A Transmit Diversity Scheme for TDS-OFDM System

Transmit diversity is especially important in broadcasting network. In this paper, a transmit diversity method is proposed for the Chinese National Digital terrestrial television broadcasting (DTTB) standard. The transmit diversity scheme is based on the design of orthogonal sequences which have perfect crosscorrelation and almost perfect autocorrelation characteristic. The characteristics of the proposed sequences can help for synchronization and channel estimation in time domain synchronous orthogonal frequency division multiplexing (TDS-OFDM) system. Simulations using space-time codes (STCs) in digital terrestrial/television multimedia broadcasting (DTMB) system with low density parity check coding (LDPC) show that the proposed transmit diversity method has about 1-2 dB signal-to-noise ratio (SNR) gain comparing with no diversity for QPSK and 16 QAM constellations at BER= 10^-4, and it can avoid the appearance of BER floor for 64 QAM constellation.