enables transmission of more data than FDM over the same fixed bandwidth. Resistance against fading and interference: OFDM is relatively robust against interference since it usually affects only a fraction of the sub-carriers. Frequency-selective fading on the other hand can affect each subcarrier's performance. However, since the bandwidth of each subcarrier is small, the performance loss of these sub-carriers can be accommodated with efficient coding. OFDM facilitates coding and interleaving across sub-carriers in the frequency domain that can provide robustness against burst errors. Reduced Computational Complexity: The FFT and IFFT reduce the modem complexity and the processing requirements grow only slightly higher than linearly with data rate or bandwidth. With the FFT, the number of operations in each OFDM symbol is in the order of N log2 N. The implementation complexity of single carrier systems with an equalizer is at least NLe, where Le is the number of taps in the equalizer. Modulation and Coding: OFDM allows different modulation and coding schemes for each subcarrier. This capability improves the end-user performance in comparison to when only one modulation and one or few code rates are used. OFDM is well suited for adaptive modulation and coding, which allows the system to make the best of the available channel conditions. 2.5 OFDM Impairments and Potential Remedies This section will look into various impairments of the OFDM systems including frequency and phase offsets, channel estimations, phase noise, High PAPR (peak to average power ratio), and SO on [2,4,5,8]. 2.5.1 Frequency Offset In communication systems a local oscillator (LO) and a mixer are used at the transmitter to convert lower frequencies onto a higher frequency carrier. The receiver reverses the operation to extract the lower frequency content. If the LOs at both ends do not use the exact same frequency, the result will be an offset in the frequency. Frequency synchronization in OFDM is carried out in two phases, namely acquisition a