Youhong Feng

Robust Cooperative Secure Beamforming for Simultaneous Wireless Information and Power Transfer in Amplify-and-Forward Relay Networks

In this paper, we investigate cooperative secure beamforming for simultaneous wireless information and power transfer (SWIPT) in amplify-and-forward (AF) relay networks. We propose a joint cooperative beamforming (CB) and energy signal (CB-ES) scheme for providing both secure communication and efficient wireless energy transfer. By considering colluding eavesdroppers with imperfect channel state information (CSI), we formulate an optimization problem for maximizing the secrecy rate between the source and the legitimate information receiver (IR) under both the power constraints at the relays and the wireless power transfer constraint at the energy-harvesting receiver (ER). Since such a problem is nonconvex and hard to tackle, we propose a two-level optimization approach that involves a 1-D search and the semidefinite relaxation (SDR) technique to solve this problem. The proposed robust scheme is compared with some other nonrobust schemes, such as a CB and artificial noise (CB-AN) scheme and a perfect scheme. Simulation results show that the proposed robust scheme achieves better worst-case secrecy rate performance than the other nonrobust schemes and the CB-AN scheme, while it approaches the perfect scheme.

Temporally and spatially correlated uplink channel estimation for massive MIMO systems

It is well known that most wireless channels are sparse. The channel impulse responses (CIRs) of certain size antenna array have a partially shared support due to the spatial correlation. Moreover, the CIRs during adjacent symbols have a common support due to the temporal correlation. In this paper, we propose a novel compressed channel estimation scheme for the uplink massive multi-input multi-out (MIMO) systems based on the assumption of time division duplexing (TDD) mode by exploiting the above mentioned temporal and spatial correlations. Then a joint subspace pursuit (JSP) algorithm is proposed. Simulation results demonstrate the proposed scheme using the JSP algorithm outperforms the classical channel estimation techniques.

Physical layer security enhancement in multi-user multi-full-duplex-relay networks

We propose a novel joint user and full-duplex (FD) relay selection (JUFDRS) scheme to enhance physical layer security in a multi-user multi-relay network. In this scheme, the user and the FD decode-and-forward relay are selected such that the capacity of the end-to-end user-relay-destination channel is maximized to ensure the highest quality of cooperative transmission. To fully examine the benefits of the JUFDRS scheme, we derive a new closed-form expression for the secrecy outage probability. We show that the JUFDRS scheme significantly outperforms the joint user and half-duplex relay selection (JUHDRS) scheme when the self-interference at the FD relay can be reasonably suppressed. This result indicates that adopting the FD technique at relays can effectively enhance the physical layer secrecy performance in the multi-user multi-relay network.

Performance analysis of a novel uplink cooperative NOMA system with full-duplex relaying

In this study, the authors examine the performance of an uplink non-orthogonal multiple access (NOMA) system with cooperative full-duplex relaying (CFR-NOMA), where the user closer to the base station (BS) is considered as a full-duplex relay to aid the transmission from the other user to the BS. The closer user first decodes the signals transmitted from the far user and then forwards them using superposition coding to the BS on top of transmitting its own information signals to the BS. First, they analyse the performance of the CFR-NOMA system in terms of the outage probability and average sum rate. Then, they analytically obtain the optimal power allocation coefficients that minimise the outage probability. They also study the optimal power allocation to maximise the average sum rate under specified constraints. Their examination demonstrates that the CFR-NOMA system can significantly outperform the uplink conventional orthogonal multiple access and uplink NOMA with half-duplex relaying system in terms of achieving a lower outage probability or a higher average sum rate.

TAS-Based Incremental Hybrid Decode–Amplify–Forward Relaying for Physical Layer Security Enhancement

In this paper, a transmit antenna selection (TAS)-based incremental hybrid decode–amplify–forward (IHDAF) scheme is proposed to enhance physical layer security in cooperative relay networks. Specifically, TAS is adopted at the source in order to reduce the feedback overhead. In the proposed TAS-based IHDAF scheme, the network transmits signals to the destination adaptive select direction transmission (DT) mode, AF mode, or DF mode depending on the capacity of the source-relay link and source-relay link. In order to fully examine the benefits of the proposed TAS-based IHDAF scheme, we first derive its secrecy outage probability (SOP) in a closed-form expression. We then conduct asymptotic analysis on the SOP, which reveals the secrecy performance floor of the proposed TAS-based IHDAF scheme when no channel state information is available at the source. Theoretical analysis and simulation results demonstrate that the proposed TAS-based IHDAF scheme outperforms the selective decode-and-forward, the incremental decode-and-forward, and the noncooperative DT schemes in terms of the SOP and effective secrecy throughout, especially when the relay is close to the destination. Furthermore, the proposed TAS-based IHDAF scheme offer a good tradeoff between complexity and performance compared with using all antennas at the source.