METHOD FOR TRANSMITTING AND RECEIVING SIGNAL IN WIRELESS COMMUNICATION SYSTEM AND APPARATUS FOR PERFORMING SAME

• US 20180076993A1
• Filed: 03/09/2016
• Published: 03/15/2018
• Est. Priority Date: 03/09/2015
• Status: Active Grant

• Current Assignee: LG Electronics, Inc. (LG Corporation)
• Original Assignee: LG Electronics, Inc. (LG Corporation)
• Inventors: SEO, Inkwon, KIM, Kijun, KIM, Hyungtae
• Granted Patent: US 10,498,574 B2
• Time in Patent Office: Days
• CPC Class Codes: H04J 11/004 using regenerative subtractive interference cancellation
• CPC Class Codes: H04J 99/00 Subject matter not provided for in other groups of this subclass
• CPC Class Codes: H04L 27/26 Systems using multi-frequency codes H04L27/32 takes precedence
• CPC Class Codes: H04L 27/2604 Multiresolution systems by means of multiresolution subcarriers H04L27/183, H04L27/3488
• CPC Class Codes: H04L 27/2655 Synchronisation arrangements
• CPC Class Codes: H04L 27/34 Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
• CPC Class Codes: H04L 27/36 Modulator circuits; Transmitter circuits
• CPC Class Codes: H04L 27/38 Demodulator circuits; Receiver circuits
• CPC Class Codes: H04W 52/18 TPC being performed according to specific parameters

Abstract

A method for receiving a signal by a first terminal in a wireless communication system supporting non-orthogonal multiple access (NOMA) according to an embodiment of the present invention comprises the steps of: receiving a NOMA signal in which signals for each of the first terminal and a second terminal belonging to the same NOMA pair are superposed; and demodulating the signal for the first terminal from the NOMA signal, using at least a part of a NOMA constellation which is configured by considering downlink transmission power and a modulation order for the second terminal, wherein only a bit corresponding to one digit is differently configured between the bit sequences of NOMA constellation points adjacent to each other in the NOMA constellation, and the complex coordinates (I, Q) of the NOMA constellation points are determined on the basis of a combination of downlink transmission power for the first terminal and the downlink transmission power for the second terminal.

Claims

1. A method for receiving a signal by a first user equipment (UE) in a wireless communication system supporting non-orthogonal multiple access (NOMA), the method comprising:

receiving a NOMA signal in which a signal for the first UE and a signal for a second UE are superposed, the first UE and the second UE belonging to a same NOMA pair; and

demodulating the signal for the first UE from the NOMA signal using at least part of a NOMA constellation configured in consideration of downlink transmit power and modulation order for the second UE,

wherein only a bit corresponding to one digit is differently configured between the bit sequences of NOMA constellation points adjacent to each other in the NOMA constellation, and

wherein complex coordinates (I, Q) of NOMA constellation points are determined based on a combination of downlink transmit power for the first UE and the downlink transmit power for the second UE.

2. The method of claim 1, wherein demodulating the signal for the first UE comprises either demodulating the signal for the first UE in a maximum likelihood (ML) manner by constructing an entirety of the NOMA constellation or demodulating the signal for the first UE in a successive interference cancellation (SIC) scheme by reconstructing constellation points corresponding to a part of the NOMA constellation.

3. The method of claim 1, wherein upper or lower N bits (c₁c₂ . . . c_N) in a bit sequence with a length of (M+N), which is mapped to each of the NOMA constellation points, are defined according to the following equation:

c₁=(((a₁{circle around (x)}a₃){circle around (x)}a₅) . . . {circle around (x)}a<sub>M−

1</sub>){circle around (z)}b₁

c₂=(((a₂{circle around (x)}a₄){circle around (x)}a₆) . . . {circle around (x)}a_M){circle around (z)}b₂

c_i=b_i(3≦

i≦

N), 

 

[Equation]

where ‘

{circle around (x)}’ and

‘

{circle around (z)}’

are identical or different predetermined bit-wise operations, ‘

b₁ b₂ . . . b_N’

is a bit sequence for the first UE, ‘

a₁ a₂ . . . a_M’

is a bit sequence for the second UE, ‘

M’

is the modulation order of the second UE, and ‘

N’

is modulation order of the first UE.

4. The method of claim 3, wherein remaining M bits in the (M+N)-length bit sequence are configured to be identical to the bit sequence of the second UE, ‘

a₁ a₂ . . . a_M’ and

wherein the predetermined bit-wise operations include at least one of an exclusive OR (XOR) operation and a not exclusive OR (XNOR) operation.

5. The method of claim 1, further comprising:

demodulating the signal for the second UE using a first constellation corresponding to the modulation order for the second UE;

cancelling the signal for the second UE from the NOMA signal using a result obtained by demodulating the signal for the second UE; and

demodulating and decoding the signal for the first UE using a residual signal after cancelling and a second constellation corresponding to modulation order for the first UE.

6. The method of claim 5, further comprising:

performing a not exclusive OR (XNOR) operation between results of the XNOR operation of odd-indexed bits of a bit sequence of the second UE and respective first bits of bit sequences of a reference constellation corresponding to the modulation order of the first UE;

performing the XNOR operation between results of the XNOR operation of even-indexed bits of the bit sequence of the second UE and respective second bits of the bit sequences of the reference constellation; and

generating a second constellation by inserting results of the XNOR operation for the respective first bits and results of the XNOR operation for the respective second bits into the reference constellation.

7. The method of claim 1, wherein the NOMA constellation includes M² constellation point groups, each having N² constellation points, where ‘

N’

is modulation order of the first UE and ‘

M’

is the modulation order of the second UE, and

wherein spacing between N² constellation points belonging to a same constellation point group is determined based on the downlink transmit power for the first UE and spacing between centers of the M² constellation point groups is determined based on the downlink transmit power of the second UE.

8. The method of claim 1, further comprising:

transmitting information on a receiver type of the first UE to a base station,

wherein the receiver type includes at least one of a maximum likelihood (ML) type and a successive interference cancellation (SIC) type.

9. A first user equipment (UE) for receiving a signal in a wireless communication system supporting non-orthogonal multiple access (NOMA), the first UE comprising:

a receiver configured to receive a NOMA signal in which a signal for the first UE and a signal for a second UE are superposed, the first UE and the second UE belonging to a same NOMA pair; and

a processor configured to demodulate the signal for the first UE from the NOMA signal using at least part of a NOMA constellation configured in consideration of downlink transmit power and modulation order for the second UE,

wherein only a bit corresponding to one digit is differently configured between the bit sequences of NOMA constellation points adjacent to each other in the NOMA constellation, and

wherein complex coordinates (I, Q) of NOMA constellation points are determined based on a combination of downlink transmit power for the first UE and the downlink transmit power for the second UE.

10. A method for transmitting a signal by a base station (BS) in a wireless communication system supporting non-orthogonal multiple access (NOMA), the method comprising:

determining a NOMA constellation by considering downlink transmit power and modulation order for each of a first user equipment (UE) and a second UE which belong to a same NOMA pair;

modulating a NOMA signal in which a signal for the first UE and a signal second UE are superposed using the NOMA constellation; and

transmitting the NOMA signal,

wherein only a bit corresponding to one digit is differently configured between the bit sequences of NOMA constellation points adjacent to each other in the NOMA constellation, and

wherein complex coordinates (I, Q) of NOMA constellation points are determined based on a combination of downlink transmit power for the first UE and the downlink transmit power for the second UE.

11. The method of claim 10, wherein upper or lower N bits (c₁ c₂ . . . c_N) in a bit sequence with a length of (M+N), which is mapped to each of the NOMA constellation points, are defined according to the following equation:

c₁=(((a₁{circle around (x)}a₃){circle around (x)}a₅) . . . {circle around (x)}a<sub>M−

1</sub>){circle around (z)}b₁

c₂=(((a₂{circle around (x)}a₄){circle around (x)}a₆) . . . {circle around (x)}a_M){circle around (z)}b₂

c_i=b_i(3≦

i≦

N), 

 

[Equation]

where ‘

{circle around (x)}’ and

‘

{circle around (z)}’

are identical or different predetermined bit-wise operations, ‘

b₁ b₂ . . . b_N’

is a bit sequence for the first UE, ‘

a₁ a₂ . . . a_M’

is a bit sequence for the second UE, ‘

M’

is the modulation order of the second UE, and ‘

N’

is the modulation order of the first UE.

12. The method of claim 11,

wherein remaining M bits in the (M+N)-length bit sequence are configured to be identical to the bit sequence of the second UE, ‘

a₁ a₂ . . . a_M’ and

wherein the predetermined bit-wise operations include at least one of an exclusive OR (XOR) operation and a not exclusive OR (XNOR) operation.

13. The method of claim 10,

wherein the NOMA constellation includes M² constellation point groups, each having N² constellation points, where ‘

N’

is the modulation order of the first UE and ‘

M’

is the modulation order of the second UE, and

wherein spacing between N² constellation points belonging to a same constellation point group is determined based on the downlink transmit power for the first UE and spacing between centers of the M² constellation point groups is determined based on the downlink transmit power of the second UE.

14. The method of claim 10,

wherein a same beam pattern is applied to the first and second UEs belonging to the same NOMA pair and

wherein a difference between the downlink transmit power of the first and second UEs is equal to or greater than a predetermined threshold.

15. The method of claim 10, further comprising:

signaling, to a UE with lower downlink transmit power among the first and second UEs, information on modulation order and downlink transmit power of the other UE with higher downlink transmit power.