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[轉載]【電信學】【2014.07】WCDMA上行鏈路的MIMO預編碼算法研究

已有 305 次閱讀 2019-5-2 12:35 |系統分類:科研筆記|文章來源:轉載


本文為瑞典查爾姆斯理工大學作者:Sheng Huang & Mengbai Tao)的碩士論文,72。

 

隨著高速數據傳輸需求的快速增長,多輸入多輸出(MIMO)技術在當前的通信網絡中得到了廣泛的應用,如寬帶碼分多址系統(WCDMA)。關于WCDMA下行鏈路中的MIMO已經研究了很長一段時間,而在WCDMA上行鏈路中,如何選擇預編碼的規范還沒有確定。預編碼是多輸入多輸出(MIMO)系統中的一個重要組成部分,目的是減輕數字編碼信號序列中不同數據流之間的干擾。目前,MIMO系統在預編碼方面存在兩個問題。由于預編碼算法需要信道信息,因此一個問題是很難對頻率選擇性信道中的信道特性進行建模。另一個問題是,只有有限的反饋才適用于實際系統,因為如果需要將全信道信息發送給發送機,反饋開銷的成本將遠遠大于預編碼的好處。本文的目的是在WCDMA上行鏈路反饋有限的情況下,通過選擇合適的預編碼算法,研究給定誤碼率(BLER)下所需信噪比(SNR)范圍內的最大潛在增益。

 

根據我們的仿真模擬,在反饋有限的情況下,預編碼的最大潛在增益是可觀的與固定預編碼相比,0:5 BLER時為1:2 dB)。在理想信道估計的假設下,通過采用最接近SVD(CSVD)算法,可以分別獲得總流和主流的0:6 dB增益和1dB增益。值得指出的是,單獨預編碼不能完全緩解串擾。為了進一步降低MIMO中串擾的影響,需要在預編碼的同時實現適當的信道均衡。預編碼的性能在很大程度上也取決于信道估計的可靠性。因此,為了在商業通信系統中實現一種良好的預編碼算法,信道估計需要更加可靠,而預編碼算法也會增加系統開銷,增大系統復雜度。因此,應該權衡預編碼所獲得的收益和相應的復雜性。

 

With rapidly increasing demand in high-speed data transmission, Multiple-Input Multiple-Output (MIMO) techniques are widely used in current communication networks, like Wideband Code Division Multiple Access (WCDMA). MIMO in downlink of WCDMA has been studied for a long time, while in WCDMA uplink, the specification of how to choose precoder is still not defined yet. Precoding is an essential element in MIMO, aiming at mitigating interference between different data streams that are sequences of digitally coded signals. Currently, a MIMO system suffer from two problems regarding precoding. Since channel information is needed for the precoding algorithm, one problem then is that it is difficult to model the channel characteristics in a frequency selective channel. The other problem is that only limited feedback is applicable in real system, since the cost of feedback overhead is far larger than the benefits from precoding if full channel information needs to be sent to the transmitter. The objective of this thesis is to investigate the maximum potential gain in the required Signal-to-Noise Ratio (SNR) range for a given Block Error Rate (BLER) by using precoding and selecting a suitable precoding algorithm in the case of limited feedback in the WCDMA uplink.

 

The maximum potential gain of precoding is considerable (1:2 dB at 0:5 BLER compared to a fixed precoder) in the case of limited feedback according to our simulations. By applying the proposed closest-to-SVD (CSVD) algorithm, 0:6 dB gain and 1 dB gain can be achieved for total stream and the primary stream, respectively, when ideal channel estimation is assumed. It is worth to point out that precoding alone can not mitigate crosstalk completely. Suitable channel equalization needs to be implemented together with precoding in order to further decrease the impact of crosstalk in MIMO. The performance of precoding depends largely on the reliability of the channel estimation as well. Thus, channel estimation needs to be more reliable in order to implement a good precoding algorithm in a commercial communication system, which on the other hand will cost more overhead and increase the system complexity. Hence, a trade-off should be made regarding the gain obtained from precoding and the complexity of the algorithm.

 

引言

2 WCDMAMIMO理論

3 WCDMA標準與仿真器描述

算法與相關結果

討論、結論與未來研究工作

附錄仿真器評估 


下載英文原文地址:

http://page2.dfpan.com/fs/dl4cdj02c2f14219160/ 


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