A low-complexity soft-output decoder for polar codes

A widely used soft-output decoder for polar codes is a message-passing algorithm based on belief propagation, which performs well at the cost of high processing and storage requirements. In this paper we propose a low-complexity alternative for soft-output decoding of polar codes that offers comparable performance but with significantly reduced processing and storage requirements. In particular we show that the complexity of the proposed decoder is about 5% of the total complexity of the belief propagation decoder for the dicode channel, while achieving comparable error-rate performance. Furthermore, we show that the proposed decoder requires about 39% of the memory required by the belief propagation decoder for a block length of 32768.