目前 3GPP 標準組織正規畫與制定 5G 通訊標準以滿足及支援多種應用及服務。其中 URLLC 為 5G 三大應用領域之一，擁有高可靠度與低延遲之特性，其要求達到之門檻為長度為 32 位元組之封包必須於 1毫秒內傳送成功，且傳輸成功率必須達到 99.999%。因此，為保證隨時可收送 URLLC 資料以滿足所制定之規範，頻譜資源之配置與傳輸方法之設計將會是研究之重點，尤其是上行傳輸策略。 隨著 Release-15 規格制定結束，URLLC 相關技術與討論已越來越多，其中 semi-persistent scheduling （SPS） 以週期性配置專屬資源（dedicated resource）搭配重傳之機制被視為可行之上行傳輸方案之一，但此策略仍具有可改進空間。目前討論之主要重傳技術可區分為回饋式重傳機制（feedback-based retransmission）和盲目重送機制（blind repetition），前者是利用初次傳送之 NACK 回報進行重傳，後者是伴隨初次傳送時進行重傳以縮短延遲。本論文嘗試分析各種技術並進行技術融合，目標為找出符合 URLLC 嚴格之可靠度與延遲標準，同時達成頻譜使用率最大化之上行傳輸方法。本計劃將分析 SPS 搭配重傳機制的多種可能組合，並以數學分析驗證其可行性並尋求最佳組合。經初步分析後，本論文提出同步上行傳輸之概念；換言之，UE（User Equipment）將於不同的頻域資源上同時進行初次傳送與重傳，以節省重傳所需之延遲並提高資料可靠度。為了提高頻譜使用率，針對重傳機制之共享資源（shared resource）資源配置需一併考量，然而其潛在碰撞發生之問題可藉由支援Successive Interference Cancellation（SIC） 接收器消除部分碰撞情況。另外，本論文將更進一步設計與分析如何將初始傳輸於 shared resource 並搭配重傳機制之策略，以節省更多資源並達到高可靠度與低延遲之目標。 ;New radio technologies for the fifth generation (5G) wireless system are currently standardized by the Third Generation Partnership Project (3GPP) to support diverse services and applications. Ultra-reliable low latency communications (URLLC) is one of the major service categories of 5G. The strict requirement of URLLC characterized by its low latency and high reliability is that the transmission latency of a 32-byte packet must be less than 1ms with a success probability of 99.999%. Therefore, in order to ensure that URLLC data can be sent and received at any time, the design of the spectrum resource configuration and transmission/retransmission method will be the main focus of this research. Since specification of Release-15 has been ratified, semi-persistent scheduling (SPS) with retransmission is considered as a promising solution for uplink transmission to achieve requirement of URLLC. The considered retransmission techniques include feedback-based retransmission and blind repetition. The former relies on the feedback of the first transmission to trigger retransmission and the latter proactively transmits one or more duplicated transmissions with the first transmission without feedback. However, there are still many issues opened to be discussed and improved. In this thesis, we aim to analyze and integrate all existing strategies, and then figure out an appropriate uplink transmission scheme that not only maximizes spectrum utilization but also copes with stringent requirement of URLLC. At first, we will analyze various possible combinations of SPS with multiple retransmission strategies to verify their feasibilities and then find out the most appropriate combination strategy. Based on analytical results, we will introduce a novel concept, called parallel transmission, in which the user equipment will perform the initial transmission and retransmission on different resources in frequency band at the same time to save the time required for feedback-based retransmission for improving data reliability. In order to improve spectrum utilization, the resource configuration of the shared resource will be considered in this thesis. The potential collision problem in strategies using shared resource will be discussed and partially solved by applying the successive interference cancellation (SIC) receiver. Besides, we will further design and analyze the possible combinations of arranging the initial transmission on shared resources with different retransmission techniques in order to further save resources, achieve high reliability and low latency at the same time.
