Mobile ad hoc networks (MANETs) represent complex distributed systems that comprise wireless mobile nodes that can freely and dynamically self-organize into arbitrary and temporary, ‘‘ad-hoc’’ network topologies, allowing people and devices to seamlessly internetwork in areas with no pre-existing communication infrastructure, e.g., disaster recovery environments. Ad hoc networking concept is not a new one, having been around in various forms for over 20 years. Traditionally, tactical networks have been the only communication networking application that followed the ad hoc paradigm. Recently, the introduction of new technologies such as the Bluetooth, IEEE 802.11 and Hyperlan are helping enable eventual commercial MANET deployments outside the military domain. These recent evolutions have been generating a renewed and growing interest in the research and development of MANET. This paper attempts to provide a comprehensive overview of this dynamic field. It first explains the important role that mobile ad hoc networks play in the evolution of future wireless technologies. Then, it reviews the latest research activities in these areas, including a summary of MANETs characteristics, capabilities, applications, and design constraints. The paper concludes by presenting a set of challenges and problems requiring further research in the future. � 2003 Elsevier B.V. All rights reserved.

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Mobile ad hoc networking: imperatives and challenges

Provided herein are methods and systems for providing controlled lighting, including methods and systems for providing both white and non-white colored lighting, including color temperature controlled lighting. Such methods and systems include optical facilities for modifying light from a lighting unit, such as an LED-based lighting unit, including variable optical facilities and fixed optical facilities. Also provided are methods and systems for using multi-color lighting units in a variety of commercial applications. Also provided are methods and systems for lighting control, including methods to assist lighting designers and installers to improve the quality of lighting in environments. Also provided are intelligent dimmers, switches, sockets and fixtures, as well as facilities for programming and using them. Also provided are various sensor-feedback applications of lighting technology, including sensor-feedback involving light sensors and forward voltage sensors. Also provided are lighting methods and systems that operate on time-based parameters.

Controlled lighting methods and apparatus

A seamless solution transparently addresses the characteristics of nomadic systems, and enables existing network applications to run reliably in mobile environments. The solution extends the enterprise network, letting network managers provide mobile users with easy access to the same applications as stationary users without sacrificing reliability or centralized management. The solution combines advantages of existing wire-line network standards with emerging mobile standards to create a solution that works with existing network applications. A Mobility Management Server coupled to the mobile network maintains the state of each of any number of Mobile End Systems and handles the complex session management required to maintain persistent connections to the network and to other peer processes. If a Mobile End System becomes unreachable, suspends, or changes network address (e.g., due to roaming from one network interconnect to another), the Mobility Management Server maintains the connection to the associated peer task—allowing the Mobile End System to maintain a continuous connection even though it may temporarily lose contact with its network medium. In one example, Mobility Management Server communicates with Mobile End Systems using Remote Procedure Call and Internet Mobility Protocols.

Method and apparatus for providing mobile and other intermittent connectivity in a computing environment

There has been an increasing deployment of content distribution networks (CDNs) that offer hosting services to Web content providers. CDNs deploy a set of servers distributed throughout the Internet and replicate provider content across these servers for better performance and availability than centralized provider servers. Existing work on CDNs has primarily focused on techniques for efficiently redirecting user requests to appropriate CDN servers to reduce request latency and balance load. However, little attention has been given to the development of placement strategies for Web server replicas to further improve CDN performance. We explore the problem of Web server replica placement in detail. We develop several placement algorithms that use workload information, such as client latency and request rates, to make informed placement decisions. We then evaluate the placement algorithms using both synthetic and real network topologies, as well as Web server traces, and show that the placement of Web replicas is crucial to CDN performance. We also address a number of practical issues when using these algorithms, such as their sensitivity to imperfect knowledge about client workload and network topology, the stability of the input data, and methods for obtaining the input.

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On the placement of Web server replicas

The World Wide Web can be considered as a large distributed information system that provides access to shared data objects. As one of the most popular applications currently running on the Internet, the World Wide Web is of an exponential growth in size, which results in network congestion and server overloading. Web caching has been recognized as one of the effective schemes to alleviate the service bottleneck and reduce the network traffic, thereby minimize the user access latency. In this paper, we first describe the elements of a Web caching system and its desirable properties. Then, we survey the state-of-art techniques which have been used in Web caching systems. Finally, we discuss the research frontier in Web caching.

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A survey of web caching schemes for the Internet

Web caching or web proxy has been considered as the prime vehicle of coping with the ever-increasing demand for information retrieval over the Internet, the WWW being a typical example. Existing work on web proxy has primarily focused on content based caching; relatively less attention has been given to the development of proper placement strategies for the potential web proxies in the Internet. In this paper, we argue that the placement of web proxies is critical to the performance and further investigates the optimal placement policy of web proxies for a target web server in the Internet. The objective is to optimize a given performance measure for the target web server subject to system resources and traffic pattern. Specifically, we are interested in finding the optimal placement of multiple web proxies (M) among potential sites (N) under a given traffic pattern. We show this can be modeled a dynamic programming problem. We further obtain the optimal solution for the tree topology using O(N/sup 3/M/sup 2/) time.

On the optimal placement of web proxies in the Internet

A method and apparatus is disclosed for providing continuation of a communication call as a user moves from the coverage area of one communication network to the coverage area of another communication network having different access media and different applications. A voice, data, video or multimedia call involving multiple end-points which may be located on different networks may be placed on hold pursuant to a pause request made by a user of one of the end-points. The networks include processors programmed to interrupt and recognize specified signals, such as a pause request signal, and to respond by providing reconnection identification information. The user making a pause request may generate a reconnection request in a different network to continue the paused call on the new network by using a calling device that is compatible with the access media and applications provided by the new network. Each network has the capability of communicating with processors associated with other networks to establish a new route for the call so that once a reconnection request is received, the call may be resumed.

Method and apparatus for providing continuation of a communication call across multiple networks

Web caching or web proxy has been considered as the prime vehicle to cope with the ever-increasing demand for information retrieval over the Internet, WWW being a typical example. The existing work on web proxy has primarily focused on content based caching; relatively less attention has been given to the development of proper placement strategies for the potential web proxies in the Internet. This paper investigates the optimal placement policy of web proxies for a target web server in the Internet. The objective is to minimize the overall latency of searching the target web server subject to the network resources and traffic pattern. Specifically, we are interested in finding the optimal placement of multiple web proxies (m) among the potential sites (n) under a given traffic pattern. We model the problem as a Dynamic Programming problem, and we obtain an optimal solution for a linear array topology using O(n 2 m) time.

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On the Optimal Placement of Web Proxies in the Internet: The Linear Topology

An optical signal access apparatus responds to variations in network traffic by dynamically assigning the number of wavelengths at originating and terminating optical signal access apparatus. A controller of an optical signal access apparatus monitors network traffic by checking the occupancy level (or other parameters) of data buffers and determines therefrom the number of optical signals that should be allocated to handle the network traffic from those buffers. When the optical signal access apparatus is part of a router it can be used to control traffic at the router as well as on the links between the routers of an optical network.

Dynamically assignable optical signal access control apparatus

A method and apparatus for separately transporting each monomedia stream of a composite multimedia signal across a network, such as an ATM network, is disclosed. The transport of monomedia traffic over different network segments, which may or may not support all multimedia components, is disclosed. Each monomedia component, n, such as video, voice and data, of the multimedia session is separately transmitted over a connection having a capacity, C n . The capacity, C n , is generally specified in number of units of information, such as the bandwidth that should be allocated to the respective monomedia component for the duration of the call, or the number of ATM cells per unit time for the duration of the call. In an illustrative ATM network implementation, individual connections can be established for each monomedia component by assigning separate VP/VC identifiers to each monomedia connection. Jitter, due to synchronization problems, is controlled by allocating appropriate bandwidth to each monomedia component. In a preferred embodiment, the respective value of each monomedia connection capacity, C n , is adjusted so that the jitter among the individual monomedia components is minimized. The capacity, C n , assigned to each monomedia connection is preferably based on the types of media included in the session, and current network conditions and can be obtained from experimental or statistical profiles of various multimedia type sessions, or dynamically adjusted based on network traffic conditions.

Kazem Anaraky Sohraby

Papers

On the optimal placement of web proxies in the Internet

Method and apparatus for providing continuation of a communication call across multiple networks

On the Optimal Placement of Web Proxies in the Internet: The Linear Topology

Dynamically assignable optical signal access control apparatus

Method and apparatus for transporting multimedia information over heterogeneous wide area networks