Showing papers on "Node (networking) published in 2000"

The capacity of wireless networks

Abstract: When n identical randomly located nodes, each capable of transmitting at W bits per second and using a fixed range, form a wireless network, the throughput /spl lambda/(n) obtainable by each node for a randomly chosen destination is /spl Theta/(W//spl radic/(nlogn)) bits per second under a noninterference protocol. If the nodes are optimally placed in a disk of unit area, traffic patterns are optimally assigned, and each transmission's range is optimally chosen, the bit-distance product that can be transported by the network per second is /spl Theta/(W/spl radic/An) bit-meters per second. Thus even under optimal circumstances, the throughput is only /spl Theta/(W//spl radic/n) bits per second for each node for a destination nonvanishingly far away. Similar results also hold under an alternate physical model where a required signal-to-interference ratio is specified for successful receptions. Fundamentally, it is the need for every node all over the domain to share whatever portion of the channel it is utilizing with nodes in its local neighborhood that is the reason for the constriction in capacity. Splitting the channel into several subchannels does not change any of the results. Some implications may be worth considering by designers. Since the throughput furnished to each user diminishes to zero as the number of users is increased, perhaps networks connecting smaller numbers of users, or featuring connections mostly with nearby neighbors, may be more likely to be find acceptance.

A scalable location service for geographic ad hoc routing

Abstract: GLS is a new distributed location service which tracks mobile node locations. GLS combined with geographic forwarding allows the construction of ad hoc mobile networks that scale to a larger number of nodes than possible with previous work. GLS is decentralized and runs on the mobile nodes themselves, requiring no fixed infrastructure. Each mobile node periodically updates a small set of other nodes (its location servers) with its current location. A node sends its position updates to its location servers without knowing their actual identities, assisted by a predefined ordering of node identifiers and a predefined geographic hierarchy. Queries for a mobile node's location also use the predefined identifier ordering and spatial hierarchy to find a location server for that node.Experiments using the ns simulator for up to 600 mobile nodes show that the storage and bandwidth requirements of GLS grow slowly with the size of the network. Furthermore, GLS tolerates node failures well: each failure has only a limited effect and query performance degrades gracefully as nodes fail and restart. The query performance of GLS is also relatively insensitive to node speeds. Simple geographic forwarding combined with GLS compares favorably with Dynamic Source Routing (DSR): in larger networks (over 200 nodes) our approach delivers more packets, but consumes fewer network resources.

Topology control of multihop wireless networks using transmit power adjustment

Abstract: We consider the problem of adjusting the transmit powers of nodes in a multihop wireless network (also called an ad hoc network) to create a desired topology. We formulate it as a constrained optimization problem with two constraints-connectivity and biconnectivity, and one optimization objective-maximum power used. We present two centralized algorithms for use in static networks, and prove their optimality. For mobile networks, we present two distributed heuristics that adaptively adjust node transmit powers in response to topological changes and attempt to maintain a connected topology using minimum power. We analyze the throughput, delay, and power consumption of our algorithms using a prototype software implementation, an emulation of a power-controllable radio, and a detailed channel model. Our results show that the performance of multihop wireless networks in practice can be substantially increased with topology control.

A Review of Routing and Wavelength Assignment Approaches for Wavelength- Routed Optical WDM Networks

Abstract: This study focuses on the routing and WavelengthAssignment (RWA) problem in wavelength-routed optical WDM networks. Most of the attention is devoted to such networks operating under the wavelength-continuity constraint, in which lightpaths are set up for connection requests between node pairs, and a single lightpath must occupy the same wavelength on all of the links that it spans. In setting up a lightpath, a route must be selected and a wavelength must be assigned to the lightpath. If no wavelength is available for this lightpath on the selected route, then the connection request is blocked. We examine the RWA problem and review various routing approaches and wavelengthassignment approaches proposed in the literature. We also briefly consider the characteristics of wavelength-converted networks (which do not have the wavelength-continuity constraint), and we examine the associated research problems and challenges. Finally, we propose a new wavelengthassignment scheme, called Distributed Relative Capacity Loss (DRCL), which works well in distributed-controlled networks, and we demonstrate the performance of DRCL through simulation.

Freenet : A Distributed Anonymous Information Storage and Retrieval System

Abstract: We describe Freenet, an adaptive peer-to-peer network application that permits the publication, replication, and retrieval of data while protecting the anonymity of both authors and readers. Freenet operates as a network of identical nodes that collectively pool their storage space to store data files and cooperate to route requests to the most likely physical location of data. No broadcast search or centralized location index is employed. Files are referred to in a location-independent manner, and are dynamically replicated in locations near requestors and deleted from locations where there is no interest. It is infeasible to discover the true origin or destination of a file passing through the network, and difficult for a node operator to determine or be held responsible for the actual physical contents of her own node.

Max-min d-cluster formation in wireless ad hoc networks

Abstract: An ad hoc network may be logically represented as a set of clusters. The clusterheads form a d-hop dominating set. Each node is at most d hops from a clusterhead. Clusterheads form a virtual backbone and may be used to route packets for nodes in their cluster. Previous heuristics restricted themselves to 1-hop clusters. We show that the minimum d-hop dominating set problem is NP-complete. Then we present a heuristic to form d-clusters in a wireless ad hoc network. Nodes are assumed to have a non-deterministic mobility pattern. Clusters are formed by diffusing node identities along the wireless links. When the heuristic terminates, a node either becomes a clusterhead, or is at most d wireless hops away from its clusterhead. The value of d is a parameter of the heuristic. The heuristic can be run either at regular intervals, or whenever the network configuration changes. One of the features of the heuristic is that it tends to re-elect existing clusterheads even when the network configuration changes. This helps to reduce the communication overheads during transition from old clusterheads to new clusterheads. Also, there is a tendency to evenly distribute the mobile nodes among the clusterheads, and evently distribute the responsibility of acting as clusterheads among all nodes. Thus, the heuristic is fair and stable. Simulation experiments demonstrate that the proposed heuristic is better than the two earlier heuristics, namely the LCA and degree-based solutions.

Achieving MAC layer fairness in wireless packet networks

Abstract: Link-layer fairness models that have been proposed for wireline and packet cellular networks cannot be generalized for shared channel wireless networks because of the unique characteristics of the wireless channel, such as location-dependent contention, inherent conflict between optimizing channel utilization and achieving fairness, and the absence of any centralized control.In this paper, we propose a general analytical framework that captures the unique characteristics of shared wireless channels and allows the modeling of a large class of system-wide fairness models via the specification of per-flow utility functions. We show that system-wide fairness can be achieved without explicit global coordination so long as each node executes a contention resolution algorithm that is designed to optimize its local utility function.We present a general mechanism for translating a given fairness model in our framework into a corresponding contention resolution algorithm. Using this translation, we derive the backoff algorithm for achieving proportional fairness in wireless shared channels, and compare the fairness properties of this algorithm with both the ideal proportional fairness objective, and state-of-the-art backoff-based contention resolution algorithms.We believe that the two aspects of the proposed framework, i.e. the ability to specify arbitrary fairness models via local utility functions, and the ability to automatically generate local contention resolution mechanisms in response to a given utility function, together provide the path for achieving flexible service differentiation in future shared channel wireless networks.

A MAC protocol for mobile ad hoc networks using directional antennas

Abstract: We propose a medium access control (MAC) protocol for an ad hoc network of mobile wireless terminals that are equipped with multiple directional antennas. Use of directional antennas in ad hoc networks can largely reduce the radio interference, thereby improving the packet throughput. However, the main problem of using directional antennas in such networks is due to the dynamic nature of the network caused by frequent node movements. This gives rise to problems such as locating and tracking during random channel access. The MAC protocol presented in this paper proposes a solution to these problems without the help of additional hardware. Results obtained from detailed computer simulations demonstrate the performance improvement obtained with the proposed scheme.

Resource management in a clustered computer system

Abstract: Methods, systems, and devices are provided for managing resources in a computing cluster. The managed resources include cluster nodes themselves, as well as sharable resources such as memory buffers and bandwidth credits that may be used by one or more nodes. Resource management includes detecting failures and possible failures by node software, node hardware, interconnects, and system area network switches and taking steps to compensate for failures and prevent problems such as uncoordinated access to a shared disk. Resource management also includes reallocating sharable resources in response to node failure, demands by application programs, or other events. Specific examples provided include failure detection by remote memory probes, emergency communication through a shared disk, and sharable resource allocation with minimal locking.

Proximity-based redirection system for robust and scalable service-node location in an internetwork

Abstract: A proximity-oriented redirection system for service-to-client attachment in a virtual overlay distribution network. The virtual overlay distribution network includes addressable routers for routing packet traffic, wherein a packet of data is routed from a source node to a destination node based on address fields of the packet. The invention includes a redirector coupled to at least one of the addressable routers and includes: logic for accepting a service request from a client; logic for determining a selected server for handling the service request, the selected server being one of a plurality of servers that can handle the service request; and logic for generating a redirection message directed to the client for redirecting the service request to the selected server.

Remote computer virus scanning

Abstract: A method of scanning electronic files for computer viruses comprises identifying at a first node 4 of a computer network 1, electronic files which require to be scanned for computer viruses The first node 4 initiates a dialogue with a second node 7 of the network 1, the second node comprising a virus scanning application During the dialogue, the second node 7 identifies to the first node 4 one or more portions of the electronic file required by the virus scanning application The first node 4 transfers the identified portions to the second node 7 which then carries out a virus scanning operation The result of this operation is then returned to the first node 4

A wap service personalisation, management and billing object-oriented platform

Abstract: An access node has a portal which performs interfacing between a wireless network domain and content/service providers in the Internet. On the wireless side the portal is linked with an SMSC, a CBC, and a USSD server for interfacing with and management of bearer stacks. Service functionality includes modular systems including a Push server, a Pre-paid calling server, and a location server in addition to internal portal functions. The latter provide for subscriber self-provisioning, customer care provisioning, subscriber device provisioning, and service provisioning. Thus, the node caters for both particular subscriber service and mobile device requirements.

System and method for disseminating topology and link-state information to routing nodes in a mobile ad hoc network

Abstract: Described is a link-state routing protocol used in a mobile ad hoc network or in an Internet for disseminating topology and link-state information throughout the network. Reverse-path forwarding is used to broadcast each update along the minimum-hop-path tree rooted at the source of the update. Each path tree has the source node as a root node, a parent node, and zero or more children nodes. Updates are received from the parent node in the path tree for the source node that originates the update. Each update includes information related to a link in the network. A determination is made whether to forward the update message to children nodes, if any, in the path tree maintained for the source node originating the update in response to information in the received update. This information itself can indicate whether the update is to be forwarded to other nodes.

Wireless communication network including plural migratory access nodes

Abstract: An amorphous communication network having no traditional wireless backbone has plural roving or migratory access node (200) or terminal devices that are carried or transported along with individuals. Each wireless node (200) has a user interface and a local ID, e.g., an IP address, URL, telephone number. Voice, data, or video is transferred to other migratory nodes (104) or to a conventional land-based telephone or data terminal via a PSTN, Internet, ATM network, etc. A geolocation detector in the node (200), such as a GPS, keeps track of the instantaneous position, which is conveyed to a locally or remotely stored database (400). A local processor (250) accesses this database (400) to determine node-to-node paths to a destination when the node (200) operates as a source. A node (200) captures a transmitted message when the destination address in the message matches its local address, or otherwise forwards the message towards a destination if the address does not match. Acknowledgements are sent between nodes (104) upon successful receipt of information. The node's wireless transceiver (260) also adapts to the environment and terrain to control transmission and reception characteristics according to bandwidth, inter-node spacing, signal strength, bit error rate, node population density, frequency spectrum, data rate and/or air interface protocol. Nodes (200) may periodically or randomly unicast or broadcast its ID and/or position data to update a database (400), which then may be propagated to other databases throughout the network. A database (400) may reside locally within a node (200) or at fixed regional locations (106) that are linked together to form a global database.

On/off keying node-to-node messaging transceiver network with dynamic routing and configuring

Abstract: The invention is a system operating on a reference frequency. The system comprises a plurality of at least three nodes. Each node hands off a message received from another node to a subsequent node. Each of the nodes comprises a transceiver receiving a message on the reference frequency from another node and transmitting the received message on the reference frequency to a subsequent node, and a controller controlling operation of the transceiver to receive the.. message transmitted by another node and to transmit the received message to a subsequent node.

An on-demand weighted clustering algorithm (WCA) for ad hoc networks

Abstract: We consider a multi-cluster, multi-hop packet radio network architecture for wireless systems which can dynamically adapt itself with the changing network configurations. Due to the dynamic nature of the mobile nodes, their association and dissociation to and from clusters perturb the stability of the system, and hence a reconfiguration of the system is unavoidable. At the same time it is vital to keep the topology stable as long as possible. The clusterheads, which form a dominant set in the network, decide the topology and are responsible for its stability. In this paper, we propose a weighted clustering algorithm (WCA) which takes into consideration the ideal degree, transmission power, mobility and battery power of a mobile node. We try to keep the number of nodes in a cluster around a pre-defined threshold to facilitate the optimal operation of the medium access control (MAC) protocol, Our clusterhead election procedure is not periodic as in earlier research, but adapts based on the dynamism of the nodes. This on-demand execution of WCA aims to maintain the stability of the network, thus lowering the computation and communication costs associated with it. Simulation experiments are conducted to evaluate the performance of WCA in terms of the number of clusterheads, reaffiliation frequency and dominant set updates, Results show that the WCA performs better than the existing algorithms and is also tunable to different types of ad hoc networks.

Cluster reserves: a mechanism for resource management in cluster-based network servers

Abstract: In network (e.g., Web) servers, it is often desirable to isolate the performance of different classes of requests from each other. That is, one seeks to achieve that a certain minimal proportion of server resources are available for a class of requests, independent of the load imposed by other requests. Recent work demonstrates how to achieve this performance isolation in servers consisting of a single, centralized node; however, achieving performance isolation in a distributed, cluster based server remains a problem.This paper introduces a new abstraction, the cluster reserve, which represents a resource principal in a cluster based network server. We present a design and evaluate a prototype implementation that extends existing techniques for performance isolation on a single node server to cluster based servers.In our design, the dynamic cluster-wide resource management problem is formulated as a constrained optimization problem, with the resource allocations on individual machines as independent variables, and the desired cluster-wide resource allocations as constraints. Periodically collected resource usages serve as further inputs to the problem.Experimental results show that cluster reserves are effective in providing performance isolation in cluster based servers. We demonstrate that, in a number of different scenarios, cluster reserves are effective in ensuring performance isolation while enabling high utilization of the server resources.

Scalable, distributed data structures for internet service construction

Abstract: This paper presents a new persistent data management layer designed to simplify cluster-based Internet service construction. This self-managing layer, called a distributed data structure (DDS), presents a conventional single-site data structure interface to service authors, but partitions and replicates the data across a cluster. We have designed and implemented a distributed hash table DDS that has properties necessary for Internet services (incremental scaling of throughput and data capacity, fault tolerance and high availability, high concurrency, consistency, and durability). The hash table uses two-phase commits to present a coherent view of its data across all cluster nodes, allowing any node to service any task. We show that the distributed hash table simplifies Internet service construction by decoupling service-specific logic from the complexities of persistent, consistent state management, and by allowing services to inherit the necessary service properties from the DDS rather than having to implement the properties themselves. We have scaled the hash table to a 128 node cluster, 1 terabyte of storage, and an in-core read throughput of 61,432 operations/s and write throughput of 13,582 operations/s.

An architecture for building self-configurable systems

Abstract: Developing wireless sensor networks can enable information gathering, information processing and reliable monitoring of a variety of environments for both civil and military applications. It is however necessary to agree upon a basic architecture for building sensor network applications. This paper presents a general classification of sensor network applications based on their network configurations and discusses some of their architectural requirements. We propose a generic architecture for a specific subclass of sensor applications which we define as self-configurable systems where a large number of sensors coordinate amongst themselves to achieve a large sensing task. Throughout this paper we assume a certain subset of the sensors to be immobile. This paper lists the general architectural and infra-structural components necessary for building this class of sensor applications. Given the various architectural components, we present an algorithm that self-organizes the sensors into a network in a transparent manner. Some of the basic goals of our algorithm include minimizing power utilization, localizing operations and tolerating node and link failures.

Route discovery based piconet forming

Abstract: A method for establishing a route over which data packets are to be sent from a source node to a destination node in an ad-hoc network is provided A source having packets to send to a destination node employs a reactive routing protocol if it does not posses the route to the destination node Initially, it may be determined whether or not the source node is a member of an existing piconet If the source node is a member of an existing piconet, a ROUTE request message may be broadcast to the nodes of the existing piconet, while the source awaits a timely REPLY message If the source node is not a member of an existing piconet, or if a time REPLY message is not received, the source node may initiate a new route discovery process wherein the nodes attempt to establish new piconets that enable more efficient communication between the source and destination nodes

Method and system for consistent cluster operational data in a server cluster using a quorum of replicas

Abstract: A method and system for increasing server cluster availability by requiring at a minimum only one node and a quorum replica set of replica members to form and operate a cluster. Replica members, independent from the nodes, maintain cluster operational data. A cluster operates when one node possesses a majority of replica members, which ensures that any new or surviving cluster includes consistent cluster operational data via at least one replica member from the immediately prior cluster. Arbitration provides exclusive ownership by one node of the replica members, including at cluster formation, and when the owning node fails. Arbitration uses a fast mutual exclusion algorithm and a reservation mechanism to challenge for and defend the exclusive reservation of each member. A quorum replica set algorithm brings members online and offline with data consistency, including updating unreconciled replica members, and ensures consistent read and update operations.

Node-based uniform strain elements for three-node triangular and four-node tetrahedral meshes

Abstract: A family of uniform strain elements is presented for three-node triangular and four-node tetrahedral meshes. The elements use the linear interpolation functions of the original mesh, but each element is associated with a single node. As a result, a favorable constraint ratio for the volumetric response is obtained for problems in solid mechanics. The uniform strain elements do not require the introduction of additional degrees of freedom and their performance is shown to be significantly better than that of three-node triangular or four-node tetrahedral elements. In addition, nodes inside the boundary of the mesh are observed to exhibit superconvergent behavior for a set of example problems.

Method and system for message transfer session management

Abstract: A method and system for managing the transfer of message packets between first and second nodes in a message queuing system utilizes a session acknowledgment protocol to coordinate the two-way flow of packet transmission. In a session initiation phase, each node specifies a session acknowledgment timeout period and a transmission window size for transmission of message packets thereto. During the session, the first node transmits multiple message packets up to the window size set by the second node and stops to wait for a session acknowledgment from the second computer. The session acknowledgment may piggyback on a message packet sent to the first node. A window-size field in the session acknowledgment allows the receiving node to dynamically adjust the incoming data flow.

Virtual backbone generation and maintenance in ad hoc network mobility management

Abstract: In this paper, we present the implementation issues of a virtual backbone that supports the operations of the uniform quorum system (UQS) and the randomized database group (RDG) mobility management schemes in an ad hoc network. The virtual backbone comprises nodes that are dynamically selected to contain databases that store the location information of the network nodes. Together with the UQS and RDG schemes, the virtual backbone allows both dynamic database residence and dynamic database access, which provide high degree of location data availability and reliability. We introduce a distributed database coverage heuristic (DDCH), which is equivalent to the centralized greedy algorithm for virtual backbone generation, but only requires local information exchange and local computation. We show how DDCH can be employed to dynamically maintain the structure of the virtual backbone, along with database merging, as the network topology changes. We also provide a means to maintain connectivity among the virtual backbone nodes. We discuss optimization issues of DDCH through simulations. Simulation results suggest that the cost of ad hoc mobility management with a virtual backbone can be far below that of the conventional link-state routing.

Activation and remote modification of wireless services in a packet network context

Abstract: A third generation (3G) mobile communication system supports an over-the-air activation scheme utilizing a wireless packet data protocol. A subscriber identity module (SIM) is preloaded with temporary operating parameters such as a temporary international mobile subscriber identity (IMSI) that is used for initial access to a network. Once a packet data protocol communication link is established between the mobile device and a network support node, the user may remotely subscribe to a number of service terms using the mobile device. In addition, an activation procedure is carried out to assign permanent operating parameters, e.g., a permanent IMSI, to the SIM. After activation, the user can remotely modify existing terms or remotely enroll in additional service features via a wireless IP link between the mobile device and a network support node.

Scalable wireless network topology systems and methods

Abstract: Wireless broadband data access is provided to and from a plurality of locations distributed randomly over a large geographic area. The network can be deployed one node at a time, with a new node incorporated into the network if within radio frequency range of any existing node in the network. The newly incorporated node can then be the attaching point for another new node that requires incorporation into the network. Data can be forwarded over multiple hops to reach its destination in the network, with the data-polling scheme self-synchronizing with minimal transmission overhead.

Hierarchical analysis of power distribution networks

Abstract: Careful design and verification of the power distribution network of a chip are of critical importance to ensure its reliable performance. With the increasing number of transistors on a chip, the size of the power network has grown so large as to make the verification task very challenging. The available computational power and memory resources impose limitations on the size of networks that can be analyzed using currently known techniques. Many of today's designs have power networks that are too large to be analyzed in the traditional way as flat networks. In this paper, we propose a hierarchical analysis technique to overcome the aforesaid capacity limitation. We present a new technique for analyzing a power grid using macromodels that are created for a set of partitions of the grid. Efficient numerical techniques for the computation and sparsification of the port admittance matrices of the macromodels are presented. A novel sparsification technique using a 0-1 integer linear programming formulation is proposed to achieve superior sparsification for a specified error. The run-time and memory efficiency of the proposed method are illustrated through the analysis of case studies of several multi-million node power grids, extracted from real microprocessor and DSP designs.

Adaptive power management for a node of a cellular telecommunications network

Abstract: Equipment and/or functions at a node (e.g., base station) of a cellular telecommunications network are turned off or put into sleep mode during periods of low traffic in order to reduce power consumption by the node. The equipment and/or functions are then turned back on again during periods of high traffic load in order to provide the required service to users. Exemplary actions which can be taken in order to save power during the power saving mode include, for example and without limitation: 1) switching off or putting to sleep one or more MCPAs, 2) turning off one or more carriers, 3) turning off one or more sectors with regard to a frequency, 4) turning off or putting to sleep at least a portion or part of one or more circuit boards, and/or 5) reducing fan speed based upon traffic load of the node. Any one or more of these or similar actions may be taken in order to enable the node to save power when its traffic load is at a low level. Power consumption can thus be reduced.