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研究生:林昱蓮
研究生(外文):Lin, Yu-Lien
論文名稱:載波干涉編碼多載波碼域多工應用於各式上傳系統之研究
論文名稱(外文):Carrier-Interferometry Coded Multi-Carrier CDMA in Various Uplink Scenarios
指導教授:蘇育德蘇育德引用關係
指導教授(外文):Su, Yu-Te
口試委員:蘇育德蘇賜麟翁芳標林茂昭呂忠津
口試委員(外文):Su, Yu-TeSu, Si-LinWeng, Fang-BiaoLin, Mao-ZhaoLu, Zhong-Jin
口試日期:2018-07-31
學位類別:碩士
校院名稱:國立交通大學
系所名稱:電信工程研究所
學門:工程學門
學類:電資工程學類
論文種類:學術論文
論文出版年:2018
畢業學年度:107
語文別:英文
論文頁數:59
中文關鍵詞:載波干涉編碼多載波碼域多工軟性最小均方誤差功率分配軟性判決反饋
外文關鍵詞:carrier-interferometry sequencesmulti-carrier code division multiple accessoverloaded systemsoft minimum mean- square-errorpower allocationsoft-decision feedback
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本論文研究使用載波干涉編碼(Carrier-Interferometry Code)多載波碼域多工(Multi-Carrier Code Division Multiple Access)的傳收系統架構和性能分析。該系統可適用於上行傳輸及下行傳輸,惟本文只探討上行傳輸之情境。由於長度為N 之載波干涉碼可產生 2N 組載波干涉碼,載波干涉碼之間具有偽正交的互相關(Cross Correlation)特性,並且它對序列長度沒有限制,故非常適合用於過載(Overloaded)多使用者系統。也因此,我們設定系統過載率為200%,可允許K 個用戶同時傳輸,亦可讓單個用戶平行傳送K 個數據流,展頻後的符元載在N (N=K/2) 個正交子載波上。我們根據傳送端通道狀態信息(Channel State Information at the transmitter, CSI-T)之有無將系統分為常規系統及預編碼系統。常規系統中我們推導多種向度合併(diversity-combining)法則並進行性能分析。在本文研究的各種向度組合策略中,軟性最小均方誤差(soft-minimum mean square error)的方式雖有最佳性能卻有較高的計算複雜度。預編碼系統可利用CSI-T 對子載波
做適當的功率分配(Power allocation)來改善性能。CSI-T 亦可用來做資源分配(resource allocation),避免產生嚴重衰減而提升性能。我們發現,只要簡單的CSI 將子載波分成兩類即可獲致相當大的改善。傳送端的資源與功率分配加上接收端的遞迴式軟性最小均方誤差向度合併與干擾消除可提供相當優良的系統效能表現。
最後,我們考慮兩種通道估計法,比較兩者的均方誤差表現並推導了有考慮CSI 誤差的信號偵測架構。另外,我們也研究使用軟性判決反饋(soft-decision feedback)作為偽前導信號來增加通道估計精確度的效果,並提出一個停走(stop-and-go)準則作為是否反饋之依據,此方法能避免誤差傳播並得到更好的性能。
This thesis studies the architecture and performance of a multi-carrier code division multiple access (MC-CDMA) system using carrier-interferometry (CI) sequences. The
system is overloaded by allowing K users to transmit their own data streams, or, a single user to transmit K data streams over N < K orthogonal sub-carriers or time-frequency units. The overloaded rate is set to be 200% in our simulation. CI sequences are selected because of their outstanding cross-correlation property, and it does not impose a constraint on the sequence length. Our emphasis is on analyzing the performance of different multi-user detectors with different power allocation schemes in such an overloaded system. Also, resource allocation is suggested to improve the performance. Among those
diversity combining strategies introduced in this thesis, the soft minimum-mean-square error MUD is the best tradeoff between performance and computational complexity.
In the second stage of this thesis, the receiver takes the pilot-assisted channel estimation structure and imperfect channel state information (CSI) into account. We also
investigate the effect of using soft decision feedback as pseudo-pilots for enhancing channel estimation accuracy. Numerical results are provided to quantify the improvements brought about by CSI awareness and decision feedback aided channel estimation.
Chinese Abstract i
English Abstract iii
Acknowledgements iv
Contents v
List of Tables viii
List of Figures ix
1 Introduction 1
1.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Contributions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.3 Organization of Thesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2 Basic Transceiver of Overloaded MC-CDMA System 6
2.1 Transmitter Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.2 Properties of CI Sequences . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.3 Receiver Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.3.1 General Diversity Combining . . . . . . . . . . . . . . . . . . . . 9
2.3.2 Iterative Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.4 Numerical Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.4.1 AWGN Case . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3 MUD Structures and Receiver Performance 15
3.1 Basic Receiver Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.1.1 Maximum Ratio Combining MUD (MRC) . . . . . . . . . . . . . 18
3.1.2 Zero-Forcing MUD (ZF) . . . . . . . . . . . . . . . . . . . . . . . 18
3.1.3 Linear Minimum Mean Square Error - Interference Rejection Combining
MUD (LMMSE-IRC) . . . . . . . . . . . . . . . . . . . . . 19
3.1.4 Soft - Minimum Mean Square Error MUD - Interference Rejection
Combining (Soft-MMSE-IRC) . . . . . . . . . . . . . . . . . . . . 20
3.2 Resource Allocation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
3.3 Power Allocation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
3.3.1 (Power) Constrained Block Water-Filling (CBWF) . . . . . . . . 23
3.3.2 Pre-equalized (PE) . . . . . . . . . . . . . . . . . . . . . . . . . . 25
3.3.3 Pre-equalized with Per-carrier Power Constrained (CPE) . . . . . 26
3.3.4 PE with Block WF on Selected Resource (PE-SBWF) . . . . . . . 27
3.4 Numerical Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
4 Channel Estimation and it’s Effect on System Performance 36
4.1 System Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
4.1.1 General Transceiver Model . . . . . . . . . . . . . . . . . . . . . . 36
4.1.2 Pilot Arrangement . . . . . . . . . . . . . . . . . . . . . . . . . . 36
4.2 Pilot-Assisted Channel Estimation . . . . . . . . . . . . . . . . . . . . . 38
4.2.1 Conventional Channel Estimation . . . . . . . . . . . . . . . . . . 38
4.2.2 Model-Based Channel Estimation . . . . . . . . . . . . . . . . . . 39
4.2.3 Detection Schemes . . . . . . . . . . . . . . . . . . . . . . . . . . 41
4.3 Soft-Decision Feedback Channel Estimation . . . . . . . . . . . . . . . . 46
4.3.1 Parallel Interference Cancellation . . . . . . . . . . . . . . . . . . 47
4.3.2 Soft-Decision Feedback . . . . . . . . . . . . . . . . . . . . . . . . 47
4.4 Numerical Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
4.4.1 Performance of Channel Estimation Techniques . . . . . . . . . . 49
4.4.2 Comparison of Receiver Performance . . . . . . . . . . . . . . . . 51
5 Conclusion and Future Works 54
5.1 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
5.2 Future Works . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Bibliography 57
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