地面数字电视承担着面向公众公益性的信息广播任务，具有建网成本低，覆盖面广等优势，是国家最基本的公众信息传播手段。另一方面，由于数字广播技术的发展，各种其他业务和各种收视方式也不断涌现，公交电视、铁路电视、USB dongle、手持电视机等多种接收终端不断涌现；股票信息、交通实况转播、电子报刊以及公交站牌等多媒体业务也通过数字广播正在兴起。数字广播技术已成为 “信息产业及现代服务业”的主要支撑技术之一。
Background on digital broadcasting
Delivering massive contents to the general public, the DTTV (digital terrestrial TV) offers arguably the most important means of wireless information dissemination in the modern era. In addition to providing public services, advances in digital broadcasting technologies have given rises to various new businesses opportunities, ranging from rich media display on public transportations (e.g., metro buses and the railway), to mobile TV and mobile data services (e.g., stock information, live traffic information, electronic newspapers, etc.) and other high bandwidth multimedia services. In short, with its unique capability to address the ever-growing demand of mobile data, digital broadcasting has become one of the irreplaceable forces in today’s IT and services industries.
The IWCT of Shanghai Jiaotong University has a long history in developing cutting-edge technologies for the digital broadcasting industry. Among others, Professor Hui Liu is the chief architect of CMMB (GY/T 220.1-2006) mobile broadcasting standard, while Professor Yunfeng Guan is one of the main drafters of the China’s terrestrial digital TV standard (GB20600-2006) - the only mandatory standard in the field of digital TV in China.
The technologies in digital broadcasting
Serving as a reliable high speed data pipe, the digital broadcasting system can be utilized in a variety of the public digital media and communications applications such as DTTB, the high-speed railway TV, the Shenzhou spacecraft ground rescue system and so on. Given the hostile wireless environment, the technical challenges associated with digital broadcasting are demanding, which include low-cost implementation, strong interference resistance, dynamic resource scheduling, and high-speed mobile reception, to name a few.
Our research over the years has resulted in a suite of new technologies on fast channel equalization, mobile data structures and networking architectures, and low cost chip implementation. Specifically, we have developed a comprehensive family of digital broadcasting theories and enabling technologies with completely independent intellectual property rights. 19 patents are authorized, with more under review.
1）For the single-carrier transmission system, we have developed a novel overlap equalizer algorithm based on LMS, which offers a highly robust, yet effective solution for single-carrier mobile reception.
2）For the multi-carrier transmission and coverage, we have proposed an integrated satellite and terrestrial Single Frequency Network (SFN) for the CMMB mobile broadcast standard. The combination of innovations (including high-speed OFDM modem, efficient LDPC codes, and fast sync design, etc.) makes CMMB one of the best in its class.
3）We have made significant contributions to the data structure of digital broadcasting, which in turn has become a key part of the China Digital Television Terrestrial Broadcasting Standard (DTMB).
3．The applications of digital broadcasting
Most of the digital broadcasting technologies developed by IWCT have found applications in a widely range of scenarios, such as the CCTV HD program system, the high-speed rail mobile TV, the Shenzhou spacecraft ground rescue system, and the rural television coverage. Many algorithms have been implemented on commercial chipsets, which resulted in tremendous social and economic benefits. Because of the above contributions, we have won the second prize of the National Science and Technology Development Award in 2008, and established the national Engineering Research Center of digital TV.