| Summary: | 碩士 === 國立中正大學 === 通訊工程研究所 === 93 === Orthogonal Frequency Division Multiplexing(OFDM) systems play a important role in physical layer
of modern WLAN.
Algorithms of energy detection, frequency synchronization, timing synchronization, channel estimation and
phase tracking effect the receivered signals directly in baseband receiver.
In communication systems, oscillators must be used for modulating signals to high frequency band then transfering signals.
But,in fact,oscillators are not ideals.
They produce phase noise and increase every samples.
It is not exception in OFDM systems, last samples are effected acutely and it is more important to correct the phase errors.
In this paper, in order to increase performances, the trick of using the pilot subcarriers of oversampled
signals to estimate phase errors by LS method is proposed.
We Combine signals by Maximal Ratio Combining(MRC).
We have the maximum limit of parameter beta that is 1MHz.
when beta is 10kHz and SNR is low, oversampling system can improve 2~3dB in AWGN channel.
when SNR is low, oversampling system can improve 2~3dB in multipath channel.
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