Method and apparatus for beam selection for a multibeam satellite communications system

1. An apparatus for beam selection for a multibeam satellite communications system comprising:

a very small aperture terminal (VSAT) comprising a remote satellite dish configured to send and receive RF signals; and

a processor configured to calculate a normalized distance metric for a plurality of user spot beams, select a user spot beam with the lowest normalized distance metric, and find an outroute on the selected user spot beam using the remote satellite dish.

2. The apparatus of claim 1 , wherein the processor is further configured to create a list of user spot beams comprising the user spot beams with normalized distance metrics that are less than a threshold value.

3. The apparatus of claim 2 , wherein the processor is further configured to determine that an outroute was not found with the selected user spot beam, select the user spot beam with the next lowest normalized distance metric from the list of user spot beams, and find an outroute with the selected user spot beam with the next lowest normalized distance metric.

4. The apparatus of claim 1 , wherein the VSAT further comprises a polarizer, and wherein the processor is further configured to select the user spot beam with a polarization that is the same as a polarization of the polarizer.

5. The apparatus of claim 1 , wherein the normalized distance metric is calculated according to the equation:

D

i

=

(

(

x

-

x

i

)

2

+

(

y

-

y

i

)

2

R

i

)

W

i

where D i is the normalized distance metric, (x, y) is location of the VSAT in horizontal one of (az/el) and U/V coordinates, (x i , y i ) is the location of the center of the user spot beam in one of az/el or U/V coordinates, R i is the radius of the user spot beam, and W i is the weight given to the user spot beam.

6. The apparatus of claim 5 , wherein the radius R i is calculated according to the equation:

R

i

=

(

(

R

1

⁢

i

*

cos

⁡

(

θ

i

-

a

i

)

*

cos

⁡

(

a

i

)

-

R

2

⁢

i

*

sin

⁡

(

θ

i

-

a

i

)

*

sin

⁡

(

a

i

)

2

+

(

R

2

⁢

i

*

sin

⁡

(

θ

i

-

a

i

)

*

cos

⁡

(

a

i

)

+

R

1

⁢

i

*

cos

⁡

(

θ

i

-

a

i

)

*

cos

⁡

(

a

i

)

)

)

2

)

where R 1i is the semi-major axis of the user spot beam, R 2i is the semi-minor axis of the user spot beam, a i is the tilt angle of the user spot beam, and is calculated according to the equation:

θ i =arctan(( y−y 01 )/( x−x 01 ))

where (x 01 , y 01 ) is the location of the centroid of the user spot beam.

7. The apparatus of claim 2 , wherein the threshold value is one.

8. The apparatus of claim 5 , wherein the radius R i is calculated according to the equation:

R i =F i ( x 01 ,y 01 )

where F i is a function particular to the user spot beam and known to the VSAT.

9. The apparatus of claim 1 , wherein the plurality of user spot beams originates from more than one satellite.

10. A method for beam selection for a multibeam satellite communications system comprising:

calculating a normalized distance metric for a plurality of user spot beams;

selecting a user spot beam with the lowest normalized distance metric; and

finding an outroute on the selected user spot beam using a very small aperture terminal (VSAT).

11. The method of claim 10 , wherein selecting the user spot beam further comprises selecting the user spot beam with a current polarity of the VSAT.

12. The method of claim 10 , further comprising:

determining an outroute was not found on the selected user spot beam.

13. The method of claim 12 , further comprising:

determining that the VSAT has already been redirected to a different user spot beam; and

outputting an indicator that the outroute cannot be found.

14. The method of claim 10 , further comprising:

determining that the VSAT has not been redirected to a different user spot beam.

15. The method of claim 14 , further comprising:

determining that there is another user spot beam with a normalized distance metric less than a threshold value.

16. The method of claim 15 , further comprising:

determining that the another user spot beam has the same polarity as the VSAT; and

finding an outroute on the another user spot beam.

17. The method of claim 15 , further comprising:

determining that the another user spot beam has an opposite polarity from the VSAT;

reversing the polarity of the VSAT; and

finding an outroute on the another user spot beam.

18. The method of claim 10 , further comprising:

receiving an indication that the outroute that has been found is on a wrong user spot beam; and

receiving instructions redirecting the VSAT to a correct user spot beam.

19. The method of claim 10 , wherein the normalized distance metric is calculated according to the equation:

D

i

=

(

(

x

-

x

i

)

2

+

(

y

-

y

i

)

2

R

i

)

W

i

where D i is the normalized distance metric, (x, y) is location of the VSAT in horizontal one of (az/el) and U/V coordinates, (x i , y i ) is the location of the center of the user spot beam in one of az/el or U/V coordinates, R i is the radius of the user spot beam, and W i is the weight given to the user spot beam.

20. The method of claim 10 , wherein the radius R i is calculated according to the equation:

R

i

=

(

(

R

1

⁢

i

*

cos

⁡

(

θ

i

-

a

i

)

*

cos

⁡

(

a

i

)

-

R

2

⁢

i

*

sin

⁡

(

θ

i

-

a

i

)

*

sin

⁡

(

a

i

)

2

+

(

R

2

⁢

i

*

sin

⁡

(

θ

i

-

a

i

)

*

cos

⁡

(

a

i

)

+

R

1

⁢

i

*

cos

⁡

(

θ

i

-

a

i

)

*

cos

⁡

(

a

i

)

)

)

2

)

where R 1i is the semi-major axis of the user spot beam, R 2i is the semi-minor axis of the user spot beam, a i is the tilt angle of the user spot beam, and is calculated according to the equation:

θ i =arctan(( y−y 01 )/( x−x 01 ))

where (x 01 , y 01 ) is the location of the centroid of the user spot beam.

21. The method of claim 10 , wherein the radius R i is calculated according to the equation:

R i =F i ( x 01 ,y 01 )

where F i is a function particular to the user spot beam and known to the VSAT.

22. The method of claim 10 , wherein the plurality of user spot beams originates from more than one satellite.

23. A method for beam selection for a multibeam satellite communications system using a very small aperture terminal (VSAT) comprising:

(1) calculating a normalized distance metric for each user spot beam on a list of user spot beams;

(2) filtering the list of user spot beams to include only the user spot beams with a normalized distance metric less than a threshold value;

(3) selecting a user spot beam from the filtered list of user spot beams with the lowest normalized distance metric and a polarizer setting that matches the current polarizer setting of the VSAT; and

(4) checking for an outroute on the selected user spot beam;

if an outroute is found,

(5) receiving an indication of whether the outroute is on the selected user spot beam;

if the outroute is on the selected user spot beam,

(6) establishing connectivity through the outroute on the selected user spot beam;

if the outroute is not on the selected user spot beam,

(7) receiving redirection to the selected user spot beam and if the selected user spot beam has a different polarization than the VSAT, reversing the polarization of the VSAT, otherwise not swapping the current polarization of the VSAT;

returning to step (4);

if an outroute is not found,

(8) determining if the VSAT has previously been redirected in step (7);

if the VSAT has previously been redirected,

(9) reporting that an outroute cannot be found;

if the VSAT has not previously been redirected,

(10) determining if there are any user spot beams on the filtered list of user spot beams that have not been checked for an outroute;

if there are user spot beams on the filtered list of user spot beams that have not been checked for an outroute,

(11) determining if there are user spot beams on the filtered list of user spot beams that have not been checked for an outroute and have the same polarization as the current polarization of the VSAT;

if there are user spot beams on the filtered list of user spot beams that have not been checked for an outroute and have the same polarization as the current polarization of the VSAT,

(12) selecting a user spot beam that has not been checked for an outroute with the lowest normalized distance metric and the same polarization as the current polarization of the VSAT from the filtered list;

(13) returning to step (4);

if there are no user spot beams on the filtered list of user spot beams that have not been checked for an outroute and have the same polarization as the current polarization of the VSAT;

(14) reversing the polarization of the VSAT; and

(15) returning to step (12);

if there are no user spot beams on the filtered list of user spot beams that have not been checked for an outroute,

(16) returning to step (9).

24. The method of claim 23 , wherein the plurality of user spot beams originates from more than one satellite.