JP2991694B1 - Digital transmitter and receiver - Google Patents

Abstract

Kind Code: A1 Abstract: In a digital data transmission system in which a transmission system is dynamically switched in one frame, desired digital data can be transmitted without generating a bit error at a switching point of each modulation system. . SOLUTION: Video, audio and various digital data are multiplexed in accordance with the MPEG2 system to generate a transport packet (TS packet) of 188 bytes. A parity check byte (101) of Reed-Solomon code is added to the 16 bytes following each TS packet, and 48 packets are combined to form one frame. By making the start point of puncturing coincide with the start point of the first slot of each transmission scheme when performing convolutional coding, it becomes unnecessary to detect the depuncturing phase on the receiver side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmitter and a receiver according to a digital modulation / demodulation technique applicable to digital broadcasting and the like.

[0002]

2. Description of the Related Art In the generally known field of digital data transmission, a transmitting side encodes a signal by a convolutional code, modulates the signal to a desired frequency, transmits the signal, demodulates the signal on a receiving side, and then performs Viterbi decoding. In many cases, error correction is performed to improve the reliability of data transmission.

As a coding rate of the convolutional code used here (= amount of data to be transmitted / amount of data to which redundancy is actually transmitted), a coding rate of 1/2 is often used. . In this case, the information amount of data that can be transmitted is そ れ ぞ れ of the data amount that is actually transmitted.

In order to transmit more information on a transmission line having the same transmission capacity, for example, 3/4 or 7 /
8, a convolutional code with a larger coding rate is used, and the coding rate is 3/2 each as compared with the case where the coding rate is 1/2.
Thus, a transmission capacity that is twice or ／ times as large can be secured.

One of the methods for constructing a convolutional encoder and a Viterbi decoder having such a large coding rate is a method using puncturing (decimation).

For example, a case will be described in which a convolutional code having a coding rate of 1/2 is used as a mother code and a convolutional code having a coding rate of 7/8 is generated therefrom. In this case, among the 14-bit data obtained by encoding the 7-bit data, 6 bits are not decimated and transmitted, and only the remaining 8 bits are transmitted. Can be realized. This is generally called a punctured code.

A value other than 1 or 0 (for example, 0.5) for the 6 bits not transmitted on the receiving side.
Then, by performing Viterbi decoding at a coding rate of 1/2 after interpolation, Viterbi decoding at a coding rate of 7/8 can be realized.

However, there is a need for a method for thinning out data on the transmission side, with some methods having little deterioration. As an example, a method of puncturing a convolutional code having a coding rate of 1/2 and generating a punctured code having a coding rate of 7/8 will be described with reference to Table 1 below.

[0009]

[Table 1]

Now, data D1, D before encoding
2, D3, D4, D5, D6, and D7 are coded by a convolutional coding apparatus having a coding rate of 1/2 .
As shown in lines 1 and 2, C1 ｛X1, X2, X3, X
4, X5, X6, X7} and C2 {Y1, Y2, Y
3, Y4, Y5, Y6, Y7} are generated .
You . As shown in the third and fourth lines, this is represented by data X
5, X7} and 6 bits {Y2, Y3, Y4, Y6} are decimated, and data {X1, X2, X3, X4,
Only 8 bits of X6} and {X1, X5, X7} are transmitted.

On the receiving side, a value other than 1 or 0 is interpolated into the data of the thinned portion, and C1'１X1 ', X2', X
3 ', X4', I5, X6 ', I7｝ and C2' ｛Y
1 ′, I2, I3, I4, Y5 ′, I6, Y7 ′} (where “′” indicates a received signal sequence, and In indicates interpolated data). Are decoded by a Viterbi decoder having a coding rate of 1/2.

At this time, if it is not known which part of the received data sequence is X1 'or Y1', this interpolation operation cannot be performed. Therefore, generally, it is assumed that arbitrary received data is X1 'and Y1', depuncturing and Viterbi decoding are performed, the reception quality at that time is monitored, and this is shifted by one bit and repeated seven times. , Where the best reception quality was obtained is X
1 'and Y1', and thereafter, the puncture code is decoded at the recognized phase.

[0013]

However, in a system in which a transmission system including a plurality of coding rates and modulation systems is dynamically switched and transmitted in one frame, each time the system is switched to each transmission system, the above-described operation is performed. Has to be detected, there is a disadvantage that a bit error of several bits always occurs at the switching point of each transmission method.

In view of the above, it is an object of the present invention to provide a digital data transmission system in which the transmission system is dynamically switched within one frame without causing a bit error at the switching of each transmission system. It is an object of the present invention to provide a digital transmission device and a reception device which enable transmission of desired digital data.

[0015]

SUMMARY OF THE INVENTION The present invention relates to a digital transmitting apparatus and a receiving apparatus applicable to digital broadcasting and the like, in which data to be transmitted has a frame structure, and In a transmission system in which a plurality of transmission methods are switched and transmitted in a frame section,
By providing a frame structure consisting of n slots (n: an integer) to the data to be transmitted and making the start point of puncturing coincide with the start point of the first slot of each transmission method when performing convolutional coding, the receiver It is unnecessary to detect the depuncturing phase on the side.

In particular, a frame synchronization signal W1 indicating the beginning of a frame in one frame period, and a TMCC (Transmission) having information on a transmission method of a main signal.
& Multiplexing Configurati
on Control; transmission multiplexing configuration control) signal, a superframe synchronization signal W2 (or W3) indicating the first frame in a superframe, and a transmission system that performs transmission using a modulated wave composed of a main signal. By performing puncturing and depuncturing that coincides with the start point of the first packet assigned to each transmission method based on the signal and the superframe synchronization signal, the need for detecting the depuncturing phase on the receiver side is eliminated. is there.

The digital transmitting apparatus according to the present invention forms a frame by providing N (N: positive integer) one slot including a packet of a multiplexed signal, and
Dividing the constituting N slots into a plurality of slot groups,
The combination of error correction coding and modulation
Transmission method selected from among multiple transmission methods
Digital transmission for allocating to each slot group and transmitting
An apparatus, after the convolutional encoding to the data sequence with the frame, for each of the respective slot group
Its match the starting point of the first slot is obtained by including a convolutional encoding means to start puncturing.

Here, the data sequence coded by the convolutional coding means is provided with coding / modulation means for performing error correction coding and modulation in a transmission system selected in packet units. It can be a transmitting device.

The modulating means includes a frame synchronization W1 at the head of each frame of the modulated wave and at least q
A TMCC signal that has information of a plurality of types of modulation schemes used after a superframe (q: a positive integer) and information that leap in the time occupancy thereof, and a superframe synchronization W2 indicating that the frame is the first frame in the superframe. Or W3 indicating that it is not the first frame in the superframe
It is preferable to encode, modulate, and multiplex with a transmission system that requires the lowest C / N among a plurality of transmission systems that can use the above.

A digital receiving apparatus according to the present invention receives a modulated wave generated by the encoding / modulating means described above,
A frame synchronization pulse is generated from the frame synchronization W1, and a superframe synchronization pulse is generated from the superframe synchronization W2 or W3.
Based on the content of the signal, gate signals required in various parts of the receiver are generated on the basis of the frame pulse and the superframe pulse on a time basis, and these gate signals W1, TMCC, W2
(Or W3) is provided with demodulation / decoding means for demodulating and decoding a main signal portion encoded / modulated by a plurality of transmission systems in a time division manner subsequent to (W3).

Here, the data sequence demodulated and decoded by the demodulation / decoding means is subjected to a depuncturing operation with the superframe synchronization pulse and the frame synchronization pulse as a reference and the beginning of each packet as a reference, thereby performing Viterbi decoding. It is possible to adopt a configuration including a Viterbi decoding means for performing the above.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention, which will be described in detail below, is a transmission system in which modulated waves by a plurality of transmission methods are time-division multiplexed and transmitted in one frame section, and frame synchronization and superframe synchronization are performed. A digital transmitting apparatus and a digital receiving apparatus that do not need to detect a depuncturing phase on the receiver side by performing puncturing and depuncturing that match the beginning of each packet as a reference.

In the embodiment shown here, a transmission system for digital satellite broadcasting by a BS (broadcast satellite) will be described as an example.

First, the configuration of a multiplexed signal handled in this transmission system will be described. In this system, MPEG
Video, audio, and various digital data are multiplexed in accordance with the two systems to generate a 188-byte transport packet (TS packet).

FIG. 1 shows this transport packet (T
2 shows an example of a frame structure of multiplexed data composed of S packets. As shown in this figure, a parity check byte (101) of Reed-Solomon code (RS (204, 188)) is added to 16 bytes following each transport packet (TS packet), and 48 packets are collected. Thus, one frame is formed.

Here, 48 positions occupied by packets in one frame are called slots. Although a 1-byte packet synchronization code (47 in hexadecimal) is originally written in the first byte of each TS packet, in this transmission system, when a frame is formed, the frame synchronization signal W1 (102 2) (16 bits), 8 bytes (64 bits) as a control signal called a TMCC signal (103), and 2 bytes (16 bits) as a superframe synchronization signal W2 (or W3) (104).
2) (96 bits).

Here, a case where only one packet in one frame is transmitted by a certain transmission method will be described. In this case, in order to perform interleaving at a depth (depth of 8 or more) sufficient to bring out the capability of the error correction code, a superframe is formed by integrating eight frames into one unit, and the same slot position is set therein. Are interleaved with the eight slots as one unit. At this time, it is necessary to be able to identify the top frame position in the superframe.
4) If W2, the first frame in the super frame,
If it is W3, it is identified as another frame.

At each slot position, a transmission system desired by the carrier occupying the slot is specified. For example, as shown in FIG. 1, for example, the first eight slots are transmitted by the transmission scheme 1, and the second half 40 slots are transmitted by the transmission scheme 2.
Is specified.

Information on the correspondence between each slot position and the transmission method is described in TMCC (Transmission Multiplexing Control Signal). The contents of the TMCC indicate the frame configuration after two superframes. When the transmission system is switched, the contents of the TMCC are changed two superframes before.

From the multiplexed signal having this frame structure,
A modulated wave like the example shown in FIG. 2 is generated. As shown in the figure, a frame synchronization W1 (3
2 symbols) (201), TMCC (128 symbols)
(202), superframe synchronization W2 (or W3)
A total of 192 symbols (32 symbols) and (203) are multiplexed by binary phase shift keying (BPSK) modulation.

The reason why the number of these symbols is twice the number of bits corresponding to W1, TMCC and W2 (W3) in the multiplexed signal shown in FIG. This is because convolutional coding at a rate of 1/2 has been performed and the same number of redundant bits as the original data amount has been added.

Subsequent to these header portions, the transmission method 1 multiplexes 8 slots of the main signal and the transmission method 2 multiplexes 40 slots. In addition, about this main signal section,
4 for every 203 symbols of modulated waves used for transmission of the main signal
A symbol random BPSK modulation wave (phase reference burst symbol) is inserted. The BPSK symbol enables carrier reproduction up to a low C / N.

On the receiver side, after capturing the frame synchronization, the TM
Performs demodulation and decoding of the CC part and starts demodulation and decoding after detecting the transmission method of the succeeding main signal part. Therefore, even if the transmission method is changed, the transmission method of each slot is dynamically switched in units of a superframe. It is possible.

Next, a more detailed description will be given with reference to a block diagram of the transmission device.

FIG. 3 shows an example of the configuration of a transmitting apparatus for generating a modulated wave from a signal in which a plurality of video signals, audio signals, and data services are multiplexed by a multiplexing apparatus and a frame composed of 48 slots is formed. FIG. In this example, 36 packets are transmitted using TC8PSK, and 7 packets are combined with error correction coding using a convolutional code having a coding rate of 7/8 and quadrature phase shift keying (QPSK) modulation. The transmission method (hereinafter, QPSK r = 7/8) is used, and for three packets, a transmission method (hereinafter, referred to as “QPSK r = 7/8”) that combines error correction coding with a convolutional code having a coding rate of 3/4 and QPSK modulation is used. In this case, transmission is performed using QPSK r = 3/4).

Here, if all data is transmitted by TC8PSK, which has the highest frequency use efficiency among the transmission systems assumed in the present system, 48 slots of data can be transmitted in one frame period. When transmitting with QPSK (r = 7/8) as in this example, the efficiency is 7/8 of TC8PSK, and QPSK (r = 3 /
When transmitted in 4), the efficiency is 3/4 of TC8PSK.
Therefore, data that cannot be transmitted is generated in one frame.

Therefore, in the example shown in FIG.
One slot of a slot 7 transmitted in (r = 7/8) that is not actually transmitted (dummy packet)
By inserting a dummy packet of one slot into slot 3 transmitted by QPSK (r = 3/4) so that the number of slots per frame is constant regardless of the modulation method. ing.

Parts (302), (303), and (304) obtained by removing the leading byte of each slot from this signal
, Data is randomized by an energy diffusion circuit 305, and a block byte interleave having a depth of 8 is applied by an interleave circuit 306. Next, the trellis / convolutional encoding circuit 307 calculates TC
Trellis coding (r = ２) is applied to the data portion transmitted by 8PSK, and QPSK (r = 7/8) and Q
Convolutional coding (r = 1/2) is performed on the part transmitted by PSK (r = 3/4).

Note that these encoding circuits are executed by the same circuit. QPSK (r = 7/8) and QP
For the part transmitted by SK (r = 3/4), the start point of the head packet of the slot allocated to each transmission scheme is set so that the coding rate becomes 7/8 and 3/4, respectively. The puncturing rate is specified by the circuit 315 so as to be the start point of the thinning, and the data is thinned out by the puncturing circuit 314 from the start point of the first slot among the slots allocated to each transmission scheme.

On the other hand, the error correction code is added to the TMCC signal portion (316) by the RS (64, 48) encoder 309, the data is randomized by the energy spreading circuit 310, and the trellis / convolutional coding circuit 307 is used. Performs convolutional coding (r = １ ／).

These encoded data are BPSK
By the / QPSK / 8PSK mapper circuit 308, W1,
For TMCC and W2 parts, TC8PS of BPSK
For the data part transmitted with K, 8PSK QPS
The portion transmitted by K (r = 7/8) and QPSK (r = 3/4) is converted into QPSK mapping, that is, converted into signals (8 bits each) representing signal points I and Q on a complex plane.

The BPSK / QPSK / 8PSK mapper circuit 308 is usually constituted by a read-only memory (ROM), and its function is as shown in FIG. In (1) of the figure, as an example, when the input 3-bit signal is “010”, the output is I = −90 and Q = + 9.
It is output like 0.

The output of the mapper circuit 308 is the quadrature modulator 31
2 to generate a quadrature modulated wave 313.

After interleaving of the processing described above,
FIG. 5 shows a time chart of the processing up to symbol mapping.

FIG. 5 is a diagram showing the generation of a symbol mapping signal from a multiplexed signal. The first row of the figure shows a bit stream of data after interleaving the main signal portion. . The first processing is performed on this bit stream signal, that is, (1) convolutional coding at a coding rate r = １ ／ is performed on the W1, TMCC, and W2 (W3) portions.

(2) For the TC8PSK portion of the main signal portion, serial / parallel (S / P) conversion of the bit string is performed.

(3) Of the main signal parts, QPSK (r = 7
/ 8) and the QPSK (r = 3/4) portion are subjected to convolutional coding at a coding rate r = 1/2.

The signal format after the processing is shown in the second row. The third processing, that is, (1) parallel / serial (P / S) conversion is performed on W1, TMCC, and W2 (W3) portions.

(2) In the TC8PSK portion of the main signal portion, a one-bit signal out of two bits is subjected to a convolutional coding at a coding rate r = 1/2 to a three-bit row signal.

(3) Of the main signal part, QPSK (r = 7
/ 8) and QPSK (r = 3/4) are punctured in accordance with the respective rates, and the positions shown in the figure (the starting point of the leading slot among the slots allocated to each modulation scheme) are determined. This is the starting point of the puncturing operation.

The signal format after the processing is shown in the third line. Further, the signal obtained here is re-stripped with a half rate symbol clock, and the signal after symbol mapping is shown in the fourth row.

Next, the circuit configuration of the receiving system will be described. FIG. 6 shows an example of the configuration of a receiving apparatus when a TMCC signal is transmitted in a time-division multiplexed manner.

In FIG. 6, first, a received signal in the 12 GHz band received by the BS antenna 601 is frequency-converted into a signal of the first intermediate frequency (IF) in the 1 GHz band, and the channel selection / frequency conversion circuit 602 converts the signal to 479.5 MHz.
Is converted to a second IF. This signal is synchronously detected by a quadrature detection circuit 603, so that I,
A Q signal is obtained.

Here, first, W1, TMCC, W2 (W
3) No depuncturing is performed on the part, Viterbi decoding is performed by the trellis / Viterbi decoder 606, energy despreading is performed by the same processing as that performed on the transmission side by randomization (611), and RS (64, 48) decoding is performed. (612)
Thus, the TMCC is decoded. The gate signal generation circuit 613 identifies the contents of the TMCC and generates a gate signal for each section of the receiver.

Next, a decoding process for the main signal portion is performed based on the gate signal obtained here.

That is, the trellis / Viterbi decoder 606
Thus, trellis decoding is performed for the TC8PSK portion of the main signal portion. QPSK of the main signal portion
For the (r = 7/8) portion, Viterbi decoding (r = 1/2) is performed while depuncturing at a coding rate r = 7/8 is performed by a depuncturing circuit.

Similarly, QPSK (r =
For the 3/4) portion, a coding rate r is obtained by a depuncturing circuit.
Viterbi decoding (r = 1/2) is performed while performing depuncturing of = 3/4.

The timing for resetting depuncturing is set to the start point of the leading slot among the slots assigned to each modulation method.

Thereafter, block byte deinterleaving with a depth of 8 is performed (608), and energy despreading is performed in the same manner as randomization performed on the transmission side (609), and 47 (hexadecimal) is placed at the head of each slot. To supplement RS (20
4,188) decoding is performed (610).

By the above processing, the original multiplexed signal can be constructed. After this, the TS of the broadcaster desired by the viewer
Is extracted based on the TS identifier (620), and MPEG
The MP @ HL decoder 621 decodes the image signal into a high-definition image signal and displays it on the display 622, thereby completing the reception.

After the interleaving of the processing described above,
FIG. 7 shows a time chart of processing up to symbol mapping.

FIG. 7 is a diagram showing generation of a multiplexed signal from a received symbol signal. The first row of the figure shows signal point positions of a received modulated wave. The first processing, that is, clock rate conversion to a double frequency, is performed on the symbol stream signal to obtain a signal in the second row. Further, the second processing, ie, (1) serial / parallel (S / P) conversion is performed on W1, TMCC, and W2 (W3) portions.

(2) The TC8PSK portion of the main signal portion is trellis-decoded to produce a 2-bit signal.

(3) Of the main signal part, QPSK (r = 7
/ 8) and QPSK (r = 3/4)
Perform depuncturing according to each rate. When performing debanking, the position shown in this figure (the start point of the leading slot among the slots allocated to each transmission method) is set as the start point of depuncturing. By performing the processing, a signal in the third row is obtained.
Further, the third processing, that is, (1) Viterbi decoding with a coding rate r = 1/2 is performed on the W1, TMCC, and W2 (W3) portions.

(2) For the TC8PSK portion of the main signal portion, the parallel / serial (P / S) conversion of the bit string is performed.

(3) Of the main signal part, QPSK (r = 7
/ 8) and QPSK (r = 3/4)
Viterbi decoding with a coding rate r = １ ／ is performed.

The signal format after the processing is shown in the fourth row. Thereafter, the signal is subjected to deinterleave energy despreading and RS decoding.

[0068]

As described above, according to the present invention, 1
In a transmission system in which transmission is performed using a modulated wave in which a plurality of transmission methods are used in a frame section, a start point of a first slot among slots allocated to each modulation method on the basis of frame synchronization and superframe synchronization. By performing the matching puncturing and depuncturing, it becomes unnecessary to detect the depuncturing phase on the receiver side.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of a frame structure of multiplexed data used in BS digital broadcasting.

FIG. 2 is a diagram illustrating a configuration example of a modulated wave of a BS digital broadcast.

FIG. 3 is a diagram illustrating an example of a configuration of a transmission device for generating a modulated wave from a multiplexed signal.

FIG. 4 is a diagram showing an example of signal point arrangement of 8PSK, QPSK, and BPSK mappers.

FIG. 5 is a diagram illustrating a process of generating a symbol mapping signal from a multiplexed signal.

FIG. 6 is a diagram illustrating a configuration example of a BS broadcast receiving device.

FIG. 7 is a diagram illustrating a process of generating a multiplexed signal from a received symbol signal.

[Explanation of symbols]

 101 RS (204,188) parity check code 102 Frame synchronization signal W1 103 TMCC (transmission multiplexing configuration control signal) 104 Superframe synchronization signal W2 or W3

Continued on the front page (72) Inventor Fumiaki Minematsu 1-10-11 Kinuta, Setagaya-ku, Tokyo Japan Broadcasting Corporation Within the Broadcasting Technical Research Institute (72) Inventor Hajime Matsumura 1-110-11 Kinuta, Setagaya-ku, Tokyo Japan Broadcasting Corporation (56) References IEICE Technical Report, Vol. 97, no. 555, pp. 35-39, SAT 97-130, “Demonstration experiment of transmission system for BS digital broadcasting” (58) Fields investigated (Int. Cl. ⁶ , DB name) H04J 11/00 H03M 13/12

Claims (5)

(57) [Claims] 1. A frame is constituted by providing N (N: positive integer) one slot including a packet of a multiplexed signal, and the N slots constituting the frame are divided into a plurality of slots.
Divided into lots, error correction coding and modulation
Each of the multiple transmission methods consisting of
The selected transmission method is assigned to each slot group and transmitted.
A digital transmitting apparatus for transmitting , by performing convolutional coding on a data sequence having the frame, starting puncturing by matching the start point of the leading slot for each of the slot groups . A digital transmission device comprising: 2. An encoding / modulating means according to claim 1, wherein said encoding / modulating means performs error correction encoding and modulation on the data sequence encoded by said convolutional encoding means in a transmission system selected in packet units. A digital transmission device, comprising: 3. The method according to claim 2, wherein the modulating means includes a frame synchronization W1 at the beginning of each frame of the modulated wave and a plurality of transmission schemes used at least after q superframes (q: positive integer). A TMCC signal having information that jumps to the type and its time occupancy and a superframe synchronization W2 indicating that the frame is the first frame in the superframe or a W3 indicating that the frame is not the first frame in the superframe can be used. A digital transmitting apparatus characterized in that multiplexing is performed using a transmission method having the lowest required C / N among a plurality of transmission methods. 4. A modulation wave generated by the encoding / modulation means according to claim 3, and receiving a frame synchronization pulse from said frame synchronization W1 to said superframe synchronization W.
2 or W3 to generate a superframe synchronization pulse, and based on the content of the TMCC signal q frames before,
A gate signal required in each part of the receiver is generated on the basis of the frame pulse and the superframe pulse on a time basis, and modulated by a plurality of transmission methods in a time division manner following these W1, TMCC, W2 (or W3). A digital receiver comprising demodulation means for demodulating a main signal portion. 5. The data sequence demodulated by the demodulation means according to claim 4, wherein the superframe synchronization pulse and the first packet of a packet allocated to each modulation method on the basis of a frame synchronization pulse are selected. A digital receiving device comprising: a Viterbi decoding unit that performs a depuncturing operation based on a start point and performs Viterbi decoding.