Optimized beamforming for satellite communication
First Claim
1. A method for communication between a satellite and a remote communication device, comprising:
- a. at the satellite;
i. receiving a signal transmitted from the remote communication device at M plurality of antenna elements of the satellite to produce M plurality of receive signals; and
ii. applying a set of fixed weights to the M plurality of receive signals to produce L plurality of weighted signals, where L is less than M;
iii. transmitting the L plurality of weighted signals on corresponding ones of L downlink channels to a ground-based station;
b. at the ground-based station;
i. receiving the L plurality of downlink channel signals;
ii. applying ground-based beamforming weights to the L plurality of downlink channel signals; and
iii. combining the L plurality of weighted downlink channel signals to produce a beamformed receive signal;
wherein for any position of the remote communication device with respect to the satellite the ground-based beamforming weights are set to values that maximize a signal-to-noise ratio of the beamformed receive signal, and the fixed weights are selected to maximize a minimum signal-to-noise ratio of the received beamformed signal with respect to position of a remote communication device.
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Abstract
A method for determining beamforming weights used onboard a satellite and ground-based beamforming weights used in a ground-based station as part of a satellite communication system. This beamforming method is a two-stage beamforming process that requires a reduced downlink bandwidth between the satellite and the ground-based station yet achieves optimal signal-to-noise ratio for bandwidth allocated for the downlink, values for the fixed onboard beamforming weights are computed to yield a maximum,
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Citations
20 Claims
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1. A method for communication between a satellite and a remote communication device, comprising:
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a. at the satellite;
i. receiving a signal transmitted from the remote communication device at M plurality of antenna elements of the satellite to produce M plurality of receive signals; and
ii. applying a set of fixed weights to the M plurality of receive signals to produce L plurality of weighted signals, where L is less than M;
iii. transmitting the L plurality of weighted signals on corresponding ones of L downlink channels to a ground-based station;
b. at the ground-based station;
i. receiving the L plurality of downlink channel signals;
ii. applying ground-based beamforming weights to the L plurality of downlink channel signals; and
iii. combining the L plurality of weighted downlink channel signals to produce a beamformed receive signal;
wherein for any position of the remote communication device with respect to the satellite the ground-based beamforming weights are set to values that maximize a signal-to-noise ratio of the beamformed receive signal, and the fixed weights are selected to maximize a minimum signal-to-noise ratio of the received beamformed signal with respect to position of a remote communication device. - View Dependent Claims (2, 3, 4)
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5. A method of determining weights to be used onboard a satellite for a signal transmitted from a communication device and received at each of a plurality of antenna elements, comprising:
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a. selecting initial values for onboard beamforming weights;
b. for each of a plurality of positions of a remote communication device in the field of view of the satellite;
i. applying the onboard beamforming weights to M signals derived from a signal received from the remote communication device at the M plurality of antenna elements of the satellite and combining the resulting signals to produce L downlink signals, where L is less than M;
ii. computing optimal ground-based beamforming weights for combining the L downlink signals;
iii. applying the optimal ground-based beamforming weights to the L downlink signals and combining the resulting signals to produce a beamformed output signal;
iv. computing a signal-to-noise ratio of the beamformed output signal;
c. determining the minimal signal-to-noise ratio for said plurality of positions; and
d. selecting values for said onboard beamforming weights to maximize the minimal signal-to-noise ratio of the beamformed output signal. - View Dependent Claims (6, 7, 8, 9, 10)
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11. A satellite communication method requiring reduced downlink bandwidth, comprising:
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a. receiving at M plurality of antennas of a satellite a signal transmitted from a remote communication device, to produce M plurality of receive signals each associated with detection of the signal transmitted by the remote communication device at a corresponding one of the M plurality of antennas;
b. applying a set of fixed beamforming weights to the M plurality of receive signals to produce L plurality of weighted signals, where L is less than M;
c. transmitting each of the L plurality of weighted signals on a corresponding one of L plurality of downlink channels to a ground-based station;
d. receiving at the ground-based station the L plurality of downlink channel signals from the satellite;
e. applying ground-based beamforming weights to the plurality of downlink channel signals; and
f. combining the plurality of weighted downlink channel signals to produce a beamformed receive signal. - View Dependent Claims (12, 13, 14, 15)
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16. A satellite communication system comprising:
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a. a satellite comprising;
i. an antenna array having M plurality of antenna elements each of which detects a signal transmitted from each of a plurality of remote communication devices to thereby produce M plurality of receive signals for each signal transmitted from a remote communication device;
ii. a signal processor unit that applies a set of fixed beamforming weights to the M plurality of receive signals to produce L plurality of weighted signals, where L is less than M; and
iii. a transmitter that transmits the L plurality of weighted signals each on a corresponding downlink channel; and
b. a ground-based station comprising;
i. a receiver unit that receives the L plurality of downlink signals for each of the plurality remote communication devices; and
ii. a signal processor unit that applies position-dependent beamforming weights to the L plurality of downlink signals and combines the resulting weighted downlink signals to produce a beamformed receive signal corresponding to the signal transmitted to the satellite from each of the plurality of remote communication devices, wherein the position-dependent beamforming weights are set to values that maximize a signal-to-noise ratio of the beamformed receive signal for any position of a remote communication device with respect to the satellite;
c. and wherein the signal processor unit of the satellite applies fixed beamforming weights that maximize a minimum signal-to-noise ratio of the received beamformed signal with respect to position of a remote communication device. - View Dependent Claims (17)
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18. In a satellite communication system comprising a satellite and a ground-based station, wherein the ground-based station receives L downlink signals from the satellite and applies position dependent beamforming weights to the L downlink signals to produce a beamformed receive signal corresponding to a signal transmitted to the satellite from a remote communication device, the satellite comprising:
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a. an antenna array having M plurality of antenna elements, and wherein each of the plurality of antenna elements detect a signal transmitted from each of a plurality of remote communication devices to thereby produce M plurality of receive signals for each signal received from a remote communication device;
b. a signal processing unit that applies a set of fixed beamforming weights to the M plurality of receive signals to produce L plurality of weighted signals associated with a signal received from each of the plurality of remote communication devices, where L is less than M; and
c. a transmitter that transmits the L plurality of weighted signals for each remote communication device each on a corresponding downlink channel to the ground-based station;
d. wherein the signal processor unit applies the fixed beamforming weights to the M plurality of receive signals so as to maximize a minimum signal-to-noise ratio of the beamformed receive signal with respect to a position of a remote communication device. - View Dependent Claims (19)
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20. In a satellite communication system comprising a satellite and a ground-based station, wherein the satellite has an antenna array of M antenna elements that detects a signal transmitted from a remote communication device to produce M plurality of receive signals and applies fixed beamforming weights to the M plurality of receive signals to produce L plurality of weighted signals that are sent as L plurality of downlink signals to the ground-base station, where L is less than M, and wherein the ground-based station comprises:
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a. a receiver unit that receives the L plurality of downlink signals; and
b. a signal processor unit that applies position-dependent beamforming weights to the L plurality of downlink signals associated with a signal received at the satellite from each of the plurality of remote communication devices, wherein the signal processing unit combines the weighted downlink signals to produce a beamformed receive signal for each of the plurality of remote communication devices, wherein the position-dependent beamforming weights are set to values that maximize a signal-to-noise ratio of the beamformed receive signal for any position of a remote communication device with respect to the satellite.
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Specification