KR20120056640A - Method and apparatus of frame construction for docsis data transmission - Google Patents

Abstract

PURPOSE: A frame construction method for transmitting DOCSIS(Data Over Cable Service Interface Specification) data and apparatus thereof are provided to minimize the temporal jitter of transmission data and the transmission over head of a downlink PHY(PHYsical) layer. CONSTITUTION: An MAC(Media Access Control) frame division block(201) divides an MAC frame into an MAC management data frame and a user data frame. An input signal processing block(101) previously processes the MAC management data frame and the user data frame. The input signal processing block receives a head-end reference time. A data slice building block(104) creates a data slice based on the user data frame and the MAC management data frame through the input signal processing block.

Description

Method and apparatus for constructing frame for transmitting DOCIS data {METHOD AND APPARATUS OF FRAME CONSTRUCTION FOR DOCSIS DATA TRANSMISSION}

The present invention relates to Digital Video Broadcasting-Cable 2 (DVB-C2), and more particularly, to a frame configuration method and apparatus for DOCSIS (Data Over Cable Service Interface Specification) data transmission using the DVB-C2 standard.

Recently, the DVB-C2 (Digital Video Broadcasting-Cable 2) standard is emerging as the next generation cable transmission standard. The DVB-C2 standard has a 30% or more improvement in physical transmission capacity compared to the conventional transmission standard. Although the DVB-C2 standard is mainly used in the cable broadcasting field, it is recently considered to be used as a downlink channel for communication in combination with a Data Over Cable Service Interface Specification (DOCSIS) standard for cable communication.

The DOCSIS standard can be largely divided into a media access control (MAC) layer transport standard and a physical (HY) layer transport standard. Currently, the downlink PHY layer transmission standard uses the International Telecommunication Union (ITU) J.83 A / B standard, and the combination of the DOCSIS standard and the DVB-C2 standard enables the use of the DVB-C2 standard as the downlink PHY layer transmission standard. In the existing downlink PHY layer, a MAC data frame needs to be converted to a Moving Picture Experts Group (MPEG) -2 TS format, which is a PHY transmission format, for data transmission of the MAC layer. That is, the input of the existing downlink PHY layer is limited to the MPEG-2 TS format. Accordingly, the MAC layer converts the MAC frame into MPEG-2 TS packets and outputs the same. When a MAC frame is converted into an MPEG-2 TS packet, an overhead of 4 to 5 bytes is basically generated for every MPEG-2 TS packet. In addition, in order to match the transmission rate of a given PHY layer, the MPEG-2 TS packet must be output at a constant rate. Therefore, even when there is no data to be transmitted, a null data packet is transmitted, thereby decreasing transmission efficiency.

On the other hand, since data is transmitted at a constant rate in the downlink PHY layer of the existing DOCSIS standard, jitter generation of transmission data may be minimized in time. Jitter means that some aspect of the wave deviates from the high frequency digital signal. On the other hand, in the DVB-C2 standard, since there are several data slices transmitting a certain amount of data in the transmission band, it is necessary to consider transmission data having data slice size and time constraints in order to minimize jitter. In particular, the SYNC (Synchronizatino) message among MAC management messages should have jitter within 500 us.

That is, since the DVB-C2 standard was developed without consideration for data transmission according to the DOCSIC standard, a new method for transmitting DOCSIS MAC data frames is proposed to use the DVB-C2 standard as a downlink PHY layer transmission standard of the DOCSIS standard. There is a need. Accordingly, there is a need to compensate for transmission overhead and inefficiency in the existing downlink PHY layer.

An object of the present invention is to provide a frame configuration method and apparatus for DOCSIS (Data Over Cable Service Interface Specification) data transmission.

In one aspect, a frame configuration apparatus for data over cable service interface specification (DOCSIS) data transmission is provided. The frame forming apparatus may include a MAC frame classification block for dividing an input MAC frame into a MAC management data frame and a user data frame, and the MAC management data frame and user data. Preprocessing a frame and generating a data slice based on an input processing block receiving a headend reference time, and the MAC management data frame and the user data frame passing through the input processing block And a data slice building block.

The MAC frame division block may classify a MAC frame input through an FC-TYPE field of a MAC frame header into a MAC management data frame and a user data frame.

The frame transmitting apparatus performs BCH and Low Density Parity Check (LDPC) encoding and bit interleaving for channel error correction by inputting the MAC management data frame and the user data frame that have passed through the input processing block. The apparatus may further include a forward error correction (FEC) coding block and a QAM mapping block that maps bit data output from the FEC coding block to a quadrature amplitude modulation (QAM) symbol.

The input processing block may include a Sync modification block that detects a SYNC (Synchronization) message frame of the MAC management data frame and changes a timestamp field in the SYNC message to the headend reference time. The Sync modification block may detect the SYNC message frame by detecting the FC field of the MAC management data frame. The input processing block may further include an input stream synchronization block for adding an input stream synchronization (ISSY) field to a last portion of the MAC management data frame that has passed through the Sync modification block.

The input processing block may further include a baseband head insertion block inserting a baseband frame header and combining a plurality of MAC management data frames to convert the baseband frame header into a baseband frame. The plurality of MAC management data frames may have different lengths. The baseband frame header may include at least one of a MATYPE field, a DFL field, a SYNCD field, and a CRC8 field. The MATYPE field may include at least one of a TS / GS field, a SIS / MIS field, an ISSYI field, an NPD field, and an EXT field PLP_ID field. The value of the TS / GS field may be '10' and the value of the EXT field may be '11'.

In another aspect, a frame composition method for DOCSIS data transmission is provided. The frame composition method may include dividing an input MAC frame into a MAC management data frame and a user data frame, receiving a headend reference time, performing preprocessing on the MAC management data frame and a user data frame; Generating a data slice based on the MAC management data frame and the user data frame that have passed through the input processing block.

By using the DVB-C2 (Digital Video Broadcasting-Cable 2) standard as a transmission standard of the downlink physical layer of the data over cable service interface specification (DOCSIS) standard, the transmission overhead and transmission data of the downlink PHY layer The temporal jitter can be minimized.

1 is a block diagram showing the structure of a general DVB-C2 system.
2 is a block diagram illustrating an example of a data slice configuration for DOCSIS frame processing according to the proposed frame configuration method.
3 is a block diagram illustrating an example of an input processing block configuration according to the proposed frame configuration method.
4 shows an example of a process of converting input MAC management data frames into baseband frames according to the proposed frame composition method.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification. In addition, even if the detailed description is omitted, descriptions of parts easily understood by those skilled in the art are omitted.

Throughout the specification and claims, when a portion is said to "include" a component, it means that it can further include other components, except to the contrary, unless otherwise stated.

1 is a block diagram showing the structure of a general DVB-C2 system.

The input processing block 101 performs pre-processing on the input data to process various input data formats. The Forward Error Correction (FEC) encoding block 102 performs BCH and Low Density Parity Check (LDPC) encoding and bit interleaving for channel error correction on input data that has passed through the input processing block. Quadrature Amplitude Modulation (QAM) mapping block 103 maps bit data into QAM symbols. The process from the input data to the input processing block 101 and output to the QAM mapping block 103 is called a PHY Layer Pipe (PLP), and a plurality of PLPs are gathered to form a data slice. Can be configured. The data slice configuration block 104 generates one data slice by inputting data streams output from the plurality of QAM mapping blocks 103. In FIG. 1, two PLPs constitute one data slice, but the present invention is not limited thereto. The time / frequency interleaving block 105 performs interleaving in the time domain and the frequency domain on the generated data slice. The frame construction block 106 receives a plurality of data slices to form a frame, and the configured frame is finally converted into a transmission signal through an orthogonal frequency division multiplexing (OFDM) generation block 107. In FIG. 1, two data slices constitute one frame, but the present invention is not limited thereto. Information on the frame configuration may be generated in the layer 1 (L1) signaling block 108 and added to the frame configuration.

As shown in FIG. 1, in the DVB-C2 standard, a plurality of data are simultaneously input in one transmission band to configure and transmit one transmission frame. As an input format for each input, a transport stream (TS), a generic encapsulated stream (GES), a generic continuous stream (GCS), or a generic fixed-length packetized stream (GFPS) may be defined. The most widely used format for transmitting DOCSIS MAC frames is TS format. In the case of using the TS format, data can be transmitted in the same format as that of the conventional downlink PHY layer. However, there is a disadvantage in that an MAC frame needs to be converted into a TS packet and overhead occurs in the conversion. Therefore, a method of transmitting a MAC frame without conversion is required. In addition, for a frame transmitting a SYNC (Synchronization) message among input frames, it is necessary to ensure that a time point at which the frame is restored and transmitted to the MAC layer is kept constant at the receiving side.

Hereinafter, a frame configuration method according to the proposed invention will be described.

2 is a block diagram illustrating an example of a data slice configuration for DOCSIS frame processing according to the proposed frame configuration method.

Referring to FIG. 2, the MAC frame classification block 201 is added before the input processing block 101 with respect to FIG. 1. When the MAC frame is input from the MAC layer of the DOCSIC standard, the MAC frame classification block 201 distinguishes between a MAC management data frame and a user data frame through the FC-TYPE field of the MAC frame header. do. MAC management data frames need to be divided into user data frames and separate PLPs because a certain amount of transmission bandwidth is maintained and time jitter needs to be minimized. The receiving end can separate the MAC management data frame and the user data frame for easier processing.

Separated MAC management data frames and user data frames are input to each input processing block. In this case, the first input processing block 101 receiving the MAC management data frame detects a SYNC message frame among the MAC management data frames, modifies a timestamp value in the message, and the compensation for the input stream transmission delay is received at the receiving end. To this end, the ISSY (Input Stream Synchronization) field defined in the DVB-C2 standard is applied to the MAC management data frame. The MAC management data frame and the user data frame that have passed through the input processing block go through the FEC encoding block 102 and the QAM mapping block 103 and are generated as one data slice in the data slice configuration block 104.

3 is a block diagram illustrating an example of an input processing block configuration according to the proposed frame configuration method. That is, FIG. 3 illustrates a first input processing block 101 for receiving a MAC management data frame in FIG. 2.

Referring to FIG. 3, the input interface block 301 converts an input MAC management data frame into a bit format for internal processing. The Sync modification block 302 first detects an FC field in a header of a MAC frame to detect a SYNC message frame among MAC input data frames. The Sync modification block 302 reads the headend reference time input at the MAC layer when a SYNC message in the SYNC message frame is detected. Sync modification block 302 changes the timestamp field in the SYNC message to the headend reference time. This is to remove temporal jitter during data transmission from the MAC layer to the PHY layer. The sync modification block 302 updates the CRC field in the message by performing Cyclic Redundancy Checking (CRC) calculation on the entire SYNC message whose timestamp field is changed. This completes the correction for the SYNC message.

Following the Sync modification block, the input stream sync block 303 records the time of the input time for all incoming MAC management data frames and adds an ISSY field to the end of each frame. The MAC management data frame with the ISSY field added may pass through the null packet removal block 304 and the CRC-8 code block 305, but only the MAC management data frame is entered and its own in the MAC management data frame. Since the CRC field already exists, the null packet removal block 304 and the CRC-8 code block 305 may be omitted. The DVB-C2 standard specifies that the input stream sync block 303, the null packet removal block 304, and the CRC-8 code block 305 can be selectively used. However, in the proposed invention, there is a constraint that the input stream sync block 303 must be used.

Referring again to FIG. 3, a base band (BB) head insertion block 306 combines the MAC management data frames and converts them into baseband frames of a predetermined size. The baseband frame into which the baseband head is inserted is finally output by the baseband scramble block 307.

4 shows an example of a process of converting input MAC management data frames into baseband frames according to the proposed frame composition method. A plurality of MAC management data frames may be included in one baseband frame. In addition, the length of each MAC management data frame may be different. In FIG. 4, the baseband frame includes three MAC management data frames, and two MAC management data frames are partially included. However, the baseband frame is not limited thereto, and the configuration of the baseband frame may vary. Can be.

The header of the baseband frame (BB header) may include fields described below. In the following description, the DOCSIS MAC frame includes a MAC management data frame and a user data frame. That is, although FIG. 4 illustrates a process of converting MAC management data frames into baseband frames, the baseband frame header described below may be equally applied to user data frames as well as MAC management data frames.

1) MATYPE field (2 bytes): The MATYPE field may internally include the detailed fields as shown below.

TS / GS (2 bits): indicates the type of data field transmitted in the baseband frame. For example, GES may be indicated when the value of the TS / GS field is '10'. This is because DOCSIS MAC frame is similar to GSE.

SIS / MIS (1 bit): Indicates whether the number of input streams is one or plural. For example, when the value of the SIS / MIS field is '1', it may indicate a single input stream.

ISSYI (1 bit): indicates whether a data packet transmitted in a baseband frame uses an ISSY field. For example, when the value of the ISSYI field is '1', it may indicate that the active, that is, the ISSY field is used.

NPD (1 bit); Indicates whether to remove null packets when generating baseband frame. For example, when the value of the NPD field is '0', it may indicate non-active.

EXT (2 bits): This field is reserved for future use. In the present invention, the value of the EXT field is set to '11' to indicate that the DOCSIC MAC frame is included in the baseband frame. This is because, in the DCB-C2 standard, when the input data format is GES, the ISSY field cannot be used when transmitting in the normal mode. Therefore, it is necessary to distinguish between using the ISSY field while transmitting in the normal mode using the EXT field. The baseband frame may be classified into a normal mode and a high efficiency mode. In this case, each field in the baseband frame header may have a different definition. In case of DOCSIS MAC frame in normal mode, transmission delay and temporal jitter need to be minimized, so an ISSY field for synchronization needs to be used every frame. On the other hand, if the high efficiency mode is used, the ISSY field can be used, but it is not applied to all MAC management data frames. This is because the ISSY field may be applied only to the first MAC management data frame located in the data field of the baseband frame.

PLP_ID (8 bits): Indicates a value assigned to the corresponding PLP in the DVB-C2 system.

2) UPL field (2 bytes): indicates the length of a user packet included in the data field of the baseband frame. In the present invention, since the length of the DOCSIS MAC frame is not constant, the UPL field may not be used.

3) DFL field (2 bytes): indicates the length of the data field of the baseband frame.

4) SYNC field (1 byte): Indicates the SYNC byte of the user packet included in the data field of the baseband frame. In the present invention, since a separate SYNC byte is not used for the DOCSIS MAC frame, the SYNC field may not be used.

5) SYNCD field (2 bytes): indicates the position of a starting packet among user packets included in the data field of the baseband frame. The SYNCD field may indicate the position of the point where the DOCSIS MAC frame starts in the data field.

6) CRC8 field (1 byte); Indicates a CRC-8 calculation value for the baseband frame header.

3 and 4 illustrate that the proposed frame configuration method is applied to a MAC management data frame among DOCSIS MAC frames, the present invention may be applied to a user data frame among DOCSIC MAC frames. When the DOCSIS MAC frame is a user data frame, the baseband frame may be transmitted in a high efficiency mode using the GES format as an input. At this time, the EXT field value of the MATYPE field in the baseband frame header may be set to '11' to indicate that the DOCSIS MAC frame is transmitted.

The proposed frame composition method can minimize the transmission overhead and the time jitter of the downlink PHY layer. According to the present invention, transmission of a 3D program or a multi-view program having a large transmission bandwidth can be performed using the current broadcasting system, and thus a high quality broadcasting service can be provided in a short time.

The present invention may be implemented in hardware, software, or a combination thereof. (DSP), a programmable logic device (PLD), a field programmable gate array (FPGA), a processor, a controller, a microprocessor, and the like, which are designed to perform the above- , Other electronic units, or a combination thereof. In the software implementation, the module may be implemented as a module that performs the above-described function. The software may be stored in a memory unit and executed by a processor. The memory unit or processor may employ various means well known to those skilled in the art.

In the above-described exemplary system, the methods are described on the basis of a flowchart as a series of steps or blocks, but the present invention is not limited to the order of the steps, and some steps may occur in different orders or simultaneously . In addition, those skilled in the art will appreciate that the steps shown in the flowcharts are not exclusive and that other steps may be included or one or more steps in the flowcharts may be deleted without affecting the scope of the present invention.

The above-described embodiments include examples of various aspects. While it is not possible to describe every possible combination for expressing various aspects, one of ordinary skill in the art will recognize that other combinations are possible. Accordingly, it is intended that the invention include all alternatives, modifications and variations that fall within the scope of the following claims.

Claims (13)

In the frame configuration device for DOCSIS (Data Over Cable Service Interface Specification) data transmission,
A MAC frame classification block for dividing an input MAC frame into a MAC management data frame and a user data frame;
An input processing block performing preprocessing on the MAC management data frame and the user data frame and receiving a headend reference time; And
And a data slice building block for generating a data slice based on the MAC management data frame and the user data frame that have passed through the input processing block. The method of claim 1,
The MAC frame classification block divides the MAC frame input through the FC-TYPE field of the MAC frame header into a MAC management data frame and a user data frame. The method of claim 1,
The frame transmission device,
Forward Error Correction (FEC) that performs BCH and Low Density Parity Check (LDPC) encoding and bit interleaving for channel error correction using the MAC management data frame and the user data frame as inputs. A coding block; And
And a QAM mapping block for mapping the bit data output from the FEC coding block to a Quadrature Amplitude Modulation (QAM) symbol. The method of claim 1,
The input processing block comprises a Sync modification block that detects a SYNC (Synchronization) message frame of the MAC management data frame and changes a timestamp field in the SYNC message to the headend reference time. Device. The method of claim 4, wherein
And the sync modification block detects the SYNC message frame by detecting an FC field of the MAC management data frame. The method of claim 4, wherein
And the input processing block further comprises an input stream synchronization block for adding an input stream synchronization (ISSY) field to a last portion of the MAC management data frame that has passed through the Sync modification block. The method of claim 1,
The input processing block further includes a baseband head insertion block inserting a baseband frame header and combining a plurality of MAC management data frames to convert the baseband frame into a baseband frame. . The method of claim 7, wherein
And a length of each of the plurality of MAC management data frames is different. The method of claim 7, wherein
Wherein the baseband frame header includes at least one of a MATYPE field, a DFL field, a SYNCD field, and a CRC8 field. The method of claim 9,
The MATYPE field includes at least one of a TS / GS field, a SIS / MIS field, an ISSYI field, an NPD field, and an EXT field PLP_ID field. 11. The method of claim 10,
And a value of the TS / GS field is '10'. 11. The method of claim 10,
And a value of the EXT field is '11'. In the frame configuration method for DOCSIS (Data Over Cable Service Interface Specification) data transmission,
Dividing the input MAC frame into a MAC management data frame and a user data frame;
Receiving a headend reference time;
Performing preprocessing on the MAC management data frame and user data frame; And
And generating a data slice based on the MAC management data frame and the user data frame that have passed through the input processing block.

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