Abdelhamid Salem

Physical Layer Security With RF Energy Harvesting in AF Multi-Antenna Relaying Networks

In this paper, we analyze the secrecy capacity of a half-duplex energy harvesting (EH)-based multi-antenna amplify-and-forward relay network in the presence of a passive eavesdropper. During the first phase, while the source is in the transmission mode, the legitimate destination transmits an auxiliary artificial noise (AN) signal which has two distinct purposes: 1) to transfer power to the relay and 2) to improve system security. Since the AN is known at the legitimate destination, it is easily cancelled at the intended destination, which is not the case at the eavesdropper. In this respect, we derive new exact analytical expressions for the ergodic secrecy capacity for various well-known EH relaying protocols, namely, time switching relaying (TSR), power splitting relaying (PSR), and ideal relaying receiver (IRR). Monte Carlo simulations are also provided throughout our investigations to validate the analysis. The impacts of some important system parameters, such as EH time, power splitting ratio, relay location, AN power, EH efficiency, and the number of relay antennas, on the system performance are investigated. The results reveal that the PSR protocol generally outperforms the TSR approach in terms of the secrecy capacity.

Improving energy efficiency in dual-hop cooperative PLC relaying systems

Energy efficiency (EE) in multi-hop cooperative communication systems, both wireless and wired, is increasingly becoming more and more critical. This has recently been extended to include power line communications (PLC). In this respect, we propose in this paper to enhance the EE of a dual-hop amplify-and-forward (AF) cooperative relaying PLC system by considering energy-harvesting (EH) at the relay node. The energy harvester exploits the high noisy PLC channel feature as well as the transmitted signal power to forward the source information. In light of this, we derive an analytical expression for the EE and verify it with Monte Carlo simulations. The performance of the conventional relaying system, i.e. without any EH, is also considered to clearly quantify the achievable gains. The results show that the proposed system can considerably improve the EE of PLC systems and that increasing the channel variance will always make the proposed system more energy-efficient.

Wireless Power Transfer in Multi-Pair Two-Way AF Relaying Networks

In this paper, we consider a wireless-powered communication network in which a multiple-antenna two-way AF relay transfers power to multi-pair of single antenna users. A harvest-then-transmit protocol is adopted where the relay first broadcasts wireless power to all the users during a power transfer phase. Multiple pairs of users then use the harvested energy to exchange information through the relay over two phases: up-link and down-link. In the up-link phase, all the users transmit their independent signals to the relay, whereas in the down-link phase, the relay amplifies and forwards the received signals to the intended users. In order to mitigate the interference, zero-forcing reception and transmission is applied at the relay. To characterize system performance, we consider ergodic spectral and energy efficiencies in three different cases based on the knowledge of the channel state information (CSI) at the relay in the power transfer phase, namely: 1) unknown CSI; 2) partially known CSI; and 3) perfectly known CSI. In light of this, new analytical expressions for the ergodic spectral and energy efficiencies are derived for the three cases and Monte Carlo simulations are provided throughout to validate our analysis. The impacts of some important system parameters, such as energy harvesting time, energy harvesting efficiency, number of user-pairs, and relay antennas, on the adopted performance metrics are investigated.

Physical layer security of cooperative relaying power-line communication systems

Power-line communications (PLC) have enabled many smart grid applications over the past years. Secure communications over such channels, however, remains a crucial aspect for the successful realization of smart grids. Many techniques have been proposed in the literature to achieve this and the most recent of which is the adoption of physical layer security for PLC systems. Unlike the existing work, in this paper, we investigate physical layer security of cooperative relaying PLC systems with artificial noise in the presence of an eavesdropper. The system performance is evaluated in terms of the average secrecy capacity. In light of this, we derive a mathematical expression for the average secrecy capacity and validate it with Monte Carlo simulations. Results reveal that the proposed system can significantly enhance the security of PLC systems.

Adaptive Relaying Protocol for Wireless Power Transfer and Information Processing

In this letter, an amplify-and-forward (AF) relaying system is considered, where an energy constrained relay node harvests energy from the received radio frequency signal and uses this harvested energy to AF the source signal to the destination. Based on the time switching (TS) and power splitting (PS) receiver architectures, an adaptive receiving architecture for energy harvesting and information processing is proposed and an adaptive relaying (AR) protocol based on it is developed to enable energy harvesting and information processing at the relay. In light of this, analytical expressions of throughput are derived for both delay-limited transmission and delay-tolerant transmission modes, when the AR protocol is implemented at the relay. Monte Carlo simulations are provided throughout to validate our analysis and the impact of some important system parameters on the adopted performance metric are investigated. In addition, we compare the system performance in terms of the throughput of AR protocol with PS relaying and TS relaying protocols proposed by Nasir et al. Results show that, the AR protocol has a better system performance around the point in which there is a throughput crossover for both PS relaying and TS relaying protocols.

Energy-harvesting in cooperative AF relaying networks over log-normal fading channels

Energy-harvesting (EH) and wireless power transfer are increasingly becoming a promising source of power in future wireless networks and have recently attracted a considerable amount of research, particularly on cooperative two-hop relay networks in Rayleigh fading channels. In contrast, this paper investigates the performance of wireless power transfer based two-hop cooperative relaying systems in indoor channels characterized by log-normal fading. Specifically, two EH protocols are considered here, namely, time switching relaying (TSR) and power splitting relaying (PSR). Our findings include accurate analytical expressions for the ergodic capacity and ergodic outage probability for the two aforementioned protocols. Monte Carlo simulations are used throughout to confirm the accuracy of our analysis. The results show that increasing the channel variance will always provide better ergodic capacity performance. It is also shown that a good selection of the EH time in the TSR protocol, and the power splitting factor in the PTS protocol, is the key to achieve the best system performance.

Performance analysis of secrecy capacity for two hop AF relay networks with zero forcing

In this paper, we analyze the secrecy capacity of a multiple-input multiple-out (MIMO) half duplex amplify-and-forward (AF) relay network in the presence of one passive eavesdropper. Zero forcing (ZF) processing is utilized at various locations to improve the capacity when the eavesdropper is equipped with a single antenna. The impact of the proposed ZF-based technique on the secrecy capacity is investigated for three different scenarios depending on where the ZF is applied, namely, 1) ZF at the relay and destination, 2) ZF at the source and relay, 3) ZF at the relay. For these configurations, analytical expressions for the ergodic-secrecy capacity are derived, and simulation results are provided throughout the paper to validate our analysis. Results reveal that reducing the number of source and/or destination antennas will enhance the ergodic-secrecy capacity and the significance of this enhancement is dependent on the particular scenario adopted. Furthermore, it will be shown that, in general, secrecy capacity improves with increasing the relay power.

Power transfer in multi-pair two-way AF relaying networks with zero-forcing

In this paper, we consider a wireless-powered communication networks (WPCNs), in which a multi-antenna two-way amplify-and-forward (AF) relay transfers power to multipair of single antenna users. A harvest-then-transmit protocol is adopted here, where the relay first broadcasts energy signals to all users during a power transfer phase. Multiple pairs of users, then use the harvested energy to exchange information signals through the relay over two phases, up-link (UL) and down-link (DL) phases. In the former phase, all the users simultaneously transmit their information signals to the relay, then in the latter phase the relay amplifies and forwards the received signals to their intended users. In addition, in order to mitigate the interference, zero-forcing reception and transmission is applied at the relay. In light of this, analytical expressions for the ergodic spectral and energy efficiencies are derived and Monte Carlo simulations are provided throughout to validate our analysis. The impacts of some important system parameters such as energy harvesting (EH) time, number of user-pairs and relay antennas, on the system performance are investigated. The results show that, good selection of the EH time is the key to achieve optimal system performance and increasing the number of relay antennas can reduce this factor.

Wireless Power Transfer in Two-Way AF Relaying Networks

In this paper, we study a wireless-powered communication network (WPCN) scenario, in which a multiple antenna amplify-and-forward (AF) two-way relay coordinates power transfer and information exchange to multiple pairs of users. A harvest-then- transmit protocol is assumed where the relay first transmits energy signals to the users in a power transfer phase. Multi-pair of users, which have rechargeable batteries, then use the harvested energy to exchange their independent signals through the relay in two phases, up-link (UL) and down-link (DL). In the UL phase, the users transmit their information signals to the relay and in the DL phase the relay amplifies and forwards the signals to the intended destinations. Furthermore, in order to cancel out the interference, zero-forcing reception and transmission (ZFR/ZFT) is implemented at the relay. In order to characterize the system performance, we consider ergodic spectral and energy efficiencies for two cases, based on the availability of the channel state information (CSI) at the relay during the power transfer, 1) unknown CSI 2) partially known CSI. In light of this, we derive new analytical expressions for the ergodic spectral and energy efficiencies for the two cases and Monte Carlo simulations are provided throughout our investigations to validate the mathematical analysis. The impacts of some system parameters such as EH time, EH efficiency, number of relay antennas and user-pairs, on the system performance are investigated.

Wireless Power Transfer over Non-Gaussian Channels with Multiple-Antenna Access Point

Wireless power transfer conveniently enables prolonging the lifetime of energy-constrained wireless nodes by means of scavenging the energy of radio-frequency signals. Most existing work on this topic assumes negligible background noise power and focuses only on harvesting the power signal transmitted by the access point (AP). In contract, in this paper we show that in Gaussian-Bernoulli (GB) impulsive noise channels such an assumption is invalid, especially in highly impulsive noise scenarios. In this respect, we study the performance of a multiple-antenna AP system with an energy- constrained single-antenna destination in various GB impulsive noise environments. The proposed system here adopts the harvest-then-transmit protocol where communication is accomplished over two distinct phases, namely, power transfer phase (down-link) and information transmission phase (up-link). To characterize system performance, we consider the ergodic capacity. An analytical expression for parameter is derived and then validated with Monte Carlo simulations. Results reveal that incorporating GB impulsive noise can considerably improve the performance of energy-harvesting based systems. It is also demonstrated that increasing the number of AP antennas will further enhance the ergodic capacity and that careful selection of the energy- harvesting time is crucial for achieving best performance.