Network of equivalent ground transmitters

Details Network of equivalent ground transmitters Network of equivalent ground transmitters

1997-07-07

2001-08-07

Blum, Theodore M. (Department: 3662)

Communications: directive radio wave systems and devices (e.g.,

Directive

Including a satellite

C342S357490, C342S457000, C342S464000, C342S357490, C701S215000

Reexamination Certificate

active

06271788

ABSTRACT:

BACKGROUND
The Global Positioning System (GPS) is a widely used satellite-based navigation system consisting of a network of satellites broadcasting pseudo-random noise (PRN) codes modulated on an L-band carrier (L1, L2). A GPS receiver uses measurements of the pseudo-random (PRN) code-phase and carrier-phase from four or more satellites to solve for the three-dimensional position of the receiver and to calibrate its internal time reference. The GPS receiver determines velocity from measurements of the carrier phase and doppler. Accuracy of the GPS solution is limited by the errors on the GPS signals and the geometry established by the positions of the satellites relative to the user.
For instance, there are areas of limited visibility of the sky where the user can observe and receive the satellite signals from only a limited number of the Satellite Positioning System (SATPS) satellites. Thus, in such an area it is impossible for the user to precisely solve for the three-dimensional position of its receiver, to calibrate its internal time reference, or to determine its velocity.
What is needed is a system of networked ground transmitters (GT) located in the well-known positions that together with the visible SATPS satellites and together with the base station positioned in the precisely known location allows the user to precisely determine its position location, its timing, and its velocity.
SUMMARY
The present invention is unique because it discloses a system of networked equivalent ground transmitters (GT) located in the well-known positions that together with the visible SATPS satellites and together with the base station allows one to precisely determine the position location, timing, and velocity of an autonomous vehicle.
The first aspect of the present invention is directed to a system (A) for accurate determination of the terrestrial position, timing coordinate, and velocity of an autonomous vehicle in real-time by transmitting signals from well-known locations.
The system (A) comprises: (1) a K-number of SATPS
j
satellites, K being an integer, j being an integer less than or equal to K, for generating satellite signals L(SATPS
j
); (2) an N-number of ground transmitters (GT
i
), N being an integer, i being an integer less or equal to N, for generating L(GT
i
) signals for providing ranging, timing, and velocity information at the user's location; (3) a base station (BS) for receiving the L(SATPS
j
) signals from each SATPS
j
satellite, for receiving the L(GT
i
) signals from each GT
i
, for calculating the differential correction data signal L(BS), and for transmitting the differential correction data signal L(BS) to the user's location; (4) a 2N-number of ground transmitter communication links CLGT
i
between each GT
i
and the user, and between each GT
i
and the base station (BS); and (5) a communication link CLB between the base station and the user. The user receives the L(SATPS
j
) signals from each satellite SATPS
j
, the L(GT
i
) signals from each GT
i
, and the differential correction data signal L(BS) from the base station. It is assumed, that the location coordinates of each GT
i
and the base station are precisely known. It is also assumed that each satellite SATPS
j
includes a satellite clock with a known clock bias CB
SATPSj
and a known clock drift CD
SATPSj
, each GT
i
includes a GT
i
clock with an unknown clock bias CB
GTi
and an unknown clock drift CD
GTi
, and the base station includes a base station clock with an unknown clock bias CB
BS
and an unknown clock drift CD
BS
.
In one preferred embodiment of system (A), the K-number of SATPS
j
satellites comprises at least one satellite, and the N-number of ground transmitters (GT
i
) comprises at least three GT
i
. In another preferred embodiment, the K-number of SATPS
j
satellites comprises at least two satellites, and the N-number of ground transmitters (GT
i
) comprises at least two GT
i
. Yet, in one more preferred embodiment, the K-number of SATPS
j
satellites comprises at least three satellites, and the N-number of ground transmitters (GT
i
) comprises at least one GT
i
. In each of these embodiments, the user utilizes the satellite signals L(SATPS
j
) generated by each SATPS
j
, the L(GT
i
) signals generated by each GT
i
, and the differential correction data signal L(BS) generated by the base station (BS) in order to determine in real-time the user's position fixes, the user's timing coordinate, and the user's velocity.
Another aspect of the present invention is directed to a system (B) comprising: (1) an N-number of ground transmitters (GT
i
), wherein each GT
i
generates its own L(GT
i
) signal for providing ranging, timing, and velocity information at the user's location; (2) a base station (BS) for receiving the L(GT
i
) signals from each GT
i
, for calculating the differential correction data signal L(BS), and for transmitting the differential correction data signal L(BS) to the user's location; (3) a 2N-number of ground transmitter communication links CLGT
i
between each GT
i
and the user, and between each GT
i
and the base station (BS); and (4) a communication link CLB between the base station and the user. The user receives the L(GT
i
) signals from each GT
i
, and the differential correction data signal L(BS) from the base station. The location coordinates of each GT
i
and the base station are precisely known. Each GT
i
includes a GT
i
clock with an unknown clock bias CB
GTi
and an unknown clock drift CD
GTi
; and the base station includes a base station clock with an unknown clock bias CB
BS
and an unknown clock drift CD
BS
.
In one preferred embodiment of system (B), the N-number of ground transmitters (GT
i
) comprises at least four GT
i
, and the user utilizes the L(GT
i
) signals generated by each GT
i
and the differential correction data signal L(BS) generated by the base station (BS) in order to determine in real-time the user's position fixes, the user's timing coordinate, and the user's velocity.
In another preferred embodiment of system (B), the N-number of ground transmitters (GT
i
) comprises at least one GT
i
, and the user utilizes the L(GT
i
) signals generated by each GT
i
and the differential correction data signal L(BS) generated by the base station (BS) in order to determine in real-time the user's timing coordinate.
The communication link CLB in both systems (A) and (B) can include a variety of embodiments. It can include a radiowave frequency band, an infrared frequency band, a microwave frequency band, or the ISM (industrial scientific medical) unlicensed operation band. The ISM band range can be selected from a class of frequency range consisting of 900 MHz, 2.4 GHz, and 5.8 GHz; wherein the user can own both ends of the ISM communication system. The communication link CLB can also include: a real time circuit switched communication link, a 1.8 GHz frequency band, wherein the 1.8 GHz band supports the personal communications services (PCS); a system of Low Earth Orbiting Satellites (LEOS), wherein the LEOS is used to store and to forward digital packet data. The communication link CLB can be selected from a class of radiowave communication links consisting of a cellular telephone communication means, paging signal receiving means, wireless messaging services, wireless application services, a wireless WAN/LAN station, and an Earth-satellite-Earth communication module that uses at least one satellite to relay a radiowave signal. The communication link CLB can also include an Advanced Mobile Phone System (AMPS) including a modem, wherein the modem is selected from a class consisting of a DSP (digital signal processor) modem, and a cellular digital packet data (CDPD) modem. It can include a digital cellular telephone communication means, wherein the digital cellular telephone communication means includes a means of modulation of digital data over a radiolink selected from a class consisting of a time division multiple access (TDMA) system, and a code division multiple access (CDMA) system.
Th

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