Digital transmission system for transmitting additional data and method thereof

1. A digital transmission system comprising:

a transmission signal generation unit which generates transmission signals by loading first data to be transmitted on multi-carrier waves; and

an additional data processing unit which loads a plurality of low power signals each expressing additional data on the multi-carrier waves on which the first data was loaded by the transmission signal generation unit, the additional data processing unit divides the multi-carrier waves into a plurality of groups, and loads the plurality of low power signals expressing respective sets of additional data on each of the plurality of groups, so that a plurality set of additional data are transmitted on the multi-carrier waves with the first data,

wherein a first group including at least one low power signal among the plurality of low power signals expresses compensation data for canceling a peak-to-average power ratio in a location where the peak-to-average power ratio is greater than a threshold value,

wherein a second group of low power signals among the plurality of low power signals express additional information to be provided to a user, different from information included in the first data, and

wherein the digital transmission system transmits the generated transmission signals loaded with the first data and the additional data.

2. The digital transmission system of claim 1 , wherein the transmission signal generation unit is further configured to generate the transmission signals using an Orthogonal Frequency Division Multiplexing scheme by loading the first data on the multi-carrier waves.

3. The digital transmission system of claim 2 , wherein the additional data processing unit is further configured to load the second group of low power signals on the multi-carrier waves using at least one of a pseudo random sequence, a gold sequence, and a Kasami sequence.

4. The digital transmission system of claim 2 , wherein the additional data processing unit is further configured to encode the second group of low power signals and load the encoded low power signals on the multi-carrier waves.

5. The digital transmission system of claim 2 , wherein the additional data processing unit is further configured to load the second group of low power signals on at least one of an in-band area, in which the first data were inserted, and an out-band area, which forms a guard between channels, in the multi-carrier waves.

6. The digital transmission system of claim 2 , wherein the transmission signal generation unit further comprises:

a data splitter which performs modulation to load the first data on the multi-carrier waves;

an inverse fast Fourier transform (IFFT) processing unit which performs an IFFT to the multi-carrier waves generated by the data splitter;

a parallel-to-serial converter which converts the IFFT-processed multi-carrier waves into a single serial signal; and

a digital-to-analog converter which converts the serial signal from a digital format to an analog format.

7. The digital transmission system of claim 6 , wherein the additional data processing unit further comprises:

a reception unit which receives the additional data from an external source, and generates the low power signals in a frequency domain; and

a signal insertion unit which loads the low power signals on the multi-carrier waves generated by the data splitter.

8. The digital transmission system of claim 6 , wherein the additional data processing unit further comprises:

a reception unit which receives the additional data from an external source, and generates the low power signals in a time domain; and

a signal insertion unit which loads the low power signals on the IFFT-processed multi-carrier waves output by the IFFT processing unit.

9. The digital transmission system of claim 6 , wherein the additional data processing unit further comprises:

a reception unit which receives the additional data from an external source, and generates the low power signals in a time domain; and

a signal insertion unit which loads the low power signals on analog signals output by the digital-to-analog converter.

10. The digital transmission system of claim 1 , wherein an electric power of the second group of low power signals expressing the additional data are less than an electric power of the multi-carrier waves on which the first data was loaded.

11. A digital transmission method comprising:

generating transmission signals, in a transmission signal generation unit, by loading first data to be transmitted on multi-carrier waves;

loading a plurality of low power signals each expressing additional data on the multi-carrier waves on which the first data was loaded by the transmission signal generation unit, wherein said loading the low power signals each expressing the additional data on the multi-carrier waves comprises dividing the multi-carrier waves into a plurality of groups, and loading the low power signals expressing respective sets of additional data on each of the plurality of groups, so that a plurality set of additional data are transmitted on the multi-carrier waves with the first data; and

transmitting the generated transmission signals including the first data and the additional data,

wherein a first group including at least one low power signal among the plurality of low power signals expresses compensation data for canceling a peak-to-average power ratio in a location where the peak-to-average power ratio is greater than a threshold value, and

wherein a second group of low power signals among the plurality of low power signals express additional information to be provided to a user, different from information included in the first data.

12. The method of claim 11 , wherein the generating the transmission signals further comprises generating the transmission signals using an Orthogonal Frequency Division Multiplexing method by loading the first data on the multi-carrier waves.

13. The method of claim 12 , wherein the loading the low power signals further comprises loading the second group of low power signals on the multi-carrier waves using at least one of a pseudo random sequence, a gold sequence, and a Kasami sequence.

14. The method of claim 12 , wherein the loading the low power signals further comprises encoding the second group of low power signals and loading the encoded low power signals on the multi-carrier waves.

15. The method of claim 12 , wherein the loading the low power signals further comprises loading the second group of low power signals on at least one of an in-band area, in which the first data were inserted, and an out-band area, which forms a guard between channels, in the multi-carrier waves.

16. The method of claim 12 , wherein the generating the transmission signals further comprises:

generating the multi-carrier waves, in a data splitter, by performing modulation to load the first data on the multi-carrier waves;

performing an inverse fast Fourier transform (IFFT) to the multi-carrier waves output by the data splitter;

converting the IFFT-processed multi-carrier waves into a single serial signal; and

converting the serial signal from a digital format to an analog format.

17. The method of claim 16 , wherein the loading the low power signals expressing the additional data further comprises:

receiving the additional data from an external source, and generating the low power signals in a frequency domain; and

loading the low power signals on the multi-carrier waves in the frequency domain.

18. The method of claim 16 , wherein the loading the low power signals expressing the additional data further comprises:

receiving the additional data from an external source, and generating the low power signals in a time domain; and

loading the low power signals on the IFFT-processed multi-carrier signals in the time domain.

19. The method of claim 16 , wherein the loading the low power signals expressing the additional data further comprises:

receiving the additional data from an external source, and generating the low power signals in a time domain; and

loading the low power signals on the digital-to-analog-converted signals in the time domain.

20. The method of claim 11 , wherein an electric power of the second group of low power signal expressing the additional data are less than an electric power of the multi-carrier waves on which the first data was loaded.