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1.
Optimal Transceiver Scheduling in WDM/TDM Networks   总被引:2,自引:0,他引:2  
In this paper, we study the benefits of using tunable transceivers for reducing the required number of electronic ports in wavelength-division-multiplexing/time-division multiplexing optical networks. We show that such transceivers can be used to efficiently “groom” subwavelength traffic in the optical domain and so can significantly reduce the amount of terminal equipment needed compared with the fixed-tuned case. Formulations for this “tunable grooming” problem are provided, where the objective is to schedule transceivers so as to minimize the required number of ports needed for a given traffic demand. We establish a relationship between this problem and edge colorings of graphs which are determined by the offered traffic. Using this relationship, we show that, in general, this problem is NP-complete, but we are able to efficiently solve it for many cases of interest. When the number of wavelengths in the network is not limited, each node is shown to only require the minimum number of transceivers (i.e., no more transceivers than the amount of traffic that it generates). This holds regardless of the network topology or traffic pattern. When the number of wavelengths is limited, an analogous result is shown for both uniform and hub traffic in a ring. We then develop a heuristic algorithm for general traffic that uses nearly the minimum number of transceivers. In most cases, tunable transceivers are shown to reduce the number of ports per node by as much as 60%. We also consider the case where traffic can dynamically change among an allowable set of traffic demands. Tunability is again shown to significantly reduce the port requirement for a nonblocking ring, both with and without rearrangements.  相似文献   

2.
In wavelength routed optical networks, the number of wavelength channels is limited due to several constraints and each wavelength as well as each lightpath support traffic in the Gbps range. On the other hand, the traffic requested by an individual connection is still in the Mbps range. Therefore, to utilize the network resources (such as bandwidth and transceivers) effectively, several low-speed traffic streams have to be efficiently groomed or multiplexed into one or more high-speed lightpaths. The grooming problem of a static demand is considered as an optimization problem. In this work, we have investigated the traffic grooming problem with the objective of maximizing the network throughput for wavelength-routed mesh networks and map this problem to the clique partitioning problem. We have proposed an algorithm to handle general multi-hop static traffic grooming based on the clique partitioning concept. The efficiency of our approach has been established through extensive simulation on different sets of traffic demands with different bandwidth granularities for different network topologies and compared the approach with existing algorithms.  相似文献   

3.
In Wavelength Division Multiplexing (WDM) networks, the huge capacity of wavelength channels is generally much larger than the bandwidth requirement of individual traffic streams from network users. Traffic grooming techniques aggregate low-bandwidth traffic streams onto high-bandwidth wavelength channels. In this paper, we study the optimization problem of grooming the static traffic in mesh Synchronous Optical Network (SONET) over WDM networks. The problem is formulated as a constrained integer linear programming problem and an innovative optimization objective is developed as network profit optimization. The routing cost in the SONET and WDM layers as well as the revenue generated by accepting SONET traffic demands are modelled. Through the optimization process, SONET traffic demands will be selectively accepted based on the profit (i.e., the excess of revenue over network cost) they generate. Consiering the complexity of the network optimization problem, a decomposition approach using Lagrangian relaxation is proposed. The overall relaxed dual problem is decomposed into routing and wavelength assignment and SONET traffic routing sub-problems. The subgradient approach is used to optimize the derived dual function by updating the Lagrange multipliers. To generate a feasible network routing scheme, a heuristic algorithm is proposed based on the dual solution. A systematic approach to obtain theoretical performance bounds is presented for an arbitrary topology mesh network. This is the first time that such theoretical performance bounds are obtained for SONET traffic grooming in mesh topology networks. The optimization results of sample networks indicate that the roposed algorithm achieves good sub-optimal solutions. Finally, the influence of various network parameters is studied.  相似文献   

4.
As the operation of our fiber-optic backbone networks migrates from interconnected SONET rings to arbitrary mesh topology, traffic grooming on wavelength-division multiplexing (WDM) mesh networks becomes an extremely important research problem. To address this problem, we propose a new generic graph model for traffic grooming in heterogeneous WDM mesh networks. The novelty of our model is that, by only manipulating the edges of the auxiliary graph created by our model and the weights of these edges, our model can achieve various objectives using different grooming policies, while taking into account various constraints such as transceivers, wavelengths, wavelength-conversion capabilities, and grooming capabilities. Based on the auxiliary graph, we develop an integrated traffic-grooming algorithm (IGABAG) and an integrated grooming procedure (INGPROC) which jointly solve several traffic-grooming subproblems by simply applying the shortest-path computation method. Different grooming policies can be represented by different weight-assignment functions, and the performance of these grooming policies are compared under both nonblocking scenario and blocking scenario. The IGABAG can be applied to both static and dynamic traffic grooming. In static grooming, the traffic-selection scheme is key to achieving good network performance. We propose several traffic-selection schemes based on this model and we evaluate their performance for different network topologies.  相似文献   

5.
Reconfiguration and Dynamic Load Balancing in Broadcast WDM Networks*   总被引:2,自引:0,他引:2  
In optical WDM networks, an assignment of transceivers to channels implies an allocation of the bandwidth to the various network nodes. Intuition suggests, and our recent study has confirmed, that if the traffic load is not well balanced across the available channels, the result is poor network performance. Hence, the time-varying conditions expected in this type of environment call for mechanisms that periodically adjust the bandwidth allocation to ensure that each channel carries an almost equal share of the corresponding offered load. In this paper we study the problem of dynamic load balancing in broadcast WDM networks by retuning a subset of transceivers in response to changes in the overall traffic pattern. Assuming an existing wavelength assignment and some information regarding the new traffic demands, we present two approaches to obtaining a new wavelength assignment such that (a) the new traffic load is balanced across the channels, and (b) the number of transceivers that need to be retuned is minimized. The latter objective is motivated by the fact that tunable transceivers take a non-negligible amount of time to switch between wavelengths during which parts of the network are unavailable for normal operation. Furthermore, this variation in traffic is expected to take place over larger time scales (i.e., retuning will be a relatively infrequent event), making slowly tunable devices a cost effective solution. Our main contribution is a new approximation algorithm for the load balancing problem that provides for tradeoff selection, using a single parameter, between two conflicting goals, namely, the degree of load balancing and the number of transceivers that need to be retuned. This algorithm leads to a scalable approach to reconfiguring the network since, in addition to providing guarantees in terms of load balancing, the expected number of retunings scales with the number of channels, not the number of nodes in the network.  相似文献   

6.
SONET/WDM rings are widely deployed in today’s networks. To reduce the total cost of such a network, an efficient way is using the traffic grooming technique to minimize the number of add/drop multiplexers (ADMs) on the ring. Since traffic often changes frequently, the problem of supporting dynamic traffic patterns with minimum number of ADMs and wavelengths becomes incresingly important, which is referred to as grooming of dynamic traffic. In this paper, we will deal with rearrangeably nonblocking grooming of arbitrary dynamic traffic in such ring networks. We will discuss in detail the benefit of splitting methods to such a grooming way and apply them to this kind of grooming. A novel genetic algorithm (GA) approach with a hierarchical chromosome structure for each individual is proposed in combination with splitting methods to address such grooming problems. Computer simulation results under different conditions show that our algorithm is efficient in reducing both the numbers of ADMs and wavelengths.  相似文献   

7.
This paper studies a traffic grooming in wavelength-division multiplexing (WDM) mesh networks for the SONET/SDH streams requested between node pairs. The traffic could be groomed at the access node before converting to an optical signal carried in the all-optical network. We design a virtual topology with a given physical topology to satisfy multiple objectives and constraints. The grooming problem of a static demand is considered as an optimization problem. The traditional algorithms found in the literatures mostly focus on a single objective either to maximize the performance or to minimize the cost. We propose a multi-objective evolutionary algorithm to solve a grooming problem that optimizes multiple objectives all together at the same time. In this paper we consider the optimization of three objectives: maximize the traffic throughput, minimize the number of transceivers, and minimize the average propagation delay or average hop counts. The simulation results show that our approach is superior to an existing heuristic approaches in an acceptable running time.  相似文献   

8.
为了解决波分复用(WDM)网状网络中的动态流量疏导问题,基于收发器节约辅助图模型,提出了一种资源效率疏导策略.它同时考虑收发器和波长链路两种网络资源的有效利用,根据当前的网络状态动态改变疏导策略,使网络不会由于某一种资源的缺乏而导致阻塞所有流量,避免了另一种资源因富余而造成的浪费,从而两种资源都能得到充分利用.在辅助图模型中,根据两种资源的可用数目比值,对各条边设置不同的权值函数,可轻易地实现该策略.仿真结果证明,不管是收发器资源受限还是波长资源受限,该策略都能取得较好的性能,降低了网络的阻塞率.  相似文献   

9.
Gateway Placement for Throughput Optimization in Wireless Mesh Networks   总被引:1,自引:0,他引:1  
In this paper, we address the problem of gateway placement for throughput optimization in multi-hop wireless mesh networks. Assume that each mesh node in the mesh network has a traffic demand. Given the number of gateways to be deployed (denoted by k) and the interference model in the network, we study where to place exactly k gateways in the mesh network such that the total throughput is maximized while it also ensures a certain fairness among all mesh nodes. We propose a novel grid-based gateway deployment method using a cross-layer throughput optimization, and prove that the achieved throughput by our method is a constant times of the optimal. Simulation results demonstrate that our method can effectively exploit the available resources and perform much better than random and fixed deployment methods. In addition, the proposed method can also be extended to work with multi-channel and multi-radio mesh networks under different interference models.  相似文献   

10.
Autonomous Reconfiguration in Free-Space Optical Sensor Networks   总被引:1,自引:0,他引:1  
This research focuses on the physical and logical control and reconfigurability of network topologies through intelligent and dynamic rearrangement of nodes in an optical wireless sensor network. We address high data rate sensor networks (e.g., infrastructure monitoring; surveillance), which consist of gigabit per second, narrow beam, free-space optical links between fixed and/or mobile nodes. In our approach, the seamless operation of such networks requires maintenance of wireless link connectivity and quality and at all times, amidst, for example, changing atmospheric, and traffic and platform conditions. This is achieved by dynamic reconfiguration through topology control. We address the problem of dynamic formulation of topologies, which contain only two transceivers per communications node or switch. The task of reconfiguration requires the formation of a biconnected graph or a ring topology. The problem is similar to the traveling salesman problem and is NP complete. We address the mixed integer programming formulation of this problem, and show that it does not scale even for a small network. We then focus on heuristics for dynamic, autonomous reconfiguration. Using simulations, we investigate tradeoff between solution quality and computational time. We also investigate the effectiveness of these dynamic reconfiguration heuristics compared to fixed, degraded topologies.  相似文献   

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