在目前的機器型態通訊(Machine Type Communication, MTC)網路中，一個機器(machine)不知道基地台什麼時候會有資料傳送給它，因此此機器必須持續開著資料接收的天線，當此機器沒有資料需要接收時，會造成不必要的耗電。因為目前4G LTE (Long Term Evolution)所使用的非連續接收(Discontinuous Reception, DRX)省電機制沒有考慮機器在資料接收的頻率差異，因此本論文修改DRX，提出一個遞迴睡眠週期與主動叫醒(Recursive Sleeping-cycles and active Wake-up, RSW)機制，RSW會讓資料接收的頻率相差很大的機器更有效地從基地台接收資料以降低能量消耗，並降低封包遺失率。在遞迴睡眠週期機制中，我們為長睡狀態設計一個長睡門檻值，當一個機器處於長睡狀態的次數到達長睡門檻值時，長睡狀態的時間會呈指數增加，讓此機器有更長的睡眠時間，以節省它的能量消耗。在主動叫醒機制中，我們為機器在基地台的buffer設計一個門檻值，當一個機器在基地台累積的資料封包數量到達此門檻值時，基地台會主動叫醒此機器來接收資料，以降低它的封包遺失率。最後，我們修改NS-3的LTE模組來做RSW與DRX的模擬，在模擬中，我們為兩種機器設計不同資料接收頻率的流量產生器，我們改變一個機器處於短睡狀態的短睡門檻值、長睡狀態的長睡門檻值與基地台buffer的門檻值來分析比較RSW與DRX的能量消耗與封包遺失率的差異。

In a Machine-Type Communication (MTC) network, since a machine has no way to know whether or not the base station has buffered data to deliver, it must continuously power on its receiving antenna. Thus, too much unnecessary energy may be consumed, if a machine in fact doesn’t have buffered data to receive. Therefore, in LTE standard, the Discontinuous Reception (DRX) mechanism for power saving is proposed to remedy the above-mentioned problem. However, DRX does not take into account the characteristics that different types of machine have different frequencies in receiving data. This thesis therefore modifies the DRX and proposes an innovative power-saving mechanism, referred to as Recursive Sleeping-cycles and active Wake-up (RSW). RSW differentiates machine types by its data-receiving frequencies and then attempts to enlarge the sleeping cycles, which can effectively reduce both power consumption and packet loss ratio. In the recursive sleeping-cycles scheme, we design a threshold for a machine to stay in the long-sleep state. When the threshold is reached, the long-sleep cycle will be increased exponentially. In the active wake-up scheme, we design a buffer threshold in the base station for each machine. When data packets accumulated in the buffer reaches the threshold, the base station will actively wake up the machine to receive the buffered data. Finally, we modified the NS-3 (Network Simulator-3) LTE modules to simulate the RSW and the DRX. Two traffic generators are designed respectively for two types of machine with high and low frequencies in receiving data. In the simulation, we vary three thresholds, respectively for short-sleep state, long-sleep state, and the buffer in base station to analyze and compare energy consumption and packet loss ratio between RSW and DRX.

論文審定書 i
致謝 ii
摘要 iii
Abstract iv
目錄 v
圖表目錄 viii
第一章 緒論 1
1.1 研究動機 1
1.2 研究方法 2
1.3 章節介紹 3
第二章 MTC使用LTE DRX的省電機制 4
2.1 MTC的網路架構 4
2.2 LTE的OFDMA Frame 6
2.3 DRX運作機制 12
2.3.1 DRX的三種狀態 12
2.3.2 DRX的運作方式 13
2.4 功率與能量計算 15
2.5 相關研究 16
2.6 本論文與相關論文的比較 17
第三章 遞迴睡眠週期與主動叫醒機制 20
3.1 RSW的狀態轉換 20
3.2 遞迴睡眠週期機制 21
3.2.1 Machines狀態間的轉換 22
3.2.2 Machines停留在三個狀態的次數 23
3.2.3 指數增加OD的間隔時間 25
3.3 遞迴睡眠週期的運作流程 26
3.3.1 在遞迴睡眠週期中eNodeB運作流程 26
3.3.1.1 PDCCH所能容納的DCI 27
3.3.2 Machine的運作流程 30
3.4 主動叫醒機制 31
3.4.1 主動叫醒machines的判斷條件 32
3.4.2 在主動叫醒中eNodeB的運作流程 33
3.5 能量消耗的計算 34
3.5.1 遞迴睡眠週期機制的能量消耗 34
3.5.2主動叫醒機制的能量消耗 35
第四章 模擬與結果討論 36
4.1 NS-3模擬拓樸 37
4.2 修改與新增的NS-3模組 38
4.2.1 Traffic Generator與eNodeB傳送 39
4.2.1.1 Traffic Generator 40
4.2.1.2 eNodeB傳送 42
4.2.2 DRX運作 43
4.2.3 RSW 的核心 47
4.2.3.1 遞迴睡眠週期機制 47
4.2.3.2 主動叫醒機制 51
4.3 模擬參數的設定 54
4.4 模擬結果與討論 55
4.4.1 遞迴睡眠週期機制的模擬結果 55
4.4.2 主動叫醒機制的模擬結果 60
4.4.3 增加machine在eNodeB的Buffer Size 66
第五章 結論與未來工作 69
5.1 結論 69
5.2 未來工作 70
References 71
Acronyms 76
Index 78

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