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Photonic Networks, 2008 ITG Symposium on

Date 28-29 April 2008

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Displaying Results 1 - 25 of 29
  • Flooding Traffic Reduction through Optimized Address Learning in Carrier-Grade Ethernet Networks

    Page(s): 1 - 7
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (880 KB)  

    As Ethernet deployments become larger and the number of active MAC addresses in the network grows, flooding (broadcast based resolution of the location of unknown addresses) becomes a scalability bottleneck. This is especially a problem during network convergence, e.g. after a spanning tree topology reconfiguration or a ring protection switch, which result in deletion of forwarding databases. Network performance may drop significantly during periods of flooding; a reason why these should be kept as short as possible. The limited learning bandwidth ¿ due to its complexity the MAC address learning process is usually not designed for wire-speed performance ¿ additionally prolongs a flooding phase. In this work, we qualitatively evaluate several means of improving the learning performance. We demonstrate that ranking the switch internal learning requests with respect to their ability to reduce flooding is a new way to mitigate the broadcast problem. View full abstract»

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  • Performance Evaluation of IP over Cost-Optimized Optical Multilayer Networks with SRLGs

    Page(s): 1 - 9
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1555 KB)  

    The design of optical transport and IP networks is investigated with respect to the effect on overall network performance when the two aspects are combined in the same network architecture. The focus is on the identification of advantages in the joint design of IP and transport networks, as well as on the shortcomings and network bottlenecks which may result from sub-optimal design. The impact of different IP routing strategies (shortest path, equal-cost multipath) on the network utilization is quantified, and potential sources for overload in the IP domain are determined. Simulations were carried out to systematically assess technical metrics like link utilization and economic parameters such as cost for a 50-node transport network with line rates up to 40 Gbit/s. The impact of fiber cuts was taken into account, leading to multiple logical IP links to fail simultaneously, i.e. shared risk link groups (SRLGs), and triggering massive IP rerouting. Applying the results allows to identify bottlenecks in the design, and to devise mechanisms which allow cost-optimal network design of future IP and optical transport networks. View full abstract»

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  • Equivalence Conditions of Buffered and Bufferless Network Architectures

    Page(s): 1 - 7
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (177 KB)  

    Buffers in network devices are expensive and undesired because of latency reasons. Nonetheless, existing packet networks are buffered for the purpose of acceptable link utilization and low loss rates at the same time. On the other hand bufferless network architectures are well known, ranging from old fashioned telephony up to optical burst switching. We show in theory the similarity between both buffered and bufferless network dimensioning and we illustrate in a number of examples to which extend this theoretical similarity results in comparable technical performance. View full abstract»

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  • Higher Speed Ethernet Developments

    Page(s): 1 - 7
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (441 KB)  

    Higher speed Ethernet interfaces with bitrates at 40 Gbit/s and 100 Gbit/s will play an increased role in mid-term development of data centers and networks due to the increase demand on transport capacity for packet oriented services and applications. In this contribution the development of higher speed interfaces will be reflected with respect to the different activities in the involved standardization bodies, and the native Ethernet and the Ethernet over OTN (optical transport network) approaches will be discussed. In future networks, higher speed interfaces will have strong impacts on the physical transmission, network architecture, network services, and network control resulting in advanced requirements. View full abstract»

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  • Cost-effective 100Gbps Optical Modulation Format for Metro Networks

    Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (133 KB)  

    When commercialized, the increase of the per-channel data rate to 100Gbps in transport systems is expected to experience strong demand within both long-haul and metro networks. We explore a modulation format that combines phase- and amplitude-shift keying towards finding a cost-effective higher-speed transport solution for metro networks, significantly reducing the cost-premium associated with several specific solutions being designed for long-haul networks and reducing the wait associated with decreases in component pricing. The respective hardware requirements and possible implementations of the proposed format are discussed, and we present numerical simulation results to explore sensitivities to several system parameters, namely chromatic dispersion tolerances, PMD tolerances, and OSNR requirements. View full abstract»

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  • 107 Gbit/s RZ-DPSK Transmission using an ETDM Integrated Receiver

    Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1442 KB)  

    High bit rate optical transmission with data rates of 100 Gbit/s and more is currently an active field of research worldwide. Serial 100 Gbit/s transmission, in contrast to parallel transmission on different wavelength channels (e.g. 10 x 10 Gbit/s or 4 x 25 Gbit/s), is seen as a cost-efficient implementation for future 100 Gb-Ethernet (100GbE) networks, in particular in the wide-area part of the network. The feasibility in terms of the technical realization of such systems based on time-division multiplexing (TDM) has already been shown using a number of different modulation formats, such as OOK (¿On-Off-Keying¿) or DQPSK (¿Differential Quarternary Phase Shift Keying¿). While DQPSK requires a more complex transmitter and receiver architecture it offers a higher spectral efficiency. The use of DPSK (¿Differential Phase Shift Key-ing¿), which enables a significantly higher sensitivity in balanced detection receivers, compared to OOK, has not been experimentally investigated so far. In this paper we report on experiments in a 107 Gbit/s RZ-DPSK system. The receiver was based on pure elec-trical time-division multiplexing. It comprised a high-bandwidth balanced photodetector (u2t) and a CDR-chip (¿Clock & Data Recovery¿, Micram) for simultaneous demultiplexing and recovery of the clock signal. The transmitter used optical time division multiplexing (OTDM) techniques. This allowed to generate a high quality 107 Gbit/s RZ-DPSK signal, which was not limited by the bandwidth of the modulator or the electrical driver amplifiers. Measurements of eye diagrams and bit-error rates for 53.5 and 107 Gbit/s are presented and com-pared. The transmission of 107 Gbit/s DPSK signals over 320 km dispersion managed fiber is demonstrated. View full abstract»

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  • TDM-to-WDM Conversion based on NOLM from 128.1 Gbit/s to 3 × 42.7 Gbit/s

    Page(s): 1 - 3
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (955 KB)  

    A nonlinear optical switch performing conversion of a 128.1 Gbit/s OTDM channel simultaneously to 3 × 42.7 Gbit/s WDM is experimentally demonstrated. The proposed scheme is based on a nonlinear optical loop mirror incorporating a broadband gate with low dispersion and low channel walk-off and thus requires the use of low-dispersion, dispersion flattened HNLF. BER measurement results show no error floor, and a maximum 3.5 dB penalty for the three WDM channels is achieved. View full abstract»

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  • Investigation of Phase Noise Compensation Methods for 43 Gbit/s RZ-DQPSK Multi-Span Transmission with Direct Detection

    Page(s): 1 - 4
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1495 KB)  

    This paper investigates the performance of different phase noise compensation options for a 43 Gbit/s RZDQPSK multi-span transmission system with distributed inline under-compensation and direct detection. The efficiency of different phase noise compensation methods, namely (i) the compensation of the mean nonlinear phase shift (MEAN), (ii) the multi-symbol phase estimation (MSPE) and (iii) the combination of both methods is examined by Monte-Carlo simulations for varying pre- and post-compensation. Furthermore, the performance of these three strategies for different average fibre input powers is investigated. Not only the optimum phase noise compensation strategy is identified, also the impact of the dispersion map is considered and compared to the conventional receiver. For the best noise tolerant receiver option a maximum Q-gain of up to 2.7 dB can be achieved for a wide range of values for the fibre input power. View full abstract»

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  • Influence of Innovations on Design, Operation, and Cost of metropolitan Optical Transport Networks

    Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (157 KB)  

    This paper provides a high level overview of recent technological and architectural innovations of DWDM based Metro networks. Planners gain significantly more flexibility in designing networks with converged network functions that better fit the Service Providers business goals. Lower network complexity reduces operational work load and associated costs. New technologies allow Metro networks to evolve into flexible architectures optimized to transport current and future services with more efficiency, higher service availability, and lower total cost of ownership (TCO). Convergence of DWDM with IP and Ethernet enables business relevant synergies that are impossible with current architectures. Positive impact on TCO, planning, and operations are shown. View full abstract»

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  • WDM-PON - A Platform for consolidated Metro Access and Backhaul

    Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (214 KB)  

    Today, there is a major trend in metro access networks towards FTTx (Fiber-To-The-x, where x stands for Home (H), Building (B), Curb, or Cabinet). Many agree that FTTH/FTTB will win mid- to long-term over other deployment scenarios because of a higher available bandwidth. Future metro networks need to maximize cost efficiency. This leads to requirements of reducing general OpEx (Operational Expenditures) and the numbers of active (concentrator) sites in the network in particular. This requires the consolidation of the three main metro area applications onto one common metro access & backhauling platform. These applications are (wireless, wireline) backhaul, business/enterprise access, and high bandwidth residential access. Whilst these applications today use different technologies (e.g., active point-to-point Ethernet, CWDM rings, VDSL and/or GPON) for the first mile, they need a converged infrastructure for efficient backhaul. In some networks, GPON is already being deployed for nonresidential services. However, it can be shown that GPON, even with 10G bit rate and wavelength extension according to ITU-T G.984.5, will run out of capacity in various networks. This is driven by the developments of backhaul capacity towards multiples of GbE per DSLAM, enterprise access bit rates towards 10GbE, and residential access bit rates towards symmetrical 100Mb/s, respectively. We show that an infrastructure based on passive WDM technology can solve the metro network consolidation requirement and make the network future-proof. WDM-PONs can provide significantly better scalability than GPON (and EPON). They can scale in per-wavelength bandwidth from 1G via 2G5 and 4G3 to 10G (and more, should this be necessary). They have advantages regarding security (because wavelengths provide point-to-point connections), and also regarding simple active-layer access. Also, they can be combined with GPON/EPON-like TDMA schemes in later steps. View full abstract»

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  • Converged Packet-based Solutions in a Realistic Metropolitan Network Scenario

    Page(s): 1 - 8
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    Behind the headline ¿Fixed Mobile Convergence¿ (FMC), network operators are busily trying to consolidate their separated fixed and mobile service platforms in the metropolitan domain to a single converged packet based network. The special challenge is to cover both, residential and business customer services which typically differ strongly in terms of quality requirements in the same aggregation network as preferred option. Traffic demand dramatically increases at the fixed and mobile subscribers¿ end with new rich media content offerings. Hence the main goal for operators is to design a consolidated aggregation network ensuring efficient transport of Terabits of traffic at lowest total cost of ownership (TCO). Inherently smooth migration of existing services onto that new network needs to be ensured as well. This paper will present a set of relevant metro network architectures considering evaluation of the above mentioned requirements with respect to the transport and switching layers of the network. Needed switching capabilities in the aggregating metro nodes, resource utilisation and cost will be analysed and compared for the different architectures based on a realistic German metropolitan area. View full abstract»

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  • 60 GHz Wireless Photonic Link System for 12.5Gb/s Data Transmission

    Page(s): 1 - 4
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (895 KB)  

    We present a 60 GHz photonic millimeter-wave wireless link system for short to medium-range broadband data transmission. The system employs advanced mm-wave photonic components and radio-over-fiber (RoF) techniques for the generation of a DSB-SC optical mm-wave carrier as well as its subsequent OOK modulation and fiber-optic transmission. For short range in-door wireless experiments, we have constructed a compact wireless RoF transmitter consisting of a high-frequency photodiode and a mm-wave antenna only, i.e. no electrical amplifier was used for in-door experiments. Employing this RoF transmitter, the system achieved broadband wireless in-door transmission of up to 12.5 Gb/s signals (231 - 1 PRBS, NRZ) with a receiver sensitivity as low as -45.4dBm. We even demonstrate 12.5 Gb/s in-door transmission when operating the mm-wave transmitter in a passive mode, i.e. without any electrical power supply. For medium-range out-door wireless access experiments an electrical RF amplifier was employed in the RoF transmitter. Here we achieved 12.5 Gb/s and 10.3125 Gb/s transmission in out-door line-of-sight (LoS) experiments over wireless distances of up to 20 m and 40 m, respectively. We expect these distances to be mainly limited by the antenna gain (20dBi) and the bandwidth of the amplifier in the RoF transmitter. When using high gain antennas and an RF transmitter amplifier with a sufficient bandwidth we have calculated that the maximum wireless distance the system could accommodate for 12.5 Gb/s is in the km-range. View full abstract»

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  • Broadband Wireless Access

    Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1071 KB)  

    In future cellular radio networks Radio over Fiber (RoF) is a very attractive technology to deliver microwave and millimeter-wave signals containing broad band multimedia services to numerous base stations of the network. The radio signals are placed on an optical carrier and distributed by means of an optical fiber network to the base stations (BS). In the BS the optical signals heterodyne in a photodiode to produce the radio signals which are then sent via a wireless link to the mobile units (MU). The optical fiber network provides high frequency, wideband, low loss and a means of signal distribution immune to electromagnetic interference. The generation of an optical double-sideband with suppressed carrier (DSB-SC) signal is a straightforward method due to the fact that only one microwave modulator driven at half the millimeter-wave frequency is required. One sideband is modulated with baseband data rates of up to 10 Gbps. Transmission experiments prove this modulation scheme to be dispersion tolerant and error free transmission was demonstrated after 40 km of single mode fiber for data rates up to 5 Gbps. The limits of the setup were tested with data rates of 10 Gbps. View full abstract»

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  • A Novel Approach to Identify Denial-of-Service Attacks against Transport Network Resources

    Page(s): 1 - 8
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (153 KB)  

    Transport networks are the core elements of todayï¿¿ï¿¿ï¿¿s communications systems. Their capability to transmit data extremely fast and secure allows network operators to interconnect a large number of users at the same time. However, the increasing number of attacks against such networks raises the challenge to deploy effective safeguards to guarantee their availability. With UNI and E-NNI, Automatically Switched Optical Networks (ASON) have become susceptible to known and ï¿¿ï¿¿ï¿¿ potentially yet unknown ï¿¿ï¿¿ï¿¿ kind of Denial-of-Service attacks as well. This paper is focusing on attacks against transport resources aiming to prevent users from setting up transport connections, which can be SDH or ODU paths, but also wavelengths in dynamically switched WDM networks. With respect to the aspects being relevant for Denial-of-Service attacks against transport resources and potential attack schemes and scenarios, we present methods for the detection of such attacks and subsequent identification of the attackers, which contribute to a comprehensive detection framework for auditing the transport network for potential attacks. Within the EIBONE research project, we have developed a simulation tool to analyze a variety of simulation scenarios on the topology of a Lab-based ASON network. Using a variety of simulated attack scenarios, the detection methods and the framework were validated for their effectiveness. The results indicate that the framework yields good detection rates for Denial-of-Service attacks, in which one user account is attacking the network at one single access point. The combination of the detection methods and the consolidation of their results allows for identification of distributed attacks, in which an attacker employs several user accounts at potentially multiple access points to, for instance, attack a particular (gateway) network element. Next to the problem and the chosen analysis tools, the results from our analysis will be explained in detail. View full abstract»

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  • Video Service Quality Estimation in Significance Aware Transport Networks

    Page(s): 1 - 8
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1299 KB)  

    As video distribution over optical transport networks becomes more and more important, considerable focus is put on providing the appropriate quality for this transport service. A typical trade-off seen in this context is between sophisticated compression techniques used in order to save required transmission bandwidth, and the sensitivity of service quality with respect to transport network induced information (packet) loss. At the application layer, sensitivity to losses due to transport level impairments is content dependent, thus introducing a gap between typically used quality of service (QoS) parameters and the actual perceived quality (quality of experience ¿ QoE). Extending a proposal to enhance transport level quality insurance mechanisms to be aware of the QoE significance of transmitted data, this paper presents a proposal to use significance information for QoE monitoring within the transport network as well. Two measurement techniques are described for delivering QoE indicators. Based on analytical expressions for the influence of packet loss on the MPEG-2 video decoding a Quality of Experience metric is derived which is applicable in significance and non-significance aware video transmission environments. The influence of different video encoding parameters on the overall achievable video quality and the expected gain in a significance aware environment are evaluated. View full abstract»

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  • Measuring the cumulative PMD of buried fibers in the network of Deutsche Telekom in a field trial using an RS-POTDR prototype

    Page(s): 1 - 4
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (237 KB)  

    An RS-POTDR prototype device is used in a field trial to investigate the spatial distribution of PMD in deployed fibers in the network of Deutsche Telekom. Results help to identify high-PMD fiber sections which contribute the most to the overall link PMD and need to be replaced to enable 40Gbit/s transmission and beyond. View full abstract»

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  • In-service measurement of the OSNR in ROADM-based Networks

    Page(s): 1 - 3
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (650 KB)  

    Optical networks using ROADMs present a challenge for OSNR testing. We propose a new method for measuring the in-band OSNR based on a high resolution optical spectrum analyzer using a new optical polarization splitting method. View full abstract»

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  • Compatible Single-Sideband Modulation for Optical Transmission of OFDM-Signals Using Direct Detection

    Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (326 KB)  

    Orthogonal frequency-division multiplexing is a flexible modulation technique well known from wireless and wireline communications. Recently, it is also under discussion for optical communications. Beside transmission with coherent detection for optimum transmission quality also less complex schemes have been proposed applying direct detection. One promising approach called compatible single side-band modulation will be discussed in this paper. View full abstract»

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  • Impairment Identification in an Optical Transparent Network Using OFDM Transmission

    Page(s): 1 - 5
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    Monitoring of optical transmission impairments is achieved by signal processing at the receiver. In an OFDM system spectral properties can be extracted for this purpose in particular. The proposed method, which allows separation of linear and non-linear impairments, is applied in simulation to monitor a number of paths in a small test network. View full abstract»

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  • Turbo Equalization with Convolutional and LDPC Codes as well as Analytically Computed Metrics

    Page(s): 1 - 8
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (566 KB)  

    This paper compares advanced electrical equalization schemes for intensity modulated high speed fiber optic transmission. The treated equalization schemes are based on the Turbo principle and apply convolutional as well as low-density parity-check (LDPC) codes with a forward error correction (FEC) overhead of 6.7%. A bit error rate (BER) and EXIT chart analysis based on a sophisticated channel model and analytically computed branch metrics for the BCJR and Viterbi equalizers give detailed insight into the performance and into the iterative equalization process, respectively. View full abstract»

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  • Investigation of Fast and Efficient Adaptation Algorithms for Linear Transversal and Decision-Feedback Equalizers in High- Bitrate Optical

    Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1015 KB)  

    We investigate fast and efficient adaptation algorithms for linear transversal feed-forward (FFE) and decision feedback (DFE) equalizers in intensity modulated optical communication systems with direct detection (IM/DD). First, we employ the well-known minimum mean square error (MMSE) adaptation criterion and give a benchmark with respect to minimal bit error rate (BER). We further take the least-mean-square algorithm (LMS) as stochastic implementation of the MMSE scheme and derive some simplified versions which use coarsely quantized signals. Consequently, the complexity of a digitally implemented adaptation circuit is reduced and application to bitrates of 40-100 Gbit/s becomes more feasible. The performance of these simplified versions is assessed with respect to adaptation speed and accuracy in comparison to the MMSE equalizer. It is shown that sufficient fast and almost accurate adaptation of the equalizer can be achieved. View full abstract»

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  • Chromatic Dispersion Compensation by Frequency Domain Based All-Pass Filtering

    Page(s): 1 - 3
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (212 KB)  

    We propose an alternative, block-wise, frequency domain based all-pass filter for chromatic dispersion compensation in uncompensated transmission links with coherent detection. Due to its structure with low complexity, we believe, that implementation in FPGAs for 40Gbit/s CP-QPSK is possible. View full abstract»

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  • Placing Bypass Capable Nodes in Two-Layer Networks

    Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1054 KB)  

    In two-layer networks there are a lot of ways to improve virtual and physical topology and capacity allocations in terms of cost. Because switching costs are usually higher in the upper layer, the introduction of bypass links, bypassing the expensive upper layer interfaces, can be beneficial. In the paper we discuss the placement of nodes with bypass functionalities. We use a physical network topology with 50 nodes based on the Germany50 reference network. Our approach for finding the bypass links and the corresponding bypass nodes is based on a mixed integer programming approach with a simple cost model for switching in both layers. Our starting point is a network without bypass functionality. This is basically a one-layer network, as all traffic is switched in the upper layer. In a first step we find the optimum capacity allocations in this network, taking the interface granularities into account. After this we calculate the resulting transit traffic in all nodes. If the transit traffic between two next nearest neighbour nodes is larger than a certain threshold, a bypass link between them is introduced between them. The new virtual (upper layer) topology is then used to optimize the network again. This procedure leads to considerable cost reductions, but is computationally much simpler than a full two layer optimisation including all possible bypass links. View full abstract»

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  • Final Achievements of IST Project MUPBED

    Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (588 KB)  

    The IST project MUPBED (www.ist-mupbed.eu) has been successfully completed in December 2007. The objectives of the project MUPBED have been centred on the establishment of an innovative, multi-layer and multidomain European test network by means of ASON/GMPLS-enabled networks and on the experimental validation of application scenarios. The key highlights of the last project phase are presented in this paper, including the final pan-European multi-layer and multi-domain network configuration and its successful integration in the OIF Worldwide Interoperability Demonstration 2007. View full abstract»

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  • Evolution to Next Generation Packet Transoport Networks

    Page(s): 1 - 15
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (948 KB)  

    (1) Data transfer is sensitive to data loss and bit errors, while delay and jitter are of relatively low importance. (2) In contrast, multimedia services are very sensitive to delay and jitter, whereas data loss and bit errors are of limited importance. (3) Some transmission schemes, such as those in ATSC and DVB, impose strict constant bit requirement on the transport stream. In order to ensure that the stream maintains a constant bitrate. View full abstract»

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