Optimized beamforming for satellite communication

• US 7,728,766 B2
• Filed: 03/30/2006
• Issued: 06/01/2010
• Est. Priority Date: 03/30/2006
• Status: Active Grant

• Current Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Original Assignee: ITT Manufacturing Enterprises, Inc. (ITT, Inc.)
• Inventors: Draganov, Alexandr, Weinberg, Aaron
• Primary Examiner(s): Tarcza; Thomas H
• Assistant Examiner(s): Nguyen; Nga X
• Application Number:
  US11/392,827
• Publication Number:
  US 20070232227A1
• Time in Patent Office: 1,524 Days
• Field of Search: 342352-354, 455/12.1, 455/13.3, 455427-429, 455/12.01, 701/13
• US Class Current: 342/354
• CPC Class Codes: H04B 7/2041 Spot beam multiple access

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,

$\underset{A}{\max }\left(\underset{U}{\min }\frac{S}{N}{|}_{W=\stackrel{⋓}{W}}\right),$
where the maximum is computed over all possible fixed weights A represented by an L×M matrix, the minimum is computed over all possible positions of remote communication devices U, and the signal-to-noise ratio (S/N) is computed for the optimal set of ground-based beamforming weights W={hacek over (W)}.

Claims

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.

2. The method of claim 1, and further comprising computing values for said fixed weights using an algorithm for constrained multivariable optimization.

3. The method of claim 1 and further comprising computing values for the fixed weights that yield a maximum,

4. The method of claim 1, and further comprising selecting the number L of downlink channel to be used based on a tradeoff between the number of downlink channels and a bandwidth or signal-to-noise ratio required for the downlink channel signals.

5. A satellite communication system comprising:

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.

6. The satellite communication system of claim 5, wherein the signal processor unit of the satellite applies the fixed beamforming weights which are derived by computing a maximum,

7. 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:

a. an antenna array having M plurality of antenna elements, and wherein each of the plurality of antenna elements detect detects 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.

8. The satellite of claim 7, wherein the signal processing unit of the satellite applies the fixed beamforming weights which are derived by computing a maximum,

9. 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:

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.