Enhancement of transmission security for OFDM based systems

Abstract

High level of security is essential in wireless communications multimedia applications. The last few years there has been an increase in research interest in the potential of the radio channel's physical properties to provide communications security. These research efforts investigate fading, interference, and path diversity to develop security techniques for implementation in wireless systems. In this paper, we propose an enhancement to existing physical layer security schemes, taking advantage of the characteristics of the OFDM technique. An OFDM symbol includes the pilot sub-carriers, essential for the pilot channel estimation process performed at the legitimate receiver. In this work we propose the positions of the sub-carriers to change on every OFDM symbol following a probability distribution known only to the legitimate transmitter and legitimate receiver. An eavesdropper receiver, does not have access to the information of the pilot sub-carriers positions so, it performs blind channel estimation. The theoretical analysis is based on the information theoretic problem formulation and is confirmed by simulations. The performance metrics used are the secrecy capacity, the outage probability, the channel mean square error and the bit error rate. The proposed scheme is very simple and robust, strengthening security in multimedia applications.