KR100941196B1 - Using digital television broadcast signals to provide gps aiding information - Google Patents

Abstract

Satellite positioning in the satellite positioning system receiver 1502 to determine the position of the satellite positioning system receiver using the propagation speed of the signal transmitted by the satellite in the satellite positioning system and the satellite positioning system assistance information 1522. Methods, apparatus, and computer-readable media for providing decision system assistance information are disclosed. The present invention

Providing satellite positioning system assistance information 1522,

Provide a digital television (DTV) signal comprising a plurality of frames, each frame comprising a plurality of data segments,

Encoding satellite positioning system assistance information into codewords,

Replace data segments in the DTV signal with codewords, and

-Transmitting DTV signal

Wherein the satellite positioning system receiver receives the DTV signal to recover satellite positioning system assistance information.

Description

Method, device, and computer-readable medium for providing GPS auxiliary information using digital television signal TECHNICAL FIELD [USING DIGITAL TELEVISION BROADCAST SIGNALS TO PROVIDE

The present application,

-US Patent Application No. 10 / 003,128, filed November 14, 2001, entitled "Robust Data Transmission Using Broadcast Digital Television Signals" by Inventor K. Omura, J.J.Spilker Jr., Matthew Rabinowitz

As a continuous division application of

U.S. Patent Application No. 60 / 281,269, filed on April 4, 2001, entitled "An ATSC Standard DTV Channel for Low Data Rate Broadcast to Mobile Receivers" (J.J. Spilker Jr., Matthew Rabinowitz)

Insist on priority. The present application

US Patent Application No. 10 / 159,478, filed May 5, 2002, entitled "Position Location using Global Positioning Signals Augmented by Broadcast Television Signals" (J.J. Spilker Jr. and Matthew Rabinowitz)

As a continuous division application of

09 / 887,158, published on June 1, 2001, "Position Location Using Broadcast Digital Television Signals," by J.J. Spilker Jr. and Matthew Rabinowitz.

Is a serial application for

U.S. Patent Application No. 60 / 361,762, filed March 3, 2002, entitled "DTV Position Location Augmented by GPS" (J.J. Spilker Jr.),

U.S. Patent Application No. 60 / 353,440, entitled "DTV Position Location Augmented by GPS" (invented by J.J. Spilker Jr.), and

-US Patent Application No. 60 / 332,504, filed November 13, 2001, entitled "DTV Augmented GPS for Robust Aircraft Navigation"

Priority is claimed, all of which are incorporated herein by reference. The present application,

U.S. Patent Application No. 60 / 281,269, filed on Apr. 2001, entitled "An ATSC Standard DTV Channel for Low Data Rates Broadcast to Mobile Receivers" by J.J. Spilker Jr., Matthew Rabinowitz

Which is hereby incorporated by reference in its entirety. The present application,

US patent application Ser. No. 09 / 932,010, entitled "Position Location using Terrestrial Digital Broadcast Television Signals" (invented by J.J. Spilker Jr. and Matthew Rabinowitz);

-US Patent Application No. 60 / 337,834, November 9, 2001, entitled "Wireless Position Location Using the Japanese ISDB-T Digital TV Signals" by J.J. Spilker Jr.

As the invention relates to, all of its disclosures are incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to data transmission over broadcast digital television signals, for example, to digital television signals conforming to the American Television Standards Committee (ATSC) format. In particular, the present invention relates to the transmission of GPS assistance information by this technique.

Beginning with the ATSC standard digital television broadcasting in the late 1990s, digital television broadcasting is expanding rapidly in the United States. By the end of 2000, more than 166 digital television transmitters were in operation. The FCC intends that by 2006 all television broadcasts will be on recently allocated digital channels and the analog channels will be returned to the information for other purposes.

Sophisticated data compression techniques and improvements in digital signal processing capabilities make it possible to transmit high quality audio and video information over the same bandwidth as analog channels. In the television broadcast area, the Advanced Television Systems Committee (ATSC) has created both digital and high definition television standards to take advantage of technological advances. These standards are called ATSC digital TVs, or simply ATSC. The current ATSC standard uses an amplitude modulated suppressed-carrier vestigial sideband modulation technique called VSB. 8-VSB modulation is used in "off air" broadcasting systems, and 16-VSB modulation is presented in higher data rate cable systems.

These standards are optimized for the broadcast of TV programming. However, due to the rapid expansion of digital TV broadcasting and the proliferation of digital television transmitters, other types of data transmission opportunities are also increasing. Other types of data may include data that allows the mobile phone to calculate the location of the phone without the need for external processing, short messages, similar devices in pagers, textual web pages, and locations of interest near the mobile phone. There are simple maps, TV program guides, radio program guides, bus schedules, store advertisements near the receiver, and all sorts of slow data movement commerce information.

Television infrastructure is not always suitable for this type of data. For example, the ATSC standard is tuned towards some spectral efficiency. That is, some amount of information will be transmitted in some spectral bandwidth. In particular, a bit rate high enough to support television program broadcasting must fit into the bandwidth allocated to a single television channel. With this operating requirement, some signal-to-noise ratio is required for successful reception of the broadcast signal. For example, the 19.2 Mbps ATSC standard broadcast data rate requires that the receiver have a theoretical signal-to-noise ratio of 15 dB.

However, other operating points may be more appropriate for other kinds of data. For example, low data rate devices can benefit from more robust transmission while still having low spectral efficiency. This kind of signal can be recovered at a much lower signal-to-noise ratio than is required for digital television broadcast reception. This allows reception in remote areas, in buildings, or in locations where interference or multipath can cause problems. In addition, a simpler receiver may be used compared to the receiver required for digital television broadcast reception.

Accordingly, there is a need for a system and method that can take advantage of the rapidly expanding digital TV (DTV) infrastructure while enabling data transmission different from television programs.

In general, according to one aspect, the present invention relates to a satellite positioning system for determining a position of a satellite positioning system receiver using propagation time of a signal transmitted by a satellite of a satellite positioning system and satellite positioning system assistance information. A method, apparatus, and computer-readable medium for providing satellite positioning system assistance information to a system receiver, the method comprising:

-Provide satellite positioning system assistance information,

Provide a digital television (DTV) signal comprising a plurality of frames, each frame comprising a plurality of data segments,

Encoding satellite positioning system assistance information into codewords,

Replace data segments in the DTV signal with codewords, and

-Transmitting DTV signal

And wherein the satellite positioning system receiver receives the DTV signal to recover satellite positioning system assistance information.                 

Particular embodiments may include one or more of the following features. The satellite positioning system is a global positioning system (GPS). The satellite positioning system receiver determines the position of the satellite positioning system receiver based on the signal received from the satellite positioning system satellite and the satellite positioning system assistance information. The satellite positioning system assistance information may include one or more of the following information.

Satellite positioning system, the position of the satellite,

-Clock calibration information of satellite positioning system satellite

Doppler information about the signal transmitted by the satellite positioning system satellite,

Information about the atmospheric effect on the signal transmitted by the satellite positioning system satellite, and

-The identity of the satellite positioning system satellite, which can be identified by the satellite positioning system receiver.

The DTV signal may include one or more of the following signals.

ATSC (American Television Standards Committee) DTV signal,

-ETSI (European Telecommunications Standards Institute) DTV-T (Digital Video Broadcasting-Terrestrial) signal, and

-Japanese Integrated Services Digital Broadcasting-Terrestrial (ISDB-T) signal.                 

In general, according to one aspect, the invention features a method, apparatus, computer-readable medium for recovering satellite positioning system assistance information from a digital television (DTV) signal, the method comprising:

Receive a DTV signal, wherein the DTV signal comprises a plurality of frames, each frame comprising a plurality of data segments, one or more data segments representing one or more satellite positioning system assistance information; Replaced by a codeword,

Selecting data segments replaced with codewords, and

Recover satellite positioning system assistance information from selected data segments;

Steps.

Certain embodiments may include one or more of the following features. The satellite positioning system is a global positioning system (GPS). The satellite positioning system assistance information includes at least one of the following information.

Satellite positioning system, the position of the satellite,

-Clock calibration information of satellite positioning system satellite

Doppler information about the signal transmitted by the satellite positioning system satellite,

Information about the atmospheric effect on the signal transmitted by the satellite positioning system satellite, and                 

-The identity of the satellite positioning system satellite, which can be identified by the satellite positioning system receiver.

The DTV signal may include one or more of the following signals.

ATSC (American Television Standards Committee) DTV signal,

-ETSI (European Telecommunications Standards Institute) DTV-T (Digital Video Broadcasting-Terrestrial) signal, and

-Japanese Integrated Services Digital Broadcasting-Terrestrial (ISDB-T) signal.

In general, according to one aspect, the invention features a method, apparatus, computer-readable medium for positioning a satellite positioning system receiver using a satellite positioning system. This way,

Receiving at a satellite positioning system receiver a signal transmitted by a satellite of the satellite positioning system,

Receiving at the satellite positioning system receiver a digital television (DTV) signal comprising a plurality of frames, each frame comprising a plurality of data segments, wherein at least one data segment contains satellite positioning system assistance information; Is replaced by one or more codewords to express,

Selecting data segments replaced with codewords,

Recover satellite positioning system assistance information from selected data segments, and

-Satellite positioning system that determines the position of the satellite positioning system receiver based on the signals received from the satellite and satellite positioning system assistance information.

Steps.

Certain embodiments may include one or more of the following features. The satellite positioning system is a global positioning system (GPS). The satellite positioning system assistance information includes at least one of the following information.

Satellite positioning system, the position of the satellite,

-Clock calibration information of satellite positioning system satellite

Doppler information about the signal transmitted by the satellite positioning system satellite,

Information about the atmospheric effect on the signal transmitted by the satellite positioning system satellite, and

-The identity of the satellite positioning system satellite, which can be identified by the satellite positioning system receiver.

The DTV signal may include one or more of the following signals.

ATSC (American Television Standards Committee) DTV signal,

-ETSI (European Telecommunications Standards Institute) DTV-T (Digital Video Broadcasting-Terrestrial) signal, and                 

-Japanese Integrated Services Digital Broadcasting-Terrestrial (ISDB-T) signal.

Embodiments,

Determining the pseudo distance between the transmitter of the DTV signal and the receiver of the satellite positioning system based on the signal component of the DTV signal; and

Determining the position of the satellite positioning system receiver based on the pseudorange, the signal received from the satellite positioning system satellite, and the satellite positioning system assistance information.

Characterized in that it further comprises steps. According to the present invention, digital data is transmitted as part of a DTV broadcast signal by encoding digital data into codewords and replacing part of the data segments of the DTV signal with codewords. By using long codewords, a much more robust transmission can be achieved than the portion of the DTV broadcast signal used for TV programming. Thus, transmission can be received at a lower signal noise ratio. By using a finite set of codewords, the receiver can recover digital data using a simple correlator bank.

In general, according to one aspect, the present invention provides a satellite positioning system for determining the position of a satellite positioning system receiver using propagation time of a signal transmitted by a satellite of a satellite positioning system and satellite positioning system assistance information. A device for providing satellite positioning system assistance information to a receiver, the device comprising:

A second satellite positioning system receiver for receiving satellite positioning system assistance information;

A channel coder for providing a digital television (DTV) signal comprising a plurality of frames, wherein each frame comprises a plurality of data segments,

An encoder for encoding satellite positioning system assistance information into codewords,

A packet multiplexer for replacing data segments in the DTV signal with codewords, and

-Transmitter to transmit DTV signal

Wherein the satellite positioning system receiver receives the DTV signal to recover satellite positioning system assistance information.

Particular embodiments may include one or more of the following features. The satellite positioning system is a global positioning system (GPS). The satellite positioning system receiver determines the position of the satellite positioning system receiver based on the signal received from the satellite positioning system satellite and the satellite positioning system assistance information. The satellite positioning system assistance information may include one or more of the following information.

Satellite positioning system, the position of the satellite,

-Clock calibration information of satellite positioning system satellite

Doppler information about the signal transmitted by the satellite positioning system satellite,                 

Information about the atmospheric effect on the signal transmitted by the satellite positioning system satellite, and

-The identity of the satellite positioning system satellite, which can be identified by the satellite positioning system receiver.

The DTV signal may include one or more of the following signals.

ATSC (American Television Standards Committee) DTV signal,

-ETSI (European Telecommunications Standards Institute) DTV-T (Digital Video Broadcasting-Terrestrial) signal, and

-Japanese Integrated Services Digital Broadcasting-Terrestrial (ISDB-T) signal.

In general, according to one aspect, the invention features an apparatus for recovering satellite positioning system assistance information from a digital television (DTV) signal, the apparatus comprising:

A front end for receiving a DTV signal, wherein the DTV signal comprises a plurality of frames, each frame comprising a plurality of data segments, one or more data segments representing satellite positioning system assistance information This front end, replaced by one or more codewords, and

A back end for recovering satellite positioning system assistance information from the selected data segments by selecting data segments replaced with codewords                 

It includes.

Certain embodiments may include one or more of the following features. The satellite positioning system is a global positioning system (GPS). The satellite positioning system receiver determines the position of the satellite positioning system receiver based on the signal received from the satellite positioning system satellite and the satellite positioning system assistance information. The satellite positioning system assistance information includes at least one of the following information.

Satellite positioning system, the position of the satellite,

-Clock calibration information of satellite positioning system satellite

Doppler information about the signal transmitted by the satellite positioning system satellite,

Information about the atmospheric effect on the signal transmitted by the satellite positioning system satellite, and

-The identity of the satellite positioning system satellite, which can be identified by the satellite positioning system receiver.

The DTV signal may include one or more of the following signals.

ATSC (American Television Standards Committee) DTV signal,

-ETSI (European Telecommunications Standards Institute) DTV-T (Digital Video Broadcasting-Terrestrial) signal, and

-Japanese Integrated Services Digital Broadcasting-Terrestrial (ISDB-T) signal.

In general, according to one aspect, the invention features an apparatus for positioning a satellite positioning system receiver using a satellite positioning system, the apparatus comprising:

A front end receiving a signal transmitted by a satellite of a satellite positioning system and receiving DTV signals comprising a plurality of frames, each frame comprising a plurality of data segments, wherein at least one data segment This front end, replaced by one or more codewords representing satellite positioning system assistance information,

A back end that selects data segments replaced with codewords to recover satellite positioning system assistance information from the selected data segments, and

-Satellite positioning system A processor for determining the position of the satellite positioning system receiver based on signals received from satellites and satellite positioning system assistance information.

It includes.

Certain embodiments may include one or more of the following features. The satellite positioning system is a global positioning system (GPS). The satellite positioning system receiver determines the position of the satellite positioning system receiver based on the signal received from the satellite positioning system satellite and the satellite positioning system assistance information. The satellite positioning system assistance information includes at least one of the following information.                 

Satellite positioning system, the position of the satellite,

-Clock calibration information of satellite positioning system satellite

Doppler information about the signal transmitted by the satellite positioning system satellite,

Information about the atmospheric effect on the signal transmitted by the satellite positioning system satellite, and

-The identity of the satellite positioning system satellite, which can be identified by the satellite positioning system receiver.

The DTV signal may include one or more of the following signals.

ATSC (American Television Standards Committee) DTV signal,

-ETSI (European Telecommunications Standards Institute) DTV-T (Digital Video Broadcasting-Terrestrial) signal, and

-Japanese Integrated Services Digital Broadcasting-Terrestrial (ISDB-T) signal.

The processor,

Determining the pseudo distance between the transmitter of the DTV signal and the receiver of the satellite positioning system based on the signal component of the DTV signal; and

Determining the position of the satellite positioning system receiver based on the pseudorange, the signal received from the satellite positioning system satellite, and the satellite positioning system assistance information.

It is characterized by.

1 is a block diagram of a system according to the present invention.

2 is a structural diagram of an ATSC frame.

3 is a flow chart of a method for transmitting and receiving data at low data rates using ATSC DTV signals.

4A-D are diagrams of data segments replaced with codewords using various approaches.

5A-B are frame diagrams when various data segments have been replaced with codewords.

6 is a block diagram of a DTV transmitter.

7 is a block diagram of a front end for use in a receiver.

8 is a block diagram of a back end based on a bank of correlators.

9 is a block diagram of one correlator.

10 is a block diagram of another correlator.

11 is a flowchart illustrating a method of recovering digital data based on frame construction.

12 is a block diagram of a back end for frame construction.

13 is a diagram of a system including one GPS receiver and multiple GPS satellites, according to one embodiment.                 

14 is a diagram of a process executed by the system of FIG. 13 according to one embodiment.

15 is a diagram of a system including one GPS receiver and one GPS satellite, according to one embodiment.

16 is a diagram of a process executed by a system according to one embodiment.

As used herein, the terms "server" and "client" refer to an electronic device or mechanism, and the term "message" refers to an electronic signal representing a digital message. The term "mechanism" as used herein refers to hardware, software, or a combination thereof. These terms are used to simplify the description below. The client, server, mechanism described herein may be implemented as a standard general purpose computer, or may be implemented as a dedicated device.

Data transmission using DTV signal

1 is a block diagram of an exemplary system 100 in accordance with the present invention. System 100 includes a receiver 102 that receives a digital television (DTV) broadcast from one or more DTV transmitters 106A-N.

One example of a DTV transmitter 106 is a transmission tower that broadcasts a DTV signal to the receiver 102 over the air. Another example is a transmitter for a cable television system, in which case the DTV signals reach the receiver 102 via a cable link. Satellite TV systems known as DBS (Direct Broadcast Satellites) are another example of digital TV broadcast systems. For example, EchoStar and DirecTV are major DBS services in the US market. In general, there are basically three kinds of commercial digital TV broadcasting systems. Terrestrial, cable, and satellite systems exist. Satellite TV systems are completely digital. Cable and terrestrial systems, on the other hand, are changing from old analog to digital. These digital TV systems use a frame structure consisting of encoded data packets. These data packets are also called data segments.

Receiver 102 refers to any object capable of implementing the low data rate channel described below. Receiver 102 may receive television program data embedded in a DTV signal, but this is not a requirement. Receiver 102 may be stationary or mobile. Any object that may include a chip or software that implements the robust slow data channel described below may be the receiver 102. Thus, DTV televisions, pagers, mobile phones, PDAs, computers, automobiles, and vehicles may be examples of receivers 102.

In system 100, DTV transmitter 106 transmits digital data to receiver 102 at a data rate much lower than that of broadcast television program data. Alert low speed digital data is inserted into the DTV signal broadcast by the transmitter 106. The DTV signal is received by the receiver 102, which recovers digital data from the DTV signal.

For example, in one device, digital data is a regional map showing a region of interest near a cellular telephone. Other devices may use data, short messages, devices similar to those on pagers, stock quotes, news headlines, TV program listings, radio program listings, bus schedules, near receivers, allowing the phone to calculate its own location without the need for external processing. It includes short text ads of stores, and all kinds of slow data M-commerce information. Based on today's technology, most of the digital data for these devices will consist of simple graphs or short text, such as displaying maps. Many data broadcast equipment may have slow data versions. For example, Wireless Application Protocol (WAP), the current mobile phone technology that reformats web pages onto small wireless screens, was introduced in 1999. The simpler text-only version is an example of a device for robust low-speed data systems using DTV signals.

2 is a diagram showing the structure of an ATSC frame from the current ATSC standard. The current ATSC signal is introduced in the March 16, 2000, "ATSC Digital Television Standard and Amendment No. 1" of the Advanced Television Systems Committee, the contents of which are hereby incorporated by reference in their entirety. ATSC signals for terrestrial broadcasting use 8th-order residual sideband modulation (8-VSB). The symbol rate of the ATSC signal is 10.76 MHz, which is derived from the 27.00 MHz clock. The structure 200 of an ATSC frame is shown in FIG. 2. Frame 200 includes a total of 626 segments, each segment having 828 symbols. Each segment is followed by four symbols that are used for synchronization purposes. This will be called a segment synchronization attachment. In FIG. 2 time flows from right to left. There are 520,832 symbols per frame. Each segment (plus corresponding segment synchronization attachment) lasts for 77.3 microseconds. The first and 314th segments of each frame are field synchronization segments. 312 data segments are located after each field synchronization segment.

Each field synchronization segment is one of two fixed 828-symbol sequences. The two 828-symbol sequences differ only by the extent that the 63 symbol sections are reversed by one sequence for the rest of the sequence. Some additional symbols of these field synchronization segments are different for each transmitter. One of these two field synchronization segments is sent every 24.2 milliseconds. This symbol sequence was included as a training sequence to enable the ATSC receiver to correct the multipath commonly found in broadcast channels. The field synchronization segment can be seen as a spread spectrum codeword embedded in the ATSC data sequence. Spread spectral codewords are typically detected by correlators (eg, matched filters). If there is a multipath signal of the ATSC broadcast signal at the receiver, the output of these correlators may provide an estimate of the parameters of the multipath signal. Since the field synchronization segment appears once every 24.2 milliseconds, correlators can be used to provide periodic snapshots of the multipath signal. In the case of a dynamically varying multipath signal, the multipath characteristics during the intermediate period can be estimated using conventional methods such as blind equalization or other interpolation techniques.

In the data segment, television program data is carried. Each data segment corresponds to a 188-byte data packet in the MPEG-2 transport layer. Each 188-byte data packet consists of 828 3-bit coded data symbols using a combination of Reed-Solomon encoder, interleaver, and rate 2/3 trellis encoder. Is expanded. Data segments may be used to carry other information, such as web content, from the Internet, or may be said to contain a null packet without being used.

The segment synchronization attachment is the same for all segments. This attachment consists of four symbol sequences (-1, 1, 1, -1) and is used primarily for segment synchronization.

The implementation of the invention can be extended to correspond to future improvements of the DTV signal. For example, the ATSC signal protocol permits high speed 16-VSB signals primarily for digital cable television. However, the 16-VSB signal generally has the same frame structure as the 8-VSB signal, and uses a field synchronization segment and a data segment. Thus, it is clear that the 8-VSB example shown below can be extended for the 16-VSB signal.

The 8-VSB signal is built by filtering. The in-phase segment of the symbol pulse has a rising cosine characteristic, as described in Digital Communications, 1995, 3rd edition of J.G.Proakis, published by McGraw-Hill. The pulse can be expressed as follows.

In this case, T is a symbol period,

Wherein β = 0.5762. This signal has the following frequency characteristics.

 From this, it can be seen that one sideband bandwidth of the signal is (1 + β) 10.762237 MHz = 5.38 MHz + 0.31 MHz. To generate a VSB signal from this in-phase pulse, the signal is filtered so that only a small portion of the lower sideband remains. This filtering can be expressed as

At this time,

H _α (f) is a filter designed to leave a residue of the low side band. This filter satisfies the characteristics of H _α (-f) = -H _α (f) and H _α (f) = 0, f> α. The response U (f) P (f) may be expressed as follows.

= - jsgn(f)P(f)는 P(f)의 Hilbert 변환이다. VSB 펄스는 다음과 같이 표현될 수 있다.At this time,

jsgn (f) P (f) is the Hilbert transform of P (f). The VSB pulse can be expressed as follows.

And the following known pulse signal is expressed as

At this time, p _vi (t) is the in-phase component, p _vq (t) is a quadrature (quadrature) component. In addition, the following formula holds.

Before data is transmitted, the ATSC signal also implements a carrier signal, which has an output of 11.5 dB less than the data signal. This carrier aids coherent demodulation of the signal. As a result, the transmitted signal can be expressed as follows.

At this time, Cn is an 8-level data signal.

3 is a flow chart illustrating a method 300 of transmitting digital data using an ATSC frame 200. In general, some data segments are replaced with codewords representing digital data to be transmitted. More specifically, the digital data to be transmitted is encoded into a codeword (310). Codewords replace the data segment in the DTV signal (320). The DTV transmitter 106 sends a DTV signal including the codewords (330). Receiver 102 receives 340 an outgoing signal from which digital data is recovered 350.

Consider a simple example where one data segment in each frame is replaced with one of two codewords. In this case, each codeword has a length of 828 symbols. In other words, each codeword is the same length as the data segment. One codeword represents binary zero, and the other codeword represents binary one. The two codewords are perpendicular to each other. In this example, one bit of data may be transmitted per ATSC frame for a data rate of approximately 21 bits / second (bps).

When both codewords are vertical, a simple non-coherent receiver has the same performance as a common non-coherent reception of binary frequency shift keyed signals. Thus, in an ideal white Gaussian noise channel model, the bit error probability appears as follows.

No is a double sided noise spectral density, and Eb is energy per bit. In this case, Eb for a single bit transmitted is the energy at the receiver for the entire 828-symbol segment. This is equivalent to the TV transmitter output at the receiver multiplied by the segment duration of 77.3 microseconds. Thus, Eb is 29 dB greater than the energy for each DTV broadcast symbol.

As a result, digital data can be recovered from broadcast signals that are much weaker than can be accommodated for TV reception. For example, signals 30 to 40 dB weaker than those required for digital TV signal reception may be suitable for use in these slow data channels. This means that digital data can be recovered in a much wider range than typical DTV reception. In addition, the reception of these slow data channels is possible in many building locations where broadcast TV reception is difficult.

Another advantage of this approach is that the reception of slow data signals can be achieved with a receiver that is much simpler than a standard DTV receiver. This will be explained further below. For this kind of data transmission, it is appropriate to simply sense the codeword in a non-coherent manner using a correlator at the receiver. This type of receiver is simple in design, small in size, and low in energy consumption.

Another advantage is that no significant cost is required to implement the transmitter, which is also described in detail below. Many DTV transmitters already include standard equipment at the station to replace the individual segments of the DTV signal. This equipment can be used to replace a null MPEG packet or to replace some segments with a field synchronization segment, which occurs, for example, because there is no VT program data to transmit at the transmission time of the data segments. To implement the required transmitter function, this equipment only needs to be modified to replace some data segments with codewords.

The simple example presented above results in a data rate of approximately 20 bps. Data rates can be increased in numerous ways. For example, bits greater than 1 may be accompanied by 828-symbol data segments each replaced in a frame. In one approach, more than two codewords are used. For example, incoming digital data may be divided into three bit long bit sequences. Each of these bit sequences is encoded into a codeword selected from the set of eight 828-symbol codewords. Each of the eight codewords corresponds to one of eight three-bit sequences. The eight codewords are perpendicular to each other to facilitate reception. According to the 3-bit sequence, one of the eight codewords is inserted into the DTV signal to replace the corresponding data segment of the frame (Figure 4A). Here, the data rate is approximately 62 bps. In the notation used, the codeword is denoted by C _n , and [C ₀ , ... C _N-1 ] denotes one codeword selected from the set consisting of N codewords. In general, one codeword selected from a finite set of N codewords is used to replace the data segment. If N = 8, the codeword will represent one of eight three bit sequences. A lookup table can be used to convert from a 3-bit sequence to the corresponding codeword. In the general form of this example, 2 ^ N codewords may be used to replace an N bit long bit sequence.

In general, the codeword set should be chosen to have a good correlation property that minimizes reception errors. In addition to being vertical, codewords should have small side lobes for low time shifted crosscorrelation and autocorrelation functions. In general, codewords based on multiple amplitude symbols will show better correlation than those based on binary amplitude symbols. This set of codewords is widely studied in many devices, especially in spread spectrum communication systems. The most popular commercial program at this time is the Code Division Mulitple Access (CDMA) system used in the US IS-95 cellular telephone standard. Since the 8-VSB ATSC standard is based on eight-level modulation, codewords using multiple amplitude symbols may be appropriate for this standard. In particular, instead of binary (two-level) symbols, four-level or eight-level symbols may be used. The set of possible codewords may include codewords that do not represent a bit sequence. For example, 3-bit sequences may be represented by a set of nine codewords, where the ninth codeword indicates "no data".

In alternative embodiments, multiple codewords may be used to replace a single data segment. As shown in Figure 4B, another way to implement three bits per data segment is to divide the data segment into three subsegments, where each subsegment has 828/3 = 276 symbol lengths. If one data segment per frame is replaced with this set of three codewords, the data rate is approximately 62 bps.

The reverse is also possible. In FIG. 4A, the digital data is divided into bit sequences, all of which have the same length. In an alternative approach, digital data is divided into bit sequences of varying lengths, with each bit sequence mapped to a corresponding codeword. Codewords may have variable lengths. All 828 symbols in the data segment need not be replaced with a codeword. For example, as shown in FIG. 4D, for 800 symbols per data segment, five bits per data segment may be encoded into five 160-symbol codewords. However, this approach is not preferred because current technology seeks to process DTV signals under segmental principles. Thus, the approach of FIG. 4D discards the remaining 28 symbols of the data segment. In general, however, codewords will have a significantly lower data rate than the data segment to be replaced. In general, as the number of bits per codeword increases, the warning low speed data receiver becomes more complex and its performance degrades.

The overall data rate can also be increased by increasing the number of data segments per frame used for the slow data channel. Under the current ATSC standard, if all data segments are used to broadcast television programs, the resulting DTV signal will have a data rate of approximately 19.2 Mbps. Current TV signals do not require this much bandwidth. For example, HDTV typically requires 12-15 Mbps, while standard definition TVs require 3-5 Mbps. This leaves 20-80% of total capacity unused anywhere. If 20% of the total capacity is used for the slow data channel, 125 data segments per data frame will be used for this channel. If 5 bits are encoded for each data segment, the overall data rate will be 12.5 Kbps. This replaces a television program of approximately 4 Mbps with a low data channel of 12.5 Kbps, but can be received over a wider range using a much more robust, simpler receiver technique.

The choice of which and how long of the data segments to replace may be implemented in a number of ways. An intuitive way is to replace the preselected data segments. For example, in FIG. 5A, data segments 10-50 of each frame are data segments that are used as slow data channels and are replaced by codewords. In this case, the receiver can be simpler. The receiver knows the priority that only data segments 10-50 can have codewords. Therefore, only these data segments for codewords need to be tested. Moreover, if a codeword is always present in these data segments, the receiver would only have to determine which of the possible codewords is the codeword to be transmitted. In other words, if there are eight possible codewords, the receiver only has to determine which of the eight codewords has been transmitted in the received data segment period. It is not necessary to determine whether a codeword exists.

In an alternative approach, data segments are replaced with codewords according to available principles. For example, the transmitter can determine whether the data segment has a data packet, or a null packet. That is, the transmitter determines whether the data segment is used. If the data segment carries data, the data segment is not used for the slow data channel. Only unused data segments, typically "null packets", are replaced with codewords. In FIG. 5B, data segments 600-624 of frame 1 are not used and replaced with codewords. In the next frame, data segments 533-597 are not used and are therefore replaced with codewords. In this case, the receiver may not know the priority of which data segment has a codeword. Using the correlation limit, the receiver must first estimate which data segment has the codeword.

These two approaches can also be combined. For example, data segments 10-50 may be used as low speed data channels, and additional unused data segments may also be available for low speed data channels.

6 is a block diagram of the DTV transmitter 106. This transmitter 106 includes the following elements connected in series. That is, data compression engine 610, data multiplexer 620, channel coder 630, packet multiplexer 640, 8-VSB modulator and transmitter 650, and transmitter tower 660. The transmitter 106 further includes a data encoder 670 coupled to the packet multiplexer 640.

The transmitter 106 operates as follows. The analog television signal is compressed by the compression engine 610. MPEG2 is a data compression standard used by the current ATSC standard. This approach allows broadcasters to transmit TV signals at data rates from 3Mbps to 15Mbps, depending on the desired reception quality. In FIG. 6, other data entering the data multiplexer 620 may include a television signal that is already in digital form, in which case no analog television signal input 610 may be present.

Since a single analog TV channel with a standard 6 MHz bandwidth can transmit 19.2 Mbps using the ATSC digital format, the conversion to digital gives the broadcaster additional capacity to transmit other data and even multiple TV channels per 6 MHz channel. do. Data multiplexer 620 combines multiple streams of data into a single ATSC signal. Other types of data examples are additional TV programs and programming information already in digital form. Since the data is packetized for the DTV broadcast signal, any kind of digital data can be transmitted for the TV program channel at the 19.2 Mbps data rate. Proposals have been made regarding the transmission of rich Internet video web traffic in such TV program channels.

Channel coder 630 encodes the final data packet for channel error correction. In a common approach, channel coder 630 implements a combination of Reed-Solomon error correction encoding, interleaving, and trellis encoding.

The terrestrial broadcast ATSC standard uses 8-VSB modulation with 3-bit symbols in the form of 8-level amplitude. After channel coding, the coded data of the eight-level symbol is divided into data segments.

The packet multiplexer 640 is a device that can replace data on a per-segment basis. The sequence of 8-level symbols is sent to an 8-VSB modulator and transmitter 650. Modulator 650 applies 8-VSB modulation. Transmitter 650 sends the final DTV signal through transmitter tower 660.

For the low speed data channel, data encoder 670 generates a codeword from the incoming digital data. For example, the data encoder 670 may convert a bit sequence into a codeword using a lookup table. For non-real-time equipment, the incoming bit sequence and the outgoing codeword can be stored and recalled from memory in turn.

As an example, if a 3-bit sequence is converted to a 828-symbol codeword, the data encoder 670 divides the incoming digital data into a 3-bit sequence and converts it to the corresponding codeword. In one embodiment, this is achieved by a lookup table with three bits of input and outputs the corresponding codeword. Codewords from data encoder 670 are inserted by the packet multiplexer 640 into an ATSC frame at the transport layer. Codeword insertion is very similar to field synchronization segment insertion. However, there is a difference in that the actual data to be inserted is different from each other. Since the packet multiplexer 640 is almost inserting the field synchronization segment, it is obvious to modify the existing packet multiplexer 640 for codeword insertion.

In one physical embodiment, blocks 610-640 are implemented with equipment located at a television station. The modulator and transmitter 650 are located very close to the tower 660, such as in the lower body of the tower. Other embodiments are of course possible. For example, some or all of blocks 610-640 may be placed in different physical locations. This is especially true if the television program is not live. In this case, the recorded program can be processed at several different locations.

7-12 illustrate various aspects of the receiver 102. Receiver 102 recovers digital data from codewords implemented in the outgoing DTV signal. 7 is a block diagram of a front end 400 for use in the receiver 102. Sampler 400 takes a sample of the received DTV signal. In the approach shown in FIG. 7, the DTV broadcast signal 402 is received by an antenna 404, followed by a filter and an amplifier 406 behind the antenna 404. The filtered and amplified DTV broadcast signal is converted into in-phase and quadrature baseband signals by local oscillators 416, mixers 408I and 408Q, and low pass filters 410I and 410Q. Specifically, the DTV broadcast signal is separated into two signals. Each mixer 408I, 408Q multiplies one of the DTV broadcast signals with a sine or cosine component of the local oscillator, respectively. Each multiplied signal is lowpass filtered by filter 410I or filter 410Q, respectively, to derive the baseband I and Q outputs of the received DTV broadcast signal. It is sampled and quantized by an analog-to-digital converter (ADC) 412. The digital samples of the baseband I and Q outputs of the ADC may be stored in memory for later processing, processed immediately by a digital processor, or input into digital circuitry that performs hardware digital processing. 7 is a typical front end for a receiver. In particular, FIG. 7 may be a front end of a conventional DTV receiver for receiving TV program data. The other kind of front end is obvious, of course.

8 is a block diagram of a back end for use with the receiver 102. The back end 800 receives digital I and Q samples from the front end of the receiver. For convenience, I and Q samples are shown by a single line in FIG. 8 rather than separate lines for I and Q. The back end 800 includes banks of correlators 805A-805N, with one correlator 805 for each possible codeword. 8 shows a general case where there are N possible codewords and corresponding N correlators 805. Each correlator 805 correlates incoming samples to templating for that codeword. In one embodiment, the template is a matched filter for codewords. Thus, the output of correlator 805A provides a measure of the likelihood that the data segment under test will contain codeword C0. Similarly, the correlation generated by the correlator 805B measures the likelihood of a codeword C1 or the like. The bank of correlator 805 is connected to comparator 810, which determines which correlation is the largest. The data bits of the selected codeword are then output. For example, when correlator 805B produces the strongest correlation, the bit sequence corresponding to codeword C1 is recovered by the receiver.

Multipath is common in wireless channels. At the receiver side, the multipath signal is several copies of the transmitted signal, each copy having a different delay. Because of this, the correlator output has multiple correlation peaks of varying magnitudes corresponding to the transmitted codewords. The receiver may use multipath and compare all of these codeword correlators by combining all of the multipath related correlation peaks from each codeword correlator. This receiver will function better than a conventional receiver that only looks at the correlator output at a particular moment. This type of receiver can be implemented by changing the principle for comparison in comparator 810.

The correlator 805 shown in FIG. 8 may be implemented in many different ways. 9 is an example of a correlator 900. I samples from the front end are input to tap delay line 910I, and Q samples from the front end are input to tap delay line 910Q. The codeword determines which of the samples of the tap delay lines 910I, 910Q are multiplied and summed at the devices 920I, 920Q. The tap delay line 910 is long enough to store a sample for the entire codeword (eg, long enough to store a sample for the entire data segment if there is a one-to-one replacement of the data segment by the codeword). At each sample time, new I and Q samples from ADC 412 are input to tap delay lines 910I and 910Q. Parallel outputs from tap delay lines 910I and 910Q flow into multiplication and summation devices 920I and 920Q, respectively. The output of these devices is squared in the squared devices 507I, 507Q and summed again in summer 508. Thus, the correlator 900 generates an output for every sample time. In one embodiment of the back end 800 of FIG. 8, the correlator 900 of FIG. 9 is repeated N times, once for each of the correlators 805 of FIG. 8. Multiplication and sum units 920I, 920Q are varied for each correlator 805 to implement correlation for different templates.

FIG. 10 illustrates another type of correlator 500 that may be used in FIG. 8. This is a serial correlator. I and Q samples from the front end are multiplied by mixers 504I and 504Q, respectively, for the I and Q components of code generator 502, which are independently determined by the codeword. The code generator 502 is synchronized with the arrival time of the samples received by the back end. The multiplied I and Q samples are summed by summer 506I, 506Q. This sum is taken over the time period of the codeword (eg, for one data segment if there is a one-to-one replacement of the data segment by the codeword). These sums are squared in the square apparatus 507I, 507Q and then summed together in the summer 508. Correlator 500 generates one output for the overall correlation. That is, the correlator 500 generates a correlation function at a specific moment (typically, a moment when a correlation peak is expected). In contrast, the correlator 900 of FIG. 9 generates samples of correlation functions at different times. In one embodiment of the back end 900 of FIG. 8, the correlator 500 of FIG. 10 is repeated N times, once for each of the correlators 805 of FIG. 8. Several other codewords are generated by the code generator 502.

In another embodiment, the back end of the receiver 102 is implemented by a digital signal processor programmed to perform the required correlation.

11 is a flow chart illustrating one method of recovering digital data by framing construction of an incoming ATSC signal. Receiver 102 establishes the framing by identifying 1210 field synchronization segments in the ATSC frame. This may be accomplished by using the correlator 900 of FIG. 9. At this time, the multiplication and sum devices 920I, 920Q are designed to implement correlation for the field synchronization segment. Framing deployment simplifies subsequent data recovery. Because, accordingly, individual data segments can be identified and the receiver 102 will know the temporary location of the codewords. If no framing is established, the receiver will detect the codeword without knowing the start and end position of each codeword at the receiver 102. This can still be achieved by using correlation or matched filtering but is more complicated by considering the unknown timing regarding when the codewords are being received by the receiver.

Specifically, consider the case where field synchronization segments occur once in every 313 segments (or once every 24.4 seconds) in the ATSC format of FIG. 2. First, a continuous stream of symbols is received by receiver 102. It is not known where the data segment starts and ends and which of the data segments is the field synchronization segment. For framing construction, all of these ambiguities are eliminated.

12 is a block diagram of an apparatus 1200 for removing this ambiguity. The device 1200 includes a back end 800, which will recover digital data when framing has been established. The remainder of the device 1200 includes the following in series. That is, it includes a correlator 900, a counter bank 1210, and a comparator 1220. These elements are used to identify field synchronization segments. Counter 1250 is used for back end 800 synchronization. The block diagram is functional. Various embodiments of the same function are also possible.

The frame function of the device 1200 operates as follows. The incoming symbol stream is divided into 24.2ms blocks, which are further divided into 313 sections each consisting of 77.3 us. The 24.2 ms block corresponds to the ATSC half-frame, and the 77.3 us interval corresponds to the data segment. In other words, the field synchronization segment will occur once for each 24.2 ms block, and the field synchronization segment will last for a time period of 77.3 us.

Correlator 900 correlates one inflow 77.3 us time interval to a "generic" field synchronization segment. The template is "generic" in that the correlator 900 detects 757 symbols common to all field synchronization segments (some symbols vary between different field synchronization segments). Correlator 900 has one output for each sample time. That is, it outputs a correlation function that is sampled at many different time points. This is useful because we do not yet know the exact ring position of the correlation peak.

In counter bank 1210, one counter is assigned for each of 313 time intervals. During each time period, the correlator output sample is compared to the limit. If the output of the correlator 900 exceeds the limit, the counter 1210 for this time interval is incremented. This is repeated, iterating through the counter 1210 repeatedly, with each of the 313 intervals appearing once every 24.4 milliseconds. Thus, each counter 1210 has its own 313th time interval (e.g., first, 314, 627, etc. for counter 1, second, 315, 628, etc. for counter 2, etc.). ) Counts the number of times beyond this limit. Over time, the counter 1210 with the maximum count will be a counter corresponding to the field synchronization segment. Comparator 1220 determines which count is the maximum, and thus identifies the field synchronization segment. Although the starting point of the field synchronization segment may not be accurately determined by the counter bank 1210 itself, the comparator will pin down the position of the field synchronization segment within 77.3 milliseconds. The exact location of the field synchronization segment time point may be determined based on the fine structure of the output from the correlator 900.

Suppose the noise at the front end of receiver 102 is white Gaussian noise with double-sided spectral density of No. In the noise-only interval without field synchronization segments, the output sample is the sum of the squares of two independent Gaussian random variables, each with a variable value of No / 2. The probability that this sample X exceeds the limit T is as follows.

P (T) = Pr {X> T} = exp {-T / No} (12)

The expected value of X is E {X}. If the limit is set at three times this average, i.e. if T = 3No,

P (3No) = 0.05 (13)

Is the probability that this noise sample exceeds the limit, and therefore the counter is incremented.

For a time period of 1 second, more than 40 decisions may be made for each of the 313 counters. When the signal-to-noise ratio at the receiver is more than 22 dB, the counter should slowly show which of the 313 intervals contains the FSS. This is because the processing gain is about 29dB, giving a 6SS to 7dB FSS correlation output that is greater than the noise background of the correlator output.

There are several ways in which the correlator output can be used to position field synchronization segments. In one example, counter bank 1210 is replaced by a bank of accumulators. Peak correlations for each of the 313 intervals are accumulated to generate 313 subtotals. In other words, the accumulator 1 accumulates the peak correlation for the first, 314th, 627th, and the like sections. For many frames, the maximum subtotal will be the sum corresponding to the field synchronization segment.

Once the field synchronization segment is identified, time-gated delay lock loops can be used to maintain a lock on the multipath component of the field synchronization segment of the received broadcast signal. Non-coherent combinations of this delay lock loop output can be done to improve processing gain.

Once the frame is built, individual data segments are identified and tested for codewords. In the example of FIG. 11, assume that some data segments are preselected for the low speed data channel. Then, the numerical position of the data segment is determined 1220 and the preselected data segments are processed for the codeword. For example, if data segments 10-50 are preselected for a slow data channel, receiver 102 only needs to count segment 10 for the field sync segment, and then segment 10- for the codeword. 50).

In FIG. 12, time interval # 137 has been identified as a field synchronization segment. Counter 1250 is counted into data segments 10-50 for the field synchronization segment, which data segments will be processed by back end 800.

If there is an opportunity and the transmitter inserts a codeword into the segment, the receiver does not know where the data segment has the codeword. As a result, after the receiver builds a frame, each data segment is processed by the correlator bank (see FIG. 8). Comparator 810 selects the most probable codeword based on the correlation strength, but there are additional decisions as to whether the codeword has been transmitted. In one approach, this decision is based on all correlator outputs. One example is to determine that there is no codeword if there is no dominant peak correlator output between all correlator outputs. This is based on the fact that when a codeword is transmitted during this interval, the correlator output for the transmitted codeword will have a high probability, having a much larger correlator output peak than other codeword correlator outputs. As an example, to determine that a codeword has been transmitted in a particular segment interval, the maximum correlator output peak must be at least twice the corresponding correlator output peak of the remaining correlator output peaks.

In an alternative embodiment, the functionality shown in FIG. 12 is implemented with a DSP processor.

Although the invention has been described in detail with reference to some preferred embodiments, other embodiments are of course possible. For example, some examples have been described using specific frequencies such as intermediate frequencies or known bands. This does not mean to limit this example to this particular frequency. In general, different implementations may operate at different frequencies. Similarly, several steps can be implemented with analog or digital processing. As another example, processing of the incoming DTV signal may be done in real time without any storage of the incoming signal, or by importing a sample of the DTV signal from memory. As a last example, several different kinds of templates can be used to achieve the desired correlation.

In the ATSC standard, field synchronization segments generally use binary amplitude symbols, and in general, amplitudes of up to eight levels are allowed in the transmitter's 8-VSB modulated signal. In common, the codewords will be selected to use the two-level, four-level, eight-level amplitude of the codeword symbol sequence. When larger levels of symbols are used for the codewords, more codewords with better autocorrelation and cross correlation properties can be selected. Thus, the detection of codewords at the receiver 102 can be improved. However, the more levels, the more complicated the correlator of the receiver 102.

In alternative embodiments, DTV signals other than ATSC signals may be used. All DTV signals depend on data segments organized into frames. Codewords can replace some of these data segments, allowing robust and low speed data transmissions unless this replacement degrades the rest of the DTV signal to an unacceptable extent. For example, if data segments in the DTV format are independently encoded so that replacement of one data segment does not affect decoding of the remaining data segments, the data segments may be replaced individually according to available principles. Data segments are preferably replaced at the transport layer.

GPS assist information transmission using DTV signal

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 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 Spilker, Jr., Global Positioning System-Theory and Applications, Volumes I and II.

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. In this case, the accuracy of GPS positioning can be greatly degraded.

However, GPS positioning can be aided by data transmission to make GPS more robust against attenuation and multipath. Examples of this kind of data are clock calibration information based on atomic standards and the current position of the GPS satellites. Additional examples include Doppler information and information about the local atmosphere, including ionospheric effects that can alter or disrupt satellite signals. Further examples are a list of satellites that can be seen at a given user location, spatial coordinate data for selected satellites, and predicted Doppler data for selected satellites. Another example is data modulated with a C / A GPS code signal. This data may include information to assist the device in tracking and determining the exact distance to the GPS satellites. This kind of data is referred to herein as GPS assistance information.

According to existing well-known techniques, such low-data-rate GPS assistance information can be used by devices to more efficiently integrate GPS satellite signals over a longer period of time. These technologies are called Assisted GPS, Added GPS, or A-GPS. Devices using GPS assistance information are more robust against attenuation by obstacles. Moreover, with GPS assistance information, these devices can obtain a heavily attenuated GPS signal from far below the noise floor. As a result, GPS positioning can be improved by using GPS assistance information, especially when the GPS pseudonoise signal is attenuated.

Moreover, GPS receivers typically determine their location by calculating the relative arrival times of signals transmitted simultaneously from multiple GPS (or NAVSTAR) satellites. These counterparts send satellite positioning data (so-called "emphemeris" data) and clock timing data as part of the message. This information is transmitted in the channel transmitted at 50 bps. In other words, the device can receive GPS assistance information directly from the GPS satellites themselves. However, the process of retrieving and acquiring GPS signals, reading celestial force data for multiple satellites, and calculating the device's position from the data is time consuming and can take several minutes. In many cases, this long processing time is unacceptable and greatly limits the battery life of the portable device. This processing time makes it very difficult to implement real-time positioning for equipment that requires continuous location updates, such as real-time electronic maps used in automobiles.

In a preferred embodiment, the GPS assistance information is transmitted to the end user device via a digital TV broadcast signal. For example, GPS assistance information typically only requires a low data rate. Thus, the techniques introduced above are suitable for disseminating GPS assistance information through DTV broadcast signals. One advantage of this approach is that this communication channel is very robust. Compared to several other types of communication channels, the above-described DTV-based communication channels can be restored to a lower signal-to-noise ratio, such as in a location or remote area where problems are caused by interference or multipath. GPS assistance information allows the GPS receiver to scan the available GPS signals more effectively. This assistance information makes it easy for the GPS receiver to find the GPS signal below the noise floor. In another embodiment, DTV signals including GPS assistance information are disseminated by means such as wired and wireless.

FIG. 13 is a diagram of a system 1300 including one GPS receiver 1302 and multiple GPS satellites 1320A-N, according to one embodiment. 14 illustrates a process 1400 executed by the system 1300 according to one embodiment.

The DTV transmitter 1306 provides the GPS assistance information (step 1420). In one embodiment, one or more monitor stations 1308 receive GPS signals transmitted by the GPS satellites 1320. The monitor stations 1308 use the received GPS signals to determine Doppler for the satellite and to determine celestial force information using existing techniques. This GPS assistance information is sent to the DTV transmitter 1306 for retransmission to the GPS receiver 1302.

DTV transmitter 1306 provides a DTV signal comprising a plurality of frames (step 1404). Each frame includes a number of data segments. The DTV transmitter 1306 encodes the GPS assistance information into a codeword (step 1406) and replaces the data segments in the DTV signal with the codeword (step 1408). This is in accordance with the above description. The DTV transmitter 1306 then sends a DTV signal 1310 that includes GPS assistance information (step 1410).                 

The GPS receiver 1302 receives the DTV signal 1310 (step 1412) to recover the GPS assistance information in accordance with the techniques described above. The GPS receiver 1302 receives the signals transmitted by the GPS satellites 1320 (step 1416) and uses the GPS assistant information and the signals transmitted by the GPS satellites 1320 according to the existing technology. Compute the position of (step 1418).

In another embodiment, navigation is different from GPS, which generates a pseudo-random noise-like signal at the receiver and uses an array of earth-orbiting satellites with known positions such that the Doppler-corrected signal propagation time is measured for user location and velocity calculations. The above approach is used with the system.

15 illustrates a system 1500 that includes one GPS receiver 1502 and one GPS satellite 1520 according to one embodiment of the invention. Of course, a single GPS satellite 1520 alone is not suitable for positioning. In this embodiment, the GPS receiver 1502 also uses pseudoranges for one or more DTV transmitters 1506 for location determination.

16 illustrates a process 1600 executed by the system 1500 according to one embodiment. The DTV transmitter 1506 provides GPS assistance information (step 1602). In one embodiment, one or more monitor stations 1508 receive GPS signals transmitted by GPS satellites 1520. The monitor station 1508 determines the Doppler for the satellite by using the received GPS signal, and determines the ephemeris information using the existing technology. This GPS assistance information is sent to the DTV transmitter 1506 for retransmission to the GPS receiver 1502.

DTV transmitter 1506 provides a DTV signal comprising a plurality of frames (step 1604). The DTV transmitter 1506 encodes the GPS assistance information into a codeword (step 1606), replacing data segments in the DTV signal with a codeword according to the technique described above (step 1608). The DTV transmitter 1506 transmits the DTV signal 1510 including the GPS assistance information (step 1610).

The GPS receiver 1502 receives the DTV signal 1510 (step 1612) and recovers GPS assistance information in accordance with the techniques described above (step 1614). The GPS receiver 1502 receives the signals transmitted by the GPS satellites 1502 (step 1616). The GPS receiver 1502 determines the pseudo distance between the GPS receiver 1502 and the DTV transmitter 1506 based on known signal components of the DTV signal transmitted by the DTV transmitter 1506 (step 1618). The GPS receiver 1502 then calculates the position of the GPS receiver 1502 using the GPS assistance information, the signal transmitted by the GPS satellites 1520, and the pseudorange between the GPS receiver 1502 and the DTV transmitter 1506. (Step 1620).

The user terminal positioning technology using ATSC DTV signal

09 / 887,158, published on June 1, 2001, "Position Location Using Broadcast Digital Television Signals," by J.J. Spilker Jr. and Matthew Rabinowitz.

Published in The contents of which are incorporated herein by reference. User terminal positioning technology using ETSI DBV-T signal

US patent application Ser. No. 09 / 932,010, entitled "Position Location using Terrestrial Digital Broadcast Television Signals," by J.J. Spilker Jr. and Matthew Rabinowitz.                 

And the entire contents of which are incorporated herein by reference. User terminal positioning technology using Japanese ISDB-T signal

-US Patent Application No. 60 / 337,834, November 9, 2001, entitled "Wireless Position Location Using the Japanese ISDB-T Digital TV Signals" by J.J. Spilker Jr.

And the entire contents of which are incorporated herein by reference.

Each of these TV signals includes known signal components that can be used to obtain pseudoranges for the transmitter of the TV signal. Suitable components in an ATSC DTV signal include synchronization codes such as a synchronization segment in a data segment in an ATSC data frame and a field synchronization segment in an ATSC data frame. Suitable components in the ETSI DVB-T and ISDB-T DTV signals include scattering pilot carriers.

The GPS receiver 1502 calculates the position of the GPS receiver 1502 using the DTV pseudorange, the GPS assistance information, and the signal transmitted by the GPS satellite 1520. Positioning technology using DTV and GPS signals

US Patent Application No. 10 / 159,478, filed May 5, 2002, entitled "Position Location using Global Positioning Signals Augmented by Broadcast Television Signals" (J.J. Spilker Jr. and Matthew Rabinowitz)

And the entire contents of which are incorporated herein by reference. The location calculation of the GPS receiver 1502 may include a calculation using weather information provided by the weather server 1514 and information describing the phase center of each of the DTV transmitters 1506 provided by the database 1512. May be executed by the GPS receiver 1502 or a separate location server 1522. Data may be relayed between the GPS receiver 1502 and the location server 1504 using the wireless base station 1504 or some other method.

Of course, using only one DTV signal and one GPS signal is inappropriate for determining three-dimensional position. Additional signals, such as a second GPS signal or a second DTV signal, can be used as the third signal. Additional GPS or DTV signals can of course also be used.

In another embodiment, a navigation system other than GPS, which generates a pseudo random noise-like signal at the receiver and uses an array of earth-orbiting satellites with known positions such that the Doppler-corrected signal propagation time is measured for user location and velocity calculations. The above approach is used with the above.

Other signals in the digital television signal can be used to transmit GPS assistance information. For example, ATSC is currently considering a new standard based on a work paper called "SYNCHRONIZATION STANDARD FOR DISTRIBUTED TRANSMISSION." This proposed standard is for adding transmitters to reach a TV transmitter that can be blocked from the main transmitter. This proposed standard introduces a technique for building a single frequency network (SFN) using multiple transmitters.

This proposed standard allows SFN transmitters to transmit identification signals called "buried identification signals" or "watermarks". These identification signals enable independent identification of transmitters, enabling system monitoring and measurement.

The identification signal carries a Kasami code binary sequence that is transmitted repeatedly throughout the period when implemented with transmissions from the particular transmitter concerned. Each casami code is determined by a code sequence generator preloaded with values unique to each transmitter. The bits of the casami code are sent to the equivalent of the 2-VSB modulator for the transmission with the host 8-VSB host signal. Typically, this identification signal will be sent at an output level low enough to minimize interference with normal VSTV reception of the 8 VSB-host signal.

The start of the Casami code sequence of the transmitter identification signal will be emitted simultaneously with the first symbol of the first data segment following the data field synchronization segment of the host 8-VSB signal. The Kasami code sequence will occur three or more times in the data field, and the fourth sequence is truncated when data segment synchronization is reached at the start of the next data frame synchronization segment. This identification signal is not transmitted during the data field synchronization segment and starts again at the data segment immediately following the data field synchronization segment.

This identification signal can be used to transmit a low data rate signal by the phase inversion of the code sequence associated with the transmitter. This phase reversal will occur in data field units. Since the data field is repeated every 24.2 ms, this data rate is 41.3 bits per second. This low data rate channel can be used to provide GPS assistance information.

The invention can be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or a combination thereof. The apparatus of the invention may be embodied as a computer program product tangibly embodied in a machine-readable storage device for execution by a programmable processor, the method of the invention executing the functions of the invention by operating on input data and generating output. May be performed by a programmable processor executing a program of instructions. 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 transmit data and commands from one or more output devices. It may be preferably implemented in. Each computer program may be realized in a high-level procedural or object oriented programming language, or in assembly or machine language. In either case, the language is the language being compiled or interpreted. Suitable processors include, for example, general purpose microprocessors and dedicated microprocessors. In general, a processor will receive instructions and data from a ROM or RAM. In general, a computer will include one or more mass storage devices for storing data files. Examples of such devices include magnetic disks such as internal hard disks and external disks, magnetic-optical disks, and optical disks. Suitable storage devices for realizing computer program instructions and data in tangible form include magnetic disks such as EPROM, EEPROM, flash memory devices, magnetic disks such as internal hard disks and external hard disks, magneto-optical disks, and CD-ROM disks. There are all types of nonvolatile memory that contain. The foregoing may be supplemented or integrated by application-specific integrated circuits (ASICs) and other forms of hardware.

Claims (56)

Satellite positioning at the first satellite positioning system receiver to determine the position of the first satellite positioning system receiver using the propagation time of the signal transmitted by the satellite in the satellite positioning system and the satellite positioning system assistance information. A device for providing system assistance information, the device comprising: A second satellite positioning system receiver for receiving satellite positioning system assistance information from a satellite within said satellite positioning system, A channel coder for providing a digital television (DTV) signal comprising a plurality of frames, wherein each frame comprises a plurality of data segments, An encoder for encoding said satellite positioning system assistance information received in said second satellite positioning system receiver into codewords, A packet multiplexer for replacing data segments in a DTV signal provided from the channel coder with the codewords, and A transmitter for transmitting a DTV signal with said data segments replaced with codewords Wherein the first satellite positioning system receiver receives the DTV signal from the transmitter to recover satellite positioning system assistance information. 2. The satellite positioning system assistance information providing apparatus according to claim 1, wherein said satellite positioning system is a global positioning system (GPS). 3. The method of claim 2, wherein the first satellite positioning system receiver determines the position of the first satellite positioning system receiver based on signals received from satellites in the satellite positioning system and satellite positioning system assistance information. A satellite positioning system auxiliary information providing device. 3. The system of claim 2, wherein the satellite positioning system assistance information is The position of the satellite in the satellite positioning system, Clock calibration information of the satellites in the satellite positioning system; Doppler information about the signal transmitted by the satellite in the satellite positioning system, Information on the atmospheric effect on the signal transmitted by the satellite in the satellite positioning system, and Identification of the satellite positioning system satellites identifiable by the first satellite positioning system receiver; Satellite positioning system assistance information providing device comprising one or more of. delete delete delete delete delete An apparatus for positioning a satellite positioning system receiver using a satellite positioning system, the apparatus comprising: A front end receiving a signal transmitted by a satellite in a satellite positioning system and receiving DTV signals comprising a plurality of frames, each frame comprising a plurality of data segments, wherein at least one data segment is This front end, replaced by one or more codewords representing satellite positioning system assistance information, A back end that selects data segments replaced with codewords to recover satellite positioning system assistance information from the selected data segments, and -Satellite positioning system A processor for determining the position of the satellite positioning system receiver based on signals received from satellites and satellite positioning system assistance information. Satellite positioning system assistance information providing apparatus comprising a. 12. The apparatus of claim 10, wherein the satellite positioning system is a global positioning system (GPS). 12. The system of claim 11, wherein the satellite positioning system assistance information is Satellite positioning system, the position of the satellite, -Clock calibration information of satellite positioning system satellite Doppler information about the signal transmitted by the satellite positioning system satellite, Information about the atmospheric effect on the signal transmitted by the satellite positioning system satellite, and -The identity of the satellite positioning system satellite, which can be identified by the satellite positioning system receiver; Satellite positioning system assistance information providing device comprising one or more of. delete The method of claim 11, wherein the processor, Determining the pseudo distance between the transmitter of the DTV signal and the receiver of the satellite positioning system based on the signal component of the DTV signal; and Determining the position of the satellite positioning system receiver based on the pseudorange, the signal received from the satellite positioning system satellite, and the satellite positioning system assistance information. Satellite positioning system auxiliary information providing device, characterized in that. Satellite positioning at the first satellite positioning system receiver to determine the position of the first satellite positioning system receiver using the propagation time of the signal transmitted by the satellite in the satellite positioning system and the satellite positioning system assistance information. A device for providing system assistance information, the device comprising: Second satellite positioning system receiver means for receiving satellite positioning system assistance information from a satellite within said satellite positioning system, Channel coder means for providing a digital television (DTV) signal comprising a plurality of frames, wherein each frame comprises a plurality of data segments, Encoder means for encoding satellite positioning system assistance information received at said second satellite into codewords, Packet multiplexer means for replacing data segments in a DTV signal provided from said channel coder with said codewords, and Transmitter means for transmitting a DTV signal with said data segments replaced with codewords Wherein the first satellite positioning system receiver receives a DTV signal from the transmitter to recover satellite positioning system assistance information. 18. The apparatus of claim 15, wherein the satellite positioning system is a global positioning system (GPS). 17. The method of claim 16, wherein the first satellite positioning system receiver determines the position of the first satellite positioning system receiver based on signals received from satellites in the satellite positioning system and satellite positioning system assistance information. A satellite positioning system auxiliary information providing device. 17. The system of claim 16, wherein the satellite positioning system assistance information is The position of the satellite in the satellite positioning system, Clock calibration information of the satellites in the satellite positioning system; Doppler information about the signal transmitted by the satellite in the satellite positioning system, Information on the atmospheric effect on the signal transmitted by the satellite in the satellite positioning system, and Identification of the satellite positioning system satellites identifiable by the first satellite positioning system receiver; Satellite positioning system assistance information providing device comprising one or more of. delete delete delete delete delete An apparatus for positioning a satellite positioning system receiver using a satellite positioning system, the apparatus comprising: Means for front-end receiving a signal transmitted by a satellite in a satellite positioning system and receiving DTV signals comprising a plurality of frames, each frame comprising a plurality of data segments, one or more data segments This front end means is replaced by one or more codewords representing satellite positioning system assistance information, Back end means for selecting data segments replaced with codewords to recover satellite positioning system assistance information from the selected data segments, and Processor means for determining the position of a satellite positioning system receiver based on signals received from satellites and satellite positioning system assistance information; Satellite positioning system assistance information providing apparatus comprising a. 25. The apparatus of claim 24, wherein the satellite positioning system is a global positioning system (GPS). 27. The system of claim 25, wherein the satellite positioning system assistance information is Satellite positioning system, the position of the satellite, -Clock calibration information of satellite positioning system satellite Doppler information about the signal transmitted by the satellite positioning system satellite, Information about the atmospheric effect on the signal transmitted by the satellite positioning system satellite, and -The identity of the satellite positioning system satellite, which can be identified by the satellite positioning system receiver; Satellite positioning system assistance information providing device comprising one or more of. delete The method of claim 25, wherein the processor means, Determining the pseudo distance between the transmitter of the DTV signal and the receiver of the satellite positioning system based on the signal component of the DTV signal; and Determining the position of the satellite positioning system receiver based on the pseudorange, the signal received from the satellite positioning system satellite, and the satellite positioning system assistance information. Satellite positioning system auxiliary information providing device, characterized in that. Satellite positioning system assistance information to the first satellite positioning system receiver to determine the position of the satellite positioning system receiver using the propagation time of the signal transmitted by the satellite in the satellite positioning system and the satellite positioning system assistance information. As a method of providing the method, Receiving satellite positioning system assistance information from the satellite positioning system at a second positioning system receiver; Receiving a digital television (DTV) signal comprising a plurality of frames at a channel coder, each of the plurality of frames comprising a plurality of data segments, Encoding, at the encoder, satellite positioning system assistance information into codewords, In a packet multiplexer, replacing data segments in a DTV signal provided from said channel coder with codewords, and Transmitting at the transmitter a DTV signal with said data segments replaced with codewords; Wherein the first satellite positioning system receiver receives the DTV signal transmitted from the transmitter to recover satellite positioning system assistance information. 30. The method of claim 29, wherein said satellite positioning system is a global positioning system (GPS). 31. The method of claim 30, wherein the first satellite positioning system receiver determines the position of the first satellite positioning system receiver based on signals received from the satellite positioning system satellites and satellite positioning system assistance information. Satellite positioning system assistance information providing method. 31. The system of claim 30, wherein the satellite positioning system assistance information is Satellite positioning system, the position of the satellite, -Clock calibration information of satellite positioning system satellite Doppler information about the signal transmitted by the satellite positioning system satellite, Information about the atmospheric effect on the signal transmitted by the satellite positioning system satellite, and -The identity of the satellite positioning system satellite, which can be identified by the satellite positioning system receiver; A satellite positioning system assistance information providing method comprising at least one of. delete delete delete delete delete A method for determining the position of a satellite positioning system receiver using a satellite positioning system, the method comprising: Receiving at a satellite positioning system receiver a signal transmitted by a satellite in the satellite positioning system, Receiving at the satellite positioning system receiver a digital television (DTV) signal comprising a plurality of frames, wherein each frame comprises a plurality of data segments, wherein at least one data segment is assisted by the satellite positioning system Replaced by one or more codewords representing information, Selecting data segments replaced with codewords, Recovering satellite positioning system assistance information from the selected data segments, and Determining the position of the satellite positioning system receiver based on the signals received from the satellite positioning system and the satellite positioning system assistance information. Positioning method of the satellite positioning system receiver comprising a. 39. The method of claim 38, wherein the satellite positioning system is a global positioning system (GPS). 40. The system of claim 39, wherein said satellite positioning system assistance information is Satellite positioning system, the position of the satellite, -Clock calibration information of satellite positioning system satellite Doppler information about the signal transmitted by the satellite positioning system satellite, Information about the atmospheric effect on the signal transmitted by the satellite positioning system satellite, and -The identity of the satellite positioning system satellite, which can be identified by the satellite positioning system receiver; A positioning method of a satellite positioning system receiver, characterized in that it comprises one or more of. delete The method of claim 39, Determining a pseudo distance between the transmitter of the DTV signal and the receiver of the satellite positioning system based on the signal component of the DTV signal, and Determining the position of the satellite positioning system receiver based on the pseudorange, the signal received from the satellite positioning system satellite, and the satellite positioning system assistance information; Positioning method of the satellite positioning system receiver, characterized in that it further comprises. Satellite positioning system assistance information to the satellite positioning system receiver to determine the position of the first satellite positioning system receiver using the propagation time of the signal transmitted by the satellite in the satellite positioning system and the satellite positioning system assistance information. A computer-readable medium having recorded thereon a program for executing the method, the method comprising: Encoding said received satellite positioning system assistance information into codewords, wherein said satellite positioning system assistance information is received from said satellite positioning system at a second satellite positioning system receiver; Replacing data segments in a DTV signal with codewords, the DTV signal being received at a television receiver, and Transmitting a DTV signal replacing the data segments with a codeword Including but not limited to: And the first satellite positioning system receiver receives the transmitted DTV signal. 44. The computer-readable medium of claim 43, wherein the satellite positioning system is a global positioning system (GPS). 45. The method of claim 44, wherein the first satellite positioning system receiver determines the position of the first satellite positioning system receiver based on signals received from the satellite positioning system satellites and satellite positioning system assistance information. Computer-readable media. 45. The system of claim 44, wherein the satellite positioning system assistance information is Satellite positioning system, the position of the satellite, -Clock calibration information of satellite positioning system satellite Doppler information about the signal transmitted by the satellite positioning system satellite, Information about the atmospheric effect on the signal transmitted by the satellite positioning system satellite, and -The identity of the satellite positioning system satellite, which can be identified by the satellite positioning system receiver; And at least one of: a computer-readable medium. delete delete delete delete delete A computer-readable medium having recorded thereon a program executing a method for determining a position of a satellite positioning system receiver using a satellite positioning system, the method comprising: Receiving at a satellite positioning system receiver a signal transmitted by a satellite in the satellite positioning system, Receiving at a satellite positioning system receiver for receiving DTV signals comprising a plurality of frames, each frame comprising a plurality of data segments, wherein at least one data segment contains satellite positioning system assistance information; Replaced by one or more codewords to express, Selecting data segments replaced with codewords, Recovering satellite positioning system assistance information from the selected data segments, and Determining the position of the satellite positioning system receiver based on the signals received from the satellite positioning system and the satellite positioning system assistance information. Computer-readable medium comprising a. 53. The computer-readable medium of claim 52, wherein the satellite positioning system is a global positioning system (GPS). 54. The system of claim 53 wherein the satellite positioning system assistance information is Satellite positioning system, the position of the satellite, -Clock calibration information of satellite positioning system satellite Doppler information about the signal transmitted by the satellite positioning system satellite, Information about the atmospheric effect on the signal transmitted by the satellite positioning system satellite, and -The identity of the satellite positioning system satellite, which can be identified by the satellite positioning system receiver; And at least one of: a computer-readable medium. delete The method of claim 53, wherein the method is Determining a pseudo distance between the transmitter of the DTV signal and the receiver of the satellite positioning system based on the signal component of the DTV signal, and Determining the position of the satellite positioning system receiver based on the pseudorange, the signal received from the satellite positioning system satellite, and the satellite positioning system assistance information; And a computer-readable medium further comprising.

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