WO2010082280A1 - Radio transmitting apparatus - Google Patents

Abstract

A radio transmitting apparatus wherein a high quality of digital signal transmission is achieved.  A radio transmitting apparatus (100) in a digital broadcast system includes a turbo encoding unit (110), which comprises: an external encoder (211); an internal encoder (214) connected in series with the external encoder (211); and a puncturing unit (215) for puncturing systematic and parity bits outputted from the internal encoder (214) in accordance with a puncture pattern.  Puncture patterns are switched in accordance with an encoding rate of transmission signals to be transmitted by the radio transmitting apparatus (100).  Specifically, according to any one of the puncture patterns prepared in the turbo encoding unit (110), in a symbol including systematic and parity bits, the systematic bit is placed on at least one of two polarity bits, while the parity bits are placed in at least one of groups of bits other than the polarity bits.

Description

Wireless transmission device

The present invention relates to a wireless transmission device.

In recent years, terrestrial broadcasting that has been analog (terrestrial analog television broadcasting) has been digitized for the purpose of effective use of radio waves. Digital broadcasting using terrestrial television broadcasting is called “terrestrial digital television broadcasting”, and audio broadcasting using terrestrial broadcasting is called “terrestrial digital audio broadcasting”.

In the digital system, a conventional TV signal (analog) or audio signal is converted into a digitized signal of 1 and 0 and transmitted. As it is, the information bandwidth to be transmitted is about 20 times larger than that of analog, so the bandwidth is compressed using a technique called code compression (practically MPEG-2) (about 1/30 to 1/60). Broadcast on signal. By using the digital system, it is possible to receive higher-quality (ghost and noise-free) video and audio than the conventional analog system. For example, Non-Patent Document 1 and Non-Patent Document 2 define the technologies related to the digital television broadcast and the digital audio broadcast, respectively.

ARIB STD-B31 Version 1.0 (April 5, 2001) ARIB STD-B29 Version 1.0 (April 5, 2001)

However, although the above-described conventional digital broadcasting technology can realize sufficiently high-quality broadcasting as compared with the analog system, further enhancement of the performance of the digital broadcasting technology is desired.

An object of the present invention is to provide a wireless transmission device that realizes high quality digital signal transmission.

The wireless transmission device of the present invention is a wireless transmission device that transmits a transmission signal in a digital broadcasting system, and includes an outer encoder, an inner encoder arranged in series with the outer encoder, and an output from the inner encoder. Puncturing means for puncturing systematic bits and parity bits according to a puncture pattern, and turbo coding means, and modulation means for forming a modulation signal based on an output signal of the turbo coding means, The puncturing means switches the puncture pattern according to the coding rate of the transmission signal.

According to the present invention, it is possible to provide a wireless transmission device that realizes high quality digital signal transmission.

FIG. 3 is a block diagram illustrating a configuration of a wireless transmission device according to the first embodiment. Diagram for explaining TS remultiplexer processing Diagram showing an example of two-layer division The figure which shows the structure of the generation circuit of PRBS (pseudo random code series) Diagram showing the amount of correction at each level The figure which shows the structural example of a byte interleave part The figure which shows the structural example of a carrier modulation part Diagram showing the amount of delay correction associated with bit interleaving Diagram showing examples of parameter settings in each mode Diagram showing the configuration of the frequency interleave unit Illustration for explaining inter-segment interleaving Diagram for explaining interleaving within a segment Diagram for explaining interleaving within a segment Diagram for explaining interleaving within a segment Diagram showing an example of information allocation to 204 bits B ₀ ~ B ₂₀₃ of the TMCC carrier Diagram showing an example of information allocation for the bit B ₂₀ ~ B ₁₂₁ for TMCC information The figure which shows the OFDM segment constitution of the differential modulation section The figure which shows the arrangement | positioning of the various control signals added by an OFDM frame structure part with the carrier number in the segment in each mode The figure which shows the arrangement | positioning of the various control signals added by an OFDM frame structure part with the carrier number in the segment in each mode The figure which shows the OFDM segment structure of the synchronous modulation part which takes a scattered pilot structure The figure which shows the arrangement | positioning of the various control signals added by an OFDM frame structure part with the carrier number in the segment in each mode Block diagram showing the configuration of the turbo encoder Block diagram showing configuration of outer encoder Block diagram showing the configuration of the inner encoder Diagram showing generator polynomial used in outer and inner encoders The figure which uses for description about the case where the bit arrangement | positioning of a systematic bit and the parity bit 0 becomes a biased structure The figure which uses for description of the puncture process in case an encoding rate is 3/4 The figure which shows the puncture pattern in case a coding rate is 5/6, 7/8 The figure which uses for description of the puncture process in case an encoding rate is 1/2 The figure which uses for description of puncture processing in case a coding rate is 2/3 The figure which uses for description of the puncture process in case an encoding rate is 3/4 The figure which uses for description of the puncture process in case an encoding rate is 1/2 The figure which uses for description of puncture processing in case a coding rate is 2/3 The figure which uses for description of the process in the outer coding part of Embodiment 2. Diagram showing distribution of residual error bits FIG. 9 is a block diagram illustrating a configuration of a wireless transmission device according to the third embodiment. The figure which shows the corrected amount in each hierarchy which concerns on Embodiment 3. FIG. Block diagram showing the configuration of the turbo encoder The figure which shows the corrected amount in each hierarchy which concerns on Embodiment 3. FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of radio transmitting apparatus 100 according to Embodiment 1 of the present invention. In FIG. 1, a radio transmission apparatus 100 includes a TS remultiplexer 101, an outer encoding unit 102, a layer division unit 103, a byte / bit MSB (Most Significant Bit) first unit 104, an energy spreading unit 105, A delay correction unit 106, a bit / byte MSB (Most Significant Bit) first unit 107, a byte interleave unit 108, a byte / bit MSB (Most Significant Bit) first unit 109, and a turbo encoding unit 110, , Carrier modulation section 111, layer synthesis section 112, time interleaving section 113, frequency interleaving section 114, scattered pilot (Scattered Pilot) signal section 115, CP signal generation section 116, and control signal generation section 117. And an additional information generation unit 118 and an OFDM frame configuration unit 119. Regarding the functional units of the wireless transmission device 100, functional units other than the turbo encoding unit 110 have the same functions as those defined in the STD-B31 standard (or STD-B29 standard).

[TS remultiplexer 101]
The TS remultiplexer 101 receives a transmission stream (that is, a transport stream (TS)) and remultiplexes the input transmission stream. The input transmission stream is, for example, an output stream of an MPEG multiplexing unit (not shown).

The transport stream after re-multiplexing is composed of a multiplex frame consisting of n transport stream packets (TSP) as a basic unit.

FIG. 2 is a diagram for explaining the processing of the TS remultiplexer 101. FIG. 2A is a table showing the number of TSPs constituting a multiplex frame with respect to the transmission mode and the guard interval ratio. The TSP constituting the multiplex frame is a 204-byte TSP in which 16-byte null data is added to 188 bytes, and this is called a transmission TS.

As shown in FIG. 2B, the transmission TSP in the multiplex frame is transmitted (TSPX) in the X layer of the OFDM signal (the X layer indicates one of the A layer, the B layer, and the C layer). Finally, it belongs to one of null packets (TSPnull) that are not transmitted as an OFDM signal.

Since the number of transport stream packets that can be transmitted per unit time varies depending on the transmission parameter setting of each layer, there is a match between the input TS of the TS remultiplexer 101 and the output single TS. I can't take it. On the other hand, by complementing an appropriate number of null packets, it is possible to interface the transport stream with a constant clock regardless of the transmission parameter setting.

Since the multiplex frame length matches the OFDM frame length, the receiver can reproduce the synchronization of the transport stream from the synchronization of the OFDM signal, and the synchronization performance is enhanced.

By associating the TSP arrangement in multiple frames with the “separation / combination operation” of the layer, the receiving side reproduces the same single TS as the transmitting side from the signal transmitted divided into multiple layers Can do.

[Outer encoding unit 102]
Outer encoding section 102 receives the transport stream packet obtained by TS remultiplexer 101, and performs error correction encoding for each transport packet. Here, the outer code applied to the outer encoding unit 102 is a shortened Reed-Solomon code (204, 188).

The shortened Reed-Solomon (204,188) code is generated by adding 51 bytes of 00HEX before the input data byte in the Reed-Solomon (255,239) code and removing the first 51 bytes after encoding.

As an element of the Reed-Solomon code, an element of GF (28) is used, and the following expression p (x) is used as a primitive polynomial that defines GF (28).
p (x) = X8 + X4 + X3 + X2 + 1

Also, the generator polynomial g (x) of the (204,188) shortened Reed-Solomon code is as follows.
g (x) = (X-λ0) (X-λ1) (X-λ2) (X-λ15) where λ = 02HEX

[Hierarchy division unit 103]
The layer division unit 103 divides the remultiplexed TS into a designated layer in units of 204 bytes (transmission TSP) from the byte next to the TS synchronization byte to the synchronization byte. At the same time, the layer division unit 103 removes null packets. The hierarchy to which each transmission TSP should belong is specified by the hierarchy information based on the organization information. Here, the maximum number of hierarchies is three. At this time, the OFDM frame synchronization is shifted by 1 byte and becomes the head of the information byte. FIG. 3 is a diagram illustrating an example of two-layer division.

[Byte / bit MSB first part 104]
The byte / bit MSB first unit 104 is provided for each layer. Therefore, here, the same number of three byte / bit MSB first units 104 as the maximum number of layers is provided. The byte / bit MSB first unit 104 receives the byte string divided by the hierarchy dividing unit 103 and performs MSB first processing on the bits in each byte.

[Energy diffusion unit 105]
The energy spreading unit 105 performs an exclusive OR operation on a PRBS (pseudo random code sequence) generated by the circuit shown in FIG. The initial value of the register in the circuit shown in FIG. 4 is “100101010000000” (D1 to D14), and is initialized for each OFDM frame. At this time, the head of the OFDM frame is the MSB position of the byte next to the TSP synchronization byte. It is assumed that the shift register operates also in the synchronous byte portion. The PRBS generator polynomial g (x) is as follows. g (x) = X15 + X14 + 1

[Delay Correction Unit 106]
The delay correction unit 106 performs delay correction on the signal subjected to the energy diffusion processing by the energy diffusion unit 105. This delay correction is for making the delay time in each layer the same by sending and receiving.

FIG. 5 is a diagram showing the correction amount in each layer. By providing a delay of the number of transmission TSPs as shown in FIG. 5, a delay amount including a transmission / reception delay amount (11 transmission TSPs) by byte interleaving is set to be 1 frame + 1 TSP.

In hierarchical transmission, different transmission parameters (number of segments, inner code coding rate, modulation method) can be set for each layer, but in this case, the transmission bit rate in each layer is different and the code of the inner code on the transmission side is different. The transmission rate from the conversion to the decoding on the receiving side is also different. Accordingly, a transmission TSP delay amount (11 TSP) caused by byte interleaving, which will be described later, also varies from layer to layer when converted to a delay time. In order to compensate for the relative delay time difference between layers, delay correction corresponding to the transmission bit rate is performed for each layer prior to byte interleaving.

[Bit / byte MSB first part 107]
The bit / byte MSB first unit 107 receives the bit sequence that has been delay-corrected by the delay correction unit 106, and performs MSB first processing on the byte sequence obtained by bundling the input bit sequence in units of bytes.

[Byte interleaving section 108]
The byte interleave unit 108 byte interleaves the byte sequence obtained by the bit / byte MSB first unit 107. The byte interleave unit 108 has a configuration as shown in FIG. 6, for example.

The total transmission and reception delay due to byte interleaving and deinterleaving on the receiving side is 17 x 11 x 12 bytes (equivalent to 11TSP). The byte interleaving unit 108 performs convolutional byte interleaving on the 204-byte transmission TSP that is error-protected and energy-spread with an 11RS code. The interleave depth is 12 bytes. However, it is assumed that the byte next to the synchronization byte passes through a reference path without delay.

In the byte interleave unit 108 having the byte interleave circuit shown in FIG. The memory capacity of path 1 is 17 bytes (each path is selected every 12 bytes, so the delay amount of path 1 is 17 x 12 bytes), and the memory capacity of path 2 is 17 x 2 = 34 bytes (delay The amount is 17 x 12 x 2 bytes). Also, input and output are cyclically switched sequentially for each byte, such as path 0, path 1, path 2,..., Path 11, path 0, path 1, path 2,.

[Byte / bit MSB first part 109]
The byte / bit MSB first unit 109 receives the byte string after byte interleaving by the byte interleaving unit 108, and performs MSB first processing on the bits in each byte.

[Turbo Encoding Unit 110]
The turbo encoding unit 110 performs turbo encoding on the bit string obtained by the byte / bit MSB first unit 109. The turbo encoding unit 110 is a serial concatenated convolutional code (SCCC) type turbo code processing unit. The turbo encoding unit 110 turbo-encodes the input bit sequence while switching the puncture pattern according to the encoding rate applied to the transmission signal. The configuration and operation of the turbo encoding unit 110 will be described in detail later.

[Carrier modulation section 111]
The carrier modulation unit 111 performs modulation mapping after bit-interleaving a bit string, which is a code word obtained by a convolutional encoder, by a method specified in advance for each layer.

Specifically, the carrier modulation unit 111 includes a delay correction unit, a bit interleaving unit 141, and a mapping unit 142 as shown in FIG.

In the bit interleaving process, a 120 carrier symbol delay occurs in transmission and reception. By adding an appropriate delay correction on the transmission side to this, the transmission and reception are corrected so as to be a delay of 2 OFDM symbols. FIG. 8 is a diagram illustrating the amount of delay correction associated with bit interleaving. In this specification, the parameter setting values differ between modes, and in modes 1 to 3, the parameter settings are as shown in FIG.

[Hierarchical synthesis unit 112]
Hierarchical combining section 112 combines the signals of the respective layers that have been subjected to channel coding and carrier modulation with parameters designated in advance, inserts them into the data segment, and performs speed conversion.

[Time interleaving unit 113]
The time interleaving unit 113 performs time interleaving on the signal subjected to hierarchical synthesis by the hierarchical synthesis unit 112 in units of modulation symbols (I and Q axis units).

[Frequency interleaving section 114]
The frequency interleaving unit 114 frequency interleaves the signal time-interleaved by the time interleaving unit 113.

FIG. 10 is a block diagram showing the configuration of the frequency interleaving unit 114. The frequency interleaving unit 114 includes, in segment division, a partial reception unit, a differential modulation unit (a segment in which carrier modulation is specified as DQPSK), and a synchronous modulation unit (a segment in which the carrier modulation is specified as QPSK, 16QAM, or 64QAM). In order, data segment numbers 0 to 12 are assigned. As for the relationship between the hierarchical structure and the data segment, the data segments of each hierarchy are sequentially arranged in the order of numbers, and the A hierarchy, the B hierarchy, and the C hierarchy are arranged from the hierarchy including the smaller number of data segments. Even when the layers are different, inter-segment interleaving is applied to data segments belonging to the same type of modulation unit.

In addition, regarding the partial receiving unit, since a receiver that receives only the segment is assumed, inter-segment interleaving, which is interleaving with other segments, is not performed. Further, as shown in the frame configuration described later, since the differential modulation unit and the synchronous modulation unit have different frame structures, inter-segment interleaving is executed in each group. Inter-segment interleaving across different layers is performed to maximize the effect of frequency interleaving.

(Inter-segment interleaving)
Inter-segment interleaving is performed for the differential modulation (DQPSK) unit and the synchronous modulation (QPSK, 16QAM, 64QAM) unit, respectively, according to FIG. In FIG. 11 _{, Si, j, k} represents a carrier symbol having a data segment structure, and n represents the number of segments assigned to the differential modulation unit and the synchronous modulation unit.

(Intra-segment interleaving)
As shown in FIG. 12, after performing carrier rotation for each segment according to the segment number, it is randomized as shown in FIGS. Here, S ′ _{i, j, k} is the carrier symbol of the kth segment after inter-segment interleaving is performed. The numbers in FIGS. 13 and 14 indicate the intra-segment carrier numbers after the carrier rotation. 13 and 14, the carrier data having the value indicated by “before” is the carrier data indicated by “after” as a result of intra-segment carrier randomization.

Note that carrier rotation and carrier randomization are performed to eliminate the periodicity of the carrier arrangement. Thereby, when frequency selective fading coincides with the carrier arrangement period after inter-segment interleaving, a phenomenon in which the carrier of a specific data segment is erroneous in a burst is avoided.

[Scattered pilot signal section 115]
Scattered pilot signal section 115 generates a pilot signal and outputs it to OFDM frame configuration section 119. The pilot signal output from the scattered pilot signal section 115 is mapped in the frame by the scattered mapping pattern in the OFDM frame configuration section 119 as will be described later.

[CP signal generator 116]
CP signal generation section 116 generates a pilot signal and outputs it to OFDM frame configuration section 119. The pilot signal output from CP signal generation section 116 is mapped to a certain carrier.

[Control Signal Generation Unit 117]
The control signal generation unit 117 generates a control signal (here, TMCC (Transmission and Modulation Configuration Control) signal) and outputs it to the OFDM frame configuration unit 119. The TMCC signal is mapped to a carrier different from the CP signal in the frame by the OFDM frame configuration unit 119 as will be described later.

FIG. 15 is a diagram illustrating an example of information allocation to 204 bits B ₀ to B ₂₀₃ of a carrier to which a TMCC signal is mapped (that is, a TMCC carrier).

In this embodiment, as shown in FIG. 16, B ₁₁₀ to B _121, which are reserved bits of TMCC in the STD-B31 standard (or STD-B29 standard), are used as new control signals. In order to notify the receiver of the bit allocation of the STD-B31 standard (or STD-B29 standard) and the bit allocation of this embodiment, the system identifiers B ₂₀ to B ₂₁ are used.

[Additional Information Generation Unit 118]
The additional information generation unit 118 generates additional information and outputs the additional information to the OFDM frame configuration unit 119.

[OFDM frame configuration unit 119]
The OFDM frame configuration unit 119 includes a data segment received from the frequency interleaving unit 114, a pilot signal received from the scattered pilot signal unit 115, a pilot signal received from the CP signal generation unit 116, a control signal received from the control signal generation unit 117, and an addition The additional signal received from the information generation unit 118 is mapped to a predetermined symbol to form a frame.

(OFDM segment structure of differential modulator)
As shown in FIG. 17, the OFDM segment configuration of the differential modulation unit is the same as the configuration defined in the STD-B31 standard (or STD-B29 standard). However, in FIG. 17, S _{i, j} represents a carrier symbol in the data segment after interleaving. CP (Continual Pilot) is a continuous carrier, TMCC (Transmission and Multiplexing Configuration Control) is a signal for transmitting control information, and AC (Auxiliary Channel) is an extension signal for transmitting additional information. is there. The carrier numbers in mode 1 are 0 to 107, while in modes 2 and 3, they are 0 to 215 and 0 to 431, respectively.

The arrangement of various control signals added by the OFDM frame configuration unit 119 is shown in FIGS. 18 and 19 with carrier numbers in segments in each mode. The CP of the differential modulator segment is a substitute for the SP of the synchronous modulator when the segment of the synchronous modulator is adjacent to the lower frequency, and is located at the low end of the differential modulator segment . In the receiver, synchronous detection is performed using this CP as the high frequency end SP of the synchronous modulation section segment. The carriers of TMCC and AC (AC1, AC2) are randomly arranged in the frequency direction in order to reduce the influence of periodic dips on transmission path characteristics due to multipath. In addition to the role of the AC pilot signal, it can also be used for additional information for transmission control. Note that the AC1 carrier is arranged at the same location as the AC1 carrier of the synchronous modulation segment.

(OFDM segment structure of synchronous modulation section)
The OFDM frame configuration unit 119 has an SP arrangement configuration (hereinafter referred to as SP Structure) defined by the STD-B31 standard (or STD-B29 standard). FIG. 20 is a diagram illustrating an OFDM segment structure of a synchronous modulation unit having a scattered pilot configuration. Also, the arrangement of various control signals added by the OFDM frame configuration section 119 is shown in FIG. 21 with the carrier numbers in the segments in each mode.

In SP Structure, SPs are arranged every 3 subcarriers in the frequency (subcarrier) direction, albeit intermittently. The arrangement interval in the frequency (subcarrier) direction of the SP uniquely determines the time length of the delay profile (spread) generated in the transmission path. In SP Structure, regression is performed in the time direction with a period of 4 OFDM symbols. This regression period uniquely determines the maximum Doppler frequency that can be accommodated.

[Configuration and Operation of Turbo Encoding Unit 110]
Here, the configuration and operation of the turbo encoding unit 110 will be described.

(Configuration of Turbo Encoding Unit 110)
FIG. 22 is a block diagram illustrating a configuration of the turbo encoding unit 110. In FIG. 22, a turbo encoding unit 110 includes an outer encoder 211, interleavers 212 and 213, an inner encoder 214, a puncture processing unit 215, and a parallel serial conversion unit. (P / S) 216.

The outer encoder 211 is a convolutional encoder, and includes adders 221, 222, and 223 and delay units 224 and 225 as shown in FIG. Here, the coding rate of the outer encoder 211 is ½. The outer encoder 211 encodes the input bit string d _k and outputs the obtained systematic bit d _k (A in FIG. 23) and parity bit P _1k (B in FIG. 23) to the interleavers 212 and 213, respectively. To do.

Interleavers 212 and 213 rearrange the input bit strings. The interleavers 212 and 213 rearrange the input bit string within the processing unit using 1TSP (that is, 204 bytes) as an interleaving processing unit. The bit string after the systematic bit d _k is rearranged by the interleaver 212 is denoted as _dn, and the bit string after the parity bit P _1k is rearranged by the interleaver 212 is denoted as P _1n .

The inner encoder 214 is a convolutional encoder, and includes adders 231, 232, and 233 and delay units 234 and 235, as shown in FIG. Here, the encoding rate of the inner encoder 214 is 2/3. The inner encoder 214 encodes the input bit strings d _n and P _1n , and the obtained systematic bits d _n (A ′ in FIG. 24), parity bits P _1n (B ′ in FIG. 24), and parity bits P _2n (C in FIG. 24) is output to the puncture processing unit 215.

As described above, in the turbo encoding unit 110, the outer encoder 211 and the inner encoder 214 perform convolutional encoding in two stages before and after the interleaving process. Here, the generator polynomial used in the outer encoder 211 and the inner encoder 214 is shown in FIG. Furthermore, systematic bits d _n next bit string systematic bits d _k obtained is sorted by the interleaver 212 at the outer encoder 211 is an output of the inner encoder 214 as it is, obtained in the outer encoder 211 The bit string in which the parity bit P _1k thus rearranged is rearranged by the interleaver 213 becomes the parity bit P _1n that is the output of the inner encoder 214 as it is.

Next, the systematic bit d _n , the parity bit P _1n, and the parity bit P _2n obtained by the inner encoder 214 are thinned out by the puncture processing unit 215. This puncturing process is performed in order to obtain a desired coding rate required when input to the carrier modulation unit provided in the output stage of the turbo coding unit 110.

The puncture processing unit 215 switches the puncture pattern depending on the carrier modulation unit 111 in the subsequent stage. That is, the puncture processing unit 215 switches the puncture pattern according to the coding rate applied to the transmission signal that is finally transmitted from the wireless transmission device 100.

(Problems in puncture processing)
Here, for example, in the transmission system of terrestrial digital television broadcasting (hereinafter referred to as ISDB-T system), DQPSK, QPSK, 16QAM, and 64QAM are used as modulation systems, and different bit interleaving is applied to each modulation system. . In general, when transmission is performed after the output of the turbo encoder is modulated by amplitude modulation, it is preferable in terms of transmission characteristics to arrange systematic bits in the polarity bits. However, when a simple puncture pattern that considers only the coding rate is applied, the systematic bit and the parity bit 0 representing the channel value cannot be arranged in (1) polarity bits (b0, b1) that are difficult to error. (2) Even if it can be arranged in the polarity bits (b0, b1) that are difficult to error, the bit arrangement of the systematic bit and the parity bit 0 is such that a specific parity bit is always arranged in an error-prone bit. There may be a biased configuration. In these cases, there is a problem that transmission characteristics deteriorate. Hereinafter, the case where this problem occurs will be described in detail.

FIG. 26 is a diagram for explaining a case where the bit arrangement of the systematic bit and the parity bit 0 is biased. FIG. 26A shows a puncture pattern 1. Here, the coding rate is 2/3, and 1 parity bit is added to 2 systematic bits. That is, as shown in FIG. 26B, the puncture processing unit 215 receives systematic bits d _n , parity bits P _1n and parity bits P _{2n and} performs puncture processing according to the puncture pattern 1 shown in FIG. 26A. A transmission signal sequence (d _n , P _1n , d _n , d _n , P _2n , d _n ,...) Is output.

When 64QAM is adopted in the carrier modulation unit 111, the transmission signal sequence output from the puncture processing unit 215 is converted into six parallel sequences in the S / P unit as shown in FIG. 26C. Is done. In 64QAM, since one symbol indicates 6 bits, the parity bit _P2n is always arranged at a bit position other than the polarity bit. Further, even if bit interleaving is performed on the output of the S / P unit, the bit position where the parity bit P _2n is arranged basically does not change in the case of 64QAM. In FIG. 26C, a delay unit (no delay, 24-bit delay, 48-bit delay, 72-bit delay, 96-bit delay, 120-bit delay) provided between the S / P unit and the mapping unit 142 is a bit. An interleaving processing function unit (that is, the bit interleaving unit 141) is configured.

Here, as described above, since the systematic bit and the parity bit 0 (that is, the parity bit P _1n ) are used as channel values at the time of decoding, the parity bit 1 (that is, the parity bit P _2n ) is used as a polarity bit. It is preferable to arrange the parity bit 0 (that is, the parity bit P _1n ) in the polarity bit rather than the arrangement. However, as in the example shown in FIG. 26C, when the parity bit 1 is not arranged at all in the polarity bit, the correction capability of the inner decoder may be reduced. As a result, the final error correction capability is reduced. It is thought that it falls.

(Details of processing in the puncture processing unit 215)
Focusing on the above-described problems, in this embodiment, in radio transmission apparatus 100 to which the ISDB-T scheme is applied, puncture processing section 215 selects an appropriate puncture pattern according to the coding rate and performs puncture processing. By improving the correction ability.

<In the case of 16QAM>
First, since one symbol indicates 4 bits in 16QAM, when the coding rate is 3/4, 5/6, or 7/8, the number of parity bits included in one symbol is 1 bit or less. .

(1) When the coding rate is 3/4, 5/6, or 7/8 When the coding rate is 3/4, 5/6, or 7/8, a symbol that includes at least one parity bit is used. A systematic bit is arranged in at least one of the two polarity bits, and a parity bit is arranged in at least one of the bit groups other than the polarity bits. Specifically, at least one bit of the bit group other than the polarity bit is b3 (that is, the fourth bit). By doing so, even if a bit interleaver is provided in the output stage of S / P 216, one parity bit can be included in one symbol.

Here, a case where the coding rate is 3/4 will be described as a specific example. FIG. 27 is a diagram for explaining the puncturing process when the coding rate is 3/4. FIG. 27A shows a puncture pattern used when the coding rate is 3/4. By using this puncture pattern, the parity bit is always arranged at b3 (that is, the fourth bit) as shown in FIG. 27B. As a result, the number of parity bits included in one symbol is 1 bit or less regardless of the delay amount of the bit interleaver, and the number of symbols composed of only systematic bits can be reduced. As a result, error correction capability can be improved.

Also, when the coding rate is 5/6 or 7/8, the same effect as in the case of 3/4 can be obtained by using the puncture pattern shown in FIG.

(2) When coding rate is ½ When coding rate is ½, only one parity bit is added to one systematic bit. Therefore, one parity bit 0 and one parity bit 1 are added to two systematic bits, thereby forming one symbol in 16QAM. As described above, since the parity bit 0 is used as a channel value at the time of outer decoding, it is desirable to arrange the parity bit in the polarity bit with higher probability than the parity bit 1.

Even when the coding rate is ½, in a symbol including at least one parity bit, a systematic bit is arranged in at least one of the two polarity bits, and a bit group other than the polarity bits is included. At least one parity bit is arranged.

FIG. 29 is a diagram for explaining the puncturing process when the coding rate is 1/2. FIG. 29A shows a puncture pattern used when the coding rate is 1/2. By using this puncture pattern, the parity bits are always arranged at b1 (that is, the second bit) and b3 (that is, the fourth bit) as shown in FIG. 29B. Even in the final mapping in consideration of the bit interleaving delay amount, the number of systematic bits and the number of parity bits constituting one symbol of 16QAM are not changed. For this reason, it is possible to avoid the appearance of a symbol composed of only systematic bits. Therefore, in a case where symbols are lost in fading, the number of systematic bits that are lost can be suppressed, and it is possible to prevent a reduction in error correction capability.

(3) When coding rate is 2/3 When coding rate is 2/3, only 1 parity bit is added to 2 systematic bits. Accordingly, by adding a total of 4 parity bits 0 and 1 to 8 systematic bits, 3 symbols in 16QAM are configured. These three symbols become one unit.

FIG. 30 is a diagram for explaining the puncturing process when the coding rate is 2/3. FIG. 30A shows a puncture pattern when the coding rate is 2/3. FIG. 30B shows the bit arrangement before and after the interleaving process when this puncture pattern is used. As shown in the bit arrangement before interleaving processing in FIG. 30B, by using this puncture pattern, parity bit 1 is a polarity bit while determining a position to leave as a puncture pattern so that parity bit 0 is arranged in a polarity bit. The case where it is not arranged at all can be avoided.

Here, in the case of ISDB-T system, b1, b2, and b3 are respectively delayed by 40 bit, 80 bit, and 120 bit by a bit interleaver. The bit arrangement after bit interleaving in this case is shown in the subsequent stage of FIG. 30B. In this case, the bits constituting the symbol are only systematic bits or parity bits. Therefore, when there are erasure symbols during fading, the number of affected systematic bits increases. However, since the case where the parity bit 1 is not arranged at all in the polarity bit can be avoided, it is possible to prevent the error correction capability of the inner encoder from being lowered.

<For 64QAM>
In the case of 16QAM described above, the puncture pattern used at each coding rate can also be used in the case of 64QAM.

(1) When coding rates are 3/4, 5/6, and 7/8 FIG. 31 is a diagram for explaining puncturing processing when a coding rate is 3/4. As shown in FIG. 31, in a symbol including at least one parity bit, a systematic bit is arranged in at least one of two polarity bits, and at least one of a bit group other than the polarity bits. Parity bits are arranged. That is, there is no symbol composed only of systematic bits, and the probability that the systematic bits are arranged in the polarity bits is high, so that the error correction capability can be improved.

(2) When coding rate is ½ Even when coding rate is ½, in a symbol including at least one parity bit, systematic bits are arranged in at least one of two polarity bits. In addition, a parity bit is arranged in at least one of the bit groups other than the polarity bits.

FIG. 32 is a diagram for explaining the puncturing process when the coding rate is 1/2. As shown in FIG. 32, the parity bits are always arranged in b1 (that is, the second bit), b3 (that is, the fourth bit) and b5 (that is, the sixth bit). Even in the final mapping in consideration of the bit interleaving delay amount, the number of systematic bits and the number of parity bits constituting one symbol of 16QAM are not changed. For this reason, it is possible to avoid the appearance of a symbol composed of only systematic bits. Therefore, in a case where symbols are lost in fading, the number of systematic bits that are lost can be suppressed, and it is possible to prevent a reduction in error correction capability.

(3) When coding rate is 2/3 FIG. 33 is a diagram for explaining puncturing processing when the coding rate is 2/3. In the case of 64QAM, even when the coding rate is 2/3, in a symbol including at least one parity bit, a systematic bit is arranged in at least one of the two polarity bits, and other than the polarity bits. Parity bits are arranged in at least one of the bit groups. That is, there is no symbol composed only of systematic bits, and the probability that the systematic bits are arranged in the polarity bits is high, so that the error correction capability can be improved.

As described above, according to the present embodiment, in radio transmitting apparatus 100 in the digital broadcasting system, turbo encoding section 110 includes outer encoder 211 and inner encoder 214 arranged in series with outer encoder 211. A puncture processing unit 215 that punctures systematic bits and parity bits output from the inner encoder 214 according to the puncture pattern, and the puncture pattern is determined according to the coding rate of the transmission signal transmitted from the wireless transmission device 100. Switch.

Specifically, the puncture pattern group includes a modulation scheme applied to a modulation unit provided at an output stage of the turbo encoding unit 110, and a delay caused by a bit interleaver provided between the turbo encoding unit 110 and the modulation unit. In consideration of the amount, it is prepared to satisfy at least one of the following two points.
(1) The systematic bits used as channel values at the time of decoding are arranged so as to come to the amplitude modulation polarity bits, and the parity bits created by the outer encoder 211 and the inner encoder 214 are either One of them is not reflected in the polarity bit at all, so that it is not biased.
(2) Each symbol is not composed of only systematic bits or only parity bits.

More specifically, according to the puncture pattern prepared in the turbo encoding unit 110, in a symbol including at least one parity bit, a systematic bit is arranged in at least one of the two polarity bits, and the polarity bit Parity bits are arranged in at least one of the other bit groups. However, when the coding rate is 3/4 and the modulation method is 16QAM, an exception is made.

In the above description, the description has been made on the premise of the 13-segment format defined in the STD-B31 standard (or STD-B29 standard). That is, for example, it is based on a transmission system for terrestrial digital television broadcasting (hereinafter referred to as ISDB-T system) and a transmission system for terrestrial digital audio broadcasting (hereinafter referred to as ISDB-Tsb system). However, the present invention is not limited to this, and can also be applied to one-segment broadcasting. That is, the present invention can also be applied to multimedia broadcasting for mobile terminals.

(Embodiment 2)
In Embodiment 2, the parity bit obtained by the outer coding process is not used, but a known bit sequence is used instead. The radio transmission apparatus according to Embodiment 2 has the same basic configuration as radio transmission apparatus 100, and will be described with reference to FIG.

In radio transmission apparatus 100 according to Embodiment 2, outer encoding section 102 receives the transport stream packet obtained by TS remultiplexer 101 as in Embodiment 1, and for each transport packet Perform error correction coding. Here, the outer code applied to the outer encoding unit 102 is a shortened Reed-Solomon code (204, 188).

However, in Embodiment 2, outer coding section 102 outputs a known bit sequence in place of the parity bit sequence obtained by the error correction coding process.

That is, as shown in FIG. 34, the TSP after encoding obtained by using the shortened Reed-Solomon code (204, 188) is a synchronization byte (1 byte), a systematic bit sequence (in the figure, a data part: 187 bytes) and a parity bit sequence (parity portion: 16 bytes in the figure). Outer encoding section 102 replaces this parity bit sequence with a known bit series, and then outputs the encoded TSP to layer division section 103. For example, the known bit sequence may be composed of only 0 values or may be composed of only 1 values.

The energy spreading unit 105 performs exclusive OR operation on the PRBS (pseudo random code sequence) generated by the circuit shown in FIG. 4 for each layer and the signal excluding the synchronization byte and the known bit sequence.

[Contrast technology]
In the ISDB-T system, a shortened Reed-Solomon code (204, 188) is applied for each TSP as outer decoding. This shortened Reed-Solomon code has the ability to correct random errors up to 8 bytes out of 204 bytes. On the other hand, the inner code in the ISDB-T system uses a punctured convolutional code having a constraint length of 7 and an encoding rate of 1/2 as a mother code. By such a combination of the outer code and the inner code, on the receiving side, for example, after performing inner decoding by Viterbi decoding to perform error correction, Reed-Solomon decoding is further performed as outer decoding. In this way, the final TSP packet error rate is reduced.

On the other hand, a turbo code is known as a technique for realizing transmission characteristics close to the limits of information theory by a realistic process. In a broadcasting system such as the ISDB-T system, a PER around 2 × 10 ⁻⁴ is required.

Therefore, as described in Embodiment 1, the wireless transmission device 100 is provided with a turbo encoding unit 110 as a turbo encoder used for inner decoding. The turbo coding unit 110 is a serial concatenated convolutional code (SCCC) type turbo code processing unit that is less likely to be flattened. As a result, it is possible to improve the BER characteristics of the inner decoding at the same CN ratio, so that the effect of reducing the final TSP packet error rate can be expected.

However, error bits remaining after turbo decoding remain concentrated on a specific TSP. Therefore, Reed-Solomon codes used for outer codes as error correction codes that are resistant to random errors cannot remove residual errors concentrated on a certain TSP, resulting in the number of error packet errors after turbo decoding. And the number of error packets after decoding in Reed-Solomon decoding are not greatly different, and there is a problem that the effect of improving the characteristics of inner decoding cannot be seen.

FIG. 35 is a diagram showing a distribution of residual error bits. FIG. 35A shows an example of the distribution of residual error bits after turbo decoding, and FIG. 35B shows an example of the distribution of residual error bits after Viterbi decoding. In FIG. 35, the vertical axis represents the number of residual bit errors after decoding for each TSP, and the horizontal axis represents the number of trials. Comparing FIG. 35A and FIG. 35B, the total number of error bits is smaller in FIG. 35A than in FIG. 35B, but in FIG. 35A, errors remain concentrated on a certain TSP. On the other hand, in FIG. 35B, the number of residual errors is more uniform for each TSP than in FIG. 35A.

As described above, even if a turbo code having a stronger error correction capability is applied as the inner code, the correction capability by the Reed-Solomon decoding in the subsequent stage cannot be expected.

Therefore, in the present embodiment, outer coding section 102 outputs a known bit sequence instead of the parity bit sequence obtained by error correction coding processing.

Here, the hierarchy division unit 103 divides the remultiplexed TS into a designated hierarchy in units of 204 bytes (transmission TSP) from the byte next to the TS synchronization byte to the synchronization byte. Therefore, the receiver side can use 17 consecutive bytes of the parity bit sequence (16 bytes) and the synchronization byte (1 byte) as known bits in turbo decoding. In particular, a known bit sequence is transmitted after being interleaved by a serial concatenated convolutional code (Serial) Concatenated 部 Convolutional Codes, SCCC) type turbo code processing unit. Mixed randomly. Thereby, the reliability of the likelihood information input to the serially connected turbo outer decoder can be improved, and as a result, the packet error rate characteristic can be improved.

In the above description, the serially connected turbo code has been described. However, the present invention is not limited to this, and the same effect can be obtained even with a parallel connected turbo code.

(Embodiment 3)
In the third embodiment, the byte interleaving unit 108 shown in FIG. 1 is not used. FIG. 36 is a block diagram of radio transmitting apparatus 100a according to the third embodiment. 36 has the same basic configuration as that of the wireless transmission device 100 shown in FIG. 1 except that the byte interleaving unit 108 is not used, and a description thereof will be omitted.

In the wireless transmission device 100 shown in FIG. 1, the error bits remaining after turbo decoding tend to harden in close proximity. Therefore, if error bits generated in a certain TSP are distributed among a plurality of TSPs by byte interleaving section 108, since Reed-Solomon decoding is not performed in Embodiments 1 and 2, an error packet after turbo decoding is used. There arises a problem that the number of final error packets increases rather than the number.

Therefore, in the third embodiment, the byte interleaving unit 108 in the first and second embodiments is deleted, and the delay correction unit 106 has no influence of the delay amount due to the byte interleaving. Therefore, the transmission as shown in FIG. By providing a delay equal to the number of TSPs, the transmission / reception delay amount is set to be 1 frame + 1 TSP. Thereby, in Embodiment 3, the subject that the number of final error packets will increase rather than the number of error packets after said turbo decoding can be solved.

Note that in Embodiment 3, the wireless transmission device 100a uses the turbo encoding unit 110 shown in FIG. 22 as the turbo encoder used for the inner decoding, but this is the turbo encoding unit 110a shown in FIG. In this manner, a configuration in which a bit interleaver 217 is further provided in the preceding stage of the outer encoder 211 may be adopted. In this case, in the third embodiment, the correction amount shown in FIG. 5 is the correction amount shown in FIG. According to this configuration, the positions of known bits can be dispersed.

The disclosure of the specification, drawings and abstract contained in the Japanese application of Japanese Patent Application No. 2009-006969 filed on Jan. 15, 2009 and the Japanese Patent Application No. 2009-025925 filed on Feb. 6, 2009 is hereby incorporated by reference. Incorporated.

The wireless transmission device of the present invention is useful for realizing high quality digital signal transmission.

Claims (3)

A wireless transmission device for transmitting a transmission signal in a digital broadcasting system,
Turbo coding means comprising: an outer encoder; an inner encoder arranged in series with the outer encoder; and puncturing means for puncturing systematic bits and parity bits output from the inner encoder according to a puncture pattern When,
Modulation means for forming a modulation signal based on the output signal of the turbo coding means;
Comprising
The puncturing means is a wireless transmission device that switches the puncture pattern according to a coding rate of the transmission signal. Among symbols that are output after being punctured by the puncturing means, in a symbol including at least one parity bit, a systematic bit is arranged in at least one of two polarity bits, and other than polarity bits. The radio transmission apparatus according to claim 1, wherein a parity bit is arranged in at least one of the bit groups. The radio transmission apparatus according to claim 1, wherein at least one systematic bit and at least one parity bit are arranged in all symbols of a symbol group output after being punctured by the puncturing means.

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