Method and apparatus for multimodal use of satellites in satellite communication systems

Abstract

The satellite communication system (SCS) operates modally, and modal operation involves selection between a first forward service mode and a second forward service mode. The first forward service mode involves ground-based beamforming, while the second forward service mode does not. Therefore, feeder link bandwidth consumed for GBBF in the first forward service mode can be used to increase data bandwidth in the second forward service mode. Modal operation extends to first and second return service modes, which complement the first and second forward service modes, respectively.

Description

Technical Field

[0001] The disclosed technology provides modal operation of satellite access nodes and associated satellites, and the signal structures of feeder link signals and user link signals vary as a function of the operating mode.

Background Art

[0002] Ground-based beamforming (GBBF) in the context of a satellite communication system (SCS) offers many advantages, particularly the potential to reduce the complexity of satellite payloads. In the forward direction, the ground network creates element signals corresponding to the satellite-mounted phased array elements used for beamforming, and these element signals are weighted. The weighting is calculated such that coherent transmission of the element signals from the satellite-mounted phased array antenna forms an overlay (constructive and destructive wavefront synthesis) of the far-field where the desired user beam is obtained.

[0003] In the return direction, the satellite receives user uplink signals that impinge on individual antenna elements within the same or another phased array antenna of the satellite, and returns these element signals to the ground network for GBBF processing. That is, the return beam is formed in the ground network (signal processing area).

[0004] While GBBF exhibits many advantages (such as the reduction in payload complexity described above), GBBF consumes a significant amount of feeder link bandwidth.

Summary of the Invention

[0005] The satellite communication system (SCS) operates modally, and modal operation involves selection between a first forward service mode and a second forward service mode. The first forward service mode involves ground-based beamforming, while the second forward service mode does not. Therefore, feeder link bandwidth consumed for GBBF in the first forward service mode can be used to increase data bandwidth in the second forward service mode. Modal operation extends to first and second return service modes, which complement the first and second forward service modes, respectively.

[0006] One embodiment includes a method of operation by a satellite in an SCS. This method includes selectively operating the satellite in either a first forward service or a second forward service mode. The first forward service mode involves receiving a first type of feeder uplink signal via the satellite's first antenna system, the plurality of forward element signals stacked in frequency and corresponding to antenna elements in a phased array antenna included in the satellite's second antenna system, the plurality of forward element signals being weighted such that the plurality of forward element signals are simultaneously transmitted from the phased array antenna as a first user downlink signal to form a far field of one or more first forward user beams, each first forward user beam corresponding to a first forward user beam coverage area The system includes having A, and transmitting and receiving traffic to one or more first user terminals located within a group of first user terminals and within a corresponding first forward user beam coverage area; unstacking multiple forward element signals via the satellite's feeder link payload to the same downlink frequency; and coupling the unstacked multiple forward element signals to a phased array antenna via the satellite's first user link payload and transmitting them from the phased array antenna as a first user downlink signal, thereby forming one or more first forward user beams.

[0007] The second forward service mode includes receiving a second type of feeder uplink signal via the satellite's first antenna system, which includes one or more forward beam signals, and transmitting one or more forward beam signals via the satellite's second user link payload to the first antenna system as one or more second user downlink signals from the first antenna system, each second user downlink signal being transmitted as a corresponding second forward user beam, the corresponding second forward user beam having a corresponding second forward user beam coverage area and transmitting traffic to one or more second user terminals within a group of second user terminals, which are located within the corresponding second forward user beam coverage area.

[0008] Relevant embodiments include a satellite configured to operate in an SCS. The satellite includes a first antenna system, a second antenna system, a feeder link payload associated with the first antenna system, a first user link payload associated with the second antenna system, a second user link payload associated with the first antenna system, and a mode control circuit configured to control the satellite's configuration to selectively operate in either a first forward service or a second forward service mode. The first and second forward service modes are as described in the method immediately above.

[0009] Another embodiment includes a method of operation by a satellite access node (SAN) in an SCS. This method includes the SAN selectively operating in either a first forward service mode or a second forward service mode.

[0010] A first forward service mode in a SAN includes forming a first type of feeder uplink signal comprising a plurality of forward element signals, the plurality of forward element signals stacked in frequency and corresponding to antenna elements in a satellite phased array antenna, the plurality of forward element signals being weighted such that the plurality of forward element signals are simultaneously transmitted from the phased array antenna as a first user downlink signal to form a far field of one or more first forward user beams, each first forward user beam having a corresponding forward user beam coverage area and transmitting traffic to one or more first user terminals within a group of first user terminals, which are located within the corresponding forward user beam coverage area, and transmitting a first type of feeder uplink signal for reception by the satellite.

[0011] A second forward service mode in a SAN includes forming a second type of feeder uplink signal, each forward beam signal, which carries traffic to one or more second user terminals in a corresponding second forward user beam coverage area; transmitting the second type of feeder uplink signal to be received by a satellite; and providing one or more forward beam signals to be transmitted as one or more second user downlink signals.

[0012] A related embodiment includes a SAN configured to operate in an SCS. The SAN includes a transmitter circuit and a signal processing circuit configured to operate in either the first forward service mode described for the SAN immediately above, or the second forward service mode described for the SAN immediately above.

[0013] Naturally, the present invention is not limited to the features and advantages described above. In fact, those skilled in the art will understand further features and advantages by reading the following detailed description and referring to the accompanying drawings. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1 is a block diagram of a satellite communication system (SCS) according to one embodiment. [Figure 2] Figure 2 is a logic flow diagram of a method for modal operation by a satellite according to one embodiment. [Figure 3] Figure 3 is a logical flowchart illustrating a method for modal operation by a corresponding satellite access node (SAN) according to one embodiment. [Figure 4] Figure 4 is a block diagram of the first signal processing and transmission circuit of the SAN for operation in a first forward service mode using ground-based beamforming, according to one embodiment. [Figure 5] Figure 5 shows a diagram illustrating the use of bandwidth for a first type of feeder uplink signal according to one embodiment. [Figure 6] Figure 6 is a block diagram of the second signal processing and transmission circuit of the SAN for operation in a second forward service mode that does not use ground-based beamforming, according to one embodiment. [Figure 7] Figure 7 shows a diagram illustrating the use of bandwidth for a second type of feeder uplink signal according to one embodiment. [Figure 8] Figure 8 is a block diagram of a first user link payload mounted on a satellite according to one embodiment. [Figure 9] Figure 9 is a block diagram of a second user link payload mounted on a satellite according to one embodiment. [Figure 10] Figure 10 is a block diagram of a second user link payload mounted on a satellite according to one embodiment. [Figure 11]FIG. 11 is a block diagram of a mode control circuit mounted on a satellite according to an embodiment. [Figure 12] FIG. 12 is a diagram of an exemplary forward user beam arrangement in a first forward service mode according to an embodiment. [Figure 13] FIG. 13 is a diagram of an exemplary return user beam arrangement in a first return service mode according to an embodiment. [Figure 14] FIG. 14 is a diagram of an exemplary forward user beam arrangement in a second forward service mode according to an embodiment. [[ID=?]] [[ID=?]] [Figure 15] FIG. 15 is a diagram of an exemplary return user beam arrangement in a second return service mode according to an embodiment.

DETAILED DESCRIPTION OF THE INVENTION

[0015] FIG. 1 shows a satellite communication system (SCS) 10 according to an embodiment. SCS 10 includes one or more satellites 12, and each satellite 12 is configured to provide services to one or more populations of user terminals (UTs). For simplicity, only one satellite 12 is shown in the figure, which includes a first antenna system 14, a second antenna system 16, a feeder link payload 18, a first user link payload 20, a second user link payload 22, and a mode control circuit 24.

[0016] One or more satellite access nodes (SANs) 30 are resident in the terrestrial network of SCS 10, and only one SAN 30 is shown in the figure for simplicity. Each SAN 30 includes a feeder link transmitter 32 and a feeder link receiver 34, along with a corresponding signal processing circuit 36 (i.e., a communication signal processing circuit that supports the transmission and reception of communication signals). Further, each SAN 30 includes a network interface 38 and a mode control circuit 40.

[0017] Note: There seems to be a formatting issue with the original text where some tags are not properly numbered. I've translated it as accurately as possible while maintaining the original structure. Also, the "?" in the translation for ID=10 and ID=11 is to indicate that the original text has some formatting irregularities in those tags which might need further clarification.As a further interesting item in the terrestrial network of the SCS10, the core network (CN) 50 can be mentioned, which includes one or more computer servers configured as a communication processing system (CPS) 52. The CPS 52 includes or is associated with a ground-based beamforming (GBBF) circuit 54 and a mode control circuit 56. The CPS 52 is configured to connect the SCS10 to one or more external networks (NW(s)) 60 (for example, the Internet or other packet data networks (PDN)), receive incoming user traffic 62 from the external NW(s) 60, and transmit outgoing user traffic 64 to the external NW(s) 60. The incoming and outgoing user traffic 62 and 64 may involve one or more external service providers 66 reachable via the external NW(s) 60, and may include any one or some combination of Internet protocol (IP) packet flows, telecommunications traffic, voice, etc.

[0018] Among some advantageous aspects of the SCS10 is its multimodal operation, where the SCS10 operates selectively with or without GBBF. When operating without GBBF, more data bandwidth is provided on the feeder link that couples the SAN 30 to the satellite 12. Thus, in the operating mode(s) without using GBBF, for example, more overall feeder link bandwidth is provided when transmitting user data to support broadband or wideband data services that select the UT.

[0019] In one or more embodiments, the mode control circuit 56 cooperates directly or indirectly with the mode control circuit 40 in the SAN 30 and the mode control circuit 24 in the satellite 16 to control the overall operating mode of the SCS10, or at least the overall operating mode of the SAN 30 and the satellite 12 regarding serving the UT. For example, the SCS10 selectively uses a first forward service mode to provide services to a first group of UTs 70.

[0020] Although Figure 1 does not show geographical details, satellite 12 serves a group of first UT70s distributed over a satellite service area divided into multiple first forward user beam coverage areas. Using GBBF, corresponding first forward user beams are formed, and each first forward user beam is a spot beam illuminating one of the corresponding first forward user beam coverage areas.

[0021] To understand this operation, the mode control circuit 56 configures the CPS 52 to operate in a first forward service mode. Similarly, the mode control circuit 40 configures the SAN 30 to operate in a first forward service mode, and the mode control circuit 24 configures the satellite 12 to operate in a first forward service mode. Mode control can be triggered via control signals propagated within the SCS 10 or based on scheduling. For example, there may be a defined service mode schedule that the CPS 52, SAN 30, and satellite 12 follow, in which they cooperate in different service modes between different intervals (e.g., between different time slots in a repeating series of time slots).

[0022] In any case, user data 62 arriving at the SCS10 for each UT70 within the first group of UT70s is processed and formatted into a plurality of first forward beam signals 72, each first forward beam signal 72 transmitting user traffic to a UT70 located within one of the corresponding forward user beam coverage areas. In the first service mode (using GBBF), these first forward beam signals 72 are applied to the GBBF circuit 54.

[0023] The GBBF circuit 54 divides each first forward beam signal 72 into duplicate signal sets. Each duplicate signal corresponds to a respective antenna element in a phased array antenna contained within a second antenna 16 mounted on satellite 12. The duplicate signal sets formed from each first forward beam signal 72 are weighted according to a corresponding beam weight (BW) set 74, which includes phase / amplitude weights corresponding to each antenna element in the phased array antenna contained within the second antenna system 16 mounted on satellite 12.

[0024] Each BW set 74 is calculated such that the transmission of a corresponding set of weighted duplicate signals from the phased array antenna results in the formation of a far-field of a forward user beam illuminating a specific one of the first forward user beam coverage areas. For example, if there are 500 antenna elements in the phased array antenna of the second antenna system 16 to be used in forward beamforming, each BW set 74 contains 500 complex weights, and each first forward beam signal 72 to be transmitted in the first service mode is divided into 500 duplicate signals to be weighted by each BW set 74 containing 500 corresponding weights.

[0025] With each of the weighted duplicate signal sets thus formed, the coupling circuit within the GBBF54 combines all such sets for each element to form a set of combined element signals 76. That is, the weighted signals from all the duplicate sets corresponding to the first antenna element of the phased array antenna are combined to form the first combined element signal to be transmitted from the first antenna element, the weighted signals from all the duplicate sets corresponding to the second antenna element of the phased array antenna are combined to form the second combined element signal to be transmitted from the second antenna element, and so on.

[0026] The network interface 38 of the SAN 30 (for example, one or more Ethernet or other computer data network interfaces) receives the coupled element signal 76. With the mode control circuit 40 configured to operate the signal processing circuit 36 ​​in a first forward service mode, the signal processing circuit 36 ​​outputs a set of forward element signals 78 that either include the coupled element signal 76 in a one-to-one correspondence or are derived one-to-one from the coupled element signal 76. For example, each forward element signal 78 is an RF or IF carrier modulated according to one of the respective coupled element signals 76.

[0027] A transmitter 32 configured to operate in a first forward service mode transmits a first type of feeder uplink signal 80 based on stacking forward element signals 78 at a frequency (in the form of frequency domain multiplexing). Thus, the overall bandwidth of the first type of feeder uplink signal 80 can be understood as being divided into multiple spectral chunks, each chunk carrying one of the respective forward element signals 78.

[0028] The first antenna system 14 mounted on satellite 12 includes a receiving (RX) antenna (e.g., a reflector antenna or receiving array) which receives a first type of feeder uplink signal 80 and outputs a corresponding received feeder uplink signal 82. The feeder link payload 18 is configured to operate in a first forward service mode and so destacks the forward element signal 78 from the received feeder uplink signal 82 and outputs a corresponding set of destacked forward element signals 84 to the first user link payload 20. Here, the destacked forward element signals 84 correspond one-to-one with the stacked forward element signals 78 in frequency and can be understood as received or recovered versions of these signals.

[0029] The first user link payload 20 (including a vent pipe payload in one or more embodiments) outputs a plurality of antenna element signals 86. Each antenna element signal 86 corresponds to one of a plurality of unstacked forward element signals 84. For example, each antenna element signal 86 includes an amplified and frequency-converted version of one of the unstacked forward element signals 84. All antenna element signals 86 have the same frequency, for example, a selected downlink signal.

[0030] Each antenna element signal 86 is transmitted from each antenna element 90 of the phased array antenna 92 ​​included in the second antenna system 16. Weighting is applied by the GBBF circuit 54, so that multiple antenna element signals 86 are simultaneously transmitted from multiple antenna elements 90 as multiple first downlink signals 94, thereby forming the intended far-field of multiple first forward user beams. Each of the first forward user beams has a corresponding first forward user beam coverage area, although such details are not shown in Figure 1.

[0031] In the relevant first return service mode, the same phased array antenna 92 ​​or another phased array antenna of the second antenna system 16 receives return uplink signals 96 (user uplink signals) from the transmitting group of the first UT70. These return uplink signals 96 collide with each antenna element of the phased array antenna used to receive them, and each such antenna element outputs a corresponding of a plurality of received antenna element signals 98. The first user link payload 20 combines these plurality of received antenna element signals 98 into the feeder link payload 18 as a plurality of return element signals 100, with, for example, filtering, amplification, and possible frequency shifting.

[0032] With the feeder link payload 18 configured to operate in a first return service mode, the feeder link payload 18 stacks the return element signals 100 in frequency to form an amplified outgoing signal 102. A transmit (TX) reflector or transmit array in the first antenna system 14 transmits the amplified outgoing signal 102 as a first type of feeder downlink signal 104.

[0033] The receiver 34 of the SAN30 is configured to operate in a first return service mode, receiving a first type of feeder downlink signal 104 and outputting a set of unstucked return element signals 106 (for example, a set of RF or IF modulated carriers). The signal processing circuit 36 ​​outputs a corresponding set of return element signals 108, for example, in the digital domain. The network interface 38 transmits the set of return element signals 108 to the CPS52. The CPS52 provides them to the GBBF circuit 54 for GBBF in the return direction.

[0034] In the case of a GBBF in the return direction, the GBBF circuit 54 maintains a BW set 110 for each first return user beam coverage area. The first return user beam coverage areas may be the same as or different from the first forward user beam coverage areas in terms of coverage and number.

[0035] Each return BW set 110 corresponds to each first return user beam having a corresponding first return user beam coverage area and is used to weight a set of return element signals 108. That is, each return BW set 110 includes complex weights corresponding to each antenna element of the phased array mounted on satellite 12 used to receive the first return uplink signal 96. Each return BW set 110 is applied to each copy of the set of return element signals 108 to form the corresponding weighted sets, which are then combined to form the corresponding first return beam signal 112.

[0036] Therefore, the GBBF circuit 54 returns multiple first return beam signals 112, each having a signal-to-noise ratio (SNR) enhanced with respect to the return uplink signal 96 originating from the first UT 70 located within the corresponding first return user beam coverage area. Thus, the GBBF in the return direction can be understood to reside within the signal processing area. The CPS 52 processes the first return beam signals 112 to recover the return user traffic and outputs it as outgoing user traffic 64 toward the external network(s) 60.

[0037] In the second forward service mode, the CPS52 forms one or more second forward beam signals 120 for one or more second UT122, where "second" is a label for differentiation from "first". For clarity, in this exemplary framework, there are one or more UT70 that are serviced in the first forward service mode using GBBF, and one or more UT122 that are serviced in the second forward service mode without GBBF.

[0038] Thus, there may be one or more second UT122s. Although not shown, there may be one or more second forward user beam coverage areas, which, in one or more embodiments, do not coincide with the first forward beam coverage areas associated with the GBBF in the forward direction. The size and location(s) of the second forward user beam coverage areas may depend on the antenna(s) type(s) and capabilities of the first antenna system 14. In one or more embodiments, the first antenna system 14 includes a transmit array, and the satellite 12 applies beamforming weights to form one or more second forward user beams, each illuminating one of the one or more second forward user beam coverage areas. In one or more other embodiments, the first antenna system 14 includes one or more spot beam antennas that provide one or more second forward user beams.

[0039] In either case, each second forward user beam coverage area may include one or more second UT122s to be served in the second forward service mode. In the exemplary configuration, there is one second forward beam signal 120 for each second forward user beam coverage area, which carries forward traffic to one or more second UT122s located within the corresponding second forward user beam coverage area.

[0040] SAN30 receives one or more second forward beam signals 120 via the network interface 38, and the signal processing circuit 36 ​​is configured to operate in a second forward service mode and outputs one or more corresponding second forward beam signals 124. Each second forward beam signal 124 is, for example, an analog domain representation of the corresponding second forward beam signal 120. Transmitter 32 transmits a second type of feeder uplink signal 126 that carries one or more second forward beam signals 124.

[0041] The second forward service mode does not use GBBF, so there is more feeder uplink bandwidth available for data transmission. Therefore, the bandwidth of each second forward beam signal 120 that the CPS 52 outputs to the SAN 30 can be much wider than that of each first forward beam signal 72 that the CPS 52 outputs to the GBBF circuit 54. In one embodiment, or under certain operating instructions, there is only one second forward beam signal 120 corresponding to a single second forward user beam coverage area containing one or more second UT 122. This single second forward beam signal 120 occupies up to the entire bandwidth used for the feeder uplink. As a result, this second forward beam signal 120 provides a potentially much higher data bandwidth than that provided by the individual element signals included in the first type of feeder uplink signal 80, although without the benefits of GBBF.

[0042] To the extent that a single second forward beam signal 120 is used to serve multiple second UTs 122, traffic to different UTs 122 may be multiplexed in time or in code domain. To the extent that multiple second forward beam signals 120 to be transmitted exist, different second forward beam signals 120 may be transmitted in different time slots in one or more embodiments, with each one potentially occupying up to the entire feeder uplink bandwidth. Alternatively, to transmit two or more second forward beam signals 120 simultaneously, the entire feeder uplink bandwidth may be divided and each second forward beam signal 120 transmitted in a different subband. This subband approach means that each second forward beam signal 120 must be smaller than the entire feeder uplink bandwidth, but nevertheless, the bandwidth of each second forward beam signal 120 can be much larger than the bandwidth of each first forward beam signal 72.

[0043] For example, assume a feeder uplink bandwidth of 5 GHz (e.g., using an optical feeder uplink). In a first forward service mode, if 1000 antenna elements 90 are used to form 1000 first forward user beams, then each of the 1000 forward element signals 78 has a bandwidth of 5 MHz, meaning the formed first forward user beam has a signal bandwidth of 5 MHz. Now, assume simultaneous transmission of 10 second forward beam signals 120 in a second forward service mode. With a 5 GHz bandwidth of the feeder uplink, each of these 10 second forward beam signals 120 can occupy up to 500 MHz.

[0044] Therefore, the first and second types of feeder uplink signals 80 and 126 may have the same overall bandwidth, but the bandwidth consumed for GBBF in the first type of feeder uplink signal 80 is available for data transmission in the second type of feeder uplink signal 126. And, in at least one embodiment, the first forward service mode may be considered a narrowband service mode compared to at least the second forward service mode.

[0045] Similar to the first type of feeder uplink signal 80, the RX reflector or array antenna of the first antenna system 14 receives the second type of feeder uplink signal 126 and outputs the corresponding received signal 128 to the feeder link payload 18. Based on being configured to operate in a second forward service mode, the feeder link payload 18 couples the received signal 128 to a second user link payload 22. The coupling may be direct, for example, via switch control in a mode control circuit 24. The second user link payload 22 outputs a transmit signal 130 containing a frequency-shifted version of the received signal 128, which is available for transmission as one or more second user downlink signals 132. For example, the first antenna system 14 includes one or more mechanically maneuvered reflectors or transmit arrays used to transmit one or more second user downlink signals 132 as one or more second forward user beams, where the formation of the second forward user beam(s) depends on the satellite 12, not the GBBF.

[0046] In an example where the second type of feeder uplink signal 126 includes two or more second forward beam signals 124 arranged in different frequency subbands, for each such second forward beam signal 124, a corresponding second forward user beam is formed or otherwise transmitted via the first antenna system 14. In at least one embodiment, the second user link payload 22 is a bent pipe payload that amplifies and frequency-shifts the received signal 128 for retransmission. In at least one such embodiment, the second user link payload 22 includes a block converter 134 that applies a group or block frequency shift to the received signal 128 for retransmission.

[0047] In the associated second return service mode, one or more of the one or more second UT122 transmit a user uplink signal 140, referred to as the second return uplink signal, to distinguish it from the first return uplink signal 96 transmitted by each of the group of first UT70s. In an exemplary embodiment, the bandwidth of each user uplink signal 140 is the same as, or up to the same bandwidth as, each second forward beam signal 120.

[0048] The first antenna system 14 includes a reflector or receiving array for receiving a second return user uplink signal(s) 140 and outputs a corresponding received signal 142 to the second user link payload 22. The second user link payload 22 outputs a received signal 144 corresponding to the received signal 142. For example, the received signal 144 is a bent-pipe passthrough of the received signal 142, possibly involving block frequency shifting, filtering, and amplification.

[0049] In one or more embodiments, the feeder link payload 18 passes the received signal 144 output by the second user link payload 22 for transmission as a second type of feeder downlink signal 148. The receiver 34 in the SAN 30 outputs a received signal 150 based on the reception of the second type of feeder downlink signal 148, and the signal processing circuit 36 ​​outputs one or more return signals 152. The one or more return signals 152 are recovered versions of one or more second user uplink signals 140 transmitted by each of the one or more second UTs 122. These return signals 152 may be digital domain streams and are sent back to the CPS 52 via the network interface 38. The CPS 52 recovers the user traffic transmitted therein by processing one of the return signals 152 for output to an external NW(multiple) 60 as outgoing user traffic 64. In this second return service mode, GBBF processing via the GBBF circuit 54 is not used.

[0050] In at least one embodiment, the second user link payload 22 is a vent pipe payload that passes the received signal 142 to the feeder link payload 18 as the received signal 144 for transmission to the SAN 30 without digital processing. For example, in the vent pipe embodiment, the second user link payload 22 applies filtering, amplification, and frequency shifting to the received signal 142 via a block converter 134 to form the corresponding received signal 144 that is output to the feeder link payload 18.

[0051] In one or more other embodiments, the second user link payload 22 is a processing payload that performs signal processing in the digital domain based on demodulation / decoding of signals in the forward and / or return directions. However, the use of onboard signal processing on satellite 12 may provide further flexibility in alternating or switching modes, but it does not alter the basic modal operation as described above.

[0052] Among the several advantages of SCS10, it can provide both GBBF and non-GBBF operation without completely losing the complexity reduction obtained in satellite 12 by using GBBF. In particular, the second user link payload 22 in one or more embodiments may be a simple vent pipe signal path that adds little or no further circuitry or other components to satellite 12. Furthermore, in the second forward and return service operation mode, the first antenna system 14 is advantageously reused for both feeder link and user link connectivity, and the same first antenna system 14 is used for feeder link connectivity in the first forward and return service operation mode.

[0053] By adding a second mode of forward and return service, the first antenna system 14 can be reused, and little additional transmit / receive circuitry is added to the satellite 12. That is, in an exemplary embodiment, when operating in the first forward and return service mode, the first antenna system 14 of the satellite 12 receives a first type of feeder uplink signal 80 and transmits a first type of feeder downlink signal 104, and the second antenna system 16 provides user downlink and user uplink transmits. However, when operating in the second forward service mode, the RX component of the first antenna system 14 receives a second type of feeder uplink signal 126, and the TX component of the first antenna system 14 transmits user downlink signal(s) 132. Similarly, when operating in a second return service mode, the RX component of the first antenna system 14 is used to receive user uplink signals 140, and the TX component of the first antenna system 14 is used to transmit second type feeder downlink signals 148.

[0054] Therefore, in this embodiment, the TX portion of the first antenna system 14 transmits user downlink signals in the second forward service mode and feeder downlink signals in the second return service mode. Similarly, the RX portion of the first antenna system 14 receives feeder uplink signals in the second forward service mode and user uplink signals in the second return service mode. The second antenna system 16 is not used for user links in these second forward and return service modes.

[0055] Similar efficiency advantages are seen in SAN30, where different types of feeder uplink and downlink signals can be transmitted and received based on the reuse of the same antenna(s) and some or all of the same transmit / receive circuits and signal processing in SAN30. In a sense, the second forward and return service mode is based on at least some of the same hardware used for the first forward and return service mode, and mode selection is performed by a relatively simple mode control circuit.

[0056] Figure 2 shows an exemplary multimodal satellite 12 operation method 200 consistent with the example described above. Method 200 includes logically checking (block 202) whether satellite 12 is operating in the first forward service mode as described above. The check includes, for example, evaluating control signals received from SAN 30, or, for example, referring to scheduling information loaded into satellite 12's memory.

[0057] If "YES", processing proceeds and satellite 12 operates in the first forward service mode (block 204), and in conjunction with that, operates in the first return service mode as described above (block 206). From there, unless there is a fault or other stop command or event, processing returns to the logical check in block 202 (see the YES branch from decision block 208). If method 200 is stopped or interrupted (see the NO branch from decision block 208), method 200 stops.

[0058] If satellite 12 is operating in the second forward service mode (NO from block 202), the process proceeds and satellite 12 operates in the second forward service mode as described above (block 210), and in conjunction with that, operates in the second return service mode as described above (block 212).

[0059] In one or more embodiments, or under certain operating conditions, Method 200 includes the satellite 12 operating on a half-duplex (alternating) basis in a first forward service mode and a first return service mode. In one or more other embodiments, or under certain other operating conditions, the satellite 12 operates on a full-duplex (simultaneous) basis in a first forward service mode and a first return service mode.

[0060] In one or more embodiments, or under certain operating conditions, Method 200 includes the satellite 12 operating on a half-duplex basis in a second forward service mode and a second return service mode. In one or more other embodiments, or under certain other operating conditions, the satellite 12 operates on a full-duplex basis in a second forward service mode and a second return service mode.

[0061] Figure 3 shows the operation method 300 by SAN 30, which directly complements method 200. Method 300 begins by determining whether SAN 30 operates in the first forward service mode. If so (YES from block 302), SAN 30 operates in the first forward service mode as previously described for SAN 30 (block 304), and in conjunction with this, SAN 30 operates in the first return service mode as previously described (block 306). Method 300 can be stopped or interrupted (NO from block 308), or it can be repeated (YES from block 308). By repeating, the process returns to block 302 for a first mode / second mode check.

[0062] When SAN30 operates in the second forward service mode (NO from block 302), SAN30 changes from operating in the first forward service mode to operating in the second forward service mode, as described above (block 310). In conjunction with operating in the second forward service mode, SAN30 operates in the second return service mode, as described above (block 312). In this case as well, the first forward / return service mode and the second forward / return service mode in SAN30 can be full-duplex or half-duplex.

[0063] Figure 4 shows a detailed example of the signal processing circuit 36 ​​and transmitter 32 of SAN30 to support operation in the first forward service mode. Assuming that M first forward user beams are formed using N antenna elements 90 of the phased array antenna 92 ​​mounted on satellite 12, there are M first forward beam signals 72, denoted as 72-1 to 72-M, where M is an integer less than or equal to an integer N.

[0064] A forward error correction (FEC) encoder 400 operates on the first forward beam signal 72 to generate a corresponding encoded signal 402. Each encoded signal 402 serves as an input to a modulator 404, which modulates the IF carrier in response to the input encoded signal 402. Note that these operations are performed in the digital domain in one or more embodiments, and as a result, the IF carrier is a digital stream, as is the first forward beam signal 72.

[0065] Each resulting modulated signal 406 is split into a set of N duplicate signals via its respective splitter and beam weighting circuit 408. Each duplicate signal corresponds to one of the N antenna elements 90 to be used for beamforming the first forward user beam (see the phased array antenna 92 ​​contained within the second antenna system 16 of satellite 12).

[0066] As described above, the N duplicate signals are weighted by the corresponding BW set 74 to generate the corresponding weighted beam element signals 410. That is, for each of the M first forward beam signals 72, there are corresponding sets of N weighted beam element signals 410, and the corresponding BW set 74 is calculated for the formation of a first forward user beam directed onto the first forward beam coverage area, which includes UT70, targeted by user traffic transmitted by the first forward beam signals 72. Thus, in the illustrated example, for the first forward user beams B1-BM, there are M sets of weighted beam element signals 410, and each such set includes element signals E1-EN corresponding to elements E1-EN of the phased array antenna 92.

[0067] As previously described, the element-wise coupler circuit 412 couples M sets of weighted beam element signals 410 on an element-wise basis to form a set of N coupled forward element signals 414, each such coupled forward element signal being a linear combination of all weighted duplicate beam element signals 410 intended for transmission from the same antenna element 90 of the phased array antenna 92. The digital-to-analog converter (DAC) 416 converts the N coupled forward element signals 414 to the analog domain, and these analog domain signals are the forward element signals 78 referred to in the context of Figure 1.

[0068] The RF multiplexer 418 and frequency converter 420 frequency stack the forward element signals 78 in the feeder uplink spectrum to form a multiplexed signal 422. The multiplexed signal 422 is amplified by the RF power amplifier 424 to form an amplified signal 426. The amplified signal 426 is emitted from the antenna 428 of SAN 30 as a first type of feeder uplink signal. Similarly, the RF multiplexer 418 may be an optical multiplexer, and the first type of feeder uplink signal 80 is a multiplexed optical signal in which each first forward element signal 78 is transmitted through its respective optical channel signal according to a wavelength division multiplexing (WDM) scheme in the optical domain. In either case, Figure 5 shows an exemplary stacking arrangement in which each forward element signal 78 occupies a different spectral chunk within the overall feeder link bandwidth.

[0069] Figure 6 shows a detailed example of SAN30 operating in a second forward service mode, in an exemplary context where the second forward service mode involves the simultaneous transmission of two second forward beam signals 120 (shown as second forward beam signals 120-1 and 120-2). Here, the simultaneous transmission is based on frequency multiplexing, although code multiplexing may be used as an alternative. Code multiplexing may allow different UT122s serviced by different second forward beam signals 120 to be located in the same geographical area (for example, second forward user beams corresponding to different second forward beam signals 120 having the same coverage area). Furthermore, multiple second forward beam signals 120 may be transmitted based on time multiplexing rather than code or frequency domain multiplexing.

[0070] The circuit shown in Figure 6 may be an addition to the one shown in Figure 4, or all or at least part of the circuit shown in Figure 4 may be reused. That is, some or all of the transmit signal path circuits and components (including the power amplifier and antenna in particular) used in SAN30 to transmit the first type of feeder uplink signal 80 may be reused to transmit the second type of feeder uplink signal 126. However, it is understood that any such reused circuit or component must accommodate the potentially much wider bandwidth of the second forward beam signal 120 compared to the bandwidth of the first forward beam signal 72.

[0071] Each of the second forward beam signals 120-1 and 120-2 is encoded via the respective FEC encoder 600, and the resulting encoded signals 602-1 and 602-2 are fed to the respective modulator 604. The resulting modulated signals 606-1 and 606-2 are fed to the DAC 608, which converts them to the analog signal domain to generate the respective second forward beam signals 124-1 and 124-2 as shown in Figure 1.

[0072] The RF multiplexer 610 / frequency converter 612 stacks two second forward beam signals 124-1 and 124-2 to form a multiplexed signal 614 in the feeder uplink spectrum, and the RFPA 616 amplifies the multiplexed signal 614 to produce an amplified signal 618. Antenna 620 of SAN30 transmits the amplified signal 618 as a second type of feeder uplink signal 126. As previously stated, the multiplexing, amplification, and especially transmitting antennas used for transmitting the second type of feeder uplink signal 126 may be the same as those used for transmitting the first type of feeder uplink signal 80.

[0073] Furthermore, similar to the first type of feeder uplink signal 80, the second type of feeder uplink signal 126 may be in the optical domain rather than the RF domain. In either case, Figure 7 shows the transmission of two second forward beam signals 124-1 and 124-2 within the overall feeder uplink bandwidth. In this example, each such beam signal occupies half of the feeder uplink bandwidth at its respective center frequency f1 or f2. In particular, when transmitting two or more second forward beam signals 124 simultaneously, the allocation of each to the feeder uplink bandwidth does not need to be uniform; for example, one of the different second forward beam signals 124 may have a different signal bandwidth.

[0074] Figure 8 shows a vent pipe embodiment of the feeder link payload 18 and the first user link payload 20 mounted on satellite 12 to support the first forward and return service mode. The first antenna system 14 provides the received feeder uplink signal 82 to the feeder link payload 18. The feeder link payload 18 includes a low-noise amplifier (LNA) 800 and an N-direction demultiplexer 802 that outputs the aforementioned unstacked forward element signal 84. Each such unstacked forward element signal 84 is input to a respective vent pipe forward transponder 804, from which the corresponding one of the aforementioned antenna element signals 86 is output.

[0075] Each vented pipe forward transponder 804 includes an unprocessed electrical signal path that provides filtering, power amplification, and frequency conversion. See mixer 810 and its associated oscillator 812, bandpass filter 814 (which may include a surface acoustic wave filter), mixer 816 and its associated oscillator 818, bandpass filter 820, power amplifier 822, and band-stop filter 824.

[0076] When operating in the first return service mode, the phased array antenna 92 ​​outputs the multiple received antenna element signals 98 described above, each such signal being input to the corresponding vent pipe return transponder 830. The multiple vent pipe return transponders 830 output the multiple return element signals 100 described above. The N-direction multiplexer 832 performs frequency stacking of the multiple return element signals 100 to form a multiplexed signal, which is amplified by the power amplifier 834 to form the amplified outgoing signal 102 described above.

[0077] In this exemplary depiction, each vent pipe return transponder 830 provides filtering, frequency conversion, and low-noise amplification. Correspondingly, each vent pipe return transponder 830 includes a bandpass filter 840, a low-noise amplifier 842, a mixer 844 and its associated oscillator 846, a bandpass filter 848, and a mixer 850 and its associated local oscillator 852.

[0078] Figures 9 and 10 show a second user link payload 22 with an exemplary vented pipe implementation. In the second forward service mode, the received signal 128 is input to the vented pipe forward transponder 900. The vented pipe forward transponder 900 includes a low-noise amplifier 902 and the aforementioned block frequency converter 134 (which may include a forward block frequency converter 134-1). Furthermore, the vented pipe forward transponder 900 includes a power amplifier 904 that outputs the aforementioned transmitted signal 130.

[0079] The second user link payload 22 in this embodiment further includes a return vent pipe transponder 910. The aforementioned received signal 142 is input to a low-noise amplifier 912 and supplied into a return block frequency converter 134-2. The frequency-converted output is applied to a power amplifier 914 to form the aforementioned received signal 144.

[0080] Figure 11 shows a mode control circuit 24 mounted on satellite 12 according to an exemplary embodiment. The mode control circuit 24 includes, for example, a processor 1100 and associated memory 1102. For example, memory 1102 stores mode control data (e.g., mode switching schedules), and processor 1100 controls the operating mode of satellite 12 according to the stored mode control data or according to live control signals incoming from SAN 30 to satellite 12. Processor 1100 includes, for example, a microprocessor specifically adapted to control the operating mode of satellite 12 based on the execution of computer program instructions stored in memory 1102 or on other computer-readable media mounted on satellite 12.

[0081] In the exemplary configuration, the mode control circuit 24 further includes RF switches 1104 and 1106. RF switch 1104 controls whether the receiving reflector or array of the first antenna system provides the received feeder uplink signal to the feeder link payload 18 or to the second user link payload 22. In the first forward service mode, the first antenna system 14 receives a first type of feeder uplink signal 80 and provides the corresponding received feeder uplink signal 82 to the feeder link payload 18 via switch 1104 at position "A". In the second forward service mode, the first antenna system 14 receives a second type of feeder uplink signal 126 and provides the corresponding received signal 128 to the second user link payload 22 via switch 1104 at position "B". Equivalently, this second mode can be understood as mode passthrough to the feeder link payload 18.

[0082] The RF switch 1106 controls the selection between operation in a first return service mode or a second return service mode. In the first return service mode, the RF switch 1106 is in position "A", and the feeder link payload 18 provides the amplified transmitting signal 102 to the first antenna system 14 for transmission as a first type feeder downlink signal 104. In the second return service mode, the RF switch 1106 is in position "B", thereby providing the second user link payload 22 to the transmitting reflector or array of the first antenna system 14 for transmission as a second type feeder downlink signal 148. Equivalently, the feeder link payload 18 can be considered to provide pass-through connectivity to the signal 144 in the second mode of return service for transmission from the first antenna system 14.

[0083] Figure 12 shows an exemplary set of M forward user beams 1200 formed by satellite 12 during operation in the first forward service mode, the beams being shown as forward user beams 1200-1 to 1200-M. Each forward user beam 1200 corresponds to one of the forward beam signals 72 introduced in Figure 1 and carries traffic to UT70 located within the corresponding forward user beam coverage area 1202 (e.g., forward user beam 1200-1), service UT70 located within forward user beam coverage area 1202-1, and so on. These forward user beam coverage areas 1202 subdivide the larger satellite service area 1204.

[0084] Figure 13 shows an exemplary set of R-return user beams 1210 formed by the satellite 12 during operation of the first return service mode, the beams being indicated as return user beams 1210-1 to 1210-R. As previously stated, these return user beams 1210 do not exist in physical space in one or more embodiments, but rather are formed within a processing area in the GBBF circuit 54 introduced in Figure 1, and their illustration here is for illustrative purposes only. Each return user beam 1210 has a corresponding return user beam coverage area 1212 (indicated as return user beam coverage areas 1212-1 to 1212-R). The integer value of R may or may not coincide with M, and the return user beams 1210 may or may not coincide with the forward user beams 1200 in terms of size, direction, and corresponding coverage.

[0085] Figure 14 illustrates the exemplary operation of satellite 12 in a second forward service mode, in a scenario where a single second forward user beam 1400 is transmitted to a single UT122 located within the corresponding coverage area 1402 of the second forward user beam 1400. In some embodiments or operating scenarios, there is no overlap between any second forward user beam coverage area 1402 and any first forward user beam coverage area 1202. In at least one such exemplary case, the second forward user beam coverage area 1402 includes or is encompassed within the SAN coverage area of ​​satellite 12.

[0086] Figure 15 illustrates the exemplary operation of satellite 12 in a second return service mode, a scenario in which a return uplink signal is received from the same single UT122 as shown in Figure 14, using a single second return user beam 1510 with a corresponding return user beam coverage area 1512. The return user beam 1510 and return user beam coverage area 1512 may substantially coincide with the forward user beam 1400 and forward user beam coverage area 1402.

[0087] In a half-duplex configuration, Figure 14 can be understood as showing satellite operation for a first interval, and Figure 15 as showing satellite operation for a different second interval. Naturally, there can be multiple UT122s serviced by the forward user beam 1400, and similarly for the return user beam 1510.

[0088] In particular, modifications and other embodiments of the disclosed invention(s) will be recalled by those skilled in the art who benefit from the teachings presented in the foregoing description and the associated drawings. Therefore, it should be understood that the invention(s) are not limited to the specific embodiments disclosed, and that modifications and other embodiments are intended to be included within the scope of this disclosure. Certain terms may be used herein, but they are used only in a general and descriptive sense and are not intended to be limiting.

Claims

1. A method of operation by a satellite in a satellite communication system, the method comprising selectively operating in either a first forward service mode or a second forward service mode, The first forward service mode is, Receiving a first type of feeder uplink signal including a plurality of forward element signals via the satellite's first antenna system, wherein the plurality of forward element signals are stacked in frequency and correspond to antenna elements in a phased array antenna included in the satellite's second antenna system, and the plurality of forward element signals are weighted such that the plurality of forward element signals are simultaneously transmitted from the phased array antenna as a first user downlink signal to form a far-field of one or more first forward user beams, each first forward user beam having a corresponding first forward user beam coverage area, and transmitting and receiving traffic to one or more first user terminals within a group of first user terminals, which are located within the corresponding first forward user beam coverage area. The feeder link payload of the satellite is used to unstack the multiple forward element signals and set them to the same downlink frequency. The process includes coupling the unstacked plurality of forward element signals via the satellite's first user link payload to the phased array antenna and transmitting them from the phased array antenna as the first user downlink signal, thereby forming one or more first forward user beams. The second forward service mode described above is: The satellite receives a second type of feeder-uplink signal, which includes one or more forward beam signals, via the first antenna system of the satellite. A method comprising coupling the one or more forward beam signals to the first antenna system via the satellite's second user link payload and transmitting from the first antenna system as one or more second user downlink signals, each second user downlink signal being transmitted as a corresponding second forward user beam, the corresponding second forward user beam having a corresponding second forward user beam coverage area and transmitting traffic to one or more second user terminals within a group of second user terminals, the one or more second user terminals located within the corresponding second forward user beam coverage area.

2. The method according to claim 1, wherein the first and second types of feeder uplink signals occupy the same first bandwidth in the same first spectrum, the one or more second forward user beams are signal frequencies in the first spectrum, and the one or more first forward user beams are signal frequencies in the second spectrum.

3. The method according to claim 2, wherein the first spectrum is an E-band spectrum, and the second spectrum is an L-band spectrum or an S-band spectrum.

4. The method according to any one of claims 1 to 3, wherein the signal bandwidth of each of the one or more first forward user beams is a function of the feeder uplink bandwidth and the number of forward element signals included in the plurality of forward element signals transmitted by the first type of feeder uplink signal, and the signal bandwidth of each of the one or more second forward user beams is a function of the feeder uplink bandwidth and the number of forward beam signals transmitted simultaneously in the second type of feeder uplink signal.

5. The method according to claim 4, wherein the signal bandwidth of each of the one or more first forward user beams is less than 10 MHz, and the signal bandwidth of each of the one or more second forward user beams is greater than 100 MHz.

6. The method according to any one of claims 1 to 5, wherein the second user link payload includes a block frequency converter that applies a defined frequency shift to the second type of feeder uplink signal, and the one or more second forward user beams are vent pipe retransmissions of the one or more forward beam signals transmitted in the second type of feeder uplink signal.

7. The method according to any one of claims 1 to 6, wherein the first user link payload includes a first vent pipe user link payload for vent pipe retransmission of the plurality of forward element signals, and the second user link payload includes a second vent pipe user link payload for vent pipe retransmission of one or more forward beam signals.

8. The system further includes operating in a first return service mode in conjunction with operating in the first forward service mode, wherein the first return service mode is Receiving a plurality of first return uplink signals transmitted by each first user terminal within the group of first user terminals, wherein each first user terminal operates within one or more respective first return user beam coverage areas, and the plurality of first return uplink signals are received as a plurality of corresponding receiving element signals in the same or a different phased array antenna in the second antenna system. The plurality of receiving element signals are coupled to the feeder link payload as a plurality of return element signals via the first user link payload, The plurality of return element signals are stacked in frequency via the feeder link payload, The method according to any one of claims 1 to 7, comprising transmitting the stacked plurality of return element signals as a first type of feeder downlink signal via the first antenna system.

9. The system further includes operating in a second return service mode in conjunction with operating in the second forward service mode, wherein the second return service mode is Receiving one or more second return uplink signals transmitted by each of the one or more second user terminals operating within one or more second return user beam coverage areas via the first antenna system, For each of the one or more second return user beam coverage areas, the correspondingly received second return uplink signals are coupled to the feeder link payload as return beam signals via the second user link payload. A second type of feeder downlink signal, including one or more return beam signals, is formed via the feeder link payload. The method according to any one of claims 1 to 8, comprising transmitting the second type of feeder downlink signal via the first antenna system.

10. The method according to claim 9, wherein the method includes operating on a half-duplex basis in the second forward service mode and the second return service mode so that the satellite operates in the second forward service mode at one or more scheduled times.

11. The method according to any one of claims 1 to 10, wherein the first antenna system includes a receiving phased array antenna and a transmitting phased array antenna, and operating in the second forward service mode includes performing onboard receive beamforming for directional reception of the second type of feeder uplink signals from a serving satellite access node (SAN) and performing onboard transmit beamforming for directional transmission of one or more corresponding second forward user beams.

12. The method according to claim 11, wherein operating in the first forward service mode includes performing onboard receive beamforming for directional reception of the first type of feeder uplink signal from the SAN.

13. The method according to any one of claims 1 to 12, wherein the first antenna system includes a mechanically controlled receiving antenna and a transmitting antenna, and operating in a second forward service mode includes oriented the mechanically controlled receiving antenna for directional reception of the second type of feeder uplink signals from a serving satellite access node (SAN) and oriented the mechanically controlled transmitting antenna for directional transmission of one or more corresponding second forward user beams.

14. The method according to any one of claims 1 to 13, further comprising changing between the first and second forward service modes in response to a command received from the ground network of the satellite communication system.

15. The method according to any one of claims 1 to 14, further comprising changing between the first and second forward service modes in response to scheduling information received from the ground network of the satellite communication system.

16. A satellite configured to operate in a satellite communications system, wherein the satellite is The first antenna system, The second antenna system, The feeder link payload associated with the first antenna system, The first user link payload associated with the second antenna system, A second user link payload associated with the first antenna system, A mode control circuit configured to control the configuration of the satellite to select operation in either a first forward service mode or a second forward service mode, For operation in the first forward service mode, the satellite: Receiving a first type of feeder uplink signal via the first antenna system, the plurality of forward element signals being stacked in frequency and corresponding to antenna elements in a phased array antenna included in the second antenna system, the plurality of forward element signals being weighted such that the plurality of forward element signals are simultaneously transmitted from the phased array antenna as a first user downlink signal to form a far-field of one or more first forward user beams, each first forward user beam having a corresponding first forward user beam coverage area, and transmitting and receiving traffic to one or more first user terminals within a group of first user terminals, located within the corresponding first forward user beam coverage area. The feeder link payload is used to unstack the multiple forward element signals and set them to the same downlink frequency. The system is configured to couple the unstacked plurality of forward element signals via the first user link payload to the phased array antenna and transmit them from the phased array antenna, thereby forming one or more first forward user beams. For operation in the second forward service mode, the satellite: The satellite receives a second type of feeder-uplink signal, which includes one or more forward beam signals, via the first antenna system of the satellite. A satellite configured to couple one or more forward beam signals to the first antenna system via a second user link payload of the satellite and transmit from the first antenna system as one or more second user downlink signals, wherein each second user downlink signal is transmitted as a corresponding second forward user beam, and the corresponding second forward user beam has a corresponding second forward user beam coverage area and transmits traffic to one or more second user terminals within a group of second user terminals, which are located within the corresponding second forward user beam coverage area.

17. A method for operation by a satellite access node (SAN) in a satellite communication system, the method comprising selectively operating in either a first forward service mode or a second forward service mode, The first forward service mode is, To form a first type of feeder uplink signal including a plurality of forward element signals, wherein the plurality of forward element signals are stacked in frequency and correspond to antenna elements in a satellite's phased array antenna, and the plurality of forward element signals are weighted such that the plurality of forward element signals are simultaneously transmitted from the phased array antenna as a first user downlink signal to form a far-field of one or more first forward user beams, each first forward user beam having a corresponding forward user beam coverage area and transmitting traffic to one or more first user terminals within a group of first user terminals, which are located within the corresponding forward user beam coverage area. This includes transmitting the first type of feeder uplink signal for reception by the satellite, The second forward service mode described above is: To form a second type of feeder-uplink signal including one or more forward beam signals, each forward beam signal transmitting traffic to one or more second user terminals in a corresponding second forward user beam coverage area, A method comprising transmitting the second type of feeder uplink signal for reception by the satellite, and providing the one or more forward beam signals for transmission as one or more second user downlink signals.

18. The method according to claim 17, further comprising transmitting a control signal to control when the satellite is operating in the first forward service mode and when the satellite is operating in the second forward service mode.

19. The method according to claim 18, further comprising receiving the control signal from a communication processing system in the ground segment of the satellite communication system.

20. The system further includes operating in a first return service mode in conjunction with operating in the first forward service mode, Receiving a first type of feeder-downlink signal, which includes a plurality of return element signals corresponding to a return uplink signal received from each of the one or more first user terminals on each element of the same or different phased array antenna mounted on the satellite, wherein the return element signals are stacked in frequency, The return element signals are unstacked to obtain multiple unstacked return element signals. The method according to any one of claims 17 to 19, comprising transmitting the plurality of unstacked return element signals to a ground-based beamformer of the communication processing system of the satellite communication system to form one or more corresponding return beam signals via return link beamforming, and providing them for recovering return user traffic from the one or more formed return user beams.

21. The system further includes operating in a second return service mode in conjunction with operating in the second forward service mode, wherein the second return service mode is Receiving a second type of feeder downlink signal, which includes one or more return beam signals corresponding to a return uplink signal received from each of the one or more second user terminals, The method according to any one of claims 17 to 20, comprising transmitting the return beam signals to a communication processing system of the satellite communication system for recovering return user traffic from one or more return beam signals.

22. The method according to any one of claims 17 to 21, wherein the first and second types of feeder uplink signals occupy the same first bandwidth in the same first spectrum.

23. The method according to claim 22, wherein the first spectrum is an E-band spectrum.

24. A satellite access node (SAN) configured to operate in a satellite communication system, wherein the SAN is Transmitter and, A signal processing circuit configured to operate in either a first forward service mode or a second forward service mode, The signal processing circuit includes a mode control circuit configured to control whether it operates in the first forward service mode or the second forward service mode, In the first forward service mode, the signal processing circuit is configured to form a first type of feeder uplink signal including a plurality of forward element signals, wherein the plurality of forward element signals are stacked in frequency and correspond to antenna elements in the satellite's phased array antenna, and the plurality of forward element signals are weighted such that the plurality of forward element signals are simultaneously transmitted from the phased array antenna as a first user downlink signal to form a far-field of one or more first forward user beams, each first forward user beam having a corresponding forward user beam coverage area and transmitting traffic to one or more first user terminals within a group of first user terminals, located within the corresponding forward user beam coverage area, to transmit the first type of feeder uplink signal via the transmitter for reception by the satellite. In the second forward service mode, the signal processing circuit is configured to form a second type of feeder uplink signal, each forward beam signal being used to transmit traffic to one or more second user terminals in a corresponding second forward user beam coverage area via the transmitter and to be received by the satellite, and to transmit the one or more forward beam signals as one or more second user downlink signals.

25. The mode control circuit is configured to control the signal processing circuit to operate in a first return service mode in conjunction with the signal processing circuit operating in the first forward service mode, and in operation in the first return service mode, the signal processing circuit Receiving a first type of feeder-downlink signal via the receiver of the SAN, which includes a plurality of return element signals corresponding to a return uplink signal received from each of the one or more first user terminals on each element of the same or another phased array antenna mounted on the satellite, wherein the return element signals are stacked in frequency, and receiving The return element signals are unstacked to obtain multiple unstacked return element signals. The SAN according to claim 24, configured to transmit the plurality of unstacked return element signals via the network interface of the SAN to a ground-based beamformer of the communication processing system of the satellite communication system to form one or more corresponding return beam signals via return link beamforming, and to recover return user traffic from the one or more formed return user beams.

26. The mode control circuit is configured to control the signal processing circuit to operate in a second return service mode in conjunction with the signal processing circuit operating in the second forward service mode, and in operation in the second return service mode, the signal processing circuit Receiving a second type of feeder downlink signal via the receiver of the SAN, which includes one or more return beam signals corresponding to a return uplink signal received from each of the one or more second user terminals, The method according to claim 24 or 25, configured to transmit the return beam signals to the communication processing system of the satellite communication system via the network interface of the SAN for the purpose of recovering return user traffic from one or more return beam signals.

Images