Research On Downlink Synchronization And Cell Search For IEEE 802.16e OFDMA Systems

This thesis mainly discusses the downlink synchronization of IEEE 802.16e standard and initial synchronization for muti-cell OFDMA systems,the phasical layer platform of downlink synchronization is established according to the requirements of IEEE 802.16e standard, focus on synchronization algorithms of the receiver.The methods of frame detection and cell search are presented based on simulation about classical algorithms and the requirements of IEEE 802.16e standard.Firstly, the standard of IEEE 802.16 and its key techniques, the principles of OFDM and OFDMA are introduced briefly. The impacts of different synchronization deviation to the receiver are resesrched by theoretical analysis, the synchronization algorithms for OFDM are described in detail,and phasical channel models are set up also.The downlink platform is realized based on IEEE 802.16e, analyzing the structure of preamble and also the synchronization consists of the following parts:frame detection, fractional carrier frequency offset(CFO) estimation, accurate frame synchronization,integer CFO estimation is studied.This thesis presents a new method based on the pseudo-periodicity property of preamble.Simulation results show that the new method gives more satisfactory frame detection performance than Schmidl &Cox's.Secondly, this thesis do research on single-cell search of IEEE 802.16e OFDMA systems, presents the scheme of integer CFO and preamble index estimation. Simulation results verify that the scheme can give excellent performance for integer CFO estimation and preamble index estimation.Finally, this thesis discusses initial synchronization for muti-cell OFDMA systems, puts emphasis on cell identification when MS locates at a cell edge and the information comes from base station(BS) superposition. A complexity reduction method is proposed to satisfy the requirements of cell identification within the shortest time. The simulation shows that the proposed method can improve the cell identification rate and is applicable to IEEE 802.16e OFDMA systems.