Rugui Yao

Optimal power allocation for achievable secrecy rate in an untrusted relay network with bounded channel estimation error

The objective of this paper is to maximize the secrecy rate in an untrusted relay network with imperfect channel state information (CSI). Considering bounded channel estimation error in cooperative jamming network, we optimize the power allocation for confidential and jamming signals to maximize the instantaneous secrecy rate. The upper and lower bounds of achievable secrecy rate are analyzed. The ergodic secrecy rate (ESR) is further derived to evaluate the maximum average secrecy rate. And the optimal power allocation is also studied based on ESR. Numerical results show optimal power allocation can increase both instantaneous secrecy rate and ESR, and at higher SNR, the impact of channel estimation error can be neglected for the maximum ESR, which is asymptotically approaches to the upper bound.

Optimal Power Allocation in an Amplify-and-Forward Untrusted Relay Network with Imperfect Channel State Information

The characteristics of the wireless medium create difficulty to shield the data transmission from unauthorized recipients. In this paper, power optimization in an amplify-and-forward untrusted relay network is presented, using cooperative jamming transmission to prevent the untrusted relay from intercepting the confidential signals. Considering imperfect channel estimation error at the destination, an optimal power allocation (OPA) is designed to maximize the achievable secrecy rate for the network. Simplified OPA is derived for high signal-to-noise ratio regime with imperfect CSI and the ergodic secrecy rate is also analyzed to evaluate the achievable average secrecy rate for different scenarios as a common performance metric. The numerical results show that when the error of CSI is considered, the proposed OPA generates limited and acceptable degradation on the secrecy rate.

Analytical Approximation of the Channel Rate for Massive MIMO System With Large But Finite Number of Antennas

In practical massive multiple-input–multiple-output (MIMO) system, limited transmitted antennas installed at the base station (BS) cannot guarantee the ideal orthogonality and the theoretical channel rate cannot thus be achieved. In this paper, we consider the approximation of channel rate for the configuration of large but finite number of antennas at BS in a massive MIMO system. A perturbation matrix is introduced to model the non-ideal orthogonality. And then, Taylor expansion of determinant is utilized to derive the closed form of the achievable channel rate. The convergence of the Taylor expansion is theoretically proved and simulated. Numerical results show that our calculation of channel rate can get a better approximation compared with the practical rate, especially in the case of high expansion order and large number of antennas.

A novel beamforming to improve secrecy rate in a DAJ based untrusted relay network

Security is a demanding request for wireless networks, with physical layer security the problems in traditional encryption algorithms and key management are vanished. In this paper, a novel beamforming scheme is proposed to improve secrecy rate in an untrusted relay network, where the untrusted relay helps to improve the network coverage area but may act as a potential eavesdroper. A destination-assisted-jamming (DAJ) is used to protect the confidential information against untrusted relays and eavesdroppers. By optimizing beamforming, we align the confidential signal to the equivalent valid signal space and force it to be orthogonal to the cooperative jamming signal space. The correctness and efficiency of the proposed beamforming scheme are validated by numerical simulations.