Showing papers on "Heterogeneous network published in 2001"

A Survey of Energy Efficient Network Protocols for Wireless Networks

Abstract: Wireless networking has witnessed an explosion of interest from consumers in recent years for its applications in mobile and personal communications. As wireless networks become an integral component of the modern communication infrastructure, energy efficiency will be an important design consideration due to the limited battery life of mobile terminals. Power conservation techniques are commonly used in the hardware design of such systems. Since the network interface is a significant consumer of power, considerable research has been devoted to low-power design of the entire network protocol stack of wireless networks in an effort to enhance energy efficiency. This paper presents a comprehensive summary of recent work addressing energy efficient and low-power design within all layers of the wireless network protocol stack.

Difficulties in simulating the internet

Abstract: Simulating how the global Internet behaves is an immensely challenging undertaking because of the network's great heterogeneity and rapid change. The heterogeneity ranges from the individual links that carry the network's traffic, to the protocols that interoperate over the links, the "mix" of different applications used at a site, and the levels of congestion seen on different links. We discuss two key strategies for developing meaningful simulations in the face of these difficulties: searching for invariants and judiciously exploring the simulation parameter space. We finish with a brief look at a collaborative effort within the research community to develop a common network simulator.

Integrated cellular and ad hoc relaying systems: iCAR

Abstract: Integrated cellular and ad hoc relaying systems (iCAR) is a new wireless system architecture based on the integration of cellular and modern ad hoc relaying technologies. It addresses the congestion problem due to unbalanced traffic in a cellular system and provides interoperability for heterogeneous networks. The iCAR system can efficiently balance traffic loads between cells by using ad hoc relaying stations (ARS) to relay traffic from one cell to another dynamically. This not only increases the system's capacity cost effectively, but also reduces the transmission power for mobile hosts and extends system coverage. We compare the performance of the iCAR system with conventional cellular systems in terms of the call blocking/dropping probability, throughput, and signaling overhead via analysis and simulation. Our results show that with a limited number of ARSs and some increase in the signaling overhead (as well as hardware complexity), the call blocking/dropping probability in a congested cell and the overall system can be reduced.

Mobility extended telephone application programming interface and method of use

Abstract: A system and method of for exchanging information between a wireless network and an external system is disclosed. The wireless network detects trigger events related to communications with wireless subscribers. Certain event triggers cause the wireless system to create a message to send to the external system. In response the external system may send information to the wireless system. The wireless system may create messages upon detection of handoff, origination, status, registration or other activity by the wireless subscriber. The invention may also detect trigger events related one mass media broadcasts. An interface translates between the different protocols of the wireless and the external or wireline networks to allow for automatic call redirection. The application can be utilized between many networks and facilitates the utilization of the architecture of a wirelined network and the home location register of the wireless network for various applications on the wireless network.

Wearable computers as packet transport mechanisms in highly-partitioned ad-hoc networks

Abstract: The decreasing size and cost of wearable computers and mobile sensors is presenting new challenges and opportunities for deploying networks. Existing network routing protocols provide reliable communication between nodes and allow for mobility and even ad-hoc deployment. They rely, however on the assumption of a dense scattering of nodes and end-to-end connectivity in the network. In this paper we address routing support for ad-hoc, wireless networks under conditions of sporadic connectivity and ever-present network partitions. This work proposes a general framework of agent movement and communication in which mobile computers physically carry packets across network partitions. We then propose algorithms that exploit the relative position of stationary devices and non-randonmess in the movement of mobile agents in the network. The learned structure of the network is used to inform an adaptive routing strategy With a simulation, we evaluate these algorithms and their ability to route packets efficiently through a highly-partitioned network.

Video multicast using layered FEC and scalable compression

Abstract: The use of scalable video with layered multicast has been shown to be an effective method to achieve rate control in heterogeneous networks. We propose the use of layered forward error correction (FEC) as an error-control mechanism in a layered multicast framework. By organizing FEC into multiple layers, receivers can obtain different levels of protection commensurate with their respective channel conditions. Efficient network utilization is achieved as FEC streams are multicast, and only to receivers that need them. Furthermore, FEC is used without overall rate expansion by selectively dropping data layers to make room for FEC layers. Effects of bursty losses are amortized by staggering the FEC streams in time, giving rise to a tradeoff between delay and quality. For rate control at the receivers, we propose an equation-based approach that computes network usage as a function of measured network characteristics. We show that equation-based rate control achieves more fair bandwidth sharing amongst competing sessions as compared to existing multicast rate control schemes such as RLM and RLC. Fairness is achieved since competing sessions sharing a path will measure similar network characteristics. Simulations and actual MBONE experiments are performed using error-resilient, scalable video compression. We find that video quality is significantly improved at the same communication rate when layered FEC is used.

Bitwise monitoring of network performance

Abstract: The present invention provides for a method and system for measuring data quality of service in a wireless network using multiple peripatetic (i.e. mobile) and/or stationary, unattended, position, and performance instruments (PUPPIs) that are remotely controlled by a back end processor. In some embodiments of the invention, the data service whose quality is measured relates to wireless Internet access, e-commerce transactions, wireless messaging, or push technologies. In other embodiments of the invention, the system includes an element that is located within the wireless network infrastructure, for example, at the WAP gateway to monitor the wireless data protocol and to perform benchmarking measurements.

Satellite-based Internet: a tutorial

Abstract: In a satellite-based Internet system, satellites are used to interconnect heterogeneous network segments and to provide ubiquitous direct Internet access to homes and businesses. This article presents satellite-based Internet architectures and discusses multiple access control, routing, satellite transport, and integrating satellite networks into the global Internet.

Issues in emerging 4G wireless networks

Abstract: Researchers and vendors are expressing a growing interest in 4G wireless networks that support global roaming across multiple wireless and mobile networks. With this feature, users will have access to different services, increased coverage, the convenience of a single device, one bill with a reduced total access cost, and more reliable wireless access even with the failure or loss of one or more networks. 4G networks will also feature IP interoperability for seamless mobile Internet access and bit rates of 50 Mbps or more. Because deployment of 4G wireless technology is not expected until 2006 or even later, developers will hopefully have time to resolve issues involving multiple heterogeneous networks.

System and method for concurrent operation of a wireless device in two disjoint wireless networks

Abstract: A system and method for wireless network communications provides a “dual-mode” wireless device that operates concurrently as a member of two disjoint wireless networks, such as an infrastructure (“IS”) network and an ad hoc (“AH”) network. The dual-mode device has a wireless controller driver inserted in its networking stack (e.g., the stack comprising of the Network and NDIS drivers) that exposes two virtual wireless network adapters, one for the first wireless network and one for the second wireless network. Each virtual wireless network adapter has an associated queue for queuing packets in the flow for the corresponding wireless network mode. The wireless controller driver controls the switching of the network mode. In one embodiment where the two networks include an IS network and an AH network, the mode switching is triggered by poll signals transmitted by an access point of the IS network. When the mode is switched from operating in the first network to operating in the second network, the first virtual network adapter is disabled and the second virtual network adapter is enabled, and the queued packets in the queue for the second virtual network adapter are transmitted over the second wireless network.

Matrix multiplication on heterogeneous platforms

Abstract: We address the issue of implementing matrix multiplication on heterogeneous platforms. We target two different classes of heterogeneous computing resources: heterogeneous networks of workstations and collections of heterogeneous clusters. Intuitively, the problem is to load balance the work with different speed resources while minimizing the communication volume. We formally state this problem in a geometric framework and prove its NP-completeness. Next, we introduce a (polynomial) column-based heuristic, which turns out to be very satisfactory: We derive a theoretical performance guarantee for the heuristic and we assess its practical usefulness through MPI experiments.

CANS: composable, adaptive network services infrastructure

Abstract: Ubiquitous access to sophisticated internet services from diverse end devices across heterogeneous networks requires the injection of additional functionality into the network to handle protocol conversion, data transcoding, and in general bridge disparate network portions. Several researchers have proposed infrastructures for injecting such functionality; however, many challenges remain before these can be widely deployed. CANS is an application-level infrastructure for injecting application-specific components into the network that focuses on three such challenges: (a) efficient and dynamic composition of individual components; (b) distributed adaptation of injected components in response to system conditions; and (c) support for legacy applications and services. The CANS network view comprises applications, stateful services, and data paths built from mobile soft-state objects called drivers. Both services and data paths can be dynamically created and reconfigured: a planning and event propagation model assists in distributed adaptation, and a flexible type-based composition model dictates how new services and drivers are integrated with existing components. Legacy components plug into CANS using an interception layer that virtualizes network bindings and a delegation model. This paper describes the CANS architecture, and a case study involving a shrink-wrapped client application in a dynamically changing network environment where CANS improves overall user experience.

Fast handovers and context transfers in mobile networks

Abstract: We describe recent work enabling fast handovers and context transfer between access routers offering Internet connectivity for mobile (often wireless) nodes. We present our framework for engineering general context transfer solutions, and a protocol which uses the framework to provide a simple yet general mechanism for carrying out context transfers during handovers. Since our mechanism operates at the network level, we expect that it will be the most expedient way to provide for seamless handovers between heterogeneous networks. We report our results which show that fast handovers with context transfer at the network layer can support uninterrupted voice over IP (VoIP). Thus, our context transfer framework will catalyze the arrival of a unified wireless telecommunications network, with voice and data connectivity anytime, anywhere. Towards that end, we describe how our results and context transfer framework relate to other work within the IETF.

A proposal for a heterogeneous cluster ScaLAPACK (dense linear solvers)

Abstract: The authors study the implementation of dense linear algebra kernels, such as matrix multiplication or linear system solvers, on heterogeneous networks of workstations. The uniform block-cyclic data distribution scheme commonly used for homogeneous collections of processors limits the performance of these linear algebra kernels on heterogeneous grids to the speed of the slowest processor. We present and study more sophisticated data allocation strategies that balance the load on heterogeneous platforms with respect to the performance of the processors. When targeting unidimensional grids, the load-balancing problem can be solved rather easily. When targeting two-dimensional grids, which are the key to scalability and efficiency for numerical kernels, the problem turns out to be surprisingly difficult. We formally state the 2D load-balancing problem and prove its NP-completeness. Next, we introduce a data allocation heuristic, which turns out to be very satisfactory: Its practical usefulness is demonstrated by MPI experiments conducted with a heterogeneous network of workstations.

Wireless network monitoring

Abstract: A system and method for monitoring performance of a wireless network. A probe server controls posts to send and receive probes of the wireless network. These probes provide feedback information, which indicates how the wireless network is performing.

Performance comparison of cellular and multi-hop wireless networks: a quantitative study

Abstract: In this paper we study the performance trade-offs between conventional cellular and multi-hop ad-hoc wireless networks. We compare through simulations the performance of the two network models in terms of raw network capacity, end-to-end throughput, end-to-end delay, power consumption, per-node fairness (for throughput, delay, and power), and impact of mobility on the network performance. The simulation results show that while adhoc networks perform better in terms of throughput, delay, and power, they suffer from unfairness and poor network performance in the event of mobility.We discuss the trade-offs involved in the performance of the two network models, identify the specific reasons behind them, and argue that the trade-offs preclude the adoption of either network model as a clear solution for future wireless communication systems. Finally, we present a simple hybrid wireless network model that has the combined advantages of cellular and ad-hoc wireless networks but does not suffer from the disadvantages of either.

Seawind: a Wireless Network Emulator .

Abstract: Wide area wireless networks are being studied worldwide in order to provide better network service with good performance to customers. The Software Emulator for Analyzing Wireless Network Data Transfers (Seawind) is a real-time network simulator that allows researchers to measure the performance of real network applications over an emulated network that follows the user specified wireless network behavior model. Using an emulator in network performance tests has several benefits. It allows constructing and repeating specific test scenarios that are interesting to the researcher. The researcher has full control over the parameters affecting the network behavior and he can run performance tests on future networks that are not yet available for testing. By using emulator the performance tests are faster and cheaper to carry out than real field tests. A benefit of real-time emulation over simulators running in virtual time is that we can study the actual protocol implementations of different operating systems and applications.

Methods and apparatus for secure wireless networking

Abstract: Techniques for secure connections between wireless network clients and wired network resources are described. An insecure wireless network comprising a plurality of wireless access points provides a connection for wireless network clients to a wired network server which in turn provides controlled access to a wired network. When a wireless network user wishes to connect to the wired network, the user provides authentication information to the wired network server through the wireless network client and the wireless network access point. Once the wired network server has verified the authentication information, the wired network server provides the wireless network client with a temporary wired network address as well as a unique session encryption key, which is used to encrypt all data transferred between the wireless network client and the wired network server during a connection session.

TCP-real: improving real-time capabilities of TCP over heterogeneous networks

Abstract: We present a TCP-compatible and -friendly protocol which abolishes thr ee major shortfalls of TCP for reliable multimedia applications over heterogeneous networks: (i) ineffective bandwidth utilization, (ii) unnecessary congestion-oriented responses to wireless link errors (e.g., fading channels) and operations (e.g. handoffs), and (iii) wasteful window adjustments over asymmetric, low-bandwidth reverse paths. We propose TCP-Real, a high-throughput transport protocol that minimizes transmission-rate gaps, thereby enabling better performance and reasonable playback timers. In TCP-Real, the receiver decides with better accuracy about the appropriate size of the congestion window. Slow Start and timeout adjustments are used whenever congestion avoidance fails; however, rate and timeout adjustments are cancelled whenever the receiving rate indicates sufficient availability of bandwidth. We detail the protocol design and we report significant improvement on the performance of the protocol with time-constrained traffic, wireless link errors and asymmetric paths.

Communicating between nodes in different wireless networks

Abstract: A method and apparatus for communicating between nodes in different wireless networks includes network address translators provided between the wireless networks. The network address translators are used to translate between private addresses of network elements within each wireless network to a public address. The network address translation is performed on both a network address in a header portion in each packet transmitted across a data network between the wireless networks, as well as on network address(es) contained within the payload portion of each of the packets.

Architecture and related methods for streaming media content through heterogeneous networks

Abstract: A system for content (e.g., streaming media) is presented comprising a server, to provide media content on request through a wireline network, coupled to a wireless host through a network gateway. The network gateway establishes a communication channel from the server to the wireless host through both a wireline network and a wireless network, wherein the communication channel includes a transport layer protocol with control parameters for network elements of each of the wireline network and the wireless network. This abstract itself is not intended to limit the scope of this patent. The scope of the present invention is pointed out in the appending claims.

Heterogeneous networking: a new survivability paradigm

Abstract: We believe that a network, to be survivable, must be heterogeneous. Just like a species that draws on a small gene pool can succumb to a single environmental threat, so a homogeneous network is vulnerable to a malicious attack that exploits a single weakness common to all of its components. In contrast, in a network in which each critical functionality is provided by a diverse set of protocols and implementations, attacks that focus on a weakness of one such protocol or implementation will not be able to bring down the entire network, even though all elements are not be bulletproof and even if some of components are compromised.Following this survivability through heterogeneity philosophy, we propose a new survivability paradigm, called heterogeneous networking, for improving a network's defense capabilities. Rather than following the current trend of converging towards single solutions to provide the desired functionality at every element of the network architecture, this methodology calls for systematically increasing the network's heterogeneity without sacrificing its interoperability.

A device and system for providing a wireless high-speed communications network

Abstract: A device and system (100) for providing a high-speed wireless communications network (300). The device (100) includes a number of individual antennas (108) that extend radially from a central axis (104) of the device (100). The antennas (108) are capable of producing circularly polarized signals. The device (100) may be capable of directing a wireless signal to an individual antenna (108). A plurality the devices (100) may be installed and configured to operate as a high-speed wireless communications network. The communications network may connect computers (520). The network may be configured such that new nodes (310) may be dynamically added and removed from the network. Each node (310) of the network may execute a routing algorithm such that information may be efficiently exchanged between nodes (310) inside and outside the communications network.

Method and system for collection and storage of traffic data from heterogeneous network elements in a computer network

Abstract: The preferred embodiments described herein provide a method and system for collection and storage of traffic data. In one preferred embodiment, traffic data is collected from a plurality of network elements in a first point of presence in a computer network. Traffic data is collected from each network element using a protocol appropriate for the network element. The collected traffic data is analyzed, and a result of the analysis is transmitted to a storage device remote from the first point of presence. Other preferred embodiments are provided herein, and any or all of the preferred embodiments described herein can be used alone or in combination with one another.

Sharing partitionable workloads in heterogeneous NOWs: greedier is not better

Abstract: We craft protocols for solving two problems related to sharing a large partitionable bag-of-tasks workload in a heterogeneous network of workstations (NOW) N. In the NOW-Rental Problem, one must complete W units of work and wishes to "rent" N for as short a time as necessary. In the NOW-Exploitation Problem, one has access to N for L time units and wishes to accomplish as much work as possible. Our protocols are crafted within an architectural model that characterizes N via parameters that measure its workstations' computational and communicational efficiencies; hence, our solutions are robust across a broad range of actual NOWs. The protocols determine both an allocation of work for each of N's workstations and a schedule for transmitting that work; hence, they are self-scheduling. The schedules provide a value for either L or W, given the other, thereby solving both motivating problems. By studying two specific protocols, we prove that the intuitive strategy of supplying as much work as possible to faster workstations is not optimal; this nonoptimality is often discernible for values of L less than one minute.

An active proxy based architecture for TCP in heterogeneous variable bandwidth networks

Abstract: In heterogeneous networks such as today's Internet, TCP must be made to handle links and paths with vastly different characteristics, including longer delays and dynamically changing available bandwidth. In this research, we first analyze the performance of TCP under networks with TCP-unfriendly characteristics and introduce an architecture to tackle the performance problems in such networks.

Personal wireless network

Abstract: The invention is a personal wireless network that generally comprises at least a lightweight wireless client to send and receive audio and video from another system component. The personal wireless network also provides a wireless-enabled routing component, which stands alone to route traffic within the personal wireless network. Also provided is a transmitter component that connects to a computing device, such as a server and sends and receives data Furthermore, a software algorithm provides a method for supporting a personal wireless network.

Wireless personal area networks

Abstract: andheld devices are rapidly becoming an integral part of our daily lives. Palmtop computers, which were initially launched as gadgets for personal productivity, have now become indispensable business tools for mobile workers. Most road warriors already carry a cell phone, a palmtop, and a laptop computer with them. Often they need to interconnect these devices to synchronize data and create backups. There are also scenarios where users wish to exchange data with other users. In most cases either devices do not have compatible communication interfaces or it is quite cumbersome to connect cables and get them configured correctly. An obvious solution is to get rid of all cables and instead use shortrange wireless links to facilitate on-demand connectivity among devices and peripherals. New R F wireless communications technologies a re emerging that would enable devices to connect easily and with little, if at all, intervention from their user through standardized air-interfaces. These wireless personal area networks (WPANs) communication technologies differ from other more traditional wireless or wired LAN technologies. WPANs primarily target the consumer market and are used for ease of connectivity of personal wearable or handheld devices. WPANs are thus designed to be inexpensive, small in size, easy to use, and power-efficient. However, independent of the specific technology used, WPANs bring a new concept in communications, that of the personal operating space (POS). Contrary to infrastructure networks that are installed, a POS is a space of small coverage around a n individual where communications occur in an ad hoc manner. The POS is tethered to an individual, and in particular to his/her personal devices, and moves as the individual moves. The POS empowers the individual with communication capabilities, allowing him/her to communicate with other devices that enter the individual's POS. A WPAN'\"l solution should be a natural and inconspicuous extension of people's personal devices. Thus, commu-