• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.17 no.11
• /
• pp.2563-2568
• /
• 2013

Recently, various solutions to support explosively growing mobile data traffic have attracted intensive attentions. However, the range of spectrum which can be exploited for mobile communications is very limited. Small cell networks are actively investigated because they can efficiently offload mobile data traffic from macro cells without using additional spectrum. In this paper, we developed a system-level simulator considering small cell networks in the indoor environments. We compare the performance of outage probability when a load-balancing algorithm is utilized or not. We can reduce the outage probability of congested BS with the load-balancing algorithm. In addition, overall outage probability of whole wireless systems can be reduced by using the proposed load-balancing algorithm.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.27 no.5
• /
• pp.438-444
• /
• 2016

In this paper, A real-time channel module which can apply the wireless propagation channel was developed using USRP and Lab-VIEW. When the proposed channel module is used in conjunction with the implemented HW(hardware) simulators for cognitive radio and frequency interference analysis and so on, it can increase the reliability about wireless propagation environments. In addition, the proposed module overcomes the limit of existing HW simulator that data transfer rate is limitative in communication system through the design of the inner parts. Along with this, it is possible to apply channel parameters necessary to estimate the easier communication performance. Also, this has the advantage that it can be flexibly applied in implementing the communication channel with the upcoming new scenarios. The proposed module can estimate the communication performance via constellation and BER using the implemented module.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.9 no.1
• /
• pp.181-187
• /
• 2005

This paper proposes and implements a service model to transfer messages safely for PDA on CDMA wireless network and a secure massage transfer protocol which considers characteristics of PDA. Proposed service uses SMS(Short Message Service) connect to a off-line client device with the wired network for data communication. After receiving SMS message, client device processes the SMS message and creates a data channel through RAS(Remote Access Service), then the data of the server can be pushed to clients. The implemented security protocol can provide safe data transmission on each communication line through two way channels(SMS and data). Also, by using security nonce table, this protocol can reduce a number of transmissions for exchanging a safe session key, so intensity of encryption can be increased.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.19 no.12
• /
• pp.2800-2804
• /
• 2015

Recently, device-to-device (D2D) direct communication is attracting much interest and many researches have been conducted. In this paper, we investigated an algorithm to support the D2D direct communication in cellular mobile communication networks. We investigated the optimal D2D scheduling algorithm which can achieve the maximal sum-rate in cellular uplink frequency. We also proposed a simple scheduling algorithm which can considerably reduce the computational complexity, compared to the optimal scheme. Finally, we analyzed the performance of the proposed scheme based on computer simulations.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2011.10a
• /
• pp.662-665
• /
• 2011

The cognitive radio (CR) network has been studied in the form of open source by vast number of communities, and the potential expectation is very high since the CR is based on reprogrammable platform. However, this characteristics of open-source software take high risk as well. As the peer-to-peer software has been abused, so high is the chance that the CR network can be abused public wide. Consequently, the benefit from the study of next-generation wireless network can be at risk because of the negative impact of violation of communication law or abusing the CR. In this contribution, we analyze the issues and the problems of the CR and discuss an efficient measure against security attacks.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.14 no.2
• /
• pp.53-58
• /
• 2014

As the amount of data between ECUs has increased, the FlexRay consortium proposed FlexRay network system which has larger bandwidth than CAN. But because of implementation cost, CAN and FlexRay hybrid network with FlexRay-CAN gateway will make up the largest part of in-vehicle networks for the present. In this paper, a FlexRay-CAN gateway for a real time feedback control system is implemented, and a data packing algorithm is presented. Finally, a real control experiment with multi-motor system is conducted to verify the proposed gateway system.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.19 no.8
• /
• pp.1853-1858
• /
• 2015

The existence communications of vessel focused on voice, FAX, ISDN, etc. using satellite on the existent most communications on the ships, and recently, the ships need high quality smart communication service environments. In the results of experiments using the existent system, it could access on board, but in the closed room of vessel, was impossible to access e-mail and smart apps except voice communication. In the present paper, we implemented a novel communication system that can access voice, text, e-mail, file, vessel monitoring apps, etc. It consists of a convergent communication terminal combined with satellite and communication for Smartphone, and smart communication environment on the closed room. As the results, we can access a variety of smart communication in anywhere on board.

• The KIPS Transactions:PartC
• /
• v.16C no.6
• /
• pp.691-698
• /
• 2009

A mobile communication device is a small size of portable computer which provides communication service, such as smart phone and PDA. Currently, one of the biggest barriers in developing the mobile communication device is security issue. Even though there are excellent security functions which can remove the security issues, there is a problem that the mobile communication device can not be loaded with all the functions because it has low storage, poor computational power, and inconvenient user interface, compared to the desktop personal computer. This paper proposes a context-aware security reconfiguration scheme for effective security management of the mobile communication device. The scheme can provide the mobile communication device with the optimized security service which is most adapted to its current security context. Through the prototype implementation and the experiments of the proposed scheme, we have confirmed that the proposed scheme is excellent in terms of computing resource efficiency and usability, without degrading security level.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.35 no.11C
• /
• pp.889-895
• /
• 2010

MIMO system generally requires more than one antenna at the communication device. However, many wireless devices are limited by size, cost or hardware complexity to one antenna. To overcome such restrictions, we used a new technique, called cooperative communication. We propose a new cooperative transmission strategy system using cross-layer coding method base on H-ARQ for optimal communication. Proposed cooperative H-ARQ system that can improve the above problems and can get the better performance. In proposed cooperative system with H-ARQ method, if the received signal from source node is satisfied by the destination preferentially, the destination transmit ACK message to both relay node and source node, and then recovers the received signal. In addition, if ARQ message indicates NACK message, relay node operates selective retransmission. Based on the simulation results in aspect to BER performance and throughput, the proposed method which combined cooperative system with H-ARQ based on cross-layer coding can improve spectral efficiency reliability of system compared with that of general one by one system.

• Journal of Digital Convergence
• /
• v.13 no.8
• /
• pp.281-288
• /
• 2015

The container terminals use convergence technology that exchange information for cargo work, using wireless communication between the TOS(Terminal Operations System) and the handling equipments(CC, TC, YT). But if the container cargoes pile up high in the container yard, delayed cargo work and cargo working list information error happen because of communication dead spots(the worker can not receive the information) which wireless communication is disconnected. At this time the driver of the yard tractor(YT) must be able to recognize the communication state. If then, delayed cargo work and cargo working list information errors that occur in the shaded communication area can be avoided, and can process the delayed work due to wireless communication break. In this project, we have built wireless communication environment to increase the efficiency of the loading and unloading operations which the operator can respond actively, when the work is delayed and work orders result in errors. That is, the flow of the wireless communication module has been changed.