Improved successive cancellation decoding of polar codes

In this thesis, we propose improved successive cancellation polar code decoding algorithms. Polar codes are fragile to error propagation. Considering this issue, in our first proposal, we consider 𝐿𝑅=1, for which decision is made for the favor of bit 0 in classical successive cancellation algorithm, and propose multi-SC decoders, where we consider more than one decoders working in parallel and these decoders make opposite decisions for 𝐿𝑅=1. The proposed technique provides a flexible configuration and leads to the pruning of unnecessary path searching operations, which provide low complexity compared to successive cancelation list decoding algorithm. Multi-Parallel SC decoding shows a significant performance improvement compared with the original SC decoding and its performance is comparable to that of the successive cancellation list decoding algorithm. In our next proposal, we propose a method for the iterative decoding of polar codes replacing the unreliable received samples with randomly generated samples. In this method, first, a straight decoding operation is performed for the received frame and CRC check is performed, and if it is not satisfied, the received symbols are passed through virtual random channels before they are sent to the polar decoders employing successive cancellation decoding algorithm. When the received symbols are passed through virtual random channels, randomly generated noise is added to the inputs of the VRCs falling into a threshold interval, which contains unreliable information about the transmitted polar code-bit before they are sent to the polar decoder. For the decoded sequence, if the CRC check is not satisfied, a different randomly generated noise sequence is added to the unreliable inputs and the decoding operation is repeated. This procedure is repeated until a predefined maximum iteration number as long as CRC is not satisfied.