EQUIVALENT ELASTIC MODULUS OF THE HONEYCOMB CORE BASED ON FEM MODEL

The honeycomb core model was built by finite element method（ FEM）. And based on Hooke ’s law,the equivalent elastic modulus of honeycomb core influenced by the change of cell number was studied. The result indicates that the horizontal equivalent elastic modulus is affected slightly while the vertical equivalent elastic modulus is influenced severely by the changes of cell number in horizontal direction. The changes of cell number in vertical direction have a strong impact on the horizontal equivalent elastic modulus while that affect the vertical equivalent elastic modulus slightly. When the ratio of honeycomb core’s size in horizontal direction to that in vertical direction is less than 1. 3,the horizontal equivalent modulus is less than the vertical equivalent elastic modulus. On the other hand,the horizontal equivalent modulus is greater than or equal to the vertical equivalent elastic modulus. For the large-scale structure,a honeycomb core with similar proportion can be established to calculate the equivalent elastic modulus

Joint Variable Width Spectrum Allocation and Link Scheduling for Wireless Mesh Networks

Abstract—In wireless mesh networks with frequency-agile radios, an algorithm of dynamically combining consecutive channels has recently been proposed. However, the available channel widths are limited in the algorithm. In order to further improve the fairness or the throughput under given fairness, we propose a joint variable width spectrum allocation and link scheduling optimization algorithm. Our algorithm is composed of time division multiple access for no interface conflict and frequency division multiple access for no signal interference. In the first phase, we use as few time slots as possible to assign at least one time slots to each radio link with Max-Min fairness. In the second phase, our design jointly allocates the lengths of time slots as well as the spectral widths and center frequencies of radio links in each time slot. Numerical results indicate that compared to the existing algorithm, our algorithm significantly increases the fairness or the throughput under given fairness. Keywords-spectrum allocation; link scheduling; variable channel width; wireless mesh networks I

Joint traffic splitting, rate control, routing, and scheduling algorithm for maximizing network utility in wireless mesh networks

The existence of multiple gateways, as is a common case in wireless mesh networks (WMNs), brings the possibility to improve network performance. However, previous studies, including both heuristic-based works and theory-driven cross-layer design works, cannot guarantee an optimal exploitation of multiple gateways. In this paper, we focus on exploiting multiple gateways optimally to achieve maximum network utility. We first extend the current framework of cross-layer design and formulate a network utility maximization (NUM) problem under WMNs with multiple gateways as a constrained optimization problem. Then, by solving this optimization problem, we propose a novel joint traffic splitting, rate control, routing, and scheduling algorithm called cross-layer control with dynamic gateway selection (CLC_DGS), which splits and distributes network traffic into multiple gateways in an optimal way. We prove that CLC_DGS can achieve maximum network utility. Finally, we run extensive simulations to demonstrate that, compared with the previous methods, CLC_DGS significantly improves the performance of WMNs under various network environments, including gateway heterogeneity, link heterogeneity, and different interference models.15 page(s

Cross-layer design with optimal dynamic gateway selection for wireless mesh networks

The existence of multiple gateways, as is a common case in Wireless Mesh Networks (WMNs), brings the possibility to improve network performance. However, previous studies, including both heuristic-based gradual-optimization work and theory-driven cross-layer design work, cannot guarantee an optimal exploitation of multiple gateways. In this paper, we first extend the current framework of cross-layer design to incorporate a dynamic gateway selection strategy, and propose a novel joint traffic splitting, rate control, routing and scheduling algorithm called CLC_DGS, which distributes traffic of a flow into multiple gateways in an optimal way so as to guarantee maximum network utility. Secondly, based on CLC_DGS, we propose an enhanced CLC_DGS_DD algorithm which in addition takes into account the delay requirements for network flows. CLC_DGS_DD provides a flexible framework for adjusting delays among different flows, and thereby achieves as low as order-optimal delays for preferential flows while simultaneously guaranteeing maximum network utility. Through theoretical analysis and simulation experiments, we demonstrate that compared with previous studies, CLC_DGS and CLC_DGS_DD significantly improve performance of WMNs.11 page(s

Low latency IP mobility management: protocol and analysis

Abstract Mobile IP is one of the dominating protocols that enable a mobile node to remain reachable while moving around in the Internet. However, it suffers from long handoff latency and route inefficiency. In this article, we present a novel distributed mobility management architecture, ADA (Asymmetric Double-Agents), which introduces double mobility agents to serve one end-to-end communication. One mobility agent is located close to the MN and the other close to the CN. ADA can achieve both low handoff latency and low transmission latency, which is crucial for improvement of user perceived QoS. It also provides an easy-to-use mechanism for MNs to manage and control each traffic session with a different policy and provide specific QoS support. We apply ADA to MIPv6 communications and present a detailed protocol design. Subsequently, we propose an analytical framework for systematic and thorough performance evaluation of mobile IP-based mobility management protocols. Equipped with this model, we analyze the handoff latency, single interaction delay and total time cost under the bidirectional tunneling mode and the route optimization mode for MIPv6, HMIPv6, CNLP, and ADA. Through both quantitative analysis and NS2-based simulations, we show that ADA significantly outperforms the existing mobility management protocols.</p