First of all, I will introduce the architecture of CMMB system. Is the name of the mobile multimedia broadcasting system being established under the leadership of the State Administration of Radio, Film and Television. Mobile multimedia broadcasting refers to a system that receives radio and television programs and information services anytime and anywhere for receiving devices such as small screens under seven inches through satellite and terrestrial wireless broadcasting. This is the architecture of CMMB system. Its main components include the first front end of broadcasting, including the content and data services of radio and television programs, which are gathered together through the program integration platform for broadcasting. Then his transmission system is mainly composed of satellite system and ground switching network. It is a system covering all of China, with satellite coverage as the main part and ground augmentation network as the supplement, and can receive broadcast signals anytime and anywhere. The system uses S-band frequency. His signal goes all the way to the satellite, and then it is relayed to the S-band signal on the satellite and sent directly to the terminal. About 5% of China is not covered by satellite signals, which is supplemented by ground systems. In other words, the receiving terminal can receive both satellite signals and ground signals. These two signals are simultaneous, with the same frequency and the same signal. At the same time, the system can also use terminals with mobile communication modules, such as mobile phones, to carry out interactive services. This is the CMMB architecture that has been determined at present. Then let me briefly introduce the standard and specification system of CMMB. At present, the State Administration of Radio, Film and Television is carrying out the formulation and implementation of standards in an all-round way according to the CMMB system framework we have determined. To this end, SARFT has set up a special CMMB technical working group. Because CMMB is a broadcasting system, its competent department, State Administration of Radio, Film and Television (SARFT), unifies the management technical specifications and operations. Now the CMMB standard system has several parts. The first part is the service information source. The other part is protocol and signaling. In addition, it also includes business expansion, and now includes emergency broadcasting, traffic information and guidance, and email. In the future, the part of expanding business will be further increased. The satellite part includes the technical requirements of the satellite, as well as the function, performance and configuration of the terminal part, the terminal reference design and interface, and the terminal software application becomes the interface. It should be said that mobile multimedia broadcasting is a special mobile field. It is different from terrestrial digital TV, cable digital TV and satellite digital TV. Therefore, it is necessary to establish a standard system in this field. At present, more than 60 members of CMMB technical research group are preparing technical specifications and experiments. Let me briefly introduce two standards that have been published now. The first standard was released in 10, GYT220. 1—2006 "Mobile Multimedia Broadcasting Part 1, Modulation of Broadcasting Channels". This standard specifies the frame structure, channel coding and modulation of broadcast channel transmission signals of mobile multimedia broadcasting system within the frequency range of 30 MHz to 3000 MHz. The system bandwidth includes two, one is 8 megabytes and the other is 2 megabytes. The channel propagation technology he adopted was multicarrier modulation. LDPC code is used in channel coding, and RS code is added to improve the effect of the receiver in some bad situations. In addition, bit block interleaving is also used. Its biggest feature is the frame structure, which can greatly reduce the power consumption of the terminal. First, there is the concept of a logical channel. This logical channel is divided into two types, one is the logical channel of control information, and the other is the logical channel of business information. The parameters of the control logic channel are fixed, which makes the control logic channel get the best receiving performance. Different traffic channels can be transmitted by multiple time systems, which can greatly save electricity. Then his structure includes a complete second, including 40 time systems, each of which is 25 milliseconds. Each time series includes 50 beacons. Beacon includes two contents, one is the identification signal of the transmitter, and the other includes two identical synchronization signals. This can be applied to fast acquisition synchronization, so that signals can be quickly acquired in the wireless channel. This is the overall function of the broadcast channel. First, there is an upper data stream. After this upper layer data stream comes, it is encoded by RS and byte interleaving, then encoded by LBPC, then inserted with continuous pilots, and finally sent to RF. Different from some other transmission systems, its winding coding is at the back rather than at the front, which makes the front structure completely unified and can be more simple and convenient in chip implementation. The byte interleaving and RS code mentioned just now are both in the form of lists, that is to say, the numbers are listed and then coded by lines. His channel coding adopts very advanced and highly structured PC coding, and the compromise of code length is 92 16 bits. This code is a very low complexity code after various practices, and its performance is excellent channel coding. In the aspect of constellation mapping, according to the characteristics of mobile multimedia broadcasting, three mapping codes, BPSK, QPSK and 16QAM, are adopted. In this way, different codes can be selected for different broadcast networks to distinguish them. The continuous pilot carries 16 bits of transmission indication information. This information is transmitted in the traditional way, so the control information can be received correctly. To sum up briefly, there are three options for RS code of 8 megabit system. This structure adopts a unified implementation structure, which also makes the implementation of the chip very simple. The system with the highest load rate of 8 Mbps can transmit the data rate of 16.58 Mbps. Just introduced the first part, now introduce the second part Gy/T 220.2-2006 "Mobile Multimedia Broadcasting Part 2: Multiplexing". The reuse standard was released at the end of 1 1 and officially implemented at 12+ 1. The first standard was released at the end of 10 and implemented on 1 1. Then this multiplexing standard does not adopt the usual multiplexing structure, but is completely aimed at the multiplexing structure of this system. The multiplex frame corresponds to a broadcast channel frame. Multiplexed channel frames have no other functions, but are only transmitted in multiplexed channels. This multiplexing has other characteristics. The first is that it adopts efficient transmission, which is completely aimed at the narrowband data transmission of our wireless mobile multimedia broadcasting. In addition, his control information and business data are separated. This can adapt to the harsh environment of wireless transmission. It supports multimedia data bearing, such as audio and video, and multiplexing services. At the same time, it has fault-tolerant design and scalability. Briefly introduce the structure of multiplex frame. It includes network information table, continuous service multiplexing configuration table, short-term service configuration table, etc. We divide our business into two categories, one is continuous business and the other is short-term business. Here, the network information describes the frequency detection information of the whole network, and the network multiplexing configuration table describes which services occupy those time series. The persistent service configuration table mainly describes which networks these services are placed in. Through this form, it becomes simple and convenient to extract business. In the current standard, the basic information description table and emergency broadcast are not explained in this standard. Then his multiplexed frame includes a multiplexed frame header and a plurality of multiplexed subframes. Each multiplexed subframe corresponds to a different service, thus realizing the application of multiple services on a logical channel. At least one of these three data segments can be selected, and video and audio data segments can be selected for general TV signals. The data of our electronic program guide can be put in the data area. If you simply do voice broadcast business, there will be no video data segments, only audio data segments. In this way, a very flexible design is realized. The simplest configuration is that the horsepower in this multiplexing frame is just right, and there can be only one multiplexing subframe. If you want to do multiple multiplexing services, you can have multiple multiplexing subframes. Now these two standards can be downloaded from the website of the Institute of Standards of the Planning Institute of the State Administration of Radio, Film and Television. In addition, some new work progress of CMMB technical work research group will be published on our work website at any time.