Network Users (network + user)

Distribution by Scientific Domains

Selected Abstracts

A constant rounds group key agreement protocol without using hash functions

Hua Zhang
It is important to encrypt and authenticate messages sent over networks to achieve security. Network users must therefore agree upon encryption keys and authentication keys. The authenticated Diffie,Hellman key agreement protocol is used to provide authentication in communication systems. In this paper we present a group key agreement protocol without using one-way hash functions that are based on the DDH problem. The protocol achieves efficiency in both communication and computation aspects. We analyzed the security in the security model formalized by Bresson et al. Copyright 2009 John Wiley & Sons, Ltd. [source]

Simple On-Line Scheduling Algorithms for All-Optical Broadcast-and-Select Networks

Marco Ajmone Marsan
This paper considers all-optical broadcast networks providing a number of slotted WDM channels for packet communications. Each network user is equipped with one tunable transmitter and one fixed receiver, so that full connectivity can be achieved by tuning transmitters to the different wavelengths. Tuning times are not negligible with respect to the slot time. A centralized network controller allocates slots in a TDWDM frame according to (long-term) bandwidth requests issued by users. Simple on-line transparent scheduling strategies are proposed, which accommodate bandwidth requests when they are received (on-line approach), with the constraint of not affecting existing allocations when a new request is served (transparency). Strategies that attempt to allocate in contiguous slots all the transmissions of each source on one wavelength reduce overheads, are simple, and provide good performance. Even better performance can be achieved, at the cost of a modest complexity increase, when the transparency constraint is not strictly imposed, i.e., when a full re-allocation of existing connections is performed once in a while. [source]

Characterizing user-perceived impairment events using end-to-end measurements

Soshant Bali
Abstract Measures of quality of service (QoS) must correlate to end-user experience. For multimedia services, these metrics should focus on the phenomena that are observable by the end-user. Metrics such as delay and loss may have little direct meaning to the end-user because knowledge of specific coding and/or adaptive techniques is required to translate delay and loss to the user-perceived performance. Impairment events, as defined in this paper, are observable by the end-users independent of coding, adaptive playout or packet loss concealment techniques employed by their multimedia applications. Time between impairments and duration of impairments are metrics that are easily understandable by a network user. Methods to detect these impairment events using end-to-end measurements are developed here. In addition, techniques to identify Layer 2 route changes and congestion events using end-to-end measurements are also developed. These are useful in determining what caused the impairments. End-to-end measurements were conducted for about 26 days on 9 different node pairs to evaluate the developed techniques. Impairments occurred at a high rate on the two paths on which congestion events were detected. On these two paths, congestion occurred for 6,8 hours during the day on weekdays. Impairments caused by route changes were rare but lasted for several minutes. Copyright 2005 John Wiley & Sons, Ltd. [source]

Secure fast WLAN handoff using time-bound delegated authentication

Hung-Yu Chien
Abstract To support multimedia applications with good quality of services for roaming wireless local area network users, it is imperative to reduce the long re-authentication latency that users experience during handoff among access points (APs). Athough a great deal of research resources have been put into the reduction of the re-authentication latency, these schemes developed so far seem to either suffer from heavy overhead problems or have weak security. In this paper, we propose a novel approach to reducing the re-authentication latency. With the authentication server (AS) periodically delegating its authentication authority to the authenticated APs, the APs can authenticate the roaming users on behalf of the AS. As our performance analysis and simulation results demonstrate, our new approach is capable of greatly reducing the latency and overhead while achieving a high security level. Furthermore, it does not increase the complexity on the AP side because only the already existing four-way handshake with new keying mechanism is required. Copyright 2008 John Wiley & Sons, Ltd. [source]

Layered view of QoS issues in IP-based mobile wireless networks

Haowei Bai
Abstract With the convergence of wireless communication and IP-based networking technologies, future IP-based wireless networks are expected to support real-time multimedia. IP services over wireless networks (e.g. wireless access to Internet) enhance the mobility and flexibility of traditional IP network users. Wireless networks extend the current IP service infrastructure to a mix of transmission media, bandwidth, costs, coverage, and service agreements, requiring enhancements to the IP protocol layers in wireless networks. Furthermore, QoS provisioning is required at various layers of the IP protocol stack to guarantee different types of service requests, giving rise to issues related to cross-layer design methodology. This paper reviews issues and prevailing solutions to performance enhancements and QoS provisioning for IP services over mobile wireless networks from a layered view. Copyright 2006 John Wiley & Sons, Ltd. [source]

Achieving proportional DiffServ per-hop behaviour with PLQF

Jung-Shian Li
Abstract We propose a novel scheme that can provide both delay and loss proportional DiffServ per-hop behaviour. DiffServ is a framework that can provide different QoS levels to different groups of network users, and eliminate the shortcoming of the best-effort delivery in today's Internet. The scheme employs probabilistic longest queue first (PLQF) as its forwarding and dropping mechanism. PLQF mainly reacts immediately to the queue-length fluctuation of each service class, and then decides the probability for each QoS class, which determines the forwarding or dropping behaviour. We couple delay and loss differentiated services in one scheme. The proposed scheme is proven to achieve proportional differentiated services after detailed evaluations. Furthermore, the implementation cost of PLQF is much less than that of the previously proposed schemes, such as WTP and PLR. Copyright 2003 John Wiley & Sons, Ltd. [source]

Dimensioning and optimization of push-to-talk over cellular server

M. T. Alam
The PoC (push-to-talk over cellular) application allows point-to-point or point-to-multipoint voice communication between mobile network users. The related work over PoC focuses on the performance analysis only and is ignorant about dimensioning a PoC controller to optimize revenue for service providers. In this paper, we dimension a PoC service with the assumption that the network grade of service is provided. The on-demand sessions should have access priority over pre-established sessions. A PoC controller should be able to terminate a PoC session based on an optimal timer. Moreover, the number of simultaneous session initiations by a PoC client is also a configurable parameter. We derived relations to provide access priority to special PoC sessions based on available transmit/receive units (TRU) and threshold level. Load sharing expressions are reported for a PoC controller using the Lagrange multiplier technique. A simple relation to control the PoC session timer is proposed. Finally, the derivation of maximum number of allowable simultaneous sessions is depicted using two-state Markov models. Numerical results have been computed with the corresponding derivation to provide a useful insight into the system behaviour. A PoC service can benefit from these optimal values of our work during the busy hour. Copyright 2007 John Wiley & Sons, Ltd. [source]

A feedback suppression algorithm for reliable satellite multicast based on spatial,temporal prediction of the satellite channel

Markos P. Anastasopoulos
Abstract The major problem limiting the scalability of large-scale multicast satellite networks is feedback implosion that arises whenever a large number of users simultaneously transmit feedback messages (FBMs) through the network, thus occupying a significant portion of satellite system resources. In satellite networks operating above 10,GHz, attenuation due to rain constitutes the dominant fading mechanism deteriorating the quality of service. In this paper, a novel scheme for providing large-scale reliable multicast services through a star-based geostationary satellite topology is presented incorporating accurate channel modeling of the propagation phenomena. The new protocol is based on the selection of an area representative that provides quick FBMs aiming at suppressing FBMs originating from the rest of the network users. The scheme provides a timely reaction to changes of either the channel conditions or the network topology by properly updating the selection of representatives. Through appropriate simulations, comparisons and examples it is demonstrated that the new approach suppresses FBMs very effectively. Copyright 2009 John Wiley & Sons, Ltd. [source]

Decision support for simulating the car park activity in an urban area

Jean-Marie Boussier
Abstract Complexity of car park activity is reproduced from a concurrent execution of behaviour of various drivers. This paper presents a step in the development of a multimodal traffic simulator based on multi-agent paradigm and designed as a decision aid tool as well as a video game. The user-player has the opportunity to test different scenarios. We propose an approach for designing the decision-making rules and the learning mechanism for a car driver agent. For that, a panel of methods such as stated preference modelling, Design Of Experiments and data fusion is used. Initial behavioural models, based on similar preferences, are developed for specified categories. Each agent will adapt its behaviour after executing its learning process. Our approach can be used in order to optimize needs of road network users and those of people in charge of traffic regulation. A demonstrator has been developed to test parking policies in an urban area as well as changes of car park characteristics. [source]

A reliability-based network design problem

Piya Chootinan
Abstract This paper presents a reliability-based network design problem. A network reliability concept is embedded into the continuous network design problem in which travelers' route choice behavior follows the stochastic user equilibrium assumption. A new capacity-reliability index is introduced to measure the probability that all of the network links are operated below their capacities when serving different traffic patterns deviating from the average condition. The reliability-based network design problem is formulated as a bi-level program in which the lower level sub-program is the probit-based stochastic user equilibrium problem and the upper level sub-program is the maximization of the new capacity reliability index. The lower level sub-program is solved by a variant of the method of successive averages using the exponential average to represent the learning process of network users on a daily basis that results in the daily variation of traffic-flow pattern, and Monte Carlo stochastic loading. The upper level sub-program is tackled by means of genetic algorithms. A numerical example is used to demonstrate the concept of the proposed framework. [source]