• Journal of KIISE:Information Networking
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• v.34 no.5
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• pp.340-347
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• 2007

Vehicle safety service can be effectively achieved with inter-vehicle communication technologies, in which moving vehicles transmit a safety related urgency information such as traffic accidents, sudden stops, obstacle appearance etc. They usually utilize a broadcast of message propagation method because the communicating vehicles are not known each other. The pure broadcasting scheme does not satisfy the requirements of vehicle safety communication service due to the transmission delay with frequent message collisions. To resolve this problem, this paper presents a group based propagation method for the multi-hop transmission, in order to deliver an urgency message to the reasonable size of vehicle troop. A group header is elected in considering of the position information of vehicles and radio transmission range. And a vehicle equivalent group is formed with the header. With benefits of the group based transmission, it is possible to minimize the unnecessary transmission and the possibility of message collisions. Simulation results show that the message propagation performance is so stable regardless of vehicle's congestion degree.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.5
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• pp.125-132
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• 2017

Vehicular safety service reduces traffic accidents and traffic congestion by informing drivers in advance of threats that may occur while driving using vehicle-to-vehicle (V2V) communications in a wireless environment. For vehicle safety services, every vehicle must broadcasts a Basic Safety Message(BSM) periodically. In congested traffic areas, however, network congestion can easily happen, reduce the message delivery ratio, increase end-to-end delay and destabilize vehicular safety service system. In this paper, to solve the network congestion problem in vehicle safety communications, we approximate the relationship between channel busy ratio and the number of vehicles and use it to estimate the total network congestion. We propose a new context-aware transmit power control algorithm which controls the transmission power based on total network congestion. The performance of the proposed algorithm is evaluated using Qualnet, a network simulator. As a result, the estimation of total network congestion is accurately approximated except in specific scenarios, and the packet error rate in vehicle safety communication is reduced through transmit power control.

• Journal of Auto-vehicle Safety Association
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• v.9 no.2
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• pp.33-39
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• 2017

In recent days, crash safety system based on vehicle-to-vehicle communication (V2V) has been legislated. This V2V based safety system collects information from nearby vehicles to predict any crash possibility. Thus, it requires accurate and reliable data. Regularly updated features of Basic Safety Message(BSM) will be used to test validity of various elements included in the BSM. Then, the focus was made on whether values of these elements had notable differences compared to previous values. Through this paper, the validation tool was implemented and the result from V2V OBU experiment was used to identify problems in the current model and additional features that need to be implemented in V2V OBU for more accurate BSM.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.12A
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• pp.1113-1121
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• 2010

The Vehicle Safety Communications (VSC) is one of VANET applications for preventing vehicle accidents, and it utilizes vehicle-to-vehicle communication to exchange emergency messages. To propagate such messages in VSC, several schemes based on selective flooding have been proposed. Their common idea is that an emergency message is relayed by one of vehicles receiving the message. However, the schemes do not consider the transmission errors and duplications of an emergency event. In the schemes, if there are transmission errors and a vehicle detects a hazard, there may be vehicles which fail to receive an emergency message. If k vehicles detect a hazard, k emergency messages are created and propagated. The duplications of an event increase reliability of the message delivery but decrease efficiency. In this paper, we propose an emergency message delivery scheme which is efficient and robust to transmission errors. Our proposed scheme utilizes clustering for massage aggregation and retransmissions in a cluster. It also uses an acknowledgment mechanism for reliable inter-cluster communication. Our simulation results show that the proposed scheme outperforms Least Common Neighbor Flooding which is one of the selective flooding schemes.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.3
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• pp.1152-1167
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• 2018

In this paper, I propose an application layer cooperative congestion control scheme for safety message broadcast in vehicular networks, called CMS, that adaptively controls a vehicle's safety message rate and transmit timing based on the channel congestion state. Motivated by the fact that all vehicles should transmit and receive an application layer safety message in a periodic manner, I directly exploit the message itself as a means of estimating the channel congestion state. In particular, vehicles can determine wider network conditions by appending their local channel estimation result onto safety message transmissions and sharing them with each other. In result CMS realizes cooperative congestion control without any modification of the existing MAC protocol. I present extensive NS-3 simulation results which show that CMS outperforms conventional congestion control schemes in terms of the packet collision rate and throughput, especially in a high-density traffic environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.2A
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• pp.203-212
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• 2007

An advanced vehicle safety system can be constructed by exchanging danger-related information ,such as urgency stop, traffic accident, obstacle, and car trouble, among the vehicles. However, because network topology changes rapidly and frequently due to the mobility of vehicles, it is impossible to configure the network for information forwarding in this environment. In the most of vehicle safety communication applications, an emergency message is propagated in a form of broadcasting. The simple broadcasting causes a lot of problems in terms of efficiency due to multi-hop area and radio collision problem. This paper proposes a method of selective message forwarding with stem and branch structure for propagating the emergency messages. However, the proposed method raise the efficiency of message transmission with the selective forwarding based on the priority assignment as its location. We analyze and evaluate the performance by comparing the proposed scheme with other schemes that are presented in the paper.

• Journal of Digital Convergence
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• v.10 no.9
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• pp.319-324
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• 2012

Vehicle safety communications is one among the important technologies in order to protect a car accident. For this, many protocols forwarding a safe message have studied to protect a chain-reaction collision when a car accident occurs. most of these protocols assume that the time of generating a safe message is the same as an accident's. If a node predicts some traffic hazard and forwards a safe message, a driver can response some action quickly. So, In this paper, we proposes a traffic hazard prediction algorithm using the communication technique. As a result, we show that the frame reception success rate of using our algorithm to the previous protocol improved about 4~5%.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.1
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• pp.9-16
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• 2017

In this paper, we introduce a warning message providing methodology by considering the elderly's walking behavior in V2P(: Vehicle-to-Pedestrian) communication systems. Using the elderly's accident records in Kyounggi-do area from 2011 to 2014, the elderly's accident behaviors are analyzed by categorizing accidents as road type (single road/ crossing road), existence of traffic signal (with signal/ without signal), existence of crosswalk (crosswalk/ jaywalk), cause of accident (jaywalk/ signal violation/ carelessness accident/ Etc.). In addition, the elderly's behavior variable and vehicle speed are applied, then some threshold values are utilized in a warning message providing in conflict area. Finally, we propose a distance which can protect an accident depending on the elderly's walking speed, safety margin and vehicle speed. By applying the results of this research to the V2P/P2V communication based road safety message providing system with the elderly's walking behavior, it may be helpful to reduce accident rate of the elderly.

• Journal of the Korean Data and Information Science Society
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• v.21 no.4
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• pp.783-793
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• 2010

Several multi-hop applications developed for vehicular ad hoc networks use broadcast as a means to either discover nearby neighbors or propagate useful traffic information to other vehicles located within a certain geographical area. However, the conventional broadcast mechanism may lead to the so-called broadcast storm problem, a scenario in which there is a high level of contention and collisions at the link layer due to an excessive number of broadcast packets. We present a fuzzy alert message dissemination algorithm to improve performance for road safety alert application in Vehicular Ad-hoc Network (VANET). In the proposed algorithm, when a vehicle receives an alert message for the first time, the vehicle rebroadcasts the alert message according to the fuzzy control rules for rebroadcast degree, where the rebroadcast degree depends on the current traffic density of the road and the distance between source vehicle and destination vehicle. Also, the proposed algorithm is the hybrid algorithm that uses broadcast protocol together with token protocol according to traffic density. The performance of the proposed algorithm is evaluated through simulation and compared with that of other alert message dissemination algorithms.

• Journal of Auto-vehicle Safety Association
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• v.12 no.4
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• pp.48-53
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• 2020

This paper describes in work which is currently underway to the minimum safety performance requirements and test methods of V2V based on IEEE 802.11p in vehicle level like below. - The ranges and positions at static and driving condition of vehicle for BSM (Basic safety message) - Various road conditions such as straight road, crossroad, slope-way Based on this study, We will define the minimum safety performance requirements and test methods of V2V in vehicle considering various road conditions.