Research On The Key Technology Of TD-LTE Physical Layer

TD-LTE physical layer, which is the basic layer of system, provides data services to higher layers, e.g. MAC, PDCP, and RRC, by transport channel. Also, it transmits higher layer data, after being proccessed by scrambling, modulation, layer mapping and precoding, to the other physical entities.Physical layer procedures describe the specific processes of the physical entities including timing synchronisation, random access procedure, and power control. The synchronization process is realized by cell search. It is the procedure by which a UE acquires downlink time and frequency synchronization with a cell, detects the physical layer Cell ID, and receives the broadcast information The UE acquires uplink timing and uplink resource based on the random access procedure. Power control compensates propagation loss, calculates proper transmission power, reduces the power consumption of a transmitter, and limits the interference.Aimed at the application key problem of downlink timing synchronization algorithm in TD-LTE system, an improved algorithm for TD-LTE downlink time synchronization is proposed in this paper. It utilizes statistical energy difference and correlation of cyclic prefix (CP) to improve the system performance, which reduces the computational complexity, improves the timing accuracy, and can detect the CP types. The simulation results demonstrate that the performance of the new method is excellent in multi-path fading channels, especially in the case of small SNR. And it is robust against the normalized frequency offset and Doppler shift.Aimed at the simulation problem of timing synchronisation, random access procedure, and power control, the paper analyses the protocol, simplifies and visualizes the abstract theory and technology. Based on the Android, it designs and implements the TD-LTE physical layer simulation system, which simulates the working procedures of timing synchronisation, random access procedure, and power control.