Adaptive Successive Cancellation List Research Articles

Adaptive successive cancellation list decoding for Polar-coded Probabilistic amplitude shaping

Adaptive successive cancellation list decoding for Polar-coded Probabilistic amplitude shaping

Approaching the Normal Approximation of the Finite Blocklength Capacity within 0.025dB by Short Polar Codes

In this letter, we explore the performance limits of short polar codes and find that the maximum likelihood (ML) performance of a simple CRC-polar concatenated scheme can approach the normal approximation of the finite blocklength capacity. To explore the performance limits, CRC-polar concatenated codes are first optimized according to the minimum weight distribution. Then, CRC-aided hybrid decoding (CA-HD) algorithm with two steps is proposed to approach the ML performance. In the first step, the received sequence is decoded by the adaptive successive cancellation list (ADSCL) decoding. In the second step, the CRC bits of the survival paths in ADSCL are recalculated and CRC-aided sphere decoding with a reasonable initial radius calculated by the newly survival paths is used. The simulation results show that CRC-polar concatenated code with codeword length 128 and code rate 1/2 can achieve within about 0.025 dB of the normal approximation of the finite blocklength capacity at the block error rate 10−3.

Enhanced Adaptive Successive-Cancellation List Decoder

Adaptive successive cancellation list decoder (ASCLD) with upsizing scheme as a well-known approach can significantly reduce the average list size of SCL algorithm for polar codes with cyclic redundancy check (CRC). Since it needs to re-decode the whole received bits if no survival path verifies CRC, it dramatically increases the decoding latency. In this paper, a segmented ASCLD is proposed to reduce the decoding delay of ASCLD, which deals with the multi-CRCs concatenated polar codes. Unlike the normal ASCLD, once all the survived paths of one decoding partition cannot pass its corresponding CRC, a new decoding attempt is immediately initiated with larger list size. Moreover, based on analyzing the performance of the proposed system, a series of optimization strategies are used to improve the performance. Simulation results show that the proposed scheme can greatly reduce the delay of upsizing ASCLD without performance loss.

An Area-Efficient Hybrid Polar Decoder With Pipelined Architecture

As the first kind of capacity-achieving forward error correction (FEC) codes, polar codes have attracted much research interest recently. Compared with traditional FEC codes, polar codes show better error correction performance when successive cancellation list (SCL) decoding with cyclic redundancy check is adopted. However, its serial decoding nature and high complexity of list management lead to its low throughput. Though the adaptive SCL decoding and hybrid decoding can improve the throughput, it comes at cost of implementation area. In this paper, we propose a pipelined hybrid decoding procedure and the corresponding hardware architecture to improve the area efficiency. In our design, the idle decoding cores are employed for successive cancellation (SC) decoding when SCL decoding is not working. The SCL decoding will be activated when the SC decoding fails. Different decoding cores work according to their own operation sequences and share one common processing array to improve the utilization ratio of processing elements. Constant receiving interval is supported with the design of input buffer to store all received codewords. A software platform is established to optimize the design parameters for each module of decoder. Moreover, the corresponding architecture is implemented using 65nm technology. Experimental results show that the proposed decoder can achieve a similar error correction performance with the SCL decoding with list size 16. Compared to the state-of-the-art available hybrid decoder, our proposed pipelined hybrid decoder is $3.07\times $ more area efficient.

Improved Adaptive Successive Cancellation List Decoding of Polar Codes

Although the adaptive successive cancellation list (AD-SCL) algorithm and the segmented-CRC adaptive successive cancellation list (SCAD-SCL) algorithm based on the cyclic redundancy check (CRC) can greatly reduce the computational complexity of the successive cancellation list (SCL) algorithm, these two algorithms discard the previous decoding result and re-decode by increasing L, where L is the size of list. When CRC fails, these two algorithms waste useful information from the previous decoding. In this paper, a simplified adaptive successive cancellation list (SAD-SCL) is proposed. Before the re-decoding of updating value L each time, SAD-SCL uses the existing log likelihood ratio (LLR) information to locate the range of burst error bits, and then re-decoding starts at the incorrect bit with the smallest index in this range. Moreover, when the segmented information sequence cannot get the correct result of decoding, the SAD-SCL algorithm uses SC decoding to complete the decoding of the subsequent segmentation information sequence. Furthermore, its decoding performance is almost the same as that of the subsequent segmentation information sequence using the AD-SCL algorithm. The simulation results show that the SAD-SCL algorithm has lower computational complexity than AD-SCL and SCAD-SCL with negligible loss of performance.

An Adaptive Successive Cancellation List Decoder for Polar Codes with Cyclic Redundancy Check

In this letter, we propose an adaptive SC (Successive Cancellation)-List decoder for polar codes with CRC. This adaptive SC-List decoder iteratively increases the list size until at least one survival path can pass CRC. Simulation shows that the adaptive SC-List decoder provides significant complexity reduction. We also demonstrate that polar code (2048, 1024) with 24-bit CRC decoded by our proposed adaptive SC-List decoder with very large maximum list size can achieve a frame error rate FER ≤ 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> {-3} at E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</sub> /N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> = 1.1dB, which is about 0.25dB from the information theoretic limit at this block length.