Characteristics and problems of Data Broadcast Technology

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【Abstract】 data broadcast is a new generation of business that emerged after audio broadcast and video broadcast in the broadcast and television system. This paper briefly introduces the features and problems of data broadcast technology.

1 Introduction

Data Broadcasting is a new generation of business that emerged in the broadcast and television system after audio and video broadcasting. It is a new army in the national informatization process.
At present, many cities in China have carried out data broadcast services in cable TV networks. With the continuous development of data technology and computer technology, data broadcast technology has also achieved unprecedented development, qualitative changes are occurring from analog to digital, from narrowband to broadband, and from unidirectional to bidirectional.
There are also some problems in the rapid development of data broadcast. This article will briefly introduce the characteristics of Data Broadcast Technology and discuss these issues.

2 Characteristics of Data Broadcast Technology

The biggest advantage of a broadcast network is the "broadcast method", that is, "one point to multiple points, opposite to a point ", the output information at the front end of the cable TV network can be broadcast to all users connected to the cable TV network. In the Radio Television Broadcasting System, one method used for information service is to transmit data through a TV channel, that is, a graphic TV (VBI) data broadcasting system. One form of information service that corresponds to a text-and-text TV and gives full play to the characteristics of cable TV is high-speed data broadcast.
2.1 data broadcast principles
Data Broadcasting is a push technology. It uses the Broadband Characteristics of the hfc-net to send a large amount of information to users at a high speed at the same time, and users can choose to receive data through dedicated devices.
The basic principle of the data broadcasting system is as follows: An information data editing and broadcasting system is established at the front end of the cable TV system. Various information and data from different channels are classified at the front end, it is edited into a unified information stream in a certain format to form a digital information channel. After digital modulation and carrier frequency modulation, it becomes a standard TV channel signal and is sent to the cable TV system. A user terminal can be a set-top box (TV user) or a data receiving card (computer user). It is used to receive data signals from the front-end and demodulated, after disturbing, you can store it in the random storage device in the receiver for you to view, and then display it in a certain format on the TV or computer through the display interface. You can use the remote control or button to query data. All interactions occur between the user and the user terminal.

Figure 1 High-Speed Data Broadcast System
2.2 modulation of Data Broadcast
Currently, there are two main modulation methods for data broadcast.
In this way, two consecutive binary data are converted into four different signals with a phase difference of 90 degrees. The transmission rate is 10 Mbit/s.
The QAM introduces discrete Amplitude Modulation on the basis of the PSK. The larger the introduced amplitude level, the larger the bandwidth expansion factor of the line, the higher the transmission rate, up to 27 Mbit/s ~ 45 Mbit/s. The coding efficiency of the QAM modulation is higher than that of the PSK modulation. However, its anti-interference capability is lower than that of the PSK modulation, and the equipment cost is high.
The 8 Mbit/s data broadcast capability can be provided in 8 MHz bandwidth by means of the PSK modulation technology. Generally, a Chinese character is represented by 16 bits in two bytes in a computer, add the control information ~ 12 Mbit/s means that 100,000 words of information can be transferred in one second. Therefore, using this method to broadcast information can accommodate a wide range of huge information content. Currently, the transmission quality of CATV networks in China is generally poor. At present, in many places, we use a better anti-interference method, and the transmission rate can also meet the needs of current users. However, in the long run, 64QAM modulation is the development trend of data broadcast.
2.3 cable TV hfns are most suitable for data broadcasting
The signal transmission on the cable TV's HFCs network adopts an asymmetric radio network structure, which features low-frequency bandwidth, large information capacity, narrow uplink band, and small information capacity. Cable TV networks can carry out data broadcast services without any transformation, with low investment and low charges for users, but users can get a lot of information, such as Internet browsing, stock information, e-newspapers, TV shopping, and remote teaching. In a analog channel bandwidth (8 MHz) of a cable TV, the transmission rate can reach 10 Gbit/s or 40 Gbit/s by means of PSK or 64QAM digital modulation.

3. Data Broadcast Problems

Theoretically, data broadcasting has many advantages and has huge market potential. Based on the current market conditions, the high-speed data broadcast service is developed, and its front-end generally develops a sub-channel, with an investment of 20 ~ More than 30 million RMB, which is acceptable for cable TV stations in cities and investment at the user end is generally less than 1000 RMB. Users can also afford attractive information sources. However, in practice, the number of users in various regions is not ideal, because data broadcast still has many problems, resulting in slow development.
3.1 Information Source Problems
As mentioned in the China data broadcast platform solution (discussion paper), the characteristics of the data broadcast mode are massive information and massive users. Data broadcasting must collect massive amounts of information and continuously provide users with high gold content to meet the information requirements of massive users. Specialized processing of information is the key to ensuring the amount of gold contained in information.
Currently, data broadcasting is mainly carried out in various regions, including financial information (stock market quotations, stock reviews, foreign exchange quotations, etc.), Internet information, electronic newspapers, education information, video on demand, and many other service functions. But in fact, the most users are the stock information service. Why? Only stock quotations are updated in real time. On some cable TV stations, due to lack of attention and manpower restrictions, the release of information is not updated in a timely manner. E-newspapers are always waiting for several days, and the distance education service is not perfect, on-demand video streaming is always a few movies.
I think the following methods can be used to resolve the information source:
(1) because the information provided by a single cable station is limited, the nationwide data broadcast network must be realized as soon as possible to achieve information sharing and expand information sources.
(2) You can also work with professional content providers who have specific information sources and rich web page production experience.
(3) There is an inexhaustible amount of information available on the Internet. We can download and broadcast the information to the user based on the user's needs.
(4) strengthen user rating surveys, understand user needs and interests, and update information in a timely manner.
3.2 client software problems
Data Broadcasting is actually a new sharing structure. Academician Li Youping of the Chinese Institute of Engineering Physics proposed three key points of the new sharing structure:
(1) families (or individuals) have their own massive data storage.
(2) Use large-scale parallel broadcast to support the spread of information in the storage.
(3) Use content positioning (UCL) software to integrate reading materials that meet Personalized Requirements in warehousing.
In this case, 3rd points involve user software issues. At present, some manufacturers do not have satisfactory data broadcast software design, and the search function is not strong. Many users report that it is not used to or inconvenient to use. We recommend that you provide improved versions to help you collect and search for information.
3.3 standardization of data broadcasting
Data Broadcasting in China was initially using analog signals to transmit data, using VBI Technology in television broadcasting, and using SCA or RDs Technology in audio broadcasting. In cable TV networks, many manufacturers have successively developed a High-Speed TTL Data Broadcast System, a QAM data broadcast system, and an interactive data broadcast system outside modem due to bandwidth. Recently, with the development of technology, data broadcast in DVB mode and data broadcast in IP Mode have emerged. This shows that the data broadcast technology is developing at a high speed, but on the other hand, there is no uniform standard officially introduced in China. The devices of different manufacturers are used in different regions, and the receiving cards of users of different manufacturers cannot be used in general, as a result, the cost is high and the user's willingness to enter the home is not strong. Product standardization can greatly reduce costs. Taking telephone modem as an example, its production standards are unified around the world to facilitate high integration and large-scale production. The lowest price is only 100 RMB. In addition, information exchange between different data broadcast networks also requires a standard. Therefore, the absence of a unified data broadcast standard is the bottleneck of the development of data broadcast.
3.4 competition problems
Data Broadcasting is a cross-cutting between the business and the graphic TV and Internet businesses. For example, the stock information service must compete with a large number of stock receiving cards. Currently, we can basically obtain data broadcast services from the Internet. With the development of broadband access network technology, the price and monthly rental fee of ADSL and Cable Modem are constantly decreasing, currently, data broadcast is a one-way broadcast. If you cannot maintain the price advantage and volume advantage, your support will be lost.

4 Conclusion

The high-speed data broadcast service is a hot topic in the Development of cable TV Integrated Services. Despite many problems, with the establishment of the national data broadcast platform, the data broadcast business of digital transmission will be networked and standardized, and users are expected to receive massive information services.