Method and system for non-orthogonal multiple access communication
A bit-level operation may be implemented prior to modulation and resource element (RE) mapping in order to generate a NoMA transmission using standard (QAM, QPSK, BPSK, etc.) modulators. In this way, the bit-level operation is exploited to achieve the benefits of NoMA (e.g., improved spectral efficiency, reduced overhead, etc.) at significantly less signal processing and hardware implementation complexity. The bit-level operation is specifically designed to produce an output bit-stream that is longer than the input bit-stream, and that includes output bit-values that are computed as a function of the input bit-values such that when the output bit-stream is subjected to modulation (e.g., m-ary QAM, QPSK, BPSK), the resulting symbols emulate a spreading operation that would otherwise have been generated from the input bit-stream, either by a NoMA-specific modulator or by a symbol-domain spreading operation.
1. A method for using a standard modulator to enable non-orthogonal multiple access (NoMA) communication, the method comprising:
generating, by a transmitter, an output bit-stream from an input bit-stream to emulate a symbol-domain operation associated with a multiple access signature without error-detection/correction in a bit domain, wherein such that a length of the output bit-stream is greater than a length of the input bit-stream, the input bit-stream being an error-detection/correction encoded bit-stream;
modulating, by the transmitter, the output bit-stream in accordance with the standard modulator to obtain a sequence of symbols, wherein a value of at least one bit of the input bit-stream is associated with at least two symbols of the sequence of symbols, and wherein the standard modulator is one of Quadrature Amplitude Modulation (QAM) modulator, a Binary
π
2
-
BPSK
Phase Shift Keying (BPSK) modulator, modulator, and a Quadrature Phase Shift Keying (QPSK) modulator;
mapping, by the transmitter, the sequence of symbols to resource elements to obtain a NoMA signal; and
transmitting the NoMA signal to a receiver.
2. The method of claim 1 , wherein the sequence of symbols comprises a plurality of different subsets of symbols, and at least two subsets are associated with different bits in the input bit-stream.
3. The method of claim 1 , wherein the sequence of symbols comprises a plurality of different subsets of symbols, and a relationship between one or both of a phase and an amplitude of symbols in a subset of the plurality depends on the input bit-stream, the relationship between the one or both of the phase and the amplitude of symbols in the subset of the plurality being at least one of:
a relationship between phases of symbols in the subset of the plurality;
a relationship between amplitudes of symbols in the subset of the plurality;
a relationship between a phase and an amplitude of a same symbol in the subset of the plurality; or
a relationship between a phase of a first symbol in the subset of the plurality and an amplitude of a second symbol in the subset of the plurality.
4. The method of claim 1 , wherein generating the output bit-stream from the input bit-stream includes applying bit-domain linear spreading to the input bit-stream.
5. The method of claim 1 , further comprising encoding, by a forward error correction (FEC) encoder, an unmodified input bit-stream to generate the error-detection/correction encoded input bit-stream.
6. The method of claim 1 , wherein the receiver is a user equipment (UE), and wherein the method further comprises transmitting an indication of a multiple access (MA) signature to the UE, the MA signature configuring the UE to distinguish the UE's uplink transmission from other UEs' uplink transmissions.
7. The method of claim 1 , wherein the receiver is a user equipment (UE), and wherein the method further comprises transmitting an indication of a multiple access (MA) signature to the UE, the MA signature configuring the UE to to decode a downlink NoMA transmission.
8. The method of claim 1 , further comprising:
selecting, by the transmitter, the multiple access signature in accordance with a radio node temporary identifier (RNTI).
9. The method of claim 1 , further comprising:
selecting, by the transmitter, the multiple access signature in accordance with an index associated with a demodulation reference signal (DM-RS) pattern.
10. The method of claim 1 , wherein the symbol-domain operation associated with the multiple access signature provides liner spreading in a symbol domain.
11. An apparatus comprising:
a processor; and
a non-transitory computer readable storage medium storing programming for execution by the processor, the programming including instructions to:
generate an output bit-stream from an input bit-stream to emulate a symbol-domain operation associated with a multiple access signature without error-detection/correction in a bit-domain, wherein a length of the output bit-stream is greater than a length of the input bit-stream, the input bit-stream being an error-detection/correction encoded bit-stream;
modulate the output bit-stream in accordance with a standard modulator to obtain a sequence of symbols, wherein a value of at least one bit of the input bit-stream is associated with at least two symbols of the sequence of symbols, and wherein the standard modulator is one of Quadrature Amplitude Modulation (QAM) modulator, a
π
2
-
BPSK
Binary Phase Shift Keying (BPSK) modulator, a modulator, and a Quadrature Phase Shift Keying (QPSK) modulator;
map the sequence of symbols to resource elements to obtain a non-orthogonal multiple access (NoMA) signal; and
transmit the NoMA signal to a receiver.
12. The apparatus of claim 11 , wherein the sequence of symbols comprises a plurality of different subsets of symbols, and at least two subsets are associated with different bits in the input bit-stream.
13. The apparatus of claim 11 , wherein the sequence of symbols comprises a plurality of different subsets of symbols, and a relationship between one or both of a phase and an amplitude of symbols in a subset of the plurality depends on the input bit-stream, the relationship between the one or both of the phase and the amplitude of symbols in the subset of the plurality being at least one of:
a relationship between phases of symbols in the subset of the plurality;
a relationship between amplitudes of symbols in the subset of the plurality;
a relationship between a phase and an amplitude of a same symbol in the subset of the plurality; or
a relationship between a phase of a first symbol in the subset of the plurality and an amplitude of a second symbol in the subset of the plurality.
14. The apparatus of claim 11 , wherein generating the output bit-stream from the input bit-stream includes applying bit-domain linear spreading to the input bit-stream.
15. The apparatus of claim 11 , wherein the programming further includes instructions to encode an unmodified input bit-stream using a forward error correction (FEC) encoder to generate the error-detection/correction encoded input bit-stream.
16. The apparatus of claim 11 , wherein different NoMA signals are transmitted to or by the same user equipment (UE).
17. The apparatus of claim 11 , wherein different NoMA signals are transmitted to or by different user equipments (UEs).
18. The apparatus of claim 11 , wherein the receiver is a user equipment (UE), and wherein the programming further includes instructions to transmit an indication of a multiple access (MA) signature to the UE, the MA signature configuring the UE to distinguish the UE's uplink transmission from other UEs' uplink transmissions.
19. The apparatus of claim 11 , wherein the receiver is a user equipment (UE), and wherein the programming further includes instructions to transmit an indication of a multiple access (MA) signature to the UE, the MA signature configuring the UE to decode a downlink NoMA transmission.
20. The apparatus of claim 11 , wherein the programming further includes instructions to:
select the multiple access signature in accordance with a radio node temporary identifier (RNTI).
21. The apparatus of claim 11 , wherein the programming further includes instructions to:
select the multiple access signature in accordance with an index associated with a demodulation reference signal (DM-RS) pattern.
22. The apparatus of claim 11 , wherein the symbol-domain operation associated with the multiple access signature provides liner spreading in a symbol domain.
23. A computer program product comprising a non-transitory computer readable storage medium storing programming, the programming including instructions to:
generate an output bit-stream from an input bit-stream to emulate a symbol-domain operation associated with a multiple access signature without error-detection/correction in a bit-domain, wherein a length of the output bit-stream is greater than a length of the input bit-stream, the input bit-stream being an error-detection/correction encoded bit-stream;
modulate the output bit-stream in accordance with a standard modulator to obtain a sequence of symbols, wherein a value of at least one bit of the input bit-stream is associated with at least two symbols of the sequence of symbols, and wherein the standard modulator is one of Quadrature Amplitude Modulation (QAM) modulator, a
π
2
-
BPSK
Binary Phase Shift Keying (BPSK) modulator, a modulator, and a Quadrature Phase Shift Keying (QPSK) modulator;
map the sequence of symbols to resource elements to obtain a non-orthogonal multiple access (NoMA) signal; and
transmit the NoMA signal to a receiver.