Orbital base station filtering of interference from terrestrial-terrestrial communications of devices that use protocols in common with orbital-terrestrial communications
An orbiting multiple access transceiver communicates with terrestrial mobile stations which are also capable of communicating with terrestrial base stations. The multiple access transceiver is configured to sample a signal when a terrestrial mobile station of interest is not transmitting to produce a sample signal. The sample signal may be processed to produce an out-of-phase signal that may be applied to a signal when the terrestrial mobile station of interest is transmitting to produce a clearer signal from the terrestrial mobile station of interest.
1. A method of processing signals received by a signal processor of an orbital base station received from a plurality of terrestrial mobile devices, the terrestrial mobile devices also capable of communicating with terrestrial base stations, the method comprising:
receiving, by a transceiver, a first signal from some of the terrestrial mobile devices;
reducing, by a filtering module as part of the signal processor of the orbital base station, a first portion of the first signal, wherein the first portion is due to a transmitting plurality of the terrestrial mobile devices that are communicating with one or more of the terrestrial base stations;
producing a filtered signal comprising a second signal from a target mobile device communicating with the orbital base station, the target mobile device being distinct from the transmitting plurality; and
demodulating, by a signal demodulator, the filtered signal to produce a demodulated signal corresponding to the second signal from the target mobile device.
2. The method of claim 1 , wherein the signal processor of the orbital base station is housed within the orbital base station in Earth orbit.
3. The method of claim 1 , wherein the demodulated signal is further processed to produce a binary code.
4. The method of claim 1 , further comprising:
determining a sounding period, during which the target mobile device is not sending a communication to be received by the signal processor;
receiving a sounding signal during the sounding period;
digitizing the sounding signal to form a digitized sounding signal;
processing the digitized sounding signal with a Fourier transform to form a transformed sounding signal; and
filtering the transformed sounding signal to form a filtered sounding signal wherein portions of the filtered sounding signal are attenuated based on frequency separation relative to a baseline frequency.
5. The method of claim 1 , wherein processing the filtered signal further comprises applying an inverse Fourier transform to the filtered signal to form a transformed sounding signal, the method further comprising:
storing the transformed sounding signal for later use;
in a signal period, applying the transformed sounding signal and a sampled signal to an adder, thereby canceling out effects from unwanted signals, to form the filtered signal;
providing the filtered signal to a demodulator that outputs phase values as constellation points; and
processing the constellation points using a demapper to generate an output bitstream.
6. The method of claim 1 , further comprising:
segmenting the filtered signal into TDMA frames, each comprising a plurality of timeslots per TDMA frame, with at least one of the TDMA frames designated a sounding timeslot that is left unassigned to any of the plurality of terrestrial mobile devices and other timeslots assigned as signaling timeslots;
generating a profile of an interference environment based on sounding signals received in the sounding timeslot;
creating an out-of-phase counterpart for the interference environment; and
processing the signaling timeslots in the TDMA frame using the out-of-phase counterpart.
7. The method of claim 6 , wherein the sounding timeslot and the signaling timeslots are the same timeslot relative to TDMA framing from different frames.
8. The method of claim 6 , further comprising processing the sounding signals to determine a phase base sounding signal measurement by bandpass filtering a Fourier transform domain representation of the sounding signals.
9. The method of claim 8 , wherein bandpass filtering the Fourier transform domain representation comprises attenuating complex values of the Fourier transform domain representation outside a designated frequency range to form a filtered Fourier domain representation.
10. The method of claim 1 , wherein the filtering module samples a frame in which the target mobile device is known to not be transmitting.
11. The method of claim 1 , wherein the target mobile device does not transmit during a first time period during which the transceiver channel sounds a channel to produce a sample from a sounding signal.
12. The method of claim 11 , wherein the filtering module converts the sample to a discretized vector in a time domain.
13. The method of claim 11 , wherein the filtering module processes the sample using a Fourier transform to produce an out-of-phase counterpart of the sample.
14. The method of claim 11 , wherein the filtering module processes the sample to produce an out-of-phase counterpart of the sample.
15. The method of claim 14 , wherein the transceiver receives a second portion of the sounding signal during a second time period that does not overlap the first time period.
16. The method of claim 15 , wherein the filtering module applies the out-of-phase counterpart to the second portion to produce the filtered signal.
17. The method of claim 16 , wherein the out-of-phase counterpart to is applied to the second portion by summing the out-of-phase counterpart with the second portion.
18. The method of claim 11 , wherein the filtering module processes the sample to measure amplitude to generate a base signal for interference reduction.
19. The method of claim 11 , wherein the filtering module processes the sample to measure amplitude and phase to generate a base signal for interference reduction.