一种适用于mesh网络的分布式恢复算法

文章简要介绍了传统的基于链路的恢复技术,并在此基础上提出一种改进的分布式恢复算法,这种新的算法不仅可以恢复链路故障,而且也可以解决节点故障。通过仿真分析可看出,它在故障恢复速度和资源利用率等方面都表现出优越的性能。     

A distributed simulation and prototyping testbed for radiocommunication networks

The authors discuss the development of a testbed, called the distributed simulation and prototyping testbed (DSPT), to model variable-connectivity radio networks. The DSPT constitutes a software environment in which distributed simulation and prototyping models of radio communication and command and control systems can easily be built. The environment consists of four separate software packages: communication simulation, communication monitor, scenario update/controller, and prototype node. These four packages work together to form a single distributed simulation and prototyping facility for communication network studies. They relieve the user from the need to consider many of the details that must be handled to implement a distributed testbed. Each package is easily extensible and can be tailored to specific networks, scenarios, monitor views, and prototyping needs     

分布式高空气球通信网络功率分配算法

针对高空气球组网通信中干扰严重和电量供应受限的问题,提出了一种基于非合作博弈的分布式功率分配模型.通过在效用函数中增加干扰限制,保证了网络的整体信干噪比,提升了网络的通信质量;通过在效用函数中关注节点的剩余能量,使高空气球的工作时间得到延长.利用数学分析验证了模型中纳什均衡点的存在性和唯一性,并给出了纳什均衡点的求解方...     

分布式声探测无线网络时间同步算法研究

分布式声探测无线网络是一种基于声达时间差(TDOA)进行目标定位的无线传感器网络;而基于TDOA算法的分布式定位需要节点之间严格时间同步,本文正是对节点之间严格时间同步进行了重点研究.文中系统分析了分布式声探测无线网络的应用环境、工作机制和硬件平台,在此基础上提出节点之间的采样同步和全网同步问题,并基于后同步思想和分级同步机制,设计了分布式声探测无线网络节点同步的整体解决方案.该方案已经进行了组网测试,有效解决了分布式身探测的时间同步问题.本文对相关工程实践具有一定的指导意义.     

A distributed routing algorithm for mobile wireless networks

We present a loop-free, distributed routing protocol for mobile packet radio networks. The protocol is intended for use in networks where the rate of topological change is not so fast as to make flooding the only possible routing method, but not so slow as to make one of the existing protocols for a nearly-static topology applicable. The routing algorithm adapts asynchronously in a distributed fashion to arbitrary changes in topology in the absence of global topological knowledge. The protocol's uniqueness stems from its ability to maintain source-initiated, loop-free multipath routing only to desired destinations with minimal overhead in a randomly varying topology. The protocol's performance, measured in terms of end-to-end packet delay and throughput, is compared with that of pure flooding and an alternative algorithm which is well-suited to the high-rate topological change environment envisioned here. For each protocol, emphasis is placed on examining how these performance measures vary as a function of the rate of topological changes, network topology, and message traffic level. The results indicate the new protocol generally outperforms the alternative protocol at all rates of change for heavy traffic conditions, whereas the opposite is true for light traffic. Both protocols significantly outperform flooding for all rates of change except at ultra-high rates where all algorithms collapse. The network topology, whether dense or sparsely connected, is not seen to be a major factor in the relative performance of the algorithms.The work of A. Ephremides was supported in part by the National Science Foundation under grants D-CDR-8803012 and EEC94-02384.     

A comparative analysis of virtual versus physical process-migration strategies for distributed modeling and simulation of mobile computing networks

Improvements in processor power and diminishing processor costs coupled with the potential of asynchronous, distributed algorithms promise to expand the frontier of mobile computing networks. In general, a mobile computing network consists of semi-autonomous or autonomous stationary and mobile agents that perform local computations, cooperate, and communicate among themselves to achieve a desired objective. While the stationary entities are connected through a static interconnection network and interact with each other, the mobile units interact dynamically with the stationary entities. Examples of newly emerging mobile computing networks include route guidance in the U.S. Department of Transportations Intelligent Vehicle Highway Systems, distributed scheduling in railway networks, semi-autonomous decision making in the battlefield environment, and the community health care network wherein mobile physicians may interact with remote patient medical records. This paper focuses on the high level principles that underlie the distributed modeling and accurate simulation of mobile computing networks on a parallel processing testbed. The testbed consists of a network of workstations configured as a loosely-coupled parallel processor and it closely resembles reality. A key issue is the representation of the stationary and mobile entities of the mobile computing network through concurrent and interacting processes in the testbed. The nature of the representation will influence the accuracy and performance of the simulation. This paper first reviews a process representation technique that has been proposed in the literature for modeling railway networks and then analyzes its limitations. This strategy is referred to as Virtual Process Migration (VPM). The paper then proposes a new strategy, termed Physical Process Migration (PPM), that aims to address the limitations of VPM. It details the software techniques underlying both approaches, describes their implementations on a realistic testbed, and then contrasts their performance under different representative scenarios. While VPM is capable of modeling modest to large-scale mobile computing networks on a testbed consisting of a few processors, the number of processors of the testbed in PPM must correspond to the number of stationary and mobile entities of the mobile computing network size that is being modeled. Analysis of the simulation results reveals that both VPM and PPM are highly effective and very useful strategies under different circumstances. For a given number of mobile and stationary entities, simulation under PPM is fast when every mobile entity requires significant computation. On the other hand, VPM exhibits superior performance relative to PPM when the number of data elements exchanged by each mobile entity at each hop is significantly high.     

WDM网络分布式物理损伤感知RWA算法

随着传输速率的不断升级,在透明传送过程中,各种损伤的积累会对光信号的质量造成严重影响,因而不能保证高QoS(服务质量)地传输信号.文章提出一种物理损伤感知的分布式RWA(波长路由分配)算法,将物理层传输质量评估分布在中继段路由和波长信道中,分别由损伤感知路由、波长通道传输质量排序和按优先级分配3部分构成.仿真实例证明了...     

A cone-based distributed topology-control algorithm for wireless multi-hop networks

The topology of a wireless multi-hop network can be controlled by varying the transmission power at each node. In this paper, we give a detailed analysis of a cone-based distributed topology-control (CBTC) algorithm. This algorithm does not assume that nodes have GPS information available; rather it depends only on directional information. Roughly speaking, the basic idea of the algorithm is that a node u transmits with the minimum power p/sub u,/spl alpha// required to ensure that in every cone of degree /spl alpha/ around u, there is some node that u can reach with power p/sub u,/spl alpha//. We show that taking /spl alpha/=5/spl pi//6 is a necessary and sufficient condition to guarantee that network connectivity is preserved. More precisely, if there is a path from s to t when every node communicates at maximum power then, if /spl alpha//spl les/5/spl pi//6, there is still a path in the smallest symmetric graph G/sub /spl alpha// containing all edges (u,v) such that u can communicate with v using power p/sub u,/spl alpha//. On the other hand, if /spl alpha/>5/spl pi//6, connectivity is not necessarily preserved. We also propose a set of optimizations that further reduce power consumption and prove that they retain network connectivity. Dynamic reconfiguration in the presence of failures and mobility is also discussed. Simulation results are presented to demonstrate the effectiveness of the algorithm and the optimizations.     

FP-MAC: A distributed MAC algorithm for 802.15.4-like wireless sensor networks

In this paper we focus on the problems of high latency and low throughput arising from the periodic operation of MAC protocols for wireless sensor networks. In order to meet both design criteria we propose an energy-efficient, low delay, fast-periodic MAC algorithm, namely FP-MAC, that is exclusively designed for 802.15.4-like networks utilizing in full the standard’s physical layer. Our proposal relies on the short periodic communication operation of the nodes comprising the WSN. This is achieved by decreasing the actions that a node needs to perform at the start of every communication period and by incorporating a variable radio-on operation. Moreover, the algorithm introduces differences in nodes’ scheduling to further reduce delay. Local synchronization and the crucial task of determining the proper timing for transmission and reception of data is achieved through the periodic broadcast of special synchronization frames at the beginning of each on-period. FP-MAC is evaluated and compared to S-MAC and T-MAC through extensive simulations, showing a significant improvement in terms of low energy consumption and average MAC delay.     

A distributed routing algorithm for datagram traffic in LEOsatellite networks

Satellite networks provide global coverage and support a wide range of services, low Earth orbit (LEO) satellites provide short round-trip delays and are becoming increasingly important. One of the challenges in LEO satellite networks is the development of specialized and efficient routing algorithms. In this work, a datagram routing algorithm for LEO satellite networks is introduced. The algorithm generates minimum propagation delay paths. The performance of the algorithm is evaluated through simulations. The robustness issues of the algorithm are also discussed     

An efficient fault-tolerant distributed channel allocation algorithm for cellular networks

A channel allocation algorithm in a cellular network consists of two parts: a channel acquisition algorithm and a channel selection algorithm. Some of the previous works in this field focused on centralized approaches to allocating channels. But, centralized approaches are neither scalable nor reliable. Recently, distributed dynamic channel allocation algorithms have been proposed, and they have gained a lot of attention due to their high reliability and scalability. But, in most of the algorithms, the cell that wants to borrow a channel has to wait for replies from all its interference neighbors and, hence, is not fault-tolerant. In this paper, we propose a new algorithm that is fault-tolerant and makes full use of the available channels. It can tolerate the failure of mobile nodes as well as static nodes without any significant degradation in service.     

A utility-based distributed maximum lifetime routing algorithm for wireless networks

Energy-efficient routing is a critical problem in multihop wireless networks due to the severe power constraint of wireless nodes. Despite its importance and many research efforts toward it, a distributed routing algorithm that maximizes network lifetime is still missing. To address this problem, this paper proposes a novel utility-based nonlinear optimization formulation to the maximum lifetime routing problem. Based on this formulation, a fully distributed localized routing algorithm is further presented, which is proved to converge at the optimal point, where the network lifetime is maximized. Solid theoretical analysis and simulation results are presented to validate the proposed solution.     

A new distributed location management algorithm for broadbandpersonal communication networks

We propose an efficient location management algorithm for broadband personal communication networks (PCNs) which reduces the complexity of network signaling and delay due to database access when locating a portable station (PS). Previous works on updating and search algorithms for personal communications have concentrated on the access delay due to signaling network traffic only. But, with the advances in fiber optic technology, it will be possible to provide the capacity of signaling network on the order of several Mbps in broadband PCNs. Thus it may be more important to simplify the signaling procedure and reduce the number of database accesses for mobility management at the cost of some increase of signaling traffic. In the proposed algorithm, we first remove all visitor location registers (VLRs) in order to achieve the simplicity of signaling procedure. Thus, only home databases for mobility management are distributed in a global network, and each database keeps only the current locations of PSs initially registered in its management area. It can solve the problem of requiring an impractically large database in a centralized database structure by distributing home location registers (HLRs) while maintaining the simplicity of mobility management and reducing database loads. This algorithm has a simple signaling procedure, and reduces database operations when compared to hierarchical algorithms as network switching hierarchy increases or relocation and calling rate increase     

A distributed link scheduling algorithm for CDMA packet radio networks

A distributed algorithm for the conflict-free channel allocation in CDMA (code division multiple access) networks is presented. Dynamic adjustment to topological changes is also considered. Though the schedules produced by our algorithm are not optimal with respect to link schedule length, the algorithm is simple and practical. The link schedule length minimization problem is NP-complete. Here the length of a link schedule is the number of time slots it uses. The algorithm guarantees a bound 2 — 1 time slots on the TDMA cycle length, where is the maximum degree of a station (i.e., maximum number of stations that a station can reach by radio links) in the network. The message complexity of a station isO().     

DIVA: a distributed divergecast scheduling algorithm for IEEE 802.15.4e TSCH networks

Wireless Networks - IEEE standardized a highly efficient, low power, reliable, deterministic and time–frequency enabled medium access control protocol, IEEE 802.15.4e time slotted channel...     

RYNSORD: a novel decentralized algorithm for railway networks with“soft reservation”

This paper presents a novel decentralized algorithm with soft reservation for efficient scheduling and congestion mitigation in railway networks (RYNSORD), wherein every train utilizes lookahead to dynamically replan its route. Thus, a train, currently at position N and headed for the ultimate destination Y, first requests and reserves N tracks, i.e., the lookahead, ahead of its current position for use at appropriate future times. The train moves through the N tracks and, upon completion, it again requests and reserves N subsequent tracks ahead of itself. The process continues until the train reaches its destination. The reservation process is characterized as “soft”, i.e., less abrupt and more flexible in negotiation between the trains and stations, in contrast to the traditional rigid “hard” reservations, RYNSORD is modeled and implemented on a network of SUN sparc workstations, configured as a loosely coupled parallel processor. Experimental results, obtained from simulating realistic example train networks and utilizing stochastic input train traffic data, reveal that: (1) soft reservation is superior to hard reservations in achieving both fast train travel times and higher quality of routing; and (2) while trains under low lookahead experience higher average hop count and high probability of doublebacks, relative to large lookahead values, they also have lower travel times     

一种配电网拓扑跟踪方法及其应用

为了满足实时跟踪的需求,在分析了3种配电网拓扑跟踪算法的基础上,提出了一种电网全局以母线为节点遍历和设备单元局部更新相结合的新型实时跟踪算法。为了便于说明算法的应用,文中还对电网拓扑变化和跟踪算法进行了阐述。最后在一个大型钢铁企业的配电网仿真系统中进行了实际的应用,该仿真说明了该跟踪算法是有效的。     

A channel assignment algorithm via conflict shifting for distributed cognitive networks

Channel assignment is a challenge for distributed cognitive networks due to spectrum mobility and lack of centralized entity. We present a dynamic and efficient algorithm via conflict shifting, referred as Shifting-based Channel Assignment (SCA). In this algorithm, the system was modeled with a conflict graph, and users cannot assign the channels that primary users (legacy users) and neighbors already occupied. In order to eliminate the conflicts between neighbors efficiently, secondary users (unlicensed users) try to transfer them through a straight path to the boundary, where conflicts are easier to solve as there are less neighbors for boundary users. Actions in one shift are executed in slots, and users act in a synchronous and separated manner. As a result, some of the conflicting channels are avoid from directly abandoned, and for this, utility of the entire network can be improved. Simulation results show that the proposed algorithm can provide similar utility performance while obviously reducing the communication cost than bargaining-base algorithms. In small scale networks with low user mobility (under 20%), it reduces 50% of the communication overhead than the later.     

A control-theoretic approach to distributed discrete-valued decision-making in networks of sensing agents

We address the problem of global sensor fusion for the purpose of distributed decision-making, from a control-theoretic perspective. In particular, we introduce a quasi-linear stochastic distributed protocol, using which a network of sensing agents can reach agreement in order to take a collective action. Using control-theoretic methods, we design the parameters of our protocol - which include weights in the local update rules used by the agents and a finite stopping time - to achieve agreement in a fair and rapid manner. We show analytically that the developed protocol achieves fair agreement with certainty in the noise-free case and achieves fair agreement with high probability even in the presence of communication noise and assuming very little information storage capability for the agents. Our development is illustrated throughout with a canonical example motivated by autonomous vehicle control.     

R-DRA: a replication-based distributed randomized algorithm for data dissemination in connected vehicular networks

Wireless Networks - As data dissemination is of great importance for applications in connected vehicular networks (VANETs), we aim to facilitate the performance of data dissemination in this study....