JP7219158B2 - DATA TRANSMISSION SYSTEM, RECEIVER AND DATA TRANSMISSION METHOD - Google Patents

Description

The present invention relates to a data transmission system for multiplexing and transmitting a plurality of data by hierarchical division multiplexing.

As part of the transition to next-generation terrestrial digital broadcasting, studies are progressing on a layered division multiplexing (LDM) system that transmits broadcast waves of a system different from the current 2K broadcasting by sharing frequency and time. there is In Non-Patent Document 1, the upper layer (Upper Layer; UL) and the lower layer (Lower Layer; LL) are OFDM (Orthogonal Frequency Division Multiplexing) with the same number of FFT (Fast Fourier Transform) points. ) and multiplex UL and LL on the same subcarrier at different levels. Also, Non-Patent Document 2 proposes a method of OFDM-modulating UL and LL with different numbers of FFT points and multiplexing them in the time domain. Hereinafter, the former method (Non-Patent Document 1) will be referred to as “synchronous LDM”, and the latter method (Non-Patent Document 2) will be referred to as “quasi-synchronous LDM”.

In quasi-synchronous LDM, as shown in FIG. 3, for UL, for example, 8192 FFT points are used to generate effective symbols, and a 1024-sample guard interval is added to generate 9216-sample OFDM symbols. On the other hand, for LL, 32768 FFT points are used to generate effective symbols, and by adding the same guard interval of 1024 samples as in UL, OFDM symbols of 33792 samples are generated. In this case, the integer ratio of 11:3 between the UL symbol and the LL symbol is the lowest common multiple, and the start timings of the UL symbols and the LL symbols match at a predetermined cycle.

Thus, in quasi-synchronous LDM, the guard interval lengths of UL and LL are the same, and the effective symbol length of LL is longer than that of UL. However, LL can improve the bit rate. Taking advantage of this feature, Non-Patent Document 2 proposes applying the quasi-synchronous LDM to the next-generation digital terrestrial system. Although Non-Patent Document 2 describes the efficiency and characteristics of quasi-synchronous LDM, it does not clarify the detailed demodulation scheme of quasi-synchronous LDM.

Akihiko Sato, 11 others, "Study on application of LDM for next-generation terrestrial broadcasting", Institute of Image Information and Television Engineers Technical Report, vol. 41, no. 6, BCT2017-34, pp.45-48, February 2017 Hiromasa Okada, 6 others, “Study on improvement of various problems when applying LDM to terrestrial digital broadcasting -Study on new broadcasting method reception area expansion method and synchronization method-”, Institute of Image Information and Television Engineers Technical Report, vol. 42, no. 28, BCT2018-76, pp.13-16, September 2018

In synchronous LDM, the same FFT time window is provided for both the UL and LL received signals, and by performing FFT on the signal within the FFT time window, each subcarrier maintains the orthogonal relationship and the frequency domain is converted to a signal. However, since the number of FFT points differs between UL and LL in quasi-synchronous LDM, the orthogonal relationship between subcarriers is lost, and demodulation cannot be performed using the same method as in synchronous LDM.

Similarly to the synchronous LDM receiver, the quasi-synchronous LDM receiver generates a replica of the UL received signal and subtracts it from the received signal to extract the LL signal. If the replica of the UL received signal cannot be generated with high accuracy, the quality of the LL signal that can be extracted from the received signal will be degraded, and demodulation of the LL signal will be hindered.

The present invention has been made in view of the conventional circumstances as described above, and an object of the present invention is to propose a technique that enables a receiving apparatus to generate a replica of a UL received signal with high accuracy.

In order to achieve the above objects, the present invention has a data transmission system configured as follows.
That is, in a data transmission system that multiplexes and transmits a plurality of data using a hierarchical division multiplexing method, a first IFFT section performs IFFT processing of a first number of points on first data, and a first IFFT section performs IFFT processing on second data. A second IFFT unit that performs IFFT processing of two points, a modulated signal of the first data generated using the IFFT processing of the first number of points, and the IFFT processing of the second number of points. a transmitter for synthesizing the modulated signal of the second data by adjusting the timing so that each start timing coincides with a predetermined period; a receiving unit for receiving a signal from the transmitting device; a first FFT unit for performing FFT processing of the first number of points on a signal received by the receiving unit; and FFT processing of the first number of points. a reception replica generation unit for generating a reception replica of the modulated signal of the first data based on the result of; a subtraction unit for subtracting the reception replica from the reception signal; a receiving device having a second FFT unit that performs FFT processing of a second number of points, wherein the reception replica generation unit includes a signal from the first IFFT unit of the transmitting device to the subtracting unit of the receiving device The reception replica is generated based on comprehensive transmission path characteristics.

Here, the overall transmission path characteristics are the characteristics of a transmission filter interposed between the first IFFT section and the transmission section of the transmission device, and the characteristics of the transmission filter between the transmission device and the reception device. and characteristics of a reception filter interposed between the receiving section and the subtracting section of the receiving device.

Further, the receiving device includes a transmission path estimating unit for estimating transmission path characteristics of the section based on the result of the FFT processing for the first number of points; and a third IFFT unit that performs IFFT processing with a number of one point, and the reception replica generator performs the above for the modulated signal of the first data regenerated using the third IFFT unit. a second transmission filter that performs filter processing corresponding to the transmission filter; a delay profile generation unit that generates a delay profile that is an impulse response based on the transmission path characteristics of the section estimated by the transmission path estimation unit; A convolution unit that performs a convolution operation of the delay profile on the output of the second transmission filter, and a second reception filter that performs filter processing corresponding to the reception filter on the output of the convolution unit, The output of the second reception filter may be output as the reception precursor.

Further, the delay profile generation unit may generate the delay profile by converting the transmission path characteristic of the section from a frequency domain signal to a time domain signal.

Further, the delay profile generation unit may be configured to generate the delay profile by removing noise components from the transmission path characteristics of the section after the conversion.

ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to generate|occur|produce the replica of a UL received signal with high precision in a receiver.

1 is a diagram showing a configuration example of a transmission device in a data transmission system according to an embodiment of the present invention; FIG. 1 is a diagram showing a configuration example of a receiving device in a data transmission system according to one embodiment of the present invention; FIG. FIG. 4 is a diagram showing an example of a modulated signal of quasi-synchronous LDM; FIG. 4 is a diagram showing an example of distributed arrangement of pilot symbols; 2 is a diagram showing an example of tap coefficients of a transmission filter unit in the transmission device of FIG. 1; FIG. FIG. 3 is a diagram showing a configuration example of a UL reception replica generator in the receiver of FIG. 2; FIG. 7 is a diagram showing a configuration example of a delay profile generator in the UL reception replica generator of FIG. 6;

A data transmission system according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a configuration example of a transmitting device in a data transmission system according to one embodiment of the present invention, and FIG. 2 is a diagram showing a configuration example of a receiving device in the same system. The data transmission system of this example is a quasi-synchronous LDM transmission system in which UL and LL are OFDM-modulated with different numbers of FFT points, multiplexed in the time domain, and transmitted.
Here, the data transmission system according to one embodiment of the present invention will be described assuming that a wireless transmission line is used between the transmission device and the reception device. A wired connection may be used.

The transmitting device includes an error correction coding unit 11, an interleaving unit 12, a mapping unit 13, a _NUL point IFFT (Inverse Fast Fourier Transform) unit 14, an error correction coding unit 15, an interleaving unit It includes a section 16 , a mapping section 17 , an _NLL point IFFT section 18 , a synthesizing section 19 , a transmission filter section 20 , a D/A (Digital to Analog) conversion section 21 , and a transmission antenna 22 .

The receiving apparatus includes a receiving antenna 31, a receiving filter section 32, an A/D (Analog to Digital) conversion section 33, a _NUL point FFT section 34, a transmission path estimation section 35, an equalization section 36, and a determination unit 37, N _UL point IFFT unit 38, UL reception replica generation unit 39, LL extraction unit 40, N _LL point FFT unit 41, transmission channel estimation unit 42, equalization unit 43, likelihood calculation It includes a section 44 , a deinterleaving section 45 , an error correction section 46 , a likelihood calculation section 47 , a deinterleaving section 48 and an error correction section 49 .

First, the operation of the transmission device shown in FIG. 1 will be described.
In the transmitting apparatus, the UL information code to be transmitted to the receiving apparatus is input to the error correction coding section 11, and the error correction coding section 11 performs error correction coding processing. The current terrestrial digital system (ARIB STD-B31) uses a convolutional code as an error correction code, but is not limited to this, and LDPC (Low Density Parity Check) code, turbo code, etc. It is also possible to employ other error correction schemes.

The coded signal output from the error correction coding unit 11 is interleaved by the interleaving unit 12 to randomly rearrange the order in the areas of frequency, time, and bits constituting subcarriers. This interleaving is used to mitigate burst errors. Interleaving increases the improvement effect as the range to be rearranged increases, but on the other hand, a delay occurs in order to return the rearranged information to its original order. In particular, delay time due to time interleaving is dominant.

The output from interleaving section 12 is input to mapping section 13 . The mapping unit 13 maps the data subcarriers from the interleaving unit 12 onto the IQ complex plane using QAM (Quadrature Amplitude Modulation), PSK (Phase Shift Keying), or the like. ARIB STD-B31 adopts 16QAM and 64QAM.

The mapping unit 13 also performs mapping such as BPSK (Binary Phase Shift Keying) on a pilot signal whose amplitude and phase are known so that the receiver can estimate the channel characteristics. ARIB STD-B31 standardizes the allocation of pilot subcarriers and data subcarriers, and in order to comply with ARIB STD-B31, it is necessary to comply with this subcarrier allocation.

The N _UL point IFFT unit 14 performs N _UL point IFFT processing on the result of the mapping and subcarrier arrangement performed by the mapping unit 13, and cyclically copies the latter half of the generated time signal to the beginning of the symbol. Add a guard interval. In this way, so-called OFDM modulation is applied to the UL information code. In ARIB STD-B31, N _UL =8192 and guard interval length=1024.

The above processing is OFDM modulation processing for the UL information code, which is the first data (for example, 2K broadcast data) among the data to be transmitted to the receiving device, but the second data different from the first data (for example, , 4K broadcast data) is also subjected to similar OFDM modulation processing. The error correction coding unit 15, the interleaving unit 16, the mapping unit 17, and the NLL point IFFT unit 18 for the _LL information code perform the same processing as the functional units 11 to 14 for the UL information code. is omitted. For the LL information code, LDPC, N _LL =32768, is applied as an error correction method in accordance with the proposal of Non-Patent Document 2.

Through the processing described above, UL and LL modulated signals are generated.
As described with reference to FIG. 3, the synthesizing unit 19 sets the ratio of the numbers of UL and LL symbols to 11:3. A quasi-synchronous LDM signal is generated by adjusting and combining at a predetermined power ratio. Here, the synthesis ratio of UL and LL is specified by IL (Injection Level) calculated by the following (Equation 1).

The quasi-synchronous LDM signal from the synthesizing section 19 is input to the transmission filter section 20 . The transmission filter unit 20 applies band-limiting filter processing to the input signal in order to suppress the frequency spread of the OFDM signal. Band-limiting filtering is generally implemented by digital signal processing, and FIR (Finite Impulse Response) filters are often used as filters. The FIR filter inputs an input signal to a shift register, multiplies the contents of each register by a tap coefficient as illustrated in FIG. 5, and adds them. In FIG. 5, the tap coefficients are changed like a sinc function according to the tap position of each register. This filter configuration is called a direct configuration, but a transposed configuration is often used as an equivalent configuration to this filter. There is no problem even if an IIF (Infinite Impulse Response) filter is used instead of the FIR filter.

The output of the transmission filter section 20 is converted into an analog signal by the D/A conversion section 21 , frequency-converted to a transmission frequency, and transmitted from the transmission antenna 22 .

Next, the operation of the receiver shown in FIG. 2 will be described.
In the receiving device, the signal transmitted from the transmitting device is received by the receiving antenna 31 and filtered by the receiving filter section 32 . The reception filter unit 32 removes unnecessary components outside the band of its own channel in order to ensure the dynamic range of signal processing and to reduce deterioration due to aliasing components at the time of rate conversion. As the configuration of the reception filter unit 32, there are an analog filter configured before the A/D conversion unit 33 and a digital filter configured after the A/D conversion unit 33. Generally, both analog and digital filters are used. There are many things.

The output of the reception filter section 32 is converted by the A/D conversion section 33 from the reception signal of the transmission frequency to the frequency of the baseband and also from the analog signal to the digital signal.

The N _UL point FFT unit 34 receives the received digital signal from the A/D conversion unit 33, provides an FFT time window having a length of N _UL for the received digital signal, and converts the time domain signal to a subcarrier unit frequency. FFT processing is applied to convert to a domain signal. The FFT time window must be set at a timing at which inter-symbol interference due to reflected waves does not occur. A signal output from the _NUL point FFT unit 34 is input to a transmission path estimation unit 35 and an equalization unit 36 .

As shown in FIG. 4, the channel estimating unit 35 performs interpolation processing in two-dimensional directions of time and frequency on pilots (SP: Scattered Pilot) that are distributed in symbols (time) and frequency. , the transmission path characteristics of the section (radio section in this example) between the transmitter and the receiver are estimated. Generally, a two-dimensional filter is often used for this interpolation processing. The passband width in the frequency direction of the two-dimensional filter corresponds to the delay time length of the reflected wave that can be estimated, and the passband width in the time direction corresponds to the time-varying frequency caused by mobile transmission or the like.

In order to improve the estimation accuracy of channel characteristics, it is necessary to set the passband width so that the time and frequency fluctuation components of the channel are within the passband of the two-dimensional filter, but it is estimated that the passband width is too wide. This leads to an increase in noise components mixed in the result. Therefore, it is desirable that the passband width of the two-dimensional filter be as narrow as possible while making it possible to estimate the transmission path characteristics.

In the situation where the LL signal is received by quasi-synchronous LDM, the noise mixed in the received signal is small. In general, the LL level is often set lower than the UL level, and IL is set to 23 dB, for example. In this case, if the required CNR (Carrier to Noise Ratio) of LL is 20 dB, in order to correctly receive LL, the total CNR when the UL level is used as a reference must be 23+20=43 dB or more.

Thus, the dominant degradation factor for UL reception is the LL signal, not the noise, because the noise power is very low for the UL. Since the LL signal behaves like noise to the UL, in the example of IL=23 dB, the CINR (Carrier to Interference and Noise Ratio) of the UL is about 23 dB. Here, the I (Interference) component of CINR is the LL signal.

The equalization unit 36 performs complex division on the received subcarrier signal Y(ω) by the transmission path estimation result Ĥ(ω) to obtain an estimated value E _UL ( ω) is calculated. Here, ω indicates the subcarrier number.

The determination unit 37 determines in which region the equalization result E _UL (ω) by the equalization unit 36 is located, and estimates a transmission mapping point. This processing is generally called hard decision processing. As mentioned above, the overall CNR is large in the environment where LL is received, so it is unlikely that the UL hard decision will be erroneous.

The transmission mapping points estimated by the determination unit 37 are subjected to IFFT processing in which the frequency domain signal is converted into a time domain signal by the _NUL point IFFT unit 38 . If there is no error in the _UL hard decision result, NUL point IFFT section 38 generates the same signal as _NUL point IFFT section 14 of the transmitting apparatus shown in FIG.
With the above processing, the receiving device can generate a UL remodulated signal.

Next, a method of generating a replica of the UL reception signal (hereinafter referred to as "UL reception replica") by the UL reception replica generator 39, which is the main focus of the present invention, will be described with reference to FIG.
The UL reception replica generation unit 39 needs to generate a _UL reception replica in consideration of overall transmission path characteristics from the NUL point IFFT unit 14 of the transmission device to the LL extraction unit 40 of the reception device. The UL reception replica generation unit 39 has a transmission filter unit 51, a delay profile generation unit 52, a convolution unit 53, and a reception filter unit 54, as shown in FIG.

The UL remodulated signal from the N _UL point IFFT section 38 is input to the transmission filter section 51 . The transmission filter section 51 has the same filter characteristics as the transmission filter section 20 of the transmission device. Among the filters provided in the transmission device, regardless of the filter configuration such as a digital filter or an analog filter, the filter that has the greatest influence on the reproduction of the UL reception replica is the filter with the narrowest band. Therefore, by configuring the transmission filter section 20 with a digital filter and setting it to the narrowest band filter in the transmission device, it is possible to improve the accuracy of reproduction of received precursors in the reception device.

The output signal from the transmission filter section 51 corresponds to the output signal of the transmission filter section 20 of the transmission device. The output signal from the transmission filter section 51 is input to the convolution section 53, and the convolution section 53 performs a convolution operation with the delay profile. A delay profile is an impulse response of a transmission path, and is generated by a delay profile generator 52, which will be described later. If the delay profile generator 52 can obtain an accurate impulse response of the transmission path, the transmission path characteristics can be reflected with high precision by convolution operation.

Also, the delay profile used is a complex number, and the convolution operation must also be calculated with a complex number. The configuration of the convolution unit 53 can be realized by a complex FIR filter, and the number of taps of the filter should be set to reflect the longest delay path in the delay profile. Generally, lines are designed so that the longest delayed wave is within the guard interval length, so the guard interval length is required as the number of taps. The convolution unit 53 having such a configuration can reproduce the transmission path characteristics in the time domain.

The output of convolution section 53 is input to reception filter section 54 . As with the transmission filter section 51, the reception filter section 54 also preferably has the same characteristics as the narrowest band filter in the reception apparatus. In FIG. 2, the receiving filter section 32 of the receiving device is composed of an analog filter and provided in the analog domain, but it does not necessarily have to be an analog filter. may The output of the reception filter section 54 is output from the UL reception replica generation section 39 as a UL reception replica.

Next, the delay profile generator 52 will be explained using FIG. The delay profile generating section 52 has an IFFT section 61, an averaging section 62, an absolute value section 63, a comparing section 64, and a zero replacing section 65, as shown in FIG.

The channel estimation result Ĥ(ω) by the channel estimation unit 35 is input to the IFFT unit 61 . Since the channel estimation result H^(ω) is the channel characteristic in the frequency domain, the IFFT unit 61 transforms the signal H^(ω) in the frequency domain into the signal Ĥ(t) in the time domain, thereby obtaining a complex A delay profile signal can be obtained. The operation of the IFFT unit 61 can be represented by the following (equation 3). In the following (Formula 3), IFFT[ ] indicates an inverse Fourier transform function.

The output ĥ(t) of the IFFT unit 61 is input to the averaging unit 62 and averaged in the averaging unit 62 in the symbol (time) direction. The purpose of this averaging process is to reduce the noise mixed in the delay profile, and it is necessary to appropriately set the cutoff frequency of the filter according to the time variation of the transmission path. If the reception environment is fixed, the cutoff frequency is set to a low frequency, and if the reception environment is mobile, the cutoff frequency is set to a high frequency. Thus, it is desirable to realize an optimum filter that can achieve both reproducibility of transmission paths and noise reduction.

The output of the averaging section 62 is input to the absolute value section 63 and the zero replacement section 65 . The absolute value unit 63 calculates the amplitude of the complex delay profile (the absolute value of the symbol direction average of the complex delay profile signal ĥ(t)). The comparison unit 64 compares the output of the absolute value unit 63 with a predetermined threshold (thr), and regards signals below the threshold as noise. The zero replacement unit 65 replaces the signal determined to be below the threshold value (that is, noise) by the comparison unit 64 with 0 in the output from the averaging unit 62 . The operation of the zero replacement unit 65 can be represented by the following (Equation 4). The output dpf(t) of the zero replacement unit 65 is output from the delay profile generation unit 52 as a delay profile.

Here, the threshold thr used in the comparison unit 64 may be set to a value obtained by multiplying the maximum value in the absolute value unit 63 by a predetermined coefficient (α), as shown in (Equation 5) below.

Alternatively, as shown in the following (Equation 6), a value obtained by multiplying the above (Equation 5) by the reciprocal of the reception CNR may be set as the threshold thr.

Various methods are conceivable for setting the threshold thr.
By performing the processing as described above, the UL reception replica generation unit 39 can generate the UL reception replica.

The LL extraction unit 40 extracts the LL signal by subtracting the UL reception replica from the reception signal in which the UL and LL are mixed.

Next, the demodulation of the LL signal will be described.
The _NLL point FFT unit 41 performs NLL point FFT processing on the _LL signal extracted by the LL extraction unit 40, and converts the signal in the time domain into a signal in the frequency domain for each subcarrier.
For example, when a pilot is inserted in the LL signal, the transmission path estimation unit 42 performs transmission path estimation based on the received pilot signal of the LL signal. This processing is the same processing as that of the transmission path estimation unit 35 .

Here, since the UL and LL transmission channel characteristics are the same, the UL transmission channel estimation result may be used as the LL transmission channel estimation result. In this case, since there is no need to insert a pilot into the LL signal, there is an advantage that the bit rate can be improved. Note that the output of the transmission path estimator 35 can be used as the UL transmission path estimation result. In this case, since the number of FFT points differs between UL and LL, it is necessary to convert the rate from N _UL points to N _LL points. Methods of rate conversion include interpolation to raise the rate and decimation to lower the rate. A combination of interpolation and decimation may also be used. Various known methods can be used for rate conversion, and detailed description thereof will be omitted.

Similar to the equalization unit 36, the equalization unit 43 estimates the LL transmission signal based on the LL received subcarrier signal from the N _LL point FFT unit 41 and the transmission channel estimation result from the transmission channel estimation unit 42. .

Finally, the likelihood calculators 44 and 47, deinterleavers 45 and 48, and error correctors 46 and 49 for UL and LL, respectively, will be explained. The functional units 44 to 46 for UL and the functional units 47 to 49 for LL perform the same processing.

The likelihood calculators 44 and 47 calculate a log likelihood ratio (LLR) corresponding to each bit from the distance between the equalization result and the ideal reception point based on the equalization result. Here, the LLR is desirably proportional to the CNR of each subcarrier, and for this purpose the power of the transmission path estimation result of each subcarrier is used. Furthermore, for bits that can be corrected by intra-symbol error correction, the magnitude of LLR may be the maximum value. Various known methods can be used to calculate the LLR, and detailed description thereof will be omitted.

The results of the likelihood calculators 44 and 47 are input to deinterleavers 45 and 48, and after being rearranged in a manner opposite to that of the interleavers 12 and 16 of the transmitter, error correction is performed by error correctors 46 and 49. Decryption takes place. As a result, UL and LL are reproduced in the receiving device.

By the above processing, when the CNR is good, it becomes possible to transmit the UL and LL information codes at the same time. It is also possible to transmit UL-only information symbols if the CNR is not so good. Therefore, it is possible to realize data transmission of the quasi-synchronous LDM method as proposed in Non-Patent Document 2, and for example, it is possible to smoothly shift from 2K broadcasting to 4K broadcasting as next-generation terrestrial broadcasting.

As described above, the transmitting apparatus of this example includes the N _{UL point IFFT unit 14 that performs N UL point} IFFT processing on UL data, and the N LL point IFFT unit that performs N _LL point IFFT processing on _LL data. A point IFFT unit 18 generates a UL modulated signal generated using N _UL point IFFT processing and an LL modulated signal generated using N _UL point IFFT processing, each of which starts at a predetermined cycle. A synthesizing unit 19 for performing timing adjustment and synthesizing so that the signals match, and a transmitting antenna 22 for transmitting the LDM signal resulting from the synthesis by the synthesizing unit 19 into space. Further, the receiving device of this example includes a receiving antenna 31 for receiving a signal from the transmitting device, and a N _UL point FFT section 34 for performing N _UL point FFT processing on the signal received from the transmitting device by the receiving antenna 31. , a UL reception replica generation unit 39 for generating a UL reception replica based on the result of FFT processing of N _UL points, and an LL extraction unit 40 (subtraction unit) for extracting the LL signal by subtracting the UL reception replica from the reception signal. , and an _NLL point FFT unit 41 for performing NLL point FFT processing on the _LL signal extracted by the LL extraction unit 40 . The UL reception replica generation unit 39 is configured to generate a _UL reception replica based on the comprehensive transmission channel characteristics from the NUL point IFFT unit 14 of the transmission device to the LL extraction unit 40 of the reception device. .

In this way, by generating a UL reception replica based on the comprehensive transmission path characteristics from the N _UL point IFFT unit 14 of the transmitting device to the LL extraction unit 40 of the receiving device, the wireless communication between the transmitting device and the receiving device Compared to the case where the UL reception replica is generated based on the transmission path characteristics of the section, the reproduction accuracy of the UL reception replica can be improved.

Here, the comprehensive transmission path characteristics are the characteristics of the transmission filter unit 20 interposed between the N _UL point IFFT unit 14 of the transmission device and the transmission antenna 22, and the radio transmission between the transmission device and the reception device. It may include the transmission path characteristics of the section and the characteristics of the reception filter unit 32 interposed between the reception antenna 31 and the LL extraction unit 40 of the reception device.

In addition, the receiving apparatus of this example includes a transmission path estimation unit 35 for estimating transmission path characteristics in a wireless section based on the N _UL point FFT processing result, and a N _UL point FFT processing result for the N _UL point FFT processing result. and a N _UL point IFFT unit 38 for performing IFFT processing of . Then, the UL reception replica generation unit 39 includes a transmission filter unit 51 that performs filtering corresponding to the transmission filter unit 20 on the UL modulated signal regenerated using the N _UL point IFFT unit 38, and a transmission path estimation unit. A delay profile generation unit 52 that generates a delay profile, which is an impulse response, based on the transmission path characteristics of the wireless section estimated by the unit 35, and a convolution unit that performs a delay profile convolution operation on the output of the transmission filter unit 51. 53, and a reception filter section 54 that performs filter processing corresponding to the reception filter section 32 on the output of the convolution section 53, and outputs the output of the reception filter section 54 as a UL reception precursor. With such a configuration, a UL reception replica can be generated with high accuracy.

Further, in the receiving apparatus of this example, the delay profile generation unit 52 is configured to generate a delay profile by converting the transmission path characteristics of the wireless section from frequency domain signals to time domain signals. A delay profile generating unit 52 is configured to generate a delay profile by removing noise components from the transmission path characteristics of the section after conversion into a time domain signal. With such a configuration, an accurate delay profile can be obtained, and the reproduction accuracy of the UL reception replica can be further improved.

Here, in the above description, two types of data are transmitted using two layers, the upper layer (UL) and the lower layer (LL). A quasi-synchronous LDM data transmission system may be used. For example, when three types of data are transmitted using three layers each having a power difference, the present invention is applied to at least one of the relationship between the first and second layers or the relationship between the second and third layers. Is possible.

In the above description, the communication between the transmitting device and the receiving device is performed wirelessly. It is possible to In this case, the "wireless section" in the above description should be replaced with the "wired section".

In the above description, data is transmitted by semi-synchronous LDM in which the number of FFT points of _UL (NUL points) and the number of FFT points of _LL (NLL points) are different. It does not preclude the configuration of matching numbers (ie applying the invention to synchronous LDM).

Although the present invention has been described in detail above, it is needless to say that the present invention is not limited to the above embodiments, and can be widely applied to applications other than those described above.
Further, the present invention can also be provided as, for example, a method or system for executing the above processes, a program for realizing such a method or system, a storage medium for storing the program, or the like.

INDUSTRIAL APPLICABILITY The present invention can be used in a data transmission system that multiplexes and transmits a plurality of data using hierarchical division multiplexing.

11: error correction coding unit, 12: interleaving unit, 13: mapping unit, 14: N _UL point IFFT unit, 15: error correction coding unit, 16: interleaving unit, 17: mapping unit, 18: N _LL point IFFT Section 19: Synthesizing section 20: Transmission filter section 21: D/A conversion section 21 22: Transmission antenna 31: Reception antenna 32: Reception filter section 33: A/D conversion section 34: N _UL Point FFT unit 35: Transmission path estimation unit 36: Equalization unit 37: Judgment unit 38: N _UL point IFFT unit 39: UL reception replica generation unit 40: LL extraction unit 41: N _LL point FFT Section 42: Channel Estimator 43: Equalizer 44: Likelihood Calculator 45: Deinterleaver 46: Error Corrector 47: Likelihood Calculator 48: Deinterleaver 49: Error correction unit 51: transmission filter unit 52: delay profile generation unit 53: convolution unit 54: reception filter unit 61: IFFT unit 62: average unit 63: absolute value unit 64: comparison unit 65: zero replacement part

Claims (7)

In a data transmission system that multiplexes and transmits a plurality of data by hierarchical division multiplexing,
A first IFFT unit that performs IFFT processing of a first number of points on the first data, a second IFFT unit that performs IFFT processing of a second number of points on the second data, and the first number of points Start timings of the modulated signal of the first data generated using the IFFT process and the modulated signal of the second data generated using the IFFT process of the second number of points match at a predetermined cycle. a transmitting device having a synthesizing unit that performs timing adjustment and synthesizing, and a transmitting unit that outputs a signal resulting from synthesis by the synthesizing unit;
a receiving unit that receives a signal from the transmitting device; a first FFT unit that performs FFT processing for the first number of points on the signal received by the receiving unit; and a result of the FFT processing for the first number of points. a reception replica generating unit for generating a reception replica of the modulated signal of the first data based on the second point; a subtraction unit for subtracting the reception replica from the reception signal; a receiving device having a second FFT unit that performs a number of FFT processing,
The data transmission, wherein the reception replica generation unit generates the reception replica based on comprehensive transmission path characteristics from the first IFFT unit of the transmission device to the subtraction unit of the reception device. system. The data transmission system according to claim 1,
The overall transmission path characteristics are the characteristics of a transmission filter interposed between the first IFFT section and the transmission section of the transmission device, and the characteristics of the section between the transmission device and the reception device. A data transmission system comprising transmission path characteristics and characteristics of a reception filter interposed between the reception section and the subtraction section of the reception device. In the data transmission system according to claim 2,
The receiving device includes a transmission path estimation unit that estimates transmission path characteristics of the section based on the result of FFT processing for the first number of points, and the first point for the result of FFT processing for the first number of points. and a third IFFT unit that performs multiple IFFT processing,
The reception replica generation unit includes a second transmission filter that performs filtering corresponding to the transmission filter on the modulated signal of the first data regenerated using the third IFFT unit, and the transmission path. a delay profile generating unit for generating a delay profile, which is an impulse response, based on the transmission path characteristics of the section estimated by the estimating unit; and performing a convolution operation of the delay profile on the output of the second transmission filter. a convolution unit; and a second reception filter that performs filtering corresponding to the reception filter on the output of the convolution unit, and outputs the output of the second reception filter as the reception replica . data transmission system. In the data transmission system according to claim 3,
The data transmission system according to claim 1, wherein the delay profile generating section converts the transmission path characteristic of the section from a frequency domain signal to a time domain signal to generate the delay profile. In the data transmission system according to claim 4,
The data transmission system, wherein the delay profile generation unit generates the delay profile by removing noise components from the transmission path characteristics of the section after the conversion. In a receiving device used in a data transmission system that multiplexes and transmits a plurality of data by hierarchical division multiplexing,
A modulated signal of first data generated using IFFT processing with a first number of points and a modulated signal of second data generated using IFFT processing with a second number of points, each having a predetermined start timing Receive from a transmission device a signal synthesized by timing adjustment so that it matches the period, perform FFT processing of the first number of points on the received signal, and reproduce the first data based on the result. generating a reception replica of the modulated signal of the first data, performing FFT processing for the second number of points on a signal obtained by subtracting the reception replica from the reception signal, and reproducing the second data based on the result is a
The reception replica is generated based on comprehensive transmission path characteristics from an IFFT unit that performs IFFT processing for the first number of points in the transmission device to a subtraction unit that performs the subtraction in the reception device. receiver. In a data transmission method for multiplexing and transmitting a plurality of data by hierarchical division multiplexing,
A transmitting device transmits a modulated signal of first data generated using IFFT processing with a first number of points and a modulated signal of second data generated using IFFT processing with a second number of points at each start Transmit the synthesized signal with the timing adjusted so that the timing matches at a predetermined cycle,
A receiving device performs FFT processing of the first number of points on the received signal from the transmitting device, reproduces the first data based on the result, and generates a reception replica of the modulated signal of the first data. and performing FFT processing of the second number of points on a signal obtained by subtracting the received replica from the received signal, and reproducing the second data based on the result,
The receiving device generates the reception replica based on comprehensive transmission path characteristics from an IFFT unit that performs IFFT processing for the first number of points in the transmitting device to a subtracting unit that performs the subtraction in the receiving device A data transmission method characterized by:

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