Yayan Ma

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In cognitive radio networks, security against eavesdroppers is a critical issue. In this paper, we consider a scenario in which the primary transmitter selects one secondary transmitter to act as a relay to enhance the security of communication. And as a reward the primary transmitter allows the selected secondary transmitter to access its spectrum. We(More)
We consider the relay-eavesdropper channel with generalized feedback at the source node. In the presence of a wire-tapper, the source can send confidential messages to an intended receiver with the help of the trusted relay. With a generalized feedback from the relay to the source node, the cooperation between the source node and relay node may be enhanced.(More)
Cooperative relay is considered as an efficient scheme to improve the physical layer security of a wireless relay system in the presence of eavesdroppers. In this paper, multiple-level relay scheme is proposed. We consider relay weight design for secrecy rate maximization subject to a power constraint. The results show that a higher achievable secrecy rate(More)
We consider single-user OFDM wiretap channel with an external cooperative jammer (CJ), where the CJ helps the destination to interfere the eavesdropper. The achievable secrecy rate is derived. The source power and CJ power are optimized over all sub-carriers to maximize the sum secrecy rate under a total system power constraint. The simulation results(More)
In this paper, the optimization problem of the multiple-hop relay channel with linear relaying is discussed. The capacity for the multiple-hop Gaussian relay channel with linear relaying is derived, which can be formulated as an optimization problem over the relaying matrices and the covariance matrix of the signals transmitted at the source. It is proved(More)
In this paper, the optimization problem of the two-hop relay channel with linear relaying is discussed. The expression of the capacity for the Gaussian two-hop relay channel with linear relaying is shown, which is an optimization problem over the relaying function and the covariance matrix of the signals transmitted by the source node. We show that the(More)
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