Decoding Polar Codes via Weighted-Window Soft Cancellation for Slowly-Varying Channel
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Polar codes are a class of structured channel codes proposed by Arıkan based on the principle of channel polarization, and can achieve the symmetric capacity of any Binary-input Discrete Memoryless Channel (B-DMC). The Soft CANcellation (SCAN) is a low-complexity iterative decoding algorithm of polar codes outperforming the widely-used Successive Cancellation (SC). Currently, in most cases, it is assumed that channel state is perfectly known at the decoder and remains constant during each codeword, which, however, is usually unrealistic. To decode polar codes for slowly-varying channel with unknown state, on the basis of SCAN, we propose the Weighted-Window SCAN (W^2SCAN). Initially, the decoder is seeded with a coarse estimate of channel state. Then after each SCAN iteration, the decoder progressively refines the estimate of channel state with the quadratic programming. The experimental results prove the significant superiority of W^2SCAN to SCAN and SC.
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