Utilisation of LDPC Decoder Parameters in DVB-S2 ACM Procedures

The provision of broadband satellite services depends on the utilisation of efficient and reliable radio interface, which has the ability to adapt to variable propagation channel conditions. In order to use the available spectrum more efficiently and to maximise the link reliability this paper presents the analysis of possible utilisation of LDPC decoder parameters to improve the performance of the DVB-S2 standard adaptive coding and modulation (ACM) procedures. A switching algorithm is proposed for selecting between the adjacent transmission schemes that is assisted by the information on the number of iterations and the number of violated parity checks in previous frames obtained from the iterative LDPC decoder. The simulation results are given in terms of BER curves and the belonging LDPC decoder´s average number of iterations and average number of violated parity checks. These results, in particular the LDPC decoder´s probability density function of the number of required iterations, are further compared with results obtained with a SNR estimation algorithm proposed in the literature for the use in DVB-S2. The comparison confirms that the LDPC decoder information can be efficiently utilised in ACM procedures.