Spread spectrum position determination, ranging and communication system

• US 5,912,644 A
• Filed: 08/05/1997
• Issued: 06/15/1999
• Est. Priority Date: 08/05/1997
• Status: Expired due to Fees

• Current Assignee: Fastrack Information Inc.
• Original Assignee: James J.M. Wang
• Inventors: Wang, James J. M.
• Primary Examiner(s): Hellner, Mark
• Application Number:
  US08/906,092
• Time in Patent Office: 679 Days
• Field of Search: 342/457, 342/463, 370/347, 370/478, 375/200, 375/203
• US Class Current: 342/457
• CPC Class Codes: A63B 2102/32 Golf
• CPC Class Codes: A63B 2220/13 Relative positions
• CPC Class Codes: A63B 2220/14 Geo-tagging, e.g. for correlating route or track location data with specific information related to that specific location
• CPC Class Codes: A63B 2244/19 Skiing
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location

Abstract

The spread spectrum wireless position determinator, ranging, and communication system is disclosed in this invention. The system consists of handheld or otherwise mobile apparatus which can be hand-carried or installed in the carts or vehicles, fixed-position reference stations deployed throughout the vicinity of the operating region of interests, and a central reference station. The mobile apparatus includes a spread spectrum transceiver, an input unit, and an output unit, which supports four functions: 1). accurately determines its position within the operating region and distance to pre-defined features within the region, 2). provides a voice communications with another mobile apparatus or central reference station within the region, 3). transmits or receives data message which can be routed via the reference stations to the central station, or other mobile apparatus within the region, 4). displays various information or stores information entered by the operator. The central reference station also has a spread spectrum radio transceiver which can transmit and receive voice or data massage to and from any mobile apparatuses or reference stations within the region and a computer which collects and processes the radio data, maintains the databases for the operation of the system, or provides a man-machine interface for the system. The reference stations are deployed in strategic locations through the region such that the mobile apparatuses in any accessible location can communicate with one or more reference stations. All reference stations contain a spread spectrum transceiver, which supports the radiolocationing function initiated by the mobile apparatuses and relays any received data packets to other reference stations, central station, or mobile apparatuses.

Claims

1. A system for determining the position and distance between a first point in a geographical region and at least one feature in the geographical region comprising:

a plurality of fixed reference stations located within or in proximity to the geographical region, each of said reference stations provided with a transceiver for receiving and transmitting time division duplex (TDD) spread spectrum RF signals modulated by a pseudo-noise (PN) coded sequence, each of said fixed reference stations also including a memory device and processor in communication with its respective transceiver;

at least two portable apparatuses each provided with an input device and a transceiver capable of transmitting signals, and receiving time division duplex (TDD) spread spectrum RF signals modulated by pseudo-noise (PN) coded sequence, said mobile apparatus also provided with a memory device and processor in communication with said mobile transceiver, said processor in said mobile apparatus determining the distance measurement between said mobile apparatus and at least three of said fixed reference stations and the position coordinates of said mobile processor based upon the time differences of said TDD spectrum signals transmitted and received between said mobile apparatus and said at least three of said fixed stations, said TDD spread spectrum signals transmitted by said fixed reference station also including the positive coordinates of the fixed reference station as well as the position coordinates of a selected feature in the geographical region, the selected feature chosen by said input device, the distance between said mobile apparatus and said selected feature calculated by said processor in said mobile apparatus based upon said position coordinates of said selected feature and the calculated position coordinate of said mobile apparatus, at least two of said mobile apparatus each further provided with a microphone, a speaker and a means for converting audio information into a digital format and converting digital information into audio information, thereby allowing voice information to be received and transmitted by said mobile apparatuses; and

output device in communication with said mobile apparatus for outputting the distance between said mobile apparatus and the selected feature.

2. The system in accordance with claim 1, further including a fixed central station located within or in proximity with the geographical region, said central station provided with a transceiver for receiving and transmitting a time division duplex (TDD) spread spectrum signal modulated by a pseudo-noise (PN) coded sequence for communication with each of said fixed reference stations, said central station provided with a processor and memory device, said central station transmitting locational information relating to a plurality of features included in the geographical region.

3. The system in accordance with claim 2, wherein said central station further includes data link and a computer, wherein said data link is communicating information between said central station and said computer, allowing updating of said locational information of said features and said reference station and to collecting and processing information received by said central station.

4. The system in accordance with claim 1, wherein each of said fixed reference station is assigned a specific identification number (ID) stored in said memory device associated with each fixed reference station and wherein each of said fixed reference stations would respond to said TDD spread spectrum signals transmitted to one of said fixed reference stations if said TDD spread spectrum signals contains said ID of that fixed reference station, and further wherein each of said mobile apparatus has been assigned an ID stored in said memory of said mobile apparatus.

5. The system in accordance with claim 3, wherein said memory of said mobile apparatus is provided with the IDs of three of said fixed reference stations for each feature in the geographical region.

6. The system in accordance with claim 5 wherein each of the IDs of three of said fixed reference stations for each feature is transmitted to said mobile apparatus via a spread spectrum signal transmitted by said central station or said fixed reference station, during initialization of said mobile apparatus memory.

7. The system in accordance with claim 2, wherein said TDD spread spectrum signals transmitted by said mobile apparatus, said fixed reference station and said central station include a unique word therein to provide synchronization of the TDD frame timing between said mobile apparatus, said fixed reference stations and said central station.

8. The system in accordance with claim 4, wherein said TDD spread spectrum signals transmitted by said mobile apparatus, said fixed reference station and said central station include a unique word therein to provide synchronization of the TDD frame timing between said mobile apparatus, said fixed reference stations and said central station.

9. The system in accordance with claim 7, wherein said mobile apparatus initially transmits a first TDD spread spectrum signal to one or more of said fixed reference station in an S-packet format at a carrier frequency, and further wherein said fixed reference stations transmits a second TDD spread spectrum signal in an S-packet format at said carrier frequency to said mobile apparatus responsive to said first TDD spread spectrum signal in a S-packet format transmitted from said mobile apparatus.

10. The system in accordance with claim 8, wherein said mobile apparatus initially transmits a first TDD spread spectrum signal to one or more of said fixed reference station in an S-packet format at a carrier frequency, and further wherein said fixed reference stations transmits a second TDD spread spectrum signal in an S-packet format at said carrier frequency to said mobile apparatus responsive to said first TDD spread spectrum signal in a S-packet format transmitted from said mobile apparatus.

11. The system in accordance with claim 9, wherein said mobile apparatus transmits a third TDD spread spectrum signal to one of said fixed reference stations in an R-packet format at a second carrier frequency and a second PN code responsive to the receipt of said second TDD spread spectrum signal in an S-packet format and further wherein said fixed reference station transmits a fourth TDD spread spectrum signal in an R-packet format at said second carrier frequency and said second PN code responsive to the receipt of said third TDD spread spectrum signal.

12. The system in accordance with claim 10, wherein said mobile apparatus transmits a third TDD spread spectrum signal to one of said fixed reference stations in an R-packet format at a second carrier frequency and a second PN code responsive to the receipt of said second TDD spread spectrum signal in an S-packet format and further wherein said fixed reference station transmits a fourth TDD spread spectrum signal in an R-packet format at said second carrier frequency and said second PN code responsive to the receipt of said third TDD spread spectrum signal.

13. The system in accordance with claim 1, wherein said memory device and said processor of said mobile apparatus is provided with a means for estimating the inaccuracy of the position calculation of said mobile apparatus due to geometry of said selected fixed reference stations and further wherein said mobile apparatus compare said estimated inaccuracy in said position calculation to a predetermined value, and further including a means for transmitting additional TDD spread spectrum PN coded signals to initiate at least one additional fixed reference station if said estimated inaccuracy of said position calculated exceeds a predetermined value.

14. The system in accordance with claim 11, wherein said digital information is transmitted by said mobile apparatus using a TDD spread spectrum signal employing an I-packet format, thereby allowing ones said mobile apparatuses to initiate voice communications with a second mobile apparatus on said central status.

15. The system in accordance with claim 9, wherein said digital information is transmitted by said mobile apparatus using a TDD spread spectrum signal employing an I-packet format, thereby allowing ones said mobile apparatuses to initiate voice communications with a second mobile apparatus on said central status.

16. The system in accordance with claim 1, wherein said mobile apparatus obtains the course features information, said fixed reference station coordinates, and other information related to a particular geographical area by receiving data via said spread spectrum transceiver in said mobile apparatus, thereby allowing said mobile apparatus to use said received information to reload its said processor memory to thus automatically re-configure said memory for different geographical areas.

26. The system in accordance with claim 1 wherein each of said mobile apparatuses receive and transmit only time division duplex (TDD) signals.

17. A method for determining the position and distance between a first point in a geographical region and at least one selected feature in the geographical region, comprising the steps of:

installing a plurality of fixed reference stations located within or in proximity to the geographical region;

determining the coordinates of each of said fixed reference stations and each of the selected features with respect to a reference point, each of said fixed reference station provided with their individual coordinates and the coordinates of the selected feature;

providing a time division duplex (TDD) spread spectrum pseudo-noise (PN) coded sequence for each of said fixed reference stations;

equipping at least two mobile apparatuses with the PN coded sequences of each of said fixed reference stations, at least two of said mobile apparatuses each provided with a microphone, a speaker and a means for converting audio information into a digital format and converting digital information into audio information, thereby allowing voice information to be received and transmitted by said mobile apparatuses;

initiating a distance request from said mobile apparatus to at least two of said fixed reference stations for determining the distance between said mobile apparatus and one of the selected features by transmitting a first TDD spread spectrum PN coded sequence as unique to at least two of said reference stations;

receiving said TDD spread spectrum PN coded sequence at one of said fixed reference stations;

transmitting a second TDD spread spectrum PN coded signal to said mobile apparatus including the coordinates of said fixed reference station and the coordinates of the selected feature;

determining the position of the mobile apparatus utilizing an algorithm provided in said mobile apparatus based upon the time differentials of the epochs of each of the fixed reference stations and said mobile apparatus;

computing the distance between said mobile apparatus and the selected feature; and

providing an output indicating the distance between said mobile apparatus and the selected feature.

18. The method in accordance with claim 17, wherein said first TDD spread spectrum PN coded sequence transmitted by said mobile apparatus is in an S-packet format and said second TDD spread spectrum PN coded signal transmitted from said fixed reference station is in an S-packet format.

19. The method in accordance with claim 18, wherein said mobile apparatus transmits a third TDD spread spectrum signal to said fixed reference station in an R-packet format responsive to the receipt of said second TDD spread spectrum signal in an S-packet format and further wherein said fixed reference station transmits a fourth TDD spread spectrum signal in an R-packet format responsive to the receipt of said third TDD spread spectrum signal.

20. The method in accordance with claim 17 further comprising the steps of

providing said mobile apparatus with a means for estimating the distance between said mobile apparatus and each of said fixed reference stations based upon the time differential of the epochs between the transmitted PN code and the received PN code at said mobile apparatus and each of said fixed reference stations;

computing the time differential of said epoch between the transmit PN and received PN code at said fixed reference stations transmitted to said mobile apparatus;

adding said time differential measured in said mobile apparatus and said time differential measured in said fixed reference station transmitted to said mobile apparatus; and

subtracting the contributions of hardware delays and the clock frequency difference error to obtain the distance estimate between said mobile apparatus and said fixed reference station.

21. The method in accordance with claim 19 further comprising the steps of:

providing said mobile apparatus with a means for estimating the distance between said mobile apparatus and each of said fixed reference stations based on time differential of the epochs between the transmitted PN code and the received PN code at the said mobile apparatus and each of said fixed reference stations;

computing the time differential of said epoch between the transmit PN and received PN code at said fixed reference stations transmitted to said mobile apparatus;

adding said time differential measured in said mobile apparatus and said time differential measured in said fixed reference station transmitted to said mobile apparatus; and

subtracting the contributions of hardware delays and the clock frequency difference error to obtain the distance estimate between said mobile apparatus and said fixed reference station.

22. The method in accordance with claim 20, further providing a means for estimating said hardware delay said mobile apparatus and said fixed reference station by the further steps of:

calibrating said hardware delay in said mobile apparatus and said fixed reference station as a function of temperature prior to deploying said fixed reference stations and said mobile apparatus;

storing in said processor memory of said mobile apparatus and said fixed reference station the table of measured delay as a function of temperature;

using a temperature sensor to determine the temperature of said mobile apparatus and said fixed reference station; and

actuating said measured delay value from processor memory as a function of temperature.

23. The method in accordance with claim 20, further providing a means for estimating a clock difference error of said mobile apparatus and said fixed reference station by the further steps of:

obtaining the carrier frequency difference between said mobile apparatus and said fixed reference station from receiver NCO frequency value in said mobile apparatus and said fixed reference station;

deriving the PN code frequency difference between said mobile apparatus and said fixed reference station from said carrier frequency difference; and

multiplying the said PN code frequency difference and the elapsed time between the pseudorange measurement in said fixed reference station and said mobile apparatus.

24. The method in accordance with claim 17, wherein said TDD spread spectrum signals transmitted by said mobile apparatus and said fixed reference stations include a unique word therein to provide time synchronization between said mobile apparatus and said fixed reference stations.

25. A method in accordance with claim 17 for sending a data message from one location within a geographical area to another location within the geographical area utilizing said mobile apparatus, comprising the steps of:

looking up in a table stored in said processor memory of said mobile apparatus, a fixed reference station based upon the location of said mobile apparatus;

sending a data message to said fixed reference station incorporating the initiating and destination station ID;

determining the next fixed reference station or central station to relay the data message by looking up in a routing table stored in the processor memory of said fixed reference station; and

re-transmitting the data message to the next fixed reference station or central station until the data message reaches the destination station.

27. The method in accordance with claim 17 wherein only time division duplex (TDD) are received and transmitted by said mobile apparatuses.