Modulation and demodulation method in layer-division multiplexing system, and receiver thereof

1. A demodulation method of a Layer-Division Multiplexing (LDM) system, comprising:

receiving an LDM modulation signal,

restoring a first-layer signal from the LDM modulation signal and remodulating the first-layer signal;

restoring and remodulating a second-layer signal by performing cancellation of an amplitude component of the first-layer signal from the LDM modulation signal using signaling information, independently of restoration and remodulation of the first-layer signal; and

restoring a third-layer signal using the first-layer signal, the second-layer signal, and the LDM modulation signal.

2. The demodulation method of claim 1 , wherein restoring and remodulating the first-layer signal is performed in parallel with restoring and remodulating the second-layer signal.

3. The demodulation method of claim 1 , wherein the cancellation is performed regardless of a result of restoration of the first-layer signal, and restoration and remodulation of the second-layer signal corresponds to Amplitude-Shift Keying (ASK).

4. The demodulation method of claim 3 , wherein the signaling information includes a first injection level that is used when the second-layer signal is modulated and a second injection level that is used when the third-layer signal is modulated.

5. The demodulation method of claim 4 , wherein remodulating the second-layer signal comprises restoring the second-layer signal from a modulated second-layer signal corresponding to a result of the cancellation using the second injection level.

6. The demodulation method of claim 1 , further comprising:

storing the received LDM modulation signal.

7. The demodulation method of claim 6 , wherein:

restoring the third-layer signal comprises removing a first LDM modulation signal from the LDM modulation signal,

the first LDM modulation signal is a signal acquired by combining a modulated first-layer signal and a modulated second-layer signal, a power level of which is changed based on a first injection level, and

the modulated first-layer signal is a signal acquired by modulating the first-layer signal using a first modulation method.

8. The demodulation method of claim 7 , wherein:

restoring the third-layer signal comprises restoring the third-layer signal from a signal from which the first LDM modulation signal is removed using a second injection level, and

the LDM modulation signal is a signal acquired by combining the first LDM modulation signal with a modulated third-layer signal, a power level of which is changed based on the second injection level.

9. A receiver of a Layer-Division Multiplexing (LDM) system, comprising:

a first-layer signal restoration and remodulation module for restoring a first-layer signal from an LDM modulation signal and remodulating the first-layer signal;

a second-layer signal restoration and remodulation module for restoring and remodulating a second-layer signal by performing cancellation of an amplitude component of the first-layer signal from the LDM modulation signal using signaling information independently of restoration and remodulation of the first-layer signal;

a third-layer restoration module for restoring a third-layer signal using the first-layer signal, the second-layer signal, and the LDM modulation signal; and

LDM signal storage for storing the LDM modulation signal,

wherein the first-layer signal restoration and remodulation module is operated in parallel with the second-layer signal restoration and remodulation module.

10. The receiver of claim 9 , wherein, in the LDM modulation signal, power of each of a modulated first-layer signal, a modulated second-layer signal, and a modulated third-layer signal is normalized to 1.

11. The receiver of claim 10 , wherein the second-layer signal restoration and remodulation module performs cancellation of the amplitude component of the first-layer signal from the normalized LDM modulation signal.

12. The receiver of claim 11 , wherein:

an amplitude of the first-layer signal is determined depending on a first injection level and a second injection level,

the first injection level is a value that is used in order to change a power level of the modulated second-layer signal when the LDM modulation signal is generated, and

the second injection level is a value that is used in order to change a power level of the modulated third-layer signal when the LDM modulation signal is generated.

13. The receiver of claim 9 , wherein the third-layer restoration module synchronizes starts of the LDM modulation signal, the first-layer signal, and the second-layer signal.

14. The receiver of claim 9 , wherein:

the first-layer signal restoration and remodulation module outputs the first-layer signal by demodulating a Quadrature Phase-Shift Keying (QPSK)-modulated signal;

the second-layer signal restoration and remodulation module outputs the second-layer signal by demodulating an Amplitude-Shift Keying (ASK)-modulated signal; and

the third-layer restoration module outputs the third-layer signal by demodulating a Quadrature Amplitude Modulation (QAM)-modulated signal.

15. A modulation method of a Layer-Division Multiplexing (LDM) system, comprising:

modulating a first-layer signal using a first modulation method,

modulating a second-layer signal using a second modulation method;

converting the modulated second-layer signal using a first injection level;

modulating a third-layer signal using a third modulation method;

converting the modulated third-layer signal using a second injection level; and

generating an LDM modulation signal by combining the modulated first-layer signal, the converted modulated second-layer signal, and the converted modulated third-layer signal,

wherein the first injection level and the second injection level are transmitted to a receiver as signaling information.

16. The modulation method of claim 15 , wherein:

the first modulation method is a Quadrature Phase-Shift Keying (QPSK) modulation method,

the second modulation method is an Amplitude-Shift Keying (ASK) modulation method, and

the third modulation method is a Quadrature Amplitude Modulation (QAM) method.

17. The modulation method of claim 15 , wherein the LDM modulation signal is generated using a two-layer multiplexing method.

18. The modulation method of claim 17 , wherein generating the LDM modulation signal comprises:

generating a first LDM modulation signal by combining the modulated first-layer signal with the converted modulated second-layer signal; and

generating a second LDM modulation signal by combining the first LDM modulation signal with the converted modulated third-layer signal.