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1. (WO2007039908) JOINT CONSTELLATION MULTIPLE ACCESS
Note: Text based on automatic Optical Character Recognition processes. Please use the PDF version for legal matters Machine translation

CLAIMS
1. A method for communication, comprising:
defining N respective symbol constellations in a signal space for N transmitters, N>2, subject to a predetermined power constraint, so as to produce a joint constellation comprising superpositions of symbols selected from the N symbol constellations;
transferring data from the N transmitters by simultaneously transmitting from the N transmitters N respective symbols selected respectively from the N symbol constellations;
receiving a composite symbol comprising a superposition of the N transmitted symbols; and
demodulating the received composite symbol using the joint constellation so as to reconstruct the data transferred from the N transmitters.
2. The method according to claim 1, wherein defining the N symbol constellations comprises applying an optimization process responsively to the power constraint.
3. The method according to claim 2, wherein applying the optimization process comprises repeatedly generating random sets of the N transmitter constellations, evaluating a minimum

Euclidean distance (DMIN) value of the produced joint constellation, and outputting a set of N transmitter constellations and joint constellation corresponding to a largest DMIN value.

4. The method according to claim 3, wherein applying the optimization process comprises evaluating Hamming distances of the produced joint constellation, and wherein outputting the set of N transmitter constellations and the joint constellation comprises verifying that the joint constellation has a minimal Hamming distance larger than a predefined threshold.
5. The method according to any of claims 1-4, wherein defining the N symbol constellations comprises maximizing distances in the signal space among joint constellation symbols of the joint constellation.
6. The method according to any of claims 1-4, wherein defining the N symbol constellations comprises defining for a first transmitter a first symbol constellation having a first number of constellation symbols, and defining for a second transmitter a second symbol constellation having a second number of constellation symbols different from the first number, so as to cause the first and second transmitters to transmit the data at different respective data rates.

7. The method according to any of claims 1-4, wherein defining the N symbol constellations comprises defining first and second power levels of respective first and second symbol constellations of first and second transmitters, so as to cause first and second symbols transmitted respectively by the first and second transmitters to be received at different power levels.
8. The method according to any of claims 1-4, wherein the power constraint comprises a maximum value set to at least one of an instantaneous power and an average power of each of the N transmitters.
9. The method according to any of claims 1-4, wherein transferring the data from the N transmitters comprises adjusting at least one of phases, magnitudes and timing offsets of the symbols transmitted from the N transmitters so as to produce the composite symbol.
10. The method according to any of claims 1-4, wherein demodulating the received composite symbol comprises selecting a symbol from among joint constellation symbols of the joint constellation responsively to the received composite symbol using a maximum likelihood (ML) detector.
11. The method according to claim 10, wherein demodulating the received composite symbol comprises approximating the ML detector based on a symmetry of the joint constellation.
12. The method according to any of claims 1-4, and comprising modifying at least one of the joint constellation and the N symbol constellation responsively to a failure of one or more of the N transmitters.
13. The method according to any of claims 1-4, and comprising periodically redefining the N symbol constellations by re-assigning the symbols among the N symbol constellations.
14. A method for communication, comprising:
defining a first plurality of symbol constellations in a signal space for a respective first plurality of transmitters, so as to produce a first joint constellation comprising superpositions of symbols selected from the first symbol constellations;
defining a second plurality of symbol constellations in the signal space for a respective second plurality of transmitters, so as to produce a second joint constellation comprising superpositions of symbols selected from the second symbol constellations; and
transferring data from the first and second pluralities of transmitters by: simultaneously transmitting from the first plurality of transmitters first respective symbols selected respectively from the first plurality of symbol constellations;
simultaneously transmitting from the second plurality of transmitters second respective symbols selected respectively from the second plurality of symbol constellations;
multiplexing the first and second symbols over a common communication channel using a multiple access method;
receiving first and second composite symbols comprising respective superpositions of the first and second transmitted symbols; and
demodulating the first and second received composite symbols using the first and second joint constellations so as to reconstruct the data transferred from the first and second pluralities of transmitters.
15. The method according to claim 14, wherein the multiple access method comprises a frequency division multiple access (FDMA) method, and wherein multiplexing the first and second symbols comprises transmitting the first and second symbols on respective different first and second carrier frequencies.
16. The method according to claim 14, wherein the multiple access method comprises a time division multiple access (TDMA) method, and wherein multiplexing the first and second symbols comprises transmitting the first and second symbols in respective different first and second time slots.
17. The method according to claim 14, wherein the multiple access method comprises a code division multiple access (CDMA) method, and wherein multiplexing the first and second symbols comprises transmitting the first and second symbols using respective different first and second CDMA sequences.
18. The method according to claim 14, wherein the multiple access method comprises orthogonal frequency division multiplexing (OFDM), and wherein multiplexing the first and second symbols comprises transmitting the first and second symbols on respective first and second OFDM sub-carriers of an OFDM signal.
19. A method for communication, comprising:
defining N respective symbol constellations in a signal space for N transmitters, N>2, so as to produce a joint constellation comprising superpositions of symbols selected from the N symbol constellations, wherein at least one of the N symbol constellations is not a rotated and scaled replica of any other of the N symbol constellations;

transferring data from the N transmitters by simultaneously transmitting from the N transmitters N respective symbols selected respectively from the N symbol constellations;
receiving a composite symbol comprising a superposition of the N transmitted symbols; and
demodulating the received composite symbol using the joint constellation so as to reconstruct the data transferred from the N transmitters.
20. A communication system, comprising:
N transmitters, N>2, which are arranged to accept definitions of N respective symbol constellations in a signal space, defined subject to a predetermined power constraint to produce a joint constellation comprising superpositions of symbols selected from the N symbol constellations, and to transfer data by simultaneously transmitting N respective symbols selected respectively from the N symbol constellations; and
a receiver, which is arranged to receive a composite symbol comprising a superposition of the N transmitted symbols, and to demodulate the received composite symbol using the joint constellation so as to reconstruct the data transferred from the N transmitters.
21. The system according to claim 20, wherein the N symbol constellations are defined by applying an optimization process responsively to the power constraint.
22. The system according to claim 21, wherein the optimization process comprises repeatedly generating random sets of the N transmitter constellations, evaluating a minimum Euclidean distance (DJVΠN) value of the produced joint constellation, and outputting a set of N transmitter constellations and joint constellation corresponding to a largest DMIN value.

23. The system according to claim 22, wherein the optimization process further comprises evaluating Hamming distances of the produced joint constellation, and outputting a set of N transmitter constellations and joint constellation having a minimal Hamming distance larger than a predefined threshold.
24. The system according to any of claims 20-23, wherein the N symbol constellations are defined so as to maximize distances in the signal space among joint constellation symbols of the joint constellation.
25. The system according to any of claims 20-23, wherein a first symbol constellation out of the N symbol constellations has a first number of constellation symbols, and wherein a second symbol constellation out of the N symbol constellations has a second number of constellation symbols different from the first number, so that respective first and second transmitters transmit the data at different respective data rates.
26. The system according to any of claims 20-23, wherein first and second transmitters out of the N transmitters are arranged to transmit at respective first and second power levels, so as to cause first and second symbols transmitted respectively by the first and second transmitters to be received by the receiver at different power levels.
27. The system according to any of claims 20-23, wherein the power constraint comprises a maximum value set to at least one of an instantaneous power and an average power of each of the N transmitters.
28. The system according to any of claims 20-23, wherein the N transmitters are arranged to adjust at least one of phases, magnitudes and timing offsets of the symbols transmitted from the N transmitters so as to produce the composite symbol.
29. The system according to any of claims 20-23, wherein the receiver comprises a maximum likelihood (ML) detector, which is arranged to demodulate the received composite symbol by selecting a symbol from among joint constellation symbols of the joint constellation responsively to the received composite symbol.
30. The system according to claim 29, wherein the ML detector comprises an approximated ML detector based on a symmetry of the joint constellation.
31. The system according to any of claims 20-23, wherein the N transmitters and the receiver are arranged to modify at least one of the joint constellation and the N symbol constellation responsively to a failure of one or more of the N transmitters.
32. The system according to any of claims 20-23, wherein the transmitters and the receiver are arranged to periodically redefine the N symbol constellations by re-assigning the symbols among the N symbol constellations.
33. A communication system, comprising:
a first plurality of transmitters, which are arranged to accept definitions of a respective first plurality of symbol constellations in a signal space, defined so as to produce a first joint constellation comprising superpositions of symbols selected from the first plurality of symbol constellations, and to transfer first data by simultaneously transmitting respective first symbols selected respectively from the first plurality of symbol constellations;
a second plurality of transmitters, which are arranged to accept definitions of a respective second plurality of symbol constellations in the signal space, defined so as to produce a second joint constellation comprising superpositions of symbols selected from the second plurality of symbol constellations, and to transfer second data by simultaneously transmitting respective second symbols selected respectively from the second plurality of symbol constellations, wherein the first and second symbols are multiplexed over a common communication channel using a multiple access method; and
a receiver, which is arranged to receive first and second composite symbols comprising respective superpositions of the first and second transmitted symbols, and to demodulate the first and second received composite symbols using the first and second joint constellations so as to reconstruct the first and second data transferred from the first and second pluralities of transmitters.
34. The system according to claim 33, wherein the multiple access method comprises a frequency division multiple access (FDMA) method, and wherein the first and second pluralities of the symbols are multiplexed by transmitting the first and second pluralities of the symbols on respective different first and second carrier frequencies.
35. The system according to claim 33, wherein the multiple access method comprises a time division multiple access (TDMA) method, and wherein the first and second pluralities of the symbols are multiplexed by transmitting the first and second pluralities of the symbols in respective different first and second time slots.
36. The system according to claim 33, wherein the multiple access method comprises a code division multiple access (CDMA) method, and wherein the first and second pluralities of the symbols are multiplexed by transmitting the first and second pluralities of the symbols using respective different first and second CDMA sequences.
37. The system according to claim 33, wherein the multiple access method comprises orthogonal frequency division multiplexing (OFDM), and wherein the first and second pluralities of the symbols are multiplexed by transmitting the first and second pluralities of the symbols on respective first and second OFDM sub-carriers of an OFDM signal.
38. A communication system, comprising:
N transmitters, N>2, which are arranged to accept definitions of N respective symbol constellations in a signal space, wherein at least one of the N symbol constellations is not a rotated and scaled replica of any other of the N symbol constellations, the symbol constellations defined so as to produce a joint constellation comprising superpositions of symbols selected from the N symbol constellations, and to transfer data by simultaneously transmitting N respective symbols selected respectively from the N symbol constellations; and a receiver, which is arranged to receive a composite symbol comprising a superposition of the N transmitted symbols, and to demodulate the received composite symbol using the joint constellation so as to reconstruct the data transferred from the N transmitters.