https://scholars.lib.ntu.edu.tw/handle/123456789/122833
標題: | 八根天線系統下低複雜度預編碼技術 Low-Complexity Precoding Technique for Eight Transmit Antenna MIMO system |
作者: | 吳至倫 Wu, Chih-Lun |
關鍵字: | 長期演進;空間多工系統;多天線干擾預編碼;八根天線碼簿;低複雜度;LTE;spatial multiplexing;Multi-antenna interference;precoding;8Tx codebook;low complexity | 公開日期: | 2012 | 摘要: | MIMO(Multi-input Multi-output)裡空間多工(Spatial multiplexing)使系統達到很高的吞吐量(throughput),但是天線和天線間會產生干擾,為了降低通道間天線間干擾,使用預編碼的觀念,透過傳送端知道通道的干擾而做預編碼去避開或使干擾減少,然而傳送端不能主動知道通道狀況下,勢必由接收端回傳通道資訊,然而接收端回傳傳送端用的技術是OFDMA,因此上傳的頻寬沒有下傳的頻寬大,所以碼簿(codebook)的使用正是為了因應有限的上傳資源。傳送端和接收端都有相同的碼簿,此時接收端找出碼簿裡的碼字當預編碼矩陣,只要回傳該碼字在碼簿的索引,傳送端就可以利用該索引找到所要的碼字,這可大幅減輕上傳的負擔。 本論文提出減少接收端的搜尋預編碼計算複雜度,假設秩數指標(rank indicator,RI)的評估完美,再利用以互消息為基準評估預編碼矩陣指數(precoding matrix indictor,PMI),利用互消息正比於碼字的子空間距離,首先先對碼簿的碼字以子空間距離做樹狀分組,利用分完組的碼字可以幫助減少尋找預編碼矩陣的複雜度。最後再衍伸八根天線碼簿的特性,減少搜尋碼字的個數與上傳的RI和PMI個數。 Spatial Multiplexing for MIMO system uses antenna arrays provide communication link with substantial capacity. Unfortunately, spatial multiplexing is sensitive to multi-antenna Interference. Precoding can improve the resilience of spatial multiplexing at the expense of full channel knowledge at the transmitter—which is often not realistic. Use quantized precoding system where the optimal precoder is chosen from a finite codebook known to both receiver and transmitter. Receiver calculate preferred codeword as precoding matrix in the codebook,and feedback index of codeword to transmiter. In order to minimize computational complexity of search precoding matrix. Assume RI evaluation perfect, PMI evaluating based on mutual information. Mutual information is proportional to its subspace distance. We group codewords based on the subspace distance, then minimize complexity of searching precoding matrix using the grouped codebook. Finally we use characteristics of 8Tx codebook and minimize number of codeword selection. |
URI: | http://ntur.lib.ntu.edu.tw//handle/246246/252547 |
顯示於: | 電信工程學研究所 |
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