Unidirectional Communications Research Articles

Performance evaluation and analysis of distributed multi-agent optimization algorithms with sparsified directed communication

There has been significant interest in distributed optimization algorithms, motivated by applications in Big Data analytics, smart grid, vehicle networks, etc. While there have been extensive theory and theoretical advances, a proportionally small body of scientific literature focuses on numerical evaluation of the proposed methods in actual practical, parallel programming environments. This paper considers a general algorithmic framework of first and second order methods with sparsified communications and computations across worker nodes. The considered framework subsumes several existing methods. In addition, a novel method that utilizes unidirectional sparsified communications is introduced and theoretical convergence analysis is also provided. Namely, we prove R-linear convergence in the expected norm. A thorough empirical evaluation of the methods using Message Passing Interface (MPI) on a High Performance Computing (HPC) cluster is carried out and several useful insights and guidelines on the performance of algorithms and inherent communication-computational trade-offs in a realistic setting are derived.

Relief and revolution: Russian émigrés’ political remittances and the building of political transnationalism

ABSTRACTThis article examines the transnational networks based in Britain between 1881 and 1914 that aspired to affect Russian politics from abroad. It contends that the emigration of Russian revolutionaries to Britain in the late nineteenth and early twentieth centuries was only the first in a series of continued political movements across national borders and beyond state structures. Rather than examining the migration of Russian political exiles as a singular flight of movement undertaken in desperation, I argue that these émigrés’ westward migration initiated transnational communities that coalesced around a common conception of fundamental political rights, that could be claimed regardless of nationality, and that these activist cohorts, in turn engaged in public endeavours designed to influence governmental actions and foment political change. For many prominent Russian radicals, emigration to places like Britain was not an enforced exile from interventions in the politics of their homeland, but rather a means to continue anti-tsarist agitation through transnational collaborative activist networks, and the international movement and exchange, rather than unidirectional distribution, of money, communications, propaganda and people; interventions that I define as political remittances.

A dual-radio approach for reliable emergency signaling in critical infrastructure assets with large wireless networks

Wireless communications techniques are finding their way into industrial applications, but commercial wireless technologies lack the dependability required for critical applications in very large networks. In many wireless-controlled industrial facilities, safety regulations mandate real-time communications for tasks such as emergency shutdowns. This requires a wireless communications architecture that supports the coexistence of non-real-time and real-time tasks. To address this requirement, this paper proposes an architecture that augments a wireless mesh network with a unidirectional long-range communications system. Various configuration parameters of the system, including its security features, are optimized. Additionally, a physical realization of the architecture is evaluated using a series of experiments, including some performed on a real solar tower power plant. The experimental results demonstrate that the extension of a wireless mesh network with a unidirectional long-range communications system provides safety and scalability for industrial applications while promoting cost effectiveness and energy efficiency.

Enhanced Effective Filtering Approach (eEFA) for Improving HSR Network Performance in Smart Grids

The effective filtering approach (EFA) is one of the most effective approaches for improving the network traffic performance of high-availability seamless redundancy (HSR) networks. However, because EFA uses port locking (PL) for detecting nondestination doubly-attached nodes with HSR protocol (DANH) rings in HSR networks, it forwards the first sent frame to all DANH rings in the network. In addition, it uses a control message for discovering passive QuadBox rings in both unidirectional and bidirectional communications. In this study, we propose an enhanced version of EFA called enhanced-EFA (eEFA) that does not forward unicast frames to nondestination DANH rings. eEFA does not use any control message to discover passive QuadBox rings in bidirectional communications. eEFA thus reduces the network traffic in HSR networks compared with EFA. Analytical and simulation results for a sample network show that the traffic reduction of eEFA was 4–26% and 2–20% for unidirectional and bidirectional communications, respectively, compared to EFA. eEFA, thus, clearly saves network bandwidth and improves the network performance.

In-band full duplex wireless communications and networking for IoT devices: Progress, challenges and opportunities

The new era of IoT devices call for wireless communications with high spectral efficiency because of the congested spectral space in reality. Current wireless communication systems work at half duplex mode in an either time-division or frequency-division approach to transmit and receive wireless signals. Half duplex results in poor spectral efficiency because only unidirectional communications are allowed. Recent research has aimed at enabling In-band full duplex wireless communication that allows a wireless node for simultaneous transmission and reception of signals. The benefits of in-band full duplex includes the doubled spectra efficiency which is in great need in the rapidly growing IoT devices and the potentials to solve the hidden terminals, unfairness and the exposed problems presented in the current single channel half duplex wireless communications. This paper investigates the research background and progress of in-band full duplex wireless. It also presents the research problems as well as opportunities. In addition, this paper summarizes the performance of literature solutions with experiment results in achieving in-band full duplex wireless communications. It also compares the Throughput and Packet Reception Ratio performance of full duplex to that of half duplex from a Software Defined Radio platform.

Conflict in invasive species management

As invasive species management becomes more ambitious in scope and scale, projects are increasingly challenged by disputes and conflicts among people, which can produce undesirable environmental and social outcomes. Here, we examine when and how conflicts have arisen from invasive species management, and consider why some management approaches may be more prone to conflict than others. Insufficient appreciation of sociopolitical context, non‐existent or perfunctory public and community engagement, and unidirectional communications can all foster “destructive” conflict. We propose that approaches to conflict in invasive species management might be transformed by anticipating disagreements, attending more carefully to the social‐ecological contexts of management, adopting more inclusive engagement mechanisms, and fostering more open, responsive communication. Conflicts may be unavoidable, but they can be anticipated and need not be destructive.

Mechanisms Underlying the Essential Role of Mitochondrial Membrane Lipids in Yeast Chronological Aging.

The functional state of mitochondria is vital to cellular and organismal aging in eukaryotes across phyla. Studies in the yeast Saccharomyces cerevisiae have provided evidence that age-related changes in some aspects of mitochondrial functionality can create certain molecular signals. These signals can then define the rate of cellular aging by altering unidirectional and bidirectional communications between mitochondria and other organelles. Several aspects of mitochondrial functionality are known to impact the replicative and/or chronological modes of yeast aging. They include mitochondrial electron transport, membrane potential, reactive oxygen species, and protein synthesis and proteostasis, as well as mitochondrial synthesis of iron-sulfur clusters, amino acids, and NADPH. Our recent findings have revealed that the composition of mitochondrial membrane lipids is one of the key aspects of mitochondrial functionality affecting yeast chronological aging. We demonstrated that exogenously added lithocholic bile acid can delay chronological aging in yeast because it elicits specific changes in mitochondrial membrane lipids. These changes allow mitochondria to operate as signaling platforms that delay yeast chronological aging by orchestrating an institution and maintenance of a distinct cellular pattern. In this review, we discuss molecular and cellular mechanisms underlying the essential role of mitochondrial membrane lipids in yeast chronological aging.

Reducing Side-Sweep Accidents with Vehicle-to-Vehicle Communication

Side-sweep accidents are one of the major causes of loss of life and property damage on highways. This type of accident is caused by a driver initiating a lane change while another vehicle is blocking the road in the target lane. In this article, we are trying to quantify the degree to which different implementations of vehicle-to-vehicle (V2V) communication could reduce the occurrence of such accidents. We present the design of a simulator that takes into account common sources of lack of driver awareness such as blind-spots and lack of attention. Then, we study the impact of both traditional, non-technological communication means such as turning signals as well as unidirectional and bidirectional V2V communications.

Instantaneous communication capacities of vehicular ad hoc networks

Wireless communications among vehicles, roadside infrastructures, and traffic management centers can enable the development of next-generation Intelligent Transportation Systems so as to tackle basic traffic problems associated with driving safety, road congestion, and vehicle emissions. This paper analytically investigates the instantaneous communication capacities of vehicular ad hoc networks (VANETs), which measure the upper bounds of the message transmission rates of vehicles. Subject to interference among wireless transmissions, the broadcast capacity is defined by the maximum number of successful receivers, and the unicast capacity by the maximum number of successful senders. With the protocol communication model and uniform vehicular traffic patterns, we derive closed-form formulas for the capacities as functions of transmission range r, interference ratio δ, vehicular density ρ, and channel capacity W. We show that broadcast capacities are approximately W(2+δ)rρ+1 for uni-directional communications, and 2W(2+δ)rρ+1 for bi-directional communications; while unicast capacities are approximately W(1+δ)rρ+1 for uni-directional communications, and W(1+δ)rρ+1 for bi-directional communications. For general vehicular traffic patterns, an optimization model is proposed to calculate the capacities, and a genetic algorithm integrated with the protocol communication model is developed to solve the optimization problem. Finally, the impacts of different transmission ranges, interference ratios, and shock waves on communication capacities are analyzed.

Design and Implementation of a Novel Compatible Encoding Scheme in the Time Domain for Image Sensor Communication.

This paper presents a modulation scheme in the time domain based on On-Off-Keying and proposes various compatible supports for different types of image sensors. The content of this article is a sub-proposal to the IEEE 802.15.7r1 Task Group (TG7r1) aimed at Optical Wireless Communication (OWC) using an image sensor as the receiver. The compatibility support is indispensable for Image Sensor Communications (ISC) because the rolling shutter image sensors currently available have different frame rates, shutter speeds, sampling rates, and resolutions. However, focusing on unidirectional communications (i.e., data broadcasting, beacons), an asynchronous communication prototype is also discussed in the paper. Due to the physical limitations associated with typical image sensors (including low and varying frame rates, long exposures, and low shutter speeds), the link speed performance is critically considered. Based on the practical measurement of camera response to modulated light, an operating frequency range is suggested along with the similar system architecture, decoding procedure, and algorithms. A significant feature of our novel data frame structure is that it can support both typical frame rate cameras (in the oversampling mode) as well as very low frame rate cameras (in the error detection mode for a camera whose frame rate is lower than the transmission packet rate). A high frame rate camera, i.e., no less than 20 fps, is supported in an oversampling mode in which a majority voting scheme for decoding data is applied. A low frame rate camera, i.e., when the frame rate drops to less than 20 fps at some certain time, is supported by an error detection mode in which any missing data sub-packet is detected in decoding and later corrected by external code. Numerical results and valuable analysis are also included to indicate the capability of the proposed schemes.

System Frequency as Information Carrier in AC Power Systems

Power generators contain control systems that are able to regulate system frequency, but the frequency setpoint values are rarely modified from nominal values. This paper describes design considerations for a communication system from generators to frequency-sensitive distributed energy resources (FS-DER) using changes to frequency setpoint values of generators. Signaling discrete system states by generating off-nominal system frequency values can be used as a novel narrowband unidirectional broadcast communications channel. This paper describes two protocols for utilizing off-nominal frequencies to carry information: First, a protocol for dispatching blocks of FS-DER that is suitable for systems restricted to relatively slow rates of change of frequency (ROCOF). Second, for systems that allow higher ROCOF values, the feasibility of using power generation resources as a power-line communication transmitter is shown. Data from an operating islanded power system with diesel generators are analyzed to demonstrate the feasibility of the proposed communication system in systems fed by rotating machines. The feasibility of the proposed communication system in systems fed by voltage-source inverters is shown with laboratory tests of a 20-kVA inverter. The inverter was found to have a maximum ROCOF of 2.2 Hz/s, sufficient to enable its use as a power-line communication transmitter.

A Magneto-Electric Dipole for Unidirectional UWB Communications

A new magneto-electric dipole antenna is designed. The antenna is composed of a horizontal bowtie electric dipole, a center-fed loop antenna functioning as a magnetic dipole and a rectangular cavity. A microstrip-to-stripline transition is employed as a balun to feed the antenna. A prototype was fabricated and measured. Results show that an impedance bandwidth of 110%, with SWR ≤ 2 from 3.08 to 10.6 GHz, was achieved. A stable gain of 8.7 ±1.9 dBi was realized by using the rectangular cavity. Stable radiation pattern with low cross polarization ( ≤ -20 dB), low back radiation ( ≤ -13 dB) and symmetrical E- and H-plane patterns was found over the operating frequencies. Moreover, the impulse response is analyzed which reveals the antenna with good time domain characteristic.

A Cooperative Network Coding Strategy for the Interference Relay Channel

In this paper, we study an interference relay network with a satellite as relay. We propose a cooperative strategy based on physical layer network coding and superposition modulation decoding for uni-directional communications among users. The performance of our solution in terms of throughput is evaluated through capacity analysis and simulations that include practical constraints such as the lack of synchronization in time and frequency. We obtain a significant throughput gain compared to the classical time sharing case.

MOS-Based Congestion Control for Conversational Services in Wireless Environments

Nowadays, multimedia applications and specifically streaming systems over wireless networks use the TCP transport protocol. Indeed, TCP can deal with practical issues such as firewalls and also deploys built-in retransmissions and congestion control mechanisms. We propose in this paper a Quality-centric Mean Opinion Score (MOS) based congestion control that determines an optimal congestion window updating policy for multimedia transmission. Unlike the standard congestion control algorithms, our approach defines a new Additive Increase Multiplicative Decrease (AIMD) algorithm given the multimedia application and the transmission characteristics. In order to get the optimal congestion policy in practice, the sender requires complete statistical knowledge of both multimedia traffic and the network environment, which may not be available in wireless systems. Hence, we propose in this paper, a Partially Observable Markov Decision Process (POMDP) framework in order to determine an optimal congestion control policy which maximizes the long term expected Quality of Experience (QoE) of the receiver. Moreover, the computation of an optimal policy is usually time/process consuming and as wireless devices are capacity-limited, we consider optimal solutions based on temporal difference (TD-λ) online learning algorithms. Finally, we do some practical experiments of our algorithm on a Microsoft Lync testbed with unidirectional and bidirectional communications over a wireless network. We observe that for both scenarios, our algorithm improves significantly the QoE compared to standard AIMD congestion control mechanism.

Integrated Safety and Efficiency in Intelligent Vehicular Networks: Issues and Novel Constructs

We present the cohort and the group constructs which are aimed at reconciling safety and efficiency for intelligent vehicular networks on roads and highways, and show how platoons and vehicular ad hoc networks can be structured as cohorts and groups. Fundamental implications of safety requirements are reviewed. A rationale for on–board systems based on diversified functional redundancy is developed, illustrated with a proposal for neighbor–to–neighbor periodic beaconing based on short range unidirectional communications meant to withstand telemetry failures. Worst–case analytical results are given for safe inter–vehicle spacing in cohorts despite inaccurate vehicle space–time coordinates and failing telemetry capabilities. The group construct is based on prefixing usage of sensing–based solutions with omnidirectional communications. Benefits resulting from prefixing vehicle maneuvers with vehicle role assignments are illustrated with the on–ramp–merging safety–critical scenario.

Triple-injection wrist arthrography: Unidirectional communications are due to technical factors

One justification for triple-injection wrist arthrography is detection of unidirectional interjoint communication that might escape notice if only a single joint were injected. To determine whether the direction of 1-way communications is related to the choice of the first joint injected, the authors prospectively randomized 100 wrists undergoing consecutive single-contrast, fluoroscopically controlled arthrograms into 2 well-matched groups. One group received the initial injections into the midcarpal and distal radioulnar joints and the other group received the initial injection into the radiocarpal joint. Two unidirectional radial capsular communications with the radiocarpal joint were detected on delayed midcarpal joint injection. No other unidirectional communications were found. No statistically significant difference was found between the midcarpal and radiocarpal study groups. Thus, the first joint injected appears to be a major determinant in demonstrating unidirectional communications between wrist compartments.

Unidirectional joint communications in wrist arthrography: an evaluation of 250 cases.

Although arthrographically demonstrable communications between various compartments of the wrist occur in older persons without symptoms, similar communications in younger persons may indicate clinically significant posttraumatic ligament tears and other pathologic processes. However, detection of communications varies depending on the arthrographic technique used. It has been claimed that if triple-compartment arthrography is not used in all patients, clinically significant unidirectional ligament tears may be overlooked. We determined the frequency and distribution of unidirectional intercompartmental communications, using a modification of techniques described in the literature. Separate injections of contrast material were made in sequence into the midcarpal, distal radioulnar, and radiocarpal joints of 250 consecutive patients. We found 38 unidirectional communications (17 lunotriquetral, nine scapholunate, three radial capsular, one ulnar capsular, six combined sites, and two indeterminate sites) between the midcarpal and radiocarpal joints. Nine unidirectional communications between the radiocarpal and distal radioulnar joints were found. Comparison of these results with the frequency and direction of unidirectional communications reported by others suggests that demonstration of communications depends on specific technical factors, such as which joint is injected first, the amount of contrast material used, and the delay between injections. This dependence on technical factors raises questions about the value of routine three-compartment wrist arthrography.

Description of Fasnet-A Unidirectional Local-Area Communications Network

Fasnet is an implicit token-passing, local-area network aimed at supporting high data rates and carrying a wide mix of traffic (data, voice, video, and facsimile). Transmission is unidirectional with stations attaching to the medium passively via directional couplers. A link consists of two lines, one to carry traffic in each direction. Unidirectional transmission provides the potential for efficient operation at high data rates, while the passive medium provides the potential for high reliability. We describe the physical configuration and the protocol and give channel utilization for the condition of continuously queued sources. Mechanisms to control the access of various traffic types are described. Finally, the interconnection of multiple Fasnets is studied for one particular configuration, a ring.