利用盲蔽偵測，可以增加通訊系統的傳輸量。但並不是所有盲蔽偵測演算法都能適用於時變或是頻域選擇性的衰減通道。此外盲蔽偵測演算法通常需要較高的複雜度。在這論文中，我們首先提出一個通式，這個通式可以將任意加導引信號的通道響應估計演算法轉變成盲蔽偵測演算法。根據這個通式，並以最小方差貼合的加導引信號的通道響應估計演算為基礎，我們推導出盲蔽偵測的數學式，必且提出一個有效率的盲蔽偵測演算法。我們提出的演算法是在一個沿著子載波或是沿著時間軸所收集到的區段符元來運算，所以我們的盲蔽偵測演算法可以適用於時變或是頻域選擇性的衰減通道。利用我們提出的樹狀搜尋法則，我們的盲蔽偵測演算法可以達到和之前演算法一樣好的錯誤率但複雜度可以大幅度地降低。我們更進一步提出事先通道估計的方法，讓樹狀搜尋可以擁有較好的初始區段符元，而更進一步的降低複雜度。
當區段符元變大時，由於它的高複雜度，很多盲蔽偵測

演算法是不能實現的。這邊我們提出了大區段縮減演算法，面對較長的區段符元，我們的盲蔽偵測演算法還是可以實行，並且提供錯誤率和複雜度的利害關係供系統做選擇。面對高速變化的時變通道，我們提出的盲蔽偵測演算法可以和子載波干擾的消除技術做結合。
關鍵字:正交分頻多工，盲蔽偵測，子載波干擾

Pilot-assisted channel estimation is frequently used for the
orthogonal frequency-division multiplexing (OFDM) system.
On the other hand, one can apply blind detection to
enhance the throughput of communications. However, not all blind algorithms
can be applied in time-varying or frequency-selective fading channels.
Furthermore, blind algorithms usually have higher complexity.
In this thesis, we first propose a general principle, by which one can build a metric
for blind detection from any pilot-assisted channel response (CR) estimation algorithm.
By this principle and based on the least-squares-fitting (LSF) pilot-assisted CR estimation,
we derive a metric for blind detection and propose an efficient blind data detection algorithm.
The proposed algorithm is operated on a block of received symbols that
are along subchannels or along time slots, and therefore the proposed blind detection
can be applied in frequency-selective or time-varying fading channels.

With the proposed tree search method, the proposed algorithm attains the same error performance
as a previous blind detection algorithm based on the same metric, while the complexity is
greatly reduced. We further apply the channel prediction to obtain a better initial block
in the tree search, such that the complexity can be further reduced.
A range-reduced scheme is also proposed to give a trade-off between performance and complexity.
In the fast time-varying channel, we can combine the proposed blind detection
with an inter-subchannel interference (ICI) self-reduction algorithm
to reduce the effect of ICI.
keywords: OFDM, blind detection, inter-subchannel interference

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