Aiming at the shortcomings of the heavy computational complexity in existing random access preamble algorithm

a 5G random access preamble detection algorithm is proposed. First

the received signal is processed by the inverse process of the transmitting end to obtain a frequency domain preamble. Then a frequency domain ZC sequence is generated and grouped

and the ZC sequences in each group are correlated with the frequency domain preamble. Finally

the threshold is detected by setting a threshold. The sequence uses a multi-antenna diversity combing to modify the Cumulative Distribution Function（CDF） of the relative threshold

and determines an absolute detection threshold. The threshold is a product of the relative detection threshold and the time-varying noise level

based on the relative detection threshold. The simulation results show that compared with the frequency domain fixed threshold preamble detection algorithm

the correct detection probability performance of the proposed algorithm is improved by 1dB in the Additive White Gaussian Noise（AWGN） channel. In the Tapped Delay Line（TDLC300-100） channel

the correct detection probability performance of the proposed algorithm is improved by 2dB.