• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.8
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• pp.1619-1624
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• 2012

If multiple Tags in the RFID System transmit their IDs to the Reader at the same time, tag identification time is delayed due to collisions. Therefore, to reduce the reader's identification time, an efficient anti-collision technology is needed. In this paper, we propose a hybrid anti-collision method based on the QT and DFSA. Then, the performances of proposed method are compared with the existing method through extensive simulations.

• Journal of Auto-vehicle Safety Association
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• v.5 no.1
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• pp.44-49
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• 2013

This paper presents a lateral collision risk index between an ego vehicle and a rear-side vehicle. The lateral collision risk is designed to represent a lateral collision risk and provide the appropriate threshold value of activation of the lateral collision management system such as the Blind Spot Detection(BSD). The lateral collision risk index is designed using the Time to Line Crossing(TLC) and the longitudinal collision index at the predicted TLC. TLC and the longitudinal collision index are calculated with the signals from the exterior sensor such as the radar equipped on the rear-side of a vehicle and a vision sensor which detects the distance and time to the lane departure. For the robust situation assessment, the perception of driving environment determining whether the road is straighten or curved should be determined. The relative motion estimation method has been proposed with the road information via the integrated estimator using the environment sensors and vehicle sensor. A lateral collision risk index was composed with the estimated relative motion considering the relative yaw angle. The performance of the proposed lateral collision risk index is investigated via computer simulations conducted using the vehicle dynamics software CARSIM and Matlab/Simulink.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.9
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• pp.884-891
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• 2008

As the scale of RFID systems grows, decrease in recognition rate of collision between readers is becoming an issue. Time division technique may solve the problem, but this will cause total recognition time to increase. This issue must be solved for real-time inventory control. In this study, total recognition time was improved by placing ARCM in RFID systems. ARCM maintains short recognition time through efficient utilization of frequency channel and manages RFID systems to recognize the tag by avoiding interference. As the result of using ARCM, saving maximum 20% of time was possible.

• Journal of the Korea Society of Computer and Information
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• v.17 no.2
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• pp.207-214
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• 2012

This paper is to improve an identification ratio of tags by analyzing Slotted ALOHA, Dynamic Slotted ALOHA, Binary-tree and Query-tree and shortening the tag identification time in mobile RFID. Also, it enables the stable information transmission of tags by saving backscattering power of tags through shortening of identification time. As a result, this increases the available time of the battery and accessibility to a RFID service. For this, we proposed the energy-efficient tag anti-collision protocol for mobile RFID. The proposed scheme shows advanced result in identification time and collision counts. This scheme may be the first attempt for the mobile anti-collision.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.8
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• pp.1517-1530
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• 2017

Traditional anti-collision algorithms determine slot size of initial frame based on the information of number of collision slots, idle slots, and success slots. Since there is no information about collision at the beginning of tag information collection, traditional anti-collision algorithms can not determine the initial frame size. Considering that performance of anti-collision algorithm is very sensitive to initial slot size traditional anti-collision algorithms need some improvements. In this study two methods are proposed to determine slot size of initial frame efficiently, through which we can improve the performance of dynamic frame slotted aloha algorithm. To verify the performance of proposed algorithms, 2.4GHz RFID system is used. Throughput and delay time are derived through simulation, which is developed using JAVA. We have seen that proposed algorithm improves throughput by 9.6% and delay time by 9.8%.

• Journal of the Korean Institute of Navigation
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• v.12 no.1
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• pp.71-84
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• 1988

For traffic proceeding in random directions on a plane surface the frequency of collision, if no avoiding action in taken ,is approximately proportional to the square of the traffic density and directly proportional to the size and speed of the ship, Avoiding is normally taken and the rte of collisions is therefore also governed by additional factors such as the visibility, the effectiveness of the collisionavoidance rules, the competence of personnel or watchkeeping attitude, the maneuverability of the ship and the efficiency of radar and other equipments. From the viewpoint of watchkeeper who is responsible for maneuvering, watchkeeping attitude such as lookout and action to avoid collision is the most controllable factor among those mentioned above. In practice, according to the investigation of the institution of marine courts, about 50% co collisions occurred is caused by disorbedience to steering and sailing rules of international regulations for preventing collision at sea including lookout. So we classify the process of collisions with first sight of another ship , assessment of risk of collisions and action to avoid collisions and make a factural survey about lookout and action to avoid collisions from the point on "time" and " distance", namely relationship among ship's size, speed, first sight time of another ship, action to avoid collisions ,and distance from sight of another ship to collision occurred. According to the results of the actual survey , we come to conclude that most of collisions occurred are due to improper lookout and ineffective action to avoid collision which means time lag from first sight of another ship to time of action taken to avoid collision is relatively long. is relatively long.

• International Journal of Aeronautical and Space Sciences
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• v.6 no.2
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• pp.97-109
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• 2005

In this paper, the critical requirement for obstacle awareness and avoidance is assessed with the compliance of the equivalent level of safety regulation, and then the collision avoidance sensor system is presented with the key design parameters for the requirement of the smart unmanned aerial vehicle in low-altitude flight. Based on the assessment of various sensors, small-sized radar sensor is selected for the suitable candidate due to the real-time range and range-rate acquisition capability of the stationary and moving aircraft even under all-weather environments. Through the performance analysis for the system requirement, the conceptual design result of radar sensor model is proposed with the range detection probability and collision avoidance mode is established based on the time-to-collision, which is analyzed by collision scenario.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.133.3-133
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• 2001

This paper analyses the real-time performance of Ethernet based intranet whether it is applicable to the real-time network. Unpredictability of transmission delay by collision-delay-retransmission mechanism in CAMA/CD(Carrier Sense Multiple Access with Collision Detect) of Ethernet is the major reason making hard to apply to real-time system. Both retransmission mechanism of TCP(Transmission Control Protocol) for reliability and sliding windows algorithm for high utilization make hard to predict transmission delay. Because real-time control network require fast responsibility and bustle of short-periodic messages, global-clock for collision avoidance and UDP(User Datagram Protocol) for high utilization of network are used. The mathematical models for time-delay that can be occured between ...

• Korean Journal of Applied Biomechanics
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• v.31 no.1
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• pp.37-43
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• 2021

Objective: The purpose of this study was to investigate the effect of mobile phone text messaging on the collision avoidance strategy for an approaching and stationary pedestrian. Method: Eighteen healthy young adults participated in this study. Each participant was asked to perform a task to walking with/without mobile phone text messaging and a task to avoid collisions with another pedestrian who was approaching or stationary during walking. Results: When text messaging with avoidance collision, it showed an early onset time, a larger mediolateral COM trajectory, trunk rotation angle and trunk rotation velocity (p<.05). Also, compared to an approaching pedestrian, when avoiding collision with a stationary pedestrian, it showed a later onset time, a lager avoidance displacement, mediolateral COM trajectory, trunk rotation angle (p<.05). Conclusion: Results suggest that mobile phone text messaging while collision avoidance leads to delay the perception stage and alters the adaptation stage. Consequently, pedestrian executed in an exaggerated avoidance action to create a greater safety margin when attending to mobile phone test messages while avoiding another pedestrian.

• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.49-52
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• 2003

IEEE 802.11 MAC uses a distributed coordination function (DCF) known as carrier sense multiple access with collision avoidance (CSMA/CA) for medium access. Random back-off algorithm helps to avoid the collision. This paper proposes virtual back-off and modified back-off algorithm for reduce a waiting time by back-off and reduce the collision. The modified DCF is consisted of these two algorithms. We expect to reduce the average waiting time of each transmission by using the modified DCF algorithm.