Antenna virtualization in communication systems
View Patent ↗Communication systems and methods are described in which multiple transmit signals are generated from an input stream or signal. The communication systems and methods, collectively referred to as antenna virtualization or virtual antenna systems, generate from each input stream multiple transmit signals that when driven into multiple antennas create a radiation pattern that effectively appears to originate from a single antenna. The communications operations include receiving at least one input stream. Multiple transmit signals are generated from the received input stream; the number of transmit signals generated is greater than the number of received input streams. Generation of the transmit signals involves transforming the input stream. The transforming includes applying one or more of a variable delay, a phase shift, and signal shaping to information of the input stream. The transmit signals are transmitted by a separate antenna of an antenna system.
1. A method comprising:
receiving at least one input stream of communication signals;
generating a plurality of transmit signals from the at least one input stream by transforming the at least one input stream, the transforming including applying a phase shift, to information of the at least one input stream; wherein the phase shift includes a phase shift of tones of the at least one input stream, and wherein the phase shift is approximately
exp(−j2πkδ/N),
wherein k represents a tone index and N represents a number of the tones; and
transmitting each one of the plurality of transmit signals by a respective one of a plurality of antennas, wherein collective transmission of the plurality of transmit signals form a radiation pattern that appears to originate from at least one virtual antenna, wherein a number of the virtual antennas is fewer than a number of the plurality of antennas.
2. The method of claim 1 , wherein the transforming varies at least one parameter of the at least one input stream.
3. The method of claim 2 , wherein the at least one parameter includes one or more of polarization angle, signal strength, phase, and symbol position.
4. The method of claim 1 , wherein the transforming varies a polarization angle of the at least one input stream.
5. The method of claim 1 , wherein the transforming varies a signal strength of the at least one input stream.
6. The method of claim 1 , wherein the transforming applies a time domain shift to the at least one input stream.
7. The method of claim 1 , wherein the transforming applies a progressive phase shift to the at least one input stream.
8. A method comprising:
receiving at least one input stream of communication signals;
generating a plurality of transmit signals from the at least one input stream by transforming the at least one input stream, the transforming including applying one or more of a variable delay, a phase shift, and signal shaping to information of the at least one input stream, wherein the transforming applies a phase ramp to the at least one input stream; and
transmitting each one of the plurality of transmit signals by a respective one of a plurality of antennas, wherein collective transmission of the plurality of transmit signals form a radiation pattern that appears to originate from at least one virtual antenna, wherein a number of the virtual antennas is fewer than a number of the plurality of antennas.
9. The method of claim 8 , wherein the phase ramp has one of a negative and positive slope.
10. A method comprising:
receiving at least one input stream of communication signals;
generating a plurality of transmit signals from the at least one input stream by transforming the at least one input stream, the transforming including applying one or more of a variable delay, a phase shift, and signal shaping to information of the at least one input stream, wherein the transforming includes a first transforming of the at least one input stream, wherein the transforming includes a second transforming applied to at least one signal output of the first transforming, wherein the second transforming outputs the transmit signals, wherein the first transforming includes a first transformation operation and a second transformation operation applied to an input stream, wherein the second transforming includes:
a third transformation operation that outputs a first transmit signal to a first antenna;
a fourth transformation operation that outputs a second transmit signal to a second antenna;
a fifth transformation operation that outputs a third transmit signal to a third antenna; and
a sixth transformation operation that outputs a fourth transmit signal to a fourth antenna; and
transmitting each one of the plurality of transmit signals by a respective one of a plurality of antennas, wherein collective transmission of the plurality of transmit signals form a radiation pattern that appears to originate from at least one virtual antenna, wherein a number of the virtual antennas is fewer than a number of the plurality of antennas.
11. The method of claim 10 , wherein the second transformation operation applies the variable delay to the input stream.
12. The method of claim 10 , wherein the third and fifth transformation operations apply a first amplitude shaping to an output of the first transformation operation, and the fourth and sixth transformation operations apply a second amplitude shaping to an output of the second transformation operation.
13. The method of claim 12 , wherein the first transformation operation applies the first amplitude shaping and the second transformation operation applies the second amplitude shaping.
14. The method of claim 10 , wherein one or more of the second transformation, fourth transformation, and sixth transformation applies one or more of a progressive phase shift operation and a time domain shift operation to an input.
15. The method of claim 10 , wherein the first transforming includes:
a first transformation operation that outputs a first transmit signal to a first antenna; and
a second transformation operation that outputs a second transmit signal to a second antenna.
16. The method of claim 15 , wherein the second transformation operation applies the variable delay to the input stream.
17. A method comprising:
receiving at least one input stream of communication signals;
generating a plurality of transmit signals from the at least one input stream by transforming the at least one input stream, the transforming including applying one or more of a variable delay, a phase shift, and signal shaping to information of the at least one input stream, wherein the transforming comprises a first transforming of first and second input streams, wherein the first transforming includes:
a first transformation operation that outputs a first transmit signal to a first antenna;
a second transformation operation that outputs a second transmit signal to a second antenna;
a third transformation operation that outputs a third transmit signal to a third antenna;
a fourth transformation operation that outputs a fourth transmit signal to a fourth antenna; and
transmitting each one of the plurality of transmit signals by a respective one of a plurality of antennas, wherein collective transmission of the plurality of transmit signals form a radiation pattern that appears to originate from at least one virtual antenna, wherein a number of the virtual antennas is fewer than a number of the plurality of antennas.
18. The system of claim 17 , wherein the first and second transformation operations apply a first amplitude shaping to the first input stream, and the third and fourth transformation operations apply a second amplitude shaping to the second input stream.
19. The method of claim 1 , wherein the transmit signals are orthogonal frequency-division multiplexing (OFDM) signals in a wireless digital communications system.
20. A method comprising:
generating a plurality of transmit signals from the at least one input stream by transforming the at least one input stream, the transforming including applying a phase shift, to information of the at least one input stream; wherein the phase shift includes a phase shift of tones of the at least one input stream, and wherein the phase shift is approximately
exp(−j2πkδ/N),
wherein k represents a tone index and N represents a number of the tones; and
transmitting each one of the plurality of transmit signals by a respective one of a plurality of antennas, wherein collective transmission of the plurality of transmit signals form a radiation pattern that appears to originate from at least one virtual antenna, wherein a number of the virtual antennas is fewer than a number of the plurality of antennas.
21. A computer readable medium including executable instructions which, when executed in a processing system, provide a communications system that transmits signals by:
receiving at least one input stream of communication signals;
generating a plurality of transmit signals from the at least one input stream by transforming the at least one input stream, the transforming including applying one or more of a variable delay, a phase shift, and signal shaping to information of the at least one input stream; wherein the phase shift includes a phase shift of tones of the at least one input stream, and wherein the phase shift is approximately
exp(−j2πkδ/N),
wherein k represents a tone index and N represents a number of the tones; and
transmitting each one of the plurality of transmit signals by a respective one of a plurality of antennas, wherein a number of the at least one input streams is less than a number of the plurality of transmit signals.
22. The medium of claim 21 , wherein the transforming varies a polarization angle of the at least one input stream.
23. The medium of claim 21 , wherein the transforming varies a signal strength of the at least one input stream.
24. The medium of claim 21 , wherein the transforming applies a time domain shift to the at least one input stream.
25. The medium of claim 21 , wherein the transforming applies a progressive phase shift to the at least one input stream.
26. The medium of claim 21 , wherein the transforming applies a phase ramp to the at least one input stream.
27. The medium of claim 21 , wherein the phase shift includes a phase shift of tones of the at least one input stream.
28. The medium of claim 21 , the signal shaping includes shaping an amplitude of tones of the at least one input stream.
29. The medium of claim 21 , wherein the transforming includes a first transforming of the at least one input stream.
30. The medium of claim 29 , wherein the transforming includes a second transforming applied to at least one signal output of the first transforming, wherein the second transforming outputs the transmit signals.