Network-controlled mobility within radio access networks based onWLAN technologies

This article presents a network-controlled approach of user terminal mobility within anIP based WirelessLAN Access Network. In a first part, this article makes a review of the mobility support, on the subject of emergingWLAN technologies asHIPERLAN/2 andIEEE 802.11, on the one hand, and, regardingIP networks as currently studied withinIETF, on the other hand. Both types ofIP mobility protocols are presented, either global mobility protocols such as MobileIP, or local mobility management protocols (micro mobility). In the next part, the overall principles of our mobility management approach are explained; this approach is based on the implementation of a new network entity dedicated to the control of user terminal mobility. The last part details a practical implementation of this approach. The implementation is carried out on the basis of Hierarchical MobileIPv6 (HMIPv6). The experimental results confirm the importance to carefully plan and control the user terminal mobility within largeIP based Access Networks, as this brings benefit to the user as well as to the operator.     

LDPC-based space-time coded OFDM systems: Turbo-EM receiver design with channel state information guessing algorithms

In this paper we study some turbo receiver architectures employing low-density parity check (Ldpc) codes together with orthogonal frequency division multiplexing (Ofdm) for high data rate wireless transmissions. Different demodulation schemes based on expectation-maximization (Em) algorithm are studied along with the channel impulse response (Em) algorithms. We studied differentCir guessing algorithms including the EM-based algorithms such as a space-alternating generalized expectation-maximization algorithm (Sage). It is shown that the proposed turbo-Em receiver employing a soft maximum a posteriori (Map)Em demodulator and a belief propagationLdpc decoder can perform within 1 dB from the ergodic capacity of the studiedMimo ofdm channels. Besides, we find that a suboptimum structure based on a soft interference cancellationMmse filtering demodulator exhibits negligible loss in non-correlated fadingMimo channels but suffer extra performance loss in highly correlatedMimo channels.     

Performance evaluation of DCCP: A focus on smoothness and TCP-friendliness

Recent years have seen dramatic increases of the use of multimedia applications on the Internet, which typically either lack congestion control or use proprietary congestion control mechanisms. This can easily cause congestion collapse or compatibility problems. Datagram Congestion Control Protocol (Dccp) fills the gap betweenUdp andTcp, featuring congestion control rather than reliability for packet-switched rich content delivery with high degree of flexibility. We present aDccp model designed and implemented withOpnet Modeler, and the experiments and evaluation focused on largely the smoothness of the data rates, and the fairness between concurrentDccp flows andTcp flows. We foundDccp-ccid3 demonstrates stable data rates under different scenarios, and the fairness betweenDccp andTcp is only achieved under certain conditions. We also validated that the throughput ofDccp-Ccid3 is proportional to the average packet size, and relatively fixed packet size is critical for the optimal operation ofDccp. Problems in the slow start phase and insufficient receiver buffer size were identified and we hereby proposed solutions on this.     

Rain depolarization measurement using INTELSAT-IV satellite in 4 GHz band at a low elevation angle

The degradation of cross polarization discrimination (XPD)due to rain has been measured at 4 GHz using the Indian Ocean INTELSAT-IV satellite at Yamaguchi in Japan, where the satellite elevation angle is as low as 9 degrees. Based on the data obtained from August 1975 to October 1976, this paper describes the analyses on the cumulative time distribution of XPD,the correlation of XPD degradation with surface rain rate and rain attenuation, and the duration characteristics of XPD degradation.     

Application of ant colony optimization to adaptive routing in aleo telecomunications satellite network

Ant colony optimization (Aco) has been proposed as a promising tool for adaptive routing in telecommunications networks. The algorithm is applied here to a simulation of a satellite telecommunications network with 72Leo nodes and 121 earth stations. Three variants ofAco are tested in order to assess the relative importance of the different components of the algorithm. The bestAco variant consistently gives performance superior to that obtained with a standard link state algorithm (Spf), under a variety of traffic conditions, and at negligible cost in terms of routing bandwidth.     

LicenseScript: a logical language for digital rights management

We propose LicenseScript, a language for digital rights management (Drm) based on multiset rewriting and logic programming. LicenseScript enjoys a precise syntax and semantics, and it is rich enough to embed other rights expression languages (Rel). We show that LicenseScript is expressive and flexible by exploring several application domains representing different aspects ofDrm. We present an implementation. Finally, we extend the core of the language to account for multiple devices in authorized domains.     

Software defined radio architecture for cellular networks base stations: TheSunbeam project

With the arrival of 3G radio mobile communications standards namelyUmts, new requirements arose for the wireless cellular networks. They concern the quality of the transmissions, the compatibility with pre-existing 2G networks and between different 3G networks and of course the increasing bandwidth to bring new high data rate demanding services through IP connections. TheSunbeam project was at the convergence of two key enabling technologies for 3G: software radio and smart antennas. Software radio appears to be an unavoidable approach to fulfil these specifications, but it needs to be used with new hardware architectures designed to support it.Acts European projectSunbeam just covered partially this subject as it concerned flexible multi-standard smart CBTS architecture study in the context of the migration of European networks from 2G (Gsm, Dcs 1800) to 3 G (Acts/Fdd, Acts/Tdd), concentrating on the physical layer. Digital smart antennas techniques were central in the scope ofSunbeam, since they are to bring the decisive performance improvements 3G transmissions require. This paper summarises the essential results achieved within the project and makes an attempt to establish global specifications for CBTS architecture design to achieve the flexibility, the reconfigurability and the scalability needed to implement software radio.     

Robust time-frequency distributions based on the robust short time fourier transform

Design of time-frequency distributions (Tfds) that are robust to the impulse noise influence is considered. The robustTfds based on the robust short-time Fourier transform (Stft) are proposed. An efficient procedure to evaluate the robustStft is given. RobustTfds based on the robustStft have better energy concentration around the signal instantaneous frequency (If) than the robustStft itself. Also, theseTfds are more resistant to higher impulse noise than the robustTfds obtained using the local autocorrelation function (Laf) based minimization problem.     

Bandwidth sharing under the assured forwarding Per-Hop behavior

The DiffServ’s Assured Forwarding (af) Per-Hop Behavior (phb) Group defines a differentiated forwarding of packets in four independent classes, each class having three levels of drop precedence. Specific end-to-end services based on thisphb are still being defined. A particular type of service that could assure a given rate to a traffic aggregate has been outlined elsewhere. In such a service, a fair distribution of bandwidth is one of the main concerns. This paper presents experimental work carried out to evaluate howaf distributes bandwidth among flows under different load conditions and traffic patterns. We focused on the effect that marking mechanisms have on bandwidth sharing among flows within a singleaf class. The traffic types we used includeudp flows, individual and aggregatedtcp flows, mix oftcp andudp, tcp sessions with heterogeneous round-trip times, as well as color-blind and color-aware re-marking at the aggregation point fortcp flows. Tests were performed on real and simulated networks. We have found certain conditions under whichaf distributes bandwidth fairly among nonadaptiveudp flows andtcp aggregates. Finally, we evaluate a basic rule for setting the parameters of the two-rate Three-Color Marker conditioning algorithm (trtcm) in order to achieve a better bandwidth distribution fortcp flows.     

Optimizing IP networks in a hybrid IGP/MPLS environment

In this paper, we consider a traffic engineering (te) approach toip networks in a hybridigp/mpls environment. Thoughigp (Interior Gateway Protocol) routing has proven its scalability and reliability, effective traffic engineering has been difficult to achieve in public IP networks because of the limited functional capabilities of conventionalip technologies.mpls (Multi-Protocol Label Switching) on the one hand enhances the possibility to engineer traffic onip networks by allowing explicit routes. But on the other hand it suffers from the scalability (n-square) problem. Hybridigp/mpls approaches rely onip native routing as much as possible and usempls only if necessary. In this work we propose a novel hybrid traffic engineering method based on genetic algorithms, which can be considered as an offlinete approach to handle long or medium-term traffic variations in the range days, weeks or months. In our approach the maximum number of hops anlsp (Label Switched Path) may take and the number oflsps which are applied solely to improve the routing performance, are treated as constraints due to delay considerations and the complexity of management. We apply our method to the German scientific network (b-win) for which a traffic matrix is available and also to some other networks with a simple demand model. We will show results comparing this hybridigp/mpls routing scenario with the result of pureigp routing and that of a full meshmpls with and without traffic splitting.     

IP-based transport of voice traffic in the UMTS radio access network: analytical study and empirical validation

In this paper, we investigate theIp protocol as a transport option for the user traffic in the UMTS Terrestrial Radio Access Network (Utran), where stringent delay bounds are to be met for both real-time and non real-time traffic. We focus on real-time voice traffic and present an analytical model for the multiplexing and transport of voice channels in theUtran usingIp. The novelty of our model is that it analytically includes and quantifies the performance of the timer used in multiplexing arriving Frame Protocol (Fp) frames into largerIp packets. We then validate our work through empirical results on a test-bed emulating theUtran transport functionalities. We show the trade-offs between performance, in terms of delay and link utilization, and quantify optimal values for the timer as well as the number ofFp frames perIp packet for a given output link capacity.     

Software radio: The challenges for reconfigurable terminals

The Software Defined Radio (Sdr) has always been considered as a promising solution for the future of wireless communications because of its ability to provide flexible architecture, enabling multimode and multistandard devices. On the network side, this technology seems to be achievable in a short-term visibility (we even are currently knowing the very beginnings ofSdr solutions in the field of network equipments), but applied to terminals, this technology is likely to reach later its maturity because the embedded issue is synonymous with high constrained architecture. The implementation of software radio terminals requires, for instance, the use of high calculation capability Digital Signal Processors (Dsp) or deeply integrated multiband rf transceiver, whose power consumption quality acts as a brake for the current development of such solutions. Nevertheless, the microelectronic industry will still provide more and more powerful components and, within a few years, theSdr dream will come true for terminal manufacturers. Furthermore, software radio is also a good opportunity to merge computer science and telecommunications technologies, in order to develop smart terminals, which may integrate software components like an operating system or Java virtual machine, etc. Hence, the software radio concept within mobile terminal is still an R&D issue, which requires effort combination in different fields but which also represents a great opportunity for the future of terminals.     

Iterative successive interference cancellation for multi-user DS/CDMA detectors in multipath channels

This paper deals with uplink Direct-Sequence Code Division Multiple Access (DS-CDMA) transmissions over mobile radio channels. A new interference cancellation scheme for multiuser detection, calledSIC/RAKE, is presented. It is based on a modified multistage Successive Interference Cancellation (sic) structure that enables efficient detection in multipath propagation environments, thanks to a single userRAKE receiver incorporated in each unit of thesic structure. Furthermore, a modified version of thesic structure, calledSIC/MMSE, that ensures convergence to theMMSE detector rather than to the decorrelating detector has been suggested. The convergence of theSIC/RAKE andSIC/MMSE methods is proved. Simulation results for the Universal Mobile Telecommunication System (UMTS) have been carried out for flat fading Rayleigh multipath channels, showing that the proposed detector is resistant to the near-far effect and that low performance loss is obtained compared to the single-user bound.     

Modélisation de la technique temporelle asynchrone

The evolution towards the integrated broadband communication network is undertaken by several countries. In France, system designers ofCnet in Lannion have assembled an experimental integrated broadband communication network (Ibcn)called Prelude based upon a 4.5 Gbit/s switching matrix and a new and promising transfer mode called the asynchronous time-division technique (Atd).During the project, performance evaluation studies have been carried through, aiming to validate the Atd concepts and to dimension the switching matrix. This paper reviews the Ibcn lab experiments in the world, with operational characteristics;Atd concepts are detailed and the most important features of Ibcn modelling are given. Finally, the network dimensioning is carried through giving packet size, buffers length, loss probabilities and waiting times.     

TMN implementation strategy based on OSI management standards

In order to facilitate the implementations ofTMN interface protocols/services studied inITU-T, it is very important to define profiles for supportingTMN management service. This paper proposes a concrete method for achieving this based on osi management standards as a promisingTMN implementation method. It proposes an idea of structuring theTMN ISP’S based on the structure of the osi managementISP’S. The paper discusses aTMN based on the osi managementISP’S. Finally the implementation as software is discussed and a software architecture for efficient application development is proposed.     

Web-based interorganizational information systems for logistics outsourcing

This article examines how web-based interorganizational information systems(ios)can efficiently support coordination mechanisms between outsourcer and third party logistics (3PL). First, we review the literature on coordination mechanisms andios. Second, we report on the methodology used for gathering information on outsourcers and 3PLs. Third, armed with limited but quality data, we identified two fundamental dimensions: 3PL involvement andios impacts on logistics outsourcing decisions. By combining the two dimensions, we propose a conceptual framework that highlights four main categories ofios that we characterize as neutralios, supply chainios, strategicios and dynamicios. After characterizing and analyzing each category, we discuss how these web basedios support outsourcers and 3PL along the supply chain. Finally, the article discusses the framework’s relevancy and its limits.     

Auto and cross-correlation analysis techniques on-board spacecraft

An efficient method of producing spectrograms of signals recorded on spacecraft is to compute on board the correlation function and, after telemetering this to ground, subjecting it to a Fft (Fast Fourier Transform). This is the procedure adopted on Geos 1and 2. Results are presented of whistlers, chorus, hiss and electrostatic waves illustrating that high quality spectrograms can be obtained by this method. Correlators to be flown on the InterKosmos spacecraft Magik,despite having a very low allocated telemetry rate still yield spectrograms on which one may distinguish chorus,hiss and whistlers.     

10 gigabit Ethernet long-haul transmission without in-line EDFAs

In this contribution, we present experimental results on optical packet transmission of two 10 gigabit ethernet channels (10Ge) over 252 km link of standard single mode fibre (Ssmf, itu-t Recommendation G.652) and 287 km long link composed of 85 km ofSsmf and 202 km of non-zero dispersion-shifted (Nz DSF, itu-t Recommendation G.655) without deployment of in-line erbium-doped fiber amplifiers (Edfas). All the active components, dispersion compensating fibre (Dcf) modules and optical band-pass filters were placed at the transmitter and at the receiver side of the link. To our best knowledge, this is the first report of pure Ethernet transmission without in-lineEdfas over such a distance. The results are encouraging especially for operators of national research and educational networks who rely on leased dark fibres and prefer as long transmission as possible without deployment of in-line amplifiers.     

Improving parallel EKF-based nonlinear channel equalization using unscented transformation

The paper presents a new review of parallel Kalman filtering for nonlinear channel equalization. A Network of Extended Kalman Filters (nekf) has already been suggested for this purpose. This equalizer gives recursively a minimum mean squared error (mmse) estimation of a sequence of transmitted symbols according to a state formulation of a digital communication scheme. It is essentially based on two mechanisms: the approximation of the non Gaussiana posteriori probability density function (pdf) of the symbol sequence by a Weighted Gaussian Sum (wgs); and the local linearization of the nonlinear channel function for each branch of the network. Since the linearization, bearing on scattered symbol states, is one of the major limitations of thenekf, a new Kalman filtering approach, the Unscented Kalman Filter (ukf) suggested by Julier and Uhlman is considered in this paper for an interesting adaptation to the equalization context. Theukf algorithm is based on the equations of a Kalman filter, as the optimal linear minimum variance estimator, and on determining conditional expectations based on a kind of deterministic Monte-Carlo simulations. The new equalizer referred to as the Network ofukf (nukf), thus combines density approximation by awgs and the Unscented Transformation (ut) principle to circumvent the linearization brought within eachekf and is shown to perform better than thenekf based equalizer for severe nonlinear channels. Also, an adaptive version of thenukf is developed using the k-means clustering algorithm for noise-free channel output identification, since thenukf-based algorithm does not require the knowledge of the channel nonlinearity model.