The practical use of Ill-posed theory: Improved dynamic subcarrier coordinated interleaving OFDM system with pre-equalization

The ultimate goal of the security of wireless communication is to ensure the normal communication of legitimate receivers and prevent the eavesdroppers from the information interception. In this paper, based on the ill-posed theory, we present a novel pre-equalization aided scheme to improve the performance of dynamic subcarrier coordinated interleaving orthogonal frequency division multiplexing (DSCI-OFDM) system. We firstly build up the mathematical model based on the ill-posed theory, which translates the randomized signal transmission into solving ill-posed equation. Then we derive the equivalent channel for the legitimate receivers and eavesdroppers respectively. Further, we present a novel pre-equalization scheme combining the feedback channel information with OFDM modulation in the transmitter. The channel estimation error is removed and hence with our scheme, the symbol error rate (SER) performance is improved for the legitimate users. Simulations are performed to compare the SER and security performance of the proposed scheme and DSCI-OFDM system. It is demonstrated that this practical use of ill-posed theory improves the SER performance for the OFDM system, and enhance the security of DSCI-OFDM system with the proposed pre-equalization scheme.