Research And Implementation Of Physical Random Access For LTE Uplink In High-speed Scene

During the past20years, with the rapid development of Mobile Communication Technology, user demand for high-speed data service has greatly increased. In order to meet user’s needs of the business and deal with other technologies’competitions,3GPP organization launched the research on the next generation mobile communication—The Long Time Evolution (LTE) framework in2004, which determine OFDM technology and MIMO technology as the core technology. It requires that the system has low delay, high rate, high mobility, configured spectrum and other advantages, and ensure that the high speed wireless access can achieve100Mbps for downlink and50Mbps for uplink under20MHz bandwidth.With rapidly revolution of the mobile communications technology, our country’s high-speed railway construction also has a rapid development. With the increase of high-speed railway lines, the importance of mobile communications technology in high mobile environment is more prominent in providing passengers with a more attractive work environment. The LTE system can achieve normal communication in the case of350km/h, even for higher speed such as500km/h it can still work, which has brought the enormous attraction to the railway operators.As the access process before normal transmission between UE and network in uplink or downlink, The Random Access’s performance has a significant effect on the processing of the whole physical layer and the next job of the high-level scheduling. However, random access’s performance is an important guarantee for efficient communication in high mobility scenarios, and it puts forward higher requirements to the entire physical random access layer process. This thesis researches the non-synchronized random access processing in FDD-LTE mode which based on the3GPP physical layer protocol. In the thesis, the existing algorithm is improved and random access algorithm of low-complexity is presented, including low-complexity fast generation algorithm for frequency-domain Zadoff-Chu sequence, the preamble generation algorithm of terminal and the improved mixed time/frequency-domain processing method etc. Effects of high Doppler frequency on detection performance of random access in LTE system is studied, and the use of cyclic shift limit sets are discussed in detail, and the high speed random access detecting is introduced step by step.In this thesis, it is verified that the improved algorithm is correct by a large number of comparisons between FPGA simulation and MATLAB simulation. The feasibility of the proposed algorithm in the FT4000cognitive radio platform is also verified. The results show that, the improved algorithm can meet the system requirements sufficiently.