• 한국컴퓨터정보학회논문지
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• 제23권2호
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• pp.53-61
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• 2018

In this paper, the author proposes an efficient group key agreement scheme in a mobile environment where group members frequently join and leave. This protocol consists of basic protocols and general ones and is expected to be suitable for communications between a mobile device with limited computing capability and a key distributing center (or base station) with sufficient computing capability. Compared with other schemes, the performance of the proposed protocol is a bit more efficient in the aspects of the overall cost for both communication and computation where the computational efficiency of the scheme is achieved by using exclusive or operations and a one-way hash function. Also, in the aspect of security, it guarantees both forward and backward secrecy based on the computational Diffie-Hellman (CDH) assumption so that secure group communication can be made possible. Furthermore, the author proves its security against a passive adversary in the random oracle model.

• 한국통신학회논문지
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• 제22권6호
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• pp.1323-1333
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• 1997

In this paper, we propose an efficient architecture for a high-speed cell concentrator/distributor(HCCD) in an ATM(Asynchronous Transfer Mode) switch and by analyzeing the simulation results evaluate the performance of the proposed architecuture. The proposed HCCD distributes cells from a switch link to local processors, or concentrates cells from local processor s to a switch link. This design is to guarntee a high throughput for the IPC (inter-processor communication) link in a distributed ATM switching system. The HCCD is designed in a moudlar architecture to provide the extensibility and the flexibility. The main characteristics of the HCCD are 1) Adaption of a local CPU in HCCD for improving flexibility of the system, 2) A cell-baced statistical multiplexing function for efficient multiplexing, 3) A cell distribution function based on VPI(Virtual Path Identifier), 4) A bypassing capability for IPC between processor attached to the same HCCD, 5) A multicasting capability for point-to-multipoint communication, 6) A VPI table updating function for the efficient management of links, 7) A self-testing function for detecting system fault.

• 한국유통학회지:유통연구
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• 제8권2호
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• pp.67-84
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• 2003

본 연구는 경로구성원의 관계가 단기적인 관점에서 장기적인 관점으로 전환되는 시점에서 경로구성원간 의사소통 질의 중요성을 확인하기 위하여 진행되었다. 과거의 영향전략 연구가 경로구성원의 힘-의존 관계에서의 불균형 관계에 주로 초점을 맞춘 반면, 의사소통 질이라는 개념을 도출하여, 관계적인 경로구성원의 의사소통 측면을 고려하였다. 기존 연구에서 다루어지고 있는 의사소통 질은 경로구성원간에 전달되는 정보의 정확성, 적시성, 유용성, 신뢰성이 확보된 것을 의미한다. 연구모형에서 의사소통 질의 선행요소로서 정보공유 의지, 정보제공 능력을 도입하였고, 의사소통 질의 성과를 검토하기 위하여 갈등수준과의 관계를 점검하였다. 실증은 PC제조업체와 대리점의 관계를 대리점의 관점에서 진행하였다. 결과는, 대체로 기대와 일치하게 나타났으나, 의사소통 질에 대한 정보공유 의지의 영향은 직접적으로 나타나기 보다 정보제공 능력을 경유하여 간접적으로 전달됨을 발견하였다.

• 한국게임학회 논문지
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• 제9권2호
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• pp.59-68
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• 2009

본 연구는 게임엔진 공급자의 기술체제와 기술혁신에 따른 Licensing 전략을 실증적으로 분석하였다. 분석 결과 게임엔진 공급자의 기술체제가 이질적으로 분화되고, 게임엔진의 기술체제가 이용자 친화적일수록 게임 개발기업(user)의 거래가 증가하였다. 게임엔진 공급자의 Licensing 전략을 결정하는 기술지식 변수로는 엔진 공급자의 기술체제의 이용자 친화성(User Friendliness)이 가장 설명력이 높다. 공급자의 엔진 구조의 모듈화, 게임엔진의 범용성, 암묵적(tacit) 기술지식의 명시화(cordifiablity), 게임엔진의 혁신정도가 클수록 엔진기술지식의 지원역량이 증가되고, 동시에 엔진기술의 거래 비용이 감소함에 따라 불완전한 게임기술시장에서 효율적인 시장거래가 이루어지고 있다.

• Journal of information and communication convergence engineering
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• 제4권4호
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• pp.162-165
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• 2006

This paper presents a bandwidth efficient self-cancellation scheme for interchannel interference (ICI) in OFDM transmission systems. Conventional self-cancellation schemes provide an excellent cancellation capability of ICI for relatively low frequency offsets. However, this capability is achieved at the expense of bandwidth efficiency and thus a higher modulation level is often used to compensate for desired throughput. By applying a partial differential coding (PDC) to the transmit data prior to the ICI self-cancellation, bandwidth efficiency is greatly improved by a factor of 2, while maintaining a string of data (+1, -1) alternately for the ICI. self-cancellation in OFDM systems. Computer simulations show that the performance of the proposed scheme is comparable to the conventional self-cancellation scheme with slight performance degradation for relatively lower frequency offsets.

• International Journal of Contents
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• 제2권1호
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• pp.9-16
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• 2006

Recently many researches are investigating for ubiquitous computing and network. In the real world many sensor devices must be equipped to provide many services for users. To make computing environment easy and more user friendly, middleware system not only hides all complexities (network, system, services, etc), but also needs to have efficient context inference scheme and system reconfiguration capability. In this paper we suggest context-aware middleware design for sensor network which provides efficient computing environment for end-users. We also present XML based implementation of our system.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권3호
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• pp.794-814
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• 2012

We propose a novel method for improving Wi-Fi positioning accuracy while reducing the energy consumption of mobile devices. Our method presents three contributions. First, we jointly and intelligently select the optimal subset of access points for positioning via maximum mutual information criterion. Second, we further propose local discriminant embedding algorithm for nonlinear discriminative feature extraction, a process that cannot be effectively handled by existing linear techniques. Third, to reduce complexity and make input signal space more compact, we incorporate clustering analysis to localize the positioning model. Experiments in realistic environments demonstrate that the proposed method can lower energy consumption while achieving higher accuracy compared with previous methods. The improvement can be attributed to the capability of our method to extract the most discriminative features for positioning as well as require smaller computation cost and shorter sensing time.

• Journal of Communications and Networks
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• 제15권4호
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• pp.422-429
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• 2013

Advances in wireless sensor network (WSN) technology have enabled small and low-cost sensors with the capability of sensing various types of physical and environmental conditions, data processing, and wireless communication. In the WSN, the sensor nodes have a limited transmission range and their processing and storage capabilities as well as their energy resources are limited. A triple umpiring system has already been proved for its better performance in WSNs. The clustering technique is effective in prolonging the lifetime of the WSN. In this study, we have modified the ad-hoc on demand distance vector routing by incorporating signal-to-noise ratio (SNR) based dynamic clustering. The proposed scheme, which is an efficient and secure routing protocol for wireless sensor networks through SNR-based dynamic clustering (ESRPSDC) mechanisms, can partition the nodes into clusters and select the cluster head (CH) among the nodes based on the energy, and non CH nodes join with a specific CH based on the SNR values. Error recovery has been implemented during the inter-cluster routing in order to avoid end-to-end error recovery. Security has been achieved by isolating the malicious nodes using sink-based routing pattern analysis. Extensive investigation studies using a global mobile simulator have shown that this hybrid ESRP significantly improves the energy efficiency and packet reception rate as compared with the SNR unaware routing algorithms such as the low energy aware adaptive clustering hierarchy and power efficient gathering in sensor information systems.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권11호
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• pp.4203-4223
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• 2021

Accelerated by the Internet of Things (IoT), the need for further technical innovations and developments within wireless communications beyond the fifth generation (B5G) networks is up-and-coming in the past few years. High altitude platform station (HAPS) communication is expected to achieve such high levels that, with high data transfer rates and low latency, millions of devices and applications can work seamlessly. The HAPS has emerged as an indispensable component of next-generations of wireless networks, which will therefore play an important role in promoting massive IoT interconnectivity with 6G. The performance of communication and key technology mainly depend on the characteristic of channel, thus we propose an efficient Markov chain based channel model, then analyze the HAPS communication system's uplink capability and swing effect through experiments. According to the simulation results, the efficacy of the proposed scheme is proven to meet the requirements of ubiquitous connectivity in future IoT enabled by 6G.

• JSTS:Journal of Semiconductor Technology and Science
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• 제13권1호
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• pp.8-14
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• 2013

A low density parity check (LDPC) decoder provides a most powerful error control capability for mobile communication devices and storage systems, due to its performance being close to Shannon's limit. In this paper, we introduce an efficient overlapped LDPC decoding algorithm using a upper dual-diagonal parity check matrix structure. By means of this algorithm, the LDPC decoder can concurrently execute parts of the check node update and variable node update in the sum-product algorithm. In this way, we can reduce the number of clock cycles per iteration as well as reduce the total latency. The proposed decoding structure offers a very simple control and is very flexible in terms of the variable bit length and variable code rate. The experiment results show that the proposed decoder can complete the decoding of codewords within 70% of the number of clock cycles required for a conventional non-overlapped decoder. The proposed design also reduces the power consumption by 33% when compared to the non-overlapped design.