Network Security Study In Two-Hop Relay Channel With Eavesdropper

Network security as a popular research areas of wireless network communications, its development tends to the actual technology than basis theory. Many researchers are interested in network security based on information theory instead of cryptography, this is not only because of cryptography technology has reached a bottleneck, but also the perspective of information theory,which is about network security,is more reliable and has the potential for sustainable development. According to the previous studies, network security research which is base on information theory mostly applied the gaussian signal. Although the findings are still of great reference value, but considering the discrete signal is mainly transmitted, so the study of network security base of discrete signals is this article focuses.Two-hop security communication with an eavesdropper in wireless environment is the basic model of network research. The basic idea is that the destination, simultaneously with the source, sends a jamming signal to interfere the eavesdropper near to or co-located with the relay,the friendly jamming signal will prevent the eavesdropper from detecting the useful information originated from the source and will not affect the destination on detecting the source information with the presence of the known jamming signal.In this paper we mainly researches the network security based on two-hop relay channel with finite constellations, but in order to fully introduce, we first introduce two-way relay wiretap channel, our research is mainly about the secrecy rate and the upper bound, and the relationship between them. Then, we introduce the Gaussian interference channel,also based on discrete signals,mainly to analyse the link between phase difference and the sum rate base of two-user model. Finally,we investigate the secrecy capacity and derive its upper bound for the two-hop relay model, by assuming an eavesdropper near the relay and the widely used M-PSK modulation. By researching the relationship between phase differences and BER,obtaining the different secrecy rate and its upper bound,then we can enable secrecy rate maximized by setting the transmission power and phase difference. Otherwise,with our upper bound, the best and worst phase differences in high SNR region are then given. It is worthy to say that if applying the Gaussian signal,only can we increase the transmission power to get bigger secrecy rate,but for discrete signal,we can obtain that by changing the phase difference of transmission signal,this is very useful for signal transmission in wiretap channel. Furthermore,numerical studies verify our analysis and show that the derived upper bound is relatively tight.