An advanced algorithm for improving DVB-T coverage in SFN

The paper analyses the coverage achievable in single frequency networks (SFN) by the European system for digital video broadcasting on terrestrial channels (DVB-T), using two different receiver structures: the conventional coherent demodulation method using the pilot tones inserted in the OFDM (orthogonal frequency division multiplexing) spectrum and the new scheme proposed by RAI, based on coded decision directed demodulation (CD3-OFDM) combined with a new lock-in algorithm. The first structure is characterised by a rapid performance degradation for echoes outside the guard interval, while the second shows a more gradual degradation, like the DAB (digital audio broadcasting) system. The performance evaluation based on theoretical analysis, software simulations and hardware laboratory tests, shows the significant coverage improvement offered by the gradual degradation CD3-OFDM algorithm, especially in the cases of omni-directional antennas, medium to high bit-rates and transmitter distances exceeding 40 km.