- 學位論文
在未知塊狀衰減通道中OSTBC-OFDM系統之最大勢然偵測
Maximum-Likelihood Detection of Orthogonal Space-Time Block Coded OFDM in Unknown Block Fading Channels
若您是本文的作者，可授權文章由華藝線上圖書館中協助推廣。
摘要
For orthogonal space-time block coded orthogonal frequency division multiplexing (OSTBC-OFDM) systems, many of the existing blind detection and channel estimation methods rely on the fundamental assumption that the channel is static for many OSTBC-OFDM blocks. This thesis considers the blind (semiblind) maximum-likelihood (ML) detection problem of OSTBC-OFDM with a single OSTBC-OFDM block only. The merit of such an investigation is the ability to accommodate channels with shorter coherence time. We examine both the implementation and identifiability issues, with a focus on BPSK/QPSK constellations. In the implementation, we propose reduced-complexity detection schemes using subchannel grouping. In the identifiability analysis, we show that under independently and identically distributed (i.i.d.) Rayleigh fading channels the proposed schemes can ensure a probability one identifiability condition using a very small number of pilots. The second part of this study is to devise transmission schemes that guarantee any nonzero channel to be uniquely identifiable by the blind ML detector, referred to as ``perfect channel identifiability (PCI)" scheme. We show that the PCI schemes can be constructed by employing the so-called nonintersecting subspace (NIS) code proposed by Oggier. Moreover, for i.i.d. Rayleigh fading channels, it can be analytically shown that the PCI schemes achieve full transmit diversity, even when the receiver does not have the channel state information. Extension of the PCI schemes as well as the blind ML detector to the distributed OSTBC-OFDM system is also investigated in the thesis.
並列摘要
現存大多數針對正交空時區塊碼正交分頻多工(orthogonal space-time block coded orthogonal frequency division multiplexing, OSTBC-OFDM)系統的盲蔽檢測與通道估測技術皆基於一根本假設，通道(channel)在多個OSTBC-OFDM區塊區間內為靜止不變的。本論文考量只需使用一個OSTBC-OFDM區塊信號之盲蔽最大勢然檢測(maximum-likelihood (ML) detection)技術。此技術的優點在於其更適合應用於具有較短同調時間(coherence time)的通道環境。基於BPSK/QPSK符碼調變，我們探討包括接收機實現(receiver implementation)及盲蔽唯一資料鑑別(blind unique data identifiability)的問題。對於接收機實現問題，我們提出降底複雜度的子通道群組(subchannel grouping)檢測機制。對於盲蔽唯一資料鑑別，我們證明所提出的檢偵機制在獨立瑞立衰減通道(Rayleigh fading channels)中只需使用非常少量的前導資料(pilot data)就能保證資料鑑別的唯一性。 本論文的第二部分更進一步針對任意非全零的通道環境，發展能夠在盲蔽接收機唯一鑑別通道的傳輸機制，我們證之為「完美之通道鑑別」(perfect channel identifiability, PCI)機制。我們證明只要使用所謂的子空間無交集碼(nonintersecting subspace codes)就能達到所期望的完美通道鑑別。此外，我們分析證明在獨立瑞立衰減通道中，此完美之通道鑑別傳輸機制能夠保證盲蔽最大勢然檢測器獲得最大之空間分集增益(spatial diversity gain)。最後，我們將所提出的完美之通道鑑別傳輸機制以及所提出之盲蔽最大勢然檢測器延伸到分散式空時編碼(distributed space time coding)系統。
參考文獻
[1] F. E. Oggier, N. J. A. Sloane, S. N. Diggavi, and A. R. Calderbank, “Nonintersecting subspaces based on finite alphabets,” IEEE Trans. Inform. Theory, vol. 51, no. 12, pp. 4320–4325, Dec. 2005.
[2] D. Gesbert, M. Shafi, D.-S. Shiu, P. J. Smith, and A. Naguib, “From theory to practice: An overview of MIMO space-time coded wireless systems,” IEEE J. Sel. Areas Commun., vol. 21, no. 2, pp. 281–302, April 2003.
[3] D. Agrawal, V. Tarokh, A. Naguib, and N. Seshadri, “Space-time coded OFDM for high data-rate wireless communication over wideband channels,” in Proc.
[4] Y. Gong and K. B. Letaief, “Low complexity channel estimation for space-time
estimation for block precoded space-time OFDM,” IEEE Trans. Signal Process.,