Degradation Of Communication Performance Research Articles

Optical wireless channel reciprocity-based temporal power allocation technique for FSO communications

We propose a temporal power allocation technique for optical transmitting power using the average limiting property of an erbium-doped fiber amplifier to secure the degradation of communication performance due to the turbulence effect of the FSO vertical link. Unlike the existing turbulence degradation prevention technology, the FSO channel reciprocity-based pre-compensation technique proposed in this study can overcome degradation caused by strong channel fading and maintain the quality of the transmission signal through sufficient transmitted power. The proposed technique was demonstrated using simulations and experiments. The transmission performance was effectively enhanced by applying the proposed technique.

Ringing Suppression in a Controller Area Network With Flexible Data Rate Using Frequency-Selective Impedance Matching and Temporal Impedance Switching

An inherent impedance mismatch in a controller area network with flexible data rate (CAN-FD) network gives rise to signal distortion called ringing. Ringing is one of the main causes of communication errors and performance degradation. In this paper, a ringing suppression system is proposed, which alleviates the impedance mismatch at two mismatch locations: the unterminated CAN nodes and the divergence points of bus lines. At the unterminated CAN nodes, a temporal impedance switching circuit, including a matching resistor and a limiting diode, is added. The circuit is controlled to only engage right after a dominant-to-recessive transition when ringing likely occurs. At the divergence points, a frequency-selective impedance matching circuit is inserted. The circuit consists of a resistor, a capacitor, and an inductor connected in parallel, which is also designed to activate only during state transitions with the dependency of their impedance on frequency. Thus, the side effects on CAN-FD operations can be prevented. The performance of the ringing suppression system is verified by experiments. The experimental results demonstrate that the proposed system reduces ringing to a level lower than the input threshold for recessive bit detection in diverse bus configurations and supports more reliable CAN-FD communication.

Pulse interference identification and suppression for OFDM signal

The new generation smart meter is the core node of information acquisition and flows in the power Internet of Things (IoT). Because it is powered by the low-voltage power line, various short-time pulse interference signals in the line can be easily coupled to the received signal of the communication module embedded in the meter, resulting in the degradation of communication performance. In view of this situation, an identification-suppression algorithm of the short-time pulse-interference signal is proposed. The core idea is to comprehensively judge the existence of the interference signal and its specific position in the time domain based on the energy ratio of adjacent OFDM symbols and the change of mean square error value between frequency domain amplitude signals. Based on this, an interference energy elimination scheme with an adaptive threshold is realized. Theoretical analysis and simulation results show that the scheme has low computational complexity, high accuracy of pulse interference identification and position judgment, and can effectively reduce the energy of pulse interference signal, and thus improving the decoding performance of OFDM while it receives signals.

Studying impacts of communication system performance on dynamic stability of networked microgrid

The development of smart grid technologies has resulted in increased interdependence between power and communication systems. Many of the operations in the existing power system rely on a stable and secured communication system. For electrically weak systems and time-critical applications, this reliance can be even greater, where a small degradation in communication performance can degrade system stability. However, despite inter-dependencies between power and communication systems, only a few studies have investigated the impacts of communication system performance on power system dynamics. This study investigates the dependencies of power system dynamics operations on a communication system performance. First, a detailed, dynamic networked microgrid model is developed in the GridLAB-D simulation environment, along with a representative multi-traffic, multi-channel, multi-protocol communication system model, developed in the network simulator (ns-3). Second, a hierarchical engine for large-scale infrastructure co-simulation framework is developed to co-simulate microgrid dynamics, its communication system, and a microgrid control system. The impact of communication system delays on the dynamic stability of networked microgrids is evaluated for the loss of generation using three use-cases. While the example use-cases examine microgrid applications and the impact to resiliency, the framework can be applied to all levels of power system operations.

Overhead of using spare nodes

With the increasing fault rate on high-end supercomputers, the topic of fault tolerance has been gathering attention. To cope with this situation, various fault-tolerance techniques are under investigation; these include user-level, algorithm-based fault-tolerance techniques and parallel execution environments that enable jobs to continue following node failure. Even with these techniques, some programs with static load balancing, such as stencil computation, may underperform after a failure recovery. Even when spare nodes are present, they are not always substituted for failed nodes in an effective way. This article considers the questions of how spare nodes should be allocated, how to substitute them for faulty nodes, and how much the communication performance is affected by such a substitution. The third question stems from the modification of the rank mapping by node substitutions, which can incur additional message collisions. In a stencil computation, rank mapping is done in a straightforward way on a Cartesian network without incurring any message collisions. However, once a substitution has occurred, the optimal node-rank mapping may be destroyed. Therefore, these questions must be answered in a way that minimizes the degradation of communication performance. In this article, several spare node allocation and failed node substitution methods will be proposed, analyzed, and compared in terms of communication performance following the substitution. The proposed substitution methods are named sliding methods. The sliding methods are analyzed by using our developed simulation program and evaluated by using the K computer, Blue Gene/Q (BG/Q), and TSUBAME 2.5. It will be shown that when failures occur, the stencil communication performance on the K and BG/Q can be slowed around 10 times depending on the number of node failures. The barrier performance on the K can be cut in half. On BG/Q, barrier performance can be slowed by a factor of 10. Further, it will also be shown that almost no such communication performance degradation can be seen on TSUBAME 2.5. This is because TSUBAME 2.5 has an Infiniband network connected with a FatTree topology, while the K computer and BG/Q have dedicated Cartesian networks. Thus, the communication performance degradation depends on network characteristics.

A Resource Usage Intensity Aware Load Balancing Method for Virtual Machine Migration in Cloud Datacenters

To provide robust infrastructure as a service (IaaS), clouds currently perform load balancing by migrating virtual machines (VMs) from heavily loaded physical machines (PMs) to lightly loaded PMs. The unique features of clouds pose formidable challenges to achieving effective and efficient load balancing. First, VMs in clouds use different resources (e.g., CPU, bandwidth, memory) to serve a variety of services (e.g., high performance computing, web services, file services), resulting in different overutilized resources in different PMs. Also, the overutilized resources in a PM may vary over time due to the time-varying heterogeneous service requests. Second, there is intensive network communication between VMs. However, previous load balancing methods statically assign equal or predefined weights to different resources, which lead to degraded performance in terms of speed and cost to achieve load balance. Also, they do not strive to minimize the VM communications between PMs. We propose a Resource Intensity Aware Load balancing method (RIAL). For each PM, RIAL dynamically assigns different weights to different resources according to their usage intensity in the PM, which significantly reduces the time and cost to achieve load balance and avoids future load imbalance. It also tries to keep frequently communicating VMs in the same PM to reduce bandwidth cost, and migrates VMs to PMs with minimum VM performance degradation. We also propose an extended version of RIAL with three additional algorithms. First, it optimally determines the weights for considering communication cost and performance degradation due to VM migrations. Second, it has a more strict migration triggering algorithm to avoid unnecessary migrations while still satisfying Service Level Objects (SLOs). Third, it conducts destination PM selection in a decentralized manner to improve scalability. Our extensive trace-driven simulation results and real-world experimental results show the superior performance of RIAL compared to other load balancing methods.

A survey of control consistency in Software-Defined Networking

Software-Defined Networking (SDN) offers a flexible and programmable model to manage and schedule network resources. With the separation of control plane and data plane in SDN, the centralized controller frequently updates the flow tables in data plane to control network, and the data plane also communicates its requests with the control plane for forwarding actions. Due to the asynchronous control nature of SDN, a SDN network may suffer from inconsistency issues caused by concurrency violations, which may lead to network misbehaviors, such as communication interruption, policy violation, and performance degradation. To make SDN correct and stable, consistency is an essential feature that SDN should possess. In this paper, we make a survey about the control consistency in SDN from three aspects: (1) a consistent network view and control decisions made by the control plane, (2) consistency and efficiency during data plane update, (3) maintaining consistent flow tables in the data plane. We summarize the fundamental causes of consistency issues, the potential inconsistency problems and the state-of-art solutions, and then discuss the challenges to guarantee the consistency for SDN.

MAJoRCom: A Dual-Function Radar Communication System Using Index Modulation

Dual-function radar communication (DFRC) systems implement both sensing and communication using the same hardware. Such schemes are often more efficient in terms of size, power, and cost, over using distinct radar and communication systems. Since these functionalities share resources such as spectrum, power, and antennas, DFRC methods typically entail some degradation in both radar and communication performance. In this work we propose a DFRC scheme based on the carrier agile phased array radar (CAESAR), which combines frequency and spatial agility. The proposed DFRC system, referred to as multi-carrier agile joint radar communication (MAJoRCom), exploits the inherent spatial and spectral randomness of CAESAR to convey digital messages in the form of index modulation. The resulting communication scheme naturally coexists with the radar functionality, and thus does not come at the cost of reduced radar performance. We analyze the performance of MAJoRCom, quantifying its achievable bit rate. In addition, we develop a low complexity decoder and a codebook design approach, which simplify the recovery of the communicated bits. Our numerical results demonstrate that MAJoRCom is capable of achieving a bit rate which is comparable to utilizing independent communication modules without affecting the radar performance, and that our proposed low-complexity decoder allows the receiver to reliably recover the transmitted symbols with an affordable computational burden.

Time reversal communication using vertical particle velocity and pressure signals in shallow water

Acoustic communication in shallow water is characterized by multipath channels, which cause significant delay spreading, leading to inter-symbol interference. This inter-symbol interference necessarily causes a significant degradation in communication performance. Although a time reversal technique has been reported to produce satisfactory performance in multipath dominant environments, this technique requires a large receiver array covering the water column to achieve reliable communication performance. In this paper, a time reversal single-input multiple-output system using the pressure signal and the vertical component of the particle velocity is presented. The vertical component of the particle velocity was estimated using the finite difference in gradient between pressures measured by two vertically adjacent receivers. The experiment was conducted in shallow water off the south coast of Korea, where the water depth is 59 m and the bottom consists of silty clay. The results showed that the time reversal communication system based on vector quantities performed better than systems where only the pressure signals were used.

Process Management in IoT Operating Systems: Cross-Influence between Processing and Communication Tasks in End-Devices.

The emergence and spread of Internet of Things (IoT) technologies along with the edge computing paradigm has led to an increase in the computational load on sensor end-devices. These devices are now expected to provide high-level information instead of just raw sensor measurements. Therefore, the processing tasks must share the processor time with the communication tasks, and both of them may have strict timing constraints. In this work, we present an empirical study, from the edge computing perspective, of the process management carried out by an IoT Operating System (OS), showing the cross-influence between the processing and communication tasks in end-devices. We have conducted multiple tests in two real scenarios with a specific OS and a set of wireless protocols. In these tests, we have varied the processing and communication tasks timing parameters, as well as their assigned priority levels. The results obtained from these tests demonstrate that there is a close relationship between the characteristics of the processing tasks and the communication performance, especially when the processing computational load is high. In addition, these results also show that the computational load is not the only factor responsible for the communication performance degradation, as the relationship between the processing tasks and the communication protocols timing parameters also plays a role. These conclusions should be taken into account for future OSs and protocol developments.

High Throughput Mobile Communication Based on OTFS System with the Delay-Doppler Compensation

In this paper, we like to propose a high throughput mobile communication system that can work even at the very high vehicular speed. Generally, mobility and data throughput has inverse relationship. Also, very complicated receiver structure is required and takes a long time processing for compensating the Doppler frequency due to the high speed mobility. Seriously, the communication performance becomes degraded with the increase of the dimension of multiple input and multiple output (MIMO), since the delay Doppler problem becomes bigger the higher dimension of MIMO. So, it is greatly important to design the very robust mobile communication that can provide the high throughput even at the very high vehicular speed system. Design and performance evaluation of the orthogonal time frequency space (OTFS) modulation system and OTFS-based MIMO system are described and analyzed at the very high mobility environment. OTFS modulation can concisely compensate the delay-Doppler spreading effect by using two dimensional inverse discrete Fourier transform and discrete Fourier transform operation. It enables OTFS system to transmit high-speed data. Especially, OTFS-MIMO system can transmit data stream of each antenna without the communication performance degradation even in the high Doppler frequency environments. As simulation results, it is confirmed that the capacity of 1 × 1 OTFS system is a similar to each stream of 2 × 2 OTFS-MIMO system. That is, 2 × 2 MIMO system can completely double the communication capacity in comparison with 1 × 1 OTFS system even in the very high Doppler frequency channel such as high speed mobile environments. This remarkable performance can continue in the very high dimensional MIMO system and simultaneously in the high mobility situation.

Wavelet transform based modulation classification for 5G and UAV communication in multipath fading channel

Nowadays, fifth generation (5G) network and unmanned aerial vehicle (UAV) are more and more important in the civil and military field. Only communicating correctly in 5G network and between UAVs, they can play a role in real world. Modulation classification is the premise to ensure communication in 5G network and between UAVs correctly. However, the effects of multipath fading always exists in the 5G communication environment and UAV communication channel, which leads to severe modulation classification performance and communication performance degradation. In order to resolve this problem, we proposed a novel modulation classification algorithm that can classify signals without priori information in multipath channel. The proposed algorithm makes the mean, variance, skewness and kurtosis of wavelet transform as the feature set, then uses principal component analysis (PCA) for feature subset selection, in the end neural network is used as classifier to classify signals. The simulation results show that the proposed algorithm can achieve the much better classification accuracy than the existing methods in multipath fading channels.

Exploring the effect of design asymmetry in vehicular communication using visible light communication technology

AbstractNature of visible light communication (VLC) in vehicle‐to‐vehicle (V2V) communication is such that it does involve certain aspects of asymmetry. This concept is known issue in wireless networking systems, and it is one of the reasons for the famous node deafness issue. It degrades network performance and it is addressed in various network layers and protocols, especially media access control protocol. This paper investigates effects of asymmetry on communication performance in V2V networks using VLC. Scientific community has recognized asymmetry as an issue that causes communication performance degradation, even in VLC communication. Furthermore, this paper defines different types of asymmetry in V2V communication networks using VLC technology. Finally, simulation experiment is conducted in a controlled environment, which tests the specific types of asymmetry (design) as a cause of network performance degradation. Data and results are analyzed and interpreted; they show that asymmetry (design) is not a significant issue in vehicular communication using VLC. However, results are strictly referring to specific domain, ie, vehicular communication using VLC technology in dense urban environments.

Frequency Domain Equalization and Post Distortion for LED Communications With Orthogonal Polynomial Based Joint LED Nonlinearity and Channel Estimation

The light-emitting diode (LED) is the major source of nonlinearity in LED communications, and the nonlinearity needs to be effectively modeled and mitigated to avoid the degradation of communication performance. In indoor LED communications, multipath dispersion can lead to inter-symbol interference (ISI) at high data rates. In this paper, we jointly estimate the LED nonlinearity and ISI channel based on an orthogonal polynomial based technique. Then, frequency domain equalization and post-distortion are adopted to mitigate the ISI and nonlinearity. Simulation results are provided to demonstrate the effectiveness of the proposed technique.

Electromagnetic Modeling of Self-Tuning RFID Sensor Antennas in Linear and Nonlinear Regimes

Multistate chips for an UHF radio frequency identification ensure self-compensation of the variations in antenna impedance. This self-tuning capability can provide a digital information about the change in local boundary conditions within the vicinity of the tag. This feature can be exploited further for low-cost wireless sensing applications. An electromagnetic model of the tag in linear and nonlinear regimes allows prediction of analog and digital responses of the device depending on the boundary conditions that cause the variation of the antenna impedance and/or gain. In addition, the model provides estimation of the degradation in communication performance of the tag due to imperfect retuning of the chip impedance. The theoretical findings of the model are verified in sensing applications using a reference self-tuning tag. Sensing measurements of liquid compounds in linear regime and of the water-filling level of a box in nonlinear regime are demonstrated as a practical application of the proposed mathematical model.

Approximate Communication

Approximate computing has gained research attention recently as a way to increase energy efficiency and/or performance by exploiting some applications’ intrinsic error resiliency. However, little attention has been given to its potential for tackling the communication bottleneck that remains one of the looming challenges to be tackled for efficient parallelism. This article explores the potential benefits of approximate computing for communication reduction by surveying three promising techniques for approximate communication: compression, relaxed synchronization, and value prediction. The techniques are compared based on an evaluation framework composed of communication cost reduction, performance, energy reduction, applicability, overheads, and output degradation. Comparison results demonstrate that lossy link compression and approximate value prediction show great promise for reducing the communication bottleneck in bandwidth-constrained applications. Meanwhile, relaxed synchronization is found to provide large speedups for select error-tolerant applications, but suffers from limited general applicability and unreliable output degradation guarantees. Finally, this article concludes with several suggestions for future research on approximate communication techniques.

A Hybrid Channel Access Scheme for Coexistence Mitigation in IEEE 802.15.4-Based WBAN

Wireless body area network (WBAN) is a communication technology, which aims providing both medical and consumer electronics services through sensor devices in, on, or around a human body. Due to the absence of the IEEE 802.15.6-based RF modules, the IEEE 802.15.4, a typical low-power communication technology of which requirements are similar, is considered to implement WBANs. In the case where a lot of WBANs coexist, meanwhile, collisions and signal attenuations may lead to their communication performance degradation. However, the IEEE 802.15.4 does not provide any solutions to solve coexistence problems, and thus, coexistence mitigation schemes for the IEEE 802.15.4-based WBANs are necessary. In this paper, we perform preliminary experiments to identify aspects of coexistence problem among the coexisting IEEE 802.15.4-based WBANs. Based on the results of preliminary experiments, we also propose a hybrid channel access scheme to mitigate coexistence problems in WBANs. The proposed scheme can be classified into two phases. In the first phase, the proposed scheme provides probabilistic collision avoidance on the contention-free period. When the pre-defined requirements of reliability cannot be satisfied with performing the first phase, the proposed scheme performs the second phase, which helps to mitigate collision or interference through changing channel access method. To evaluate the performance of the proposed scheme, we implement our scheme and perform experiments by comparing with an IEEE 802.15.4-based WBAN.

Ionizing radiation impact on communications performance of optical multi-hop inter-satellite relay link

Ionizing radiation impact on communications performance of optical multi-hop inter-satellite relay links is studied in this paper. Essential optoelectronic devices involved in optical communication system were irradiated by Co60 gamma ray and BER models of OOK, DPSK and homodyne BPSK of multi-hop inter-satellite links were proposed. On this basis, performance degradations under ionizing radiation were simulated, and on-orbit performance degradations were further discussed. Research results show that EDFA of ionizing radiation is the dominant cause of optical relay link communication performance degradation and the choosing of relay satellite has significant influence on on-orbit performance of links. The anti-ionizing radiation capability of homodyne BPSK model obviously outperforms OOK and DPSK models.

Analytical Characterisation of the Terahertz In-Vivo Nano-Network in the Presence of Interference Based on TS-OOK Communication Scheme

The envisioned dense nano-network inside the human body at terahertz (THz) frequency suffers a communication performance degradation among nano-devices. The reason for this performance limitation is not only the path loss and molecular absorption noise, but also the presence of multi-user interference and the interference caused by utilising any communication scheme, such as time spread ON—OFF keying (TS-OOK). In this paper, an interference model utilising TS-OOK as a communication scheme of the THz communication channel inside the human body has been developed and the probability distribution of signal-to-interference-plus-noise ratio (SINR) for THz communication within different human tissues, such as blood, skin, and fat, has been analyzed and presented. In addition, this paper evaluates the performance degradation by investigating the mean values of SINR under different node densities in the area and the probabilities of transmitting pulses. It results in the conclusion that the interference restrains the achievable communication distance to approximate 1 mm, and more specific range depends on the particular transmission circumstance. Results presented in this paper also show that by controlling the pulse transmission probability and node density, the system performance can be ameliorated. In particular, SINR of in vivo THz communication between the deterministic targeted transmitter and the receiver with random interfering nodes in the medium improves about 10 dB, when the node density decreases one order. The SINR increases approximate 5 and 2 dB, when the pulse transmitting probability drops from 0.5 to 0.1 and 0.9 to 0.5.

Orthogonal Polynomial-Based Nonlinearity Modeling and Mitigation for LED Communications

The light-emitting diode (LED) is the major source of nonlinearity in LED communications, and the nonlinearity needs to be effectively modeled and thereby mitigated through predistortion or postdistortion to avoid degradation of communication performance. A memory polynomial is often used for LED nonlinearity modeling and mitigation in the literature. However, the estimation of memory polynomial coefficients suffers from numerical instability, resulting in inaccurate modeling and poor performance in nonlinearity mitigation. In this paper, we propose an orthogonal polynomial-based nonlinearity modeling and mitigation technique for LED communications with pulse amplitude modulation (PAM) signaling and show that the proposed technique significantly outperforms the conventional memory polynomial-based techniques.