極化碼(Polar codes)與低密度奇偶檢查碼(LDPC codes)在近幾年已經被選為未來5G通訊標準中，增強型行動寬頻(Enhance mobile broadband；eMBB)應用情境的控制通道(Control channel)與數據通道(Data channel)的編碼方式。極化碼被理論證明可以達到通道容量(Channel capacity)；低密度奇偶檢查碼則是在實作上證明可以非常趨近通道容量。然而，對於超高可靠及低延遲通訊(Ultra-reliable and low latency communications；URLLC)應用情境，碼長越長會造成更高的延遲，所以通道編碼(Channel coding)必須應用在短碼長，因此本論文實際模擬當碼長為308時，這兩種編碼方式之間性能的差異，並探討低密度奇偶檢查碼的解碼方式。利用找出的停止集(Stopping set)與增強型置信度傳播演算法(Reinforced belief propagation)，我們提出了新的解碼方法，時間複雜度與置信度傳播(Belief propagation)演算法相近，我們的模擬結果顯示，使用5G通訊標準的eMBB應用場景時，新的演算法與傳統的置信度傳播演算法的解碼效能相比，有更佳的結果。

Most recently, polar codes and low-density parity check (LDPC) codes have been adopted as the channel coding schemes for the enhanced mobile broadband (eMBB) control and data channels of 5G new radio (NR), respectively. Polar codes and LDPC codes are capacity-achieving and capacity-approaching codes for very large block lengths. However, for ultra-reliable low-latency communications (URLLC), channel coding with short block lengths is a significant issue due to a high latency at long block lengths. For this purpose, we compare these two 5G standard coding schemes with the block length of 308, and then explore a better LDPC decoding algorithm in order to improve the performance degradation caused by short cycles. Based on stopping sets and (BP) algorithm, we develop a simple algorithm to improve the standard belief propagation algorithm. Simulation results show that the proposed stopping sets based reinforced belief propagation (SS-RBP) decoder performs better than conventional BP decoder.

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