Abstract: With the introduction of 5G wireless technology, mankind has achieved a massive leap in data throughput of gigabits per second thanks to the combination of multiple input, multiple output, and orthogonal frequency division multiplexing technologies. Multiple (OFDM MIMO) can be achieved via frequency selective fading. PAPR (Peak-to-Average Power Ratio) is one of the most crucial performance concerns, since it makes OFDM particularly prone to harmonic distortion, reducing channel estimate accuracy and resulting in a lower bit error rate (BER). In the MIMO-OFDM system, we present a selective codeword shift mapping approach (SCS-SLM). It lowers the PAPR and forces the power amplifier to operate in the non-linear region, resulting in sub-carrier intermodulation, signal constellation, bit error rate distortion, and improved system performance. Additionally, using orthogonal frequency division multiplexing with space-time-frequency block code (STFBC OFDM) may increase BER performance. Selective Mapping is mentioned in this research as an effective approach for reducing PAPR. Furthermore, the bit error rate performance of this system is reviewed, as well as the process complexity as a result. A complete examination of the mutual independence of the alternative OFDM signals generated using this technique is also discussed, in addition to the previously mentioned analysis. Furthermore, the superfluous bits on the side of the transmitted OFDM signal are removed with this new technique. Keywords: (peak-average power ratio (PAPR), Multiple-input, multiple-output & orthogonal frequency-division multiplexing (MIMO-OFDM), space-time frequency block codes (STFBC), Selective Codeword Shift Selective mapping (SCS-SLM)