Zichun Le

Prediction of particular matter concentrations by developed feed-forward neural network with rolling mechanism and gray model

Abstract Particular matter (PM) due to its side effects on human health like increase the risk of lung cancer and vision impairment has been one of the major concerns for air quality. These particles are now considered as one of the high priorities issues by health organizations in China. In this study, daily PM2.5 and PM10 concentrations data from November 2013 to January 2014 in Hangzhou, Shanghai and Nanjing (three important cities in Yangtze River delta of China) were used to introduce more suitable method to forecast air PM2.5 and PM10 concentrations. Feed-forward neural networks (FFNN) have been introduced as a possible forecasting model for complex air quality prediction. However, due to its deficiency to assess the possible correlation between different input variables, an enhanced FFNN with rolling mechanism (RM) and accumulated generating operation (AGO) of gray model (RM-GM-FFNN) was developed. RM and AGO were used to address the trends of input samples of FFNN and detract the randomness of the input data of FFNN, respectively. Both FFNN and RM-GM-FFNN were tested for prediction of the daily PM2.5 and PM10 concentrations with meteorological parameters and historical PM concentration during the given time. The numerical results showed that in all cases, the coefficient of determination (R2) and the index of agreement of RM-GM-FFNN increased, while the root-mean-square error (RMSE) and mean absolute error of RM-GM-FFNN decreased. In addition, the mean bias error was more close to zero when compared with that of FFNN, indicating that RM-GM-FFNN performed a better accuracy.

BFD-based failure detection and localization in IP over OBS/WDM multilayer network

Optical burst switching (OBS), which takes advantage of both high capacity of optical fiber and sophisticated control of electronics, has been considered as a promising paradigm for the modern Internet. In this paper, the recovery procedures for IP over OBS/WDM multilayer network are addressed, which focus on the failure detection and failure localization. Bidirectional forwarding detection (BFD) mechanism which provides low-overhead, short-duration detection of failures in the path between adjacent forwarding engines, including the interfaces, data link(s) is introduced for the failure detection and localization in the IP over OBS/WDM multilayer network, especially at the OBS/WDM layer. The unique feature of OBS and the easy-to-implement merit of BFD make it feasible for BFD adopted at OBS/WDM layer. Besides, BFD is a highly cost effective method when compared with traditional methods such as detecting the Loss of Light of each wavelength. Not only the implementation details of BFD-based failure detection for the OBS/WDM layer are demonstrated in this paper, but also how the BFD localizes failures such as fiber failure, link failure and node failure. Moreover, extensive simulations have been done at different scenarios such as single failure and multiple failures. And the numerical results concerning the performance of BFD-based failure detection and localization in terms of failure detection and localization time and BDP lost rate verified the proposed solution. Copyright

Performance evaluation of the survivability schemes in WOBAN: a quality of recovery (QoR) method

Summary The hybrid wireless optical broadband access network (WOBAN) is a combination of an optical backhaul and a wireless front-end, which combine the huge amount of available bandwidth of optical networks and the ubiquity and mobility of wireless access networks with the objective of reducing their cost and complexity. Survivability is one of the most important issues in WOBAN. In this paper, the survivability schemes in WOBAN are addressed from a particular point of view of the quality of recovery (QoR) method. The QoR is a comprehensive measure to evaluate the survivability schemes in terms of availability, recovery time, redundancy, and bandwidth of backup path. The specific procedures to set up the analytical models for the survivability schemes in WOBAN are given based on the QoR concept, including abstract, normalization, and application. Besides, the weights assignment is provided to calculate the QoR value for the operators, home users, or business users with different requirements, which in turn offers the user-perceptive quality of service. To verify the performance of the survivability schemes by the QoR method, extensive simulations are made under different WOBAN configurations. Numerical results show that for the intra-domain survivability schemes, the wireless and optical mixed protection scheme is the best choice for failure recovery in WOBAN. The wireless scheme is the second choice for the solution, which emphasizes cost control, while for the solution that emphasizes the network performance, the 1:1 scheme is the second choice. The 1:N scheme obtains the worst QoR value as the splitter ratios increase. For the inter-domain survivability schemes, optimizing backup optical networking units selection and backup fibers deployment scheme outperforms maximum protection with minimum cost scheme from the point of view of QoR. Copyright

A novel segment protection with segment route scheme in multicasting survivable networks

The protection scheme is a key issue in survivable wavelength division multiplexing (WDM) optical networks. In this paper, we investigate the problem of multicast requests in survivable networks against any single-link failure and propose a novel scheme called segment protection with segment route (SPSR). Through dynamically adjusting link-cost according to the current network state, SPSR establishes a primary light-tree and corresponding link-disjoint backup segments for each multicast connection request. An analytical model was proposed for blocking probability analysis and adaptive routing algorithm to solve the potential shortcomings in the real network. We make the use of the idea of segmented routes according to the branch nodes. We then combine the each segment to get the whole blocking probability. Simulation results show that with the consideration of load balancing SPSR exhibits better blocking probability and resource utilization performance relative to other schemes.

Liquid Gradient Refractive Index Microlens for Dynamically Adjusting the Beam Focusing

An in-plane liquid gradient index (L-GRIN) microlens is designed for dynamically adjusting the beam focusing. The ethylene glycol solution (core liquid) withde-ionized (DI) water (cladding liquid) is co-injected into the lens chamber to form a gradient refractive index profile. The influences of the diffusion coefficient, mass fraction of ethylene glycol and flow rate of liquids on the refractive index profile of L-GRIN microlens are analyzed, and the finite element method and ray tracing method are used to simulate the convection-diffusion process and beam focusing process, which is helpful for the prediction of focusing effects and manipulation of the device. It is found that not only the focal length but the focal spot of the output beam can be adjusted by the diffusion coefficient, mass fraction and flow rate of liquids. The focal length of the microlens varies from 942 to 11 μm when the mass fraction of the ethylene glycol solution varies from 0.05 to 0.4, and the focal length changes from 127.1 to 8 μm by varying the flow rate of the core liquid from 0.5 × 103 to 5 × 103 pL/s when there is no slip between the core and cladding inlet. The multiple adjustable microlens with a simple planar microfluidic structure can be used in integrated optics and lab-on-chip systems.

DAART: Delay-aware Adaptive Round Time MAC Protocol to Improve Throughput in Light-trail Networks

Abstract Light-trail (LT) has been proposed as an attractive solution for optical networks to support emerging services such as video-on-demand, pseudo-wires, data-centers, etc. Due to the fact that light-trail (LT) is a shared-medium network, the media access control (MAC) protocol is essential to be implemented in the whole network. In this paper, we propose a novel MAC protocol called DAART (Delay-aware Adaptive Round Time) to improve the throughput in LT network. DAART MAC adopts the delay-aware mechanism to calculate the actual token holding time for every transmission node. More specifically, the token holding time can be evaluated from queue delay, transmission delay and slot-synchronization delay. To estimate the throughput performance of DAART MAC protocol, we give three different patterns of traffic and compare the throughput between DAART MAC and ART MAC. Simulation results show that DAART has more stable throughput performance than ART, which in return enhances the throughput of LT networks.

Design and Simulation of the Light-trail Node for Mesh WDM Networks

Abstract Light-trails have been proposed as a solution for optical networking to provide support for emerging services such as video-on-demand, pseudo-wires, data-centers, etc. Node architecture and its transmission performance are one of the most important issues for the physical layer of light trail network. In this paper, the light trail node architectures designed specially for the mesh topology WDM network are addressed. A novel node architecture is proposed, which supports both global wavelength switching and local access wavelength switching with lower costs. In order to verify the transmission performance of the proposed node architecture, a DWDM based optical communication platform is built. Extensive simulations are made for the light trails when changing the LT node number from three to six. In the mean time, the optical spectrums of signal and noise as well as the eye diagrams of OSC channel, local access wavelength channel and global wavelength channel are measured and recorded. Simulation results show that the light trail which adopted the proposed LT node architecture can travel up to five nodes. In this case, the BER of the OSC channel is 1.73e-015 and Q factor is 7.86. The BER of the local access wavelength channel is 1.84e-016 and Q factor is 8.14. The BER of global wavelength channel is 3.53e-015 and Q factor is 7.78. Hence, the proposed light trail node architecture can meet the requirement of physical layer at mesh WDM networks for most cases.

Quality of Recovery (QoR) Analysis for the ONU Protection in WOBAN

The wireless-optical broadband access network (WOBAN) is a promising architecture for future access networks. In this paper, the survivability problem of WOBAN with respect to ONU protection is addressed. And, a new concept called Quality of recovery (QoR) is introduced as the assessment of different protection schemes. Availability, recovery time, redundancy are chosen as the main factors in QoR. To verify the analytical models for four ONU protection schemes, simulation has been done on the basis of a WOBAN with 32 ONUs. Simulation results show that the weakest selection protection scheme is seemed as the scheme with best cost effective when compared with other schemes.

Delay Aware Time Slot Allocation Algorithm in Light-Trail Network

Light trail (LT) is a generalization of lightpath with ability to provision emerging IT applications such as data center, clod computing, etc. The time slot allocation (TSA) problem is addressed with respect to delay aware ability. In addition, a delay aware TSA algorithm is given on the basis of bidding policy. The bid value is composed of two parts: the delay bid and the buffer bid. The node which sends the highest bid will get the transmission right of the light trail for the next time slot. Simulation results concerning the traffic and delay in a 5 and 6 nodes light trail network show that: by means of adopting the delay aware TSA algorithm, higher loads which usually need longer delay are allocated the time slots preferentially. Hence, the delay aware TSA algorithm can improve the LT network throughput when assures the transmitting delay less than the maximum-tolerant delay.

Design of a practical optical cross-connect with limited-range wavelength conversion

The architecture of and the corresponding control algorithm for a devised optical cross-connect, limitedrange wavelength converision wavelength interchangeable cross-connect (L-WIXC), are presented. The performances of L-WIXC including blocking probability, switching time, and throughput are simulated. Cost comparison with wavelength selective cross-connect (WSXC) and WIXC is calculated. Key optical parameters, such as crosstalk, eye diagram, bit error rate, and linear Q factor, are measured and discussed.