Satellite communications using spread signals

Abstract

Methods, systems, and devices for satellite operation are described. A satellite communications system may include a transmitter that applies multiple spreading codes to a data signal to obtain multiple spread data signals. The transmitter may transmit the multiple spread data signals from multiple antenna elements in a composite signal. The satellite communications system may also include a receiver that receives the composite signal and applies multiple despreading codes to the composite signal to obtain multiple despread data signals. The receiver may combine the multiple despread data signals to obtain a combined data signal corresponding to the data signal processed by the transmitter. To combine the multiple despread data signals, the receiver may estimate coefficients for each of the despread data signals.

Description

[Technical Field]

[0001] The following relates generally to satellite communications, and more particularly to satellite communications using spread or wide-area coverage signals.

[0002] A portion of the radio spectrum (e.g., one or more frequency bands) can be used by a satellite communications system to conduct wireless communications. The satellite communications system can use communications techniques that increase the utilization of the portion of the radio spectrum available to the satellite communications system, thereby increasing the throughput of the wireless communications system. In some examples, communications techniques enable the satellite communications system to serve the same number of user terminals at an increased data rate, an additional number of users at the same data rate, or an additional number of user terminals at an increased data rate. Some communications techniques can divide the radio spectrum into separate communications resources (e.g., in terms of time and / or frequency) used to transmit to individual user terminals. Other communications techniques can cause multiple communications for multiple user terminals to be transmitted over the same set of communications resources (e.g., such communications techniques may be referred to as spreading). Additional communications techniques can enable portions of the radio spectrum to be reused in different geographic regions of the geographic area served by the satellite (e.g., such communications techniques may be referred to as beamforming). Summary of the Invention

[0003] The described technology relates to improved methods, systems, devices, and apparatus for supporting satellite communications using spread or wide-area coverage signals. A satellite communications system may use an enhanced communications technique that includes applying multiple sequences to a data signal to obtain multiple spread signals and transmitting the spread signals via multiple antenna elements having wide-area native beam patterns. This enhanced communications technique may be referred to as "feed-specific spreading." In some examples, to perform feed-specific spreading, a satellite communications system may include multiple signal spreaders, each coupled to one or more antenna elements via one or more power amplifiers. In some examples, each signal spreader may apply a different sequence (e.g., a pseudo-random sequence or an orthogonal code) to a common data signal to obtain multiple spread signals, where the common signal may include data for a single user terminal. The signal spreaders then pass the multiple spread signals to a set of antenna elements, which together may radiate a combined signal including the spread signals over the satellite's coverage area.

[0004] A user terminal having an unknown location within the satellite's coverage area can receive the combined signal, for example, during an interval for spread communications. The receiving device can apply a set of sequences (e.g., pseudorandom sequences or orthogonal codes) to the received combined signal to obtain multiple despread signals, where the set of sequences can be the same as or based on the set of sequences used to transmit the combined signal. The receiving device can then process and combine the multiple despread signals to obtain a data signal that can be demodulated and decoded, where the data signal can have a higher SNR than any of the individual despread signals. In some examples, the SNR of the data signal can be proportional to the amount of spread signal included in the combined signal. The use of extended spreading can serve mission-sensitive user terminals without compromising the security of the user terminal. In some examples, the increased SNR provided by extended spread communications can be used to support communications with user terminals that have known locations but are unable to reliably communicate with the satellite, for example, because they have inadequate antennas or are located in dead zones. Such user terminals may similarly be scheduled to receive the combined signal, e.g., during intervals for spread communications. In some examples, feed-specific spreading may be offered as a premium service to user terminals with valid subscriptions, e.g., disadvantaged user terminals, security-conscious user terminals, etc. [Brief explanation of the drawings]

[0005] [Figure 1] 1 shows a diagram of a communication system that supports satellite communications using spread or wide-area coverage signals, according to an embodiment disclosed herein.

[0006] [Figure 2] 1 illustrates a transmission system supporting satellite communications using spread or wide-area coverage signals, according to an embodiment disclosed herein.

[0007] [Figure 3] 1 illustrates a receiver supporting satellite communications using spread or wide-area coverage signals, according to an embodiment disclosed herein.

[0008] [Figure 4] 1 illustrates a beam diagram for supporting satellite communications using a spread or wide area coverage signal, according to an embodiment disclosed herein.

[0009] [Figure 5] 1 illustrates a beam diagram for supporting satellite communications using a spread or wide area coverage signal, according to an embodiment disclosed herein.

[0010] [Figure 6] 1 illustrates a diagram of a process for supporting satellite communications using spread or wide-area coverage signals according to embodiments disclosed herein. [Figure 7] 1 illustrates a diagram of a process for supporting satellite communications using spread or wide-area coverage signals according to embodiments disclosed herein. [Figure 8] 1 illustrates a diagram of a process for supporting satellite communications using spread or wide-area coverage signals according to embodiments disclosed herein. DETAILED DESCRIPTION OF THE INVENTION

[0011] Data may be communicated between access node terminals and user terminals in one or more beams. In some examples, a satellite (e.g., a broadcast satellite) may use a single broad beam to communicate data (e.g., common data) to user terminals located within the satellite's coverage area. In such cases, the satellite may include a single feed connected to a single antenna, and the energy of a signal transmitted from the antenna may be spread throughout the satellite's coverage area. A satellite communication system using a single broad beam may be referred to as a single beam system. In other examples, a satellite (e.g., a communication satellite) may use multiple narrow beams (or "spot beams") to communicate data to user terminals located within the satellite's coverage area. A satellite communication system using multiple spot beams may be referred to as a spot beam system. A spot beam system may spatially divide the satellite's coverage area into geographic regions, each of which may be covered by a spot beam. Each spot beam may then be assigned a portion of communication resources (e.g., bandwidth, polarization).

[0012] In a spot beam system, a satellite (e.g., a communications satellite) may use multiple broad beams to form spot beams within the satellite's coverage area. In such cases, the satellite may include an antenna assembly including multiple antenna elements, each of which may have a native broad beam pattern. To form the spot beams, beam weights may be applied to signals transmitted through a set of antenna elements (e.g., using phase shifters and amplitude adjusters), such that the signals transmitted from the set of antenna elements combine constructively and destructively to focus the energy of the resulting signals within a subregion of the coverage area. In the case of a dynamic spot beam system, the size of the spot beams formed by the satellite may be based on the beam weights used to form the spot beams. In some examples, communications transmitted using spot beams may have higher data rates and provide more favorable signal characteristics (e.g., a higher signal-to-noise ratio (SNR)) than communications transmitted using broad beams. In some examples, forming a spot beam using multiple antenna elements may be referred to as beamforming, a satellite transmission system that supports forming spot beams using multiple antenna elements may be configured according to a beamforming architecture, and information transmitted using multiple antenna elements may be referred to as beamformed communications.

[0013] Different communication technologies may be used to communicate data within a beam (e.g., broad beam or spot beam). Some of these communication technologies may include sharing communication resources within the beam among user terminals included in the coverage area. To support multiple user terminals within a beam, the communication resources may be partitioned (e.g., in time and frequency) among the user terminals. That is, each user terminal may be assigned unique communication resources over which transmissions for that user terminal may be transmitted (e.g., using time-division multiple access (TDMA) techniques, frequency-division multiple access (FDMA) techniques, or any combination thereof). Additionally or alternatively, user terminals may be scheduled to use common time and frequency resources. That is, multiple user terminals may be assigned the same set of communication resources, and transmissions for the user terminals may be spread across the communication resources (e.g., in time and / or frequency) using unique patterns that allow the transmissions to be separated at the user terminals. Spreading techniques may include frequency-hopping spread spectrum, time-hopping spread spectrum, or direct-sequence spread spectrum (DSSS) techniques. DSSS techniques may include applying a sequence (e.g., a pseudorandom sequence or an orthogonal code) to a data signal prior to transmission of the data signal. To support communication to multiple user terminals using DSSS, unique sequences may be applied to data signals intended for different user terminals before the data signals are simultaneously transmitted over the same set of communications resources. Applying unique sequences to data signals intended for different users prior to transmission may be an example of code division multiple access (CDMA) techniques.

[0014] In some examples, a satellite communications system may determine location information for a user terminal before performing beamformed communications to the user terminal within a spot beam, thereby enabling a transmitting device to identify a spot beam having a coverage area encompassing the user terminal for transmission. For example, the user terminal may be a fixed terminal with a known location, or the mobility of the user terminal may be tracked to determine how to transition (e.g., handoff) the user terminal from one spot beam to another. However, in some examples, the location of the user terminal may be unknown to the satellite communications system (e.g., to a controller that allocates satellite communications system resources to various user terminals). In some examples, the location of the user terminal is intentionally withheld from the satellite communications system by the user terminal. Additionally or alternatively, intentional measures may be taken by the user terminal to prevent the satellite communications system from determining the location of the user terminal. In such cases, a satellite communications system using spot beams may be unable to transmit to the user terminal, for example, because the satellite communications system may be unable to determine the spot beam in which the user terminal is located. In some examples, even when the location of a user terminal is known, the SNR of a signal received at the user terminal may be below a threshold associated with reliably communicating with the user terminal. In some examples, if a user terminal has an insufficient (e.g., small) antenna or is located in a poor coverage zone, the SNR of the signal will be below the threshold, and such a user terminal may be referred to as a disadvantaged user terminal.

[0015] To support communications with user terminals with unknown locations (and disadvantaged user terminals with known or unknown locations), satellite communications systems supporting dynamic spot beamforming can use an enhanced communications technique that includes applying multiple sequences to a data signal to obtain multiple spread signals and transmitting the spread signals via multiple antenna elements with wide-area native beam patterns. This enhanced communications technique may be referred to as “enhanced spreading” or “feed-specific spreading.” In some examples, to perform feed-specific spreading, a satellite communications system may include multiple phase shifters and multiple signal spreaders, each coupled to one or more antenna elements via one or more power amplifiers. In some examples, each signal spreader may apply a different sequence (e.g., a pseudorandom sequence or an orthogonal code) to a common data signal to obtain multiple spread signals, where the common signal may include data for a single user terminal. The signal spreaders then pass the multiple spread signals to sets of antenna elements that can together radiate a combined signal including the spread signals over the satellite's coverage area. In contrast to the correlated signals transmitted from the antenna elements for beamforming, the spread signals radiated from the antenna elements may be uncorrelated due to the spreading sequence, and therefore they do not combine constructively or destructively and may therefore form independent broad beams without forming spot beams.

[0016] A user terminal having an unknown location within the satellite's coverage area can receive the combined signal, for example, during an interval for spread communications. The receiving device can apply a set of sequences (e.g., pseudorandom sequences or orthogonal codes) to the received combined signal to obtain multiple despread signals, where the set of sequences can be the same as or based on the set of sequences used to transmit the combined signal. The receiving device can then process and combine the multiple despread signals to obtain a data signal that can be demodulated and decoded, where the data signal can have a higher SNR than any of the individual despread signals. That is, the receiving device can coherently add the spread signals received at the receiving device to obtain a combined signal with an improved SNR. In some examples, the SNR of the data signal can be proportional to the amount of spread signal included in the combined signal. The use of extended spreading can serve mission-sensitive user terminals without compromising the security of the user terminals. In some examples, the increased SNR provided by enhanced spread spectrum communications can be used to support communications with user terminals that have known locations but are unable to reliably communicate with the satellite, e.g., because they have inadequate antennas or are located in dead zones. Such user terminals can similarly be scheduled to receive the combined signal, e.g., during intervals for spread spectrum communications. In some examples, feed-specific spreading can be offered as a premium service to user terminals with valid subscriptions, e.g., disadvantaged user terminals, security-conscious user terminals, etc.

[0017] In some examples, the satellite communications system can switch between beamforming and feed-specific spreading to support communications with both known-location user terminals and unknown-location user terminals without significantly impacting the performance of the satellite communications system. In some examples, the satellite communications system can transmit to known-location user terminals using beamforming during a first interval and transmit to unknown-location user terminals using feed-specific spreading during a second interval. In some examples, the throughput of the satellite communications system can be greater during the first interval than during the second interval, and the first interval can be longer than the second interval.

[0018] This description provides various examples of techniques for satellite communications using spread or wide-area coverage signals, and such examples are not intended to limit the scope, applicability, or configuration of examples in accordance with the principles described herein. Rather, the following description will provide those skilled in the art with an enabling description for implementing embodiments of the principles described herein. Various changes may be made in the function and arrangement of elements.

[0019] Thus, various embodiments according to the examples disclosed herein may omit, substitute, or add various procedures or components, as appropriate. For example, it should be understood that methods may be performed in an order different from that described, and that various steps may be added, omitted, or combined. Also, aspects and elements described with respect to particular examples may be combined in various other examples. It should also be understood that the following systems, methods, devices, and software, individually or collectively, may be components of larger systems, and that other procedures may supersede or otherwise modify their application.

[0020] FIG. 1 illustrates a diagram of a communications system supporting satellite communications using diffuse or wide-area coverage signals, according to embodiments disclosed herein. The communications system 100 can employ several network architectures, including a space segment 101 and a ground segment 102. The space segment 101 can include one or more satellites 120. The ground segment 102 can include one or more access node terminals 130 (e.g., gateway terminals, ground stations), and a network device 141, such as a network operations center (NOC), satellite and gateway terminal command center, or other central processing center or device. The network device 141 can interface with the access node terminals 130 and control aspects of the communications system 100. In various examples, the network device 141 can be co-located with or otherwise located nearby the access node terminals 130, or can be a remote facility that communicates with the access node terminals 130 and / or the network 140 via wired and / or wireless communications links. In some examples, the terrestrial segment 102 may also include user terminals 150 that are provided communication services via satellites 120 .

[0021] User terminals 150 may include various devices configured to communicate signals with satellites 120, which may include fixed terminals (e.g., ground-based stationary terminals) or mobile terminals such as terminals for boats, aircraft, ground-based vehicles, etc. User terminals 150 may communicate data and information with access node terminals 130 via satellites 120. The data and information may be communicated to a destination device, such as network device 141, or to other devices or distributed servers associated with network 140.

[0022] The access node terminal 130 can transmit forward uplink signals 132 to the satellite 120 and receive return downlink signals 133 from the satellite 120. The access node terminal 130 may also be known as a ground station, gateway, gateway terminal, or hub. The access node terminal 130 may include an access node terminal antenna system 131 and an access node terminal transceiver 135. The access node terminal antenna system 131 is capable of two-way communication and may be designed with appropriate transmit power and receive sensitivity to reliably communicate with the satellite 120. In some examples, the access node terminal antenna system 131 may comprise a parabolic reflector with high directivity in the direction of the satellite 120 and low directivity in other directions. The access node terminal antenna system 131 may include a variety of alternative configurations and may include operating characteristics such as high isolation between orthogonal polarizations, high efficiency in the operating frequency band, low noise, etc.

[0023] When supporting a communication service, the access node terminal 130 may schedule traffic to the user terminal 150. Alternatively, such scheduling may be performed elsewhere in the communication system 100 (e.g., in one or more network devices 141, which may include a network operations center (NOC) and / or a gateway command center). Although one access node terminal 130 is shown in FIG. 1 , examples according to the present disclosure may be implemented in a communication system having multiple access node terminals 130, each of which may be connected to each other and / or to one or more networks 140.

[0024] The access node terminal 130 may provide an interface between the network 140 and the satellite 120 and, in some examples, may be configured to receive directed data and information between the network 140 and one or more user terminals 150. The access node terminal 130 may format the data and information for delivery to the respective user terminals 150. Similarly, the access node terminal 130 may be configured to receive signals from the satellite 120 (e.g., from one or more user terminals 150) directed to destinations accessible via the network 140. The access node terminal 130 may also format the received signals for transmission over the network 140.

[0025] Network 140 may be any type of network, including, for example, the Internet, an internet protocol (IP) network, an intranet, a wide-area network (WAN), a metropolitan area network (MAN), a local-area network (LAN), a virtual private network (VPN), a virtual private network (VLAN), an optical fiber network, a hybrid fiber coaxial network, a cable network, a public switched telephone network (PSTN), a public switched data network (PSDN), a public land mobile network, and / or any other type of network supporting communication between devices as described herein. Network 140 may include both wired and wireless connections, as well as optical links. Network 140 may connect access node terminal 130 to other access node terminals that may communicate with the same satellite 120 or with different satellites 120 or other vehicles.

[0026] Satellite 120 may be configured to support wireless communications between one or more access node terminals 130 and / or various user terminals 150 located within its service coverage area. In some examples, satellite 120 may be deployed in a geostationary orbit such that its orbital position with respect to terrestrial devices is relatively fixed or fixed within an operating tolerance or other orbital window (e.g., within an orbital slot). In other examples, satellite 120 may operate in any suitable orbit (e.g., low Earth orbit (LEO), medium Earth orbit (MEO), etc.).

[0027] The satellite 120 may include an antenna assembly 121 having one or more antenna feed elements. Each of the antenna feed elements may include, for example, a feed horn, a polarization transducer (e.g., a septum-polarized horn that can function as two combined elements with different polarizations), a multiport multiband horn (e.g., a dual-band 20 GHz / 30 GHz with dual-polarized LHCP / RHCP), a cavity-slot, an inverted-F, a slotted waveguide, a Vivaldi, a helical, a loop, a patch, or any other antenna element configuration or combination of interconnected subelements. Each of the antenna feed elements may also include or be connected to a radio frequency (RF) signal transducer, a low noise amplifier (LNA), or a power amplifier (PA), and may be connected to one or more transponders within the satellite 120. The transponders may be used for signal processing such as amplification, frequency conversion, beamforming, etc.

[0028] In some embodiments, a multi-frequency time division multiple access (MF-TDMA) scheme may be used for the forward uplink signal 132 and the return uplink signal 173, allowing efficient streaming of traffic while maintaining flexibility in allocating capacity among user terminals 150. In these embodiments, several frequency channels may be assigned in a fixed manner, or alternatively, may be assigned in a dynamic manner. A time division multiple access (TDMA) scheme may also be used for each frequency channel. In this scheme, each frequency channel may be divided into several time slots that may be assigned to a connection (e.g., to a particular user terminal 150). In other embodiments, one or more of the forward uplink signal 132 and the return uplink signal 173 may be configured using other schemes, such as Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Code Division Multiple Access (CDMA), or any number of hybrid or other schemes known in the art. In various embodiments, the physical layer technology may be the same for each of the forward uplink signal 132, the return downlink signal 133, the forward downlink signal 172, or the return uplink signal 173, or some of the signals may use a different physical layer technology than the other signals.

[0029] When supporting communication services, the satellite 120 may receive forward uplink signals 132 from one or more access node terminals 130 and provide corresponding forward downlink signals 172 to one or more user terminals 150. The satellite 120 may also receive return uplink signals 173 from one or more user terminals 150 and provide corresponding return downlink signals 133 to one or more access node terminals 130. Various physical layer transmit modulation and coding techniques may be used by the access node terminals 130, satellite 120, and user terminals 150 for communicating signals (e.g., adaptive coding and modulation (ACM)). The satellite 120 may include one or more transponders, each coupled to one or more receive elements of an antenna and one or more transmit antenna elements, to form K receive / transmit paths with different radiation patterns (e.g., by using different frequency ranges and polarization combinations). Each of the K receive / transmit paths may be assigned as a forward path or a return path at any time.

[0030] In some examples, satellite 120 may communicate data using a single beam (which may be referred to as an access node beam) for communicating with access node terminals 130 and a single beam (which may be referred to as a user beam) for communicating with user terminals 150. In some examples, each of these beams covers the satellite's 120 service area, which may span a large geographic area (e.g., half the Earth). In such cases, the access node beam and the user beam may be referred to as broad beams. Also, communication resources (e.g., time and / or frequency resources) allocated to communication system 100 may be shared among user terminals 150 within the coverage area of ​​user beam 125-b. In some examples, communication resources may be divided in time and / or frequency among user terminals 150, and separate communications may be transmitted to user terminals 150 via different communication resources. Additionally or alternatively, multiple user terminals 150 may use the same time and frequency resources, and separate communications may be transmitted to user terminals 150 via the same communication resources. When multiple user terminals 150 use the same time and frequency resources, the satellite communications system may apply spreading to the separate communications before transmission. For example, a sequence (e.g., a pseudo-random sequence or an orthogonal code) may be applied to the separate communications before they are transmitted in a combined signal over the same time and frequency resources.

[0031] In some examples, each sequence may be assigned to a different user terminal 150. Communications spread using a sequence may be referred to as DSSS communications, and simultaneously transmitting transmissions for different users spread using unique sequences may be an example of CDMA technology. The user terminal 150 may determine the sequence used for communications to the user terminal 150 and apply the sequence to the combined signal to extract the signal components carrying the communications intended for the user terminal 150. A satellite 120 performing CDMA communications may include multiple spreaders and one or more power amplifiers coupled to the spreaders and antenna elements of the antenna array. In some examples, a separate data signal may be provided to each spreader, which may apply a unique spreading code to the data signal to obtain multiple spread signals. The spread signals may be combined and provided to one or more power amplifiers, which may provide an amplified signal to an antenna of the satellite 120.

[0032] In another example, the satellite 120 may communicate data using multiple beams covering the satellite's 120 coverage area, e.g., to increase the capacity of the communications system. That is, the satellite 120 may communicate data using multiple beams that are arranged or tiled to cover the satellite's 120 coverage area. Some satellites 120 may include several transponders, each capable of independently receiving and transmitting signals. Each transponder may be connected to one or more antenna elements (e.g., a receive element and a transmit antenna element) to form receive / transmit signal paths with radiation patterns (antenna patterns) different from other receive / transmit signal paths, creating unique beams that may be assigned to the same (e.g., using different frequency ranges or polarizations) or different beam coverage areas. In some cases, a single receive / transmit signal path may be shared across multiple beams using input and / or output multiplexers. In such cases, the number of simultaneous beams that may be formed may generally be limited by the number of receive / transmit signal paths deployed on the satellite.

[0033] In some examples, access node terminal beams or user beams may be obtained through beamforming (and may be referred to as "spot beams"). In such cases, access node beam 125-a may be one of multiple access node terminal beams covering the coverage area of ​​satellite 120. Similarly, user beam 125-b may be one of multiple user node beams covering the coverage area of ​​satellite 120. Beamforming for a communication link may be performed by adjusting the signal phase (or time delay), and possibly the signal amplitude, of signals transmitted and / or received by multiple elements of one or more antenna arrays. This phase / amplitude adjustment is generally referred to as applying "beam weights" or "beam coefficients" to the transmitted signals. In the case of reception (by receiving elements of one or more antenna arrays), the relative phase, and possibly the amplitude, of the received signals are adjusted (i.e., the same or different beam weights are applied) so that the energy received from a desired location by the multiple receiving antenna elements constructively overlaps. Within a spot beam, communication resources may be divided among user terminals, as similarly described with reference to communication using a broad beam. Also, in some examples, the same set of communication resources may be shared by user terminals, as similarly described with reference to communication using a broad beam.

[0034] The satellite 120 can communicate with the access node terminal 130 by transmitting a return downlink signal 133 and / or receiving a forward uplink signal 132 via one or more access node terminal beams (e.g., access node beam 125-a, which may be associated with a respective access node beam coverage area 126-a). The access node beam 125-a can support, for example, communication services to one or more user terminals 150 (e.g., relayed by the satellite 120), or any other communication between the satellite 120 and the access node terminal 130. In some examples, the access node beam 125-a is one of a plurality of spot beams. The satellite 120 can communicate with the user terminal 150 by transmitting a forward downlink signal 172 and / or receiving a return uplink signal 173 via one or more user beams (e.g., user beam 125-b, which may be associated with a respective user beam coverage area 126-b). User beam 125-b may support communication services to one or more user terminals 150 or any other communication between satellite 120 and user terminal 150. In some examples, user beam 125-b is one of multiple spot beams. In some examples, satellite 120 may use one of access node beam 125-a or user beam 125-b to relay communications from access node terminal 130 to user terminal 150 (i.e., access node terminal 130 and user terminal 150 may share a beam).

[0035] To support beamforming operations, satellite 120 may use a phased array antenna assembly (e.g., a direct radiating array (DRA)), a phased array feed reflector (PAFR) antenna, or any other mechanism known in the art for receiving or transmitting signals (e.g., for communications or broadcast services, or data collection services). A phased array antenna assembly may be used to both receive uplink signals (e.g., forward uplink signal 132, return uplink signal 173, or both) and transmit downlink signals (e.g., return downlink signal 133, forward downlink signal 172, or both). A relatively large reflector may be illuminated by a phased array of antenna feed elements, supporting the ability to create a variety of spot beam patterns within constraints set by the size of the reflector and the number and placement of antenna feed elements.

[0036] Each of the antenna feed elements may also include or otherwise be connected to an RF signal transducer, LNA, phase shifter, or PA, and may be connected to one or more transponders within the satellite 120, which may perform other signal processing such as frequency conversion, beamforming, etc. In some examples, each phase shifter may be connected to one or more power amplifiers, and each power amplifier may be connected to one or more antenna elements. In some examples, the phase shifters and / or weighting amplifiers may be located in the access node terminal 130. Communications for different user terminals 150 may be provided to a set of phase shifters, which generate sets of phase-shifted signals and provide the sets of phase-shifted signals to a set of amplifiers. The set of amplifiers may amplify the phase-shifted signals (e.g., with different amplitude degrees) to obtain weighted signals and provide the weighted signals to a set of antenna elements. When radiated by the set of antenna elements, the weighted signals may combine constructively and / or destructively, such that the weighted signals form a single signal that is focused to a geographic region of a larger geographic area served by the satellite 120. A transponder connected with multiple antenna feed elements can perform beamformed communications.

[0037] In some examples, some or all of the antenna feed elements may be arranged as an array of component receive and / or transmit antenna feed elements that cooperate to enable various beamforming examples, such as ground-based beamforming (GBBF), on-board beamforming (OBBF), end-to-end (E2E) beamforming, or other types of beamforming. In the case of OBBF, the satellite 120 may include N transmitters, and an N x K beam weight matrix may be used to generate K user beams. Similarly, in the case of GBBF, the satellite 120 may include N transmitters and may receive N signals from one or more access node terminals, corresponding to respective transmitters (e.g., frequency division multiplexing) within the satellite. The one or more access node terminals may apply the N x K beam weight matrix to generate K user beams. In the case of E2E beamforming, the satellite 120 may include N strandponders. N1 transponders may be used to receive signals from M access node terminals, and the received signals may be weighted prior to transmission by the access node terminals to support beamforming of K1 user beams (e.g., weighting each of the K1 beam signals of a respective set of one or more access node terminals). Note that while this example describes the forward link, a similar arrangement may be made for the return link. Regardless of the beamforming technique used, to communicate data to user terminal 150, access node terminal 130 and / or satellite 120 may determine the location of user terminal 150 so that, for example, the data may be transmitted via a beam (e.g., user beam 125-b) having a coverage area that encompasses user terminal 150.

[0038] In some examples, beamforming allows satellite 120 to communicate more data than if a single broad beam were used, for example, because beamformed communications allow available frequency resources (e.g., satellite bandwidth) to be reused in multiple geographic regions within a larger geographic area served by satellite 120. That is, a given set of frequency resources can be reused in non-overlapping geographic regions. In some examples, satellite 120 may increase the amount of data that can be communicated as a function of the number of geographic regions. In some examples, a satellite 120 using beamforming technology may communicate data at a data rate of 100 Megasymbols per second (Msym / s), while a satellite 120 using a single broad beam and DSSS technology may communicate data at a data rate of 1 Msym / s. Additionally, beamforming may increase the SNR for communications between satellite 120 and user terminal 150 compared to DSSS communication technology, for example, because satellite 120 may concentrate the transmit power used to transmit the beam signal within the transmit beam rather than spreading it across the satellite's 120 service area. Thus, beamformed communications may be more reliable than non-beamformed (e.g., broad beam) communications, in which the transmit power for a communication is spread over a geographic area.

[0039] In some examples, the location of a user terminal may be unknown to the satellite communications system (e.g., to a controller that allocates satellite communications system resources to various user terminals). In some examples, the location of a user terminal is intentionally withheld from the satellite communications system by the user terminal. Additionally or alternatively, intentional steps may be taken by the user terminal to prevent the satellite communications system from determining the location of the user terminal. In such cases, a satellite communications system using spot beams may be unable to transmit to the user terminal, for example, because the satellite communications system may be unable to determine the spot beam on which the user terminal is located. In some examples, even if the location of the user terminal is known, the SNR of the signal received at the user terminal may be below a threshold associated with reliably communicating with the user terminal. In some examples, if the user terminal has an insufficient (e.g., small) antenna or is located in a poor coverage zone, the SNR of the signal may be below the threshold, and such a user terminal may be referred to as a disadvantaged user terminal.

[0040] In some examples, regardless of whether beamforming or broad beam techniques are used, the SNR of a signal received at a user terminal having a known location may be below a threshold associated with reliably communicating with the user terminal. In some examples, if a user terminal has an insufficient (e.g., small) antenna or is located in a poor coverage zone, the SNR of the signal will be below the threshold, and such a user terminal may be referred to as a disadvantaged user terminal.

[0041] To support communications with user terminals with unknown locations (and disadvantaged user terminals with known or unknown locations), satellite communications systems supporting dynamic spot beamforming can use an enhanced communications technique that includes applying multiple sequences to a data signal to obtain multiple spread signals and transmitting the spread signals via multiple antenna elements with wide-area native beam patterns. This enhanced communications technique may be referred to as “feed-specific spreading.” In some examples, to perform feed-specific spreading, a satellite communications system may include multiple phase shifters and multiple signal spreaders, each coupled to one or more antenna elements via one or more power amplifiers. In some examples, each signal spreader may apply a different sequence (e.g., a pseudorandom sequence or an orthogonal code) to a common data signal to obtain multiple spread signals, where the common signal may include data for a single user terminal. The signal spreaders then pass the multiple spread signals to sets of antenna elements, which together can radiate a combined signal including the spread signals over the satellite's coverage area.

[0042] A user terminal having an unknown location within the satellite's coverage area can receive the combined signal, for example, during an interval for spread communications. The receiving device can apply a set of sequences (e.g., pseudorandom sequences or orthogonal codes) to the received combined signal to obtain multiple despread signals, where the set of sequences can be the same as or based on the set of sequences used to transmit the combined signal. The receiving device can then process and combine the multiple despread signals to obtain a data signal that can be demodulated and decoded, where the data signal can have a higher SNR than any of the individual despread signals. In some examples, the SNR of the data signal can be proportional to the amount of spread signal included in the combined signal. The use of extended spreading can serve mission-sensitive user terminals without compromising the security of the user terminal. In some examples, the increased SNR provided by extended spread communications can be used to support communications with user terminals that have known locations but are unable to reliably communicate with the satellite, for example, because they have inadequate antennas or are located in dead zones. Such user terminals may similarly be scheduled to receive the combined signal, e.g., during intervals for spread communications. In some examples, feed-specific spreading may be offered as a premium service to user terminals with valid subscriptions, e.g., disadvantaged user terminals, security-conscious user terminals, etc.

[0043] In some examples, the satellite communications system can switch between beamforming and feed-specific spreading to support communications with both known-location user terminals and unknown-location user terminals without significantly impacting the performance of the satellite communications system. In some examples, the satellite communications system can transmit to known-location user terminals using beamforming during a first interval and transmit to unknown-location user terminals using feed-specific spreading during a second interval. In some examples, the throughput of the satellite communications system can be greater during the first interval than during the second interval, and the first interval can be longer than the second interval.

[0044] 2 illustrates a transmission system supporting satellite communications using spread or wide-area coverage signals according to embodiments disclosed herein. Transmission system 200 can be configured to transmit communication signals (e.g., data / control signals) to user terminals. Transmission system 200 can be further configured to switch between a beamforming mode and a spread mode to communicate with different types of user terminals, e.g., user terminals with known locations and user terminals with unknown locations, respectively. In some examples, transmission system 200 switches between the beamforming mode and the spread mode according to a schedule, e.g., transmitting beamformed communications during a first interval comprising a first amount of communication slots and transmitting spread communications during a second interval comprising a second amount of communication slots.

[0045] When configured in beamforming mode, the transmission system 200 can be configured to use a beamformer 205 to separate a data signal for a user terminal into multiple data signals and apply a phase shift and / or modify the amplitude of each of the multiple data signals so that the transmitted data signal is transmitted within a spot beam encompassing the user terminal. The beamformer 205 can include multiple phase shifters (e.g., a first phase shifter 210, a second phase shifter 215, and an nth phase shifter 220) and can modify the amplitude of each signal transmitted from the antenna elements (e.g., a first antenna element 240, a second antenna element 245, and an nth antenna element 250) via power amplifiers (e.g., a first power amplifier 225, a second power amplifier 230, and an nth power amplifier 235).

[0046] When configured in spreading mode, transmission system 200 may be configured to use spreader 260 to separate a data signal for a user terminal into multiple data signals and apply a unique sequence (e.g., a pseudo-random sequence or an orthogonal code) to each of the multiple data signals so that the transmitted data signal is transmitted, for example, in a broad beam or multiple spot beams spanning the entire satellite coverage area. Spreader 260 may include multiple component spreaders (e.g., first component spreader 265, second component spreader 270, and nth component spreader 275).

[0047] In some examples, the transmission system 200 may be included in a single device (e.g., a satellite or an access node terminal). In other examples, the transmission system 200 may be split across multiple devices (e.g., across a satellite and an access node terminal, or across a satellite and multiple access node terminals). For example, if on-board beamforming is used, at least the beamformer 205, spreader 260, power amplifier, and antenna may be included in the satellite. The communications manager 253, modulator 255, and buffer 257 may be included in the access node terminal or the satellite. In another example, if ground-based beamforming is used, the communications manager 253, modulator 255, buffer 257, beamformer 205, and spreader 260 may be included in the access node terminal, while the power amplifier and antenna may be included in the satellite. In such cases, the satellite may include a transponder used to relay signals received from the access node terminal. In yet another example, if end-to-end beamforming is used, the beamformer 205 and spreader 260 components can be distributed across multiple access node terminals, with each access node terminal including one or more phase shifters and one or more component spreaders. The communications manager 253, modulator 255, and buffer 257 can be located in a central device connected to multiple access node terminals. The amplifiers and antennas can then be included in a satellite. In such a case, the satellite can include a transponder used to relay signals received from the access node terminals.

[0048] The communications manager 253 can be configured to switch between a beamforming mode and a spreading mode. The communications manager 253 can indicate to the modulator 255 whether beamforming or spreading mode is activated. In some examples, the communications manager 253 can switch between the beamforming mode and the spreading mode according to a communication schedule, where the communications manager 253 can activate the beamforming mode during a first interval and the spreading mode during a second interval. When beamforming is enabled, the communications manager 253 can also determine and provide the location of the user terminal to other components in the transmission system 200. In some examples, the communications manager 253 can identify a user beam having a coverage area that encompasses the location of the user terminal and allocate data for the user terminal to a data stream associated with the user beam.

[0049] The switch 256 can be configured to control the data path from the modulator 255 to the beamformer 205 and the spreader 260. In some examples, the communications manager 253 is configured to control the switch 256 based on whether a beamforming mode or a spreading mode is configured. For example, the communications manager 253 can open the switch connecting the modulator 255 and the beamformer 205 and close the switch connecting the modulator 255 and the spreader 260 when spreading is activated.

[0050] The modulator 255 may be configured to modulate a data stream (e.g., a stream of binary values) to obtain a data signal including data symbols. The modulator 255 may be configured to modulate the data stream according to one or more modulation techniques and / or coding rates. In some examples, the modulator 255 uses a first modulation and coding scheme when the beamformer 205 is used and a second modulation and coding scheme when the spreader 260 is used; for example, when the spreader 260 is used, the modulator 255 may use a modulation and coding scheme with a higher modulation order. The modulator 255 may provide a modulated signal to one of the beamformer 205 or the spreader 260 based on, for example, whether a beamforming mode or a spreading mode is enabled. In some cases, the modulator 255 may generate multiple data streams for each user beam, and the beamformer 205 may apply respective coefficients (e.g., beam weights) to each of the data streams to obtain multiple phase-shifted signals. Thus, multiple data streams can be transmitted on respective beams formed by applying respective coefficients and combining multiple phase-shifted signals.

[0051] In some examples, transmission system 200 includes multiple modulators. For example, transmission system 200 may include modulator 255 and a second modulator. In such a case, modulator 255 may be connected to one of beamformer 205 and spreader 260, while the other modulator may be connected to the other of beamformer 205 and spreader 250. Additionally or alternatively, modulator 255 may be connected to a first subset of component spreaders 265, while the other modulator may be connected to a second subset of component spreaders 265. Communications manager 256 can send data to one of the modulators based on which communications mode is activated. For example, communications manager 256 can send data to modulator 255 if modulator 255 is connected to beamformer 205 and a beamforming mode is activated. The communications manager 256 can also transmit data to other modulators if they are connected to the spreader 260 and the spreading mode is activated. In other examples, the communications manager 256 can transmit data to both of the modulators as well as send commands indicating which of the modulators are enabled to output data (in such cases, the switch 256 can be optional).

[0052] Buffer 257 can be configured to store data to be transmitted to user terminals connected to transmission system 200. In some examples, buffer 257 stores data for user terminals reached at a first location using beamforming and data for user terminals reached at a second location using spreading. Buffer 257 can output data for user terminals to modulator 255 when the user terminals are scheduled to receive data from transmission system 200.

[0053] The beamformer 205 can be configured to combine with the antenna elements to transmit data signals in spot beams that cover geographic regions within the satellite's coverage area. The beamformer 205 can be configured to apply beamforming weights (e.g., phase shifts and amplitude adjustments) to the data signals received from the modulator 255 to obtain multiple weighted signals that can be transmitted simultaneously via different antenna elements. In some examples, the weighted signals transmitted by the beamformer 205 combine constructively and / or destructively to form a combined signal, the energy of which is concentrated within the coverage area of ​​the corresponding spot beam.

[0054] The first phase shifter 210 through the nth phase shifter 220 can be configured to apply phase shifts to received signals directed to the user terminal. In some examples, the phase shifters apply different phase shifts to the received signals. In some examples, the phase shifters are also configured to apply amplitude adjustments to the received signals. The first phase shifter 210, the second phase shifter 215, and the nth phase shifter 220 can output phase-shifted signals to the first power amplifier 225, the second power amplifier 230, and the nth power amplifier 235. In some examples, the first power amplifier 225, the second power amplifier 230, and the nth power amplifier 235 can be configured to adjust (e.g., increase or decrease) the amplitude of the received phase-shifted signals to obtain weighted signals. The first power amplifier 225, the second power amplifier 230, and the nth power amplifier 235 may output weighted signals to the first antenna element 240, the second antenna element 245, and the nth antenna element 250. In some examples, the phase shifters and amplifiers may be configured to apply a combination of phase shifts and amplitude adjustments (which may also be referred to as weights) such that the energy of the resulting signals transmitted from the antenna elements is concentrated within the spot beam coverage area.

[0055] In some examples, the beamformer 205 includes an additional set of phase shifters used in combination with the additional set of amplifiers and antenna elements to transmit beamformed signals in different spot beams. Additionally or alternatively, the first phase shifter 210, the second phase shifter 215, and the nth phase shifter 220 may be used to apply phase shifts to multiple data signals for user terminals located in different spot beam coverage areas, the resulting phase-shifted signals may be amplified by the first power amplifier 225, the second power amplifier 230, and the nth power amplifier 235, and the resulting weighted signals may be radiated by the first antenna element 240, the second antenna element 245, and the nth antenna element 250. In some examples, the multiple beamformed signals may be radiated such that the first beamformed signal is directed to the first spot beam coverage area and the second beamformed signal is directed to the second spot beam coverage area.

[0056] Spreader 260 may be configured to transmit a spread data signal via a broad beam that, in combination with the antenna elements, covers the entire (or a large portion) of the satellite's coverage area, where the native coverage area of ​​the antenna elements covers the entire (or a large portion) of the satellite's coverage area. Spreader 260 may be configured to apply a sequence (e.g., a unique pseudo-random sequence or an orthogonal code) to the data signal received from modulator 255 to obtain multiple coded signals that can be transmitted simultaneously via different antenna elements. In some examples, the coded signals transmitted by beamformer 205 do not combine constructively or destructively with each other (or have minimal effect on each other), spreading the energy of the coded signals across the satellite's coverage area.

[0057] The first component spreader 265 through the nth component spreader 275 can be configured to apply sequences to received data signals destined for a user terminal (or group of user terminals). In some examples, the component spreaders apply different sequences to the received signals. The first component spreader 265, the second component spreader 270, and the nth component spreader 275 can output coded signals to the first power amplifier 225, the second power amplifier 230, and the nth power amplifier 235. In some examples, the component spreaders may each be coupled to one or more of the power amplifiers, e.g., the first component spreader 265 may be coupled to the first power amplifier 225 and the second power amplifier 230. The first power amplifier 225, the second power amplifier 230, and the nth power amplifier 235 can be configured to amplify the encoded signal and output the amplified signal to the first antenna element 240, the second antenna element 245, and the nth antenna element 250. In some examples, the energy of the resulting signal transmitted from the antenna elements is spread across the satellite's coverage area, for example, based on the native coverage area of ​​the antenna elements. In some examples, the data signal can be received by multiple user terminals. Each user terminal receiving the data signal can apply the same set of despreading sequences to the data signal to extract the data.

[0058] In some examples, spreader 260 includes an additional set of code generators that are used in combination with an additional set of amplifiers and antenna elements to transmit additional coded signals for data signals directed to a user terminal. In some examples, spreader 260 includes an additional set of code generators that are used in combination with an additional set of amplifiers and antenna elements to transmit additional coded signals for data signals directed to another user terminal. For example, a first subset of antenna elements can transmit a first set of coded signals for a first user terminal, and a second subset of antenna elements can simultaneously transmit a second set of coded signals for a second user terminal. The first set of coded signals and the second set of coded signals can also be transmitted simultaneously using the same bandwidth.

[0059] In some examples, transmission system 200 includes multiple modulators 255 and multiple spreaders 260. In such cases, transmission system 200 can transmit multiple spread communications to multiple user terminals using different modulator / spreader pairs. In some examples, each modulator / spreader pair can be configured to transmit one stream of data to one or more user terminals. In some examples, different spreaders in different modulator / spreader pairs can use orthogonal codes, allowing the modulator / spreader pairs to perform simultaneous spread communications to multiple user terminals (or multiple groups of user terminals). Each modulator / spreader pair can be connected to the same or different (e.g., non-overlapping or partially overlapping) subsets of amplifiers and antenna elements.

[0060] While the spreader 260 is illustrated as being in parallel with the beamformer 205, in some examples the spreader 260 may be in series with the beamformer 205 (e.g., it may occur in the communication path before or after the beamformer 205). When the spreader 260 is positioned in series with the beamformer 205, the spreader 260 may be disabled when the transmission system 200 is in beamforming mode, and the sequence or a sequence of all 1s is not applied to the signals received from the modulator 255. Then, when the transmission system 200 is in spreading mode, a unique sequence may be applied to the signals received from the modulator 255, and the beamformer 205 may be disabled so that coefficients (e.g., beam weights) are not applied to the signals received from the spreader 260. Alternatively, when the transmission system 200 is in spreading mode, the beamformer 205 may apply beam weights to suppress spot beamforming (e.g., to provide a broad beam for spread signal coverage).

[0061] FIG. 3 illustrates a receiver supporting satellite communications using a spread or wide-area coverage signal according to an embodiment disclosed herein. The receiver 300 may be configured to receive a spread signal including multiple coded signals that have been spread using multiple sequences and are intended for a user terminal. The receiver 300 may be configured to separate the multiple coded signals by applying the multiple sequences to the received signal. In some examples, the sequences may be the same as the sequences applied to the data signals used to generate the spread signal at a transmitter (e.g., the transmission system 200 of FIG. 2). In some examples, the sequences may be based on the sequences applied to the data signals at the transmitter, but may also be different; for example, the sequences may be selected based on a combination of sequences applied at the transmitter. The receiver 300 may be further configured to decimate the separated signal and apply a filter (e.g., a low-pass filter) to the decimated signal to obtain a despread data signal. The receiver 300 may also be configured to estimate signal characteristics of the despread signals (which may include a header for estimating the signal characteristics) and combine the resulting despread signals to obtain a combined data signal that includes a data signal that can be demodulated and decoded.

[0062] The receiver 300 may be included in a user terminal. The receiver 300 may be connected to one or more antennas used to receive RF signals from satellites. In some examples, the receiver 300 may also be connected to an analog-to-digital converter that digitizes the resulting RF signal. The receiver 300 may include a despreader 305, a combiner 340, and a decoder 370. The despreader 305 may be configured to despread (e.g., using a direct sequence) multiple spread signals included in a signal received by the receiver 300. To despread the spread signals, the despreader 305 may be configured to apply a sequence to the received signal and pass the resulting signal through a decimating low-pass filter. The despreader 305 may include a first multiplier 310 and an nth multiplier 325, a first component despreader 320 and an nth component despreader 335, a first decimating filter 315, and an nth decimating filter 330.

[0063] The first multiplier 310 can be configured to apply a first sequence generated by the first component despreader 320 to the received communication signal. In some examples, the first multiplier 310 applies the complex conjugate of the first sequence to the received communication signal. After the first sequence is applied to the received communication signal, components of the received signal that were spread using a corresponding sequence (e.g., the first sequence or a related sequence) can be separated from other components of the received signal. Similarly, the nth multiplier 325 can apply an nth sequence generated by the nth component despreader 335 to the received communication signal. After the set of sequences is applied to the received signal, the separated signal can be passed to a corresponding decimating filter.

[0064] The first decimating filter 315 may decimate (e.g., discard or otherwise downsample) the first separated signal output from the first multiplier 310 to obtain a first downsampled signal. The decimation used by the first decimating filter 315 may depend on the spreading code (e.g., the length of the spreading code), for example, to obtain a signal having the bandwidth of the original data stream. After decimation, the first decimating filter 315 may apply a low-pass filter to the remaining samples to remove alias components in the downsampled signal. In some examples, the low-pass filter may be applied before decimation. Similarly, the nth decimating filter may decimate and low-pass filter the nth separated signal output from the nth multiplier 325 to obtain an nth downsampled signal. After downsampling and filtering the separated signal, the decimating filter may output a despread signal to the combiner 340.

[0065] The combiner 340 may be configured to combine the despread signals output by the despreader 305. To combine the despread signals, the combiner 340 may be configured to estimate signal characteristics (e.g., phase, amplitude, timing, and frequency characteristics) of the despread signals based on the corresponding headers. The signal characteristics of the despread signals may also be referred to as coefficients for the despread signals. The combiner 340 may include a first header estimator 355 and an nth header estimator 365, a second multiplier 345 and an mth multiplier 360, and a summing circuit 350.

[0066] The first header estimator 355 may be configured to identify a header of the despread signal obtained from the first decimating filter 315. In some examples, the first header estimator 355 determines an amplitude and phase reference of the despread signal from the header. The first header estimator 355 may also determine frequency and timing information of the despread signal from the header. The amplitude and phase reference of the despread signal may be used to determine the amplitude and phase of the despread signal relative to the amplitude and phase reference. In some examples, the header may also be used to determine characteristics of a channel between the receiver 300 and an antenna element used to transmit a spread signal corresponding to the despread signal obtained from the first decimating filter 315. In some examples, the second multiplier 345 is configured to apply the amplitude and phase reference to the despread signal to obtain a data signal included in the despread signal. In some examples, the second multiplier applies the complex conjugate of the amplitude and phase reference to the despread signal. In some examples, the obtained data signal is calculated based on the SNR or symbol-to-noise ratio (which is equivalent to the energy density per symbol E s Density to noise

number

[0067] The summing circuit 350 can be configured to combine the resulting data signals with each other to obtain a combined data signal. In some examples, the summing circuit 350 adds the resulting data signals together without affecting signal noise, increasing the SNR (and / or symbol-to-noise ratio) of the data signal by a factor based on some spreading component included in the received signal. The summing circuit 350 can output the combined data signal to the decoder 370.

[0068] Decoder 370 may be configured to demodulate and decode the combined data signal obtained from combiner 340. In some examples, decoder 370 may be configured to demodulate the combined data signal by mapping symbols included in the combined data signal to locations within a signal constellation, each associated with a unique binary value. After mapping the symbols to locations, decoder 370 may be configured to generate a data stream from the symbols and decode the data stream to obtain data included in the communication signal received at despreader 305.

[0069] FIG. 4 shows a beam diagram supporting satellite communications using a spread or wide-area coverage signal according to embodiments disclosed herein. Beam diagram 400 illustrates a pattern of spot beam coverage areas configured for a satellite within the satellite's service area. The spot beam coverage areas may be distributed (e.g., in a tiled pattern) across the service area 405. In some examples, adjacent spot beam coverage areas use different portions of the radio spectrum and / or different polarizations to avoid inter-spot beam interference. In some examples, a set of spot beam coverage areas (e.g., four spot beams, seven spot beams) may use the entire radio spectrum and a set of polarizations. In some examples, the spot beam coverage areas are formed by a satellite communications system when the transmitting system (e.g., transmitting system 200 of FIG. 2) activates a beamforming mode. In some examples, the spot beam coverage areas are formed by applying a fixed set of beamforming weights to data signals prior to transmission via antenna elements. In some examples, the spot beam coverage area corresponds to a configurable spot beam formed by applying configurable beamforming weights to a data signal prior to transmission via a set of antenna elements in an antenna array.

[0070] A user terminal can be located within one or more spot beams. For example, the user terminal 415 can be located within the spot beam coverage area 410. To communicate with the user terminal 415, the satellite communications system can transmit communications to the user terminal 415 on a spot beam having the spot beam coverage area 410. Thus, to communicate with the user terminal 415, the satellite communications system can first determine the location of the user terminal 415 to determine which spot beam to use for transmission to the user terminal 415. In some examples, the user terminal 415 has a fixed location known to the satellite communications system. In some examples, the satellite communications system and the user terminal 415 implement a procedure that allows the satellite communications system to determine the location of the user terminal 415, for example, by exchanging location information using a broad beam channel, tracking the movement of the user terminal 415 for beam handoff, or by the user terminal 415 transmitting its location or via a given return link beam.

[0071] In some examples, a user terminal may be located in a dead zone within a spot beam or at the edge of a spot beam coverage area. In such cases, the user terminal may be unable to receive communications from the satellite communications system. Also, in some examples, the user terminal may be unable to receive communications from the satellite communications system if the user terminal's antenna gain is insufficient, for example, because the SNR may be below a threshold. In such cases, other communications techniques, such as the spreading techniques described herein and with reference to FIG. 2, may be able to provide more reliable service to the user terminal.

[0072] FIG. 5 shows a beam diagram supporting satellite communications using a spread or wide-area coverage signal according to embodiments disclosed herein. Beam diagram 500 illustrates a pattern of broad beam coverage areas configured for a satellite within the satellite's service area. In some examples, the broad beam coverage areas correspond to native beams of separate antenna elements in an antenna array (e.g., antenna elements used for beamforming spot beams as shown in FIG. 4). The broad beam coverage areas can have a high degree of overlap with one another. For example, a broad beam coverage area can overlap at least 50% with at least one other broad beam, or can overlap at least 50% with more than a number of adjacent broad beam coverage areas (e.g., two, three, four, five, etc.). In some examples, the broad beam coverage area spans a significant portion (e.g., more than 20%, more than 50%, more than 70%, more than 80%) of the service area 505. In some cases, the service area 505 is defined by an area having at least some amount or percentage of a broad beam coverage area. In some examples, the overlapping broad beam coverage areas use overlapping portions of the radio spectrum. In some examples, the service area 505 is the coverage area of ​​a satellite communications system when the transmission system (e.g., transmission system 200 of FIG. 2) activates a spread mode.

[0073] As discussed herein and with reference to Figure 2, each broad beam (or set of broad beams) may include a communication signal for a user terminal that is spread using a unique sequence (e.g., a pseudo-random sequence or an orthogonal code). The user terminal 515 may receive a respective communication signal (e.g., in a combined signal) in each of the broad beams that encompass the user terminal 515, despread the received communication signals, and combine the resulting data signals to obtain a combined received data signal for decoding.

[0074] A user terminal may be located within multiple broad beams. In some examples, a user terminal 515 may be located within multiple broad beams while being located outside the broad beam coverage area 510. In such cases, a communication signal containing data for the user terminal 515 transmitted in the broad beam coverage area 510 may not be received by the user terminal 515. However, if another communication signal containing data for the user terminal 515 is transmitted in an additional broad beam coverage area (including one or more broad beam coverage areas encompassing the user terminal 515), the user terminal 515 may still obtain the data. Thus, a satellite communication system using spreading can communicate data to the user terminal 515 without knowing the location of the user terminal 515. In some examples, the user terminal 515 may take measures to prevent the satellite communication system from determining the location of the user terminal 515. In some examples, the transmission system determines the user terminal's general location (e.g., Central America) and transmits data for the user terminal via antenna elements associated with a broad beam that covers the general location.

[0075] FIG. 6 illustrates a diagram of a process for supporting satellite communications using spread or wide-area coverage signals according to embodiments disclosed herein.

[0076] Process flow 600 may be performed by a transmission system 601, which may be an example of an access node terminal, a satellite, or a combination thereof, as described above with reference to Figures 1 and 2. Process flow 600 may also be performed by a first user terminal 603 and a second user terminal 605, which may be examples of user terminals described above with reference to Figures 1 and 3. In some examples, the transmission system 601 may be able to determine the location of the first user terminal 603 but may not be able to determine the location of the second user terminal 605.

[0077] In some examples, process flow 600 illustrates an exemplary sequence of operations performed to support satellite communications using spread or wide-area coverage signals. For example, process flow 600 depicts operations for switching between a beamforming mode and a spread mode to transmit information to user terminals within the coverage area of ​​transmission system 601. It is understood that one or more of the operations described in process flow 600 may be performed earlier or later in the process, omitted, replaced, supplemented, or performed in combination with another operation. Also, additional operations described herein that are not included in process flow 600 may be included.

[0078] At 610, the second user terminal 605 may determine spreading parameters that may be used for subsequent transmissions from the transmission system 601. In some examples, the second user terminal 605 determines the spreading parameters based on the geographic location of the second user terminal 605, e.g., the second user terminal may determine that the transmission system 601 is configured to use a set of spreading codes for broadcasting to user terminals in North America. In other examples, the second user terminal 605 may be programmed (e.g., prior to deployment) to receive transmissions from the transmission system 601 using a set of spreading codes, where the transmission system 601 may be provided with a mapping between the set of spreading codes and the second user terminal 605.

[0079] At 615, the transmitting system 601 may activate a beamforming mode to perform communications. In some examples, the transmitting system 601 activates the beamforming mode based on a communication schedule indicating a first interval for beamforming in a scheduling period and a second interval for spreading in the scheduling period. The first interval may be longer than the second interval, e.g., the first interval may span 97% of the scheduling period and the second interval may span 3% of the scheduling period. In some examples, the throughput of the transmitting system 601 may be greater during the first interval than during the second interval, e.g., for a 100 MHz channel, the throughput may be approximately 10 Gigasymbols (Gsym) per second (Gsym / s) during the first interval and approximately 1 Msym / s during the second interval, and the aggregate throughput of the transmitting system 601 over the scheduling period may be approximately 9.7 Gsym / s. In some examples, the SNR (and / or symbol-to-noise ratio) of communications transmitted in the first interval is less than the SNR (and / or symbol-to-noise ratio) of communications transmitted in the second interval; for example, the symbol-to-noise ratio may be approximately 22 dB higher during the second interval.

[0080] At 620, the transmitting system 601 can apply beam weights to a data signal for transmission to one or more user terminals (e.g., including the first user terminal 603). In some examples, the data signal includes a header portion and a data portion, and the header portion can be used by the user terminal to determine signal coefficients (e.g., amplitude, phase, frequency, and timing information) of the received data signal. In some examples, the header portion can be used to estimate a channel between the user terminal and the transmitting system 601. The determined signal coefficients can be used to assist in demodulating and decoding the data portion. In some examples, the transmitting system 601 applies beam weights to the data signal directed to the first user terminal 603, which concentrates the energy of the resulting beamformed signal within a spot beam coverage area encompassing the first user terminal 603. Before applying the beam weights to the data signal, the transmitting system 601 can modulate the data to obtain the data signal. In some examples, the transmitting system 601 can use a first modulation and coding scheme based on whether a beamforming mode is enabled.

[0081] At 625, the transmission system 601 may transmit beamformed signals to the user terminals. In some examples, the transmission system 601 may transmit one or more beamformed signals to the first user terminal 603 using a spot beam having a coverage area that encompasses the first user terminal 603. The transmission system 601 may transmit additional beamformed signals to other user terminals using other spot beams. Some of the spot beams (e.g., adjacent or overlapping spot beams) may use different portions of the wireless spectrum than each other, while other spot beams (e.g., non-adjacent or non-overlapping spot beams) may use a common portion of the wireless spectrum.

[0082] At 630, the first user terminal 603 can obtain data from the received beamformed signal. In some examples, the first user terminal 603 can apply receive beam weights to the received beamformed signal to enhance signal characteristics of the received beamformed signal before demodulating the received beamformed signal. In some examples, the first user terminal 603 determines a set of receive beam weights to apply to the received beamformed signal based on a header portion of the beamformed signal and / or a previous beamformed signal. After receiving the beamformed signal, the first user terminal 603 can demodulate the beamformed signal by mapping data symbols in the beamformed signal to positions within a symbol constellation associated with the first modulation and coding scheme. Based on mapping the data symbols to the symbol constellation, the first user terminal 603 can decode the data symbols to obtain a stream of binary data.

[0083] At 635, the transmitting system 601 may switch to a spreading mode to perform communications. In some examples, the transmitting system 601 activates the spreading mode based on the second interval of the start of the scheduling period. As part of switching to the spreading mode, the transmitting system 601 may access a buffer used to store data for a user terminal whose location is unknown and / or a buffer used to store data to be broadcast to multiple user terminals. Also, as part of switching to the spreading mode, the transmitting system 601 may deactivate a beamformer and activate a spreader connected to the same set of power amplifiers and antenna elements as the beamformer.

[0084] At 640, the transmitting system 601 may apply spreading codes to a data signal intended for a user terminal and / or set of user terminals of unknown location (e.g., if broadcasting is enabled). In some examples, the transmitting system 601 applies a set of unique spreading codes to the data signal to obtain multiple spread signals, each carrying the same data. In some examples, the data signal is intended for a user terminal of unknown location (e.g., the second user terminal 605). In other examples, the data signal is intended for multiple user terminals (e.g., including the second user terminal 605). The transmitting system 601 may then output the multiple spread signals to a set of power amplifiers coupled to the set of antenna elements and configured to amplify the multiple spread signals before providing the spread signals to the set of antenna elements. Before applying beam weights to the data signal, the transmitting system 601 may modulate the data to obtain the data signal. In some examples, the transmitting system 601 may use a first modulation and coding scheme based on whether a beamforming mode is enabled. Prior to applying the spreading code to the data signal, the transmitting system 601 may modulate the data to obtain the data signal. In some examples, the transmitting system 601 may use a second modulation and coding scheme based on the spreading mode being enabled. In some examples, the symbols generated using the second modulation and coding scheme convey additional information related to the symbols generated using the modulation and coding scheme used when the beamforming mode is enabled.

[0085] At 645, the transmission system 601 can transmit spread signals to the user terminal. In some examples, the transmission system 601 can transmit one or more spread signals to the second user terminal 605 using multiple broad beams that cover a significant portion of the service and have coverage areas that significantly overlap with each other. In some examples, a subset (or all) of the broad beams encompass the second user terminal 605. In some examples, the transmission system 601 can transmit one or more spread signals to multiple user terminals (including the second user terminal 605) using multiple broad beams that cover a significant portion of the service and have coverage areas that significantly overlap with each other. In some examples, a subset (or all) of the broad beams encompass the second user terminal 605. Similarly, a subset (e.g., a different subset) (or all) of the broad beams can encompass additional user terminals of the multiple user terminals.

[0086] In some examples, the transmission system 601 transmits a first set of spread signals using a first set of sequences and a second set of spread signals using a second set of sequences. The first set of sequences may be directed to a second user terminal 605, and the second set of spread signals may be directed to a third user terminal (not shown). Additionally, the first set of sequences may be orthogonal to the second set of sequences.

[0087] At 650, the second user terminal 605 can apply a set of despreading codes to the spread transmission received at the second user terminal 605. In some examples, the second user terminal 605 applies the same set of spreading codes to the received spread transmission as the transmission system 601 applied to obtain the spread transmission. In other examples, the second user terminal 605 applies a different set of despreading codes to the received spread transmission, where the different set of despreading codes can be based on the set of spreading codes applied by the transmission system 601 to obtain the spread transmission. For example, the different set of despreading codes can be based on a combination of the sets of spreading codes applied by the transmission system 601 to obtain the spread transmission. After applying the set of despreading codes to the received spread transmission, the second user terminal 605 can separate the spread signals transmitted from different antenna elements at the transmission system 601. The second user terminal 605 can then apply a decimating filter to the separated spread signals to obtain despread signals corresponding to the original data signal.

[0088] In some examples, all or a subset of the spread signals transmitted from the transmission system are intended for multiple user terminals. In such cases, a third user terminal receiving the spread signals can apply the same (or similar) set of despreading codes to the spread signals. In other examples, a first subset of the spread signals is intended for a second user terminal 605, and another subset of the spread signals is intended for a third user terminal. The second user terminal 605 can apply a first set of despreading codes to the received spread signals to despread the first subset of the spread signals, and the third user terminal can apply a second set of despreading codes to the received spread signals to despread the second subset of the spread signals. In some examples, the first set of despreading codes is orthogonal to the second set of despreading codes.

[0089] At 655, the second user terminal 605 can combine the despread signals with each other to obtain a combined data signal having enhanced signal characteristics. The second user terminal 605 can use the header portion of the despread signal to determine signal coefficients (e.g., phase, amplitude, frequency, timing parameters) of the despread signal and reconstruct original data symbols included in the original data signal. In some examples, each original data symbol can have a first symbol-to-noise ratio. After reconstructing the original data symbols, the second user terminal 605 can combine the reconstructed data symbols to obtain combined data symbols. In some examples, the combined data symbols can have a second symbol-to-noise ratio greater than the first symbol-to-noise ratio, for example, based on the number of despread signals obtained at the second user terminal 605. The second user terminal 605 can use the combined data symbols to reconstruct the data signal transmitted from the transmission system 601. A third user terminal can similarly generate a combined data signal using a set of received data signals transmitted from transmission system 601 using a different set of spreading codes.

[0090] At 660, the second user terminal 605 can obtain data from the reconstructed data signal. In some examples, the second user terminal demodulates the combined data symbols and maps the data symbols to locations within a symbol constellation associated with a second modulation and coding scheme. Based on mapping the data symbols, the second user terminal can generate a stream of binary data. If the spread transmission received from the transmission system 601 includes data for multiple user terminals, another user terminal can similarly receive the spread transmission via multiple broad beams and extract the data from the spread transmission. A third user terminal can similarly obtain data from the reconstructed data signal using the combined data signal.

[0091] In some examples, a user terminal (e.g., user terminal 603 and / or user terminal 605) can receive both beamformed and spread transmissions. In such cases, to receive beamformed transmissions, the user terminal can bypass the despreader (e.g., despreader 305) used to receive the spread signal. In other examples, the user terminal may not bypass the despreader but instead apply a sequence to the signal received at the user terminal that does not alter the received signal (e.g., a sequence of all ones or zeros). In some examples, the user terminal can also disable a decimating filter in the receive path.

[0092] To receive a spread transmission, a user terminal may apply a despreading sequence to the received spread transmission and combine the resulting despread signals. In some examples, the user terminal includes a communications manager that is used to activate and deactivate a despreader within the user terminal. In some examples, the communications manager controls a switch (or set of switches) that controls the receive path of a received signal. For example, the communications manager may open a switch that connects one or more antennas to the despreader and close a switch that bypasses the despreader, or vice versa, when beamforming mode is enabled.

[0093] As suggested herein, the SNR (and / or symbol-to-noise ratio) of a spread transmission may be greater than the SNR (and / or symbol-to-noise ratio) of a beamformed transmission, e.g., because multiple versions of the same data signal may be transmitted to a single user terminal when a spreading mode is enabled. For example, consider the following scenario: M users may be supported by the transmission system 601, and M symbols [a1, a2, ..., a M ] is transmitted simultaneously to M users.

number

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[0094] To obtain the spread symbols, the matrices A and P may be multiplied together, resulting in

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[0095] The channel between the M transmit antenna elements and the M user locations can be represented using a matrix C, where the waveforms received at the M user locations can be equal to CBAP. Each user experiences additive white Gaussian noise, which can be represented by a matrix W, where the white noise E{WW H The expected value of} is 2σ 2 *I, where I is an M-by-K identity matrix. Thus, the waveforms received at M user locations can be represented by a matrix R, which can be equal to CBAP+W, where the m-th row and k-th column of R is r m,k which may be equal to the received sample at location m during time sample k.

[0096] To obtain the received symbols, a matched filter can be applied to the received waveform, for example, based on the spreading sequence used in matrix P. The matched filter output can then be represented by a complex-valued matrix Y, where Y=PR H The rows of matrix Y may store the matched filter outputs of one spreading code across M terminal locations, and the columns of matrix Y may store the matched filter outputs of a different spreading code at one terminal location. Expanding this equation yields Y=P[CBAP+W] H Using the Hermitian transpose property, the general expression for the matched filter output is Y=PP H A H B H C H +PW H where PP H may provide spatial information of the matched filter output (e.g., cross-correlation between the formed beams), and B H C H can provide time information (eg, spreading code cross-correlation) of the matched filter output.

[0097] The general formula can be used to compare the performance of beamformed transmission using spot beams and spread-spectrum transmission using broad beams. For example, for beamformed communication to M user terminals using equal power in M ​​orthogonal beams, B H C H can be equal to MI, where I is the identity matrix, and the power amplifier can be

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[0098] When spreading communication is performed to a user terminal using orthogonal (or nearly orthogonal) spreading codes for each of M transmit antenna elements, PP H may be equal to KI, where I is the identity matrix and B may be equal to the MxM identity matrix. Also, if only one signal passes through each power amplifier and each power amplifier is connected to one transmit antenna element, |a m |is,

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[0099] For spot beams, K may be greater than or equal to 1 and M may be equal to 100. For broad beams using multiple spreading codes for users, K may be greater than or equal to M and M may be equal to 1. In such cases, the symbol-to-noise ratio for communications using spot beams is

number

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[0100] Although described in the context of a satellite communications system, aspects of the communications techniques described herein can also be used in non-satellite communications (e.g., terrestrial communications). For example, a transmitting device (e.g., a wireless access point) may include a transmission system similar to transmission system 200 and may switch between beamforming and the enhanced spreading techniques described herein (which involve applying multiple spreading codes to data signals directed to one or more users). A receiving device (e.g., a wireless terminal) may also include a receiver similar to receiver 300 and may receive signals transmitted in accordance with the enhanced spreading techniques described herein.

[0101] 7 shows a diagram of a process for supporting satellite communications using spread or wide-area coverage signals according to embodiments disclosed herein. The operations of method 700 may be implemented by a user terminal or components thereof, as described herein. In some examples, a processing system of the user terminal may execute a set of instructions for controlling functional elements of a satellite to perform the described functions. Additionally or alternatively, the processing system may perform aspects of the described functions using dedicated hardware.

[0102] At 705, the satellite communications system may switch from a first mode for transmitting beam signals via beamformed spot beams over a geographic area to a second mode that bypasses the beamformer used to form the spot beams. The operations of 705 may be performed in accordance with techniques described herein. In some examples, aspects of the operations of 705 may be performed by a transmission system, such as transmission system 200 of FIG. 2 using a communications manager, as described herein.

[0103] At 710, the satellite communications system may generate a modulated signal including data for one or more user terminals based on switching to the second mode, the modulated signal including a set of modulated data symbols. The operations of 710 may be performed in accordance with techniques described herein. In some examples, aspects of the operations of 710 may be performed by a modulator (e.g., modulator 255 of FIG. 2 ) as described herein.

[0104] At 715, the satellite communications system may apply a set of spreading codes to modulated data symbols of the modulated data symbols to obtain a set of spread data symbols. The operations of 715 may be performed in accordance with techniques described herein. In some examples, aspects of the operations of 715 may be performed by a spreader (e.g., spreader 260 of FIG. 2 ) as described herein.

[0105] At 720, the satellite communications system may transmit each spread data symbol of the set of spread data symbols using one or more antenna elements of the set of antenna elements. The operations of 720 may be performed in accordance with techniques described herein. In some examples, aspects of the operations of 720 may be performed by a transmitting system (e.g., transmitting system 200 of FIG. 2 using the set of antennas) as described herein.

[0106] In some examples, an apparatus described herein may perform a method such as method 700. The apparatus may include features, means, or instructions (e.g., a non-transitory computer-readable medium storing instructions executable by a processor) for: switching from a first mode for transmitting beam signals via beamformed spot beams over a geographic area to a second mode that bypasses the beamformer used to form the spot beams; generating, based on the switching to the second mode, a modulated signal including data for one or more user terminals, the modulated signal including a set of modulated data symbols; applying a set of spreading codes to the modulated data symbols of the modulated data symbols to obtain a set of spread data symbols; and transmitting each spread data symbol of the set of spread data symbols using one or more antenna elements of the set of antenna elements.

[0107] Some examples of the methods 700 and apparatus described herein may further include operations, features, means, or instructions for receiving data for a user terminal within a geographic area having a location unknown to the transmitter used to transmit the set of spread data symbols.

[0108] Some example methods 700 and apparatus described herein may further include operations, features, means, or instructions for switching from the second mode to the first mode based on a schedule for switching between the first mode and the second mode.

[0109] Some example methods 700 and devices described herein may further include operations, features, means, or instructions for identifying a first interval for operating in a first mode and a second interval for operating in a second mode, and switching to the second mode may be based on the occurrence of the second interval.

[0110] Some example methods 700 and apparatuses described herein may further include operations, features, means, or instructions for receiving second data for a second user terminal having a known location within the geographic area, generating a second modulated signal including the second data based on switching to the first mode, the second modulated signal including a second set of modulated data symbols, applying a set of beam weights to the second modulated data symbols of the second set of modulated data symbols to obtain a set of weighted data symbols, and transmitting each weighted data symbol of the set of weighted data symbols using one or more antenna elements of the set of antenna elements.

[0111] Some example methods 700 and apparatuses described herein may further include operations, features, means, or instructions for amplifying the set of spread data symbols included in the transmission.

[0112] 8 shows a diagram of a process for supporting satellite communications using spread or wide-area coverage signals according to embodiments disclosed herein. The operations of method 800 may be implemented by an access node terminal and / or a satellite or components thereof, as described herein. In some examples, a processing system of the access node terminal and / or satellite may execute a set of instructions for controlling functional elements of the satellite to perform the described functions. Additionally or alternatively, the processing system may perform aspects of the described functions using dedicated hardware.

[0113] At 805, a composite signal including a set of spread data symbols associated with common data symbols may be received. The operations of 805 may be performed in accordance with techniques described herein. In some examples, aspects of the operations of 805 may be performed by a receiver (e.g., using one or more antennas, e.g., using receiver 300 of FIG. 3) as described herein.

[0114] At 810, the set of spread data symbols may be despread to obtain a set of despread data symbols. The operations of 810 may be performed in accordance with techniques described herein. In some examples, aspects of the operations of 810 may be performed by a despreader (e.g., despreader 305 of FIG. 3 using a code generator, a multiplier, and a decimating filter) as described herein.

[0115] At 815, a set of coefficients for the set of despread data symbols may be estimated. The operations of 815 may be performed in accordance with techniques described herein. In some examples, aspects of the operations of 815 may be performed by a header estimator (e.g., first header estimator 355 of FIG. 3 ), as described herein.

[0116] At 820, the set of despread data symbols may be combined to obtain combined data symbols that correspond to the common data symbols based on the estimation. The operations of 820 may be performed in accordance with techniques described herein. In some examples, aspects of the operations of 820 may be performed by a combiner (e.g., combiner 340 of FIG. 3 using a summing circuit, for example) as described herein.

[0117] In some examples, an apparatus described herein may perform a method such as method 800. The apparatus may include features, means, or instructions (e.g., a non-transitory computer-readable medium storing instructions executable by a processor) for receiving a composite signal including a set of spread data symbols associated with a common data symbol, despreading the set of spread data symbols to obtain a set of despread data symbols, estimating a set of coefficients for the set of despread data symbols, and combining the set of despread data symbols to obtain combined data symbols that correspond to the common data symbol based on the estimation.

[0118] Some examples of the methods 800 and apparatus described herein may further include operations, features, means, or instructions for adjusting a set of despread data symbols using a set of coefficients, where the adjusted set of data symbols may be obtained based on using the set of coefficients, including combining.

[0119] In some examples of the methods 800 and apparatus described herein, despreading the set of spread data symbols may include acts, features, means, or instructions for applying a set of despreading codes to the set of spread data symbols.

[0120] Some example methods 800 and apparatuses described herein may further include operations, features, means, or instructions for decimating the set of despread data symbols, where decimating includes, for each despread data symbol, filtering a set of frequencies from the respective despread data symbol and downsampling the respective despread data symbol after filtering.

[0121] In some examples of the methods 800 and apparatus described herein, estimating a set of coefficients for a set of despread data symbols may include operations, features, means, or instructions for estimating amplitude, phase, timing, frequency, or any combination thereof for the set of despread data symbols.

[0122] Some example methods 800 and apparatuses described herein may further include operations, features, means, or instructions for demodulating the combined data symbols to obtain demodulated data symbols and decoding the demodulated data symbols.

[0123]

[0013] It should be noted that the methods described herein are possible implementations, and that operations and steps may be rearranged or otherwise modified, and that other implementations are possible. Furthermore, portions from two or more methods may be combined.

[0014] A system for satellite communications is described. The system may include a plurality of component spreaders, each of which applies a respective spreading code of a plurality of spreading codes to a common data symbol of a modulated signal to obtain a plurality of spread data symbols, a plurality of antenna elements connected to the plurality of component spreaders, each antenna of the plurality of antenna elements configured to obtain one or more spread data symbols of the plurality of spread data symbols and radiate element signals including one or more spread data symbols, and a composite signal including the signals radiated from the plurality of antenna elements.

[0124] The system may also include a receiver configured to receive the composite signal, comprising: a plurality of component despreaders, each component despreader of the plurality of component despreaders configured to apply a despreading code of the plurality of despreading codes to the composite signal to obtain a plurality of despread data symbols; a plurality of signal component estimators coupled to the plurality of component despreaders, each signal component estimator of the plurality of signal component estimators configured to estimate one or more coefficients for a respective despread data symbol of the plurality of despread data symbols; and a combiner coupled to the plurality of signal component estimators, the combiner configured to combine the plurality of despread data symbols based at least in part on the one or more coefficients estimated for the plurality of despread data symbols to obtain a combined data symbol corresponding to the common data symbol.

[0125] The system may also include a plurality of decimators coupled to the plurality of component despreaders and the plurality of signal component estimators and configured to obtain a plurality of decimated data symbols, each decimator of the plurality of decimators configured to filter and downsample a respective despread data symbol of the plurality of despread data symbols to obtain a decimated data symbol.

[0126] In some examples of the system, each signal component estimator of the plurality of signal component estimators is configured to estimate one or more coefficients for a respective despread data symbol based at least in part on a respective decimated data symbol of the plurality of decimated data symbols.

[0127] In some examples of the system, the receiver may include a demodulator coupled to the combiner, the demodulator configured to demodulate the combined data symbols to obtain demodulated data symbols, and a decoder configured to decode the plurality of demodulated data symbols comprising the demodulated data symbols.

[0128] In some examples of the system, each antenna element of the plurality of antenna elements is configured to obtain a respective spread data symbol of the one or more spread data symbols.

[0129] In some examples of the system, an antenna element of the plurality of antenna elements is configured to obtain two or more of the plurality of spread data symbols.

[0130] In some example systems, two or more of the plurality of antenna elements are configured to obtain spread data symbols from one of the plurality of component spreaders.

[0131] In some examples of the system, the one or more coefficients include amplitude, phase, timing, frequency, or any combination thereof.

[0132] In some examples of the system, the modulated signal is a first modulated signal, and the transmitter further includes a beamformer configured to apply beamforming coefficients to the second modulated signal to obtain a plurality of beamformed data symbols, and a communications manager configured to switch between a first mode for transmitting the plurality of beamformed data symbols via the plurality of antenna elements for communication via a beamformed spot beam and a second mode that causes the first modulated signal to bypass the beamformer.

[0133] In some examples of the system, the communications manager is configured to activate the first mode for a first interval of duration and to activate the second mode for a second interval of duration that is smaller than the first interval.

[0134] In some examples of the system, the transmitter includes a modulator coupled to a plurality of component spreaders, the modulator configured to generate a plurality of data symbols including a common data symbol.

[0135] The system may also include a satellite comprising a plurality of antenna elements and a gateway communicatively connected to the satellite, the gateway comprising a plurality of component spreaders.

[0136] The system may also include a satellite with multiple component spreaders and multiple antenna elements of the transmitter.

[0137] The system may also include a plurality of gateways, wherein the transmitter comprises a plurality of gateways, each gateway of the plurality of gateways comprising a respective component spreader of the plurality of component spreaders and a respective antenna element of the plurality of antenna elements, and a satellite comprising a plurality of transponders configured to relay the composite signal.

[0138] An apparatus for satellite communications is described that may include: a set of component despreaders configured to receive a set of spread data symbols associated with a common data symbol and to despread the set of spread data symbols to obtain a set of despread data symbols, a set of signal component estimators coupled to the set of component despreaders and configured to estimate one or more coefficients for the set of despread data symbols, and a combiner coupled to the set of signal component estimators and configured to combine the set of despread data symbols to obtain combined data symbols corresponding to the common data symbol.

[0139] Some examples of the apparatus may include a set of decimators configured to apply a low pass filter to and downsample the set of despread data symbols.

[0140] Some examples of the apparatus may include a demodulator configured to demodulate the combined data symbols to obtain demodulated data symbols, and a decoder configured to decode the demodulated data symbols.

[0141] An apparatus for satellite communications is described that may include: a communications manager configured to switch from a first mode for transmitting beam signals via beamformed spot beams over a geographic area to a second mode that bypasses a beamformer used to form the spot beams; a modulator configured to generate a modulated signal including data for one or more user terminals based on switching to the second mode, the modulated signal including a set of modulated data symbols; a set of component spreaders coupled to the modulator and configured to apply a set of spreading codes to modulated data symbols of the set of modulated data symbols to obtain a set of spread data symbols; and a set of antenna elements coupled to the set of component spreaders and configured to transmit each spread data symbol of the set of spread data symbols using one or more antenna elements of the set of antenna elements.

[0142] Some examples of the apparatus may include a data buffer coupled to the modulator and configured to receive data for a user terminal having an unknown location within the geographic area, wherein the data included in the modulated signal includes data for the user terminal.

[0143] Some examples of the apparatus may include a data buffer coupled to the modulator and configured to receive second data for a user terminal having a known location within the geographic area, wherein the second data included in the modulated signal includes data for the user terminal.

[0144] Some examples of the apparatus may include a set of beamformers coupled with the modulator and configured to apply a set of beam weights to second modulated data symbols of the second set of modulated data symbols to obtain a set of weighted data symbols, and a set of antenna elements configured to transmit associated weighted data symbols of the set of spread data symbols.

[0145] Some examples of apparatus may include a set of amplifiers coupled to the set of component spreaders and the set of antenna elements and configured to amplify the set of spread data symbols.

[0146] 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 voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0147] The various example blocks and modules described in connection with the disclosure herein may be implemented or performed by 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. A general-purpose processor may be a microprocessor, but alternatively, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices (e.g., a combination of a digital signal processor (DSP) and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration).

[0148] The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions may be stored on or transmitted as one or more instructions or code on a computer-readable medium. Other examples and implementations are within the scope of this disclosure and the appended claims. For example, due to the nature of software, the functions described herein may be implemented using software executed by a processor, hardware, firmware, hardwiring, or any combination thereof. Features implementing the functions may also be physically located in various locations, including being distributed such that parts of the functions are implemented in different physical locations.

[0149] 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. Non-transitory storage media may be any available medium that can be accessed by a general-purpose or special-purpose computer. By way of example, and not limitation, non-transitory computer-readable media may include random-access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory, compact disk read-only memory (CDROM), or other optical, magnetic, 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 can be accessed 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 coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, microwave, etc., the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included within the definition of media. As used herein, disk and disc include CDs, laser discs, optical discs, digital versatile discs (DVDs), floppy disks, and Blu-ray discs, where discs typically reproduce data magnetically, while discs reproduce data optically using lasers. Combinations of the above are also included within the scope of computer-readable media.

[0150] As used herein, including the claims, the use of "or" in a list of items (e.g., a list of items preceded by a phrase such as "at least one of" or "one or more of") indicates an inclusive list, so that, for example, a list of 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 referring to an exclusive set of conditions. For example, an example step described as "based on condition A" could 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" is to be interpreted the same as the phrase "based at least in part on."

[0151] In the accompanying drawings, similar components or features may have the same reference label. Furthermore, various components of the same type may be distinguished by following the reference label with a dash and a second label that distinguishes among the similar components. If only a first reference label is used herein, the description is applicable to any of the similar components having the same first reference label, regardless of a second reference label or other subsequent reference label.

[0152] The description set forth herein, with reference to the accompanying drawings, describes exemplary configurations and does not represent every example that may be implemented or that is within the scope of the claims. As used herein, the term "exemplary" means "serving as an example, instance, or illustration," and does not mean "preferred" or "advantageous over other examples." The detailed description includes specific details for the purpose of providing an understanding of the described technology. However, these technologies may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the described examples.

[0153] The description herein is provided to enable any person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily 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 disclosure. Thus, the disclosure is not intended to be limited to the embodiments 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 (100) for satellite communications, comprising: A transmitter (200) configured to transmit a composite signal, comprising: a plurality of component spreaders (265, 270, 275), each component spreader of the plurality of component spreaders (265, 270, 275) configured to apply a respective spreading code of a plurality of spreading codes to a common data symbol of the modulated signal to obtain a respective spread data symbol of a plurality of spread data symbols, the plurality of spread data symbols being output by the plurality of component spreaders based at least in part on the common data symbols; a plurality of antenna elements (240, 245, 250) connected to the plurality of component spreaders (265, 270, 275), each antenna element of the plurality of antenna elements (240, 245, 250) configured to acquire a respective spread data symbol of the plurality of spread data symbols and radiate a respective element signal including the respective spread data symbol, and the composite signal includes the element signals radiated from the plurality of antenna elements (240, 245, 250); and a receiver (300) configured to receive the composite signal, a plurality of component despreaders (320, 335), each component despreader of the plurality of component despreaders (320, 335) configured to apply a despreading code of a plurality of despreading codes to the composite signal, and a plurality of despread data symbols output by the plurality of component despreaders based at least in part on the composite signal; a plurality of header estimators (355, 365) coupled to the plurality of component despreaders (320, 335), each of the plurality of header estimators (355, 365) configured to estimate one or more coefficients for a respective despread data symbol of the plurality of despread data symbols; a summing circuit (350) connected to the plurality of header estimators (355, 365), the summing circuit (350) configured to combine the plurality of despread data symbols based at least in part on the one or more coefficients estimated for the plurality of despread data symbols to obtain a combined data symbol corresponding to the common data symbol.

2. The receiver (300) 2. The system of claim 1, further comprising: a plurality of decimators coupled to the plurality of component despreaders and the plurality of header estimators and configured to obtain a plurality of decimated data symbols, each decimator of the plurality of decimators configured to filter and downsample a respective despread data symbol of the plurality of despread data symbols to obtain a decimated data symbol.

3. 3. The system of claim 2, wherein each header estimator of the plurality of header estimators is configured to estimate the one or more coefficients for the respective despread data symbol based at least in part on a respective decimated data symbol of the plurality of decimated data symbols.

4. The receiver (300) a demodulator (370) coupled to the summing circuit (350), the demodulator (370) configured to demodulate the combined data symbols to obtain demodulated data symbols; A system (100) according to any one of claims 1 to 3, further comprising: a decoder (370) configured to decode a plurality of demodulated data symbols including the demodulated data symbol.

5. The system (100) of any one of claims 1 to 4, wherein one antenna element of the plurality of antenna elements (240, 245, 250) is configured to acquire two or more of the plurality of spread data symbols.

6. 5. The system (100) of claim 1, wherein two or more of the plurality of antenna elements (240, 245, 250) are configured to obtain spread data symbols from one of the plurality of component spreaders (265, 270, 275).

7. The system (100) of any one of claims 1 to 6, wherein the plurality of despreading codes are the same as the plurality of spreading codes.

8. The system (100) of any one of claims 1 to 7, wherein the one or more coefficients include amplitude, phase, timing, frequency, or any combination thereof.

9. The modulated signal is a first modulated signal, and the transmitter (200) a beamformer (205) configured to apply beamforming coefficients to the second modulated signal to obtain a plurality of beamformed data symbols; 9. The system (100) of claim 1, further comprising: a communications manager (253) configured to switch between a first mode for transmitting the plurality of beamformed data symbols via the plurality of antenna elements (240, 245, 250) for communication via beamformed spot beams and a second mode for causing the first modulated signal to bypass the beamformer (205).

10. The communication manager (253) 10. The system (100) of claim 9, further configured to activate the first mode for a first interval of time and activate the second mode for a second interval of time that is less than the first interval.

11. The transmitter (200) 11. The system (100) of claim 1, further comprising a modulator (255) coupled to the plurality of component spreaders (265, 270, 275), the modulator (255) configured to generate a plurality of data symbols including the common data symbol.

12. a satellite (120) comprising the plurality of antenna elements (240, 245, 250); The system (100) of any one of claims 1 to 11, further comprising: a gateway (130) communicatively connected to the satellite (120), the gateway (130) comprising the plurality of component spreaders (265, 270, 275).

13. The system (100) of any one of claims 1 to 11, further comprising a satellite (120) comprising the plurality of component spreaders (265, 270, 275) and the plurality of antenna elements (240, 245, 250) of the transmitter (200).

14. a plurality of gateways (130), the transmitter (200) comprising the plurality of gateways, each gateway of the plurality of gateways (130) comprising a respective component spreader of the plurality of component spreaders (265, 270, 275) and a respective antenna element of the plurality of antenna elements (240, 245, 250); A system (100) according to any one of claims 1 to 11, further comprising a satellite (120) comprising a plurality of transponders configured to relay said composite signal.

15. 1. A method for satellite communications, comprising: receiving a composite signal from a transmission system (200), the composite signal including a plurality of element signals, each element signal of the plurality of element signals including a common data symbol and a respective spread data symbol associated with a respective antenna element of the transmission system (200); applying a plurality of despreading codes to the composite signal, wherein a plurality of despread data symbols are obtained based at least in part on said applying; estimating one or more coefficients for each despread data symbol of the plurality of despread data symbols; combining the plurality of despread data symbols based at least in part on the one or more coefficients estimated for the plurality of despread data symbols to obtain combined data symbols corresponding to the common data symbols.

16. and further comprising adjusting the plurality of despread data symbols using the one or more coefficients, wherein a plurality of adjusted data symbols are obtained based at least in part on using the one or more coefficients, and the combining comprises: The method of claim 15 , comprising combining the plurality of adjusted data symbols to obtain the combined data symbols.

17. 17. The method of claim 15 or 16, further comprising decimating the plurality of despread data symbols, wherein the decimating comprises, for each despread data symbol, filtering a set of frequencies from the respective despread data symbol, and downsampling the respective despread data symbol after the filtering.

18. estimating the one or more coefficients for the plurality of despread data symbols comprises: The method of any one of claims 15 to 17, comprising estimating the amplitude, phase, timing, frequency, or any combination thereof, of the plurality of despread data symbols.

19. demodulating the combined data symbols to obtain demodulated data symbols; The method of any one of claims 15 to 18, further comprising: decoding the demodulated data symbols.

20. 15. The system (100) of claim 1, wherein each component spreader of the plurality of component spreaders (265, 2670, 275) is configured to output the one or more spread data symbols to a respective subset of the plurality of antenna elements (240, 245, 250).

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