Simplified LLR calculation for DVB-S2 LDPC decoder

The computation of the Log-Likelihood Ratio (LLR) at the channel output may impose great demand of memory and hardware area, especially for high-order modulations. This paper introduces a new approach for the approximation of the LLR in AWGN channels based on the splitting of the original constellation into smaller sectors. Each new sector has a less complex configuration in which it is possible to take into account only two symbols besides the received one. The proposed solution is applied for the 8-PSK and 16-APSK constellations adopted in the Digital Video for Satellite Second Generation standard (DVBS2).