• Journal of Communications and Networks
• /
• v.8 no.4
• /
• pp.475-479
• /
• 2006

In Korea, we witness vivid evidences of changing trend in communication that insist the emergence of new networking architecture. To accommodate the changing trend and to hold current strong position in global IT industry, Korea have launched broadband convergence network (BcN) initiative. BcN vision for Korea is to be the first in the world to realize converged network infrastructure and ubiquitous service environment. In this paper, we have introduced the concept and the vision of BcN with a viewpoint of a new paradigm to prepare future-proof communication environment. And then, we have disclosed BcN research and development (R&D) activities including R&D philosophy, R&D phases, and key technologies required. Also, we have discussed current development issues in three technology branches including service and control technology, unified transport technology, and next-generation access technology.

• Journal of Communications and Networks
• /
• v.14 no.4
• /
• pp.418-428
• /
• 2012

With the requirement for providing multiple levels of access control for group members, many group key management schemes designed for hierarchical access control have been put forward. However, most of these schemes focus on the efficiency of group key establishment and rekeying in centralized environments. This paper proposes an integrated group key agreement (IGK) scheme for contributory environments. The IGK scheme employs the integrated key graph to remove key redundancies existing in single key trees, and reduces key establishment and rekeying time while providing hierarchical access control. Performance analyses and simulations conducted with respect to computation and communication overheads indicate that our proposed IGK scheme is more efficient than the independent group key agreement scheme.

• Journal of Communications and Networks
• /
• v.16 no.3
• /
• pp.293-300
• /
• 2014

As energy harvesting communication systems emerge, there is a need for transmission schemes that dynamically adapt to the energy harvesting process. In this paper, after exhibiting a finite-horizon online throughput-maximizing scheduling problem formulation and the structure of its optimal solution within a dynamic programming formulation, a low complexity online scheduling policy is proposed. The policy exploits the existence of thresholds for choosing rate and power levels as a function of stored energy, harvest state and time until the end of the horizon. The policy, which is based on computing an expected threshold, performs close to optimal on a wide range of example energy harvest patterns. Moreover, it achieves higher throughput values for a given delay, than throughput-optimal online policies developed based on infinite-horizon formulations in recent literature. The solution is extended to include ergodic time-varying (fading) channels, and a corresponding low complexity policy is proposed and evaluated for this case as well.

• Journal of Communications and Networks
• /
• v.15 no.5
• /
• pp.464-468
• /
• 2013

The widespread use of cryptographic technologies is complicated by inconsistencies and duplication in the key management systems supporting their applications. The proliferation of key management systems or protocols also results in higher operational and infrastructure costs, and fails in interoperability. Thus, it is essential to realize key management interoperability between different and heterogeneous cryptosystems. This paper presents a practical and separable key management system for heterogeneous public-key cryptosystems. We achieve the interoperability between different cryptosystems via cryptography approaches rather than communication protocols. With our scheme, each client can freely use any kind of cryptosystemthat it likes. The proposed scheme has two advantages over the key management interoperability protocol introduced by the organization for the advancement of structured information standards. One is that all the related operations do not involve the communication protocol and thus no special restrictions are taken on the client devices. The other is that the proposed scheme does not suffer from single-point fault and bottleneck problems.

• Proceedings of the IEEK Conference
• /
• 2009.05a
• /
• pp.3-5
• /
• 2009

In this paper, we exploit the cooperative diversity relay protocol to compensate for defects of wireless communication in 60 GHz. We derive and proof results of the numerical expressions versus various scenarios using the computer simulations. Optimal location and scaling factor of relay are presented through analysis of performances and compared between direct-path and time diversity transmission. Consequently, our results confirm that cooperative diversity relay protocol is an effective mean of enhancing the performance of wireless communication systems in 60 GHz.

• Proceedings of the IEEK Conference
• /
• 2008.06a
• /
• pp.797-798
• /
• 2008

Visual quality of video telephony over 3G networks is not satisfactory due to limited bandwidths. Therefore, it is worthwhile to enhance subjective visual quality based on ROI coding. In this paper, we propose a rate-control algorithm for video telephony with ROI based H.264|AVC coding. The QP values are increasingly assigned in non-ROI away from the ROI so that graceful degradation of visual quality can be achieved, which is more visually pleasant.

• Proceedings of the IEEK Conference
• /
• 2002.07b
• /
• pp.1117-1120
• /
• 2002

In general, standard TCP/IP (transmission control protocol-internet protocol), which is called TCP/IP, is using as the communication basis protocol between any collections of networks that is connected. In this paper, using this TCP/IP implementation of remote system and suitable program for long distance communication is proposed. This system can make system, which basic Ethernet and TCP/IP used system, to mini modeling, so all module that is using here can be used. Therefore, intention of this paper is to reduce expenses, to effective manage for plant and to increase of productivity as linking each plant of several factories to TCP/IP and Ethernet, and then many control plant and manager minimize the needed course.

• Proceedings of the IEEK Conference
• /
• 2000.11b
• /
• pp.144-147
• /
• 2000

Data security is an important issue in today's computer networks. In order to construct a safe infra in the open communication network, a cryptography is necessarily applied to several communication application fields like a high-speed networking system supporting real-time operation. A cryptography which has already realized by a software is designed by using a hardware to improve a throughput. In this paper, we design hardware architecture of IDEA by using a single iterative round method to improve a encryption throughput. In addition, we intend to develop a hardware design methodology that a specific cryptography operate with high-speed. The hardware model is described in VHDL and synthesized by the Samsung KG 80 Library in the Synopsys development software tool. With a system clock frequency 20MHz, this hardware permits a data conversion rate of more than 116 Mbit/s.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
• /
• 2000.11a
• /
• pp.44-48
• /
• 2000

In this study was modify the PRMA for supporting various types of traffic classes such as CBR, VBR, ABR and UBR. For uplink, we use reservation slots and so the performance will not degrade in case of over load conditions. For downlink broadcasting slots for informing the status of slot reservations are used so the high priority priority terminal can preempt. And we use almost same size buffer as the frame size. So we can dynamically deal with, the traffic changes of VBR terminals. It makes easy for the terminals to reserve supplementary slots. Each terminal is reallocated by the priority of traffic classes and so we can easily select the dropping packets in case of overload conditions. As a result, using our scheme, we can get high channel efficiency and get low packet dropping ratio and delay.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2003.06a
• /
• pp.181-184
• /
• 2003

Recently, the fieldbus becomes an indispensable component for many automated systems. In the fieldbus system, realtime data containing sensor values and control commands has a tendency to rapidly lose its value as time elapses after its creation. In order to deliver these data in time, the fieldbus network should be designed to have short delay compared to the maximum allowable delay. Because the communication delay is affected by performance parameters such as target rotation timer of token passing protocol, it is necessary to select proper parameter settings to satisfy the real-time requirement for communication delay. This paper presents the timer selection method for Profibus token passing networks using genetic algorithm (GA) to meet the delay requirements.