Channel Estimation for OFDM in Amplify and Forward elay Systems
Date Issued
2009
Date
2009
Author(s)
Chen, Chong-Heng
Abstract
Cooperative communication is a promising technologyhich can provide the space diversity and increase the reliability in wireless communication. Most existing analyses of relay systems assume that the perfect channel state information is known at the receiver, and pay less attention to the channel estimation. However, channel estimation is an indispensable technique in relay systems. In this thesis, we consider orthogonal frequency division multiplexing (OFDM)- based amplify-and-forward (AF) relay systems. We divide this thesis into three topics. In the first topic, multiple relay systems over slow fading channels are considered. The optimal training sequences for least squares (LS) and linear minimum mean squared error (LMMSE) are proposed. Through simulations, it is shown that the optimal training sequences proposed in this thesis significantly outperform the other training sequences. In the second topic, single relay systems over fast fading channels are considered. We propose three time-domain pseudo-pilot algorithms. All of the proposed algorithms can improve the performance of channel estimation and achieve better performance than Chang''s method. In the final topic, we still focus on the single relay systems over fast fading channels. We propose the adaptive pseudo-pilot conjugate gradient (APPCG) algorithm which does not need to perform the inverse matrix operation and has lower computational complexity. Moreover, it has better performance than other channel estimation methods.
Subjects
cooperative communication
orthogonal frequency division multiplexing (OFDM)
amplify-and-forward (AF) relay
channel estimation
optimal training
pseudo-pilot algorithm
conjugate gradient algorithm
Type
thesis
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