Ha-Vu Tran

Design of Simultaneous Wireless Information and Power Transfer Scheme for Short Reference DCSK Communication Systems

Recently, a short reference differential chaos shift keying system (SR-DCSK) has been proposed to overcome the dominant drawbacks related to low data rate and energy efficiency fondness of conventional DCSK systems. The fact that terminals on a network have a limited battery capacity and are in desperate need to high energy efficiency transmission schemes compels us to tackle these crucial challenges. In this paper, we propose an SR-DCSK system that performs simultaneous wireless information and power transfer (SWIPT). This promising design exploits the saved time gained from the fact that reference signal duration of SR-DCSK scheme occupies less than half of the bit duration to transmit a signal. The aim of this system is to allow receivers to perform without being equipped with any external power supply. Furthermore, at the receiver side, an RF-to-dc conversion is first performed, followed by data recovery without the need to any channel estimator. Closed-form expressions of multiple-input single-output SR-DCSK SWIPT system, such as ergodic rate, harvesting time, energy shortage, and data outage as well as exact and approximate bit error rate probabilities are derived under Rayleigh fading channel and are validated via simulation. Our results show that the proposed solution saves energy without sacrificing the non-coherent fashion of the system or reducing the rate compared to conventional DCSK, while keeping the design simple.

Time Reversal SWIPT Networks with an Active Eavesdropper: SER-Energy Region Analysis

This paper analyzes a novel multiple-input single- output (MISO) simultaneous wireless information and power transfer (SWIPT) system model in the presence of an active eavesdropper over the frequency-selective fading channel. In this model, a transmitter applies the time reversal (TR) beamforming technique to combat the fading effects whereas a legitimate user employs a power splitter to jointly receive information and energy, and the active eavesdropper jams the user. Given the system model, the system performance in terms of symbol error rate (SER) and energy harvesting (EH) is analyzed. In particular, we devise a SER-energy region, instead of the conventional rate-energy region, to evaluate system performance of the SWIPT model. A moment generating function (MGF)-based method is presented to exactly derive the average SER analysis. Moreover, the closed-form expression of average effective harvested energy is then provided to complete SERenergy region analysis. Finally, analytical results confirmed by numerical simulations show that the TR technique can support the SWIPT system to notably improve the SER performance whereas the jamming signal can enhance the EH performance.

Performance Analysis of Two-Way Relaying System with RF-EH and Multiple Antennas

In this paper, we investigate the performance of an amplify-and-forward two-way relay network, in which the relay can harvest the energy from the radio frequency and all channels are subject to Nakagami- \textit{m} fading. In particular, we assume that the relay has a single antenna, while two sources are equipped with multiple antennas. Also, two sources use the maximal ratio transmission (MRT) and maximal ratio combining (MRC) techniques to process the transmit and received signals. Moreover, the multiple access broadcast (MABC) protocol, which can improve the spectrum efficiency, is employed to coordinate the bidirectional communication of the two- way relay network. Given these settings, we derive analytical expressions for the throughput under the delay-limited and delay-tolerant transmission modes and the outage probability. Finally, Monte-Carlo simulations are provided to verify our calculation.

Effective secrecy-SINR analysis of time reversal-employed systems over correlated multi-path channel

Based on the capability of harvesting the energy of all paths in the multipath environment, time-reversal (TR) transmission technique offers a great potential of low-complexity energy-efficient communications for future wireless network. The TR-employed systems benefit from a significantly reduced leakage of message-bearing signal to unintended users or eavesdroppers. In this paper, we propose a term so-called average effective secrecy signal-to-interference-plus-noise ratio (SINR) which represents the secrecy performance of TR-employed systems. Furthermore, we also consider: (i) the channel correlation between transmit antennas, and (ii) the channel correlation between a legitimate user and an eavesdropper. Accordingly, we derive the average effective secrecy-SINR in a closed-form expression of TR-employed systems. The obtained expression is based on the exact power-averaged expressions of the desired signal and the inter-symbol interference (ISI) components at both the legitimate user and eavesdropper side. The analytical results confirmed by numerical simulations show that the average effective secrecy-SINR metric is preferred to the average secrecy-SINR term in the perspective of measuring secrecy performance over correlated multi-path channel.

Downlink Power Optimization for Heterogeneous Networks With Time Reversal-Based Transmission Under Backhaul Limitation

In this paper, we investigate an application of two different beamforming techniques and propose a novel downlink power minimization scheme for a two-tier heterogeneous network (HetNet) model. In this context, we employ the time reversal (TR) technique to a femtocell base station, whereby we assume that a macrocell base station uses a zero-forcing-based algorithm, and the communication channels are subject to frequency selective fading. Additionally, the HetNet backhaul connection is unable to support a sufficient throughput for signaling an information exchange between two tiers. Given the considered HetNet model, a downlink power minimization scheme is proposed, and closed-form expressions concerning the optimal solution are provided by taking this constraint into account. Furthermore, considering imperfect channel estimation at TR-employed femtocell, a worst-case robust power minimization problem is formulated. By devising TR worst-case analysis, this robust problem is transformed into an equivalent formulation that is tractable to solve. The results presented in our paper, show that the TR technique outperforms the zero-forcing one from the perspective of beamforming methods for femtocell working environments. Finally, we validate the proposed power loading strategy for both cases of perfect and imperfect channel estimations.