Technique for end-to-end beamforming using multiple areas of simultaneous user coverage

Abstract

A satellite communications system and method of operation provides service to multiple user terminals in multiple non-overlapping user coverage areas based on simultaneously performing ground-based end-to-end beamforming for the multiple user coverage areas. A satellite communications system and method of operation provides service to multiple user terminals in multiple non-overlapping user coverage areas based on simultaneously performing ground-based end-to-end beamforming for the multiple user coverage areas. The system provides multiple simultaneous beams in a forward or reverse direction and determines capacity allocation for each user coverage area by controlling assignment of the beams to each user coverage area. Multiple transmit / receive paths onboard satellites in the system support end-to-end beamforming and controlling beam assignment is based on controlling assignment of such paths to each user coverage area.

Description

Technical Field

[0001] The disclosed technology uses end-to-end beamforming to perform beamforming simultaneously within non-overlapping coverage areas geographically via an end-to-end repeater such as a satellite.

Background Art

[0002] Wireless communication systems such as satellite communication systems provide a means by which information including voice, video, and various other types of data can be communicated from one location to another using a communication satellite. Typically, a communication satellite includes one or more antenna assemblies for communicating with various terrestrial target devices, which may include ground-based access node terminals or user terminals, any of which may be fixed (e.g., installed at a permanent installation location, moved from one fixed location to another, etc.) or mobile (e.g., vehicle, boat, airplane, handheld, etc.).

[0003] The antenna assembly of a communication satellite can be configured to transmit a downlink signal (e.g., a forward link signal to a user terminal or a return link signal to an access node) and / or receive an uplink signal (e.g., a forward link signal from an access node and a return link signal from a user terminal). The antenna assembly may be associated with a service coverage area within which communication services may be provided to devices via the antenna assembly.

[0004] In some cases, the communication satellite may be a geostationary satellite, in which case the orbit of the communication satellite is synchronized with the rotation of the Earth and may maintain a service coverage area that is essentially stationary with respect to the Earth. In other cases, different orbits (e.g., a low Earth orbit) may be used to move the service coverage area over the Earth's surface as the communication satellite moves along its orbital path.

[0005] Some communications satellites may position the coverage area of ​​a spot beam in a fixed location. However, these satellites may not have the capability to move the spot beam to accommodate changes in the service coverage area. Furthermore, such satellite communications architectures inherently provide capacity uniformly distributed across the service coverage area. For example, the capacity per spot beam is strongly related to the allocated bandwidth per spot beam and can be predetermined for each spot beam, thus little consideration is given to flexibility or configurability.

[0006] These satellite communication architectures can be valuable when the desired service coverage area is known and capacity requirements are evenly distributed across the service coverage area; however, the lack of flexibility in the aforementioned architectures can be limiting for certain applications. For example, communication satellites may be re-tasked, or their deployment conditions (e.g., orbital slots) may be changed. In addition, satellite communication services may observe changes in user requirements (e.g., fixed users versus mobile users).

[0007] While signal processing techniques such as beamforming provide some degree of capability to adapt spot beam placement and service coverage areas, greater flexibility in adapting service coverage areas and spot beam placement is sometimes desired. For example, it may be desirable for satellite communication systems and their associated communication satellites to flexibly and dynamically adjust the location and dimensions of service coverage areas based on factors such as the location of user terminals and access node terminals, the spatial distribution of communication service capacity, and the capacity allocation of communication services. In addition, it may be desirable for satellite communication systems and their associated communication satellites to flexibly and dynamically allocate communication resources between different service coverage areas, for example, to shift higher-throughput services to different coverage areas based on dynamically changing conditions. [Overview of the project]

[0008] Methods, systems, and devices for end-to-end beamforming using multiple areas of simultaneous user coverage are described.

[0009] Further scope of applicability of the described methods and apparatus will become apparent from the following detailed description, claims, and drawings. Since various changes and modifications within the scope of the description will be apparent to those skilled in the art, the detailed description and specific examples are given merely as illustrations. [Brief explanation of the drawing]

[0010] Further understanding of the nature and advantages of the embodiments of this disclosure can be achieved by referring to the following drawings. In the accompanying drawings, similar components or mechanisms may have the same reference label. Furthermore, various components of the same type may be distinguished by a dash and a second label that distinguishes similar components after the reference label. Where only the first reference label is used herein, this description is applicable to any one of the similar components having the same first reference label, notwithstanding the second reference label.

[0011] [Figure 1] Figure 1 illustrates a satellite communications system that supports end-to-end beamforming using multiple areas of simultaneous user coverage, according to an aspect of this disclosure. [Figure 2] Figure 2 illustrates a satellite communication system configuration that supports end-to-end beamforming using multiple areas of simultaneous user coverage, according to an aspect of this disclosure. [Figure 3] Figure 3 illustrates an illustrative diagram of a forward-link satellite antenna switching scheme that supports end-to-end beamforming using multiple areas of simultaneous user coverage, according to an aspect of this disclosure. [Figure 4] Figure 4 shows an exemplary forward signal path that supports end-to-end beamforming using multiple areas of simultaneous user coverage according to an aspect of the present disclosure. [Figure 5] Figure 5 illustrates an illustrative diagram of a return link satellite antenna switching scheme that supports end-to-end beamforming using multiple areas of simultaneous user coverage, according to an aspect of this disclosure. [Figure 6] Figure 6 shows an example of an exemplary return signal path that supports end-to-end beamforming using multiple areas of simultaneous user coverage according to an aspect of the present disclosure. [Figure 7] Figure 7 shows a block diagram of an end-to-end communication processor that supports end-to-end beamforming using multiple areas of simultaneous user coverage, according to an aspect of this disclosure. [Figure 8] Figure 8 shows a block diagram of a controller that supports end-to-end beamforming using multiple areas of simultaneous user coverage, according to an aspect of this disclosure. [Figure 9] Figure 9 shows a flowchart illustrating an exemplary method for supporting end-to-end beamforming using multiple areas of simultaneous user coverage, according to an aspect of this disclosure. [Modes for carrying out the invention]

[0012] The satellite communication system 10 ("the System") shown in Figure 1 provides service to multiple user terminals 12 in multiple non-overlapping user coverage areas 14, for example, a first user coverage area 14-1 and a second user coverage area 14-2, based on simultaneously performing ground-based end-to-end beamforming for multiple user coverage areas 14. Hereafter, unless otherwise stated or made clear from the context, the term "beamforming" refers to ground-based end-to-end beamforming, and suffix reference numbers are discussed only when clarity requires the inclusion of the suffix.

[0013] Figure 1 highlights the details for beamforming in the forward direction toward user terminal 12, relying on some simplifications to facilitate explanation and maintain clarity. The main simplifications are the depiction of a single user terminal 12-1 in a first user coverage area 14-1 and a single user terminal 12-2 in a second user coverage area 14-2, with the corresponding forward beam 16-1 servicing the first user terminal 12-1 and the corresponding forward beam 16-2 servicing the second user terminal 12-2. "Serving" means the fact that forward user signals 18-1 intended for user terminal 12-1 are carried into the forward beam 16-1. Similarly, the forward beam 16-2 carries forward user signals 18-2 intended for user terminal 12-2.

[0014] The operation of system 10 involves the simultaneous formation of potentially many forward beams 16 in the first user coverage area 14-1 and the second user coverage area 14-2. Each forward beam 16 serves one or more user terminals 12, and each forward beam 16 serves multiple user terminals 12 that are "clustered" in the sense that they are all located within the same beam coverage area 20. Figure 1 shows an example of beam coverage area 20-1 as the ground "footprint" of forward beam 16-1 and an example of beam coverage area 20-2 as the ground footprint of forward beam 16-2. User terminals 12 within the footprint of forward beam 16-1 may be served by that beam, and similarly, user terminals 12 within the footprint of forward beam 16-2 may be served by that beam.

[0015] From a system design perspective, consider an exemplary approach in which each user coverage area 14 is logically divided into multiple beam coverage areas 20, i.e., a predetermined pattern of beam coverage areas 20 based on the known or expected size of the beam footprint 20, to provide forward coverage across the entire user coverage area 14. To service the user coverage area 14, it is not necessary to simultaneously form the same number of forward beams 16 as there are predefined beam coverage areas 20. Instead, a time-division multiplexing (TDM) pattern may be used, where a smaller number of forward beams 16 are used to illuminate different subsets of a given beam coverage area 20 at different times.

[0016] To form an arbitrary given forward beam 16 to illuminate a specific geographic area, i.e., to form a forward beam 16 where the beam coverage area 20 is located at a desired location within the entire user coverage area 14, it is necessary to have a channel estimate that describes the transmission channel from each access node 22 involved in beamforming to a receiver located at or near the geographic center of the desired beam center. Beamforming requires the use of multiple geographically dispersed access nodes 22 that form part of the ground segment 24 of the system 10.

[0017] In practice, for each forward beam 16 formed, the system 10 obtains a channel estimate for user terminals 12 that are served by that forward beam 16 and are located at or sufficiently close to a geographical location designated as the beam center. Such user terminals 12 may be referred to as reference user terminals (RUTs) or designated user terminals (DUTs). Thus, for a given cluster of user terminals 12 that are served by the same forward beam 16, the one located in the center of them functions as the RUT for estimating the end-to-end channel used to form the forward beam 16. In particular, the satellite communication system 10 uses channel "sounding" with respect to the RUT associated with each forward beam 16 to determine the end-to-end channel from each access node 22 to the RUT. "Sounding" refers to the transmission of a known reference signal for use in estimating the channel between the RUT and each access node 22. Sounding is performed periodically to adapt beamforming weights in response to, for example, fluctuating atmospheric conditions.

[0018] Each channel between the RUT and one of the access nodes 22 is a multipath channel, with the satellite 26 of system 10 acting as an end-to-end repeater between the ground segment 24 and the user terminal 12. Here, the induction of multipath is intentional and arises from the existence of multiple forward signal paths through the satellite 26 to each access node 22. To understand the induced multipath, consider that each access node 22 transmits a forward uplink signal 28 that is received by some or all of the feeds 30 of a feeder link array 32 mounted on the satellite 26. The feeder link array 32 may be referred to as a feeder link antenna subsystem, and at the same time, as a feeder link component configured so that individual feeds 30 illuminate the access node area to receive multiple combined input forward signals.

[0019] Each feed 30 receives a superposition of the forward uplink signals 28, i.e., a superposition signal 34 composed of individual forward uplink signals 28 from two or more of the access nodes 22. The superposition signal 34 at each feed 30 is unique and depends on the channels between the feed 30 and the individual ones of the access nodes 22, and the access nodes 22 may be referred to as "satellite access nodes" or SANs. Also, the superposition signal 34 may also be referred to as a combined input forward signal.

[0020] Therefore, each feed 30 receives the combined input forward signal 34 and provides it as a received combined input forward signal 36 to the input terminal of a transponder 38 mounted on the satellite 26. Each transponder 38 can be regarded as a signal path in the satellite 26 for carrying each of the received combined input forward signals 36. The number of feeds 30 can be large, for example, it can be 500 or more, and the satellite 26 includes a transponder 38 for each feed 30. As an alternative to a malfunctioning transponder 38, additional spare transponders 38 may be mounted.

[0021] Each transponder 38 provides a non-processing signal path, which means that it does not perform signal demodulation and remodulation with respect to the combined input forward signal 36. However, the transponder 38 in one or more embodiments includes a filter, an amplifier, and a frequency shifter for shifting from the uplink frequency to the downlink frequency. In such an operation, the received combined input forward signal 36 input to each transponder 38 is converted into a corresponding forward combined downlink signal 40 transmitted from a corresponding feeder 42 in either the first user link feed array 44-1 or the second user link feed array 44-2 as the transmitted forward combined downlink signal 46. The first user link feed array 44-1 serves the first user coverage area 14-1, and the second user link feed array 44-2 serves the second user coverage area 14-2.

[0022] Controlling the number of forward beams 16 assigned to the first user coverage area 14-1 and the number of forward beams 16 assigned to the second user coverage area 14-2 is a function of controlling transponder connectivity within the satellite 26, that is, controlling how many of the transponders 38 are assigned to the first user link feed array 44-1 and how many of the transponders 38 are assigned to the second user link feed array 44-2. To understand this arrangement, consider simultaneously forming a total of K forward beams 16 based on M access nodes 22 that cooperate in beamforming, using N feeds 30 in the feeder link array 32, N transponders 38 mounted on the satellite 26, and up to N feeds 42 in each of the user link feed arrays 44-1 and 44-2. As a non-limiting example, K is equal to 5¹², and M and N are equal to K. Assume that each user link feed array 44-1 or 44-2 contains N feeds 42, and that a switching circuit 48 mounted on the satellite 26 operates to switch the output terminal of each transponder 38 to either the first user link feed array 44-1 or the second user link feed array 44-2.

[0023] Switching the output terminals of all N transponders 38 to each of the N feeds 42 of the first user link feed array 44-1 can be understood as allocating all K forward beams 16 to the first user coverage area 14-1, and switching all the output terminals of the N transponders 38 to each of the N feeds 42 of the second user feed link array 44-2 is to allocate the K forward beams 16 to the second user coverage area 14-2. Switching R of the output terminals of the N transponders 38 to each of the N feeds 42 of the first user feed link array 44-1, the output allocates R forward beams 16 to the first user coverage area 14-1, and leaves (N-R) of the N transponders 38 that can be allocated to form (N-R) forward beams 16 for the second user coverage area 14-2.

[0024] In one or more embodiments, each of the first and second user link feed arrays 44-1 includes fewer feeds 42 than the feeds 30 included in the feeder link array 32. As a non-limiting example, there are 512 feeds 30 in the feeder link array 32, 358 feeds 42 in the first user link feed array 44-1, and another 358 feeds 42 in the second user link feed array 44-2. Such an arrangement allows up to 70 percent (358 / 512) of the forward capacity to be allocated to either the first user coverage area 14-1 or the second user coverage area 14-2 at any given time. That is, up to 358 feeds 30 and the corresponding transponders 38 can be connected to either the first user coverage area 14-1 or the second user coverage area 14-2 at any given time. Of course, the satellite 26 may change the capacity allocation over time slots or other scheduling intervals, and the 70% example is non-limiting.

[0025] The flexibility of maximum allocation arises in embodiments where all transponders 38 can be assigned to either the first user link feed array 44-1 or the second user link feed array 44-2. This flexibility comes at the cost of additional switching or splitting circuitry, and the number of dynamically assignable transponders 38 may be less than the total number.

[0026] In at least one embodiment, each user link feed array 44-1 and 44-2 includes N / 2 or more feeds 42, so that more than half of the N transponders 38 can be assigned to one of the user coverage areas 14-1 or 14-2 at any given time. For example, each user link feed array 44 includes 2N / 3 feeds 42, so that up to two-thirds of the transponders 38 can be assigned to one of the selected user link feed arrays 44-1 or 44-2. In practice, the number of feeds 42 included in each user link feed array 44 does not need to be the same among all user link feed arrays 44, but the number of feeds 42 included in each user link feed array 44 imposes an upper limit on the number of forward beams 16 that can be assigned to the user coverage area 14 served by that user link feed array 44.

[0027] The switching circuit 48 operates as a “selector subsystem” and determines which transponders 38 are switchable between the first user link feed array 44-1 and the second user link feed array 44-2, and the number of transponders 38. For example, it controls the connectivity (allocation) of the transponders 38 in response to a control signal output from the control circuit 50. Next, the control circuit 50 includes or is associated with storage 52, for example, one or more types of memory circuits, which stores a schedule used to control the dynamic allocation of capacity between user coverage areas 14, for example, between the first user coverage area 14-1 and the second user coverage area 14-2. The schedule may be dynamically determined or updated based on uploaded control information determined by the ground segment 24, depending on general conditions such as different capacity needs between user coverage areas 14.

[0028] The allocation of "capacity" in the forward direction refers to how the total number of forward beams 16 is divided among the respective user coverage areas 14. In one or more embodiments, each subset of transponders 38 may be dedicated to a corresponding user coverage area 14, while other subsets of the entire set of transponders 38 can be dynamically switched between the user coverage areas 14 to accommodate the changing capacity needs in each service area.

[0029] To further understand beamforming according to the details described above, consider user data streams 62 arriving at the ground segment 24 of the satellite communication system 10 from one or more external networks 60. The exemplary external networks include one or more of the following: the Internet or other packet data networks (PDNs), public land mobile networks (PLMNs), public switched telephone networks (PSTNs), etc. Each user data stream 62 targets a respective user terminal 12 in one of the user coverage areas 14 served by the satellite 26. One or more network devices 64 included in the ground segment 24 receive the user data streams 62 and, for each user data stream 62, determine the target user terminal 12 and the forward beam 16 to be used to serve the target user terminal 12. User data streams 62 assigned to the same forward beam 16 are used to form the corresponding forward beam signal 66.

[0030] Multiple forward beam signals 66 are provided to a beamformer 68 located in the ground segment 24. A beam weight generator 70 generates beamforming weights 72, and the beamformer 68 uses the beamforming weights 72 to generate corresponding forward access node signals 74 for each access node 22 cooperating in beamforming to transmit as forward uplink signals 28. The forward access node signals 74 are synchronized to support an end-to-end beamforming process.

[0031] The beamforming weights 72 are based on the end-to-end channels determined between each access node 22 and the RUT associated with each forward beam 16. Specifically, the beamforming weights 72 are responsible for the end-to-end channels from each access node 22 to each RUT, which include the uplink channels from each access node 22 to each of the feeds 30 in the feeder link array 32, the multipath channels through the satellite 26, and the downlink channels from each of the feeds 42 in the user link feed array 44 to the RUT.

[0032] As a detailed example based on the existence of M access nodes 22 and K forward beams 16, the beamformer 68 overlaps each of the K forward beam signals 66 into M groups of the K forward beam signals 66. The beamformer 68 includes a forward weighting and summation module (not shown) for each of the M access nodes, each such module receiving one of the M groups of the K forward beam signals 66. The beamweight generator 70 generates an M×K forward beam weight matrix based on a channel matrix that estimates the end-to-end forward gain for each of the K×M end-to-end forward multipath channels.

[0033] The first weighting and summing module in the beamformer 68 applies a weight equal to the value of the 1,1 element of the M×K forward beam weight matrix to the first of the K forward beam signals 66. A weight equal to the value of the 1,2 elements of the M×K forward beam weight matrix is ​​applied to the second of the K forward beam signals 66. The other weights of the matrix are applied in a similar manner to the Kth forward beam signal 66, which is weighted with values ​​equal to the 1,K elements of the M×K forward beam weight matrix. Each of the K weighted forward beam signals 66 is then summed up and output by the first weighting and summing module as one of the corresponding forward access node signals 74 shown in Figure 1. The forward access node signals 74 output by the first weighting and summing module can be time-coordinated for synchronization of transmission across multiple access nodes 22. Similarly, each of the other weighting and summing modules of the beamformer 68 (not shown) receives each set of K overlapping forward beam signals 66, weights them using the corresponding elements of M × K forward beam weight matrices, and sums them. The outputs from each of the M weighting and summing modules may be tuned for timing, e.g., delay and jitter, as part of forming / providing the forward access node signal 74.

[0034] As a result of the beam weighting applied by the beamformer 68 in the ground segment 24, the forward uplink signal 28 transmitted from the access node 22 to / through the satellite 26 forms a forward beam 16. The satellite 26 functions as an end-to-end repeater in this beamforming context. The size and location of the formed forward beam 16 may be a function of the number of access nodes 22 deployed, the number and antenna pattern of the repeater antenna elements (feeds 30 and 42) through which the signal passes, the location of the satellite 26, and / or the geographical spacing of the access nodes 22.

[0035] Figure 2 shows the return direction, i.e., beamforming from user terminal 12 to access node 22. The return user beam, not shown in the diagram, is formed digitally within the ground segment 24, rather than in free space. The return beamforming provides separation or interference reduction between uplink signals transmitted by user terminals 12 located in adjacent beam coverage areas 20.

[0036] Consider an example where a user terminal 12-1 in beam coverage area 20-1 of the first user coverage area 14-1 transmits an uplink signal 80-1, for example, an uplink signal containing user data destined for an external network(s) 60. Simultaneously, a user terminal 12-3 in an adjacent beam coverage area 20-3 within the first user coverage area 14-1 transmits an uplink signal 80-3. Similarly, a user terminal 12-2 in beam coverage area 20-2 of the second user coverage area 14-2 transmits an uplink signal 80-2, for example, an uplink signal containing user data destined for an external network(s) 60. Simultaneously, a user terminal 12-4 in an adjacent beam coverage area 20-4 within the second overall user coverage area 14-2 transmits an uplink signal 80-4. In beamforming in the return direction, such signal interference is reduced, and frequency reuse on each beam coverage area 20 is facilitated.

[0037] To understand return beamforming, consider that each feed 84 in the first user link feed array 86-1 receives a superposition signal 82, which is a unique superposition of the uplink signal 80 transmitted by the user terminal 12 in the corresponding user coverage area 14-1. Similarly, each feed 84 in the second user link feed array 86-2 receives a superposition signal 82, which is a unique superposition of the uplink signal 80 transmitted by the user terminal 12 in the corresponding user coverage area 14-2. The same applies to each of the additional user coverage areas 14, up to the extent that further user coverage areas 14 exist.

[0038] Each feed 82 outputs a return-combined return-uplink signal 90, which is switched by a switching circuit 88 to one of the transponders 92. Similar to forward beamforming, the number of transponders 92 assigned to the second user-link feed array 86-2 relative to the number of transponders 92 assigned to the first user-link feed array 86-1 determines the number of return beams assigned to the first user-coverage area 14-1 relative to the second user-coverage area 14-2. In one or more embodiments, the configuration and assignment of the return beams (not shown) correspond to the configuration and assignment of the forward beams 16.

[0039] Each transponder 92 outputs a return-composite return-downlink signal 94 transmitted from the corresponding feed 96 in the feeder-link antenna subsystem 98. The transmitted version of each return-composite return-downlink signal 94 is shown in the diagram as the transmitted signal 100. Correspondingly, each access node 22 receives a superimposed signal 102, which is a unique superposition of the transmitted signal 100, and provides the corresponding return-composite signal 104 to the beamformer 68. The return-composite signal 104 may be time-synchronized for coherence, and the beamformer 68 applies beamforming weights 108 to form a return beam in the digital domain, represented by the return beam signal 106.

[0040] The beamforming weights 108 include a K×M return beam weight matrix based on information stored in the channel datastore, which is fed into the channel estimator implemented in or associated with the beamformer 68. The derivation of the beamforming weights 108 in the beamweight generator 70 relies on channel estimation, for example, end-to-end channel estimation based on return link signals transmitted from each RUT within each user coverage area 14. These return link end-to-end channel estimations are responsible for the multipath return link channels between each RUT and each access node 22.

[0041] For return beam formation, the beamformer 68 has a beam weight input, and via the beam weight input, the beamformer 68 receives a return beam weight matrix (beamformation weights 108) from the beam weight generator 70. Each of the return combined signals 104 is coupled to the relevant one of M splitter and weighting modules (not shown) in the beamformer 68.

[0042] Each splitter and weighting module divides the time-synchronized return composite signal 104 into K copies. Each splitter and weighting module weights each of the K copies using the k and m elements of a K × M return beam weight matrix. Each set of K weighted composite return signals is then combined into a coupling module (not shown) that outputs k return beam signals 106. Each of the K return beam signals 106 contains communication signal samples from all user terminals 12 that are active within the corresponding beam coverage area.

[0043] With the details of the above example in mind, a satellite communication system 10 comprises a satellite 26 for providing communication between multiple access nodes 22 and multiple user terminals 12. The multiple access nodes 22 are geographically distributed within corresponding access node areas, and the multiple user terminals 12 are geographically distributed within a first user coverage area 14-1 and a second user coverage area 14-2. In other words, some of the user terminals 12 are distributed within the first user coverage area 14-1, and some of the user terminals 12 are distributed within the second user coverage area 14-2.

[0044] The feeder link array 32 mounted on satellite 26 may be referred to as the feeder link antenna subsystem 32, while the feed 30 may be referred to as multiple feeder link components 30 of the feeder link antenna subsystem 32. Each feeder link component 30 is configured to illuminate the access node area and receive a unique superposition of multiple forward uplink signals 28 from multiple access nodes 22 as a composite input forward signal 34.

[0045] The transponder 38 may be referred to as a forward signal path 38, and the satellite 26 provides a plurality of forward signal paths 38. Each of the plurality of forward signal paths 38 has an input coupled to one of a plurality of feeder link components 30, and receives one of a plurality of combined input forward signals 34 as a received combined input forward input signal 36. Correspondingly, each forward signal path 38 provides one of a plurality of combined forward downlink signals 40 at its respective output.

[0046] The first user link array 44-1 of satellite 26 may be referred to as the first user link antenna subsystem 44-1, and the feed 42 of the first user link antenna subsystem 44-1 may be referred to as the first user link components 42, which are configured to illuminate the first user coverage area 14-1. Similarly, the second user link array 44-2 of satellite 26 may be referred to as the second user link antenna subsystem 44-2, and the feed 42 of the second user link antenna subsystem 44-2 may be referred to as the second user link components 42, and the second user link component elements 42 are configured to illuminate the second user coverage area 14-2. The second user coverage area 14-2 does not overlap with the first user coverage area 14-1.

[0047] The switching circuit 48 may include a switch matrix having complete cross-switching connectivity between any switch matrix input and any switch matrix output, and may be referred to as a selector subsystem 48. The selector subsystem 48 is reconfigurable in response to a control signal to dynamically allocate a plurality of forward signal paths 38 between a first user-link antenna subsystem 44-1 and a second user-link antenna subsystem 44-2. In particular, in a first configuration of the selector subsystem 48, the output of each of the first subsets of the plurality of forward signal paths 38 is selectively coupled to one of each of the first subsets of the plurality of first user-link components 42, and the output of each of the second subsets of the plurality of forward signal paths 38 is selectively coupled to one of each of the first subsets of the plurality of second user-link components 42.

[0048] In the second configuration of the selector subsystem 48, a third subset of the plurality of forward signal paths 38 has an output coupled with one of each of the second subsets of the plurality of first user link components 42, and a fourth subset of the plurality of forward signal paths 38 has an output coupled with one of each of the second subsets of the second user link components 42. The first subset of the first user link component 42 is a first number of first user link components 42, and the second subset of the first user link component 42 is a second number of first user link components 42, where the first number is different from the second number. The first subset of the second user link component 42 is a third number of second user link components 42, and the second subset of the second user link component 42 is a fourth number of second user link components 42, where the third number is different from the fourth number. In at least one embodiment, the sum of the first number and the second number is equal to the sum of the third number and the fourth number.

[0049] The first configuration of the selector subsystem 48 defines a first allocation of capacity between the first user coverage area 14-1 and the second user coverage area 14-2. The second configuration of the selector subsystem 48 defines a second allocation of capacity between the first user coverage area 14-1 and the second user coverage area 14-2, and the second allocation of capacity is different from the first allocation of capacity. The first configuration corresponds to a first beam weight matrix, and the second configuration corresponds to a second beam weight matrix that is different from the first beam weight matrix. Referring to the beamforming weights 72 shown in Figure 1, there may be different sets of beamforming weights 72—different beamforming matrices—corresponding to different capacity allocations between the first user coverage area 14-1 and the second user coverage area 14-2.

[0050] A first subset of multiple first user link components 42 is configured to transmit a first subset of multiple forward composite downlink signals 40 generated by a first subset of multiple forward signal paths 38 as a transmitted forward composite downlink signal 46. The transmitted first subset of multiple forward composite downlink signals 40 overlaps to contribute to the formation of a first user beam (first forward beam 16) in a first user coverage area 14-1. A second subset of multiple second user link components 42 is configured to transmit a second subset of multiple forward composite downlink signals 40 generated by a second subset of multiple forward signal paths 38. The transmitted second subset of multiple forward composite downlink signals 40 overlaps to contribute to the formation of a second user beam (second forward beam 16) in a second user coverage area 14-2.

[0051] Each of the multiple forward uplink signals 28 contributes to the formation of both a first user beam and a second user beam. The first user beam corresponds to a first user data stream 62 for a first subset of multiple user terminals 12 in a first user coverage area 14-1. Similarly, the second user beam corresponds to a second user data stream 62 for a second subset of multiple user terminals 12 in a second user coverage area 14-2.

[0052] In one or more embodiments, the selector subsystem 48 comprises a plurality of forward link switches coupled to the outputs of a plurality of forward signal paths 38. Each of the plurality of forward link switches responds to a control signal given to the selector subsystem 48 by selectively coupling each output of one of the plurality of forward signal paths 38 to one of a plurality of first user link components 42 via a first switch state, or to one of a plurality of second user link components 42 via a second switch state. Thus, in the first configuration of the selector subsystem 48, a first subset of the plurality of forward link switches coupled to the outputs of each of the first subset of the plurality of forward signal paths 38 is in a first switch state, and a second subset of the plurality of forward link switches coupled to the outputs of each of the second subset of the plurality of forward signal paths 38 is in a second switch state.

[0053] As shown in Figure 2, satellite 26 also includes multiple return signal paths, represented by the transponder 92 shown in the figure. Each of the multiple return signal paths 92 has an output coupled to one of each of the feeds 96 in the feeder link antenna subsystem 98. Switching circuit 88 controls the connectivity between the feeds 84 in the first user link array 86-1 and the second user link array 86-2 and the feeds 96 in the feeder link antenna subsystem 98 in response to a control signal from control circuit 50. For example, in a first configuration of selector subsystem 88, selector subsystem 88 supports return beamforming with respect to the first user coverage area 14-1 by controlling the connectivity between the input terminal of transponder 92 and the feeds 84 of the first user link array 86-1 and the second user link array 86-2, such that a first subset of the feeds 84 of the first user link array 86-1 is coupled to each of the feeds 96 in the feeder link antenna subsystem 98. Furthermore, a second subset of feeds 84 in the second user link array 86-2 is coupled to each feed 96 in the feeder link antenna subsystem 98 to support return beam formation for the second user coverage area 14-2.

[0054] The above can be understood as controlling the number of return beams used for each user coverage area 14 by assigning first and second subsets of the transponder 92 to the first user coverage area 14-1 and the second user coverage area 14-2, respectively. A third subset of the transponder 92 may be assigned to the third user coverage area 14.

[0055] Certain components mounted on satellite 26 may be shared between forward link communication and return link communication, for example, any reflectors included in each antenna subsystem may be shared. In one or more embodiments, antenna feeds may be shared. However, in at least one embodiment, transponder 92 is partially or completely different from transponder 38.

[0056] The target items within the ground segment 24 include a beamformer 68, as shown in Figures 1 and 2. In practice, the beamformer 68 may comprise a forward beamformer and a return beamformer. For forward beamforming, the beamformer 68 has a forward beam signal input. See the forward beam signal 66 supplied to the beamformer 68 in Figure 1. Furthermore, the beamformer 68 has multiple end-to-end beam-weighted forward uplink signal outputs that communicate with multiple access nodes 22. See the forward access node signal 74 in Figure 1. The end-to-end beam-weighted forward uplink signal outputs correspond to the respective weightings of the forward beam signal input according to a set of end-to-end forward beam weights provided by the beam weight generator 70. In one or more embodiments, the multiple access nodes 22 pre-correct the multiple forward uplink signals 74 to compensate for the respective path delays and phase shifts introduced between the multiple access nodes 22 and the satellite 26.

[0057] In at least one embodiment, the selector subsystem 48 dynamically allocates a plurality of forward signal paths 38 between the first user link antenna subsystem 44-1 and the second user link antenna subsystem 44-2 in order to dynamically allocate capacity between the first user coverage area 14-1 and the second user coverage area 14-2.

[0058] Figure 3 shows an exemplary implementation of satellite 26, which includes transponders 38 configured as forward / return signal paths, some or all of which can be dynamically allocated between a first user coverage area 14-1 and a second user coverage area 14-2, for example, based on the capacity needs of user terminals 12 operating in each user coverage area 14-1 and 14-2. Satellite 26 includes a first user link antenna subsystem 44-1, which operates to serve user terminals 12 in the first user coverage area 14-1 in both forward and return directions, i.e., transmit and receive directions. Furthermore, satellite 26 includes a second user link antenna subsystem 44-2, which operates to serve user terminals 12 in the second user coverage area 14-2 in both forward and return directions. Furthermore, satellite 26 includes a feeder link antenna subsystem 32 that operates to communicate (transmit and receive) with multiple access nodes 22 within access node area 120. Areas 14-1, 14-2, and 120 do not overlap.

[0059] Figure 4 shows illustrative details of the forward and return signal paths in an exemplary configuration in which satellite 26 supports simultaneous beamforming for three user coverage areas 14-1, 14-2, and 14-3. A first user link antenna subsystem 44-1 supports beamforming for the first user coverage area 14-1, a second user link antenna subsystem 44-2 supports beamforming for the second user coverage area 14-2, and a third user link antenna subsystem 44-3 supports beamforming for the third user coverage area 14-3.

[0060] A key point of terminology to note is that the connection circuit between the forward signal path or the input terminal of the transponder 38 and each of the feeds 30 in the feeder link antenna subsystem 32 may be referred to as the forward receive path 400. Similarly, the connection circuits between the forward signal path or the output terminal of the transponder 38 and each of the feeds 42 of the first user link antenna subsystem 14-1, the second user link antenna subsystem 14-2, and the third user link antenna subsystem 14-3 may be referred to as the forward transmit paths 404-1, 404-2, and 404-3. Such circuits may be part of the selector circuitry included in the selector subsystem 48, or may be coupled with the selector circuitry included in the selector subsystem 48. That is, each individual path of the forward receive path 400 and / or each individual path of the forward transmit paths 404-1, 404-2, and 404-3 may be switched to control whether a particular transponder 38 is coupled to a feed 42 in the first user link antenna subsystem 14-1, to a feed 42 in the second user link antenna subsystem 14-2, or to a feed 42 in the third user link antenna subsystem 14-3. It should also be noted that the forward signal path or transponder 38 may include a group of radio frequency conversion stacks (RFCs).

[0061] In at least one embodiment, a first subset of transponders 38 is dedicated to the first user-link antenna subsystem 44-1 for beamforming with respect to the first user-coverage area 14-1, a second subset of transponders 38 is dedicated to the second user-link antenna subsystem 44-2 for beamforming with respect to the second user-coverage area 14-2, and a third subset of transponders 38 is dedicated to the third user-link antenna subsystem 44-3 for beamforming with respect to the third user-coverage area 14-3. Individual transponders 38 or groups thereof within further subsets of transponders 38 can be assigned to any of the three user-coverage areas 14-1, 14-2, and 14-3, depending on their respective capacity requirements in each user-coverage area 14.

[0062] In at least one embodiment, some or all of the transponders 38 can be assigned to any one of the user coverage areas 14, or can be assigned to each user coverage area 14 in any desired ratio. As previously mentioned, there is a trade-off between the complexity and weight of the selector subsystem 48's assignment capability, which includes, for example, switches or splitters located in each of the forward receive paths 400 and / or forward transmit paths 404-1, 404-2, and 404-3, with the selector subsystem 48 controlling which transponder inputs are switched to which feed 30, or which transponder outputs are switched to which feed 42. Thus, although the selector subsystem 48 is depicted as a self-contained entity in the diagram, it may comprise a distributed set of switches or switch matrices, or a set of splitters, that control signal path connectivity within the satellite 26 in response to control signals from the control circuit 50.

[0063] In at least one embodiment, the output terminal of each transponder 38, either all or a defined subset of the transponders 38, can be selectively connected to one of the feeds 42 of the user link antenna subsystem 44. For a dual-polarized feed 42, the selector subsystem 48 may also control which feed port the transponder output is connected to.

[0064] In one example, satellite 26 has N transponders 38 (for example, this may be equal to the number of forward receiving paths 400), and the selector subsystem 48 has N·2 switching outputs, each selectively coupled to a forward transmitting path between forward transmitting paths 404-1, 404-2, and 404-3. That is, the number of forward transmitting paths 404-1, 404-2, and 404-3 may be equal to N·2. For example, forward transmitting path 404-1 may include a P_1 transmitting path, forward transmitting path 404-2 may include a P_2 transmitting path, and forward transmitting path 404-3 may include a P_3 transmitting path, where in the equation P_1+P_2+P_3=N·2.

[0065] In some embodiments, the number of forward transmit paths coupled to each antenna subsystem may be the same. For example, satellite 26 may have P_1 transmit paths 404-1 coupled to the feed 42 of the first user link antenna subsystem 44-1 and P_2 transmit paths 404-2 coupled to the feed 42 of the second user link antenna subsystem 44-2, where P_1 and P_2 may be equal. However, the number of transmit paths coupled to each antenna subsystem may be different. For example, satellite 26 may have P_3 forward transmit paths 404-3 coupled to the feed 42 of the third user link antenna subsystem 44-3, where P_3 may not be equal to P_1 or P_2 (for example, in some cases P_3 may be smaller than P_1 and P_2). In at least one embodiment, one or more output ends of the transponder 38 have a switch for selectively switching the transponder output to one of the selected forward transmit paths 404. Such switches may be considered part of the selector subsystem 48, or part of their respective forward transmission paths, and may operate under the control of the selector subsystem 48.

[0066] In some embodiments, each of the forward transmit paths to the antenna subsystem may be coupled to a feed of the same polarization. For example, each of the forward transmit paths 404-1, 404-2, and 404-3 may be coupled to a port of a feed with a single polarization (e.g., RHCP or LHCP). Alternatively, for some antenna subsystems, the forward transmit paths may be coupled to ports of feeds with one or more polarizations.

[0067] In the example considering only two user-link antenna subsystems 44-1 and 44-2, the forward transmission paths 404-1 and 404-2 may be coupled to ports of feeds for multiple polarizations. For example, the feed for the first group (e.g., half or P_1 / 2) of the forward transmission path 404-1 may be coupled to the feed 42 of the first user-link antenna subsystem 44-1 for a first polarization (e.g., LHCP), and the feed for the second group (e.g., half or P_1 / 2) of the forward transmission path 404-2 may be coupled to the feed 42 of the first user-link antenna subsystem 44-1 for a second polarization (e.g., RHCP). Similarly, the first group (e.g., half or P_2 / 2) feed 42 of the forward transmission path 404-2 may be coupled with the feed 42 of the second user link antenna subsystem 42-2 for a first polarization (e.g., LHCP), and the second group (e.g., half or P_2 / 2) feed of the transmission path 42-2 may be coupled with the feed 42 of the second user link antenna subsystem 44-2 for a second polarization (e.g., RHCP).

[0068] Considering the illustrative context of the three user-link antenna subsystems 44-1, 44-2, and 44-3 mounted on satellite 26, the individual switches of the selector subsystem 48 may be independently configurable (for example, according to a configuration that can be transmitted to satellite 26 via control signals from ground segment 24). Thus, from among the N transponders 38, S of the N transponders 38 may be selectively switched to S of the forward transmission paths 404-1, L of the N transponders 38 may be selectively switched to L of the transmission paths 404-2, and T of the N transponders 38 may be selectively switched to T of the transmission paths 404-3, where S is between zero (0) and P_1, L is between zero (0) and P_2, and T is between zero (0) and P_3.

[0069] In some embodiments, the quantity of transmit feed for each antenna selected using the selector subsystem 48 may be determined based on the service capacity associated with each of the respective user coverage areas 14. For example, if a relatively high capacity is desired in the first user coverage area 14-1 illuminated by the first user link antenna subsystem 44-1, more transmit paths in the forward transmit path 404-1 may be selected or activated, while relatively fewer of the forward transmit paths 404-2 and 404-3 may be selected or activated.

[0070] Additionally or alternatively, the selection of transmission paths within a group or set of selected forward transmission paths 404-1, 404-2, and 404-3 may depend on beamforming configurations for providing communication services through their respective user coverage areas 14-1, 14-2, and 14-3. For example, each beamforming configuration may be determined to serve each of the user coverage areas 14, and specific feed 30 and corresponding transponder 38 combinations selectively associated with transmission paths 404-1, 404-2, and 404-3 may be analyzed to determine the placement of the feed 30 to enhance or optimize the beamforming configuration (e.g., to provide a higher signal gain for a desired beamforming configuration while reducing or minimizing the amount of parasitic or undesirable signal power in areas outside the desired beamforming configuration).

[0071] In other words, rather than simply determining the number of transponders 38 to allocate to each user coverage area 14-1, the satellite 26 or system 10 determines which particular feeds 30 to associate with each of the user link antenna subsystems 14. There may be specific patterns of feed allocation that improve beamforming performance. In some embodiments, the capacity demand across a given irradiation area of ​​the antenna may be non-uniform. Therefore, the selection of beamforming configurations and transmission paths may depend on the capacity demand in areas within the irradiation area. For example, if more capacity is desired in a portion of the irradiation area, more feeds directed to that area may be selected to enhance the capacity in that area compared to other parts of the irradiation area. Thus, the feed pattern used for beamforming with respect to a particular user coverage area may be based on the distribution of user terminals 12 or the required capacity within the user coverage area.

[0072] In some embodiments, the satellite 26 may operate according to a plurality of configurations from the forward receive path 400 and the transponder 38 to the forward transmit paths 404-1, 404-2, and 404-3. For example, in the first configuration, a first subset of the transponder 38 may have outputs coupled to each feed 42 of the first user-link antenna subsystem 44-1 (e.g., via the selector subsystem 48), and a second subset of the transponder 38 may have outputs coupled to each feed 42 of the second user-link antenna subsystem 44-2 (e.g., via the selector subsystem 48). The ground segment 24 may apply one or more sets of end-to-end beam weights to the forward uplink signal 28 while the satellite 26 is operating in the first configuration and providing one or more sets of forward beams 16 associated with the first user-link antenna subsystem 44-1, the second user-link antenna subsystem 44-2, and the third user-link antenna subsystem 44-3.

[0073] In the second configuration, a third subset of transponders 38 may have outputs coupled to each feed 42 of the first user-link antenna subsystem 44-1 (e.g., via selector subsystem 48), and a fourth subset of transponders 38 may have outputs coupled to each feed 42 of the second user-link antenna subsystem 44-2 (e.g., via selector subsystem 48). Similarly, while satellite 26 operates in the second configuration and provides one or more sets of forward link user beams associated with the first user-link antenna subsystem 44-1, or the second user-link antenna subsystem 44-2, or the third user-link antenna 44-3, the ground network 24 may apply end-to-end beam weights of one or more sets to the forward uplink signal 28. In some cases, the total number of transponders 38 in the first and second subsets of transponders 38 may be equal to the total number of transponders in the third and fourth subsets of transponders 38.

[0074] In some cases, a single polarization for each antenna may be associated with the configuration of the transponder 38. For example, for a first configuration, a first subset of transponders 38 may be selected from transponders coupled (e.g., via selector subsystem 48) to the ports of feed 42 of a first user-link antenna subsystem 44-1 associated with the first polarization. Similarly, for a first configuration, a second subset of transponders 38 may be selected from transponders coupled (e.g., via selector subsystem 48) to the ports of feed 42 of a second user-link antenna subsystem 44-2 associated with the first polarization. Alternatively, for a first configuration, a second subset of transponders 38 may be selected from transponders coupled (e.g., via selector subsystem 48) to the respective feeds 42 of a second user-link antenna subsystem 44-2 associated with the second polarization.

[0075] In some cases, two or more polarizations for at least one antenna may be associated with the configuration of the transponder 38. For example, for a first configuration, a first subset of the transponder 38 may include transponders coupled (e.g., via selector subsystem 48) to the respective feeds of a first antenna associated with both a first and a second polarization. Similarly, for a second configuration, a second subset of the transponder 38 may include transponders coupled (e.g., via selector subsystem 48) to the respective feeds of a second antenna associated with both a first and a second polarization. In addition, although illustrated and described in selector subsystem 48, selector subsystem 48 may include signal divider elements instead of one subset or all of the described switches. Thus, the output of at least one subset of the transponder 38 may be divided to be simultaneously provided to two or more feeds of two or more antennas.

[0076] Figure 4 also shows details of an example of a return signal path or transponder 92 within satellite 26 that provides a return signal flow. The return receiving paths 410-1, 410-2, and 410-3 couple the feeds 84 in their respective user link antenna subsystems 86-1, 86-2, and 86-3 to the input terminals of transponder 92. The output terminals of transponder 92 are coupled to their respective feeds 96 in the feeder link antenna subsystem 98. As previously mentioned, at least some of the antenna-related elements mounted on satellite 26 may be shared for forward and return communications, for example, antenna subsystems used in the forward and return link directions may use the same reflector.

[0077] The switching circuit 88 operates as a selector subsystem that controls connectivity between feed 84 in the user link antenna subsystem 86 and feed 96 in the feeder link antenna subsystem 98, according to the currently configured capacity allocation which can be updated on a schedule or command basis. Switching may be controllable individually per feed / path, as described above for the forward direction, and the same polarization-based connectivity described for the forward direction may be applied to the return direction. Thus, there may be N return transmit paths 412 that connect each feed 96 in the feeder link antenna subsystem 98 to a return signal path or transponder 92, and there may be N or fewer paths in each of the return receive paths 410-1, 410-2, and 410-3. The selector subsystem 88 includes or controls switches or splitters that control connectivity between the return signal path or transponder 92 and the return receive paths 410-1, 410-2, and 410-3. In other words, the number and / or pattern of feeds 96 used to service each of the user coverage areas 14-1, 14-2, and 14-3 in the return direction can be dynamically controlled according to capacity requirements or other considerations.

[0078] Figure 5 shows an exemplary forward signal path 500, also known as a forward link transponder 500. A satellite 26 having multiple such forward signal paths 500 according to an aspect of this disclosure supports end-to-end beamforming using multiple areas of simultaneous user coverage. The forward signal path 500 is an exemplary implementation of any one of the transponders 38 described above.

[0079] The illustrated forward signal path 500 extends from feed 532 to one of selected feeds 512 or 522. Feed 532 is one of a plurality of feeders 530 corresponding to feed 30 in the feeder link antenna subsystem 32. Feed 512 is one of a first plurality of feeds 510 and corresponds to feed 42 in the first user link antenna subsystem 44-1. Feed 522 is one of a plurality of second plurality of feeds 520 and corresponds to feed 42 in the second user link antenna subsystem 44-2.

[0080] The connectivity between the input terminal of the forward signal path 500 and the feed 532 may be considered as one of the forward receive paths 400 shown in Figure 4. Similarly, the connectivity switched from the output terminal of the forward signal path 500 to the feed 512 may be considered as one of the forward transmit paths 404-1, and the connectivity switched from the output terminal of the forward signal path 500 to the feed 522 may be considered as one of the forward transmit paths 404-2.

[0081] Feeds 510 and 520 are used to transmit forward downlink signals to user terminals 12 in user coverage areas 14-1 and 14-2, respectively, and feed 530 is used to receive forward uplink signals from multiple access nodes 22. Thus, the forward signal path 500 can be assigned to either the first user coverage area 14-1 or the second user coverage area 14-2 by controlling whether either feed 512 or 522 is coupled to the output end of the forward signal path 500. Its connectivity is controlled by a switch 556 included in the selector subsystem 544. Feeds 532, 512, and 522 may be polarized (to one or both LHCP or RHCP), and the selector subsystem 544 may include connectivity control to / from the selected polarization(s) of feeds 532, 512, and 522.

[0082] The forward signal path 500 has an LNA 541 that constitutes the input terminal of the forward signal path 500. The forward signal path 500 further includes a frequency converter and associated filter 542, a channel amplifier 543, a phase shifter 545, a power amplifier 546 (e.g., a traveling wave tube amplifier (TWTA), a solid-state power amplifier (SSPA), etc.), and a harmonic filter 547. Some implementations may have more or fewer components. For example, the frequency converter and associated filter 542 may be useful when the uplink and downlink frequencies are different. As an example, each forward signal path 500 may accept an input in a first frequency range and output in a second frequency range.

[0083] In one or more embodiments, the forward signal path 500 may be coupled to any combination of polarizations, and different groups of the forward signal path 500 mounted on the satellite 26 may be coupled to different polarizations. For example, a first group of the forward signal path 500 may have an input coupled to a port of feed 532 of a first polarization (e.g., RHCP) and an output selectively coupled (e.g., via switch 556) to ports of feeds 512 and 522 of the same polarization. A second group of the forward signal path 500 may have an input coupled to a port of feed 532 associated with a first polarization (e.g., RHCP) and an output coupled (e.g., via switch 556) to ports of feeds 512 and 522 associated with a different polarization (e.g., LHCP).

[0084] In some cases, there may be three or more groups of forward signal paths 500 mounted on satellite 26. For example, multiple forward signal paths 500 may have their inputs coupled to a port of a first polarization (e.g., RHCP), and different groups may have different polarization assignments for the ports of feeds 512 and 522. For example, various configurations for the groups include two groups, three groups, or four groups, each having a different set of polarizations (e.g., {RHCP, RHCP}, {RHCP, LHCP}, {LHCP, RHCP}, or {LHCP, LHCP}). In addition, if switch 556 has two or more outputs, additional configurations for the groups may be possible, including any combination of polarizations for each group of forward signal paths 500.

[0085] Figure 6 shows an exemplary return signal path 600, also referred to as a return link transponder 600. The return signal path 600 can be understood as an exemplary implementation of each transponder 92 shown in Figure 2. A satellite 26 having multiple such return signal paths 600 according to an aspect of this disclosure supports end-to-end beamforming in the return direction for multiple areas of simultaneous user coverage.

[0086] The example return signal path 600 connects one of the selected feeds 612 or 620 to feed 632. Feed 612 is one of several feeds 610 and corresponds to a given feed 84 in the first user link antenna subsystem 86-1. Feed 622 is one of several feeds 610 and corresponds to a given feed 84 in the second user link antenna subsystem 86-2. Feed 632 is one of several feeds 630 and corresponds to a given feed 96 in the feeder link antenna subsystem 98. In other words, the return signal path 600 can be assigned to either the first user link antenna subsystem 86-1 for servicing the first user coverage area 14-1, or the second user link antenna subsystem 86-2 for servicing the second user coverage area 14-2.

[0087] In the context of Figure 6, feeds 610 and 620 are then used to receive return uplink signals from user terminals 12 in user coverage areas 14-1 and 14-2, respectively, and feed 630 is used to transmit return downlink signals to multiple access nodes 22. The return signal path 600 can be assigned to either the first user coverage area 14-1 or the second user coverage area 14-2 by controlling which of feeds 612 or 622 is coupled to the input terminal of the illustrated return link transponder 640. Its connectivity is controlled by switch 656. Although shown as part of the return signal path 600, switch 656 may be considered as part of the selector subsystem 644, for example, as part of the switching circuit 88 introduced in Figure 2.

[0088] Feeds 612 and 622 may be polarized and may provide one or both of LHCP or RHCP. A selector subsystem 644 may include connectivity control to the selected polarization(s) from feeds 612 and 622 along the lines described above for the forward signal path 500. The return link transponder 600 includes a frequency conversion and filtering circuit 642, a channel amplifier 643, a phase shifter 645, a power amplifier 646 (e.g., a traveling wave tube amplifier (TWTA), a solid-state power amplifier (SSPA), etc.), and a harmonic filter 647. Some implementations may have more or fewer components. For example, the frequency converter and associated filter 642 may be useful when the uplink and downlink frequencies are different. As an example, each return link transponder 600 may accept input in a first frequency range and output in a second frequency range.

[0089] Referring back to Figure 4, the connectivity between the input terminal of the return link transponder 600 and feeds 612 and 622 can be understood as being in return receive paths 410-1 and 410-2, respectively. Similarly, the connectivity between the output terminal of the return link transponder 600 and feed 632 can be understood as being in one of the return transmit paths 612.

[0090] Figure 7 is a block diagram of an end-to-end communication processor 705 that supports end-to-end beamforming using multiple areas of simultaneous user coverage, according to an aspect of this disclosure. The end-to-end communication processor 705 may include a beam signal interface 710, an end-to-end beamforming processor 720, an end-to-end repeater configuration management program 730, and an end-to-end beamforming matrix generator 740. Each of these modules may communicate with each other directly or indirectly (for example, via one or more buses). The end-to-end communication processor 705 may represent an aspect of the network device 64 shown in Figure 1.

[0091] The end-to-end communication processor 705 may be configured to provide communication between an access node cluster and a plurality of user terminals 12 via a satellite 26 that functions as an end-to-end repeater with multiple receive / transmit signal paths. The access node cluster may include a plurality of access nodes 22 geographically distributed within an access node area 120. The plurality of user terminals 12 may be geographically distributed between a first user coverage area 14-1 illuminated by a first user link antenna subsystem 44-1 of satellite 26 and a second user coverage area 14-2 illuminated by a second user link antenna subsystem 44-2 of satellite 26. Satellite 26 has multiple forward signal paths, for example, forward signal path 500, and at least a portion of the forward signal path 500 can be dynamically assigned to either the first user coverage area 14-1 or the second user coverage area 14-2 to control, for example, how many of the K forward beams 16 are assigned to the first user coverage area 14-1 and how many of the K forward beams 16 are assigned to the second user coverage area 14-2. Of course, there may be three or more user coverage areas 14, and beam assignment control may be performed across three or more user coverage areas 14.

[0092] For forward link communication, the beam signal interface 710 may receive a forward link beam signal 715 (shown as beam signal 66 in Figure 1) which includes a forward link user data stream 62 for communication to the user terminal 12. The beam signal interface 710 may pass the forward link beam signal to the end-to-end beamforming processor 720 of the beam signaling 725.

[0093] The end-to-end repeater configuration management program 730 may manage the configuration of satellite 26 for end-to-end relay. For example, the end-to-end repeater configuration management program 730 may configure satellite 26 having multiple antennas and multiple receive / transmit signal paths that can be individually and selectively coupled to one of multiple antennas in order to provide communication services to multiple geographical areas simultaneously. The end-to-end repeater configuration management program 730 may configure an end-to-end repeater according to one of multiple configurations. For example, for a first configuration of a forward link, a first subset of the multiple receive / transmit signal paths of the end-to-end repeater may be selectively coupled between a first subset of the feeds of a first antenna and the feeds of a first subset of the feeds of a second antenna, and a second subset of the multiple receive / transmit signal paths of the end-to-end repeater may be selectively coupled between a second subset of the feeds of a first antenna and the feeds of a first subset of the feeds of a third antenna. For a second configuration of a forward link, a third subset of multiple receive / transmit signal paths of an end-to-end repeater may be selectively coupled between the feeds of the third subset of the first antenna feed and the second subset of the second antenna feed, and a fourth subset of multiple receive / transmit signal paths of an end-to-end repeater may be selectively coupled between the feeds of the fourth subset of the first antenna feed and the second subset of the third antenna feed.

[0094] The end-to-end repeater configuration management program 730 may configure end-to-end repeaters by sending control signaling 765 to end-to-end repeaters that constitute the selector subsystem. The end-to-end repeater configuration management program 730 may determine the distribution of multiple receive / transmit signal paths for end-to-end repeaters selectively coupled with the first and second antennas for a first configuration, at least in part on the relative throughput requirements of the first and second user coverage areas. Additionally or alternatively, the end-to-end repeater configuration management program 730 may determine the distribution of multiple receive / transmit signal paths for end-to-end repeaters selectively coupled with the first and second antennas for a first configuration, at least in part on the throughput capacity of the access node cluster. The end-to-end repeater configuration management program 730 may configure the selector subsystem to switch between multiple configurations. For example, the end-to-end repeater configuration management program 730 may configure the end-to-end repeater in a second configuration in which a third subset of the multiple receive / transmit signal paths of the end-to-end repeater is selectively coupled between the ports of the third subset of the feed of the third antenna and the ports of the second subset of the feed of the first antenna, and a fourth subset of the multiple receive / transmit signal paths of the end-to-end repeater is selectively coupled between the ports of the fourth subset of the feed of the third antenna and the ports of the second subset of the feed of the second antenna.

[0095] In the first configuration, a first subset of the feed of the first antenna may have a first quantity feed, and a first subset of the feed of the second antenna may have a second quantity feed. In the second configuration, a second subset of the feed of the first antenna may have a third quantity feed, and a second subset of the feed of the second antenna may have a fourth quantity feed. In some embodiments, the sum of the first quantity feed and the second quantity feed is equal to the sum of the third quantity feed and the fourth quantity feed. Various polarization configurations may be selected using a selector subsystem. For example, in the first configuration, each of the first and second antennas may be used to transmit a forward link signal having the same polarization as the signal received through the third antenna. That is, the ports of the first subset of the feed of the third antenna and the ports of the first subset of the feed of the second antenna may be associated with a first polarization, and the ports of the second subset of the feed of the third antenna and the ports of the first subset of the feed of the second antenna may be associated with a first polarization.

[0096] Alternatively, in the first configuration, one or more of the first or second antennas may be used to transmit a forward link signal having a different polarization from the signal received through the third antenna. For example, ports of a first subset of the feed of the third antenna and ports of a first subset of the feed of the first antenna may be associated with a first polarization, ports of a second subset of the feed of the third antenna may be associated with a first polarization, and ports of a first subset of the feed of the second antenna may be associated with a second polarization.

[0097] Similarly, for the second configuration, each of the first and second antennas may be used to transmit a forward link signal having the same polarization as the signal received via the third antenna, or one or more of the first or second antennas may be used to transmit a forward link signal having a different polarization than the signal received via the third antenna. Additionally or alternatively, for either the first or second configuration, either or both of the first or second antennas may be used to transmit forward link signals with multiple polarizations. For example, for the first or second configuration, a subset of the receive / transmit signal paths coupled with the first or second antenna may be coupled with the feed ports of the antennas with multiple polarizations. Thus, a communication service may be provided using a single polarization on the forward uplink, while multiple coverage areas for the forward downlink may be illuminated simultaneously by one or more polarizations for each antenna.

[0098] The end-to-end repeater configuration management program 730 may also configure a selector subsystem to switch between multiple return link configurations. For example, for a first return link configuration, a third subset of the end-to-end repeater's multiple receive / transmit signal paths may be selectively coupled between the ports of a second subset of the first antenna's feed and the ports of a third subset of the third antenna's feed, and a fourth subset of the end-to-end repeater's multiple receive / transmit signal paths may be selectively coupled between the ports of a second subset of the second antenna's feed and the ports of a fourth subset of the third antenna's feed. One or more additional return link configurations may include inputs to different subsets of the end-to-end repeater's multiple receive / transmit signal paths, selectively coupled between different arrangements of the first, second, and third antenna's feeds.

[0099] In some embodiments, the end-to-end repeater configuration management program 730 may determine the distribution of multiple receive / transmit signal paths of end-to-end repeaters selectively coupled to a first antenna and a second antenna for a first configuration (e.g., a forward link or a return link) based at least in part on the relative throughput demands of a first user coverage area and a second user coverage area. In some embodiments, the end-to-end repeater configuration management program 730 may determine the distribution of multiple receive / transmit signal paths of end-to-end repeaters selectively coupled to a first antenna and a second antenna for a first configuration based at least in part on the throughput capacity of the access node cluster. In some embodiments, the capacity demands across a given illumination area of ​​an antenna may be non-uniform, and therefore the selection of beamforming configurations and transmit paths may depend on the capacity demands in areas within the illumination area. For example, if more capacity is desired in a portion of the illumination area, more feeds directed to that area may be selected to improve the capacity in that area compared to other portions of the illumination area. The end-to-end repeater configuration management program 730 may provide the configuration of the receive / transmit signal path 735 to the end-to-end beamforming matrix generator 740. The configuration of the receive / transmit signal path 735 may include, for example, a first forward link beam weight matrix for a first configuration and a second forward link beam weight matrix for a second configuration.

[0100] The end-to-end beamforming matrix generator 740 may generate beamforming matrices 745 for forward and return link communications via an end-to-end repeater having multiple antennas that simultaneously illuminate multiple coverage areas. For example, for the first configuration, the end-to-end beamforming matrix generator 740 may identify a first forward link beamweight matrix for end-to-end beamforming of transmissions from multiple access nodes to multiple user terminals via the end-to-end repeater. The end-to-end beamforming matrix generator 740 may identify additional forward link beamweight matrices for the first configuration. For example, an end-to-end beamforming matrix generator 740 may identify a first set of forward link beam weight matrices for a first configuration, and an end-to-end beamforming processor 720 may apply one or more of the first set of forward link beam weight matrices (e.g., cycling through at least a subset of the first set of forward link beam weight matrices, or selecting one or more of the first set of forward link beam weight matrices based on factors such as demand in various beams). In addition, the end-to-end beamforming matrix generator 740 may identify a second forward link beam weight matrix for a second configuration for end-to-end beamforming of transmissions from multiple access nodes to multiple user terminals via an end-to-end repeater. The forward and return link beamforming matrices may be generated based on the configuration of the receive / transmit signal path 735 (e.g., forward link or return link) determined by the end-to-end repeater configuration management program 730. The end-to-end beamforming matrix generator 740 may identify an additional forward link beam weight matrix or a return link beam weight matrix for the second configuration.For example, the end-to-end beamforming matrix generator 740 may identify a second set of forward link beam weight matrices for a second configuration, and the end-to-end beamforming processor 720 may apply one or more of the second set of forward link beam weight matrices (for example, cycling at least a subset of the second set of forward link beam weight matrices, or selecting one or more of the second set of forward link beam weight matrices based on factors such as demand in various beams). The end-to-end repeater configuration management program 730 may determine additional configurations for multiple receive / transmit signal paths of the end-to-end repeater, and the end-to-end beamforming matrix generator 740 may identify additional sets of forward link or return link beam weight matrices for the additional configurations.

[0101] The end-to-end beamforming processor 720 may receive a beamforming matrix 745 and apply the beamforming matrix 745 to the forward and return link signals in order to acquire or process access node-specific signals 755. For example, the end-to-end beamforming processor 720 may generate a first set of access node-specific forward link signals for transmission by a plurality of access nodes, each of which may include a synthesis of each forward link beam signal from at least a subset of the first set, weighted by their respective forward link beam weights according to a first forward link beam weight matrix for the first configuration. The end-to-end beamforming processor 720 may apply the beamforming matrix to the forward and return link signals over an additional time period using the same or different beamforming matrices for the first configuration. Furthermore, the end-to-end beamforming processor 720 may generate a second set of access node-specific forward link beam signals for transmission by a plurality of access nodes, each of which may include a synthesis of the respective forward link beam signals according to a second forward link beam weight matrix for the second configuration.

[0102] In addition, the end-to-end beamforming processor 720 may apply a return link beam weight matrix to each return link signal received at multiple access nodes in order to obtain the respective return link data streams associated with the first and second subsets of multiple user terminals. The end-to-end beamforming processor 720 may also apply beamforming matrices to the forward and return link signals during additional periods using the same or different beamforming matrices for the second configuration. Each of the respective return link signals may include a composite of signals relayed by at least one of a third subset of multiple receive / transmit signal paths of the end-to-end repeater and at least one of a fourth subset of multiple receive / transmit signal paths of the end-to-end repeater.

[0103] Figure 8 is a block diagram of controller 800 according to an exemplary embodiment. Controller 800 supports end-to-end beamforming using multiple areas of simultaneous user coverage, as described in this disclosure. Controller 800 may include an end-to-end communication processor 805, a processor 810, a memory 815, and a communication interface 840. Each of these components may communicate with each other directly or indirectly through one or more buses 835. Controller 800 may be implemented on one of the network devices 64 of the ground segment 24, on the satellite 26, or distributed between the ground segment 24 and the satellite 26.

[0104] Memory 815 may include random access memory (RAM) and / or read-only memory (ROM). Memory 815 may store an operating system (OS) 820 (for example, built on a Linux or Windows kernel). Memory 815 may also store computer-readable computer-executable code 825. The computer-executable code 825 includes instructions, which, when executed, cause the processor 810 to perform various functions described herein related to providing communication services according to different native antenna patterns. Alternatively, the code 825 may not be directly executable by the processor 810, but may be configured to cause a controller 800 to perform one or more of the functions described herein (for example, at compilation and runtime).

[0105] The controller 800 may include an end-to-end communication processor 805, which may manage one or more aspects of a communications satellite to support end-to-end beamforming with multiple areas of simultaneous user coverage, as described herein. For example, communication services may be provided via a communication interface 840.

[0106] The controller 800, which includes an end-to-end communications processor 805 operating as a communications service management program, a processor 810, memory 815, and / or communications interface 840, may be implemented or run using a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. The general-purpose processor may be a microprocessor, but alternatively, the processor may be any conventional processor, controller, microcontroller, or state machine. The controller 800 may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in use with a DSP core, integrated memory, isolated memory, or any other such configuration.

[0107] Figure 9 is a flowchart of an exemplary method 900 supporting end-to-end beamforming using multiple areas of simultaneous user coverage, according to an aspect of this disclosure. The operation of method 900 may be implemented by a controller for a communications satellite including multiple antennas or components thereof, as described herein. In some embodiments, the controller may execute a set of instructions for controlling the controller's functional elements to perform the functions described below. Additionally or alternatively, the controller may perform aspects of the functions described below using dedicated hardware.

[0108] Method 900 may provide communication between an access node cluster and a plurality of user terminals via an end-to-end repeater having a plurality of receive / transmit signal paths, wherein the access node cluster comprises a plurality of access nodes geographically distributed within an access node area, the plurality of user terminals geographically distributed across a first user coverage area illuminated by a first antenna and a second user coverage area illuminated by a second antenna, and the plurality of receive / transmit signal paths of the end-to-end repeater have an input coupled with the feed of a third antenna illuminating the access node area, and an output that can be individually selected between the first antenna and the second antenna.

[0109] In 905, the controller may acquire a first set of forward link beam signals containing a forward link user data stream for transmission to multiple user terminals.

[0110] In 910, the controller may be configured such that in the first configuration, a first subset of the multiple receive / transmit signal paths of the end-to-end repeater is selectively coupled between the ports of the first subset of the feed of the third antenna and the ports of the first subset of the feed of the first antenna, and a second subset of the multiple receive / transmit signal paths of the end-to-end repeater is selectively coupled between the ports of the second subset of the feed of the third antenna and the ports of the first subset of the feed of the second antenna. The ports of the first subset of the feed of the third antenna and the ports of the first subset of the feed of the second antenna may be associated with a first polarization, and the ports of the second subset of the feed of the third antenna and the ports of the first subset of the feed of the second antenna may be associated with a first polarization. Alternatively, the ports of the first subset of the feed of the third antenna and the ports of the first subset of the feed of the first antenna may be associated with a first polarization, the ports of the second subset of the feed of the third antenna may be associated with a first polarization, and the ports of the first subset of the feed of the second antenna may be associated with a second polarization.

[0111] For the first configuration, the distribution of multiple receive / transmit signal paths of end-to-end repeaters selectively coupled to the first and second antennas may be determined at least in part on the relative throughput demands of the first and second user coverage areas. For the first configuration, the distribution of multiple receive / transmit signal paths of end-to-end repeaters selectively coupled to the first and second antennas may be determined at least in part on the throughput capacity of the access node cluster.

[0112] In 915, for the first configuration, the controller may identify a first forward link beam weight matrix for end-to-end beamforming of transmissions from multiple access nodes to multiple user terminals via an end-to-end repeater. The controller may identify additional forward link beam weight matrices for the first configuration.

[0113] In 920, the controller may generate a first set of access node-specific forward link signals for transmission by a plurality of access nodes, each of which access node-specific forward link signals may include a synthesis of each forward link beam signal from at least a subset of the first set of forward link beam signals, weighted by their respective forward beamforming weights according to a first forward link beam weight matrix for a first configuration. The controller may use the first forward link beam weight matrix or an additional forward link beam weight matrix to generate an additional set of access node-specific forward link signals for additional periods.

[0114] In 925, multiple access nodes may transmit a first set of forward link signals specific to each access node to an end-to-end repeater. The receive / transmit signal path of the end-to-end repeater may relay the first set of forward link signals specific to each access node to simultaneously form beams within a first user coverage area and a second user coverage area.

[0115] Therefore, Method 900 can support end-to-end beamforming having multiple areas of simultaneous user coverage. Note that Method 900 describes exemplary implementations, and the operation of Method 900 may be rearranged or otherwise modified to allow for other implementations. For example, certain described operations may be optional (e.g., those enclosed in boxes with dashed lines, those described as optional), where the optional operations may be performed when certain criteria are met, when performed based on configuration, when the optional operations are intermittently omitted, or when they are completely omitted.

[0116] The various illustrative blocks and components described in connection with the disclosure herein may be implemented or run using general-purpose processors, DSPs, ASICs, FPGAs or other programmable logic devices, discrete gates or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. The general-purpose processor may be a microprocessor, but alternatively, the processor may be any conventional processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices, for example, a combination of a DSP and a microprocessor, multiple microprocessors, a microprocessor combined with a DSP core, or any other such configuration.

[0117] The detailed description above, in relation to the attached drawings, describes illustrative embodiments and does not represent the only embodiments that may be practiced or that fall within the claims. The term “example” as used herein means “serving as an example, illustration, or demonstrative,” and does not mean “preferred” or “advantageous over other embodiments.” The detailed description includes specific details for the purpose of providing an understanding of the described art; however, these arts can be practiced without these specific details. In some embodiments, well-known structures and devices are shown in the form of block diagrams to avoid obscuring the concepts of the described embodiments.

[0118] Information and signals can be represented using any of the various different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips, which may be referenced throughout the above description, may be represented by voltage, current, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0119] The functions described herein may be implemented in various ways using different materials, features, shapes, sizes, etc. Other examples and implementations are within the scope of this disclosure and the appended claims. Mechanisms implementing the functions may also be physically arranged in various locations, such as being distributed in such a way that parts of the functions are implemented in different physical locations. Furthermore, as used herein, including in the claims, "or" in a list of items (e.g., a list of items preceded by phrases such as "at least one" or "one or more") indicates a disjunct list, such as the list "at least one A, B, or C" meaning A or B or C or AB or AC or BC or ABC (i.e., A and B and C).

[0120] In this specification, when referring to an electrical signal path or node, the term “coupled” means electrically connected, whether directly or indirectly. Furthermore, when referring to an electrical signal path or node, the term “selectively coupled” means a node that is directly or indirectly connected via one or more selectable elements such as switches, and “selectively coupled” signal paths or nodes may be coupled, and one or more nodes may be separated from alternative nodes or signal paths.

[0121] Computer-readable media include both computer storage media and communication media, which include any media that facilitates the transfer of computer programs from one location to another. Storage media may be any available media accessible by a general-purpose or specialized computer. In non-limiting examples, computer-readable media may include RAM, ROM, EEPROM, flash memory, CD-ROM or other optical disk storage devices, magnetic disk storage or other magnetic storage devices, or any other media that can be used to carry or store desired program code means in the form of instructions or data structures, and that can be accessed by a general-purpose or specialized computer, or a general-purpose or specialized processor. Any connection is also correctly referred to as computer-readable media. 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, and microwave, then coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of media. As used herein, "disk" and "disc" include compact discs (CDs), laser discs, optical discs, digital multipurpose discs (DVDs), floppy disks, and Blu-ray discs, where a "disk" typically reproduces data magnetically, while a "disc" reproduces data optically using a laser. Any combination of the above is also included within the scope of computer-readable media.

[0122] The descriptions contained herein are provided so that those skilled in the art can create or utilize the disclosure. Various modifications to the disclosure will be obvious to those skilled in the art, and the general principles defined herein can be applied to other variations without departing from the scope of the disclosure. Accordingly, this disclosure should not be limited to the examples and designs described herein, but rather given the broadest scope that is consistent with the principles and novel features disclosed herein.

Claims

1. A method of operation of a satellite communication system including a satellite having multiple geographically distributed access nodes and multiple forward signal paths, Transmitting from the plurality of access nodes to the satellite between each of two or more scheduled intervals, wherein each access node transmits one of a plurality of forward uplink signals, and each forward signal path relays the superposition of each of the plurality of forward uplink signals as a corresponding forward downlink signal, the superposition of the plurality of forward downlink signals forming a plurality of simultaneous forward beams depending on the beam weight matrix used to form the plurality of forward uplink signals, and the beam weight matrix comprises end-to-end forward beam weights. For each scheduling interval, Determining forward signal path assignments for non-overlapping first and second user coverage areas, wherein the forward signal path assignments are such that a first non-zero subset of the forward signal paths is assigned to the first user coverage area, and a second non-zero subset of the forward signal paths is assigned to the second user coverage area. In accordance with the forward signal path assignment, the connectivity to the plurality of forward signal paths is controlled, and the output terminals of the first subset of the forward signal paths are switched to connections to the respective feeds of the first user link array configured to illuminate the first user coverage area, and the output terminals of the second subset of the forward signal paths are switched to connections to the respective feeds of the second user link array configured to illuminate the second user coverage area. A method comprising: calculating the beam weight matrix for use during the scheduling interval based on the end-to-end forward channels corresponding to the forward signal path assignment.

2. The method according to claim 1, wherein each user coverage area is divided into a predetermined pattern of beam coverage areas, and the calculation of the beam weight matrix for use during each scheduling interval includes calculating the beam weight matrix depending on the beam coverage areas illuminated by each user coverage area during the scheduling interval.

3. The method according to claim 2, wherein each beam coverage area includes a geographical location representing a desired beam center, the satellite communication system receives sounding signals from each reference user terminal (RUT) located at or near each of the geographical locations, and the method includes estimating the end-to-end forward channel from the received sounding signals.

4. The method according to claim 1, wherein each forward signal path has an input terminal connected to each feed in a feeder link array, and the output terminal of each forward signal path is switchable between each feed in the first user link array and each feed in the second user link array, and determining the forward signal path assignment includes determining which feed pattern to use for simultaneous beamforming in the first and second user coverage areas, depending on the respective distribution of user terminals in the first and second user coverage areas, and the feed pattern includes determining which of the forward signal paths are included in the first subset and which of the forward signal paths are included in the second subset.

5. The method according to claim 1, wherein the forward signal path allocation changes over two or more of the scheduling intervals in accordance with a change in the determination of capacity requirements between the first and second user coverage areas.

6. The method according to claim 1, wherein controlling the connectivity to the plurality of forward signal paths in accordance with the forward signal path assignments includes providing the satellite with a schedule indicating the forward signal path assignments to be used for a plurality of scheduled intervals, and the satellite has an onboard switching circuit that operates to switch the output terminals of the forward signal paths in accordance with the schedule.

7. The method according to claim 1, wherein controlling the connectivity to the plurality of forward signal paths in accordance with the forward signal path assignment includes transmitting commands to the satellite to control a switching circuit of the satellite that operates to switch the output terminals of the forward signal paths.

8. In satellite communication systems, A satellite with multiple forward signal paths, A plurality of geographically dispersed access nodes, included in the ground segment of a satellite communications network and configured to transmit to the satellite between each of two or more scheduled intervals, wherein each access node transmits one of a plurality of forward uplink signals, and each forward signal path relays the superposition of each of the plurality of forward uplink signals as a corresponding forward downlink signal, and the superposition of the plurality of forward downlink signals forms a plurality of simultaneous forward beams, depending on a beam weighting matrix used to form the plurality of forward uplink signals, wherein the beam weighting matrix has end-to-end forward beam weights, A controller further included in the ground segment of the satellite communication network, wherein the controller comprises a communication interface and one or more processors. For each scheduling interval, a forward signal path assignment is determined, and the forward signal path assignment for each scheduling interval is determined with respect to non-overlapping first and second user coverage areas, and a first non-zero subset of the forward signal paths is assigned to the first user coverage area, and a second non-zero subset of the forward signal paths is assigned to the second user coverage area, With respect to the first and second subsets of the forward signal paths determined for each scheduling interval, the connectivity of the forward signal paths is controlled according to the forward signal path assignment determined for each scheduling interval, such that the output terminals of the first subset of the forward signal paths are switched to connect to the respective feeds of the first user link array configured to illuminate the first user coverage area, and the output terminals of the second subset of the forward signal paths are switched to connect to the respective feeds of the second user link array configured to illuminate the second user coverage area. A satellite communication system comprising: a controller comprising: one or more processors configured to calculate the beam weight matrix for use during each scheduling interval based on end-to-end forward channels corresponding to the forward signal path assignment determined for each scheduling interval; and a controller comprising:

9. The satellite communication system according to claim 8, wherein each user coverage area is divided into a predetermined pattern of beam coverage areas, and the controller is configured to calculate the beam weight matrix for use during each scheduling interval, depending on the beam coverage areas illuminated by each user coverage area during the scheduling interval.

10. The satellite communication system according to claim 9, wherein each beam coverage area encompasses a geographical location representing a desired beam center, the satellite communication system is configured to receive sounding signals from each reference user terminal (RUT) located at or near each of the geographical locations, and the controller is configured to estimate the end-to-end forward channel from the received sounding signals.

11. The satellite communication system according to claim 8, wherein each forward signal path has an input terminal connected to each feed in a feeder link array, and the output terminal of each forward signal path is switchable between each feed in the first user link array and each feed in the second user link array, and the controller is configured to determine, as part of determining the forward signal path assignment, which feed pattern to use for simultaneous beamforming in the first and second user coverage areas, depending on the respective distribution of user terminals in the first and second user coverage areas, and the feed pattern determines which of the forward signal paths are included in the first subset and which of the forward signal paths are included in the second subset.

12. The satellite communication system according to claim 8, wherein the forward signal path allocation changes over two or more of the scheduling intervals in accordance with a change in the determination of capacity requirements between the first and second user coverage areas.

13. The satellite communication system according to claim 8, wherein the controller is configured to control the connectivity of the plurality of forward signal paths based on providing the satellite with a schedule indicating the forward signal path assignments to be used for a plurality of scheduled intervals, and the satellite has an onboard switching circuit that operates to switch the output terminals of the forward signal paths according to the schedule.

14. The satellite communication system according to claim 8, wherein the controller is configured to control the connectivity of the forward signal path by transmitting a command to the satellite, and to control a switching circuit of the satellite that operates to switch the output terminal of the forward signal path in accordance with the command.

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