本論文考量只須使用一個正交空時區塊碼正交分頻多工(orthogonal space-time block coded orthogonal frequency division multiplexing, OSTBC-OFDM)區塊信號之半盲蔽最大似然檢測(semiblind maximum-likelihood (ML) detection)技術。張等人[5]已證明了一個有趣的通道鑑別(channel identifiability)結果，那結果是，在無雜訊的情況下只須讓一個子通道傳輸前導資料(pilot data)，整個時域通道就能被唯一的鑑別。但是，這個結果必須在通道的數學統計上做一些假設。本論文藉由使用所謂的子空間無交集碼(nonintersecting subspace codes)和一些前導資料，建立一個「完美之通道鑑別」(perfect channel identifiability, PCI)傳輸機制，我們證明在這個機制下通道總是能被唯一的鑑別。此完美之通道鑑別傳輸機制雖然比張等人[5]的研究提出的機制所使用前導資料的數量還要多，但是卻比最小平方通道估計演算法還要少。此外，我們分析證明在獨立瑞立衰減通道(Rayleigh fading channels)中，使用此完美之通道鑑別傳輸機制的半盲蔽最大似然檢測器能夠獲得和相干最大似然接收機(coherent ML receiver)相同的完全空間多樣(full spatial diversity)。對於接收機實現問題，我們也提出降底複雜度的子通道群組(subchannel grouping)檢測機制。考量到最近令人感興趣的分散式空時編碼(distributed space- time coding)技術，本論文也將我們提出的完美之通道鑑別傳輸機制和半盲蔽最大似然檢測器延伸到分散式OSTBC-OFDM系統。透過電腦模擬也證實我們提出的機制不管在點對點(point-to-point)的或分散式的OSTBC-OFDM系統都比一些現存的方法提供了更好的效能。

This thesis considers semiblind maximum-likelihood (ML) detection of orthogonal space-time block coded OFDM (OSTBC-OFDM) systems within one OSTBC-OFDM block. Chang et al. [5] have shown an interesting channel identifiability result, that the whole time-domain multiple-input multiple-output (MIMO) channel can be uniquely identified in the noise-free situation by only using one of the subchannels to transmit pilots. However, this identifiability condition is in a probability-one sense relying on some mild assumptions on the channel statistics. In this thesis, through judicious use of so-called non-intersecting subspace OSTBCs and pilots over a small amount of subchannels, we establish a “perfect” channel identifiability (PCI) condition under which the channel is uniquely identifiable. The proposed scheme has the total number of pilots larger than that used in the previous probability-one identifiability achieving scheme, but smaller than that required in conventional pilot-aided channel estimation schemes. Also, it is shown that, in additive Gaussian noise and independent and identically distributed Rayleigh fading channels, the semiblind ML detector using the proposed PCI achieving scheme can achieve the same full spatial diversity as the coherent ML receiver. For the application in distributed (cooperative) space-time coding systems, we also extend the semiblind ML detector and the proposed PCI achieving scheme to that for a distributed OSTBC-OFDM scenario. Simulation results are presented to show that the proposed scheme can provide better performance than some existing schemes in both point-to-point and distributed OSTBC-OFDM systems.

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