Efficient soft demodulation scheme for digital video broadcasting via satellite - Second generation system

In this study, the authors propose a compact soft demodulation method for M-ary modulation schemes defined in the Digital Video Broadcasting via Satellite - Second Generation (DVB-S2) system. They first derive a conventional soft demodulation method for quadrature phase shift keying and 8-ary phase shift keying with a linear order of complexity, and apply this to the modulation schemes defined in DVB-S2. In particular, they propose a new constellation for 32-ary amplitude and phase shift keying (32-APSK), which provides better performance, regardless of the soft demodulation scheme. In addition, the proposed constellation enables us to apply a very simple and efficient soft demodulation method. The proposed soft demodulation method estimates the soft information by simple distance calculation, and greatly reduces the computational complexity, compared with maximum-log-likelihood detection. They demonstrate the bit error rate (BER) performance of various soft demodulation methods, combined with the low density parity check codes specified in DVB-S2. The BER simulation results reveal that the proposed constellation for 32-APSK can achieve better performance than the conventional one, regardless of the soft demodulation method. In addition, the proposed soft demodulation method can highly reduce the computational complexity, with reasonable performance degradation.