| Summary: | 碩士 === 國立交通大學 === 電信工程研究所 === 106 === In 5G cellular system, there exists the problem of initial cell search when the mobile boots up in the cellular system. In this thesis, we studied the cell search procedure in 5G massive antenna multipath division multiple access (MDMA) cellular system. In our proposed system, traffic data is transmitted by orthogonal frequency division multiplexing (OFDM) in frequency domain, and control data is transmitted by polyphase sequence in time domain. A frame structure design is proposed in order to support mobile station with velocity lower than 90 m/s, then, the initial cell search procedure is divided into three different stages. In the first stage, we use conventional synchronization algorithm that uses cyclic prefix (CP) to estimate symbol timing offset (STO) and fractional frequency offset (FCFO), the STO estimation is combined with median filter to eliminate the effect of outlier in symbol timing estimation. In the second stage, we use primary control tone (PCT) as an indicator on whole transmission spectrum to estimate the integer frequency offset (ICFO), PCT transmission is also combined with the antenna hopping technique and is averaged over several symbols to obtain diversity. In the final stage, preamble and cell ID sequence is set to be a modified ZC sequence and transmitted in time domain after we explored the property of modified ZC sequence. We use the matched filter (MF) that matches modified ZC sequence to detect frame header and cell ID after being averaged over several frames for reliability. The simulation results are shown under the corresponding cellular environment.
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