Research On Physical Layer Security Of Feedback Channel

The wiretap channel with noiseless feedback is an important model in the research of physical layer security in modern communication systems.Ahlswede and Cai first proposed the model and proved that if the legitimate receiver transmits its channel output to the sender through a noiseless feedback channel,the secrecy capacity of the wiretap channel can be improved.The basic principle of most current feedback coding schemes is to generate a key to encrypt a private message by feedback,because the eavesdropper cannot obtain the channel output of the legitimate recipient,so the key is known only to the legitimate recipient and the eavesdropper does not know,thus ensuring private message is not stolen by eavesdropper.When the channel noise between the sender and the eavesdropper is less than the channel noise from the sender to the legitimate recipient,the basic wiretap channel secrecy capacity is zero.Ahlswede and Cai have demonstrated that when the channel noise between the sender and the eavesdropper is less than the channel noise from the sender to the legitimate receiver,the secrecy rate obtained using the existing feedback coding scheme is larger than secrecy capacity of the basic wiretap channel.In order to make full use of the feedback,this paper proposes a new feedback coding scheme based on the existing feedback coding scheme and the lossy compression with side information.In this scheme,feedback is used not only to generate a key to encrypt a private message,but also to generate an update information to help legitimate recipient to better decode.According to the new feedback coding scheme,the basic wiretap channel with noiseless feedback is first studied.It is found that when the channel noise between the sender and the eavesdropper is smaller than the channel noise from the sender to the legitimate receiver,the secrecy rate obtained using the new feedback coding scheme is larger than that of Ahlswede and Cai,which is verified by rigorous proof and a binary example.Then the broadcast channel with private message and noiseless feedback is studied.It is found that when the channel noise between the sender and the eavesdropper is smaller than the channel noise from the sender to the legitimate receiver and the rate of the common message is small,the secrecy rate of private message using the new feedback coding scheme is larger than that of Ahlswede and Cai,which is proved by rigorous proof and a binary example.Finally,the finite state Markov wiretap channel with delay feedback is studied.It is found that when the channel noise between the sender and the eavesdropper is smaller than the channel noise from the sender to the legitimate receiver,the secrecy rate of private message using the new feedback coding scheme is larger than that of Dai et al.,which is proved by rigorous proof and a Gaussian channel example.