使用雙極化天線的空間調變技術：訊號映射、通道估測及訊號偵測

Abstract

空間調變 (SM) 是近年來被提出的一種提升頻譜效率及降低傳送接收端複雜度的技術。 這是由於SM可避免傳統MIMO技術中通道間交互干擾 (ICI) 的問題，且大量減少硬體上射頻鏈路 (RF chain) 的高花費。 大多數對於MIMO訊號的偵測，傳送或是接收端需要知道通道資訊 (CSI)，此通道資訊可透過某種估計演法得到。在本文中，提出了兩種基於SM 系統下，隨時間變動的通道估測方法，此方法可以省掉領航信號 (pilot) 的額外負擔因此而提升系統效能。 因為共置 (co-located) 雙極化天線的使用可以節省空間和花費，因此我們也探討使用雙極化天線的SM技術及其訊號偵測的方法，其中所提出的次佳化的偵測器複雜度只需要將近最大似然偵測法 (ML) 的一半，且效果比基於匹配濾波器(MF-based) 的偵測法更好。在使用雙極化天線及有空間相關性的通道模型中，我們也引進了一個較一般性的通道模型並提出相對應的通道估測方法。 由於SM系統在傳送訊號時，一次只使用單根傳送天線，利用Alamouti的時空編碼可以使SM系統更具彈性。本文中提出了在SM系統下差分的Alamouti時空編碼技術，此法接收端不須要通道資訊即可解碼。 針對所提出的方法，我們透過了模擬結果來檢驗其效能並與現有的方法做比較。

Spatial modulation (SM) technique has received intensive interest recently for its capability to improve the spectral efficiency and lower the transceiver complexity. This is because SM induces zero inter-channel interference and requires a single RF chain only. To detect or encode SM signals, channel state information (CSI), which is to be obtained by a channel estimator at either the transmit or the receive side, is needed for spatial identification. The first SM-related issue investigated in this thesis concerns channel estimation in a correlated time-varying channel. We propose superimposedpilot-assisted and decision-directed spatial channel estimation schemes. These schemes improve the system throughput by either removing or reducing the pilot overhead. Since the use of co-located dual-polarized antennas offers a space- and cost-effective alternative for multiple antenna systems, we then review the feasibility of using such antenna arrays and present a new SM scheme which takes advantage of the channel decorrelation inherited in a dual-polarized antenna array. A suboptimal detector which needs only half of the ML detector complexity is proposed. This suboptimal detector performs much better than the MF-based method. For a dual-polarized antenna array based SM system, we suggest a general channel model which takes into account the spatial correlation and introduce a model-based spatial channel estimator. Finally, to avoid the CSI requirement, we propose an Alamouti coding based differential space time block coded SM (DSTBC-SM) scheme. For each proposed scheme, we provide computer simulation results to demonstrate and verify its superiority against the existing solutions.