Where an is the data symbol on the n-th subcarrier. Equation (1) is equivalent to the N-point inverse discrete Fourier transform (IDFT). The subcarrier spacing and frequencies are carefully selected to achieve subcarrier orthogonality.1/T ∫_0^T▒〖x(t) y(t) dt =0〗 (2) The equation (2) means that the signals are not correlated, that is, they are two different and independent signals. In OFDM, sinc-shaped pulses are used as subcarrier spectra. According to the properties of sinusoidal pulses, zero crossings occur at multiples of 1/T. Using sinusoidal pulses and fi selection of the subcarrier center frequency with equation (3) ensures that subcarrier orthogonality is maintained.f_i= f_c + i/T i= (-N)/2……N/2 (3)Where fc is the center frequency of the channel and N is the number of subchannels. This way, each subcarrier has the maximum at its own center frequency and zero at the center frequency of the other subcarrier.Fig.2. OFDM Transmitter ModelAfter the series-to-parallel conversion, the inverse discrete Fourier transform (IDFT) is applied to each flow. In practice, this transformation can be implemented very efficiently by the inverse fast Fourier transform (IFFT). This is equivalent to a transition from the frequency domain to the time domain. After IFFT, all parallel data are summed and transmitted. CHALLENGES OF USING OFDM One of the major problems of the OFDM system is the high peak power to average power ratio (PAPR) that occurs in the modulated signal. High PAPR occurs when the signal in the subchannels adds constructively in phase. Due to modulation, high peaks are produced. Once several sinusoids, which are in phase, are added together to form high multicarrier signal peaks, they are generated. On the other hand, the region ...... middle of paper ....... However, this solution decreases the energy efficiency of the PA. On the other hand, the PAPR reduction technique offers a more energy-efficient solution. POWER AMPLIFIER REDUCTION OPERATION In order to ensure that the PA operates within its linear region, the input signal is attenuated and said to be in power reduction mode. This power reduction application results in an increase in the power specifications of the AP. As a result, the PA design is oversized, resulting in reduced energy efficiency. This is the main reason why power reduction is limited to applications where low PA efficiency requirements are required. The quantities used to measure the level of power reduction are: input power reduction (IPBO) and output power reduction (OPBO). They are defined by equations (4) and (5).IPBO=10 〖log〗_(10) P_(i,sat)/P_i (4)