• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.2
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• pp.114-122
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• 2014

Beacon transmission is one of the fundamental mechanisms in vehicular ad hoc networks. Variety services including context awareness can be embodied by exchanging beacons in each vehicle. In this paper, we propose dual beacon transmission instead of traditional single beacon transmission for beaconing mechanism. dual beacon transmission divides beacon into two functions and operates two beaconing process independently. We verified the superiority of dual beacon transmission by comparing beacon packet delivery ratio with single beacon transmission. In conclusion, dual beacon transmission can reduce channel load and have both wider communication range and effective context awareness. In addition, implementing dual beacon transmission has less complexity and appliable with conventional adaptive beaconing schemes.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.12
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• pp.2272-2293
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• 2011

Communication technology of future networks is predicted to provide a large variety of services including WiFi service in vehicular network. In this paper, we assume that vehicles are embedded with WiMAX antenna and in-vehicle terminals receive WiMAX traffic through WiFi interface. This assumption will impose severe performance degradation due to interference among mobile BSSs when WiFi access points (APs) are densely located. Existing interference avoidance techniques cannot properly resolve the above problems and do not cope with dynamically moving vehicular scenario since they focus only on the fixed network topology. In this paper, we propose a mobility-aware interference avoidance scheme for WiFi services. The proposed scheme computes the interference duration by exploiting mobility vector and location information of neighboring APs. If the interference duration is not negligible, our scheme searches for another channel in order to avoid interference. However, if the interference duration is negligible, our scheme continues to use the channel to reduce switching overhead. To measure the effectiveness of the proposed scheme against other existing techniques, we evaluated performance by using OPNET simulator. Through the simulation, we obtained about 60% reduction in the maximum interference frequency and about 67% improvement in throughput. Furthermore, our scheme provides fair channel usage.

• Journal of the Korea Society for Simulation
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• v.20 no.1
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• pp.19-28
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• 2011

The safety applications based on the IEEE 802.11p, periodically transmit the safety-related information to all surrounding vehicles with high reliability and a strict timeline. However, due to the high vehicle mobility, dynamic network topology and limited network resource, the fixed beacon scheduling scheme excess delay and packet loss due to the channel contention and network congestion. With this motivation, we propose a novel beacon scheduling algorithm referred to as spatial-aware(SA) beacon scheduling based on the spatial context information, dynamically rescheduling the beaconing rate like a TDMA channel access scheme. The proposed SA beacon scheduling algorithm was evaluated using different highway traffic scenarios with both a realistic channel model and 802.11p model in our simulation. The simulation results showed that the performance of our proposed algorithm was better than the fixed scheduling in terms of throughput, channel access delay, and channel load. Also, our proposed algorithm is satisfy the requirements of vehicular safety application.

• KIPS Transactions on Computer and Communication Systems
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• v.7 no.6
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• pp.137-144
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• 2018

Vehicular Ad-hoc Networks (VANETS) have enabled to provide a variety of applications such as accident notification, content usage, etc. These applications have spatio-temporal data which have an interesting region and a lifetime according to their properties. However, geocasting protocols to deliver data to an interesting region can provide data to all vehicles in the region through a single transmission only at the current time, but cannot provide data to vehicles passing through the region during the lifetime of the data. Thus, we propose a spatio-temporal geocasting protocol called STGP using a regional caching scheme to send data to vehicles in an interesting region during a data lifetime in VANETs. For efficient and reliable regional caching, the proposed protocol uses the beacon-based data sharing, the extra caching elimination, and the distance-based caching exchange. Simulation results verify that the proposed protocol achieves more reliable and efficient data delivery compared with the existing protocol.

• The KIPS Transactions:PartC
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• v.18C no.4
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• pp.207-212
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• 2011

Vehicular Ad Hoc Network(VANET) is a communication technology between vehicles and vehicles(V2V) or vehicles and infrastructures(V2I) for offering a number of practical applications. Considering the importance of communicated information through VANET, data authentication, confidentiality and integrity are fundamental security elements. Recently, to enhance a security of VANET in various circumstances, message authentication is widely researched by many laboratories. Among of them, Zhang. et. al. is an efficient method to authenticate the message with condition of anonymity in dense space. In the scheme, to obtain the vehicular ID with condition of anonymity, the k-anonymity is used. However it has a disadvantage, which conducts hash operations in case of determining the vehicular ID. In the paper, we present a location based algorithm using received signal strength for the location based authentication and encryption technique as well, and to enhance the accuracy of algorithm we apply a location determination technique over the 3-dimensional space.

• Journal of Communications and Networks
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• v.6 no.4
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• pp.295-306
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• 2004

In this paper, a novel air-interface is presented for Fleet-Net1, a self-organizing network for inter-vehicle and vehicle-toroadsidecommunication. The air-interface is based upon the lowchip-rate version of UMTS/TDD. To adapt the cellular UMTS standard to an air-interface for ad hoc networks, changes of the physical layer, medium access control sub-layer and radio resource management are required. An overview of the required modifications is given here. Particularly, a decentralized synchronization mechanism is presented and analyzed by means of simulations. Furthermore, changes for the medium access control are explained in detail, which allow for an efficient operation in partly meshed networks and prioritization. Performance results of the overall system considering throughput and delay are derived by means of analytical evaluations and event-driven simulations. Based on realistic mobility models, it is shown that the presented solution provides a robust communication platform even in vehicular environments. The proposed air-interface is a cost-effective solution not only for inter-vehicle communication, but also for ad hoc networking in general, benefiting from the mass-market of UMTS.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.7
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• pp.878-883
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• 2018

This paper proposes a method for transmitting instruction between vehicles in a moving situation using RC Car having camera. Information of preceding RC Car was transmitted by LED using Optical Camera Communication(OCC). Rear RC Car follows the preceding one by analyzing transmitted OCC data based on image processing. Through this procedure, the information reception ratio according to the distance change of two RC Cars is confirmed. Through experiments, we showed that our proposed scheme enables the possibility of vehicle platooning.

• Proceedings of the Korea Information Processing Society Conference
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• 2014.04a
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• pp.170-172
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• 2014

트래픽 텔레매틱스 어플리케이션으로 알려진 차량 무선통신 서비스는 현재 교통에 대해서 차량 주행환경에 대해 더욱 안전하고 효율적으로 연구되고 발전하고 있는 추세이다. 차량 통신에서는 WAVE (Wireless Access in Vehicular Environments) 표준을 채택함으로써 차량 간 통신 과 차량과 기지국 간 통신에 WAVE 표준을 지킨다. 차량 통신에서는 다양한 주행환경에 따라 전파에 따른 경로 손실 모델이 적용될 수 있다. 본 논문에서는 파라미터에 따른 주행환경을 구분하고 구분된 주행환경에 따라 적합한 경로 손실 모델에 대해서 연구한다.

• IEIE Transactions on Smart Processing and Computing
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• v.2 no.2
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• pp.45-56
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• 2013

The precise identification of vehicle positions, known as the vehicle localization problem, is an important requirement for building intelligent vehicle ad-hoc networks (VANETs). To solve this problem, two categories of solutions are proposed: stand-alone and data fusion approaches. Compared to stand-alone approaches, which use single information including the global positioning system (GPS) and sensor-based navigation systems with differential corrections, data fusion approaches analyze the position information of several vehicles from GPS and sensor-based navigation systems, etc. Therefore, data fusion approaches show high accuracy. With the position information on a set of vehicles in the preprocessing stage, data fusion approaches is used to estimate the precise vehicular location in the local map building stage. This paper proposes an efficient local map building scheme, which increases the accuracy of the estimated vehicle positions via V2V communications. Even under the low ratio of vehicles with communication modules on the road, the proposed local map building scheme showed high accuracy when estimating the vehicle positions. From the experimental results based on the parameters of the practical vehicular environments, the accuracy of the proposed localization system approached the single lane-level.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.4 no.3 s.8
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• pp.1-8
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• 2005

IEEE WAVE(Wireless Access in Vehicular Environment) is being developed to operate in 5 GHz DSRC band to provide cars moving at high-speed with vehicle-to-vehicle and vehicle-to-roadside communication. IEEE P 1609.3 of the WAVE protocol stack defines how multiple channels are used based on the exchange of provider-service-tables (PST) and user-service-tables (UST) for rapid link establishment and data transmission. This paper presents the design and implementation of an IEEE WAVE multi-channel transmission emulator that we have developed to study the operation of protocol and applications. Applications for a public-safety and a download service have been implemented and are shown to operate effectively on top of the emulator.