• Journal of IKEEE
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• v.19 no.3
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• pp.385-391
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• 2015

In this paper, we analyze the communication performance in a time synchronous multi-channel environment and deal with a packet collision avoidance technique to improve it based on IEEE1609.4 for increasing the efficiency of the control channel IEEE802.11p WAVE communication system. In previous works, they tried to solve this problem by message scheduling method on application layer software or changing the value of the random back-off optionally Contention Window. In this paper, we propose a method for adjusting the Channel Guard Interval for packet collision avoidance. The performance was evaluated by the actual vehicle test. The result was confirmed performance over 90% PDR(Packet Delivery Ratio).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.5B
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• pp.463-468
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• 2009

In VANET(Vheicle Ad hoc Network), the researches based on the wireless LAN are conducting and the method based on 802.11a is being adapted in IEEE 802.11p WAVE(Wireless Access in Vehicular Environments). However, wireless LAN which uses a single channel in a competition can cause transmission delays because of a frequent collision and a use of CSMA/CA to avoid competition in VANET requiring a fast access. In this paper, we designed CMMP (Clustering based Multi-channel MAC protocol) adequate to VANET and then confirmed the appropriate channel conditions in a V2V communication on the basis of this protocol. The simulation results showed that a packet collision and a transmission delay by the use of an existing single channel based on the contention decreased more than 60% by CMMP.

• Journal of Satellite, Information and Communications
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• v.10 no.1
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• pp.29-32
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• 2015

It has been a big trend of the convergence technologies about communication systems and vehicular industry to improve safety and convenience. To achieve a number of infotainment vehicular applications, vehicles should transmit information with high reliability. A robust and accurate channel estimation scheme is of great importance to achieve the goal. In this paper, we present a novel enhanced decision-directed channel estimation scheme called FADP (Frequency Averaging Data Pilot) for dynamic time-varying vehicular channels in IEEE 802.11p. We use linear averaging filtering in frequency domain, and utilize the correlation characteristic of the channels between the adjacent two data symbols, update the CR in time domain to get more accuracy. Finally, analysis and simulation results reveal that compared with exist schemes, the proposed scheme has a good performance in mean square error (MSE) and bit error rate (BER).

• Korea Information Processing Society Review
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• v.15 no.5
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• pp.103-111
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• 2008

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.3
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• pp.180-187
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• 2014

This paper introduces reliable multicast MAC protocol for cooperative unmanned vehicles. cooperative unmanned vehicles communicate with infrastructure and other unmanned vehicles in order to increase driving safety. They exchange information related to driving and thus it requires real-time and reliable multicast. However, the international vehicular communication standard, IEEE 802.11p WAVE, does not provide a reliable multicast scheme on the MAC layer. To address the problems of reliability, we propose a reliable multicast protocol called WiVCL, which avoids contention and collision. Our evaluation shows that the WiVCL achieves a high degree of reliability and real-time features.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.12 no.5
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• pp.52-60
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• 2013

ITS technologies are in the research and development around the world as a solution for maximizing the efficiency of the existing road infrastructure, solving the complex traffic problems and providing the convenient driving services. The core of these ITS technologies is to provide the information for the requesting users in fast and accurate way from the server. In real driving conditions, there are many communication barriers around the vehicles and the base stations so that an accurate and robust handover technology is needed in order to ensure seamless ITS services. This paper introduced an WAVE handover algorithm implemented in a real communication device and five parameters mainly affecting the handover performance are evaluated. The handover performance is measured by changing the parameter values at a highway testbed. The test results show that the handover algorithm parameter values should be configured carefully to remove the handover ping-pong problems.

• International Journal of Internet, Broadcasting and Communication
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• v.12 no.1
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• pp.7-13
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• 2020

We describes V2X technology, a connectivity-based recognition technology that is attracting attention as a key technology for implementing autonomous driving technology, and autonomous communication modules that implement ADAS technology, a sensor-based recognition technology. It also explains the trends in V2X technology standardization centered on IEEE 802.11p, which is a WAVE technology standard based on Wi-Fi/DSRC. Finally, we will discuss the market growth trend of V2X communication modules in the United States, the leading V2X technology module, and the development of technology development trends of major domestic and international companies that are leading the global technology market related to V2X communication modules. V2X and ADAS technologies will be the biggest influence on automotive purchasing decisions. In recent years, V2I mandates have been promoted beyond V2V, mainly in developed countries such as the United States. The related industry needs to focus on the development of information transmission network technology that can support high frequency high efficiency(transmission rate) and sophisticated positioning accuracy beyond conventional vehicle communication.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.1
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• pp.33-39
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• 2017

In mission-critical applications such as vehicular networks, distributed robotics, and other cyber-physical systems, the requirements for latency are more stringent than traditional applications. Among them, autonomous V2V communication is a rapidly emerging domain of applications with a few milliseconds' latency requirements. Today's systems utilizing 802.11p or LTE-direct standards are not primarily designed for ultra-low latency. Because the medium access function contributes to a significant portion of the total latency, it is necessary to modify Layer2 in order to solve the problem. Focusing on MAC layer, we developed a scalable and latency-guaranteed MAC by devising Autonomous TDMA (ATDMA) in which autonomous joining/leaving is allowed without scheduling by coordinator. We also evaluated the performance of the algorithm by comparing with the WAVE protocol.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.1B
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• pp.1-8
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• 2012

In this paper, we propose an algorithm to improve collision avoidance in Vehicle-to-Vehicle (V2V) networks based on IEEE 802.11p. Since IEEE 802.11p adopts CSMA/CA as a multiple access scheme and an emergency warning message (EWM) is delivered to behind vehicles in a multi-hop manner, due to transmission collision, the more vehicles in the vehicle chain results in a longer delay. The longer delay increases the possibility of a rear-end collision. In order to ensure message reception with low latency, we consider implicit acknowledgement of a broadcasted EWM message and propose an algorithm to reduce redundant message transactions, called Two-Way Implicit Acknowledgement (TWIA). By simulations, we show that our proposed algorithm can reduce the latency until the last car receives the message by 9% and the success rate every car receives the message within 0.7sec by 12% at 100 fixed-number-of-car environment.

• Journal of Internet Computing and Services
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• v.14 no.1
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• pp.15-22
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• 2013

WAVE(Wireless Access for Vehicular Environment) is new concepts and Vehicles communications technology using for ITS(Intelligent Transportation Systems) service by IEEE standard 802.11p. Also it increases the efficiency and safety of the traffic on the road. However, the efficiency of Scrambler bit computational algorithms of OFDM modulation in WAVE systems will fall as it is not able to process in parallel in terms of hardware and software. This paper proposes an algorithm to configure 64-bits matrix table in scambler bit computation as well as an algorithm to compute 64-bits matrix table and input data in parallel. The proposed algorithm on this thesis is executed using 64-bits matrix table. In the result, the processing speed for 1 and 1000 times is improved about 40.08% ~ 40.27% and processing rate per sec is performed more than 468.35 compared to bit operation scramble. And processing speed for 1 and 1000 times is improved about 7.53% ~ 7.84% and processing rate per sec is performed more than 91.44 compared to 32-bits operation scramble. Therefore, if the 64 bit-CPU is used for 64-bits executable scramble algorithm, it is improved more than 40% compare to 32-bits scrambler.