Approximate Successive Cancellation Decoder for Polar Codes

Abstract

Polar codes are the forward error correcting (FEC) codes renowned for achieving channel capacity for various codeword lengths. A low-complexity decoder, termed a Successive Cancellation (SC) decoder, is commonly employed to decode polar codes. However, the SC decoder’s sequential nature leads to a drawback in terms of decoding speed. This paper proposes an approximate successive cancellation decoder (ASCD), which incorporates approximate computing techniques that are equivalent alternatives to the exact computational units. The comparator, adder-subtractor block, is replaced by approximate units in the merged processing unit, and an approximate two-bit processing unit is designed at the last stage of the decoder to reduce the hardware complexity and delay with negligible performance degradation. The overall design of the proposed ASCD is implemented targeting the Xilinx Virtex-6 FPGA platform. With the proposed approximate counterparts, the ASCD achieves an average throughput improvement of 68 % compared to the former decoders. In addition, the usage of overall hardware resources is reduced by 41 %, reducing the processing complexity. The proposed decoder proves beneficial for error-resilient applications in 5G wireless communications.