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First, the optical burst switching (OBS) network with limited wavelength conversion capability (LWCC) is decomposed into multiple wavelength continuous segments according to the position of wavelength converters. Based on the decomposed network model, two reservation signalling mechanisms for OBS-LWCC networks, namely wavelength-amend-on-demand (WAoD) and contention-based limited signalling protocol (CLSP), are proposed to reduce the blocking probability in the OBS-LWCC networks. In WAoD, the congested node sends a feedback message to the closest upstream switch with wavelength conversion capability. The notified switch will change the burst wavelength to the one assigned by the congested node to avoid collision in advance. Extensive simulation results indicate that by applying the wavelength reconfiguration method to the core nodes without wavelength conversion capability, the proposed WAoD scheme can improve the blocking performance in the OBS-LWCC networks significantly. Furthermore, CLSP, which combines the burst time-slot reconfiguration with the wavelength reconfiguration of WAoD, always has the lowest burst loss probability when compared with both the conventional and the proposed reservation mechanisms. 相似文献
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A strategy for minimising the probability of contention in optical burst-switching (OBS) networks, by combining traffic engineering in the wavelength domain with delayed burst scheduling at the ingress nodes, has been proposed. The implementation of this strategy only requires an increase on the processing and electronic buffering capacities of the ingress nodes, while avoiding the use of complex and expensive optical buffers at the core nodes. The performance evaluation study has shown that the proposed strategy outperforms the burst-scheduling strategies described in the literature by several orders of magnitude, in terms of burst-blocking probability. Moreover, the performance improvements have been shown to depend on the average offered traffic load, number of wavelengths per link and maximum delay allowed at the ingress nodes. 相似文献
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Reconfigurable optical add/drop multiplexers (ROADMs) will play a key role in next-generation dynamically provisioned wavelength networks. Existing ROADM subsystems, manufactured with different designs and technologies, are suffering from either high insertion losses, especially for the passing-through (express)-channels, or high manufacturing costs that are preventing their rapid deployment in networks. An architecture for an ROADM subsystem that integrates the best features of the latest available ROADM designs is proposed. The proposed ROADM subsystem, denoted as a Hybrid-ROADM, exhibits a lower insertion loss (~7 dB for express-channels) than existing ROADMs while offering simplification and cost benefit. A metro network testbed has been configured to demonstrate and compare the performance of the proposed Hybrid-ROADM module against currently available ROADM subsystems. The obtained results indicate that our Hybrid-ROADM shows better performance in metro networks than the latest available ROADM subsystems and will reduce the overall network operating costs. 相似文献
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Network lifetime-aware data collection in Underwater Sensor Networks for delay-tolerant applications
Development of energy-efficient data collection and routing schemes for Underwater Wireless Sensor Networks (UWSNs) is a challenging issue due to the peculiarities of the underlying physical layer technology. Since the recharging or replacement of sensor nodes is almost impossible after deployment, the critical issue of network lifetime maximization must be considered right from the beginning of designing the routing schemes. We propose a mobile sink (MS)-based data collection scheme that can extend network lifetime, taking into account power-constrained sensor nodes, partitioned networks with geographically distant data collection points and periodic monitoring applications with delay-tolerance. Lifetime extension is achieved by mitigating the ‘sink neighbourhood problem’ and by deferring the data transmissions until the MS is at the most favourable location for data transfer. Unlike the models available for terrestrial WSNs, we consider non-zero travel time of the MS between data collection points, thus making our model more realistic for UWSNs, both connected and partitioned. The performance of the proposed mobility-assisted data collection scheme is thoroughly investigated using both analytical and simulation models. The analytical results are compared to those of existing models to assess their effectiveness and to investigate the trade-offs. Results show that, with a network size of 60 nodes, the network lifetime achieved by the proposed model is 188% higher than that of static sink model and 91% higher than that of mobile sink model (MSM). The proposed maximum lifetime routing scheme is implemented in the network simulation platform OMNET++, for validating the analytical results as well as for evaluating other performance metrics that are not tractable via analytical methods. Both analytical and simulation results demonstrate the superiority of the proposed model in capturing realistic network conditions and providing useful performance indicators prior to network deployment. 相似文献
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The authors proposed a selective assign shortest path first (SASPF) algorithm for routing and wavelength assignment in the presence of four wave mixing (FWM) in wavelength division multiplexing network with a design parameter Vm. In order to maintain a reasonably good performance in terms of blocking probability to fulfil the connection requests but also to allow acceptable FWM effects, Vm is an important design parameter (number of established optical channels to fulfil the connection requests but also to allow acceptable FWM effects). If its value is too low, many connection requests will not be able to establish, which may lead to higher blocking probability. On the other hand, if its value is too high, it may lead to obvious FWM effects that will affect the network performance. Thus, Vm must be optimum to balance the requirement of the connection requests and also the induced FWM crosstalks. Performance results show that SASPF algorithm outperforms the comparison scheme such as traditional assign shortest path first resulting in low blocking probability with a specific value of Vm. 相似文献
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ABSTRACTReal-time wavelength conversion and traffic routing at key network nodes is a fundamental requirement for current optical interconnects. This work experimentally demonstrates a broadband wavelength conversion from O-band to C-band employing commercially available, power efficient VCSELs. A 1310?nm VCSEL is directly modulated with 8.5 Gbps data and transmitted over 22?km G. 652 fibre with a 0.53 dB penalty. The received data is used to run a 1550?nm VCSEL located at the network integration node, achieving the first reported wavelength conversion from O-to-C-band. VCSEL wavelength tuneability with changing bias current functionality is further exploited to route the converted wavelength over 400?GHz spectra range for integration into wavelength flexible networks. The newly converted wavelength is transmitted over 24.7?km of G. 655 fibre, incurring a maximum penalty of 1.86?dB. Results from this work proves an enabling development technology for wavelength converters for transparent contention resolution in current and future optical Interconnects. 相似文献
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We propose a novel system of the dynamic optical tweezers generated by a dark soliton in the fiber optic loop. A dark soliton known as an optical tweezer is amplified and tuned within the microring resonator system. The required tunable tweezers with different widths and powers can be controlled. The analysis of dark-bright soliton conversion using a dark soliton pulse propagating within a microring resonator system is analyzed. The dynamic behaviors of soliton conversion in add/drop filter is also analyzed. The control dark soliton is input into the system via the add port of the add/drop filter. The dynamic behavior of the dark-bright soliton conversion is observed. The required stable signal is obtained via a drop and throughput ports of the add/drop filter with some suitable parameters. In application, the trapped light/atom and transportation can be realized by using the proposed system. 相似文献
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Abstract This paper proposes a new switching architecture to be used in all optical packet switching networks. The proposed switch is derived from an original 2 × ?2 two‐stage multi‐buffer switched delay line based optical switching node, known as an M‐Quadro node. By incorporating bypass lines into the M‐Quadro architecture and employing a novel switch control strategy, the optical packet switching node can effectively resolve packet contentions, thus reducing the packet deflection probability substantially. Furthermore, we show that such architecture is scalable for a generic multiple stages optical packet switch with a larger number of input/output ports. 相似文献
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An efficient analytical method is presented for the calculation of blocking probabilities in a tandem queuing network with simultaneous resource possession. This queuing network model is motivated from the need to model optical burst switching networks, where the size of the data bursts varies and the link distance between two adjacent network elements also varies depending on the network?s topology. A fast single-node decomposition algorithm is developed to compute the blocking probabilities in the network. The algorithm extends the popular link-decomposition method from teletraffic theory by allowing dynamic simultaneous link possession. Simulation is used to validate the accuracy of the algorithm. 相似文献
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ABSTRACTWe experimentally demonstrate the first VCSEL-based all-optical wavelength reuse technique with reconfigurable fibre Bragg grating add and drop multiplexer. EDFA gain saturation and Bragg trans-reflection effect on a single FBG are respectively, adopted for full-duplex reference frequency and data transfer. A 1550 nm energy-efficient VCSEL is modulated with 1.7?GHz clock signal and transferred downstream over 26.6?km fibre OLT attain a phase noise stability of ?54.01 dBc/Hz at 10?kHz offset frequency. A saturated EDFA is exploited to optically reduce the peak-to-peak voltage of the incoming downstream RF, allowing for wavelength reuse with 10?Gbps upstream data. A 1.57 dB transmission penalty is incurred over the transmission fibre. An all-passive OADM is developed exploiting Bragg trans-reflection at 1549.45?nm. The reflected wavelength is routed over another 24.7?km fibre network attaining an extinction ratio of 6.1?dB and a SNR of 5.8?dB. This work provides an all-optical technique for routing and spectral management in flexible networks. 相似文献
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The author evaluates the performance of bufferless optical packet switches equipped with shared tuneable optical wavelength converters (TOWC) and supporting the quality of service (QoS). The TOWCs are shared per output fibre and, hence each output fibre has a dedicated pool of TOWCs. The TOWCs are not completely shared within the node. The QoS, expressed in terms of the packet loss probability, is differentiated by giving the packets different priorities in accessing both the output wavelengths and the TOWCs. A scheduling algorithm is proposed and its complexity is evaluated. The QoS technique?s effectiveness is studied by means of an analytical model based on a probabilistic approach and validated by simulation results. The results show that the proposed technique to support the QoS facilitates a good differentiation of the QoS offered to packets. 相似文献
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In transport networks, human beings are moving objects whose moving direction is stochastic in emergency situations. Based on this idea, a new model—stochastic moving network (SMN) is proposed. It is different from binary-state networks and stochastic-flow networks. The flow of SMNs has multiple-saturated states, that correspond to different flow values in each arc. In this paper, we try to evaluate the system reliability, defined as the probability that the saturated flow of the network is not less than a given demand d. Based on this new model, we obtain the flow probability distribution of every arc by simulation. An algorithm based on the blocking cutset of the SMN is proposed to evaluate the network reliability. An example is used to show how to calculate the corresponding reliabilities for different given demands of the SMN. Simulation experiments of different size were made and the system reliability precision was calculated. The precision of simulation results also discussed. 相似文献
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Research in the field of free-space optical interconnection networks has reached a point where simulators and other design tools are desirable for reducing development costs and for improving design time. Previously proposed methodologies have only been applicable to simple systems. Our goal was to develop a simulation methodology capable of evaluating the performance characteristics for a variety of different free-space networks under a range of different configurations and operating states. The proposed methodology operates by first establishing the optical signal powers at various locations in the network. These powers are developed through the simulation by diffraction analysis of the light propagation through the network. After this evaluation, characteristics such as bit-error rate, signal-to-noise ratio, and system bandwidth are calculated. Further, the simultaneous evaluation of this process for a set of component misalignments provides a measure of the alignment tolerance of a design. We discuss this simulation process in detail as well as provide models for different optical interconnection network components. 相似文献
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讨论了WDM光网中,在动态业务流量和有限范围波长变换情况下的动态路由和波长分配问题。基于Moone-Dijkstra算法,考虑到动态波长变换的可能和限制,提出了一种新型的、可实现动态最小代价路由和最佳虚波长通道的综合启发式算法(DMC-OVWP)。该算法对路由子问题和波长分配子问题既相互独立,又相互结合,优化了RWA。以中国教育和科研计算机网(CERNET)为拓扑背景,基于本算法进行了计算机仿真,并对实验结果进行了比较分析,证明本算法可充分利用网络信息获取较低的阻塞率。 相似文献
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In this paper new analytical travel time models for the computation of cycle times for unit-load double-deep automated storage and retrieval systems (in continuation double-deep AS/RS) are presented. The proposed models consider the real operating characteristics of the storage and retrieval machine and the condition of rearranging blocking loads to the nearest free storage location during the retrieval process. With the assumption of the uniform distributed storage rack positions and the probability theory, the expressions of the single and modified dual command cycle have been determined. The proposed models enable the calculation of the mean cycle time for single and dual command cycles, from which the performance of the double-deep AS/RS can be evaluated. A simulation model of the selected double-deep AS/RS has been developed to compare the performances of the proposed analytical travel time models. The numerical analyses show that with regard to the examined type of double-deep AS/RS with a different fill-grade factor, the results of the proposed analytical travel time models correlate with the results of simulation models of double-deep AS/RS. 相似文献