Secure OFDM with Peak-to-Average Power Ratio Reduction Using the Spectral Phase of Chaotic Signals

In this paper, a new physical layer security technique is proposed for Orthogonal Frequency Division Multiplexing (OFDM) communication systems. The security is achieved by modifying the OFDM symbols using the phase information of chaos in the frequency spectrum. In addition, this scheme reduces the Peak to Average Power Ratio (PAPR), which is one of the major drawbacks of OFDM. The Selected Mapping (SLM) technique for PAPR reduction is employed to exploit the random characteristics of chaotic sequences. The reduction with this algorithm is shown to be similar to that of other SLM schemes, but it has lower computational complexity and side information does not have to be sent to the receiver. The security of this technique stems from the noise like behavior of chaotic sequences and their dependence on the initial conditions of the chaotic generator (which are used as the key). Even a slight difference in the initial conditions will result in a different phase sequence, which prevents an eavesdropper from recovering the transmitted OFDM symbols.

Peak to Average Power Ratio Reduction Techniques

Multiple-input to multiple-output (MIMO) and orthogonal frequency division multiplexing (OFDM) are the utmost widely used wireless communication system because of its large benefits and advantageous. Though MIMO OFDM systems have high advantages there is a major drawback that makes the system noisy and the inefficient use of bandwidth. This drawback mainly occurred due to the spikes in the transmitting signal. These spikes make the value of peak to average power ratio of the signal high and results in distortion and noise in the signal. To avoid these spikes there are number of techniques introduced. We will discuss about the three methods namely partial transmit sequence, clipping and filtering method, Selective Mapping technique. All these methods are used to decrease the high peak to the average ratio by removing the spikes in the signal. And we will see the outputs obtained by using MATLAB software. Clipping and filtering technique would be the simplest technique to lower the peak to average power ratio while partial transmit technique is the most efficient method to diminish the peak to the average power ratio.