JP2018137675A - Transmitting device and receiving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmitting device capable of suiting data of coded modulation of 64APSK to ISDB-S3 and securing a desired transmission performance by eliminating influences of nonlinear distortion in a satellite transmission line when transmitting the data via the satellite transmission line, and a receiving device.SOLUTION: When performing signal transmission via a nonlinear transmission line, a transmitting device 10 generates a main transmission signal to which coded modulation processing of 64APSK is applied. A pilot signal indicating signal point arrangement information of 64APSK is bisected into first-half 32 symbols and second-half 32 symbols in a known order between transmission and reception that becomes an ascending order or descending order of symbols. Each of transmission pilot signals to which energy diffusion processing is applied is periodically multiplexed with an odd-numbered modulation slot and an even-numbered modulation slot to which the main transmission signal is allocated, in a time-dividing manner. A receiving device 20 receives the transmission pilot signal and utilizes a phase error in the case of carrier reproduction or a likelihood table in the case of LDPC decoding for update.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a transmission apparatus and a reception apparatus that perform signal transmission of 64 APSK (Amplitude and Phase Shift Keying) coded modulation via a non-linear transmission path.

  In recent years, there is an increasing demand for transmission at a high bit rate such as 4K / 8K ultra-high-definition video, and an increase in transmission capacity is required. One approach for expanding the transmission capacity is to increase the multi-level number of the multi-level modulation system, but in a modulation system with a high multi-level number such as 64APSK, it is easily affected by noise and requires a high required C / N. It becomes. Particularly in a non-linear transmission line, a modulation signal having a higher multi-level number is more susceptible to non-linear distortion, which causes deterioration in transmission performance.

  As a conventional technique for improving the influence of nonlinear distortion in a satellite transmission path, a transmission signal point arrangement signal (hereinafter also referred to as “pilot signal”) employed in a transmission system (ISDB-S3) of advanced broadband satellite digital broadcasting is multiplexed. A technique is known (see, for example, Non-Patent Document 1).

"Transmission system for advanced broadband satellite digital broadcasting (ISDB-S3) standard ARIB STD-B44 version 2.1", Radio Industry Association (ARIB), revised on March 25, 2016

  As described above, there is known a technique for multiplex transmission of pilot signals employed in the transmission system (ISDB-S3) of advanced broadband satellite digital broadcasting.

  However, in ISDB-S3, the maximum number of modulation multilevels that can be applied as coded modulation is 32. Therefore, a pilot signal is included in each modulation slot constituting a frame of a modulated wave that is multiplexed and transmitted in ISDB-S3. As the transmission area, only 32 symbols defined as the maximum modulation multi-level number are secured.

  For this reason, even if it is attempted to transmit 64APSK encoded modulation data from the transmitting apparatus to the receiving apparatus in ISDB-S3, it is not a mechanism for transmitting a 64APSK pilot signal. As a result, there arises a problem that sufficient transmission performance cannot be obtained.

  In view of the above-described problems, the present invention adapts ISDB-S3 when transmitting 64 APSK coded modulation data via a satellite transmission line, and further improves the influence of nonlinear distortion in the satellite transmission line. It is an object of the present invention to provide a transmission device and a reception device that can ensure the transmission performance of the above.

  A transmission apparatus according to the present invention is a transmission apparatus that performs coded modulation signal transmission via a non-linear transmission path, and generates a transmission main signal obtained by performing 64 APSK coded modulation processing on the data of the main signal to be transmitted. The transmission main signal generating means and the pilot signal indicating the 64APSK signal point arrangement information are divided into two parts of the first half 32 symbols and the second half 32 symbols in a known order between transmission and reception in the ascending or descending order of the symbols, respectively. Pilot signal multiplexing means for periodically time-division-multiplexing the transmission pilot signals of the first half 32 symbols and the second half 32 symbols subjected to the processing to the odd modulation slots and even modulation slots to which the transmission main signal is assigned. Features.

  In the transmission apparatus of the present invention, the transmission apparatus includes transmission means for transmitting the transmission main signal and the transmission pilot signal with a modulated wave having a multi-frame structure defined by a transmission system for advanced broadband satellite digital broadcasting. It is characterized by.

  Also, in the transmission apparatus of the present invention, the pilot signal indicating the 64 APSK signal point arrangement information is composed of Table 1 shown below.

  Further, the receiving apparatus of the present invention receives the 64 APSK transmission pilot signal divided into the first 32 symbols and the second 32 symbols transmitted from the transmitting apparatus of the present invention, performs energy despreading processing, And a means for reconstructing and averaging the signal point arrangement of the pilot signal according to a known order and updating a phase error table as a reference coordinate at the time of carrier reproduction using the averaged symbol. .

  Further, the receiving apparatus of the present invention receives the 64 APSK transmission pilot signal divided into the first 32 symbols and the second 32 symbols transmitted from the transmitting apparatus of the present invention, performs energy despreading processing, And a means for restoring and averaging the signal point arrangement of the pilot signal according to a known order, and updating a likelihood table at the time of LDPC decoding using the averaged symbol.

  According to the present invention, 64APSK coded modulation data is adapted to ISDB-S3 when transmitted through a satellite transmission line, and further, the influence of nonlinear distortion in the satellite transmission line is improved and desired transmission performance is ensured. can do.

It is a block diagram which shows schematic structure of the transmitter of one Embodiment by this invention. It is a block diagram which shows schematic structure of the receiver of one Embodiment by this invention. It is a block diagram which shows schematic structure of the orthogonal detection part in the receiver of one Embodiment by this invention. It is a block diagram which shows schematic structure of the LDPC decoding part in the receiver of one Embodiment by this invention. It is a figure which shows the signal point arrangement | positioning and bit allocation of 64 APSK encoding modulation of one Example which concerns on the transmitter and receiver of one Embodiment by this invention. It is a figure which shows the flame | frame structure of the 64APSK code modulation of one Example which concerns on the transmitter and receiver of one Embodiment by this invention. (A) is a simulation of transmission signal points and reception signal points after passing through a non-linear transmission line when data of 64APSK coded modulation is transmitted in the absence of a pilot signal according to the transmitter and receiver of one embodiment of the present invention. A constellation showing the results, wherein (b) is an average after passing through a non-linear transmission line when 64APSK coded modulation data is transmitted in the presence of a pilot signal according to the transmitting apparatus and the receiving apparatus of one embodiment of the present invention. 6 is a constellation showing simulation results of pilot signal points after conversion and reception signal points after passing through a nonlinear transmission path. The transmission performance of 64APSK coded modulation data in the absence of a pilot signal (pilot signal OFF) and the presence of a pilot signal (pilot signal ON) according to one embodiment of the present invention It is a figure which shows a comparison.

  Hereinafter, a transmission device 10 and a reception device 20 according to an embodiment of the present invention will be described with reference to the drawings.

[Transmitter]
FIG. 1 is a block diagram showing a schematic configuration of a transmission apparatus 10 according to an embodiment of the present invention. The transmitter 10 is configured in the same manner as the transmission system (ISDB-S3) of the advanced broadband satellite digital broadcasting as a schematic configuration, but performs 64 APSK data transmission according to a predetermined signal point arrangement and bit allocation. However, the difference is that the pilot signal corresponding to the 64APSK signal point arrangement is configured to be multiplex-transmittable. More specifically, the transmission apparatus 10 according to the embodiment of the present invention shown in FIG. 1 is further provided with a pilot signal distribution unit 17 in order to multiplex-transmit pilot signals corresponding to the 64 APSK signal point arrangement. Is different from the transmission apparatus defined in ISDB-S3.

  That is, in ISDB-S3, π / 2 shift BPSK (1 bit / symbol), QPSK (2 bits / symbol), 8PSK (3 bits / symbol), 16APSK (or 16QAM, 4 bits / symbol), And 32APSK (or 32QAM, 5 bits / symbol) are defined, but in addition to this, in the transmission apparatus 10 according to the present invention, 64APSK (or 64QAM, 6 bits / symbol) data transmission and its The pilot signal is configured to be multiplexed and transmitted in conformity with the ISDB-S3 frame configuration.

  The transmission apparatus 10 includes a frame generation unit 11, a BCH encoding unit 12, an energy spreading unit 13, an LDPC encoding unit 14, a bit interleaver 15, an orthogonal modulation / time division multiplexing unit 16, a TMCC signal generation unit 11a, and a BCH encoding. Unit 12a, energy spreading unit 13a, LDPC encoding unit 14a, energy spreading unit 13b, and pilot signal distributing unit 17.

  The frame generation unit 11 includes control information, outer code parity in which the control information and data (main signal) are encoded by the BCH encoding unit 12, stuff bits, and control information, data, and outer information by the LDPC encoding unit 14. A frame composed of slots # 1 to # 120 is generated to form the code parity and the inner code parity in which the stuff bits are LDPC-encoded. The slot length is 44880 bits.

  The BCH encoding unit 12 generates an outer code parity by performing an outer code encoding process on the control information and data (main signal) in each slot in one frame using a BCH code according to the modulation scheme / coding rate information. And added to the control information and data (main signal).

  The energy spreading unit 13 performs energy spreading processing (bit randomization) on control information, data, outer code parity, and stuff bits in each slot in one frame. This is realized by generating pseudo-random “1” and “0” patterns using the M-sequence and performing MOD2 addition on this and the data in the slot.

  The LDPC encoding unit 14 performs an inner code encoding process on the control information, data, outer code parity, and stuff bits after the energy spreading process in each slot by using an LDPC code to generate an inner code parity. It is added to control information, data, outer code parity, and stuff bits.

The bit interleaver 15 is 8PSK, 16APSK in ISDB-3.
And in the case of 32APSK, bit interleaving is performed within the one frame, and the same bit interleaving is performed for 64APSK according to the present invention.
Thereby, the transmission main signal of each modulation system is formed through the LDPC encoding unit 14 or the bit interleaver 15.

  The TMCC signal generation unit 11a generates a TMCC signal that stores transmission control information (TMCC information) describing modulation scheme / coding rate information and the like related to data transmission of the main signal, and outputs the TMCC signal to the BCH encoding unit 12a.

  The BCH encoding unit 12a performs outer code encoding processing on the TMCC signal using the BCH code to generate and add an outer code parity.

  The energy spreading unit 13a performs energy spreading processing (bit randomization) on the TMCC signal and the outer code parity.

The LDPC encoding unit 14a applies an inner code encoding process to the TMCC signal and the outer code parity after the energy spreading process using an LDPC code to generate and add an inner code parity.
Thus, a transmission TMCC signal is formed through the LDPC encoding unit 14a.

  The energy spreading unit 13b performs energy spreading processing on a pilot signal indicating signal point arrangement information according to the modulation scheme of each slot, and generates a transmission pilot signal.

  Although details will be described later, in ISDB-S3, pilot signals of π / 2 shift BPSK, QPSK, 8PSK, 16APSK, and 32APSK are the number of symbols (32 symbols) that can be accommodated in one slot. The 64 APSK pilot signal according to the above does not fit within one slot.

Therefore, the transmission apparatus 10 according to the present invention includes a pilot signal distribution unit 17 for multiplex transmission of 64APSK pilot signals. The transmitting apparatus 10 according to the present invention is configured to transmit the 64 APSK pilot signal in two parts, and in order to increase the processing efficiency on the receiving side, the ascending order of the symbols constituting the 64 APSK signal point arrangement (Or descending order).
More specifically, the energy spreading unit 13 b first performs energy spreading processing on the first 32 symbols in the ascending order (or descending order) of symbols in the 64 APSK pilot signal and inputs the result to the pilot signal distributing unit 17. The pilot signal distribution unit 17 performs quadrature modulation so that the 64 APSK pilot signals of the first half 32 symbols subjected to the energy spreading process are allocated to the odd modulation slots (modulation slots # 1, # 3,... # 119) as transmission pilot signals. / Output to time division multiplexing unit 16.

Similarly, the energy spread unit 13 b performs energy spread processing on the latter 32 symbols in ascending order (or descending order) of symbols in the 64 APSK pilot signal, and inputs the result to the pilot signal sorting unit 17. Pilot signal allocating unit 17 performs quadrature modulation so that the latter 32 symbols of 64 APSK pilot signals subjected to energy spreading processing are allocated to even modulation slots (modulation slots # 2, # 4,..., # 120) as transmission pilot signals. / Output to time division multiplexing unit 16.
For this reason, in the 64 APSK pilot signal, the first 32 symbols are assigned to odd modulation slots and the last 32 symbols are assigned to even modulation slots in ascending (or descending) order of symbols.

  As a result, the processing itself for the 64 APSK pilot signal in the energy spreading unit 13b can be performed in the same manner as other modulation schemes, so that the processing load on the receiving side does not deteriorate.

  The orthogonal modulation / time division multiplexing unit 16 performs π / 2 shift BPSK modulation, QPSK modulation, 8PSK modulation, 16APSK modulation, 32APSK modulation, or 64APSK modulation for the transmission main signal and the transmission pilot signal, and transmits the TMCC signal, the frame synchronization signal The slot synchronization signal is time-division multiplexed as π / 2 shift BPSK modulation, and a modulated wave of 120 modulation slots per multiplexed frame is generated and output to the outside. Since this modulated wave is transmitted to the receiving side via the satellite transmission path, it is affected by the nonlinear distortion.

[Receiver]
FIG. 2 is a block diagram illustrating a schematic configuration of the receiving device 20 according to an embodiment of the present invention. 3 is a block diagram showing a schematic configuration of the quadrature detection unit 22 in the receiving apparatus 20, and FIG. 4 is a block diagram showing a schematic configuration of the LDPC decoding unit 24 in the receiving apparatus 20.

  The receiver 20 is configured in the same manner as the advanced broadband satellite digital broadcasting transmission system (ISDB-S3) as a schematic configuration, but the 64 APSK signal points that are transmitted according to the predefined signal point arrangement and bit allocation. A difference is that a pilot signal corresponding to the arrangement is received, and 64 APSK data transmitted from the transmission device 10 is demodulated and decoded based on the signal point of the received pilot signal so as to be received. doing.

  The receiving device 20 includes a channel selection unit 21, an orthogonal detection unit 22, a TMCC decoding unit 23, an LDPC decoding unit 24, an energy despreading unit 25, and a BCH decoding unit 26.

  The channel selection unit 21 receives a modulated wave transmitted from the transmission device 10 via a satellite transmission path via a predetermined satellite broadcasting antenna, and a frequency conversion unit (see FIG. A BS-IF signal (first intermediate frequency signal) is input via a signal (not shown), a channel is selected, and the second intermediate frequency signal of each of the in-phase component (I) and quadrature component (Q) is selected as the channel signal. And output to the quadrature detection unit 22.

  The quadrature detection unit 22 performs synchronous detection on the second intermediate frequency signal (baseband signal) of the signal points (I signal and Q signal) detected in a state where complete synchronous detection is not performed (I signal and Q signal) is converted to a synchronous baseband signal and output to the LDPC decoding unit 24.

  The TMCC decoding unit 23 receives the synchronous baseband signal obtained from the quadrature detection unit 22, first detects a synchronous byte of the TMCC signal from the synchronous baseband signal, and uses this as a reference to periodically BPSK multiplexed. The position of the phase reference burst signal, which is a modulated wave, is also detected and demodulated. Subsequently, the TMCC decoding unit 23 performs a predetermined likelihood determination, decodes the TMCC signal LDPC-encoded by the transmission-side LDPC encoding unit 14a, and despreads the energy corresponding to the transmission-side energy spreading unit 13a. TMCC information is extracted by performing processing and performing BCH code decoding processing corresponding to the BCH encoding unit 12a on the transmission side.

  The TMCC decoding unit 23 generates a modulation scheme / coding rate selection signal to be described later based on the extracted TMCC information, detects a transmission pilot signal from the quadrature detection output of the quadrature detection unit 22, and transmits the transmission pilot signal. A timing pulse is generated and output to the quadrature detection unit 22 and the LDPC decoding unit 24. In addition, the TMCC decoding unit 23 converts each spreading code corresponding to the energy spreading unit 13 and the energy spreading unit 13b on the transmission side based on the extracted TMCC information to the energy despreading unit 25, the orthogonal detection unit 22, and the LDPC decoding unit, respectively. 24.

  The LDPC decoding unit 24 performs predetermined likelihood determination described later, decodes data related to the main signal LDPC-encoded by the LDPC encoding unit 14 on the transmission side, and outputs the decoded data to the energy despreading unit 25. When the modulation method for the main signal is 8PSK, 16APSK, 32APSK, and 64APSK according to the present invention, bit deinterleaving corresponding to the bit interleaver 15 on the transmission side is performed at the input stage of the LDPC decoding unit 24. .

  The energy despreading unit 25 subjects the data related to the main signal output from the LDPC decoding unit 24 to energy despreading processing corresponding to the energy spreading unit 13 on the transmission side, and outputs the result to the BCH decoding unit 26.

  The BCH decoding unit 26 performs a BCH code decoding process corresponding to the BCH encoding unit 12 on the transmission side for the data related to the main signal subjected to the energy despreading process, restores the data of the main signal, and outputs the data to the outside .

  A pilot signal corresponding to a 64APSK signal point constellation transmitted according to a predetermined signal point constellation and bit allocation is used in the quadrature detection unit 22 and the LDPC decoding unit 24 as described below.

(Orthogonal detector)
As shown in FIG. 3, the quadrature detection unit 22 includes a complex multiplication unit 221, route roll-off filters (RRF) 222-1 and 222-2, a transmission pilot signal extraction unit 223, an energy despreading unit 224, and pilot signal averaging. A unit 225, a phase error table generation unit 226, a phase error table storage unit 227, a loop filter (LF) 228, and a numerically controlled oscillator (NCO) 229.

  The complex multiplication unit 221 uses the second intermediate frequency signal of the signal points (I signal and Q signal) detected in a state where complete synchronous detection is not performed, so that the I signal and Q signal become stationary signal points. A numerically controlled oscillator (NCO) 229 inputs a signal whose phase error has been corrected based on a pilot signal, which will be described later, and performs complex multiplication, and a root roll-off filter (RRF) for each of the I signal and the Q signal as stationary signal points. Output to 222-1 and 222-2.

  The root roll-off filters (RRF) 222-1 and 222-2 limit the frequency of the I and Q signals obtained from the complex multiplier 221 and use the obtained I and Q signals as quadrature detection outputs as phase error tables. The data is output to the storage unit 227 and the LDPC decoding unit 24.

  The phase error table storage unit 227 inputs the quadrature detection output from the root roll-off filters (RRF) 222-1 and 222-2 to perform frequency control in the complex multiplication unit 221, and the received signal point and the ideal The phase difference between the signal point of the quadrature detection output and the reference signal point according to the pilot signal by referring to the held phase error table for obtaining the phase difference between the correct signal point and the reference signal point corrected according to the pilot signal. The comparison is performed, and a value proportional to the phase error amount is output to the loop filter (LF) 228.

  The phase error table is updated and generated by signal point arrangement information (pilot signal) affected by transmission path distortion obtained based on a transmission pilot signal described later.

  The loop filter (LF) 228 performs smoothing processing on a value proportional to the phase error amount obtained from the phase error table storage unit 227 and outputs the result to the numerically controlled oscillator (NCO) 229.

  A numerically controlled oscillator (NCO) 229 sets a value proportional to the amount of phase error smoothed by the loop filter (LF) 228, generates a signal with a phase error corrected based on the pilot signal, and generates a complex signal. The result is output to the multiplication unit 221.

  Transmission pilot signal extraction section 223 uses the pilot signal timing pulse obtained from TMCC decoding section 23 to extract the portion of the transmission pilot signal from the outputs of route roll-off filters 222-1 and 222-2, and reverses the energy inverse. The data is output to the diffusion unit 224.

  The energy despreading unit 224 subjects the transmission pilot signal extracted by the transmission pilot signal extraction unit 223 to energy despreading processing corresponding to the transmission side energy spreading unit 13b, and outputs the result to the pilot signal averaging unit 225. In addition, the spreading code of this energy despreading process is obtained from the TMCC No. decoding unit 23 (not shown).

  The pilot signal averaging unit 225 accumulates the signal points of the pilot signal periodically transmitted for each pilot symbol for the pilot signal obtained by performing the energy despreading process, and the signal point position on the IQ plane Is obtained, and the value is output to the phase error table generation unit 226. In the case of the 64APSK pilot signal according to the present invention, the first 32 symbols are in the order of “000000”, “000001”, “000010”,. Since the transmission is performed in the even modulation slots in the order of “100010”... “111111”, the pilot signal averaging unit 225 accumulates the signal points of the pilot signal transmitted periodically for each symbol. Find the average value.

  The phase error table generation unit 226 generates a phase error table using an average value of signal point positions on the IQ plane of the pilot signal obtained from the pilot signal averaging unit 225 and outputs the phase error table to the phase error table storage unit 227. To update and maintain. In other words, signal points whose average value of signal point positions of each symbol is on the same circumference are extracted and grouped for each circumference radius, and a phase error table is generated therein.

  In this way, the phase error table generation unit 226 updates the phase error table held by the phase error table storage unit 227 based on the pilot signal, so that transmission is performed due to aging of the satellite repeater or change of the backoff amount. Even when the path characteristic changes, the receiver 2 can always detect the optimum phase error and can perform stable synchronous detection in which cycle slip is unlikely to occur.

(LDPC decoding unit)
On the other hand, as shown in FIG. 4, the LDPC decoding unit 24 includes an LDPC code decoder 241, a transmission pilot signal extraction unit 242, an energy despreading unit 243, a pilot signal averaging unit 244, a likelihood table generation unit 245, and a likelihood. A degree table storage unit 246 is provided.

  The LDPC code decoder 241 refers to the likelihood table specified by the modulation scheme / coding rate selection signal input from the TMCC decoding unit 23 among the likelihood tables held in the likelihood table storage unit 246, The LDPC code is decoded and output to the energy despreading unit 25.

  The likelihood table further includes a log likelihood ratio (0) for a certain received signal point of each modulation scheme according to the LDPC coding rate, from the value of the posterior probability that 0 is transmitted and the value of the posterior probability that 1 is transmitted. The value which calculated | required LLR: Log-Lilelihood Ratio is shown.

  Each likelihood table held in the likelihood table storage unit 246 is updated by a likelihood table generation unit 245 described later on the basis of the pilot signal. Even when the transmission path characteristics change due to a change in the amount of off, etc., the receiving apparatus 20 can follow up and always perform optimum code decoding, and the required C / N can be reduced.

  The transmission pilot signal extraction unit 242 uses the pilot signal timing pulse obtained from the TMCC decoding unit 23 to extract the portion of the transmission pilot signal from the outputs of the route roll-off filters 222-1 and 222-2 in the quadrature detection unit 22. Extracted and output to the energy despreading unit 243.

  The energy despreading unit 243 subjects the transmission pilot signal extracted by the transmission pilot signal extraction unit 242 to energy despreading processing corresponding to the transmission side energy spreading unit 13b, and outputs the result to the pilot signal averaging unit 244. In addition, the spreading code of this energy despreading process is obtained from the TMCC No. decoding unit 23 (not shown).

  The pilot signal averaging unit 244 accumulates the signal points of the pilot signal periodically transmitted for each pilot symbol for the pilot signal obtained by performing the energy despreading process, and the signal point position on the IQ plane Is obtained, and the value is output to the phase error table generation unit 245. In the case of the 64APSK pilot signal according to the present invention, the first 32 symbols are in the order of “000000”, “000001”, “000010”,..., “011111”, and the second half 32 symbols are “100000”, “100001”. Since the transmission is performed in the even modulation slots in the order of “100010”... “111111”, the pilot signal averaging unit 225 accumulates the signal points of the pilot signal transmitted periodically for each symbol. Find the average value.

  The likelihood table generation unit 245 generates a likelihood table using an average value of signal point positions on the IQ plane of the pilot signal obtained from the pilot signal averaging unit 244 and outputs the likelihood table to the likelihood table storage unit 246. To update and maintain.

  The likelihood table storage unit 246 holds a likelihood table corresponding to the LDPC coding rate of each modulation method in the modulation method / coding rate selection signal generated by the likelihood table generation unit 245.

  Hereinafter, more specifically, the transmitting apparatus 10 and the receiving apparatus 20 according to the present invention will be described in detail with a focus on the 64APSK signal point arrangement and bit allocation according to the present invention and pilot signals corresponding to the 64APSK signal point arrangement. explain.

  First, the transmission device 10 and the reception device 20 according to the present invention are configured to improve the transmission performance of 64APSK coded modulation affected by nonlinear distortion in the satellite transmission path.

  In the nonlinear transmission path of the satellite repeater, nonlinear distortion in the amplitude and phase directions occurs. In particular, in multi-valued APSK such as 64APSK, the signal points on the outer periphery are subjected to amplitude suppression and phase rotation. Therefore, on the receiving device 20 side, transmission performance is degraded due to the influence of nonlinear distortion in carrier reproduction and LDPC decoding. Therefore, on the receiving apparatus 20 side, the pilot signal is used in each process of carrier recovery and LDPC decoding to suppress deterioration due to nonlinear distortion and improve transmission performance.

(Career regeneration)
The carrier reproduction is performed by the quadrature detection unit 22 shown in FIG. As described above, the quadrature detection unit 22 outputs a synchronous baseband signal by performing quadrature detection on the received signal using the same carrier as that on the transmission side generated from the baseband IQ signal and the phase error table.

  At this time, when the phase error table used for carrier recovery is an ideal signal point arrangement at the time of transmission by the transmission apparatus 10, the detection accuracy of the phase error is lowered, and the transmission performance is deteriorated due to an increase in cycle slip probability and a decrease in synchronization accuracy. . This is because the received signal undergoes amplitude suppression and phase rotation due to nonlinear distortion, whereas a phase error table is generated based on the ideal signal point arrangement during transmission that is not affected by nonlinear distortion, and carrier recovery is performed. This is because.

(LDPC decoding)
The LDPC decoding is performed by the LDPC decoding unit 24 shown in FIG. As described above, the LDPC decoding unit 24 performs LDPC decoding using the likelihood table.

  At this time, since the signal to be subjected to LDPC decoding is a signal affected by nonlinear distortion, if LDPC decoding is performed using the likelihood table obtained using the ideal signal point arrangement at the time of transmission of the transmission apparatus 10 as reference coordinates, Good transmission performance cannot be obtained. This is because the received signal is subjected to nonlinear distortion in the amplitude and phase directions due to the influence of nonlinear characteristics, whereas the generation of a likelihood table applied to LDPC decoding is not affected by the nonlinear distortion. This is because the point arrangement is the reference coordinate.

  Therefore, the transmitting apparatus 10 and the receiving apparatus 20 according to the present invention are configured to transmit a pilot signal of 64APSK coded modulation in order to improve performance against these nonlinear distortions.

  In the case of a 64APSK pilot signal according to the present invention, the transmitter 10 in this example is in ascending order, and the first 32 symbols are assigned to odd modulation slots in the order of “000000”, “000001”, “000010”,... “011111”. The latter 32 symbols are transmitted in the even modulation slots in the order of “100000”, “100001”, “100010”... “111111”.

  The receiving apparatus 20 receives a pilot signal affected by nonlinear distortion. However, since the transmission order of symbols during transmission is defined as described above, even a pilot signal subjected to nonlinear distortion is known. According to the mapping order, signal point arrangement and bit allocation can be obtained correctly. When the ideal signal point arrangement at the time of transmission of the transmission apparatus 10 is used as a reference coordinate by obtaining a phase error table at the time of carrier reproduction and a likelihood table at the time of LDPC decoding using the pilot signal subjected to the nonlinear distortion as a reference coordinate More accurately, carrier reproduction and likelihood calculation can be performed.

  As a result, transmission performance degradation due to nonlinear characteristics can also be improved with respect to 64APSK signal transmission. Further, even when receiving the 64 APSK pilot signal obtained by dividing the symbol into two, the receiving apparatus 10 can restore the signal by simple bit increment (or bit decrement), and therefore, the processing efficiency can be improved.

(Example)
In the example described below, transmission performance is evaluated by computer simulation using a nonlinear transmission path model that simulates the characteristics of a 12 GHz band satellite repeater as the nonlinear characteristics. The influence of distortion due to the non-linear characteristics varies depending on the back-off value of the satellite repeater. Here, the back-off value was set to 5.0 dB and the evaluation was performed.

  FIG. 5 is a diagram illustrating a signal point arrangement and bit allocation of 64 APSK encoding modulation according to an example of the transmission apparatus 10 and the reception apparatus 20 according to an embodiment of the present invention. Further, the transmission symbol order of pilot signals transmitted corresponding to the signal point arrangement of 64APSK encoded modulation shown in FIG. 5 is as shown in Table 1 above. 5, as shown in association with Table 1, the 6 bits assigned to the signal points are the first bit (a1), second bit (a2),..., Sixth bit (a6) from the left. And octal notation (example: 26 = 010: 110).

  Regarding Table 1, the transmission performance affects not only the presence / absence of pilot signal transmission but also the signal point arrangement and bit allocation of 64APSK coded modulation. Here, the evaluation mainly based on the presence / absence of pilot signal transmission will be described.

  By the way, in ISDB-S3, the maximum number of modulation multi-values that can be applied as coded modulation is 32. For this reason, each modulation slot constituting a modulated wave frame multiplexed in ISDB-S3 has a pilot signal. As the transmission area, only 32 symbols defined as the maximum modulation multi-level number are secured.

  For this reason, even if it is attempted to transmit 64APSK encoded modulation data from the transmitting apparatus to the receiving apparatus in ISDB-S3, it is not a mechanism for transmitting a 64APSK pilot signal. As a result, there arises a problem that sufficient transmission performance cannot be obtained.

  Therefore, as shown in FIG. 6, the structure of the multiplex frame in the transmission apparatus 10 and the reception apparatus 20 according to the present invention is a multiplex frame structure composed of 120 modulation slots so as to correspond to ISDB-S3. In order to transmit the pilot signal, the first 32 symbols of the 64 APSK pilot signal are transmitted in the ascending order to the odd modulation slot, and the latter 32 symbols are transmitted in the ascending order to the even modulation slot. Instead of ascending order, descending order may be used.

  As described above, the receiving apparatus 20 receives a pilot signal at the time of carrier reproduction and LDPC decoding, averages the received pilot signal, and removes noise, thereby being influenced by the nonlinear characteristics of the transmission path. Can be known.

  Then, the receiver 20 uses this signal point arrangement as a reference coordinate for generating the phase error table during carrier reproduction, thereby suppressing cycle slip probability, improving carrier synchronization accuracy, and improving transmission performance deterioration due to nonlinear distortion. It becomes possible to do.

  In addition, at the time of LDPC decoding, the receiving device 20 can generate a likelihood table in consideration of the influence of nonlinear distortion by using this signal point arrangement for generating the likelihood table.

  Thereby, deterioration of transmission performance due to nonlinear characteristics at the time of 64APSK code modulation can be improved while conforming to the configuration defined in the current ISDB-S3.

  FIG. 7A shows a transmission signal point and data after passing through a non-linear transmission path when transmitting 64 APSK coded modulation data in the absence of a pilot signal according to the transmission apparatus 10 and the reception apparatus 20 according to an embodiment of the present invention. It is a constellation which shows the simulation result of a received signal point. FIG. 7 (b) shows the averaging after passing through the non-linear transmission path when 64APSK coded modulation data is transmitted in the presence of pilot signals related to the transmission apparatus 10 and the reception apparatus 20 according to an embodiment of the present invention. It is a constellation which shows the simulation result of a later pilot signal point and a received signal point after passing through a nonlinear transmission path.

  Referring to FIG. 7A, it can be seen that the received signal after passing through the nonlinear transmission path is subjected to the influence of nonlinear distortion, the signal point is suppressed to the inner side and the phase is rotated as the outer circumference circles. For this reason, the center of each received signal is deviated from the signal point arrangement of the transmitted signal shown in FIG. Therefore, even if the ideal signal point arrangement at the time of transmission is used as a reference coordinate as it is and a likelihood table for LDPC decoding is obtained, good decoding characteristics cannot be obtained.

  On the other hand, referring to FIG. 7 (b), it can be seen that the averaged pilot signal is arranged approximately at the center of the received signal. By updating the likelihood table using the pilot signal subjected to the nonlinear distortion as a reference coordinate, a good LDPC decoding characteristic considering the nonlinear distortion can be obtained.

  FIG. 8 shows the 64 APSK coding modulation according to FIG. 5 for a state where there is no pilot signal (pilot signal OFF) and a state where there is a pilot signal (pilot signal ON) according to the transmission apparatus 10 and the reception apparatus 20 according to an embodiment of the present invention. It is a figure which shows the comparison of the transmission performance at the time of transmitting the data. In FIG. 8, the LDPC coding rate of the 64APSK coded modulation signal is 4/5.

  From FIG. 8, it can be seen that the transmission performance can be improved by about 0.53 dB by generating a likelihood table for LDPC decoding in which nonlinear distortion is taken into account by the pilot signal.

  The present invention is not limited to the above-described exemplary embodiments, but is limited only by the description of the scope of claims. For example, in the example of the above-described embodiment, only the evaluation result of the transmission performance for the specific LDPC coding rate 4/5 has been described, but the performance improvement is similarly performed for the other LDPC coding rate 4/5. Is possible.

  According to the present invention, 64APSK coded modulation data is adapted to ISDB-S3 when transmitted through a satellite transmission line, and further, the influence of nonlinear distortion in the satellite transmission line is improved and desired transmission performance is ensured. Therefore, the present invention is useful for the application of a transmitter and a receiver that perform 64APSK coded modulation signal transmission via a nonlinear transmission path.

DESCRIPTION OF SYMBOLS 10 Transmitter 11 Frame generation part 12 BCH encoding part 13 Energy spreading part 14 LDPC encoding part 15 Bit interleaver 16 Orthogonal modulation / time division multiplexing part 17 Pilot signal distribution part 11a TMCC signal generation part 12a BCH encoding part 13a Energy Spreading unit 14a LDPC encoding unit 13b Energy spreading unit 20 Receiver 21 Channel selection unit 22 Orthogonal detection unit 23 TMCC decoding unit 24 LDPC decoding unit 25 Energy despreading unit 26 BCH decoding unit 221 Complex multiplication units 222-1 and 222-2 Route roll-off filter (RRF)
223 Transmission pilot signal extraction unit 224 Energy despreading unit 225 Pilot signal averaging unit 226 Phase error table generation unit 227 Phase error table storage unit 228 Loop filter (LF)
229 Numerically controlled oscillator (NCO)
241 LDPC code decoder 242 Transmission pilot signal extraction unit 243 Energy despreading unit 244 Pilot signal averaging unit 245 Likelihood table generation unit 246 Likelihood table storage unit

Claims (5)

A transmission device that performs signal transmission of coded modulation via a non-linear transmission path,
Transmission main signal generation means for generating a transmission main signal obtained by performing 64APSK encoding modulation processing on the data of the main signal to be transmitted;
The pilot signal indicating the 64 APSK signal point arrangement information is divided into the first 32 symbols and the second 32 symbols in a known order between transmission and reception in the ascending or descending order of the symbols, and the first 32 symbols subjected to energy spreading processing, respectively. Pilot signal multiplexing means for time-division-multiplexing each of the transmission pilot signals of the latter half 32 symbols periodically with respect to the odd modulation slots and even modulation slots to which the transmission main signals are assigned,
A transmission device comprising:   2. The transmission device according to claim 1, further comprising: a transmission unit configured to transmit the transmission main signal and the transmission pilot signal using a modulated wave having a multi-frame structure defined by a transmission system of advanced broadband satellite digital broadcasting. The transmitting device described. The pilot signal indicating the 64 APSK signal point arrangement information is:
The transmission device according to claim 1 or 2, characterized by comprising:   4. The 64 APSK transmission pilot signal divided into the first 32 symbols and the second 32 symbols transmitted from the transmission device according to claim 1 is received, energy despreading processing is performed, and the transmission / reception is performed. Means for restoring and averaging the signal point arrangement of the pilot signals according to a known order between them, and using the averaged symbols to update a phase error table as reference coordinates at the time of carrier reproduction, Receiving device.   4. The 64 APSK transmission pilot signal divided into the first 32 symbols and the second 32 symbols transmitted from the transmission device according to claim 1 is received, energy despreading processing is performed, and the transmission / reception is performed. A receiving apparatus comprising: means for restoring and averaging signal point arrangements of the pilot signals according to a known order, and updating a likelihood table at the time of LDPC decoding using the averaged symbols.