• Current Optics and Photonics
• /
• 제4권4호
• /
• pp.277-285
• /
• 2020

Computer-generated holograms (CGH) are the core devices to solve the problem of freeform surface measurement. In view of the overlay error introduced in the manufacturing process of CGH, this paper proposes an evaluation model for analyzing the overlay error of CGH. The detection method of extracting CGH profile information by an ultra-depth of field micro-measurement system is presented. Furthermore, based on the detection method and technical scheme, the effect of overlay error on the wavefront accuracy of CGH can be evaluated.

• Journal of KIISE:Information Networking
• /
• 제34권4호
• /
• pp.239-245
• /
• 2007

New multimedia services over the cellular/WLAN overlay networks require different Quality of Service (QoS). In the cellular/WLAN overlay structure, the main issue of load balancing is to balance the available bandwidth among different networks. In this paper, we propose a new online network management scheme. Our proposed scheme is designed to improve bandwidth utilization by balancing the traffic load between the cellular network and WLANs. Simulation results indicate the superior performance of our proposed framework to strike the appropriate performance balance between contradictory QoS requirements under widely varying diverse traffic loads.

• The KIPS Transactions:PartC
• /
• 제14C권1호
• /
• pp.81-86
• /
• 2007

New multimedia services over the cellular/WLAN overlay networks require different Quality of Service (QoS). Therefore, efficient network management system is necessary in order to provide QoS sensitive multimedia services while enhancing network performance. In this paper, we propose a new online network management scheme that implements bandwidth reservation, congestion and transmission control strategies. Our online approach to network management exhibits dynamic adaptability, flexibility, and responsiveness to the current traffic conditions in multimedia overlay networks. Simulation results indicate the superior performance of our proposed scheme to strike the appropriate performance balance between contradictory QoS requirements under widely varying diverse traffic loads.

• Journal of Broadcast Engineering
• /
• 제23권1호
• /
• pp.26-35
• /
• 2018

The recent development of overlay network technology enables distributed sharing of various types of contents. Although overlay network has great advantages as a huge content repository, it is practically difficult to directly provide such Internet service as streaming of contents. On the other hand, the media server, which is specialized in content services, has excellent service capabilities, but it suffers from the huge contents that are constantly created and requires large expansion of severs and storages, and thus requires much effort for efficient management of the huge repository. Hence, the association of an overlay network of huge storage with a media server of high performance content service will show a great synergy effect. In this paper, a location-aware scheme of constructing overlay networks and associating it with media server is proposed, and then cache-based contents management and service policy are proposed for efficient content service. The performance is analysed for one of the content services, streaming service.

• Proceedings of the IEEK Conference
• /
• 대한전자공학회 2008년도 하계종합학술대회
• /
• pp.245-246
• /
• 2008

A cell planning and resource allocation scheme called the proposed is presented for improving channel capacity and for maintaining a proper QoS (Quality of Service) over the downlink OFDMA (Orthogonal Frequency Division Multiple Access) system. Through an optimal combination of sectorization and frequency overlay, the proposed scheme accomplishes an improvement in both channel capacity and outage probability. In the simulation, the proposed scheme outperforms 3-sectorization in terms of throughput and outage probability.

• Journal of Korea Multimedia Society
• /
• 제16권7호
• /
• pp.862-869
• /
• 2013

In order to support a cell-independent traffic asymmetry, the conventional TDD system cannot avoid crossed time slot (CTS) interference. Moreover, the TDD/FDD hierarchical overlay cellular systems is taken into account as a generally accepted cell model in a heterogeneous radio environment. In this paper, we propose an interference resolving radio resource allocation technique in a TDD-OFDMA cellular system that overlays a FDD-CDMA cell. In our proposed scheme, we exploit under-used FDD-CDMA uplink resource by TDD mobile abiding by a region based time slot(TS) allocation which in turn mitigates CTS interference considerably. It is demonstrated that combined with under-used resource utilization scheme based on mobile's location, the proposed technique can reduce CTS interference considerably and support the asymmetric traffic in TDD system.

• Journal of the Korea Safety Management & Science
• /
• 제7권5호
• /
• pp.255-273
• /
• 2005

Overlay parameter control of the semiconductor photolithography process is researched in this paper. Overlay parameters denote the error in superposing the current pattern to the pattern previously created. The reduction of the overlay deviation is one of the key factors in improving the quality of the semiconductor products. The semiconductor process is affected by numerous environment and equipment factors. Through process condition prediction and control, the overlay inaccuracy can be reduced. Generally, three types of process condition change exist; uncontrollable white noise, slowly changing drift, and abrupt condition shift. To effectively control the aforementioned process changes, control scheme using adaptive deadband is proposed. The suggested approach and existing control method are cross evaluated through simulation.

• ETRI Journal
• /
• 제28권4호
• /
• pp.411-424
• /
• 2006

This paper presents a multimedia streaming platform for efficiently transmitting MPEG-4 content over IP networks. The platform includes an MPEG-4 compliant streaming server and client, supporting object-based representation of multimedia scenes, interactivity, and advanced encoding profiles defined by the ISO standard. For scalability purposes, we employ an application-layer multicast scheme for media transmission using overlay networks. The overlay network, governed by the central entity of the network distribution manager, is dynamically deployed according to a set of pre-defined criteria. The overlay network supports both broadcast delivery and video-on-demand content. The multimedia streaming platform is standards-compliant and utilizes widespread multimedia protocols such as MPEG-4, real-time transport protocol, real-time transport control protocol, and real-time streaming protocol. The design of the overlay network was architected with the goal of transparency to both the streaming server and the client. As a result, many commercial implementations that use industry-standard protocols can be plugged into the architecture relatively painlessly and can enjoy the benefits of the platform.

• Journal of the Korean Institute of Landscape Architecture
• /
• 제20권2호
• /
• pp.119-126
• /
• 1992

The purpose of this study is to develop the allocation method which could be applied to the transitional stage between analysis and synthesis to select the best alternative in landscape planning process. By using the matrix of alternatives with site-planning elements locational drawing in each, the combinational allocation method can make the process more rational and also more efficient. Hand-drawn map overlay technique accommodates the work I handy way. The method is useful in building conceptual scheme in landscape planning especially when it is applied to small scale project.

• Journal of KIISE:Information Networking
• /
• 제32권5호
• /
• pp.593-602
• /
• 2005

Overlay multicast delivery method is a new approach in which multicast functionality is implemented at the end-hosts application layer in the timing of sparse deployment of IP multicast. However, existing overlay multicast protocols are not being standardization and many restrictions occur when delivering high capacity contents. Therefore, new delivery mechanism is required for the overlay multicast based high capacity contents delivery. In this paper. we separate group management and delivery management of overlay multicast and describe a capable group management. We also defined high speed delivery method better than that of existing overlay multicast through use of collaborated distribute downloading. This improved efficiency of massive contents transmission.