• Journal of Communications and Networks
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• v.11 no.5
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• pp.509-517
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• 2009

This work proposes a new distributed and self-organized authentication scheme for mobile ad-hoc networks (MANETs). Apart from describing all its components, special emphasis is placed on proving that the proposal fulfils most requirements derived from the special characteristics of MANETs, including limited physical protection of broadcast medium, frequent route changes caused by mobility, and lack of structured hierarchy. Interesting conclusions are obtained from an analysis of simulation experiments in different scenarios.

• Journal of Communications and Networks
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• v.16 no.2
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• pp.183-192
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• 2014

This paper proposes a payment-based power control scheme using non-cooperative game with a novel pricing function in cognitive radio networks (CRNs). The proposed algorithm considers the fairness of power control among second users (SUs) where the value of per SU' signal to noise ratio (SINR) or distance between SU and SU station is used as reference for punishment price setting. Due to the effect of uncertainty fading environment, the system is unable to get the link gain coefficient to control SUs' transmission power accurately, so the quality of service (QoS) requirements of SUs may not be guaranteed, and the existence of Nash equilibrium (NE) is not ensured. Therefore, an alternative iterative scheme with sliding model is presented for the non-cooperative power control game algorithm. Simulation results show that the pricing policy using SUs' SINR as price punishment reference can improve total throughput, ensure fairness and reduce total transmission power in CRNs.

• Journal of IKEEE
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• v.17 no.4
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• pp.484-491
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• 2013

In this paper, we proposed an internal multiband loop embedded monopole antenna for mobile handset that could be used for smart phones. The proposed antenna has a volume of 40 mm(W) ${\times}$ 15 mm(L) ${\times}$ 5 mm(H), ground plane size is 40 mm(W) ${\times}$ 80 mm(L), and covers the GSM900 (Global System for Mobile communications : 880-960 MHz), K-PCS (Korea-Personal Communications Service : 1750-1870 MHz), US-PCS (US Personal Communications Service : 1850-1990 MHz), WCDMA (Wideband Code Division Multiple Access : 1920-2170 MHz), Wibro (2300-2390 MHz), Bluetooth (2400-2483 MHz) and WLAN (Wireless Local Area Network : 2400-2483.5 MHz) bands for VSWR (voltage standing wave ration) less than 3. The proposed loop adding design at middle section of longest branch showed wide impedance bandwidth for the lowest resonance frequency band. The proposed antenna have a lowest resonance frequency band from 738 MHz to 1075 MHz for S11 value of -6dB. A HFSS (High Frequency Structure Simulator) of the Ansys Corporation based on a finite element method is employed to analyze the proposed antenna in the design process and to compare the simulation and experimental results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.11
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• pp.934-936
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• 2013

A routing scheme for a group of mobile users for wireless ad-hoc networks is presented. The proposed scheme mines social activity patterns from wireless traces, and exploits social user group for efficient data routing among users based on a data publish approach. Simulation results based on real-world wireless traces show that our routing scheme reduces routing cost for a large mobile user group with a factor of 1.8 compared to a baseline counterpart.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.2
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• pp.209-215
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• 2013

Currently Plastic Student Identity Card has not been used frequently because it is inconvenient to possess. In this paper, we propose and develope Mobile Student Identity Card(MSIC) which consists of combination of smart phone and student identity card to support convenient campus life for students in school. The main features of the developed MSIC are as follows. First, it can confirm student identity and offer MSIC to each students by using Database. Second, it can support convenient campus life for students by adequate layout. In the performance evaluation, we use development kit based on Android and AVD(Android Virture Device) for simulation.

• The Transactions of the Korea Information Processing Society
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• v.7 no.4
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• pp.1279-1289
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• 2000

Recently, research activities for combining portable computer technology and wireless communication technology are in progress to realize mobile computing environment that designed to support mobile hosts in the existing network environments. For PCN environments, the location management strategies are particularly emphasized among various strategies necessary for the mobile computing environment. Location management strategy for PCN environment, which is mostly based on the IS-41 standards brings an issue that additional network traffics are generated to deliver updata messages to home location server whenever a mobile host changes its location server. In this paper, we propose an innovative updata strategy and a search strategy that resolves the problem shown in the IS-41 scheme for HLR/VLR structure of CDMA environments. Also, this paper presents the performance comparison of proposed scheme and scheme used in IS-41 obtained from a simulation. The simulation was conducted based on the number of messages, the rate of database accesses, and the number of hops visited when the location management scheme is executed.

• ETRI Journal
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• v.44 no.3
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• pp.361-378
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• 2022

In 5G, the required target for interruption time during a handover (HO) is 0 ms. However, when a handover failure (HOF) occurs, the interruption time increases significantly to more than hundreds of milliseconds. Therefore, to fulfill the requirement in as many scenarios as possible, we need to minimize HOF rate as close to zero as possible. 3GPP has recently introduced conditional HO (CHO) to improve mobility robustness. In this study, we propose "ZEro handover failure with Unforced and automatic time-to-execute Scaling" (ZEUS) algorithm to optimize HO parameters easily in the CHO. Analysis and simulation results demonstrate that ZEUS can achieve a zero HOF rate without increasing the ping-pong rate. These two metrics are typically used to assess an HO algorithm because there is a tradeoff between them. With the introduction of the CHO, which solves the tradeoff, only these two metrics are insufficient anymore. Therefore, to evaluate the optimality of an HO algorithm, we define a new integrated HO performance metric, mobility-aware average effective spectral efficiency (MASE). The simulation results show that ZEUS provides higher MASE than LTE and other CHO variants.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.3C
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• pp.211-219
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• 2002

Mobile IP(RFC2002) is representative protocols that support mobility to host. In this paper, we propose a mobile IP registration protocol using public-key based certificates and CA(certification authority). Our proposed protocol authenticates the registration message of mobile node and prevents replay attack and minimal use of public key cryptography, Also, Our proposed protocol directly authenticates between agents and mobile nodes using certificates. Though the computer simulation, we prove that our proposal has better performance than the previous public-key based Mobile IP registration protocol.

• Proceedings of the Korea Information Processing Society Conference
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• 2002.04b
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• pp.1539-1542
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• 2002

Many routing protocols have been proposed for mobile ad-hoc networks, but most protocols do not consider the physical location of the communicating nodes. In this paper we propose adaptive zoning approach with multiple hosts for reducing the number of route request messages. The proposed approach makes the sub-request zone has shorter interval than the existing schemes between the source and destination. This results in significantly lower routing overhead than the existing schemes as verified by computer simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.5
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• pp.1283-1293
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• 1996

This paper descries design concepts, structure and charracteristics of personal communications system based on wideband CDMA under developing for general low-tier mobile telecommunications services as the first step of the next generation mobile telecommunications systems that provide timely exchange of various types of information with anyone, from anywhere, at anytime. Also, wedesign a reverse linktransmitter/receiver structure for personal communications system based on wideband CDMA and validata the performance of the designed structure and establish the each parameter via computer simulation. Simulaation results on the effects of reverse link synchronous transmission and the effects of power control and control and channel coding in pedestrian environment for low-tier services are presented.