Transmitters Separation for Single Frequency Networks

In a Single Frequency Network (SFN), the signals coming from nearby transmitters are mixed. Since the interfering signals can be seen as (very) long term echoes, an effective method to combat echoes, such as OFDM, is a natural candidate for SFN. However, although OFDM is a very efficient method, the very long delays that characterise SFN echoes require extremely long packets in OFDM transmissions and high stability of the subcarriers frequencies. An alternative approach based on array processing is proposed. The signals received by the sensors are filtered and downconverted. Then, source separation is performed using transmitters localisation and multiplication by the pseudo-inverse of the estimated mixture matrix. Symbol Timing and Carrier Recovery is then performed on each separated component. Furthermore, in order to increase the SNR, these components can be globally synchronised (using a correlator) and summed. Experimental results are finally presented and show good performances of the approach in a realistic configuration.