| Summary: | 碩士 === 國立交通大學 === 電子工程學系 電子研究所 === 102 === Orthogonal frequency division multiple access (OFDMA) technique has drawn much interest recently in the mobile transmission environment and been successfully applied to a wide variety of digital communications applications over the past several years. One of the main reason to use OFDMA is its robustness against frequency selective fading. We focus on the OFDMA downlink (DL) channel estimation based on LTE and LTE-A.
The main channel estimation method is linear-minimum-mean-square-error (LMMSE) channel estimation in this thesis. In LMMSE channel estimation for multicarrier systems, one needs to know the channel correlation function. This brings up a problem for systems with a small number of reference signals (RSs). To solve this problem, we approximate the channel power-delay profile (PDP) that can completely be described in two channel delay parameters, i.e., the initial delay and the root-mean-square (RMS) delay. In addition, we develop a technique to estimate these delay parameters. For improving the accuracy of the estimated channel delay parameters, we employ an idea, producing pseudo RR, to meet our purpose. Then we find the autocorrelation function associated with the approximate PDP. Finally base on this autocorrelation function, do LMMSE filtering to estimate the data subcarrier response. We verify our simulation program and channel estimation methods on AWGN channel and then do the simulation on several multipath channels.
In this thesis, we first introduce the standard of the LTE and LTE-A DL. Then we describe the channel estimation methods we use and discuss the performance in each transmission condition for LTE and LTE-A.
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