(IJACSA) International Journal of Advanced Computer Science and Applications, Vol. 7, No. 9, 2016 Multi- Spectrum Bands Allocation for Time-Varying Traffic in the Flexible Optical Network KAMAGATE Beman Hamidja Laboratoire de Recherche en Informatique et Télécommunication (LARIT) Ecole Doctorale Polytechnique de l’INP-HB Yamoussoukro, Côte d’Ivoire Michel BABRI Laboratoire de Recherche en Informatique et Télécommunication (LARIT) INPH-HB Yamoussoukro, Côte d’Ivoire GOORE Bi Tra Laboratoire de Recherche en Informatique et Télécommunication (LARIT ) INP-HB Yamoussoukro, Côte d’Ivoire Souleymane OUMTANAGA Laboratoire de Recherche en Informatique et Télécommunication (LARIT) INP-HB Yamoussoukro, Côte d’Ivoire Abstract—The flexible optical networks are the promising solution to the exponential increase of traffic generated by telecommunications networks. They combine flexibility with the finest granularity of optical resources. Therefore, the flexible optical networks position themselves as a better solution than conventional WDM network. In the operational phase, traffic of connections fluctuates. In fact, the user’s need is not the same during day periods. Such traffic may experiment evidence of rising working hours, end of months or years and decreases during the night or on holidays. This variation requires the expansion or contraction of the number of frequency slots allocated to a connection to match the exact needs of the moment. The expansion of the traffic around the reference frequency of connection may lead to blockage because it must share frequency slots with neighboring connections in compliance with the constraints of continuity, contiguity, and non-overlapping. In this study, we offer a technique for allocating frequency slots for time-varying traffic connections. We share out the additional traffic load on different spectrum paths by respecting the constraint of time synchronization related to the differential delay to reduce the blocking rate due to traffic fluctuation. Keywords—Spectrum band; Multi-spectrum bands; time- varying traffic; elastic optical network I. INTRODUCTION The flexible optical network constitutes an efficient alternative facing the exponential rise of traffic. It compensates for the shortcomings of conventional WDM network which are the rigidity of the frequency spectrum and ressources waste. Based on the Optical-Orthogonal Frequency Division Multiplexing (O-OFDM) technology, it provides a finer granularity and allows the use of several parallel subcarriers or frequency slots for transmitting the traffic of a connection from a source node to a destination node on a definite physical path. The set defined by subcarriers and the physical path is the optical channel or spectrum path. The bandwidth of the optical channel is the sum of bandwidth of adjacent frequency slots that form it. Each frequency slot with a bandwidth typically set to 12.5GHz. The number of frequency slots allocated to a connection depends on the flow of its traffic and transmission distance [1]. The allocation of frequency slots is subject to constraints. The first is the contiguity constraint, according to which frequency slots allocated to the same connection must be adjacent. The second constraint is the continuity of the frequency slots allocated to each link of the optical path, i.e., the utilization of the same frequency slots on all links which compose optical path, based on the assumption that there is no conversion. The last constraint is the constraint of non-overlapping, i.e.two different connections cannot simultaneously use the same frequency slots. The management of these constraints and the multiplicity of frequency slots is a challenge in the determination of optimal spectrum path for a connection. That problem of optimal spectrum allocation is an Integer Linear Program (ILP) problem optimization. It includes two aspects that are the determination of physical path from the source to the destination of the connection and the determination of the frequency slots on that physical path which respects the constraints of flexible optical networks. Besides, this problem known as Routing and Spectrum Allocation (RSA) is reckoned as np-hard [2]. It is an extension of the well-known RWA problem in the conventional WDM networks [3]. The resolution of this problem is even more complex in the case of dynamic traffic variables in time. In fact, the fluctuating traffic of connection leads to resource sharing problems with neighboring connections. One has to ensure that different connections do not simultaneously seek the same frequency slots because it can cause the rejection of the request. This paper aims to contribute at solving that problem by developing a spectrum allocation mechanism which takes into account the possibility of sharing out traffic over different optical paths to reduce the blocking rate when the traffic of a connection undergoes a fluctuation. This mechanism is the multi- spectrum bands allocation; the frequency slots allocated to the connection are on different spectrum bands. A spectrum band 176 | Page www.ijacsa.thesai.org