Open nature of wireless networks leads to being sensitive to eavesdropping. Hence, a tremendous growth of literature has carried out challenges in privacy and security in wireless networks. Conventional techniques would be highly susceptible to technological imperfections, over-exposed to eavesdroppers and dependent on complicated mathematics, leading to failure for deploying secure transmission wireless channels. In this study, we have significantly boosted the performance of the physical layer security in the 5G downlink transmission system by implementing the Orthogonal Frequency Division Multiplexing (OFDM) technique twice in the wiretap channel. We have fully compared the performance of exploiting the OFDM technique twice in the wiretap channel with its counterpart available approach with the one OFDM technique. This study has a major contribution to compare the performance of the two aforementioned techniques in terms of the secrecy capacity, the success rate of an eavesdropper, and the OFDM-modulation efficiency. The simulation results have verified that an extreme security rate and a very low success rate for the eavesdropper in the proposed technique. In addition, we have confirmed that the OFDM-64-QAM3/4 technique shows the ultimate performance in terms of a smaller number of errors, less value of BERs, and high rate modulation compared to the other modulation techniques. In the following, we have represented the simulation results of the active user throughput for the further evaluation of the proposed channel model.