Method and system for determining absolute positions of mobile communications devices using remotely generated positioning information

• US 6,922,635 B2
• Filed: 08/11/2003
• Issued: 07/26/2005
• Est. Priority Date: 08/13/2002
• Status: Active Grant

• Current Assignee: DRS Signal Solutions, Inc. (Leonardo S.p.A.)
• Original Assignee: DRS Communications Co. LLC (Leonardo S.p.A.)
• Inventors: Rorabaugh, C. Britton
• Primary Examiner(s): Black, Thomas G.
• Assistant Examiner(s): Mancho, Ronnie
• Application Number:
  US10/639,022
• Publication Number:
  US 20040034471A1
• Time in Patent Office: 715 Days
• Field of Search: 701/207, 701/213, 701/225, 701/220, 701/216, 342/357.14, 342/357.03, 342/357.02, 342/357.16
• US Class Current: 701/213
• CPC Class Codes: G01S 19/51 Relative positioning
• CPC Class Codes: G01S 5/0072 Transmission between mobile stations, e.g. anti-collision systems
• CPC Class Codes: G01S 5/0284 Relative positioning

Abstract

Absolute positions of global position system (“GPS”) enabled mobile communications devices, which form a wirelessly networked group of GPS mobiles, can be determined at each of the mobiles based on use of wireless communications capabilities of the mobiles for obtaining relative positioning information or range measurements for the mobiles of the group. Although each of the mobiles of a group cannot establish line of sight (“LOS”) communications signal reception paths with more than three GPS satellites to permit each mobile to determine its absolute position solely based on GPS signal transmissions, the mobiles can compute their respective absolute positions and the absolute positions of other mobiles if a predetermined number of LOS paths can be established and range or relative positioning information can be obtained.

Claims

1. A method for determining absolute positions of respective first and second mobile communications devices, wherein each of the first and second mobiles can receive usable positioning information signals transmitted from at most three visible remotely located positioning information signal sources such that each of the first and second mobiles cannot determine its absolute position solely based on the usable received positioning information signals, the method comprising:

obtaining first-to-second mobile position information based on wireless communications between the first and second mobiles;

establishing at least a predetermined number of line of sight (“

LOS”

) communications signal reception paths between each of the first mobile and the second mobile and and the remotely located positioning information signal sources visible to the first mobile or the second mobile; and

computing the absolute positions of the respective first and second mobiles based on the first-to-second mobile position information and positioning information signals transmitted over the predetermined number of LOS paths by the sources visible to the first mobile or second mobile and received at the first mobile or the second mobile.

2. The method of claim 1, wherein the first-to-second mobile information includes the position of the first mobile relative to the second mobile, wherein the first and second mobiles in combination (i) can receive positioning information signals transmitted from as few as three visible remote positioning information signal sources, and (ii) can establish at least five LOS paths to the as few as three visible remote sources.

3. The method of claim 1, wherein the first-to-second mobile information includes range and relative clock bias between the first mobile and the second mobile, and wherein the first and second mobiles in combination can establish at least six LOS paths to remote positioning information signal sources visible to the first mobile or the second mobile.

4. A method of determining absolute positions of respective first and second global positioning system (“

GPS”

) mobile communications devices, wherein each of the first and second mobiles can receive usable GPS positioning information signals transmitted from at most three visible GPS satellites such that each of the first and second mobiles cannot determine its absolute position solely based on the usable received GPS positioning information signals, the method comprising;

(a) providing that the first and second mobiles in combination can receive GPS information positioning signals from as few as three visible GPS satellites and that at least five line of sight (“

LOS”

) communications signal reception paths can be established between the as few as three GPS satellites and the first and second mobiles;

(b) at the first mobile, obtaining first-to-second mobile relative position information based on wireless communications between the first and second mobiles;

(c) at the first mobile, assuming a position for the first mobile and computing an assumed position for the second mobile based on the relative position information;

(d) computing GPS range estimates at each of the first and second mobiles based on the GPS positioning information signals transmitted on the five LOS paths;

(e) wirelessly communicating the GPS range estimates computed at the second mobile to the first mobile; and

(f) computing absolute positions of the respective first and second GPS mobiles using a system of pseudorange equations including at least five pseudorange equations, wherein the five equations respectively correspond to the five LOS paths and include the assumed positions of the respective first and second mobiles.

5. The method of claim 4 further comprising:

(g) computing a root mean square error (“

RMS”

) associated with the estimated absolute position of the first GPS mobile;

(h) updating the assumed values for the first mobile if the RMS error exceeds a predetermined threshold; and

(i) repeating steps (d), (e) and (f).

6. The method of claim 4 further comprising;

(g) computing a root mean square error associated with the estimated absolute position of the first GPS mobile; and

(h) communicating the absolute positions of the first and second mobiles from the first mobile to the second mobile if the RMS error does not exceed a predetermined threshold.

7. A method of determining absolute positions of respective first and second global positioning system (“

GPS”

) mobile communications devices, wherein each of the first and second mobiles can receive usable GPS positioning information signals transmitted from at most three visible GPS satellites such that each of the first and second mobiles cannot determine its absolute position solely based on the usable received GPS positioning information signals, the method comprising;

(a) providing that the first and second mobiles together can establish at least six line of sight (“

LOS”

) communications signal reception paths with visible GPS satellites;

(b) assuming nominal positions for the respective first and second mobiles and a GPS clock offset for the first mobile;

(c) at the first mobile, measuring signal propagation time between the first mobile and the second mobile based on transmission or wireless communications signers from the first mobile to the second mobile;

(d) at the second mobile, measuring signal propagation time between the first mobile and the second mobile based on transmission of communications signals from the second mobile to the first mobile and wirelessly transmitting the measured propagation time at the second mobile to the first mobile;

(e) at the first mobile, determining range between the first and second mobiles based on the signal propagation times measured at the first and second mobiles;

(f) computing GPS range estimates at each of the first and second mobiles based on the GPS positioning information signals transmitted on the six LOS paths;

(g) wirelessly communicating the GPS range estimates computed at the second mobile to the first mobile; and

(h) computing absolute positions of the first and second GPS mobiles using a system of pseudorange equations including at least six pseudorange equations, wherein the six equations respectively correspond to the six LOS paths and include the assumed positions of the respective first and second mobiles.

8. The method of claim 7 further comprising:

(i) computing a root mean square (“

RMS”

) error associated with the estimated absolute position of the first GPS mobile;

(j) updating the assumed values for the first mobile if the RMS error exceeds predetermined threshold; and

(k) repeating step (h).

9. The method of claim 7 further comprising:

(i) computing a root mean square (“

RM”

) error associated with the estimate absolute position of the first GPS mobile; and

(i) communicating the absolute positions of the first and second mobiles from the first mobile to the second mobile if the RMS error does not exceed a predetermined threshold.

10. The method of claim 7, wherein step (h) further comprises, at the first mobile:

computing pseudoranges (1) between each OPS satellite visible to the first mobile and the assumed position of the first mobile and (2) between each GPS satellite visible to the second mobile and the assumed position of the second mobile; and

computing a pseudorange between the assumed position of the first mobile and the assumed position of the second mobile.

11. A system for determining absolute positions of at least two mobile communications devices, the system comprising:

at least first and second mobile communications devices each including a ranging transceiver module coupled to a position processing module, wherein the ranging transceiver module of each of the first and second mobiles can receive usable positioning information signals transmitted from at most three visible remotely located positioning information signal sources such that the position processing module in each of the first and second mobiles cannot determine its absolute position solely based on the usable received positioning information signals;

wherein each of the first and second mobiles includes a wireless data transceiver module coupled to the position processing module and for receiving first-to-second mobile position information carried on wireless communications signals transmitted between the first and second mobiles;

wherein the ranging transceiver module of each of the first and second mobiles is for establishing at least a predetermined number of line of sight (“

LOS”

) communications signal reception paths between the first mobile or the second mobile and the remotely located positioning information signal sources visible to the first mobile or the second mobile; and

wherein the position processing module of each of the first and second mobiles is for computing the absolute positions of the respective first and second mobiles based on the first-to-second mobile position information and positioning information signals transmitted over the predetermined number of LOS paths by the sources visible to the first mobile or second mobile and received at the first mobile or the second mobile.

12. The system of claim 11, wherein the first-to-second mobile information includes the position of the first mobile relative to the second mobile, wherein the ranging transceiver modules of the respective first and second mobiles in combination (i) can receive positioning information signals transmitted from as few as three visible remote positioning information signal sources, and (ii) can establish at least five LOS paths to the as few as three visible remote sources.

13. The system of claim 11, wherein the ranging transceiver module of each of the first and second mobiles include;

a time of day clock, wherein the first-to-second mobile information includes range and relative clock bias between the respective clocks of the first mobile and the second mobile, and wherein the ranging transceiver modules of the respective first and second mobiles in combination can establish at least six LOS paths to remote positioning information signal sources visible to the first mobile or the second mobile.

14. A system for determining absolute positions of at least two global positioning system (“

GPS”

) mobile communications device comprising;

at least first and second GPS mobiles each including a ranging transceiver module coupled to a position processing module, wherein the ranging transceiver module of each of the first and second GPS mobiles can receive usable GPS positioning information signals transmitted from at most three visible GPS satellites such that the position processing module in each of the first and second mobiles cannot determine its absolute position solely based on the usable received GPS positioning information signals;

wherein the ranging transceiver modules of the respective the first and second GPS mobiles in combination can receive GPS information positioning signals from as few as three visible GPS satellites and can establish at least five line of sight (“

LOS”

) communications signal reception paths between the as few as three GPS satellites and the first and second mobiles;

wherein the first and second GPS mobiles each include a data transceiver module coupled to the position processing module and for receiving first-to-second mobile relative position information carried on wireless communications transmitted between the first and second mobiles;

wherein the position processing modules of the respective first and second GPS mobiles perform the following processing steps;

(a) the position processing module at the first mobile obtains the first-to-second mobile relative position information based on wireless communications between the first and second mobiles;

(b) the position processing module at the first mobile assumes a position for the first mobile and computes an assumed position for the second mobile based on the relative position information;

(c) the position processing modules at the respective first and second mobile compute GPS range estimates based on the GPS positioning information signals transmitted to the ranging transceiver modules of the respective first and second mobiles on the five LOS paths;

(d) the data transceiver module at the second GPS mobile wirelessly communicates the GPS range estimates computed at the second mobile to the data transceiver module of the first mobile; and

(e) the position processing module at the first mobile computes absolute positions of the respective first and second GPS mobile'"'"'s using a system of pseudorange equations including at least five pseudorange equations, wherein the five equations respectively correspond to the five LOS paths and include the assumed positions of the respective first and second mobiles.

15. The system of claim 14, wherein the position processing module of the first GPS mobile computes a root mean square error (“

RMS”

) associated with the estimated absolute position of the first GPS mobile and updates the assumed value for the first mobile if the RMS error exceeds a predetermined threshold; and

wherein the position processing modules of the respective first and second GPS mobiles repeat steps (c), (d) and (e).

16. The system of claim 14, wherein the position processing module of the first GPS mobile computes a root mean square error associated with the estimated absolute position of the first GPS mobile, and

wherein the data transceiver module of the first GPS mobile communicates the absolute positions of the first and second mobiles from the first mobile to the second mobile if the RMS error does not exceed a predetermined threshold.

17. A system for determining absolute positions of at least two global positioning system (“

GPS”

) mobile communications devices comprising;

first and second GPS mobiles each including a ranging transceiver module coupled to a position processing module, wherein the ranging transceiver module of each of the first and second mobiles can receive usable GPS positioning information signals transmitted from at most three visible GPS satellites such that the position processing module in each of the first and second mobiles cannot determine its absolute position solely based on the usable received GPS positioning information signals,

wherein the ranging transceiver modules of the respective first and second mobiles include time of day clocks and together can establish at least six line of sight (“

LOS”

) communications signal reception paths with visible GPS satellites;

wherein the modules of the respective first and second GPS mobiles perform the following steps;

(a) the position processing module at the first mobile assumes nominal positions for the respective first and second mobile and a GPS clock offset for the first mobile;

(b) the position processing module at the first mobile determines signal propagation time between the first mobile and the second mobile based on transmission of wireless communications signals from the ranging transceiver module of the first mobile to the ranging transceiver module of the second mobile;

(c) the position processing module at the second mobile determines signal propagation time between the first mobile and the second mobile based on transmission of wireless communications signals from the ranging transceiver module of the second mobile to the ranging transceiver module of the first mobile;

(d) the data transceiver module of the second GPS mobile wirelessly transmits the propagation time determined at the second mobile to the data transceiver module of the first mobile;

(e) the position processing module at the first mobile determines range between the first and second mobiles based on the signal propagation times measured at the first and second mobiles;

(f) the ranging transceiver modules at the respective first and second GPS mobiles compute GPS range estimates based on the GPS positioning information signals transmitted on the six LOS paths;

(g) the data transceiver module at the second module mobile wirelessly communicates the GPS range estimates computed at the second mobile to the data transceiver module of the first mobile; and

(h) the position processing module at the first GPS mobile computes absolute positions of the first and second GPS mobiles using a system of pseudorange equations including at least six pseudorange equations, wherein the six equations respectively correspond to the six LOS paths and include the assumed positions of the respective first and second mobiles.

18. The system of claim 17, wherein the position processing module the first GPS mobile computes a root mean square (“

RMS”

) error associated with the estimated absolute position of the first GPS mobile, updates the assumed values for the first mobile if the RMS error exceeds a predetermined threshold and again performs step (h).

19. The system of claim 17, wherein the position processing module of first GPS mobile computes a root mean square (“

RMS”

) error associated with the estimated absolute position of the first GPS mobile; and

wherein the data transceiver module of the first mobile communicates the absolute positions of the first and second mobiles from the first mobile to the second mobile if the RMS error does not exceed a predetermined threshold.

20. The system of claim 17, wherein the position processing module at the first mobile in step (h):

computes pseudoranges (1) between each GPS satellite visible to the first mobile and the assumed position of the first mobile and (2) between each GPS satellite visible to the second mobile and the assumed position of the second mobile; and

computes a pseudorange between the assumed position of the first mobile and the assumed position of the second mobile.