Vol. 58, n°7-8, july-august 2003
Open Topics
Maximum a posteriori fast fading channel estimation for Alamouti's space-time transmit diversity
Inès KAMMOUN*, Mohamed SIALA**
*GET/Télécom Paris, 46 rue Barrault - 75634 Paris Cedex 13 - France - E-mail: ines.kammoun@enst.fr
** Département MASC - Sup'Com, Cité Technologique des Communications, Route de Raoued Km 3.5 - 2083 El Ghazala, Ariana - Tunisie
Abstract: This paper considers the Alamouti's two-branch transmit diversity scheme. This scheme supports a maximum likelihood detection based on linear processing at the receiver. When no knowledge of the channel is available - at the transmitter and the receiver- the above scheme requires in general the estimation of the two discrete propagation channels seen from the two transmit antennas. Our objective is to evaluate the Alamouti's technique of diversity with a realistic estimation algorithm considering a very fast time-varying channel. For a robust channel estimation, we propose an EM-based maximum a posteriori semi-blind algorithm. This algorithm requires a convenient representation of the time-varying fading channel using a discrete version of the Karhunen-Loève expansion theorem. The iterative receiver optimally uses pilot as well as unknown data symbols for improving channel estimation quality. The validity of the proposed algorithm is highlighted by simulation results. Moreover, a complexity evaluation of this algorithm and a comparison is provided for different scenarii.
Key words: Radio channel, Time variable channel, Fading, UMTS, Space diversity, Statistical estimation, Signal detection, Maximum likelihood, Iteration, A posteriori probability, Numerical simulation, Algorithm complexity.
Computer-aided optimization of cellular networks: the RNO (Radio Network Optimisation) software
Béatrix de CAMBRAY-de MATHAN*, Florent COLIN**, Jean-Roch HOULLIER***
* Alcatel Research & Innovation, Route de Nozay, 91460 Marcoussis France.
** Alcatel MND / Professional Customer Service (PCS).
*** Alcatel / Evolium / Direction Technique, 1 à 7 rue Nieuport, BP 138, 78148 Vélizy Cedex France.
Abstract: Quality of service has become today a major concern for operators of mobile communication networks. The massive development of networks and strong competition between operators has lead to the necessary and daily follow-up of network quality of service, a key factor for its subscriber's fidelity. This article aims at presenting the optimization methodology and proposes its illustration with a case of RNO (Radio Network Optimisation) software usage, one of the Alcatel optimization toolchain component. After a short presentation of cellular network, the optimization basic principles are described. RNO software and its main functionnalities are then detailed before a last part dedicated to a real case of optimization done with RNO software.
Key words: Mobile radiocommunication, Cellular network, Telecommunication network planning, Computer aid, Optimization, Quality of Service, Software, User interface.
Inter-domain security for Mobile Ipv6
Maryline LAURENT-MAKNAVICIUS*, Julien BOURNELLE*
* GET/INT/LOR, 9 rue Charles Fourier, 91011 Evry, France {Maryline.Maknavicius, Julien.Bournelle}@int-evry.fr.
Abstract: Mobile IPv6 is only adapted to the mobile's movements within its own administrative domain. As Mobile IPv6 is expected to be the basis for beyond 3G networks, a solution for inter-domain security is required allowing the visited domain to authenticate any mobile to grant it access. As such, new concepts known as AAA for Authentication, Authorization, Accounting were defined by the IETF. The IETF is currently defining the Diameter protocol to support those three functions in a Mobile IPv4 environment. Today's difficulty is to adapt the Diameter protocol to Mobile IPv6. After introducing the Mobile IPv6, IPsec and Diameter protocols, this paper presents our solution (IETF draft of December 2001), and an IETF alternative for adapting Diameter to Mobile IPv6. It gives a comparison and describes our prototype.
Key words: Land mobile service, Internet protocol, Addressing, Roaming, Security, Authentification, Accounting.
Synthesis of non-periodic microstrip antennas arrays from equivalent models. Optimization by the genetic algorithm
Fethi-Tarik BENDIMERAD*, Nourreddine BOUKLI-HACENE*, Nawel HASSAINE*
* Laboratoire de Télécommunications, Faculté des Sciences de l'Ingénieur, Université Abou-Bekr Belkaid - Tlemcen, BP 230, 13000 Tlemcen, Algérie, E-mail : bouklin@yahoo.com
Abstract: The majority of the methods used for the radioelectric characterization of the microstrip antennas require long and tiresome numerical calculations in general. The goal of this study is to use simple and precise equivalent electric models, making it possible to take account of the whole of the geometrical, electric and technological characteristics of the antennas and their feed. From the equivalent model of the transmission line, the synthesis of microstrip antennas in non-periodic arrays for various configurations of feed by microstrip line is elaborate. The method of synthesis of these arrays is developed by employing a stochastic technique of optimization based on the genetic algorithm.
Key words : Radiating element, Patch antenna, Antenna array, Antenna synthesis, Equivalent circuit, Genetic algorithm, Modeling, Antenna feed, Optimization, Radiation pattern, Linear antenna, Two dimension network, Plane antenna.
Performance Evaluation of the AAL2 protocol within the UTRAN
Rani MAKKÉ*, Samir TOHMÉ*, Jean-Yves COCHENNEC**, Sophie PAUTONNIER***
* GET/Télécom Paris, 46 rue Barrault - 75634 Paris Cedex 13 - France
** France Télécom R&D, 2 avenue Pierre Marzin 22300 Lannion, France
** Mitsubishi Electric ITE-TCL, 1 allée de Beaulieu, CS 10806, 35708 Rennes CEDEX 7, France
Abstract: The AAL2 protocol was chosen as a transport protocol within the UMTS Terrestrial Radio Access Network (UTRAN). This protocol handles the radio channels between the mobile terminal and the Radio Network Controller (RNC). On radio channels, the time constraints are stringent because of the synchronisation mechanisms at the MAC layer. The AAL2 protocol should guarantee a certain Quality of Service (QoS) for the traffic handled on the AAL2 connections. In this paper, we introduce a general description of the AAL2 protocol and its position in the UTRAN and we study some performance issues of this protocol. We propose two schemes to transport the AAL2 traffic on the Iub and Iur interfaces and we study different scheduling algorithms (FCFS, RR, WRR, EDF, Priority) at AAL2 level in order to evaluate the performance of each algorithm. The optimal Timer-CU value is studied in this paper in order to choose a trade-off between time constraints and bandwidth efficiency. The equivalent bandwidth is calculated in order to evaluate the capacity of a VC supporting AAL2 connections. Finally, the AAL2 switching technology is compared with the ATM switching technology in the case of a traffic concentrator in order to evaluate the advantages of the AAL2 switching.
Key words: Transmission protocol, Mobile radiocommunication, UMTS, Performance evaluation, ATM adaptation layer, Access network, Simulation model, Bandwidth, Scheduling, Virtual circuit.
Autonomic Addressing and Internetworking on Unlimited Scale
V. GURUPRASAD *
* Columbia University, New York. vg96@columbia.edu. Inspired Research LLC Apt B6, 35 Oakstreet Brewster NY 10509 U.S.A
Abstract: Following host software evolution and experience, it is pointed out that the namespace is the only appropriate application-system boundary even for networking, and that in analogy to host operating systems, the namespace is in fact necessary and sufficient for automatic, efficient management of the Internet addresses and routes. A simple, elegant namespace construction is described which does not need a global address infrastructure, provides addressing, routing and flow setup signalling over an unconstrained number of independent IP address spaces or realms, reducing to IP and DNS within a single realm and degrading softly on the multirealm scale.
Key words: Networking, Internet, Addressing, Network routing, Network interworking, Thoretical study.
Key management and multicast security: a survey
Hamida SEBA*, Abdelmadjid BOUABDALLAH*, Nadjib BADACHE**, Hatem BETTAHAR*, Djamal TANDJAOUI***
* Heudiasyc-UMR CNRS 6599, UTC , BP 20529, 60205, Compiègne Cedex France
** LSI, USTHB, BP 32, El-Alia, Bab-Ezzoaur, 16111, Alger, Algérie
***CERIST, 3 rue des Frères Aissaou, Ben Aknoun, Alger, Algérie
Abstract: Multicast routing is an efficient communication mechanism for group-oriented applications. Several such applications need security guarantees : authentication, integrity confi- dentiality and access control. Techniques implementing these security services for point-to-point communications can not be directly used in a group communication settings. Consequently, group communication security has been extensively studied. Much current research has been dedicated to key management, which is a building block for all security mechanisms. In this paper, we describe the different existing approaches for managing keys within a group. We discuss the advantages and drawbacks of key management protocols existing in the literature and present a classification and a comparative study of these protocols. We also provide some criticisms and future directions.
Key words: Multicast, Communication security, Key management, Network routing, Cryptography, Closed user group, Centralized system, Review, Comparative study.
A computation time optimization for the radio coverage prediction
Pierre COMBEAU*, Rodolphe VAUZELLE*, Lilian AVENEAU*, Yannis POUSSET*
* Université de Poitiers, IRCOM-SIC UMR CNRS n°6615 86962 FUTURSCOPE CHASSENEUIL Cedex, France
Abstract : This article presents a method which optimises the computation time for the prediction of a radio coverage, whatever the propagation model used. The principle consists in reducing the number of application points of the propagation model in relation to a classical technique. The proposed method is based on a multi resolution analysis of measured signals carried out around 2 GHz, and on an electromagnetic analysis of the propagation environment. The performances of the method are evaluated in term of reduction in computation time and of accuracy, in comparaison with the classical technique.
Key words : Mobile radiocommunication, Transmitter coverage, Electromagnetic wave propagation, Radio wave, Multipath propagation, Wave reflection, Wave diffraction, Computation time, Wavelet expansion, Optimization, Partition.
A Galerkin moment method for the analysis of insulated wires above a lossy half-space
Xianshan LI*, Khalil EL KHAMLICHI DRISSI*, Françoise PALADIAN*
* LASMEA laboratory of Blaise Pascal University, UMR 6602, 24 Avenue des Landais, 63177 Aubière Cedex, France.
Email: lixianshan@mail.com, drissi@lasmea.univ-bpclermont.fr, paladian@lasmea.univ-bpclermont.fr
Abstract: In this paper, an efficient method is proposed for the analysis of insulated wires above a lossy half-space. The reaction concept is used to formulate the electromagnetic boundary value problem. The solution is a Galerkin moment method solution with piecewise sinusoids as basis and testing functions. The influence of lossy half-space is taken into account via equivalent images, and the currents of images are related to the source current. The dielectric coating is modeled by equivalent volume polarization currents, which are simply related to the conduction current distribution. In this way, the dielectric-coating and lossy half-space cause no new unknowns to the problem solution, the size of the impedance matrix for insulated wires above lossy ground is the same as that of bare wires in free space. The insulation is accounted for entirely through a modification of the symmetric impedance matrix. The results obtained exhibit excellent agreement with those by rigorous method or experiments.
Key words: Electromagnetism, Transmission line, Wire antenna, Insulating material, Half space, Dissipating medium, Moment method, Ground effect, Galerkin method, Dipole.
Spectral behavior of domestic microwave ovens and its effects on the ISM band
Abdelilah GHAMMAZ*,**, Serge LEFEUVRE *, Norbert TEISSANDIER *
* Microwave laboratory of the ENSEEIHT-INPT, 2 rue Charles Camichel, 31071 Toulouse, France.
** LGEM - Faculty of Sciences and Technology of University Cadi Ayyad, BP 549 Marrakech, Morroco.
Abstract: The use of RF and microwave heating techniques implies to take into account the electromagnetic compatibility of the generators and the equipements for heating with the radio services already installed or in project, but also with all surrounding nearby electronic equipement. In 1992, the World Administrative Radio Conference (WARC) allocated the 2.4835- 2.500 GHz band to Mobile Satellite Service (Space to earth) all over the world. But the 2.400-2.500 GHz band is also allocated to ISM (Industrial, Scientific and Medical apparatus). This paper scans the leakage of an oven and suggests some technical improvement in order to reduce it.
Key words: Oven, Microwave, Electromagnetic comptability, Radio spectrum, Spectrum analyser, Transient state, Magnetron.