unit (MSU), by
`James J. Spilker and Matthew Rabinowitz, filed May 25,
`2001; Ser. No. 60/293,813, “DTV Position Location Range
`And SNR Performance.” by James J. Spilker and Matthew
`Rabinowitz, filed May 25, 2001; and Ser. No. 60/293,646,
`“Time-Gated Noncoherent Delay Lock Loop Tracking Of
`DTV Signals.” by James J. Spilker and Matthew Rabinow
`30
`itz, filed May 25, 2001.
`The subject matter of all of the foregoing are incorporated
`herein by reference.
`
`25
`
`BACKGROUND
`
`35
`
`The present invention relates generally to position deter
`mination, and particularly to position determination using
`DTV signals.
`There have long been methods of two-dimensional lati
`tude/longitude position location systems using radio signals.
`In wide usage have been terrestrial systems such as Loran C
`and Omega, and a satellite-based system known as Transit.
`Another satellite-based system enjoying increased popular
`ity is the Global Positioning System (GPS).
`Initially devised in 1974, GPS is widely used for position
`location, navigation, survey, and time transfer. The GPS
`system is based on 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
`can be precisely tracked to determine pseudo-range. By
`tracking 4 or more satellites, one can determine precise
`position in three dimensions in real time, world-wide. More
`details are provided in B. W. Parkinson and J. J. Spilker, Jr.,
`Global Positioning System-Theory and Applications, Vol
`umes I and II, AIAA, Washington, D.C. 1996.
`GPS has revolutionized the technology of navigation and
`position location. However in some situations, GPS is less
`effective. Because the GPS signals are transmitted at rela
`tively low power levels (less than 100 watts) and over great
`distances, the received signal strength is relatively weak (on
`the order of -160 dBw as received by an omni-directional
`antenna). Thus the signal is marginally useful or not useful
`at all in the presence of blockage or inside a building.
`There has even been a proposed system using conven
`tional analog National Television System Committee
`(NTSC) television signals to determine position. This pro
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`2
`posal is found in a U.S. Patent entitled “Location Determi
`nation System And Method Using Television Broadcast
`Signals.” U.S. Pat. No. 5,510,801, issued Apr. 23, 1996.
`However, the present analog TV signal contains horizontal
`and vertical synchronization pulses intended for relatively
`crude synchronization of the TV set sweep circuitry. Further,
`in 2006 the Federal Communication Commission (FCC)
`will consider turning off NTSC transmitters and reassigning
`that valuable spectrum so that it can be auctioned for other
`purposes deemed more valuable.
`
`SUMMARY
`
`In general, in one aspect, the invention features a method
`and computer program product for determining the position
`of a user terminal. It includes receiving at the user terminal
`a plurality of digital television (DTV) broadcast signals from
`a plurality of DTV transmitters, wherein each of the DTV
`signals is a European Telecommunications Standards Insti
`tute (ETSI) Digital Video Broadcasting-Terrestrial (DVB-T)
`signal; determining a pseudo-range between the user termi
`nal and each DTV transmitter based on the DTV broadcast
`signals based on a known component in the DTV signals;
`and determining a position of the user terminal based on the
`pseudo-ranges and a location of each of the DTV transmit
`ters.
`Particular implementations can include one or more of the
`following features. Determining a position of the user ter
`minal includes adjusting the pseudo-ranges based on a
`difference between a transmitter clock at one of the DTV
`transmitters and a known time reference; and determining
`the position of the user terminal based on the adjusted
`pseudo-ranges and the location of each of the DTV trans
`mitters. The known component is a scattered pilot carrier.
`Determining a position of the user terminal includes deter
`mining an offset between a local time reference in the user
`terminal and a master time reference; and determining the
`position of the user terminal based on the pseudo-ranges, the
`location of each of the DTV transmitters, and the offset.
`Implementations include determining a Subsequent position
`of the user terminal using the offset. Determining a pseudo
`range includes storing a portion of each of the DTV signals;
`and Subsequently correlating each of the stored portions and
`a signal generated by the user terminal to produce the
`pseudo-ranges. Determining a pseudo-range includes corre
`lating each of the DTV signals with a signal generated by the
`user terminal as the DTV signals are received to produce the
`pseudo-ranges. Determining a position of the user terminal
`includes determining a general geographic area within
`which the user terminal is located; and determining the
`position of the user terminal based on the pseudo-ranges and
`the general geographic area. The general geographic area is
`a footprint of an additional transmitter communicably linked
`to the user terminal. Determining a position of the user
`terminal includes determining a tropospheric propagation
`Velocity in a vicinity of the user terminal; adjusting the value
`of each pseudo-range based on the tropospheric propagation
`Velocity; and determining the position of the user terminal
`based on the adjusted pseudo-ranges and the location of each
`of the DTV transmitters. Determining a position of the user
`terminal includes adjusting each pseudo-range based on a
`terrain elevation in a vicinity of the user terminal; and
`determining the position of the user terminal based on the
`adjusted pseudo-ranges and the location of each of the DTV
`transmitters. Implementations include selecting the DTV
`signals based on an identity of an additional transmitter
`communicably linked to the user terminal and a stored table
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`correlating the additional transmitter and the received DTV
`broadcast signals. Implementations include accepting a loca
`tion input from a user, and selecting the DTV signals based
`on the location input. Implementations include scanning
`available DTV signals to assemble a fingerprint of the
`location; and selecting the DTV broadcast signals used to
`determine the pseudo-ranges based on the fingerprint and a
`stored table that matches known fingerprints with known
`locations. Implementations include using receiver autono
`mous integrity monitoring (RAIM) to check the integrity of
`each pseudo-range based on redundant pseudo-ranges from
`the DTV transmitters.
`Advantages that can be seen in implementations of the
`invention include one or more of the following. Implemen
`tations of the invention may be used to position cellular
`telephones, wireless PDAs (personal digital assistant), pag
`ers, cars, OCDMA (orthogonal code-division multiple
`access) transmitters and a host of other devices. Implemen
`tations of the inventions make use of a DTV signal which
`has excellent coverage. Implementations of the present
`invention require no changes to the Digital Broadcast Sta
`tions.
`The DTV signal has a power advantage over GPS of more
`than 50 dB, and substantially superior geometry to that
`which a satellite system could provide, thereby permitting
`position location even in the presence of blockage and
`indoors. The DTV signal has roughly eight times the band
`width of GPS, thereby minimizing the effects of multipath.
`Due to the high power and sparse frequency components of
`the DTV signal used for ranging, the processing require
`ments are minimal. Implementations of the present inven
`tion accommodate far cheaper, lower-speed, and lower
`power devices than a GPS technique would require.
`In contrast to satellite systems such as GPS, the range
`between the DTV transmitters and the user terminals
`changes very slowly. Therefore the DTV signal is not
`significantly affected by Doppler effects. This permits the
`signal to be integrated for a long period of time, resulting in
`very efficient signal acquisition.
`The frequency of the DTV signal is substantially lower
`that that of conventional cellular telephone systems, and so
`has better propagation characteristics. For example, the
`DTV signal experiences greater diffraction than cellular
`signals, and so is less affected by hills and has a larger
`horizon. Also, the signal has better propagation character
`istics through buildings and automobiles. Further, imple
`mentations of the present invention utilize a component of
`the DVB-T signal that is continuous and constitutes a large
`percentage of the power of the DVB-T signal.
`Unlike the terrestrial Angle-of-Arrival/Time-of-Arrival
`positioning systems for cellular telephones, implementa
`tions of the present invention require no change to the
`hardware of the cellular base station, and can achieve
`positioning accuracies on the order of 1 meter. When used to
`position cellular phones, the technique is independent of the
`air interface, whether GSM (global system mobile), AMPS
`(advanced mobile phone service), TDMA (time-division
`multiple access), CDMA, or the like. A wide range of UHF
`60
`(ultra-high frequency) frequencies has been allocated to
`DTV transmitters. Consequently, there is redundancy built
`into the system that protects against deep fades on particular
`frequencies due to absorption, multipath and other attenu
`ating effects.
`The details of one or more embodiments of the invention
`are set forth in the accompanying drawings and the descrip
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`tion below. Other features, objects, and advantages of the
`invention will be apparent from the description and draw
`ings, and from the claims.
`
`DESCRIPTION OF DRAWINGS
`
`FIG. 1 depicts an implementation of the present invention
`including a user terminal that communicates over an air link
`with a base station.
`FIG. 2 illustrates an operation of an implementation of the
`invention.
`FIG. 3 depicts the geometry of a position determination
`using 3 DTV transmitters.
`FIG. 4 depicts an implementation of a receiver for use in
`generating a pseudo-range measurement.
`FIG. 5 illustrates a simple example of a position location
`calculation for a user terminal receiving DTV signals from
`two separate DTV antennas.
`FIG. 6 depicts the effects of a single hill on a circle of
`constant range for a DTV transmitter that is located at the
`same altitude as the Surrounding land.
`FIG. 7 shows the carrier numbers for the first 50 continu
`ous pilot carriers.
`FIG. 8 depicts the first 50 carriers of the continuous pilot
`carriers.
`FIG. 9 depicts the autocorrelation function of the com
`posite continuous pilot carriers with 177 parallel carriers in
`the 8K mode.
`FIG. 10 depicts the frequency hopping of the first 5
`scattered pilot carriers.
`FIG. 11 depicts the waveform of one example carrier with
`no sign reversals over 8 time increments.
`FIG. 12 is another view of the scattered pilot carriers.
`FIG. 13 depicts the autocorrelation function of the com
`posite set of 568 frequency-hopped scattered pilot carriers.
`FIG. 14 shows the detailed fine structure of the scattered
`pilot composite signal observed over the first 100 time
`increments.
`FIG. 15 shows the fine Structure of the doublet sidelobe of
`the scattered pilot composite carrier.
`FIG. 16 depicts an implementation of a monitor unit.
`FIG. 17 illustrates one implementation for tracking in
`software.
`Like reference symbols in the various drawings indicate
`like elements.
`
`DETAILED DESCRIPTION
`
`Introduction
`Digital television (DTV) is growing in popularity. DTV
`was first implemented in the United States in 1998. As of the
`end of 2000, 167 stations were on the air broadcasting the
`DTV signal. As of Feb. 28 2001, approximately 1200 DTV
`construction permits had been acted on by the FCC. Accord
`ing to the FCC's objective, all television transmission will
`Soon be digital, and analog signals will be eliminated. Public
`broadcasting stations must be digital by May 1, 2002 in
`order to retain their licenses. Private stations must be digital
`by May 1, 2003. Over 1600 DTV transmitters are expected
`in the United States. Other regions are implementing similar
`DTV systems. The European Telecommunications Stan
`dards Institute (ETSI) has defined a terrestrial DTV signal
`for Europe, referred to herein as the Digital Video Broad
`casting-Terrestrial (DVB-T) signal. These new DTV signals
`permit multiple standard definition TV signals or even high
`definition signals to be transmitted in the assigned 8 MHz
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`channel. These new DVB-TDTV signals are completely
`different from the analog NTSC TV signals, are transmitted
`on new 8 MHz frequency channels, and have completely
`new capabilities. The inventors have recognized that the
`DVB-T signal can be used for position location, and have
`developed techniques for doing so. These techniques are
`usable in the vicinity of DVB-T DTV transmitters with a
`range from the transmitter much wider than the typical DTV
`reception range. Because of the high power of the DTV
`signals, these techniques can even be used indoors by
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`handheld receivers, and thus provide a possible solution to
`the position location needs of the Enhanced 911 (E911)
`system.
`The techniques disclosed herein can be applied to other
`DTV signals that include known sequences of data by
`simply modifying the correlator to accommodate the known
`sequence of data, as would be apparent to one skilled in the
`relevant arts. These techniques can also be applied to a range
`of other orthogonal frequency-division multiplexing
`(OFDM) signals such as satellite radio signals.
`In contrast to the digital pseudo-noise codes of GPS, the
`DTV signals are received from transmitters only a few miles
`distant, and the transmitters broadcast signals at levels up to
`the megawatt level. In addition the DTV antennas have
`significant antenna gain, on the order of 14 dB. Thus there
`is often sufficient power to permit DTV signal reception
`inside buildings.
`As described below, implementations of the present
`invention utilize a component of the DVB-T signal that is
`referred to as the “scattered pilot signal.” The use of the
`scattered pilot signal is advantageous for several reasons.
`First, it permits position determination indoors, and at great
`distances from DTV transmitters. Conventional DTV
`receivers utilize only one data signal at a time, and so are
`limited in range from the DTV transmitter by the energy of
`a single signal. In contrast, implementations of the present
`invention utilize the energy of multiple scattered pilot sig
`nals simultaneously, thereby permitting operation at greater
`range from DTV transmitters than conventional DTV
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`receivers. Further, the scattered pilots are not modulated by
`data. This is advantageous for two reasons. First, all of the
`power in the scattered pilots is available for position deter
`mination; none of the power is devoted to data. Second, the
`scattered pilots can be observed for long periods of time
`without Suffering the degradation that data modulation
`would produce. Thus the ability to track signals indoors at
`substantial range from the DTV tower is greatly expanded.
`Furthermore, through the use of digital signal processing it
`is possible to implement these new tracking techniques in a
`single semiconductor chip.
`Referring to FIG. 1, an example implementation 100
`includes a user terminal 102 that communicates over an air
`link with a base station 104. In one implementation, user
`terminal 102 is a wireless telephone and base station 104 is
`a wireless telephone base station. In one implementation,
`base station 104 is part of a mobile MAN (metropolitan area
`network) or WAN (wide area network).
`FIG. 1 is used to illustrate various aspects of the invention
`but the invention is not limited to this implementation. For
`example, the phrase “user terminal' is meant to refer to any
`object capable of implementing the DTV position location
`described. Examples of user terminals include PDAs, mobile
`phones, cars and other vehicles, and any object which could
`include a chip or software implementing DTV position
`location. It is not intended to be limited to objects which are
`“terminals’ or which are operated by “users.”
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`Position Location Performed by a DTV Location Server
`FIG. 2 illustrates an operation of implementation 100.
`User terminal 102 receives DTV signals from a plurality of
`DTV transmitters 106A and 106B through 106N (step 202).
`Various methods can be used to select which DTV chan
`nels to use in position location. In one implementation, a
`DTV location server 110 tells user terminal 102 of the best
`DTV channels to monitor. In one implementation, user
`terminal 102 exchanges messages with DTV location server
`110 by way of base station 104. In one implementation user
`terminal 102 selects DTV channels to monitor based on the
`identity of base station 104 and a stored table correlating
`base stations and DTV channels. In another implementation,
`user terminal 102 can accept a location input from the user
`that gives a general indication of the area, such as the name
`of the nearest city; and uses this information to select DTV
`channels for processing. In one implementation, user termi
`nal 102 scans available DTV channels to assemble a fin
`gerprint of the location based on power levels of the avail
`able DTV channels. User terminal 102 compares this
`fingerprint to a stored table that matches known fingerprints
`with known locations to select DTV channels for processing.
`User terminal 102 determines a pseudo-range between the
`user terminal 102 and each DTV transmitter 106 (step 204).
`Each pseudo-range represents the time difference (or equiva
`lent distance) between a time of transmission from a trans
`mitter 108 of a component of the DTV broadcast signal and
`a time of reception at the user terminal 102 of the compo
`nent, as well as a clock offset at the user terminal.
`User terminal 102 transmits the pseudo-ranges to DTV
`location server 110. In one implementation, DTV location
`server 110 is implemented as a general-purpose computer
`executing Software designed to perform the operations
`described herein. In another implementation, DTV location
`server is implemented as an ASIC (application-specific
`integrated circuit). In one implementation, DTV location
`server 110 is implemented within or near base station 104.
`The DTV signals are also received by a plurality of
`monitor units 108A through 108N. Each monitor unit can be
`implemented as a small unit including a transceiver and
`processor, and can be mounted in a convenient location Such
`as a utility pole, DTV transmitters 106, or base stations 104.
`In one implementation, monitor units are implemented on
`satellites.
`Each monitor unit 108 measures, for each of the DTV
`transmitters 106 from which it receives DTV signals, a time
`offset between the local clock of that DTV transmitter and
`a reference clock. In one implementation the reference clock
`is derived from GPS signals. The use of a reference clock
`permits the determination of the time offset for each DTV
`transmitter 106 when multiple monitor units 108 are used,
`since each monitor unit 108 can determine the time offset
`with respect to the reference clock. Thus, offsets in the local
`clocks of the monitor units 108 do not affect these determi
`nations.
`In another implementation, no external time reference is
`needed. According to this implementation, a single monitor
`unit receives DTV signals from all of the same DTV
`transmitters as does user terminal 102. In effect, the local
`clock of the single monitor unit functions as the time
`reference.
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`In one implementation, each time offset is modeled as a
`fixed offset. In another implementation each time offset is
`modeled as a second order polynomial fit of the form
`Offset=a+b(t-T)+c(t-T)?
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`(1)
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`The three ranges can be expressed as
`r1=X-X1
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`r2=X-X2
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`p3=X-X3
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`(5)
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`(6)
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`(7)
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`that can be described by a, b, c, and T. In either implemen
`tation, each measured time offset is transmitted periodically
`to the DTV location server using the Internet, a secured
`modem connection or the like. In one implementation, the
`location of each monitor unit 108 is determined using GPS
`receivers.
`DTV location server 110 receives information describing
`the phase center (i.e., the location) of each DTV transmitter
`106 from a database 112. In one implementation, the phase
`center of each DTV transmitter 106 is measured by using
`monitor units 108 at different locations to measure the phase
`center directly. In another implementation, the phase center
`of each DTV transmitter 106 is measured by surveying the
`antenna phase center.
`In one implementation, DT