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.     

Business opportunities throughUMTS-WLAN networks

This article outlines the economic feasibility of mobile operators that combine nationwide mobility with 3G networks and hot spot coverage withWLANS, WLANS are based onHIPERLAN/2 architecture and theUMTS network exploitswCDMA/FDD technology. The evaluated business scenarios are focused on two different deployment areas, in terms of demographic characteristics and mobile penetration: a large and a small European country. The business case spans 2002 to 2011 withUMTS’ roll-out year in 2002 andWLAN’s in 2004, covering indoor hot-spot areas (stations, airports, stadiums, etc.) where demand is high. The demand for thisUMTS-WLAN roaming case is evaluated based on observations from Europe’s current mobile market and its evolution. Usage scenarios of different service packages corresponding to both residential and business markets have been taken into account. Direct investments and operational costs as well as revenue streams from traffic have been calculated. The methodology and the tool developed inACTS-TERA [1] andIST-TONIC [2] projects have been utilized for this case study. Economic conclusions have been derived, presented and discussed using key profitability factors. Profitability for all scenarios and business profiles has been calculated, presented and discussed. It includes a sensitivity analysis in order to identify the major opportunities and threats, for specific service sets as well as critical parameters and uncertainties. A wide audience from mobile operators and service providers to retail companies interested in entering the 3G market, can exploit this information.     

EnhancingIEEE 802.11 performance in congested environments

IEEE 802.11 is the most deployed wireless local area networking standard nowadays. It uses carrier sense multiple access with collision avoldance (CSMA/CA) to, resolve contention between nodes. Contention windows (CW) change dynamically to adapt to the contention level: Upon each collision a node doubles itsCW to, reduce further collision risks. Upon a successful transmission theCW is reset, assuming the contention level dropped. However, contention level is more likely to change slowly, and resetting theCW causes new collisions and retransmissions before reaching the optimal value again. This wastes bandwidth and increases delays. In this paper we propose simple slowCW decrease functions and compare their performances to the legacy standard. We analyze them through simulation and show their considerable enhancement at all congestion levels and transient phases.     

Les outils du commerce électronique

Electronic commerce (ec) is a combination of practices, strategies, processes, applications and technologies, enabling business transactions. This paper focuses on software and technologies forec. In the first part, the different categories of applications forec are reviewed. A fully integrated solution does not seem to be the major trend. However, the “best of breed” approach implies an integration problem. The second part of the paper includes modeling languages andec applications core technologies. Theuml appears to be used at different levels in the development of anec solution. Web technologies are continually evolving:XML could be the language of the future for information exchanges between heterogeneous applications. The third part deals with component and application integration. In spite of converging standards for languages as well as for models, system interoperability is a major problem, when informations are to be shared and processes to be jointed. Two major trends can be identified: Web services andEDI approaches.     

Location discovery in enterprise-based wireless networks: Case studies and applications

We have designed and implemented a Web service for location discovery (LODS) and a location-based printing service that usesLODS on a network with wirelessLAN connectivity based onIEEE 802.11 that is typical to campuses and enterprises. The need for location management and location-based services is linked to the mobility of the users. While location discovery is already implemented in cellular telecommunication networks since the system needs to know where are the users to connect them to incoming calls, the need for such a service was not so crucial in data network where in general the mobile user is the client and initiates the connections. We propose several solutions to implement our location discovery service depending on the underlying networking architecture and compare these solutions in terms of several criteria.LODS allows mobile users to find their approximate location within the campus or the enterprise and allows location-based applications to find out the location of a user to suggest the nearest points of interest, e.g., printers, elevators, and vending machines. We also present the case of our location-based remote printing service that was deployed in Purdue wireless network.     

ATM and AAL layer issues concerning multimedia applications

This paper presents an overview of the facilities that should be provided by theAtm layer and the adaptation layer (Aal) in order to support multimedia communications. From the analysis of data flows generated by well known multimedia applications and the services that could be offered byAtm networks both in the public and the private domain, we propose solutions enabling the availability of such applications onAtm networks taking into account both economical andQos parameters.     

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.     

A MC-CDMA system analysis in a software radio context

This paper presents a Multi-Carrier Code Division Multiple Access (Mc-Cdma) system analysis in a software radio context. Based on a combination of multi-carrier modulation and code division multiple access,Mc-Cdma benefits from the main advantages from both schemes: high spectral efficiency, high flexibility, multiple access capabilities, etc. It is firstly shown why, nowadays,Mc-Cdma is undoubtedly a high potential candidate for the air interface of the 4G cellular networks. TheMc-Cdma concept and the block-diagrams of the transmitter and the receiver are presented first. Afterwards, the technical issues concerning the processing devices for the implementation ofMc-Cdma systems in a software radio context are analysed. The advantages and disadvantages of Digital Signal Processors (Dsps) and Field Programmable Gate Arrays (Fgpas) components are discussed. The implementation ofMc-Cdma systems and the integration of signal processing algorithms as Fast Hadamard Transform (Fht) and Inverse Fast Fourier Transform (Ifft) are considered and analysed for the first time. Finally, implementation results with a mixed prototyping board are presented. Then, it is shown that a new combination of the flow graphs ofFht andIfft leads to interesting computation savings and that hardware structures asFgpas are more adapted thanDsps to those intensive computation functions. Finally, for the completeMc-Cdma modem implementation, the necessity of a Co-Design methodology is highlighted in order to obtain the best matching between algorithms and architecture.     

Challenges for Wi-Fi, business models and spectrum issues

Amongst the various versions ofWLAN, Wi-Fi is widely used and raises two interesting issues from an economic, strategic and regulatory perspective. One deals with the perspectives of the two business models appeared so far: a cooperative, non-commercial one, for local use and a commercial one involving WirelessISPS and broadband access aggregators for roaming. Both show robust growth today but present weaknesses. The other issue deals with spectrum allocation as Wi-Fi uses an unlicensed frequency band. Its development challenges traditional spectrum management, putting forward “open spectrum” management models. But while in theUS Wi-Fi has been able to develop without any significant regulation hurdles, the situation is more complicated in Europe and especially in France where regulation authorities have more recently addressed the issue.     

Space applications of optical communications

Optical communication in Space is now a reality. In this paper we present the recent developments that were undertaken in Europe for this application. We first describe the different missions where optical communications are useful: link between two geostationary satellites (geo-geo), Data Relay Mission (leo-geo) and High Data Rate Satellite Constellation Network. Then we detail the different candidate laser technologies from the most straightforward technologies that have been developed for optical fiber applications (λ=1.55 µm) and 0.8 µm technology based on Silicon detector to the recent developments based on high power fiber amplifiers. In the last chapter we describe thesilex (Semi conductor Intersatellite Link Experiment) program which performs optical communication betweenspot4 Earth observation satellite (cnes) andartemis (esa). The excellent results based on 0.8 µm laser diode technology are considered to be a major milestone in optical intersatellite communication     

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.     

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.     

A scheduler for relative delay service differentiation

We propose a new delay-based scheduler called asRD-VC (Relative Delay VirtualClock). Since it performs a delay-based service differentiation among flow aggregates, the quality at microflow level is the same as that at aggregate level. This is not easily achievable when the service differentiation is bandwidth-based or loss-based. Unlike theEDF (Earliest Deadline First) scheduler [1], our proposed scheduler self-regulates and adapts the delays according to load changes. This characteristic permits us to implement it in an AF-likePHB providing the relative quantification service in a DiffServ network. Finally, we compare our proposedrd-vc scheduler with two important existing propositions:WTP (Waiting Time Priority) [2, 3] andex-vc (Extended VirtualClock) [4]. Both these propositions are delay-based and have self-regulation property. All three schedulers (RD-VC, WTP andEX-VC) maintain the required service differentiation among aggregates and have comparable long term average performance like mean throughput per aggregate and packet loss ratio etc. However,RD-VC and WTP take an edge overEX-VC at short-term performance like jitter. Bothrd-vc andWTP have good long term and short-term performance. Our proposedrd-vc, compared to existingWTP, has two additional characteristics, i.e. unlike WTP which is limited to architectures with one queue per Qos class, it has no limitation on implementation scope (with or without separate queues per class) and it has lower complexity. This rendersRD-VC an interesting proposition.     

A countermeasure againstDDOS attacks using active networks technologies

A Distributed Denial of Service (DDoCS) attack consumes the resources of a remote host or network by sending a massive amount ofIP packets from many distributed hosts. It is a pressing problem on the Internet as demonstrated by recent attacks on major e-commerce servers andISPs. Since the attack is distributed and the attack tools evolve at a rapid and alarming rate, an effective solution must be formulated using a distributed and adaptive approach. In this paper, we propose a countermeasure againstDDoCS attacks using a method we call Active Shaping. Our method employs the Active Networks technologies, which incorporates programmability into network nodes. The Active Networks technology enables us to deter congestion and bandwidth consumption of the backbone network caused byDDoCS attacks, and to prevent our system from dropping packets of legitimate users mistakenly. This paper introduces the concept of our method, system design and evaluates the effectiveness of our method using a prototype.     

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.     

Characterization and evaluation of TCP and UDP-based transport on real networks

StandardTcp (RenoTcp) does not perform well on fast long distance networks, due to its AMD congestion control algorithm. In this paper we consider the effectiveness of various alternatives, in particular with respect to their applicability to a production environment. We then characterize and evaluate the achievable throughput, stability and intra-protocol fairness of differentTcp stacks (Scalable,Hstcp,Htcp, FastTcp, Reno,Bictcp, hstcp-lp andLtcp) and aUdp based application level transport protocol (Udtv2) on both production and testbed networks. The characterization is made with respect to both the transient traffic (entry and exit of different streams) and the steady state traffic on production Academic and Research networks, using paths withRtts differing by a factor of 10. We also report on measurements made with 10 Gbit/secNics with and withoutTcp Offload Engines, on 10 Gbit/s dedicated paths set up forSc2004.     

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.     

AIMD-based online MPLS traffic engineering for TCP flows via distributed multi-path routing

With this paper, we propose a distributed online traffic engineering architecture formpls networks. In this architecture, a primary and secondarympls lsp are established from an ingresslsr to every other egresslsr. We propose to split thetcp traffic between the primary and secondary paths using a distributed mechanism based onecn marking andaimd-based rate control. Inspired by the random early detection mechanism for active queue management, we propose a random early reroute scheme to adaptively control the delay difference between the primary and secondarylsps. Considering the adverse effect of packet reordering ontcp performance for packet-based load balancing schemes, we propose that thetcp splitting mechanism operates on a per-flow basis. Using flow-based models developed for Internet traffic and simulations, we show that flow-based distributed multi-path traffic engineering outperforms on a consistent basis the case of a single path in terms of per-flow goodputs. Due to the elimination of out-of-order packet arrivals, flow-based splitting also enhancestcp performance with respect to packet-based splitting especially for longtcp flows that are hit hard by packet reordering. We also compare and contrast two queuing architectures for differential treatment of data packets routed over primary and secondarylsps in thempls data plane, namely first-in-first-out and strict priority queuing. We show through simulations that strict priority queuing is more effective and relatively more robust with respect to the changes in the traffic demand matrix than first-in-first-out queuing in the context of distributed multi-path routing.     

MOEMS devices and their applications to optical telecommunication systems

This paper describes first the basicmoems technologies and attempts to point out the various degrees of freedom that are available for the designer. Then, it will review some of the most important architectures ofmoems demonstrated up to now, for optical switching and wavelength management inWDM networks. These technologies are also very promising for optical connectorization, and could open the way to new components that could be cheap enough for being used at the subscriber level. An analysis of the present status ofmoems technologies, the main short term issues, and some development prospects will finally be given.