隨著物聯網(Internet Of Things, IoT)概念的興起，越來越多相關的標準與技術都逐一被提出與討論。而在這當中，如何妥善運用既有的Long Term Evolution (LTE)網路架構與硬體去建構IoT也成為一個很重要的議題。但是，LTE跟LTE-Advanced (LTE-A)都已被證實無法有效的應用在IoT的情境上。因為對於IoT的設計來說，最優先考量的事情不再是良好的網路服務品質或是快速的資料交換速度。相反的，IoT的技術最重要的是著重在如何擴大訊號涵蓋範圍、降低整體複雜度、減少能源消耗等。此外，倘若繼續採用LTE或LTE-A，也無法有效處理大量連接的裝置。因此，窄頻物聯網 (NB-IoT)技術由3GPP在release 13中提出，用以在兼容既有LTE網路架構的前提上，建構可以迎合IoT特性的標準技術。而在窄頻物聯網的眾多討論子議題中，能夠讓基地台與UE進行同步，進而互相傳送資料的隨機接入 (Random Access)程序又是一個極為重要的關鍵議題。因此對於隨機接入程序的研究非常的多樣化，那對於眾多學術或商業研究來說，由於硬體限制、成本考量等因素，一個適當的網路模擬器便成為不可或缺的工具。我們的目標是基於release 13實現NB-IoT隨機程序的模擬模型。在本文中，除了提供LTE和NB-IoT隨機程序的概述，我們也基於網路模擬工具ns-3的LTE-EPC Network simulAtor (LENA)模組，設計並實現了NB-IoT隨機程序的模擬。此外，本文還提供了模擬結果的驗證和分析，如平均訪問延遲，中斷概率等。同時也通過模擬結果，驗證了模擬模型中的步驟和時域參數使用的正確性。

With the rise of the concept of Internet Of Things (IoT), more and more related technologies have been proposed and discussed. Among them, how to properly use the existing Long Term Evolution (LTE) network architecture to construct IoT has become an important issue. However, both LTE and LTE-Advanced (LTE-A) have been proven to be ineffective in the context of IoT. Because for IoT design, the top priority is no longer network service quality or data exchange speed. Conversely, the most important aspect of IoT technology is how to expand the coverage of the signal, reduce the overall complexity, and reduce energy consumption. Therefore, the narrowband Internet of Things (NB-IoT) technology was proposed by 3GPP in Release 13 to construct a standard technology that can meet the IoT characteristics on the premise of compatibility with existing LTE network architectures. Among the sub-topics of the NB-IoT, the Random Access(RA) procedure that allows the eNB to synchronize with the User Equipments (UEs) and transmit data to each other is an extremely important issue. Therefore, the research on RA procedures is very diverse. For many academic or commercial research, an appropriate network simulator becomes an indispensable tool due to hardware limitations and cost considerations. Our goal is to implement a simulation model of the NB-IoT RA procedure. In this paper, in addition to providing an overview of LTE and NB-IoT RA procedures, we also designed and implemented a simulation of the NB-IoT RA procedure based on the LTE-EPC Network simulAtor (LENA) module of the network simulation tool ns-3. In addition, the paper also provides verification and analysis of simulation results, such as average access latency and outage probability. At the same time, the correctness of the steps and time domain parameters in the simulation model is also verified by the simulation results.

摘要
Abstract
Contents
List of Figures
List of Tables
1 Introduction--------------------------------------1
2 Related Work--------------------------------------3
3 Random Access Procedure in LTE and NB-IoT---------6
3.1 LTE RA procedure--------------------------------6
3.2 NB-IoT RA procedure-----------------------------7
3.2.1 Preprocedure----------------------------------9
3.2.2 Message 1 (Preambles transmission)------------9
3.2.3 Message 2 (Random Access Response)-----------10
3.2.4 Message 3 (Request the Connection)-----------11
3.2.5 Message 4 (Contention Resolution)------------11
4 NS-3 LTE RA procedure----------------------------13
4.1 Preprocedure-----------------------------------13
4.2 Message 1 (Preambles transmission)-------------15
4.3 Message 2 (Random Access Response)-------------16
4.4 Message 3 (Request the Connection)-------------16
4.5 Message 4 (Contention Resolution)--------------18
5 NS-3 LTE MODULE ADJUSTMENTS----------------------19
5.1 Preprocedure-----------------------------------20
5.1.1 RSRP changes---------------------------------20
5.1.2 SIB2 reconfiguration-------------------------21
5.1.3 Thresholds definition and CE level judgment--27
5.2 Message 1 : Preambles transmission-------------29
5.3 Message 2 : Random Access Response-------------30
5.4 Message 3 : Request the Connection-------------32
5.5 Message 4 : Contention Resolution--------------32
6 VALIDATION---------------------------------------33
6.1 Experimental setup-----------------------------33
6.2 Simulation result------------------------------36
6.2.1 Average access delay evaluation--------------36
6.2.2 Outage probability evaluation----------------38
6.2.3 Simulation correctness evaluation------------41
7 CONCLUSIONS--------------------------------------44

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