Data transmission system for multiplexing a plurality of pieces of data in a layered division multiplexing (LDM) method and transmitting multiplexed data, reception device used in the data transmission system, and data transmission method therefor
[Problem] To propose a technology capable of appropriately demodulating, in a receiving device, a plurality of pieces of data multiplexed through the quasi-synchronous LDM method. [Solution] A transmission device generates a UL modulated signal by using an IFFT process of N UL points, generates an LL modulated signal by using an IFFT process of N LL points different from the N UL points, and transmits signals obtained by timing-adjusting the modulated signals such that the start timings thereof coincide with each other in a predetermined cycle, and combining the timing-adjusted signals at a predetermined power ratio. In addition, the receiving device performs an N UL point FFT process on the reception signal from the transmitting device, reproduces UL and generates UL reception replica, on the basis of the result, and performs an N LL point FFT process on a signal obtained by subtracting the UL reception replica from the reception signal, and reproduces LL on the basis of the result.
1. A data transmission system for multiplexing a plurality of pieces of data in a layered division multiplexing (LDM) method and transmitting multiplexed data, the data transmission system comprising:
a transmission device configured to generate a modulated signal of first data using Inverse Fast Fourier Transform (IFFT) processing of a first number of points, generate a modulated signal of second data using IFFT processing of a second number of points different from the first number of points, and transmit a composite of these modulated signals which are adjusted in timing so that their start timings match at a predetermined cycle; and
a reception device configured to perform Fast Fourier Transform (FFT) processing of the first number of points on the signal received from the transmission device, reproduce the first data based on a result of the FFT processing while generating a reception replica of the modulated signal of the first data, perform FFT processing of the second number of points on a signal obtained by subtracting the reception replica from the received signal, and reproduce the second data based on a result of the FFT processing.
2. The data transmission system of claim 1 , wherein the transmission device performs first error correction encoding processing and interleaving processing on the first data, performs second error correction encoding processing on a result of the interleaving processing, and then performs the IFFT processing of the first number of points to generate the modulated signal of the first data; and
the reception device performs first error correction processing corresponding to the first error correction encoding processing and deinterleaving processing corresponding to the interleaving processing based on a result of the FFT processing of the first number of points to reproduce the first data, while performing second error correction processing corresponding to the second error correction encoding processing and IFFT processing of the first number of points based on the result of the FFT processing of the first number of points to generate the reception replica.
3. The data transmission system of claim 2 , wherein the reception device estimates a transmission path characteristic between the transmission device and the reception device using a result of the second error correction processing and generates the reception replica using the estimated transmission path characteristic.
4. The data transmission system of claim 3 , wherein the reception device reproduces at least one of the first data or the second data using the estimated transmission path characteristic.
5. The data transmission system of claim 3 , wherein the reception device estimates the transmission path characteristic from the first number of points, rate-converts the estimated transmission path characteristic, and reproduces the second data based on the second number of points by using the rate-converted transmission path characteristic.
6. The data transmission system of claim 2 , wherein the transmission device allocates a result of the second error correction encoding processing to an auxiliary channel (AC) carrier provided as a spare carrier in a frequency domain for transmission of the first data and the second data, or to an extended area added to at least one side frequency band of the frequency domain.
7. A reception device used in a data transmission system for multiplexing a plurality of pieces of data in a layered division multiplexing (LDM) method and transmitting multiplexed data, the reception device configured to:
receive, from a transmission device, a composite of a modulated signal of first data generated using Inverse Fast Fourier Transform (IFFT) processing of a first number of points and a modulated signal of second data generated using IFFT processing of a second number of points different from the first number of points, the modulated signals of first data and second data being adjusted in timing so that their start timings match at a predetermined cycle;
perform Fast Fourier Transform (FFT) processing of the first number of points on the received signal;
reproduce the first data based on a result of the FFT processing while generating a reception replica of the modulated signal of the first data;
perform FFT processing of the second number of points on a signal obtained by subtracting the reception replica from the received signal; and
reproduce the second data based on a result of the FFT processing.
8. A data transmission method of multiplexing a plurality of pieces of data in a layered division multiplexing (LDM) method and transmitting multiplexed data, the data transmission method comprising:
by a transmission device, generating a modulated signal of first data using Inverse Fast Fourier Transform (IFFT) processing of a first number of points, generating a modulated signal of second data using IFFT processing of a second number of points different from the first number of points, and transmitting a composite of these modulated signals which are adjusted in timing so that their start timings match at a predetermined cycle; and
by a reception device, performing Fast Fourier Transform (FFT) processing of the first number of points on the signal received from the transmission device, reproducing the first data based on a result of the FFT processing while generating a reception replica of the modulated signal of the first data, performing FFT processing of the second number of points on a signal obtained by subtracting the reception replica from the received signal, and reproducing the second data based on a result of the FFT processing.