5G的時代即將來臨，這也意味著數位傳輸的重要性，尤其又以低延遲性與高可靠度為討論的重點，高可靠度的實現可藉由錯誤更正碼與重傳機制來達成，然而取而代之的是傳輸延遲也因此而增加，藉此提前回饋機制的應用可有效地降低延遲。
封包實際解碼需要時間，而提前回饋的關鍵就在於未經過解碼先進行是否需要重傳的預測判斷，達到節省解碼時間的效果。因此我們使用預測與實際解碼的比較來進行分析，判別出的各種預測狀況再個別分析使用的能量與延遲。
提前回饋的應用起先用於turbo codes與LDPC codes這類需要重複迭代的錯誤更正碼，本論文著重在5G的Polar Code中，並且搭配HARQ的CC軟結合方式，來增加對抗雜訊的能力，使重傳次數降低且也簡化了複雜的延遲分析。
然而使用提前回饋的代價就是整體傳輸的能量會增加，且初始設定的預測門檻值如果選擇不良，根據分析不但會耗費更多的能量，延遲也會發生不減反增的反效果，因此必須依照訊雜比設定適合的預測門檻值。

The era of 5G is coming, which also means the importance of digital transmission, with emphasis on low latency and high reliability. The realization of high reliability can be achieved by error correction codes and retransmission mechanisms. However, at the same time, the transmission delay is increased. The application of the early feedback mechanism can effectively reduce the delay.

The actual decoding of the packet takes time, and the key to early feedback is to make a prediction judgment on whether retransmission is needed before the decoding is actually completed. Therefore, we use the comparison between prediction and actual decoding, and the various predicted conditions identified can be individually analyzed for the energy and delay used.

The application of early feedback was first used for error correction codes such as turbo codes and LDPC codes that require repeated iterations. This paper focuses on the 5G Polar Code and uses HARQ’s CC soft combination method to increase the ability to combat noise and make the number of retransmissions is reduced and complex delay analysis is also simplified.

However, the cost of using early feedback is that the overall transmitted energy will increase, and if the initial set prediction threshold is poorly selected, not only will it consume more energy according to the analysis, but the delay will also have the opposite effect of not decreasing and increasing. Therefore, we need to choose a suitable threshold.

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