Low Complexity Demapping of Rotated and Cyclic Q Delayed Constellations for DVB-T2

The new digital video broadcasting standard DVB-T2 includes the mandatory use of constellation rotation and cyclic Q delay (CRCQD) as a signal-space diversity technique. After transmission on the channel by orthogonal frequency division multiplexing (OFDM), at the receiver the constellation does not exhibit the regular shape of QAM and in particular optimum demapping must be jointly performed on the real-imaginary axis for both hard and soft decoding. We propose a low complexity demapping strategy for the CRCQD modulation. In the proposed approach, only a subset of the constellation points close to the received samples is considered for demapping. The proposed method is compared with existing techniques both in terms of complexity and performance over reference DVB-T2 channels.