Method and apparatus for optimizing forward link data rate for radio frequency transmissions to mobile platforms

• US 20040158863A1
• Filed: 02/10/2003
• Published: 08/12/2004
• Est. Priority Date: 02/10/2003
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: McLain, Christopher J.
• Granted Patent: US 7,751,337 B2
• Time in Patent Office: Days
• US Class Current: 725/73
• CPC Class Codes: H04B 7/18506 Communications with or from aircraft, i.e. aeronautical mobile service
• CPC Class Codes: H04L 1/0002 by adapting the transmission rate
• CPC Class Codes: H04L 1/0015 characterised by the adaptation strategy
• CPC Class Codes: H04L 1/0026 Transmission of channel quality indication

Abstract

A system and method for monitoring and adjusting the data transmission rate of a forward link RF signal from a base station to a mobile platform to maintain a desired, minimum link margin with each of the mobile platforms. The system involves using a signal quality monitoring subsystem carried by each mobile platform during the normal course of its operation to transmit signal quality information via a return link to the base station. The base station uses the signal quality information to monitor and adjust the signal quality of subsequent forward link signals transmitted to the mobile platforms in a manner that optimizes the data transmission rate of the forward link signals. The present invention better accounts for time varying factors that influence the signal quality of received forward link signals by the mobile platforms and obviates the need for mobile test platforms or other expensive and relatively complex methods for predicting needed data transmission rates for the forward link signals.

Claims

1. A method for monitoring a signal quality of a forward link radio frequency (RF) signal transmitted from a first communications station to a second communications station to maintain a signal quality of said forward link RF signal at a predetermined level, said method comprising:

transmitting said forward link RF signal from said first communications station to said second communications station;

using said second communications station to receive said forward link RF signal and to generate a signal quality value representative of a signal quality of said received forward link RF signal;

using said second communications station to transmit said signal quality value back to said first communications station in a return link RF signal; and

using said first communications station to adjust a data transmission rate for said forward link RF signal to maintain said signal quality at a predetermined level.

2. The method of claim 1, wherein using said second communications station to generate a signal quality value comprises generating a signal representative of a ratio of energy-per-bit to noise spectral density (Eb/No) of said received forward link RF signal.

3. The method of claim 1, wherein the step of using said second communications station to transmit signal quality value information further comprises transmitting location information indicative of a geographic location of said second communications station.

4. The method of claim 1, wherein using said second communications station to generate a signal quality value comprises generating a signal representative of a ratio of carrier power to noise power (C/N) of said received forward link RF signal.

5. The method of claim 1, wherein the step of using said first communications station to adjust said data transmission rate comprises only adjusting said data transmission rate after a predetermined quantity of return link RF signals from said second communications station of said signal quality value have been received.

6. The method of claim 1, wherein the step of using said first communications station to adjust said data transmission rate comprises:

using said second communications station to generate location information and to supply said location information in said return link RF signal, said location information being representative of a geographic location of said second communications station at a given time; and

only adjusting said data transmission rate after receiving return link RF signals originating from a predetermined range of geographic locations, as reported by said second communications station.

7. A method for managing the transmission of information from a base station, via a radio frequency (RF) link, to a space based RF transponder and then to a RF receiver on-board a mobile platform operating within a predetermined geographic coverage region, wherein the mobile platform includes a signal quality monitoring subsystem, said method comprising:

transmitting said information to said mobile platform via a forward link signal that is relayed by said space based RF transponder to said mobile platform;

using said signal quality monitoring subsystem to determine a signal quality of said forward link signal;

using said RF transceiver of said mobile platform to transmit a return link signal, via said RF space based transponder, back to said base station, which includes information relating to a signal quality of said forward link signal received by said RF transceiver of said mobile platform; and

using said base station to adjust a data rate of said forward link signal to achieve a desired level of signal quality of subsequent transmissions of said forward link signal.

8. The method of claim 7, wherein the step of using said signal quality monitoring system comprises:

determining an Eb/No (energy per bit divided by spectral noise density) value of said forward link signal received by said RF transceiver of said mobile platform.

9. The method of claim 7, wherein the step of using said signal quality monitoring system comprises:

determining a carrier-power-to-noise-power ratio value of said forward link signal received by said RF transceiver of said mobile platform.

10. The method of claim 7, wherein the step of using said base station to adjust a data rate of said forward link signal comprises:

collecting signal quality information transmitted via a plurality of said return link signals over a predetermined period of time; and

using said collected signal quality information to adjust said data transmission rate for subsequent forward link signals transmitted from said base station.

11. The method of claim 7, wherein the step of using said base station to adjust a data rate of said forward link signal comprises:

collecting a predetermined quantity of signal quality information from said return link signals; and

using said predetermined quantity of signal quality information to adjust said data transmission rate for subsequent forward link signals transmitted from said base station.

12. The method of claim 7, wherein the step of using said base station to adjust a data rate of said forward link signal comprises:

collecting signal quality information from a plurality of mobile platforms operating over a predetermined range of geographic sub-regions of said predetermined geographic coverage region; and

using said collected signal quality information from said plurality of mobile platforms to adjust said data transmission rate for subsequent forward link signals transmitted from said base station.

13. The method of claim 7, wherein said mobile platform is commanded by said base station, via said forward link signal, when to make a signal quality determination.

14. The method of claim 7, wherein the step of using said base station to adjust a data rate of said forward link signal comprises:

collecting signal quality information via return link signals from said mobile platform; and

adjusting said data transmission rate only after said base station determines that said signal quality of said forward link signal has changed by a predetermined value.

15. A method for monitoring a signal quality of forward link radio frequency (RF) signals transmitted from a base station, to a space based RF transponder, and then to a RF transceiver on-board each of a plurality of mobile platforms operating within a predetermined geographic coverage region, wherein each said mobile platform includes a signal quality monitoring subsystem, said method comprising:

using said RF transceiver on board each of said mobile platforms to receive said forward link RF signals;

using said signal quality monitoring subsystem on each said mobile platform to determine a signal quality of said received forward link RF signals and to generate signal quality information corresponding thereto; and

using said RF transceiver of said mobile platform to transmit said signal quality information back to said base station; and

using said base station to determine if an adjustment to a data rate of said forward link RF signals needs to be performed to maintain a desired level of signal quality for said forward link RF signals.

16. The method of claim 15, further comprising the step of causing said base station to modify said data transmission rate of said forward link RF signals based on signal quality information received from said mobile platforms.

17. The method of claim 16, wherein said base station only adjusts said data transmission rate of said forward link signals after obtaining a predetermined quantity of said signal quality information.

18. The method of claim 16, wherein said base station only adjusts said data transmission rate of said forward link signals after obtaining signal quality information from said mobile platforms operating in a predetermined range of different geographic locations within said predetermined geographic coverage region.

19. The method of claim 16, wherein said base station only adjusts said data transmission rate of said forward link signals after said signal quality information has changed by a predetermined value.

20. The method of claim 15, wherein said step of using said signal quality monitoring subsystem of each said mobile platform to generate signal quality information comprises generating Eb/No (energy per bit divided by noise spectral density) information.

21. The method of claim 15, wherein said step of using said signal quality monitoring subsystem of each said mobile platform to generate signal quality information comprises generating information representing a ratio of carrier power to noise power (C/N);

using said base station to adjust a data rate of said forward link signal to achieve a desired level of signal quality of subsequent transmissions of said forward link signal.

22. A method of operating a radio frequency (RF) communications system to maintain a signal quality of RF signals transmitted from a base station to a remote platform, said method of operating comprising:

using said remote platform to receive forward link RF signals transmitted from said base station;

using said remote platform to generate signal quality information relating to a signal quality of said received forward link RF signals;

using said remote platform to transmit said signal quality information back to said base station in return link RF signals; and

using said base station to modify said forward link RF signals as needed to maintain a desired signal quality level of said forward link RF signals.

23. The method of claim 22, wherein the step of using said remote platform to generate signal quality information comprises using said remote platform to generate information on its location within a geographic region.

24. The method of claim 22, wherein the step of using said remote platform to generate signal quality information comprises using said remote platform to generate at least one of:

information relating to a ratio of energy-per-bit to noise spectral density (Eb/No) of said received forward link RF signal; and

information relating to a ratio of carrier power to noise power (C/N) of said received forward link RF signal.

25. The method of claim 22, wherein the step of modifying said forward link RF signals comprises modifying a data transmission rate of said forward link RF signals from said base station.

26. A communications system for monitoring a quality of a forward link radio frequency (RF) signal transmitted to a mobile platform operating within a predefined geographic coverage region, the system comprising:

a RF transceiver carried on said mobile platform;

a signal quality monitoring subsystem operably associated with said RF transceiver that operates to generate signal quality information relating to a signal quality of received forward link RF signals from said base station; and

a base station for transmitting forward link RF signals to said mobile platform, monitoring return link RF signals transmitted from said RF transceiver of said mobile platform back to said base station, and for determining if said subsequently transmitted forward link RF signals need to be modified to maintain a desired signal quality level.

27. The system of claim 26, wherein said base station further operates to modify a data transmission rate of said forward link RF signal.