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Wireless powered cooperative communications with direct links over correlated channels

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Publication date: Available online 4 April 2018
Source:Physical Communication
Author(s): Dan Deng, Minghui Yu, Junjuan Xia, Zhenyu Na, Junhui Zhao, Qinghai Yang
In this paper, we investigate the impact of correlated channels on the wireless powered cooperative networks, where the direct links between the source and destination exist and are correlated with the relaying links. In the considered system, the time switching-based relaying protocol of simultaneous wireless information and power transfer is used. In order to enhance the system performance, a better branch between the relaying link and the direct link is selected. We evaluate the system transmission performance by deriving the closed-form expression on outage probability as well as the asymptotic results for the proposed scheme, in the high regime of transmit power. Based on the theoretical analysis, we investigate the effects of the system parameters, such as channel correlation coefficient, average channel fading power, energy harvesting coefficient and slot allocation coefficient, on the system outage probability. Numerical results are provided to verify the theoretical analysis.


Joint relay-user selection in energy harvesting relay network with direct link

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Publication date: Available online 5 April 2018
Source:Physical Communication
Author(s): Chenchen Liu, Tiejun Lv
In this paper, a joint relay-user selection (JRUS) scheme is proposed for an amplify-and-forward full-duplex (FD) relay network which includes one source node, multi-relay node and multi-user node, and the direct link between the source node and the user node is considered to convey information. Each FD relay node is energy-constrained and the simultaneous wireless information and power transfer technology is employed to harvest energy. A power splitter at each FD relay node splits the received signals into two components for energy harvesting and information processing. The implementation of the proposed JRUS scheme includes two steps: (1) the optimal user node is selected according to signal-to-noise ratio of the direct link between the source node and the user nodes; (2) the optimal energy harvesting relay node with optimal power splitting (PS) factor is picked out based on signal-to-interference-plus-noise ratio of the relaying link. The outage probability of the investigated relay network with the JRUS scheme is derived. In order to characterize the diversity order, we further present the asymptotic outage probability at high SNR. Moreover, the optimal PS factor of each relay node is calculated by minimizing the outage probability of the reconstructed relay network. Finally, numerical results demonstrate the accuracy of our performance analysis and the efficiency of the proposed scheme.

A novel bidirectional half-duplex fronthaul system using MMW/RoF and analog network coding

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Publication date: Available online 5 April 2018
Source:Physical Communication
Author(s): Thu A. Pham, Lam T. Vu, Ngoc T. Dang
A novel bidirectional half-duplex fiber-wireless fronthaul system is proposed in this paper. Bidirectional relaying transmission is deployed in both optical fiber and wireless link thanks to millimeter-wave radio over fiber (MMW/RoF) and analog network coding (ANC) techniques. The architecture of the proposed fronthaul system is simplified significantly since it requires only an optical fiber with a single wavelength and a wireless link with a single MMW frequency. The detailed architectures of the subsystems such as the central station, the remote antenna unit, and the remote radio head are also designed. Mathematical expressions for the performance analysis of the proposed fronthaul system are derived considering the effects of various physical layer impairments. The numerical results demonstrate not only the feasibility of our proposed system but also the gain in terms of throughput of ANC-based relaying compared to conventional and digital network coding (DNC) -based relaying.

Photonic millimeter-wave bridge for multi-Gbps passive optical networks

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Publication date: Available online 7 April 2018
Source:Physical Communication
Author(s): Ivan Aldaya, Carolina Del-Valle-Soto, Gabriel Campuzano, Elias Giacoumidis, Rafael González, Gerardo Castañón
Survivability is a critical requirement of optical communication networks that is typically addressed implementing path diversity. However, due to the elevated cost of fiber installation, this approach may prove prohibitively expensive in optical access networks. In this paper, a novel cost-efficient photonic millimeter (mm) - wave bridge is proposed, which converts passive optical network (PON) signals to radiofrequency signals at mm-wave bands. The performance of the mm-wave photonic bridge is numerically tested, revealing its feasibility to transmit a 2.5-Gbps PON with –55.6 dB wireless link gain (WLG) using the 81-86 GHz band and 10-Gbps PON with –35 dB at the 102–109.5 GHz band. The effect of fiber is also analyzed, showing that fiber cuts closer to the optical network unit degrades more the system performance.

Design of incentive scheme using contract theory in energy-harvesting enabled sensor networks

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Publication date: Available online 8 April 2018
Source:Physical Communication
Author(s): Linqing Gui, Yun Shi, Wenlong Cai, Feng Shu, Xiaobo Zhou, Tingting Liu
Wireless energy harvesting (EH) has been proven to be a promising technique for sensor networks to enhance self-sustainability and robustness. Due to the popularity and the inherent mobility, mobile phones will become excellent EH sources for sensor nodes, especially when sensor nodes cannot harvest energy from other fixed ambient sources. In order to motivate ambient mobile phones to transfer power, incentive mechanisms should be provided. Therefore in this paper, a contract-theory based incentive scheme is proposed. Compared to relevant incentive schemes, the proposed scheme not only overcomes the information asymmetry problem caused by privacy-protection nature of mobile users, but has also taken some important characteristics (e.g., time cost of users and remaining capacity of batteries) of mobile users into consideration. Simulation results have shown the feasibility of the proposed contract as well as the effectiveness of the proposed incentive scheme.

Coexistence in fourth generation digital subscriber lines: Experiment, modeling, and simulation results

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Publication date: June 2018
Source:Physical Communication, Volume 28
Author(s): Sanda Drakulić, Martin Wolkerstorfer, Driton Statovci
The deployment of fourth generation digital subscriber line (DSL) technology (“G.fast”) will be gradual and it may therefore share the cable infrastructure with legacy DSL technologies such as Very high speed DSL transceivers 2 (VDSL2). We perform experiments on coexistence of G.fast with legacy VDSL2, highlighting the practical relevance of out-of-band leakage and aliasing. Furthermore, the differences in transmission parameters (e.g., carrier width and sampling rate) and asynchronous transmission results in inter-carrier and inter-symbol interference (ICSI). Previous work on modeling ICSI in the communication field focused on modeling only a subset of these effects. Hence, we analytically derive a simplified ICSI model, which notably includes the effects of aliasing, leakage, and worst-case symbol misalignment. Our results partially based on simulations show that a) neglecting ICSI potentially leads to significant bit-rate overestimation (e.g., 18 % in G.fast rates); and b) a G.fast start frequency of approximately 23 MHz may provide sufficient spectral separation with VDSL2 profile 17a transceivers.

Optimal design of energy efficient two-tier HetNets with massive MIMO by coordinated multipoint beamforming

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Publication date: Available online 21 April 2018
Source:Physical Communication
Author(s): Yinghui Zhang, Yang Liu, Jing Gao
This paper presents an energy-efficient (EE) coordinated multipoint beamforming (CMBF) approach that minimizes the total power consumption based on both the dynamic emitted power and static hardware power while maintaining necessary quality of service (QoS) constraints and different coordinated schemes. We deduce expressions the optimal value of each parameter in a two-tier heterogeneous networks (HetNets) from the perspective of energy efficiency (EE), considering a massive multiple-input multiple output (MIMO) system in conjunction with CMBF and small cell deployment. We find that the EE of HetNets is sensitive to the coordinated scheme design, the number of macro-cell and small-cell base station antennas, and QoS constraints. As such, all these factors should be taken into account in system design. Furthermore, we provide promising analytical and simulation results demonstrating that the proposed HetNets generally provides a solution for achieving maximal EE performance with relatively low-complexity CMBF.

Performance analysis of energy harvesting DF relay system in generalized-K fading environment

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Publication date: Available online 21 April 2018
Source:Physical Communication
Author(s): Vesna M. Blagojević, Aleksandra M. Cvetković, Predrag N. Ivaniš
The performance of decode-and-forward (DF) relaying systems is analyzed for the energy constrained relay and Generalized-K fading environment, assuming that the communication in both links of relaying system is corrupted by effects of multipath fading and shadowing. We analyze the ergodic and outage capacities for two representative cases: in one case energy harvesting and information transmission are arranged based on time-switching relaying protocol, while in the other analyzed case they are arranged based on power-splitting relaying protocol. The novel analytical closed-form results for error performance of DF energy harvesting system are applicable for wide range of modulation formats. The derived closed-form capacity and error rate expressions are valid for both relaying protocols and various scenarios of composite fading environment. Analytical results are corroborated by an independent simulation method. Finally, the impact of the system and channel parameters on the system performance is demonstrated through numerical analysis.


Resource allocation for hybrid TS and PS SWIPT in massive MIMO system

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Publication date: Available online 21 April 2018
Source:Physical Communication
Author(s): Kui Xu, Zhexian Shen, Yurong Wang, Xiaochen Xia
In this paper, we consider the hybrid time switching (TS) and power splitting (PS) simultaneous wireless information and power transfer (SWIPT) protocol design in massive MIMO system. In this system, the base station (BS) simultaneously serves a set of half-duplex (HD) sensor nodes which are uniformly distributed in its coverage. The whole protocol can be divided into two phases based on the idea of TS. The first phase is designed for sensor nodes energy harvesting as well as downlink training. During this phase, the BS transmits energy signals to the sensor nodes. Based on the idea of PS, the sensor nodes utilize the received energy signals for energy harvesting and downlink channel estimation. In the second phase, the BS schedules the sensors intelligently based on the beam-domain distributions of channels to mitigate interference between sensors and enhance transmission spectral efficiency. Then, the BS forms the receive beamformers for the reception of signals transmitted by sensors. By optimizing transmit powers at the BS and the TS ratio, the system achievable sum rate performance is maximized. Simulation results show the superiority of the proposed protocol on spectral efficiency compared with conventional massive MIMO SWIPT protocol.

A new clipped PIC detector for asynchronous upstream OCDMA-PON

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Publication date: June 2018
Source:Physical Communication, Volume 28
Author(s): Abdelouahab Bentrcia
Optimization-based approaches have been used to develop several interference cancellation detectors for incoherent direct access OCDMA systems. Some of these interference cancellation detectors exploit the non-negativity of the solution, while other detectors exploit in addition to the non-negativity constraint, the noise variance information. In this paper, we devise a new PIC detector that exploits not only the aforementioned information but also the fact that the amplitude of the solution is confined to a unit hypercube. Up to our knowledge, no such detector exists in the literature. After analyzing the convergence behavior and evaluating the computational complexity of the novel PIC detector, extensive simulations are conducted to assess the performance of the proposed PIC detector. Numerical results show that the proposed PIC significantly outperforms other PIC detectors in terms of both BER and convergence speed.

Ultra-wide band impulse radar for life detection using wavelet packet decomposition

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Publication date: Available online 24 April 2018
Source:Physical Communication
Author(s): Xiaolin Liang, Hao Zhang, Tingting Lyu, Lingwei Xu, Conghui Cao, Thomas Aaron Gulliver
This paper develops an improved algorithm for life detection based on ultra-wide band (UWB) impulse radars in through-wall condition. Usually, the cardiac-respiratory movement is the most significant sign of a living person, which can be extracted from the collected pulses. The proposed algorithm analyzes the variances of the collected pulses, which are mixed with various clutters. The time of arrival (TOA) between UWB radar and human target can be calculated by performing the wavelet packet decomposition on the calculated variances. The rates of human cardiac-respiratory movement are acquired based on the variable time-window (VTW) method. Compared with several well-known algorithms, the developed method can provide competitive performance in life detection. Results acquired from different sites prove the efficiency and reliability of the method.

Wireless energy transfer in downlink and wireless communications in uplink for multi-user MIMO networks

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Publication date: Available online 25 April 2018
Source:Physical Communication
Author(s): Juan Zhao, Xiaolong Xu
In this paper, the energy is wireless transferred in the multi-user multi-input multi-output (MU-MIMO) broadcast channel and the information is wireless transmitted in the MAC MU-MIMO channel. The energy efficiency metric and the spectral efficiency objective are theoretically traded off for the wireless energy and information transmission networks, which results in the analytical expression. Moreover, the number of the transmit antennas and that of the mobile terminals are optimized to the closed form expression by maximizing the energy efficiency with the quality of service (QoS) in terms of the required spectral efficiency. Finally, the optimal energy efficiency of the whole networks is obtained with the optimized number of both antennas and mobile terminals. The key feature of this paper is the analytical expression of the power allocation for the best energy efficiency. Numerical simulations demonstrate the effectiveness of the proposed method for the MU-MIMO wireless energy and information transmission networks.

Constellation design for color space-based modulation in visible light communications

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Publication date: Available online 25 April 2018
Source:Physical Communication
Author(s): D.U. Campos-Delgado, J.M. Luna-Rivera, R. Perez-Jimenez, C.A. Gutierrez, V. Guerra, J. Rabadan
In this paper, we present a new strategy to design the constellation symbols in a visible light communication (VLC) system by considering multiple LED transmitters at different wavelengths. For this purpose, the LED transmitters are modeled as fixed points in a color space, and the constellation symbols are obtained by convex combinations of these points. In our formulation, the resulting constellation symbols have to reproduce on average a desired white tonality. Hence, the constellation design strategy is defined as a constrained optimization problem that seeks to maximize the minimum distance among the resulting symbols, but at the same time, to yield a desired white tonality on average. For evaluation purposes, we consider the CIE 1931 color space with 3 and 5 LED transmitters, and constellations with 4, 8 and 16 symbols. Our proposed methodology is compared with a previous work in the state of the art, where an important improvement is achieved with respect to the resulting Euclidean distance among constellation symbols.

A comparative analysis of local and global adaptive threshold estimation techniques for energy detection in cognitive radio

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Publication date: Available online 26 April 2018
Source:Physical Communication
Author(s): A.J. Onumanyi, A.M. Abu-Mahfouz, G.P. Hancke
In this paper, we compare local and global adaptive threshold estimation techniques for energy detection in Cognitive Radio (CR). By this comparison we provide a sum-up synopsis on the effective performance range and the operating conditions under which both classes best apply in CR. Representative methods from both classes were implemented and trained using synthesized signals to fine tune each algorithm’s parameter values. Further tests were conducted using real-life signals acquired via a spectrum survey exercise and results were analysed using the probability of detection and the probability of false alarm computed for each algorithm. It is observed that while local based methods may be adept at maintaining a low constant probability of false alarm, they however suffer a grossly low probability of detection over a wide variety of CR spectra. Consequently, we concluded that global adaptive threshold estimation techniques are more suitable for signal detection in CR than their local adaptive thresholding counterparts.

Power analysis based side-channel attack on visible light communication

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Publication date: Available online 27 April 2018
Source:Physical Communication
Author(s): Damla Yucebas, Heba Yuksel
Visible light communication (VLC) technology has emerged as a significant and necessary improvement to the wireless communication technologies; VLC systems are considered to be more secure than wireless fidelity (Wi-Fi) systems by design, since light cannot penetrate most walls and obstacles. This paper presents a design for a bidirectional VLC system, and it also introduces a method to jeopardize the security aspect of this system. The methodology in this paper is side-channel attack which is defined as exploiting data based on the information gained from physical implementation. It is not a cyber attack on the theoretical weaknesses in the algorithms, but rather is a sideway approach to a fully-functioning physical system. Thus, the authors became the attackers and implemented a current sensor on the power lines from the power supply to the VLC system; the instantaneous power consumed by the communication system has become their main source to obtain the binary data transmitted by visible light. The work has resulted in effective attacks which could successfully extract the information and it has demonstrated side channel attacks on VLC systems through their instantaneous power consumption analysis.


A closed-form expression for performance optimization of subcarrier intensity QAM signals-based relay-added FSO systems with APD

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Publication date: Available online 30 April 2018
Source:Physical Communication
Author(s): Ha Duyen Trung, Nguyen Tien Hoa, Nguyen Huu Trung, Tomoaki Ohtsuki
This study characterizes the overall bit-error-rate (BER) performance optimization of avalanche photodiode (APD) receiver-based amplify-and-forward (AF) relay-added free-space optical (FSO) communication system. The system of interest uses subcarrier intensity quadrature amplitude modulation (QAM) signals and subjects to scintillation due to optical turbulence. A weak atmospheric turbulence (clear-air condition) scenario is considered, for which the received signal intensity fluctuation can be modeled as a log-normal random process. A closed-form expression of the overall BER is derived by taking into account the impact of atmospheric loss, turbulence strength, thermal-noise and shot-noise limited conditions. It can be inferred from the numerical results that using AF relay nodes can extend the transmission distance and minimize BER performance of FSO system significantly compared with the direct transmission. Moreover, the selection of APD’s gain values is indispensable to minimize the system’s BER performance. Hence, the designed system could achieve the minimal BER by selecting an optimal APD gain value appropriately. In addition, the optimal gain values of APD significantly depend on various conditions, such as noise temperature, link distance, and the number of relay nodes.

Max-min fair beamforming designs of SWIPT-aided full-duplex two-way relay systems

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Publication date: Available online 30 April 2018
Source:Physical Communication
Author(s): Wei Wang, Liyuan An, Rui Wang, Liuguo Yin, Guoan Zhang
A full-duplex two-way relaying (FD-TWR) system with an energy-constrained relay is studied with simultaneous wireless information and power transfer (SWIPT). In this network, the sources have a reliable power supply, whereas the relay has to harvest energy from the source-emitted radio-frequency signal via time switching (TS) operation. Our aim is to maximize the minimum achievable rate of the two sources by jointly optimizing the relay beamforming vector and TS ratio under the energy-harvesting-then-transmitting mode, i.e., the relay harvested energy need to meet the consumed energy. Specifically, the max–min fairness beamforming design problems are formulated for both the perfect channel state information (CSI) model and imperfect CSI model. A one-dimensional search algorithm and the semidefinite relaxation technique are proposed to solve these complex non-convex problems. It is shown that the optimal beamforming vectors and the TS ratio can always be found under the two considered CSI model. Numerical results show that the proposed two FD schemes achieve significant performance improvement compared to the traditional half-duplex (HD) scheme. Moreover, the robust scheme can get most of the performance gain of the perfect scheme. Some tradeoffs are elucidated among the achievable rate and the TS ratio, the system performance and the self-interference cancellation (SIC) level under a max–min fairness criterion.

Resource allocation and interference management in OFDMA-based VLC networks

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Publication date: Available online 30 April 2018
Source:Physical Communication
Author(s): Marwan Hammouda, Anna Maria Vegni, Harald Haas, Jürgen Peissig
Resource allocation and interference management are two main issues that need to be carefully addressed in visible light communication (VLC) systems. In this paper, we propose a resource allocation scheme that can also handle the inter-cell interference in a multi-user VLC system that employs orthogonal frequency division multiple access (OFDMA). Particularly, we suggest dividing the cell coverage into two non-overlapping zones and performing a two-step resource allocation process, in which each step corresponds to a different level of allocating resources, i.e., zone and user levels. We initially define both zones in terms of the physical area and the amount of allocated resources and we investigate the impact of illumination requirements on defining both zones. Through simulations, we evaluate the performance of the proposed scheme in terms of the area spectral efficiency and the fairness level between the two zones. We show that both performance measures can be potentially enhanced by carefully setting a certain design parameter that reflects the priority level of the users located in the region around the cell center, denoted as Zone 0, in terms of the achievable rate. We further eventuate the system performance in a realistic transmission scenario using a simulation tool.

Outage performance of mobile V2V cooperative networks

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Publication date: Available online 1 May 2018
Source:Physical Communication
Author(s): Lingwei Xu, Lingling Huang, Conghui Cao, Han Wang, Ye Li, T. Aaron Gulliver
In this paper, the outage probability (OP) performance of mobile vehicle-to-vehicle (V2V) networks with incremental hybrid decode-amplify-forward (IHDAF) relaying is investigated. Exact closed-form expressions for the OP are derived. The impact of the power allocation on the OP is evaluated. Theoretical and Monte-Carlo simulation results are compared to validate the analysis.

An improved channel estimation method using doubly reduced matching pursuit over fractional delay multipath channel

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Publication date: Available online 1 May 2018
Source:Physical Communication
Author(s): Ziji Ma, Qiang Peng, Hongli Liu, Zhi Yan
Owing to the inherent sparse channel feature in multi-carrier modulation systems, compressed sensing (CS)-based techniques have been used for channel estimation with less pilot subcarriers for orthogonal frequency division multiplexing (OFDM) systems. Because of a sparse multipath channel’s characteristic of fractional delay, the channel measurement matrix that is generated by conventional time-domain sampling approaches cannot perfectly recover the channel impulse response (CIR), especially in the case of two adjacent paths that both have with non-negligible power. In this study, a fractional delay multipath channel model is used to simulate the wireless multipath channel. In addition, a time-domain oversampling based doubly reduced matching pursuit (DRMP) algorithm at the receiver is proposed to improve the estimation accuracy while reducing the computational complexity. Simulation results show that the proposed method can improve both the bit error rate (BER) performance and estimation time compared to conventional methods in an environment with fractional delay.

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