WO2025171325A1

WO2025171325A1 - Methods and apparatuses for performing dynamic assignments of user terminals to respective spot beams of a satellite communications system

Info

Publication number: WO2025171325A1
Application number: PCT/US2025/015104
Authority: WO
Inventors: Aniruddha Das
Original assignee: Viasat Inc
Current assignee: Viasat Inc
Priority date: 2024-02-09
Filing date: 2025-02-07
Publication date: 2025-08-14
Anticipated expiration: 2026-08-09

Abstract

An example satellite communications system (SCS) disclosed herein bases beam assignments for user terminals not according to a static mapping of terminal locations to predefined beam coverage areas corresponding to spot beams, and instead dynamically identifies some or all possible beam assignments and then determines a combination of beam assignments predicted as yielding the most favorable utilization of a communications resource of the SCS. Among the various advantages of this dynamic assignment procedure is the fact that beam assignments account for changing conditions, while enjoying the relative simplicity of predefined beam coverage areas.

Description

METHODS AND APPARATUSES FOR PERFORMING DYNAMIC ASSIGNMENTS OF USER TERMINALS TO RESPECTIVE SPOT BEAMS OF A SATELLITE COMMUNICATIONS SYSTEM

TECHNICAL FIELD

[0001] The present invention generally relates to performing dynamic assignments of user terminals to respective spot beams of a satellite communications system.

BACKGROUND

[0002] Satellite communication systems often employ spot beams to increase spectral efficiency and reuse frequencies across multiple geographic regions. Assigning user terminals to these spot beams is a critical task that influences system performance, resource allocation, and user experience. Various approaches to beam assignment exist.

[0003] One common approach is static beam assignment in a case where a satellite provides a set of spot beams, for example, with correspondingly static beam coverage areas. Static beam assignment in this context pre-assigns user terminals to specific spot beams based on the static beam coverage areas and, at least for stationary user terminals, the beam assignments do not change.

[0004] For example, an overall satellite service area is subdivided into a plurality of beam coverage areas having fixed geographic boundaries, with each beam coverage area corresponding to a respective spot beam. Terminal to beam assignments then rely on a static association between terminal locations and fixed beam coverage areas. Advantages associated with static beam assignments include network simplicity and beamforming simplicity.

[0005] At the expense of significantly greater complexity, other known approaches involve dynamic management of the spot beams. For example, dynamic management involves varying beam coverage locations and/or beam resource allocations, to account for changing traffic loads within an overall satellite coverage area. Manipulating beam parameters to better match beam capacities and geographic coverage with changing traffic needs over the satellite coverage area increases network efficiency. However, such manipulation comes at the expense of significant network and beamforming complexity.

SUMMARY

[0006] An example satellite communications system (SCS) disclosed herein bases beam assignments for user terminals not according to a static mapping of terminal locations to predefined beam coverage areas corresponding to spot beams, and instead dynamically identifies some or all possible beam assignments and then determines a combination of beam assignments predicted as yielding the most favorable utilization of a communications resource of the SCS. Among the various advantages of this dynamic assignment procedure is the fact that beam assignments account for changing conditions, while enjoying the relative simplicity of predefined beam coverage areas.

[0007] An example embodiment comprises a method of operation by a SCS, where the method comprises performing a dynamic assignment procedure, according to which the terminal-to-beam assignments are determined dynamically. The procedure includes determining, for each user terminal among a plurality of user terminals, which spot beams among a plurality of spot beams of the SCS are candidate beams for serving the user terminal. The determination is based at least on determining which ones among the plurality of spot beams satisfy radio link requirements for serving the user terminal.

[0008] Further, the method includes identifying a set of beam assignment decisions that optimizes utilization of a communications resource that is consumed in dependence on which combination of candidate beams is used for serving the plurality of user terminals. The identified set of beam assignment decisions assign each user terminal to one and only one of the candidate beams determined for the user terminal, and the method further includes implementing the identified set of beam assignment decisions, for serving the plurality of user terminals via the plurality of spot beams.

[0009] A related embodiment comprises a computer apparatus that is configured for use in a SCS. The computer apparatus includes a communications interface and processing circuitry. The processing circuitry is operative to carry out a dynamic assignment procedure, based on the processing circuitry being configured to: determine, for each user terminal among a plurality of user terminals, which spot beams among a plurality of spot beams of the SCS are candidate beams for serving the user terminal, based at least on determining which ones among the plurality of spot beams satisfy radio link requirements for serving the user terminal; identify a set of beam assignment decisions that optimizes utilization of a communications resource that is consumed in dependence on which combination of candidate beams is used for serving the plurality of user terminals, the identified set of beam assignment decisions assigning each user terminal to one and only one of the candidate beams determined for the user terminal; and implement, via control signaling output via the communications interface, the identified set of beam assignment decisions, for serving the plurality of user terminals via the plurality of spot beams.

[0010] Another embodiment comprises a SCS that includes one or more satellites, for providing a plurality of spot beams, each spot beam having a fixed nominal beam coverage area. The SCS further includes a ground network configured to support the one or more satellites, for serving a plurality of user terminals via the plurality of spot beams. In this context, any particular user terminal is served by only one spot beam at a time, and the ground network further includes a computer apparatus as described immediately above, for carrying out the dynamic assignment procedure on a recurring or triggered basis, with respect to the plurality of user terminals and the plurality of spot beams. [0011] Of course, the present invention is not limited to the above features and advantages. Those of ordinary skill in the art will recognize additional features and advantages upon reading the following detailed description, and upon viewing the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Fig. 1 is a diagram of an example satellite service area and a corresponding subdivision thereof into nominal beam coverage areas having fixed geographic boundaries. [0013] Figure 2 is a block diagram illustrating a satellite of a satellite communications system (SCS), according to an example embodiment.

[0014] Figure 3 is a diagram of beam contour lines associated with adjacent spot beams of a SCS.

[0015] Figure 4 is a block diagram illustrating further details for the SCS introduced in Figure 2, according to an example embodiment.

[0016] Figures 5-7 are logic flow diagrams of methods of operation for carrying out a dynamic assignment procedure, according to one or more example embodiments.

DETAILED DESCRIPTION

[0017] Figure 1 illustrates an example satellite service area 10 in which a plurality of user terminals 12 is distributed. The satellite service area 10 is logically subdivided into fixed nominal beam coverage areas 14, each having a geographic center 16. Although only a few fixed nominal beam coverage areas 14 appear in the diagram, there may be hundreds of such areas, e.g., dividing the Continental United States or other large satellite service area 10.

[0018] Figure 2 partially illustrates a satellite communications system (SCS) 18 according to one or more embodiments, in which one or more satellites 20 — one is shown — support a plurality of spot beams 22, for serving the plurality of user terminals 12. In one or more embodiments, the satellite(s) 20 that support the plurality of spot beams 22 is/are geostationary. In one or more other embodiments, the satellite(s) 20 is/are non-geo satellites. [0019] In an example embodiment involving non-geo satellites, the nominal beam coverage areas 14 may be understood as fixed Earth “cells” that are served by Medium Earth Orbit (MEO) or Low Earth Orbit (LEO) satellites. In one or more other embodiments, the nominal beam coverage areas 14 correspond to the spot beam configuration of one or more geosynchronous satellites. In one or more MEO/LEO embodiments, the spot beams 22 are steered to maintain illumination of the nominal beam coverage areas 14, at least over some duration of time. In at least one embodiment, the spot beams 22 are fixed spot beams, e.g., such as provided by a geosynchronous or geostationary satellite, according to a static beam layout.

[0020] In an example embodiment, each satellite 20 of the SCS 18 includes a feeder link interface 24 configured for radiofrequency (RF) or optical communications with a ground network of the SCS 18. Further, the satellite 20 includes a user link antenna system 26 to support the plurality of spot beams, which may be forward link user beams used for serving the plurality of user terminals 12 in the forward link direction, or which may be return link user beams for serving the plurality of user terminals 12 in the return link direction.

[0021] In one or more embodiments, the user link antenna system 26 comprises a phased array antenna for beamformed reception and/or transmission. The phased array antenna may be used with or without an associated reflector. In one or more other embodiments, the user link antenna system comprises a plurality of horn antennas, each providing a respective spot beam. Other alternatives include implementation of the user link antenna system 26 as a plurality of feed horns working in conjunction with a parabolic reflector antenna.

[0022] A payload 28 onboard the satellite 20 comprises forward and return link transponders or other arrangements of communications circuitry. Such circuitry is configured for reception of one or more feeder uplink signals via the feeder link interface 24, and the corresponding transmission of user downlink signals via the user link antenna system 26. Further, such circuitry is configured for the reception of user uplink signals via the user link antenna system 26, and the corresponding transmission of feeder downlink signals via the feeder link interface 24.

[0023] Such circuitry may be configured for bent-pipe operation, wherein signals are received and retransmitted in the analog domain, without decoding and processing. That is, in one or more embodiments, the one or more satellites 20 used to support the plurality of spot beams 22 comprise bent-pipe satellites. In one or more other embodiments, the satellite(s) 20 include payload(s) 28 that are configured for digital-domain processing of received signals and corresponding remodulation and transmission.

[0024] In any case, for ease of illustration, Figure 2 depicts only three spot beams 22. However, there is a one-to-one relationship between the plurality of spot beams 22 and the plurality of nominal beam coverage areas 14 used to subdivide the satellite service area 10 shown in Figure 1. Consequently, there are as many spot beams 22 as there are nominal beam coverage areas 14, with each nominal beam coverage area 14 corresponding to one and only one among the plurality of spot beams 22.

[0025] As seen in Figure 2, each spot beam 22 has a free-space beam cross section 30, with a corresponding beam center 32. Each beam center 32 may be aligned with the geographic center 16 of the corresponding fixed nominal beam coverage area 14. According to that arrangement, the highest beam strength or power is at the geographic center 16 of the corresponding fixed nominal beam coverage area 14, with the beam power decreasing with increasing distance from the geographic center 16.

[0026] In one or more example arrangements, the fixed nominal beam coverage areas 14 correspond with the 3dB beamwidth, meaning that the beam power at the predefined boundary of any given fixed nominal beam coverage area 14 is down roughly 3dB. Of course, beam power does not “stop” at these artificial geographic boundaries and example methods and apparatuses disclosed herein exploit the fact that even with a fixed plurality of spot beams 22, there is beam overlap and, depending on various factors, there are options for which particular beam is used to serve any one or more of the user terminals 12. In other words, for any given user terminal 12 among the plurality of user terminals 12, there may be more than one spot beam 22 among the plurality of spot beams 22 that are “candidates” for serving the given user terminal 12.

[0027] Figure 3 illustrates radio coverage overlap for two spot beams 22-1 and 22-2 that are “adjacent” in the sense that their corresponding fixed nominal beam coverage areas 14 are abutting. The beam contour lines 34 for each spot beam 22-1 or 22-2 depict decreasing beam strength with increasing distance from the geographic center 16 of the respective fixed nominal beam coverage area 14-1 or 14-2.

[0028] The given user terminal 12 depicted in Figure 3 is located within the fixed nominal user beam coverage area 14-1 associated with the spot beam 22-1, but that position also lies within, say, a 6dB contour line of the spot beam 22-2. As such, depending upon various factors, such as the capabilities of the user terminal 12, the prevailing radio conditions, and the particular radio link requirements for serving the user terminal 12, both the spot beam 22- 1 and the spot beam 22-2 may be candidates for serving the user terminal 12 — i.e., for any given user terminal 12 in the plurality of user terminals 12, there may be multiple — two or more — candidate beams, any of which can be used to serve the user terminal 12.

[0029] A particular formulation of these circumstances relevant to a dynamic assignment procedure disclosed herein is that there are various possibilities for assigning particular user terminals 12 to particular spot beams 22, despite the static nature of the spot beams 22 and the corresponding static nature of the fixed nominal beam coverage areas 14. A specific advantage of the dynamic assignment procedure in one or more embodiments is the determination of an optimal set of beam assignment decisions for the plurality of user terminals 12.

[0030] Here, “optimal” may be the globally optimal assignment, or may be a local or constrained optimization. In either case, however, the dynamic assignment procedure represents a sophisticated joint consideration of multiple combinations of possible beam assignments for the plurality of user terminals 12, where “possible beam assignments” refers to terminal-to-beam assignments that are possible based on determination of which spot beams 22 are candidate beams for each user terminal 12 considered in the dynamic assignment procedure.

[0031] An example implementation of the dynamic assignment procedure is given in the context of Figure 4, which illustrates a more detailed example of a SCS 18 according to one or more embodiments. In this example, two satellites 20-1 and 20-2 together support or otherwise provide a plurality of spot beams 22 for serving a plurality of user terminals 12 distributed over a satellite service area 10. For clear reference to the fixed nominal beam coverage areas 14, each spot beam 22 is illustrated as illuminating a single corresponding fixed nominal beam coverage area 14.

[0032] However, it shall be understood that the actual radio “footprint” of each spot beam 22 extends beyond the geographic boundaries that define the corresponding fixed nominal beam coverage area 14, such as suggested by the beam contour lines illustrated in Figure 3. As such, individual user terminals 12 may “see” favorable or at least sufficient radio link quality with respect to more than one spot beam 22, meaning that there are multiple possible combinations of terminal-to-beam assignments that would allow the SCS 18 to serve the plurality of user terminals 12. [0033] Here, “serving” a user terminal 12 means satisfying all applicable requirements, including, at a minimum, meeting the service demands of the user terminal 12. At a minimum, a given spot beam 22 is a candidate for serving a particular user terminal 12 — i.e., is a “candidate beam” with respect to that user terminal 12 — only if the radio link conditions associated with the use of that spot beam 22 satisfy radio link requirements. Such requirements may depend on the particular communication services in use and/or on other factors, such as service level agreement (SLA) obligations, terminal priority, etc.

[0034] According to the example details, the SCS 18 includes a ground segment 40, also referred to as a ground network 40, and a space segment 42. The space segment 42 includes the satellite(s) 20 used to support the plurality of spot beams 22 involved in the dynamic assignment procedure, while the ground segment 40 includes one or more terrestrial gateways 44, which are also referred to as ground stations 44 or satellite access nodes (SANs) 44. For example, there may be multiple SANs 44 within the ground network 40, with one or more such SANs 44 used to support feeder link communications with respective satellites 20 in the space segment 42.

[0035] The feeder link 46 that communicatively couples each satellite 20 to the ground network 40 carries feeder uplink signals comprising various control or other network signaling and forward user traffic. The feeder link 46 further carries feeder downlink signals comprising various control or other network signaling and return user traffic. In one or more example embodiments, some or all of the user terminals 12 provide channel state information (CSI) or other radio-measurement feedback that provides at least a partial basis for deciding which spot beams 22 are candidates for serving which user terminals 12.

[0036] The feeder links 46 are optical in one or more embodiments, where each SAN 44 includes one or more optical transmitters for feeder uplink transmission and one or more optical receivers for feeder downlink reception. In such embodiments, the previously mentioned feeder link interface 24 onboard each satellite 20 comprises one or more optical receivers for receiving optical feeder uplink signals and one or more optical transmitters for transmitting optical feeder downlink signals. In one or more other embodiments, the feeder links are radiofrequency (RF) links, in which case the SANs 44 and the satellites 20 respectively include RF transceivers for transmitting and receiving on the feeder links 46. [0037] One or more ground nodes 48 comprised in the ground network 40 provide communications signal processing and overall control of the SCS 18. Such nodes comprise, for example, one or more computer servers executing communications processing and network control programs and interfaced via Ethernet or other data networking connections. The ground nodes 48 may also include packet data routers, switches, or other networking equipment for exchanging communications signals 50 with one or more external networks 52.

[0038] For example, the external network(s) 52 include the Internet and the exchanged communications signals 50 include incoming packet data streams for forwarding to targeted user terminals 12 as forward user traffic conveyed on the spot beam(s) 22 to which those targeted user terminals 12 are currently assigned, and outgoing packet data streams originating from respective ones of the user terminals 12. In this regard, the illustrated spot beams 22 may be forward user beams or may be return user beams and it shall be understood that the dynamic assignment procedure can be applied in either case.

[0039] For example, there may be a plurality of spot beams 22 used for forward link service and another plurality of spot beams 22 used for return link service, where the dynamic assignment procedure is applied separately in the forward direction and in the return direction. Such an approach has particular advantages in cases where the spot beams 22 used for return link service do not have the same geometry or layout or radio coverage characteristics as the spot beams 22 used for forward link service. [0040] It should be understood that a spot beam 22 used for forward link service is associated with the directed transmission of RF energy, whereas as spot beam 22 used for return link service represents a directional reception of RF energy, i.e., a directionally sensitive antenna gain. In one or more embodiments, spot beams 22 used for return link service are associated with analog beamforming, and in other embodiments are associated with digital beamforming or hybrids of analog and digital beamforming.

[0041] An element in the ground network 40 of particular note in the example context of Figure 4 is a computer apparatus 60 that is configured to carry out a dynamic assignment procedure, according to an example embodiment. The computer apparatus 60 comprises a computer server or other computer processing node, and it may be implemented via virtualization on a host machine in a cloud data center. Nonetheless, the computer apparatus 60 comprises a tangible entity in which underlying processing circuitry 62 and a communications interface 64 are used for realization of the dynamic assignment procedure, including implementation of the decided beam assignments.

[0042] In an example embodiment, the processing circuitry 62 comprises one or more microprocessors or digital signal processors (DSPs) or other digital processing circuitry that is specially adapted to carry out the dynamic assignment procedure, based on the execution of computer program instructions contained in associated storage, such as one or more memory circuits or other type of computer readable media. In another example embodiment, the processing circuitry 62 comprises one or more Application Specific Circuits (ASICs) or Field Programmable Gate Arrays (FPGAs).

[0043] The communications interface 64 comprises, for example, an Ethernet interface or other data networking interface. For example, certain types of input data feed the dynamic assignment procedure, where all or some of that data is received by the processing circuitry 62 via signaling incoming through the communications interface 64. Likewise, implementation of the dynamically decided beam assignments involves the processing circuitry 62 using the communications interface 64 for outputting signaling that indicates the decisions or signaling comprising command and/or configuration signaling that initiates adoption of the decisions within the SCS 18 and the plurality of user terminals 12.

[0044] Thus, in one or more embodiments, the computer apparatus 60, which is configured for use in the SCS 18, comprises processing circuitry 62 and a communications interface 64, with the processing circuitry 62 configured to carry out a dynamic assignment procedure. For implementation of the procedure, the processing circuitry 62 is configured to determine which spot beams 22 among a plurality of spot beams 22 of the SCS 18 are candidate beams for serving each user terminal 12 among a plurality of user terminals 12. The determination of candidate beams for each user terminal 12 considered is based at least on determining which ones among the plurality of spot beams 22 satisfy radio link requirements for serving the user terminal 12.

[0045] Further, the processing circuitry 62 is configured to identify a set of beam assignment decisions that optimizes utilization of a communications resource that is consumed in dependence on which combination of candidate beams is used. The identified set of beam assignment decisions assigns each user terminal 12 to one and only one of the candidate beams determined for the user terminal 12. In other words, here and elsewhere in this disclosure, a “set” of beam assignment decisions allows for potentially many user terminals 12 to be assigned to any given spot beam 22, but the assignment scheme is premised on the rule that any given user terminal 12 is assigned to only a single one of the spot beams 22 at a time. Thus, for any given beam assignment period over which a given set of beam assignment decisions is in force, each user terminal 12 is assigned to one and only one among the spot beams 22 that were identified as candidates for serving the user terminal [0046] With respect to the identified set of beam assignment decisions, the processing circuitry 62 is configured to implement those decisions by outputting control signaling via the communications interface 64. For example, the ground node(s) 48 of the ground network 40 include a communications processing system (CPS) that maps forward and return user traffic to particular ones of the spot beams 22 in dependence on the per-terminal beam assignments, and the processing circuitry 62 outputs control signaling indicating to the CPS the identified set of beam assignment decisions. Additional control signaling may propagate to the respective user terminals 12, to ensure that they are “tuned” or retuned to their respectively assigned beams.

[0047] Another embodiment is a SCS 18 comprising one or more satellites 20, for providing a plurality of spot beams 22, each spot beam 22 having a fixed nominal beam coverage area 14, and further comprising a ground network 40 configured to support the one or more satellites 20, for serving a plurality of user terminals 12 via the plurality of spot beams 22. Here and elsewhere, it should be understood that any particular user terminal 12 is served by only one spot beam 22 at a time.

[0048] The ground network 40 in this example embodiment includes a computer apparatus 60, such as described immediately above, for carrying out the dynamic assignment procedure on a recurring or triggered basis, with respect to the plurality of user terminals 12 and the plurality of spot beams 22.

[0049] To appreciate the step or operation of identifying the set of beam assignment decisions that optimizes utilization of the communications resource at issue — i.e., makes the most efficient use of the resource with respect to meeting the service needs of the involved user terminals 12 — consider a much simplified example that assumes three user terminals 12, referred to as Tl, T2, and T3, and further assumes two spot beams 22, referred to as Bl and B2. Further, the simplified example assumes that, based on radio measurements, such as may be fed back from the user terminals 12, the following candidate determinations are made: T1 has sufficient radio link quality with respect to Bl and B2; T2 has sufficient radio link quality with respect only to B2; and, like Tl, T3 has sufficient radio link quality with respect to Bl and B2.

[0050] Thus, the “candidate beams” for serving each of the three terminals can be expressed as a “candidate beam set.” The candidate beam set for Tl is {Bl, B2}, the candidate beam set for T2 is { B2 } , and the candidate beam set for T3 is {Bl, B2}. As such, the possible sets of beam assignment decisions taken over the three terminals are Set 1 = {Bl, B2, B 1 } , Set 2 = { B2, B2, B 1 } , and Set 3 = { B2, B2, B2 } .

[0051] The question in this simplified example then becomes which one of these possible sets of beam assignment decisions makes the best use of one or more communications resources in the SCS 18. For example, a communications resource of the SCS 18 that is “shared” or commonly consumed for serving the overall plurality of user terminals 12 is time slots that are used for time division multiplexing of the user traffic for different user terminals 12. In another example, the communications resource in question is an overall transmit power budget associated with transmitting on the plurality of spot beams 22, in which case the question would be which one of the possible sets of beam assignment decisions minimizes the aggregate transmit power.

[0052] In these two examples (time slots and transmit power) and in other examples of particular types of communications resources for which utilization is being optimized, the computer apparatus 60 may be configured to represent the utilization using a related metric, such as the sum of the symbol rates needed to serve all user terminals 12 being considered. Because the symbol rate needed for serving any given user terminal 12 depends on, among other things, the beam-specific link quality between the user terminal 12 and the SCS 18, it will be appreciated that different spot beams 22 in the candidate beam set for the given user terminal correspond to different symbol rates, despite all of them satisfying the applicable minimum required link quality. Expounding from there, then, each possible set of beam assignment decisions for the overall plurality of user terminals 12 being considered will, as a general proposition, map to different sum totals of needed symbol rates.

[0053] One approach to determining which possible set of beam assignment decisions offers the most favorable utilization of the communications resource(s) used to serve the plurality of user terminals 12 is the evaluation of an objective function that yields the minimum sum total of symbol rates needed to serve the plurality of user terminals 12 — i.e., to meet the service needs and any priority or SLA requirements. Of course, the optimization may be qualified, such as where a mathematical cost is assigned to beam switching, and there may be one or more constraints considered in the optimization as well, such as minimum required service levels defined by one or more SLAs.

[0054] Figure 5 illustrates a method 500 of operation and stands as an example implementation of a dynamic assignment procedure used to determine how best to serve a plurality of user terminals 12 via a plurality of spot beams 22, wherein, during any given serving interval, each user terminal 12 is served with one and only one spot beam 22. The computer apparatus 60 described above is, for example, configured to carry out the method 500.

[0055] The method 500 includes: determining (Block 502) which spot beams 22 among a plurality of spot beams 22 of a SCS 18 are candidate beams for serving each user terminal 12 among a plurality of user terminals 12, based at least on determining which ones among the plurality of spot beams 22 satisfy radio link requirements for serving the user terminal 12; identifying (Block 504) a set of beam assignment decisions that optimizes utilization of a communications resource that is consumed in dependence on which combination of candidate beams is used, the identified set of beam assignment decisions assigning each user terminal 12 to one and only one of the candidate beams determined for the user terminal; and implementing (Block 506) the identified set of beam assignment decisions, for serving the plurality of user terminals 12 via the plurality of spot beams 22.

[0056] The candidate beam set for each user terminal 12 may include two or more of the spot beams 22, and this may be the case in particular for user terminals 12 that are at or near the geographic boundaries between respective fixed nominal beam coverage areas 14. As a general proposition, the candidate beam set identified for each user terminal 12 will be a nonzero set of one or more spot beams 22 and, in the context of the dynamic assignment procedure, over the plurality of user terminals 12 being considered, one or more of the user terminals 12 will have two or more candidate beams in their respective candidate beam set, such that the optimization process will have two or more combinations of candidate beam selections to consider. As a general proposition, the candidate beam set for any given user terminal 12 will include at least the spot beam 22 in current use for serving the user terminal 12, or the spot beam 22 associated with the fixed nominal beam coverage area 14 in which the user terminal 12 is located.

[0057] In one or more embodiments of the method 500, implementing the identified set of beam assignment decisions comprises generating control signaling to configure the SCS 18 and the user terminals 12 according to the identified set of beam assignment decisions.

[0058] Performing the dynamic assignment procedure comprises, for example, performing the dynamic assignment procedure repeatedly, responsive to a triggering event, which may be a defined periodicity — e.g., recurring expiry of a timer — or other event type, such as reaching a loading threshold on one or more beams. In one example of a triggered basis, the computer apparatus 60 or other entity within the SCS 18 monitors for beam congestion or beam loading imbalances, with the dynamic assignment procedure triggered responsive to detecting the presence of a defined congestion or loading imbalance condition. [0059] In addition to triggered performance, or as an alternative to triggered performance, one or more embodiments perform the dynamic assignment procedure on a periodic basis, which can be understood as a form of time-based triggering. The periodicity may be fixed or the periodicity may be dynamic, e.g., increased or decreased as a function of monitored network conditions. Each performance of the dynamic assignment procedure yields a new or updated set of beam assignment decisions, which are implemented and maintained for some subsequent serving interval, which could be minutes, hours, or days, for example.

[0060] Notably, each successive performance of the dynamic assignment procedure may or may not involve the identical pluralities of spot beams 22 and/or user terminals 12. For example, one or more spot beams 22 considered in one performance of the dynamic assignment procedure may be excluded from a later performance, or the later performance may add one or more spot beams 22 to the considered plurality. Likewise, there may be a greater or lesser number of user terminals 12 considered in one performance versus another, or new terminals may be added or old terminals may be dropped from consideration.

[0061] In at least one embodiment, the dynamic assignment procedure includes determining the plurality of user terminals 12 to be considered in the procedure by logically filtering a larger plurality of user terminals 12, to exclude one or more particular user terminals 12 or one or more particular classes of user terminals 12 from the dynamic assignment procedure. For example, one or more user terminals 12 may have designated priorities or known security considerations, according to which they are excluded from considering for beam reassignments. Put simply, for a given overall population of user terminals 12 operating within a satellite service area 10, the dynamic assignment procedure may consider all of them, or only some of them, and the particular ones considered may change over successive or recurring performances of the procedure. [0062] Similarly, in one or more embodiments, the dynamic assignment procedure includes determining the plurality of spot beams 22 to be considered in the procedure, by logically filtering a larger plurality of spot beams. The filtering excludes one or more particular spot beams 22 from the dynamic assignment procedure. For example, there may be one or more spot beams 22 among the larger plurality that should be excluded on the basis of service agreements, security considerations, etc. Thus, with respect to an overall set or plurality of spot beams 22 that are used with respect to a particular satellite service area 10, all or only some of them may be used as the plurality of spot beams 22 considered in the dynamic assignment procedure, and the particular beams considered may change over multiple performances of the procedure.

[0063] Further, in at least one embodiment, each performance of the dynamic assignment procedure includes compiling evaluation data indicating beam loading for individual spot beams 22 among the plurality of spot beams 22, and indicating for each user terminal 12 among the plurality of user terminals 12, a current geographic location, a current usage, and current radio conditions with respect to one or more spot beams 22 among the plurality of spot beams 22. The evaluation data is used in determining the candidate beams for each user terminal 12, and for identifying the set of beam assignment decisions that optimizes utilization of the communications resource.

[0064] The plurality of spot beams 22 considered in any given performance of the dynamic assignment procedure either is a first plurality of forward spot beams used to serve a plurality of user terminals 12 in a forward link direction of the SCS 18, or a second plurality of return spot beams used to serve a plurality of user terminals 12 in a return link direction of the SCS 18. In at least one embodiment, the method 500 comprises performing the dynamic assignment procedure separately, for the first plurality of forward spot beams and for the second plurality of return spot beams. In this manner, the beam assignment decisions for forward link service are made separately from the beam assignment decisions made for return link service, which is advantageous not least because forward link radio conditions may differ from return link radio conditions.

[0065] In one or more embodiments or operational scenarios, the plurality of spot beams 22 considered in the dynamic assignment procedure is associated with a single satellite 20 of the SCS 18. In one or more other embodiments or operational scenarios, the plurality of spot beams 22 is associated with two or more satellites 20 of the SCS 18, with each satellite 20 providing a nonzero subset of spot beams 22 among the plurality of spot beams 22. Again, in at least one embodiment, the satellite(s) 20 used to provide the plurality of spot beams are geosynchronous satellites, and may be geostationary.

[0066] As for the step or process of determining which spot beams 22 among the considered plurality of spot beams 22 are candidate beams for serving each user terminal 12, the determinations may be simplified by, for each user terminal 12, constraining a candidate beam evaluation procedure to considering, as possible candidate beams, only a relevant subset of spot beams 22 from the plurality of spot beams 22. For example, the relevant subset of spot beams 22 may be identified based on at least one of a geographic location of the user terminal 12, or a current beam assignment of the user terminal 12. This approach obviates the need to carry out candidate-beam evaluations for any given user terminal 12, with respect to any spot beams 22 that are not plausible candidates for serving the user terminal 12.

[0067] As noted earlier, determining the best or most favorable combination of candidatebeam assignments over the plurality of user terminals 12 being considered may be based on expressing the utilization of the subject communications resource as the sum of symbol rates needed to serve the plurality of user terminals 12. With this framing, the identified set of beam assignment decisions — i.e., the decisions to be implemented — minimizes the sum of symbol rates needed to serve the plurality of user terminals 12. This approach inherently accounts for the particular communications service needs of the individual user terminals 12. [0068] More broadly, in one or more embodiments, identifying the set of beam assignment decisions that optimizes the utilization of the communications resource comprises determining which possible set of beam assignment decisions minimizes an objective function. Here, each possible set of beam assignment decisions is a unique combination of candidate beam assignments for the plurality of user terminals 12. Notably, the optimization may be constrained such that not all possible combinations in the overall universe of possible combinations is considered, and it thus shall be understood that the optimization may therefore be a qualified or constrained optimization.

[0069] In one or more embodiments, the objective function minimizes the sum total of symbol rates needed to serve the plurality of user terminals 12. In the same or in one or more other embodiments, the objective function accounts for a mathematical cost of beam reassignments, thereby biasing beam assignment decisions in favor of retaining existing beam assignments. Further, in at least one embodiment, the objective function accounts for respective beam loadings among the plurality of spot beams 22. The beam loading of any particular spot beams 22 relates to one or both of: the number of user terminals 12 currently assigned to the particular spot beam 22, or data demands associated with the user terminals 12 currently assigned to the particular spot beam 22.

[0070] In addition to the constraint that each user terminal 12 be assigned to one and only one of the candidate beams determined for the user terminal 12, minimization of the objective function in one or more embodiments is constrained with respect to any one or more of: SLAs governing service to one or more of the user terminals 12, per beam throughput limits, or per beam symbol rate limits. [0071] In one approach to supporting the dynamic assignment procedure, the method 500 includes maintaining electronic data within the SCS 18. This electronic data, which may be referred to as collected data or evaluation data, indicates geographic locations of individual user terminals 12 among the plurality of user terminals 12, and further indicates, for each user terminal 12, current data usage and current radio conditions. The current radio conditions indicate radio signal quality with respect to one or more spot beams 22 among the plurality of spot beams 22, and the electronic data associated with each user terminal 12 are used for determining the candidate beams for each user terminal 12.

[0072] That is, the data collected with respect to each user terminal 12 indicates which spot beam(s) 22 are viable for serving the user terminal 12 in terms of meeting minimum radio link requirements associated with serving the user terminal 12. Of course, this radio link viability may not be dispositive with respect to determining that a given spot beam 22 is a candidate beam for a given user terminal 12. Instead, the radio link viability may be a necessary but not sufficient condition, with candidacy ultimately determined in dependence on one or more further factors, such as SLA restrictions, terminal priority, etc.

[0073] However the candidate beams are determined, one or more embodiments of the method 500 include a particular approach to identifying the set of beam assignment decisions to be implemented. In such embodiments, the identification comprises determining which possible configuration of a beam assignment matrix optimizes the utilization of the communications resource.

[0074] Here, the beam assignment matrix has a corresponding row for each spot beam 22 among the plurality of spot beams 22 and has a corresponding column for each user terminal 12 among the plurality of user terminals 12. Correspondingly, each “possible configuration” of the beam assignment matrix is a unique combination of candidate beam assignment decisions for the plurality of user terminals 12. Determining which possible configuration of the beam assignment matrix optimizes the utilization of the communications resource comprises, for example, evaluating some or all of the possible configurations of the beam assignment matrix according to an objective function.

[0075] Figure 6 illustrates a method 600 of operation by a SCS 18, which can be understood as a specific implementation or variation of the method 500 according to one embodiment. The SCS 18 in question supports a plurality of spot beams 22 for serving a population of user terminals 12. Each spot beam 22 is characteristically associated with a corresponding RF carrier and a geographic region of illumination — i.e., a fixed nominal beam coverage areas 14.

[0076] The method 600 comprises performing a dynamic assignment procedure that includes evaluating (Block 602) radio link conditions for each user terminal 12 among the population of user terminals 12 to identify for each user terminal 12 a corresponding set of spot beams 22 that are candidate beams for serving the user terminal 12. Each candidate beam for each user terminal 12 being one among the plurality of spot beams 22 that satisfies a radio link budget for communications between the user terminal 12 and the SCS 18. Of course, as noted before, there may be one or more additional qualifications or conditions that must be met before a spot beam 22 is deemed to be a candidate beam for a given user terminal 12.

[0077] The method 600 further comprises determining (Block 604) a collection of beam assignment decisions for the population of user terminals 12, based on evaluating an aggregate consumption of a resource of the SCS 18 that is jointly consumed for serving the population of user terminals 12, for a plurality of hypothetical collections of beam assignment decisions.

[0078] Each hypothetical collection of beam assignment decisions is a unique collection of beam assignment decisions in which each user terminal 12 in the population of user terminals 12 is assigned to a particular one among the corresponding set of spot beams that are candidate beams for serving the user terminal 12. With reference to the method 500, each hypothetical collection of beam assignment decisions is a particular combination of candidate beams to be used for serving the population of user terminals 12, such that the determined collection of beam assignment decisions is a set of beam assignment decisions identified as yielding a best or most favorable utilization of the communications resource.

[0079] Further, the method 600 includes initiating (Block 606) per user terminal beam assignments for the population of user terminals 12, according to the determined collection of beam assignment decisions. For example, the aforementioned computer apparatus 60 outputs data or control signaling that indicates the determined collection of beam assignment decisions, for configuration or adaptation of the SCS 18 in accordance with those decisions, including adjusting to spot beams 22 are used for carrying the user traffic flows of respective ones among the population of user terminals 12.

[0080] The dynamic assignment procedure may be performed on a recurring basis, such that there is a new determined collection of beam assignment decisions for each recurrence of the dynamic assignment procedure, with that new determined collection applicable for SCU operation until a next recurrence. The recurrences may be triggered, such as event or condition triggered or time triggered, e.g., responsive to expiry of a timer.

[0081] Performing the dynamic assignment procedure on a triggered basis comprises, for example, monitoring the aggregate consumption of the resource of the SCS 18 that is jointly consumed for serving the population of user terminals 12, and triggering the dynamic assignment procedure responsive to the consumption reaching a threshold level of consumption.

[0082] At least some of the user terminals 12 in the population of user terminals 12 are stationary, in one or more embodiments. For example, all user terminals 12 considered in the dynamic assignment procedure are stationary. However, in at least some embodiments, at least some of the user terminals 12 are mobile or at least movable. In at least one such embodiment, user terminals 12 having a mobility — e.g., speed — above some defined threshold are not considered in the dynamic assignment procedure.

[0083] One or more embodiments of the method 600 include reducing a processing load associated with identifying the candidate beams corresponding to each user terminal 12 in the population of user terminals 12 by, for each user terminal 12, assuming that spot beams 22 having corresponding nominal beam coverage areas 14 not covering or not adj cent to a location of the user terminal 12, cannot be candidate beams for serving the user terminal 12. As a particular example, a geographic region defined as a satellite service area 10 is logically subdivided into a plurality of nominal user beam coverage areas 14. Each spot beam 22 among the plurality of spot beams 22 is oriented for illumination of a corresponding one among the plurality of nominal user beam coverage areas 14. The particular ones among the plurality of spot beams 22 that are numerically evaluated for consideration as candidate beams for any particular one among the population of user terminals 12 is a function of a location of the user terminal 12 within the satellite service area 10.

[0084] The radio link budget for each user terminal 12 may depend on one or more factors. For example, the radio link budge may be a function of at least one of: a terminal type of the user terminal 12, or a communications service used by the user terminal 12. In any case, determining the collection of beam assignment decisions for the population of user terminals 12 in one or more embodiments comprises evaluating the aggregate consumption of the resource for respective ones in the universe of hypothetical collections of beam assignment decisions according to one or more constraints.

[0085] As an example, the one or more constraints include a restriction that each user terminal 12 is served by only one spot beam at a time, along with any one or more of: applicable regulatory limits on user terminal transmit power; a defined mathematical cost for switching a given user terminal 12 from one beam to another; priority assignments for one or more user terminals 12 among the population of user terminals; SLAs governing service to one or more of the user terminals 12 among the population of user terminals 12; per beam throughput limits; and per beam symbol rate limits.

[0086] Evaluating the aggregate consumption of the resource for each hypothetical collection of beam assignment decisions comprises, for example, predicting a sum total of resource consumption for each hypothetical collection, based on evaluating a function and comparing evaluation results for the respective hypothetical collections. For example, the evaluation results for each hypothetical collection is a sum of symbol rates needed to serve the population of UTs. In one or more embodiments, the evaluation results for each hypothetical collection are predicted in dependence on the following data: a current location of each user terminal 12; an estimated current signal to noise ratio (SNR) associated with each user terminal 12; and an estimated current usage of each user terminal 12, expressed in bits per second.

[0087] Each hypothetical collection of beam assignment decisions is, for example, expressed as a unique instance of a beam assignment matrix having a vector of binary elements for each user terminal 12 in the population of user terminals 12. Each vector has single nonzero element representing the hypothetical assignment of the corresponding user terminal 12 to one and only one spot beam 22 among the plurality of spot beams 22.

[0088] In one or more embodiments, the beam assignment matrix has a row for each spot beam 22 in the plurality of spot beams 22 and has a column for each user terminal 12 in the population of user terminals 12. As such, for each unique instance of the beam assignment matrix, each column has exactly one nonzero element representing the hypothetical assignment of the corresponding user terminal 12 to a particular one among the plurality of spot beams 22.

[0089] Determining the collection of beam assignment decisions for the population of user terminals 12 in one or more embodiments comprises determining an optimal value of the beam assignment matrix subject to one or more constraints. The optimal value in this sense is a particular collection of beam assignment decisions that optimizes utilization of the resource. [0090] A further detailed example of the dynamic assignment procedure assumes the existence of the following information: (a) the availability of latitude-longitude (location) for all user terminals 12 to be considered; and (b) the availability of current usage and current SNR for all user terminals 12 to be considered. The dynamic assignment procedure runs with respect to successive time periods T, which may be measured in minutes, for example. In at least one embodiment, the procedure operations on 15-minute periods. In at least one embodiment, a new or updated set of beam assignment decisions is made at the end of each period, based on data collected during that period (or filtered over a running window of periods), with the new decisions applied at the beginning of the next period.

[0091] A beam assignment matrix B is used to determine or otherwise represent the collection of beam assignment decisions used with respect to the plurality of user terminals 12 may be expressed at any time t as a B x N matrix. Here, B is the number of spot beams 22 involved in the dynamic spot beam assignment procedure, and N is the number of user terminals 12 subject to the procedure.

[0092] Thus, the matrix B is given as:

The j-th column of this matrix, b is a B x 1 vector, and b is nonzero in the position of the assigned beam index and zero everywhere else. Thus for example, if “terminal 10” is in the 23rd beam at time t = 43 in a system with B = 1000 beams, then b g is a 1000 x 1 vector with 1 in position 23 and zero everywhere else. By definition, B_t is binary (only 0 or 1 are possible values) and sparse with only N non- zero elements.

[0093] The data used in one or more embodiments of the dynamic assignment procedure are collected for every /-th time interval, for each n-th terminal. These time intervals may be of the same duration on which the beam assignment decisions are updated, or they may be a fraction of the update interval. In that latter case, data may be collected multiple times over a current beam update interval, with that data filtered or otherwise aggregated for use in deciding the beam assignments for the next beam update interval.

[0094] The total number of terminals is N and can be large, such as hundreds of thousands, or even more than a million, and the data collected includes: the current location Z(n, t) in lat-lon of each terminal, the current beam matrix B_t (i.e., the decision set currently in use), the current SNR snr_t(n, 1) in dB (i.e., the current SNR for each terminal), and the current usage d_t(n, l)in bits/second for each terminal.

[0095] Based on the past samples of this same data, a prediction is made for the same metrics at time t + 1. This prediction can be a basic linear extrapolation or use more complicated algorithms. In the simplest example, the same values at time t are predicted to be valid for time t + 1.

[0096] Point Link Budget (PLB) tools are used to predict the SNRs of the same terminal at time t + 1 in adjacent beams. Thus for each terminal, there is now a list of predicted SNRs smy ₁(n, b), where the ^: indicates that it is a predicted/estimated value, and the index b indicates the prediction for beam b. The list of beams for each terminal includes both the current beam and the other beams in the beam plurality. As a simplifying step, beams that are not nominal adjacent to current beam may be assigned an impractically low SNR value, e.g.

-lOOdB, without carrying out the actual PLB computations. [0097] A real time assignment algorithm embodied in the dynamic assignment procedure has as its overall task the prediction of the optimal value, B_t+1, for the matrix B_t+1, subject to several constraints. Here, the ^: denotes the fact that B_t+1 is a predicted value. Note that it is also true that the actual value of B_t+1may differ from the predicted value B_t+1 because the SCS 18 may fail for one reason or another to make all beam changes predicted by the algorithm. Thus, any reference herein to implementing a determined set of beam assignment decisions shall be understood as meaning that the intent is to implement them, with the understanding that not every single beam assignment decision in the set will necessarily be realized in the SCS 18.

[0098] Because B_t+1 is a binary sparse matrix, the applicable class of optimization problems is known as a Binary Integer Program (BIP), which is a sub class of Mixed Integer Program (MIP). Problems in the BIP/MIP class have known optimizations, and, for example, the computer apparatus 60 may be programed to solve the specific optimization of B_t+1 based on applying BIP/MIP based optimization. The general problem is an NP-Hard problem and so the globally optimal solution may not be found. That is, the optimal set of beam assignment decisions determined by the dynamic assignment procedure is not necessarily a globally optimal solution in the mathematical sense.

[0099] Inputs to the optimization algorithm include, for each terminal: (a) the predicted values at time t+1 for the location of the terminal, (b) the set of predicted SNRs for the respective beams, (c) the usage of the terminal, (d) any contractual SLA/data rates applicable for the terminal; (e) the cost, c, of a beam switch, which may be expressed in the form of the capacity overhead needed in the SCS for a beam switch; (f) any regulatory limits on transmissions, such as may be applied to the terminal in the reverse link direction; (g) actual/true beam assignments of the terminal at time t, i.e. B_t; (h) terminal priority level; and (i) mapping of SNR to bits/symbol in the SCS, after taking into account the system margin in dB.

[00100] With the foregoing algorithmic inputs, the optimization algorithm determines the optimal set or collection of beam assignments for the terminals at time t + 1. That is, it determines B_t+1. For those terminals where a beam change is needed, the computer apparatus 60 shall initiate the beam change/handover promptly.

[00101] As for optimization problem definitions and details, an objective function is defined according to the metric to be minimized. An example metric is the sum total of resources needed to satisfy the demand from the terminals. More particularly, an example metric is the sum of the symbol rates needed to serve the terminals, which may be expressed as

[00102] Constraints applicable to the optimization include: (a) an inequality constraint for symbol rate, where the total symbol rate demanded from a beam cannot be greater than what has been assigned to the beam by the SCS 18; (b) regulatory constraints per terminal, including any regulatory limits on transmit power; (c) SLA constraints that must be met on a per terminal basis; (d) the rule that elements of B_t+1 must be 0 or 1 (binary constraint); (e) the rule that each column of B_t+1 must sum to 1 (i.e., each terminal must have one and only one beam assigned); (f) and an infeasibility problem constraint, wherein, if the Binary Integer Problem (BIP) as defined above is infeasible, the problem may be relaxed by taking into account terminal priority, such that higher priority terminals would be prioritized and lower priority terminals deemphasized or even dropped, until the problem becomes feasible. For example, one, some, or all lower priority terminals may be excluded from consideration in the optimization problem. [00103] There are steps that can be used to simplify the optimization algorithm as described above. Further, it must be noted that a substantive difference between conventional “load balancing” techniques and the dynamic assignment procedure is that load balancing is typically done on a local set of data over a longer time period. Contrastingly, the dynamic assignment procedure is an overall optimization, using the data from all terminals included in a plurality of terminals considered in the optimization. This approach relies on the per terminal usage and physical layer characteristics on a quasi-real time basis.

[00104] As another notable point, the objective function may be structured such that it does not reduce the amount of system resources used, but rather maximizes revenue. That is, the optimal utilization of the communication resource(s) used for serving the subject plurality of user terminals may be understood in terms of operator revenue. Broadly, as described herein, global metrics are used to determine beam reassignments in a real time basis and do not require adherence to predefined 3dB contours of the beam boundaries associated with a plurality of spot beams.

[00105] Figure 7 illustrates the above described optimization algorithm in the form of a method 700. Figure 7 thus can be understood as a further example implementation of the method 500.

[00106] The method 700 includes collecting (Block 702) the data described above as inputs to the optimization algorithm, where the collection may be done on a running basis. The method 700 further includes determining whether it is time to determine a new set of beam assignment decisions for the involved plurality of user terminals. If not (NO from Block 704), operations continue with data collection. If so (YES from Block 704), operations continue with carrying out (Block 706) the optimization algorithm described above, and then applying (Block 708) the optimal beam assignments, as determined by the optimization algorithm. Here, it should be noted that applying the optimal set of beam assignment decisions does not mean that every single decision in the set must ultimately be realized in the SCS 18, e.g., there may be failures or overrides or other circumstances that prevent a complete realization. Even so, operation of the SCS 18 is improved if at least some of the decisions in the optimal set are realized within the SCS 18.

[00107] Another point to note is that the degree or overall extent of optimization may be varied without departing from the underlying technique. For example, as noted elsewhere, the set of user terminals considered in the optimization problem may be filtered, as may be the set of spot beams. Further, the candidate beam sets may be made more or less inclusive. For example, for any given terminal, there may be three spot beams that satisfy link requirements, but only the two best are considered in the optimization problem, and this same logic may be applied to limit the candidate beam set size for all terminals considered in the optimization. Further, the objective function in one or more embodiments may consider less than the full universe of possible beam assignment decisions.

[00108] Notably, modifications and other embodiments of the disclosed invention(s) will come to mind to one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention(s) is/are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of this disclosure. Although specific terms may be employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

CLAIMS What is claimed is:

1. A method of operation by a satellite communications system (SCS), the method comprising performing a dynamic assignment procedure comprising: determining, for each user terminal among a plurality of user terminals, which spot beams among a plurality of spot beams of the SCS are candidate beams for serving the user terminal, based at least on determining which ones among the plurality of spot beams satisfy radio link requirements for serving the user terminal; identifying a set of beam assignment decisions that optimizes utilization of a communications resource that is consumed in dependence on which combination of candidate beams is used for serving the plurality of user terminals, the identified set of beam assignment decisions assigning each user terminal to one and only one of the candidate beams determined for the user terminal; and implementing the identified set of beam assignment decisions, for serving the plurality of user terminals via the plurality of spot beams.

2. The method according to claim 1, wherein implementing the identified set of beam assignment decisions comprises generating control signaling to configure the SCS and the user terminals according to the identified set of beam assignment decisions.

3. The method according to claim 1 or 2, wherein performing the dynamic assignment procedure comprises performing the dynamic assignment procedure repeatedly, responsive to a triggering event.

4. The method according to claim 3, further comprising, for each performance of the dynamic assignment procedure, compiling evaluation data indicating beam loading for individual spot beams among the plurality of spot beams, and indicating for each user terminal, a current geographic location, a current usage, and current radio conditions with respect to one or more spot beams among the plurality of spot beams, the evaluation data used in determining the candidate beams for each user terminal, and for identifying the set of beam assignment decisions that optimizes utilization of the communications resource.

5. The method according to any one of claims 1-4, wherein the plurality of spot beams either is a first plurality of forward spot beams used to serve the plurality of user terminals in a forward link direction of the SCS, or a second plurality of return spot beams used to serve the plurality of user terminals in a return link direction of the SCS, and wherein the method comprises performing the dynamic assignment procedure separately, for the first plurality of forward spot beams and for the second plurality of return spot beams.

6. The method according to any one of claims 1-5, wherein the plurality of spot beams is associated with a single satellite of the SCS.

7. The method according to any one of claims 1-5, wherein the plurality of spot beams is associated with two or more satellites of the SCS, with each satellite providing a nonzero subset of spot beams among the plurality of spot beams.

8. The method according to any one of claims 1-7, wherein at least some among the plurality of user terminals are stationary user terminals.

9. The method according to any one of claims 1-8, further comprising determining the plurality of user terminals by logically filtering a larger plurality of user terminals, to exclude one or more particular user terminals or one or more particular classes of user terminals from the dynamic assignment procedure.

10. The method according to any one of claims 1-9, further comprising determining the plurality of spot beams by logically filtering a larger plurality of spot beams, to exclude one or more particular spot beams from the dynamic assignment procedure.

11. The method according to any one of claims 1-10, wherein determining which spot beams among the plurality of spot beams of the SCS are candidate beams for serving each user terminal is simplified by, for each user terminal, constraining a candidate beam evaluation procedure to considering, as possible candidate beams, only a relevant subset of spot beams from the plurality of spot beams.

12. The method according to claim 11, further comprising identifying the relevant subset of spot beams for each user terminal based on at least one of: a geographic location of the user terminal, or a current beam assignment of the user terminal.

13. The method according to any one of claims 1-12, further comprising expressing the utilization of the communications resource as a sum of symbol rates needed to serve the plurality of user terminals, and wherein the identified set of beam assignment decisions minimizes the sum of symbol rates needed to serve the plurality of user terminals.

14. The method according to any one of claims 1-13, wherein identifying the set of beam assignment decisions that optimizes the utilization of the communications resource comprises determining which possible set of beam assignment decisions minimizes an objective function, each possible set of beam assignment decisions being a unique combination of candidate beam assignments for the plurality of user terminals.

15. The method according to claim 14, wherein minimizing the objective function minimizes a sum total of symbol rates needed to serve the plurality of user terminals.

16. The method according to claim 14 or 15, wherein the objective function accounts for a mathematical cost of beam reassignments, thereby biasing beam assignment decisions in favor of retaining existing beam assignments.

17. The method according to any one of claims 14-16, wherein the objective function accounts for respective beam loadings among the plurality of spot beam, wherein the beam loading of any particular spot beams relates to one or both of: the number of user terminals currently assigned to the particular spot beam, or data demands associated with the user terminals currently assigned to the particular spot beam.

18. The method according to any one of claims 14-17, wherein, in addition to the constraint that each user terminal be assigned to one and only one of the candidate beams determined for the user terminal, minimization of the objective function is constrained with respect to any one or more of: service level agreements (SLAs) governing service to one or more of the user terminals, per beam throughput limits, or per beam symbol rate limits.

19. The method according to any one of claims 1-18, further comprising maintaining electronic data within the SCS, indicating geographic locations of individual user terminals among the plurality of user terminals, and further indicating, for each user terminal, current data usage and current radio conditions, the current radio conditions indicating radio signal quality with respect to one or more spot beams among the plurality of spot beams, the electronic data used for determining the candidate beams for each user terminal.

20. The method according to any one of claims 1-14, wherein identifying the set of beam assignment decisions comprises determining which possible configuration of a beam assignment matrix optimizes the utilization of the communications resource, the beam assignment matrix having a corresponding row for each spot beam among the plurality of spot beams and having a corresponding column for each user terminal among the plurality of user terminals, and each possible configuration of the beam assignment matrix being a unique combination of candidate beam assignment decisions for the plurality of user terminals.

21. The method according to claim 21, wherein determining which possible configuration of the beam assignment matrix optimizes the utilization of the communications resource comprises evaluating some or all of the possible configurations of the beam assignment matrix according to an objective function.

22. A computer apparatus configured for use in a satellite communications system (SCS), the computer apparatus comprising: communications interface; and processing circuitry operative to carry out a dynamic assignment procedure, based on the processing circuitry being configured to: determine, for each user terminal among a plurality of user terminals, which spot beams among a plurality of spot beams of the SCS are candidate beams for serving the user terminal, based at least on determining which ones among the plurality of spot beams satisfy radio link requirements for serving the user terminal; identify a set of beam assignment decisions that optimizes utilization of a communications resource that is consumed in dependence on which combination of candidate beams is used for serving the plurality of user terminals, the identified set of beam assignment decisions assigning each user terminal to one and only one of the candidate beams determined for the user terminal; and implement, via control signaling output via the communications interface, the identified set of beam assignment decisions, for serving the plurality of user terminals via the plurality of spot beams.

23. The computer apparatus according to claim 22, wherein, for implementing the identified set of beam assignment decisions, the processing circuitry is configured to generate control signaling to configure the SCS and the user terminals according to the identified set of beam assignment decisions.

24. The computer apparatus according to claim 22 or 23, wherein the processing circuitry is configured to perform the dynamic assignment procedure repeatedly, responsive to a triggering event.

25. The computer apparatus according to claim 24, wherein the processing circuitry is configured to: for each performance of the dynamic assignment procedure, compile evaluation data indicating beam loading for individual spot beams among the plurality of spot beams, and indicating for each user terminal, a current geographic location, a current usage, and current radio conditions with respect to one or more spot beams among the plurality of spot beams; and use the evaluation data used in determining the candidate beams for each user terminal, and for identifying the set of beam assignment decisions that optimizes utilization of the communications resource.

26. The computer apparatus according to any one of claims 22-25, wherein the plurality of spot beams either is a first plurality of forward spot beams used to serve the plurality of user terminals in a forward link direction of the SCS, or a second plurality of return spot beams used to serve the plurality of user terminals in a return link direction of the SCS, and wherein the processing circuitry is configured to perform the dynamic assignment procedure separately, for the first plurality of forward spot beams and for the second plurality of return spot beams.

27. The computer apparatus according to any one of claims 22-26, wherein the plurality of spot beams is associated with one or more satellites of the SCS.

28. The computer apparatus according to any one of claims 22-27, wherein the processing circuitry is configured to determine the plurality of user terminals by logically filtering a larger plurality of user terminals, to exclude one or more particular user terminals or one or more particular classes of user terminals from the dynamic assignment procedure.

29. The computer apparatus according to any one of claims 22-28, wherein the computer apparatus is configured to determine the plurality of spot beams by logically filtering a larger plurality of spot beams, to exclude one or more particular spot beams from the dynamic assignment procedure.

30. The computer apparatus according to any one of claims 22-29, wherein determining which spot beams among the plurality of spot beams of the SCS are candidate beams for serving each user terminal is simplified by the processing circuitry being configured to constrain, for each user terminal, a candidate beam evaluation procedure to consider, as possible candidate beams, only a relevant subset of spot beams from the plurality of spot beams.

31. The computer apparatus according to any one of claims 22-30, wherein the processing circuitry is configured to express the utilization of the communications resource as a sum of symbol rates needed to serve the plurality of user terminals, and wherein the identified set of beam assignment decisions minimizes the sum of symbol rates needed to serve the plurality of user terminals.

32. The computer apparatus according to any one of claims 22-31, wherein, to identify the set of beam assignment decisions that optimizes the utilization of the communications resource, the processing circuitry is configured to determine which possible set of beam assignment decisions minimizes an objective function, each possible set of beam assignment decisions being a unique combination of candidate beam assignments for the plurality of user terminals.

33. The computer apparatus according to claim 32, wherein minimizing the objective function minimizes a sum total of symbol rates needed to serve the plurality of user terminals.

34. The computer apparatus according to claim 32 or 33, wherein the objective function accounts for a mathematical cost of beam reassignments, thereby biasing beam assignment decisions in favor of retaining existing beam assignments.

35. The computer according to any one of claims 32-34, wherein the objective function accounts for respective beam loadings among the plurality of spot beams, wherein the beam loading of any particular spot beams relates to one or both of: the number of user terminals currently assigned to the particular spot beam, or data demands associated with the user terminals currently assigned to the particular spot beam.

36. The computer apparatus according to any one of claims 32-35, wherein, in addition to the constraint that each user terminal be assigned to one and only one of the candidate beams determined for the user terminal, minimization of the objective function is constrained with respect to any one or more of: service level agreements (SLAs) governing service to one or more of the user terminals, per beam throughput limits, or per beam symbol rate limits.

37. The computer apparatus according to any one of claims 22-36, wherein, to identify the set of beam assignment decisions, the processing circuitry is configured to determine which possible configuration of a beam assignment matrix optimizes the utilization of the communications resource, the beam assignment matrix having a corresponding row for each spot beam among the plurality of spot beams and having a corresponding column for each user terminal among the plurality of user terminals, and each possible configuration of the beam assignment matrix being a unique combination of candidate beam assignment decisions for the plurality of user terminals.

38. The computer apparatus according to claim 37, wherein, to determine which possible configuration of the beam assignment matrix optimizes the utilization of the communications resource, the processing circuity is configured to evaluate some or all of the possible configurations of the beam assignment matrix according to an objective function.

39. A satellite communications system (SCS) comprising: one or more satellites, for providing a plurality of spot beams, each spot beam having a fixed nominal beam coverage area; a ground network configured to support the one or more satellites, for serving a plurality of user terminals via the plurality of spot beams, wherein any particular user terminal is served by only one spot beam at a time; and wherein the ground network includes a computer apparatus according to claim 22, for carrying out the dynamic assignment procedure on a recurring or triggered basis, with respect to the plurality of user terminals and the plurality of spot beams.