KR20050044347A - Position location using integrated services digital broadcasting - terrestrial broadcast television signals - Google Patents

Abstract

A method, apparatus, and computer- readable media for determining the position of a user terminal (102) comprises receiving at the user terminal (102) a digital television (DTV) broadcast signal from a DTV transmitter (106A, 106B..., 106N)), wherein the DTV signal comprises an Integrated Services Digital Broadcasting - Terrestrial (ISDB-T) signal; determining a pseudo-range between the user terminal (102) and the DTV transmitter (106A, 106B,..., 106N) based on a known component in the broadcast DTV signal; and determining a position of the user terminal (102) based on the pseudo-range and a location of the DTV transmitter (106A, 106B,..., 106N).

Description

POSITION LOCATION USING INTEGRATED SERVICES DIGITAL BROADCASTING-TERRESTRIAL BROADCAST TELEVISION SIGNALS}

The present invention relates to positioning, and in particular, to positioning using a digital television (DTV) signal.

The two-dimensional latitude / longitude positioning system method using broadcast signals has been used for a long time. Satellite-based systems known as Transit and terrestrial systems such as Logan C and Omega are widely used. Another popular satellite-based system is the Global Positioning System (GPS).

GPS was first developed in 1974 and is widely used for positioning, conducting, and surveying. The GPS system is based on an array of 24 orbital satellites in sub-synchronous 12 hour orbits. Each satellite has an accurate field of view and transmits a pseudo-noise signal. This pseudo noise signal can be accurately tracked to determine the pseudo-range. By tracking four or more satellites, a person can determine accurate three-dimensional positions in real time around the world. For more details, see 1996 B.W. Parkinson and J.J. See Golbal Positioning System-Theory and Applications, Volumes I and II, proposed by Spilker, Jr.

GPS has revolutionized navigation and positioning technology. In some situations, however, GPS is inefficient. Since the GPS signal is transmitted over a long distance at a relatively low power level (less than 100 watts), the received signal strength is weak (-160 dB level when received by the omni-directional antenna). Therefore, this signal may not be useful if there are interiors or barriers in the building.

A system using a conventional analog NTSC (National Television System Committee) television signal for positioning has already been proposed. This proposal is described in US Patent 5,510,801, "Location Determination and Method Using Television Broadcasting Signals," issued April 23, 1996. However, current analog TV signals have horizontal and vertical synchronization pulses that direct the relatively early synchronization of the TV receiver sweep circuit. Furthermore, in 2006, the Federal Communications Commission (FCC) is considering reassigning this valuable spectrum so that it can stop using NTSC transmitters and be auctioned for other more valuable uses.

1 is a diagram of one embodiment of the present invention;

2 is a view for explaining the operation of the embodiment;

3 is a geometric diagram for position determination using three DTV transmitters.

4 illustrates an embodiment of a receiver for use in generating pseudorange measurements.

5 is an example of a simplified location determination operation for a user terminal.

6 shows the effect of a single hill on a range of circles for a DTV transmitter located at the same altitude as the surroundings.

7 is a diagram of several scattering pilots transmitting all at once.

8 is a diagram of a coherent autocorrelation function.

9 illustrates an embodiment of a monitor unit.

10 illustrates one embodiment of a software receiver.

In general, in one aspect, the invention features methods, apparatus, and computer-readable media for determining the location of a user terminal. Invention

Receiving a DTV broadcast signal from a DTV transmitter at a user terminal, wherein the DTV signal includes an Integrated Services Digital Broadcasting (Terrestrail) signal;

Determine a pseudo-range between the user terminal and the DTV transmitter based on the known component of the DTV broadcast signal, and

-Determining the position of the user terminal based on the position and pseudo range of the DTV transmitter

Steps.

Particular embodiments may include one or more of the following features. Positioning of the user device,

-Adjust the pseudo range based on the difference between the transmitter clock of the DTV transmitter and the known time reference, and

-The position of the user terminal is determined based on the adjusted pseudo range and the position of the DTV transmitter.

Process. Known components are scattered pilot carriers. The positioning of the user terminal

Determine a difference between a local time criterion and a master time criterion of the user terminal, and

Determining the location of the user terminal based on the pseudorange, the DTV transmitter location, and the difference.

Process. Embodiments include a process of determining a future position of a user terminal using the difference, and the decision range determination step,

Storing a portion of the DTV signal, and

Correlate the stored part with the signal generated by the user terminal in order to generate pseudo range

Process. The pseudo range determining step includes a step of generating a pseudo range by correlating the DTV signal with a signal generated by a user terminal as the DTV signal is received. The positioning of the user terminal

Determine a general geographic area where the user terminal is located, and

Determining the location of the user terminal based on the pseudorange and general geographic area;

Process. The general geographic area is the footprint of an additional transmitter that is communicatively linked to the user terminal. The positioning of the user terminal

Determine a tropospheric propagation speed near the user terminal,

-Adjusts the range of each pseudo on the basis of the tropospheric propagation rate, and

-The position of the user terminal is determined based on the position of the DTV transmitter and the adjusted pseudo range.

Process.

User terminal location determination step

Adjust the range of coverage based on the height of the zone near the user's terminal, and

Determining the position of the user terminal based on the position of the DTV transmitter and the adjusted pseudo range.

Process. Embodiments include selecting a DTV signal from a plurality of DTV signals based on a stored table correlating the received DTV signal with the additional transmitter and the identity of the further transmitter linked to the user terminal. Embodiments include receiving a location input from a user and selecting a DTV signal from a plurality of DTV signals based on the location input. Embodiments are used to scan an available DTV signal to combine a fingerprint of a location and determine pseudorange from available DTV signals based on a stored table and fingerprint that matches the known fingerprint to a known location. Selecting a DTV signal. Embodiments include using Receiver Autonomous Integrity Monitoring (RAIM) to verify the integrity of the pseudorange based on redundant pseudo-range from the DTV transmitter.

In general, in one aspect, the invention features methods, apparatus, and computer-readable media for determining the location of a user terminal. The invention,

Receiving a DTV broadcast signal from a DTV transmitter at a user terminal, wherein the DTV signal comprises an ETSI (European Telecommuncations Standards Institute) digital video broadcast-terrestrial (ISDB-T) signal,

Determining a pseudo-range between the user terminal and the DTV transmitter based on the DTV broadcast signal, and

Transmitting the pseudorange to a location server configured to determine the location of the user terminal based on the location and pseudorange of the DTV transmitter.

Steps.

Certain embodiments may include one or more of the following features. The step of determining the pseudo range,

Determine a transmission time of a known component of the DTV broadcast signal from the DTV transmitter,

Determine a reception time of said known component at a user terminal, and

Determine a time difference between the transmission time and the reception time,

It includes the above steps. The known component is a scattered pilot carrier. The step of determining the pseudo range,

Storing a portion of the DTV signal, and

Correlating the stored portion with the signal generated by the user terminal for generating pseudo range,

Steps. The step of determining the pseudo range,

Correlating the DTV signal to a signal generated by a user terminal as the DTV signal is received for generating a pseudo range;

Steps.

In general, according to one aspect, the invention features a method, apparatus, computer readable medium for determining the location of a user terminal. The present invention,

Receive a pseudo range from the user terminal, wherein the pseudo range is determined between the user terminal and the DTV transmitter based on the DTV signal broadcast by the DTV transmitter, the DTV signal being the European Telecommunications Standards Institute (ETSI) digital video Digital Video Broadcasting-Terrestrial (ISDB-T) signal, the pseudo range is determined based on known components of the ISDB-T signal, and

Determining the position of the user terminal based on the pseudo range and the position of the DTV transmitter.

Steps.

Certain embodiments may include one or more of the following features. The step of determining the location of the user terminal,

Adjust the pseudo range based on the time difference between the transmitter clock of the DTV transmitter and the known time reference; and

Determining the position of the user terminal based on the adjusted pseudo range and the position of the DTV transmitter.

Steps. The known component is a scattered pilot carrier. The step of determining the location of the user terminal,

Determine a time difference between the local time criterion of the user terminal and the master time criterion, and

Determining the position of the user terminal based on the pseudo range, the position of the DTV transmitter, and the time difference.

Steps. Embodiments

Determining a future position of the user terminal using the time difference.

It further comprises a step. The step of determining the location of the user terminal,

Determine the general geographic area where the user terminal is located, and

Determining a location of a user terminal based on the pseudo range and the general geographic area.

Steps. The general geographic area is the footprint of an additional transmitter that is communicatively linked to the user terminal. The step of determining the location of the user terminal,

Determine a tropospheric propagation velocity near the user terminal,

Adjust pseudo range based on the tropospheric propagation rate, and

Determining the position of the user terminal based on the adjusted pseudo range and the position of the DTV transmitter.

Steps. The step of determining the location of the user terminal,

-Adjust the pseudo range based on the height of the zone near the user's terminal, and

Determining the position of the user terminal based on the adjusted pseudo range and the position of the DTV transmitter.

Steps.

Advantages presented in embodiments of the invention include one or more of the following. Embodiments of the invention can be used to indicate the location of a mobile phone, a wireless PDA, a pager, a vehicle, an orthogonal code-division multiple access (OCDMA) transmitter, and a host of other devices. Embodiments of the invention may utilize DTV signals that cover the entire United States well. Embodiments of the invention do not require any change to a digital broadcast station (DBS).

DTV signals have an output advantage over GPS of 50dB and provide superior geographic information compared to geospatial information that satellite systems can provide. Therefore, the location can be displayed even when the barrier is present or located inside the building. The DTV signal is six to eight times the GPS bandwidth, thus minimizing multipath effects. Due to the sparse frequency components and high power of the DTV signal used for ranging, processing requirements are minimal. Embodiments of the invention accommodate devices that are much cheaper, slower and lower power than GPS technology requires.

Compared to satellite systems such as GPS, the range between the DTV transmitter and the user terminal changes very slowly. Thus, the DTV signal is not significantly affected by the Doppler effect. This allows signals to be integrated for long periods of time, thus achieving very efficient signal acquisition.

The frequency of the DTV signal is substantially lower than that of the conventional mobile telephone system, and thus the propagation characteristics are excellent. For example, DTV signals are more diffractive than cellular signals in mobile phones, and are therefore less affected by hills and have a wider range. The signal also shows better propagation characteristics in buildings and automobiles. Moreover, embodiments of the present invention utilize components of the ISDB-T signal that are continuous and constitute a significant percentage of the output of the ISDB-T signal.

Unlike the Angle-of-Arrival / Time-of-Arrival positioning system for a mobile phone, embodiments of the present invention do not require any modification to the hardware of the mobile base station. Meter-level positioning accuracy can be achieved. When used to locate mobile phones, this technology is independent of the air interface. It is irrelevant whether it uses Global System Mobile (GSM), Advanced Mobile Phone Service (AMPS), Time-Division Multiple Access (TDMA), or CDMA. A wide range of UHF frequencies is assigned to DTV transmitters. As a result, redundancy is built into the system to prevent deep fade due to absorption, multipath, and other damping effects.

Introduction

The popularity of digital television (DTV) is skyrocketing. DTV was first realized in 1998 in the United States. By the end of 2000, 167 broadcasters began broadcasting DTV signals. On February 28, 2001, approximately 1200 DTV facilities were built by the FCC. According to the FCC goal, all television transmissions will soon be digital, and analogue signal transmissions will disappear. Airwave stations must be digital by May 1, 2002 to maintain license. Private stations must be digital by 1 May 2003. More than 1600 DTV transmitters are expected in the United States. Other regions have implemented similar DTV systems. Japan's NHK has defined a Japanese terrestrial DTV signal called ISDB-T signal. This new DTV signal allows multiple TV signals to be sent on the assigned 6MHz channel. These new ISDB-T DTV signals are completely different from analog NTSC TV signals and have a completely new function. The inventors recognize that ISDB-T signals can be used for position determination and are developing techniques for this. These techniques can be used in the vicinity of ISDB-T DTV transmitters with ranges from transmitters that are much wider than typical TV reception ranges. Because of the high power of the DTV signal, these techniques can be used indoors by handheld receivers, thus providing a solution to the need for positioning of an Enhanced 911 (E911) system.

The technique proposed here can be applied to other DTV signals including known sequences of data by simply modifying the correlator to accommodate the known sequences of data. These techniques can also be applied to a range of other frequency-division multiplexing (OFDM) signals, such as satellite radio signals.

Compared to GPS's digital pseudo noise code, DTV signals are received from transmitters only a few miles away, and transmitters broadcast broadcast signals with up to several hundred kilowatts of effective radiated output. In addition, the DTV transmitter has a significant antenna gain of 14 dB. Therefore, there is often an output sufficient to receive a DTV signal in a building.

As described below, some embodiments of the present invention utilize a component of an ISDB-T signal called a "scattered pilot signal". There are several advantages to using scattered pilot signals. Firstly, positioning is possible at a considerable distance from the DTV transmitter and within the building. Conventional DTV receivers use only one data signal at a time, and thus the range from the DTV transmitter is limited by the energy of a single signal. In contrast, embodiments of the present invention utilize the energy of scattered multiple pilot signals simultaneously, thus enabling operation at a greater range from a DTV transmitter than conventional DTV receivers. Moreover, the scattered pilot is not modulated by the data. This is advantageous for two reasons. First, all outputs of the scattered pilot are used for positioning. No output is dedicated to the data. Secondly, the scattered pilot can be observed for a long time without showing any degradation that data modulation can produce. Thus, the ability to track signals in buildings within substantial range from the DTV tower is greatly improved. Moreover, by using digital signal processing, it is possible to implement this new tracking technique with a single semiconductor chip.

In FIG. 1, one example 100 includes a user terminal 102 in communication with a base station 104 over an air link. In one embodiment, user terminal 102 is a wireless telephone and base station 104 is a wireless telephone base station. In one embodiment, the base station 104 is a mobile metropolitan area network (MAN) or wide area network (WAN).

1 is used to illustrate various aspects of the invention, but the invention is not limited to this embodiment. For example, the term "user terminal" refers to any object that can implement DTV location determination. Examples of user terminals include PDAs, mobile phones, vehicles, and any other object that may include a chip or software that implements DTV positioning. It is not limited to the object operated by "terminal" or "user".

2 illustrates the operation of the embodiment 100. User terminal 102 receives DTV signals from multiple DTV transmitters 106A, 106B, and 106N (step 202).

Several methods can be used to select the DTV channel used for positioning. In one embodiment, the DTV location server 110 informs the user terminal 102 of the optimal DTV channel to monitor. In one embodiment, user terminal 102 exchanges messages with DTV location server 110 using base station 104. In one embodiment, user terminal 102 selects a DTV channel to monitor based on the identity of base station 104 and a stored table that correlates the DTV channel with the base station. In another embodiment, user terminal 102 may accept location input from a user providing a general representation of an area, such as the nearest city name, and use this information to select a processing DTV channel. In one embodiment, the user terminal 102 scans the available DTV channels to combine the fingerprint of the location based on the output level of the available DTV channels. The user terminal 102 compares this fingerprint to a stored table to select a processing DTV channel. The stored table functions to match the known fingerprint with the known location. This selection is based on the output level of the DTV channel, and also based on the direction in which each signal comes in, minimizing the dilution of precision (DOP) for position computation.

The user terminal 102 determines the pseudorange between the user terminal 102 and each DTV transmitter 106 (step 204). Each pseudo range represents a time difference between the transmission time from the transmitter 106 of one component of the DTV broadcast signal, the reception time at the user terminal 102 of the component, and a clock difference (clock difference) at the user terminal. .

User terminal 102 transmits a pseudo range to DTV location server 110. In one embodiment, the DTV location server 110 is implemented with a general purpose computer running software designed to perform the operations described herein. In another embodiment, the DTV location server is implemented with an ASIC. In one embodiment, DTV location server 110 is implemented within or near base station 104.

DTV signals are also received by multiple monitor units 108A-N. Each monitor unit may be implemented as a small unit including a transceiver and a processor, and may be mounted at a convenient location such as a DTV utility pole, transmitter 106, or base station 104. In one embodiment, the monitor units are implemented in a satellite.

Each monitor unit 108 measures, for each DTV transmitter 106, the time difference between the local clock and the reference clock of the DTV transmitter. In one embodiment, the reference clock is derived from a GPS signal. Using a reference clock, it is possible to determine the time difference for each DTV transmitter 106 when multiple monitor units 108 are used. This is because each monitor unit 108 can determine the time difference with respect to the reference clock. Thus, the time difference of the local clocks of the monitor units 108 does not affect this determination.

In one embodiment, no external time reference is needed. According to this embodiment, a single monitor unit receives DTV signals from all the same DTV transmitters as in the user terminal 102. Indeed, the local clock of a single monitor unit functions as a time reference.

In one embodiment, each time difference is modeled as a fixed difference. In another embodiment, each time difference is modeled as a quadratic polynomial of the formula below.

Time difference = a + b (tT) + c (tT) ² (1)

In either embodiment, each measured time difference is periodically transmitted to the DTV location server using the Internet, a secure modem connection, and the like. In one embodiment, the location of each monitor unit 108 is determined using a GPS receiver.

DTV location server 110 receives information (ie, location) describing the phase center of each DTV transmitter 106 from database 112. In one embodiment, the phase center of each DTV transmitter 106 is measured by using the monitor unit 108 at several different locations to directly measure the phase center. One approach to this is to use multiple time-synchronization monitor units arranged in known locations. These units make pseudorange measurements for the TV transmitter at the same instant, which measurements can be used to inverse-triangle the position of the TV transmitter phase center. In another embodiment, the phase center of each DTV transmitter 106 is measured by examining the antenna phase center. Once determined, the phase center is stored in the database 112.

In one embodiment, the DTV location server 110 receives weather information describing the atmospheric temperature, air pressure, and humidity near the user terminal 102 from the weather server 114. Weather information can be obtained from the Internet or from other sources such as NOAA. The DTV location server 110 is published in B. Parkinson and J.Spilker Jr.'s Global Positioning System-Theory and Applications, AIAA, Washington, DC, 1996, Volume 1, Chapter 17 Tropospheric Effects on GPS, J.Spilker Jr. Techniques, such as techniques, are used to determine the tropospheric propagation rate from weather information.

The DTV location server 110 may also receive information from the base station 104 information identifying the general geographical location of the user terminal 102. For example, this information can identify the cell or cell sector in which the mobile phone is located. This information is used for ambiguous minimum resolution resolution.

The DTV location server 110 determines the location of the user terminal 102 based on the location and pseudo range of each transmitter (step 206). 3 shows the geographical arrangement of location determination using three DTV transmitters 106. DTV transmitter 106A is located at position (x1, y1). The range between the user terminal 102 and the DTV transmitter 106A is r1. DTV transmitter 106B is located at position (x2, y2). The range between the user terminal 102 and the DTV transmitter 106B is r2. The DTV transmitter 106N is located at positions x3 and y3, and the range between the user terminal 102 and the DTV transmitter 106N is r3.

The DTV location server 110 may adjust the value of each pseudo range according to the tropospheric propagation speed, and adjust the time difference to the corresponding DTV transmitter 106. The DTV location server 110 uses the phase center information from the database 112 for the positioning of each DTV transmitter 106.

The user terminal 102 uses three pseudorange measurements to derive the unknown three values of the user terminal 102, namely the position (x, y) and the clock difference T. In other embodiments, the techniques proposed herein are used to determine location in three dimensions, such as longitude, latitude, and altitude, and may include elements such as altitude of a DTV transmitter.

Three pseudorange measurements pr1, pr2 and pr3 are given below.

pr1 = r1 + T (2a)

pr2 = r2 + T (3a)

pr3 = r3 + T (4a)

The three ranges can be expressed as

r1 = ｜ X-X1 ｜ (5)

r2 = ｜ X-X2 ｜ (6)

r3 = ｜ X-X3 ｜ (7)

In this case, X denotes the two-dimensional vector positions (x, y) of the user terminal 102, X1 denotes the two-dimensional vector positions (x1, y1) of the DTV transmitter 106A, and X2 denotes the DTV transmitter 106B. Two-dimensional vector positions (x2, y2) and X3 represent two-dimensional vector positions (x3, y3) of the DTV transmitter 106N. These relationships produce three equations that yield three unknowns x, y, and T. The DTV location server 110 solves these equations according to conventional known methods. In an E911 environment, the location of the user terminal 102 is sent to the E911 location server 116 for decentralization of the appropriate authorities. In another embodiment, the location is sent to the user terminal 102.

Now, the technique of projecting the measurements at the same instant in the user terminal 102 is described. This procedure is not necessary if the clock of the user terminal 102 is calibrated or stabilized using signals from the DTV transmitter 106 or the cellular base station. If the user clock is not stabilized or calibrated, the user clock difference can be expressed as a function of time, i.e., T (t). For a very small time period Δ, the clock difference T (t) can be modeled by a constant and a first order term. In other words,

T (t + Δ) = T (t) + (∂T / ∂t) Δ (8)

Now consider the equations (2a-4a) that handle clock skew as a function of time. As a result, pseudorange measurements are also a function of time. For clarity, it is assumed that the ranges remain constant during the interval Δ. Pseudo-range measurement can be expressed as

pr1 (t1) = r1 + T (t1) (2b)

pr2 (t2) = r2 + T (t2) (3b)

prN (tN) = r3 + T (tN) (4b)

In one embodiment, user terminal 102 begins with a pseudorange additional measurement set at some time Δ after the initial measurement set. This measure can be expressed as follows.

pr1 (t1 + Δ) = r1 + T (t1) + (∂T / ∂t) Δ (2c)

pr2 (t2 + Δ) = r2 + T (t2) + (∂T / ∂t) Δ (3c)

prN (tN + Δ) = r3 + T (tN) + (∂T / ∂t) Δ (4c)

The user terminal 102 projects all pseudorange measurements at some point in time so that the effects of the first term are substantially eliminated. For example, consider the case where some common time reference t0 is used. Applying equations (2b-4b) and (2c-4c), it can be readily seen that the measurement can be projected as follows at any common time point.

pr1 (t0) = pr1 (t1) + [pr1 (t1 + Δ) -pr1 (t1)] (t0-t1) / Δ (2c)

pr2 (t0) = pr2 (t2) + [pr2 (t2 + Δ) -pr2 (t2)] (t0-t2) / Δ (3c)

prN (t0) = prN (tN) + [prN (tN + Δ) -prN (tN)] (t0-tN) / Δ (4c)

These projected pseudorange measurements are passed to a location server, where they are used to find solutions of the three values x, y, and T. It should be noted that the projection of equations (2d-4d) is not accurate and the quadratic terms are not taken into account. However, the resulting error is negligible. It will be appreciated that by making three or more pseudorange measurements for each projection, the second or more terms can be secured. It should also be understood that there are several different approaches to implementing this concept of projecting pseudorange measurements at the same time instant. For example, one approach may be to implement a delay sync loop (DLL) as disclosed in the following document.

-Digital Communications by Satellite, Prentice-Hall, Englewood Cliffs, New Jersey, 1977, 1995, by J.J.Spilker, Jr., and

-Global Positioning System by B.W.Parkinson and J.J.Spilker, Jr.- Theory and Applications, AIAA, Washington, DC, 1996, Volume 1.

These two documents are incorporated herein by reference. A separate tracking loop can be dedicated to each DTV transmitter 106. These tracking loops effectively interpolate between pseudorange measurements. The state of each of these tracking loops is sampled at the same instant.

In another embodiment, the user terminal 102 does not compute pseudoranges, but takes measurements of DTV signals sufficient for pseudorange calculations (eg, segments of the correlator output) and sends these measurements to the DTV location server 110. send. The DTV location server 110 calculates a pseudo range based on these measurements, and calculates a location based on the pseudo range.

Location determination by user terminal

In another embodiment, the location of the user terminal 102 is computed by the user terminal 102. In this embodiment, all necessary information is transmitted to the user terminal 102. This information may be transmitted to the user terminal using the DTV location server 110, the base station 104, one or more DTV transmitters 106, or some other combination. The user terminal 102 measures the pseudo range and solves the equations as described above. This embodiment is now described.

The user terminal 102 receives the time difference between the local clock and the reference clock of each DTV transmitter. The user terminal 102 also receives information describing the phase center of each DTV transmitter 106 from the database 112.

The user terminal 102 receives the tropospheric propagation speed computed by the DTV location server 110. In another embodiment, user terminal 102 receives weather information describing temperature, air pressure, and humidity near user terminal 102 from weather server 114, and uses tropospheric from weather information using conventional techniques. Determine the speed of propagation.

User terminal 102 may also receive information from base station 104 identifying the approximate location of user terminal 102. For example, this information can identify the cell or cell sector in which the mobile phone is located. This information is used for ambiguous minimum identification distance identification.

The user terminal 102 receives DTV signals from the plurality of DTV transmitters 106 and determines the pseudo range between the user terminal 102 and each of the DTV transmitters 106. The user terminal 102 determines its position based on the phase center and pseudorange of the transmitters.

In any of these embodiments, if only two DTV transmitters are available, the location of the user terminal 102 may be determined using the time difference T calculated during the previous position determination and the two DTV transmitters. The T value can be stored or maintained according to conventional methods. This assumes that the local clock is stable enough for the time since T was computed.

In one embodiment, base station 104 determines the clock difference of user terminal 102. In this embodiment, only two DTV transmitters are needed for positioning. The base station 104 transmits the clock difference T to the DTV location server 110, and then determines the location of the user terminal 102 from the pseudo range computed for each DTV transmitter.

In another embodiment, if only one or two DTV transmitters are available for positioning, GPS is used to improve the positioning and each GPS satellite is treated as another transmitter in the positioning solution.

Receiver structure

4 illustrates one embodiment of a receiver 400 for use in generating pseudocritical measurements. In one embodiment, receiver 400 is implemented within user terminal 102. In another embodiment, the receiver 400 is implemented within the monitor unit 108.

The tuner 406 clocked by the clock 416 tunes the antenna 404 with the DTV signal 402 in the area according to the control provided by the tuner controller 420. In some embodiments, tuner 406 downconverts the received DTV signal to an intermediate frequency (IF). Mixers 408I and 408Q combine the carrier signal generated by carrier generator 418 with the tuned DTV signal to produce in-phase and quadrature DTV signals of intermediate frequency (IF) or baseband. In one embodiment, clock 416 operates at 27 MHz. Each of these signals is filtered by one of the filters 41OI and 410Q, and digitized by one of the A / D converters 411I and 411Q, producing signals m [t-T] and Q [t-t], respectively. In another embodiment, a single A / D converter with a switch is used to alternately sample in-phase and quadrature channels. Correlator 412I combines signal m [t-T] with synchronization signal S [t-t *] to provide a correlation output to search controller 414.

The delay lock loop 422 includes a correlator 412Q, a filter 424, a numerically controlled oscillator (NCO) 426, and a synchronization generator 428, where the NCO 426 is clocked into the clock 416. Clocked by, the synchronization generator 428 generates a digital representation of the scattering pilot signals. Correlator 412Q combines signal Q [t-T] with synchronization signal S [t-T] to provide a correlated output to NCO 426 after filtering by filter 424. NCO 426 drives synchronization generator 428 in accordance with search controller 414.

Control is provided by search controller 414 during signal acquisition and by NCO 426 during signal tracking after acquisition. The pseudo range is obtained by sampling the NCO 426.

Location operations on a subscriber handset or other device only occur when the subscriber needs location. For subscribers who are walking slowly, boarding in a slowly traveling vehicle, or sitting in buildings or outdoors in an emergency, this location information does not need to be measured frequently. Thus, the battery or other power supply can be very compact.

Of course, for example, by processing the received DTV signal using a fast Fourier transform (FFT) method, it is possible to implement a different version of the receiver 400 using the above-described concept. Additionally, the sum of nine chirp signals or all 117 chirp carriers can be simply digitized and done in a near-optimal fashion.

To implement this, it is important to correlate all the scattering pilots in parallel, or to correlate at least nine into a single segment. The wider the bandwidth of the composite signal, the higher the positioning accuracy. Timing accuracy is inversely proportional to bandwidth.

Other signals may be used within the ISDB-T structure for location. For example, a wide laning technique can be applied to continuous pilot signals. However, techniques such as wide access include inherent identification of cycle ambiguity, and techniques for identifying such ambiguity are well known in the art.

The user terminal local oscillator has relatively poor stability in terms of frequency. This instability affects two different receiver parameters. First, this causes a frequency offset in the receiver signal. Second, this slips the received bit pattern against the symbol rate of the reference clock. These two effects can limit the integration time of the receiver, thus limiting the processing gain of the receiver. Integration time can be improved by calibrating the receiver reference block. In one embodiment, the delay synchronization loop automatically corrects the receiver clock.

Improved location

Deductive knowledge of the location of cellular sites can be used to improve location determination. This is conceptually shown in FIG. 5 shows a simple example of a location determination operation for user terminal 102 receiving DTV signals from two separate DTV antennas 106A, 106B. For this purpose, assume that the user clock offset is already known. Based on the range measurements, circles of a range 502A, 502B are drawn for the transmit antennas 106A, 106B, respectively. The position of the user terminal lies at one of the intersections 504A, 504B of the two circles 502A, 502B, including a correction for the user terminal clock difference. Ambiguity can be resolved by notifying that the base station 104 can determine the sector 508 of its footprint (ie, coverage area) 506 where the user terminal is located. Of course, if there are more than two DTV transmitters, the ambiguity can be solved by taking the intersection of three circles. Since the synchronization code from the TV transmitter has a repetitive attribute, there is a cycle ambiguity determined by the repetition period of the TV synchronization code, which causes distance ambiguity such as the product of the luminous flux and the repetition period. This cycle ambiguity can be solved by the same technique described by the simplified example of FIG. 5. However, it is limited to the case where the distance ambiguity is large compared to the cell size. This is a common case.

In one embodiment, instead of using the cell site to first determine the approximate location, user terminal 102 may accept input from a user that provides a general representation of the area, such as the nearest city name. In one embodiment, user terminal 102 scans for available DTV channels to combine the fingerprint of the location. User terminal 102 compares the fingerprint to a stored table that matches the known fingerprint with the known location for current approximate location identification of user terminal 102.

In one embodiment, the positioning operation includes effects of ground elevation. Thus, in hills and valleys with respect to the phase center of the DTV antenna 106, a range of circles are distorted. 5 illustrates the effect of a single hill 604 on a range of circles 602 for a DTV transmitter 106 located at the same altitude as the surrounding ground.

User location calculations are easily completed by a simple computer having a zone tropoographic map into its database, and perform calculations involving user elevation effects on the geoid, the ground surface. This operation has the effect of crushing a range of circles as shown in FIG.

ISDB-T Signal Description

ISDB-T signals are complex orthogonal frequency-division multiplexing (OFDM) signals carrying 188 byte MPEG packets using 1512 or 6048 carriers. Most of these components carry arbitrary data modulation of the video TV signal and are less useful for fine tracking at low signal levels. It should be noted that for our location purposes, the user terminal may be placed in a location where the entire information content of the ISDB-T signal is not available.

The ISDB-T signal is a band division transmission (BST) orthogonal frequency division multiplexing (OFDM) signal and has a function of carrying various video, audio, and data services. Since it is an OFDM system, it is resistant to multipath. The use of so-called band-divided transmissions shows flexibility in the information transmitted. The division has a bandwidth of 3000/7 = 428.5714286 kHz.

ISDB-T signals have synchronization components that are very useful for positioning. This signal has both wideband and narrowband formats. The wideband format has a bandwidth of 5.6 MHz and is good for television and data. The narrowband format has a bandwidth of 430 kHz and is suitable for low bandwidth signal processing. The signal characteristics for the three modes of the wideband format are shown in Table 1. The carrier interval is the inverse of the useful symbol time period. Segments modulated in a coherent manner have a scattering pilot. Differently, the coherent segment has a continuous pilot. For each mode, the total number of segments Ns is 13 = ns + nd. In this paragraph, one of all three of the wide bandwidth formats is described. However, the same concept can be applied to all three modes.

parameter 2K mode 8K mode Number of carriers K 1705 6817 Symbol duration 224 microseconds 896 microseconds Carrier spacing 4464 Hz 1116 Hz Full spacing of the signal 7.61 MHz 7.61 MHz

The wideband signal consists of 13 OFDM segments, each segment consisting of 108 frequencies. The bandwidth of the OFDM segment of 108 carriers is 430 kHz.

OFDM carriers are mostly modulated by video information in MPEG-2 format using quadrature amplitude modulation (QAM) and robust error correcting coding. However, within the set of 108 frequencies some are located separately for synchronization. These are the so-called scattering and continuous pilots. Some embodiments use a continuous pilot for center frequency measurement. However, scattering pilots are more useful for high accuracy position measurements.

The ISDB-T standard includes differential quadrature phase shift keying (DQPSK), quadrature phase shift keying (QPSK), 16 QAM, 64 QAM, and 1/2, 2/3, 3/4, 5/6, 7/8 A number of modulation schemes are provided that include coding rates for the inner code of s. These parameters can be selected independently for each segment. The total data rate in wideband mode is only 3.651 Mbps for differential coherent modulation DPQSK. Narrowband single segment mode produces a data rate of 280.85 kbps for DQPSK modulation and half coding rate. Other modes are coherent and produce data rates up to 23.234 Mbps for 64 QAM with 7/8 rate inner code.

There are 36 scattering pilots in each of the 13 OFDM segments. Thus, within all 13 segments there are 468 scattering pilots in each wideband DTV signal. In one OFDM segment, scattering pilots change frequency per symbol. The size of this frequency hopping corresponds to three carriers. The same carrier is transmitted for one symbol and has a repeating pattern every four symbols. Thus there are several scattering pilots that are transmitted all at once, which is shown in FIG. The maximum scattering pilot frequency is 105 in FIG. 7.

As shown in FIG. 7, this set of scattering pilots can be represented by nine scattering pilots that harness three carriers for each symbol. A good approach is nine 'chirp' carriers with 13 segments each for a total of 117 scattering pilots.

The bandwidth of the scattering pilot is substantially flat with respect to the spectral occupancy area, but with line components in the period of four symbols. However, the period of four symbols represents a very large distance because of the relatively small symbol rate. The ambiguity caused by the signal is negligible and easily resolved.

The composite scattering pilot signal is combined with the ATSC delay lock loop introduced by US Patent Application No. 10 / 210,847, July 31, 2002, "Position Location Using Broadcast Digital Television Signals" (James J. Spilker, Jr. and Matthew Rabinowitz). Along with the pseudo-noise signal used in the correlator, it can be represented in digital form and written as s [t]. The exact form of the ISDB-T signal is different, but signal tracking can be implemented in a similar manner to the reference signal s [t].

ISDB-T signals were published in IEEE 1999, IEEE Transactions on Consumer Electronics, "Digital Transmission Scheme for ISDB-T and Reception Characteristics of Digital Terrestrial Television Broadcasting in Japan" (S. nakahara et al.), And February 1999. It is further described in the "Transmissions Schemes for the Terrestrial ISDB System" (M. Uehara et al.) In IEEE Transactions on Consumer Electronics.

Autocorrelation of Single Segment

A single segment of 108 carriers has 36 scattering pilots at frequency intervals of three units. The transmission sequence of tones is repeated every 105/3 = 35 symbols. The coherent autocorrelation function of this signal for a single segment is shown in FIG. 8 assuming a sample rate of 1/400 symbol. The autocorrelation width for a single segment of approximately 430 kHz can provide a time resolution of approximately 1 millisecond. By using the total bandwidth of the signal with 13 segments and correlating over the total frequency domain, the autocorrelation peak can be reduced by approximately the same ratio by approximately 1000/13 = 77 ns or 77 feet. When the signal noise ratio is sufficient and there is no multipath error, approximately 5 meters or better pseudo noise accuracy can be achieved.

Monitor unit

9 shows one embodiment 900 of the monitor unit 108. Antenna 904 receives GPS signal 902. GPS time transfer unit 906 develops a master clock signal based on the GPS signal. To determine the time difference of the DTV transmitter clock, a numerically controlled oscillator (NCO) code synchronization timer 908A develops a master synchronization signal based on the master clock signal. The master synchronization signal may comprise an ISDB-T scattering pilot carrier. In one embodiment, the NCO field synchronization timer 908A of all monitor units 108 is synchronized to a base date and time. In an embodiment where a single monitor unit 108 receives a DTV signal from all DTV transmitters that the user terminal 102 is receiving, the monitor unit 108 and some other monitor unit for positioning of the user terminal 102. ), There is no need to synchronize. This synchronization is also unnecessary if all monitor stations 108 or all DTV transmitters are synchronized to a common clock.

DTV antenna 912 receives a number of DTV signals 910. In another embodiment, several DTV antennas are used. Amplifier 914 amplifies the DTV signal. Each of the one or more DTV tuners 916A-N may generate a DTV channel signal by tuning to a DTV channel from the received DTV signal. Each of the plurality of NCO code synchronization timers 908B-908M receives one of the DTV channel signals. Each NCO code synchronization timer 908B-908M extracts a channel synchronization signal from the DTV channel signal. The channel synchronization signal may comprise an ISDB-T scattering pilot carrier. In one embodiment, a continuous pilot signal and a symbol clock signal in the ISDB-T signal are used for acquisition assistance.

Each of the plurality of summers 918A-N generates a clock difference between the master synchronization signal and one of the channel synchronization signals. The processor 920 formats the final data and transmits the final data to the DTV location server 110. In one embodiment, this data includes, for each DTV channel measured, the ID number of the DTV transmitter, the DTV channel number, the antenna phase center for the DTV transmitter, and the clock difference. This data may be transmitted by one of a number of methods, including air link and internet. In one embodiment, the data is broadcast in spare MPEG packets on the DTV channel itself. The clock difference for each channel may be modeled as a function of time.

Software receiver

One approach to mitigate multipath effects is to sample the entire autocorrelation function rather than using only the initial and late samples as in a hardware setup. The multipath effect can be mitigated by selecting the earliest autocorrelation peaks.

In cases where the position can be computed with a simple delay, a simple approach is to use a software receiver to sample the sequence of filtered signals and process these samples in firmware on a digital signal processor.

10 illustrates one embodiment of a software receiver 1000. Antenna 1002 receives the DTV signal. Antenna 1002 may be a magnetic dipole or any other kind of antenna capable of receiving DTV signals. Bandpass filter 1004 sends the entire DTV signal spectrum to LNA 1006. In one embodiment, filter 1004 is a tunable bandpass filter that passes the spectrum for a particular DTV channel under the control of a digital signal processor (DSP) 1014.

The low noise amplifier (LNA) 1006 amplifies the selected signal and sends it to the DTV channel selector 1008. The DTV channel selector 1008 selects a particular DTV channel under the control of the DSP 1014 and, according to the conventional method, filters the selected channel signal to downconvert from UHF to IF (intermediate frequency). An amplifier (AMP) 1010 amplifies the selected IF channel signal. The amplifier can use automatic gain control (AGC) to improve the dynamic range of the structure. The analog-to-digital converter and sampler (A / D) 1012 generates a digital sample s _samp (t) of the DTV channel signal s (t) and sends these samples to the DSP 1014.

DTV channel signal processing by the DSP 1014 is now described for a coherent software receiver. Assume a typical difference frequency for the downconverted sampled signal. If this signal is downconverted to baseband, the typical difference is 0 Hz. This process generates a complete autocorrelation function based on a sample of the signal s _samp (t). This process can be implemented more effectively for low duty factor signals. Let Ti be the period of the sampled frequency, ω _in is the typical difference frequency of the sampled incident signal, and ω _offset is the maximum possible difference frequency due to Doppler shift and oscillator frequency drift. This process implements the pseudocodes listed below.

Rmax = 0

Generate the complex code signal as below

S _code (t) = C _i (t) + _j C _q (t)

In this case, C _i is a function representing the in-phase baseband signal, C _q is a function representing the quadrature baseband signal.

Calculate F (S _code ) ^* . Where F is a Fourier transform operator and ^* is a conjugate operator.

For ω = ω _in -ω _offset to ω _in + ω _offset, step 0.5π / Ti

Generate complex mixing signals

s _mix (t) = cos (ωt) + jsin (ωt), t = [0 ... Ti]

Combination of input signal s (t) and mixing signal s _mix (t)

S _comb (t) = S _samp (t) S _mix (t)

Compute the correlation function R (τ) = F ^-1 {F (S _code ) ^* F (S _comb )}

If max _τ | R (τ) |> R _max , then R _max <-max _τ | R (τ) |, R _store (τ) = R (τ)

Next ω

Exiting from this process, R _store (τ) will _store the correlation between the input sample signal s _samp (t) and the complex code signal s _code (t). R _store (τ) may be further refined by searching for smaller steps of ω. The initial step size for ω must be less than half of the Nyquist rate 2π / T _i .

The time difference τ that produces the maximum correlation output is used as the pseudo range.

Alternative embodiment

The invention can be implemented in digital electronic circuitry or computer hardware, firmware, software, or a combination thereof. The apparatus of the invention may be embodied as a computer program product substantially embedded in a machine-readable storage device for execution by a programmable processor. And the method steps of the invention can be executed by a programmable processor executing a program of instructions that executes the functions of the invention by operating on input data and generating output. One or more computer programs executable on a programmable system comprising a data storage system, one or more input devices, and one or more programmable processors coupled to receive and send data and commands to and from the one or more output devices. It can be implemented as. Each computer program may be implemented in a high level procedural / object-oriented programming language, or assembly or machine language, if desired. In either case, the language may be a language that is compiled or interpreted. Suitable processors include, for example, dedicated and general purpose microprocessors. In general, a processor receives instructions and data from a ROM or a RAM. Generally, 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 substantially embedding computer program instructions and data include 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 all forms of nonvolatile memory, including CD-ROM disks. Any of these may be replaced by or included in application-specific integrated circuits (ASICs).

A number of embodiments of the invention have been introduced. Nevertheless, various modifications and changes may be made without departing from the scope and spirit of the invention.

For example, while one method of traversing an ISDB-T signal has been described, there are several ways to track these signals through various types of conventional delay lock loops and several types of matched filters.

Although embodiments of the invention have been described with reference to an 8 MHz signal, embodiments may be used with signals of other bandwidths. Moreover, embodiments of the invention may utilize a bandwidth subset of the ISDB-T signal. For example, one embodiment of the invention can achieve satisfactory results using only 6 MHz of the 8 MHz ISDB-T signal.

Embodiments of the present invention take advantage of the fact that the DTV signal has a high output and that the DTV signal can be tracked by using a low duty factor that does not use all the input signal energy or by capturing the burst of the signal. For example, one embodiment shows J.J. Use the time-gate DLL introduced in Spilker, Jr.'s "Digital Communications by Satellite", Prentice-Hall, Englewood Cliffs NJ, 1977, Chapter 18-6.

Other embodiments are described in J.J. Spilker, Jr., "Digital Communications by Satellite", Prentice-Hall, Englewood Cliffs NJ, 1977, Chapter 18, and B.Parkinson and J.Spilker, Jr., "Global Positioning System-Theory and Applications", AIAA, Washington Several variants of the DLL, including coherent, non-coherent, and quasi-coherent DLLs, introduced in DC, 1996, Vol. 1, Chapter 17, Fundamentals of Signal Tracking Theory by J.Spilker, Jr. I use it. Other embodiments use several types of matched filters, such as recycle matched filters.

As a last example, in some embodiments, the DTV location server 110 uses redundant signals available at the system level, such as pseudoranges available from the DTV transmitter. Thus, additional confirmation can be made to validate each DTV channel and pseudorange and to identify a faulty DTV channel. One such technique is conventional receiver autonomous integrity monitoring (RAIM).

Still other embodiments of the invention combine the DTV range signals described above with other types of signals capable of computing pseudo ranges. For example, the use of a combination of DTV and GPS satellite signals is disclosed in US Patent Application No. 10 / 159,478, March 31, 2002, "Position Location Using Global Postioning Signals Augmented by Broadcast Television Signals" by inventors Matthew Rabinowitz and JJSpilker, Jr. Is introduced. The contents of which are incorporated herein by reference. Additionally, the DTV signals may be combined with cellular base station signals or digital radio signals, and may be combined with other signals including synchronization codes for combined location resolution.

Accordingly, other embodiments are within the scope of the following claims.

Claims (87)

As the location determination method of the user terminal, this method, Receiving a digital television (DTV) broadcast signal from a DTV transmitter at a user terminal, wherein the DTV signal is an ISDB-T (Integrated Services Digital Broadcasting-Terrestrial) signal, Determine a pseudo range between the DTV transmitter and the user terminal based on a known component of a DTV broadcast signal, and Determining the position of the user terminal based on the position of the DTV transmitter and the pseudo range; And determining the location of the user terminal. The method of claim 1, wherein the determining of the location of the user terminal comprises: Adjust the pseudo range based on the time difference between the known time reference and the transmitter clock of the DTV transmitter, and Determining the position of the user terminal based on the position of the DTV transmitter and the adjusted pseudo range; And determining the location of the user terminal. The method of claim 1, wherein the known component is a scattered pilot carrier. The method of claim 1, wherein the determining of the location of the user terminal comprises: Determine a time difference between the local time criterion of the user terminal and the master time criterion, and Determining a location of a user terminal based on the pseudo range, the DTV transmitter location, and the time difference. And determining a location of the user terminal. The method of claim 4, wherein Determining a future position of the user terminal using the time difference. And determining the location of the user terminal. The method of claim 1, wherein the determining the pseudo range comprises: To store part of the DTV signal, Correlating the stored part with the signal generated by the user terminal for generating pseudo range And determining a location of the user terminal. The method of claim 1, wherein the determining the pseudo range comprises: Correlating the DTV signal to a signal generated by the user terminal as the DTV signal is received for generating a pseudo range; And determining a location of the user terminal. The method of claim 1, wherein the determining of the location of the user terminal comprises: Determine a general geographic area where the user terminal is located, and Determining a location of a user terminal based on the pseudo range and the general geographic area. And determining a location of the user terminal. 9. The method of claim 8, wherein the general geographic area is a footprint of an additional transmitter that is communicatively linked to the user terminal. The method of claim 1, wherein the determining of the location of the user terminal comprises: Determine a tropospheric propagation velocity near the user terminal, -Adjust the pseudorange based on the tropospheric propagation rate, and Determining the position of the user terminal based on the adjusted pseudo range and the position of the DTV transmitter. And determining a location of the user terminal. The method of claim 1, wherein the determining of the location of the user terminal comprises: -Adjust the pseudo range based on the height of the zone near the user's terminal, and Determining the position of the user terminal based on the adjusted pseudo range and the position of the DTV transmitter. And determining a location of the user terminal. The method of claim 1, Select the DTV signal from the plurality of DTV signals, wherein the DTV signal is derived from the plurality of DTV signals based on the identity of an additional transmitter communicatively linked to the user terminal and a storage table that correlates the additional transmitter and the DTV signals; To choose And determining the location of the user terminal. The method of claim 1, Accept location input from the user, and Selecting the DTV signal from a plurality of DTV signals based on the position input And determining the location of the user terminal. The method of claim 1, Scan for available DTV signals for fingerprint combination of location, and Selecting a DTV signal used to determine a pseudorange from an available DTV signal based on the fingerprint and a storage table that matches the known fingerprint with known locations. And determining the location of the user terminal. The method of claim 1, -Using Receiver Autonomous Integrity Monitoring (RAIM) to check the integrity of pseudo range based on redundant pseudorange from DTV transmitter And determining the location of the user terminal. As the location determination method of the user terminal, the method, Receiving a DTV broadcast signal from a DTV transmitter at a user terminal, wherein the DTV signal is an ETSI digital video broadcasting-terrestrial (ISDB-T) signal, Determine a pseudo range between the DTV transmitter and the user terminal based on the DTV broadcast signal; and Transmitting the pseudo range to a location server set to determine the location of the user terminal based on the location and pseudo range of the DTV transmitter; And determining the location of the user terminal. 17. The method of claim 16, wherein determining the pseudoranges comprises: Determine a transmission time of a known component of the DTV broadcast signal from the DTV transmitter, Determine a reception time of said known component at a user terminal, and Determine a time difference between the transmission time and the reception time, And determining the location of the user terminal. 17. The method of claim 16, wherein the known component is a scattered pilot carrier. 17. The method of claim 16, wherein determining the pseudoranges comprises: Storing a portion of the DTV signal, and Correlating the stored portion with the signal generated by the user terminal for generating pseudo range, And determining a location of the user terminal. The method of claim 16, wherein the determining the pseudo range is, Correlating the DTV signal to a signal generated by a user terminal as the DTV signal is received for generating a pseudo range; And determining a location of the user terminal. A method for determining the location of a user terminal, which method is Receive a pseudo range from the user terminal, wherein the pseudo range is determined between the user terminal and the DTV transmitter based on the DTV signal broadcast by the DTV transmitter, the DTV signal being the European Telecommunications Standards Institute (ETSI) digital video Digital Video Broadcasting-Terrestrial (ISDB-T) signal, the pseudo range is determined based on known components of the ISDB-T signal, and Determining the position of the user terminal based on the pseudo range and the position of the DTV transmitter. And determining a location of the user terminal. The method of claim 21, wherein determining the location of the user terminal comprises: Adjust the pseudo range based on the time difference between the transmitter clock of the DTV transmitter and the known time reference; and Determining the position of the user terminal based on the adjusted pseudo range and the position of the DTV transmitter. And determining a location of the user terminal. 22. The method of claim 21 wherein the known component is a scattered pilot carrier. The method of claim 21, wherein determining the location of the user terminal comprises: Determine a time difference between the local time criterion of the user terminal and the master time criterion, and Determining the position of the user terminal based on the pseudo range, the position of the DTV transmitter, and the time difference. And determining a location of the user terminal. The method of claim 24, Determining a future position of the user terminal using the time difference. And determining the location of the user terminal. The method of claim 21, wherein determining the location of the user terminal comprises: Determine the general geographic area where the user terminal is located, and Determining a location of a user terminal based on the pseudo range and the general geographic area. And determining a location of the user terminal. 27. The method of claim 26, wherein the general geographic area is a footprint of an additional transmitter that is communicatively linked to the user terminal. The method of claim 21, wherein determining the location of the user terminal comprises: Determine a tropospheric propagation velocity near the user terminal, Adjust pseudo range based on the tropospheric propagation rate, and Determining the position of the user terminal based on the adjusted pseudo range and the position of the DTV transmitter. And determining a location of the user terminal. The method of claim 21, wherein determining the location of the user terminal comprises: -Adjust the pseudo range based on the height of the zone near the user's terminal, and Determining the position of the user terminal based on the adjusted pseudo range and the position of the DTV transmitter. And determining a location of the user terminal. A device for determining the location of a user terminal, the device comprising: Means for receiving a DTV broadcast signal from a DTV transmitter at a user terminal, wherein the DTV signal is an European Telecommunications Standards Institute (ETSI) Digital Video Broadcasting-Terrestrial (ISDB-T) signal. , Means for determining the pseudo range between the user terminal and the DTV transmitter based on known components of the DTV broadcast signal; Means for determining the position of the user terminal based on the position of the DTV transmitter and the pseudo range; Positioning device of the user terminal comprising a. 31. The apparatus of claim 30, wherein the means for determining the location of the user terminal is Means for adjusting the pseudorange based on a known time reference and the time difference between the transmitter clock of the DTV transmitter, and Means for determining the position of the user terminal based on the position of the DTV transmitter and the adjusted pseudo range; Positioning device of the user terminal comprising a. 32. The apparatus of claim 31, wherein the known component is a scattered pilot carrier. 31. The apparatus of claim 30, wherein the means for determining the location of the user terminal is Means for determining a time difference between the local time base of the user terminal and the master time base, and Means for determining the location of the user terminal based on the pseudorange, the DTV transmitter location, and the time difference; Positioning device of the user terminal comprising a. The method of claim 33, wherein Means for determining a later position of the user terminal using the time difference Position determination apparatus of the user terminal, characterized in that it further comprises. 31. The apparatus of claim 30, wherein said means for determining pseudoranges is Means for storing a portion of the DTV signal, and Means for correlating the stored part with the signal generated by the user terminal for generating pseudo range Positioning device of the user terminal comprising a. 31. The apparatus of claim 30, wherein said means for determining pseudoranges is Means for correlating the DTV signal to a signal generated by the user terminal as the DTV signal is received for generating pseudo ranges. Positioning device of the user terminal comprising a. 31. The apparatus of claim 30, wherein the means for determining the location of the user terminal is Means for determining the general geographic area in which the user terminal is located, and Means for determining the location of the user terminal based on the pseudorange and the general geographic area; Positioning device of the user terminal comprising a. 38. The apparatus of claim 37, wherein the general geographic area is a footprint of an additional transmitter that is communicatively linked to the user terminal. 31. The apparatus of claim 30, wherein the means for determining the location of the user terminal is Means for determining the tropospheric propagation velocity near the user terminal, Means for adjusting pseudoranges based on tropospheric propagation rate, and Means for determining the position of the user terminal based on the adjusted pseudo range and DTV transmitter position Positioning device of the user terminal comprising a. 31. The apparatus of claim 30, wherein the means for determining the location of the user terminal is Means for adjusting the pseudo range based on the height of the zone near the user's terminal, and Means for determining the position of the user terminal based on the adjusted pseudo range and DTV transmitter position Positioning device of the user terminal comprising a. The method of claim 30, Means for selecting the DTV signal from a plurality of DTV signals, wherein the DTV signal is based on the identity of an additional transmitter that is communicatively linked to a user terminal and a storage table that correlates the additional transmitter and the DTV signals. These means to choose from the signal Position determination apparatus of the user terminal, characterized in that it further comprises. The method of claim 30, Means for receiving location input from the user, and Means for selecting the DTV signal from a plurality of DTV signals based on the position input Position determination apparatus of the user terminal, characterized in that it further comprises. The method of claim 30, Means for scanning the available DTV signals for a fingerprint combination of location, and Means for selecting a DTV signal used to determine a pseudorange from an available DTV signal based on the fingerprint and a storage table that matches the known fingerprint with known locations. Position determination apparatus of the user terminal, characterized in that it further comprises. The method of claim 30, Means for verifying the integrity of the pseudorange based on redundant pseudoranges from the DTV transmitter using Receiver Autonomous Integrity Monitoring (RAIM) Position determination apparatus of the user terminal, characterized in that it further comprises. A positioning device of a user terminal, the device comprising: Means for receiving a DTV broadcast signal from a DTV transmitter at a user terminal, wherein the DTV signal is an European Telecommunications Standards Institute (ETSI) digital video broadcast-terrestrial (ISDB-T) signal , Means for determining a pseudo range between a DTV transmitter and the user terminal based on a known component of the DTV broadcast signal; and Means for transmitting the pseudo range to a location server set to determine the location of the user terminal based on the location and pseudo range of the DTV transmitter; Positioning device of the user terminal comprising a. 46. The apparatus of claim 45, wherein said means for determining pseudo range is: Means for determining the transmission time of one component of the DTV broadcast signal from the DTV transmitter, Means for determining a reception time of said component at a user terminal, and Means for determining a time difference between the transmission time and the reception time Positioning device of the user terminal comprising a. 46. The apparatus of claim 45, wherein the component is a scattered pilot carrier. 46. The apparatus of claim 45, wherein said means for determining pseudo range is: Means for storing a portion of the DTV signal, and Means for correlating the stored portion with the signal generated by the user terminal for generating pseudo range Positioning device of the user terminal comprising a. 46. The apparatus of claim 45, wherein said means for determining pseudo range is: Means for correlating the DTV signal to a signal generated by a user terminal as the DTV signal is received for generating a pseudo range; Positioning device of the user terminal comprising a. A device for determining the location of a user terminal, the device comprising: Means for receiving a pseudo range from a user terminal, wherein the pseudo range is determined between the user terminal and the DTV transmitter based on a DTV signal broadcast by the DTV transmitter, the DTV signal being the European Telecommunications Standards Institute (ETSI) Digital video broadcasting-terrestrial (ISDB-T) signals, the pseudo range being determined based on known components of the DTV signal, and Means for determining the position of the user terminal based on the pseudo range and the position of the DTV transmitter Positioning device of the user terminal comprising a. 51. The apparatus of claim 50, wherein the means for determining a location of a user terminal is Means for adjusting the pseudo range based on the time difference between the transmitter clock of the DTV transmitter and the known time reference; Means for determining the position of the user terminal based on the adjusted pseudo range and DTV transmitter position Positioning device of the user terminal comprising a. 51. The apparatus of claim 50, wherein the known component is a scattered pilot carrier. 51. The apparatus of claim 50, wherein the means for determining a location of a user terminal is Means for determining a time difference between the local time base of the user terminal and the master time base, and Means for determining the position of the user terminal based on the pseudorange, the position of the DTV transmitter, and the time difference; Positioning device of the user terminal comprising a. The method of claim 53, wherein Means for determining a later position of the user terminal using the time difference Position determination apparatus of the user terminal, characterized in that it further comprises. 51. The apparatus of claim 50, wherein the means for determining a location of a user terminal is Means for determining the general geographic area in which the user terminal is located; and Means for determining the location of the user terminal based on the pseudorange and the general geographic area; Positioning device of the user terminal comprising a. 56. The apparatus of claim 55, wherein the general geographic area is a footprint of an additional transmitter communicatively linked to the user terminal. 51. The apparatus of claim 50, wherein the means for determining a location of a user terminal is Means for determining the tropospheric propagation velocity near the user terminal, Means for adjusting the pseudorange based on the tropospheric propagation rate, and Means for determining the position of the user terminal based on the adjusted pseudo range and DTV transmitter position Positioning device of the user terminal comprising a. 51. The apparatus of claim 50, wherein the means for determining a location of a user terminal is Means for adjusting the pseudo range based on the height of the zone near the user's terminal, and Means for determining the position of the user terminal based on the adjusted pseudo range and the position of the DTV transmitter Positioning device of the user terminal comprising a. A computer program product tangibly stored on a computer-readable medium for determining the location of a user terminal, Receiving a digital television (DTV) broadcast signal from a DTV transmitter at a user terminal, wherein the DTV signal is an European Telecommunications Standards Institute (ETSI) digital video broadcast-terrestrial (ISDB-T) signal, Determine a pseudo range between the DTV transmitter and the user terminal based on a known component of a DTV broadcast signal, and Determining the position of the user terminal based on the position of the DTV transmitter and the pseudo range; Computer program product tangibly stored on a computer-readable medium for determining a location of a user terminal comprising computer instructions for causing the programmer to execute the above operations. 60. The method of claim 59, wherein determining the location of the user terminal comprises: Adjust the pseudo range based on the time difference between the known time reference and the transmitter clock of the DTV transmitter, and Determining the position of the user terminal based on the position of the DTV transmitter and the adjusted pseudo range; A computer program product comprising the above operations. 60. The computer program product of claim 59, wherein the known component is a scattered pilot carrier. 60. The method of claim 59, wherein determining the location of the user terminal comprises: Determine a time difference between the local time criterion of the user terminal and the master time criterion, and Determining a location of a user terminal based on the pseudo range, the DTV transmitter location, and the time difference. A computer program product comprising an operation. The method of claim 62, Determining a future position of the user terminal using the time difference. A computer program product further comprising an action. 60. The method of claim 59, wherein determining the pseudo range is: To store part of the DTV signal, Correlating the stored part with the signal generated by the user terminal for generating pseudo range A computer program product comprising an operation. 60. The method of claim 59, wherein determining the pseudo range is: Correlating the DTV signal to a signal generated by the user terminal as the DTV signal is received for generating a pseudo range; A computer program product comprising an operation. 60. The method of claim 59, wherein determining the location of the user terminal comprises: Determine a general geographic area where the user terminal is located, and Determining a location of a user terminal based on the pseudo range and the general geographic area. A computer program product comprising an operation. 67. The computer program product of claim 66, wherein the general geographic area is a footprint of an additional transmitter that is communicatively linked to a user terminal. 60. The method of claim 59, wherein determining the location of the user terminal comprises: Determine a tropospheric propagation velocity near the user terminal, -Adjust the pseudorange based on the tropospheric propagation rate, and Determining the position of the user terminal based on the adjusted pseudo range and the position of the DTV transmitter. A computer program product comprising an operation. 60. The method of claim 59, wherein determining the location of the user terminal comprises: -Adjust the pseudo range based on the height of the zone near the user's terminal, and Determining the position of the user terminal based on the adjusted pseudo range and the position of the DTV transmitter. A computer program product comprising an operation. The method of claim 59, Select the DTV signal from the plurality of DTV signals, wherein the DTV signal is derived from the plurality of DTV signals based on the identity of an additional transmitter communicatively linked to the user terminal and a storage table that correlates the additional transmitter and the DTV signals; To choose A computer program product further comprising an action. The method of claim 59, Accept location input from the user, and Selecting the DTV signal from a plurality of DTV signals based on the position input A computer program product further comprising an action. The method of claim 59, Scan for available DTV signals for fingerprint combination of location, and Selecting a DTV signal used to determine a pseudorange from an available DTV signal based on the fingerprint and a storage table that matches the known fingerprint with known locations. A computer program product further comprising an action. The method of claim 59, -Using Receiver Autonomous Integrity Monitoring (RAIM) to check the integrity of pseudo range based on redundant pseudorange from DTV transmitter A computer program product further comprising an action. A computer program product tangibly stored on a computer-readable medium for determining the location of a user terminal, Receiving a DTV broadcast signal from a DTV transmitter at a user terminal, wherein the DTV signal is an ETSI digital video broadcasting-terrestrial (ISDB-T) signal, Determine a pseudo range between the DTV transmitter and the user terminal based on a known component of the DTV broadcast signal; and Transmitting the pseudo range to a location server set to determine the location of the user terminal based on the location and pseudo range of the DTV transmitter; Computer program product tangibly stored on a computer-readable medium for determining a location of a user terminal comprising: instructions for causing a program processor to execute the above operation. 75. The method of claim 74, wherein determining the pseudo range is: Determine a transmission time of one component of the DTV broadcast signal from the DTV transmitter, Determine a reception time of said component at a user terminal, and Determine a time difference between the transmission time and the reception time, A computer program product comprising the above operations. 75. The computer program product of claim 74, wherein said known component is a scattered pilot carrier. 75. The method of claim 74, wherein determining the pseudo range is: Storing a portion of the DTV signal, and Correlating the stored portion with the signal generated by the user terminal for generating pseudo range, A computer program product comprising an operation. 75. The method of claim 74, wherein determining the pseudo range is: Correlating the DTV signal to a signal generated by a user terminal as the DTV signal is received for generating a pseudo range; A computer program product comprising an operation. A computer program product tangibly stored on a computer-readable medium for determining the location of a user terminal, Receive a pseudo range from the user terminal, wherein the pseudo range is determined between the user terminal and the DTV transmitter based on the DTV signal broadcast by the DTV transmitter, the DTV signal being the European Telecommunications Standards Institute (ETSI) digital video Digital Video Broadcasting-Terrestrial (ISDB-T) signal, the pseudo range is determined based on known components of the ISDB-T signal, and Determining the position of the user terminal based on the pseudo range and the position of the DTV transmitter. Computer program product tangibly stored on a computer-readable medium for determining a location of a user terminal comprising instructions for causing a programmable processor to execute the above operation. The method of claim 79, wherein the operation of determining the location of the user terminal, Adjust the pseudo range based on the time difference between the transmitter clock of the DTV transmitter and the known time reference; and Determining the position of the user terminal based on the adjusted pseudo range and the position of the DTV transmitter. A computer program product comprising an operation. 80. The computer program product of claim 79, wherein said known component is a scattered pilot carrier. The method of claim 79, wherein the operation of determining the location of the user terminal, Determine a time difference between the local time criterion of the user terminal and the master time criterion, and Determining the position of the user terminal based on the pseudo range, the position of the DTV transmitter, and the time difference. A computer program product comprising an operation. 83. The method of claim 82, Determining a future position of the user terminal using the time difference. A computer program product further comprising an action. The method of claim 79, wherein the operation of determining the location of the user terminal, Determine the general geographic area where the user terminal is located, and Determining a location of a user terminal based on the pseudo range and the general geographic area. A computer program product comprising an operation. 85. The computer program product of claim 84, wherein the general geographic area is a footprint of an additional transmitter communicatively linked to a user terminal. The method of claim 79, wherein the operation of determining the location of the user terminal, Determine a tropospheric propagation velocity near the user terminal, Adjust pseudo range based on the tropospheric propagation rate, and Determining the position of the user terminal based on the adjusted pseudo range and the position of the DTV transmitter. A computer program product comprising an operation. The method of claim 79, wherein the operation of determining the location of the user terminal, -Adjust the pseudo range based on the height of the zone near the user's terminal, and Determining the position of the user terminal based on the adjusted pseudo range and the position of the DTV transmitter. A computer program product comprising an operation.