• Communications of the Korean Mathematical Society
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• v.24 no.4
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• pp.501-508
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• 2009

This paper presents a new representation algorithm which computes the representation for elements of a free group generated by two linear fractional transformations and also the justification of the algorithm in order to show how it operates correctly and efficiently according to inputs.

• Communications of the Korean Mathematical Society
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• v.28 no.4
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• pp.649-667
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• 2013

In this paper we give an explicit formula for the total number of subgroups of a finite abelian $p$-group up to rank three.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.2 s.93
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• pp.167-173
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• 2005

The isolation of the series PIN diode switch is restricted by the parallel capacitance of PIN diode and the switch driver circuit limits switching speed of PIN diode switch. To overcome these problems, a high isolation and high switching speed Pin diode switch is proposed adapting the parallel resonant inductance and TTL compatible switch driver circuit. The measurement results of the 3 GHz PM diode switch show 1 GHz frequency band, less than 1.5 dB insertion loss, 65 dB isolation, more than 15 dB return loss and less than 30 ns switching speed. In particular the 3 GHz PIN diode switch using the parallel resonant inductance exhibits the improvement of isolation by 15 dB.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.2
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• pp.498-514
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• 2012

Machine to machine (M2M) communications is the hottest issue in the standardization and industry area, it is also defined as machine-type communication (MTC) in release 10 of the 3rd Generation Partnership Project (3GPP). Recently, most research have focused on congestion control, sensing, computing, and controlling technologies and resource management etc., but there are few studies on security aspects. In this paper, we first introduce the threats that exist in M2M system and corresponding solutions according to 3GPP. In addition, we present several new security issues including group access authentication, multiparty authentication and data authentication, and propose corresponding solutions through modifying existing authentication protocols and cryptographic algorithms, such as group authentication and key agreement protocol used to solve group access authentication of M2M, proxy signature for M2M system to tackle authentication issue among multiple entities and aggregate signature used to resolve security of small data transmission in M2M communications.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.2
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• pp.245-251
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• 2016

Despite the exponential throughput improvement in mobile communications systems, their ability to satisfy requirements of state-of-the-art and future applications of advanced metering infrastructure (AMI) is still under investigation. Challenges are mainly due to the inadequacy of third generation partnership project (3GPP) networks to support large amounts of devices simultaneously, while the number of AMI end-devices and the frequency of their data transmission increase with new AMI-based applications. In this introductory survey, innovative and future AMI applications and their communication requirements are first reviewed. Then, we identify challenges of 3GPP long term evolution (LTE) in enabling future AMI applications. More importantly, the latest improvements to LTE-A standard release 12 and 13 are reviewed and analyzed with regards to their potential to improve the quality of LTE-enabled AMI. It is found that 3GPP enhancements on machine type communications (MTC) standards will significantly enhance AMI communications. Beyond MTC specifications, non-MTC-specific enhancements such as carrier aggregation and multi-connectivity for user equipment will also contribute greatly to improving reliability and availability of AMI devices. The paper's focus is towards improved backhaul support for innovative and future AMI applications, beyond traditional automatic meter reading.

• International Journal of Contents
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• v.13 no.4
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• pp.47-62
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• 2017

This paper analyzes how much the gap existed between the public group and expert group using future issues and future core technologies that are announced in government institutions based on ontology. We calculated gap with two groups' point of view, one is expert groups' ideas that are based on future hopeful technologies documents, and another is public people ideas that are based on documents of contest that is hosted by 'Ministry of Science, ICT and Future Planning (MSIP)', and 'Institute for Information & communications Technology Promotion (IITP)'. For calculating these, we suggested SDGM model. In the case of ETRI Meta-trend ICT Field, there is a little gap between expert group and public group, and another case that is XT (ETRI determined future technologies excluding ICT field) Field, the gap is increasing annually. Moreover, in the case of all ETRI Meta trend, the gap is bigger than ICT and XT field. We analyzed, also, KEIT's future issues for generalizing this model. The gap existed between two groups. Utilizing SDGM model of this paper, people can interpret easily how much the gap exists between future technologies and issues that are announced in institutions.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.991-994
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• 2005

In the uni-directional broadcasting environments, almost TV programs are scheduled depending on the viewers' popular watching time, and the advertisement contents in these TV programs are mainly arranged by the popularity and the ages of the audience. However, the advertisement programs which support the TV programs the audiences want are not served to the appropriate audiences efficiently. In this paper, we propose the prototype of target advertisement system for the appropriate distribution of the advertisement contents. The proposed target advertisement system estimates the audience's profile without private information and provides the target advertisement contents by using his/her inferred profile. And we show the accuracy of the proposed algorithm, Multistage Classifier, for the target advertisement system and the implementation of our target advertisement system.

• Proceedings of the Korean Information Science Society Conference
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• 2006.10d
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• pp.223-227
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• 2006

인터넷의 발전에 따라 다자간 그룹 통신 환경이 주목을 받게 되었고 이를 위해 다대다 멀티캐스트를 이용한 통신 기법들이 제안되었다. 이들 중 GAM (Group Aided Multicast) 은 다대다 멀티캐스트의 신뢰적 전달을 보장하기 위해 트리 기반의 손실 복구 기법을 제안하고, 제어 트리 관리 비용과 손실 복구 효율성간의 접점을 찾기 위해 그룹 개념을 도입하고 그룹의 대표로서 코어 노드를 정의한다. 코어 노드는 네트워크 상의 특정 지점에 미리 설치된 전용 노드로서 그룹 내의 손실 복구와 그룹 간의 손실 제어를 담당한다. 그러나 이러한 전용 코어 노드의 도입은 프로토콜의 가용성을 제한하고 코어 노드의 설치 부담을 가지게 된다. 따라서 본 논문에서는 별도의 코어 노드의 설치 없이 프로토콜이 동작할 수 있도록 세션 참가자 중에서 코어 노드를 동적으로 선택하고, 로컬 그룹 노드 중에서 제어 트리의 효율성을 최대한 보장하는 노드의 위치를 결정하는 기법을 제안한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.6
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• pp.1127-1136
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• 1997

A vector timestamp is used to satisfy message ordering in a group communications. In this paper, we propose a new vector timestamp compression method which is applicable to a single process group environment where one process belongs to only one precess group. An existing compression method compares the fields of the previously sent vector timestamp with thouse of the currently updated vector timestamp, then sends only the modified fields of the vector timestamp. Unlike the previous one, a proposed compression method performs individual compression for each process using the locally maintained vector timestamp information on other processes. Also, we logicallyproved the causal ordering algorithm using the new compression method and compared the performance of the proposed method with one of the previous compression method by computer simulation. Using the proposed compression method, the message overhead required for causal ordering can be reduced.

• Journal of Korea Multimedia Society
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• v.13 no.6
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• pp.865-874
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• 2010

Recently, Hao et al. proposed a privacy preservation protocol based on group signature scheme for secure vehicular communications to overcome a well-recognized problems of secure VANETs based on PKI. However, although efficient group signature schemes have been proposed in cryptographic literatures, group signature itself is still a rather much time consuming operation. In this paper, we propose a more efficient privacy preservation protocol than that of Hao et al. In order to design a more efficient anonymous authentication protocol, we consider a key-insulated signature scheme as our cryptographic building block. We demonstrate experimental results to confirm that the proposed protocol is more efficient than the previous scheme.