KR19990053523A - Cable modem downstream system The puncturing device of the TCM encoder - Google Patents

Abstract

The present invention relates to a puncturing apparatus for a cable modem downstream system TCM encoder, and more particularly, to a puncturing apparatus for a cable modem downstream system TCM encoder which receives punctured 8-bit signals X1, Y1, X2, Y2, X3, Y3, X4, And outputting 5 bits (X1, Y1 to Y4) after the first and second storing units 51 and 52 and the selecting unit 53. The puncturing apparatus of the cable modem downstream system TCM encoder outputs five bits (X1, Y1 to Y4) The first and second storage units 51 and 52 store the X signal and the Y signal, respectively, and output the X1, X1, X2, X3, X4 and Y1, Y1, Y2, and Y4 signals for five clocks in accordance with the buffer control signal B_CONTROL, Y3, and Y4, and the selector 53 sequentially selects the X1 signal output at the first clock and the Y1 through Y4 signals output at the second through fifth clocks in accordance with the selection control signal M_COMTROL Output.

Accordingly, in the present invention, the 8 bits encoded from the binary convolutional encoder are input and punctured to output 5 bits. The X and Y signals are separately stored according to the control signal, and the 5 bits are sequentially selected for 5 clocks Thus, there is an effect that the input bits can be efficiently punctured.

Description

Cable modem downstream system A puncturing device of a TCM encoder (a TCM encoder in a cable modem downstream system)

The present invention relates to a cable modem downstream system TCM decoder, and more particularly, to a puncturing apparatus for a cable modem downstream system TCM encoder that punctures 8 bits encoded from a convolutional encoder of a TCM encoder to output only 5 bits.

The cable modem network is a remote access network system such as ISDN and xDSL. It is connected to the Internet and intranet and provides high-speed data transfer rate of Mbps to subscribers for telecommuting, video conferencing, web Search, and so on.

The concept of a cable modem network is similar to that of coaxial cable, which brings cable TV networks to the field of data communications, but cable TV connects external coaxial cable to a set-top box and then connects the TV to the set- The cable modem network, on the other hand, is a cable modem that connects the coaxial cable to the PC. At this time, the number of PCs connected to the cable modem may be one or several.

FIG. 1 is a diagram illustrating a network constructed using a general cable modem. In FIG. 1, a plurality of cable modems (CM) 11 to 14 are connected to a cable network 20, The subscriber is provided with services such as the Internet from the backbone network 40 and the cable modem terminal system 30 is located at the head end and serves to provide the uplink channel and the downlink channel . The CMTS 30 broadcasts broadband data at a transmission rate of 500 kbps to 30 Mbps on the downlink channel and each CM transmits narrowband query data on the uplink channel at a rate of 96 kbps to 10 Mbps in a point-to-point manner .

FIG. 2 is a block diagram showing a cable transmission processing step in the cable modem system. The MPEG frame unit 21, the FEC encoder 22, the QAM modulation unit 23, the MPEG frame unit 27 of the reception unit, the FEC A decoder 26, a QAM demodulator 25, and a channel 24. [

The MPEG frame unit 21 of the transmission unit receives the MPEG-2 data stream composed of 188-byte fixed-length packets and transmits the synchronization of the MPEG packet to the receiver. The FEC (Forward Error Correction) Interleaving, randomizing, and trellis coding in order to reliably transmit data through the cable channel 24. The QAM modulator 23 uses a modulation scheme of 64 QAM or 256 QAM do. The MPEG frame unit 27, the FEC decoder 26, and the QAM demodulation unit 25 of the receiving unit perform opposite functions of the transmitting unit.

2, the FEC encoder 22 includes a Reed Solomon encoder 22-1, an interleaver 22-2, a randomizer 22-3, and a Trellis encoder 22-4 And the FEC decoder 26 includes a trellis decoder 26-1, a reverse randomizer 26-2, a deinterleaver 26-3, and a Reed Solomon decoder 26-4.

The Reed-Solomon encoder 22-1 performs Reed Solomon encoding using a (128,122) code, error correction is possible up to three symbols, and the RS code is used for both 64QAM and 256QAM. The interleaver 22-2 prevents cluster noise that causes an error, and has a programmable structure in the case of 64QAM and 256QAM. The randomizer 22-3 randomizes the data for synchronization of the QAM demodulator 25 and the trellis encoder 22-4 encodes the internal code of the concatenated coding technique and encodes the transmitted signal by performing binary convolutional encoding using inner code. The TCM decoder 26-1, the randomizer 26-2, the deinterleaver 26-3 and the Reed Solomon decoder 26-4 of the FEC decoder 26 are connected to the FEC encoder 22 Function.

The TCM encoder 22-4 receives the bit stream from the randomizer 22-3 and performs QAM mapping on the bit stream and outputs the QAM to the QAM modulator 23. The TCM encoder for 64 QAM is a An input symbol distribution unit 31, an uncoded block 32, a coded block 33, and a QAM mapper 34 as shown in FIG.

A5, A4, A2, and A1), A2 symbols (A9, A6, A3, A0, A13 , A12, and A11), B1 symbols (B10, B8, B7, B5, B4, B2, B1), and B2 symbols (B9, B6, B3, B0, B13, B12, and B11) And the non-coding processing unit 32 transfers the input symbol to the QAM mapper 34 as it is. The sign processor 33 comprises a Differential Precoder 33-1 and two Binary Convolutional Coders 33-2 and 33-3. The input symbol distributor 33-1, 31, A2, A3, A9, and B2 of the A2 symbol, and 4 bits B0, B3, B6, and B9 of the B2 symbol are differentially encoded and convolutionally encoded by using the 5 bits of the encoded bits U1, U2, U3, U4 And the QAM mapper 34 outputs 4 bits which are not encoded from the non-coding processing unit 32 and encoded from the code processing unit 33 for each clock, 2 bits, total of 6 bits (C5 to C0), and converts the input symbols into 64 (= ²⁶ ) level symbols, and outputs the symbols to the QAM modulation unit (23 in FIG.

The TCM encoder for 256 QAM receives the 38 bit stream from the randomizer 22-3 and QAM-maps it to the QAM modulator 23. The configuration and operation of the QAM encoder are the same as that of the 64 QAM TCM encoder same. That is, the QAM mapper receives 8 bits (C7 to C0) of each clock outputted from the input symbol distribution unit through the unsigned processing unit and the sign processing unit, converts them into 256 (= 2 ⁸ ) level symbols, and outputs them.

In the 64 QAM and 256 QAM TCM encoders, each binary convolutional coder (BCC) of the sign processing unit has a puncturing function of 4/5 code rate. The puncturing is used to obtain a higher transmission rate, and it is employed in various digital transmission systems because a transmission rate higher than the conventional transmission rate can be obtained by 20% or more. That is, the binary convolutional encoder having a bit rate of 1/2 has to transmit 8 bits by encoding four input bits. The 8 bits to be transmitted are transmitted with only a 5 bits by a puncturing function of a 4/5 code rate , So that more data can be transmitted on the same channel.

Therefore, it is necessary to design a puncturing apparatus that can increase the transmission rate of the binary convolutional encoder according to the standard of the cable modem system.

It is therefore an object of the present invention to provide a puncturing apparatus for a cable modem downstream system TCM encoder that outputs only 5 bits out of 8 bits encoded from a binary convolutional encoder.

According to another aspect of the present invention, there is provided an apparatus for decoding a binary convolutional encoder, the apparatus comprising: a decoder for receiving and encoding 8-bit encoded signals X1, Y1, X2, Y2, X3, Y3, X4, (X1, Y1 to Y4). The puncturing apparatus of the cable modem downstream system TCM encoder outputs the X1 to X4 signals and stores the X1 to X4 signals. The first to fifth clock signals A first storage unit for receiving the Y1 to Y4 signals and outputting the signals in the order of X1, X1, X2, X3 and X4 during a clock period, and for storing the Y1 to Y4 signals in response to the buffer control signal B_CONTROL, A second storage unit for sequentially outputting Y1, Y1, Y2, Y3, and Y4, and X1 output from the first storage unit at the first clock in accordance with the selection control signal M_CONTROL, And a selector for sequentially selecting and outputting Y1 to Y4 output from the second storage unit for 5 clocks And it is characterized in that configuration.

1 is a diagram illustrating a network constructed using a general cable modem,

2 is a block diagram showing a cable transmission processing step in a cable modem system;

3 is a block diagram illustrating the configuration of a TCM encoder for 64 QAM;

4 is a block diagram showing the input / output signal relationship between the convolutional encoder and the punching block,

5 is a block diagram illustrating the configuration of a puncturing device of a cable modem downstream system TCM encoder according to the present invention.

DESCRIPTION OF THE REFERENCE NUMERALS

51, 52: storage unit 53:

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

First, the input / output relationship between the binary convolutional encoder and the puncturing block will be described in order to facilitate understanding of the present invention.

4 shows input and output signals of a convolutional encoder and a puncturing block. The binary convolutional encoder 41 receives four bits (S1 to S4) of 1 bit over 4 clocks, 2, Y 2, S 3? X 3, Y 3, S 4? X 4, and Y 4 every time according to the coding rate. When the output signal is represented by a matrix .

The puncturing block 42 receives the 8 bits encoded through the encoder 41 as a puncturing matrix (Here, 1 means to transmit and 0 means not to transmit) . The puncturing block of the cable modem system sequentially receives 'X1, Y1', 'X2, Y2', 'X3, Y3', and 'X4 and Y4' from the convolutional encoder and receives 3 bits by puncturing matrix And the remaining X1, Y1, Y2, Y3, and Y4 are sequentially transmitted to the QAM mapper.

FIG. 5 is a block diagram showing the configuration of a puncturing apparatus of a cable modem downstream system TCM encoder according to the present invention, which includes first and second storage units 51 and 52, and a selecting unit 53 .

The first and second storage units 51 and 52 receive and store the X1 to X4 signals and the Y1 to Y4 signals from the binary convolutional encoder 41, respectively, and store the X1 to X4 signals and the Y1 to Y4 signals according to the buffer control signal B_CONTROL. The second storage unit 52 sequentially outputs Y1, Y1, Y2, Y3, and Y4 in order, and outputs X1, X2, X3, do. The selector 53 selects and outputs the X1 signal first outputted from the first storage unit 51 at first according to the selection control signal M_CONTROL and then outputs the X1 signal outputted from the second storage unit 52 to the second The Y2 signal, the Y3 signal, and the Y4 signal, which are outputted from the Y1 signal, in this order.

That is, when the first and second storage units 51 and 52 output X1 and Y1 to the first clock, respectively, the selecting unit 53 selects the X1 and the first and second storing units 51 and 52, The selector 53 selects the Y1 and when the first and second storage units 51 and 52 output X2 and Y2 to the third clock, respectively, The selector 53 selects the Y2 and the selector 53 selects the Y3 when the first and second storage units 51 and 52 output X3 and Y3 to the fourth clock, 2 storage units 51 and 52 output X4 and Y4 to the fifth clock, the selector 53 selects the Y4 and transfers the Y4 to the QAM mapper of the TCM encoder.

As described above, the apparatus of the present invention receives 8 bits encoded from a binary convolutional encoder and punctures and outputs 5 bits. In accordance with the control signal, the X and Y signals are separately stored, By selecting and outputting 5 bits in order, it is possible to effectively puncture the input bits.

Claims (1)

A cable modem downstream system that receives and punctures 8 bits (X1, Y1, X2, Y2, X3, Y3, X4 and Y4) encoded from a binary convolutional encoder and outputs 5 bits (X1, Y1 to Y4) A puncturing apparatus for a TCM encoder, A first storage unit 51 for receiving and storing the signals X1 to X4 and outputting X1, X1, X2, X3 and X4 in order from the first clock to the fifth clock in accordance with the buffer control signal B_CONTROL; A second storage unit 52 for receiving and storing the Y1 to Y4 signals and sequentially outputting Y1, Y1, Y2, Y3 and Y4 for the first to fifth clocks according to the buffer control signal B_CONTROL, ; And Selects X1 output from the first storage unit 51 at the first clock and Y1 through Y4 output from the second storage unit 52 during the second to fifth clocks in accordance with the selection control signal M_CONTROL, And a selection unit (53) for sequentially selecting and outputting the output of the cable modem downstream system TCM encoder.