物聯網正在改變整個社會，它代表著網際網路的下一個發展，將顯著提高收集和分析數據的能力以及遠程控制設備的能力。隨著提供給個人和行業應用的擴展，連接設備也正在不斷增長。為了滿足物聯網市場的需求，已經開發了許多低功耗廣域(low-power wide-area, LPWA)技術，例如:窄頻物聯網 (Narrowband Internet of Things, NB-IoT)與長期演進技術 (Long Term Evolution-M, LTE-M)。
窄頻物聯網是一種新興的蜂巢式行動技術，它將為大量低吞吐量低成本設備提供更好的覆蓋範圍，並且在應用中具有較低的設備功耗。在第三代合作夥伴計劃的窄頻物聯網規範中，一種新型窄頻物理隨機存取通道訂定為單音跳頻前導碼。當多個用戶經其上行鏈路嘗試同時連接基地台時，基地台將接收疊加窄頻物理隨機存取通道的前導碼，並且必須偵測所有用戶，並獲取各別的同步參數。
本論文主要在研究偵測數個疊加窄頻物理隨機存取通道的前導碼，解決因載波偏移造成偵測上的錯誤，並提出一種接收器的設計，最後比較套用接收器狀況下對於偵測錯誤的改善。模擬結果表明，接收器確實對於偵測錯誤有著顯著的改善，並且也討論了不同狀況下對於接收器的變化與相對應的原因。

The Internet of Things (IoT) is changing the entire society. It represents the next development of the Internet and will significantly improve the ability of collecting and analyzing, as well as the ability to control devices remotely. With the expansion of personal and industrial applications, the number of connected devices is also growing. In order to meet the needs of the IoT market, many low-power wide-area (LPWA) technologies have been developed, e.g., Narrowband-IoT (NB-IoT) and Long-Term Evolution-M (LTE-M).
Narrowband Internet-of-Things (NB-IoT) is an emerging cellular technology, which provides better coverage for a massive number of low-throughput, low-cost devices and has lower device power consumption in delay-tolerant applications. In the third-generation partnership project (3GPP), narrowband Internet-of-Things specifications, a new narrowband physical random-access channel (NPRACH) has been specified as a single-tone frequency-hopping preamble. When multiple uplink users attempt to attach at the same time, the base station will receive superimposed NPRACH preambles. It must detect all users and must obtain their synchronization parameters.
This paper mainly studies the detection of superimposed NB-IoT NPRACH preambles, to solve the detection error caused by carrier frequency offset, and proposes a receiver design. Finally, the improvement of detection error is compared under the condition of applying receiver. The simulation results show that the receiver can greatly improve the detection error, and the corresponding reasons for the change of the receiver under different conditions are also discussed.

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