• Journal of the Korea Institute of Information Security & Cryptology
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• v.20 no.4
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• pp.53-62
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• 2010

In VANETs (Vehicular Ad hoc NETwork), conditional anonymity must be provided to protect privacy of vehicles while enabling authorities to identify misbehaving vehicles. To this end, previous systems provide a mechanism to revoke the anonymity of individual messages. In VANET, if we can trace the movement path of vehicles, it can be useful in determining the liability of vehicles in car accidents and crime investigations. Although route tracing can be provided using previous message revocation techniques, they violate privacy of other vehicles. In this paper, we provide a route tracing technique that protects privacy of vehicles that are not targeted. The proposed method can be employed independently of the authentication mechanism used and includes a mechanism to prevent authorities from abusing this new function.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.8
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• pp.1695-1703
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• 2011

According to increase of the number of electronic devices for user comfort and safety, electronic systems are being constructed by using network to effectively control the devices. In this paper, we design and implement the MOST network diagnostic system by using wireless LAN to diagnose MOST network and the devices connected by the network and to effectively manage them. MOST, which is a vehicle multimedia network standard for the next generation, is being used for construction of car infotainment systems, and enables to develop various devices which are required for them. The wireless diagnostic system implemented in this paper enables to self-diagnose MOST network and also to check errors by diagnosing status of MOST electronic devices. We also can check and manage status of a in-vehicle MOST network system using mobile devices based on wireless LAN.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.1
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• pp.63-71
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• 2019

The two-fluid model proposed by Herman and Prigogine is useful for analyzing macroscopic traffic flow in a network. The two-fluid model is used for analyzing a network through the relationship between the ratio of stopped vehicles and the average moving speed of the network, and the two-fluid model has also been applied in the urban transportation network where many signalized or unsignalized intersections existed. In general, the average travel speed and moving speed of a network decrease, and the ratio of stopped vehicles and low speed vehicles in network increase as the traffic demand increases. This study proposed the two-fluid model considering congested and uncongested traffic situations. The critical velocity and the weight factor for congested situation are calibrated by minimizing the root mean square error (RMSE). The critical speed of the Seoul network was about 34 kph, and the weight factor of the congestion on the network was about 0.61. In the proposed model, $R^2$ increased from 0.78 to 0.99 when compared to the existing model, suggesting that the proposed model can be applied in evaluating network performances or traffic signal operations.

• Journal of Digital Convergence
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• v.10 no.9
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• pp.325-332
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• 2012

VANET(Vehicular Ad-hoc Network), which is a technology to create a network among vehicles, decides the route to the destination using information of neighbors within the transmission range as transmission nodes. The existing routing protocol which uses geographical information can cause delay and disconnection of the network when the density of nodes is not high enough to communicate because it only considers the distance of the relay nodes or destination nodes from the source nodes. To solve the problem, this dissertation suggests a routing algorithm based on zones for stable communications among vehicles in the environment of VANET. I minimize the packet loss rate by dividing the city environment into zones and taking into account not only the distance of the destination but also the density of vehicles to choose the best communications environment. This results in a better performance than the established research when the performance evaluation is implemented.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.6
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• pp.175-181
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• 2014

With rapid growth of the wireless mobile computing network technologies, various mobile ad hoc network applications converged with other related technologies are rapidly disseminated nowadays. Vehicular Ad Hoc Networks are self-organizing mobile ad hoc networks that typically have moving vehicle nodes with high speeds and maintaining its topology very short with unstable communication links. Therefore, VANETs are very vulnerable for the malicious noise of sensors and anomalies of the nodes in the network system. In this paper, we propose an anomaly detection method by using big data techniques that efficiently identify malicious behaviors or noises of sensors and anomalies of vehicle node activities in these VANETs, and the performance of the proposed scheme is evaluated by a simulation study in terms of anomaly detection rate and false alarm rate for the threshold ${\epsilon}$.

• Journal of the Korea Society of Computer and Information
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• v.17 no.5
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• pp.41-48
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• 2012

A Vehicular Ad-hoc Network (VANET) is a vehicular specific type of a mobile ad-hoc network, to provide temporary communications among nearby vehicles. Mobile node of VANET consumes energy and resource with participating in the member of network. In a VANET, data replication and cooperative caching have been used as promising solutions to improve system performance. Existing cooperative caching scheme in a VANET mostly focuses on weak consistency is not always satisfactory. In this paper, we propose an efficient cache management scheme to maintain strong data consistency in a VANET. We make an adaptive scheduling scheme to broadcast Invalidation Report (IR) in order to reduce query delay and communication overhead to maintain strong data consistency. The simulation result shows that our proposed method has a strength in terms of query delay and communication overhead.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.11 no.3
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• pp.70-80
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• 2012

In Vehicular Ad-hoc Network(VANET) which constructs networks without fixed infrastructure among vehicles, network topology is frequently changed due to high mobility. In case of urban model, communication disconnections caused by interruptions of communication propagation such as buildings and constructions could be often occurred. Therefore, in VANET environment a routing protocol to complement its characteristics is needed. This paper suggests an algorithm to improve the transmission performance at intersections by approaching of the distance-based broadcasting which utilizes the information of vehicle's position. By using relative velocity among vehicles, it makes the stability of route decision improved and reduces packet collisions through graded priorities in the intersection, and simultaneously improves the performance of data rate. It can be seen that the performance compared with previous algorithm is significantly improved when using the suggested algorithm in the urban traffic environment.

• Journal of Navigation and Port Research
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• v.28 no.3
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• pp.227-232
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• 2004

Vehicle dynamics control systems are complex and non-linear, so they have difficulties in developing a controller for the anti-lock braking systems and the auto-traction systems. Currently the fuzzy-logic technique to estimate the absolute vehicle speed supplies good results in normal conditions. But the estimation error in severe braking is discontented In this paper, we estimate the absolute vehicle speed of UCT(Unmanned Container Transporter) by using the wheel speed data from standard anti-lock braking system wheel speed sensors. Radial symmetric basis function of the neural network model is proposed to implement and estimate the absolute vehicle speed, and principal component analysis on input data is used 10 algorithms are verified experimentally to estimate the absolute vehicle speed and one of them is perfectly shown to estimate the vehicle speed within 4％ error during a braking maneuver.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.5
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• pp.1003-1010
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• 2018

The geomagnetic sensor nodes are usually designed with wireless communication and battery for easy installation on the road without cable connection and wiring. To minimize operation cost of a system, it is important to prolong the battery lifetime of the geomagnetic sensors installed on the road. In this paper, we propose a low-power TDMA MAC protocol that reduces energy consumption while guaranteeing the real-time vehicle detection information in the vehicle detection system. The performance evaluations are conducted through a real testbed of a vehicle detection system, and it proves that the proposed low-power protocols provides 5 year lifetime by improving energy efficiency up to about 62%.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.21 no.4
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• pp.161-169
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• 2011

There is a consensus in the field of vehicular network security that public key cryptography should be used to secure communications. A certificate revocation list (CRL) should be distributed quickly to all the vehicles in the network to protect them from malicious users and malfunctioning equipment as well as to increase the overall security and safety of vehicular networks. Thus, a major challenge in vehicular networks is how to efficiently distribute CRLs. This paper proposes a CRL distribution method aided by terrestrial digital multimedia broadcasting (T-DMB). By using T-DMB data broadcasting channels as alternative communication channels, the proposed method can broaden the network coverage, achieve real-time delivery, and enhance transmission reliability. Even if roadside units are not deployed or only sparsely deployed, vehicles can obtain recent CRLs from the T-DMB infrastructure. A new transport protocol expert group (TPEG) CRL application was also designed for the purpose of broadcasting CRLs over the T-DMB infrastructure.