On design of physical random access channel in high-speed railway LTE systems  

作　　者：Gang Wu Hang Yuan Wei Guo Su Hu Shaoqian Li 

机构地区：[1]National Key Laboratory of Science and Technology on Communications,University of Electronic Science and Technology of China

出　　处：《Chinese Science Bulletin》2014年第35期5042-5050,共9页

基　　金：supported by National Natural Science Foundation of China(61032002,61101090 and 61471100)

摘　　要：For the uplink in the long-term evolution(LTE)systems,the physical random access channel(PRACH)adopts Zadoff–Chu(ZC) sequences as preamble sequences,and each user can choose a unique cyclic shift for user identification.In high-mobility scenario,the Doppler frequency shift raises up the false alarm probability by inducing the correlation peak offsetting at the receiver side.Traditional detection method utilizes multiple search windows for searching the potential uplink users.When the Doppler frequency shift is larger than the subcarrier spacing,the energy of correlation peak leaks outside the search window and increases the false alarm probability.In this paper,we present a novel design for PRACH preamble sequence for high-speed railway scenario.Through numerical observation,we find out that the offset of the correlation peaks only depends on the initial root sequence number and the length of ZC sequences.Therefore,the root number of ZC sequences should be carefully designed to generate a preamble sequence to fight against the Doppler frequency shift.Consequently,those offsets of the correlation peaks are concentrated within a single search window,resulting in lower complexity of detection and lower probability of false alarm for random access in LTE uplink.For the uplink in the long-term evolution （LTE） systems, the physical random access channel （PRACH） adopts Zadoff-Chu （ZC） sequences as preamble sequences, and each user can choose a unique cyclic shift for user identification. In high-mobility scenario, the Doppler fre- quency shift raises up the false alarm probability by inducing the correlation peak offsetting at the receiver side. Traditional detection method utilizes multiple search win- dows for searching the potential uplink users. When the Doppler frequency shift is larger than the subcarrier spac- ing, the energy of correlation peak leaks outside the search window and increases the false alarm probability. In this paper, we present a novel design for PRACH preamble sequence for high-speed railway scenario. Through numerical observation, we find out that the offset of the correlation peaks only depends on the initial root sequence number and the length of ZC sequences. Therefore, the root number of ZC sequences should be carefully designed to generate a preamble sequence to fight against the Doppler frequency shift. Consequently, those offsets of the corre- lation peaks are concentrated within a single search win- dow, resulting in lower complexity of detection and lower probability of false alarm for random access in LTE uplink.

关 键 词：随机接入信道 高速铁路 LTE 设计 系统 物理 多普勒频移 频率偏移 

分 类 号：TN929.5[电子电信—通信与信息系统]