The Study Of Mobile Reception Technique For HDTV

So far, high-definition television (HDTV) is developing very fast in USA, France, Germany and Australia. HDTV adopts the High-Level, Main-Profile definition (MP@HL) of the MPEG-2 Standard. Normally images of up to 1080 lines by 1920 pixels, with aspect ratio 16:9 can be processed. As the information amount of HDTV is about 5 times of SDTV, so a modulation method supporting high bit rates must be used to transmit programs, which requires a high-quality receiver. Also because of the complexity of mobile channel, the received signal is dropped off and interfered by noise and echo, so C/I ratio of signal is low usually. Moreover receiver must overcome doppler effect. Due to above reasons, normal receiver is very difficult to be applied in high speed mobile environment. In order to solve above problems, this paper proposes a solution in which diversity technology based on Maximum Ratio Combining(MRC) is applied.Firstly the paper analyses three key technology of mobile reception, that is, Coded Orthogonal Frequency Modulation(COFDM), diversity reception and MPEG-2 video decoding. Based on these technology , the 3^th chapter gives a detailed description on the proposed scheme through both software and hardware part point of view, which on the whole is more focused on the software architecture based on platform independent layer concept. The 4^th chapter introduces the software and hardware design of diversity receiver, with emphasis on dual IF/RF AGC control circuit and blind scan algorithm. The 5^th chapter introduces the hardware and software architecture of a video decoding system for HDTV, describes the function and control of each module in this system, emphasizes the working states transforming relationship of video decoding flow and decoding interrupt handling.In the end, the paper gives performance comparison for outdoor mobile and indoor portable environment. It shows that diversity not only gives more margin on C/N (about 9 to 13 dB) and doppler frequency (about twice) , but also suppresses part of the ingress noise and short echoes problems, thus offering sufficient quality with portable and mobile reception in places where a single receiver would absolutely not work. In terms of coverage increasing, this corresponds to a gain of 67% to 95% of the apartment. This diversity solution was tested in different countries, with different DVB-T parameters, and whatever the parameters are, mobile reception without diversity is often a nightmare, whereas it works well with diversity which effectively increases the sensitivity and doppler frequency.