Number Of Available Wavelengths Research Articles

Bin-packing based offline dynamic bandwidth and wavelength allocation algorithms for power efficiency in Super-PON

Enduring the rapidly growing demand for high data rates is the main challenge for the current network providers. Super passive optical network (Super-PON), a prominent next generation Ethernet PON (NG-EPON) candidate, can suffice this exponentially increasing data rate requirements. However, to appease such requirements, it employs many transceivers and increases the power-consumption of the network. In this work, we focus on reducing the carbon footprint of Super-PON and propose power-efficient dynamic bandwidth and wavelength allocation (DBWA) algorithms, namely best fit bin-packing sleep mode aware (BF-SMA) and updated BF-SMA (UBF-SMA). The proposed algorithms use SMA for bandwidth scheduling and different bin-packing techniques for wavelength allocation. In bin-packing, the number of available wavelengths and their efficient allocation is based on the network load. For restricting the number of available wavelengths, we can switch off the non-essential transceivers at the OLT, which also helps in maximizing the wavelength utilization and increasing the power efficiency. The simulation results show that in comparison to the state-of-the-art DBWA algorithms, the proposed algorithms improve the power efficiency and reduce the average delay of a Super-PON system. Furthermore, we use Jain’s fairness index to validate the fairness of the proposed DBWA algorithms.

Modelling and Simulation Analysis of Routing Algorithms in Multichannel Optical Communication Networks

In this paper, it is considered the broadband backbone optical networks with wavelength routing and circuit switching used to build long-range wide area networks. In this type of network, if there is an available and acknowledged connection request, it is necessary to determine the optimal path between the optical communication nodes in the network. This also requires the assignment of an optimal set of wavelengths along the selected route between these nodes. This paper takes into account the multichannel optical communication networks with spectral multiplexing. Four different routing algorithms are modeled and analyzed for which their weight functions are determined to take into account various factors, such as the total distance of the individual routes, the total number of available wavelengths for a given route and how many of them are available for use. It is studied and compared the performance of the proposed algorithms in a multichannel optical network in terms of blocking probability.

Performance Analysis of a Novel 2-D Code in the Network Access Segment

AbstractIn this paper, the performance of one-coincidence frequency hopping code/quadratic congruence code (OCFHC/QCC) is analysed and compared with the existing codes. The impact of variation in code weight, code length and number of wavelengths on error probability is evaluated. It is observed that for the same code weight, code length and number of available wavelengths, error probability of OCFHC/QCC is better than the existing codes under certain conditions. The large cardinality, simple design methodology and good performance suggest its use in local area network, multi-code keying and multi-rate multimedia applications.

Minimum multiplicity edge coloring via orientation

We study an edge coloring problem in multigraphs, in which each node incurs a cost equal to the number of appearances of the most frequent color among those received by its incident edges. We seek an edge coloring with a given number w of colors, that minimizes the total cost incurred by the nodes of the multigraph. We consider a class of approximation algorithms for this problem, which are based on orienting the edges of the multigraph, then grouping appropriately the incoming and outgoing edges at each node so as to construct a bipartite multigraph of maximum degree w, and finally obtaining a proper edge coloring of this bipartite multigraph. As shown by Nomikos et al. (2001), simply choosing an arbitrary edge orientation in the first step yields a 2-approximation algorithm. We investigate whether this approximation ratio can be improved by a more careful choice of the edge orientation in the first step. We prove that, assuming a worst-case bipartite edge coloring, this is not possible in the asymptotic sense, as there exists a family of instances in which any orientation gives a solution with cost at least 2−Θ(1w) times the optimal. On the positive side, we show how to produce an orientation which results in a solution with cost within a factor of 2−12w of the optimal, thus yielding an approximation ratio strictly better than 2. This improvement is important in view of the fact that this graph-theoretic problem models, among others, wavelength assignment to communication requests in multifiber optical star networks. In this context, the parameter w corresponds to the number of available wavelengths per fiber, which is limited in practice due to technological constraints.

An improved least cost routing approach for WDM optical network without wavelength converters

Abstract Routing and wavelength assignment (RWA) problem has been an attractive problem in optical networks, and consequently several algorithms have been proposed in the literature to solve this problem. The most known techniques for the dynamic routing subproblem are fixed routing, fixed-alternate routing, and adaptive routing methods. The first one leads to a high blocking probability (BP) and the last one includes a high computational complexity and requires immense backing from the control and management protocols. The second one suggests a trade-off between performance and complexity, and hence we consider it to improve in our work. In fact, considering the RWA problem in a wavelength routed optical network with no wavelength converter, an improved technique is proposed for the routing subproblem in order to decrease the BP of the network. Based on fixed-alternate approach, the first k shortest paths (SPs) between each node pair is determined. We then rearrange the SPs according to a newly defined cost for the links and paths. Upon arriving a connection request, the sorted paths are consecutively checked for an available wavelength according to the most-used technique. We implement our proposed algorithm and the least-hop fixed-alternate algorithm to show how the rearrangement of SPs contributes to a lower BP in the network. The numerical results demonstrate the efficiency of our proposed algorithm in comparison with the others, considering different number of available wavelengths.

Model-hierarchical column generation and heuristic for the routing and wavelength assignment problem

The routing and wavelength assignment (RWA) problem typically occurs in wavelength division multiplexing optical networks. Given a number of available wavelengths, we consider here the problem of maximising the number of accepted connections with respect to the clash and continuity constraints. We first propose a new strategy which combines two existing models. This leads to an improved column generation scheme. We also present two heuristics to compute feasible solutions: a hybrid heuristic and the integer solution at the root node of the column generation. Our approaches are compared with the best existing results on a set of classic RWA instances.

Offline Impairment-Aware Routing and Wavelength Assignment Algorithms in Translucent WDM Optical Networks

Physical impairments in optical fiber transmission necessitate the use of regeneration at certain intermediate nodes, at least for certain lengthy lightpaths. We design and implement impairment-aware algorithms for routing and wavelength assignment (IA-RWA) in translucent optical networks. We focus on the offline version of the problem, where we are given a network topology, the number of available wavelengths and a traffic matrix. The proposed algorithm selects the 3R regeneration sites and the number of regenerators that need to be deployed on these sites, solving the regenerator placement problem for the given set of requested connections. The problem can be also posed in a slightly different setting, where a (sparse) placement of regenerators in the network is given as input and the algorithm selects which of the available regenerators to use, solving the regenerator assignment problem. We formulate the problem of regenerator placement and regenerator assignment, as a virtual topology design problem, and address it using various algorithms, ranging from a series of integer linear programming (ILP) formulations to simple greedy heuristic algorithms. Once the sequence of regenerators to be used by the non-transparent connections has been determined, we transform the initial traffic matrix by replacing non-transparent connections with a sequence of transparent connections that terminate and begin at the specified 3R intermediate nodes. Using the transformed matrix we then apply an IA-RWA algorithm designed for transparent (as opposed to translucent) networks to route the traffic. Blocked connections are re-routed using any remaining regenerator(s) in the last phase of the algorithm.

Wavelength Management in WDM Rings to Maximize the Number of Connections

We study computationally hard combinatorial problems arising from the important engineering question of how to maximize the number of connections that can be simultaneously served in a wavelength division ultiplexing (WDM) optical network. In such networks, WDM technology can satisfy a set of connections by computing a route and assigning a wavelength to each connection so that no two connections routed through the same fiber are assigned the same wavelength. Each fiber supports a limited number of w wavelengths and in order to fully exploit the parallelism provided by the technology, one should select a set of connections of maximum cardinality which can be satisfied using the available wavelengths. This is known as the maximum routing and path coloring (maxRPC) problem. Our main contribution is a general analysis method for a class of iterative algorithms for a more general coloring problem. A lower bound on the benefit of the solution computed by such an algorithm in terms of the optimal benefit and the number of available wavelengths is given by a benefit-revealing linear program. We apply this method to maxRPC in both undirected and bidirected rings to obtain upper bounds on the approximation ratio of several algorithms. The best bounds obtained are $4/3$ and $103/73\approx1.41096$ for undirected and bidirected rings; these results improve known bounds of $3/2$ and $11/7\approx1.57143$, respectively. Our results extend to multifiber ring networks and also apply to the maximum path coloring (maxPC) problem, where paths instead of connection requests are given as part of the input. We also study the profit version of maxPC in rings where each path has a profit and the objective is to satisfy a set of paths of maximum total profit. We present an algorithm based on linear programming and randomized rounding with approximation ratio 1.49015, improving on the $\frac{e}{e-1}\approx1.58198$ bound obtained by a simple iterative algorithm.

A new approach for routing and wavelength assignment for permanent and reliable wavelength paths in wide all-optical WDM networks

This article proposes a new approach for routing and wavelength assignment (RWA) for permanent and reliable wavelength paths (WP) in wide all-optical WDM networks with wavelength continuity constraint. Given a number of available wavelengths on each optical fiber, for each simple link failure of the network, we seek to maximize the number of satisfied requests for connections. This is known as RWAP problem. In our algorithm, called RWA with Minimum Loaded Link for Permanent and Reliable wavelength paths (MLL-PR), routing is based on the search for the optimal path while trying to minimize the maximum load on the links of the network in order to minimize the maximum link capacity and then minimize the number of dropped lightpaths after any link failure. The wavelength assignment is based on a graph coloring method using tabu-search. A series of experiments using two well-known networks (ARPANET and NSFNET) have been carried out in order to evaluate the performance of our approach, in terms of the number of blocked demands, for different failure scenarios. Generally, our results are better than those provided by the current solving approaches taken as reference.

Construction and performance analysis of a 2D optical orthogonal code

Feature Issue on Optical Code Division Multiple AccessWhat we believe to be a new 2D optical orthogonal code, named PC/OCS, is constructed using PC (prime code) for time spreading and OCS (one-coincidence sequence) for wavelength hopping. Cross-correlation performance of PC/OCS is analyzed. Compared with PC/PC, the number of wavelengths for PC/OCS is not limited to a prime number. PC/OCS can be constructed flexibly and also can use available wavelengths effectively. When the number of available wavelengths is larger than a prime number, PC/OCS not only has a larger code cardinality than PC/PC, but it also has a better cross-correlation performance. Theoretical analysis shows that PC/OCS can reduce the bit error rate and enhance system throughput of multiple-wavelength (MW) optical code-division multiple access networks. When the number of available wavelengths is 16 and code length is 121, code cardinality of PC/OCS can increase approximately 17% more than that of PC/PC, and the peaked throughput can increase approximately 20%.

Code Flexibility of 2-D Time-Spreading Wavelength-Hopping In OCDMA Systems

The potential performance and successful experimental demonstrations of two-dimensional time-spreading wavelength-hopping (TW) optical code-division multiple access systems have motivated a large volume of research into the development of new TW codes. The choice of the code is crucial in network design since the code not only affects the overall system performance but also sets limits on the physical implementation of the encoding-decoding process. In this paper, ldquoflexibilityrdquo of TW codes is investigated, providing clarity on the tradeoff between key code factors, specifically the number of available wavelengths and time chips. Network performance is evaluated by taking into consideration multiple access interference and beat noise at both the physical and link layers. Furthermore, a general formula describing the impact of the extinction ratio (ER) on the bit-error probability is explored. The results indicate the importance of code flexibility and ER in system performance optimization.

Wavelength assignment with sparse wavelength conversion for optical multicast in WDM networks

This paper addresses the problem of multicast wavelength assignment for sparse wavelength conversion (MWA-SWC) in wavelength-routed wavelength-division-multiplexing (WDM) networks. It aims to optimally allocate the available wavelength for each link of the multicast tree, given a sparse wavelength conversion network and a multicast request. To our knowledge, little research work has been done to address this problem in literature.In this paper, we propose a new technique called MWA-SWC algorithm to solve the problem. The algorithm first maps the multicast tree from the sparse conversion case to the full conversion case by making use of a novel virtual link method to carry out the tree mapping. The method provides a forward mapping to generate an auxiliary tree as well as a reverse mapping to recover the original tree. Applying the auxiliary tree, we propose a dynamic programing algorithm for the wavelength assignment (WA) aiming to minimize the number of wavelength converters (NWC) required. Simulation results show that our new algorithm outperforms both random and greedy algorithms with regard to minimizing the NWC. Testing on various scenarios by varying the number of wavelength conversion nodes in the tree has confirmed the consistency of the performance. The primary use of the MWA-SWC algorithm is for static traffic. However, it can also serve as a baseline for dynamic heuristic algorithms. Typically, the MWA-SWC algorithm will provide great benefit when the number of available wavelengths on each link of the multicast tree is relatively large and the performance advantage is significant.

Code-based all optical routing using two-level coding

Code-based all optical routing employing a two-level-coding scheme is proposed. The first level of coding is employed to establish connections between users within a local area network; a second level of coding provides routing/interconnectivity between networks. The limitations due to physical-layer impairments, such as relative intensity noise (RIN) of the optical source, the signal-dependent shot noise, optical beat interference (OBI), and thermal noise at the receiver, which are some of the fundamental issues in the design of practical optical code division multiple access (CDMA) systems, are analyzed for the two-level scheme. The throughput in terms of "packets/time slot" offered by the scheme is also compared with that of the wavelength division multiple access (WDMA) system. The system capacity in WDMA is limited by the number of available wavelengths; optical CDMA, on the other hand, has many codes (user addresses), but the throughput is limited by multiple user interference, OBI, and RIN. System designs that overcome these effects and thereby improve the throughput are suggested.

A new family of 2-D optical orthogonal codes and analysis of its performance in optical CDMA access networks

A new family of two-dimensional optical orthogonal code (2-D OOC), one-coincidence frequency hop code (OCFHC)/OOC, which employs OCFHC and OOC as wavelength hopping and time-spreading patterns, respectively, is proposed in this paper. In contrary to previously constructed 2-D OOCs, OCFHC/OOC provides more choices on the number of available wavelengths and its cardinality achieves the upper bound in theory without sacrificing good auto-and-cross correlation properties, i.e., the correlation properties of the code is still ideal. Meanwhile, we utilize a new method, called effective normalized throughput, to compare the performance of diverse codes applicable to optical code division multiple access (OCDMA) systems besides conventional measure bit error rate, and the results indicate that our code performs better than obtained OCDMA codes and is truly applicable to OCDMA networks as multiaccess codes and will greatly facilitate the implementation of OCDMA access networks.

A tabu search heuristic for the routing and wavelength assignment problem in optical networks

This letter proposes a tabu search heuristic for solving the routing and wavelength assignment (RWA) problem in optical WDM networks, considering the wavelength continuity constraint and a given set of connections to satisfy. For a number of available wavelengths on each link, this algorithm attempts to maximize the number of routed connections. The algorithm has been implemented and tested on NSFNET and EONNET networks and comparisons have been done with other algorithms in terms of the blocking rate. Generally, the results obtained with our tabu search heuristic are better than those provided by these algorithms.

Optical Network Design with Optical Constraints in IP/WDM Networks

In this paper we consider algorithms for the logical topology design and traffic grooming problem in WDM networks with router interface constraints as well as optical constraints. The optical constraints include restricted transmission range due to optical impairments as well as limits on the number of available wavelengths. We formulate this problem as an integer linear program which is NP-complete. We then introduce heuristic algorithms which use a graphical modeling tool called the Virtual Neighbor Graph and add lightpaths sequentially. The best performing heuristic uses a so-called Resource Efficiency Factor to determine the order in which paths are provisioned for the traffic demands. By giving priority to demands that can be routed over paths that make efficient use of network resources, it is able to achieve good performance both in terms of weighted hop count and network throughput. For finding optimal multi-hop paths sequentially, we introduce interface constraint shortest path problem and solve it using minimum weight perfect matching.

A tabu search heuristic for the routing and wavelength assignment problem in optical networks

This letter proposes a tabu search heuristic for solving the routing and wavelength assignment (RWA) problem in optical WDM networks, considering the wavelength continuity constraint and a given set of connections to satisfy. For a number of available wavelengths on each link, this algorithm attempts to maximize the number of routed connections. The algorithm has been implemented and tested on NSFNET and EONNET networks and comparisons have been done with other algorithms in terms of the blocking rate. Generally, the results obtained with our tabu search heuristic are better than those provided by these algorithms.

Multiple-Length Multiple-Wavelength Optical Orthogonal Codes for Optical CDMA Systems Supporting Multirate Multimedia Services

Multiple-wavelength optical orthogonal codes (MWOOCs) with autocorrelation sidelobes and cross-correlation values of both at most one were recently proposed for wavelength-time optical code-division multiple-access (O-CDMA) systems. The codes have cardinality as a quadratic function of the number of wavelengths and find applications in high bit-rate O-CDMA systems with broadband supercontinuum lasers, in which the number of available wavelengths is larger than the number of time slots. To support multimedia services with different bit-rate and quality-of-service requirements, a new class of multiple-length constant-weight MWOOCs with autocorrelation sidelobes of zero and cross correlations of at most one is constructed algebraically in this paper. The performance of these new codes in an O-CDMA system with double-media services is analyzed. In contrary to conventional single-length codes, our study shows that the performance of these multiple-length codes improves as the code length decreases. This unique property supports prioritization in O-CDMA.

Extended Carrier-Hopping Prime Codes for Wavelength-Time Optical Code-Division Multiple Access

A two-dimensional wavelength-hopping time-spreading coding scheme has been recently studied for optical code-division multiple access, owing to maturity in fiber-Bragg grating (FBG) and arrayed-waveguide grating (AWG) technologies. Most of the optical codes designed for the scheme were based on an assumption, which may not be true in high data-rate systems, that the number of chips is higher than the number of available wavelengths. To provide a flexible code design without the assumption, this paper studies and analyzes a new family of carrier-hopping prime codes with expanded cardinality and ideal correlation properties. Flexible implementation of programmable AWG- and FBG-based coding hardware by using the wavelength-shift property of the codes is discussed.

Approximating call-scheduling makespan in all-optical networks

We study the problem of routing and scheduling requests of limited durations in all-optical networks with restrictions on the number of available wavelengths on each link. The task is servicing the requests, assigning each of them a route from source to destination, a starting time and a wavelength with the goal of minimizing the overall time needed to serve all requests. We study the relationship between this problem and minimum path coloring and we show how to exploit known results on path coloring to derive approximation scheduling algorithms for meshes, trees and nearly-Eulerian, uniformly high-diameter graphs. We also propose different approximation algorithms for stars, trees and in trees of rings.