Iterative per-Frame Gain and SNR Estimation for DVB-S2 receivers

In future 2nd-generation digital video broadcasting (DVB-S2) receivers working in ACM (Adaptive Coded Modulation) mode, an unknown residual gain must be estimated before the low-density parity-check (LDPC) decoding stage. Moreover, the signal-to-noise ratio (SNR) has to be estimated also, since the iterative decoding algorithms, such as those employed to decode LDPC codes, require its knowledge. Due to the presence of a time-varying phase, classical coherent algorithms for gain and SNR estimation cannot be carried out. We propose a novel gain and SNR estimator which works in conjunction with a recently proposed detection algorithm for channels with phase noise, known as CBC algorithm. In this way, implicit phase estimates by the CBC algorithm are employed to perform a partially coherent estimation of gain and SNR, which is iteratively refined.