Patent Related to Digital Terrestrial Television Broadcasting (ISDB-T) Patent No.2904986 Method and Apparatus for Digital Signal Transmission Using Orthogonal Frequency Division Multiplexing (Patent No.5406551(U.S.), Patent No.0553841 (U.K.), Patent No.0553841 (Germany), Patent No.0553841 (France)) Figure 1: A block diagram of a transmitter device This invention involves transmitting and receiving devices for digital signal transmission by an Orthogonal Frequency Division Multiplexing (OFDM) modulation scheme, which uses multiple orthogonal carriers to transmit digital signals. This is an essential patent for digital terrestrial television broadcasting (Integrated Services Digital Broadcasting-Terrestrial: ISDB-T) standards in Japan. The ISDB-T digital broadcasting scheme is superior because it provides a variety of services, ranging from Hi-Vision (HDTV) broadcasting to multimedia broadcasting for mobile terminals. In Japan, digital BS (broadcasting satellite) broadcasting started in December of last year, and preparations are being made to begin digital terrestrial broadcasting in the Tokyo, Nagoya, and Osaka regions in 2003, followed by a nationwide service in 2006. The Japanese ISDB-T standard was also adopted as an ITU-R international standard. By employing the patented orthogonal frequency division multiplexing technology, the transmitter makes use of multi-level carrier modulation. It also periodically interleaves predetermined reference data, indicating the amplitude and phase of the respective carriers at a prescribed position within a frame, which consists of multiple transmission symbols. The system's transmitted data, by means of transmission symbols, includes the amplitude and phase reference data for a fixed number of partial carriers from the total available, and a group of transmission symbols includes the amplitude and phase reference data for all the carriers. For a single carrier, multiple, different amplitude and phase reference data are transmitted in sequence. At the receiver, the system stores the received amplitude and phase reference data for each carrier in order to obtain valid data sequence and reference data for use in the reproduction of the transmitted data. Thus, this system enables a receiver to receive valid data without requiring carrier recovery. This prevents the increase in signal power or peak signal level, which might accompany the addition of the amplitude and phase reference data, and reduces the influence of possible errors in the transmitted amplitude and phase reference data by dispersing the necessary data across the entire range of carriers. The transmission data switch control unit generates data switch control signals based on outputs from the reference data position memory, the transmission symbol number counter, and the carrier number counter. According to this data switch control signal, the amplitude and phase reference data are switched to the valid transmitted data, which are then modulated at the OFDM modulator for transmission. In the receiver, the OFDM modulator demodulates the received data, and the received data switch control unit generates switch control signals based on outputs from the reference data position memory, the transmission symbol number counter, and the carrier number counter. According to this generated switch control signal, the received data is separated into amplitude and phase reference data, as well as valid received data. The received amplitude and phase reference data is stored in the received reference data memory. In the end, the transmission data is reproduced through an estimation of the original amplitude and phase values at the interleave matrix unit, based on the three kinds of valid received data, the received reference data, and the predetermined reference data for respective transmission symbols in each carrier.