Ground Terminals via Remote Digital-Beam-Forming Networks for Satellites in Non-Geostationary Orbit

Abstract

A communication system comprises a remote digital beam-forming network configured to receive a set of input signals destined for a set of user devices and generate element signals to be radiated by a set of remote antenna array elements; a pre-processor coupled to the remote digital beam-forming network, configured to perform a wavefront multiplexing transform on signal waveforms including the element signals and generate wavefront multiplexed signals; an optical line terminal coupled to the pre-processor, configured to process the wavefront multiplexed signal streams to generate optical waveform streams; and optical fibers coupling the optical line terminal to a set of optical network units.

What is claimed is: 
     
         1 . A communication system comprising:
 a remote digital beam-forming network configured to receive a set of input signals destined for a set of user devices and generate element signals to be radiated by a set of remote antenna array elements;   a pre-processor coupled to the remote digital beam-forming network, configured to perform a wavefront multiplexing transform on signal waveforms including the element signals and generate wavefront multiplexed signals;   an optical line terminal coupled to the pre-processor, configured to process the wavefront multiplexed signal streams to generate optical waveform streams; and   optical fibers coupling the optical line terminal to a set of optical network units.   
     
     
         2 . The communication system of  claim 1 , wherein the remote digital beam-forming network comprises:
 a digital beam forming network configured to receive the set of input signals and generate the element signals.   
     
     
         3 . The communication system of  claim 1 , wherein the optical line terminal comprises:
 a time division multiplexer configured to receive and perform time division multiplexing (TDM) on the wavefront multiplexed signals and generate a TDM muxed signal stream;   an optical modulator configured to convert the TDM muxed signal stream to a muxed optical signal stream; and   an optical laser to provide an optical carrier source for the optical modulator.   
     
     
         4 . The communication system of  claim 1  further comprising:
 optical dividers coupled to the optical fibers and to the set of optical network units. 
 
     
     
         5 . The communication system of  claim 3 , wherein each of the optical network units comprises:
 an optical demodulator configured to convert the muxed optical signal stream to a TDM muxed signal stream;   a time division demultiplexer configured to perform TDM demultiplexing on the TDM muxed signal stream and generate TDM demuxed signal streams; and   a wavefront demultiplexer configured to perform a wavefront demultiplexing transform on the TDM demuxed signal streams, the wavefront demultiplexing transform being an inverse of the wavefront multiplexing transform, and generate wavefront demultiplexed signals which include recovered element signals.   
     
     
         6 . The communication system of  claim 5 , wherein each of the optical network units further comprises:
 a set of adaptive equalizers coupled to the time division demultiplexer to perform pre-distortion compensation; and   an optimization loop unit coupled to the wavefront demultiplexer and the set of adaptive equalizers for controlling the set of adaptive equalizers.   
     
     
         7 . The communication system of  claim 5 , wherein each of the optical network units is coupled to a user processor, the user processor comprising:
 a picocell hub for receiving the wavefront demultiplexed signals including the recovered element signals; and   the set of remote antenna array elements coupled to the picocell hub, configured to radiate the recovered element signals to the set of user devices that are cellphones over a coverage area.   
     
     
         8 . The communication system of  claim 5 , wherein each of the optical network units is coupled to a user processor, the user processor comprising:
 a WiFi hub receiving the wavefront demultiplexed signals including the recovered element signals; and   the set of remote antenna array elements coupled to the WiFi hub, configured to radiate the recovered element signals to the set of user devices that are personal devices over a coverage area.   
     
     
         9 . The communication system of  claim 1 , wherein the set of user devices is a set of cellphones and wherein the set of remote antenna array elements form an antenna array by the first remote digital beam-forming network to provide a clean connection to the set of cellphones over a coverage area, the coverage area including respective fields of view of the set of remote antenna array elements. 
     
     
         10 . The communication system of  claim 1 , wherein the remote digital beam-forming network generates each of the element signals as a dynamically shaped beam for each of the remote antenna array elements, each of the dynamically shaped beams includes a tracking beam peak at a location of one of the user devices and tracking nulls at locations of remaining ones of the user devices. 
     
     
         11 . A communication system comprising:
 a first remote digital beam-forming network configured to receive a first set of input signals destined for a first set of user devices and generate a first output signal including first element signals to be radiated by a first set of remote antenna array elements;   a second remote digital beam-forming network configured to receive a second set of input signals destined for a second set of user devices and generate a second output signal comprising second element signals to be radiated by a second set of remote antenna array elements;   a pre-processor configured to perform a wavefront multiplexing transform on signal waveforms including the first output signal and the second output signal and generate wavefront multiplexed signals;   an optical line terminal coupled to the pre-processor, configured to process the wavefront multiplexed signal streams to generate optical waveform streams; and   optical fibers coupling the optical line terminal to a set of optical network units.   
     
     
         12 . The communication system of  claim 11 , wherein the first remote digital beam-forming network comprises:
 a digital beam forming network configured to receive the first set of input signals and generate the first element signals; and   a frequency division multiplexer configured to perform frequency division multiplexing on the first element signals and generate the first output signal.   
     
     
         13 . The communication system of  claim 11  further comprising:
 a muxing device configured to multiplex the first output signal and the second output signal and generate a multiplexed signal as one of the signal waveforms for the pre-processor. 
 
     
     
         14 . The communication system of  claim 11 , wherein the optical line terminal comprises:
 a time division multiplexer configured to receive and perform time division multiplexing (TDM) on the wavefront multiplexed signals and generate a TDM muxed signal stream;   an optical modulator configured to convert the TDM muxed signal stream to a muxed optical signal stream; and   an optical laser to provide an optical carrier source for the optical modulator.   
     
     
         15 . The communication system of  claim 11  further comprising:
 optical dividers coupled to the optical fibers and to the set of optical network units. 
 
     
     
         16 . The communication system of  claim 14 , wherein each of the optical network units comprises:
 an optical demodulator configured to convert the muxed optical signal stream to a TDM muxed signal stream;   a time division demultiplexer configured to perform TDM demultiplexing on the TDM muxed signal stream and generate TDM demuxed signal streams; and   a wavefront demultiplexer configured to perform a wavefront demultiplexing transform on the TDM demuxed signal streams, the wavefront demultiplexing transform being an inverse of the wavefront multiplexing transform, and generate wavefront demultiplexed signals which include a recovered first output signal.   
     
     
         17 . The communication system of  claim 16 , wherein each of the optical network units further comprises:
 a set of adaptive equalizers coupled to the time division demultiplexer to perform pre-distortion compensation; and   an optimization loop unit coupled to the wavefront demultiplexer and the set of adaptive equalizers for controlling the set of adaptive equalizers.   
     
     
         18 . The communication system of  claim 16 , wherein each of the optical network units is coupled to a user processor, the user processor comprising:
 a picocell hub receiving the wavefront demultiplexed signals including the recovered first output signal;   a frequency division demultiplexer coupled to the picocell hub, configured to frequency division demultiplexing the recovered first output signal and generate recovered first element signals; and   the first set of remote antenna array elements coupled to the frequency division demultiplexer, configured to radiate the recovered first element signals to a plurality of cellphones over a coverage area.   
     
     
         19 . The communication system of  claim 16 , wherein each of the optical network units is coupled to a user processor, the user processor comprising:
 a WiFi hub receiving the wavefront demultiplexed signals including the recovered first element signals; and   the first set of remote antenna array elements coupled to the WiFi hub, configured to radiate the recovered first element signals to a plurality of personal devices over a coverage area.   
     
     
         20 . The communication system of  claim 11 , wherein the set of user devices is a set of cellphones, and wherein the first set of remote antenna array elements form an antenna array by the first remote digital beam-forming network to provide a clean connection to the set of cellphones over a coverage area, the coverage area including respective fields of view of the first set of remote antenna array elements.