適用於 3GPP-LTE/LTE-A多輸入輸出系統之預編碼選擇方案

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研究生：	王銓 Chuan Wang
論文名稱：	適用於 3GPP-LTE/LTE-A多輸入輸出系統之預編碼選擇方案 MIMO Precoder Selection for 3GPP-LTE/LTE-A Systems
指導教授：	蔡佩芸 Pei-Yun Tsai
口試委員:
學位類別：	碩士 Master
系所名稱：	資訊電機學院 - 電機工程學系 Department of Electrical Engineering
論文出版年：	2013
畢業學年度：	101
語文別：	中文
論文頁數：	83
中文關鍵詞：	第三代合作夥伴計劃、4G 、預編碼、分群
外文關鍵詞：	3GPP, 4G, Precoding, Group
相關次數：	點閱：6 下載：0
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本篇論文主題為適用3GPP-LTE/LTE-A 的架構下的預編碼碼簿的選擇，長期演進技術
/長期演進技術昇級版(3GPP-LTE/LTE-A)為4G 技術之一，除了提供更高的吞吐量也同時支
援動態傳輸的不同工作模式的選擇，本篇論文即利用動態傳輸中閉環路(close-loop)傳輸
的概念。閉環路傳輸利用接收端回傳給傳送端的通道資訊，來得到更好的傳輸品質，
接收端根據碼簿的選擇方法做出選擇，再將所選的碼簿資訊回傳給傳送端，為整體預編
碼傳輸的概念。
本篇論文選擇的為 K-Best 的球型解碼器，球型解碼器在解碼的效果上比傳統的
MMSE 與ZF 演算法來的更精準，但同時也需要付出較高的硬體複雜度，在此利用的是
略為減低其複雜度的K-Best 球型解碼器，並利用所提出的Trace criterion 來將經過QR 分
解的R 矩陣取得各層的平衡，最後我們將不同排序種類的QR 分解與我們所提出的Trace
Criterion 作結合，以達到更好的效果。本篇論文在模擬的部分選擇適用於3GPP-LTE 底下
的碼簿進行模擬，在最後的模擬結果也可見，所提出的方法確實有不錯的增益。
另外考慮到LTE 時頻域衰退通道的影響與降低運算量的需求，我們選擇使用分群作
為方法，這邊提出的分群方法，可以有效避免大量的效能衰退，也具有相當大的運算量
降低功能。
在硬體實作方面則使用所提出的預編碼系統下的關鍵性模組—高吞吐量之8×8
Sorted QR 分解—進行設計，最大特色為同時運算3 個4×4 Sorted QR 分解，並且提供不
同層數的排序功能以搭配前述的預編碼選擇機制。

Precoder Selection Under MIMO Detection
for 3GPP-LTE/LTE-A Systems
Abstract
Precoding by using a finite-set codebook at transmitters is an effective approach to
improve the performance of multiple-input multiple-output (MIMO) systems with reduced
feedback overhead. K-Best sphere decoders are popular for high-throughput
spatially-multiplexed MIMO signal detection at receivers.
In this paper, we propose a precoding-matrix-index (PMI) selection criterion suitable for
K-best MIMO detectors by minimizing the trace of the upper triangular matrix after QR
decomposition (QRD). To further improve the system performance, fully-sorted QRD,
per-layer sorted QRD and partially-sorted QRD are also proposed to be incorporated in the
minimum-trace PMI selection criterion. Simulation results based on the MIMO codebooks of
3GPP-LTE/LTE-A systems show the improvements of the proposed scheme compared to the
non-precoding MIMO schemes and the precoding schemes using the conventional PMI
selection criterions.
Considering the fading channel in time/frequency domain of LTE system, we propose a
group solution, which not only provide much lower computation, but also avoid more
degradating.
As to the hardware implementation, we use a scalable design of high throughput 8×8
Sorted QRD. It can compute three sets of 4×4 Sorted QRD simultaneously. Various numbers
of sorting layers are supported for our proposed precoding criterion.

目錄 ................................................................................................................................... iv
圖示目錄 ...................................................................................................................................vii
表格目錄 .................................................................................................................................... x
第一章 緒論 ............................................................................................................................ 1
1 簡介 ............................................................................................................................. 1
2 研究動機 ..................................................................................................................... 1
3 論文組織 ..................................................................................................................... 2
第二章 多輸入多輸出(MIMO)系統 ......................................................................................... 3
1 介紹 ............................................................................................................................. 3
2 傳統的接收機 ............................................................................................................. 5
2.1 強制歸零(Zero-Forcing, ZF) ............................................................................. 5
2.2 最小均方誤差(Minimum Mean Square Error, MMSE) .................................... 6
2.3 最大相似度(Maximum Likelihood, ML) .......................................................... 6
2.4 球面解碼(Sphere Decoder) ............................................................................. 7
3 多輸入多輸出預編碼(MIMO Precoding) .................................................................. 11
4 實數系統(Real Value System) .................................................................................... 11
第三章 碼本搜尋機制(Codebook Searching Mechanism) .................................................. 13
1 介紹 ........................................................................................................................... 13
2 碼本(Codebook)的設計 ............................................................................................ 16
3 現有的方法 ............................................................................................................... 21
3.1 Mean Squared Error Selection Criterion, MSE-SC ........................................... 21
3.2 Singular Value Decomposition Selection Criterion, SVD-SC ............................ 22
3.3 Capacity-based Selection Criterion ................................................................. 22
v
3.4 QR Decomposition based selection ................................................................ 23
4 所提出的碼本搜尋機制 ............................................................................................ 23
4.1 Trace Criterion ................................................................................................. 25
5 搭配Sorted QR 的能量分配機制 ............................................................................. 26
5.1 不同排序(Sort)方法的統計特性 .................................................................... 26
5.2 最佳的Sorting 方案 ....................................................................................... 27
6 增強型搜索方案(Enhanced or fully-sorted) ............................................................. 28
7 模擬與比較 ............................................................................................................... 30
第四章 時頻域衰退下通道之LTE 系統碼簿選擇 ................................................................. 33
1 介紹 ............................................................................................................................ 33
2 LTE 時頻域衰退通道模型 .......................................................................................... 34
2.1 LTE 下多輸入多輸出通道空間模型 ............................................................... 35
2.2 通道模型參數 ................................................................................................. 38
3.1 時頻域衰退通道模擬結果 ............................................................................. 41
3 基於時頻域衰退下的碼本選取 ................................................................................ 44
3.1 頻域評估 ......................................................................................................... 45
3.2 時域評估 ......................................................................................................... 50
4 複雜度分析 ................................................................................................................ 54
第五章 硬體實現 .................................................................................................................... 56
1 硬體設計 ................................................................................................................... 56
2 硬體時脈 ................................................................................................................... 58
3 8×8 Sorted QRD 硬體介紹 ......................................................................................... 59
3.1 4×4 Sorted QRD 硬體介紹 .............................................................................. 59
3.2 8x8 Sorted QR 設計 ......................................................................................... 63
3.3 CORDIC 之硬體 ............................................................................................... 66
vi
3.4 Processing element, PE ................................................................................... 69
3.5 Norm 值之計算單元 ....................................................................................... 71
3.6 計算剩餘向量Norm 之值單元 ..................................................................... 72
4 字元長度 ................................................................................................................... 74
5 實現結果 ................................................................................................................. 76
6 硬體實現之模擬 ....................................................................................................... 78
第六章 結論 ............................................................................................................................ 81
參考文獻 .................................................................................................................................. 82
                                

參考文獻
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