Transmit Diversity for Coded OFDM Systems in Single Frequency Networks

Orthogonal frequency division multiplexing (OFDM) systems are employed or proposed in many commercial data transmission systems such as high-quality digital audio broadcasting (DAB) and terrestrial HDTV broadcasting. These applications require transmission of very high data rates and OFDM system are capable of providing frequency diversity without resorting to complex equalizers. To improve coverage and efficiency of the system some terrestrial broadcasting systems employ a network of single frequency transmitters all transmitting the same program synchronized in time and frequency. Although these single frequency networks (SFN) usually provide diversity in some cases frequency diversity is not available when the path differences between the stations are very small. We address this situation and introduce a very simple transmit diversity technique. This diversity technique does not introduce any changes at the receiver. We provide analytical and simulation results to demonstrate the significant performance advantages that can be obtained using this transmit diversity technique.