A new cascade decoder for precoded OFDM with analog linear block codes

Space-time codes and OFDM represent a key technology for future broadband wireless communication systems. In this paper a class of space-time block codes according to Marc Kuhn (2002) in combination with OFDM, is used which can lead to intersymbol interference (ISI) due to an optimized diversity performance. Therefore ISI compensation is an important task of the decoding process of these codes. Several known ISI compensation methods can he applied for example MMSE equalization or parallel or serial ISI cancellation. In this publication a new scalable decoder that works according to the parallel ISI cancellation method is presented. This decoder bases on a cascade structure with two branches for each cascade stage. The sub decoders in each branch were calculated coupledly according to the MMSE criterion. The inputs of the cascade are the receiver symbols and an estimation of the transmitter symbols realized with a MMSK estimator. The prioritization of the branches is made through the a priori symbol error probability. This probability bases on the transmitter symbols estimation. By varying the number of the cascade stages or the block length the performance of the decoder can be scaled.