• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.9
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• pp.53-63
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• 1994

In indoor radio systems, vehicular communication systems, and land mobile systems, a very important problem is that of maintaining stable communications at all locations. Therefore solutions for the indoor propagation problem are important aspects of the mobile communication system. leaky coxial cables are finding increasing use in communications systesm involving mines, tunnels, tailroads, and highways, and in new obstacle detection, or guided radar, schemes for ground transportation and perimenter surveilance. In this paper a leaky coaxial cable having periodic slots in the outer conductor is described to obtain the propagation modes in the various environments. We use aneccentric cylindrical model to develop the theory for surface-wave propagation on the cable. Numerical Results are also included for the propagation constants, field distribution and current distribution. First, we derive the electromagnetic equation for leaky coaxial cable having symmetrical periodic slots using mode-matching method and Floquet's theorem, and then find various modes, propagation constants, field distribution, etc.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2013.11a
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• pp.34-35
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• 2013

기존 연구에서 무선 인지 네트워크의 성능 분석에 관한 연구는 많았지만 무선 인지 네트워크에 차량 통신을 접목시킨 무선 인지 차량 네트워크의 성능 분석에 관한 연구는 많지 않았다. 또한 최근 실질적인 채널환경을 고려하기 위해 불완전한 채널정보를 가잔 시스템에서의 성능 분석에 대한 연구가 많이 진행되고 있는데 무선 인지 차량 네트워크에서의 연구는 아직 진행되지 않았다. 본 논문에서는 불완전한 채널정보가 존재하는 인지 차량 네트워크의 성능 분석을 한다. 본 논문에서는 언더레이 (underlay) 무선 인지 네트워크를 가정하고 차량간 통신이 일어나는 2차 사용자 네트워크의 채널들을 double Rayleigh fading으로 모델링한다. 성능 분석의 지표로 불능 확률을 사용하고 컴퓨터 모의실험을 통해 분석된 불능확률 값이 상관계수가 변화함에 따라 어떠한 변화가 있는지 확인하였다.

• Proceeding of EDISON Challenge
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• 2015.03a
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• pp.527-529
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• 2015

The control delays at signal intersections have proved the source of numerous vehicular and environmental complications. Control delays both directly and indirectly hinder time- and cost-effective driving by extending the duration of time spent on the road and exhausting excessive amounts of fuel. They furthermore cause traffic congestion, thereby raising overall emission levels. It is therefore imperative to reduce control delays in order to achieve time and fuel economy and reduce vehicle-related pollution. The following study accordingly uses genetic algorithms to optimize traffic signals in congested environments.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.235-236
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• 2006

IEEE 802.16 networks support mobile stations (MSs) to access broadband wireless networks while moving at a vehicular speed. However, IEEE 802.16 networks do not provide link layer native multicast capability because of point-to-multipoint connection characteristic. Due to this feature, it is not easy to adopt protocols or applications which need native link layer multicast capability. In order to solve the multicast support problem, we use the built-in LAN emulation feature of IEEE 802.16 which is based on Convergence Sublayer (CS). Our proposed operational procedures support not only the delivery of link local scope multicast packets, but also the delivery of non-link local scope multicast packets such as site local or global scope multicast packets. We also present the method of forming multicast Connection Identifier (CID) which is used to transport IP packets over IEEE 802.16 networks.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.12
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• pp.1903-1909
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• 1989

In this paper, the mobile communication CH simulator is implemented in the baseband, using the Digital Signal Processor(TMS320C25), A/D and D/A converters. The Rayleigh CH is modeled by shaping the random noise source power spectrum. The statistical characteristics(Level Crossing Rate, Cumulative distribution Function, Probability Density Function) and the received fading signal's power's spectrum is observed when the doppler frequency is varied according to the variation of the vehicular velocity at the 222MHz band. And also the BER is measured when the baseband mobile CH simulator is applied to the GMSK(Gaussian Minimum Shift Keying` transmission rate: 16kbps, Bb T=0.25) modulator. The results shows the similar characteristics to be compared with the theoritically derived BER values of the discriminator type GMSK detection.

• Journal of Korea Multimedia Society
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• v.21 no.12
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• pp.1448-1458
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• 2018

Vehicular Ad-Hoc Networks (VANETs) have become one of the active areas of research, standardization, and development because they have tremendous potentials to improve vehicle and road safety, traffic efficiency, and convenience as well as comfort to both drivers and passengers. However, message trustfulness is a challenge because the propagation of false message by malicious vehicles induces unreliable and ineffectiveness of VANETs, Therefore, we need a reliable reputation method to ensure message trustfulness. In this paper, we consider a vulnerability against the Sybil attack of the previous reputation systems based on blockchain and suggest a new reputation system which resists against Sybil attack on the previous system. We propose an initial authentication process as a countermeasure against a Sybil attack and provide a reliable reputation with a cooperative message delivery to cope with message omission. In addition, we use Homomorphic Commitment to protect the privacy breaches in VANETs environment.

• International Journal of Computer Science & Network Security
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• v.21 no.12spc
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• pp.636-642
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• 2021

Vehicular Ad hoc Networks (VANET's) are gaining popularity in research community with every passing year due to the key role they play in Intelligent Transportation System. Their primary objective is to provide safety, but their potential to offer a variety of user-oriented services makes them more attractive. The biggest challenge in providing all these services is the inherent characteristics of VANET itself such as highly dynamic topology due to which maintaining continuous communication among vehicles is extremely difficult. Here comes the importance of routing solutions which traditionally are designed using strict layered architecture but fail to address stringent QoS requirements. The paradigm of cross-layer design for routing has shown remarkable performance improvements. This paper aims to highlight routing challenges in VANET, limitations of single-layer solutions and presents a survey of cross-layer routing solutions that utilize the information from the MAC layer to improve routing performance in VANET.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.3
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• pp.48-58
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• 2009

Geo-graphical routing protocols as GPSR are known to be very suitable and useful for vehicular ad-hoc networks. However, a corresponding node can include some stale neighbor nodes being out of a transmission range, and the stale nodes are pone to get a high priority to be a next relay node in the greedy mode. In addition, some useful redundant information can be eliminated during planarization in the recovery mode. This paper deals with a new recovery mode, the Greedy Border Superiority Routing(GBSR), along with an Adaptive Neighbor list Management(ANM) scheme. Each node can easily treat stale nodes on its neighbor list by means of comparing previous and current Position of a neighbor. When a node meets the local maximum, it makes use of a border superior graph to recover from it. This approach improve the packet delivery ratio while it decreases the time to recover from the local maximum. We evaluate the performance of the proposed methods using a network simulator. The results shown that the proposed protocol reveals much better performance than GPSR protocol. Please Put the of paper here.

• Journal of Digital Convergence
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• v.12 no.2
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• pp.549-554
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• 2014

Studies on the intelligent vehicles that are converged with IT and vehicular technologies are currently under active discussion. A variety of communication technologies for safety intelligent vehicle services are support. As such intelligent vehicles use communication technologies, they are exposed to the diverse factors of security threats. To conduct intelligent vehicle security authentication solutions, there are some factors that can be adopted ownership, knowledge and biometrics[6,7]. This paper proposes to analyze the factors to threaten intelligent vehicle, which are usually intruded through communication network system and the security solution using biometric authentication scheme. This study proposed above user's biometrics information-based authentication scheme that can solve the anticipated problems with an intelligent vehicle, which requires a higher level of security than existing authentication solution.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.7
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• pp.1471-1478
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• 2011

A typical standard of vehicular ad hoc networks, WAVE which consists of IEEE 1609.x Family standards and IEEE 802.11p standard, includes the multi-channel coordination and channel synchronization function to provide safety services or public services during a car is driven. Generally, the performance of data communication and networking technologies is evaluated by using simulation tools, such as ns-2, OPNET, OPNET++, etc. However, these tools doesn't provide the operations of WAVE protocol. Therefore, in this paper, we implement and verify WAVE simulation program based on ns-2.