Protection of Digital Terrestrial Television Signals Against Analog Signal Interference

Abstract

The draft standard for the Digital Terrestrial Television Broadcasting (DTTB) system of Japan using Orthogonal Frequency Division Multiplexing (OFDM) digital transmission was approved in 1998. DTTB services are provided along with analog television services, so that DTTB signals can be interfered with by analog signals.Various ratios for protecting DTTB signals against analog television signals, have been tested. The results show that co-channel protection ratios of 25 dB, and adjacent-channel protection ratios of no more than-20 dB are required when the DTTB signals are modulated by 64 QAM-OFDM and convolutionally coded at a rate of 7/8. The BER performance for co-channel interference was improved by using soft decision decoding with erasure.