• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.37 no.7A
• /
• pp.528-534
• /
• 2012

In order to achieve high capacity and reliable link quality of the overlay convergent networks with the cognitive networking based on the advanced capability of the mobile terminal, a Distributed Wireless Communication System (DWCS) can provide the capability of enhancing the link quality. This paper has considered virtual cell: the Dual Virtual Cell (DVC), and also proposes DVC employment strategy based on radio resource monitering. The considered system constructs DVC for multi-user high-rate data transmission, and the DWCS system exploits space-time trellis codes i.e., STTC to improve a spectral efficiency. The effects of imperfect CSI(channel state information) on the system performance has also been investigated.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.10 no.11
• /
• pp.5253-5270
• /
• 2016

With device-to-device (D2D) communications, an inactive user terminal can be utilized as a relay node to support multi-hop communication so that connective experience of the cell-edge user as well as the capacity of the whole system can be significantly improved. In this paper, we investigate the spectrum sharing for a cooperative relay assisted D2D communication underlying a cellular network. We formulate a joint relay selection and channel assignment problem to maximize the throughput of the system while guaranteeing the quality of service (QoS) requirements of cellular users (CUs) and D2D users (DUs). By exploiting coalition formation game theory, we propose two algorithms to solve the problem. The first algorithm is designed based on merge and split rules while the second one is developed based on single user's movement. Both of them are proved to be stable and convergent. Simulation results are presented to show the effectiveness of the proposed algorithms.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.29 no.3A
• /
• pp.266-275
• /
• 2004

Recently, wireless networks require an efficient handover scheme due to increase of mobile devices. But Bluetooth has several problems to support the efficient handover, which are the additional increase of signaling traffic and long time of the initial setup processes of inquiry and paging processes. This paper suggests an efficient Soft Handover method for Bluetooth (eSoHoB), which reduces the eplased time of the inquiry and paging process and supports a soft handover using the anticipation method. This paper implements the eSoHoB using two Bluetooth hardware modules and a testbed to be able to receive streaming data while a Bluetooth terminal is moving. This paper measures handover delays and the operation of the soft handover to verify the proposed mhthod.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.40 no.7
• /
• pp.1248-1256
• /
• 2015

It is necessary to apply an exact data and a precise prediction model for a rain attenuation to design the link margin for a data link using Ku-band with the serious effect by rain. In this paper, we investigate the regional rainfall-rate distribution of Korea proposed in TTAK.KO-06.0122/R1 and compare it with the distribution provided by Rec. ITU-R PN.837-1 and Crane. And, the rain rate climate regions similar with the rainfall-rate distribution of Korea in Rec. ITU-R PN.837-1 and Crane model are selected. Finally, using Rec. ITU-R P.618-8 and Crane rain attenuation prediction model, we derive and analyze the rain attenuation for Ku-band frequency according to the time percentage of an average year and the distance of wireless communication link between unmanned aerial vehicle (UAV) and ground data terminal (GDT).

• Journal of Digital Contents Society
• /
• v.8 no.3
• /
• pp.371-376
• /
• 2007

Many modules such as controller, sensor, telematics terminal, navigation, audio and video are connected each other via vehicle network (CAN, MOST, etc). Futhermore, users can have ITS or internet services in moving by connecting to wireless mobile network. These network capabilities can cause a lots of security issues such as data hacking, privacy violation, location tracking and so on. Some possibilities which raise a breakdown or accident by hacking vehicle operation data (sensor, control data) are on the increase. In this paper, we propose a security module which has encryption functionalities and can be used for vehicle network system such as CAN, MOST, etc. This security module can provide conventional encryption algorithms and digital signature processing functionality such as DES, 3-DES, SEED, ECC, and RSA.

• Proceedings of the Korean Information Science Society Conference
• /
• 2003.10c
• /
• pp.610-612
• /
• 2003

본 논문은 무선 셀룰러 시스템 환경에서 일정구간을 이동하는 지하철, 기차와 같이 규칙적인 이동 패턴을 보이는 운송 매체에 탑승한 사용자들의 이동성을 지원하기 위해 PGLT(Profile­based Group Location Tracking) 기법을 제안한다. 최근 무선 통신 기술의 발전으로 인한 이동 사용자(Mobile Terminal, MT)의 급증은 시그널링 트래픽의 증가로 이어져 결국 위치 관리 비용까지 높아지게 되었다. MT들이 동시에 새로운 등록 영역으로 이동할 때 GLT(Group Location Tracking) 위치 관리 기법에서는 기존 IS­41의 각 사용자들의 개별적인 위치 갱신 요청 대신에 그룹을 이용한 위치 갱신 요청으로써 위치 관리 비용을 줄였다. 그러나 본 논문에서 제안하는 PGLT 기법은 GLT 기법을 향상시킨 기법으로서, 사용자들의 규칙적인 이동 패턴 특성을 살린 프로파일 정보를 이용하여 그룹에 대한 위치 갱신 비용까지도 줄일 수 있다. MSRP­VLR(Mobility Scheduler on Regular Path)과 RMB(Regular path Movement Buffer)를 이용하여 일정구간을 이동하는 TV(Transportation Vehicle)가 위치 갱신 요청을 하면, MSRP­VLR은 이동 경로에 대한 프로파일 정보를 보내어 TV의 RMB에 저장함으로써 그 경로를 이동 시 그룹에 대한 위치 갱신 요청을 할 필요가 없게 된다. 따라서 PGLT 기법은 GLT 기법의 그룹 위치 갱신 비용을 줄임으로써 일정구간을 이동하는 TV에 탑승한 많은 사용자들에 대한 위치 관리 비용을 현저히 줄일 수 있다.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.13 no.5
• /
• pp.65-70
• /
• 2013

In this paper, we propose a multi-hop cooperative transmission protocol to obtain energy savings in static wireless networks. Each terminal in the network is equipped with a single antenna and each receiver uses equal gain combining technique (EGC) to combine received signals. We also propose a power allocation strategy which optimizes the total transmit power at each stage. Monte-Carlo simulations are presented to evaluate and compare performance of the proposed protocol with the multi-hop direct transmission (MDT) and the cooperative routing protocol proposed by Khadani [8], in terms of the average total transmit power and the average number of required stages.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2017.05a
• /
• pp.300-302
• /
• 2017

The Internet of Things allows you to connect everything around you to your network and make it easy to reach anytime, anywhere. The Internet of Things uses various devices such as smart devices and wireless sensors connected to the network. When any small information about command or result is exposed to the outside during communication between each terminal, there is a serious risk. The Internet has a characteristic that it is much weaker than general network in terms of security because it has limited hardware performance. In this paper, I propose an enhanced security architecture of Internet of Things considering the limitation of hardware.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2018.10a
• /
• pp.639-640
• /
• 2018

Currently, the technique of identifying location using radio wave fingerprint is widely used in indoor positioning field. At this time, in order to confirm a successful position, it is necessary to construct the data necessary for learning and testing and to construct the multidimensional data. That is, location data collection and data management technology capable of responding to environmental changes that may occur due to various changes in peripheral radio wave fingerprint such as wireless AP, BLE iBeacon, and mobile terminal are required. Therefore, this paper proposes a technique to construct and manage multidimensional data which is less sensitive to environmental changes of radio wave fingerprinting required for positioning.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.36 no.10B
• /
• pp.1175-1181
• /
• 2011

For vertical handover, the part for the homogeneous handover needs to be modified, which allows users to utilize the various wireless access schemes with a mobile terminal with PFMIPv6. In this paper, we considered a cross-layer design for fast vertical handover between MIH and PFMIPv6, where two MIH-layer messages are suggested to reduce handover latency and integrate between MIH and PFMIPv6 efficiently. The proposed scheme is evaluated with handover latency. The results show that the proposed handover procedure reduces handover latency compared with the existing one.