A dvb-based Data Broadcast System developed by the Blue topology company for cable TV networks

[Abstract]: This paper introduces the DVB-based Data Broadcast System (IP over DVB) developed by the Blue topology company for cable TV networks, which focuses on the system structure, the front-end system structure and implementation, and the design and implementation of the backend data receiving card.
Key parts of the system: Front-End Server software, multi-protocol wrappers, and data receiving cards are independently developed by Alibaba Cloud and have completely proprietary intellectual property rights. The system complies with national and international standards.

I. Preface

At present, all countries in the world are implementing their respective information highway plans to welcome the arrival of the information age in the new century. Public information on a variety of data services, including various public information, distance education content, financial business information, data on-demand (DOD) and various multimedia data service content, high-speed Internet access needs are not only realistic, but also some are quite urgent. It is essential to construct a broadband multimedia data transmission system for information highways with Chinese characteristics. China has a large number of cable TV users (80 million) and a large cable TV network, taking full advantage of this huge resource to meet the public's demand for broadband data services, there are infinite business opportunities.

China's radio and television systems are transforming from analog to digital systems, and the cable trunk networks between cities have also been built. Radio and television networks) with its massive bandwidth and the advantages of connecting thousands of households, it is incomparable to other networks. The digitization of broadcast and television will provide convenient interfaces for the data transmission system. We need to see that the transition from a simulated system to a digital system takes time, so we can develop a way to run on a simulated network, multimedia Data Transmission System, an information expressway that can adapt to the digital broadcasting system in the future, can effectively solve the practicability and economy of this system.

First, the information highway needs to be selected. The fiber-optic coaxial hybrid network (HFCs) of Radio and Television uses its backbone network as its high-capacity fiber-optic network, and uses the client as the coaxial cable. It has abundant frequency resources, large user volumes, and wide coverage, should be the first choice. This type of network is particularly suitable for broadcast-type businesses. Powered by the popularity of the simple uplink of the telephone network, most interactive services can be solved. Data Services Running in China are basically implemented through radio/TV networks.

Next, select the modulation method. Currently, text-and-text data broadcasting uses the reverse field of television broadcasting to transmit data. Due to the carrier limitations, the maximum speed is 266 kbps. Obviously, it is impossible to meet the needs of large-capacity real-time data services. In addition, some systems use a complete 8 MH analog channel with a higher speed (up to 14 Mbps) by using the PSK modulation method ), however, there is still a waste of suspicion, in addition, it is not compatible with the DVB-C system planned to adopt in China. This will inevitably result in a waste of device incompatibility in the future.

Therefore, the use of DVB-C QAM modulation, not only improve the network capacity, but also compatible with the future development trend. It is the rational choice of broadband multimedia information system, which is suitable for the expressway of China's national conditions by adopting the QAM modulation method of DVB-C. Using a data broadcast system that complies with the DVB standard has the following advantages:
1. the DVB standard has a wide range of complete transmission interface protocols, data can be easily transmitted through almost all existing channels, such as satellite, cable TV, SDH, PDH, ATM, MMDS and terrestrial digital television broadcasting (DVB-T, it is suitable for transmitting data from the backbone network to the regional network, the Metropolitan Area Network, and the residential area on different scales.
2. The data transmission rate is high and the error rate is low. The 64-QAM modulation method is adopted in the HFCs. The data transmission rate of a standard 8 m TV channel can reach 40 Mbps.
3. compatible with digital video programs, user terminals can receive both data and digital video broadcast programs. data and video programs can be transmitted on the same channel.
4. General-purpose front-end devices, using the same standard DVB multipleer and QAM modulation as video broadcast, can choose the most cost-effective among many manufacturers.
5. A complete DVB conditional receiving (CA) system can be used to ensure a complete authorization control mechanism.
6. DVB has a complete network and return protocol. You can select multiple return modes. In the next 10 years, we will gradually improve the existing wired network facilities to achieve real two-way network transmission.

2. Data Broadcast System Based on DVB standards

The blue topology company has developed a data broadcast IP-OVER-DVB system that fully complies with the DVB protocol.

System Principle 1:

The system functions are as follows:

The entire system adopts the DVB standard
● Supports live video and audio services
● Support video, audio, and on-demand data services
● Support for user management systems and authorization systems
● The return channel supports dialing, lan, FDDI, and ISDN.
● The client supports modem and Ethernet Card
● Supports conditional receiving of the DVB standard
● Program broadcast management and program content management
● Channel bandwidth management
● User management, Bill Management, charge management, and authorization management
● Quick File Download
● Collection and carousel Homepage
● Live video multimedia service
● Playback of real-time update data
● Bidirectional interaction

Our company has completed the development of the entire system, including

Hardware:
● Multi-protocol wrappers (compliant with the en301 192 Standard)
● QAM modulation (compliant with DVB-C Standards)
● Data receiving card (PCI interface)

Software:
● Manage Server Software Development
● Broadcasting Control Server Software Development
● Website broadcast (push) software (server and client)
● File broadcasting software (server and client)
● Multimedia live broadcasting Software

Among them, the multi-protocol package is the key equipment of the data broadcast system. After painstaking research, our company has developed a stable and reliable system, which is equivalent to the latest foreign products, some indicators are superior to those of the overseas products.

Our system can adopt completely localized front-end devices and localized data receiving cards, fully complying with the relevant DVB standards. The experiments that can be run without any modifications on the existing cable TV network by using the QAM modulation method have been completed. Our devices are independently designed to ensure quality and system reliability, and form a high-speed multimedia data transmission system with Chinese characteristics. Both the above equipment and software R & D have full proprietary intellectual property rights for independent development.

Modem dial-up is used for uplink traffic and cable is used for downlink traffic. The charge for the card is 1-card-1, which can be embedded into the standard DVB receiving system. The maximum speed is 36 Mbps. Data Service charges are recorded in bits.

Main technical indicators:
1. The system is transparent to IP addresses and can run any IP-based data service.
2. Implement compatibility with analog wired bandwidth 8 MHz, up to 64 QAM modulation of dvbc standard signals, broadcast systems that can run on existing analog networks
3. Within 8 MHz of a wired bandwidth, the maximum operating speed is 36 Mbps.
4. The minimum number of users is 0.1 million, and the maximum number is 1 million.
5. Standard DVB conditional receiving system can be embedded
6. The front-end server can interface with ATM or high-speed Ethernet.
7. Consider future transmission of HDTV.

Iii. System Composition

(1) Front-end software structure

The front-end of the Data Broadcast System is composed of Management Servers, broadcast control servers, content servers, and interactive servers. The key of the system is our self-developed multi-protocol wrappers (IPE ), the server and the IPE form a Local Area Network. The TS stream output by the Data packer is sent to the QAM modulation and frequency conversion. The receiving end is inserted into the computer and the data broadcast receiving card is directly processed with the cable TV. For bidirectional interaction systems, front-end interaction servers should also include routers connected to the Wan, and the user end should also include modem devices connected to the local Wan.

Front-end servers are the core of the system. The multi-protocol package (including management and control) is responsible for encapsulating IP data into DVB data, and the Management Server is responsible for all management functions of the entire data broadcast system, including program content arrangement and broadcasting management, channel bandwidth management, user Bill Management, charge management, authorization management, etc. The Broadcasting Control Server broadcasts data from various content servers according to the Configuration Requirements of the management server, the traffic of each data is controlled according to the configured bandwidth and sent to the multi-protocol package. For two-way systems, the interactive server implements access control for interactive users, at the same time, it works with the relevant underlying drivers to achieve high-speed channel downlink and low-speed channel uplink control.

The structure of the front-end software is shown in figure 2.

The receiver is a receiver card, which implements RF signal demodulation and channel Decoding to obtain the DVB transmission stream. The acceptor software consists of several layers, including hardware drivers, NDIS middle-layer drivers, upper-layer broadcast interface libraries, and client applications for various services. The data is obtained from the bottom-layer data receiving card, then forwarded to the middle-layer driver and protocol driver, and then to the application based on the IP protocol. The software structure of the receiving end is shown in figure 3.

(2) Server Management

The Management Server is the control core of the broadband data broadcast system. It stores and manages the data necessary for the entire system operation. it mainly includes all information about the program to be broadcast and all information about the system users. Therefore, it is vital to manage servers for officially running systems.

1. design purpose

Management service software is an important module to ensure the operation of IP over DVB data broadcast services. Management service software mainly includes program management, billing management, user management, and authorization management. Program Management Software ensures that programs are reasonably organized and provided to users for program orders; user management software controls all user account information; and authorization management software ensures that only legitimate users can receive programs; the billing management software collects billing statistics for users who receive programs.

2. Achieve indicators

The system is designed to support 1 million end users and 1000 two-way concurrent users. 1000 concurrent users are defined as 1000 users who can log on to the two-way interactive server at the same time to obtain special two-way services (content outside the broadcast service ). User Management manages user accounts, collects traffic statistics and bills based on user usage, and authorizes legal users. Program Management provides the DVB Broadcast Server with the basic basis and parameters for broadcasting data programs.
● Provides a web-based DVB program broadcast database management system, establishes a stable and reliable database server for data broadcast information, and provides administrators with a web-based convenient, fast, and efficient interactive interface.
● Provides a web-based user information database management system, establishes a stable and reliable user information database server, and provides administrators with a convenient, fast, and efficient web-based interactive interface.
● Provides a web-based authorization information database management system and a web-based interactive interface for administrators.

3. system running environment:
System Platform: Windows NT 4.0 Server;
Database platform: SQL Server7.0;
Web server: iis4.0

(3) Broadcasting Control Server

The Broadcasting Control Server is responsible for broadcasting control tasks throughout the broadcasting system, and provides functions such as scheduled broadcasting, broadcast Rate Control, bandwidth allocation and monitoring, and traffic statistics.

1. Function Description

(1) broadcast Rate Control

The total bandwidth of the broadcast device is used to control the rate of the broadcast program not higher than the specified rate. This module can provide a certain amount of buffer (stored in linked lists). However, if the broadcast rate required by the user exceeds the actual bandwidth for a long time, data will eventually be lost. User data loss means that the TCP connection of the user end will time out if the response fails to be received for a long time. Even if the buffered packet is sent to the user end, the user end will not receive the response. In this case, the packet is lost. Theoretically, the buffer size only depends on the memory that can be provided by the operating system running on the broadcasting server.

(2) Bandwidth Allocation and Monitoring

Allocates dynamic bandwidth to users based on the user data provided by the user database (including user service priority, bandwidth, and other data) and total bandwidth, and monitors bandwidth changes at any time. The user service priority is tentatively set to 256. The priority is divided based on the importance of the user and the user's specified situation (different priorities are charged, and users can choose to pay ).

The user's bandwidth is calculated by the Broadcasting Control Server's statistics on the data traffic transmitted to the user in the recent period. Formula: F/T. F indicates the data traffic transmitted to a user within t time, and t indicates a fixed time. The Dynamic Distribution of bandwidth indicates that the bandwidth is first allocated by priority, and a superior user gets the specified bandwidth first; after the bandwidth requirements of all users are met, the remaining bandwidth in the system will be distributed by priority. The advantage of doing so is to make full use of the bandwidth (up to 100%) and provide better services to users when the bandwidth is surplus. The disadvantage of dynamic bandwidth allocation is that the allocation algorithm is very complicated.

(3) Traffic Statistics

Count the total traffic of each user. After the statistics are completed, the results are written to the user database provided by the Management Server, which serves as the basis for the final charge. This module obtains the user's fee information from the user database and stops serving the user when the balance is insufficient.

The traffic statistics are real-time, but the settlement is timed, so that if the balance between two settlements is zero (this situation can be considered as not a "Malicious Overdraft ") the service will not be stopped immediately. the user's negative balance will be written to the user database and the service will be stopped only at the last settlement.

2. Runtime Environment

The operating system is Windows NT4.0, and the software environment requires the SQL Server database.

(4) multi-protocol wrappers (IPE)

Multi-Protocol package is the core equipment of IP over DVB data broadcasting system. The multi-protocol package bluecast in this system is based on our mature MPEG-2 code stream broadcasting card, after painstaking research on DVB-related protocol standards and successful development, its main indicators have reached or exceeded the level of similar foreign products.

(5) Content Server

The system supports transparent IP services. any third-party IP-based application software can run in the system, the blue topology company has developed practical file broadcast, website Broadcast Server, and client software.

(6) data receiving card

The data receiving card is an extended plug-in card for IBM compatibility with personal computers (using a PCI local bus) that enables a PC with this plug-in card to receive DVB-DATA (en300 192) that is transmitted over a cable television network) standard high-speed broadband multimedia data. According to the requirements of the design objectives, the specific implementation of the receiving card includes several functional modules shown in Figure 4:

1. RF and Antenna Control Module

This part completes the conversion from RF to baseband signals and provides the working power supply and various control signals for the antenna LNB, in line with the related requirements of the digital compression wired receiver technical requirements (interim.

2. Channel Decoding

This part completes the recovery from the baseband signal to the transmission data stream (TS), fully meeting the requirements of the DVB-C (EN 300 429.

3. Data Processing

In the Data Processing Section, the data transmission stream is deduplicated and the data is processed according to the service content. The processing of this part should comply with the corresponding standards: MPEG-2 (ISO/iec13818), DVB-SI (en300 468), DVB-CA (etr289) and so on.

4. central processor (CPU ):

The CPU is the core of the card, controls the operations of other parts, and completes some data processing. It features high processing speed, low power consumption, and convenient interfaces with related parts.

5. CA system

Can be embedded into a CA system that complies with the DVB standard, and the card has corresponding processing capabilities. Has a smart card interface compliant with ISO-7816 standards.

6. Memory System

Memory includes program memory on the card, data memory, NVRAM required by the CA system, and interface data buffer memory.

7. Host Data Interface

Because the data exchange speed with the host is up to 60 Mbps, And the ISA bus is gradually eliminated, the interface with the host uses the PCI bus interface.
· Pci2.1 compatible with local bus
· Host bus width: 32-bit
· Host bus burst rate (burst rate) 133 MB/S

The rapid development of digital TV will gradually replace analog TV. There will be more and more demand for digital TV multimedia services based on the DVB standard, and the digital TV business is no longer limited to video, more importantly, it is used in interactive services, such as on-demand video, data broadcast, and high-speed Internet. The digital multimedia integrated service based on the ground has broad application prospects.

As a product closest to the people, the development of multi-media cable TV business provides a new way to carry out value-added services on the cable TV platform, which will promote the development of the digital TV industry, it greatly enriches people's cultural life and plays a positive role in social prosperity and stability.

Digital TV and network technology are a new growth point of the national economy. They provide integrated digital multimedia services on cable TV platforms, network operators, set-top boxes, receiver card manufacturers, and program providers can all gain considerable economic income, thus increasing social and economic benefits.