Hop Channel Research Articles

Multihop underwater optical wireless communication system for internet of underwater things applications

SummaryInternet of underwater things (IoUT) has garnered significant attention for monitoring and exploration applications in underwater scenarios. The interconnected devices used in IoUT have power constraint as batteries are difficult to recharge or replace. Multihop cooperative communication can help reduce the power requirement of a single node by breaking the long distance links into two or more high quality segments. In this paper, we investigate the end‐to‐end average bit error rate (BER) of the multihop underwater relay network. The nodes are connected to each other using optical wireless communication link which provides high data rates with low latency. Closed form expressions for average BER are derived for two scenarios: (1) where every hop channel has the same statistical behavior and (2) each channel is characterized by different statistical behavior. Further, the impact of channel parameters on the system performance is analyzed and discussed.

Performance analysis and optimization of polarized on‐body relay channels

On-body propagation channels show significant polarization selectivity that has dominant impacts on the on-body link quality in wireless body area networks. For on-body relay channels over long distances across the body, the antenna polarization configurations of the relaying nodes are crucial to determine the relay performance, thereby requiring polarization optimization schemes. In this article, narrow band flat-fading on-body channels at 2.484 GHz are measured to analyse their polarization distribution above the skin under static postures. The measured on-body channels show full-space polarization convergence and dispersion, which are modelled by an extended 3 by 3 channel polarization matrix, and a statistical channel model is also proposed. Multi-hop polarized on-body relay channels are analysed on the relay link capacity, which shows polarization dependency between adjacent hop channels when relaying nodes are mounted by linearly polarized antennas. Both regular and iterative polarization selection algorithms are then designed to optimise the antenna polarization configuration of the nodes. Simulations based on the proposed polarization distribution model show significant link capacity increases for two-hop and tfhree-hop on-body relay channels by the optimization algorithms. The results confirm the necessity of proper polarization selection schemes for on-body relay channels.

Batteries State of Health Estimation via Efficient Neural Networks With Multiple Channel Charging Profiles

The prognostics and health management (PHM) plays the main role to handle the risk of failure before its occurrence. Next, it has a broad spectrum of applications including utility networks, energy storage systems (ESS), etc. However, an accurate capacity estimation of batteries in ESS is mandatory for their safe operations and decision making policy. ESS comprises of different storage mechanisms such as batteries, capacitors, etc. Consequently, the measurement of different charging profiles (CPs) has a strong relation to battery capacity. These profiles include temperature (T), voltage (V), and current (I) where the CPs patterns vary as the battery ages with cycles. Consequently, estimating a battery capacity, the conventional methods practice single channel charging profile (SCCP) and hop multiple channel CPs (MCCPs) that cause incorrect battery health estimation. To tackle these issues, this article proposes MCCPs based battery management system (BMS) to estimate batteries health/capacity through the deep learning (DL) concept where the patterns in these CPs are changed as the battery ages with time and cycles. Thus, we deeply investigate both machine learning (ML) and DL based methods to provide a concrete comparative analysis of our method. The adaptive boosting (AB) and support vector regression (SVR) are widely compared with long short-term memory (LSTM), multi-layer perceptron (MLP), bi-directional LSTM (BiLSTM), and convolutional neural network (CNN) to attain the appropriate approach for battery capacity and state of health (SOH) estimation. These approaches have a high learning capability of inter-relation between the battery capacity and variation in CPs patterns. To validate and verify the proposed technique, we use NASA battery dataset and experimentally prove that BiLSTM outperforms all the approaches and obtains the smallest error values for MAE, MSE, RMSE, and MAPE using MCCPs compared to SCCP.

Relay Selection Optimization for SWIPT-Enabled Cooperative Networks

Simultaneous wireless information and energy transfer based on radio frequency (RF) energy harvesting can transmit power and information at the same time and can use the same wireless signal to decode the information and to charge the battery. In order to improve spectrum efficiency of energy-constrained networks, we consider combining cooperative relay with simultaneous information and energy transfer in this paper. The optimal relay power allocation and relay selection algorithms based on statistical channel state information (CSI) and perfect CSI are proposed, respectively. Specifically, the system first selects the relay nodes that can correctly decode the source information and, then among them, selects the node with the best second hop channel condition. We derive the exact analytical outage probability of the proposed algorithms by using order statistical tool. The analytical results are compared and verified by Monte Carlo simulations. It is observed that the outage probabilities of our proposed algorithms based on statistical CSI and perfect CSI are all lower than that of the corresponding traditional max–min algorithms.

Optimized Routing Protocols for Data Monitoring in Wireless Sensor Network

In recent, the wireless networking technologies have witnessed monumental growth. The discovery of IEC (Integrated Electronic Circuits) which provide minute, intelligent sensory nodes that are being embedded within the human body has resulted in the formation of WBANs - Wireless Body Area Networks. The technology of WSN (wireless sensor networks) aids in uninterrupted monitoring of an individual’s health and the patient’s diabetes practice period with no involvement in patient’s mundane activities on local servers. There is a central sink node present within the sensor network, which supervises wireless transmission, optimizes the lifetime of the network and picks out the optimal path. The present research work proposes the framework of DCDH-SRP (dynamic channel direction and hop count based secure routing protocol) also termed as a secure communication monitoring system for transmitting and receiving the sensitive data in a secured way form the server to the network users. In the enhanced EAODV protocols, each node possesses the transmission rate as TX and receiving rate being RX. TX and RX rely upon the chosen optimal path. ACO - Ant Colony Optimization which is founded on the ODMRP-ACO (optimized dynamic, secure multipath routing protocol) is adapted for transmission of data in the wireless sensor networks. ACO determines the shortest path amidst the source and the destination node. The protocol recommended is DCDH-SRP which aids in data transmission and determining of shortest path relies upon the direction of dynamic channel node and minimum hop count in wireless sensor networks. For analyzing the performance related to the path duration and hop count metric, a network (n) model for DCDH-SRP is being formulated. A comparison is made between the proposed system and the improvised (Enhanced -Ad Hoc On-Demand Distance Vector) EAODV and (Optimized Dynamic Multi-path Routing Protocol- Ant Colony Optimization) ODMRP-ACO (of an earlier work). According to the output generated, the performance is enhanced using the proposed protocol than the other existing systems. In order to verify the mathematical models and perform extensive testing of the proposed protocol, the NS2 simulator is adopted. Remarkable and improvised performance is revealed by the DCDH-SR Protocols.

Throughput of Underlay Cognitive Energy Harvesting Relay Networks With an Improved Time-Switching Protocol

We consider a two-hop underlay cognitive relay network with an energy harvesting (EH) relay. A simple improved time-switching protocol is proposed in which energy is transmitted in subslots until the relay node is sufficiently charged. The number of charging energy subslots required is fed back to the source by the relay node after the first energy subslot. We demonstrate that the proposed EH transmission scheme can yield better secondary throughput performance as compared to that achieved by an optimal EH transmission protocol using a fixed charging duration, while at the same time eliminating the need for feedback of channel estimates. We first analyze throughput when the source does not possess first-hop channel knowledge, but the relay possesses second hop channel knowledge. We then analyze throughput performance in the important case when the second hop channel estimate is in error, or the practical case when this channel estimate is not available. We show that when the second hop channel estimate is poor, it might be beneficial to use knowledge of only its statistical value. We show that the proposed scheme is energy efficient in terms of energy required per transmitted bit. Computer simulation results validate the derived expressions.

Half-Duplex or Full-Duplex Communications: Degrees of Freedom Analysis Under Self-Interference

In-band full-duplex (FD) communication provides a promising alternative to half-duplex (HD) for wireless systems, due to increased spectral efficiency and capacity. In this paper, HD and FD radio implementations of two way, two hop and two way two hop communication are compared in terms of degrees of freedom (DoF) under a realistic residual self-interference (SI) model. DoF analysis is carried out for each communication scenario for HD, antenna conserved (AC) and RF chain conserved (RC) FD radio implementations. The DoF analysis indicates that for the two way channel, the achievable AC FD with imperfect SI cancellation performs strictly below HD, and RC FD DoF trade-off is superior when the SI can be sufficiently cancelled. For the two hop channel, FD is better when the relay has large number of antennas and enough SI cancellation. For the two way two hop channel, when both nodes require similar throughput, the achievable DoF pairs for FD do not outperform HD. FD still can achieve better DoF pairs than HD, provided the relay has sufficient number of antennas and SI suppression.

It’s not all about the money: media responsibility and commercial preschool television in Israel

The establishment of local television networks for preschool children since the 1990s can be conceptualized as a response to the twin dynamics of commercialization and globalization. This paper examines this response through the case of the Israeli commercial preschool channel Hop!, using media responsibility and corporate social responsibility as analytical frameworks for the network’s off-screen operations. Ethnographic research revealed three types of off-screen activities: (1) activities geared at maintaining a relationship with the public; (2) ongoing, non-publicized activities; and (3) activities responding to national emergencies, enhancing the network’s “local” image and reinforcing ties with its viewers. Together, these activities reveal the conflict between the commercial imperative for a private channel to turn a profit, and the ethical responsibilities entailed in broadcasting to children, as well as some of the advantages of local over global networks in the preschool context.

Power Allocation and Performance of Multiuser Mixed RF/FSO Relay Networks With Opportunistic Scheduling and Outdated Channel Information

This paper studies the performance of a multiuser mixed radio frequency (RF)/free space optical (FSO) relay network with transmit opportunistic scheduling. The outdated channel information (OCI) on the first relaying hop and its effect on the system performance is also studied in this paper. Furthermore, a power allocation scheme is proposed for optimizing the overall system performance. The considered system includes $K$ sources (users), one amplify-and-froward relay and one destination. The users are connected with the relay node through RF links and the relay is connected with the destination through an FSO link. In the analysis, the first hop channels are assumed to follow Rayleigh fading model and the second hop channel is assumed to follow Gamma–Gamma fading model with considering the effect of pointing errors. Closed-form expressions are derived for the outage probability, average symbol error probability, and ergodic channel capacity. Furthermore, the system performance is studied at high signal-to-noise ratio regime, where the diversity order and coding gain are derived and analyzed. Using the asymptotic results, the power of users and relay are determined to minimize the system outage probability under a total power constraint. Monte–Carlo simulations are provided to validate the achieved exact and asymptotic results. Main results show that under weak atmospheric turbulence conditions, the system performance is dominated by the RF channels and a diversity order of $K$ is achieved by the system, whereas under severe atmospheric turbulence conditions, the system is dominated by the FSO channel and the diversity order is determined by the minimum value of the turbulence fading and pointing error parameters.

Ergodic Achievable Secrecy Rate of Multiple-Antenna Relay Systems With Cooperative Jamming

This paper investigates the ergodic achievable secrecy rate (EASR) of multiple-antenna amplify-and-forward relay systems, where one eavesdropper can wiretap the relay. To reveal the capability of the multiple-antenna relay in improving the secrecy performance, we derive new tight closed-form expressions of the EASR for three secure transmission schemes: artificial noise aided precoding (ANP), destination based jamming (DBJ) and eigen-beamforming (EB). We also derive the lower bounds of the EASR for ANP and DBJ with a large antenna array at the relay, and investigate their corresponding asymptotic performance in the high SNR and low SNR regimes to show valuable intrinsic insights as well. Based on the asymptotic analysis, we optimally allocate the power to the information signal and the artificial noise. Both the analysis and simulation results indicate that, in the moderate-to-high SNR regime, ANP achieves considerable performance gain over DBJ and EB, while in the low SNR regime, EB outperforms the other two schemes with equal power allocation. As SNR grows large, the EASR of EB approaches a constant independent of the first hop channel. Moreover, in the high SNR regime, it is optimal to allocate around half of total power to artificial noise for ANP and most of the power to artificial noise for DBJ.

The Degrees of Freedom of Two-Unicast Layered MIMO Interference Networks With Feedback

Two-unicast layered interference networks under the Shannon feedback and limited Shannon feedback settings are studied from a degrees of freedom (DoF) perspective. The main focus is on the archetypal two-hop multiple-input, multiple-output (MIMO) $(M,N)\, \times \, (M,N) \,\times \, (M,N) $ network, denoted here as the $(M,N)^{3}$ network, which is a layered two-unicast network with two transmitters, two relays, and two receivers, with the first hop network between the transmitters and the relays, and the second hop network between the relays and the receivers, both being MIMO Gaussian interference channels. In particular, the first transmitter–receiver pair and the first relay have $M$ antennas each and the second transmitter–receiver pair and the second relay having $N$ antennas each. The (full) Shannon feedback setting for the $(M,N)^{3}$ network is one in which the transmitters have delayed knowledge of the first and second hop channel coefficients and the relay and destination outputs and the relays have delayed knowledge of the second hop channel coefficients and destination outputs. The DoF region under this setting is established. A key result in this paper shows that this Shannon feedback DoF region can in fact be achieved with much less side information—under what we refer to as the limited Shannon feedback setting—wherein the transmitters have no channel state or output feedback whatsoever and only the $M$ -antenna relay (assuming $M \geq N$ ) has delayed knowledge of the coefficients of the second-hop channel and of only the received signal of the $N$ -antenna receiver. For this limited Shannon feedback setting, the DoFs region of the $(M,N)^{3}$ network is established by introducing a retro-cooperative interference alignment scheme. These DoF region results for the $(M,N)^{3}$ network with feedback are also extended to more general layered interference networks including the two-unicast $l$ -hop layered networks as well as layered networks with more general numbers of antennas at the various terminals.

Performance of Switch-and-Examine DF Relay Systems With CCI at the Relays and Destination Over Rayleigh Fading Channels

In this paper, we evaluate the outage performance of a decode-and-forward (DF) relay system with two low-complexity relay selection schemes and interference at the relays and the destination. The schemes are mainly based on the switch-and-examine diversity combining (SEC) and SEC postexamine selection (SECps) techniques in which a relay out of multiple relays is selected to forward the source message to the destination. The selection process is performed such that the signal-to-noise ratio (SNR) of the second hop of the selected relay satisfies a predetermined switching threshold. In this paper, we first derive the probability density function (pdf) of the SNR of the relay selection scheme and the conditional cumulative distribution function (cdf) of the end-to-end (e2e) signal-to-interference-plus-noise ratio (SINR), assuming Rayleigh fading channels. The derived statistics, along with the statistics of first-hop channels of the relays and the direct link, are then used to derive a closed-form expression of the e2e outage probability. Maximal-ratio combining (MRC) is used at the destination to combine the signals from the relay and the direct link. Furthermore, the outage performance is studied at the high-SNR regime where approximate expressions for the outage probability, diversity order, and coding gain are derived and analyzed. Monte Carlo simulations and some numerical examples are provided to illustrate the validity of the derived results and to show the effect of interference and other parameters on the system performance. Main results illustrate that when the interference power is fixed, the system can still achieve some performance gain when more relays are added, particularly at SNR values that are comparable with the switching threshold. Asymptotic results show that at a high SNR, the system with the SEC and SECps relaying schemes achieves a diversity order of 2 and approximately the same coding gain. Finally, findings illustrate that the interference at the destination is more severe on the system performance compared with that at the relays.

CR-CEA: A collision- and energy-aware routing method for cognitive radio wireless sensor networks

Currently, working in the overcrowded shared unlicensed spectrum band, leads to a reduction in the quality of communications in wireless networks. This makes a considerable increase in packet loss caused by collisions that necessitates packets retransmissions. In the case of wireless sensor networks (WSN), a large amount of energy of sensor nodes will be wasted by these retransmissions. Cognitive radio technology makes it possible for sensor nodes, to opportunistically use licensed bands with better propagation characteristics and less congestion. In this paper a routing method for cognitive radio wireless sensor networks (CR-CEA) is presented, that is based on a cross-layer design that jointly considers route and spectrum selection. The CR-CEA method has two main phases: next hop selection and channel selection. The routing is performed hop-by-hop with local information and decisions, which are more compatible with sensor networks. Primary user activity and prevention from interference with them, is considered in all spectrum decisions. It uniformly distributes frequency channels between adjacent nodes, which lead to a local reduction in collision probability. This clearly affects energy consumption in all sensor nodes. In CR-CEA, route selection is energy-aware and a learning-based technique is used to reduce the packet delay in terms of hop-count. The simulation results reveal that by applying cognitive radio technology to WSNs and selecting a proper operating channel, we can consciously decrease collision probability. This saves energy of sensor nodes and improves the network lifetime.

Decentralized transceiver optimization for multi-relay aided multiuser MIMO networks

In this paper, the decentralized transceivers and corresponding channel state information (CSI) signaling concepts are proposed for weighted sum rate (WSR) maximization, via linear downlink transceiver optimization in multi-relay aided multiuser multiple-input multiple-output (MIMO) networks. Three decentralized algorithms are proposed with the local CSI requirements at the base station (BS) and the relay nodes. In the first proposed algorithm, the generalized channel inversion precoding is used at the BS to avoid the second hop channel sharing requirements among the relay nodes, and decentralized transceiver optimization of the relay nodes and users are developed to maximize the WSR. A minimum mean square error (MMSE)-based enhanced method is proposed as well. To further improve the performance, we provide a novel structure of the precoding matrix of the BS. The decentralized joint BS, relay and user transceiver optimization problem is formulated and solved. Also, the CSI signaling and decentralized processing in the time division duplex (TDD) system are analyzed. Simulation results show the effectiveness of the decentralized transceiver design compared to the existing algorithms.

Performance Analysis of Amplify-and-Forward Relay Systems with Interference-Limited Destination in Various Rician Fading Channels

In this paper, we investigate the performance of a dual-hop fixed-gain amplify-and-forward relay system in the presence of co-channel interference at the destination node. Different fading scenarios for the desired user and interferers' channels are assumed in this study. We consider the Rician/Nakagami- $$m$$ m , the Rician/Rician, and the Nakagami- $$m$$ m /Rician fading environments. In our analysis, we derive accurate approximations for the outage probability and symbol error probability (SEP) of the considered scenarios. The generic independent non-identically distributed (i.n.d.) case of interferers' channels is considered for the Rician/Nakagami- $$m$$ m scenario; whereas, the independent identically distributed (i.i.d.) case is studied for the Rician/Rician and the Nakagami- $$m$$ m /Rician environments. Furthermore, to get more insights on the considered systems, high signal-to-noise ratio (SNR) asymptotic analysis of the outage probability and SEP is derived for special cases of the considered fading scenarios. Monte-Carlo simulations and numerical examples are presented in order to validate the analytical and asymptotic results and to illustrate the effect of interference and other system parameters on the system performance. Results show that the different fading models of interferers' channels have the same diversity order and that the interference degrades the system performance by only reducing the coding gain. Furthermore, findings show that the case where the fading parameter of the desired user first hop channel is better than that of the second hop gives better performance compared to the vise versa case, especially, at low SNR values; whereas, both cases almost behave the same at high SNR values where the performance of the system is dominated by the interference affecting the worst link. Finally, results show the big gap in system performance due to approximating the Rician fading distribution with the Nakagami- $$m$$ m distribution which is an indication on the inaccuracy of making such approximations in systems like the considered.

Performance Analysis of Dual-Hop AF Relaying Systems over Mixed $\eta{-}\mu$ and $\kappa{-} \mu$ Fading Channels

This paper investigates the end-to-end performance of a dual-hop amplify-and-forward (AF) relaying communication system where the source-to-relay and the relay-to-destination channels are subject to different fading conditions. The relay is assumed to either possess perfect channel state information (CSI) or have a fixed gain. We consider the case where the one hop's channel is subject to <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\eta$</tex></formula> – <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu$</tex></formula> fading, whereas the other hop's channel is subject to <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\kappa$</tex></formula> – <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu$</tex> </formula> fading. This mixed fading propagation channel is capable of accurately modeling various practical dual-hop transmissions. Examples of such environments are encountered in micro-/macrocellular systems and/or hybrid satellite/terrestrial wireless communication systems, where typically, only the one hop's channel has a line-of-sight (LOS) component. For both CSI-assisted and fixed-gain relaying and for integer-valued fading parameters, exact analytical expressions in the form of rapidly convergent infinite series for the outage probability (OP) and average bit error probability (ABEP) of several modulation schemes are derived. Moreover, for CSI-assisted relaying and arbitrary-valued fading parameters, closed-form lower bounds [tight for high values of the signal-to-noise ratio (SNR)] for the OP and ABEP performance are obtained. The analysis is also substantiated by obtaining previously published equivalent performance expressions as special cases of our generic fading models, namely, those available for Nakagami- <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$m$</tex></formula> and Rice fading channels. In addition, the derived analytical expressions have been numerically evaluated, and the performance evaluation results have been further validated by comparing them with equivalent results that have been obtained by means of Monte Carlo computer simulations.

New Metric for HWMP Protocol (NMH)

The IEEE 802.11s Wireless Mesh Networks (WMN) is a new multi -hop technology increasing the coverage of IEEE 802.11 Wireless Network and providing Internet access. Recently, many researchers proposed several metric routing protocols for wireless mesh networks(WMNs). Some metrics consider the interferences and other study the channel diversity of the distant links along the path between the source and the destination. In order to provide the best path between the source and the destination, this paper proposes a new routing metric named (NMH) New Metric for Hybrid Wireless Mesh Protocol(HWMP). NMH is based on two hop channel diversity and hop delay. The simulation results show that NMH out performs WCETT in terms of average network throughput, end -to-end delay and number of flows.

On the Capacity of Two-Hop AF Relaying in the Presence of Interference Under Nakagami-m Fading

This letter studies the ergodic capacity of channel state information (CSI)-assisted two-hop amplify-and-forward (AF) relaying system, in which the relay and the destination undergo independent sources of co-channel interference. The fading envelopes associated with the desired and interfering users are assumed to follow independent but non-identically distributed (i.n.d.) Nakagami-m fading models. Through the analysis and by assuming the fading parameter m of the two hop channels being integer, exact and approximate results for the system average ergodic capacity under different conditions are derived. They are valid for arbitrary numbers of interfering signals, and can be used to study the case of independent and identically distributed (i.i.d.) channels as a limiting application. Simulation results are provided to validate the analytical development, and to clarify the average ergodic capacity under different conditions.

Explicit Rate Control for MANET

Streaming applications over Mobile Ad-hoc Networks (MANET) require a smooth transmission rate. The Internet is unable to provide this service during traffic congestion in the network. Designing congestion control for these applications is challenging, because the standard TCP congestion control mechanism is not able to handle the special properties of a shared wireless multi hop channel well. In particular, the frequent changes to the network topology and the shared nature of the wireless channel pose major challenges. In this paper, we propose a novel approach, which allows a quick increase of throughput by using explicit feedback from routers.

多天线放大转发中继系统基于MMSE的重传预编码设计

Aiming at minimizing mean-squared-error of symbol estimations, a novel progressive retransmission precoder is proposed for multi-input multi-output (MIMO) amplify-and-forward (AF) relay systems. The re-transmission precoder design problem is decomposed into two subproblems: a discrete channel pairing problem and a continuous joint source/relay power allocation (PA) problem. Optimizing the channel pairing requires an exhaustive search over all possible channel pairings. Moreover, for each channel pairing, the joint source/relay PA is a non-convex multi-variable optimization problem. We propose an optimal PA algorithm and a suboptimal iterative PA algorithm. However, the optimal retransmission precoder that depends on the exhaustive search over all possible channel pairings has high computational complexity. Fortunately, we prove that when one hop channels signal-to-noise ratio (SNR) goes to in nity, the optimal channel pairing should pair current singular values of the other hop channel and the previous subchannel gains in the reversed order. Motivated by reducing the computational complexity, a simpli ed channel pairing searching method is proposed, in which the optimal channel pairing in asymptotic performance is applied to all the SNR regions. Numerical results show that the proposed simpli ed channel pairing and the iterative PA algorithm both always achieve the near-optimal perfor- mance. Compared with conventional retransmission precoder schemes of MIMO AF relay systems, our proposed retransmission precoder can improve the system performance significantly.