Finite spectrum assignment of unstable time-delay systems with a safe implementation

The instability mechanisms, related to the implementation of distributed delay controllers in the context of finite spectrum assignment, were studied in detail in the past few years. In this note we introduce a distributed delay control law that assigns a finite closed-loop spectrum and whose implementation with a sum of point-wise delays is safe. This property is obtained by implicitly including a low-pass filter in the control loop. This leads to a closed-loop characteristic quasipolynomial of retarded type, and not one of neutral type, which was shown to be a cause of instability in previous schemes.     

Distributed Coordination in Heterogeneous Multi-Robot Systems

Coordination in multi-robot systems is a very active research field in Artificial Intelligence and Robotics, since through coordination one can achieve a more effective execution of the robots' tasks. In this paper we present an approach to distributed coordination of a multi-robot system that is based on dynamic role assignment. The approach relies on the broadcast communication of utility functions that define the capability for every robot to perform a task and on the execution of a coordination protocol for dynamic role assignment. The presented method is robust to communication failures and suitable for application in dynamic environments. In addition to experimental results showing the effectiveness of our approach, the method has been successfully implemented within the team of heterogeneous robots Azzurra Robot Team in a very dynamic hostile environment provided by the RoboCup robotic soccer competitions.     

Modeling high assurance agent-based Earthquake Management System using formal techniques

Disaster management systems are complex applications due to their distributed and decentralized nature. Various components execute in parallel with high need of coordination with each other. In such applications, interaction and communication issues are difficult to model and implement. In this paper, we have proposed agent-based Earthquake Management System (EMS) which is modeled and analyzed using formal approach. Traditionally, such systems undergo through various transformations starting from requirement models and specification to analysis, design and implementation. A variety of formal approaches are available to specify systems for analyzing their structure and behavior; however, there are certain limitations in using these techniques due to their expressiveness and behavior requirements. We have adopted combination of Pi-calculus and Pi-ADL formal languages to model EMS from analysis to design. The formal approach helps to enhance reliability and flexibility of the system by reducing the redundant information. It reduces chances of errors by explicitly mentioning working flow of information. Additionally, a prototype application is presented as proof of concept in EMS context. We have also evaluated our formal specification by using ArchWare and ABC tools; also, comparison of prototype application with major existing techniques is highlighted.     

Finite spectrum assignment of systems with general delays

This article presents a new framework for dealing with pure and distributed delays simultaneously and impartially as general delays in algebraic finite spectrum assignment. The framework based on an important property common to general delays gives a sufficient condition for finite spectrum assignability of scalar systems with several general delays and a design method of a controller achieving finite spectrum assignment. Especially in algebraic control theory for delay systems, pure and distributed delays have never been dealt with simultaneously and impartially. The framework is significantly important also for multidimensional system theory because its potential applicability to the discussion on systems with general delays, i.e. the possibility that especially distributed delay operators are used as variables for describing multidimensional systems, is clarified for the first time.     

WDM网络中实时组播的分布式优化RWA算法

在WDM网络中,由于每条链路上可用波长是动态变化的,在考虑波长转换延迟时间的条件下,实现实时组播连接的路由选择与波长分配是十分困难的。论文提出了一种用于建立实时组播连接的分布式路由选择与波长分配算法。该算法将路由选择与波长分配统一进行,大大减少连接的建立时间。组播路由算法以Prim最小生成树算法为基础,生成一棵满足给定延迟时限的最小成本树。波长分配使用最少波长转换和同一波长最长使用策略。     

Coordinated problem solving through resource sharing in a distributed environment.

An important feature in a distributed problem solving system is that the resources of different nodes can be shared through cooperation. In this paper, the generalized partial global planning (GPGP) approach used for multiagent systems is extended by providing a coordination mechanism for resource sharing across nodes. In our framework, multiple conflicting criteria (or objectives) like quality, cost, and duration may be associated with an input task. Preference ratings expressed subjectively may be assigned to each of the criteria. Task assignment in this system, which is a multiobjective decision making problem, is important for the satisfaction of the criteria. It has to be done with imprecise information since the system is dynamic and preference ratings are specified subjectively. A technique for task assignment using the fuzzy set approach is also presented in this paper. Simulation studies for the coordination mechanism and the task assignment have been performed to demonstrate their effectiveness.     

WDM全光网络中实时组播的分布式路由与波长分配算法

在WDM网络中，由于每条链路上可用波长是动态变化的，在考虑波长转换延迟的条件下，实现实时组播连接的路由与波长分配是十分困难的．假定WDM网络中每条链路有多根光纤，只有部分结点具有波长转换器且波长转换时间是不可忽略的，据此提出了一种用于建立实时组播连接的分布式路由与波长分配算法．该算法以Prim最小生成树算法为基础，生成一棵满足给定延迟时限的最小成本树．当最小成本树不能包括所有目的结点时，对剩余目的结点生成一棵最短延迟树，然后合并两棵树得到一棵组播树．波长分配使用最少波长转换和负载平衡策略．     

WDM网络中实时组播的分布式路由与波长分配算法

在WDM网络中,由于每条链路上可用波长是动态变化的,在考虑波长转换延迟时间的条件下,实现实时组播连接的路由与波长分配是十分困难的。该文提出了一种用于建立实时组播连接的分布式路由与波长分配算法。该算法将路由与波长分配统一进行,大大减少连接的建立时间。组播路由算法以Prim最小生成树算法和K-度宽度优先搜索方法为基础,生成一棵满足给定延迟时限的最小成本树。波长分配使用最少波长转换和负载平衡策略。     

WDM网络中满足延迟和延迟差约束的分布式组播路由与波长分配算法

在WDM网络中,由于每条链路上可用波长是动态变化的,在考虑波长转换延迟时间的条件下,实现实时组播连接的路由与波长分配是十分困难的。论文提出了一种用于建立满足延迟时限和延迟差要求的实时组播连接的分布式路由与波长分配算法。该算法假定每个节点没有全局路由信息,只根据关联链路的信息进行路由选择,且将路由与波长分配统一进行。组播路由算法以Prim最小生成树算法为基础,生成一棵满足给定延迟时限的最小成本树。对不满足延迟时限的目的节点,通过增加回路边构造回路再消除长延迟路径的方式,加入到组播树中。对不满足延迟差的目的节点,采用重构Steiner树的方法,使其满足延迟差的要求。波长分配使用最少波长转换和负载平衡策略。     

Asynchronously compensated synchronization algorithm for multiple harmonic oscillators with communication delay

Synchronization problem is investigated for multiple harmonic oscillators with identical communication delay in this paper. We propose a new distributed control algorithm in asynchronously compensated form and a corresponding reduced‐order observer‐based distributed control algorithm. By using frequency‐domain analysis, delay‐dependent and delay‐independent convergence conditions are obtained for our proposed algorithms under leader‐following and leaderless coordination control structures, respectively, and the results can be directly extended to the observer‐based algorithm based on the separation principle. Numerical examples illustrate the validity of the theoretical findings. Copyright © 2016 John Wiley & Sons, Ltd.     

A distributed channel assignment control for QoS support in mobile ad hoc networks

Recently, one of the most critical issues in mobile ad hoc networks (MANETs) is providing quality of service (QoS) through routing, access/admission control, resource reservation, and mobility management. However, most existing solutions do not provide QoS effectively due to the interference arising from mobility. In this paper, we refer to interference as a quasi-exposed node problem. To solve this problem, a new algorithm, named a distributed channel assignment control, is proposed that focuses on performance enhancements related to QoS and mathematical analysis techniques for the channel bandwidth. This novel algorithm uses channel assignment control with a power control to reduce the negative effects induced by the quasi-exposed node problem, and then the channels are adaptively negotiated to allow communication in the interference region. The proposed algorithm has been evaluated via extensive simulations, and the results show that it can successfully guarantee QoS by maintaining good throughput, reducing control message overhead, and enhancing delay.     

Ad hoc网络中TDMA分布式动态时隙分配算法

基于时分多址(TDMA)的时隙分配算法能够提供很好的无线资源利用率,特别是在高负载的环境下.提出了一种适于Ad hoc基于TDMA的无冲突动态分布式时隙分配算法,通过动态改变帧长来控制未用时隙的过量增长,提高了系统吞吐量.该算法通过设置帧长为时隙2的次方,使其在不同帧长的节点中无冲突地包传输.节点间的同步采用本地同步方式.仿真结果表明该算法与IEEE 802.11相比提高了系统吞吐量并降低了端-端延迟.     

一种新的组密钥管理算法

在对组密钥管理算法进行全面研究的基础上,提出了一种新的用于安全组播的组密钥管理算法。本算法将集中式密钥分配算法与分布式密钥协商算法相结合,吸取了集中式密钥分配算法的可扩展性的优点,同时克服了其单点失效的问题,将密钥分配思想用于密钥协商算法中,产生了一种底层基于密钥链而上层组织为三叉密钥树的密钥分发算法。本算法可以代替密钥协商算法应用于所有成员关系对等且不存在可信第三方的组播组中,并克服了分布式密钥协商算法中的大计算延时问题,适用于成员关系变化频繁的大型组播组,具有较高的可扩展性。     

Concurrent counting is harder than queuing

We compare the complexities of two fundamental distributed coordination problems, distributed counting and distributed queuing, in a concurrent setting. In both distributed counting and queuing, processors in a distributed system issue operations which are organized into a total order. In counting, each participating processor receives the rank of its operation in the total order, where as in queuing, a processor receives the identity of its predecessor in the total order. Many coordination applications can be solved using either distributed counting or queuing, and it is useful to know which of counting or queuing is the easier problem.Our results show that concurrent counting is harder than concurrent queuing on a variety of processor interconnection topologies, including high and low diameter graphs. For all these topologies, we show that the concurrent delay complexity of a particular solution to queuing, the arrow protocol, is asymptotically smaller than a lower bound on the complexity of any solution to counting.     

Congestion-aware channel assignment for multi-channel wireless mesh networks

In this paper, we propose a distributed congestion-aware channel assignment (DCACA) algorithm for multi-channel wireless mesh networks (MC–WMNs). The frequency channels are assigned according to the congestion measures which indicate the congestion status at each link. Depending on the selected congestion measure (e.g., queueing delay, packet loss probability, and differential backlog), various design objectives can be achieved. Our proposed distributed algorithm is simple to implement as it only requires each node to perform a local search. Unlike most of the previous channel assignment schemes, our proposed algorithm assigns not only the non-overlapped (i.e., orthogonal) frequency channels, but also the partially-overlapped channels. In this regard, we introduce the channel overlapping and mutual interference matrices which model the frequency overlapping among different channels. Simulation results show that in the presence of elastic traffic (e.g., TCP Vegas or TCP Reno) sources, our proposed DCACA algorithm increases the aggregate throughput and also decreases the average packet round-trip compared with the previously proposed Load-Aware channel assignment algorithm. Furthermore, in a congested IEEE 802.11b network setting, compared with the use of three non-overlapped channels, the aggregate network throughput can further be increased by 25% and the average round-trip time can be reduced by more than one half when all the 11 partially-overlapped channels are used.     

基于反向平衡聚合树的无线传感器网络分布式TDMA调度算法*

讨论了已有的TDMA算法在端到端延时上的弊端,在优化时隙数的基础上引入链路的使用顺序与数据流向的相关性,提出了分布式TDMA调度算法,利用反向平衡聚合树的生成过程分配时隙,通过控制链路染色顺序分布式优化延时与避免冲突。仿真结果验证了算法在端到端延迟和通信开销上的性能提升。     

未知环境下分布式多机器人避碰协作算法

针对多机器人协作问题,提出一种未知环境下分布式多机器人协作避碰算法。该算法基于分布式投标模型协调多机器人运动,改进过去算法的前提假设,综合考虑机器人的实际尺寸和传感误差,通过自适应设定投标时间,提高算法的效率,针对通信延时引起的信息不一致,采用按优先级顺序进行探测的方法。仿真实验验证了该算法的可行性。     

一种基于网格的分布计算协同机制

通过对网格计算中资源协同调度机制的研究,根据该机制的资源协同分配需求,提出一个以Globus Toolkit为平台的基于网格计算的分布协同计算模型。在基于经济模型的作业调度机制的竞价机制中,给出一个较为完善的价格函数模型以及相应的作业预测完成时间模型,利用设计的价格函数模型实现资源提供的主观能动性,使得资源的调配更加合理、快速。同时,在分布式计算模型中还给出一个基于备份的作业调度容错机制。     

基于概率的水下传感器网络CDMA编码分配算法

水下传感器网络采用声波进行通信,具有高时延、低带宽、高误码率等特点,使得适用于无线电信道的MAC协议无法直接应用于水声信道,给水下传感器网络协议的设计带来了很大的挑战．因此,我们提出了一种可以较高概率避免扩频码冲突的分布式的基于概率的水下传感器网络CDMA编码动态分配算法．该算法不需要精确的时间同步,并且能够动态适应水下传感器网络拓扑结构的变化,适用于基于发送端的编码分配和基于接收端的编码分配．仿真实验表明,与传统的编码分配方式相比,我们的算法突出了节点的个性化,进一步降低了冲突的风险．     

Emergency medical services and beyond: Addressing new challenges through a wide literature review

One of the most important health care services is emergency medical service as it plays a vital role in saving people's lives and reducing the rate of mortality and morbidity. Over the last years, many review papers have discussed emergency medical services (EMS) location problems, however, only few review papers consider the full range of EMS systems. This review paper tries to fill this gap. Our review introduces the concept of emergency care pathway following the current trend in health care systems, i.e., shifting the central role from health care providers to patients. Considering the emergency care pathway, we provide a broad literature review and analysis in order to identify emerging challenges for future research.