Underlying Communication Mechanism Research Articles

A Hybrid Routing Pattern in Human Brain Structural Network Revealed By Evolutionary Computation.

The human brain functional connectivity network (FCN) is constrained and shaped by the communication processes in the structural connectivity network (SCN). The underlying communication mechanism thus becomes a critical issue for understanding the formation and organization of the FCN. A number of communication models supported by different routing strategies have been proposed, with shortest path (SP), random diffusion (DIF), and spatial navigation (NAV) as the most typical, respectively requiring network global knowledge, local knowledge, and both for path seeking. Yet these models all assumed every brain region to use one routing strategy uniformly, ignoring convergent evidence that supports the regional heterogeneity in both terms of biological substrates and functional roles. In this regard, the current study developed a hybrid communication model that allowed each brain region to choose a routing strategy from SP, DIF, and NAV independently. A genetic algorithm was designed to uncover the underlying region-wise hybrid routing strategy (namely HYB). The HYB was found to outperform the three typical routing strategies in predicting FCN and facilitating robust communication. Analyses on HYB further revealed that brain regions in lower-order functional modules inclined to route signals using global knowledge, while those in higher-order functional modules preferred DIF that requires only local knowledge. Compared to regions that used global knowledge for routing, regions using DIF had denser structural connections, participated in more functional modules, but played a less dominant role within modules. Together, our findings further evidenced that hybrid routing underpins efficient SCN communication and locally heterogeneous structure-function coupling.

Modeling of optical wave propagation through turbulent atmosphere using fractional approach for FSO wireless communication

Free space optical (FSO) wireless communication has emerged as a viable alternative to the existing fiber optics and radio frequency (RF) communications due to its ability to operate in unlicensed spectrum, offering huge data handling capacities and being cost effective with easy deployment. The underlying communication mechanism in the FSO link is based upon the laser beam propagation model. The propagating free space optical beam undergoes signal degradation due to refraction and diffraction caused by atmospheric turbulence measured by refractive index structure parameter (C n 2). In this work, a novel, robust analytical model for propagating Gaussian-beam through atmospheric turbulence is presented, by solving the space-fractional paraxial wave equation. We report analytical expressions for the intensity and long-term beam spreading of a Gaussian beam in terms of space-fractional parameter D, for the range 2 < D ≤ 3. This range of parameter D, defines the effective number of euclidean space corresponding to atmospheric turbulence levels faced by the propagating Gaussian beam in the FSO link. The results of the proposed fractional model and the existing models agreed well, therefore the D-dimensional parameter can be used to effectively express the value of refractive index structure parameter (C n 2). The classical values of C n 2 ranges form 10−13 to 10−16 for strong to weak fluctuations respectively. However, in fractional-dimension scale, these fluctuations can be express as D = 2.668 (strong fluctuations) to D = 2.999 (weak fluctuations). The ideal case of free space beam propagation can be expressed as D = 3, with no turbulence. Moreover, we have studied the fractional-dimension model performance for varying wavelengths. Further, based upon a practical example, we proposed a self-sustainable FSO link architecture to efficiently minimize the effect of weak and strong fluctuations on the propagating optical beam, based upon the D-dimension fractional parameter, hence ensuring reliability of FSO link.

Enabling imitation-based cooperation in dynamic social networks

The emergence of cooperation among self-interested agents has been a key concern of the multi-agent systems community for decades. With the increased importance of network-mediated interaction, researchers have shifted the attention to the impact of social networks and their dynamics in promoting or hindering cooperation, drawing various context-dependent conclusions. For example, some lines of research, theoretical and experimental, suggest the existence of a threshold effect in the ratio of timescales of network evolution, after which cooperation will emerge, whereas other lines dispute this, suggesting instead a Goldilocks zone. In this paper we provide an evolutionary game theory framework to understand coevolutionary processes from a bottom up perspective - in particular the emergence of a cooperator-core and defector-periphery - clarifying the impact of partner selection and imitation strategies in promoting cooperative behaviour, without assuming underlying communication or reputation mechanisms. In doing so we provide a unifying framework to study imitation-based cooperation in dynamic social networks and show that disputes in the literature can in fact coexist in so far as the results stem from different equally valid assumptions.

Noise and turn-taking impact postanesthesia care unit handoff efficiency

Background Optimal handoffs are pivotal for patient safety, yet some of the underlying communication mechanisms which support effective handoffs remain to be understood. As handoffs are conversations between providers, understanding communication mechanisms is necessary to improve handoff protocol development. The objective of this study was to characterize communication variables influencing the efficiency of handoffs in the postanesthesia care unit. Methods We conducted a single-center, observational study of handoffs over a three-week period in June/July of 2017. We recorded 96 handoffs between the cardiac operating room and postanesthesia care unit. We defined and measured efficiency by dividing the count of unique, nonrepetitive pieces of information by duration of the handoff conversation. Furthermore, we calculated and measured two communication variables: turn-taking and noise. We utilized West and Zimmerman’s Syntactic Scale to analyze turn taking by segregating noise into three subcategories: environmental noise caused by equipment, environmental noise caused by staff, and third-party interruptions. Finally, we recorded and measured the frequency and duration of noise and turn-taking during the handoff events. Results Due to technical issues, we transcribed and analyzed a total of 85 observations. Providers passed an average of 31.68 unique pieces of information during each handoff with the average length being 1 min and 46 s. Overlaps was the most common type of turn-taking behavior. Activity noise was the most common type of noise. Activity noise took place an average of 3.64 times per handoff and lasted an average of 9.83 s. Turn-taking accounted for 15.6% of variance in handoff efficiency. Together, noise and turn-taking accounted for 25.2% of the variance in handoff efficiency. Conclusion Because turn-taking and noise account for over a quarter the variance in handoff efficiency, recommendations include providing quiet locations for handoffs to take place. Additionally, we recommend that receivers provide input in any handoff interventional studies as their involvement would decrease the need to interrupt or clarify information from the sender.

Recursive fusion estimation for stochastic discrete time-varying complex networks under stochastic communication protocol: The state-saturated case

In this paper, we investigate the recursive fusion estimation problem for time-varying state-saturated complex networks under stochastic communication protocol (SCP). To cater for physical limitations of network components, the phenomenon of state saturations is taken into account in the complex network model. The underlying communication mechanism is to ensure that just one sensor node is permitted to send its collected measurement at each time, and the SCP determines the permission to use the network channel for each sensor at each transmission time. A key issue of the addressed problem is to construct a time-varying state estimator such that an upper bound is guaranteed on the filtering error covariance subjected to both the state saturations and the SCP. By applying two sets of matrix difference equations, we first derive an upper bound according to the error covariance of the state estimation and then minimize such an upper bound by precisely calculating the estimator parameters. Then, the performance analysis of the obtained state estimator is given in terms of the boundedness. Finally, we provide a simulation example to illustrate the validity of the designed state estimator.

Physical fitness contributes to cardio-respiratory synchronization.

Cardio-respiratory synchronization is a phenomenon of particular interest- especially at a 1:1 ratio- and may give greater insight into the underlying mechanisms of cardio-respiratory communication. Synchronization of this ratio is hypothesised to occur when breathing rate exceeds heart rate, which is the premise of this research. A novel experimental design focused on guiding elevated respiration to induce the entrainment of heart rate, and produce an equivalent rise in value. Application of instantaneous phase for identification and analysis of synchronization allowed for a reliable method of measuring the interaction between these stochastic processes. We have identified 1:1 phase synchronization in all volunteers measured. Longer synchronization episodes were observed reliably in athletic individuals, corroborating previous research for spontaneous breathing. This observation suggests that cardio-respiratory synchronization at all respiration rates is associated with a common underlying communication mechanism. Furthermore, it presents cardio-respiratory synchronization as a potential future measurement of fitness and autonomic health.

Control of heart rate through guided high-rate breathing

Understanding the complex dynamics of cardio-respiratory coupling sheds light on the underlying mechanisms governing the communication between these two physiological systems. Previous research has predominantly considered the coupling at respiratory rates slower than the heart rate and shown that respiratory oscillations lead to modulation and/or synchronization of the heart rate. Whereas the mechanisms of cardio-respiratory communication are still under discussion, peripheral nervous regulation is considered to be the predominant factor. This work offers a novel experimental design and applies the concept of instantaneous phase to detect cardio-respiratory entrainment at elevated respiration rates, close to the resting heart rate. If such 1:1 entrainment exists, it would suggest direct neuronal communication between the respiration and heart centres in the brain. We have observed 1:1 entrainment in all volunteers, with consistently longer synchronization episodes seen in physically fitter people, and demonstrated that cardio-respiratory synchronization at both low and high respiration rates is associated with a common underlying communication mechanism.

ARINC659总线接口组件抗单粒子翻转加固设计及试验验证

ARINC659是一种标准的多点串行通信总线，具有通用、高效、高可靠等优点，已经越来越多地成为航天器综合电子系统计算机背板总线的理想选型。本文在对ARINC659总线架构和工作机制研究的基础上，对ARINC659总线标准背板总线组件在空间环境应用下的单粒子翻转效应敏感环节进行识别，并提出了有针对性的抗单粒子翻转加固设计措施，最后通过地面模拟试验对抗单粒子翻转加固措施的正确性和有效性进行了验证。试验表明进行单粒子翻转加固设计后的ARINC659总线接口组件满足辐照环境下的应用要求，为ARINC659总线应用于航天领域奠定了基础。 ARINC659 as a standard multipoint serial communication bus, and with the advantage of more general, high efficiency and reliability, has increasingly become the idea selection of backplane bus within the computer of spacecraft avionics system. This paper based on the study of ARINC659 bus architecture and underlying communication mechanism, identifies the sensitive of single event upset for ARINC659 bus interface components applied to space radiation environment, and a set of targeted reinforcement design is put forward for single event upset hardened. Finally, the correction and validity of the reinforcement design are verified by ground simulation experiment, which shows that ARINC659 bus interface components after reinforcement design meet the application in the radiation environment and provide the basis for the application of ARINC659 bus in aerospace.

Kassandra : A framework for distributed simulation of heterogeneous cooperating objects

Abstract To address the heterogeneity and scalability issues of simulating Cooperating Objects (COs) systems, we propose Kassandra , a conceptual framework for enabling distributed COs simulation by integrating existing simulation tools. Moreover, Kassandra exploits the communication middleware used by real-world COs as underlying communication mechanism for integrating Kassandra -enabled simulation tools. In this way, real-world COs can be included with simulated objects in a seamless way to perform more accurate system performance evaluation. Moreover, such a hardware-in-the-loop approach is not limited to pre-deployment performance analysis, and can offer possibilities to analyse performance at different phases of CO applications. The concept of Kassandra has been carried out in the EU PLANET project. In this paper, we introduce the Kassandra framework components and show their interactions at different phases for node deployments in PLANET use cases. The result demonstrates the applicability of Kassandra to facilitate the development of CO applications.

Synthesizing Globally Asynchronous Locally Synchronous Systems With IEC 61499

The IEC 61499 standard defines a generic architecture for designing distributed industrial control systems based on function blocks. The standard, however, lacks a formal model of computation to describe the behavior of function block compositions. While various models have been prescribed in the literature to define the composite behavior on a single computational node, few have been proposed to directly address compositions in a distributed setting. This paper proposes a globally asynchronous locally synchronous (GALS) model for distributed function block systems. The model provides an abstract way to view communication between function blocks without implying yet any particular implementation. This abstraction can then be subsequently refined to obtain various implementations with different tradeoffs. We do so using an approach that is fully compatible with the standard's notion of communication function blocks, which abstract underlying communication mechanisms from the application. As a contribution, we have developed a compiler that automatically synthesizes separate programs for a given distributed function block system without needing any additional middleware or run-time environment to execute the resulting distributed code. The efficacy of the proposed approach is demonstrated through an industrial case study.

Adaptive heterogeneous language support within a cloud runtime

Cloud runtimes are an effective method of distributing computations, but can force developers to use the runtime’s native language for all computations. We have extended the Granules cloud runtime with a bridge framework that allows computations to be written in C, C++, C#, Python, and R. We have additionally developed a diagnostics system which is capable of gathering information on system state, as well as modifying the underlying bridge framework in response to system load. Given the dynamic nature of Granules computations, which can be characterized as long-running with intermittent CPU bursts that allow a state to build up during successive rounds of execution, these bridges need to be bidirectional and the underlying communication mechanisms decoupled, robust and configurable. Granules bridges handle a number of different programming languages and support multiple methods of communication such as named pipes, unnamed pipes, and sockets. This choice of underlying communication mechanisms allows limited resources, such as sockets, to remain available for use by the runtime.

Identifying frequent items in a network using gossip

We present algorithms for identifying frequently occurring items in a large distributed data set. Our algorithms use gossip as the underlying communication mechanism, and do not rely on any central control, nor on an underlying network structure, such as a spanning tree. Instead, nodes repeatedly select a random partner and exchange data with that partner. If this process continues for a (short) period of time, the desired results are computed, with probabilistic guarantees on the accuracy. Our algorithm for identifying frequent items is built by layering a novel small space “sketch” of data over a gossip-based data dissemination mechanism. We prove that the algorithm identifies the frequent items with high probability, and provides bounds on the time till convergence. To our knowledge, this is the first work on identifying frequent items using gossip.

A Compute Unified System Architecture for Graphics Clusters Incorporating Data Locality

We present a development environment for distributed GPU computing targeted for multi-GPU systems, as well as graphics clusters. Our system is based on CUDA and logically extends its parallel programming model for graphics processors to higher levels of parallelism, namely, the PCI bus and network interconnects. While the extended API mimics the full function set of current graphics hardware-including the concept of global memory-on all distribution layers, the underlying communication mechanisms are handled transparently for the application developer. To allow for high scalability, in particular for network-interconnected environments, we introduce an automatic GPU-accelerated scheduling mechanism that is aware of data locality. This way, the overall amount of transmitted data can be heavily reduced, which leads to better GPU utilization and faster execution. We evaluate the performance and scalability of our system for bus and especially network-level parallelism on typical multi-GPU systems and graphics clusters.

Realizing Effective MPI-I/O to a Remote Computer Using a Parallel Virtual File System

This paper presents a newly implemented remote MPI-I/O mechanism using a Parallel Virtual File System (PVFS) to achieve high performance data-intensive I/O operations among computers. MPI-I/O extensions were realized in a flexible intermediate library named Stampi to support seamless MPI-I/O operations among computers. With the help of a flexible underlying communication mechanism of the library, MPI-I/O operations are available both inside a computer and among computers with the same MPI-I/O APIs without awareness of underlying communication and I/O mechanisms. To cope with recent data-intensive applications, PVFS was developed, and it provides a huge amount of parallel file system on a Linux PC cluster. Although it is available inside a PC cluster, it is not accessible from a remote computer. To exploit advantage of the PVFS file system in the remote MPI-I/O operations using Stampi, PVFS I/O functions have been implemented in the remote MPI-I/O mechanism. Through performance measurement of primitive MPI-I/O functions, sufficient performance has been achieved and effectiveness of the implementation has been confirmed.

A real-time primary-backup replication service

This paper presents a real-time primary-backup replication scheme to support fault-tolerant data access in a real-time environment. The main features of the system are fast response to client requests, bounded inconsistency between primary and backup, temporal consistency guarantee for replicated data, and quick recovery from failures. The paper defines external and interobject temporal consistency, the notion of phase variance, and builds a computation model that ensures such consistencies for replicated data deterministically where the underlying communication mechanism provides deterministic message delivery semantics and probabilistically where no such support is available. It also presents an optimization of the system and an analysis of the failover process which includes failover consistency and failure recovery time. An implementation of the proposed scheme is built within the x-kernel architecture on the MK 7.2 microkernel from the Open Group. The results of a detailed performance evaluation of this implementation are also discussed.

Introduction To A Fault-Tolerant Distributed Real-Time System Simulator

This paper describes a distributed simulation package for real-time systems. The purpose of the simulator is to study recoveiy strategies for embedded systems, task allocation and scheduling algorithms, network protocols, and dynamic reconfiguration techniques. The current version of the simulator runs on a network of workstations, connected by an Ethernet. The underlying communication mechanism is PVM (parallel virtual machine) software.

Hot Potato Worm Routing via Store-and-Forward Packet Routing

The theory of worm routing (rather than packet routing) has recently attracted increased attention as an abstraction of the underlying communication mechanisms in many parallel machines. Routing the worms in the hot potato style is a desired form of communication in high-speed optical interconnection networks. In this work, we develop a simple method for the design of parallel hot potato worm routing algorithms. Our basic approach is to simulate known packet routing algorithms, so that in each step worms are moved around instead of packets. By plugging in known results for packet routing, we get the fastest (so far) deterministic batch worm routing algorithms. Although the results are given for permutation routing on the mesh and the hypercube, the general method can be applied to many other networks and to more general communication patterns as well. Moreover, once better routing algorithms are found for the underlying network, the worm routing algorithms improve as well.

Formal specification and compositional verification of an atomic broadcast protocol

We apply a formal method based on assertions to specify and verify an atomic broadcast protocol. The protocol is implemented by replicating a server process on all processors in a network. We show that the verification of the protocol can be done compositionally by using specifications in which timing is expressed by local clock values. First the requirements of the protocol are formally described. Next the underlying communication mechanism, the assumptions about local clocks, and the failure assumptions are axiomatized. Also the server process is represented by a formal specification. Then we verify that parallel execution of the server processes leads to the desired properties by proving that the conjunction of all server specifications and the axioms about the system implies the requirements of the protocol.

Control integration through message-passing in a software development environment

Understanding tool integration in a software development environment (SDE) is one of the key issues being addressed in current work on providing automated support for large-scale software production. Work has been taking place at both the conceptual level (‘what is integration?’) and the mechanistic level (‘how do we provide integration?’). Many people see the answers to these questions as providing the corner-stone to real progress in the area. Until recently, existing integration mechanisms have been very rigid in the support they provide for integration. Users have been offered a fixed level of integration with little flexibility. However, one approach that has been recently implemented employs a control integration paradigm which appears to be flexible, supportive and adaptable to a wide range of end-user needs. Implementations of this paradigm are based on the notion of ‘message-passing’ as the underlying communication mechanism between SDE services. In this paper, we examine the message-passing approach to integration in an SDE, look at the general principles of the approach, describe some existing implementations, and discuss the use of such a mechanism as the basis for a more flexible environment that is open to experimentation with different approaches to integration.