<title>Three-level hierarchical HDTV broadcasting system</title>

Abstract

Digital HDTV broadcast differs from digital point-to-point transmission in that different receivers have reception condition which depend on the distance from the emitter and on the others disturbances (multipaths, shadowing, etc...). Therefore, a very robust transmission concept taking into account the graceful degradation effect is required. The aim of this article is to show the possibility of designing a transmission scheme supporting three-level hierarchical HDTV signal: HDTV, TV , and Personal Video PV for stationary and portable receivers, respectively. The system is based on a combination of Multiresolution Modulation and Multilevel coding using the principle of OFDM to combat against multipath interferences. The system is designed such that different receiver can receive its desired signal with different complexity according to the image quality. The system also supports graceful degradation. The optimization of the different parameters of the system is done under different reception conditions i.e. we suppose that a HDTV/TV image signal is received in an AWGN/Rician fading channel condition. And a PV image quality is expected in a Rician/Rayleigh fading channel. An example of combined Rate-Compatible-Punctured-Convolutional codes with 3-resolution 64-QAM in a 8MHz channel showed that even if the received power of a portable receiver is 29dB lower than a stationary receiver, one can achieve the desired hierarchical image qualities in these channels.