-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 algorithms found in the literatures 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 for the 6-node benchmark network in an acceptable running time.KEYWORDS -Multi-Objective Evolutionary Algorithm, Grooming, WDM, mesh optical networks, Pareto Optimal. INTRODUCTIONA grooming is a process of multiplexing low-speed traffic onto the high-capacity pipe. It is a challenging technology that could cut costs, improve the protection and decrease provisioning time in the Optical network. While the Optical switch can handle up to OC-768, the electronic switching technologies at the access node can only feed the rates much lower than the full capacity of the Optical network. Therefore, the grooming is the right solution to lower this gap.Literatures on grooming are mainly based on a ring topology. Our research work is on the traffic grooming in WDM mesh networks with static traffic demand that is similar to [1]. It is considered as an optimization problem. The main purpose is to design the virtual topology that optimizes both a performance and a cost. The objectives include a maximization of a throughput as found in [1], a minimization of the network cost like number of transceivers as found in [2] and a minimization of the average propagation delay of the lightpaths. To achieve these objectives, we propose a multi-objective evolutionary algorithm to search for the solution.The structure of the remainder of this paper is as follows. Section II presents mathematical formulation of the virtual topology design in the traffic grooming problem. Section III explains the Multi-Objective Evolutionary Algorithm in general. Then in Section IV, we propose how to apply the MOEA for the traffic grooming problem. Section V shows the performance of our approach comparing to the heuristics on a 6-node network. The conclusion of our approach and suggestions for the future work are in Section VI.
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.
We propose a method for dealing with semantic complexities occurring in information retrieval systems on the basis of linguistic observations. Our method follows from an analysis indicating that long runs of content words appear in a stopped document cluster, and our observation that these long runs predominately originate from the prepositional phrase and subject complement positions and as such, may be useful predictors of semantic coherence. From this linguistic basis, we test three statistical hypotheses over a small collection of documents from different genre. By coordinating thesaurus semantic categories (SEMCATs) of the long run words to the semantic categories of paragraphs, we conclude that for paragraphs containing both long runs and short runs, the SEMCAT weight of long runs of content words is a strong predictor of the semantic coherence of the paragraph.
In this paper we simplify the 4.4BSD TCP/IP protocol suite, in support of the design and implementation of embedded high performance communication software. Perfonnance is achieved by employing a jlat memory model. The jlat memory model does not require protection between user mode and kernel mode. This model corresponds to the environment of current embedded systems. Additionally, we validate a technique called DAP (Direct Access Packet-handler) to improve the performance of processing the upward jlow of packets from the network interface to the network protocol layer in the communicationssoftware. An summary of communication software on some commercial real-time OS is presented here. The structure of communication software in VRTX, which is implemented by modifying the 4.3 BSD TCP/IP protocol suite, is a two-level packet processing mechanism based on IPC using a mailbox to provide communication between the hardware interrupt-handler and packet processing-task. It uses interrupt enable and disable techniques to support the synchronization to access to shared data. The remaining structure of communication software is similar to the 4.3BSD TCP/IP protocol suite.The communication software of VXWORKS is also implemented by modifying the 4.3BSD TCP/IP protocol suite. It uses a semaphore to support synchronization to access shared data. The rest of its structure is similar to the 4.3 BSD TCP/IF' protocol suite except that managing the resources in the communication the monopoly of resources by tasks accessing the protocol layers in communication software. However the fair policy can degrade the performance of communication software when it supports multimedia services requiring real-time and high-speed because it causes frequent context switching and redundant task rescheduling of tasks that want to access the resources of the communications software. We found out the cost to pass the packet received by the network adapter to the correspondent task is expensive under this mechanism.I i Figure 6 . Structure of direct access packet-handler 6. Experiments and Results 6.1. Development environment for the implementation of communication software Figure 7 shows the environment for the development of communication software and embedded OS. The embedded OS and communication software are implemented by the gnu c compiler, gcc-2.6.1, under the FreeBSD 2.2.8. The FreeBSD 2.2.8 bootstrap is used to load and run the embedded OS kemel and communication software. For I/O, serial communication is used to verify the operational result of the kernel and communication software. This I/O environment is implemented by the YO subsystem of the embedded OS kemel which provides serial communication and the dual console mode of FreeBSD 2.2.8. With this approach, we tested the communication performance of FreeBSD2.2.8 and our own communication software in same development environment as (A) shown in Figure 7.
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