【摘要】：作為3G技術(shù)的演進技術(shù),LTE以其更高的系統(tǒng)容量、傳輸可靠性及頻譜利用率,已經(jīng)成為全球各大主流運營商的共同選擇,并且在全球商用過程中已經(jīng)取得重大進展。MIMO技術(shù)毫無疑問是LTE的核心技術(shù)之一,但是由于MIMO系統(tǒng)中普遍存在的多個數(shù)據(jù)流及多個用戶間的干擾問題以及各用戶接收機的分布式處理,在接收端進行聯(lián)合檢測已然不實際,因此在發(fā)送端利用信道狀態(tài)信息(CSI)調(diào)整發(fā)射策略的預(yù)編碼技術(shù)應(yīng)運而生,預(yù)編碼技術(shù)有效地抑制MIMO系統(tǒng)中的多個數(shù)據(jù)流及多個用戶間的干擾,在大幅降低接收機處理復(fù)雜度的前提下顯著提升信道容量,因而有助于MIMO獲得其特有的復(fù)用增益和分集增益。本文對LTE中MIMO下行鏈路的預(yù)編碼技術(shù)進行了研究。相對于線性預(yù)編碼算法,如ZF(迫零)預(yù)編碼和MMSE(最小均方誤差)預(yù)編碼算法,以THP(模代預(yù)編碼)和VP(矢量擾動)等為代表的非線性預(yù)編碼算法及它們的一些衍生算法能以可接受的復(fù)雜度為代價,獲得相比于線性預(yù)編碼更顯著的性能增益。然而,THP和VP預(yù)編碼算法都需要引入取模操作,由于THP算法在發(fā)送和接受端都采用了取模操作,這將會引入取模損耗、成形損耗及功率損耗。而VP在接收端也采用了取模操作,也會引入取模損耗。這些損耗都會給THP和VP預(yù)編碼的性能帶來不小的負增益,嚴重影響非線性預(yù)編碼下的MIMO系統(tǒng)的性能。針對以上問題,本文將提出改進后的THP和VP預(yù)編碼的收發(fā)算法。文章主要工作如下:簡單回顧MIMO系統(tǒng)中預(yù)編碼技術(shù)的原理及其作用,闡述ZF及MMSE等線性預(yù)編碼算法和THP及VP等非線性預(yù)編碼算法的設(shè)計原理,并利用MATLAB仿真,驗證各種預(yù)編碼算法的性能,總結(jié)對比它們各自的優(yōu)缺點。分析THP預(yù)編碼算法因收發(fā)端均引入取模操作而帶來的取模損耗、成形損耗及功率損耗等各種損耗,考慮基于Turbo信道編碼下的擴展星座圖的軟解調(diào)方案。另一方面,針對取模操作可能使得接收端的符號飄移到取模界限之外,本文考慮擴展取模間隔方案,但是擴展取模間隔的系統(tǒng)在減小取模損耗的同時也會增加功率損耗,因此本文提出找到折衷取模損耗和功率損耗的最優(yōu)取模擴展因子,使得加入取模擴展因子之后,系統(tǒng)的整體性能仍能夠有增益。研究VP預(yù)編碼的簡化方案——LRA-VP預(yù)編碼,并提出適用于帶有AMC的鏈路和系統(tǒng)級仿真的基于LRA-VP的多用戶不同調(diào)制方式下的預(yù)編碼算法。分析LRA-VP預(yù)編碼算法因接收端引入取模操作而帶來的取模損耗,考慮基于Turbo信道編碼下的擴展星座圖的軟解調(diào)方案。同樣,針對取模操作可能使得接收端的符號飄移到取模界限之外,本文考慮擴展取模間隔方案,但是擴展取模間隔的系統(tǒng)在減小取模損耗的同時也會降低VP的預(yù)編碼增益,所以本文提出找到折衷取模損耗和預(yù)編碼增益的最優(yōu)取模擴展因子,以使得加入取模擴展因子之后,系統(tǒng)的整體性能仍可以得到提升。
[Abstract]:As the evolution technology of 3G technology, LTE has become the common choice of major operators in the world because of its higher system capacity, transmission reliability and spectrum efficiency. And has made significant progress in global commercial processes. MIMO technology is undoubtedly one of the core technologies of LTE. However, due to the common problems of multiple data streams and interference between multiple users in MIMO system and the distributed processing of each user receiver, it is no longer practical to carry out joint detection at the receiving end. Therefore, a precoding technique using channel state information (CSI) to adjust the transmission strategy is proposed at the transmitter. The precoding technique can effectively suppress the interference between multiple data streams and users in MIMO system. While greatly reducing the processing complexity of the receiver, the channel capacity is significantly increased, which is helpful for MIMO to obtain its unique multiplexing gain and diversity gain. In this paper, the precoding technology of MIMO downlink in LTE is studied. Compared with linear precoding algorithms, such as ZF (zero forcing) precoding and MMSE (least mean square error) precoding, Nonlinear precoding algorithms, such as THP (Modular precoding) and VP (Vector perturbation), and some of their derivation algorithms can obtain more significant performance gains than linear precoding at the cost of acceptable complexity. However, both the THP and VP precoding algorithms need to introduce the mold extraction operation. Because the THP algorithm uses the mold extraction operation at both the sending and receiving end, this will introduce the die extraction loss, the shaping loss and the power loss. The VP also uses the mode-taking operation at the receiving end, which will also introduce the loss of the mode-fetching. These losses will bring negative gain to the performance of THP and VP precoding, which will seriously affect the performance of MIMO systems under nonlinear precoding. In order to solve the above problems, this paper proposes an improved transceiver algorithm for THP and VP precoding. The main work of this paper is as follows: briefly review the principle and function of precoding technology in MIMO system, expound the design principle of linear precoding algorithm such as ZF and MMSE and nonlinear precoding algorithm such as THP and VP, and make use of MATLAB simulation. Verify the performance of various pre-coding algorithms and compare their advantages and disadvantages. This paper analyzes the loss of THP precoding algorithm which is caused by the introduction of mode-taking operation into the transceiver, and considers the soft demodulation scheme of extended constellation diagram based on Turbo channel coding, such as the loss of mode-fetching, the loss of shaping and the loss of power. On the other hand, in view of the fact that the mode-taking operation may cause the symbol of the receiver to drift beyond the mode-taking limit, this paper considers the extended mode-taking interval scheme, but the system with the extended mode-taking interval will increase the power loss while reducing the mode-taking loss. In this paper, we propose to find out the optimal modulus extraction expansion factor between the mode extraction loss and the power loss, so that the overall performance of the system can still have gain after the addition of the mode extraction expansion factor. In this paper, the simplified scheme of VP precoding, LRA-VP precoding, is studied, and a precoding algorithm based on multi-user modulation schemes based on LRA-VP is proposed for link and system-level simulation with AMC. This paper analyzes the loss of LRA-VP precoding algorithm caused by the introduction of mode-removal operation at the receiver, and considers the soft demodulation scheme based on the extended constellation diagram based on Turbo channel coding. Similarly, in view of the fact that the mode-taking operation may cause the symbol of the receiver to drift beyond the threshold of the mode-taking, this paper considers the extended mode-taking interval scheme, but the system with the extended mode-taking interval can reduce the loss of the mode-fetching and the precoding gain of the VP at the same time. In this paper, we propose to find the optimal modulus extraction expansion factor between the loss and the precoding gain, so that the overall performance of the system can be improved after the addition of the modulus extraction expansion factor.
【學(xué)位授予單位】：電子科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TN929.5

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