Soft handoff method and apparatus for mobile vehicles using directional antennas

• US 9,306,657 B2
• Filed: 12/21/2005
• Issued: 04/05/2016
• Est. Priority Date: 04/08/2005
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: de La Chapelle, Michael, Monk, Anthony D.
• Primary Examiner(s): Patel, Ajit
• Application Number:
  US11/314,647
• Publication Number:
  US 20060229104A1
• Time in Patent Office: 3,758 Days
• Field of Search: 455/436, 455/443, 455/562.1
• US Class Current: 1/1
• CPC Class Codes: H01Q 1/28 Adaptation for use in or on aircraft, missiles, satellites, or balloons
• CPC Class Codes: H01Q 1/283 Blade, stub antennas
• CPC Class Codes: H01Q 1/3208 characterised by the application wherein the antenna is used
• CPC Class Codes: H01Q 3/2611 Means for null steering; Adaptive interference nulling
• CPC Class Codes: H04B 7/18506 Communications with or from aircraft, i.e. aeronautical mobile service
• CPC Class Codes: H04W 36/08 Reselecting an access point
• CPC Class Codes: H04W 36/18 for allowing seamless reselection, e.g. soft reselection
• CPC Class Codes: H04W 84/06 Airborne or Satellite Networks space-based or airborne stations H04B7/185

Abstract

A method of providing a communication link for a mobile platform. The method may involve generating a single beam and controlling the single beam to simultaneously generate first and second communication lobes from the single beam, with the first communication lobe being steered to communicate with a first base transceiver station (BTS). The method may further involve simultaneously using the second communication lobe to communicate with the second BTS and fading out the first lobe so that communication with the mobile platform is transferred to the second BTS.

Claims

1. A method of providing a communication link for a mobile platform, the method comprising:

transmitting signals from a single beam forming circuit to a single group of antenna elements of a phased array antenna, thereby producing a single beam having simultaneous and independently steerable first and second communication lobes, the relative strength of the produced first and second communication lobes controlled based on a predetermined initial value of a blending factor, wherein producing the single beam comprises;

calculating first and second complex voltage distributions respectively corresponding to the first and second communication lobes; and

applying the blending factor to each of the first and second complex voltage distributions to produce a complex blended dual-beam voltage distribution; and

updating, during a period in which the first communication lobe communicates with a first base transceiver station (BTS) and the second communication lobe communicates with a distinct second BTS, the blending factor with a plurality of subsequent values to thereby gradually fade out the first communication lobe such that communication with the mobile platform is transferred to the second BTS.

2. The method of claim 1, further comprising calculating one or more values of signal-to-noise ratio (SNR) for signals received by the first communication lobe,

wherein fading out the first communication lobe is based on the calculated SNR values relative to a predetermined threshold.

3. The method of claim 1, further comprising determining a respective distance value for each of the first and second BTS from a predetermined reference point,

wherein fading out the first communication lobe is based on the determined distance values.

30. The method of claim 1, wherein updating the blending factor causes the second communication lobe to gradually fade in while the first communication lobe is gradually faded out.

31. The method of claim 1, wherein applying the blending factor to produce a complex blended dual-beam voltage distribution is controlled according to:

V_iDB=α

V_i1+(1−

α

)V_i2,

where V_iDB represents the complex blended dual-beam voltage distribution, V_i1 and V_i2 represent the respective first and second complex voltage distributions, and α

represents the blending factor.

4. A system for providing a communications link between a mobile platform traversing a region served by at least first and second base transceiver stations (BTSs), the system comprising:

an antenna controller;

a single beam forming network in communication with the antenna controller;

a radio transceiver configured to communicate signals between electronic devices traveling on the mobile platform and at least one of the first and second BTSs via the single beam forming network; and

an antenna system carried on the mobile platform and including a single group of antenna elements coupled with the radio transceiver and the single beam forming network, the antenna system configured to produce, responsive to signals from the beam forming network, a single antenna beam radiated from the group of antenna elements and having first and second lobe coverage patterns, the second lobe coverage pattern steerable toward the second BTS to establish a second communications link with the second BTS while the first lobe coverage pattern maintains a first communications link with the first BTS,

wherein the single beam forming network is configured to;

calculate first and second complex voltage distributions respectively corresponding to the first and second communication lobe coverage patterns;

apply a blending factor to each of the first and second complex voltage distributions to produce a complex blended dual-beam voltage distribution;

reduce, based on a plurality of predetermined values of the blending factor, a first gain of the first lobe coverage pattern to gradually fade out the first communications link, and

increase, during the reduction of the first gain and based on the predetermined values of the blending factor, a second gain of the second lobe coverage pattern to gradually increase a quality of the second communications link, thereby enabling a communications handoff from the first BTS to the second BTS.

5. The system of claim 4, further comprising a BTS-locating subsystem in communication with the antenna system and configured to provide locations of the BTSs located in the region.

6. The system of claim 5, wherein the BTS-locating subsystem comprises a look-up table in communication with the antenna controller and configured to provide latitude, longitude and altitude position information for each of the BTSs located in the region,

wherein the antenna controller is further configured to access the look-up table to acquire location information for various BTSs.

7. The system of claim 4, wherein the group of antenna elements of the antenna system;

comprises a phased array antenna disposed on an exterior surface of the mobile platform.

8. The system of claim 4, wherein the antenna system is further configured to:

scan the second lobe about a predetermined azimuth arc;

sample, during the scan, signal strengths of remotely located BTSs within the region;

discover, based on the sampled signal strengths, the second BTS; and

determine that the communications handoff is required to the second BTS.

9. The system of claim 4, wherein the antenna system is further configured to:

scan the second lobe as a continuous search for a BTS providing a higher quality communications link than the first communications link, and

enabling, upon discovering the second BTS providing a higher quality communications link, the communications handoff from the first BTS to the second BTS.

10. A system for providing air-to-ground (ATG) communications between an airborne mobile platform traversing a region served by a set of base transceiver stations (BTS) comprising first and second BTSs, the system comprising:

an antenna controller;

a single beam forming circuit in communication with the antenna controller;

a subsystem configured to provide location information to the antenna controller for the set of BTSs;

a radio transceiver configured to communicate signals between electronic devices traveling on the mobile platform and at least one of the set of BTSs via the single beam forming circuit; and

an antenna system carried on the mobile platform and responsive to signals from the radio transceiver, the antenna system including a single plurality of antenna elements configured to form a single antenna beam that;

when no communications handoff is required, has a single lobe coverage pattern oriented toward the first BTS, and

when a communications handoff from the first BTS to the second BTS is required, selectively has a dual-lobed coverage pattern in which a first lobe is oriented toward the first BTS and a second lobe is oriented toward the second BTS, wherein gain values applied to the single plurality of antenna elements are controlled based on predetermined values of a blending factor to influence the first and second lobes to effect the communications handoff,

wherein the single beam forming circuit is configured to;

calculate first and second complex voltage distributions respectively corresponding to the first and second lobes; and

apply the blending factor to each of the first and second complex voltage distributions to produce a complex blended dual-beam voltage distribution.

11. The system of claim 10, wherein the antenna system comprises components operable to control the gain values associated with the first and second lobes to fade out the first lobe while fading in the second lobe such that communication with the radio transceiver is gradually transferred from the first BTS to the second BTS.

12. The system of claim 10, wherein the single plurality of antenna elements comprises a phased array antenna configured to radiate the single antenna beam in each of the single lobe and dual-lobed coverage patterns.

13. The system of claim 11, further comprising an aircraft navigation system configured to provide real-time latitude, longitude and altitude information for the mobile platform to the antenna controller.

14. The system of claim 10, further comprising:

at least one of a server and router in communication with the radio transceiver and with a local area network (LAN) on the mobile platform.

15. The system of claim 10, wherein the antenna system comprises a phased array antenna including the single plurality of antenna elements and supported from an undercarriage of the mobile platform.

16. The system of claim 10, wherein the subsystem comprises a look-up table including longitude, latitude, and altitude information for the BTSs within the region.

17. A system for providing continuous communications between a mobile platform having an antenna system and traversing a region served by a plurality of base transceiver stations (BTSs) comprising first and second BTSs, each of the plurality of BTSs serving a respective subregion of the region and having unique location information, the system comprising:

a subsystem configured to provide the unique location information for at least one of the plurality of BTSs to the antenna system;

a radio transceiver coupled with the antenna system and configured to communicate cellular signals with at least one of the plurality of BTSs located within the region by said subsystem;

a single beam forming circuit coupled with the antenna system and operable to form a single beam using a single plurality of antenna elements of the antenna system for communication with at least one of the plurality of BTSs, wherein;

(1) the single beam has a single lobe coverage pattern for communication with the first BTS, and

(2) when a communications handoff is to be made from the first BTS to the second BTS, the single beam selectively has a dual-lobed coverage pattern comprising a first lobe coverage pattern for communication with the first BTS and a second lobe coverage pattern for communication with the second BTS, wherein the single plurality of antenna elements is controlled based on predetermined values of a blending factor to perform the communications handoff,

wherein the single beam forming circuit is configured to;

calculate first and second complex voltage distributions respectively corresponding to the first and second lobe coverage patterns; and

apply the blending factor to each of the first and second complex voltage distributions to produce a complex blended dual-beam voltage distribution.

18. The system of claim 17, wherein the subsystem comprises a look-up table including latitude and longitude information for the plurality of BTSs.

19. The system of claim 17, further comprising at least one of a server and router in communication with the radio transceiver and with a local area network (LAN) on-board the mobile platform.

20. The system of claim 17, wherein the antenna system comprises a phased array antenna system supported on an undercarriage of the mobile platform.

21. The system of claim 17, wherein the mobile platform comprises an aircraft.

22. The system of claim 17, wherein the antenna system comprises a phased array antenna, and wherein the single plurality of antenna elements comprises a single plurality of adjacently positioned monopole antenna elements.

23. The system of claim 17, further comprising an aircraft navigation system configured to provide real-time latitude, longitude, and altitude information for the mobile platform to said antenna controller.

24. A system for providing communications between a first platform and a plurality of second platforms, comprising:

an antenna system carried on the first platform and including a single plurality of antenna elements; and

a single beam former configured to;

provide electrical signals to the antenna system to form a single beam pattern using the single plurality of antenna elements, the single beam pattern having first and second lobes, with the first lobe able to be steered toward one of the plurality of second platforms, and the second lobe able to be simultaneously steered toward another one of the plurality of second platforms,

calculate first and second complex voltage distributions respectively corresponding to the first and second lobes, and

apply a blending factor to each of the first and second complex voltage distributions to produce a complex blended dual-beam voltage distribution,

wherein the relative strength of the produced first and second lobes is controlled based on predetermined values of the blending factor.

25. The system of claim 24, wherein the first and second lobes each comprise a receive lobe for receiving electromagnetic wave signals.

26. The system of claim 24, wherein the first and second lobes each comprise transmit lobes for radiating electromagnetic wave energy.

32. The system of claim 24, wherein the beam former is further configured to:

update, during communication with the first and second of the second platforms, the blending factor with a plurality of the predetermined values to thereby gradually fade out the first lobe while gradually fading in the second lobe.

33. The system of claim 24, wherein applying the blending factor to produce a complex blended dual-beam voltage distribution is controlled according to:

V_iDB=α

V_i1+(1−

α

)V_i2,

where V_iDB represents the complex blended dual-beam voltage distribution, V_i1 and V_i2 represent the respective first and second complex voltage distributions, and α

represents the blending factor.

27. A method for providing communications between a mobile platform and a terrestrial cellular network employing at least first and second base transceiver stations (BTSs) at dispersed locations within a region being traversed by the mobile platform, the method comprising:

forming, using a single plurality of antenna elements coupled with a single beam forming circuit, a single beam with at least a first lobe;

establishing, using the first lobe, a first communications link between the first BTS and a radio transceiver located on the mobile platform and coupled with the single beam forming circuit; and

performing, upon determining an availability of the second BTS providing a higher quality communications link than the first communications link, a communications handoff from the first BTS to the second BTS, wherein performing the communications handoff comprises;

establishing, using a second, independently aimable lobe of the single beam, a second communications link with the second BTS while maintaining said first communications link with the first BTS, wherein establishing the second communications link comprises;

calculating first and second complex voltage distributions respectively corresponding to the first and second lobes; and

applying a blending factor to each of the first and second complex voltage distributions to produce a complex blended dual-beam voltage distribution; and

gradually adjusting, based on a predetermined plurality of values of the blending factor, a respective gain for each of the first and second lobes to fade out the first communications link while fading in the second communications link.

28. The method of claim 27, wherein establishing each of the first and second communications links comprises aiming the respective first and second lobes of the single beam using location information for the first and second BTSs obtained from a look-up table.

29. The method of claim 27, wherein determining the availability of the second BTS comprises:

continuously scanning the second lobe about a predetermined arc;

receiving, via the second lobe, radio frequency (RF) signals from one or more remotely located BTSs; and

determining, based on a determined signal strength of the received RF signals, whether at least one of the remotely located BTSs will provide a higher quality communications link than the first communications link.