Demapping Algorithm for Rotated Constellation and Its Improvement Based on DVB-T2

Constellation rotation as a diversity technology of new concept in the field of broadcast and communication is used in DVB-T2 standard. The two-dimension iterative LLR solution for rotated QAM constellation based on hard decision simplified calculation,but due to the hard decision to bring the error propagation,and the judgment for the first time operation is more complex. Two improved schemes are presented in this paper,respectively improing from the aspects of BER performance and computation complexity. The simulation results show that under bad channel conditions,improving methods on the performance is better than that of the original system.