A General Framework of Wiretap Channel With Helping Interference and State Information

This paper considers a general framework of the wiretap channel with helping interference and state information (WT-HI-SI), where a transmitter-receiver pair wishes to keep the message secret from a passive eavesdropper in the presence of an interferer and a random state. The interferer is to help the legitimate transceivers to enhance their security level, and the state information is available at the transmitter, but not at the eavesdropper. For the discrete memoryless WT-HI-SI, an achievable scheme is proposed by combining the noise forward scheme and the double binning coding scheme. Some previously proposed schemes can be viewed as special cases of the proposed scheme. Then, the achievable scheme is applied to two special channels, the Gaussian WT-HI-SI and the Gaussian WT-HI, respectively. For the Gaussian WT-HI-SI, there exists an external random state noncausally available to the transmitter in advance. But for the Gaussian WT-HI, there does not exist any external random state. In this case, we propose a novel achievable scheme that requires the transmitter to artificially generate the random state whose power can be adjusted adaptively according to dynamic channel conditions. Both the analytic and numerical results are provided to demonstrate that the use of the state information can generally improve the secrecy performance. A more important contribution of this paper is that even for the scenario where no external state information is available to the transmitter, the proposed scheme with the artificial state can still achieve a strictly larger secrecy rate in comparison with existing interference assisted schemes.