Relay selection and power allocation for energy-efficient cooperative cognitive radio networks

December 9, 2017, 5:50 am

≫ Next: Downlink user association and uplink scheduling for energy harvesting users in software-defined mobile networks

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Publication date: Available online 6 December 2017
Source:Physical Communication
Author(s): M. Soleimanpour-moghadam, S. Talebi
In this paper, we apply the innovative multi-objective optimization methods to the challenge posed by rate maximization, total transmission power minimization and relay selection in cooperative cognitive radio networks. The proposed methods which are based on amplify and forward relaying strategy optimize the three conflicting objectives and, at same time, they maximize the rate quality, minimize the total transmission power allocated to the network relays and make the best relay node selection. The multi-objective optimization studied is a non-convex non-linear combinatorial algorithm which is converted to its convex smooth equivalent through two efficient approximation methods. We apply the multi-objective lexicographic method to overcome the challenge posed by these conflicting objectives simultaneously. The proposed relay node selection method is based on zero-norm principle which provides an effective technique to obtain a minimum node selection. Simulation results confirm that the proposed approaches offer superior performance over known schemes in terms of throughput gain and number of active relays.

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Downlink user association and uplink scheduling for energy harvesting users in software-defined mobile networks

March 11, 2018, 4:31 am

≫ Next: Secrecy energy efficiency optimization for MISO SWIPT systems

≪ Previous: Relay selection and power allocation for energy-efficient cooperative cognitive radio networks

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Publication date: Available online 9 March 2018
Source:Physical Communication
Author(s): Hassan Yeganeh, Javane Rostampoor
In this paper we consider a heterogeneous network which consists of a macro base station and some pico base stations utilizing massive MIMO and MIMO techniques, respectively. A central software-defined mobile network (SDMN) controller is adopted in order to provide user association and energy scheduling. The users are considered battery limited and are capable of simultaneous wireless information and power transfer (SWIPT) in order to harvest energy and address the energy shortage issue. These users harvest energy from the received signals in the downlink and consume it via their uplink communications. This paper deals with the downlink user association by jointly optimizing the overall sum-rate of the network and the harvested energy by introducing an appropriate utility function. In this regard, the optimum user association and power splitting factor for each user are calculated via the downlink optimization stage. Then, the process of uplink scheduling is defined as choosing the best users in each time epoch to transfer data as well as optimizing their transmit power by solving Lyapunov drift-plus-penalty function. Simulation results are provided in order to confirm the optimality of the proposed algorithm in comparison with the previous user association and uplink scheduling approaches in terms of providing fairness and battery management among users.

Secrecy energy efficiency optimization for MISO SWIPT systems

March 17, 2018, 3:10 am

≫ Next: Improved RMS Delay and optimal system design of LED based indoor mobile visible light communication system

≪ Previous: Downlink user association and uplink scheduling for energy harvesting users in software-defined mobile networks

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Publication date: Available online 14 March 2018
Source:Physical Communication
Author(s): Xiaobo Zhou, Wenlong Cai, Riqing Chen, Linqing Gui, Feng Shu, Jinyong Lin, Shuo Zhang, Yijin Zhang
In this paper, we investigate the secrecy energy efficiency (SEE) optimization of the multiple-input single-output (MISO) system. First, transmission beamforming vector is designed to achieve the SEE maximization subject to the constraints of transmission power, minimum secrecy rate threshold and harvested energy threshold. The optimization problem belongs to the category of fractional optimization, which is non-convex and is very difficult to tackle. In order to solve the optimization problem, we propose an algorithm that can obtain a near-optimal solution, which consists of outer-tier and inner-tier iterations. For the outer-tier iteration, we first employ the Dinkelbach method to convert the fractional objective function into a polynomial form, and then transform the optimization problem into a difference of concave (DC) programming. For the inner-tier iteration, we employ the first-order Taylor expansion and successive convex approximation (SCA) method to solve the DC optimization problem. Then, we analyze the computational complexity of the proposed algorithm. In addition,we prove that the rank relaxation is tight. The simulation results show that the SEE performance of our proposed algorithm is obviously superior to that of secrecy rate maximization scheme and zero-forcing scheme.

Improved RMS Delay and optimal system design of LED based indoor mobile visible light communication system

March 24, 2018, 2:17 am

≫ Next: Switch-and-stay combining for energy harvesting relaying systems

≪ Previous: Secrecy energy efficiency optimization for MISO SWIPT systems

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Publication date: Available online 21 March 2018
Source:Physical Communication
Author(s): Ram Sharma, A. Charan Kumari, Mona Aggarwal, Swaran Ahuja
The light emitting diode (LED) based lighting systems can be used for creation of the indoor communication network for sending information besides serving its main purpose of illumination. However, there are a number of impediments which are still under resolution in order to realize the full potential of such a system. In particular, the visible light communication (VLC) systems suffer due to high inter symbol interference (ISI) mainly on account of multi path propagation which impacts the spectral efficiency of the system. Besides ensuring ubiquitous coverage, it is also important to improve the system’s bandwidth within the indoor scenario. The optimal deployment of such systems may result in optimum resource utilization (LEDs and driver circuits etc.) to minimize the energy consumption and to achieve improved operational efficiency. In this paper, we propose two types of LED deployment strategies- centralized and distributed and compare their performances on the basis of average outage area ratio, effect of semi-angle, root mean square delay delay and data transmission rate. The hyper heuristic evolutionary algorithm (HypEA) has been implemented to optimize the performance of the systems to achieve full receiver mobility in the indoor environment. The experimental results show that the distributed deployment strategy is able to optimize the system performance significantly in comparison to centralized deployment strategy.

Switch-and-stay combining for energy harvesting relaying systems

March 24, 2018, 2:17 am

≫ Next: Green energy driven cellular networks with JT CoMP technique

≪ Previous: Improved RMS Delay and optimal system design of LED based indoor mobile visible light communication system

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Publication date: Available online 21 March 2018
Source:Physical Communication
Author(s): Hai Huang, Junjuan Xia, Xin Liu, Zhenyu Na, Qinghai Yang, Hongbin Chen, Junhui Zhao
In this paper, we study the switch-and-stay combining technique into the energy-harvesting relaying networks, where the relay obtains its transmit power from the source through wireless energy harvesting. The moderate shadow environments are applied, so that the data transmission from the source to the destination can go through the direct link. Although the conventional selection combining technique can exploit both the direct and relaying branches for data transmission, it has to require to know the channel parameters of both branches, and results into frequent branch switching. To solve these issues, switch-and-stay combining (SSC) is proposed into the energy-harvesting relaying networks, where the same branch keeps to be used for data transmission when it can support the transmission quality. The branch switching occurs only when the branch cannot support the transmission quality. We study the system transmission performance by deriving expression for the system analytical outage probability. We also provide the asymptotic outage probability when the transmit power is high, from which we obtain more insights on the system design, such as the system diversity order and the impact of parameters on the system performance. Simulation and numerical results are provided to validate the proposed studies in this paper.

Green energy driven cellular networks with JT CoMP technique

March 24, 2018, 2:17 am

≫ Next: Computationally and energy efficient symbol-level precoding communications demonstrator

≪ Previous: Switch-and-stay combining for energy harvesting relaying systems

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Publication date: Available online 22 March 2018
Source:Physical Communication
Author(s): Abu Jahid, Abdullah Bin Shams, Md. Farhad Hossain
Concerns about global warming and increasing number of base stations (BSs) leading to rising energy consumption have prompted extensive research effort focusing on energy efficiency (EE) issue for cellular networks. As a result, cellular operators are increasingly deploying renewable energy (RE) sources in BSs as a promising way to reduce the on-grid consumption and operational expenditure. In this paper, we propose a novel framework on green energy driven cellular networks aiming to maximize the utilization of the green energy and minimize the grid energy consumption considering stochastic traffic demand profile. Each BS is equipped with renewable energy generators, such as solar panel along with a set of batteries as an energy storage device and also connected to commercial grid supply. In addition, joint transmission (JT) coordinated multi-point (CoMP) transmission technique is integrated with the proposed model for selecting the best serving BSs for a user equipment (UE). The prime goal is to quantify the EE of various selection schemes namely, distance based, SINR based and SINR-distance based JT CoMP techniques under the proposed network model. Provision of sleep mode approach in BSs is also considered. A thorough investigation in the downlink of LTE-Advanced (LTE-A) cellular system is carried out for evaluating EE performance of the proposed framework under a wide range of network settings. Numerical results validate the proposed network models demonstrating a considerable enhancement in network EE compared to other counterparts.

Computationally and energy efficient symbol-level precoding communications demonstrator

March 24, 2018, 2:17 am

≫ Next: Application of wavelet transform in spectrum sensing for cognitive radio: A survey

≪ Previous: Green energy driven cellular networks with JT CoMP technique

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Publication date: Available online 22 March 2018
Source:Physical Communication
Author(s): Jevgenij Krivochiza, J.C. Merlano-Duncan, Stefano Andrenacci, Symeon Chatzinotas, Björn Ottersten
We demonstrate forward link interference mitigation techniques in a precoded multi-user communication scenario for the efficient frequency reuse. The developed test-bed provides an end-to-end precoding demonstration, which includes a transmitter, a multi-beam satellite channel emulator and user receivers. Precoded communications allow efficient frequency reuse in multiple-input multiple-output (MIMO) channel environments, where several coordinated antennas simultaneously transmit to a number of independent receivers. We implement and demonstrate the new Symbol-Level Precoding (SLP) technique and benchmark it against Zero-Forcing and MMSE techniques in realistic transmission conditions. We show performance of the SLP in various MIMO channel conditions and outline the impact of the modified constellation by the SLP on a conventional receiver.

Application of wavelet transform in spectrum sensing for cognitive radio: A survey

March 25, 2018, 7:54 am

≫ Next: Efficient algorithms for physical layer security in two-way relay systems

≪ Previous: Computationally and energy efficient symbol-level precoding communications demonstrator

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Publication date: Available online 23 March 2018
Source:Physical Communication
Author(s): P.Y. Dibal, E.N Onwuka, J. Agajo, C.O. Alenoghena
Spectrum sensing is an important technological requirement in the quest to realize dynamic spectrum access (DSA) in today’s wireless world. Cognitive radio (CR) has been identified as an enabling technology that will considerably mitigate the effect of spectrum underutilization and cushion spectrum scarcity. But for this to happen, fast and accurate sensing technique must be developed. Quite a number of spectrum sensing techniques are available in literature, but these are not without inherent short comings. Recently, applications of wavelet techniques for spectrum sensing is receiving attention in the research community, this is attributed to its unique ability to operate both in the time and frequency domains and its suitability for wideband sensing. This paper takes a general look at the applications of wavelets in solving problems in science and engineering and then focused on its recent applications in spectrum sensing. Besides discussing the general spectrum sensing techniques in literature, the paper also discussed wavelet-based spectrum sensing, and its variants; pointing out the merits and limitations of each. It noted that, like any other sensing technique, wavelet-based technique has its strengths and weaknesses, hence, the advantages and disadvantages of this technique are also highlighted. Also, wavelet techniques in spectrum sensing was variously compared with existing wavelet sensing techniques; other spectrum sensing techniques; and existing wideband sensing techniques. Emerging research trends involving wavelets in wireless communications systems design are discussed while some challenges posed by wavelet techniques are mentioned. The paper is intended to provide necessary information and serve as a pointer to relevant literatures for researchers seeking information about wavelets and their applications in science and engineering and particularly in spectrum sensing for CR.

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Efficient algorithms for physical layer security in two-way relay systems

March 27, 2018, 2:42 pm

≫ Next: Cross-layer design benchmark for throughput maximization with fairness and delay constraints in DCF systems

≪ Previous: Application of wavelet transform in spectrum sensing for cognitive radio: A survey

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Publication date: Available online 26 March 2018
Source:Physical Communication
Author(s): Mohanad Obeed, Wessam Mesbah
In this paper, we study the physical layer security in a two-way relay system (TWRS) consisting of two transceivers, one eavesdropper, and multiple relays. The channel state information (CSI) of the eavesdropper is assumed to be known. We consider the problem of maximizing the secrecy sum rate by optimizing the relay beamforming vector and the transceivers’ powers under total power constraint. The optimization problem of the beamforming vector has been formulated in the literature as a product of three Rayleigh quotients which is very difficult to solve, and the best proposed solution was a suboptimal solution to the null space beamforming. Here, we propose two approaches: 1) Optimal solution to the null space beamforming approach, and 2) Ignoring one Rayleigh quotient (IORQ) approach (which has not been proposed before). In the first approach, we convert the nonconvex product of two Rayleigh quotients to a quadratically constrained quadratic program (QCQP) and then to a convex problem with one dimensional search using semidefinite programming (SDP). Then we significantly simplify the problem by providing a new approach that uses the generalized eigenvalues. This new approach can be used to solve all QCQPs with positive definite objective function and two trace constraints. In the second proposed approach, we look for a beamforming vector that does not eliminate the complete information signal at the eavesdropper aiming to increase the whole secrecy sum rate. This approach provides a substantial contribution in improving the secrecy sum especially when the number of relays is low. Numerical results show that the proposed algorithms provide higher secrecy sum rates than the existing algorithms. ¹ 1 This Work is a part of the MSc thesis of the first author (Obeed, 2016, [1]).

Cross-layer design benchmark for throughput maximization with fairness and delay constraints in DCF systems

March 27, 2018, 2:42 pm

≫ Next: A new scheme of dynamic power allocation in wireless powered communication

≪ Previous: Efficient algorithms for physical layer security in two-way relay systems

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Publication date: Available online 26 March 2018
Source:Physical Communication
Author(s): Zihao You, I-Tai Lu
This paper proposes a cross-layer design for the stations (STAs) in a distributed coordination function (DCF) network. By selecting the modulation scheme, coding scheme, and packet length of each STA in the network, the design aims to maximize the total throughput of all the STAs and satisfy the minimum throughput requirement or delay requirement of each STA, thus addressing the fairness and delay issues. The proposed scheme applies to the system where each STA employs a contention based channel access mechanism, Furthermore, unlike the existing optimization schemes, it takes two important factors, changeable data rate and changeable packet error rate (PER), into consideration. Using an existing Markov chain model to predict the performance of the STAs, we propose an approach that updates the selection of each STA sequentially, thus avoiding the large complexity from the exhaustive search. Many issues are discussed based on the numerical results, including how the approximations in our design affect the processing time and result of the design, how the change of one STA affects the performance of the other STAs, how the minimum throughput constraints affect the fairness and total throughput, how to select these constraints to satisfy the delay requirements, etc.

A new scheme of dynamic power allocation in wireless powered communication

March 31, 2018, 1:08 am

≫ Next: MM-wave wideband propagation model for wireless communications in built-up environments

≪ Previous: Cross-layer design benchmark for throughput maximization with fairness and delay constraints in DCF systems

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Publication date: June 2018
Source:Physical Communication, Volume 28
Author(s): Chengcheng Han, Li Chen, Huarui Yin, Guo Wei
In this article, we propose a new generalized selection transmit scheme (GSTS) for wireless powered communication (WPC), where data access point (DAP) is powered by energy access point (EAP) to communicate with wireless device (WD). Theoretically speaking, allocating all harvesting energy to the antenna with the best channel gain will achieve the optimal performance. While the harvesting energy is dynamic and may exceed the power limitation of single antenna, we should allocate the harvesting energy to the best antennas subset with the minimum number of antennas. That is GSTS. For GSTS, we derive the new closed-form probability density function (PDF) of signal to noise ratio (SNR). According to the derived PDF, the approximate outage probability is derived. In order to depict the trend of outage probability at high SNR area, the diversity order is derived. It is determined by the minimum one of the transmit antenna number of EAP and that of DAP. Besides, the influence of line-of-sight (LOS) component in wireless power transfer (WPT) is also discussed.

MM-wave wideband propagation model for wireless communications in built-up environments

April 1, 2018, 4:31 am

≫ Next: 5G-based green broadband communication system design with simultaneous wireless information and power transfer

≪ Previous: A new scheme of dynamic power allocation in wireless powered communication

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Publication date: Available online 31 March 2018
Source:Physical Communication
Author(s): Anwar Jarndal, Khawla Alnajjar
Millimeter-wave technology is promising for the next generation of wireless communication. An appropriate channel model for typical scenarios in a built-up environment is crucially needed for development of future technologies such as 5G. This paper presents an efficient millimeter wave wideband propagation model that can be used for analysis and design purposes. Unlike the commonly used two-ray and statistical models, the proposed model has higher reliability and accuracy to simulate the considered environment. The uniform theory of diffraction has been used to calculate the total received signal due to multi-reflection-diffraction for both linear and circular polarization. Mathematical formulas have been derived for each considered ray contribution in terms of the building dimensions and the distances between the building, mobile and transmitter. The model has been used to evaluate the performance of the communication system at 28 and 73 GHz based on signal fading characteristics and power delay profile, and the simulation results have been compared with other published works

5G-based green broadband communication system design with simultaneous wireless information and power transfer

April 4, 2018, 11:42 am

≫ Next: Wireless powered cooperative communications with direct links over correlated channels

≪ Previous: MM-wave wideband propagation model for wireless communications in built-up environments

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Publication date: Available online 3 April 2018
Source:Physical Communication
Author(s): Xin Liu, Xueyan Zhang, Min Jia, Lisheng Fan, Weidang Lu, Xiangping Zhai
In 5G communications, the increasing demand for high data rate and ubiquitous services has led to a large energy consumption in both transmitter and receiver. Wireless power transfer (WPT) has been proposed as an effective energy saving method. However, WPT and wireless information transfer (WIT) are often separated in a communication system. In this paper, a 5G-based green broadband communication system with simultaneous wireless information and power transfer (SWIPT) is proposed to combine WIT and WPT. In the system, the subband sets available for WIT and WPT are defined by two complementary spectrum marker vectors, and two independent frequency domain signals using different subband sets are achieved by calculating the inner product of spectrum marker vector, pseudo-random (PR) phase and power scaling vector. Time domain fundamental modulation waveform (FMW) is generated by doing inverse fast fourier transform (IFFT) of the frequency domain signal. The data stream is modulated on the FMW for WIT, while the FMW for WPT is transmitted directly. The BER performance of the system is analyzed. A joint optimization unit has been deployed to maximize the system throughput by jointly optimizing subbband sets and subband powers subject to the constraints of energy requirement and interference. The simulation results have shown the outstanding performance of the designed system.

Wireless powered cooperative communications with direct links over correlated channels

April 5, 2018, 12:00 pm

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

≪ Previous: 5G-based green broadband communication system design with simultaneous wireless information and power transfer

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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

April 6, 2018, 12:20 pm

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

≪ Previous: Wireless powered cooperative communications with direct links over correlated channels

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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.

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

April 6, 2018, 12:20 pm

≫ Next: Photonic millimeter-wave bridge for multi-Gbps passive optical networks

≪ Previous: 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): 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

April 8, 2018, 4:12 pm

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

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

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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

April 8, 2018, 4:12 pm

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

≪ Previous: Photonic millimeter-wave bridge for multi-Gbps passive optical 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

April 15, 2018, 12:08 pm

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

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

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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$\text{\%}$ 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

April 23, 2018, 2:14 pm

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

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

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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

April 23, 2018, 2:14 pm

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

≪ Previous: 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): 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

April 23, 2018, 2:14 pm

≫ Next: A new clipped PIC detector for asynchronous upstream OCDMA-PON

≪ Previous: 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): 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.

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A new clipped PIC detector for asynchronous upstream OCDMA-PON

April 23, 2018, 2:14 pm

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

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

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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.

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

April 26, 2018, 8:50 pm

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

≪ Previous: A new clipped PIC detector for asynchronous upstream OCDMA-PON

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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.

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

May 1, 2018, 9:21 am

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

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

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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.

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

May 1, 2018, 9:21 am

≫ Next: Power optimization of LTE-800 and coexistence with DVB-T services

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

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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.

Power optimization of LTE-800 and coexistence with DVB-T services

May 1, 2018, 9:21 am

≫ Next: SINR balancing technique for robust beamforming in V2X-SWIPT system based on a non-linear EH model

≪ Previous: 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): Marija Denkovska, Daniel Denkovski, Vladimir Atanasovski, Liljana Gavrilovska
The emergence of cognitive radio technologies and the reallocation of the upper Ultra High Frequency (UHF) band ($790-862$ MHz) for broadband services has led to interference concerns for the DVB-T (Digital Video Broadcasting - Terrestrial) services. The DVB-T receivers need to be protected from aggregate interference coming from in-band and out-of-band transmissions, especially from the LTE-800 (Long-Term Evolution at 800 MHz) networks due to the operation in near spectral and location proximity. Although operating in different, but neighboring bands, the LTE-800 networks can be a serious threat to the DVB-T services due to excessive aggregate out-of-band interference caused to the DVB-T receivers. The regulators have assessed and defined the protection criteria for these cases. The power optimization of the LTE cellular networks, operating in near one spectral reuse factor, also remains an open issue due to the non-convex optimization problems. This paper proposes a novel algorithm for LTE-800 power allocation algorithm for capacity maximization of an LTE-800 network under DVB-T protection criteria. The algorithm uses k-means clustering to find the most critical geographical areas based on the DVB-T receivers protection ratios. It also adapts a local D.C. (Difference of two Convex functions/sets) programming approach to make the power optimization problem convex and perform the LTE-800 coverage and capacity optimization. The simulation analysis of the algorithm include realistic data for DVB-T modeling and Poisson Point Process for LTE-800 base stations (BS) spatial modeling. The proposed algorithm is compared to two extreme approaches, i.e. the max LTE BS power approach totally ignoring the DVB-T protection and the uniform power scaling approach that certainly protects the DVB-T service. The results prove the performance increase introduced by the proposed algorithm in terms of spatial capacity and coverage and DVB-T service protection.

SINR balancing technique for robust beamforming in V2X-SWIPT system based on a non-linear EH model

May 3, 2018, 10:35 pm

≫ Next: First and Second-Order Semi-Hidden Fritchman Markov models for a multi-carrier based indoor narrowband power line communication system

≪ Previous: Power optimization of LTE-800 and coexistence with DVB-T services

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Publication date: Available online 3 May 2018
Source:Physical Communication
Author(s): Shidang Li, Chunguo Li, Shi Jin, Mingsheng Wei, Luxi Yang
Vehicle to everything (V2X) is emerging as a promising application scenario of next generation mobile communications. In V2X systems, a series of applications (information transmission, in-car entertainment, etc.) rely on the limited vehicle battery. However, most prior work limits to the automatic piloting, channel measurement/estimation and high speed transmissions, seldom study has been done on the battery-limited for V2X. In light of this, here we investigate the problem of the downlink beamforming design for signal-to-interference ratio balancing in a V2X-SWIPT environment with imperfectly estimated channels at the base station, where a practical non-linear energy harvesting model is considered. The problem is further transformed into a two-layer optimization problem, where we solve the inner-level problem by exploiting S-Procedure, and the outer-level problem through bisection approach. Finally, simulation results are carried out to confirm that the proposed robust beamforming design obtains a favorable result in applications of practical interest.

First and Second-Order Semi-Hidden Fritchman Markov models for a multi-carrier based indoor narrowband power line communication system

May 5, 2018, 5:32 am

≫ Next: Performance of a frequency-domain OFDM-frame detector

≪ Previous: SINR balancing technique for robust beamforming in V2X-SWIPT system based on a non-linear EH model

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Publication date: Available online 4 May 2018
Source:Physical Communication
Author(s): Ayokunle Damilola Familua, Ling Cheng
The realization of a Semi-Hidden Fritchman Markov models (SHFMMs) for power line communication (PLC) channel is only practicable if combined with efficient algorithms for learning and inference. This article thus reports First and Second-Order SHFMMs for the bit error pattern at the output of an Orthogonal Frequency Division Multiplexing based system for in-home narrowband PLC applications. Accurate SHFMMs have been derived for a residential and laboratory environment using the efficient iterative Baum-Welch algorithm. The log-likelihood ratio plots, the error-free run distribution plots, the mean square error and Chi-Square $\left({\chi }^2\right)$ test validates the accuracy of the derived models. The reliability and accuracy of resulting models are confirmed by a close match between the measured bit error sequences and the model generated bit error sequences. The estimated Second-Order SHFMMs have been validated to be superior to the First-Order models, although at the expense of more computational complexity. Resulting models assist designers to speed up and facilitate the process of designing and evaluating novelties for PLC systems.

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Performance of a frequency-domain OFDM-frame detector

May 6, 2018, 11:44 am

≫ Next: Simultaneous cooperative spectrum sensing and wireless power transfer in multi-antenna cognitive radio

≪ Previous: First and Second-Order Semi-Hidden Fritchman Markov models for a multi-carrier based indoor narrowband power line communication system

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Publication date: Available online 5 May 2018
Source:Physical Communication
Author(s): Chantri Polprasert, Tanee Demeechai
A frequency-domain algorithm for orthogonal frequency-division multiplexing (OFDM)-frame detection is considered useful when the OFDM system is to operate in a known narrowband interference (NBI) channel, e.g., in a cognitive radio OFDM-based overlay system. While frame detection algorithm based on state-of-the-art time-domain correlation perform poorly in such a channel, we propose a frame detection algorithm based on energy detection in frequency domain. By exploiting the NBI band information obtained during sensing period, the proposed algorithm exhibits strong performance and outperforms other existing frequency-domain OFDM frame detection alternatives even at the signal-to-interference ratio (SIR) below 0 dB. Moreover, simulation results are confirmed by the analytical performance presented as a linear combination of the incomplete gamma function. The weight of each component is a function of the eigenvalues of the matrix associated with the detection metric and the number of summation is proportional to the number of non-zero eigenvalues of the matrix associated with the detection metric.

Simultaneous cooperative spectrum sensing and wireless power transfer in multi-antenna cognitive radio

May 8, 2018, 5:11 pm

≫ Next: Joint optimization of power splitting and allocation for SWIPT in interference alignment networks

≪ Previous: Performance of a frequency-domain OFDM-frame detector

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Publication date: Available online 7 May 2018
Source:Physical Communication
Author(s): Zhiqun Song, Zhongzhao Zhang, Xin Liu, Yutao Liu, Lisheng Fan
In multi-antenna cognitive radio (CR), the sensing performance of detecting the presence of primary user (PU) in fading channel can be improved through multi-antenna cooperative spectrum sensing. However, the CR may consume more stored energy due to the cooperative spectrum sensing and thus decrease its transmission performance. In this paper, to guarantee the transmission performance, a simultaneous cooperative spectrum sensing and wireless power transfer (SCSSWPT) scheme has been proposed, which can harvest the radio frequency (RF) energy of the PU signal to supply the consumed energy of spectrum sensing. Time splitting model, power splitting and antenna splitting model are proposed to implement cooperative spectrum sensing, energy harvesting and data transmission simultaneously. Three optimization problems have been formulated to maximize spectrum efficiency of the CR in the three SCSSWPT models, respectively, subject to the constraints of detection probability and harvested energy. The simulation results have shown that there is an optimal number of sensing antennas to maximize the spectrum efficiency of the CR, and the time splitting model can achieve higher spectrum efficiency.

Joint optimization of power splitting and allocation for SWIPT in interference alignment networks

May 8, 2018, 5:11 pm

≫ Next: Editorial Board

≪ Previous: Simultaneous cooperative spectrum sensing and wireless power transfer in multi-antenna cognitive radio

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Publication date: August 2018
Source:Physical Communication, Volume 29
Author(s): Nan Zhao, Bingcai Chen
Interference alignment (IA) is a promising solution for interference management in wireless networks. On the other hand, simultaneous wireless information and power transfer (SWIPT) has become an emerging technique. Although some works have been done on IA and SWIPT, these two important areas have traditionally been addressed separately in the literature. In this paper, we propose to use a common framework to jointly study IA and SWIPT with perfect channel state information (CSI). We analyze the performance of SWIPT in IA networks. Specifically, we derive the upper bound of the power that can be harvested in IA networks. In addition, we show that, to improve the performance of wireless power transfer and information transmission, users should be dynamically selected as energy harvesting (EH) or information decoding (ID) terminals. Furthermore, we design two easy-implemented SWIPT-user selection (SWIPT-US) algorithms in IA networks based on the assumption of perfect CSI. To optimize the ID and EH performance of SWIPT in IA networks, a power-splitting optimization (PSO) algorithm is proposed when power splitters are available, and its closed-form optimal solutions are derived. Power allocation in the PSO algorithm is also studied to further optimize the performance. Simulation results are presented to show the effectiveness of the proposed algorithms.

Editorial Board

May 9, 2018, 5:30 pm

≫ Next: An investigation of S-DF cooperative communication protocol over keyhole fading channel

≪ Previous: Joint optimization of power splitting and allocation for SWIPT in interference alignment networks

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Publication date: June 2018
Source:Physical Communication, Volume 28

An investigation of S-DF cooperative communication protocol over keyhole fading channel

May 18, 2018, 6:39 pm

≫ Next: Reduced complexity Kalman filtering for phase recovery in XPIC systems

≪ Previous: Editorial Board

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Publication date: Available online 15 May 2018
Source:Physical Communication
Author(s): R.S. Tripathi, Ritesh Kumar Mishra
This paper investigates the keyhole or pinhole effect on the pairwise error probability (PEP) performance of the multiple-input multiple-output (MIMO) space–time block-code (STBC) based selective decode and forward (S-DF) protocol. The closed form PEP expressions are derived for several configurations in terms of number of hops, phases, and relays over Nakagami-m fading channel, with perfect and imperfect channel state information (CSI), and with and without the keyhole condition. Further, a framework is developed for deriving the diversity order (DO) for each configuration. It demonstrates that full DO for cooperation protocol can be achieved when there is a knowledge of perfect CSI. A convex optimization framework is formulated for obtaining the optimal source-relay power allocation factors which significantly improve the end-to-end reliability of the system under power constraint scenarios. Monte Carlo simulations are performed for both equal and optimal power allocation factors and results show the substantial improvement in PEP performance with an increase in the value of the shape parameter and relay to destination (RD) link channel variance. Results show an improved PEP performance by increasing the RD link channel variance in comparison to increasing the source to relay (SR) link channel variance. Also PEP performance degrades for keyhole Nakagami-m fading channel as compared to Nakagami-m fading channel. Simulation results are in close agreement with the analytical results at high signal to noise ratio (SNR) regimes.

Reduced complexity Kalman filtering for phase recovery in XPIC systems

May 18, 2018, 6:39 pm

≫ Next: Performance analysis of hybrid PAPR reduction technique for LTE uplink communications

≪ Previous: An investigation of S-DF cooperative communication protocol over keyhole fading channel

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Publication date: August 2018
Source:Physical Communication, Volume 29
Author(s): Farzana Kulsoom, Anna Vizziello, Roberta Borra, Pietro Savazzi
Reduced-complexity Kalman-based algorithms are proposed to recover the phase of cross-polar interference cancellation (XPIC) receivers in microwave radio relay links. In particular, two completely independent radio frequency (RF) transceiver chains are considered for the two different polarizations, in order to have the maximum flexibility to connect different single carrier transceivers to dual-polarized antennas. A one-state Kalman model is proposed, which is of low complexity and thus suitable for a modern higher data rates M-ary quadrature amplitude modulation (M-QAM) receiver. Moreover, a further reduced complexity version is developed that uses a lower amount of information to recover the phase at the receiver, as well as a downsampling procedure to speed up the Kalman algorithm, and an alternative error computation that is essential to ease the Kalman implementation. It is worth noting that the three last simplifications are general and can be applied not only to a one-state Kalman model. Simulation results compare the proposed simplified Kalman solutions to typical phase-locked loop (PLL) algorithms proving their comparable performance with the benefit of lower complexity. Finally, the relationships between the Extended Kalman and the PLL approaches are investigated. The obtained relation is essential for the cross-polar phase recovery, since, as far as the authors know, there are not closed-form solutions for the PLL parameter optimization in cross schemes.

Performance analysis of hybrid PAPR reduction technique for LTE uplink communications

May 18, 2018, 6:39 pm

≫ Next: Trellis coded quadrature spatial modulation

≪ Previous: Reduced complexity Kalman filtering for phase recovery in XPIC systems

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Publication date: August 2018
Source:Physical Communication, Volume 29
Author(s): Shri Ramtej Kondamuri, Anuradha Sundru
Long Term Evolution standard implemented Single Carrier Frequency Division Multiple Access (SC-FDMA) in the uplink communications due to its low peak to average power ratio (PAPR). But for higher order modulations, there is a need for further reduction of PAPR in SC-FDMA systems. There are numerous techniques to decrease PAPR, but clipping and companding techniques are very simple to implement without any side information. $\mu$ law companding provides good PAPR reduction but increases the average power of companded signal. In this paper, the distribution of SC-FDMA signal is approximated, and a companding technique is proposed to transform the approximated distribution into a uniform distribution, which reduces PAPR without increasing average power of the signal. For further improvement in PAPR, a hybrid technique is also proposed where the companded signal is clipped to a specific threshold value. Simulation results show that PAPR reduction achieved by the proposed companding technique is better than that of $\mu$ law companding with a slight degradation in bit error rate (BER) performance. The proposed companding technique with no decompanding operation has better BER performance when compared to that with approximated decompanding operation. The hybrid technique further reduces PAPR with similar BER performance as that of proposed companding technique by carefully choosing the clipping ratio.

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Trellis coded quadrature spatial modulation

May 26, 2018, 7:24 pm

≫ Next: Subcarrier allocation based Simultaneous Wireless Information and Power Transfer algorithm in 5G cooperative OFDM communication systems

≪ Previous: Performance analysis of hybrid PAPR reduction technique for LTE uplink communications

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Publication date: Available online 22 May 2018
Source:Physical Communication
Author(s): Zehra Yigit, Ertugrul Basar, Raed Mesleh
In this paper, a novel multiple-input multiple-output (MIMO) transmission scheme called trellis coded quadrature spatial modulation (TC-QSM), is proposed. In the proposed scheme, trellis coded modulation (TCM) principle is applied to the emerging quadrature spatial modulation (QSM) scheme, and a trellis encoder and a QSM mapper are jointly designed to benefit from both coding and multiplexing gains. At the receiver side, a soft-decision Viterbi decoder is used along with a QSM decoder to obtain the optimum error performance. Considering our design criterion, TC-QSM schemes are designed for different number of trellis states, transmit antennas and spectral efficiencies. The pairwise error probability (PEP) of the TC-QSM scheme is derived over quasi-static Nakagami- $m$, Rician and Rayleigh fading channels and an upper bound on the average bit error probability (BEP) is obtained. Through comprehensive Monte Carlo simulations, the effect of signal and spatial bits on uncoded and trellis coded SM and QSM schemes over Nakagami- $m$ andRician fading channels are investigated for different fading parameters. Moreover, the error performance of the TC-QSM and SM with trellis coding (SM-TC) schemes are compared for different spectral efficiency values, where it is revealed that the proposed TC-QSM scheme provides an interesting trade-off between performance and implementation cost, and achieves an improved error performance over reference schemes including SM, QSM and SM-TC.

Subcarrier allocation based Simultaneous Wireless Information and Power Transfer algorithm in 5G cooperative OFDM communication systems

May 26, 2018, 7:24 pm

≫ Next: Optimal selection of spatial dimensions of signal subspace for relay constellation decoding

≪ Previous: Trellis coded quadrature spatial modulation

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Publication date: Available online 23 May 2018
Source:Physical Communication
Author(s): Zhenyu Na, Yuyao Wang, Xiaotong Li, Junjuan Xia, Xin Liu, Mudi Xiong, Weidang Lu
Self-sustainable communications are highly vital for large amounts of mobile terminals in the Fifth Generation (5G) communication systems. Simultaneous Wireless Information and Power Transfer (SWIPT) makes it possible that terminal transfers information while prolonging battery life by harvesting Radio Frequency (RF) energy. Though the traditional sub-carrier allocation based SWIPT algorithm in OFDM communication systems can optimize resource allocation, the receiver often cannot achieve higher information decoding rate when the channel condition of direct transmission deteriorates. In view of this situation, a sub-carrier allocation based SWIPT algorithm in 5G cooperative OFDM communication systems is proposed in this paper. The amplify-and-forward protocol is adopted by relay node which transmits information from source node to destination node by using a part of its sub-carriers. The remaining sub-carriers are used for energy harvesting. On the premise of minimum threshold of harvested energy, the sub-carrier and power allocations at relay node are optimized by establishing and solving the corresponding optimization model. Simulation results reveal that the proposed algorithm not only achieves the optimal sub-carrier and power allocations, but also improves information decoding rate with fast converging speed.

Optimal selection of spatial dimensions of signal subspace for relay constellation decoding

May 27, 2018, 7:25 pm

≫ Next: A simple approach for the suppression of Rician interference in a relay backhaul using limited feedback

≪ Previous: Subcarrier allocation based Simultaneous Wireless Information and Power Transfer algorithm in 5G cooperative OFDM communication systems

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Publication date: Available online 26 May 2018
Source:Physical Communication
Author(s): Xiyuan Wang, Yong Wang
The dimension of the right null space is only one for traditional signal space alignment with the minimum configuration of antennas. Then, the direction of a pair of alignment signal space is fixed and cannot be flexibly adjusted. Although the different alignment directions are mutually independent to facilitate relay decoding, the minimum Euclidean distance between modulated signals code words is small, which affects the decoding accuracy. In this paper, we design a novel alignment signal transmission scheme using degrees of freedom of null space generated by redundant antennas. The scheme selects the mutually orthogonal space dimension in the redundant null space as the signal alignment direction. It optimizes the minimum Euclidean distance in the system by maximizing the minimum constellation point distance. Simulation results show that the distances between the constellation points of different code symbols become significantly larger. The larger constellation distance of different coded symbols can improve the decoding accuracy. By optimizing the distance between the minimum constellation points, the transmission performance of each link is balanced and the whole system performance is improved.

A simple approach for the suppression of Rician interference in a relay backhaul using limited feedback

June 6, 2018, 5:58 pm

≫ Next: Coded color shift keying with frequency domain equalization for low complexity energy efficient indoor visible light communications

≪ Previous: Optimal selection of spatial dimensions of signal subspace for relay constellation decoding

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Publication date: Available online 4 June 2018
Source:Physical Communication
Author(s): Inam Ullah, Edward Mutafungwa, Jyri Hämäläinen, David González González
The benefits of Decode and Forward (DF) relaying span from deployment flexibility to coverage extension and improved capacity distribution in the network. Accordingly, relaying has become an integral part of the modern radio access network standards. Besides the evident benefits of DF relaying, the fact is that it uses part of the valuable radio access resources for the communication between network elements. Thus, the amount of radio resources allocated to the Relay Link (RL) between serving Donor Base Station (DBS) and the Relay Node (RN) should be minimized. This easily makes the RL a bottleneck in conventional two-hop infrastructure relaying. Furthermore, current mobile systems apply universal frequency reuse in macrocell deployments where macrocell BS’s serve RN’s as well. As a result, RL’s may suffer from severe interference. We propose a practical limited feedback approach that can be used to simultaneously improve the signal strength and to suppress the interference in the RL. To that end, we deduce analytical formulas for the distribution of the Signal to Interference and Noise Ratio (SINR) in the RL by assuming Rice and Rayleigh fading combinations in desired and interfering links. Furthermore, we compute two-hop end-to-end (e2e) outage probabilities for different interference and limited feedback scenarios. Results show that especially in Rice fading environment, large performance gains can be obtained with only few bits feedback in case where RL has scarce radio resources and suffers from dominant interferer. This makes the proposed method very feasible for the infrastructure relaying where RN’s can be placed either in the rooftop level or other locations that provide a line of sight towards macro BS’s.

Coded color shift keying with frequency domain equalization for low complexity energy efficient indoor visible light communications

June 6, 2018, 5:58 pm

≫ Next: Reliability benefit of network coding and cooperative communication

≪ Previous: A simple approach for the suppression of Rician interference in a relay backhaul using limited feedback

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Publication date: Available online 4 June 2018
Source:Physical Communication
Author(s): Ravinder Singh, Timothy O’Farrell, Mauro Biagi, John P. David
The adaptive tri-chromatic color shift keying (CSK) modulation standardised in IEEE 802.15.7 and the advanced quad-chromatic CSK are unable to utilize their entire spectral efficiency range over dispersive indoor VLC channels and incur large power penalties without the use of channel equalization and forward error correction. This degrades the energy efficiency and limits the throughput capability of CSK schemes to approximately half of the data-rates specified in the IEEE standard for multimedia services in wireless personal area networks. To comply with the desire for low latency and minimal implementation complexity in the CSK standardisation framework, we consider an industry standard binary convolutional code and frequency domain equalization (FDE) which provide one-shot data packet processing. Our results show that when operating over hybrid indoor visible light communication (VLC) links, the FDE based rate-adaptive coded modulation CSK scheme achieves a significant 11 dB SNR gain over an uncoded, unequalized system.

Reliability benefit of network coding and cooperative communication

June 6, 2018, 5:58 pm

≫ Next: A two-timescale graph-based resource allocation scheme combing dynamic eICIC in Heterogeneous Networks

≪ Previous: Coded color shift keying with frequency domain equalization for low complexity energy efficient indoor visible light communications

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Publication date: Available online 5 June 2018
Source:Physical Communication
Author(s): Arghyadip Roy, Rajarshi Roy
Network coding (NC) can reduce the number of packet retransmissions and improve the network reliability in lossy networks. Reliability gain of NC over traditional error control mechanisms has been investigated in recent works. In this paper, we study reliable broadcast in a real-world topology where link loss probabilities are different from each other. We derive approximate closed-form expressions and analyse asymptotic behaviour for expected number of transmissions employing stop-and-wait automatic repeat request (ARQ) and NC as error control mechanisms. In physical layer cooperative communication, multiple nodes can transmit collectively to take advantage of spatial diversity. We incorporate the idea of physical layer cooperative communication with ARQ and NC separately, to obtain further reliability. Numerical results based on our asymptotic analysis indicate that NC offers more reliability than stop-and-wait ARQ. However, as the size of the cooperating set increases, both the schemes offer the same reliability. Approximate closed-form expressions for the reliability metric of these schemes and their asymptotic results match well with simulation results. Furthermore, simulation results establish that the proposed NC scheme outperforms existing schemes in literature.

A two-timescale graph-based resource allocation scheme combing dynamic eICIC in Heterogeneous Networks

June 7, 2018, 7:20 pm

≫ Next: Improved decomposition-based multi-objective cuckoo search algorithm for spectrum allocation in cognitive vehicular network

≪ Previous: Reliability benefit of network coding and cooperative communication

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Publication date: Available online 6 June 2018
Source:Physical Communication
Author(s): Feifei Zhao, Wenping Ma, Momiao Zhou, Chengli Zhang
Heterogeneous Network (HetNet) has been viewed as an effective way to meet the tremendous growth of mobile traffic, in which the cross-tier and co-tier interference are the key limitations. Most of the traditional interference management strategies only focus on addressing either cross-tier interference or co-tier interference. We in this paper propose a resource allocation scheme to systematically cope with both of them in Orthogonal Frequency Division Multiple Access (OFDMA)-based HetNets. Specifically, the proposed scheme combines the dynamic enhanced inter-cell interference coordination (eICIC) and orthogonal resource allocation (ORA), to eliminate the cross-tier and co-tier interference respectively. Furthermore, with tracking the real-time variations of the user information (e.g., locations or service requirements), the proposed scheme is separated into two timescales. At the large timescale, a centralized strategy is performed to roughly allocate resource blocks (RBs) to cells; at the small timescale, a distributed strategy is performed to further schedule RBs among users. Also, we formulate two optimization problems to maximize the minimum of users’ throughput satisfaction rate (TSR) for our proposed scheme, followed by two graph-based algorithms to solve them with low complexity. Simulation results manifest the superiority of our proposed scheme in guaranteeing the fairness of users’ TSR.

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Improved decomposition-based multi-objective cuckoo search algorithm for spectrum allocation in cognitive vehicular network

June 22, 2018, 1:15 pm

≫ Next: Carrot and stick model for dynamic secondary radio spectrum trade with QoS optimization

≪ Previous: A two-timescale graph-based resource allocation scheme combing dynamic eICIC in Heterogeneous Networks

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Publication date: Available online 15 June 2018
Source:Physical Communication
Author(s): Ruining Zhang, Xuemei Jiang, Ruifang Li
The allocation of spectrum resources efficiently and equitably in dynamic cognitive vehicular networks is more challenging than static cognitive networks. Currently, most spectrum allocation algorithms are on the basis of a fixed network topology, thereby ignoring the mobility of cognitive vehicular users (CVUs ), timeliness of licensed channels, and uncertainty of spectrum sensing in complex environments. In this paper, a cognitive vehicular network spectrum allocation model for maximizing the network throughput and fairness is established considering these factors. A rapid convergence, improved performance algorithm for solving this multi-objective problem is necessary to adapt to a dynamic network environment. Therefore, an improved decomposition-based multi-objective cuckoo search (MOICS/D) algorithm is proposed. This algorithm integrates a decomposition-based multi-objective optimization framework and an improved CS algorithm. The multi-objective problem is decomposed into multiple scalar sub-problems with different weight coefficients, and the cuckoo algorithm with adaptive steps is used to optimize these sub-problems simultaneously. Simulation results show that the MOICS/D algorithm has faster and more stable convergence than the MOEA/D and NSGA-II algorithms and can improve the throughput and fairness of the network.

Carrot and stick model for dynamic secondary radio spectrum trade with QoS optimization

June 22, 2018, 1:15 pm

≫ Next: Non-renewable energy efficiency optimization in energy harvesting relay-assisted system

≪ Previous: Improved decomposition-based multi-objective cuckoo search algorithm for spectrum allocation in cognitive vehicular network

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Publication date: Available online 19 June 2018
Source:Physical Communication
Author(s): Mubbashar Altaf Khan, Mohsin M. Jamali
Cognitive Radios (CR) propose for an opportunistic access to new Secondary Users (SUs) in the white spaces existing in the already licensed radio spectrum on a non-interfering basis with the current Primary Users (PUs). The Secondary Spectrum Markets (SSMs) have lower operating costs as compared to those for the Primary Licensed Operators (PLOs) as they do not require to license dedicated spectrum bands for their operation. This naturally makes CR a disruptive technology and its emergence is inevitably subject to economic viability challenges and technological hijack threats by the PLOs. The existing literature does not address the possible use of economic malpractices by the PLOs to raise the spectrum reuse costs to be no longer affordable by their direct competitors. This research proposes a secondary spectrum trade model based on a carrot and stick rule to keep the business in the SSMs competitive and fair using monetary incentives and penalties based on participation behaviors. A methodology for QoS optimization using Genetic Algorithms (GAs) with respect to those requested by the SUs is implemented. The simulation results indicate that the overall revenues of the participating PLOs with unfair bidding behaviors are lowered due to the incurrence of penalty costs.

Non-renewable energy efficiency optimization in energy harvesting relay-assisted system

June 22, 2018, 1:15 pm

≫ Next: Coordinated multipoint in dense heterogeneous networks with overlapping microcell expanded regions and its effect on backhaul links

≪ Previous: Carrot and stick model for dynamic secondary radio spectrum trade with QoS optimization

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Publication date: August 2018
Source:Physical Communication, Volume 29
Author(s): Ming Zhao, Dan Deng, Wuyang Zhou, Lisheng Fan
In this paper, we consider a scenario where the source node powered by the conventional power grid transmits data with the assistance of some energy harvesting (EH) decode-and-forward (DF) relay nodes. Unlike EH providing renewable energy, most power grids are supported by the non-renewable fossil fuels. So our goal is to maximize the non-renewable energy efficiency (EE) of the non-EH source throughout multiple timeslots. To deal with the randomness of energy arrivals and non-ideal circuit power, we formulate the EE optimization problem of the relaying system by combining the power allocation and the sleep mode in both the source and the relay. We firstly deal with this problem in a special case with just one timeslot and then solve it in a multi-timeslot scenario with dynamic programming (DP) approach. We also propose a heuristic algorithm with a complexity lower than the DP algorithm. We compare the performance of the two algorithms with a baseline scheme. Simulation results show that the heuristic algorithm provides close EE with the DP algorithm, and a significant EE gain over the baseline scheme.

Coordinated multipoint in dense heterogeneous networks with overlapping microcell expanded regions and its effect on backhaul links

June 29, 2018, 11:47 am

≫ Next: ETRT – Cross layer model for optimizing transmission range of nodes in low power wireless networks – An Internet of Things Perspective

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Publication date: Available online 26 June 2018
Source:Physical Communication
Author(s): Jessica Khoriaty, Hassan Artail, Youssef Nasser
One of the goals of Heterogeneous Networks (HetNets) is to offload traffic from the macrocell BS to the microcell base stations (BSs). It has been proposed that in order for the microcell to acquire more users and offload increasing amounts of traffic, its region of coverage must be expanded. This however causes significant cross-tier interference, which can be remedied by utilizing coordinated multipoint (CoMP) within the microcell expanded region (ER). Our methodology considers the effect of overlapping ERs, and proposes the cooperation of concerned microcell BSs with the macro cell BS to further reduce the outage probability and improve throughput. Another important consideration in our analysis is the effect of having non-ideal backhaul on the system’s performance. That is, CoMP increases the strain on the backhaul network, since additional data that is proportional to the number of cooperating BSs needs to travel on the backhaul links. Furthermore, the delay should be minimal and less than one subframe duration in order for reported channel state information to remain valid. With this in mind, our proposed system considers the effect of having non-ideal backhaul in a cellular network with CoMP, while taking into account overlaps in the microcell ERs.

ETRT – Cross layer model for optimizing transmission range of nodes in low power wireless networks – An Internet of Things Perspective

June 29, 2018, 11:47 am

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Publication date: Available online 28 June 2018
Source:Physical Communication
Author(s): Sarwesh P., N. Shekar V. Shet, K. Chandrasekaran
Internet of Things network is managed by battery operated devices and low power radio links since they are referred to low power networks. In present communication era, many research works are concentrating on low power wireless network. Cross layer design is one of the acclaimed technique that decidedly improves the network performance. In this article, we come up with the cross-layer model that satisfies distinct network requirements and prolongs network lifetime. It integrates physical layer, data link layer (Media Access Control) and network layer in the protocol stack. In our model, a threshold value called ETRT (Expected Transmission Range Threshold) is introduced, which is computed with the help of routing information. Later, MAC based power control technique utilizes the ETRT value and assigns optimum transmission range for every node. The idea at the heels of proposed cross layer model is estimating the capability (ETRT value) of the particular node and assigning the suitable transmission power for every node, based on its capability (ETRT value). Hence, assigning optimum transmission power based on ETRT information prolongs the network lifetime with better reliability and Quality of Service(QoS). From our results, it is noticed that the ETRT based cross layer model performs twice better than the standard model.

Modified switching DE algorithm to facilitate reduction of PAPR in OFDM systems

June 29, 2018, 11:47 am

≫ Next: A novel sensing and primary user protection algorithm for cognitive radio network using IoT

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Publication date: Available online 28 June 2018
Source:Physical Communication
Author(s): Mahua Rakshit, Subhankar Bhattacharjee, Sanjib Sil, Amlan Chakrabarti
Partial Transmit Sequence (PTS) currently can be regarded as an extremely attractive and popular method which allows the achievement of very good Peak to Average Power Ratio (PAPR) reduction for signals that have undergone Orthogonal Frequency Division Multiplexing (OFDM), while also is being a technique which does not distort the signals being processed. In this method, a comprehensive search is conducted taking into account all possible combinations of phase-factors that can occur, leading to an increasing complexity of computation with respect to increasing in sub-blocks. The current paper outlines a novel low complexity sub-optimal PTS technique with its basis in an altered implementation of Differential Evolution (DE) algorithm shortly MBLX-DE which significantly diminishes the PAPR of OFDM signals. More specifically SWDE_Sucess_MBLX (Switched parameter Differential Evolution with success based mutation and modified blending crossover) algorithm (Ghosh et al., 0000) is modified in an efficient way and has been implemented for the PTS scheme. The proposed algorithm introduces modifications in three stages of SWDE_Sucess_MBLX like population central tendency based mutation scheme is incorporated along with the success based mutation, a random selection between two cross-over strategies with blending rate concept and threshold-based selection. A theoretical performance study with general formulas of the proposed scheme is presented and a comparative analysis is done with existing algorithms. Extensive simulation results demonstrate that our proposed method can substantially outperform against the currently best-known algorithms in the context of reduction of PAPR as well as performance in terms of complexity of the computations to be performed.

A novel sensing and primary user protection algorithm for cognitive radio network using IoT

July 1, 2018, 11:39 pm

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Publication date: Available online 30 June 2018
Source:Physical Communication
Author(s): Vivek Rajpoot, Vijay Shanker Tripathi
Internet of things (IoT) is a technology which facilitates passive devices to participate in active communication. In the presented work the radio frequency identification (RFID) system is used to access information from passive primary receiver (PURx). This inspires to develop a novel sensing algorithm along with PURx protection from harmful transmissions of cognitive radio (CR) nodes in CR network. The novelty in the sensing and protection lies in the approach of accessing information from primary users. Here a CR node can detect occupancy of primary channel from both, primary transmitter (PUTx) end as well as from PURx end on the basis of relative distance. For protection of PURx a novel power control algorithm is proposed and implemented. The results indicate less energy is needed to run the network along with a notable improvement in average throughput and reduction in delay for increasing amount of CR traffic.

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