多輸入多輸出系統中空間調制之預編碼器設計

Abstract

由於空間調制(spatial modulation) 於多輸入多輸出系統中擁有低複雜度以及高能量效率的特性，此類系統被視為未來極有可能被使用的通訊系統之一，此外由於預編碼器的使用被證實可以進一步降低系統錯誤率，因此在本篇論文中，吾人針對預編碼器的設計作進一步的研究。在利用了最大化最小差距(minimum distance)的概念以及最佳化理論的技巧後，吾人提出兩種使用在傳送端擁有完整通道資訊時的預編碼器的設計方法，這兩種方法中都各自包含了一個最佳化公式以及一個共同的反覆演算法，並且皆能有效地於任何空間調製系統上設計預編碼器。在考慮了更實際的系統後，本論文引入基於碼簿的有限回授預編碼(codebook-based precoding with limited feedback)技術。為了能設計高效能的碼簿，吾人於探討碼簿的設計法則後引入向量量化的技巧以最大化傳送符碼間的平均最小差距，並提出三種適用於不同情況的碼簿設計演算法。經由模擬結果證實，吾人所提出之預編碼器設計可以有效地降低系統效錯誤率，此外吾人提出的設計方式的也被證實可使用在各式系統中。最後在比較了其他現有的預編碼器技術後發現，吾人所提出之設計可比其他技術更有效地降低錯誤率。

Spatial modulation in MIMO system (SM-MIMO) is a promising approach due to its low complexity and high energy efficiency properties. To enhance the SM-MIMO system performance, precoding at transmitter is shown to be effective. In this thesis, we investigate the precoder design techniques. With channel state information at transmitter, we propose two general precoder designs, including the problem formulations and its iterative algorithm, by manipulating the distance between codewords using optimization techniques. The designs can be virtually used in any type of SM-MIMO system. For practical concerns, codebook-based precoding is then introduced for SM-MIMO systems with limited feedback. To construct the effective codebook, we investigate the design criterion and propose three codebook design algorithms with different design considerations through exploiting the vector quantization techniques to maximize the average distance among codewords. Finally, the simulations show the effectiveness of the proposed designs in improving system performance, and confirm their superiority to existing works. Moreover, their feasibility in general SM-MIMO systems is verified as well. Furthermore, the proposed designs can indeed outperform other existing works.