Secrecy rate of channel-aware randomized secure transmission schemes in multicarrier systems

In this paper, we study channel-aware (CA) randomization for secure transmissions in a multicarrier system based on partial channel state information (CSI). In order to see the performance gain by CA randomization, we consider the secrecy rate and show that i) a positive secrecy rate can be obtained even if the channel to an adversary is stochastically more capable than the channel to a legitimate receiver and ii) the normalized secrecy rate can increase with the number of subcarriers. More importantly, it is shown that there is an additional gain due to CA randomization that allows a growth rate of the normalized secrecy faster than linear.