| Summary: | 碩士 === 國立臺灣大學 === 電信工程學研究所 === 95 === With the rapid growth of wireless communications and high speed rail, the need for high speed data transmission in high speed train environment is increased. Orthogonal Frequency Division Multiplexing (OFDM) is recently becoming very popular for achieving high data rates due to its resistance to ISI. OFDM has also been chosen as the transmission method for many standards, such as the IEEE 802.11 and 802.16. The accuracy of pilot-aided channel estimation at a desired Doppler frequency is highly dependent on how the pilots are arranged. In this paper, we describe the effect of Doppler frequency on different pilot arrangements in wireless OFDM systems and simulate the performance using the parameters of the IEEE 802.16 standard in high mobility environment. According to sampling theorem and channel parameters, we propose a new pilot insertion scheme and compare it with conventional 802.16 frame format. In the end, we use characterization of rail environment to improve system performance.
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