Analysis of Frequency Offset Effect on PRACH in 5G NR Systems

Abstract

Physical Random Access Channel (PRACH) in 5G new radio (NR) systems transmits random access preamble for the user equipment (UE) to access the network. In 5G NR systems, Zadoff-Chu (ZC) sequences are used as random access preamble sequences. Frequency offset severely affects the perfect autocorrelation properties of the preamble sequences, thereby affecting the preamble detection performance and timing accuracy. In this paper, frequency offset effect on PRACH preamble miss detection rate and timing error in 5G NR systems is analyzed. Firstly, the frequency offset effect on inter-carrier interference and the correlation of general sequences is derived. Then, based on the former derivation and characteristics of ZC sequences, the frequency offset effect on correlation of ZC sequences is derived. Moreover, PRACH preamble miss detection rate and timing error are analyzed. The analytical results show that for different random access UEs with different PRACH preamble numbers, the random access performances are differently affected by the same frequency offset. Besides, the higher miss detection rate, the smaller timing error. The simulation results show the rationality of the analysis.