Method and apparatus for transmitting and receiving signal using non-orthogonal multiple access in wireless communication system
The present specification provides an operation method of a base station for transmitting and receiving a signal using non-orthogonal multiple access (NOMA) in a wireless communication system. The method comprises the steps of: setting a first modulation scheme and a first transmission power for a first signal to be transmitted to a first user equipment; setting a second modulation scheme and a second transmission power for a second signal to be transmitted to a second user equipment; overlapping the first signal and the second signal; and transmitting a signal obtained by overlapping, wherein the transmission of the overlapped signal uses an overlapping constellation defined in advance or configured by a predetermined notation.
1. A method for transmitting and receiving signals using non-orthogonal multiple access (NOMA) in a wireless communication system, the method performed by a base station (BS) comprising: configuring a first modulation scheme and first transmission power for a first signal to be transmitted to a first user equipment (UE); configuring a second modulation scheme and second transmission power for a second signal to be transmitted to a second UE; generating a superposed constellation based on a first constellation and a second constellation, generating the first signal based on the first constellation, generating the second signal based on the second constellation, and generating a superposed signal based on the superposed constellation; and transmitting the superposed signal to the first UE and the second UE, wherein at least one of the first constellation or the second constellation is rotated by a predetermined value based on a first precoding vector applied to the first UE and a second precoding vector applied to the second UE when the first precoding vector is different from the second precoding vector, wherein the superposed constellation is generated by superposing the first constellation and the second constellation based on a predetermined rule, and wherein the predetermined rule is determined based on the first precoding vector, the second precoding vector, the first modulation scheme and the second modulation scheme.
2. The method of claim 1 , wherein the superposed constellation is configured such that a difference between bit values regarding a bit sequence of adjacent points is 1 bit or less.
3. The method of claim 1 , wherein when a specific column of the first precoding vector and a specific column of the second precoding vector are not the same, the first precoding vector is different from the second precoding vector.
4. The method of claim 1 , further comprising: transmitting control information related to cancellation of interference generated by the first signal to the first UE.
5. The method of claim 4 , wherein the control information includes at least one of the predetermined value and a precoding vector index representing a precoding vector of the first UE and the second UE.
6. The method of claim 1 , wherein the predetermined rule uses a relation between a bit value constituting a bit sequence corresponding to the modulation symbol of the first signal and a bit value constituting a bit sequence corresponding to the modulation symbol of the second signal.
7. The method of claim 1 , wherein the first transmission power is set to be lower than the second transmission power.
8. The method of claim 1 , wherein a distance between the first UE and the BS is shorter than a distance between the second UE and the BS.
9. The method of claim 1 , wherein the first modulation scheme and the second modulation scheme each are any one of QPSK, 16 QAM, and 64 QAM.
10. The method of claim 1 , wherein the superposed constellation is generated based on a second rule when the first precoding vector is the same as the second precoding vector, when both of the first constellation and the second constellation are rotated by the predetermined value, and wherein the second rule is different from the predetermined rule.
11. The method of claim 1 , wherein the predetermined value is 45°.
12. A base station (BS) for transmitting and receiving data using non-orthogonal multiple access (NOMA) in a wireless communication system, the base station comprising: a transmitter and receiver; and a processor functionally connected to the transmitter and receiver, wherein the processor is configured to: configure a first modulation scheme and first transmission power for a first signal to be transmitted to a first user equipment (UE), configure a second modulation scheme and second transmission power for a second signal to be transmitted to a second UE, generate a superposed constellation based on a first constellation and a second constellation, generate the first signal based on the first constellation, generate the second signal based on the second constellation, and generate a superposed signal based on the superposed constellation; and control the transmitter to transmit the superposed signal to the first UE and the second UE, wherein at least one of the first constellation or the second constellation is rotated by a predetermined value based on a first precoding vector applied to the first UE and a second precoding vector applied to the second UE when the first precoding vector is different from the second precoding vector, wherein the superposed constellation is generated by superposing the first constellation and the second constellation based on a predetermined rule, and wherein the predetermined rule is determined based on the first precoding vector, the second precoding vector, the first modulation scheme and the second modulation scheme.