COORDINATED SATELLITE-TERRESTRIAL FREQUENCY REUSE

REUTILISATION COORDONNEE DE FREQUENCES ENTRE DES SATELLITES ET LA TERRE

English Abstract

A system and method of operation for efficiently reusing and/or sharing at least a portion of the frequency spectrum between a first satellite spot beam and a second satellite spot beam, and/or an underlay terrestrial network associated with a second satellite spot beam. The spectrum is efficiently reused and/or shared between respective spot beams and/or associated underlay terrestrial systems in a manner minimizes interference between the respective satellite and terrestrial systems.

French Abstract

Méthode et système de fonctionnement pour la réutilisation et/ou le partage efficaces d'au moins une partie du spectre de fréquences entre un premier faisceau fin de satellite et un second faisceau fin du même type, et/ou un réseau terrestre sous-jacent associé à un faisceau fin du second satellite. Le spectre est réutilisé et/ou partagé efficacement entre les faisceaux fins et/ou les réseaux terrestres sous-jacents connexes de manière à minimiser les interférences entre le satellite et les réseaux terrestres respectifs.

Claims

15

CLAIMS


1. A method of at least one of assigning and reusing frequencies between one
or more
communication systems, comprising the steps of:

configuring a first satellite spot beam having a first set of frequencies
associated therewith and
comprising a first substantially central portion and a first plurality of
subareas, each of
the first plurality of subareas extending substantially from a periphery of
the first
substantially central portion to substantially near a circumference of the
first satellite spot
beam;

configuring a second satellite spot beam having a second set of frequencies
associated
therewith and comprising a second substantially central portion and a second
plurality of
subareas, each of the second plurality of subareas extending substantially
from a
periphery of the second central portion to substantially near a circumference
of the
second satellite spot beam;

configuring at least one terrestrial cell that at least partially overlaps the
first satellite spot beam
having a third set of frequencies associated therewith; and

at least one of assigning, reusing and borrowing, by the terrestrial system,
at least one of a
portion of the second set of frequencies and a portion of the first set of
frequencies used
in the first central portion, responsive to predetermined criteria associated
with the third
set of frequencies, including at least one of assigning, reusing and borrowing
at least one
of the second set of frequencies when the second set of frequencies are at
least
substantially geographically distant from the first satellite spot beam.


2. The method of claim 1 wherein the first plurality of subareas are
substantially equal sized
cells having a first size and the second plurality of subareas are
substantially equal sized cells having a
second size.


3. The method of claim 2 wherein the first size and the second size are
approximately equal.

4. The method of claim 1 wherein the second set of frequencies are
substantially distant from
the first satellite spot beam when they are at least one of assigned, reused
and borrowed for use in
those first plurality of subareas not sharing a common boundary with the
second satellite spot beam.



16

5. The method of claim 1 wherein the first set of frequencies used in the
first central portion
comprise at least one of those frequency sets respectively associated with
satellite spot beams directly
adjacent to the first satellite spot beam.


6. The method of claim 1 wherein said step of assigning, reusing and borrowing
is based on
prioritization rules.


7. The method of claim 6 wherein the prioritization rules include dynamic load
and capacity
constraints of cells that frequencies are taken from.


8. The method of claim 1 wherein a subscriber terminal positioned within the
first central
portion can be assigned, reuse and/or borrow use any of the respective set of
frequencies associated
with the at least one second satellite spot beam.


9. The method of claim 1 wherein a subscriber terminal positioned within the
first central
portion can be assigned, reuse and/or borrow use any of the respective set of
frequencies associated
with any spot beams adjacent the first satellite spot beam.


10. The method of claim 1 wherein a subscriber terminal positioned within a
subarea of the first
spot beam not sharing at least a portion of a common boundary with the second
satellite spot beam
can be assigned, reuse and/or borrow any of the second set of frequencies
associated with the second
satellite spot beam.


11. The method of claim 1 wherein the predetermined criteria is at least one
of load balancing
and received signal strength interference.


12. The method of claim 1 further comprising the steps of:

configuring a second terrestrial cell that at least partially overlaps the
second satellite spot beam
having a fourth set of frequencies associated therewith; and

at least one of assigning, reusing and borrowing, by the second terrestrial
cell, at least one of
the first set of frequencies and the frequencies used in the second central
portion,
responsive to predetermined criteria associated with the fourth set of
frequencies,
including at least one of assigning, reusing and borrowing at least one of the
first set of



17

frequencies when the first set of frequencies are at least substantially
geographically
distant from the second satellite spot beam.


13. The method of claim 1 wherein the first central portion and the second
central portion
comprise approximately twenty five percent of the area covered by the first
satellite spot beam and the
second satellite spot beam, respectively.


14. The method of claim 1 wherein the first set of frequencies and the second
set of frequencies
comprise a plurality of paired uplink and downlink frequencies.


15. The method of claim 14 wherein a downlink frequency of a frequency set is
used in a first
subarea of the first spot beam, and wherein a corresponding one of the uplink
frequencies is reused in
a second subarea of the first spot beam.


16. The method of claim 1 wherein the area of coverage of a spot beam
comprises an area
having a radius substantially equal to a distance from a center of the spot
beam having a substantially
maximum signal strength to a distance from the center of the spot beam where
the signal strength of
the spot beam is attenuated by approximately 3 dB.


17. The method of claim 1 wherein an area of coverage of at least one of a
spot beam and a
terrestrial cell comprises an area corresponding to a bit error rate in the
range of at least one of 10 -2 to
-3 for voice and 10 -5 to 10 -6 for data.


18. The method of claim 1 wherein the number of subareas is equal to a number
of spot beams
comprising a cluster minus one.


19. A method of at least one of assigning and reusing frequencies, comprising
the steps of:
configuring a first communications area having a first set of frequencies
associated therewith
and comprising a first substantially central portion and a first plurality of
subareas, each
of the first plurality of subareas extending substantially from a periphery of
the first
substantially central portion to substantially near a circumference of the
first
communications area;

configuring a second communications area having a second set of frequencies
associated
therewith and comprising a second substantially central portion and a second
plurality of



18

subareas, each of the second plurality of subareas extending substantially
from a
periphery of the central portion to substantially near a circumference of the
second
communications area;

configuring at least one third communications area that at least partially
overlaps the first
communications area, having a third set of frequencies associated therewith;
and

at least one of assigning, reusing and borrowing, by the third communications
area, at least one
of a portion of the second set of frequencies and a portion of the first set
of frequencies
used in the first central portion, responsive to predetermined criteria
associated with the
third set of frequencies, including at least one of assigning, reusing and
borrowing at
least one of the second set of frequencies when the second set of frequencies
are at least
substantially geographically distant from the first satellite spot beam.


20. The method of claim 19 wherein the first plurality of subareas are
substantially equal sized
cells having a first size and the second plurality of subareas are
substantially equal sized cells having a
second size.


21. The method of claim 20 wherein the first size and the second size are
approximately equal.

22. The method of claim 19 wherein the second set of frequencies are
substantially distant from
the second communications area when they are at least one of assigned, reused
and borrowed for use
in those first plurality of subareas not sharing a common boundary with the
second communications
area.


23. The method of claim 19 wherein the first set of frequencies used in the
first central portion
comprise at least one of those frequency sets respectively associated with
communication areas
external to and directly adjacent to the first communications area.


24. The method of claim 19 wherein said step of assigning, reusing and
borrowing is based on
prioritization rules.


25. The method of claim 24 wherein the prioritization rules include dynamic
load and capacity
constraints of candidate cells that frequencies are being taken from.



19

26. The method of claim 19 wherein a user positioned within the first central
portion can be
assigned, reuse and/or borrow use any of the respective set of frequencies
associated with the at least
one second satellite spot beam.


27. The method of claim 19 wherein a user positioned within the first central
portion can be
assigned, reuse and/or borrow use any of the respective set of frequencies
associated with any
communication areas adjacent the first satellite spot beam.


28. The method of claim 19 wherein a user positioned within a subarea not
sharing at least a
portion of a common boundary with the second communications area can be
assigned, reuse and/or
borrow any of the second set of frequencies associated with the second
communications area.


29. The method of claim 19 wherein the predetermined criteria is at least one
of load balancing
and received signal strength interference.


30. The method of claim 19 further comprising the steps of:

configuring a fourth communications area within the second communications area
having a
fourth set of frequencies associated therewith; and

at least one of assigning, reusing and borrowing, by the fourth communications
area, at least
one of the first set of frequencies and the frequencies used in the second
central portion,
responsive to predetermined criteria associated with the fourth set of
frequencies,
including at least one of assigning, reusing and borrowing at least one of the
first set of
frequencies when the first set of frequencies are at least substantially
geographically
distant from the second communications area.


31. The method of claim 19 wherein the first central portion and the second
central portion
comprise approximately twenty five percent of the area covered by the first
communications area and
the second communications area, respectively.


32. The method of claim 19 wherein the first and second set of frequencies
comprise a plurality
of paired uplink and downlink frequencies, wherein a downlink frequency of a
frequency set is used
in a first subarea of the first communications area, and wherein a
corresponding one of the uplink
frequencies is reused in a second subarea of the first communications area.



20

33. The method of claim 19 wherein the area of coverage of a communications
area comprises
an area having a radius substantially equal to a distance from a center of the
communications area
having a substantially maximum signal strength to a distance from the center
of the communications
area where the signal strength of the communications area is attenuated by
approximately 3 dB.


34. The method of claim 19 wherein an area of coverage of at least one of a
spot beam and a
terrestrial cell comprises an area corresponding to a bit error rate in the
range of at least one of 10 -2 to
-3 for voice and 10 -5 to 10 -6 for data.


35. A method of at least one of assigning and reusing frequencies between one
or more
communication systems, comprising the steps of:

configuring a first satellite spot beam having a first set of frequencies
associated therewith and
comprising a first substantially central portion and a first plurality of
subareas, each of
the first plurality of subareas extending substantially from a periphery of
the first
substantially central portion to substantially near a circumference of the
first satellite spot
beam;
configuring a second satellite spot beam having a second set of frequencies
associated
therewith and comprising a second substantially central portion and a second
plurality of
subareas, each of the second plurality of subareas extending substantially
from a
periphery of the central portion to substantially near a circumference of the
second
satellite spot beam;

configuring at least one terrestrial cell that at least partially overlaps the
first satellite spot beam
having a third set of frequencies associated therewith; and

at least one of assigning, reusing and borrowing, by the second satellite spot
beam, at least one
of a portion of the third set of frequencies responsive to predetermined
criteria, including
at least one of assigning, reusing and borrowing at least one of the third set
of
frequencies associated with the at least one terrestrial cell when the
terrestrial cell is at
least substantially geographically distant from the second set of frequencies.


36. A method of at least one of assigning and reusing frequencies between one
or more
communication systems, comprising the steps of:

configuring a first satellite spot beam having a first set of frequencies
associated therewith and
comprising a first substantially central portion and a first plurality of
subareas, each of
the first plurality of subareas extending substantially from a periphery of
the first



21

substantially central portion to substantially near a circumference of the
first satellite spot
beam;

configuring a second satellite spot beam having a second set of frequencies
associated
therewith;

configuring at least one terrestrial cell that at least partially overlaps the
first satellite spot beam
having a third set of frequencies associated therewith; and

at least one of assigning, reusing and borrowing, by the terrestrial cell, at
least one of a portion
of the second set of frequencies and a portion of the first set of frequencies
used in the
first central portion, responsive to predetermined criteria associated with
the third set of
frequencies, including at least one of assigning, reusing and borrowing at
least one of the
second set of frequencies when the second set of frequencies are at least
substantially
geographically distant from the terrestrial cell.


37. The method of claim 36 wherein the first plurality of subareas are
substantially equal sized.

38. The method of claim 36 wherein the second set of frequencies are
substantially distant from
the first satellite spot beam when they are at least one of assigned, reused
and borrowed for use in
those first plurality of subareas not sharing a common boundary with the
second satellite spot beam.


39. The method of claim 36 wherein the first set of frequencies used in the
first central portion
comprise at least one of those frequency sets respectively associated with one
or more satellite spot
beams directly adjacent to the first satellite spot beam.


40. The method of claim 36 wherein said step of assigning, reusing and
borrowing is based on
prioritization rules.


41. The method of claim 40 wherein the prioritization rules include dynamic
load and capacity
constraints of candidate cells that frequencies are being taken from.


42. The method of claim 36 wherein a user positioned within the first central
portion can be
assigned, reuse and/or borrow use any of the respective set of frequencies
associated with the second
satellite spot beam.



22

43. The method of claim 36 wherein a subscriber terminal positioned within the
first central
portion can be assigned, reuse and/or borrow use any of the respective set of
frequencies associated
with any spot beams adjacent the first satellite spot beam.


44. The method of claim 36 wherein a subscriber terminal positioned within a
subarea of the
first spot beam not sharing at least a portion of a common boundary with the
second satellite spot
beam can be assigned, reuse and/or borrow any of the second set of frequencies
associated with the
second satellite spot beam.


45. The method of claim 36 wherein the predetermined criteria is at least one
of load balancing
and received signal strength interference.


46. The method of claim 36 further comprising the steps of:

configuring a second terrestrial cell that at least partially overlaps the
second satellite spot beam
having a fourth set of frequencies associated therewith; and

at least one of assigning, reusing and borrowing, by the second terrestrial
cell, at least one of
the first set of frequencies and the frequencies used in the second central
portion,
responsive to predetermined criteria associated with the fourth set of
frequencies,
including at least one of assigning, reusing and borrowing at least one of the
first set of
frequencies when the first set of frequencies are at least substantially
geographically
distant from the second terrestrial cell.


47. The method of claim 36 wherein the first central portion comprises
approximately twenty
five percent of the area covered by the first satellite spot beam.


48. The method of claim 36 wherein the first and second set of frequencies
comprise a plurality
of paired uplink and downlink frequencies, wherein a downlink frequency of a
frequency set is used
in a first subarea of the first spot beam, and wherein a corresponding one of
the uplink frequencies is
reused in a second subarea of the first spot beam.


49. The method of claim 36 wherein the area of coverage of a spot beam
comprises an area
having a radius substantially equal to a distance from a center of the spot
beam having a substantially
maximum signal strength to a distance from the center of the spot beam where
the signal strength of
the spot beam is attenuated by approximately 3 dB.





23

50. The method of claim 36 wherein an area of coverage of at least one of a
spot beam and a
terrestrial cell comprises an area corresponding to a bit error rate in the
range of at least one of 10 -2 to
-3 for voice and 10 -5 to 10 -6 for data.


51. A method of at least one of assigning and reusing frequencies between one
or more
communication systems, comprising the steps of:

configuring a first satellite spot beam having a first set of frequencies
associated therewith and
comprising a first plurality of subareas, each of the first plurality of
subareas extending
from a substantially center area of the first satellite spot beam to
substantially near a
circumference of the first satellite spot beam in a fan-like manner thereby
forming the
first plurality of subareas;

configuring a second satellite spot beam having a second set of frequencies
associated
therewith;

configuring at least one terrestrial cell that at least partially overlaps the
first satellite spot beam
having a third set of frequencies associated therewith; and

at least one of assigning, reusing and borrowing, by the at least one
terrestrial cell, at least one
of a portion of the second set of frequencies and a portion of the first set
of frequencies
used in the first central portion, responsive to predetermined criteria
associated with the
third set of frequencies for communication therewith, including at least one
of assigning,
reusing and borrowing at least one of the second set of frequencies when the
second set
of frequencies are at least substantially geographically distant from the
first spot beam.


52. The method of claim 51 wherein the first plurality of subareas are
substantially equal sized.

53. The method of claim 51 wherein the second set of frequencies are
substantially distant from
the second satellite spot beam when they are at least one of assigned, reused
and borrowed for use in
those first plurality of subareas not sharing a common boundary with the
second satellite spot beam.


54. The method of claim 51 wherein the first set of frequencies used in the
first central portion
comprise those frequency sets respectively associated with at least one of the
satellite spot beams
directly adjacent to the first satellite spot beam.




24

55. The method of claim 51 wherein said step of assigning, reusing and
borrowing is based on
prioritization rules.


56. The method of claim 55 wherein the prioritization rules include dynamic
load and capacity
constraints of candidate cells that frequencies are being taken from.


57. The method of claim 55 wherein the prioritization rules further include
signal strength.

58. The method of claim 51 wherein a user positioned within the first central
portion can be
assigned, reuse and/or borrow use any of the respective set of frequencies
associated with the second
satellite spot beam.


59. The method of claim 51 wherein a user positioned within the first central
portion can be
assigned, reuse and/or borrow use any of the respective set of frequencies
associated with any spot
beams adjacent the first satellite spot beam.


60. The method of claim 51 wherein a user positioned within a subarea not
sharing at least a
portion of a common boundary with the second satellite spot beam can be
assigned, reuse and/or
borrow any of the second set of frequencies associated with the second
satellite spot beam.


61. The method of claim 51 wherein the predetermined criteria comprise at
least one of load
balancing and received signal strength interference.


62. The method of claim 51 further comprising the steps of:

configuring a terrestrial cell that at least partially overlaps the second
satellite spot beam having
a fourth set of frequencies associated therewith; and

at least one of assigning, reusing and borrowing, by the terrestrial cell, at
least one of the first
set of frequencies and the frequencies used in the second central portion,
responsive to
predetermined criteria associated with the fourth set of frequencies,
including at least one
of assigning, reusing and borrowing at least one of the first set of
frequencies when the
first set of frequencies are at least substantially geographically distant
from the terrestrial
cell.



25

63. The method of claim 51 wherein the first and second set of frequencies
comprise a plurality
of paired uplink and downlink frequencies.


64. The method of claim 63 wherein a downlink frequency of a frequency set is
used in a first
subarea of the first spot beam, and wherein a corresponding one of the uplink
frequencies is used in a
second subarea of the first spot beam.


65. The method of claim 51 wherein the area of coverage of a spot beam
comprises an area
having a radius substantially equal to a distance from a center of the spot
beam having a substantially
maximum signal strength to a distance from the center of the spot beam where
the signal strength of
the spot beam is attenuated by approximately 3 dB.


66. The method of claim 51 wherein an area of coverage of at least one of a
spot beam and a
terrestrial cell comprises an area corresponding to a bit error rate in the
range of 10 -2 to 10 -3 for voice
and 10 -5 to 10 -6 for data.


67. A system for at least one of assigning and reusing frequencies between one
or more
communication systems, comprising:

at least one satellite capable of configuring: a) a first spot beam having a
first set of frequencies
associated therewith, the first spot beam comprising a first substantially
central portion
and a first plurality of subareas, each of the first plurality of subareas
extending
substantially from a periphery of the first substantially central portion to
substantially
near a circumference of the first satellite spot beam, and b) a second
satellite spot beam
having a second set of frequencies associated therewith, the second spot beam
comprising a second substantially central portion and a second plurality of
subareas, each
of the second plurality of subareas extending substantially from a periphery
of the second
central portion to substantially near a circumference of the second satellite
spot beam;

a terrestrial base station positioned within the first satellite spot beam for
configuring a
terrestrial cell having at least partially overlapping coverage with the first
spot beam, the
terrestrial cell having a third set of frequencies associated therewith and an
area coverage
at least partially overlapping with an area of coverage associated with the
first spot beam;

a first subscriber terminal positioned within the terrestrial base station
area of coverage; and
means for at least one of assigning, reusing and borrowing, by the terrestrial
base station and
for use by said first subscriber terminal in communicating with at least one
of a second
subscriber terminal and other communications device, at least one of a portion
of the



26

second set of frequencies and a portion of the first set of frequencies used
in the first
central portion, responsive to predetermined criteria associated with the
third set of
frequencies, including at least one of assigning, reusing and borrowing at
least one of the
second set of frequencies when the second set of frequencies are at least
substantially
geographically distant from the second satellite spot beam.


68. The system of claim 67 wherein the first plurality of subareas are
substantially equal sized
and having a first size, and the second plurality of subareas are
substantially and having a second size.

69. The system of claim 68 wherein the first size and the second size are
approximately equal.

70. The system of claim 67 wherein the second set of frequencies are
substantially distant from
the second satellite spot beam when they are at least one of assigned, reused
and borrowed for use by
subscriber terminals positioned in those first plurality of subareas not
sharing a common boundary
with the second satellite spot beam.


71. The system of claim 67 wherein the first set of frequencies used by
subscriber terminals
positioned in the first central portion comprise at least one of those
frequency sets respectively
associated with one or more satellite spot beams directly adjacent to the
first satellite spot beam.


72. The system of claim 67 wherein at least one of assigning, reusing and
borrowing is based
on prioritization rules.


73. The system of claim 72 wherein the prioritization rules include dynamic
load and capacity
constraints of cells that frequencies are taken from.


74. The system of claim 67 wherein a subscriber terminal positioned within the
first central
portion can be assigned, reuse and/or borrow any of the respective set of
frequencies associated with
the at least one second satellite spot beam.


75. The system of claim 67 wherein a subscriber terminal positioned within the
first central
portion can be assigned, reuse and/or borrow use any of the respective set of
frequencies associated
with any spot beam directly adjacent the first satellite spot beam.




27

76. The system of claim 67 wherein a subscriber terminal positioned within a
subarea of the
first spot beam not sharing at least a portion of a common boundary with the
second satellite spot
beam can be assigned, reuse and/or borrow any of the second set of frequencies
associated with the
second satellite spot beam.


77. The system of claim 67 wherein the predetermined criteria is at least one
of load balancing
and received signal strength interference.


78. The system of claim 67 further comprising:

a second terrestrial base station positioned within the second satellite spot
beam and having at
least partially overlapping coverage with the first spot beam, for configuring
at least one
terrestrial cell therein, wherein the terrestrial cell has a fourth set of
frequencies
associated therewith; and

at least one of assigning, reusing and borrowing, by said second terrestrial
base station, at least
one of the first set of frequencies and the frequencies used in the second
central portion,
responsive to predetermined criteria associated with the fourth set of
frequencies for
establishing communication between the second subscriber unit positioned
within an area
of coverage of said second base station and at least one of the first
subscriber terminal
and other communications device, including at least one of assigning, reusing
and
borrowing at least one of the first set of frequencies when the first set of
frequencies are
at least substantially geographically distant from the second satellite spot
beam.


79. The system of claim 67 wherein the first central portion and the second
central portion
comprise approximately twenty five percent of the area covered by the first
satellite spot beam and the
second satellite spot beam, respectively.


80. The system of claim 67 wherein the first and second set of frequencies
comprise a plurality
of paired uplink and downlink frequencies.


81. The system of claim 80 wherein a downlink frequency of a frequency set is
used in a first
subarea of the first spot beam, and wherein a corresponding one of the uplink
frequencies is reused in
a second subarea of the first spot beam.



28

82. The system of claim 67 wherein the area of coverage of a spot beam
comprises an area
having a radius substantially equal to a distance from a center of the spot
beam having a substantially
maximum signal strength to a distance from the center of the spot beam where
the signal strength of
the spot beam is attenuated by approximately 3 dB.


83. The system of claim 67 wherein an area of coverage of at least one of a
spot beam and a
terrestrial cell comprises an area corresponding to a bit error rate in the
range of 10 -2 to 10 -3 for voice
and 10 -5 to 10 -6 for data.


84. The system of claim 67 wherein the number of subareas is equal to a number
of spot beams
comprising a cluster minus one.


85. A system for making a telephone call using a satellite-terrestrial
communications system
that at least one of assigns and reuses frequencies between a first satellite
spot beam and a second
satellite spot beam, comprising:

a subscriber terminal for dialing a telephone number to communicate with at
least a second
communications device;

a first terrestrial cell having said subscriber terminal positioned therein;

at least one satellite for configuring: a) a first satellite spot beam
associated with said first
terrestrial cell and having a first set of frequencies associated therewith,
the first satellite
spot beam comprising a first substantially central portion and a first
plurality of subareas,
each of the first plurality of subareas extending substantially from a
periphery of the first
substantially central portion to substantially near a circumference of the
first satellite spot
beam, and b) a second satellite spot beam having the second communications
device
positioned therein and a second set of frequencies associated therewith; and

means for establishing a connection between the subscriber terminal and at
least the second
communications device, by at least one of assigning, reusing and borrowing, by
the first
spot beam, at least one of the second set of frequencies, responsive to
predetermined
criteria including at least one of assigning, reusing and borrowing at least
one of the
second set of frequencies when the subscriber terminal is substantially
geographically
distant from the second satellite spot beam.


86. A system for use in at least one of assigning and reusing frequencies,
comprising:

at least a first satellite for: a) configuring a first communications area
having a first set of
frequencies associated therewith, the communications area comprising a first



29

substantially central portion and a first plurality of subareas, each of the
first plurality of
subareas extending substantially from a periphery of the first substantially
central portion
to substantially near a circumference of the first communications area, and
for b)
configuring a second communications area having a second set of frequencies
associated
therewith and comprising a second substantially central portion and a second
plurality of
subareas, each of the second plurality of subareas extending substantially
from a
periphery of the central portion to substantially near a circumference of the
second
communications area;

a terrestrial base station positioned within the first communications area and
having at least
partially overlapping coverage with the first communications area, that
configures at least
a third communications area within the first communications area, the third
communications area having a third set of frequencies associated therewith;
and

means for at least one of assigning, reusing and borrowing, by said
terrestrial base station, at
least one of a portion of the second set of frequencies and a portion of the
first set of
frequencies used in the first central portion for facilitating communications
between a
subscriber terminal positioned within the first communications area and a
second
communications device, and responsive to predetermined criteria associated
with the
third set of frequencies, including at least one of assigning, reusing and
borrowing at
least one of the second set of frequencies when the second set of frequencies
are at least
substantially geographically distant from the first satellite spot beam.


87. The system of claim 86 wherein the first plurality of subareas are
substantially equal sized
and having a first size and the second plurality of subareas are substantially
equal sized and having a
second size.


88. The system of claim 87 wherein the first size and the second size are
approximately equal.

89. The system of claim 86 wherein the second set of frequencies are
substantially distant from
the second communications area when they are at least one of assigned, reused
and borrowed for use
in those first plurality of subareas not sharing a common boundary with the
second communications
area.


90. The system of claim 86 wherein the first set of frequencies used in the
first central portion
comprise those frequency sets respectively associated with communication areas
external to and
directly adjacent to the first communications area.



30

91. The system of claim 86 wherein the assigning, reusing and borrowing is
based on
prioritization rules.


92. The system of claim 91 wherein the prioritization rules comprise dynamic
load and capacity
constraints of candidate cells that frequencies are being taken from.


93. The system of claim 86 wherein a user positioned within the first central
portion can be
assigned, reuse and/or borrow use any of the respective set of frequencies
associated with the second
communications area.


94. The system of claim 86 wherein when the subscriber terminal is positioned
within the first
central portion it can be assigned, reuse and/or borrow any of the respective
set of frequencies
associated with any communication areas adjacent the first communications
area.


95. The system of claim 86 wherein when the subscriber terminal is positioned
within a subarea
of the first communications area not sharing at least a portion of a common
boundary with the second
communications area it can be assigned, reuse and/or borrow any of the second
set of frequencies
associated with the second communications area.


96. The system of claim 86 wherein the predetermined criteria is at least one
of load balancing
and received signal strength interference.


97. The system of claim 86, further comprising:

a second terrestrial base station positioned within the second communications
area and having
at least partially overlapping coverage with the second communications area,
wherein the
second communications area comprises at least one terrestrial cell within the
second
communications area, and wherein said second terrestrial base station has a
fourth set of
frequencies associated therewith; and
at least one of assigning, reusing and borrowing, by said second terrestrial
base station, at least
one of the first set of frequencies and the frequencies used in the second
central portion,
responsive to predetermined criteria associated with the fourth set of
frequencies, for
establishing communication between a second subscriber unit positioned within
an area
covered by said second terrestrial base station and at least one of the first
subscriber unit



31

and the second communication device, including at least one of assigning,
reusing and
borrowing at least one of the first set of frequencies when the first set of
frequencies are
at least substantially geographically distant from the second terrestrial base
station.

98. The system of claim 86 wherein the first central portion and the second
central portion
comprise approximately twenty five percent of the area covered by the first
communications area and
the second communications area, respectively.


99. The system of claim 86 wherein the first and second set of frequencies
comprise a plurality
of paired uplink and downlink frequencies, wherein a downlink frequency of a
frequency set is used
in a first subarea of the first communications area, and wherein a
corresponding one of the uplink
frequencies is reused in a second subarea of the first communications area.


100. The system of claim 86 wherein the area of coverage of a communications
area comprises
an area having a radius substantially equal to a distance from a center of the
communications area
having a substantially maximum signal strength to a distance from the center
of the communications
area where the signal strength of the communications area is attenuated by
approximately 3 dB.


101. The system of claim 86 wherein an area of coverage of at least one of a
spot beam and a
terrestrial cell comprises an area corresponding to a bit error rate in the
range of 10 -2 to 10 -3 for voice
and 10 -5 to 10 -6 for data.


102. A system for at least one of assigning and reusing frequencies between a
plurality of
communication systems, comprising:

at least one satellite capable of: a) configuring a first satellite spot beam
having a first set of
frequencies associated therewith and comprising a first substantially central
portion and a
first plurality of subareas, each of the first plurality of subareas extending
substantially
from a periphery of the first substantially central portion to substantially
near a
circumference of the first satellite spot beam, and b) configuring a second
satellite spot
beam having a second set of frequencies associated therewith and comprising a
second
substantially central portion and a second plurality of subareas, each of the
second
plurality of subareas extending substantially from a periphery of the central
portion to
substantially near a circumference of the second satellite spot beam,

a terrestrial base station positioned within the first satellite spot beam and
having at least
partially overlapping coverage with the first spot beam, for configuring at
least one



32

terrestrial cell within the first satellite spot beam having a third set of
frequencies
associated therewith and having an area of coverage at least partially
overlapping with
the first satellite spot beam; and

means for at least one of assigning, reusing and borrowing, by the second
satellite spot beam, at
least one of a portion of the third set of frequencies responsive to
predetermined criteria,
including at least one of assigning, reusing and borrowing at least one of the
third set of
frequencies associated with the at least one terrestrial cell when the portion
is at least
substantially geographically distant from the second set of frequencies.


103. A system of at least one of assigning and reusing frequencies between a
plurality of
communication systems, comprising:

a first satellite capable of a) configuring a first satellite spot beam having
a first set of
frequencies associated therewith and comprising a first substantially central
portion and a
first plurality of subareas, each of the first plurality of subareas extending
substantially
from a periphery of the first substantially central portion to substantially
near a
circumference of the first satellite spot beam, and b) configuring a second
satellite spot
beam having a second set of frequencies associated therewith;

a terrestrial base station positioned within the first satellite spot beam and
having at least
partially overlapping coverage with the first spot beam, for configuring at
least one
terrestrial cell within the first satellite spot beam, the terrestrial cell
having a third set of
frequencies associated therewith and having an area of coverage at least
partially
overlapping with an area of coverage of the first satellite spot beam; and

means for at least one of assigning, reusing and borrowing, by the terrestrial
base station for use
in establishing communications between a first subscriber terminal positioned
within an
area of coverage of said terrestrial base station and at least one of a second
subscriber
terminal and communications device, at least one of a portion of the second
set of
frequencies and a portion of the first set of frequencies used in the first
central portion,
responsive to predetermined criteria associated with the third set of
frequencies,
including at least one of assigning, reusing and borrowing at least one of the
second set
of frequencies when the second set of frequencies are at least substantially
geographically distant from the first satellite spot beam.


104. The system of claim 103 wherein the first plurality of subareas are
substantially equal
sized.



33

105. The system of claim 103 wherein the second set of frequencies are
substantially distant
from the second satellite spot beam when they are at least one of assigned,
reused and borrowed for
use in those first plurality of subareas not sharing a common boundary with
the second satellite spot
beam.


106. The system of claim 103 wherein the first set of frequencies used in the
first central
portion comprise those frequency sets respectively associated with satellite
spot beams directly
adjacent to the first satellite spot beam.


107. The system of claim 103 wherein said step of assigning, reusing and
borrowing is based on
prioritization rules.


108. The system of claim 107 wherein the prioritization rules include dynamic
load and
capacity constraints of candidate cells that frequencies are being taken from.


109. The system of claim 103 wherein a subscriber terminal positioned within
the first central
portion can be assigned, reuse and/or borrow any of the respective set of
frequencies associated with
the second satellite spot beam.


110. The system of claim 103 wherein a subscriber terminal positioned within
the first central
portion can be assigned, reuse and/or borrow any of the respective set of
frequencies associated with
any spot beams adjacent the first satellite spot beam.


111. The system of claim 103 wherein a subscriber terminal positioned within a
subarea not
sharing at least a portion of a common boundary with the second satellite spot
beam can be assigned,
reuse and/or borrow any of the second set of frequencies associated with the
second satellite spot
beam.


112. The system of claim 103 wherein the predetermined criteria is at least
one of load
balancing and received signal strength interference.


113. The system of claim 103 further comprising:

a second terrestrial base station positioned within the second satellite spot
beam and having at
least partially overlapping coverage with the second spot beam, wherein the
second



34

satellite spot beam further comprises at least one terrestrial cell having a
fourth set of
frequencies associated therewith,

wherein said means facilitates at least one of assigning, reusing and
borrowing, by said second
terrestrial base station for use with a second subscriber terminal positioned
within an area
covered by said second terrestrial base station, at least one of the first set
of frequencies
and the frequencies used in the second central portion, responsive to
predetermined
criteria associated with the fourth set of frequencies for establishing
communication
between the second subscriber terminal and at least one of the first
subscriber terminal
and communications device, including at least one of assigning, reusing and
borrowing at
least one of the first set of frequencies when the first set of frequencies
are at least
substantially geographically distant from the second satellite spot beam.


114. The system of claim 103 wherein the first central portion comprises
approximately twenty
five percent of the area covered by the first satellite spot beam.


115. The system of claim 103 wherein the first and second set of frequencies
comprise a
plurality of paired uplink and downlink frequencies, wherein a downlink
frequency of a frequency set
is used in a first subarea of the first spot beam, and wherein a corresponding
one of the uplink
frequencies is reused in a second subarea of the first spot beam.


116. The system of claim 103 wherein an area of coverage of at least one of a
spot beam and a
terrestrial cell comprises an area corresponding to a bit error rate in the
range of 10 -2 to 10 -3 for voice
and 10 -5 to 10 -6 for data.


117. The system of claim 103 wherein the area of coverage of a spot beam
comprises an area
having a radius substantially equal to a distance from a center of the spot
beam having a substantially
maximum signal strength to a distance from the center of the spot beam where
the signal strength of
the spot beam is attenuated by approximately 3 dB.


118. A system of at least one of assigning and reusing frequencies between a
plurality of
communication systems, comprising:

a first satellite capable of: a) configuring a first satellite spot beam
having a first set of
frequencies associated therewith and comprising a first plurality of subareas,
each of the
first plurality of subareas extending from a substantially center area of the
first satellite
spot beam to substantially near a circumference of the first satellite spot
beam in a fan-



35

like manner thereby forming the first plurality of subareas, and b)
configuring a second
satellite spot beam having a second set of frequencies associated therewith;

a terrestrial base station positioned within the first satellite spot beam and
having at least
partially overlapping coverage with the first spot beam, for configuring a
terrestrial cell,
the terrestrial cell having a third set of frequencies associated therewith
and having an
area of coverage at least partially overlapping with an area of coverage
associated with
the first spot beam; and

means for at least one of assigning, reusing and borrowing, by said
terrestrial base station and
for use by a first subscriber terminal in communicating with at least one of a
second
subscriber terminal or communications device, at least one of a portion of the
second set
of frequencies and a portion of the first set of frequencies used in the first
central portion,
responsive to predetermined criteria associated with the third set of
frequencies,
including at least one of assigning, reusing and borrowing at least one of the
second set
of frequencies when the second set of frequencies are at least substantially
geographically distant from the first satellite spot beam.


119. The system of claim 118 wherein the first plurality of subareas are
substantially equal
sized.


120. The system of claim 118 wherein the second set of frequencies are
substantially distant
from the second satellite spot beam when they are at least one of assigned,
reused and borrowed for
use in those first plurality of subareas not sharing a common boundary with
the second satellite spot
beam.


121. The system of claim 118 wherein the assigning, reusing and borrowing is
based on
prioritization rules.


121. The system of claim 121 wherein the prioritization rules include dynamic
load and
capacity constraints of candidate cells that frequencies are being taken from.


123. The system of claim 118 wherein a subscriber terminal positioned within a
subarea not
sharing at least a portion of a common boundary with the second satellite spot
beam can be assigned,
reuse and/or borrow any of the second set of frequencies associated with the
second satellite spot
beam.



36

124. The system of claim 118 wherein the predetermined criteria is at least
one of load
balancing and received signal strength interference.

125. The system of claim 118 further comprising:

a second terrestrial base station positioned within the second satellite spot
beam and having at
least partially overlapping coverage with the second spot beam, and associated
with a
terrestrial cell having a fourth set of frequencies associated therewith; and

at least one of assigning, reusing and borrowing, by said second terrestrial
base station, at least
one of the first set of frequencies and the frequencies used in spot beams
adjacent to the
second spot beam, responsive to predetermined criteria associated with the
fourth set of
frequencies, for establishing communication between a second subscriber
terminal
positioned within the area of coverage of said second terrestrial base station
and at least
one of a subscriber terminal and communications device, including at least one
of
assigning, reusing and borrowing at least one of the first set of frequencies
when the first
set of frequencies are at least substantially geographically distant from the
second
satellite spot beam.


126. The system of claim 118 wherein the first and second frequencies comprise
a plurality of
paired uplink and downlink frequencies, wherein one of the frequency sets is
used in a first subarea of
the first spot beam, and wherein a corresponding one of the uplink frequencies
is reused in a second
subarea of the first spot beam.


127. The system of claim 118 wherein an area of coverage of at least one of a
spot beam and a
terrestrial cell comprises an area corresponding to a bit error rate in the
range of 10 -2 to 10 -3 for voice
and 10 -5 to 10 -6 for data.


128. The system of claim 118 wherein the area of coverage of a spot beam
comprises an area
having a radius substantially equal to a distance from a center of the spot
beam having a substantially
maximum signal strength to a distance from the center of the spot beam where
the signal strength of
the spot beam is attenuated by approximately 3 dB.


129. A system for at least one of assigning and reusing frequencies between
one or more
communication systems, comprising:

means for configuring: a) a first spot beam having a first set of frequencies
associated
therewith, the first spot beam comprising a first substantially central
portion and a first



37

plurality of subareas, each of the first plurality of subareas extending
substantially from a
periphery of the first substantially central portion to substantially near a
circumference of
the first satellite spot beam, and b) a second satellite spot beam having a
second set of
frequencies associated therewith, the second spot beam comprising a second
substantially
central portion and a second plurality of subareas, each of the second
plurality of
subareas extending substantially from a periphery of the second central
portion to
substantially near a circumference of the second satellite spot beam;

means positioned within the first satellite spot beam for configuring a
terrestrial cell having at
least partially overlapping coverage with the first spot beam, the terrestrial
cell having a
third set of frequencies associated therewith and an area coverage at least
partially
overlapping with an area of coverage associated with the first spot beam;

a first subscriber terminal positioned within the terrestrial base station
area of coverage; and
means for at least one of assigning, reusing and borrowing, by the terrestrial
base station and
for use by said first subscriber terminal in communicating with at least one
of a second
subscriber terminal and other communications device, at least one of a portion
of the
second set of frequencies and a portion of the first set of frequencies used
in the first
central portion, responsive to predetermined criteria associated with the
third set of
frequencies, including at least one of assigning, reusing and borrowing at
least one of the
second set of frequencies when the second set of frequencies are at least
substantially
geographically distant from the second satellite spot beam.


130. A system for making a telephone call using a satellite-terrestrial
communications system
that at least one of assigns and reuses frequencies between a first satellite
spot beam and a second
satellite spot beam, comprising:

a subscriber terminal for dialing a telephone number to communicate with at
least a second
communications device;

a first terrestrial cell having said subscriber terminal positioned therein;

means for configuring: a) a first satellite spot beam associated with said
first terrestrial cell,
having a first set of frequencies associated therewith, and having at least
partially
overlapping coverage with the first terrestrial cell, the first satellite spot
beam comprising
a first substantially central portion and a first plurality of subareas, each
of the first
plurality of subareas extending substantially from a periphery of the first
substantially
central portion to substantially near a circumference of said first satellite
spot beam, and
b) a second satellite spot beam having the second communications device
positioned
therein and a second set of frequencies associated therewith; and



38

means for establishing a connection between said subscriber terminal and at
least the second
communications device, by at least one of assigning, reusing and borrowing, by
the first
spot beam, at least one of the second set of frequencies, responsive to
predetermined
criteria including at least one of assigning, reusing and borrowing at least
one of the
second set of frequencies when the subscriber terminal is substantially
geographically
distant from the second satellite spot beam.


131. A system for use in at least one of assigning and reusing frequencies,
comprising:
means for configuring: a) a first communications area having a first set of
frequencies
associated therewith, the communications area comprising a first substantially
central
portion and a first plurality of subareas, each of the first plurality of
subareas extending
substantially from a periphery of the first substantially central portion to
substantially
near a circumference of the first communications area, and b) a second
communications
area having a second set of frequencies associated therewith and comprising a
second
substantially central portion and a second plurality of subareas, each of the
second
plurality of subareas extending substantially from a periphery of the central
portion to
substantially near a circumference of the second communications area;

means positioned within the first satellite spot beam for configuring at least
a third
communications area within the first communications area, the third
communications
area having a third set of frequencies associated therewith and having at
least partially
overlapping coverage with the first spot beam; and

means for at least one of assigning, reusing and borrowing, by said
terrestrial base station, at
least one of a portion of the second set of frequencies and a portion of the
first set of
frequencies used in the first central portion for facilitating communications
between a
subscriber terminal positioned within the first spot beam and a second
communications
device, and responsive to predetermined criteria associated with the third set
of
frequencies, including at least one of assigning, reusing and borrowing at
least one of the
second set of frequencies when the second set of frequencies are at least
substantially
geographically distant from the first satellite spot beam.


132. A system for at least one of assigning and reusing frequencies between a
plurality of
communication systems, comprising:

means for: a) configuring a first satellite spot beam having a first set of
frequencies associated
therewith and comprising a first substantially central portion and a first
plurality of
subareas, each of the first plurality of subareas extending substantially from
a periphery




39

of the first substantially central portion to substantially near a
circumference of the first
satellite spot beam, and b) configuring a second satellite spot beam having a
second set
of frequencies associated therewith and comprising a second substantially
central portion
and a second plurality of subareas, each of the second plurality of subareas
extending
substantially from a periphery of the central portion to substantially near a
circumference
of the second satellite spot beam;

means positioned within the first satellite spot beam for configuring at least
one terrestrial cell
within the first satellite spot beam having a third set of frequencies
associated therewith
and having an area of coverage at least partially overlapping with the first
satellite spot
beam; and

means for at least one of assigning, reusing and borrowing, by the second
satellite spot beam, at
least one of a portion of the third set of frequencies responsive to
predetermined criteria,
including at least one of assigning, reusing and borrowing at least one of the
third set of
frequencies associated with the at least one terrestrial cell when the portion
is at least
substantially geographically distant from the second set of frequencies.


133. A system of at least one of assigning and reusing frequencies between a
plurality of
communication systems, comprising:

means for: a) configuring a first satellite spot beam having a first set of
frequencies associated
therewith and comprising a first substantially central portion and a first
plurality of
subareas, each of the first plurality of subareas extending substantially from
a periphery
of the first substantially central portion to substantially near a
circumference of the first
satellite spot beam, and b) configuring a second satellite spot beam having a
second set
of frequencies associated therewith;

means positioned within the first satellite spot beam for configuring at least
one terrestrial cell
within the first satellite spot beam, the terrestrial cell having a third set
of frequencies
associated therewith and having an area of coverage at least partially
overlapping with an
area of coverage of the first satellite spot beam; and
means for at least one of assigning, reusing and borrowing, by the terrestrial
base station for use
in establishing communications between a first subscriber germinal positioned
within an
area of coverage of said terrestrial base station and at least one of a second
subscriber
terminal and communications device, at least one of a portion of the second
set of
frequencies and a portion of the first set of frequencies used in the first
central portion,
responsive to predetermined criteria associated with the third set of
frequencies,
including at least one of assigning, reusing and borrowing at least one of the
second set



40

of frequencies when the second set of frequencies are at least substantially
geographically distant from the first satellite spot beam.


134. A system of at least one of assigning and reusing frequencies between a
plurality of
communication systems, comprising:

means for: a) configuring a first satellite spot beam having a first set of
frequencies associated
therewith and comprising a first plurality of subareas, each of the first
plurality of
subareas extending from a substantially center area of the first satellite
spot beam to
substantially near a circumference of the first satellite spot beam in a fan-
like manner
thereby forming the first plurality of subareas, and b) configuring a second
satellite spot
beam having a second set of frequencies associated therewith;

means positioned within the first satellite spot beam for configuring a
terrestrial cell, the
terrestrial cell having a third set of frequencies associated therewith and
having an area of
coverage at least partially overlapping with an area of coverage associated
with the first
spot beam; and

means for at least one of assigning, reusing and borrowing, by said
terrestrial base station and
for use by a first subscriber terminal in communicating with at least one of a
second
subscriber terminal or communications device, at least one of a portion of the
second set
of frequencies and a portion of the first set of frequencies used in the first
central portion,
responsive to predetermined criteria associated with the third set of
frequencies,
including at least one of assigning, reusing and borrowing at least one of the
second set
of frequencies when the second set of frequencies are at least substantially
geographically distant from the first satellite spot beam.


135. A method of at least one of assigning and reusing frequencies between one
or more
communication systems, comprising the steps of:

configuring a first satellite spot beam having a first set of frequencies
associated therewith and
comprising a first substantially central portion;

configuring a second satellite spot beam having a second set of frequencies
associated
therewith and comprising a second substantially central portion

configuring at least one terrestrial cell within the first satellite spot beam
having a third set of
frequencies associated therewith and having at least partially overlapping
coverage with
the first spot beam; and

at least one of assigning, reusing and borrowing, by the terrestrial system,
at least one of a
portion of the second set of frequencies and a portion of the first set of
frequencies used



41

in the first central portion, responsive to predetermined criteria associated
with the third
set of frequencies, including at least one of assigning, reusing and borrowing
at least one
of the second set of frequencies when the second set of frequencies are at
least
substantially geographically distant from the first satellite spot beam.


136. The method of claim 135 wherein the second set of frequencies are
substantially distant
from the first satellite spot beam when they are used in subareas of the
second spot beam that do not
share a common boundary with the first satellite spot beam.


137. The method of claim 135 wherein the first set of frequencies used in the
first central
portion comprise at least one of those frequency sets respectively associated
with satellite spot beams
directly adjacent to the first satellite spot beam.


138. The method of claim 135 wherein said step of assigning, reusing and
borrowing is based
on prioritization rules.


139. The method of claim 138 wherein the prioritization rules include dynamic
load and
capacity constraints of cells that frequencies are taken from.


140. The method of claim 135 wherein a subscriber terminal positioned within
the first central
portion can be assigned, reuse and/or borrow use any of the respective set of
frequencies associated
with the at least one second satellite spot beam.


141. The method of claim 135 wherein a subscriber terminal positioned within
the first central
portion can be assigned, reuse and/or borrow use any of the respective set of
frequencies associated
with any spot beams adjacent the first satellite spot beam.


142. The method of claim 135 wherein the predetermined criteria is at least
one of load
balancing and received signal strength interference.


143. The method of claim 135 further comprising the steps of:

configuring a second terrestrial cell within the second satellite spot beam
having a fourth set of
frequencies associated therewith and having at least partially overlapping
coverage with
the second spot beam; and



42

at least one of assigning, reusing and borrowing, by the second terrestrial
cell, at least one of
the first set of frequencies and the frequencies used in the second central
portion,
responsive to predetermined criteria associated with the fourth set of
frequencies,
including at least one of assigning, reusing and borrowing at least one of the
first set of
frequencies when the first set of frequencies are at least substantially
geographically
distant from the second satellite spot beam.


144. The method of claim 135 wherein the first central portion and the second
central portion
comprise approximately twenty five percent of the area covered by the first
satellite spot beam and the
second satellite spot beam, respectively.


145. The method of claim 135 wherein the first set of frequencies and the
second set of
frequencies comprise a plurality of paired uplink and downlink frequencies,
wherein a downlink
frequency of a frequency set is used in the first spot beam, and wherein a
corresponding one of the
uplink frequencies is reused in the second spot beam.


146. The system of claim 136 wherein an area of coverage of at least one of a
spot beam and a
terrestrial cell comprises an area corresponding to a bit error rate in the
range of 10 -2 to 10 -3 for voice
and 10 -5 to 10 -6 for data.


147. The method of claim 135 wherein the area of coverage of a spot beam
comprises an area
having a radius substantially equal to a distance from a center of the spot
beam having a substantially
maximum signal strength to a distance from the center of the spot beam where
the signal strength of
the spot beam is attenuated by approximately 3dB.

Description

CA 02334447 2001-02-06
111223-122 PRO PATENT
1
COORDINATED SATELLITE-TERRESTRIAL
FREQUENCY REUSE
DESCRIPTION
BACKGROUND OF 'THE INVENTION
Field of the Invention
The present invention generally relates to frequency reuse and/or sharing
among satellite-terrestria communications systems and, more particularly, to a
satellite-terrestrial communications system and method of operation thereof
that
provides frequency reuse: and/or sharing between the respective portions of
the
satellite system and terrestrial underlay systems associated therewith, while
substantially reducing interference therebetween.
Background Description
In present satellite-terrestrial systems, there is a need to separately
allocate
at least a portion of the Frequency spectrum for the satellite , while
allocating a
separate portion for the terrestrial network. The present invention provides a
system and method for c;fficiently reusing and/or sharing the spectrum between
satellite and terrestrial base stations in a manner that facilitates efficient
and
optionally complete spectrum usage by both the satallite and terrestrial
networks,
while minimizing interference between the respective satellite and terrestrial
systems.


CA 02334447 2001-02-06
111223-122 PRO PATENT
2
SUMMARY OF THE INVENTION
It is a feature and .advantage of the present invention to provide a satellite-

terrestrial communications system and method of operation thereof that
facilitates
efficient spectrum usage and/or reuse.
It is another feature and advantage of the present invention provide a
satellite-terrestrial communications system and method of operation thereof'
that
minimizes interference beaween the satellite and terrestrial systems.
It is still another feature and advantage of the present invention to provide
a satellite-terrestrial communications system and method of operation thereof
that
enables at least a portion of the frequency spectrum of, for example, a
portion of
the frequencies associated with a first satellite spot beam to be utilized by
a
terrestrial system having overlapping coverage with a second satellite spot
beam.
The satellite-terrestrial communications system and method according to
the present invention enhances spectrum usage by allocating at least a portion
of
the spectrum of, for example, at least a first satellite spot beam to an
underlay
terrestrial system preferably associated with or having overlapping coverage
with,
for example, at least a second satellite spot beam. The satellite-terrestrial
communications system of the present invention also minimizes interference
between each of the respective satellite and terrestrial systems that reuse or
share a
portion of the spectrum. The system and method according to the present
invention will hereinafter be called the satellite-terrestrial frequency reuse
system
(STFRS). It should be understood that the STFRS can be deployed with all
satellite (e.g., low-Earth orbit (LEO), mid-Earth orbit (MEO), geosynchronous
orbit (GEO), etc.) and cellular or other terrestrial technologies as long as
the
frequency planning is maintained dynamically or substantially dynamically
(e.g.,
time division multiple access (TDMA), code division multiple access (CDl'riA),


CA 02334447 2001-02-06
111223-122 PRO PATENT
3
Global System for Mobile Communication (GSM), Time Division Duplex (TDD),
Frequency Hopping (FHIVIA), etc.).
Within any given satellite spot beam of the STFRS, the frequencies (e.g.,
Radio frequency channels) used in a first spot beam are preferably not used in
the
underlay terrestrial system associated with the first spot beam. For example,
an
area of coverage by a satellite system may comprise seven spot beams, with
each
spot beam having nine channels. Thus, the system would have sixty three
channels that can be allocated between the satellite and the respective
underlay
terrestrial systems. The satellite may use, for example, nine (9) of the
channels,
and the remaining fifty four (54) may therefore be allocated to the respective
underlay terrestrial systems associated with each respective spot beam. In
such a
system, the nine channels associated with, for example, a first spot beam are
preferably not utilized by the underlay terrestrial system associated with the
first
spot beam. The general concept is to efficiently allocate (e.g., based on
demand)
the total frequency band {e.g., sixty three channels) between the terrestrial
and
satellite systems within <~ach of the spot beams and each of the respective
terrestrial underlay systems associated therewith, while minimizing
interference
therebetween.
To accomplish this objective, the present invention provides both a
terrestrial frequency reuse plan and a satellite frequency reuse plan. FIG. 2
shows
one example of a satellii:e frequency reuse plan. As shown, there are seven
regions/cells, each of which represents a spot beam designated by fi, f2, f 3,
fa, fs, f6
and f7, respectively. Note that FIG. 2 does not show the terrestrial system
underlaying each of the respective spot beams which will include a plurality
of
terrestrial cell therein. 'lChe reuse scheme employed by the satellite is
generally
dependent on the satellite technology being used. The technology can, for
example, be GSM/TDMfA based, spread spectrum CDMA, and the like, where
there may be a single antenna that is making multiple spot beams, multiple
antennas, and the like.


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4
In any given spot lbeam, the channels allocated to the satellite within that
spot beam are used for satellite transmissions, whereas the terrestrial
transmissions within that spot beam may use all channels except those
allocated to
the satellite. For example;, with regard to FIG. 3a, a superscript T
represents a
terrestrial system, and the frequencies without a superscript T represent
satellite
systems. The terrestrial frequency sets (designated by ( f3, f4, f5~ fl ~ f6)T
~ etc.)
associated with the f7 spot beam use, in various combinations, fi, fz, fs, fa,
fs, and
f6. However, the channels used by spot beam f7 are preferably not used by the
underlay terrestrial systenn associated with the f7 satellite spot beam. In
this
manner, the different channels are preferably allocated among the various spot
beams and associated underlay terrestrial systems such that any interfere
between
them is minimized. To accomplish this, the STFRS according to the present
invention utilizes the inter-spot beam isolation (e.g., the isolation between
the
various spot beams). Thus, the terrestrial system associated with a particuh~r
spot
beam preferably uses the channels that are not utilized by the spot beam since
the
spot beam provides an isolation that can be utilized in reducing interference.
In
other words, the present invention takes the co-channel, co-beam and
"transfers" it
to co-channel, adj scent beam interference.
Refernng now to FIG. 3a, it is preferred that the distance between the
terrestrial frequencies and the satellite frequencies be maximized. It is
further
preferred that the interference between adjacent satellites/spot beams and
adjacent
cells be minimized. However, even when these objectives are accomplished, the
transmissions by the terrestrial networks) will generally, to a certain extent
and
depending on the local attenuation, be "heard" by the associated satellite. As
shown in FIG. 3a, frequency reuse planning must be carefully done along
adjacent
spot beam boundaries to ensure that interferences are minimized.
Consider FIG. 3a from a geographic perspective. As shown, New Fork
city falls within spot beam fl, Philadelphia falls within spot beam f7, and
Washington, D.C. falls within spot beam f4. In general, the channels
associated


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with one particular spot beam can be reassigned for satellite and/or
terrestrial
reuse in conjunction with any other spot beam. The channels within spot beam
f4,
for example, can also be used as a terrestrial frequency in, for example, spot
beam
f7. It is preferred that the f4 channels are used in five of the six cell
sites of f~. As
5 shown in FIG. 3a, it is also preferred, however, that the channels of spot
beam f4
not be used in the cell site of spot beam f7 that is contiguous with the f4
spot beam.
Any energy that is being generated by the f4 channels within the f7 spot
beam is attenuated by the; antenna pattern of the f7 spot beam satellite, so
that the
f4 terrestrial frequencies cased within spot beam f7 are not interfering with
the f7
spot beam satellite frequencies. Nor, in a preferred embodiment, will the f4
channels within the f7 spot beam interfere with the f4 spot beam since, as
previously discussed, it is preferred that the channels of spot beam f4 not be
used
in the cell site of spot beam f7 that is contiguous with the f4 spot beam. At
some
point the f4 terrestrial frequencies within the f7 spot beam will interfere
with the f4
spot beam satellite transmissions, but any potential interference can be
minimized
by managing the frequency reuse and the size of these networks.
The present invention thus provides a system and method for coordinating
a reuse plan between a satellite network and a terrestrial network using the
same
frequencies on an interference managed basis. In general, if one spot beam
(e.g.,
f7) gets too congested, it can borrow frequency spectrum from other spot beams
(e.g., f,, fi, f3, fa, fs ~d~or fs) that have available capacity. The present
invention
thus provides different ways of using the same frequencies between the
satellite,
which employs frequency reuse, and using that fact to allow one or more
satellite
channel sets to be selected for within a terrestrial network on a non-
interfering
basis with the satellite.
FIG. 3a also illu<.~trates how to maximize the frequency distance of the
terrestrial system. As shown, f7 represents 9 frequency channels. Therefore,
in
the embodiment shown in FIG. 3a, each spot beam cell will have 45 terrestrial
frequencies available. For example, consider spot beam cell A within f7. Since


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6
each of f2, fs, f4~ f5 and f6 has 9 frequencies, 45 terrestrial frequencies
are thus
available in cell A within the f7 spot beam cell. Similarly, 45 frequencies
are also
available within spot bean cells B, C, D, E and F. It should be understood
that
this is a single embodiment, and that the present invention generally works
regardless of haw many spot beams there are or how many channels there are per
satellite spot beam.
Thus, in each of tile seven satellite spot beams shown in FIG. 3a, the
possible terrestrial frequencies that can be used are all satellite spot beam
frequencies except the satellite spot beam associated with the spot beam under
consideration and those used by the spot beam closest to the particular cell
of the
spot beam under consideration. The system and method of the present invention
therefore maximizes the l:requency distance between the terrestrial and the
satellite frequencies.
The frequencies being assigned are thus preferably location dependent
upon where the spot beam hits. Thus, if spot beam f, has nine frequencies and
only three of the nine frequencies are needed for satellite transmission, the
remaining six frequencies can dynamically be reassigned to either a
terrestrial
system or to increase capacity in, for example, an adjacent or non-adjacent
satellite spot beam. The present invention thus provides a novel system and
method of using satellite channels within a given spot beam and allocating at
least
a portion of those channe:l(s) to one or more ground based terrestrial
networks
within one or more respective spot beams.
It should be understood that repeat patterns other than a seven cell repeat
pattern can be used. For example, a fourteen cell repeat pattern could provide
additional separation between the terrestrial networks and the satellite
networks.
The allocation of frequencies between the terrestrial network and the
satellite
network should be managed efficiently. For example, a large reuse repeat
pattern
on the satellite and a small repeat pattern terrestrial network may give rise
to
inefficient use of spectrum on the satellite (unless there is sufficient
excess


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7
spectrum), which could render the satellite capacity limited rather than power
limited.
In this regard, it will be realized that one technique that may be practiced
with the present invention is increasing the reuse cluster size. This will
generally
minimize the interference between the satellite and terrestrial systems. For
example, in a reuse pattern traditionally associated with GSM systems, a
pattern
of four cells with three sectors each is used. Thus the same frequency is
reused in
every fifth cell.. If instead, twenty-four channels, for example, are assigned
across
the cells, one site in eight has the same frequency, as opposed to one site in
four
having the same frequency as with the four cell three sector pattern. Thus,
the
number of instances where the same frequency exists has been halved, and the
energy density of an individual channel has also been reduced by half. In this
example, the interference between the satellite and terrestrial systems would
be
reduced by approximately 3dB vis-a-vis the traditional four cell three sector
reuse
pattern.
DETAILED DESCRIPTION OF A PREFERRED
EMBODIMENT OF THE INVENTION
Before explaining at least one embodiment of the invention in detail, it is
to be understood that the; invention is not limited in its application to the
details of
construction and to the ~urangements of the components set forth in the
following
description or illustrated in the drawings. The invention is capable of other
embodiments and of being practiced and earned out in various ways. Also, it is
to
be understood that the phraseology and terminology employed herein are for the
purpose of description and should not be regarded as limiting.
As such, those spilled in the art will appreciate that the conception, upon
which this disclosure is based, may readily be utilized as a basis for the
designing
of other structures, methods and systems for carrying out the several purposes
of


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8
the present invention. It i.s important, therefore, that the invention be
regarded as
including equivalent constructions to those described herein insofar as they
do not
depart from the spirit and scope of the present invention.
To better appreciate the novelty and advantages provided by the present
invention, a brief discussion of satellite terrestrial frequency reuse
management is
presented. It should be understood, however, that the techniques presented are
general, and are indepenele.nt of any specific values of parameters used to
illustrate
the concepts.
The capacity of a satellite network utilizing spot beams is directly
proportional to the number of times a cluster of spot beams is replicated. The
cluster size, N , chosen for the satellite system is seven (7). Other sizes
may
optionally be used. It is ~~ssumed that each spot beam has a frequency set
containing nine 200 k.Ilz channels ( f; _ ~q;,, , q;,z , q;.3 ~ - ~ ~ ~ 9a.9 ~
for ~ = Z . .. 7 ). Other
sets of frequencies may optionally be used. It is also assumed that there is a
spot
beam to adjacent spot beam average isolation of 8 dB. It should also be
understood that the satellite terrestrial frequency reuse can operate in
normal
mode or reversed mode, and that the techniques presented here are applicable
to
both normal mode operation and reverse mode operation. As such, further
reference to specific mode of operation will not be made. In the normal mode,
shown in FIG. la, the terrestrial forurard (Fl) and reverse(F2) bands are the
same
as the satellite network. However, in the reverse mode operation, shown in
FIG.
lb, the satellite forward lband is the same as the terrestrial reverse band,
and the
satellite reverse band is the same as the terrestrial forward band.
Co-Channel /Adjacent Beam Technique
Within each spot beam, the use of satellite frequency set by the terrestrial
network results in the worst case interference, called co-channel/co-beam
interference. To utilize the isolation rendered by the availability of the
spot
beams, satellite terrestria frequency reuse should preferably be implemented
on


CA 02334447 2001-02-06
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9
adjacent spot beams. The resulting co-channel/adjacent beam interference will
generally be approximate;ly reduced by the spot beam to adjacent spot beam
isolation factor. It should be noted, however, that in a cluster of, for
example,
seven spot beams, as shown in FIGS. 2 and 3, each spot beam has six adjacent
spot beams that can contribute to the interference received. The advantage of
co-
channel/adjacent beam technique over co-channel/co-beam technique lay with the
fact that not all spot beams have equal service demand. Consequently, the
distribution of interference between adjacent spot beams can reduce the
average
interference in a high service demand beam.
The STFR plan for the adjacent beam interference case is shown in FIG. 2.
In this configuration, each spot beam is assigned a set of frequencies that
will be
used exclusively by the satellite network ( f; ) and likewise the terrestrial
network
in each spot beam uses a set of frequency exclusive to the terrestrial network
~; )T .
The satellite frequencies used in the center spot beam is f, , and the
terrestrial
frequencies in this spot beam can include all other frequency sets
ff~ ~ .f2~ f3,~~~, fe ~= ~f~ )T . Note that in this configuration the entire
spectral
allocation is shared or substantially shared between the satellite network and
the
terrestrial network in each of the seven spot beams.
'Terrestrial Cluster Size Technique
Cross network interference occurs when an RF channel is utilized both in
the terrestrial network and in the satellite network, either in the co-beam
configuration or in the adjacent-beam configuration. The severity of such
interference depends on the power received by the competing network. In
particular, the terrestrial networks reuse an RF channel or channels many
times in
an area covered by a given satellite spot beam or beams. Each occurrence of
this
RF channel gives rise to increased co-channel interference for the satellite
network.
In the case of the: co-beam configuration, the co-channel interference can


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be approximated by N11, where M is the number of times an RF channel is reused
and 1 is the interference lpower of one source. For the adjacent-beam
configuration the co-channel interference from one adjacent beam can be
approximated by aMt , where a accounts for the fraction of power leaked from
5 the adjacent beam. Thus, in both co-beam and adjacent beam configuration,
the
co-channel interference is directly proportional to the number of times a
particular
frequency is reused terrestrially.
Increasing Cluster Size
10 By increasing the cluster size for the terrestrial network the reuse of a
particular frequency is reduced. To illustrate the point, consider a
terrestrial
network in the center spot beam in FIG. 4a. As shown, the terrestrial network
has
12 available RF channels for reuse with a cluster size of four and three
sectors per
cell site. In each terrestrial cluster, the skyward energy from one sector
will
interfere with all satellite co-channels in the adjacent spot beams (in the
same spot
beam for co-beam configuration). FIG. 4b shows a terrestrial network with 16
cell sites (48 sectors), each RF channel is repeated four times in this
network. In
this same 16 site network:, if twenty-four RF channels are used, for example,
in a
cluster of 8, then the number of co-channel sectors is reduced from 4 to 2. In
general, this type of txade;off between bandwidth and interference can be
employed
to reduce co-channel interference.
Terrestrial Frequency Plan Technique
In addition to increasing terrestrial cluster size within a satellite spot
beam
to decrease co-channel interference, careful frequency planning can help to
reduce
interference through may;imizing satellite-terrestrial frequency reuse
distance. To
demonstrate this concept., again consider a terrestrial network in the center
spot
beam in FIG. 2. Suppose that the terrestrial network has 45 available RF
channels
for reuse with a cluster size of 15. As shown in FIG. 2, any satellite
frequency sets


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11
that do not include f, can be used in the terrestrial network to provide
adjacent
beam isolation.
A random selection from the pool of 54 frequencies available for
terrestrial use may result in areas where the distance between the terrestrial
frequencies and satellite frequencies used in the adjacent spot beams is
minimum.
However, selective assignment of terrestrial frequencies to the immediate area
adjacent to each spot beam in accordance with the present invention can result
in
increased satellite-terrestrial frequency reuse distance. FIG. 3a shows a
terrestrial
frequency allocation that result in maximum terrestrial-satellite frequency
distance. As shown, the terrestrial network underlay in the center spot beam
has
been partitioned into six separate sections. In each section, the terrestrial
frequency sets have been selected in order to maximize the frequency reuse
distance from the satellite frequency sets in neighboring spot beams. For
example, in section A of the center spot beam, the spot beam with the largest
distance from this section has the assigned frequency set f, . The spot bearns
with
next largest distance have the assigned satellite frequency sets f, and j5 ,
and
finally the last set of the spot beams have the assigned frequency sets fz
anal fb .
In general, the terrestrial network within each spot beam must also be
sectioned in
the same way that has been done for the center spot beam as shown in FIG. 3a.
Satellite spot beams at the edge of the service area do not have the lull
complement of six neighbors. As such, the terrestrial network within the areas
covered by this type of spot beams will have slightly different configuration.
FIG.
3b shows the terrestrial network frequency plan for such a spot beam. The spot
beam with assigned satellite frequency of f, has only three adjacent spot
beam ( f, , f5 , fb ) . The spot beams with frequency assignment fz , f, , and
f, are
missing from the f, cluster. As a result, the fz , f3 , a.nd f, frequency sets
can be
assigned to all terrestrialL underlay partitions in f, spot beam. The
remaining
terrestrial frequency assignments for this spot beam follow the procedure
described above with the exception of section B. In section B, there are two


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12
choices for one frequency set assignment, fs and f, , either of these
frequency
sets can be assigned to thiis section. This is because both f, and fs are
equidistant
from section B.
~%requency Borrowing Technique
In highly populated areas where terrestrial coverage can present great
spectral efficiency over the satellite coverage, the terrestrial cell site
density will
be high. Accordingly, thf: interference generated in these cell sites will
also be
high. In such circumstances, it is advantageous to trade part of the satellite
frequency spectrum of thc: spot beam (and even part of adjacent spot beams) to
the
terrestrial network. Such a trade off results in lower co-channel interference
levels. As an example of a frequency borrowing technique, consider the example
discussed in the previous section where each of the terrestrial networks have
been
configured with 45 RF channels and the satellite network in the corresponding
spot beam has been configured with nine (9) RF channels. To reduce the
interference by increasing; the cluster size, three (3) RF channels from the
satellite
network can be reassigned to the terrestrial network resulking in 48 RF
channels
for reuse terrestrially and six (6) RF channels for the corresponding
satellite; spot
beam.
Use Of A,nd Prediction Of Terrain Clutter To
Protect They Satellite From Terrestrial Energy
Terrestrial units acre always going to be working in some sort of clutter.
For example, handsets, say, six feet above the ground generally must work
through buildings, trees, etc. The base stations themselves can be installed
in such
a manner as to provide as much isolation from the satellite as possible by,
for
example, putting antenn~~s on sides of buildings (e.g., away from direct line
of


CA 02334447 2001-02-06
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13
sight from the satellite).
This present invention provides a system and method that ensures that
potential attenuators are used to provide maximum separation between a
terrestrial
base station and a satellite. The present invention considers the
morphological
and/or topological characaeristics to increase the separation between the
satellite
and the terrestrial system.. This enables, for example, the capacity and
density of
terrestrial networks in urban areas to be increased without giving rise to
objectionable interference on the satellite or satellites.
The present invention utilizes shadow analysis (e.g., modeling tools) that,
as shown in FIG. 5, have information about not only the terrain in an area but
the
buildings, trees, etc. As shown in FIG. 6, a three dimensional picture of the
morphology in the area is thus provided. This information is used to do a
shadow
analysis between the satellite and any potential base station in the area so
that base
stations can be optimally located in areas that do not, for example, have a
line of
sight to the satellite. Base stations can thus be optimally located such that
they
preferably have no view or minimal view of the sky, and thus, no view or a
minimal view of the satellite. Energy is thus optimally directed to covering;
ground users within an area covered by the base station.
In accordance with the present invention, a standard system is provided
that enables standard measurements to be taken pertaining to how much
satellite
energy and/or how much satellite visibility there is in any particular
location. This
data can in turn be used in deciding upon base station location(s). Generally,
base
stations should be located where there is more shadowing, and where there is
minimal signal strength directed towards the satellite and therefore
interference.
The system and method quantifies the shadowing, where the more shadowing, the
better possible location for a terrestrial base station.
For example, goiing from the south side of a building to the north side of a
building (or vice-versa) can add a significant attenuation towards the
satellite
because these may be additional signal blockage. The present invention thus


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14
enhances spectral efficiency and interference protection, particularly within
a
combined satellite-terrestrial network.
The many features; and advantages of the invention are apparent from the
detailed specification, and thus, it is intended by the appended claims to
cover all
such features and advantages of the invention which fall within the true
spirit and
scope of the invention. Further, since numerous modifications and variations
will
readily occur to those skilled in the art, it is not desired to limit the
invention to
the exact construction and operation illustrated and described, and
accordingly, all
suitable modifications and equivalents may be resorted to, falling within the
scope
of the invention. While tlhe foregoing invention has been described in detail
by
way of illustration and example of preferred embodiments, numerous
modifications, substitutions, and alterations are possible without departing
i:rom
the scope of the invention.
20
30
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Representative Drawing