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博碩士論文 etd-0605113-184955 詳細資訊
Title page for etd-0605113-184955
論文名稱
Title
雙向中繼傳輸系統中考慮量化通道資訊的束波賦形向量設計
Beamforming Design in Two-Way Relaying System with Quantized CSI
系所名稱
Department
畢業學年期
Year, semester
語文別
Language
學位類別
Degree
頁數
Number of pages
51
研究生
Author
指導教授
Advisor
召集委員
Convenor
口試委員
Advisory Committee
口試日期
Date of Exam
2013-06-28
繳交日期
Date of Submission
2013-07-08
關鍵字
Keywords
雙向中繼傳輸、分支界定法、回傳通道、量化通道資訊、合作式通訊
Feedback channel, Quantized channel state information, Two-way relaying, Cooperative communication, Branch-and-bound algorithm
統計
Statistics
本論文已被瀏覽 5716 次,被下載 516
The thesis/dissertation has been browsed 5716 times, has been downloaded 516 times.
中文摘要
近年來,無線通訊設備的出貨量成長快速,每人至少擁有一個以上的手持通訊設備,造成無線頻寬的需求量增加[13],因此無線頻寬顯得格外珍貴,然而各大電信業者擁有的頻帶有限,如何在有限的頻寬內服務更多的使用者,並使細胞邊緣(cell-edge)的使用者輸出效能變佳,這是值得深思的課題。在本論文中,我們提出雙向中繼傳輸系統(two-way relaying system)[12],利用此系統可解決上述問題,因其傳輸所耗時間短,且頻譜效益(spectral efficiency)比單向中繼傳輸(one-way)[14]系統高一倍。此外,我們採用放大後傳送(amplify-and-forward, AF)的中繼策略,藉由多個中繼站的協助,達成訊息交換。若是傳送端知道瞬時通道資訊(instantaneous channel state information, instantaneous CSI),就可選擇不同的合作式策略來提升系統效能,像束波賦形傳送(transmit beamforming)[11]、天線選擇性傳輸(antenna selection)[15]等。文獻[9][10][16][17]中,傳送節點皆需完美的通道資訊,換言之,兩個傳送節點間需要大量的資訊交換量,但在實際系統中,此假設會消耗龐大的系統成本(overhead)。因此,本論文將考慮量化的通道資訊(quantized CSI),即兩傳送節點將通道資訊量化後,藉由回傳通道(feedback channel)以有限位元的方式交換此資訊[2][6]-[8],得此資訊後,我們可以在各中繼端設計傳送機制。使得整體系統的總通道容量(sum-rate)最大化,由於此最佳化問題既不是凸函數(convex),也不為凹函數(concave),無法使用既有的最佳化工具求解[18],因此利用分支界定法(branch-and-bound algorithm)[4]來幫助我們得到最佳的預編碼向量,我們將分析在完美通道資訊以及量化通道資訊下的總通道容量表現。然而,在量化通道資訊時,我們將通道資訊拆解為通道質量資訊(channel quality information, CQI)及通道方向資訊(channel direction information, CDI)兩部分,並分別量化,前者表示通道的強度,後者表示通道的方向。利用量化誤差的模型分析總通道容量,並採取分支界定法。
關鍵字 : 合作式通訊、雙向中繼傳輸、分支界定法、量化通道資訊、回傳通道。
Abstract
In recent years, the productivity for mobile devices has astonishing increase, and almost everyone has one hand-held device, which results in large demand of wireless bandwidth. However, spectrum resource is scarce and expensive. Thus, how to increase the number of served users and per-user throughput becomes an important issue, especially for those users located at cell-edge. In this thesis, we propose two-way relaying scheme[12] to deal with aforementioned challenges because two-way relaying systems require half transmission-time compared with one-way relaying systems[14]. Besides, we adopt amplify-and-forward relaying protocol to assist message exchange between two nodes. Under the assumption that instantaneous CSI is known globally, we can employ various cooperative strategies to exploit spatial diversity such as transmit beamforming[11], antenna selection[15]. Most existing works on two-way relaying scheme adopt assumption of perfect CSI[9][10][16][17]. Nevertheless, it demands great amount of information exchange between nodes, which leads to huge system overhead. To be more practical, we consider that channel information is first quantized and exchanged with limited bits through feedback channel[2][6]-[8]. Based on the quantized CSI, we design precoder of relays to maximize sum-rate of two source users. However, this optimization problem is neither convex nor concave, and it can’t be solved by existing CVX tool[18]. Therefore, we adopt branch-and-bound algorithm to approach optimal precoder iteratively. More specifically, channel information can be decomposed into channel quality information(CQI) and channel direction information(CDI), where the former represents the magnitude of channel vector, and the latter indicates the direction of channel vector, and both are quantized accordingly. We will explore statistical properties of quantization error to take expectation on the sum-rate, and adopt branch-and-bound algorithm to perform precoder optimization. Finally, we will demonstrate system performance through computer simulations.

Index Terms-Cooperative communication, Two-way relaying, Branch-and-bound algorithm, Quantized channel state information, Feedback channel.
目次 Table of Contents
論文審定書…………………………………………………………………………...i
誌謝…………………………………………………………………………………...ii
摘要……………………………………………………………………………….... .iii
Abstract……………………………………………………………………………... iv
目錄…………………………………………………………………………………. vi
圖索引…………………………………………………………………………........ vii
表索引……………………………………………………………………………... viii
第一章 簡介………………………………………………………………………. .01
第二章 相關背景………………………………………………………………….. 05
2.1 合作式束波賦形設計………………………………………………………. 05
2.2 使最差訊雜比最大化的束波賦形設計……………………………………. 07
2.3 雙向中繼傳輸系統結合有限位元回傳技術………………………………. 10
第三章 系統模型………………………………………………………………….. 13
第四章 量化通道資訊下的束波賦形向量設計………………………………….. 17
4.1 完美通道資訊下的束波賦形向量設計……………………………………. 17
4.2 通道資訊的量化及量化誤差分析…………………………………………. 22
4.2.1 通道方向資訊量化的有限位元回傳模型…………………………….. 23
4.2.2 量化誤差分析及模型………………………………………………….. 24
4.2.3 通道質量資訊量化的有限位元回傳模型…………………………….. 26
4.3 總通道容量…………………………………………………………………. 28
第五章 模擬結果與討論………………………………………………………….. 32
第六章 結論……………………………………………………………………….. 36
參考文獻…………………………………………………………………………… 37
附錄………………………………………………………………………………… 40
參考文獻 References
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