Abstract:
An example system for satellite payload communications includes a digital channelizer and a regenerative communications subsystem (RCS). The digital channelizer includes a plurality of inputs for receiving a plurality of signals from a plurality of uplink beams and a plurality of outputs for outputting the plurality of signals. The RCS includes a plurality of inputs selectably coupled to the digital channelizer outputs to receive signals from selected ones of the digital channelizer outputs and a plurality of outputs selectably coupled to the digital channelizer inputs to transmit the processed signals to selected ones of the digital channelizer inputs. The RCS is configured to process selected ones of the plurality of signals to produce processed signals.

Description:
BACKGROUND 
       [0001]    The field of the disclosure relates generally to satellite communications, and more particularly relates to methods and apparatus for routing Internet Protocol (IP) packets in a satellite network. 
         [0002]    A typical modern transponded (or “bent-pipe”) satellite has a metal or composite frame that houses a power source (e.g., one or more batteries, solar cells, and/or the like) and various electronic components, as well as one or more antennas. The components generally include one or more “transponders” that contain one or more radio receivers, frequency translators, and/or transmitters. The total bandwidth of the satellite is based on the number of transponders. For example, one known commercially-available satellite has a total available bandwidth of 3,528 MHz divided across forty-five C-band and sixteen Ku-band transponders. Such transponders are collectively referred to as “the payload” of the satellite. 
         [0003]    A typical analog transponded communications payload receives multiple uplink beams from the earth or another satellite via an uplink antenna. Each received beam is amplified with a low noise amplifier (LNA) and down-converted (D/C) for additional processing. The down-converted beams can then be switched, multiplexed (MUX) or otherwise routed and combined prior to upconversion and re-transmission to the Earth or another satellite. 
         [0004]    Digital satellite payloads generally function in either a channelized manner or a regenerative manner. A channelized payload emulates traditional fixed analog transponders, but also includes the ability to finely divide, control, and monitor bandwidth and power allocation onboard the satellite. Digital transponded payloads normally have flexible switching of inputs to outputs. Transponded channels are merely repeated signals, without any modification. Accordingly, transponder payloads can carry any type of signal without regard to format or modulation mode. Digital transponder systems may be relatively easily modified to be backward compatible with analog transponder systems. Unlike transponded payloads, regenerative payloads can perform demodulation and remodulation of uplinked signals. In such systems, the user signal and the user data embedded in the signal are recovered and processed to enable the payload to act upon the user data in a desired manner. Embedded data has historically been used for autonomous switching in packet or frame-based systems and/or for security functions. In particular, error detection and correction can be performed on the embedded data before it is retransmitted. However, because of their requirements for specific signal and data types, regenerative systems are generally not backward compatible. 
       BRIEF DESCRIPTION 
       [0005]    According to one aspect of the present disclosure, an example system for satellite payload communications includes a digital channelizer and a regenerative communications subsystem (RCS). The digital channelizer includes a plurality of inputs for receiving a plurality of signals from a plurality of uplink beams and a plurality of outputs for outputting the plurality of signals to a plurality of downlink beams. The RCS includes a plurality of inputs selectably coupled to the digital channelizer outputs to receive signals from the digital channelizer outputs and a plurality of outputs selectably coupled to the digital channelizer inputs to transmit the processed signals to the digital channelizer inputs. The RCS is configured to process selected signals of the plurality of signals from the plurality of uplink beams to produce processed signals to the plurality of signals sent to the plurality of downlink beams. 
         [0006]    Another aspect of the present disclosure is a method for use in satellite communications. The method includes receiving a plurality of signals from an uplink beam, providing the plurality of signals to a plurality of inputs of a digital channelizer including a plurality of outputs, providing output signals from at least one of the digital channelizer outputs to a regenerative communications subsystem (RCS), and providing processed signals from the RCS to at least one of the digital channelizer inputs, to allow the processed signals to be switched by the digital channelizer to a plurality of signals for a downlink beam. 
         [0007]    Yet another aspect of the present disclosure is a system for satellite payload communications. The system includes a channelizer, a regenerative communication subsystem (RCS), and a controller. The channelizer includes a plurality of inputs and a plurality of outputs. The plurality of inputs is configured to receive signals from a plurality of uplink beams. The plurality of outputs is configured to couple output signals to a plurality of downlink beams. The RCS includes a plurality of inputs and a plurality of outputs. Each of the plurality of RCS outputs is coupled to a different one of the channelizer inputs. The RCS is configured to regeneratively process signals received at its inputs and to output processed signals via its outputs. The controller is configured to selectively switch output signals of one or more of the channelizer outputs from the downlink beams to one or more of the RCS inputs. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a block diagram of an exemplary satellite system. 
           [0009]      FIG. 2  is a block diagram of an exemplary payload that may be used in the satellite system shown in  FIG. 1 . 
           [0010]      FIG. 3  is a flow diagram of an exemplary method of operating the system and payload of  FIGS. 1 and 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    As used herein, an element or step recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural elements or steps unless such exclusion is explicitly recited. Furthermore, references to “one embodiment” of the present invention or the “exemplary embodiment” are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. 
         [0012]    The exemplary methods and systems described herein relate to satellite-based communications. More particularly the exemplary embodiments described herein facilitate efficient routing of Internet protocol (IP) packets in a multi-beam satellite network environment. The methods and systems described herein generally combine a channelizer-based satellite payload and a digital-regenerative communications system. One or more of the outputs of the channelizer are directed to the regenerative communications system for processing and output back to the channelizer as IP packets. The resulting systems may facilitate reducing the number of satellite hops needed to deliver data, and thus reduce the delay in the transmission of signals, while improving the quality of service for users. Moreover, the described methods and apparatus provide a relatively low cost, incremental approach to providing regenerative systems in a satellite network. Furthermore, the reduced satellite hops may enable packet-based networks that span multiple satellite beams to be more responsive to failures because of the reduced delay in resynchronizing routing databases across the network. 
         [0013]    Referring more particularly to the drawings,  FIG. 1  is a block diagram of an exemplary satellite communications system  100 . In the exemplary embodiment, satellite communications system  100  includes an uplink antenna  102  and a downlink antenna  104 . Uplink antenna  102  receives uplink beams  106  from one or more terrestrial sources (not shown) and/or from other satellites (not shown). Downlink antenna  104  transmits downlink beams  108  to one or more terrestrial sources (not shown) and/or to other satellites (not shown). Although only a single uplink antenna  102  and a single downlink antenna  104  are illustrated in  FIG. 1 , communications satellite  100  may include any suitable number of uplink and downlink antennas  102  and  104 . 
         [0014]    Uplink beams  106  are filtered, amplified, and down-converted by satellite communications system  100 . The resulting signals are provided to a channelizer  110  via a plurality of selectors  112 . A different one of the uplink beams  106  may be coupled to each of selectors  112 . Selectors  112  selectively provide one of their two selector inputs to a channelizer input  114  of channelizer  110 . In other embodiments, selectors  112  may include more than two selector inputs. Channelizer  110  digitally divides each sub-band of the input signals into frequency slices that can be separately, switched, processed, routed, and/or recombined in output subbands provided to channelizer outputs  116 . In other embodiments, input signals are switched and multiplexed without additional processing. Although three channelizer inputs  114  and three channelizer outputs  116  are illustrated in  FIG. 1 , channelizer  110  may include any suitable number of channelizer inputs  114  and channelizer outputs  116 . 
         [0015]    Switches  118  are coupled to channelizer outputs  116 . Each of switches  118  may be configured to receive signals from a different one of the channelizer outputs  116 . Switches  118  selectively provide the output signals from channelizer  110  to downlink antenna  104  or to a regenerative communications sub-assembly (RCS)  120 . RCS  120  includes RCS inputs  122  for receiving output signals from channelizer  110 . RCS  120  performs any suitable regenerative processing on the output signals from channelizer  110 . For example, in one embodiments, RCS  120  demodulates the signals and accesses data stored therein. In some embodiments, the data is used for IP packet-routing, cryptographic security and authentication, session establishment for voice and data services, error detection, and/or correction. After Processing the data embedded in the output signals provided to RCS  120  by switches  118 , the data is remodulated and output to selectors  112  via RCS outputs  124 . 
         [0016]    Output signals from RCS  120  are coupled into channelizer  110  through selectors  112 . For example, each of the selectors  112  may be coupled to a respective RCS output  124 , one of the uplink beams  106 , and to one of the channelizer inputs  114 . More specifically, the RCS output signals are handled by channelizer  110  in the same manner described above for signals from uplink beams  106  and routed to switches  118  for delivery to downlink antenna  104 . 
         [0017]    In the exemplary embodiment, satellite  100  includes a controller  126 . Controller  126  controls operation of switches  118 , selectors  112 , channelizer  110 , and RCS  120  in the manner described herein. Although illustrated as a single, discrete controller, satellite communications system  100  may include multiple, separate controllers  126 . For example, RCS  120  may include one or more controllers  126 , channelizer  110  may include one or more controllers  126 , etc. Controller  126  may be any other suitable analog and/or digital controller used to control operation of satellite communications system  100  as described herein. 
         [0018]      FIG. 2  is a block diagram of an alternative embodiment of satellite communications system  100 . In this embodiment, uplink beams  106  are processed by an analog front end  200 , and analog-to-digital converter  202 , and digital signal processor  204  prior to signals being routed to channelizer  110  via selectors  112 . The digital output signals from channelizer  110  that are not switched to RSC  120  are processed by a DSP processor  206 , a digital-to-analog converter  208 , and an analog back end  210  prior to transmission to downlink antenna  104 . The signals switched to RSC  120  are coupled to RSC  120  via a protection switch  212 . In the exemplary embodiment protection switch  212  is an N:M protection switch providing redundancy within system  100 . In other embodiments, any other suitable type of protection switch may be used. 
         [0019]    In this embodiment, RCS  120  includes a baseband modem  214 , an aggregation switch  216 , and an IP router  218 . The aggregation switch  216  may be coupled between the IP router  218  and at least one of the RCS  120  inputs. The baseband modem  214  may be coupled between the aggregation switch  216  and at least one of the RCS  120  inputs. Baseband modem  214  includes inputs  122  to receive the signals from channelizer  110  and outputs baseband signals to aggregation switch  216 . Aggregation switch  216  aggregates packet traffic to/from unidirectional downlink/uplink beams and presents the aggregate traffic to the bidirectional interfaces of the IP router  218 . IP router  218  routes the processed signals through outputs  124 . The processed signals output from RSC  120  are provided to selectors  112  via a protection switch  220 . In the exemplary embodiment protection switch  220  is an N:M protection switch providing redundancy within system  100 . In other embodiments, any other suitable type of protection switch may be used. 
         [0020]      FIG. 3  is a flow diagram of an exemplary method  300  of operating a system and payload, such as system  100 . Method  300  includes receiving  302  a plurality of signals from an uplink beam. The plurality of signals are provided  304  to a plurality of inputs of a digital channelizer including a plurality of outputs. Output signals from at least one of the digital channelizer outputs are provided  306  to a regenerative communications subsystem (RCS). Processed signals from the RCS are provided  308  to at least one of the digital channelizer inputs. 
         [0021]    The exemplary methods and systems described herein facilitate an efficient routing of IETF-standard Internet protocol (IP) packets in a multi-beam satellite network environment, allowing for the design of IP-based networks that span multiple satellite beams (or earth coverage areas). The resulting systems facilitate reducing the number of satellite hops needed to deliver data, thereby reducing delay in the transmission of signals and improving quality of service for users. Moreover, embodiments described herein provide a relatively low cost, incremental approach to providing regenerative systems in a satellite network. Furthermore, the reduced satellite hop may allow packet based networks that span multiple satellite beams to be more responsive to failures because the inclusion of the satellite node as a routing peer in the IP network topology enables reduced delay in resynchronizing routing databases across the network. 
         [0022]    The description of the different advantageous embodiments has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the embodiments in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. Further, different advantageous embodiments may provide different advantages as compared to other advantageous embodiments. The embodiment or embodiments selected are chosen and described in order to best explain the principles of the embodiments, the practical application, and to enable others of ordinary skill in the art to understand the disclosure for various embodiments with various modifications as are suited to the particular use contemplated. This written description uses examples to disclose various embodiments, which include the best mode, to enable any person skilled in the art to practice those embodiments, including making and using any devices or systems and performing any incorporated methods. The patentable scope is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.