An Efficient Approach for Squared Crest Factor Reduction in Ofdm Systems Using Tone Reservation with Customized Convex Optimization

Orthogonal frequency-division multiplexing (OFDM) is a method of encoding digital data on multiple carrier frequencies. This scheme uses a number of sub-carriers and converts a frequency selective fading channel to a set of parallel flat fading channels. The OFDM signal is having a drawback that some signal values can be much higher than the average value. This results in high Squared Crest Factor (SCF). This paper deal with the Tone Reservation (TR) technique for reducing SCF. In this scheme few subcarriers are reserved to reduce the peak signal. These reserved carriers are called as Peak Reduction Carriers (PRCs) and these PRCs are used to reduce the SCF of the original signal. Similarly the Bit Error Rate also gets lowered. In contrast to previous methods, the TR method with Customized Convex Optimization implies a very quick convergence of minimum SCF and the bit error rate solution at a lower computational cost. The proposed method is compared with the SCF reduction techniques like Differential Scaling. The proposed OFDM system also discusses about the effects of oversampling at different rates.