Vol. 64, n° 3-4, March-April 2009
Content available on SpringerLink
A next-generation service overlay architecture
Emmanuel Lavinal1, Noëmie Simoni1, Meng Song2, Bertrand Mathieu2
1 Télécom ParisTech, France
2 France Télécom R&D, Lannion, France
Abstract The rapid evolution of next-generation networks and, in particular, fixed mobile convergence infrastructures raises the issue of providing personalized services adapted to the user’s context such as its device, access network, preferences, or quality of service (QoS) requirements. To design such value-added services, one solution consists in composing dynamically distributed service entities. In this paper, we propose a service overlay architecture in which a service level path is dynamically established to fulfill the user’s requirements. In order to meet this goal, two main issues have to be considered: service components discovery and service path management (i.e., setup, reconfiguration,release). The former issue is addressed based on a peer-to peer approach in which QoS features are integrated in service lookup. For the latter issue, we rely on the Session Initiation Protocol to automate the setup of the service composition as well as its adaptation in case of perturbations (e.g., user switching device or service component failure).
Keywords Next-generation services – QoS-based service discovery – SIP-based service paths
Service business processes for the netx generation of services: a required step to achieve service convergence
Emmanuel Bertin*, Noël Crespi**
* Orange Labs, Caen, France
** Télécom SudParis, Evry, France
Abstract Users’ needs are the driver of the next generation of telecom services. Founding the services on users’ needs requires that various services cooperate together to meet specific needs. As a consequence, services should no more be developed as “silo” but with composable service enablers. This enabler paradigm raises the issues of the identification of the enablers and of the consistency of a service composed from various enablers. These issues must be addressed by considering the service from the user point of view: what is the added value for the user and through which perceived steps is this added value provided? Such service business processes are then a key tool to identify enablers and to ensure the coherence of composed service.
Keywords NGS – Service enabler – Business process – Service modeling
WComp middleware for ubiquitous computing: Aspects and composite event-based Web services
Jean-Yves Tigli, Stéphane Lavirotte, Gaëtan Rey,Vincent Hourdin, Daniel Cheung-Foo-Wo, Eric Callegari, Michel Riveill
Université de Nice – Sophia Antipolis/CNRS, France
Abstract After a survey of the specific features of ubiquitous computing applications and corresponding middleware requirements, we list the various paradigms used in the main middlewares for ubiquitous computing in the literature. We underline the lack of works introducing the use of the concept of Aspects in middleware dedicated to ubiquitous computing, in spite of them being used for middleware improvement in other domains. Then, we introduce our WComp middleware model, which federates three main paradigms: eventbased Web services, a lightweight component-based approach to design dynamic composite services, and an adaptation approach using the original concept called Aspect of Assembly. These paradigms lead to two ways to dynamically design ubiquitous computing applications. The first implements a classical component-based compositional approach to design higher-level composite Web Services and then allow to increment the graph of cooperating services for the applications. This approach is well suited to design the applications in a known, common, and usual context. The second way uses a compositional approach for adaptation using Aspect of Assembly, particularly well-suited to tune a set of composite services in reaction to a particular variation of the context or changing preferences of the users. Having detailed Aspect of Assembly concept, we finally comment on results indicating the expressiveness and the performance of such an approach, showing empirically that principles of aspects and program integration can be used to facilitate the design of adaptive applications
Keywords Ubiquitous computing · Web services for devices · Event-based component middleware · Software composition
TCP throughput guarantee in the DiffServ Assured Forwarding service: what about the results ?
Emmanuel Lochin* · Pascal Anelli**
* Université de Toulouse/LAAS-CNRS, Toulouse, France
** Université de la Réunion, Saint-Denis Messag, France
Abstract Since the proposition of quality of service (QoS) architectures by the Internet Engineering Task Force (IETF), the interaction between TCP and the QoS services has been intensively studied. This paper proposes to look forward to the results obtained in terms of TCP throughput guarantee in the Diff- Serv assured forwarding (DiffServ/AF) service and to present an overview of the different proposals to solve the problem. It has been demonstrated that the standardized IETF DiffServ conditioners such as the token bucket color marker and the time sliding window color maker were not good TCP traffic descriptors. Starting with this point, several propositions have been made, and most of them present new marking schemes in order to replace or improve the traditional token bucket color marker. The main problem is that TCP congestion control is not designed to work with the AF service. Indeed, both mechanisms are antagonists. TCP has the property to share in a fair manner the bottleneck bandwidth between flows while DiffServ network provides a level of service that is controllable and predictable. In this paper, we build a classification of all the propositions made during the past few years and compare them. As a result, we will see that these conditioning schemes can be separated into three sets of action levels and that the conditioning at the network edge level is the most accepted one. We conclude that the problem is still unsolved and that TCP, conditioned or not conditioned, remains inappropriate for the DiffServ/AF service.
Keywords QoS · End to end guarantee · TCP · DiffServ · Assured forwarding
Quality of service for voice over IP in networks with congestion avoidance
Vitalio A. Reguera* · Evelio M. G. Fernandez** · Felix A. Paliza* · Walter Godoy J***. · Eduardo P. Ribeiro**
* Central University of Las Villas, Santa Clara, Cuba
** Federal University of Parana, Curitiba, Brazil
*** Federal University of Technology-Parana, Curitiba, Brazil
Abstract This paper assesses the impact of active queue management schemes on the quality of service of voice over Internet protocol applications. A new analytical method based on a fixed point approach to estimate the end-user satisfaction is proposed. The results obtained were validated using discrete event simulation techniques. In all the studied cases, it was observed a great deal of agreement between the analytical results and the results obtained through simulation. The theoretical predictions, as well as the presented empirical evidences confirm, as demonstrated in previous works, that the use of active queue management offers better quality of service than the traditional queue control mechanisms used in Internet. From these results, we may reasonably conclude that the presented method can be used for network design in the presence of voice traffic.
Keywords VoIP · Congestion avoidance · AQM · Quality of service · Internet
Internet connection with UMTS
Jahangir Dadkhah Chimeh*, Mohammad Hakkak** Paeiz Azmi**, Hamidreza Bakhshi***
* Iran Telecommunication Research Center, Tehran, Iran
** Tarbiat Modares University, Tehran, Iran
*** Shahed University, Tehran, Iran
Abstract Mobile telecommunication new services are based on data networks specially Internet. These services include http, telnet, ftp, Simple Mail Transfer Protocol, etc. Besides, we recognize a mobile network as a multiuser network. Transmission Control Protocol (TCP)/Internet Protocol which is sensitive to link congestion in wireline data links is also used in wireless networks. In order to improve the system performance, the TCP layer uses flow control and congestion control. Besides, radio link control (RLC) and medium access control sublayers have been introduced to compensate the deficiency of TCP layer in wireless environment. RLC has an important role in quality of service enhancement of the Universal Mobile Telecommunications System (UMTS). In this paper, we review the protocol stack of UMTS Terrestrial Radio Access Network which is based on Third-Generation Partnership Project. Then, we evaluate its layer 2 error control mechanisms and verify TCP over automatic repeat request error control mechanism and finally quality of service improvement results from it in fading channels.
Keywords TCP/ARQ · UTRAN · Fading channel
Some experimental investigation of the effect of railway tunnels on mobile communications in Western India
M. V. S. N. Prasad*, P. K. Dalela**
* National Physical Laboratory, New Delhi, India
** C-DOT, New Delhi, India
Abstract Establishing of mobile communications in guided structures like railway tunnels, coal mines, etc., is gaining increasing importance due to the passage of high speed and high density of trains in tunnels and for monitoring of information on safety of workers and dayto- day operations in various mines. The present study reports investigation of mobile communication experiments in ultra high frequency band in railway tunnels of western India conducted in a moving train both in uplink and downlink directions. The observed signal fluctuations are discussed in terms of tunnel characteristics and different modes of propagation in tunnels and compared with model deduced values.
Keywords Mobile communications · Path loss measurements · Tunnels
An efficient receiver scheme for downlink ZP-CDMA
F. S. Al-kamali*, M. I. Dessouky**, & B. M. Sallam**, F. E. Abd El-Samie**
* Department of Electronics, Faculty of Engineering, Ibb University, Ibb, Yemen
** Department of Electronics and Electrical Communications, Faculty of Electronic Engineering, Menoufia University, Menouf 32952, Egypt
Abstract A signal transmitted through a wireless channel may be severely distorted by intersymbol interference (ISI) and multiple access interference (MAI). In this paper, we propose an efficient CDMA receiver based on frequency domain equalization (FDE) with a regularized zero forcing (RZF) equalizer and parallel interference cancellation with a unit clipper decision function (CPIC) to combat both the ISI and the MAI. We call this receiver the FDE-RZF-CPIC receiver. This receiver is suitable for downlink zero padding CDMA cellular systems. The effects of the decision function, the channel estimation, the number of cancelled users, and the user loading on the performance of the proposed receiver are discussed in the paper. The bit error rate (BER) of the data received by the proposed receiver is evaluated by computer simulations. The experimental results show that the proposed receiver provides a good performance, even with a large number of interfering users. At a BER of 10-3, the performance gain of the proposed receiver is about 2 dB over the RAKE receiver with a clipper decision function and PIC in the half-loaded case (eight users) and is much larger in the full-loaded case (16 users).
Keywords Downlink CDMA · Decision functions · PIC · Zero padding · Channel estimation