Transmission Performance Depending on OFDM Symbol Duration and Scattered Pilot for Digital Terrestrial Broadcasting

Abstract

Orthogonal Frequency Division Multiplexing (OFDM) is a prime candidate for use as a modulation method for digital terrestrial broadcasting, because it is robust against multipath interference and can be demodulated correctly under Single Frequency Network circumstances Mobile reception or HDTV broadcasting can be achieved by using DQPSK or 64 QAM modulation, respectively, as the carrier modulation method for OFDM When a receiver demodulates 64 QAM, pilot symbols are necessary as amplitude and phase references This paper describes a study on how transmission performance depends on symbol duration for mobile reception, and on the frequency, time intervals, and level of pilot symbols The results show that a 500 μs OFDM symbol duration can support mobile reception in the case of DQPSK OFDM It is suitable for the pilot symbols to have a frequency interval of 3, time interval of less than 5, and a data symbol level of 1 2 to 1 4 times that of the average level of data symbols