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1,  DVB 's main objectives and standards

DVB (Digital Video Broadcasting) digital video broadcasting means . DVB has more than 170 organizations in Europe to participate in a project. It includes satellite, cable and terrestrial television broadcasting regular TV and high-definition television broadcasting and transmission. DVB Project 's main objective is to find a transmission media are applicable to all digital television technologies and systems ,
Its requirements are :
⑴ transmission system should be flexible MPEG-2 video , audio, and other data signals.
⑵ system uses a unified MPEG-2 transport bit stream multiplexing .
⑶ systems using a unified information system to provide broadcast services details and other information.
⑷ system uses a unified Reed - Solomon forward error correction system in front .
⑸ scrambled using a unified system, but may have different encryption.
⑹ select for different transmission media, the modulation method and the channel coding method, and any necessary additional error correction method .
⑺ encouraged to use outside the European DVB standard , promote the establishment of a worldwide Digital Video Broadcast standards. This goal has been supported ITU satellite radio .
⑻ support digital systems teletext systems .
There are three main criteria :
DVB-S satellite digital television , DVB-C cable digital television and digital television DVB-T , respectively, for satellite, cable and terrestrial broadcasting , has been ETS (European Telecommunication standard) approval. ITU DVB-S has been recommended. The standard DVB-S is ETS300421, DVB-C standard is ETS300429, DVB-T standard is ETS300.

1.2 DVB system used by major technical
DVB various system 's core technology is generic MPEG-2 video and audio encoding . Currently used in digital satellite and cable television broadcasting is MP @ ML. So that the first generation of European DVB receiver will provide until " 625 studio quality " (ITU-R Rec.BT 601) image , which can be 4:3 or 16:9 aspect ratio . Can also be used according to business requirements to determine the rate . Generally , the higher the selected bit rate , the better the image quality , but take up more wide-band . Rate selection and image content has a lot more to moving images such as sports programs, etc. should be used to a greater rate ; while cartoons and other programs can be used for a smaller rate . Therefore, the plurality of programs currently in the multiplexed bit streams into one bit stream, the statistical multiplexing methods are used , at different bit rates between programs require flexible allocation of total bit rate . To meet the requirements of all kinds of the material , IT U-Rec TB 601 studio-quality digital rate needed 9Mbps, PAL / SECAM broadcast quality digital rate needed 5Mbps, the MPEG-2 transport stream is a bit packet structure , so you can easily add the appropriate information to a variety of different services, such as voice and data services images together , and format of the information service for the detailed requirements for the formation of the standard is service information standards ETS300468. MPEG-2 also determined as the actual system and the scramble key management system , DVB Decoder Applications developed a condition to receive public interface.

1.3 DVB - S system
DVB-S system is suitable for a variety of satellite radio systems, satellite transponder bandwidth from 26MHz to 72MHz. Transponder power from 49dBW to 61dBW.
Sender signal processing divided into the following levels :
First, the MPEG-2 source coding and multiplexing the input video signals, audio signals and data encoded according to MPEG-2 format , and then the program multiplexing and transmitting multiplexed form useful packet format , packet length 188 beit , including a synchronous beit . Then flows through a number of processing this data code . Its purpose is to increase the resistance of the signal on the bit error and adapt channel transmission characteristics. These processes include: using a pseudo-random sequence so that the data randomization , the use of Reed - Solomon code RS (204, 188 T = 8) and convolutional interleaving coding techniques to improve the bit error resistance. Finally, QPSK modulation is sent to the transponder . DVB-S frame structure shown in Figure 13-1. In order to achieve maximum power efficiency without making a great reduction in spectrum utilization , the best satellite system using QPSK modulation and convolutional error correction code and RS cascade approach can achieve better results . The system is preferably a carrier for a transponder system , a good multi-carrier system can be used .

1.4 DVB - C system
Cable TV system block diagram of Figure 13-2 can be expressed , which is divided into two parts : CATV receiver front-end and integrated decoder (IRD, also known as integrated receiver decoder ) . In order to make a variety of transmission as compatible as possible , in addition to the majority of the processing channel modulations are the same as the processing in the satellite , i.e. the same pseudo- random sequence of scrambling , the same RS error correction , the same convolutional interleaving . Subsequent treatment is designed for cable television . Beit symbol for the first conversion, such as 64QAM is the 8-bit data is converted into six -bit symbols as a group , and the first two bits of the differential encoding and then with the remaining 4 bits into the corresponding constellation point . The program can accommodate 16,32,64 QAM three kinds of modulation. Table 13-1 is the use of DVB-C standard CATV application rate examples.
On cable TV standards, including DVB :
ETS300468 - cable system channel coding and modulation ;
ETS300472 - ITU-R System B Teletext in transmission ;
ETS300473 - SMATV System Channel Coding and Modulation ;
ETS300743 - DVB subtitling system time ;
ETR154 - For MPEG-2 implementation guidance ;
ETR162 - SI code location ;
ETR211 - SI role in the realization of guidance ;
ETR289 - Shared scrambling ;
EN50083 - transport stream interface with the cable headend .

2 MCNS Standard
2.1 MCNS standard system
MCNS is "Multimedia Cable Network System" acronym, that the meaning of multimedia cable network system . MCN S standards have become the standard digital cable systems , and has become the international standard for basic . MCNS for fiber - cable networks , namely HFC network . MCNS gives the data transmission in the cable network in the reference model, based on this model provides various interfaces interface , as well as the technical requirements of each interface . Thus allowing different manufacturers top boxes and data modem cable system in the same work , with good uniformity and interchangeability.
MCNS standard system include the following :
SP-CMCI Cable Modem to Customer Premises Equipment Interface ;
SP-CMRFI Cable Modem to the RF interface ;
SP-CMTRI Cable Modem telecommunications loopback interface ;
SP-CMTS-DRFSI Cable Modem transmission system downstream RF interface ;
SP-CMTS-NSI Cable Modem transmission system network side of the interface ;
SP-CMTS-SMI Cable Modem transmission system security management interface ;
SP-CMTS-URFSI Cables Modem Upstream RF transmission system side interfaces ;
SP-OSSI work support system interface ;
TR-OSSI work support system .
Which represents Specification SP ie specifications , TR represents technical reports, in order to understand SP content. In this conventional cable television systems , retitled Cable Modem transmission system , because in addition to a variety of television signals transmitted data outside also , to distinguish between the previous cable television system . Modem the modem.

2.2 data in the cable network in the reference model
Data in the cable network in the reference model shown in Figure 13-3. 

2.3  MCNS technical specifications
(1) front-end called the Cable Modem Termination System (CMTS). MCNS requires a suitable front-end hardware, such as those containing a universal broadband router, using a standard Cisco 7200 routers and IOS software , and telephone support MCNS RF loopback mode . Network Interface : 10BaseT, 100BaseT, ATM, HSSI.
( 2 ) Cable Modem (CM)  MCNS required for client hardware devices. And PC interfaces: Ethernet 10BaseT. planned Interface: USB and IEEE1394.
( 3 ) Data Protocol : TCP / IP
( 4 ) through the Simple Network Management Protocol (SNMP) for
( 5 ) Remote Management down by ITUJ  83 Appendix B requirements.
Modulation : 64QAM or 256QAM.
Maximum data rate : 27Mbps or 38Mbps.
Bandwidth : 6MHz channel bandwidth , and also supports 7MHz and 8MHz.
Frequency range :88-860MHz.
Transport Protocol : MPEG-2.
( 6 ) upstream
Modulation : 16QAM or QPSK, variable symbol rate .
Data rate : 320kbps ~ 10Mbps.
Bandwidth : 200KHz ~ 3  2MHz.
Frequency range :5-42MHz.
System according to the modulation mode is set to the highest at the beginning of the symbol rate , and based on the detected noise level to be adjusted to a suitable rate .

3,   DAVIC System Description
DAVIC Digital Audio-Visual Council is the acronym for digital audio and video referred to the Council , based in Geneva , is a non-profit organization . Aims to promote the broadcasting and interactive digital audio , video, applications, and business development, formulation can adapt to a variety of video and audio applications and services that can have different environments across the world end to end interoperability of open interfaces , protocols and regulations , DAVIC including almost all digital video and audio applications and services , which is extremely comprehensive and extensive .
DAVIC for all government agencies, international organizations, corporations , and individuals , to December 1995 , DAVIC has 202 members in more than 20 countries , including almost the world relates to digital video and audio applications and services to all companies and organizations . DAVIC is not a specific provision for the system , but for the use of technology and tools required . Because the requirements for the system are often application specific , which is required to be DAVIC specific system , to be applied in various industrial and systems. A tool provided for the main process are: first analysis of the target system , the system is divided into various parts , to identify the common elements in the system , the various parts of the requirements necessary to check whether the provisions of the tool adapted to combine the entire system. As far as technically feasible , to perfect the tools required to reposition the movable position . DAVIC requires only one features a tool , and is everywhere the same, but can have different levels of performance , such as the general performance requirements can be specified , but you can keep it for future improvement backward compatible . Figure 13-4 can be used to briefly describe the DAVIC system . Any one DAVIC system can be decomposed into five parts: content providing system (CPS: Content Provider System), service delivery systems (SPS: Service Consumer Provider System) and service consumption system (SCS: Service System) as well as their delivery systems CPS-SPS delivery system and SPS-SCS Delivery System . Principle, DAVIC can use the same method to define any subsystem. In the analog world , all similar systems are independently by each company or group of companies , as defined in the analog system is not as flexible as digital systems and linkages . Simulation system services and applications are often closely linked with the delivery system , which is usually no matter what we say quality , television always use 8MHz channel bandwidth, transmission , telephone always 4kHz dedicated system to send more. Cause a variety of services a variety of devices . The digital system will be unified together a variety of business , which requires a strict definition of the system and the division of labor . In order to ensure a variety of devices and a variety of system interoperability . DAVIC defines a large number of interfaces and levels , as shown by the A11, A10, A9, A1 interface and physical layer interface , the network service interface , meet and delivery services interfaces, application service interface and basic services interface, and gives a variety of interface and the level of detail definition.

3.1 DAVIC file
DAVIC files, total 13 parts , divided into two categories, one is the official document , the equipment must comply with , and the other is informal, but it is currently informal part in the future could become official .
(1) DAVIC system functional description.
( 2 ) the system reference model and programs.
( 3 ) service supply system structure and interface.
( 4 ) delivery system structures and interfaces.
( 5 ) service consumption system architecture and high-level application programming interface .
( 6 ) Temporary no content reserved for other uses.
( 7 ) senior and middle Agreement Appendix A: STB Management Information Base .
( 8 ) lower layer protocols and physical interfaces .
( 9 ) Information representation , Appendix : Personal data package.
( 10 ) confidentiality.
( 11 ) use of information agreements .
( 12 ) reference point.
( 13 ) interoperability and compliance.
The downlink data transmission to provide a two frame structures, one is carrying the MPEG-2 transport stream packet , and the other is carrying the ATM cell . The RF carrier is to be able to use these two structures. Cable Unidirectional physical layer interface frequency configuration shown in Figure 13-5 , the frequency from 54MHz to 1000MHz, press 6 or 8MHz QAM modulation interval is divided into various channels. STB should be able to operate in the full frequency range specified and can support at least a frame structure . The sending device as long as the work in the specified operating band can be. QAM There are three levels : 16QAM, 32QAM and 256QAM. A block diagram of the codec consistent DVB-C , the difference is that the DVB-C QAM using three levels 16,32,64 , interleaving depth L = 12; the DAVIC use 16,64,256 QAM, for 16 and 64QAM, interleaving depth is 12, but for 256QAM, the interleaving depth L = 204. Chucierwai , MPEG-TS stream with the DAVIC frame structure identical with DVB-C . Also every 8 188 Beit packet synchronization flip once, other processes are the same DVB-C, shown in Figure 13-6 . ATM packet for transmission , in order to provide interleaved error correction code block synchronization and alignment , using the same 188 DVB-C Beit ATM multiplexing packages, the package structure shown in Figure 13-7. As can be seen from the figure . ATM packet transmission using a dual structure of the frame structure , it will be seven with 48 Beit information Beit Baotou 5 of 53 Beit an ATM packets into two with 187 Beit information , a header 188 Beit Beit package . DAVIC also provides an improved synchronization reliability criteria are transparent to the transfer tool "High reliability flag " DAVIC standard also defines a number of DVB-C has not been involved in a number of programs and parameters , as defined in the QAM 2 levels , the first level a, involves only 16 and 64QAM, the second level B, including 16, 64 and 256QAM. From the foregoing , DAVIC and DVB-C Most of the requirements are the same, but have something to add .

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