Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N7/00—Television systems
  • H04N7/015—High-definition television systems
• • 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]
  • H04N21/60—Network structure or processes for video distribution between server and client or between remote clients; Control signalling between clients, server and network components; Transmission of management data between server and client, e.g. sending from server to client commands for recording incoming content stream; Communication details between server and client 
  • H04N21/61—Network physical structure; Signal processing
  • H04N21/615—Signal processing at physical level
• • 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
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
  • G01C21/00—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00
  • G01C21/20—Instruments for performing navigational calculations
  • G01C21/206—Instruments for performing navigational calculations specially adapted for indoor navigation
• • 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
  • 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
  • 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
  • H04N21/25—Management operations performed by the server for facilitating the content distribution or administrating data related to end-users or client devices, e.g. end-user or client device authentication, learning user preferences for recommending movies
  • H04N21/258—Client or end-user data management, e.g. managing client capabilities, user preferences or demographics, processing of multiple end-users preferences to derive collaborative data
  • H04N21/25808—Management of client data
  • H04N21/25841—Management of client data involving the geographical location of the client
• • 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
  • H04N21/25—Management operations performed by the server for facilitating the content distribution or administrating data related to end-users or client devices, e.g. end-user or client device authentication, learning user preferences for recommending movies
  • H04N21/266—Channel or content management, e.g. generation and management of keys and entitlement messages in a conditional access system, merging a VOD unicast channel into a multicast channel
  • H04N21/2668—Creating a channel for a dedicated end-user group, e.g. insertion of targeted commercials based on end-user profiles
• • 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
  • H04N21/41—Structure of client; Structure of client peripherals
  • H04N21/414—Specialised client platforms, e.g. receiver in car or embedded in a mobile appliance
  • H04N21/41422—Specialised client platforms, e.g. receiver in car or embedded in a mobile appliance located in transportation means, e.g. personal vehicle
• • 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
• • A—HUMAN NECESSITIES
  • A63—SPORTS; GAMES; AMUSEMENTS
  • A63F—CARD, BOARD, OR ROULETTE GAMES; INDOOR GAMES USING SMALL MOVING PLAYING BODIES; VIDEO GAMES; GAMES NOT OTHERWISE PROVIDED FOR
  • A63F2300/00—Features of games using an electronically generated display having two or more dimensions, e.g. on a television screen, showing representations related to the game
  • A63F2300/20—Features of games using an electronically generated display having two or more dimensions, e.g. on a television screen, showing representations related to the game characterised by details of the game platform
  • A63F2300/205—Features of games using an electronically generated display having two or more dimensions, e.g. on a television screen, showing representations related to the game characterised by details of the game platform for detecting the geographical location of the game platform
• • 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
  • G01S5/02—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
  • G01S5/0218—Multipath in signal reception

Definitions

• GPS is less effective. Because the GPS signals are transmitted at relatively 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.
• the current position location systems have significant drawbacks that prevent or inhibit their use for many of these services.
• the proposed NTSC system is not suitable for services that require high precision.
• the NTSC transmitters may be turned off in 2006, services that require large initial investments are also less attractive since the time to recover the investment may be limited.
• GPS systems generally have higher precision than the NTSC system.
• the receivers are relatively complex and expensive, thus making the GPS approach inappropriate for services that require simple and/or low-cost receivers.
• the GPS signal is not particularly robust. GPS' low signal power makes it marginally useful in the presence of blockage or inside buildings. Its low bandwidth signal also makes it susceptible to multipath effects.
• the present invention overcomes the limitations of the prior art by providing a service according to a location of a device.
• the location is determined based on pseudo-ranges between the device and a plurality of digital television (DTV) transmitters.
• the pseudo-ranges are calculated based on broadcast DTV signals received by the device from the DTV transmitters.
• DTV signals include the American Television Standards Committee (ATSC) signals, the European Telecommunications Standards Institute Digital Video Broadcasting - Terrestrial (DVB-T) signals and the Japanese Integrated Service Digital Broadcasting-Terrestrial (ISDB-T) signals.
• ATSC American Television Standards Committee
• DVD-T European Telecommunications Standards Institute Digital Video Broadcasting - Terrestrial
• ISDB-T Japanese Integrated Service Digital Broadcasting-Terrestrial
• FIG. 2 is a flow diagram illustrating a method according to the present invention.
• FIG. 25 shows the carrier numbers for the first 50 continuous pilot carriers.
• FIG. 28 depicts the frequency hopping of the first 5 scattered pilot carriers.
• the user device 102 performs all functions.
• the device 102 calculates
• FIG. 3D is a variant of FIG. 3C, in which the location calculation is performed by an external DTV location server 110. This permits more robust and/or accurate calculation of the device location but still maintains some of the mobility of the approach of FIG. 3C.
• the navigation information provided is a map of the local vicinity around the device 102. This map may be updated as the location of the device 102 is updated.
• the service provider system 120 accesses the location of the user device 102, which location is determined as described above. The system 120 retrieves the relevant map data from the database 422 based on the location of the device 102 and transmits the map data to the device for display. In an alternate embodiment, the service provider system renders the map data into a viewable map image and transmits the image to the device 102, which receives and displays the map.
• the service provider system 120 assists in providing navigation services but the map database 422 is accessed by the device 102.
• the service provider system 120 might identify which map data is relevant (e.g., U.S. Geological Survey grid no. xxx) and send a key code for this map data to the user device 102.
• the user device 102 retrieves the map data from database 422 based on the key code.
• the map database is accessed by the user device 102 but controlled by a third party.
• the service provider system transmits a key code to the user device 102 which authorizes the device to access the relevant portion of the database.
• a company might wish to track various objects (e.g., inventory, containers) as part of its internal operations or to reduce theft and loss.
• the tracking information might be provided to the owner of the object, an insurer of the object or law enforcement for similar reasons.
• the tracking data from the objects can be collected at one location (e.g., a central database) and conventional tracking software may be used to analyze and present the tracking data in an efficient manner.
• the history of the location of the device is recorded for later use.
• One example is a "black-box" application. If the black box is self-contained, the device determines its own location and stores the history of its location locally within the device without relying on external entities (such as the DTV location server 110 or service provider system 120).
• FIG. 5 shows an example in which the adjustments depend on geographic domain.
• the domains 510 correspond to the cells in the coverage area. Each cell is served by a different base station. Thus, knowing in which cell the device 102 is located permits optimization of the device 102 for that particular base station. For example, when the device 102 crosses from one cell to another, its antenna might be oriented towards the base station for the new cell. As another example, if the base stations can use different coding or modulation techniques, the device 102 can be configured to take advantage of this. As a final example, each cell may offer different types of services or quality of service (e.g., local, local long distance, long distance, etc.). Thus, knowing in which cell it is located permits the user device 102 to configure itself to take advantage of the different services or quality of service.
• different types of services or quality of service e.g., local, local long distance, long distance, etc.
• the adjustments can also be determined entirely by the device 102 (e.g., as in FIG.
• Physical services may also be enabled or enhanced by knowing the location of the device 102. As one example, knowing the location of the device permits delivery of the physical service to that specific location. Emergency roadside assistance, emergency 911 service, and food delivery are examples of these types of services. In the E-911 example, the location of the device 102 requesting E-911 is determined based on DTV signals. The appropriate E-911 unit(s) are then dispatched to the device location.
• physical services may be rendered in a number of ways.
• the service provider system 120 when the service provider system 120 receives a request for a physical service, the service provider itself may travel to the device location and perform the physical service.
• the service provider itself does not perform the physical service. Instead, it contacts a local service provider, which provides the service. For example, referring to FIG. 5, there may be local service providers which service each of the domains 510.
• the service provider system 120 determines in which domain the device is located, it then contacts the corresponding local service provider to provide the service.
• the service provider could be a central automobile club which uses a network of local towing companies to provide the roadside assistance.
• the service provider system 120 transmits a key code to the device, which authorizes provision of the physical service. For example, the user could present the key code to a local towing company to have his car towed.
• the service provider system 120 determines the localized information, for example pulling it from a central database.
• the information is transmitted to the device 102, which displays it to the user.
• the central database may include news from many different municipalities.
• the service provider system 120 determines in which municipality the device is located and transmits the local news for that municipality to the device.
• the service provider system 120 may transmit a key code to the device 102 instead.
• the key code enables the device 102 to retrieve the local news from a different source, for instance a third party which maintains a news database.
• the news is localized based on municipality, which follows the domain-based model shown in FIG. 5. Each municipality is a separate domain 510 and the local news provided to the user depends on in which municipality the user is located.
• a tour guide In this application, a tour of a point of interest is given via the device 102.
• the device might provide information describing the penguin exhibit when the user is located in the vicinity of the penguin exhibit, and so on. If the user is touring a historic battlefield, the device might provide information describing the events which occurred in the general location of the device. As the device moves, the information changes to describe the new location. The information can take many forms: video, graphics and audio being a few.
• the user is offered "electronic postcards" of the point of interest, which he may purchase. The device offers the postcards based on its current location. For example, when the device is located in the vicinity of the Hoover Dam, it offers images of the Hoover Dam rather than images of Disneyland.
• the device 102 is used to provide safety or relief information.
• the user requests the localized information.
• the user might request and pay for local news, similar to purchasing a newspaper.
• the localized information is unsolicited.
• the user might generate a coupon for the store.
• the user might automatically receive information about safety procedures and relief efforts.
• the user can select from among different options with respect to unsolicited information.
• One possible option is that the user device 102 is continuously tracked and continuously receives unsolicited information.
• Another option is that all unsolicited information is refused.
• a third option is that the user receives information only when he so requests.
• the user could also receive information based on a previously registered profile.
• the user might indicate a preference for ice cream and a dislike for cookies.
• the user strolls around town he receives information about local ice cream parlors but not about local cookie vendors.
• FIG. 6 depicts a system in which the service provided is video gaming.
• the service provider system 120 determines the users' locations according to the location of the wireless gaming devices, which have been determined using DTV signals, and updates the video game accordingly. Video games for one player or more than two players can also be implemented in this fashion.
• the location of the device 102 is used as an aid in surveying.
• a surveyor could carry the device 102 with him at a site and then record the locations at various points around the site.
• the device 102 is used to alert the user when certain other individuals are close by.
• the user might indicate in his profile that he is interested in meeting other individuals with an interest in Civil War memorabilia.
• the user's profile is stored at the service provider system 120.
• the service provider system 120 tracks the location of the device, as well as the locations of devices of other users. If any of the other users are nearby and also indicate an interest in Civil War memorabilia, the service provider system 120 alerts the users so that they may meet each other if they so desire. Different criteria, including for dating and matchmaking, may be used.
• the choice of user device 102, DTV location server 110 and service provider system 120 depends on the nature of the service to be provided. It also depends on the nature of the communications links between the user device 102, DTV location server 110 and service provider system 120.
• Land lines e.g., fiber optic, cable, electrical
• microwave links are alternatives which are well-suited for non- mobile endpoints (e.g., between the DTV location server 110 and service provider system 120 in the implementation of FIG. 1).
• the different communications links can be either one-way or two-way, depending on the application.
• the actions required to implement a service may be allocated between the user device 102, DTV location server 110 and service provider system 120 in many ways. The user device 102 may perform some, all or none of these actions locally. Similarly, the service provider system 120's role may vary from minor to major. Actions may also be allocated in various ways between the DTV location server 110 and service provider system 120.
• the service provider system 120 may communicate with user device 102 via the DTV location server 110, instead of directly as shown in FIG. 1.
• the reverse is also possible.
• the user device 102, DTV location server 110 and service provider system 120 are shown as separate in FIG. 1, this is not required.
• the services which may be provided are not limited to those discussed above.
• Another service is the purchase of good or services, including for example movie tickets, restaurant reservations, consumer goods, guided tours and local tour books.
• Additional services include the transmission of information from local commercial establishments (e.g., show times for theaters, menus from restaurants, etc.) or localized information, such as local news, traffic and weather.
• Table 1 lists rough data rates suggested for certain types of information using current technology and quality standards. Data rates are not restricted to those shown in the table.
• voice with data refers to information stream which includes voice traffic along with text information and or text messaging. This would include speech recognition applications and text messages that accompany standard voice applications.
• DTV techniques are used in conjunction with or as a supplement to other positioning techniques, including for example those based on GPS, analog TN CDMA Network, TDMA network, and E-OTD.
• GPS analog TN CDMA Network
• TDMA Time Division Multiple Access
• E-OTD E-OTD
• a DTV location server 110 informs the user device 102 of the best DTV channels to monitor.
• user device 102 exchanges messages with DTV location server 110 by way of base station 104.
• user device 102 selects DTV channels to monitor based on the identity of base station 104 and a stored table correlating base stations and DTV channels.
• user device 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.
• user device 102 scans available DTV channels to assemble a fingerprint of the location based on power levels of the available DTV channels. User device 102 compares this fingerprint to a stored table that matches known fingerprints with known locations to select DTV channels for processing.
• User device 102 determines a pseudo-range between the user device 102 and each
• Each pseudo-range represents the time difference (or equivalent distance) between a time of transmission from a transmitter 108 of a component of the DTV broadcast signal and a time of reception at the user device 102 of the component, as well as a clock offset at the user device.
• DTV location server 110 is implemented within or near base station 104.
• the DTV signals are also received by a plurality of monitor units 108 A through
• 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. [0119]
• 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.
• 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 determinations.
• a single monitor unit receives DTV signals from all of the same DTV transmitters as does user device 102.
• the local clock of the single monitor unit functions as the time reference.
• each time offset is modeled as a fixed offset.
• each time offset is modeled as a second order polynomial fit of the form
• each measured time offset is transmitted periodically to the DTV location server using the Internet, a secured modem connection or the like.
• 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.
• the phase center of each DTV transmitter 106 is measured by using monitor units 108 at different locations to measure the phase center directly.
• the phase center of each DTV transmitter 106 is measured by surveying the antenna phase center.
• DTV location server 110 receives weather information describing the air temperature, atmospheric pressure, and humidity in the vicinity of user device 102 from a weather server 114.
• the weather information is available from the Internet and other sources such as NOAA.
• DTV location server 110 determines tropospheric propagation velocity from the weather information using techniques such as those disclosed in B. Parkinson and J. Spilker, Jr., Global Positioning System - Theory and Applications, AIAA, Washington, DC, 1996, Vol. 1, Chapter 17 Tropospheric Effects on GPS by J. Spilker, Jr., which is incorporated herein by reference.
• DTV location server 110 can also receive from base station 104 information which identifies a general geographic location of user device 102.
• the information can identify a cell or cell sector within which a cellular telephone is located. This information is used for ambiguity resolution, as described below.
• DTV location server 110 determines a location of the user device 102 based on the pseudo-ranges and a location of each of the transmitters (step 706).
• FIG. 8 depicts the geometry of a location determination using three DTV transmitters 106.
• DTV transmitter 106 A is located at position (xl, yl).
• the range between user device 102 and DTV transmitter 106A is rl.
• DTV 106B transmitter is located at position (x2,y2).
• the range between user device 102 and DTV transmitter 106B is r2.
• DTV transmitter 106N is located at position (x3, y3).
• the range between user device 102 and DTV transmitter 106N is r3.
• DTV location server 110 may adjust the value of each pseudo-range according to the tropospheric propagation velocity and the time offset for the corresponding DTV transmitter
• DTV location server 110 uses the phase center information from database 112 to determine the location of each DTV transmitter 106.
• User device 102 makes three or more pseudo-range measurements to solve for three unknowns, namely the position (x, y) and clock offset T of user device 102.
• the techniques disclosed herein are used to determine location in three dimensions such as longitude, latitude, and altitude, and can include factors such as the altitude of the DTV transmitters .
• X represents the two-dimensional vector position (x, v) of the user device 102
• XI represents the two-dimensional vector position (xl, yl) of DTV transmitter 106 A
• X2 represents the two-dimensional vector position (x2, y2) of DTV transmitter 106B
• X3 represents the two-dimensional vector position (x3, y3) of DTV transmitter 106N.
• user device 102 does not compute pseudo-ranges, but rather takes measurements of the DTV signals that are sufficient to compute pseudo-range, and transmits these measurements to DTV location server 110.
• DTV location server 110 then computes the pseudo-ranges based on the measurements, and computes the user's location based on the pseudo-ranges, as described above.
• the position of user device 102 is computed by user device 102. In this implementation, all of the necessary information is transmitted to user device
• This information can be transmitted to user device by DTV location server 110, base station
• User device 102 receives the time offset between the local clock of each DTV transmitter and a reference clock. User device 102 also receives information describing the phase center of each DTV transmitter 106 from a database 112.
• User device 102 receives the tropospheric propagation velocity computed by DTV locations server 110. In another implementation, user device 102 receives weather information describing the air temperature, atmospheric pressure, and humidity in the vicinity of user device
• User device 102 can also receive from base station 104 information which identifies the rough location of user device 102.
• the information can identify a cell or cell sector within which a cellular telephone is located. This information is used for ambiguity resolution, as described below.
• User device 102 receives DTV signals from a plurality of DTV transmitters 106 and determines a pseudo-range between the user device 102 and each DTV transmitter 106. User device 102 then determines its location based on the pseudo-ranges and the phase centers of the transmitters.
• the location of user device 102 can be determined using the two DTV transmitters and the offset T computed during a previous position determination.
• the values of T can be stored or maintained according to conventional methods.
• base station 104 determines the clock offset of user device
• Base station 104 transmits the clock offset Tto DTV location server 110, which then determines the position of user device 102 from the pseudo-range computed for each of the DTV transmitters.
• GPS is used to augment the position determination.
• FIG. 9 illustrates a simple example of a position location calculation for a user device 102 receiving DTV signals from two separate DTV antennas 106A and 106B. Circles of constant range 902 A and 902B are drawn about each of transmit antennas 106 A and 106B, respectively.
• the position for a user device including correction for the user device clock offset, is then at one of the intersections 904A and 904B of the two circles 902 A and 902B.
• the ambiguity is resolved by noting that base station 104 can determine in which sector 908 of its footprint (that is, its coverage area) 906 the user device is located. Of course if there are more than two DTV transmitters in view, the ambiguity can be resolved by taking the intersection of three circles.
• user device 102 can accept an input from the user that gives a general indication of the area, such as the name of the nearest city.
• user device 102 scans available DTV channels to assemble a fingerprint of the location. User device 102 compares this fingerprint to a stored table that matches known fingerprints with known locations to identify the current location of user device 102.
• the position location calculation includes the effects of ground elevation.
• the circles of constant range are distorted.
• FIG. 10 depicts the effects of a single hill 1004 on a circle of constant range 1002 for a DTV transmitter 106 that is located at the same altitude as the surrounding land.
• FIGS. 11-23 illustrate various receivers for use with American Television Standards
• 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 February 28 2001, approximately 1200 DTV construction permits had been acted on by the FCC. According 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.
• These new DTV signals permit multiple standard definition TV signals or even high definition signals to be transmitted in the assigned 6 MHz channel.
• These new American Television Standards Committee (ATSC) DTV signals are completely different from the analog NTSC TV signals, are transmitted on new 6 MHz frequency channels, and have completely new capabilities.
• ATSC American Television Standards Committee
• the inventors have recognized that the ATSC signal can be used for position location, and have developed techniques for doing so. These techniques are usable in the vicinity of ATSC 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 handheld receivers.
• the DTV signals are received from transmitters only a few miles distant, and the transmitters broadcast signals at levels up to the megawatt level.
• the DTV antennas have significant antenna gain, on the order of 14 dB.
• the DTV signal can be correlated for a period roughly a million times longer than the period of single data symbol.
• the ability to track signals indoors at substantial range from the DTV tower is greatly expanded.
• digital signal processing it is possible to implement these new tracking techniques in a single semiconductor chip.
• FIG. 11 depicts an implementation 1100 of a sampler for use in taking samples of received DTV signals.
• sampler 1100 is implemented within user device 102.
• sampler 1100 is implemented within monitor units 108.
• the sampling rate should be sufficiently high to obtain an accurate representation of the DTV signal, as would be apparent to one skilled in the art.
• Sampler 1100 receives a DTV signal 1102 at an antenna 1104.
• FIG. 12 depicts an implementation 1200 of a noncoherent correlator for use in searching for the correlation peak of the DTV signal samples produced by sampler 1100.
• correlator 1200 is implemented within user device 102.
• correlator 1200 is implemented within monitor units 108.
• Correlator 1200 retrieves the I and Q samples of a DTV signal from memory 1114.
• Correlator 1200 processes the samples at intermediate frequency (IF).
• Other implementations process the samples in analog or digital form, and can operate at intermediate frequency (IF) or at baseband.
• a code generator 1202 generates a code sequence.
• the code sequence is a raised cosine waveform.
• the code sequence can be any known digital sequence in the ATSC frame.
• the code is a synchronization code.
• the synchronization code is a Field Synchronization Segment within an ATSC data frame.
• the synchronization code is a Synchronization Segment within a Data Segment within an ATSC data frame.
• the synchronization code includes both the Field Synchronization Segment within an ATSC data frame and the Synchronization Segments within the Data Segments within an ATSC data frame.
• Other components of the DTV signal such as pilot, symbol clock, or carrier, can be used for position location.
• Mixers 12041 and 1204Q respectively combine the I and Q samples with the code generated by code generator 1202.
• the outputs of mixers 12041 and 1204Q are respectively filtered by filters 12061 and 1206Q and provided to summer 1207.
• the sum is provided to square law device 1208.
• Filter 1209 performs an envelope detection for non-coherent correlation, according to conventional methods.
• Comparator 1210 compares the correlation output to a predetermined threshold. If the correlation output falls below the threshold, search control 1212 causes summer 1214 to add additional pulses to the clocking waveform produced by clock 1216, thereby advancing the code generator by one symbol time, and the process repeats.
• the clocking waveform has a nominal clock rate of 10.76 MHz, matching the clock rate or symbol rate the received DTV signals. [0155] When the correlation output first exceeds the threshold, the process is done. The time offset that produced the correlation output is used as the pseudo-range for that DTV transmitter 106.
• receiver correlators and matched filters there are two important sources of receiver degradation.
• the user device local oscillator is often of relatively poor stability in frequency. This instability affects two different receiver parameters. First, it causes a frequency offset in the receiver signal. Second, it causes the received bit pattern to slip relative to the symbol rate of the reference clock. Both of these effects can limit the integration time of the receiver and hence the processing gain of the receiver. The integration time can be increased by correcting the receiver reference clock. In one implementation a delay lock loop automatically corrects for the receiver clock.
• a NCO (numerically controlled oscillator) 1218 adjusts the clock frequency of the receiver to match that of the incoming received signal clock frequency and compensate for drifts and frequency offsets of the local oscillator in user device 102. Increased accuracy of the clock frequency permits longer integration times and better performance of the receiver correlator.
• the frequency control input of NCO 1218 can be derived from several possible sources, a receiver symbol clock rate synchronizer, tracking of the ATSC pilot carrier, or other clock rate discriminator techniques installed in NCO 1218.
• the current ATSC signal is described in "ATSC Digital Television Standard and
• the ATSC signal uses 8-ary Vestigial Sideband Modulation (8VSB).
• the symbol rate of the ATSC signal is 10.762237 MHz, which is derived from a 27.000000MHz clock.
• the structure 1300 of the ATSC frame is illustrated in FIG. 13.
• the frame 1300 consists of a total of 626 segments, each with 832 symbols, for a total of 520832 symbols.
• the structure 1400 of the field synchronization segment is illustrated in FIG. 14.
• the two field synchronization segments 1400 in a frame 1300 differ only to the extent that the middle set of 63 symbols are inverted in the second field synchronization segment.
• the structure 1500 of the data segment is illustrated in FIG. 15.
• the first four symbols of data segment 1500 (which are -1, 1, 1, -1) are used for segment synchronization.
• the other 828 symbols in data segment 1500 carry data. Since the modulation scheme is 8VSB, each symbol carries 3 bits of coded data. A rate 2/3 coding scheme is used.
• Implementations of the invention can be extended to use future enhancements to
• the ATSC signal specification allows for a high rate 16VSB signal.
• the 16VSB signal has the same field synch pattern as the 8VSB signal. Therefore, a single implementation of the present invention can be designed to work equally well with both the 8VSB and the 16VSB signal.
• the 8VSB 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
• This signal has a frequency characteristic
• the signal is filtered so that only a small portion of the lower sideband remains. This filtering can be described as:
• HJf is a filter designed to leave a vestigial remainder of the lower sideband.
• the response U(f)P(f) can be represented as
• P(f) - -j sgn(f)P(f) is the Hubert transform of P(f).
• p vt (t) is the in-phase component
• p vq (t) is the quadrature component
• C comfort is the 8-level data signal.
• FIG. 17 depicts an implementation 1700 of monitor unit 108.
• An antenna 1704 receives GPS signals 1702.
• a GPS time transfer unit 1706 develops a master clock signal based on the GPS signals.
• a NCO (numerically controlled oscillator) field synchronization timer 1708 A develops a master synchronization signal based on the master clock signal.
• the master synchronization signal can include one or both of the ATSC segment synchronization signal and the ATSC field synchronization signal.
• the NCO field synchronization timers 1708A in all of the monitor units 108 are synchronized to a base date and time.
• a DTV antenna 1712 receives a plurality of DTV signals 1710. In another implementation, multiple DTV antennas are used.
• An amplifier 1714 amplifies the DTV signals.
• One or more DTV tuners 1716A through 1716N each tunes to a DTV channel in the received DTV signals to produce a DTV channel signal.
• Each of a plurality of NCO field synchronization timers 1708B through 1708M receives one of the DTV channel signals.
• Each of NCO field synchronization timers 1708B through 1708M extracts a channel synchronization signal from a DTV channel signal.
• the channel synchronization signal can include one or both of the ATSC segment synchronization signal and the ATSC field synchronization signal. Note that the pilot signal and symbol clock signal within the DTV signal can be used as acquisition aids.
• Each of a plurality of summers 1718 A through 1718N generates a clock offset between the master synchronization signal and one of the channel synchronization signals.
• Processor 1720 formats and sends the resulting data to DTV location server 110.
• this data includes, for each DTV channel measured, the identification number of the DTV transmitter, the DTV channel number, the antenna phase center for the DTV transmitter, and the clock offset.
• This data can be transmitted by any of a number of methods including air link and the Internet.
• the data is broadcast in spare MPEG packets on the DTV channel itself.
• FIG. 18 illustrates one implementation 1800 for tracking in software.
• Antenna 1802 receives a DTV signal.
• Antenna 1802 can be a magnetic dipole or any other type of antenna capable of receiving DTV signals.
• a bandpass filter 1804 passes the entire DTV signal spectrum to an LNA 1806.
• filter 1804 is a tunable bandpass filter that passes the spectrum for a particular DTV channel under the control of a digital signal processor (DSP) 1814.
• DSP digital signal processor
• a low-noise amplifier (LNA) 1806 amplifies and passes the selected signal to a low-noise amplifier (LNA) 1806
• DTV channel selector 1808 selects a particular DTV channel under the control of DSP 1814, and filters and downconverts the selected channel signal from UHF (ultra-high frequency) to IF (intermediate frequency) according to conventional methods.
• An amplifier (AMP) 1810 amplifies the selected IF channel signal.
• An analog-to-digital converter and sampler (A/D) 1812 produces digital samples of the DTV channel signal ⁇ (t) and passes these samples to DSP 1814.
• R st0 r e ( will store the correlation between the incident signal s(t) and the complex code signal s CO de( ⁇ - R s t 0 e T may be further refined by searching
• the initial step size for ⁇ must be less then half the Nyquist rate — .
• T samp where T per is the period of the code being used, and T samp is the sample interval ; - Create a reference code mixing signal
• ⁇ is the nominal IF frequency of the incident signal
• v is the frequency offset of the mixing signal relative to the incident signal
• ⁇ is the phase offset of the mixing signal from the incident signal
• FIG. 20 displays an example spectrum for a 1 millisecond sample of the signal from a KICU channel 52 DTV broadcast from San Jose.
• the signal was downconverted to a center frequency of 27MHz, which corresponds to a digital frequency of 0.54 for a sampling rate of 100 mega-samples per second.
• the signal was digitally bandpass filtered to a bandwidth of 6MHz.
• ETSI Standards Institute
• DVB-T Digital Video Broadcasting-Terrestrial
• 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 handheld receivers.
• the techniques disclosed herein and with respect to the ATSC DTV signals previously 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.
• OFDM orthogonal frequency-division multiplexing
• the DTV signals are received from transmitters only a few miles distant, and the transmitters broadcast signals at levels up to the megawatt level.
• 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.
• 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 signals simultaneously, thereby permitting operation at greater range from DTV transmitters than conventional DTV receivers. Further, the scattered pilots are not modulated by data. This is advantageous for two reasons.
• FIG. 24 depicts an implementation 2400 of a receiver for use in generating a pseudo-range measurement.
• receiver 2400 is implemented within user device 102.
• receiver 2400 is implemented within monitor units 108.
• the position location operation at the subscriber handset or other device need only take place when the subscriber needs position location. For a subscriber walking slowly, in a slowly moving vehicle, or sitting in a building or field in an emergency, this location information need only be measured infrequently. Thus the battery or other power source can be very small.
• receiver correlators and matched filters there are two important sources of receiver degradation.
• the user device local oscillator is often of relatively poor stability in frequency. This instability affects two different receiver parameters. First, it causes a frequency offset in the receiver signal. Second, it causes the received bit pattern to slip relative to the symbol rate of the reference clock. Both of these effects can limit the integration time of the receiver and hence the processing gain of the receiver. The integration time can be increased by correcting the receiver reference clock. In one implementation a delay lock loop automatically corrects for the receiver clock.
• Each pilot carrier is given a ⁇ 1 sign amplitude as governed by a PN sequence of an
• k [t, p] 3Mod[n[t], 4] + 12 p (20) where p is the number of the pilot and n[t] is the quantized time interval
• the total scattered pilot signal is then the sum of 568 frequency hopped individual pilot carriers
• FIG. 31 depicts the autoconelation function of the composite set of 568 frequency-hopped scattered pilot caniers.
• FIGS. 32 and 33 show the detail over much smaller time increments.
• FIG. 32 shows the detailed fine structure of the scattered pilot composite signal observed over the first 100 time increments. Note the low levels of the autocorrelation function outside of the peak.
• FIG. 33 shows the fine structure of the doublet sidelobe of the scattered pilot composite carrier. Note again the very small values of the autoconelation function of this signal outside of the main peak and the 4 sidelobe peaks.
• FIG. 34 depicts an implementation 3400 of monitor unit 108.
• An antenna 3404 receives GPS signals 3402.
• a GPS time transfer unit 3406 develops a master clock signal based on the GPS signals.
• a NCO (numerically controlled oscillator) code synchronization timer 3408A develops a master synchronization signal based on the master clock signal.
• the master synchronization signal can include the DVB-T scattered pilot earners.
• the NCO field synchronization timers 3408A in all of the monitor units 108 are synchronized to a base date and time.
• a single monitor unit 108 receives DTV signals from all of the same DTV transmitters that user device 102 does, it is not necessary to synchronize that monitor unit 108 with any other monitor unit for the pu ⁇ oses of determining the position of user device 102. Such synchronization is also unnecessary if all of the monitor stations 108, or all of the DTV transmitters, are synchronized to a common clock.
• ADTV antenna 3412 receives a plurality of DTV signals 3410. In another implementation, multiple DTV antennas are used.
• An amplifier 3414 amplifies the DTV signals.
• One or more DTV tuners 3416A through 3416N each tunes to a DTV channel in the received DTV signals to produce a DTV channel signal.
• Each of a plurality of NCO code synchronization timers 3408B through 3408M receives one of the DTV channel signals.
• Each of NCO code synchronization timers 3408B through 3408M extracts a channel synchronization signal from a DTV channel signal.
• the channel synchronization signal can include the DVB-T scattered pilot carriers.
• C is the function describing the in-phase baseband signal and C is the function
• R s i o r e ( ) will store the correlation between the incident signal s(t) and the complex code signal s C0 d e (t)- R s tore( ) may be further refined by searching
• the initial step size for ⁇ must be less then half the Nyquist rate — .
• the invention can be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in combinations thereof.
• Various signals and signal processing techniques can be implemented in either the digital or analog domain.
• 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.

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