JP4249253B1 - Digital terrestrial broadcast transmitter and receiver - Google Patents

Abstract

Provided are a terrestrial digital broadcast transmitter and receiver for a hierarchical transmission system in which different hierarchical parameters are set so that the delay amount between transmission and reception in each hierarchical layer is as short as possible and the timings between the hierarchical layers are aligned. .
A terrestrial digital broadcast transmission apparatus according to the present invention is a terrestrial digital broadcast transmission apparatus of a hierarchical transmission system in which different hierarchical parameters are set, and the apparatus includes a segment that constitutes a hierarchy of a delay caused by a bit interleave unit. According to a value defined by the number, there is provided means for performing delay correction so that the delay amount of each layer is transmitted and received to be a delay of 2 symbols, and after performing the delay correction, performs bit interleaving.
[Selection] Figure 1

Description

  The present invention relates to a digital terrestrial broadcast transmission apparatus and reception apparatus in Japan, and more particularly to a transmission apparatus and a reception apparatus that switch hierarchical parameters when transmitting and receiving.

  In terrestrial digital broadcasting in Japan, a narrowband OFDM signal having the specifications shown in Table 1 is used as a basic unit (hereinafter referred to as an OFDM segment), and several OFDM signals are combined to form one OFDM signal. In the case of terrestrial digital television broadcasting, it is composed of 13 OFDM segments, and in the case of terrestrial digital audio broadcasting, one or three are combined.

  For OFDM segments, modes with different carrier intervals (thus, different effective symbol lengths, which are the reciprocal of carrier intervals), guard interval lengths, error correction (convolutional code coding rate), time interleaving depth, carrier modulation scheme There are multiple options for transmission parameters such as

  Of these, the mode and guard interval length must be the same value for the OFDM segments that make up one OFDM signal, but the error correction, time interleaving depth, and carrier modulation scheme are different for each OFDM segment. It can be set differently, and it can be a hierarchical transmission in which signals of different transmission parameters are mixed in one OFDM signal (hereinafter, these three transmission parameters that can be set for each OFDM segment are referred to as hierarchical parameters). Call).

  Regarding the layer parameters that can be set for each OFDM segment, OFDM layers having the same layer parameter are grouped to form one layer. In the case of television broadcasting, since it is composed of 13 OFDM segments as described above, in principle it can be set up to a maximum of 13 layers, but the number of layers is maximum in the Japanese terrestrial digital television broadcasting system. Limited to 3. Further, in the case of digital terrestrial audio broadcasting, the case where it is composed of three OFDM segments is limited to two layers.

  FIG. 1 shows a system of a Japanese terrestrial digital broadcasting transmitter. In FIG. 1, a multiplexed frame-2 MPEG-2 transport stream (hereinafter referred to as TS) is output from the multiplexing unit 1, and TS is a 204-byte TS packet (hereinafter referred to as TSP) in consideration of outer coding. This is a continuous signal. The TS is subjected to outer coding by the outer coding unit 2 and is then allocated to each layer in units of packets by the layer division unit 3, and is subjected to convolutional coding for each layer by the convolution coding unit 4 through energy spreading and byte interleaving, Further, OFDM modulation (carrier modulation, time axis interleaving, frequency interleaving, and OFDM frame) is performed in the OFDM modulation unit 5.

  An OFDM frame is composed of 204 symbols in the time axis direction, and a signal of multiple frames is transmitted in one OFDM frame (strictly speaking, the amount of data is the same because of the interleaving described below, but the contents do not match). In addition, a pilot signal and a control signal called TMCC, which are used as a reference for demodulation during OFDM frame formation, are incorporated. The hierarchical parameters of each segment of the OFDM signal are transmitted to the receiving device by this TMCC. The setting of each layer parameter can be switched at the boundary between the multiplexed and OFDM frames. In TMCC, the layer parameter after switching is transmitted to the receiving side in addition to the current layer parameter, and 15 frames of layer switching are transmitted. Inform the switch by countdown from the front.

  FIG. 2 shows a system of the OFDM modulation unit 5 in FIG. By the way, in the transmitting apparatus, the convolutional interleaving scheme is used as the interleaving scheme in the byte interleaving section 6, the bit interleaving section 7 in the carrier modulation section 8, and the time interleaving section 9, and the receiving apparatus deinterleaves each. 3 and 4 showing the system of the receiving apparatus, the deinterleave unit corresponding to the interleave units 6, 7, and 9 is the code 6 ', the bit deinterleave units 7' and 9 'in the carrier demodulation unit 8' Respectively). Reference numeral 10 denotes an OFDM frame configuration unit.

  FIGS. 5A and 5B show the operations of convolutional interleaving and convolutional deinterleaving in the transmission device and the reception device, respectively. As shown in FIGS. 5A and 5B, the convolutional interleaving in the transmission device changes the data arrangement order by switching data in units of bits or bytes and passing through buffers having different depths. In addition, the deinterleaving in the receiving apparatus is configured so that the depth is symmetric with respect to the interleave buffer on the transmission side, and by making the delay amount in transmission and reception equal, the interleaved data is converted into the original data. Restore the order.

  However, the layer parameters differ from layer to layer, and when transmitting multiple layers at the same time, the amount of delay between transmission and reception varies from layer to layer. It becomes a problem.

  An object of the present invention is to reduce the amount of delay between transmission and reception in each layer as much as possible in a hierarchical transmission system terrestrial digital broadcast transmission device and reception device in which different hierarchical parameters are set, It is an object of the present invention to provide a digital terrestrial broadcasting transmission device and reception device in which the timings between them are aligned.

  In order to achieve the above object, a terrestrial digital broadcast transmission device according to the present invention is a transmission device for terrestrial digital broadcast of a hierarchical transmission scheme in which different hierarchical parameters are set. According to a value defined by the number of segments to be configured, there is provided means for performing delay correction so that the delay amount of each layer is transmitted and received to be a delay of 2 symbols, and after performing the delay correction, a means for performing bit interleaving is provided. Features.

  The present invention is also characterized as a terrestrial digital broadcast receiver that receives a transmission radio wave transmitted by a terrestrial digital broadcast transmitter.

  Advantageous Effects of Invention According to the present invention, in a terrestrial digital broadcasting transmitter and receiver using a hierarchical transmission scheme in which different hierarchical parameters are set, it is possible to reduce the delay amount between transmission and reception in each layer as much as possible and to align the timing between the layers. it can.

  Hereinafter, the present invention will be described in detail based on an embodiment of the invention with reference to the accompanying drawings. Tables 2 and 3 show the parts that require processing change according to the present invention when switching hierarchical parameters, respectively, with respect to the transmission device and the reception device. From Table 2, in the transmission apparatus (see FIGS. 1 and 2), the parts that need to be changed when the hierarchical parameters are switched are the byte interleaving unit 6, the convolutional coding unit 4, the carrier modulation unit 8, and the time interleaving unit. 9 and OFDM frame configuration unit 10. Also, from Table 3, in the receiving apparatus (see FIGS. 3 and 4), the parts that need to be changed when layer parameters are switched are the time deinterleaving unit 9 ′, the carrier demodulating unit 8 ′, and the convolutional decoding unit. 4 ′ and byte deinterleave unit 6 ′.

  Regarding the processing units that are affected when the hierarchical parameters are switched as shown in Tables 2 and 3, operation procedures when switching the buffers of each processing unit, switching of input signals to each processing unit, switching of frame points and output signals Define the correspondence of frame points. As is clear from Tables 2 and 3, when actual hierarchical parameters are switched, a plurality of processing units are switched. This can be realized by combining switching operations of the respective processing units.

  In addition, by clarifying the amount of data lost or damaged, it is possible to take into account the amount of data lost or damaged during TS generation.

  As described with reference to FIGS. 5A and 5B, convolutional interleaving and deinterleaving are performed by switching buffers having different depths. In the following description, FIGS. As indicated by a broken line in b), each buffer of the interleave buffer is simply expressed by triangles 11 and 11 'which are symmetrically sent and received.

Hereinafter, switching processing of each unit of the transmission device and the reception device according to the present invention will be described.
1-1. Byte Interleaving Unit (Transmission Side) Switching Process FIG. 6 shows the configuration of the byte interleaving unit. In FIG. 6, the byte interleaving unit is composed of a delay correction buffer and a byte convolutional interleaving, and the delay correction buffer, as shown in Table 4, shows a mode, a carrier parameter modulation method of a hierarchical parameter, a convolutional coding rate and its hierarchy. The value is defined by the number of segments to be configured, and is sent and received to be one frame.

  FIG. 7 shows the operation of the byte interleave unit. Now, the operation of the byte interleave unit will be considered according to FIG. Here, symbols A, B, C, and D indicate frames that are input to the byte interleave unit after energy diffusion of multiple frames, and it is assumed that switching of hierarchical parameters has occurred at the beginning of frame C. That is, the switching frame point is set to the head of frame C. Through the byte interleaving process, each frame is mixed with the data of the previous frame remaining in the buffer. For example, a part of the data of the frame B is interleaved with the data of the frame A remaining in the byte interleave delay correction buffer and the interleave buffer. The output at this time is represented as a frame BA. The remaining data of frame B remains in the byte interleave delay correction buffer and interleave buffer.

  When the hierarchical parameter is changed, the size of the delay correction buffer of the byte interleave unit is changed on the transmission device side so as to conform to the size of one frame according to Table 4. The switching process is performed immediately after all of the frame C enters the byte interleave unit and immediately before the frame D enters the buffer. At this time, since the delay correction buffer is still the buffer amount before switching, it is not consistent with the data amount of one frame of frame C.

  FIGS. 8A and 8B show two examples of the configuration of the byte interleave unit, respectively. Since the delay correction buffer is not consistent with the data amount of one frame of frame C, as shown in FIG. 8A, the byte data correction unit 12 is arranged before the original byte interleaving unit and the data Correct the amount. As shown in FIG. 7, if the data amount of the frame C is larger than the frame B, the difference data between the frame C and the frame B that cannot be input to the interleave unit is stored in the accumulation buffer 13 of the byte data correction unit 12. Buffer and store. Since the data amount of the difference is the same as the amount of the delay correction buffer that is increased when the byte interleave unit is switched, the data buffered in the switching correction unit is inserted therein for matching.

  Further, when the data amount after switching is smaller, there is insufficient data to be input to the interleave unit by the difference data of frame B and frame C, so that the deficit is used as the dummy data generation unit 14 of the byte data correction unit 12. The delay correction buffer is filled by generating dummy data from. Since the amount of the difference data is the same as the delay correction buffer amount that decreases at the time of switching, the extra buffer containing the dummy data is deleted and the data amount is matched. As a result of such processing, an output signal shown in FIG. 7 is obtained. Here, the switching frame point after byte interleaving is the head of the frame DC (see FIG. 7).

  The byte interleave unit has a delay correction buffer amount equal to or larger than the maximum value in Table 4 in advance, and by controlling the read and write addresses of the delay correction buffer, an output equivalent to the above can be obtained. A configuration example of such a byte interleave unit is shown in FIG. Even when the size of the delay correction buffer does not change due to the hierarchical parameters before and after switching, the switching frame points of the input / output signals have the same relationship as described above.

  1-2. Byte Deinterleaving Unit (Reception Side) Switching Process FIG. 9 shows the configuration of the byte deinterleaving unit. In FIG. 9, the byte interleaving unit performs processing by the byte interleaving unit having the configuration shown in FIG. 6 on the transmission side, so that this byte deinterleaving unit performs buffer clearing when switching hierarchical parameters as shown in FIG. Decoding can be performed without performing a special switching operation. The input / output signal switching frame point is at the head of the frame C in the output signal when the input signal is at the head of the frame DC.

  1-3. When the number of layers increases In the terrestrial digital television system, the number of layers may increase. FIG. 11 shows the processing of the byte interleave unit on the transmission side of the increased hierarchy. For the byte interleave unit of the increased hierarchy, a delay correction buffer suitable for the input stream is prepared, and the buffer is initialized with an initial value N. Frames CN, DC, and ED are obtained as output streams. Since the switching frame point is the head of the frame DC, the frame CN is discarded by the hierarchical synthesis unit (see FIG. 2). In order to clear the buffer initial values of the unit and the carrier modulation unit, the data is transmitted to the layer synthesis unit.

  On the other hand, on the receiving side, as shown in FIG. 12, before the frames DC and ED are input, a deinterleave buffer initialized with the initial value N is prepared. As shown in the figure, the first first frame of the output signal is not correctly transmitted. TS needs to be generated in consideration of this point.

  1-4. When the number of hierarchies decreases Next, when the number of hierarchies decreases, the processing of the byte interleaving unit on the transmission side of the hierarchies to decrease is shown in FIG. Now, it is assumed that the input signal ends in frames Z, A, and B. On the transmission side, after frame B is input, it is assumed that frame N is virtually input, and the delay correction buffer of the byte interleave unit and the data of frame C remaining in the interleave buffer are sent out. This can be realized by generating data corresponding to the virtual frame N in the dummy data generation unit 14 in FIG. 8A showing a configuration example of the byte interleave unit. As a result, the output signal shown in FIG. 13 is obtained from the transmission apparatus, and therefore the reception apparatus can correctly decode frames Z, A, and B as shown in FIG.

  2-1. As shown in FIG. 15, the switching process convolutional encoding unit of the convolutional encoding unit (transmission side) includes a 1/2 convolutional encoding unit and a punctured unit. FIG. 16 shows a circuit configuration example of the 1/2 convolutional encoding unit, and Table 5 shows a puncturing pattern. Assume that the output signal frames BA, CB, and DC of the byte interleave unit are input, and the head of the frame DC is a switching frame point. At this time, the 1/2 convolutional coding unit does not change the process before and after switching, and the punctured unit changes the punctured pattern from the beginning of the frame DC. As a result, frames BA ′, CB ′, and DC ′ are output, and the switching frame point is the head of the frame DC ′.

  At this time, it should be noted that a part of the data included in the frame C before byte interleaving included in the previous frame CB is encoded at the convolutional coding rate of the previous hierarchical parameter. is there. In particular, when switching in a direction in which the convolutional coding rate is increased (for example, switching from 5/6 to 1/2), a part of data of the first frame to be switched is encoded at the previous coding rate. Therefore, since the transmission characteristics are weakened, it is safer to switch the program on the TS from the next frame where the hierarchical parameter is switched.

  2-2. The switching process convolutional decoding unit of the convolutional decoding unit (reception side) is composed of a depunctured unit and a 1/2 Viterbi decoding unit as shown in FIG. Now, assuming that the switching frame point of the input signal is the head of the frame DC ′, the depuncturing pattern is changed at the head of the frame DC ′. As a result, the output signal switching frame point is the head of the frame DC. The 1/2 Viterbi decoding unit can perform decoding without changing the process before and after switching. In particular, at the time of switching, a fixed pattern of Ox47, which is a synchronization byte of TSP, is used. Once the Viterbi decoding process is terminated, error propagation due to a difference in the convolutional coding rate can be prevented.

  2-3. When the number of hierarchies increases, the transmission side 1-3. A frame starting from the output signals CN, DC, and ED described in the section is an input signal. When the frame CN that is not actually transmitted is input to the 1/2 convolutional coding unit, the initial value of the buffer of the 1/2 convolutional coding unit is cleared, and the frame DC and subsequent are processed without any problem.

  2-4. When the number of hierarchies decreases, the transmitting side is 1-3. A frame ending with the output signals AZ, BA, NB described in the section becomes an input signal. Since the last remaining data in the buffer of the 1/2 convolutional coding unit is a NULL part of the final frame NB, there is no particular problem even if the data is discarded.

3. Carrier modulation unit (transmission side)
As shown in FIG. 18, the carrier modulation unit includes a delay correction unit, a bit interleave unit, and a modulation mapping unit. The bit interleaving unit has a circuit configuration as shown in FIGS. 19A, 19B, and 19C for each modulation method. The size of the delay correction unit (delay correction buffer) is defined by the mode, the carrier modulation scheme, and the number of segments constituting the hierarchy, as shown in Table 6, so that a delay of 2 symbols is obtained by transmission and reception. It has become. In consideration of the delay of 2 symbols, in the transmission signal, the frame boundary is shifted forward by 2 symbols after bit interleaving processing. Now, assuming that the frames W, X, Y, and Z are input to the carrier modulation unit, when the signal processing for the frames X and Y is seen, the frames Y ′ and Z ′ that are output from the carrier modulation unit respectively The data of the previous frame is mixed with 2 symbols. Further, the frames Y ″ and Z ″ are output by shifting the head of the frame by two symbols.

  3-1. Switching carrier modulation unit When the carrier modulation parameter changes in the carrier modulation unit, the size of the bit interleave delay correction buffer, the configuration (size and number) of the interleave buffer, and the modulation mapping change.

  Now, as shown in FIG. 20, it is assumed that frames W, X, Y, and Z are input to the carrier modulation unit, the head of frame Y is the switching frame point, and the carrier modulation method is switched from 16QAM to QPSK. At this time, some data of the last two symbols of the frame X remaining in the buffer of the 16QAM carrier modulation unit is not transmitted. On the other hand, the bit interleave buffer of QPSK after switching is initialized (set to value N). Therefore, the initial value N of the buffer of the QPSK carrier modulation unit is mixed with the first two symbols of the frame Y ′. As a result, the frame synchronization is shifted by 2 symbols, and therefore, for the last 2 symbols of the frame X ″ of the output signal, a part of the top 2 symbols of the frame Y and data in which the buffer initial value N is QPSK mapped It has become. As shown in FIG. 20, the output signal switching frame point is the head of the frame Y ″.

  3-2. Switching of carrier demodulator (receiving side) As shown in FIG. 21, 3-1. When the output data described in the section is input to the receiving apparatus, the switching frame point is Y ″. Since the frame X ″ is demapped by 16QAM, the data of the last two symbols mapped by QPSK cannot be correctly decoded. That is, the last two symbols of data in frame X cannot be correctly decoded. Subsequently, when Y ″ which is switched at the receiver side is input, the bit deinterleave unit is switched, so that the first two symbols of the frame Y remaining in the 16QAM bit deinterleave buffer are not output. . Further, since the QPSK bit deinterleave buffer is initialized to the initial value N, the initial value N is mixed in the first two symbols of the frame Y, and cannot be correctly decoded. Note that the switching frame point of the output signal is the head of the frame Y as shown in FIG. 21, and the two symbols before and after the frame switching cannot be correctly decoded.

  3-3. Switching method of carrier modulation section (transmission side) A method of eliminating the damage of the frame before switching and making only the error of the first two symbols after switching will be described. FIG. 22 shows an example of a method for switching carrier modulation from 16QAM to QPSK. As shown in FIG. 22, at the time of switching, both the carrier modulation units before and after switching are operated in parallel, and the output is selected by the switch. The frame Y immediately after switching is input to the carrier modulation unit after switching, and the output data from the dummy data correction unit 15 is input to the carrier modulation unit before switching. As for the output of the carrier modulation unit, for the first two symbols, the carrier modulation unit before switching is selected, and thereafter, switching to the carrier modulation unit after switching is performed.

  As a result, a part of the data of frame X remaining in the buffer of the time interleave part before switching is output, and the contents of the initialized buffer of the carrier modulation part after switching are updated to a part of data of frame Y can do. In this way, it is possible to eliminate the damage of the frame before switching and to make only the error of the first two symbols after switching.

  23 (a), (b), and (c) show the data flow when the above-described carrier modulation switching is performed. The input signal, the output signal after carrier modulation, and the output signal after two symbols shift in synchronization. They are shown in order.

  3-4. As shown in FIG. 24, on the switching reception side of the receiving device, 3-2. The same processing as described in the section is performed. Now, on the transmission side, 3-3. When the signal subjected to the processing described in the section is input, the frame X ″ is decoded and the frame X is output. Subsequently, when the frame Y ″ is input, the configuration of the receiving apparatus is switched. At this time, the dummy data of the frame X ″ remains in the bit deinterleave buffer. For the frame Y, 3-2. As described in the section, since the initial value of the buffer is output for the first two symbols of data, correct data cannot be decoded.

  3-5. When the hierarchical structure increases, on the transmission side, the input signal is assumed to be a frame starting with X, Y, Z, and the output signal is assumed to be a frame X ″, Y ″, Z ″ after the frame synchronization is shifted by two symbols. . Since X is a non-transmitted frame generated by byte interleaving, the switching frame point of the input signal is Y. Therefore, the output signal switching frame point is Y ″. Further, since the initial value of the bit interleave buffer is cleared by the frame X, the output signal Y ″ frame and subsequent frames are transmitted without any problem.

  On the receiving side, 3-4. As described in the section, since the initial value of the bit deinterleave buffer is output to the first two symbols of data, it cannot be decoded correctly.

  3-6. Assuming that the input signal is a frame ending with X, Y, and Z on the transmission side when the hierarchical structure decreases, the switching frame point is the last of the last Z frame. If the output signal is a frame X ″, Y ″, Z ″ after the frame synchronization is shifted by 2 symbols, the switching frame point is the last of Z ″. Now, assuming that no processing is performed, two symbols of the final frame Z remain in the bit interleave buffer. Further, since the frame synchronization is shifted by two symbols, the last two symbols of the frame Z ″ are insufficient. Therefore, 3-3. The dummy data correction unit 15 shown in FIG. 22 described in the section adds data for two symbols, and adds data in the bit interleave buffer after the frame Z. As a result, the frame Z ″ can be transmitted correctly.

  As described above, the frame before switching can be received without being damaged. On the other hand, since the first two symbols are damaged in the frame after switching, it is necessary to configure the original TS in consideration of this point. Two-symbol data is distributed by byte interleaving, and if there is no transmission error, it falls within a range that can be corrected by Reed-Solomon. However, it should be noted that the signal during this period is less resistant to transmission errors.

  4). Switching of Time Interleave Unit FIGS. 25A and 25B show the configuration and modeled diagram of the time interleave unit (transmission side), respectively. FIGS. 26A and 26B respectively show the configuration and modeled diagram of the time deinterleave unit (reception side). As shown in FIG. 25A, the time interleave unit includes a delay correction buffer and a time interleave buffer. As shown in Table 7, the time interleaving unit defines the number of delay correction symbols for the time interleaving length and mode, and the delay time becomes an integral multiple of the frame when transmitted and received. Yes.

In the time interleave unit, the buffer amount does not increase or decrease monotonously with respect to the carrier number, but in the following description, it is modeled as shown in FIG. Also, assume that the input frames to the time interleaving process are α ₁ , α ₂ , ---, β ₁ , β ₂ , ----, and time interleave switching occurs at the head of the frame β ₁ . At this time, the frame α _i represents the frame before switching, and the frame β _i represents the frame after switching. Further, it is assumed that the frame α _i is time interleaved with the transmission / reception delay frame number L in Table 6 and the frame β _i is transmission / reception delay frame number L ′.

  The time deinterleave unit is composed of a time deinterleave buffer as shown in FIG. The time deinterleave unit is also modeled as shown in FIG. 26B in the following description.

4-1. First Method of Switching Time Interleave Units An example of signal processing when switching the length of time interleaving is shown in FIGS. 27 and 28 corresponding to when the transmission and reception delay amounts increase and decrease, respectively. . That is, in FIG. 27, the number of delayed frames is larger after switching than before switching (L <L ′), and in FIG. 28, the number of delayed frames is small (L> L ′). is there. Switching of the time interleave unit is performed after L frames, that is, after all the data of the frame α _i are output from the buffer of the time interleave process. Thereby, the frame α before switching is transmitted without breakage. On the other hand, after switching the configuration of time interleaving, the initial value N of the buffer is mixed in the output signal over the L ′ frame. As a result, the outputs shown in FIGS. 27 and 28 are obtained, and the switching frame point is also in the position shown in the figure.

  4-2. Second Method of Switching Time Interleave Unit FIGS. 29 and 30 show a method of switching time interleaving without mixing the initial value N of the buffer in the output signal after the time interleave switching. Here, FIG. 29 corresponds to the case where the number of delayed frames is larger after switching than before switching, and FIG. 30 corresponds to the case where the number of delayed frames is smaller after switching than before switching. As shown in FIG. 29 and FIG. 30 as a delay correction buffer and an interleave buffer, these buffers are prepared in advance both before and after switching. Data is input to both buffers, and at the time of switching, the output of the buffer is switched. For frame switching, refer to 4-1. As described in the section, it is assumed that after the L frame, that is, immediately after all the data of the frame α is output from the buffer of the time interleave processing. Thereby, the data α before switching is transmitted without being damaged. On the other hand, the initial value of the buffer after time interleave configuration switching is sufficiently cleared, an output not including the initial value N is obtained, and the switching frame point is also in the position shown in the figure.

  4-3. Switching method of time deinterleaving unit The switching of the time deinterleaving unit on the reception side is performed at the switching frame point of the frame to be transmitted. When the time interleave unit is switched by the first method described in the section 4, and 4-2. This will be described separately for the case where the time interleave unit switching is performed by the second method described in the section.

4-3-1. Method of switching time deinterleave part when time interleave part switching is performed by the first method on the transmission side The first method, that is, the reception process of the output signal obtained by the processes of FIG. 27 and FIG. This is shown in FIGS. 31 and 32, respectively. The receiving apparatus switches time deinterleaving with the switching frame. At this time, the buffer is initialized with the initial value N. As a result, the frame α before switching can be correctly decoded. However, because of the initial value N in the input signal and the initial value N of the entire buffer, a frame damaged by the number of delayed frames L ′ after switching is output. For example, as shown in FIG. 31, when the number of delay frames increases from L = 2 to L ′ = 4, damage of L ′ = 4 occurs. That is, two frames β ₁ and β ₂ are damaged, and two incorrect frames are inserted. Further, as shown in FIG. 32, when the number of delay frames is reduced from L = 4 to L ′ = 2, a corrupted frame of L ′ = 2 is output. However, it should be noted that a loss of 2 frames occurs in the received signal, and 4 frames β ₁ , β ₂ , β ₃ , and β ₄ cannot be received correctly.

4-3-2. The method of switching the time deinterleave part when the time interleave part is switched by the second method on the transmission side. The second method, that is, the reception process of the output signal obtained by the processes of FIG. 29 and FIG. This is shown in FIGS. 33 and 34, respectively. The receiving apparatus switches time deinterleaving with the switching frame. At this time, the buffer is initialized with the initial value N. Since the initial value N is not included in the transmission signal, data (a part of β ₂ shown in FIG. 29 and a part of β ₄ shown in FIG. Part) does not cause damage. Therefore, whether the transmission / reception delay time increases or decreases, the above-described 4-3-1. Compared with the method described in the section, switching is performed with less damage by the delay correction buffer after switching.

  4-4. Switching method that inherits the value of the time deinterleave buffer Previously, when switching the time interleave on the receiving side, the data in the previous buffer was discarded. A method for reducing the size will be described.

First, a method of using the contents of the time deinterleave buffer before switching for the time deinterleave buffer after switching will be described.

When the time interleaving length becomes long, the transmitting side performs the above-described second method, that is, 4-2. Switch time interleaving using the method described in section. FIG. 35 illustrates a switching process when the output signal of FIG. 29 is input, that is, the number of time interleave delay frames is switched from L = 2 to L = 4. The switching operation is performed when a switching frame (β ₃ β ₂ β ₁ α ₃ α ₂ ) is received. FIG. 36 shows the operation of the time deinterleave buffer of the receiving apparatus.

The switching of the time deinterleave buffer uses the contents of the time deinterleave buffer before switching according to (1) of [Outside 1]. That is, when the value of each buffer for time deinterleaving before switching is B (i, j) and the value of each buffer after switching is b (i, k), 0 ≦ j + 204 × (I′−I) When switching in the range of / 2 <I ′ × (95−m _i ), the value of B (i, j) is entered in b (i, j + 204 × (I′−I) / 2). Here, (I′−I) / 2 represents the difference before and after switching of the number of transmission / reception delay frames in Table 7. This process extracts part of β ₂ β ₁ from the time deinterleave buffer before switching and substitutes it into the buffer after switching so that the frame β ₂ β ₁ can be output correctly when the frame after switching is received. Yes. As a result, as shown in FIG. 35, an incorrect frame is output in the portion corresponding to N ((L′−L) frame) whose value is the initial value, but β ₁ and β ₂ are correct frames. Is output. However, since the above formula cannot be applied when I = 1 in Mode 3, the switching method described here cannot be applied.

FIG. 37 shows a configuration method on the transmission side when the delay time is shortened, taking as an example the case where the delay amount changes from L = 4 to L ′ = 2. The operation at the time of switching on the transmission side is basically the same as that shown in FIG. 30, but the data from the LL ′ frame before switching (2 frames before in FIG. 37) to the buffer after switching. Stop input. When the head of the frame β ₅ comes, the insertion into the buffer after switching is resumed, and the data output is switched from before switching to the buffer after switching. As a result, the illustrated output result is obtained.

FIG. 38 shows a switching operation on the receiving side. As shown in FIG. 38, switching on the receiving side is performed when the frame β ₅ β ₂ β ₁ is received, based on the operation of the time deinterleave buffer of the receiving apparatus shown in FIG. 39, and before the switching described above. By substituting the value of B (i, j) into b (i, j) for 0 ≦ j <I ′ × (95−m _i ) according to (2) of the contents of the time deinterleave buffer of [1] Do. Thereby, all the contents of the buffer before switching can be used after switching, and the frames β ₁ and β ₂ can be correctly decoded. However, the LL ′ frame disappears from the output signal. In the illustrated example, the frames β ₃ and β ₄ are lost. It should be noted that by shifting the output switching frame point of the time interleaving unit (see FIG. 37) forward by LL ′, it is possible to make the lost frame immediately after the switching frame point of the time deinterleaving output. That is, the switching frame point and the discontinuous point of the frame can be matched. In the example shown in FIG. 38, .beta.1, beta ₂ becomes lost frame, it is possible to decode the beta ₃ after correctly.

On the receiving side, 4-3. When the buffer is initialized by the method described in the section, the output shown in FIG. 40 is obtained. In the signal sending method shown in FIG. 37, as shown in FIG. 38, there is a problem that β ₃ and β ₄ disappear in the output of time deinterleaving. Thus, FIG. 41 shows a method of inserting a NULL frame in advance on the transmitting side into a frame to be lost. Thereby, it is possible to eliminate frames that are lost even in the reception method of FIG.

  Note that, on the transmitting side, even when the time interleave configuration does not change due to the change of the hierarchical parameter, the switching frame point of the output signal with respect to the switching frame point of the input signal is the data before switching as in the above examples. Are all output from the time interleave buffer. The receiving side also follows the switching frame point of the received signal as described above.

  As described above, since data corruption or loss occurs when switching time interleaving, it is necessary to configure the TS in consideration of this point.

  5). Influence of switching of OFDM frame configuration As shown in FIGS. 42 and 43, the OFDM frame has a configuration in which pilot and data symbol arrangements are different between the synchronous modulation unit and the differential modulation unit. For this reason, when the carrier modulation is changed from the synchronous modulation unit to the synchronous modulation unit by switching (for example, when the carrier modulation scheme is changed from 16QAM to 64QAM), the configuration is not changed, but the carrier modulation is different from the synchronous modulation unit. The configuration of the OFDM frame changes when the dynamic modulation unit or the differential modulation unit is changed to the synchronous modulation unit.

  Also, as shown in FIG. 44, the switching frame point of the input signal and the switching frame point of the OFDM frame match. Up to the previous section, the switching position in each processing unit is set to be the head of the frame next to the last frame of the frame including the data before switching. Therefore, if the number of time interleaved delay frames before switching is L, data modulated by the modulation scheme after switching over L frames + 2 symbols is included in the OFDM frame before switching. In particular, when the OFDM frame configuration changes at the time of switching, a symbol modulated by a synchronous system (for example, 16QAM) is transmitted as a symbol of a differential modulation unit. Further, since the symbol modulated by the differential modulation unit is transmitted as the symbol of the synchronous modulation unit, it cannot be demodulated correctly, and an error is mixed in the frame after switching accordingly. Therefore, it is necessary to configure the TS in consideration of these points.

  6). 3. Effect on the entire hierarchy 4. Term (switching between time interleave part and time deinterleave part), and In the section (switching of OFDM frame configuration), the process of switching the hierarchical parameter is defined for each segment. Therefore, as shown in FIG. 45, when the number of segments constituting a hierarchy does not change when the hierarchy parameter is switched, the data corruption and loss that occur in the segment unit occur in common in the segments of the hierarchy. That is, in FIG. 45, data corruption / disappearance that occurs when the time interleave length is changed in the A layer occurs in common in each segment (0 to 4) that configures the A layer. On the other hand, when the number of segments constituting a hierarchy changes due to the switching of the hierarchy parameter, the switching process differs depending on the segment, so that the data is damaged or lost.

  For example, as shown in FIG. 46, when the time interleave length of the A layer is different from the time interleave length of the B layer, the layer A increases by 2 segments when the layer parameter is switched, and the number of segments in the layer B decreases accordingly. To do. The segments 0 to 4 are not damaged or lost because the parameters are not changed, but at least the delay time difference is damaged or lost due to time interleaving in the segments 5 and 6 after switching. It should be noted that the damage / disappearance after the layer parameter switching affects the data in all segments of the layer A by the decoding process after time deinterleaving.

The system of the transmission apparatus for digital broadcasting is shown. The system of the OFDM modulation part in FIG. 1 is shown. The system of the receiver for digital broadcasting is shown. The system of the receiver for digital broadcasting is shown. The operations of convolutional interleaving and convolutional deinterleaving in the transmission device and the reception device are respectively shown. The structure of the byte interleave part is shown. The operation of the byte interleave unit is shown. Two examples of the configuration of the byte interleave unit are shown. The structure of the byte deinterleave part is shown. FIG. 7 shows the effect on the reception side by performing processing by the byte interleave unit having the configuration shown in FIG. The processing of the increased hierarchy in the byte interleave part is shown. When the number of layers increases, the receiving side indicates that a deinterleave buffer initialized with an initial value N is prepared before the frames DC and ED are input. The processing of the hierarchy which decreases in a byte interleave part is shown. When the number of layers is reduced, it indicates that the receiving device can correctly decode the frames Z, A, and B. The structure of the convolution encoding part is shown. The circuit structural example of the 1/2 convolution encoding part is shown. The structure of the convolution decoding part is shown. The structure of the carrier modulation part is shown. The circuit configuration of the bit interleaving unit in FIG. 18 is shown. This shows switching of the carrier modulation scheme from 16QAM to QPSK. Switching of the carrier demodulator is shown. It shows a method for switching carrier modulation from 16QAM to QPSK. The flow of data when switching carrier modulation is shown. The figure shows switching of the configuration of the receiving device. The structure of the time interleave part and the modeled figure are shown, respectively. The structure of the time deinterleave part and the modeled figure are each shown. An example of signal processing when the length of time interleaving is switched is shown in correspondence with an increase in transmission and reception delay amounts. An example of signal processing in the case of switching the length of time interleaving is shown corresponding to a case where the amount of delay in transmission and reception decreases. This shows a method of switching time interleaving without mixing the initial value N of the buffer in the output signal after time interleaving switching. This shows a method of switching time interleaving without mixing the initial value N of the buffer in the output signal after time interleaving switching. The output signal reception process obtained by the process of FIG. 27 is shown. FIG. 29 shows reception processing of an output signal obtained by the processing of FIG. The output signal reception process obtained by the process of FIG. 29 is shown. The output signal reception processing obtained by the processing of FIG. 30 is shown. The switching process when the output signal of FIG. 29 is input is shown. It shows the operation of the time deinterleave buffer of the receiving device. The processing on the transmission side when the delay time is shortened is shown by taking the case where the delay amount changes from L = 4 to L ′ = 2 as an example. The switching operation on the receiving side is shown. It shows the operation of the time deinterleave buffer of the receiving device. It shows the output obtained when the buffer is initialized on the receiving side. 37 shows a method of inserting a NULL frame in advance into a frame that is lost in the processing on the transmission side in FIG. The symbol arrangement | positioning of the pilot and data in the differential modulation part of an OFDM frame is shown. The symbol arrangement | positioning of the pilot and data in the synchronous modulation part of an OFDM frame is shown. This indicates that the switching frame point of the input signal and the switching frame point of the OFDM frame match. This shows that the data corruption and loss that occurs when the time interleave length is changed in the A layer due to the switching of the OFDM frame configuration occurs in common in each segment constituting the A layer. If the layer A increases by 2 segments and the number of segments in the layer B decreases due to the switching of the OFDM frame configuration, the segments 0 to 4 are not damaged or lost, but at least the delay time difference due to time interleaving in the segments 5 and 6 This indicates that damage or disappearance occurs.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Multiplexing part 2 Outer encoding part 3 Hierarchical division part 4 Convolutional encoding part 4 'Convolutional decoding part 5 OFDM modulation part 6 Byte interleaving part 6' Byte deinterleaving part 7 Bit interleaving part 7 'Bit deinterleaving part 8 Carrier Modulation unit 8 'Carrier demodulation unit 9 Time interleaving unit 9' Time deinterleaving unit 10 OFDM frame configuration unit 11 Triangle 12 Byte data correction unit 13 Storage buffer 14 Dummy data generation unit 15 Dummy data correction unit

Claims (2)

  In a transmission apparatus for digital terrestrial broadcasting of a hierarchical transmission method in which different hierarchical parameters are set, the apparatus determines the delay by the bit interleave unit according to the value defined by the number of segments constituting the hierarchy, A transmission apparatus for digital terrestrial broadcasting, comprising: means for performing delay correction so that a delay of two symbols is obtained by transmission and reception, and performing bit interleaving after the delay correction.   A terrestrial digital broadcast receiver for receiving a transmission radio wave transmitted by the terrestrial digital broadcast transmitter according to claim 1.

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