Browsing by Author "Raffaelli, C."

Now showing 1 - 8 of 8

Open Access
Analytical model of asynchronous shared-per-wavelength multi-fiber optical switch
(IEEE, 2011) Akar, Nail; Raffaelli, C.; Savi, M.
In this paper, a buffer-less shared-per-wavelength optical switch is equipped with multi-fiber interfaces and operated in asynchronous context. An analytical model to evaluate loss performance is proposed using an approximate Markov-chain based approach and the model is validated by simulations. The model is demonstrated to be quite accurate in spite of the difficulty in capturing correlation effects especially for small switch sizes. The model is also applied to calculate the number of optical components needed to design the optical switch according to packet loss requirements. The impact of the adoption of multiple fiber interfaces is outlined in terms of the remarkable saving in the number of wavelength converters employed, while increasing at the same time the number of optical gates needed by the space switching subsystem. The numerical results produced are a valuable basis to optimize overall switch cost. © 2011 IEEE.
Open Access
Comparative analysis of power consumption in asynchronous wavelength modular optical switching fabrics
(Elsevier, 2011-04-02) Akar, N.; Eramo, V.; Raffaelli, C.
Next-generation optical routers will be designed to support the flexibility required by Future Internet services and, at the same time, to overcome the power consumption bottleneck which appears to limit throughput scalability in today routers. A model to evaluate average power consumption in asynchronous optical switching fabrics is here presented to compare these architectures with other synchronous and asynchronous solutions. The combination of wavelength modular switching fabrics with low spatial complexity and asynchronous operation is demonstrated to be the most power-efficient solution among those considered which employ wavelength converters, through presentation and discussion of a thorough set of numerical results.
Open Access
Fixed point analysis of limited range share per node wavelength conversion in asynchronous optical packet switching systems
(Springer New York LLC, 2009) Akar, N.; Karasan, E.; Raffaelli, C.
In this article, we study an asynchronous optical packet switch equipped with a number of wavelength converters shared per node. The wavelength converters can be full range or circular-type limited range. We use the algorithmic methods devised for Markov chains of block-tridiagonal type in addition to fixed-point iterations to approximately solve this relatively complex system. In our approach, we also take into account the finite number of fiber interfaces using the Engset traffic model rather than the usual Poisson traffic modeling. The proposed analytical method provides an accurate approximation for full range systems for relatively large number of interfaces and for circular-type limited range wavelength conversion systems for which the tuning range is relatively narrow. © 2009 Springer Science+Business Media, LLC.
Open Access
Packet loss analysis of synchronous buffer-less optical switch with shared limited range wavelength converters
(IEEE, 2007) Raffaelli, C.; Savi, M.; Akar, Nail; Karasan, Ezhan
Application of synchronous optical switches in Optical Packet/Burst switched networks is considered. The shared per node architectural concept, where wavelength converters are shared among all input and output channels, is applied for contention resolution in the wavelength domain. A semi-analytical traffic model suitable to represent the different contributions to packet loss is proposed and validated. Full and limited range wavelength conversion capabilities are considered, and loss results obtained to support switch design. An approximated fully analytical approach for the limited range case is also described and comparison with simulation results is presented to assess the capability to capture the main aspects of packet loss behavior.
Open Access
Performance analysis of an optical packet switch employing full/limited range share per node wavelength conversion
(IEEE, 2007) Akar, Nail; Karasan, Ezhan; Muretto, G.; Raffaelli, C.
In this paper, we study an asynchronous optical packet switching node equipped with a number of limited range or full range wavelength converters shared per node. The packet traffic is realistically modeled by a superposition of a finite number of on-off sources as opposed to the traditional Poisson model which ignores the limited number of ports on a switch. We both study circular and non-circular limited range wavelength conversion schemes. In our simulations, we employ the far conversion policy where the optical packet is switched onto the farthest available wavelength in the tuning range, which is known to outperform the random conversion policy. We propose an approximate analytical method based on block tridiagonal Markov chains and fixed point iterations to solve for the blocking probabilities in share per node wavelength conversion systems. The method provides an accurate approximation for full range systems and acceptable results for limited range systems.
Open Access
Research in optical burst switching within the e-Photon/ONe network of excellence
(Elsevier BV, 2007) Aracil, J.; Akar, N.; Bjornstad, S.; Casoni, M.; Christodoulopoulos, K.; Careglio, D.; Palacios, J. F.; Gauger, C.; Dios, O. G.; Hu, G.; Karasan, E.; Klinkowski, M.; Morato, D.; Nejabati, R.; Overby, H.; Raffaelli, C.; Simeonidou, D.; Stol, N.; Tossi-Beleffi, G.; Vlachos, K.
This paper presents a summary of Optical Burst Switching (OBS) research within the VI framework program e-Photon/ONe network of excellence. The paper includes network aspects such as routing techniques, resilience and contention resolution, together with burst switch architectures. On the other hand, we also discuss traffic analysis issues, Quality of Service (QoS) schemes, TCP/IP over OBS and physical layer aspects for OBS.
Open Access
Research on optical core networks in the e-Photon/ONe network of excellence
(IEEE, 2006) Callegati, F.; Aracil, J.; Wosinska, L.; Andriolli, N.; Careglio, D.; Giorgetti, A.; Fdez-Palacios, J.; Gauger, C.; Klinkowski, M.; Gonzáles De Dios, O.; Hu, G.; Karasan, Ezhan; Matera, F.; Overby, H.; Raffaelli, C.; Rea, L.; Şengezer, Namık; Tornatore, M.; Vlachos, K.
This papers reports the advances in Optical Core networks research coordinated in the framework of the e-Photon/ONe and e-Photon/ONe+ networks of excellence.
Open Access
State aggregation-based model of asynchronous multi-fiber optical switching with shared wavelength converters
(Elsevier, 2013) Akar, N.; Raffaelli, C.; Savi, M.
This paper proposes new analytical models to study optical packet switching architectures with multi-fiber interfaces and shared wavelength converters. The multi-fiber extension of the recently proposed Shared-Per-Input-Wavelength (SPIW) scheme is compared against the multi-fiber Shared-Per-Node (SPN) scheme in terms of cost and performance for asynchronous traffic. In addition to using Markov chains and fixed-point iterations for modeling the mono-fiber case, a novel state aggregation technique is proposed to evaluate the packet loss in asynchronous multi-fiber scenario. The accuracy of the performance models is validated by comparison with simulations in a wide variety of scenarios with both balanced and imbalanced input traffic. The proposed analytical models are shown to remarkably capture the actual system behavior in all scenarios we tested. The adoption of multi-fiber interfaces is shown to achieve remarkable savings in the number of wavelength converters employed and their range. In addition, the SPIW solution allows to save, in particular conditions, a significant number of optical gates compared to the SPN solution. Indeed, SPIW allows, if properly dimensioned, potential complexity and cost reduction compared to SPN, while providing similar performance.