• Proceedings of the Korean Institute of Communication Sciences Conference
• /
• 2006.07a
• /
• pp.39-55
• /
• 2006

• Journal of Korea Multimedia Society
• /
• v.19 no.12
• /
• pp.1992-1999
• /
• 2016

In layered communication architecture, each layer is designed to service its own functions to higher layer while getting serviced by lower layer. Usually layered architectures are not optimized in a total view of whole services and functions. So cross layer design pursues performance enhancements by optimizing in various ways. In LTE, MAC layer uses HARQ mechanism and RLC layer uses ARQ mechanism for retransmission. According to the 3GPP 36.331 specification, two layers' cooperation may not happen in an optimized way. This paper suggests an adaptive MAC layer approach which RLC layer's function might be initiated in MAC layer in advance to utilize MAC layer's idling wasting time for RLC layer's next decision. This adaptive ARQ method in MAC layer speeds up the next retransmission and reduces the overall transmission time. Emulation shows the improved performance in total retransmission time and retransmission success ratio. In wireless shadow area, the retransmission occurs frequently. Our approach has strong points in this poor wireless condition.

• Journal of Communications and Networks
• /
• v.11 no.5
• /
• pp.489-499
• /
• 2009

We describe the fundamental issue of scheduling the allocation of wireless network resources and provide several formulations of the associated problems. The emphasis is on scheduling transmission attempts. We place this problem in the context of existing approaches, like information theoretic and traditional network theoretic ones, as well as novel avenues that open up the possibility of addressing this issue for non-stationary and non-ergodic environments. We summarize concrete recent results for specific special cases that include unicast and multicast traffic, different objective functions, and reduced complexity versions of the problem. We conclude with some thoughts for future work. We identify and single out the cross-layer nature of the problem and include a simple physical-layer criterion in what is mostly a medium access control (MAC) problem.

• Journal of IKEEE
• /
• v.11 no.4
• /
• pp.165-170
• /
• 2007

The main goal of research concerning clustering protocols is to minimize the energy consumption of each node and maximize the network lifetime of wireless sensor networks. However, most existing clustering protocols mainly focused on the design and formation of clusters, leaving the consideration of communication between the cluster head and the sink behind. In this paper, we propose efficient multi path routing algorithm by using MAC-NET Cross-layering. multi path needed only one tiny packet from sink to setup. In addition proposed algorithm can be used for any cluster-based hierarchical inter-clustering routing algorithm. The simulation results demonstrate that proposed algorithm extended the overall survival time of the network by reducing the load of cluster heads. The performance of proposed algorithm is less affected by the extension of sensing field than other inter-clustering operation.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.51 no.12
• /
• pp.30-45
• /
• 2014

Recently, multimedia application users who demand for ubiquitous computing environment are rapidly increasing, and wireless mesh network is receiving attention as a cost-effective key technology for next generation wireless networking. When multiple flows are transmitting data at the same time in the network, routing for path selection of each flow and link resource allocation for data transmission of each flow are one of the key factors that influence to the effectiveness of the network directly. In this paper, we consider problems for path discovery and resource allocation of links at the same time and we propose an algorithm based on mathematical modeling using a technique for cross-layer optimization design in STDMA-based wireless mesh networks that can enhance transfer performance for each flow. We show by performance analysis that the proposed algorithm can enhance the throughput performance by maximally utilizing given bandwidth resources when the number of flows increase in multi-hop wireless mesh networks.

• Journal of the Korea Society of Computer and Information
• /
• v.13 no.4
• /
• pp.177-184
• /
• 2008

The design goal of protocols in wireless sensor networks (WSN) is mainly energy efficiency because of their stringent resource and energy constraints. In this paper, we propose a simple cross-layered protocol for WSNs, so called EATD(Energy-Aware Tree based Delivery scheme). EATD is a tree-based energy aware data delivery algorithm by using a SYNC packet with link and node cost to maximize the network lifetime. Our simulation results show significant improvements compared with existing schemes in terms of energy efficiency and delay.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.35 no.12B
• /
• pp.1749-1757
• /
• 2010

This paper considers the cost minimization problem to satisfy QoS (Quality of Service) requirements for a given network, in particular when communication resources to each link can be additionally assigned. For the purpose of quantifying QoS requirements such as data transfer delay and packet loss, we introduce the cost function considering both the link utilization factor and the additionally assigned resource. To minimize this cost function, we firstly formulate a Basic Capacity Planning (BCP) problem, a special case of Network Utility Maximization (NUM). We show that the solution of this BCP problem cannot be optimal via a counter example. In this paper, we suggest the cross-layer design of both additionally assigned resource and routing path, whose initial values are set to the result of BCP problem. This cross-layer design is based on a heuristic approach which presents an effective way to plan how much communication resources should be added to support the QoS requirements in future. By simulation study, we investigate the convergence of the cost function in a more general network topology as well as in a given simple topology.

• Structural Engineering and Mechanics
• /
• v.56 no.4
• /
• pp.667-694
• /
• 2015

The suspended dome system is a new structural form that has become popular in the construction of long-span roof structures. Suspended dome is a kind of new pre-stressed space grid structure that has complex mechanical characteristics. In this paper, an optimum topology design algorithm is performed using the enhanced colliding bodies optimization (ECBO) method. The length of the strut, the cable initial strain, the cross-sectional area of the cables and the cross-sectional size of steel elements are adopted as design variables and the minimum volume of each dome is taken as the objective function. The topology optimization on lamella dome is performed by considering the type of the joint connections to determine the optimum number of rings, the optimum number of joints in each ring, the optimum height of crown and tubular sections of these domes. A simple procedure is provided to determine the configuration of the dome. This procedure includes calculating the joint coordinates and steel elements and cables constructions. The design constraints are implemented according to the provision of LRFD-AISC (Load and Resistance Factor Design-American Institute of Steel Constitution). This paper explores the efficiency of lamella dome with pin-joint and rigid-joint connections and compares them to investigate the performance of these domes under wind (according to the ASCE 7-05), dead and snow loading conditions. Then, a suspended dome with pin-joint single-layer reticulated shell and a suspended dome with rigid-joint single-layer reticulated shell are discussed. Optimization is performed via ECBO algorithm to demonstrate the effectiveness and robustness of the ECBO in creating optimal design for suspended domes.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.18 no.3
• /
• pp.66-73
• /
• 2019

Recently, FDM-type 3D printer technology has been developed, and efforts have been made to improve the output formability and characteristics further. Through this, 3D printers are used in various fields, and printer technologies are suggested according to usage, such as FDM, SLA, DLP, and SLM. In particular, the FDM method is the most widely used, and the FDM method technology is being developed further. The characteristics of the output are produced by the FDM-type 3D printer, which is determined by various factors, and particularly the perspective of the Inter-Layer Fill Factor, which is the volume ratio of the laminated material that exerts a direct influence. In this study, the Inter-Layer Fill Factor is theoretically obtained by presenting the internal space between each layer according to the laminate thickness as a cross-sectional shape model, and the cross section of the actual laminated sample is compared with the theoretical model through experiments. Then, the equation for the theoretical model is defined, and the strength change according to each condition (tensile strength of material, reduction slope, strength reduction rate, and output strength) is confirmed. In addition, we investigated the influence on the correlation and strength between laminate thickness and the Inter-Layer Fill Factor.

• Journal of IKEEE
• /
• v.24 no.1
• /
• pp.326-332
• /
• 2020

This paper presents the design of a routing metric for energy-efficient and low-delay path selection and a new routing protocol utilizing the metric in duty-cycyled wireless sensor networks. The new routing metric based on duty cycle, EDW, can reduce the energy and delay of transmission paths, which represents total waiting time from source to destination due to duty cycle. Therefore, in this paper, we propose a new multipath routing protocol based on cross-layer information utilizing the new routing metric, and simulation results show that the proposed protocol shows better performance of end-to-end delay and energy consumption.