An efficient soft decision demapping for multi-carrier systems

Multi-carrier systems employ various modulation modes to support a variety of services with scalable Quality of Service (QoS) requirements. However, the implementation cost of traditional soft demapping methods is relatively high in multi-mode modulation systems. By introducing partial hard decision, an efficient soft decision demapping method is derived based on bit confidence metric in this paper. Then a hardware structure with two-stage metric generation is developed to realize the algorithm, which is applicable for arbitrary Gray-coded modulation demapping. The performance of bit error rate (BER) is examined in the design of the digital terrestrial television multimedia broadcasting (DTMB) receiver. It is shown by simulations that the performance penalty of the proposed method, induced by introducing partial hard decision, is negligible with reduced complexity compared with those of traditional methods.