Lens Observation Using Low Earth Orbit Repeaters

Abstract

The present invention describes a method, system, and device for communication operations. A first satellite may be in a first orbit, and a set of second satellites may be in a second orbit below the first orbit. The second satellites may detect signal components of signals originating from a geographical area and relay the corresponding signal components to the first satellite. A beamformer coupled to the first satellite may form a beam associated with the geographical area. The beamformer may also obtain a beam signal based on the corresponding signal components and a return channel, where the return channel includes at least a channel component between the geographical area and the set of second satellites.

Description

BACKGROUND OF THE DISCLOSURE

[0001] The following generally relates to communications and more specifically to signal detection.

[0002] An antenna array at a satellite in a geostationary orbit may illuminate a geographical area associated with the coverage area of the satellite. In some examples, the satellite may be used to support communication between an access node terminal and a user terminal in the coverage area. The satellite may also be used to detect signals transmitted within the coverage area of the satellite. In some examples, the detection resolution of the satellite may be limited, for example, due to the distance of the satellite from the target geographical area. For example, the satellite may not be able to detect signals transmitted or emitted within the geographical area at a low power level or signals that are not intentionally directed to the satellite. SUMMARY OF THE DISCLOSURE

[0003] The techniques relate to improved methods, systems, devices, and apparatus for supporting lensing using a low Earth orbit repeater. A first satellite may be in a first orbit, and a set of second satellites may be in a second orbit below the first orbit. The second satellites may detect signal components of signals originating from a geographical area within the coverage area of the first satellite. The second satellites may relay the respective signal components to the first satellite. A beamformer coupled to the first satellite may form a beam associated with the geographical area. The beamformer may also obtain a beam signal based on the respective signal components forming the beam and a return channel. The return channel may include at least the channel between the geographical area and the set of second satellites. BRIEF DESCRIPTION OF THE DRAWINGS

[0004] Figure 1A A schematic diagram of a communication system supporting lensing using a low Earth orbit repeater according to an example disclosed herein is shown.

[0005] Figure 1B Components of a satellite supporting lensing using a low Earth orbit repeater according to an example disclosed herein are shown.

[0006] Figure 2 An example of a coverage map supporting lensing using a low Earth orbit repeater according to an example disclosed herein is shown.

[0007] Figure 3 An example of a set of exemplary operations supporting lensing using a low Earth orbit repeater according to an example disclosed herein is shown.

[0008] Figure 4 An example of a constellation map supporting lensing using a low Earth orbit repeater according to an example disclosed herein is shown.

[0009] Figure 5A block diagram of a signal analyzer that supports lens observations using a low Earth orbit repeater, according to an example disclosed herein, is shown.

[0010] Figure 6 A schematic diagram of a communication device that supports lens observations using a low Earth orbit repeater, according to an example disclosed herein, is shown.

[0011] Figure 7 A flowchart is shown that depicts a method that supports lens observations using a low Earth orbit repeater, according to an example disclosed herein. Detailed Description

[0012] A satellite communication system can include satellites in geostationary orbit (GEO), which can be referred to as GEO satellites; and satellites in non-GEO Earth orbits, which can be referred to as non-GEO satellites. In some examples, the altitude of non-GEO is lower than the altitude of GEO. Some examples of non-GEO satellites include satellites in medium Earth orbit (MEO), which can be referred to as MEO satellites; and satellites in low Earth orbit (LEO), which can be referred to as LEO satellites. Satellites (e.g., GEO, MEO, or LEO satellites) can be used to detect signals transmitted from fixed or mobile sources on land, water, or in the air. In some examples, satellite network operators can use the detected signals to determine whether known or unknown transmitters are in a geographic area.

[0013] GEO satellites can be used to detect known and unknown signal transmitters in a geographic area. In some examples, the resolution of a GEO satellite associated with surveying a particular geographic area can be limited based on the size of the antenna array at the GEO satellite. Thus, for a GEO satellite, the 3dB boundary of the beam used to survey a geographic area of interest may be too large relative to the boundary of the geographic area of interest.

[0014] In accordance with various aspects described herein, multiple non-GEO satellites can be used to survey large geographic areas with increased resolution, e.g., based on multiple non-GEO satellites having a larger aperture than a single satellite. In some examples, a relay link can be established between a first satellite (e.g., a GEO satellite) in a first orbit (e.g., GEO) and one or more second satellites (e.g., non-GEO satellites) in one or more second orbits (e.g., one or more non-GEO). Using one or more second satellites as relay satellites to the first satellite can allow the second satellites to have a relatively low complexity (e.g., lower cost, smaller size, etc.) compared to a full-featured satellite having a high-power transponder and a high-gain tracking antenna system to transmit signals directly to a ground station. Each of the one or more second satellites can have one or more antennas illuminated by at least a portion of one or more geographic areas and can each detect signal components of one or more signals transmitted in the one or more geographic areas. Each of the one or more second satellites can relay the respective signal components of the one or more signals to the first satellite. In some examples, when using ground-based beamforming, the first satellite can transmit a signal component or a representation of a signal component in the one or more signals to a ground system. In some examples, the ground system can determine beamforming weights and apply them to the one or more signals received from the first satellite to obtain one or more beam signals corresponding to the signals detected in the one or more geographic areas.

[0015] In other examples, when using satellite-carrier beamforming, the first satellite can process the signal components, thereby determining beamforming weights and applying them to the signal components to obtain one or more beam signals corresponding to the signals detected from the one or more geographic areas. In this case, the first satellite can transmit a representation of the one or more beam signals to the ground system. By using the signal components detected at the one or more second satellites, post-processing can be performed such that the processing system can focus on the one or more geographic areas with enhanced sensitivity, effectively increasing the detection resolution of the first satellite.

[0016] In some examples, in addition to the respective signal components received from one or more second satellites, a first satellite may detect an additional signal component of one or more signals in one or more geographic regions, for example, via a direct path. In such a case, the second satellite may effectively increase the aperture of the first satellite. In some examples, the first satellite may transmit an additional signal component of one or more signals, or a representation of the detected additional signal component of one or more signals, to a ground system. The ground system may use the additional signal component to obtain a representation of one or more signals detected in one or more geographic regions. In other examples, the first satellite may use the additional signal component to obtain a representation of one or more signals. By supplementing the direct signal components received at the first satellite with the signal components received at one or more second satellites, the quality of the signals detected by the first satellite may be improved (e.g., the signal strength may be increased) as compared to the case of detecting signals using only the direct signal components.

[0017] Aspects of the present disclosure are first described in the context of a satellite communication system. Specific examples of coverage maps, process flows, and constellation diagrams are then described. Aspects of the present disclosure are further illustrated by means of apparatus diagrams and flowcharts related to lens observations using low Earth orbit repeaters and are described with reference to these diagrams.

[0018] Figure 1A A schematic diagram of a communication system supporting lens observations using a low Earth orbit repeater according to an example as disclosed herein is shown. The satellite communication system 100 may include a satellite network that includes a first satellite 105 and a second satellite 115. The satellite communication system 100 may also include a ground system 130 that includes one or more gateways 135. One or more gateways 135 may include a beamformer 155 (or be otherwise coupled thereto). In some examples, the beamformer 155 may be included in a ground station processor 153. The ground station processor 153 may use the beamformer 155 to determine beam coefficients. The ground station processor 153 may also be configured to demodulate (and in some examples, decode) the beam signals generated by the beamformer 155.

[0019] A satellite (e.g., the first satellite 105 or the second satellite 115) may be configured to support wireless communication between one or more access node terminals (e.g., in the terrestrial system 130) and user terminals located in a coverage area (e.g., the coverage area 150). The satellite may also be configured to detect signals transmitted within the coverage area 150. In some examples, the satellite may include an antenna assembly having one or more antenna feed elements. Each of these antenna feed elements may also include (or otherwise be coupled to) a radio frequency (RF) signal transducer, a low noise amplifier (LNA), or a power amplifier (PA), and may be coupled to one or more transponders in the satellite.

[0020] In some examples, some or all of the antenna feed elements at the satellite may be arranged to form an array of constitutive receive feed elements and / or transmit feed elements that cooperate to implement various examples of beamforming (such as ground-based beamforming (GBBF), on-board beamforming (OBBF), end-to-end (E2E) beamforming, or other types of beamforming). For OBBF, the satellite may include N 1 transmitters, and an N 1 xK 1 beam weight matrix may be used to generate K 1 user beams. Similarly, for GBBF, the satellite may include L 1 transmitters, and receive L 1 signals (e.g., frequency division multiplexed) corresponding to the respective transmitters in the satellite from one or more access node terminals. One or more access node terminals may apply an L 1 xK 1 beam weight matrix to generate K 1 user beams. For E2E beamforming, the satellite may include L 1 transponders. The L 1 transponders may be used to receive signals from M access node terminals, where the received signals may be weighted (e.g., each of the K 1 beam signals for a respective group of one or more access node terminals is weighted) before transmission by the access node terminals to support beamforming for K 1 user beams. It should be noted that this example describes the forward link, and a similar arrangement may be made for the return link.

[0021] Satellites can be launched into different orbits, GEO or non-GEO orbits. Satellites in GEO can be referred to as GEO satellites. Non-GEO orbits can include MEO, LEO, equatorial low earth orbit (ELEO), etc. Satellites in MEO can be referred to as MEO satellites, satellites in LEO can be referred to as LEO satellites, and so on. GEO satellites can orbit the earth at a speed that matches the earth's rotation speed, and thus can remain in a single position relative to a point on the earth. LEO satellites can orbit the earth at a speed that exceeds the earth's rotation speed (e.g., relative to the ground), and thus the position of the satellite relative to a point on the earth can change as the satellite travels in LEO. LEO satellites can be launched at a low inclination (e.g., ELEO) or a high inclination (e.g., polar orbit) to provide different types of coverage and revisit times for a given region of the earth. MEO satellites can also orbit the earth at a speed that exceeds the earth's rotation speed, but can be at a higher altitude than LEO satellites. HEO satellites can orbit the earth in an elliptical pattern, in which the satellite moves closer to and farther from the earth throughout the HEO.

[0022] In some examples, GEO satellites may be more expensive and architecturally more complex than non-GEO satellites (e.g., may include more repeaters, antenna elements, transponders, etc.). Despite the increased complexity of GEO satellites, a network of non-GEO satellites may be able to provide service and monitor the earth more granularly than GEO satellites (e.g., based on a larger number and being closer to the earth). In some examples, GEO satellites and non-GEO satellites operate independently of each other. In some examples, the first satellite 105 can be a GEO satellite. The second satellite 115 can include a LEO satellite, a MEO satellite, or a combination thereof.

[0023] In some examples, a satellite network can be used to monitor at least a portion of the earth to obtain signals transmitted from known and unknown transmitters. For example, the satellite network can use the first satellite 105 to detect signals originating from a geographical region (e.g., a geographical region surrounded by the coverage area 150). In some examples, the first satellite 105 can transmit the detected signal energy to a ground system 130 (e.g., to one or more gateways 135), and the ground system processes (e.g., determines beamforming coefficients and applies them to) the detected signal energy, such as when using ground-based beamforming, to obtain one or more signals. In other examples, the first satellite 105 can process (e.g., determine beamforming coefficients and apply them to) the detected signal energy, such as when using satellite-carrier beamforming, and transmit one or more signals to the ground system 130.

[0024] GEO satellites can be used to detect known and unknown signal transmitters in a geographical area. In some examples, the resolution of a GEO satellite associated with surveying a particular geographical area can be limited based on the size of the antenna array at the GEO satellite and the distance of the GEO satellite from the point of interest. Thus, for a GEO satellite, the 3dB boundary of the beam used to survey the geographical area of interest may be too large relative to the boundary of the geographical area of interest.

[0025] In accordance with various aspects described herein, multiple non-GEO satellites can be used to survey a large geographical area with increased resolution, e.g., based on multiple non-GEO satellites having a larger aperture than a single satellite (e.g., GEO, MEO, or LEO satellite). In some examples, a relay link can be established between a first satellite 105 (e.g., a GEO satellite) in a first orbit (e.g., GEO) and one or more second satellites 115 (e.g., non-GEO satellites) in one or more second orbits (e.g., one or more non-GEO). Each of the one or more second satellites 115 can have one or more antennas that illuminate at least a portion of one or more geographical areas 140 and can each detect signal components 125 of one or more signals transmitted in the one or more geographical areas. In accordance with various aspects described herein, the one or more antennas of the second satellite 115 are described as being illuminated (rather than illuminating) by a portion of the one or more geographical areas 140. Notably, these terms can be used interchangeably to describe that the one or more antennas of the second satellite 115 can be used to transmit signals to or detect signals from the one or more geographical areas 140.

[0026] Each of the one or more second satellites 115 can relay the respective signal components 125 of the one or more signals to the first satellite 105. In some examples, when using ground-based beamforming, the first satellite 105 can transmit a signal component or a representation of a signal component in the one or more signals to a ground system 130. In some examples, the ground system 130 can determine beamforming weights and apply them to the one or more signals received from the first satellite 105 to obtain one or more beam signals corresponding to the one or more signals detected in the one or more geographical areas 140.

[0027] In other examples, when using satellite beamforming, the first satellite 105 may process the relay signal components 110 to determine beamforming weights and apply them to the signal components to obtain one or more beam signals corresponding to one or more signals. In this case, the first satellite 105 may transmit a representation of the one or more beam signals to the ground system 130. By using the signal components detected at one or more second satellites 115, post-processing may be performed such that the processing system can focus on one or more geographical regions 140 with enhanced sensitivity, thereby effectively increasing the detection resolution of the first satellite 105.

[0028] In some examples, in addition to the respective signal components relayed from one or more second satellites 115, the first satellite 105 may detect additional signal components of one or more signals in one or more geographical regions (e.g., direct signal component 120), for example, via a direct path. In this case, the second satellites may effectively increase the aperture of the first satellite. In some examples, the first satellite 105 may use the additional signal components to obtain a representation of one or more signals. In other examples, the first satellite 105 may transmit the additional signal components of one or more signals, or a representation of the detected additional signal components of one or more signals, to the ground system 130. The ground system 130 may use the additional signal components to obtain a representation of the one or more signals detected in one or more geographical regions 140. By supplementing the direct signal component 120 received at the first satellite 105 with the signal components received at one or more second satellites 115, the quality of the signals detected by the first satellite 105 (e.g., the signal strength may be increased) may be improved compared to the case of detecting signals using only the direct signal component 120.

[0029] When RF signal energy is radiated from a transmitter (e.g., a transmitter or a thermal energy transmitter), each second satellite 115 detects components of the signal (e.g., having corresponding phase shifts or amplitude variations due to different channels between the transmitter and the respective second satellite 115). When used in conjunction with the first satellite 105 to detect signal components in a geographical region 140 corresponding to the location of a transmitter (e.g., transmitter 145), the second satellite 115 may be referred to as a relay satellite 115. The geographical region 140 may be located within the coverage area 150 of the first satellite 105. For example, the first relay satellite 115-1 may receive a first detected signal component 125-1 based on a signal transmitted from a transmitter 145 within the first geographical region 140-1. In some examples, the first relay satellite 115-1 receives the first detected signal component 125-1 via a first return channel (which may be referred to as ) and the second relay satellite 115-2 receives the first detected signal component 125-1 via a second return channel (which may be referred to as ) Receive the second detected signal component, and so on. In some examples, the return channel between the relay satellite 115 and the first geographical area 140-1 may be included in a combined return channel matrix (which may be referred to as A1 RTN ) In. The relay satellite 115 may similarly receive signal components detected from other geographical areas 140 (including the Pth geographical area 140-P).

[0030] In some examples, the return channels between the relay satellite 115 and a group of geographical areas 140 may be included in the combined return channel matrix A1 RTN In. Matrix A1 RTN May include the number of rows based on the number of repeaters included in the relay satellite 115 and the number of relay satellites 115, and the number of columns based on the number of geographical areas 140 monitored by the relay satellite 115. For example, if S relay satellites 115 include Q repeaters and are used to monitor P geographical areas 140, then A1 RTN The matrix may have Q·S rows and P columns.

[0031] The relay satellite 115 may relay the detected signal component 125 (or a representation of the detected signal component) to the first satellite 105. In some examples, relaying the detected signal component 125 involves frequency-shifting the detected signal component, amplifying the detected signal component, or both, before relaying the detected signal component to the first satellite 105.

[0032] Figure 1B Illustrates components of a satellite that supports lens observations using low Earth orbit repeaters according to examples disclosed herein. As Figure 1B Shown, the relay satellite 115 may include one or more repeaters 160 that are configured to amplify and / or frequency-shift a detected signal before relaying the detected signal to the first satellite 105. The repeater 160 may be a non-processing repeater. That is, the repeater 160 may perform operations of interpreting or reformulating data within the signal waveform. For example, before relaying the detected signal to the first satellite 105, the repeater 160 may not digitize, demodulate, decode, apply beamforming weights, or reformulate the detected signal. The repeater 160 may include a frequency converter 165, an amplifier 170, or both. The frequency converter 165 may be configured to shift the frequency of the detected signal (e.g., by mixing the detected signal with another frequency). In some examples, the frequency converters 165 in different relay satellites 115 may be configured to apply different frequency shifts to the detected signal. The amplifier 170 may be configured to amplify the detected signal before relaying the amplified signal to the first satellite 105.

[0033] In some examples, the first relay satellite 115-1 may send a first relay signal component 110-1 (which may correspond to an amplified version of the first detection signal component 125-1) to the first satellite 105. In some examples, the first relay satellite 115-1 transmits the first relay signal component 110-1 to the first satellite 105 via a first return channel (which may be referred to as ), the second relay satellite 115-2 transmits a second transmission signal component via a second return channel (which may be referred to as ), and so on. The return channel between the relay satellite 115 and the first satellite 105 may be included in a second combined return channel matrix (which may be referred to as A2 RTN ). The relay satellite 115 may similarly transmit signal components detected from other geographical regions 140 (including the P-th geographical region 140-P) via the second combined return channel A2 RTN .

[0034] Matrix A2 RTN may include the number of rows based on the number of uplink / downlink transponder paths at the first satellite 105, and the number of columns based on the number of relay satellites 115 and the number of transponders included in the relay satellites 115. For example, if the first satellite 105 includes L uplink / downlink transponder paths and there are S relay satellites 115 each having Q transponders, then the A2 RTN matrix may have L rows and Q·S columns.

[0035] Therefore, the return channel between the geographical region 140 and the first satellite 105 may be a composite return channel, which includes multiple components: a first channel component between the relay satellite 115 and the geographical region 140 (which may be represented by A1 RTN ) and a second channel component between the relay satellite 115 and the first satellite 105 (which may be represented by A2 RTN ). In some examples, the composite return channel between the geographical region 140 and the first satellite 105 may be represented by the A2 RTN A1 RTN matrix. In some examples, if the first satellite 105 includes L uplink / downlink transponder paths and P geographical regions 140 are monitored, then the A2 RTN A1 RTN matrix may have L rows and P columns.

[0036] In some examples, the first satellite 105 may receive direct signal components from one or more geographical regions 140. For example, the first satellite 105 may receive via a direct return channel between the first satellite 105 and the first geographical region 140-1 (which may be denoted as A TG)Receives the direct signal component 120 from the transmitter 145. In some examples, the return channel between the geographical area 140, the relay satellite 115, and the first satellite 105 can be combined with the direct return channel to form a composite return channel matrix (which can be represented as A RTN ), where matrix A RTN can include the number of rows based on the number of uplink / downlink transponder paths included in the first satellite 105, and the number of columns based on the number of geographical areas 140 monitored by the relay satellite 115. For example, if the first satellite 105 includes L uplink / downlink transponder paths and is used to monitor P geographical areas 140, then A RTN can have L rows and P columns.

[0037] Similarly, the full return channel between the geographical area 140 and the ground system 130 can be a composite return channel including multiple components. In some examples, the full return channel includes the channel component between the geographical area 140 and the first satellite 105 (which can be represented by A2 RTN A1 RTN or A RTN ); the channel component within the first satellite 105 between the uplink transponder and the downlink transponder on the first satellite 105 (which can be represented by the matrix E RTN ); and the channel component between the first satellite 105 and the ground system 130 (which can be represented by the matrix C RTN ).

[0038] As Figure 1B shown, the first satellite 105 can include one or more transponders 175, which are used to amplify and / or frequency-shift the detected signal before transmitting the received signal to the first satellite 105. The transponder 175 can include a frequency converter 165, an amplifier 170, or both. The frequency converter 180 can be configured to shift the frequency of the received signal (e.g., by mixing the detected signal with another frequency). The amplifier 185 can be configured to amplify the received signal before transmitting the amplified signal to the ground system 130. In some examples, the transponder 175 can be coupled to on-board processing components, such as a beamformer 190, a demodulator, a decoder, a reformatting component, or a combination thereof. In some examples, the on-board processing components can be included in an on-board processor 187. In some examples, when the beamformer 190 is included in the first satellite 105, the ground system 130 may not use the beamformer 155 to process the signals received from the first satellite 105.

[0039] In some examples, the channel component within the first satellite 105 is based on the paths through the transponders in the first satellite 105, where the matrix E RTNmay include the number of rows and columns based on the number of transponders included in the first satellite 105. For example, if the first satellite 105 includes L transponders, then E RTN the matrix may include L rows and L columns.

[0040] In addition, the channel components between the first satellite 105 and the ground system 130 (represented by the C RTN matrix) may be based on the number of ground stations included in the ground system 130 and the number of repeaters included in the first satellite 105. For example, if the ground system includes M ground stations (e.g., gateways) and the first satellite 105 includes L uplink / downlink transponder paths, then C RTN the matrix may include M rows and L columns.

[0041] In some examples, the full return channel between the geographical area 140 and the ground system 130 may be represented by the matrix H RTN where H RTN = C RTN E RTN A2 RTN A1 RTN . In some examples, if the ground system 130 includes M ground stations and P geographical areas 140 are monitored, then the H RTN matrix may have M rows and P columns.

[0042] In some examples, the ground system 130 may estimate the full return channel H RTN based on signals received from known transmitters located within the coverage area 150. The ground system 130 may use the signals received from the known transmitters to determine the return channels associated with the received signals and may interpolate the determined return channels to estimate the return channel between the geographical area 140 and the ground system 130. In some examples, the ground system 130 may use the received signals to estimate a portion of the full return channel components. For example, the ground system 130 may use the signals to estimate the channel components associated with A1 RTN where the other channel components may be estimated based on reference signals transmitted between devices supporting channel estimation.

[0043] The ground system 130 may use the estimated channel components to determine the return covariance (which may be represented by the matrix R RTN ). In some examples, the ground system may use the estimated channel components to determine the return covariance between signals received from different geographical areas 140 at M different ground stations, where where is the noise term associated with the downlink (which may also be referred to as the forward link); is the noise term associated with the uplink (which may also be referred to as the reverse link); and Im is the MxM identity matrix. In some examples, the returned covariance may also include the covariance caused by interfering user traffic (e.g., for J interferers). In such cases, where J RTN can be the channel between the interferer and the terrestrial system. R RTN and R’ RTN matrices can both have M rows and M columns.

[0044] The terrestrial system 130 can use the estimated full return channel and the estimated return covariance to determine the beamforming coefficients to be applied to the signals received through the full return channel. In some examples, the beamforming coefficients are represented by the matrix B RTN where B RTN =(R RTN -1 H RTN ) H . The matrix B RTN can include the number of rows based on the number of monitored geographical regions 140 and the number of columns based on the number of ground stations in the terrestrial system 130. For example, for P geographical regions and M ground stations, the matrix B RTN can include P rows and M columns. Thus, the beamformed channel between the terrestrial system 130 and one or more geographical regions 140 can be represented as H RTN-BF where H RTN-BF =B RTN H RTN =B RTN C RTN E RTN A RTN .

[0045] In some examples, the first satellite 105 can apply the similarly determined beamforming coefficients to the signals received from the relay satellite 115 instead of applying the beamforming coefficients to the signals received at the terrestrial system 130. In such examples, the first satellite 105 can transmit a composite signal to the terrestrial system 130, the composite signal including a representation of the signals detected in each monitored geographical region 140. When beamforming is performed at the first satellite 105, the C RTN matrix can be the identity matrix (e.g., MxL identity matrix, where M can be equal to 1).

[0046] In some examples, the relay satellite 115 may transmit the detected signal components directly to the ground system 130 instead of transmitting the signal components detected at the relay satellite 115 to the first satellite 105. In addition to the signal components transmitted to the ground system 130, the first satellite 105 may transmit direct signal components to the ground system 130. In such a case, the signal components of the signal detected at the relay satellite 115 may supplement the direct signal components of the signal detected by the first satellite 105.

[0047] Although generally described with reference to detecting signals originating from the geographical area 140 within the coverage area 150, similar techniques may be used to transmit signals to user terminals having the geographical area 140 on the forward link. In such a case, the forward channel between the ground system 130 and the geographical area 140 may similarly include multiple channel components, including the channel component between the ground system 130 and the first satellite 105, the channel component between the first satellite 105 and the relay satellite 115, and the channel component between the relay satellite 115 and the geographical area 140. In such a case, the ground system 130 may similarly estimate the forward channel (and in some examples, estimate one or more forward channel components individually). Additionally, the ground system 130 may determine beam coefficients and apply them to signals to be transmitted in different geographical areas. For example, applying a first set of beam coefficients to a first signal so that the relay satellite 115 focuses the transmission of the first signal within a first geographical area 140-1, applying a second set of beam coefficients to a second signal so that the relay satellite 115 focuses the transmission of the second signal within a second geographical area, and so on. In such examples, the first satellite 105 may transmit different components of a signal to the relay satellite 115, and the relay satellite 115 may transmit different signal components that coherently combine within the desired geographical area 140. In some examples, the relay satellite 115 may reduce the transmission power of different signal components to comply with signal strength thresholds on Earth (e.g., as set by a regulatory agency).

[0048] Figure 2 An example of a coverage map supporting lens observations using a low Earth orbit repeater according to an example disclosed herein is shown. The coverage map 200 depicts the coverage area of a first satellite (e.g., a GEO satellite, the first satellite 105 of FIG. 1) and a GEO satellite using one or more second satellites (e.g., LEO satellites, MEO satellites, LEO and MEO satellites, the relay satellite 115 of FIG. 1) to focus on a geographical area.

[0049] In some examples, an antenna array at a first satellite is associated with a coverage area 250. The boundary of the coverage area 250 may represent the point at which the signal received at the antenna array has a signal strength at the 3 dB point. In some cases, the coverage area 250 may represent the coverage area of a beamforming beam for transmission or reception via the first satellite from the coverage area 250. In some examples, the first satellite may be capable of processing signals received from within the coverage area 250. However, with respect to detecting signals within the coverage area 250, the first satellite may not be able to determine where within the coverage area 250 the signal originated. As described herein, to increase the detection resolution of the first satellite (and in some examples, to effectively increase the aperture), one or more second satellites (whose orbits are lower than that of the first satellite) may be used to detect signals originating from a geographical area within the coverage area 250.

[0050] In some examples, each of the second satellites may have a coverage area 205 that is smaller than that of the first satellite. Similar to the coverage area 250, the boundary of the coverage area 205 may represent the 3 dB point for detecting signals originating from within the coverage area 205. For example, for a first focused coverage area 205-1, the corresponding second satellite may be capable of detecting signals originating from the geographical area corresponding to the first focused coverage area 205-1, but not signals originating from within the coverage area 250 but outside the first focused coverage area 205-1. In some examples, the energy within the overlapping coverage areas 205 from the second satellites may be combined to focus on a particular geographical area 240. For example, the second satellites may be used to focus on a first geographical area 240-1.

[0051] In some examples, the second satellites may be used to focus (e.g., simultaneously) on multiple geographical areas 240 within the coverage area 250 to detect signals. For example, in addition to focusing on the first geographical area 240-1, the second satellites may be used to focus on other geographical areas (e.g., the first geographical area 240-1, the Pth geographical area 240-P). The different geographical areas 240 monitored using the second satellites may be non-overlapping or overlapping. In some examples, the second satellites may similarly be used to focus on one or more geographical areas within the coverage area 250 for transmitting signals to user equipment within the one or more geographical areas.

[0052] Figure 3Illustrates a set of exemplary operations in support of lens observations using a low Earth orbit repeater, according to an example as disclosed herein. Process flow 300 may be performed by second satellite 303, first satellite 305, and ground system 307, which may be examples of second satellite 115, first satellite 105, and ground system 130 as described with respect to FIG. 1. In some examples, process flow 300 illustrates an exemplary sequence of operations performed in support of operations using a low Earth orbit repeater. For example, process flow 300 depicts operations for detecting a signal transmitted in a geographic area within the coverage area of a GEO satellite.

[0053] It should be understood that one or more of the operations described in process flow 300 may be performed earlier or later in the process, may be omitted, replaced, supplemented, or combined with another operation. Additionally, additional operations as described herein that are not included in process flow 300 may be included.

[0054] At arrow 315, transmitter 301 may transmit a signal while being positioned within the geographic area. In some examples, transmitter 301 transmits a signal while wirelessly communicating with another device that is not second satellite 303 or first satellite 305. In other examples, transmitter 301 inadvertently transmits a signal (e.g., transmitter 301 may be a rocket, and the signal may be associated with a flash generated by the rocket). One or more second satellites 303 may detect the signal. That is, the signal may radiate from transmitter 301, and each of the second satellites 303 may detect a different signal component associated with the transmitted signal. In some examples, in addition to detection at second satellite 303, a direct signal component of the transmitted signal may be detected at first satellite 305.

[0055] At arrow 320, second satellite 303 may relay the detected signal component (or a representation of the received signal component) to first satellite 305. In some examples, second satellite 303 may apply the detected signal component to one or more repeaters that are used to relay the detected signal component to first satellite 305. The repeaters may be used to amplify, apply a frequency shift, or apply a phase shift (or a combination thereof) to the detected signal component prior to transmission to first satellite 305. In some examples, first satellite 305 may receive the signal component at one or more antenna elements. First satellite 305 may also receive a direct signal component at one or more antenna elements.

[0056] At arrow 325, the first satellite 305 may transmit a representation of the signal transmitted by the transmitter 301 to the ground system 307. The first satellite 305 may transmit signal components (including, in some examples, a direct signal component) to the ground system 307. In some examples, the first satellite 305 transmits signal components to the ground system 307 in one or more beams to one or more ground stations. The ground system 307 may receive the signal transmitted from the first satellite 305. In some examples, the ground system 307 may receive the signal transmitted from the first satellite 305 at one or more ground stations.

[0057] At block 330, the ground system 307 may estimate the channel between the ground system 307 and the transmitter 301 (which may be referred to as the return channel and is represented by H RTN based on the received signal. In some examples, the ground system 307 may also estimate the channel based on signals received from known transmitters located within or around the geographical area including the transmitter 301 (e.g., geographical area 140 in FIG. 1 or Figure 2 geographical area 240 in ). In some examples, the signals received from the known transmitters may be transmitted simultaneously with the signals detected by the second satellite 303. In some examples, the signals received from the known transmitters may be transmitted before the signals are detected by the second satellite 303, and in some cases, the signals may be received by a different set of second satellites than the second satellite 303. That is, information on signals from known transmitters relayed by a different (e.g., non - overlapping, partially overlapping) set of second satellites may be used for channel estimation relayed by a given set of second satellites.

[0058] In some examples, to estimate the return channel, the ground system 307 may estimate a portion of the return channel between the transmitter 301 and the second satellite 303 (which may be represented by A1 RTN ), a portion of the return channel between the second satellite 303 and the first satellite 305 (which may be represented by A2 RTN ), a portion of the return channel between the uplink repeater and the downlink repeater within the first satellite 305 (which may be represented by E RTN ), and a portion of the return channel between the first satellite 305 and the ground system 307 (which may be represented by C RTN ). When the first satellite also receives the direct signal component, the ground system may estimate a portion of the return channel between the transmitter 301 and the first satellite 305 (which may be represented by A RTN ).

[0059] In some examples, the ground system 307 estimates the channel (A1) between the transmitter and the second satellite 303 by interpolating signals transmitted by known transmitters in the vicinity of a set of monitored geographical areasRTN )。 And the channel between the second satellite 303 and the ground system 307 is estimated based on reference signals transmitted from known transmitters in a set of monitored geographical regions (e.g., A2 RTN , E RTN and C RTN ). In other examples, the components of the channel are estimated separately. For example, the channel between the second satellite 303 and the first satellite 305 can be estimated (e.g., by the first satellite 305) based on reference signals transmitted between the second satellite 303 and the first satellite 305 (A2 RTN ). The return channel (E RTN ) of the transponder of the first satellite can also be estimated by the first satellite 305. The first satellite 305 can indicate the estimated channel to the ground system 307. And the channel between the first satellite 305 and the ground system 307 can be estimated (e.g., by the ground system 307) based on reference signals transmitted between the first satellite 305 and the ground system 307 (C RTN ).

[0060] At block 335, the ground system 307 can estimate the covariance associated with the return channel, for example, based on the estimated return channel / estimated components of the return channel. The covariance can provide information about interference between signal components detected in different geographical regions in transmission to the ground system 307 and interference from other communications with the ground system 307. In some examples, the interference between signal components from different geographical regions can be represented by . Additionally, the interference between J users can be represented by . And the combined covariance can be represented by R′ RTN = R RTN + R RTN-int .

[0061] At block 340, the ground system 307 can use the estimated return channel and the estimated return covariance to determine the beam coefficients applied to the signals received from the first satellite 305. In some examples, the beam coefficients can be represented by the matrix B RTN , where B RTN can be equal to (R RTN -1 H RTN ) H. In some examples, the beam coefficients and the return channel are determined based on the same time period, and the signals received to estimate the channel can also be used to determine the beam coefficients. In some examples, the ground system 307 can continuously (e.g., every millisecond) update the estimated return channel and beam coefficients based on the received signals. For example, the ground system 307 can process a first set of signals to estimate the return channel and reprocess the first set of signals based on the estimated return channel to determine the beam coefficients.

[0062] At block 345, the ground system 307 can apply the beam coefficients to the signals received from the first satellite 305 to obtain one or more beam signals corresponding to one or more geographic regions. In some examples, the one or more beam signals correspond to representations of one or more signals transmitted in the geographic regions. The one or more beam signals can include beam signals that are representations of signals transmitted by the transmitter 301 in the geographic regions. In some examples, when using digital beamforming, applying the beam coefficients can include, for example, multiplying a beam coefficient matrix by a matrix representing the signal to apply the beam coefficients to the digital representation of the signal. In other examples, applying the beam coefficients can include combining components of the analog signals received at the ground system 307 to obtain an analog beam signal.

[0063] At block 350, the ground system 307 can process (e.g., filter, analyze, demodulate, decode) one or more beam signals to determine whether a signal has been detected in the geographic region of interest. In some examples, the ground system 307 determines the type of signal (e.g., communication signal, signal associated with a rocket, etc.) that has been detected in the geographic region of interest.

[0064] As suggested above, the order of operations of the process flow 300 can be changed. In some examples, the operations for estimating the return channel and the covariance associated with the return channel and determining the beam coefficients can be performed by the ground system 307 before receiving the representation of the signal transmitted by the transmitter 301 from the first satellite 305.

[0065] In some examples, the operations of the process flow 300 can be performed by different devices. For example, the operations for estimating the return channel and the covariance associated with the return channel; determining the beam coefficients; and applying the beam coefficients can be performed by the first satellite 305 (e.g., if the first satellite is configured to perform OBBF). In this case, the first satellite 305 can transmit one or more beam signals corresponding to the signals transmitted by the transmitter 301 to the ground system 307. And the ground system 307 can process the received one or more beam signals as described herein.

[0066] Although described in the context of using a second satellite 303 to detect signals via a return channel associated with a geographic area within the coverage area of a first satellite 305, similar operations may be performed to estimate a forward channel associated with the geographic area and to relay signals to user equipment within the geographic area using the second satellite 303.

[0067] Figure 4 An example of a constellation supporting lens observations using a low Earth orbit repeater, according to an example disclosed herein, is shown. The constellation 400 depicts a set of second satellites (e.g., LEO satellites, MEO satellites, the relay satellite 115 of FIG. 1, etc.) that may be used in combination with a first satellite (e.g., a GEO satellite, the first satellite 105 of FIG. 1, etc.) to increase the detection resolution of the first satellite (and in some examples, effectively increase the aperture) for detecting signals within the coverage area. In some examples, the coverage area of the second satellite 415 may correspond to Figure 2 the corresponding focused coverage area 205 described in

[0068] The constellation 400 may include S second satellites 415, where S may be equal to nine. Multiple sets of second satellites 415 may be positioned in different orbital planes 405 (e.g., in K orbital planes). In some examples, the second satellites 415 are distributed in three orbital planes 405, where the first orbital plane 405-1 may have an inclination of negative five (-5) degrees, the second orbital plane 405-2 may have an inclination of zero (0) degrees, and the third orbital plane 405-3 may have an inclination of five (5) degrees. In some examples, the second satellites 415 may be evenly distributed in the three orbital planes 405 such that each orbital plane includes three second satellites 415. In some examples, the second satellites 415 included in the same orbital plane 405 may be separated from each other based on a separation angle. For example, the separation angle between the second satellites 415 included in the same orbital plane 405 may be equal to (or approximately) five (5) degrees.

[0069] Figure 5 A block diagram of a signal analyzer supporting lens observations using a low Earth orbit repeater, according to an example disclosed herein, is shown. The signal analyzer 520 may be an example of aspects of a first satellite or a ground station as described in reference to Figure 1A The signal analyzer 520 or its various components may be examples of apparatus for performing various aspects of lens observations using a low Earth orbit repeater as described herein. For example, the signal analyzer 520 may include a channel estimator 525, a beamformer 530, a signal manager 535, a covariance estimator 540, a demodulator 545, a decoder 550, or any combination thereof. Each of these components may communicate directly or indirectly with each other (e.g., via one or more buses).

[0070] The signal analyzer 520 may support communications according to examples as disclosed herein. The beamformer 530 may be configured to or otherwise support an apparatus for: obtaining beam coefficients of a beam associated with a geographical area at least in part based on an estimated return channel, the estimated return channel including a first channel component between the geographical area and a plurality of second satellites and a second channel component between the plurality of second satellites and the first satellite; and forming a beam associated with the geographical area to obtain a beam signal at least in part based on the beam coefficients and a plurality of signal components of a signal originating from the geographical area and relayed to the first satellite by the plurality of second satellites.

[0071] In some examples, the channel estimator 525 may be configured to or otherwise support an apparatus for: estimating a return channel from a geographical area, the return channel including a first channel component between the first satellite and a plurality of second satellites and a second channel component between the plurality of second satellites and the geographical area. In some examples, to support estimating the return channel of a geographical area, the channel estimator 525 may be configured to or otherwise support an apparatus for: determining a plurality of return channels at least in part based on one or more other signals received from known geographical locations. In some examples, the one or more other signals include one or more reference signals transmitted by a transmitter in a known geographical location. In some examples, to support estimating the return channel of a geographical area, the channel estimator 525 may be configured to or otherwise support an apparatus for: interpolating characteristics of the plurality of return channels to estimate characteristics of the return channel.

[0072] In some examples, the signal manager 535 may be configured to or otherwise support an apparatus for: obtaining representations of a plurality of signal components relayed by a plurality of second satellites and a direct signal component of a signal received from the geographical area at the first satellite, wherein the beam signal is determined at least in part based on the representations of the plurality of signal components and the direct signal component.

[0073] In some examples, the covariance estimator 540 may be configured to or otherwise support an apparatus for: estimating a return covariance associated with a geographical area at least in part based on the return channel. In some examples, the beamformer 530 may be configured to or otherwise support an apparatus for: determining beam coefficients of a beam at least in part based on the return channel and the return covariance.

[0074] In some examples, to support obtaining the beam signal, the beamformer 530 may be configured to or otherwise support an apparatus for: applying the beam coefficients of the beam to representations of a plurality of signal components of a signal to obtain one or more beam signals.

[0075] In some examples, the channel estimator 525 may be configured to or otherwise support a device for: estimating a plurality of return channels from a plurality of geographical regions, the plurality of return channels including the return channel, and the plurality of geographical regions including the geographical region. In some examples, the covariance estimator 540 may be configured to or otherwise support a device for: estimating a return covariance based at least in part on the plurality of return channels. In some examples, the beamformer 530 may be configured to or otherwise support a device for: determining a plurality of beam coefficients for a plurality of beams based at least in part on the plurality of return channels and the return covariance.

[0076] In some examples, the beamformer 530 may be configured to or otherwise support a device for: applying the plurality of beam coefficients for the plurality of beams to a representation of a plurality of signal components associated with a plurality of signals originating from a plurality of geographical regions to obtain one or more beam signals, the one or more beam signals including the beam signal.

[0077] In some examples, the demodulator 545 may be configured to or otherwise support a device for: demodulating the beam signal. In some examples, the decoder 550 may be configured to or otherwise support a device for: decoding the demodulated beam signal.

[0078] Figure 6 A schematic diagram of a communication device supporting lens observations using a low Earth orbit repeater according to an example as disclosed herein is shown. The communication device 605 may be an example of or include components of the first satellite 105 (e.g., a geosynchronous satellite supporting satellite carrier beamforming) or the ground system 130 as described herein. The communication device 605 may include components for processing signals, such as an input / output (I / O) controller 610, a transceiver 615, an antenna 625, a signal analyzer 620, a memory 630, code 635, and a processor 640. These components may be electronically communicated or otherwise (e.g., operatively, communicatively, functionally, electronically, electrically) coupled via one or more buses (e.g., bus 645).

[0079] The I / O controller 610 may manage the input and output signals of the communication device 605. The I / O controller 610 may also manage peripheral devices not integrated into the communication device 605. In some cases, the I / O controller 610 may represent a physical connection or port to an external peripheral device. In some cases, the I / O controller 610 may utilize, such as of the operating system or other known operating systems. Additionally or alternatively, the I / O controller 610 may represent, or interact with, a modem, keyboard, mouse, touch screen, or similar device. In some cases, the I / O controller 610 may be implemented as part of a processor such as the processor 640. In some cases, the user may interact with the communication device 605 via the I / O controller 610 or via hardware components controlled by the I / O controller 610.

[0080] In some cases, the antenna 625 may be a single antenna. In some other cases, the antenna 625 may include multiple antennas (or antenna elements) that may be capable of simultaneously transmitting or receiving multiple wireless transmissions. The transceiver 615 may communicate bidirectionally via one or more antennas 625, wired or wireless links as described herein. For example, the transceiver 615 may represent a wireless transceiver and may communicate bidirectionally with another wireless transceiver. The transceiver 615 may also include a modem for modulating data packets, providing the modulated data packets to one or more antennas 625 for transmission, and demodulating data packets received from one or more antennas 625.

[0081] The memory 630 may include random access memory (RAM) and read only memory (ROM). The memory 630 may store code 635. The code 635 may be computer-readable and computer-executable code and may include instructions that, when executed by the processor 640, cause the communication device 605 to perform the various functions described herein. The code 635 may be stored in a non-transitory computer-readable medium such as system memory or another type of memory. In some cases, the code 635 may not be directly executable by the processor 640 but may cause a computer (e.g., when compiled and executed) to perform the functions described herein. In some cases, the memory 630 may particularly contain a basic input / output system (BIOS) that may control basic hardware or software operations such as interaction with peripheral components or devices.

[0082] The processor 640 may include intelligent hardware devices (e.g., general-purpose processors, DSPs, CPUs, microcontrollers, ASICs, FPGAs, programmable logic devices, discrete gate or transistor logic components, discrete hardware components, or any combination thereof). In some cases, the processor 640 may be configured to operate a memory array using a memory controller. In some other cases, the memory controller may be integrated into the processor 640. The processor 640 may be configured to execute computer-readable instructions stored in a memory (e.g., the memory 630) to cause the communication device 605 to perform various functions (e.g., functions or tasks supporting reporting of angle offsets within a reporting frequency range). For example, the communication device 605 or components of the communication device 605 may include the processor 640 and the memory 630 coupled to the processor 640, and the processor 640 and the memory 630 are configured to perform the various functions described herein. The processor 640 may include the ground station processor 153 or the spaceborne processor 187 (or examples thereof).

[0083] The signal analyzer 620 may support signal analysis at a first satellite (e.g., a geostationary satellite) or a ground station according to examples disclosed herein. For example, the signal analyzer 620 may be configured to or otherwise support a device for: obtaining beam coefficients of a beam associated with a geographical region based at least in part on an estimated return channel, the estimated return channel including a first channel component between the geographical region and a plurality of second satellites and a second channel component between the plurality of second satellites and the first satellite. The signal analyzer 620 may be configured to or otherwise support a device for: forming a beam associated with the geographical region to obtain a beam signal based at least in part on the beam coefficients and a plurality of signal components of signals originating from the geographical region and relayed to the first satellite by the plurality of second satellites.

[0084] In some examples, the signal analyzer 620 may be configured to use the transceiver 615, one or more antennas 625, or any combination thereof or otherwise cooperate therewith to perform various operations (e.g., receive, monitor, transmit). Although the signal analyzer 620 is shown as a separate component, in some examples, one or more functions described with reference to the signal analyzer 620 may be supported or performed by the processor 640, the memory 630, the code 635, or any combination thereof. For example, the code 635 may include instructions executable by the processor 640 to cause the communication device 605 to perform aspects of reporting angle offsets within the reporting frequency range as described herein, or the processor 640 and the memory 630 may otherwise be configured to perform or support such operations.

[0085] Figure 7A flowchart is shown that illustrates a method for supporting lens observations using a low Earth orbit repeater according to an example as disclosed herein. Operations of the method may be implemented by components of a first satellite (e.g., a geostationary satellite supporting satellite carrier beamforming) or a ground station as described herein. In some examples, the first satellite or the ground station may execute a set of instructions to control functional elements of the first satellite or the ground station to perform the functions. Additionally or alternatively, the first satellite or the ground station may use dedicated hardware to perform aspects of the functions.

[0086] At 705, the method may include obtaining beam coefficients of a beam associated with a geographic region, at least in part based on an estimated return channel that includes a first channel component between the geographic region and a plurality of second satellites and a second channel component between the plurality of second satellites and the first satellite. The operation of 705 may be performed according to an example as disclosed herein. In some examples, aspects of the operation of 705 may be performed by a channel estimator 525 as described with reference to Figure 5 description.

[0087] At 710, the method may include forming a beam associated with the geographic region to obtain a beam signal, at least in part based on the beam coefficients and a plurality of signal components of a signal originating from the geographic region and relayed to the first satellite by the plurality of second satellites. The operation of 710 may be performed according to an example as disclosed herein. In some examples, aspects of the operation of 710 may be performed by a beamformer 530 as described with reference to Figure 5 description.

[0088] In some examples, an apparatus as described herein may perform one or more methods, such as method 700. The apparatus may include features, circuitry, logic, devices, or instructions (e.g., a non-transitory computer-readable medium storing instructions executable by a processor) for obtaining beam coefficients of a beam associated with a geographic region, at least in part based on an estimated return channel that includes a channel component between the geographic region and a plurality of second satellites; and forming a beam associated with the geographic region to obtain a beam signal, at least in part based on the beam coefficients and a plurality of signal components associated with a signal originating from the geographic region.

[0089] Some examples of method 700 and apparatus described herein may further include operations, features, devices, or instructions for receiving a representation of a plurality of signal components, wherein the beam signal is obtained at least in part by applying beam coefficients of the beam to the representation of the plurality of signal components.

[0090] Some examples of the method 700 and apparatus described herein may also include operations, features, apparatus, or instructions for estimating a return channel from a geographical area, the return channel including a first channel component between a first satellite and a plurality of second satellites and a second channel component between the plurality of second satellites and the geographical area.

[0091] In some examples of the method 700 and apparatus described herein, estimating the return channel from a geographical area may include operations, features, circuitry, logic, apparatus, or instructions for determining a plurality of return channels based at least in part on one or more other signals received from known geographical locations, and interpolating characteristics of the plurality of return channels to estimate characteristics of the return channel.

[0092] In some examples of the method 700 and apparatus described herein, the one or more other signals include one or more reference signals transmitted by a transmitter in a known geographical location.

[0093] Some examples of the method 700 and apparatus described herein may also include operations, features, apparatus, or instructions for obtaining a representation of a plurality of signal components relayed by a plurality of second satellites and a representation of a direct signal component of a signal received at the first satellite from the geographical area, wherein a beam signal may be determined based at least in part on the representation of the plurality of signal components and the representation of the direct signal component.

[0094] Some examples of the method 700 and apparatus described herein may also include operations, features, apparatus, or instructions for estimating a return covariance associated with the geographical area based at least in part on the return channel and determining beam coefficients of a beam based at least in part on the return channel and the return covariance.

[0095] In some examples of the method 700 and apparatus described herein, obtaining the beam signal may include operations, features, circuitry, logic, apparatus, or instructions for applying the beam coefficients of the beam to the representation of the plurality of signal components of the signal to obtain one or more beam signals.

[0096] Some examples of the method 700 and apparatus described herein may also include operations, features, apparatus, or instructions for estimating a plurality of return channels from a plurality of geographical areas, the plurality of return channels including the return channel and the plurality of geographical areas including the geographical area; estimating a return covariance based at least in part on the plurality of return channels; and determining beam coefficients of a plurality of beams based at least in part on the plurality of return channels and the return covariance.

[0097] Some examples of the method 700 and apparatus described herein may also include operations, features, apparatus, or instructions for applying a plurality of beam coefficients of a plurality of beams to a representation of a plurality of signal components associated with a plurality of signals originating from a plurality of geographical regions to obtain one or more beam signals, the one or more beam signals including the beam signal.

[0098] A system for communication is described. The system may include a first satellite in a first orbit; a plurality of second satellites in a second orbit below the first orbit, wherein the plurality of second satellites are configured to detect respective signal components of signals originating from geographical regions and relay the respective signal components to the first satellite; and a beamformer configured to form a beam associated with a geographical region to obtain a beam signal based at least in part on the respective signal components and an estimated return channel, wherein the estimated return channel includes channel components between the geographical region and the plurality of second satellites.

[0099] In some examples of the system, the first satellite includes a plurality of transponders, wherein, in order to transmit a representation of a signal to a terrestrial system, each of the plurality of transponders may be configured to receive the respective signal component relayed by the plurality of second satellites and transmit a representation of the respective signal component to the terrestrial system.

[0100] In some examples of the system, each of the plurality of second satellites includes at least one repeater, wherein, in order to relay the respective signal component to the first satellite, the repeaters of the plurality of second satellites may be configured to amplify the respective detected signal component and transmit the respective amplified signal component to the first satellite. In some examples of the system, at least one repeater may be a non-processing repeater.

[0101] In some examples of the system, the repeaters of the plurality of second satellites may be configured to transmit the respective amplified signal component at the same frequency as the respective signal component detected at the repeater.

[0102] In some examples of the system, the repeaters of the plurality of second satellites may be configured to transmit the respective amplified signal component at a frequency different from the respective signal component detected at the repeater.

[0103] In some examples of the system, each of the repeaters of the plurality of second satellites may be configured to transmit the respective amplified signal component at a respective one of a plurality of frequencies.

[0104] In some examples of the system, the respective signal components detected by the plurality of second satellites may be detected via a first channel between the plurality of second satellites and a geographical area, the respective signal components may be relayed to the first satellite via a second channel between the plurality of second satellites and the first satellite, and the first satellite may be configured to transmit a representation of the respective signal components to the ground system via a third channel between the first satellite and the ground system.

[0105] In some examples of the system, the beamformer may be further configured to estimate a return covariance associated with the estimated return channel, determine beam coefficients of the beam at least in part based on the estimated return channel and the return covariance, and apply the beam coefficients to the respective signal components to obtain a beam signal.

[0106] In some examples, the system may include a ground system that includes a plurality of gateways configured to receive representations of the respective signal components; and a beamformer, where the beamformer may be coupled to the plurality of gateways and configured to apply beam coefficients of the beam to the representations of the respective signal components to obtain a beam signal.

[0107] In some examples of the system, the first satellite includes a beamformer and may be further configured to transmit the beam signal to the ground system.

[0108] In some examples of the system, the plurality of second satellites may be configured to detect a plurality of respective signal components of a plurality of signals originating from a plurality of geographical areas, the plurality of signals including the signal, and the plurality of geographical areas including the geographical area, and the beamformer may be configured to form a plurality of beams associated with the plurality of geographical areas to obtain a plurality of beam signals at least in part based on the plurality of respective signal components and a plurality of estimated return channels, the plurality of estimated return channels including the estimated return channel.

[0109] In some examples of the system, the beamformer may be further configured to estimate a return covariance associated with the plurality of geographical areas, determine beam coefficients of the beam at least in part based on the estimated return channel and the return covariance, and apply the beam coefficients of the beam to the plurality of respective signal components to obtain a plurality of beam signals.

[0110] In some examples of the system, the first satellite may be configured to detect a direct signal component of the signal.

[0111] In some examples of the system, the beamformer may be further configured to obtain a beam signal at least in part based on the direct signal component.

[0112] In some examples of the system, the beamformer may be further configured to estimate the estimated return channel at least in part based on other signals received from one or more other geographic regions. In some examples of the system, the other signals include one or more reference signals transmitted by transmitters at known locations.

[0113] In some examples of the system, the plurality of second satellites include a first group of satellites in a first orbital plane of a second orbit. In some examples of the system, the plurality of second satellites include a second group of satellites in a second orbital plane of the second orbit.

[0114] In some examples, the system includes a processor configured to demodulate the beam signal. In some examples, the system includes a processor that includes a beamformer. In some examples of the system, the first orbit may be a geostationary orbit.

[0115] A communication device is described. The communication device may include a processor and a memory coupled to the processor and including instructions executable by the processor to cause the communication device to perform the following operations: estimate a return channel from a geographic region, the return channel including a first channel component between a first satellite and a plurality of second satellites and a second channel component between the plurality of second satellites and the geographic region; and obtain a beam signal at least in part based on a plurality of signal components associated with a signal originating from the geographic region, wherein the plurality of signal components are relayed by respective second satellites of the plurality of second satellites.

[0116] In some examples of the communication device, the instructions for estimating the return channel may also be executable by the processor to determine a plurality of return channels at least in part based on one or more other signals received from a known geographic location and interpolate characteristics of the plurality of return channels to estimate characteristics of the return channel.

[0117] In some examples of the communication device, the instructions may also be executable by the processor to obtain a representation of the plurality of signal components relayed by the plurality of second satellites and a representation of a direct signal component of the signal received at the first satellite from the geographic region, wherein the beam signal may be determined at least in part based on the representation of the plurality of signal components and the representation of the direct signal component.

[0118] In some examples of the communication device, the instructions may also be executable by the processor to estimate a return covariance associated with the geographic region at least in part based on the return channel and determine beam coefficients of the beam at least in part based on the return channel and the return covariance.

[0119] In some examples of the communication device, the instructions for obtaining the beam signal may also be executable by the processor to apply the beam coefficients of the beam to the representation of the plurality of signal components of the signal to obtain one or more beam signals.

[0120] In some examples of the communication device, the instruction may also be executable by a processor to: estimate a plurality of return channels from a plurality of geographical regions, the plurality of return channels including the return channel and the plurality of geographical regions including the geographical region; estimate a return covariance based at least in part on the plurality of return channels; and determine a plurality of beam coefficients of a plurality of beams based at least in part on the plurality of return channels and the return covariance.

[0121] In some examples of the communication device, the instruction may also be executable by a processor to apply the plurality of beam coefficients of the plurality of beams to a representation of a plurality of signal components associated with a plurality of signals originating from a plurality of geographical regions to obtain one or more beam signals, the one or more beam signals including the beam signal.

[0122] It should be noted that these methods describe examples of specific implementations, and the operations and steps may be rearranged or otherwise modified such that other specific implementations are possible. In some examples, aspects from two or more of the methods may be combined. For example, aspects of each of the methods may include steps or aspects of other methods, or other steps or techniques described herein.

[0123] The information and signals described herein may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the specification may be represented by voltage, current, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0124] The various exemplary blocks and modules described in connection with the disclosure herein may be implemented or executed using: a general purpose processor, a DSP, an ASIC, an FPGA, or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. The general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices (e.g., a combination of a digital signal processor (DSP) and a microprocessor, a combination of multiple microprocessors, a combination of one or more microprocessors with a DSP core, or any other such configuration).

[0125] The functions described herein can be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions can be stored on or transmitted via a computer-readable medium as one or more instructions or code. Other examples and implementations are within the scope of the present disclosure and the appended claims. For example, due to the nature of software, the functions described herein can be implemented using software executed by a processor, hardware, firmware, hardwiring, or any combination thereof. The features implementing the functions can also be physically located in various positions, including being distributed such that the functional portions are implemented at different physical locations.

[0126] Computer-readable media includes both non-transitory computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A non-transitory storage medium can be any available medium that is accessible by a general purpose or special purpose computer. By way of example, and not limitation, non-transitory computer-readable media can include RAM, ROM, electrically erasable programmable read-only memory (EEPROM), flash memory, compact disc read-only memory (CDROM) or other optical disc storage, magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that can be used to carry or store desired program code in the form of instructions or data structures and that is accessible by a general purpose or special purpose computer, or a general purpose or special purpose processor. Also, any connection is properly termed a computer-readable medium. For example, if software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technology such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technology such as infrared, radio, and microwave is included in the definition of medium. As used herein, disk and disc include CD, laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Blu-ray disc where disks typically reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above are also included within the scope of computer-readable media.

[0127] As used herein, including in the claims, the "or" used in a list of items (e.g., a list of items prefaced by a phrase such as "at least one of..." or "one or more of...") indicates an inclusive list, such that for example the list "at least one of A, B, or C" means A or B or C or AB or AC or BC or ABC (i.e., A and B and C). Also, as used herein, the phrase "based on" should not be construed as a reference to a closed set of conditions. For example, an exemplary step described as "based on condition A" may be based on both condition A and condition B without departing from the scope of the present disclosure. In other words, as used herein, the phrase "based on" should be interpreted in the same manner as the phrase "at least partially based on".

[0128] In the drawings, like parts or features may have the same reference labels. Additionally, various parts of the same type may be distinguished by following the reference label with a dash and a second label, which may distinguish similar parts. If only the first reference label is used in this specification, the description applies to any of the similar parts having the same first reference label, regardless of the second reference label, or any other subsequent reference labels.

[0129] The specification set forth herein in conjunction with the drawings describes exemplary configurations and does not represent all examples that may be implemented or that are within the scope of the claims. The term "exemplary" as used herein means "serving as an example, instance, or illustration" and not "preferred" or "better than other examples". The detailed description includes specific details to provide an understanding of the described technologies. However, the technologies may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form to avoid obscuring the concepts of the described examples.

[0130] The present description is provided to enable a person skilled in the art to make or use the present disclosure. Various modifications to the present disclosure will be apparent to those skilled in the art, and the general principles defined herein may be applied to other variations without departing from the scope of the present disclosure. Thus, the present disclosure is not limited to the examples and designs described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A system for communication, the system comprising: a first satellite (105) in a first orbit; a plurality of second satellites (115) in a second orbit below the first orbit, wherein the plurality of second satellites (115) have respective antennas that illuminate respective portions of a geographical area (140), and are configured to detect respective signal components (125) of signals originating from the geographical area (140), and to transmit respective relay signal components (110) obtained from the respective signal components (125) to the first satellite (105); and a beamformer (155, 190) located in a ground system (130) or in the first satellite (105) and configured to form a beam associated with the geographical area (140) to obtain a beam signal based at least in part on the respective relay signal components (110) and an estimated return channel, wherein the estimated return channel includes channel components between the geographical area (140) and the plurality of second satellites (115).

2. The system according to claim 1, wherein the beamformer (155) is located in the ground system (130), and wherein the first satellite (105) comprising: a plurality of transponders (175), wherein each of the plurality of transponders (175) is configured to receive the respective relay signal component (110) transmitted by the plurality of second satellites (115), and to transmit a representation of the respective relay signal component (110) to the ground system (130), wherein the beamformer (155) is further configured to form the beam signal based at least in part on the representation of the respective relay signal component (110), the representation of the respective relay signal component being at least in part based on the respective relay signal component (110).

3. The system according to any one of claims 1 or 2, wherein each of the plurality of second satellites (115) comprising: at least one repeater (160), wherein, in order to transmit the respective relay signal component (110) to the first satellite (105), the repeaters (160) of the plurality of second satellites (115) are configured to amplify the detected respective signal component (125) to obtain the respective relay signal component (110).

4. The system according to claim 3, wherein the at least one repeater (160) is a non-processing repeater.

5. The system according to any one of claims 3 or 4, wherein the repeaters (160) of the plurality of second satellites (115) are configured to transmit the respective relay signal component (110) at the same frequency as the respective signal component (125) detected at the repeater (160).

6. The system according to any one of claims 3 or 4, wherein the repeaters (160) of the plurality of second satellites (115) are configured to transmit the respective relay signal components (110) at a frequency different from the respective signal components (125) detected at the repeaters (160).

7. The system according to any one of claims 3 to 6, wherein each of the repeaters (160) of the plurality of second satellites (115) is configured to transmit a respective relay signal component at a respective frequency among a plurality of frequencies.

8. The system according to any one of claims 1 or 4 to 7, wherein: the beamformer (155) is located in the ground system (130), detects the respective signal components (125) detected by the plurality of second satellites (115) via a first channel between the plurality of second satellites (115) and the geographical area (140), the respective relay signal components (110) are transmitted to the first satellite (105) via a second channel between the plurality of second satellites (115) and the first satellite (105), the first satellite (105) is configured to transmit a representation of the respective relay signal components (110) to the ground system (130) via a third channel between the first satellite (105) and the ground system (130), and the beamformer (155) is configured to form the beam signal at least in part based on the representation of the respective relay signal components (110), the representation of the respective relay signal components being at least in part based on the respective relay signal components (110).

9. The system according to any one of claims 1 to 8, wherein the beamformer (155, 190) is further configured to: estimate a return covariance associated with the estimated return channel; and determine beam coefficients of the beam at least in part based on the estimated return channel and the return covariance.

10. The system according to any one of claims 1, 4 to 7 or 9, wherein the beamformer (155) is located in the ground system (130), and the system further comprises: the ground system (130), the ground system comprising: at least one gateway (135) configured to receive a representation of the respective relay signal components (110); and the beamformer (155), wherein the beamformer (155) is coupled to the at least one gateway (135) and is configured to apply beam coefficients of the beam to the representation of the respective relay signal components (110) to obtain the beam signal, wherein the representation of the respective relay signal components (110) is at least in part based on the respective relay signal components (110).

11. The system according to claim 1, wherein the beamformer (190) is located in the first satellite (105) and is further configured to: Estimate a return covariance associated with the estimated return channel; Determine beam coefficients of the beam based at least in part on the estimated return channel and the return covariance; And Apply the beam coefficients to the respective relay signal components (125) to obtain the beam signal.

12. The system according to claim 11, wherein the first satellite (105) is configured to transmit the beam signal to the terrestrial system (130).

13. The system according to claim 1, wherein: The beamformer (190) is located in the first satellite (105); The plurality of second satellites (115) are configured to detect a plurality of respective signal components (125) of a plurality of signals originating from a plurality of geographical regions (140), and transmit a plurality of respective relay signal components (110) obtained from the respective signal components (125) to the first satellite (105), the plurality of signals including the signal, and the plurality of geographical regions (140) including the geographical region (140); and The beamformer (190) is configured to form a plurality of beams associated with the plurality of geographical regions (140) to obtain a plurality of beam signals based at least in part on the plurality of respective relay signal components (110) and a plurality of estimated return channels, the plurality of beams including the beam, the plurality of beam signals including the beam signal, and the plurality of estimated return channels including the estimated return channel.

14. The system according to claim 13, wherein the beamformer (155, 190) is further configured to: Estimate a return covariance associated with the plurality of geographical regions (140); and Determine beam coefficients of the beam based at least in part on the estimated return channel and the return covariance.

15. The system according to any one of claims 1 to 14, wherein the first satellite (105) is configured to detect a direct signal component (120) of the signal.

16. The system according to claim 15, wherein the beamformer (155, 190) is further configured to: Obtain the beam signal based at least in part on the direct signal component (120).

17. The system according to any one of claims 1 to 16, wherein the beamformer (155, 190) is further configured to: Determine the estimated return channel based at least in part on other signals received from one or more other geographical regions (140).

18. The system according to claim 17, wherein the other signals include one or more reference signals transmitted by transmitters at known locations.

19. The system according to any one of claims 1 to 18, wherein the plurality of second satellites (115) comprises: A first group of satellites in a first orbital plane (405-1) of the second orbit.

20. The system according to claim 19, wherein the plurality of second satellites (115) further comprises: A second set of satellites in the second orbital plane (405-2) of the second orbit.

21. The system according to any one of claims 1 to 20, the system further comprises: Processors (153, 187), the processors being configured to demodulate the beam signals.

22. The system according to any one of claims 1 to 21, the system further comprises: Processors (153, 187), the processors including the beamformers (155, 190).

23. The system according to any one of claims 1 to 22, wherein the first orbit is a geostationary orbit.

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