The Research On Access Technology For LTE-A Terminal Software Baseband

Cell search is the first physical layer process after user equipment is powered in the LTE-A system.Through cell research,the synchronization signal is used by the user equipment to gain downlink time and frequency synchronization with its base station,and detected the cell identification of its physical layer.Only if the cell search is in a correct way,the system information from physical broadcast channel could be received correctly.And then through the random access process,the uplink synchronization with the base station will be achieved,and uplink resources be applied.After that,the normal data transmission and reception between two equipments will be finally realized.Therefore the algorithm and implementation of cell search and random access preamble sequences will be studied respectively.First,the generation of PSS and SSS in the physical layer of LTE-A system will be discussed,and then their signal mapping position in time and frequency domain be described,on which a set of fast,accurate LTE-A cell search algorithm process will be finally put forward.PSS sequence is generated by ZC sequence which has a fine correlation,thus related algorithms based on PSS sequence are employed by the PSS detection to complete the rough timing.The PSS is sent twice in every frames and its sequence exists in every half frames.And half frame synchronization can be achieved in no time by reducing the sample rate and Piecewise linear convolution of half frame data.The PSS time domain conjugate correlation algorithm is adopted to obtain the fractional frequency offset estimation based on the achievement of the rough timing to complete the frequency synchronization.Finally,a method for the correlation of odd-even sequences is proposed to reduce the complexity of the algorithm.Secondly,the function and process of random access is analyzed,and the generation of random access preamble sequence is also studied in details after that.Besides,this paper discusses the format,time frequency structure and generation method.Complexity of the algorithm is reduced by using DSP parallel processing mechanism and simplifying FFT algorithm by adopting some simplified algorithm such as CZT algorithm,looking up table and so on.Finally,the terminal physical layer cell search and random access algorithm are simulated on the Diamond-DSP simulation platform,and a manual assembly optimization is applied to the function of high complexity.What's more,the simulation results are compared with the theoretical value of MATLAB,which proves the correctness of the algorithm proposed in this paper.The operation period of cell search and random access are reduced through the manual assembly optimization,and the obvious optimization effect has been obtained.