Experimental Evaluation of High-Bit-Rate Transmission Using DAPSK-OFDM Modulation Schem

Abstract

Digital transmission signals are distorted by multi-path fading in a mobile radio channel. This is a severe problem, especially when a digital field pick-up unit transmits high-bit-rate data such as HDTV digital signals. The OFDM (orthogonal-frequency-division-multiplexing) modulation scheme mitigates the adverse effects of multi-path fading by distributing the transmission data into a large number of carriers with low-bit-rate modulation. To reduce the degradation due to multi-path fading in high-bit-rate transmission, we have developed an experimental OFDM modem that uses multi-mode modulation : 16/32 DAPSK (differential amplitude phase shift keying). Transmission experiments showed that the a 16/32 DAPSK-OFDM modem can transmit data at 23.7 Mbps by 16 DAPSK modulation and at 29.7 Mbps by 32 DAPSK modulation within a bandwidth of 13.5 MHz in a frequency-selective Rayleigh fading channel.