• Journal of the Korea Society of Computer and Information
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• v.25 no.7
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• pp.93-101
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• 2020

Regional CRL(certificate revocation list) in vehicular communications is to partition Full CRL into several small CRLs according to geographic location to keep the size of individual CRLs with smaller. However, since a Regional CRL includes vehicle's revoked certificates within its administrative region, it has to know vehicle' location. For this, how to know vehicle' location effectively corresponding to every region represents a major challenge. This paper proposes a Regional CRL scheme which is envisioned to achieve vehicle's location and to make regional CRLs according to vehicles current location efficiently. The scheme is based on the short-lived pseudonyms defined by WAVE standard. It also acquires issued pseudonyms, vehicle's id and region information whenever a vehicle initiates pseudonyms refill after that, utilizes them to create and distribute the Regional CRL. To keep location privacy-preserving for vehicles, the scheme uses the blockchain technology in the network. The analysis results show that it reduces CRL size and database query time for finding revoked certificates sharply in the vehicle's on-board unit.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.7
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• pp.1-8
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• 2011

Vehicular Ad-hoc Network (VANET) is a special form of Mobile Ad-hoc Network designed to provide communications among nearby vehicles without communications infrastructure. Some characteristics in VANET environment such as high mobility, dynamic topology and selfishness of nodes can cause degradation of network quality. In this paper, we propose an adaptive incentive/topology control scheme to improve network quality in VANET by stimulating real time data forwarding and reporting changes of network topology. In the proposed scheme, an incentive suggested by the source node is updated in real time simultaneously with data transmission to stimulate real time data forwarding. In addition, when the order of the nodes in the path is changed, nodes which report the changes of network topology will get an additional incentive. By computer simulation, it is shown that the proposed incentive/topology control scheme outperforms the conventional schemes with respect to data delivery time and data delivery ratio.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.7
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• pp.543-552
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• 2013

For the safety messages in IEEE 802.11p/WAVE vehicles network environment, strict periodic beacon broadcasting requires status advertisement to assist the driver for safety. In crowded networks where beacon message are broadcasted at a high number of frequencies by many vehicles, which used for beacon sending, will be congested by the wireless medium due to the contention-window based IEEE 802.11p MAC. To resolve the congestion, we consider a MAC scheme based on slotted p-persistent CSMA as a simple non-cooperative Bayesian game which involves payoffs reflecting the attempt probability. Then, we derive Bayesian Nash Equilibrium (BNE) in a closed form. Using the BNE, we propose new congestion control algorithm to improve the performance of the beacon rate under saturation condition in IEEE 802.11p/WAVE vehicular networks. This algorithm explicitly computes packet delivery probability as a function of contention window (CW) size and number of vehicles. The proposed algorithm is validated against numerical simulation results to demonstrate its stability.

• IEIE Transactions on Smart Processing and Computing
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• v.6 no.2
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• pp.133-139
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• 2017

Vehicles have increasingly evolved and become intelligent with convergence of information and communications technologies (ICT). Vehicle communications (VC) has become one of the major necessities for intelligent vehicles. However, VC suffers from serious security problems that hinder its commercialization. Hence, the IEEE 1609 Wireless Access Vehicular Environment (WAVE) protocol defines a security service for VC. This service includes Advanced Encryption Standard-Counter with CBC-MAC (AES-CCM) for data encryption in VC. A high-speed AES-CCM crypto module is necessary, because VC requires a fast communication rate between vehicles. In this study, we propose and implement an efficient AES-CCM hardware architecture for high-speed VC. First, we propose a 32-bit substitution table (S_Box) to reduce the AES module latency. Second, we employ key box register files to save key expansion results. Third, we save the input and processed data to internal register files for secure encryption and to secure data from external attacks. Finally, we design a parallel architecture for both cipher block chaining message authentication code (CBC-MAC) and the counter module in AES-CCM to improve performance. For implementation of the field programmable gate array (FPGA) hardware, we use a Xilinx Virtex-5 FPGA chip. The entire operation of the AES-CCM module is validated by timing simulations in Xilinx ISE at a speed of 166.2 MHz.

• Information and Communications Magazine
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• v.29 no.2
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• pp.3-10
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• 2012

산업화, 도시화가 이루어지면서 자동차가 현대인의 필수품으로 자리잡았다. 그러나 차량 소유가 증가함에 따라 도로를 포함한 사회 인프라 구축에 한계를 드러내고 있으며, 이로 인한 교통 혼잡 등의 문제가 사회적으로 대두되고 있다. 또한 기계 장치 및 센서 디바이스 등 기존의 자차의 정보만을 이용한 차량 안전 서비스에서 한계를 드러내고 있다. 따라서 주변 차량 정보를 활용한 교통 및 안전 서비스를 개발하기 위해서는 차량 통신기술이 필수적이다. 이를 위한 국제적인 표준화 활동이 활발히 진행되고 있으며, 대표적인 국제단체로 ISO와 IEEE가 있다. 이곳에서 각각 CALM(Communications Access for Land Mobiles) 및 WAVE(Wireless Access in Vehicular Environments) 통신 기술에 대한 표준이 제정되고 있으며, 다양한 프로젝트를 통해 관련 기술과 서비스가 제시되고 검증되고 있다. 따라서 차량 통신을 활용한 ITS(Intelligent Transport System) 분야의 새로운 시장확대와 경제적 효과를 선점하기 위해서는 이러한 표준동향을 주시하고 참여할 필요가 있다. 본고에서는 차량 통신에 대한 최신 국제 표준화 현황 및 민간 표준화 기구에 대해 살펴보고 전망을 제시한다.

• 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.

• Journal of Communications and Networks
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• v.15 no.2
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• pp.179-190
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• 2013

Given the bandwidth assignment for dedicated short range communications for use in vehicular ad-hoc network (VANET) and the expected introduction of equipment in the next few years, we elaborate on how VANET can support infotainment services. We define an architectural model for the integration of VANETs and cellular networks, according to a push mode paradigm where VANETs are used primarily to disseminate service announcements and general interest messages. Cooperation with cellular network is addressed by comparing architecture alternatives. A set of information dissemination protocols for VANETs is compared via simulations on a real urban map. Some results from a lab testbed based on IEEE 802.11p boards are presented along with an application developed for Android operating system to demonstrate the concept of the paper.

• ETRI Journal
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• v.45 no.5
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• pp.758-767
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• 2023

In this study, we introduce a loosely coupled relative position estimation method that utilizes a decentralized ultrawideband (UWB), Global Navigation Support System and inertial navigation system for flight controllers (FCs). Key obstacles to multidrone collaboration include relative position errors and the absence of communication devices. To address this, we provide an extended Kalman filter-based algorithm and module that correct distance errors by fusing UWB data acquired through random communications. Via simulations, we confirm the feasibility of the algorithm and verify its distance error correction performance according to the amount of communications. Real-world tests confirm the algorithm's effectiveness on FCs and the potential for multidrone collaboration in real environments. This method can be used to correct relative multidrone positions during collaborative transportation and simultaneous localization and mapping applications.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.8 no.4
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• pp.53-64
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• 2009

Inter-vehicular communication that propagates information without infrastructures has drawn a lot of interest. However, it is difficult to apply conventional ad-hoc routing protocols directly in inter-vehicular communication due to frequent changes in the network topology caused by high mobility of the vehicles. MMFP(Multi-hop MAC Forwarding) is a unicast forwarding protocol that transport packets based on the reachability information instead of path selection or position information. However, delivering public safety messages informing road conditions such as collision, obstacles and fog through inter-vehicular communication requires broadcast rather than unicast since these messages contain information valuable to most drivers within a close proximity. Flooding is one of the simplest methods for multi-hop broadcast, but it suffers from reduced packet delivery-ratio and high transmission delay due to an excessive number of duplicated packets. This paper presents two multi-hop broadcast protocols for inter-vehicular communication that extend the MMFP. UMHB(Unreliable Multi-Hop Broadcast) mitigates the duplicated packets of MMFP by limiting the number of nodes to rebroadcast packets. UMHB, however, still suffers from low delivery ratio. RMHB(Reliable Multi-Hop Broadcast) uses acknowledgement and retransmission in order to improve the reliability of UMHB at the cost of increase in transmission delay, which we show through simulation is within an acceptable range for collision avoidance application.

• Journal of KIISE:Information Networking
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• v.37 no.6
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• pp.420-430
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• 2010

Due to increasing demand for improving road safety and optimizing road traffic, Vehicular Ad-Hoc Networks (VANET) have been subject to extensive attentions from all aspects of commercial industry and academic community. Security and user privacy are fundamental issues for all possible promising applications in VANET. Most of the existing security proposals for secure VANET concentrate authentication with privacy preservation in vehicle-to-vehicle (V2V) and vehicle-to-roadside infrastructure (V2I) communications and require huge storage and network capacity for management of revocation list. Motivated by the fact, we propose a new scheme with security and privacy preservation which combines V2V and V2I communication. With our proposed scheme, the communication and computational delay for authentication and overhead for management of revocation list can be significantly reduced due to mutual authentication between a vehicle and a Roadside Unit (RSU) requires only two messages, and the RSU issues the anonymous certificate for the vehicle on behalf of the Trust Authority (TA). We demonstrate that the proposed protocol cannot only guarantee the requirements of security and privacy but can also provide efficiency of authentication and management of revocation list.