臺灣博碩士論文加值系統

LTE與Wi-Fi整合技術(LTE-WLAN Aggregation, LWA)在數據聚合協定(Packet Data Convergence Protocol, PDCP)中將資料進行分流與重組，本論文在開放原始碼的OpenAirInterface (OAI)平台上實作LWA的雙介面(Dual-Mode)傳送機制(LWA-DM)，並且在UE端採用srsUE軟體實作PDCP層的封包重組。在OAI平台的eNB上，我們實作兩種雙介面傳送的技術，並且使用影音串流的資料來傳輸，其中第一種是以串流為基礎，我們是將整條串流經由LTE介面或Wi-Fi介面傳送，第二種是以支流為基礎，我們是將一條串流分成LTE及Wi-Fi兩條支流，並且將兩條支流分別經由LTE及Wi-Fi介面傳送，這兩種技術我們都會解讀封包的目的地IP住址來判斷串流的不同，若要將eNB上的資料流經由Wi-Fi介面傳送給UE，我們會在PDCP層建立UDP Tunnel。為了同時接收從LTE與Wi-Fi介面傳送的資料流，我們必須在UE端多加入一個執行緒來處理經由Wi-Fi介面傳送的封包，接著為了要在PDCP層進行封包序列的重組，我們使用兩個Buffer來分別緩衝LTE介面與Wi-Fi介面的封包。在實作完成後，我們比較有無使用LWA-DM機制在eNB及UE的單位時間吞吐量以及eNB的負載變化與封包處理延遲時間的變化。

LTE-WLAN Aggregation (LWA) splits a stream or streams in the Packet Data Convergence Protocol (PDCP) layer. In this thesis, LTE-WLAN Aggregation Dual-Mode (LWA-DM) is implemented on an open-source platform - OpenAirInterface (OAI), and srsUE software is used in UE to reassemble packets in the PDCP layer. In the eNB of OAI platform, we implement two kinds of dual-mode stream transmission technologies and use video streaming to transmit. The first one is for a number of single streams, an entire stream is transmitted via LTE interface or via Wi-Fi interface. The second one is for a single stream, we split a single stream into two substreams, one substream over LTE and another substream over Wi-Fi interface. In these two technologies, PDCP layer interprets packet’s destination IP address to differentiate different streams. To transmit a stream from eNB to UE via the Wi-Fi interface, in PDCP layer, an UDP tunnel is built. In order to receive a stream from LTE and Wi-Fi interfaces at the same time, we must add a process thread at UE to receive packets over the Wi-Fi interface. In order to reassemble packets at the PDCP layer, we use two buffers to temporily store packets which came from the LTE interface and the Wi-Fi interface, respectively. After the implementation, we compare the throughput of eNB and UE, the load of eNB, and the average packet processing delay with and without LWA-DM.

致謝 i
摘要 ii
Abstract iii
目錄 iv
圖表目錄 vii
第一章　導論 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　LWA與OAI平台 4
2.1 3GPP-LTE 4
2.1.1 GTP IP、GTP UDP與GTP-U 5
2.1.2 PDCP與RLC 6
2.2 LWA的網路架構 8
2.3 OAI實作平台 10
2.4 相關研究 10
2.5 本論文的機制 12
第三章　LWA的雙介面傳送機制 14
3.1 LWA-DM的系統架構 14
3.1.1 eNB完成雙介面傳送的模組 16
3.1.2 UE完成雙介面傳送的模組 17
3.2 eNB的雙介面傳送 18
3.2.1 以串流為基礎的雙介面傳送 19
3.2.2 以支流為基礎的雙介面傳送 21
3.3 UDP Tunnel 23
3.3.1 建立UDP Tunnel 25
3.3.2 使用NAT做IP住址轉換 26
3.3.3 解除UDP Tunnel 26
3.4 UE的封包重組 27
3.4.1 以PDCP序列號碼重組封包 27
3.4.2 逾時封包的判斷 31
第四章　OAI平台的實作與分析 35
4.1 實驗環境與設備規格 35
4.2 OAI平台上的實作 37
4.2.1 雙介面傳送模組的程式實作 38
4.2.2 建立UDP Tunnel模組的程式實作 43
4.2.3 解除UDP Tunnel模組的程式實作 46
4.2.4 封包重組模組的程式實作 48
4.3 實作結果與分析 54
4.3.1 參數設定與實作環境 55
4.3.2 結果分析 58
第五章　結論與未來工作 73
5.1 結論 73
5.2 未來工作 74
Reference 76
Acronyms 81
Index 83

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