Nam-Phong Nguyen

Secure 5G Wireless Communications: A Joint Relay Selection and Wireless Power Transfer Approach

In this paper, we investigate the secrecy performance of an energy harvesting relay system, where a legitimate source communicates with a legitimate destination via the assistance of multiple trusted relays. In the considered system, the source and relays deploy the time-switching-based radio frequency energy harvesting technique to harvest energy from a multi-antenna beacon. Different antenna selection and relay selection schemes are applied to enhance the security of the system. Specifically, two relay selection schemes based on the partial and full knowledge of channel state information, i.e., optimal relay selection and partial relay selection, and two antenna selection schemes for harvesting energy at source and relays, i.e., maximizing energy harvesting channel for the source and maximizing energy harvesting channel for the selected relay, are proposed. The exact and asymptotic expressions of secrecy outage probability in these schemes are derived. We demonstrate that applying relay selection approaches in the considered energy harvesting system can enhance the security performance. In particular, optimal relay selection scheme outperforms partial relay selection scheme and achieves full secrecy diversity order, regardless of energy harvesting scenarios.

Secure Full-Duplex Small-Cell Networks in a Spectrum Sharing Environment

In this paper, we propose three relay selection schemes for full-duplex heterogeneous networks in the presence of multiple cognitive radio eavesdroppers. In this setup, the cognitive small-cell nodes (secondary network) can share the spectrum licensed to the macro-cell system (primary network) on the condition that the quality-of-service of the primary network is always satisfied subjected to its outage probability constraint. The messages are delivered from one small-cell base station to the destination with the help of full-duplex small-cell base stations, which act as relay nodes. Based on the availability of the networks channel state information at the secondary information source, three different selection criteria for full-duplex relays, namely: 1) partial relay selection; 2) optimal relay selection; and 3) minimal self-interference relay selection, are proposed. We derive the exact closed-form and asymptotic expressions of the secrecy outage probability for the three criteria under the attack of non-colluding/colluding eavesdroppers. We demonstrate that the optimal relay selection scheme outperforms the partial relay selection and minimal self-interference relay selection schemes at the expense of acquiring full channel state information knowledge. In addition, increasing the number of the full-duplex small-cell base stations can improve the security performance. At the illegitimate side, deploying colluding eavesdroppers and increasing the number of eavesdroppers put the confidential information at a greater risk. Besides, the transmit power and the desire outage probability of the primary network have great influences on the secrecy outage probability of the secondary network.

Secure Cooperative Half-Duplex Cognitive Radio Networks With

In this paper, we study the secrecy performance of a half-duplex cognitive relay network in the presence of multiple eavesdroppers and multiple primary users. In particular, generic

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-th Best Relay Selection

th best relay selection schemes for opportunistic relay selection (ORS) and partial relay selection (PRS) are proposed. Exact closed-form and asymptotic expressions for secrecy outage probability (SOP) of the considered schemes are derived. The outcome shows that ORS is able to achieve full secrecy diversity order while PRS obtains unit diversity order. Besides, the order of the selected relay is proved to affect the secrecy diversity order in the ORS scheme but not the PRS scheme, while the number of primary users does not have influence on the diversity order. Additionally, the significance of the change in the number of relays on the SOP enhances at higher orders of selected relay. Nevertheless, increasing the number of eavesdroppers reduces the secrecy diversity gain of the considered system in both schemes.

Impact of primary networks on the performance of energy harvesting cognitive radio networks

In this paper, we investigate the effect of of the primary network on the secondary network when harvesting energy in cognitive radio in the presence of multiple power beacons and multiple secondary transmitters. In particular, the influence of the primary transmitters transmit power on the energy harvesting secondary network is examined by studying two scenarios of primary transmitters location, i.e., the primary transmitters location is near to the secondary network and the primary transmitters location is far from the secondary network. In the scenario where the primary transmitter locates near to the secondary network, although secondary transmitter can be benefit from the harvested energy from the primary transmitter, the interference caused by the primary transmitter suppresses the secondary network performance. Meanwhile, in both scenarios, despite the fact that the transmit power of the secondary transmitter can be improved by the support of powerful power beacons, the peak interference constraint at the primary receiver limits this advantage. In addition, the deployment of multiple power beacons and multiple secondary transmitters can improve the performance of the secondary network. The analytical expressions of the outage probability of the secondary network in the two scenarios are also provided and verified by numerical simulations.

Outage probability of full-duplex cognitive relay networks with partial relay selection

This paper investigates the outage performance of full duplex cognitive radio networks. We consider that a dual-hop system with multiple decode-and-forward (DF) relays. We assume that there is no direct link between secondary source terminal (S) and destination (D), and self-interference exists at the relays. All the links are independent identically distributed (IID) Rayleigh distributed. In order to analysis the outage performance, the exact closed-form expression of the outage probability is derived. Then we do simulations in different conditions to corroborate our theoretical analyses. Our results show that the system outperforms when the relay (R) is close to D and P is far away S.

Secure communications in cognitive underlay networks over Nakagami-m channel

Abstract In this paper, the secure communication of a cognitive radio network (CRN) over Nakagami- m fading channel is investigated. An underlay protocol is used in the considered network, where the unlicensed users or secondary users (SUs) can operate simultaneously with the primary users (PUs) in the same spectrum bands providing that the transmit power of the SUs is constrained by not only the maximum tolerance interference at the PU’s receiver but also the maximum transmit power at the SU’s transmitter. The exact closed-form expressions of important secure performance metrics, i.e., secrecy outage probability (SOP) and secrecy capacity (SC), are derived. In addition, to give a deep insight into the secure performance trends, the asymptotic expression of the SOP is also obtained when the average signal-to-noise ratio (SNR) of the legitimate channel is high. It is proven that the considered system achieves full diversity gain regardless of the number of antennas at the eavesdropper. Finally, the correctness of our mathematical framework is verified by Monte Carlo simulations.

Secure Energy Harvesting Communications with Relay Selection over Nakagami-m Fading Channels

In this paper, an energy harvesting relay network over Nakagami-m fading is investigated. In the considered system, the power beacon can provide wireless energy for the source and relays which deploy time-switching-based radio frequency energy harvesting technique. Two relay selection schemes, namely partial relay selection and optimal relay selection, are proposed in order to enhance the system performance. In the former, the source only has the channel state information of the first hop, while in the latter it has the full knowledge of the channel state information. The eavesdropper is able to wiretap to the signal transmitted from the source and the relays. The exact closed-form expressions of secrecy outage probability are derived. The results show that optimal relay selection performs better than partial relay selection. With increasing number of relays, the considered system shows better performance. In addition, the energy harvesting duration has a significant effect on the secrecy outage probability.

Chaos-based spread-spectrum using M-ary PSK and OFDM-MIMO

This paper proposes a chaos-based direct-sequence spread-spectrum (CDSSS) communication system using M-ary PSK modulation in combination with MIMO-OFDM technique. This combination aims at improving the performance as well as capacity of the conventional CDSSS systems over multipath fading channels. In the transmitter, the data is modulated by an M-PSK modulator whose output is fed to a MIMO encoder. Two resulting signals are spread by directly multiplying with chaos-NRZ sequences and then put into the corresponding OFDM modulators. The output signals are transmitted through a multipath fading channel using multiple transmitting and receiving antennas. In the receiver, beside the use of OFDM demodulation, chaotic despread-spectrum, and M-PSK demodulation, a V-BLAST algorithm with Minimum mean squared error (MMSE) equalization is applied to decode and recover the data. Schemes for the transmitter and receiver are described in detail and their BER performance over the multipath Rayleigh fading channel is evaluated by means of numerical simulations. The obtained results prove that the performance and capacity of the proposed system are significantly enhanced and can be adjusted by changing the values of M-ary level, spreading factor or the number of used antennas.