Impact of channel estimation error on secure transmission design

In this paper, we investigate the secure transmission design with practical assumptions on the channel state information (CSI). Specifically, the CSI of the legitimate link is imperfectly estimated and the CSI of the eavesdropper is unknown to the legitimate users. We derive both a fixed-rate and an adaptive-rate transmission schemes by explicitly considering the rate parameters of the wiretap code in the secure transmission design. The derived schemes achieve the maximum throughput subject to constraints on the secrecy performance against eavesdropping and the reliability performance against channel estimation error. For a given target throughput requirement, our numerical results illustrate how the security performance needs to be compromised when the accuracy of channel estimation reduces. One interesting finding is that the security cost of having a small amount of channel estimation error is low, while the security cost increases fast when the channel estimation error becomes considerable.