Research On Lte Cell Search And Downlink Synchronization Process

ABSTRACT:LTE system which is proposed by 3GPP organization is deemed to the communication standard towards future 4G system in the next ten years. It applies many new technologies such as OFDM, MIMO and link adaptation. The fundamental targets of LTE are increasing data rates, reducing latency, improving system capacity and coverage as well as reducing operator costs.In mobile communication system, cell search is one of the key procedures and the premise of establishment of communication link between eNB and UE. Whether the terminal is initial power on in the cell or hands over in the communication process, it is necessary to apply a cell search procedure to establish a link to the eNB. Cell search procedure is mainly to obtain time synchronization, frequency synchronization cell ID, system bandwidth and other cell basic information.This paper briefly introduces LTE PHY layer standard and key technologies at the beginning, focus on OFDM technology and wireless channel characteristics. Then take this as basis, for the design of synchronization signal at the transmitter part, the structure of synchronization channel and the selection of synchronization signal was analyzed, getting the assessment and simulation result respectively. Because of applying OFDM technology in LTE system, it has a disadvantage of the sensitivity of the frequency error, so that the terminal has to detect frame starting position and estimate frequency error. For this, a timing algorithm and frequency error estimation algorithm was designed and getting the simulation result as well.In recent years, the development of China Railway High Speed attracts the world's attention. For wireless communication for high-speed railway, the main difficulty is the rapid Doppler changes because of high speed. In the final part of this paper, a special cell search algorithm for special scenario of high speed railway was proposed.