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  • Low complexity PAPR reduction techniques for clipping and quantization noise mitigation in direct-detection O-OFDM systems

     Nadal Reixats, Laia; Svaluto Moreolo, Michela; Fàbrega, Josep Maria; Junyent Giralt, Gabriel
    Optical fiber technology
    Date of publication: 2014-06-01
    Journal article

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    We present different distortionless peak-to-average power ratio (PAPR) reduction techniques that can be easily applied, without any symmetry restriction, in direct-detection (DD) optical orthogonal frequency division multiplexing (O-OFDM) systems based on the fast Hartley transform (FHT). The performance of DD O-OFDM systems is limited by the constraints on system components such as digital-to-analog converter (DAC), analog-to-digital converter (ADC), the Mach-Zehnder modulator (MZM) and electrical amplifiers. In this paper, in order to relax the constraints on these components, we propose to symmetrically clip the transmitted signal and apply low complexity (LC) distortionless PAPR reduction schemes able to mitigate, at the same time, PAPR, quantization and clipping noise. We demonstrate that, applying LC-selective mapping (SLM) without any additional transform block, the PAPR reduction is 1.5dB with only one additional FHT block using LC-partial transmit sequence (PTS) with random partitions; up to 3.1dB reduction is obtained. Moreover, the sensitivity performance and the power efficiency are enhanced. In fact, applying LC PAPR reduction techniques with one additional transform block and a 6 bit DAC resolution, the required receiver power for 8 dB clipping level and for a 10-3BER is reduced by 5.1dB. © 2014 Elsevier Inc. All rights reserved.

    We present different distortionless peak-to-average power ratio (PAPR) reduction techniques that can be easily applied, without any symmetry restriction, in direct-detection (DD) optical orthogonal frequency division multiplexing (O-OFDM) systems based on the fast Hartley transform (FHT). The performance of DD O-OFDM systems is limited by the constraints on system components such as digital-to-analog converter (DAC), analog-to-digital converter (ADC), the Mach-Zehnder modulator (MZM) and electrical amplifiers. In this paper, in order to relax the constraints on these components, we propose to symmetrically clip the transmitted signal and apply low complexity (LC) distortionless PAPR reduction schemes able to mitigate, at the same time, PAPR, quantization and clipping noise. We demonstrate that, applying LC-selective mapping (SLM) without any additional transform block, the PAPR reduction is 1.5dB with only one additional FHT block using LC-partial transmit sequence (PTS) with random partitions; up to 3.1dB reduction is obtained. Moreover, the sensitivity performance and the power efficiency are enhanced. In fact, applying LC PAPR reduction techniques with one additional transform block and a 6 bit DAC resolution, the required receiver power for 8 dB clipping level and for a 10-3BER is reduced by 5.1dB. © 2014 Elsevier Inc. All rights reserved.

  • Finding an objective cost for sliceable flexgrid transponders

     Velasco Esteban, Luis; Gonzalez de Dios, Oscar; López, Victor; Fernández-Palacios, Juan Pedro; Junyent Giralt, Gabriel
    Optical Fiber Communication Conference and Exposition and National Fiber Optic Engineers Conference
    Presentation's date: 2014
    Presentation of work at congresses

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    We analyze the objective cost of SBVTs as a function of the traffic conveyed by IP/MPLS-over-flexgrid networks. Optimal results show that cost increment with respect to BVTs is related to the aggregation level.

  • Experimental assessment of a high performance back-end PCE for Flexgrid optical network re-optimization

     Gifre Renom, Lluis; Velasco Esteban, Luis; Navarro Mas, Nacho; Junyent Giralt, Gabriel
    Optical Fiber Communication Conference and Exposition and National Fiber Optic Engineers Conference
    Presentation's date: 2014-03
    Presentation of work at congresses

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    A specialized high performance Graphics Processing Unit (GPU)-based back-end Path Computation Element (PCE) to compute re-optimization in Flexgrid networks is presented. Experimental results show 6x speedups compared to single centralized PCE.

    A specialized high performance Graphics Processing Unit (GPU)-based back-end Path Computation Element (PCE) to compute re-optimization in Flexgrid networks is presented. Experimental results show 6x speedups compared to single centralized PCE.

  • Decomposed radio access network over deployed passive optical networks using coherent optical OFDM transceivers

     Fabrega Sanchez, Josep Maria; Svaluto Moreolo, Michela; Chochol, Marcin; Junyent Giralt, Gabriel
    Journal of optical communications and networking
    Date of publication: 2013-04-04
    Journal article

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    In this paper, it is proposed to take advantage of the deployed passive optical network (PON) infrastructure by overlaying a decomposed radio access network (RAN) using a very dense WDM. Coherent optical orthogonal frequency-division multiplexing technology is investigated for achieving the desired narrow channel spacings while minimizing the impact on the performance of legacy equipment. A practical implementation is evaluated using simulations. Within the analyzed configurations, a trade-off is found between time-division multiplexed (TDM)-PON and RAN performance. The optimum balance is found for additional losses in the TDM-PON path of less than 1 dB, ensuring simultaneous service to a maximum of 145 metro cells together with the PON customers and within a reach of 24 km.

    In this paper, it is proposed to take advantage of the deployed passive optical network (PON) infrastructure by overlaying a decomposed radio access network (RAN) using a very dense WDM. Coherent optical orthogonal frequency-division multiplexing technology is investigated for achieving the desired narrow channel spacings while minimizing the impact on the performance of legacy equipment. A practical implementation is evaluated using simulations. Within the analyzed configurations, a trade-off is found between time-division multiplexed (TDM)-PON and RAN performance. The optimum balance is found for additional losses in the TDM-PON path of less than 1 dB, ensuring simultaneous service to a maximum of 145 metro cells together with the PON customers and within a reach of 24 km.

  • Saving CAPEX by extending flexgrid-based core optical networks toward the edges

     Velasco Esteban, Luis; Wright, Paul; Lord, Andrew; Junyent Giralt, Gabriel
    Journal of optical communications and networking
    Date of publication: 2013-10
    Journal article

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    National IP/multiprotocol label switching (MPLS) networks have been designed using a multilayer approach to take advantage of the optical layer¿s longer reach. In that approach, the IP/MPLS layer performs routing and flow aggregation, whereas the optical layer, based on wavelength division multiplexing technology, transports those aggregated flows into optical connections. However, the flexgrid technology, featuring a finer granularity, also allows the performance of grooming at the optical layer, and hence, the aggregation level of the incoming flows can be reduced. Taking advantage of that fact, in this paper we propose a new network architecture consisting of a number of IP/MPLS areas performing routing and aggregating flows to the desired level and a flexgrid-based core network connecting the areas among them. A two-step procedure to design the whole network is presented where locations are first partitioned into a set of areas, and then each area network and the flexgrid core is designed separately. Mixed-integer linear programming models are developed for the resulting optimization problems. Solving these models, however, becomes impractical for real-sized scenarios so evolutionary heuristics based on the biased random-key genetic algorithm framework are also proposed. Extending the core toward the edges results in significant savings in both the core and IP/MPLS networks.

  • Designing national IP/MPLS networks with flexgrid optical technology

     Velasco Esteban, Luis; Wright, Paul; Lord, Andrew; Junyent Giralt, Gabriel
    Optics express
    Date of publication: 2013-02
    Journal article

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  • Dynamic restoration in multi-layer IP/MPLS-over-flexgrid networks

     Castro Casales, Alberto; Velasco Esteban, Luis; Comellas Colome, Jaume; Junyent Giralt, Gabriel
    Design of Reliable Communication Networks (DRCN)
    Presentation's date: 2013-03
    Presentation of work at congresses

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    The recent advances in photonic technology will allow deploying flexgrid-based optical core networks in the near future. Although that technology favors more efficient spectrum utilization, multilayer IP/MPLS-over-flexgrid networks would still be needed to groom together client flows, coming from access and metro networks, into optical connections. In this scenario, multi-flow transponders (MF-TPs) will provide additional flexibility allowing reconfiguration of optical connections to be performed. To be operated, a distributed control plane together with a centralized Path Computation Element (PCE) could be used. In the event of a failure, tens or hundreds of client flows could become disconnected and thus, restoration routes need to be found by the PCE for these flows. In standard restoration, path computation for each client flow is performed which derives into resource contention as a result of several connections trying to use some common resources, and poor resource utilization as a result of the reduction of grooming levels. In this paper, we deal with these problems and solve the DYNamic restorAtion in Multi-layer IP/MPLS-over-flexgrid Optical networks (DYNAMO) problem. Client flows' restoration requests are grouped into a single bulk in the PCE. Afterwards, a Global Concurrent Optimization (GCO) module solves the DYNAMO problem finding routes for all the flows in the bulk. The DYNAMO problem is modeled by using mathematical programming. However, as a consequence of its complexity and the stringent times within which the problem has to be solved, a GRASP-based heuristic is used. Exhaustive simulation results performed on two national core topologies show that a PCE with a GCO module solving DYNAMO highly improves restorability and reduces remarkably the number and capacity of MF-TPs, at the expense of some increment in restoration times.

    The recent advances in photonic technology will allow deploying flexgrid-based optical core networks in the near future. Although that technology favors more efficient spectrum utilization, multilayer IP/MPLS-over-flexgrid networks would still be needed to groom together client flows, coming from access and metro networks, into optical connections. In this scenario, multi-flow transponders (MF-TPs) will provide additional flexibility allowing reconfiguration of optical connections to be performed. To be operated, a distributed control plane together with a centralized Path Computation Element (PCE) could be used. In the event of a failure, tens or hundreds of client flows could become disconnected and thus, restoration routes need to be found by the PCE for these flows. In standard restoration, path computation for each client flow is performed which derives into resource contention as a result of several connections trying to use some common resources, and poor resource utilization as a result of the reduction of grooming levels. In this paper, we deal with these problems and solve the DYNamic restorAtion in Multi-layer IP/MPLS-over-flexgrid Optical networks (DYNAMO) problem. Client flows' restoration requests are grouped into a single bulk in the PCE. Afterwards, a Global Concurrent Optimization (GCO) module solves the DYNAMO problem finding routes for all the flows in the bulk. The DYNAMO problem is modeled by using mathematical programming. However, as a consequence of its complexity and the stringent times within which the problem has to be solved, a GRASP-based heuristic is used. Exhaustive simulation results performed on two national core topologies show that a PCE with a GCO module solving DYNAMO highly improves restorability and reduces remarkably the number and capacity of MF-TPs, at the expense of some increment in restoration times.

  • Adaptive bit loading in FHT-based OFDM transponders for flexi-grid optical networks

     Vila Nadal, Laia; Svaluto Moreolo, Michela; Fàbrega, Josep Maria; Junyent Giralt, Gabriel
    International Conference on Transparent Optical Networks
    Presentation's date: 2013
    Presentation of work at congresses

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    In this paper, we propose to use adaptive bit loading (BL) in OFDM transponders based on the fast Hartley transform (FHT) for flexi-grid optical networks. A direct-detection (DD) optical system is implemented and a double-side band (DSB) signal with reduced guard band is transmitted for cost-sensitive applications. Different bit loading schemes are analysed to obtain a net data rate of 10 Gb/s for a maximum link of 120 km, occupying only one slot of 12.5 GHz or two slots of 6.25 GHz, according to the proposed spectrum sliced optical path network (SLICE) architecture.

  • Digitally processed modulation formats and integrated photonics for flexible optical metro-access networks

     Lazaro Villa, Jose Antonio; Schrenk, Bernhard; Malligaraj, M.; Cano Valadez, Ivan Nicolas; Parra, M.; Sridharan, Madanagurusamy; Junyent Giralt, Gabriel
    International Conference on Transparent Optical Networks
    Presentation's date: 2013-06-23
    Presentation of work at congresses

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    Digitally processed modulations formats such as Nyquist-WDM are investigated for implementation of future flexible optical networks, by using integrated photonic devices and moderate speed optoelectronics. We compare with other modulation formats as OFDM regarding complexity and adaptability to transceiver limitations.

  • Phase modulated optical OFDM upstream with IM/DD downstream for full-duplex 10 Gb/s bidirectional transmission over a single wavelength with a reflective SOA

     Fàbrega, Josep Maria; Chochol, Marcin; Svaluto Moreolo, Michela; Lazaro Villa, Jose Antonio; Junyent Giralt, Gabriel
    International Conference on Transparent Optical Networks
    Presentation's date: 2013-06
    Presentation of work at congresses

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    The feasibility of a phase modulated optical OFDM upstream transmission employing IM/DD downstream for achieving a bidirectional transmission with symmetric data rate of 10 Gb/s over a single wavelength is investigated for a passive optical access network scenario. Upstream modulation is performed using a reflective semiconductor amplifier, and coherent detection is employed at the central office. The system performance is assessed in terms of transmission distance and possible back-reflections.

    The feasibility of a phase modulated optical OFDM upstream transmission employing IM/DD downstream for achieving a bidirectional transmission with symmetric data rate of 10 Gb/s over a single wavelength is investigated for a passive optical access network scenario. Upstream modulation is performed using a reflective semiconductor amplifier, and coherent detection is employed at the central office. The system performance is assessed in terms of transmission distance and possible back-reflections.

  • Bandwidth variable transponders based on OFDM technology for elastic optical networks

     Svaluto Moreolo, Michela; Fàbrega, Josep Maria; Vila Nadal, Laia; Vilchez, Francisco Javier; Junyent Giralt, Gabriel
    International Conference on Transparent Optical Networks
    Presentation's date: 2013
    Presentation of work at congresses

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    n this paper, the flexible features of bandwidth variable transponders based on OFDM technology are investigated. The limiting factors due to the subsystem components and the trade-off between cost-effectiveness, capacity and reach are taken into account for designing this fundamental building block of elastic optical networks. Advanced functionalities, including sliceability, are discussed. Performance is analysed by means of numerical simulations. Furthermore, the experimental results, achieved within the EOS platform (Experimental platform for Optical OFDM Systems) of the ADRENALINE testbed, are presented.

  • A traffic intensity model for flexgrid optical network planning under dynamic traffic operation

     Ruiz Ramírez, Marc; Velasco Esteban, Luis; Comellas Colome, Jaume; Junyent Giralt, Gabriel
    Optical Fiber Communication Conference and Exposition and National Fiber Optic Engineers Conference
    Presentation's date: 2013-03
    Presentation of work at congresses

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    We obtain a model to estimate the highest traffic intensity that a flexgrid-based network can support in dynamic scenarios. A design problem is introduced to illustrate its application. Numerical results validate both accuracy and utility.

  • Global concurrent optimization: advantages and opportunities in flexgrid-based networks

     Castro Casales, Alberto; Velasco Esteban, Luis; Comellas Colome, Jaume; Junyent Giralt, Gabriel
    International Conference on Transparent Optical Networks
    Presentation's date: 2013-06
    Presentation of work at congresses

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    In future flexgrid core networks the amount of lightpaths might increase significantly as a consequence of the finer granularity in the use of the optical spectrum. Different spectrum bandwidth can be allocated to each lightpath as a function of, among others, the bitrate amount to be conveyed and the modulation format used. As result, spectrum fragmentation might appear leading to non-optimal resource utilization. In addition, a failure in a fibre link could trigger hundreds, or even thousands, of path computations requests to a centralized Path Computation Element (PCE). Latter examples can benefit from using the recently standardized Global Concurrent Optimization (GCO), which enhances PCE's computation capabilities. In this paper we present two opportunities to take advantage of the PCE+GCO architecture: spectrum defragmentation and restoration.

  • Access to the full text
    How national IP/MPLS networks can benefit from flexgrid optical technology?  Open access

     Velasco Esteban, Luis; Wright, Paul; Lord, Andrew; Junyent Giralt, Gabriel
    Optical Fiber Communication Conference and Exposition and National Fiber Optic Engineers Conference
    Presentation's date: 2013-03
    Presentation of work at congresses

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    We design a 1113-node network and show that the optimum is a large Flexgrid core serving small metro areas. Cost savings of about 31% in the core and 23% in the metro are shown

    We design a 1113-node network and show that the optimum is a large Flexgrid core serving small metro areas. Cost savings of about 31% in the core and 23% in the metro are shown.

  • Strategies for virtual optical network allocation

     Pages Cruz, Albert; Perello Muntan, Jordi; Spadaro, Salvatore; Junyent Giralt, Gabriel
    IEEE communications letters
    Date of publication: 2012-02
    Journal article

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  • Statistical approach for fast impairment-aware provisioning in dynamic all-optical networks

     Velasco Esteban, Luis; Jirattigalachote, Amo; Ruiz Ramírez, Marc; Monti, Paolo; Wosinska, Lena; Junyent Giralt, Gabriel
    Journal of optical communications and networking
    Date of publication: 2012-02
    Journal article

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  • Enhanced Optical Networks Featuring Adaptable and Highly Scalable Multi-granular Transport Services (ELASTIC) - TEC2011-27310

     Junyent Giralt, Gabriel; Spadaro, Salvatore; Comellas Colome, Jaume; Gené Bernaus, Joan M.; Velasco Esteban, Luis; Perello Muntan, Jordi; Conesa Fernandez, Josep; Agraz Bujan, Fernando; Ruiz Ramírez, Marc; Hernandez Sola, Guillem; Pages Cruz, Albert; Khodashenas, Pooria Saiyad
    Participation in a competitive project

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  • Industry-Driven Elastic and Adaptive Lambda Infrastructure for Service and Transport Networks

     Ruiz Ramírez, Marc; Castro Casales, Alberto; Comellas Colome, Jaume; Junyent Giralt, Gabriel; Gifre Renom, Lluis; Velasco Esteban, Luis
    Participation in a competitive project

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  • Enhanced optical networks featuring adaptable and highly scalable multi-granular transport services

     Ruiz Ramírez, Marc; Junyent Giralt, Gabriel; Comellas Colome, Jaume; Gené Bernaus, Joan M.; Conesa Fernandez, Josep; Velasco Esteban, Luis; Perello Muntan, Jordi; Agraz Bujan, Fernando; Hernandez Sola, Guillem; Pages Cruz, Albert; Khodashenas, Pooria Saiyad; Spadaro, Salvatore
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  • Low complexity bit rate variable transponders based on optical OFDM with PAPR reduction capabilities

     Nadal Reixats, Laia; Svaluto Moreolo, Michela; Fabrega Sanchez, Josep Maria; Junyent Giralt, Gabriel
    European Conference on Networks and Optical Communications
    Presentation's date: 2012
    Presentation of work at congresses

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    In this paper, we propose low complexity bit rate variable transponders for adaptive DC biased Optical OFDM systems. The transponders are based on an alternative transform, the fast Hartley transform (FHT), and use adaptively modulated O-OFDM (AMO-OFDM) to introduce flexibility to optical networks. Additionally, low complexity selective mapping (LC-SLM) technique is included in the bit rate variable transponders to mitigate the effects of the peak-to-average power ratio (PAPR)and reduce the clipping noise, enabling the use of low bias values.

  • Path-based recovery in flexgrid optical networks

     Castro Casales, Alberto; Ruiz Ramírez, Marc; Velasco Esteban, Luis; Junyent Giralt, Gabriel; Comellas Colome, Jaume
    International Conference on Transparent Optical Networks
    Presentation's date: 2012
    Presentation of work at congresses

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    With the advent of flexgrid optical networks, the rigid wavelength-division multiplexing (WDM) technology will be enhanced by providing better spectrum efficiency and flexibility. In those future flexible optical networks, optical connections (lightpaths) can allocate a flexible number of spectrum slices, also known as frequency slots, so to match better with its requested bitrate. In this paper, we propose to take advantage of this flexible spectrum allocation in recovery mechanisms to be triggered when a failure occurs to provide recovery of part of the requested bitrate, i.e. the allocated spectrum by backup lightpaths could be lower than that of the working lightpaths provided that client service level agreements are fulfilled. This reduction in the recovered bitrate (bitrate squeezing) allows optimizing the use of network capacity. We propose path-based recovery alternatives, based on protection and restoration, specially designed for flexgrid networks. The performance of the proposed recovery mechanisms is exhaustively evaluated on a national reference network

  • Elastic spectrum allocation for variable traffic in flexible-grid optical networks

     Velasco Esteban, Luis; Klinkowski, Miroslaw; Ruiz Ramírez, Marc; López Álvarez, Victor; Junyent Giralt, Gabriel
    Optical Fiber Communication Conference and Exposition and National Fiber Optic Engineers Conference
    Presentation's date: 2012-03
    Presentation of work at congresses

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  • Access to the full text
    CAPEX study for grid dependent multi-layer IP/MPLS-over-EON using relative BV-WSS costs  Open access

     Pedrola Escriba, Oscar; Velasco Esteban, Luis; Fernández-Palacios, Juan Pedro; Castro Casales, Alberto; Careglio, Davide; Junyent Giralt, Gabriel
    Optical Fiber Communication Conference and Exposition and National Fiber Optic Engineers Conference
    Presentation's date: 2012-03
    Presentation of work at congresses

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    The impact of the frequency grid on the CAPEX required to deploy a multi-layer IP/MPLS-over-EON is analyzed. Results showing significant savings at the electronic layer motivate the introduction of narrower grids with enhanced BV-WSS.

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    Designing national IP/MPLS networks with flexgrid optical technology  Open access

     Velasco Esteban, Luis; Wright, Paul; Lord, Andrew; Junyent Giralt, Gabriel
    European Conference and Exhibition on Optical Communication
    Presentation's date: 2012-09
    Presentation of work at congresses

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    We propose a two-step procedure to design flexgrid-based national networks. Locations are first partitioned into a set of metro areas interconnected through a flexgrid optical network. Next, each network is designed separately. Optimal results show a future large (>200 nodes) flexgrid core network inter-connecting small (~10 nodes) metro regions.

  • Optical filter cascading effects in a phase modulated coherent optical OFDM transmission system based on Hartley transform

     Chochol, Marcin; Fàbrega, Josep Maria; Svaluto Moreolo, Michela; Junyent Giralt, Gabriel
    International Conference on Transparent Optical Networks
    Presentation's date: 2012
    Presentation of work at congresses

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    Effects of cascading optical filters are investigated for a phase modulated coherent optical OFDM system based on Hartley transform. The evaluation is performed by means of numeric simulations in a 10 Gb/s system with a total bandwidth of 10 GHz. First a back-to-back (no fiber) case is assessed. Results show a 3 dB power penalty after a single filter of only 68% of the signal bandwidth. The same penalty is achieved when cascading 10 filters of 21.6 GHz bandwidth. Additionally, the penalties associated to the introduction of fiber spans between filters are investigated.

    Effects of cascading optical filters are investigated for a phase modulated coherent optical OFDM system based on Hartley transform. The evaluation is performed by means of numeric simulations in a 10 Gb/s system with a total bandwidth of 10 GHz. First a back-to-back (no fiber) case is assessed. Results show a 3 dB power penalty after a single filter of only 68% of the signal bandwidth. The same penalty is achieved when cascading 10 filters of 21.6 GHz bandwidth. Additionally, the penalties associated to the introduction of fiber spans between filters are investigated.

  • WDM overlay of distributed base stations in deployed passive optical networks using coherent optical OFDM transceivers

     Fàbrega, Josep Maria; Svaluto Moreolo, Michela; Chochol, Marcin; Junyent Giralt, Gabriel
    International Conference on Transparent Optical Networks
    Presentation's date: 2012-07-05
    Presentation of work at congresses

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    It is proposed to reuse the deployed PON infrastructure by overlaying distributed radio base stations by means of very dense WDM with narrow channel spacings. In order to cope with that while minimizing its impact onto the performance of legacy equipment, coherent optical OFDM technology is used. Furthermore, the case of a practical implementation using CPRI is analyzed by means of simulations for several use cases. Within the analyzed use cases, a rural PON with 50 km reach has proven to support splitting ratios of up to 32 users, whereas an urban radio access network has been demonstrated to support ratios of up to 256 users within a radius of 2 km.

  • Enhanced domain disjoint backward recursive TE path computation for PCE-based multi-domain networks

     Hernandez Sola, Guillem; Perello Muntan, Jordi; Agraz Bujan, Fernando; Velasco Esteban, Luis; Spadaro, Salvatore; Junyent Giralt, Gabriel
    Photonic network communications
    Date of publication: 2011-04
    Journal article

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    The ability of computing optimal routes poses new challenges when extending it to larger multi-domain network scenarios, as the quality of these computed endto-end inter-domain routes depends on the selection of the domain sequence to be traversed. In the scope of the Internet Engineering Task Force (IETF), the Path Computation Element (PCE) Working Group has not provided definitive solutions to address the domain sequence selection problem, being still a work in progress. To this goal, the Path Computation Flooding (PCF) approach appears as a possible extension to Backward Recursive PCE-based Computation (BRPC) to calculate optimal end-to-end inter-domain paths without requiring a pre-configured domain sequence. Nonetheless, PCF presents major scalability issues in terms of network control overhead and path computation complexity, thus pleading for more accurate domain sequence selection techniques. This paper describes two novel mechanisms to establish inter-domain paths calculating the sequence of domains to be crossed when it is not known in advance. Both procedures make a good trade-off between the control overhead introduced and the accuracy of the computed end-to-end route. The obtained simulation results show the benefits of the proposed contributions, drastically reducing the control overhead while keeping the connection blocking probability close to the optimal values.

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    Survivable IP/MPLS-Over-WSON multilayer network optimization  Open access

     Ruiz Ramírez, Marc; Pedrola Escriba, Oscar; Velasco Esteban, Luis; Careglio, Davide; Fernández Palacios, Juan Pedro; Junyent Giralt, Gabriel
    Journal of optical communications and networking
    Date of publication: 2011-08-01
    Journal article

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    Network operators are facing the problem of dimensioning their networks for the expected huge IP traffic volumes while keeping constant or even reducing the connectivity prices. Therefore, new architectural solutions able to cope with the expected traffic increase in a more cost-effective way are needed. In this work, we study the survivable IP/multi-protocol label switching (MPLS) over wavelength switched optical network (WSON) multilayer network problem as a capital expenditure (CAPEX) minimization problem. Two network approaches providing survivability against optical links, IP/MPLS nodes, and opto-electronic port failures are compared: the classical overlay approach where two redundant IP/MPLS networks are deployed, and the new joint multilayer approach which provides the requested survivability through an orchestrated interlayer recovery scheme which minimizes the over-dimensioning of IP/MPLS nodes. Mathematical programming models are developed for both approaches. Solving these models, however, becomes impractical for realistic networks. In view of this, evolutionary heuristics based on the biased random-key genetic algorithm framework are also proposed. Exhaustive experiments on several reference network scenarios illustrate the effectiveness of the proposed approach in minimizing network CAPEX.

  • GMPLS control plane network design with resilience guarantees

     Ruiz Ramírez, Marc; Perello Muntan, Jordi; Velasco Esteban, Luis; Spadaro, Salvatore; Comellas Colome, Jaume; Junyent Giralt, Gabriel
    Journal of lightwave technology
    Date of publication: 2011-01-01
    Journal article

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    A one-to-one association between data and control channels has traditionally existed in transport networks. Being the control plane embedded in the data plane, the design of the former, as well as its resilience, has been addressed in the latter’s one. However, a main GMPLS architectural requirement is to provide a clean separation between control and data planes. In this sense, the control plane in GMPLS networks may describe a different topology than the data plane, even realized over a separated IP network. As a consequence of this, data and control network design become no more linked in such scenarios. To the best of our knowledge, no works in the literature have addressed an independent design of the control plane in GMPLS-enabled networks regardless of the data plane. In this paper, we provide a method to obtain the optimal GMPLS control plane design, minimizing the network Capital Expenditures (CAPEX) while matching specific resilience requirements. To this goal, the problem of finding an optimal control plane topology that ensures a certain resilience level is formulated as a non-linear combinatorial model. This model, however, does not scale properly for large backbone networks. In view of this, a constructive linear method is also presented and its optimality validated through simulations on several reference network scenarios. Furthermore, its benefits in terms of total execution time are also highlighted.

  • InvestigaCión y desArrollo de módulos de monitorizacióN permanente (7x24) de

     Junyent Giralt, Gabriel
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  • Future Internet testbeds/experimentation between BRazil and Europe - EU

     Junyent Giralt, Gabriel; Perello Muntan, Jordi; Spadaro, Salvatore
    Participation in a competitive project

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  • Scalable hybrid path computation procedure for PCE-based multi-domain WSON networks

     Hernandez Sola, Guillem; Perello Muntan, Jordi; Agraz Bujan, Fernando; Spadaro, Salvatore; Comellas Colome, Jaume; Junyent Giralt, Gabriel
    International Conference on Transparent Optical Networks
    Presentation's date: 2011
    Presentation of work at congresses

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    In the Hierarchical Path Computation Element (H-PCE) architecture, an optimum end-to-end path is computed using a hierarchical relationship among PCEs. An H-PCE-based path computation procedure provides low network blocking probability meanwhile it results on a great amount of control overhead messages. In this paper we propose a hybrid path computation procedure based on the H-PCE architecture and the Backward Recursive PCE-Based Computation (BRPC). Extensive simulation results show that the proposed approach performs better than H-PCE in terms of network control overhead.

  • Optical network net present value optimization in shared path protection environments

     Ruiz Ramírez, Marc; Velasco Esteban, Luis; Comellas Colome, Jaume; Junyent Giralt, Gabriel
    Design of Reliable Communication Networks
    Presentation's date: 2011-10-10
    Presentation of work at congresses

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    Network operators are facing hard competition for opportunities in the telecommunications market, thus network investments must be carefully evaluated from the costs and revenues viewpoint before the decision making process. Since a great part of core network operators’ revenues comes from the provisioned connectivity services, in this work we study the value expected to generate by optical networks when provisioning differentiated services in Shared Path Protection (SPP) environments. In this regard, two wavelength partitioning schemes are compared: the shared (sh-WS) and the differentiated (diff-WS). The benefits of both schemes are evaluated from an economic perspective defining costs and revenues models and using Net Present Value (NPV). We define the Optical Network NPV Optimization (OVALO) problem as a NPV maximization problem. To solve OVALO, a linearized version of NPV is proposed as objective function of the Integer Linear Programming (ILP) model and an iterative algorithm is used to finally solve OVALO. The partitioning schemes are numerically compared on two network topologies. From the results, we show that diff-WS maximizes resource utilization in the network without significantly increasing network costs, thus maximizing the network’s value.

  • A GRASP-based heuristic to design the GMPLS control plane network topology with resilience guarantees

     Ruiz Ramírez, Marc; Velasco Esteban, Luis; Junyent Giralt, Gabriel; Comellas Colome, Jaume
    International Conference on Transparent Optical Networks
    Presentation's date: 2011-06-28
    Presentation of work at congresses

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    The control plane topology has traditionally followed that of the data plane and therefore the design of the former, as well as its resilience, has been addressed in the latter's one. Owing to the fact that a clear separation between control and data planes is a main GMPLS architectural requirement, the control plane in GMPLS networks may describe a different topology than the data plane, even realized over a separated IP network. As a consequence of this, data and control network design become no more linked in such scenarios. In this paper, we design a heuristic algorithm to obtain the optimal GMPLS control plane design, minimizing the network Capital Expenditures (CAPEX) while matching specific resilience requirements. The performance of the heuristic algorithm is compared with exact solutions obtained by solving an Integer Linear Programming (ILP) model on several reference network scenarios. Furthermore, its benefits in terms of total execution time are also highlighted.

  • Scalable hybrid path computation procedure for PCE-based

     Hernandez Sola, Guillem; Perello Muntan, Jordi; Agraz Bujan, Fernando; Spadaro, Salvatore; Comellas Colome, Jaume; Junyent Giralt, Gabriel
    International Conference on Transparent Optical Networks
    Presentation's date: 2011-06-27
    Presentation of work at congresses

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  • A feedback-based hybrid OBS/OCS architecture with fast-over-slow capability

     Khodashenas, Pooria Saiyad; Perello Muntan, Jordi; Spadaro, Salvatore; Comellas Colome, Jaume; Junyent Giralt, Gabriel
    International Conference on Optical Network Design and Modeling
    Presentation's date: 2011-02-08
    Presentation of work at congresses

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  • NORMA: Network Operator Revenues Maximization

     Velasco Esteban, Luis; Ruiz Ramírez, Marc; Comellas Colome, Jaume; Junyent Giralt, Gabriel
    International Conference on Transparent Optical Networks
    Presentation's date: 2011-05-27
    Presentation of work at congresses

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    A great part of core network operators’ gross profit comes from the provisioned connectivity services. In this work, we analyze the provisioning of differentiated services in current Shared Path Protection (SPP) environments. This analysis concludes that, with current resource assignment policies, only a very poor grade of service can be provided to the carried best effort traffic. Hence, we propose diff-WS, a resource partitioning scheme that differentiates those wavelengths supporting each class of service in the network. The benefits of diff-WS in front of current resource assignment policies are afterwards evaluated from an economic perspective. To this goal, we define the NORMA problem as a revenue maximization problem. To solve NORMA, we introduce statistical models to obtain, for a given grade of service, the highest traffic intensity for each supported class of service and resource assignment scheme. From the numerical results, we show that diff-WS maximizes resource utilization in the network and, thus, network operator’s profit.

  • Access to the full text
    Novel power efficient optical OFDM based on Hartley transform for intensity-modulated direct-detection systems  Open access

     Svaluto Moreolo, Michela; Muoz, R.; Junyent Giralt, Gabriel
    Journal of lightwave technology
    Date of publication: 2010-03
    Journal article

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    We present a novel optical orthogonal frequency division multiplexing (O-OFDM) scheme, suitable for intensity-modulated direct-detection systems, where the modulation/demodulation processing takes advantage of the fast Hartley transform algorithm. Due to the properties of the discrete Hartley transform (DHT), the conventional transmission scheme can be streamlined. We demonstrate that asymmetrically clipping (AC) technique can also be applied to DHT-based OFDM; the signal can be transmitted without the need of a DC bias, resulting in a power-efficient system, not affected by clipping noise. Hermitian symmetry is not required for the input signal. Therefore, this technique supports the double of input symbols compared to both AC and DC-biased O-OFDM, based on standard Fourier processing. The analysis in an additive white Gaussian noise channel shows that the same performance can be achieved by replacing 4, 16, and 64 QAM (quadrature-amplitude modulation) AC optical-OFDM with a simpler system based on DHT, using binary phase-shift keying (BPSK), 4 and 8 PAM (pulse-amplitude modulation), respectively.

    We present a novel optical orthogonal frequency division multiplexing (O-OFDM) scheme, suitable for intensity-modulated direct-detection systems, where the modulation/demodulation processing takes advantage of the fast Hartley transform algorithm. Due to the properties of the discrete Hartley transform (DHT), the conventional transmission scheme can be streamlined. We demonstrate that asymmetrically clipping (AC) technique can also be applied to DHT-based OFDM; the signal can be transmitted without the need of a DC bias, resulting in a power-efficient system, not affected by clipping noise. Hermitian symmetry is not required for the input signal. Therefore, this technique supports the double of input symbols compared to both AC and DC-biased O-OFDM, based on standard Fourier processing. The analysis in an additive white Gaussian noise channel shows that the same performance can be achieved by replacing 4, 16, and 64 QAM (quadrature-amplitude modulation) AC optical-OFDM with a simpler system based on DHT, using binary phase-shift keying (BPSK), 4 and 8 PAM (pulse-amplitude modulation), respectively.

  • GMPLS-based multidomain restoration: analysis, strategies, policies and experimental assessment

     Velasco Esteban, Luis; Agraz Bujan, Fernando; Martínez, Ricardo; Casellas, Ramón; Spadaro, Salvatore; Muñoz González, Raul; Junyent Giralt, Gabriel
    Journal of optical communications and networking
    Date of publication: 2010-07-01
    Journal article

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    A connection spanning, for example, several countries crosses multiple optical backbone networks, each one controlled by different administrators or operators. In this context, the interworking of these networks is thus necessary to set up end-to-end optical connections. A key issue when delivering such optical services is the use of efficient and fast restoration strategies to recover a connection disruption. To this end, there are several issues and policies that a network operator should address, such as interdomain failure information exchange and the point of repair (PoR) placement problem. Upon a failure’s occurrence, exchanging interdomain failure information results is essential to attain both an efficient use of the network resources (i.e., wavelength channels) and a fast restoration time. In this regard, within the GMPLS (Generalized Multi-Protocol Label Switching) framework, interdomain information exchange remains unstandardized. Three network operator policies are proposed to yield different restoration mechanisms according to different interdomain failure exchanges. Additionally, three PoR strategies are pointed out and are qualitatively compared. Finally, selected policies and restoration strategies are experimentally validated and compared in terms of the restoration time. Experiments have been carried out over a multidomain optical network infrastructure connecting the GMPLS-based control planes of the UPC CARISMA and the CTTC ADRENALINE test beds.

  • Using updated neighbor state information for efficient contention avoidance in OBS networks

     Perello Muntan, Jordi; Agraz Bujan, Fernando; Spadaro, Salvatore; Comellas Colome, Jaume; Junyent Giralt, Gabriel
    Computer communications
    Date of publication: 2010-01
    Journal article

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  • Trigonometric transforms for high-speed optical networks: all-optical architectures and optical OFDM

     Svaluto Moreolo, Michela; Sacchieri, Valentina; Cincotti, Gabriella; Junyent Giralt, Gabriel
    Journal of networks
    Date of publication: 2010-11
    Journal article

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  • Deployment and validation of GMPLS-controlled multi-layer integrated routing over the ASON/GMPLS CARISMA test-bed

     Agraz Bujan, Fernando; Velasco Esteban, Luis; Perello Muntan, Jordi; Ruiz Ramírez, Marc; Spadaro, Salvatore; Junyent Giralt, Gabriel; Comellas Colome, Jaume
    Journal of networks
    Date of publication: 2010-11
    Journal article

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  • Scalable, Tunable and Resilient Optical Networks Guaranteeing Extremely-high Speed Transport

     Spadaro, Salvatore; Sole Pareta, Josep; Perello Muntan, Jordi; Careglio, Davide; Velasco Esteban, Luis; Junyent Giralt, Gabriel; Comellas Colome, Jaume
    Participation in a competitive project

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  • SILVIA

     Junyent Giralt, Gabriel
    Participation in a competitive project

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  • projecte GEYSERS

     Junyent Giralt, Gabriel; Spadaro, Salvatore; Comellas Colome, Jaume; Perello Muntan, Jordi
    Participation in a competitive project

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  • AJUT ICREA ACADEMIA 2010

     Junyent Giralt, Gabriel; Sallent Ribes, Sebastia; Mataix Oltra, Jorge; Alcober Segura, Jesus Angel; Rincon Rivera, David; Cervelló Pastor, Cristina; Paradells Aspas, Jose; Garcia Ojalvo, Jorge
    Participation in a competitive project

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  • Experimental UpdateLess Evolutive Routing

     Junyent Giralt, Gabriel; Comellas Colome, Jaume; Cabellos Aparicio, Alberto; Careglio, Davide; Perello Muntan, Jordi; Sole Pareta, Josep; Spadaro, Salvatore
    Participation in a competitive project

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