In this paper we analyze the secrecy capacity of a halfduplex energy harvesting (EH)-based multi-antenna amplify-andforward (AF) relay network in the presence of a passive eavesdropper. During the first phase, while the source is in transmission mode, the legitimate destination transmits an auxiliary artificial noise (AN) signal which has here two distinct purposes, a) to transfer power to the relay b) to improve system security. Since the AN is known at the legitimate destination, it is easily canceled 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.Index Terms-Amplify-and-forward relays, cooperative communications, energy harvesting, secrecy capacity, wireless power transfer. Abdelhamid Salem (S'12), received the B.Sc. degree in Electrical and Electronic Engineering from the University of Benghazi, Benghazi, Libya, in 2002 and the M.Sc. degree (with distinction) in Communication Engineering from the University of Benghazi, Benghazi, Libya, in 2009, he is currently working toward the Ph.D. degree in wireless communications with The University of Manchester, United Kingdom . His current research interests include Physical Layer Security, signal processing for interference mitigation, energy harvesting, wireless power transfer, MIMO systems, wireless optical communication systems and power line communications. Khairi Ashour Hamdi (M'99-SM'02) received the B.Sc. degree in electrical engineering from the Alfateh University, Tripoli, Libya, in 1981, the M.Sc. degree (with distinction) from the Technical University of Budapest, Budapest, Hungary, in 1988, and the Ph.D. degree in telecommunication engineering in 1993, awarded by the Hungarian Academy of Sciences. His current research interests include modelling and performance analysis of wireless communication systems and networks.

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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.

In this paper, we analyze the sum rate performance of multi-user multiple-input multiple-output (MU-MIMO) systems, with a finite constellation phase-shift keying (PSK) input alphabet. We analytically calculate and compare the achievable sum rate in three downlink transmission scenarios: 1) without precoding, 2) with zero forcing (ZF) precoding 3) with closed form constructive interference (CI) precoding technique. In light of this, new analytical expressions for the average sum rate are derived in the three cases, and Monte Carlo simulations are provided throughout to validate the analysis. Furthermore, based on the derived expressions, a power allocation scheme that can ensure fairness among the users is also proposed. The results in this work demonstrate that, the CI strictly outperforms the other two schemes, and the performance gap between the considered schemes increases with increase in the MIMO size. In addition, the CI provides higher fairness and the power allocation algorithm proposed in this paper can achieve maximum fairness index.Index Terms-Finite constellation signaling, zero forcing, constructive interference, phase-shift keying signaling, multiple-input multiple-output.

In this paper, an amplify-and-forward (AF) relaying system is considered, where an energy constrained relay node harvests energy from the received radio frequency (RF) signal and uses this harvested energy to amplify and forward 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 delaylimited transmission (DLT) and delay-tolerant transmission (DTT) 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 in [1]. 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.