基于蚂蚁算法的WDM网络动态逻辑拓扑重配置

本文提出了基于蚂蚁选路的WDM网络动态逻辑拓扑重配置算法。利用蚁群选路的天然特性,在作了适当的假设后,我们推导出基于动态负载平衡的蚂蚁选路概率表达式,一方面使所选路由尽量短,另一方面尽量保持负载分布的平衡性。当业务动态变化时,网络节点根据算法的收敛结果做出相应调整。仿真结果表明,算法对动态业务方式的逻辑拓扑重配置是很有效的。     

Virtual topologies for multicasting with multiple originators in WDM networks

In this paper, we consider the problem of multicasting with multiple originators in WDM optical networks. In this problem, we are given a set S of source nodes and a set D of destination nodes in a network. All source nodes are capable of providing data to any destination node. Our objective is to find a virtual topology in the WDM network which satisfies given constraints on available resources and is optimal with respect to minimizing the maximum hop distance. Although the corresponding decision problem is NP-complete in general, we give polynomial time algorithms for the cases of unidirectional paths and rings.     

两纤WDM全光环网的保护和恢复与波长分配

研究了WDM环网的保护和恢复与波长分配问题，提出了一种改进的Greedy波长分配算法，仿真计算结果表明，该算法应用于WDM共享保护环(SPRING)获得了较高的波长利用率，同时本文比较了WDM环网的不同保护和恢复结构对波长资源配置的要求。     

Optimal routing and wavelength assignment to minimize the number of SONET ADMs in WDM rings

In this study, we consider the routing and wavelength assignment problem on SONET over WDM ring networks. Our problem is the minimum ADM (add-drop multiplexer) cost problem of minimizing the number of ADM equipment instead of the minimum wavelength problem. To deal with the complexity of the problem, we create a new mathematical formulation and suggest an efficient solution method based on the branch-and-price method. We exploit the structure of the ring network to develop an efficient algorithm and show the efficiency using computer simulations.     

Cost-effective traffic grooming in WDM rings

We provide network designs for optical add-drop wavelength-division-multiplexed (OADM) rings that minimize overall network cost, rather than just the number of wavelengths needed. The network cost includes the cost of the transceivers required at the nodes as well as the number of wavelengths. The transceiver cost includes the cost of terminating equipment as well as higher-layer electronic processing equipment, which in practice can dominate over the cost of the number of wavelengths in the network. The networks support dynamic (i.e., time-varying) traffic streams that are at lower rates (e.g., OC-3, 155 Mb/s) than the lightpath capacities (e.g., OC-48, 2.5 Gb/s). A simple OADM ring is the point-to-point ring, where traffic is transported on WDM links optically, but switched through nodes electronically. Although the network is efficient in using link bandwidth, it has high electronic and opto-electronic processing costs. Two OADM ring networks are given that have similar performance but are less expensive. Two other OADM ring networks are considered that are nonblocking, where one has a wide-sense nonblocking property and the other has a rearrangeably nonblocking property. All the networks are compared using the cost criteria of number of wavelengths and number of transceivers     

Application-aware virtual paths insertion for NOCs

Network-on-chip (NoC) has rapidly become a promising alternative for complex system-on-chip architectures including recent multicore architectures. Additionally, optimizing NoC architectures with respect to different design objectives that are suitable for a particular application domain is crucial for achieving high-performance and energy-efficient customized solutions. Despite the fact that many researches have provided various solutions for different aspects of NoCs design, a comprehensive NoCs system solution has not emerged yet. This paper presents a novel methodology to provide a solution for complex on-chip communication problems to reduce power, latency and area overhead. Our proposed NoC communication architecture is based on setting up virtual source–destination paths between selected pairs of NoCs cores so that the packets belonging to distance nodes in the network can bypass intermediate routers while traveling through these virtual paths. In this scheme, the paths are constructed for an application based on its task-graph at the design time. After that, the run time scheduling mechanism is applied to improve the buffer management, virtual channel and switch allocation schemes and hence, the constructed paths are optimized dynamically. Moreover, in our design the router complexity and its overheads are reduced. Additionally, the suggested router has been implemented on Xilinx Virtex-5 FPGA family. The evaluation results captured by SPLASH-2 benchmark suite reveal that in comparison with the conventional NoC router, the proposed router takes 25% and 53% reduction in latency and energy, respectively besides 3.5% area overhead. Indeed, our experimental results demonstrate a significant reduction in the average packet latency and total power consumption with negligible area overhead.     

Genetic algorithm to design logical topologies in reconfigurable WDM networks

A new method to design logical topologies based on genetic algorithms is presented. Not only does the algorithm determine which nodes should be connected by means of lightpaths with the aim of minimizing congestion, but it also solves the routing and wavelength assignment problem. In this way, the algorithm guarantees that the logical topology obtained can be embedded in the optical network subject to the available set of resources. The algorithm is effective in terms of both congestion and fairness. For instance, when compared with other work, the congestion is significantly reduced (from 20% to 75% depending on the matrix of traffic considered), and the fairness, when evaluated in terms of the Jain index, is generally higher than 0.94. Moreover, the algorithm brings advantages when employed in dynamic scenarios where the logical topology is frequently reconfigured, as it is fast and, in contrast to other algorithms previously proposed, the calculation process can be stopped at any time (if required) in order to give the best virtual topology found up to the moment.

On optimal traffic grooming in WDM rings

We consider the problem of designing a virtual topology to minimize electronic routing, that is, grooming traffic, in wavelength routed optical rings. The full virtual topology design problem is NP-hard even in the restricted case where the physical topology is a ring, and various heuristics have been proposed in the literature for obtaining good solutions, usually for different classes of problem instances. We present a new framework which can be used to evaluate the performance of heuristics and which requires significantly less computation than evaluating the optimal solution. This framework is based on a general formulation of the virtual topology problem, and it consists of a sequence of bounds, both upper and lower, in which each successive bound is at least as strong as the previous one. The successive bounds take larger amounts of computation to evaluate, and the number of bounds to be evaluated for a given problem instance is only limited by the computational power available. The bounds are based on decomposing the ring into sets of nodes arranged in a path and adopting the locally optimal topology within each set. While we only consider the objective of minimizing electronic routing in this paper, our approach to obtaining the sequence of bounds can be applied to many virtual topology problems on rings. The upper bounds we obtain also provide a useful series of heuristic solutions     

A near-optimal routing and dimensioning algorithm for dynamic WDM rings

In this paper a novel algorithm which jointly solves the problems of routing and dimensioning in dynamic WDM rings is proposed. The algorithm is simple, very fast (processing time <1 s) and applicable to rings of any size. After applying the algorithm to rings of 6–20 nodes, it was found that it outperformed the best proposal to date. In the cases where the optimal solution could be obtained by solving an ILP (Integer Linear Programming) model, the algorithm proposed here obtained exactly the same results. These facts make the proposed method the best solution to date for the routing and dimensioning of dynamic WDM rings, the most popular topology in metropolitan networks.     

Design for WDM rings based on differentiated path availability

A mechanism of reusing protection wavelengths in Wavelength Division Multiplexing (WDM) ring networks based on Differentiated Path Availability (DPA) is presented. A heuristic algorithm—Difficult Reuse First (DRF) is used to sub-optimally solve the Routing and Wavelength Assignment (RWA) problem. This algorithm can minimize the total wavelength mileage of a ring, while guaranteeing the required availability degree of each connection. The simulation results show that in the uniform traffic case, under different traffic proportion scenarios, the used wavelength mileage decreases while the reused wavelength mileage increases, as the required availability degree of connection decreases. This rule also fits in the nonuniform traffic case.     

Optimal WDM schedules for optical star networks

We consider single-hop wavelength-division multiplexed networks in which the transmitters take a nonzero amount of time, called tuning latency, to tune from one wavelength to another. For such networks, we show that, under certain conditions on the traffic matrix, there exist polynomial-time algorithms that produce the optimal schedule. Further, the tuning latency is masked in the length of the optimal schedule. Using Chernoff-Hoeffding bounds, we show that the condition on the traffic matrix is satisfied with high probability when the wavelength reuse factor is large, i.e., the number of nodes is large compared to the number of wavelengths. Simulation results show the dramatic improvement in the performance of the network using our algorithm as compared with other heuristics     

On scheduling all-to-all personalized connection and cost-effectivedesigns in WDM rings

We consider the problem of scheduling all-to-all personalized connections (AAPC) in WDM rings. Scheduling one connection for every source-destination pair in a network of limited connectivity provides a way to reduce routing control and guarantee throughput. For a given number of wavelengths K and a given number of transceivers per node T, we first determine the lower bound (LB) on the schedule length, which depends on both K and T. To achieve the LB, either the network bandwidth, the I/O capacity, or both should be fully utilized. This approach first constructs and then schedules circles, each of which is formed by up to four non-overlapping connections and can fully utilize the bandwidth of one wavelength. The proposed circle construction and scheduling algorithms can achieve the LB if K⩽T相似文献   

Effective wavelength assignment algorithms for optimizing designcosts in SONET/WDM rings

In high-speed wavelength-division-multiplexed synchronous optical network (SONET) ring networks, the terminal equipment costs associated with electronic multiplexing can be predominantly high. Placing a wavelength add-drop multiplexer (WADM) at each network node allows certain wavelengths to optically bypass the node without being electronically terminated. This approach can effectively reduce the total equipment cost if connections and channels are appropriately assigned in traffic grooming. In this paper, we present a series of wavelength optimization and wavelength assignment algorithms with the objective to optimize the number of required SONET add-drop multiplexers and yet minimizes the number of wavelengths in both unidirectional and bidirectional rings under an arbitrary grooming factor. In our analysis, we have considered both uniform and general nonuniform all-to-all network traffic. As a simple model for realistic traffic patterns, a special case of nonuniform traffic, distance-dependent traffic, is analyzed in detail. Significant ADM savings are observed for different traffic scenarios using our proposed algorithms     

Optimal dispersion management schemes for WDM soliton systems

Optimal dispersion profiles for a WDM soliton system are obtained by minimising the radiative noise and the collision-induced frequency shift. A two-step optimal profile without dispersion slaving to the ideal exponential profile allows a large increase in the amplifier spacing with no significant deterioration of the system performance     

Strategy for protection and restoration of optical paths in WDM backbone networks for next-generation Internet infrastructures

This paper proposes and analyzes a strategy for protection and restoration of optical paths in wavelength division multiplexing (WDM) networks for next-generation Internet infrastructure. Assuming a network model in which a multiprotocol label switching (MPLS) layer is overlaid on top of a WDM layer, and a segregation of the traffic on a wavelength basis, the strategy is based on a network dimensioning aiming at: 1) the support of different types of traffic, relating to different service categories; 2) the guarantee that all the wavelength paths carrying mission-critical services (with stringent quality of service requirements) are protected against failure; and 3) the possibility of restoring a large amount of wavelength paths carrying Internet best-effort services, i.e., low-priority (LP) preemptible traffic with no QoS requirements. The reference network scenario is an overlay model in which the optical network interacts with an MPLS network with a separated control plane; the optical network manages its resources to better serve the traffic coming from the MPLS network. Two path protection schemes, namely, disjoint path (DP) and single-link basis (SLB), and a link protection mechanism, namely, local repair (LP), are investigated. Furthermore, the paper considers both the case of using wavelength conversion in the optical nodes and the case in which wavelength conversion is not used at all. The analysis compares the performance of the different strategies in terms of the percentage of optical paths carrying LP traffic not served by the optical network after a failure and of the dimensions of the optical nodes for all the schemes. The analysis reveals that the proposed approach allows the restoration of a large amount of best-effort traffic with a reasonable increase of network redundancy.     

Backscattering-induced crosstalk in WDM optical wireless communication

The crosstalk effect of aerosol backscatter on the performance of a wavelength-division-multiplexed (WDM) optical wireless communication (OWC) system is investigated, analyzed, and quantified. An OWC link could be a segment within a metropolitan area network (MAN) or a ground-station-to-space link of a satellite communication system. In these cases, a WDM transmitter and receiver are housed in one transceiver unit with parallel, or near-parallel, optic axes. The crosstalk at the receiver is caused by light from the transmitted signal of the same transceiver, which has been backscattered by molecules and aerosols in the atmosphere. This is exacerbated in the presence of fog and haze, in which case both the desired signal from another transceiver is attenuated by scattering and the backscatter-induced crosstalk increases. A bit-error-rate (BER) model is derived that takes into consideration the dominant noise sources, including backscatter-induced crosstalk and signal mixing with amplified stimulated emission (ASE) from an optical preamplifier at the receiver. The numerical calculations in this paper indicate that, in moderate fog, the BER may increase by an order of magnitude or more due to backscatter, depending upon the atmospheric extinction coefficient.     

IP over WDM网络中一种新型虚拓扑构造算法

对IP over WDM的虚拓扑设计算法进行了研究，选择网络整体流量的均衡性作为优化目标，提出了一种新型的虚拓扑构造算法。在算法中，选择负载分布方差作为评价流量均衡性的指标，并给出其定义和计算方法。主要针对拥塞概率性能，在光层和IP层将提出的新型虚拓扑构造算法与其他算法进行比较。在光层的算法比较部分，选择负载均衡启发式路由算法（RLBH，routing with load balancing heuristics）与提出的算法进行比较；在IP层的算法比较部分，选择固定路径最小拥塞路由算法（FPLC，fixed-path least-congestion）与提出的算法进行比较，并对比较结果进行了讨论。比较结果显示在拥塞概率性能方面，提出的新型虚拓扑构造算法优于RLBH算法和FPLC算法。     

Optimal nonuniform wavebanding in WDM mesh networks

Grouping together a set of consecutive wavelengths in a WDM network and switching them together as a single waveband could achieve savings in switching costs of an optical cross-connect. This technique is known as waveband switching. While previous work has focused on either uniform band sizes or nonuniform band sizes considering a single node or ring networks, in this paper we focus on optimizing the number of wavebands and their sizes for mesh topologies. We formulate a problem of optimizing the number of wavebands in a mesh network for a given set of lightpaths. The objective of the band minimization problem is to minimize the number of nonuniform wavebands in the network while satisfying the traffic requests. We formulate an integer linear program and propose efficient heuristics. Simulation results are presented to demonstrate the effectiveness of the proposed approaches under static traffic case. Our results show that the number of switching elements can be reduced by a large amount using waveband switching compared to wavelength switching. We also apply the proposed waveband strategy to the dynamic stochastic traffic case and evaluate the network performance in terms of blocking probability through numerical simulations.