in this paper, we consider a cooperative cognitive radio network in which there is an ofdm primary link and multiple single carrier secondary links.the primary link is required to maintain its secrecy rate above a predefined threshold. if the secrecy rate requirement is not satisfied, the secondary system help primary link to maintain its secrecy rate requirement. in doing so, the secondary trans...

We consider a class of Gaussian layered networks where a source communicates with a destination through L intermediate relay layers with N nodes in each layer in the presence of a single eavesdropper which can overhear the transmissions of the nodes in any one layer. The problem of maximum secrecy rate achievable with analog network coding for a unicast communication over such layered wireless ...

In this work, a class of information theoretic secrecy problems is addressed where the eavesdropper channel states are completely unknown to the legitimate parties. In particular, MIMO wiretap channel models are considered where the channel of the eavesdropper is arbitrarily varying over time. Assuming that the number of antennas of the eavesdropper is limited, the secrecy rate of the MIMO wire...

In this work, a multiple-input single-output (MISO) simultaneous wireless information and power transfer (SWIPT) system including one base station (BS) equipped with multiple antennas, one desired single-antenna information receiver (IR) and N (N > 1) single-antenna energy-harvesting receivers (ERs) is considered. Assuming that the information signal to the desired IR may be eavesdropped by ERs...

This paper considers secrecy enhancement mechanisms in visible light communication (VLC) systems with spatially distributed passive eavesdroppers (EDs) under the assumption that there are multiple LED transmitters and one legitimate receiver (UE). Based on certain amplitude constraints, we propose an optimal beamforming scheme to optimize secrecy performance. Contrary to the case where null-ste...

We investigate the secure communications over correlated wiretap Rayleigh fading channels assuming the full channel state information (CSI) available. Based on the information theoretic formulation, we derive closed-form expressions for the average secrecy capacity and the outage probability. Simulation results confirm our analytical expressions.

Wyner’s results for discrete memoryless wire-tap channels are extended to the Gaussian wire-tap channel. It is shown that the secrecy capacity C, is the difference between tbe capacit ies of the main and wire-tap channels. It is further shown tbat Rd= C, is the upper boundary of the achievable rate-equivocation region.