• Title/Summary/Keyword: Transit Delay

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Proposed Message Transit Buffer Management Model for Nodes in Vehicular Delay-Tolerant Network

  • Gballou Yao, Theophile;Kimou Kouadio, Prosper;Tiecoura, Yves;Toure Kidjegbo, Augustin
    • International Journal of Computer Science & Network Security
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    • v.23 no.1
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    • pp.153-163
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    • 2023
  • This study is situated in the context of intelligent transport systems, where in-vehicle devices assist drivers to avoid accidents and therefore improve road safety. The vehicles present in a given area form an ad' hoc network of vehicles called vehicular ad' hoc network. In this type of network, the nodes are mobile vehicles and the messages exchanged are messages to warn about obstacles that may hinder the correct driving. Node mobilities make it impossible for inter-node communication to be end-to-end. Recognizing this characteristic has led to delay-tolerant vehicular networks. Embedded devices have small buffers (memory) to hold messages that a node needs to transmit when no other node is within its visibility range for transmission. The performance of a vehicular delay-tolerant network is closely tied to the successful management of the nodes' transit buffer. In this paper, we propose a message transit buffer management model for nodes in vehicular delay tolerant networks. This model consists in setting up, on the one hand, a policy of dropping messages from the buffer when the buffer is full and must receive a new message. This drop policy is based on the concept of intermediate node to destination, queues and priority class of service. It is also based on the properties of the message (size, weight, number of hops, number of replications, remaining time-to-live, etc.). On the other hand, the model defines the policy for selecting the message to be transmitted. The proposed model was evaluated with the ONE opportunistic network simulator based on a 4000m x 4000m area of downtown Bouaké in Côte d'Ivoire. The map data were imported using the Open Street Map tool. The results obtained show that our model improves the delivery ratio of security alert messages, reduces their delivery delay and network overload compared to the existing model. This improvement in communication within a network of vehicles can contribute to the improvement of road safety.

A Study on the Active Transit Signal Priority Control Algorithm based on Bus Demand using UTIS (UTIS를 활용한 수요 기반의 능동형 버스우선신호 제어 알고리즘에 관한 연구)

  • Hong, Gyeong-Sik;Jeong, Jun-Ha;An, Gye-Hyeong;Lee, Yeong-In
    • Journal of Korean Society of Transportation
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    • v.29 no.6
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    • pp.107-116
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    • 2011
  • In this paper, we implement an algorithm of transit signal priority control that not only maximizes service quality and efficiency of bus, but also minimizes the control delay of passenger cars using UTIS currently being deployed and operated in Seoul national capital area. For this purpose, we propose an algorithm that coordinates the strength of TSP by estimating bus demand. Typically, the higher the strength of TSP is on main street, the bigger the control delay is on the cross street. Motivated by this practical difficulty, we proposes an algorithm that coordinates TSP's strength by checking the degree of saturation of cross street. Also, we verify the possibility of field implementation via simulation analysis using CORSIM RTE based HILS (Hardware In the Loop Simulation). The result shows that travel time of bus improves about 10 percent without increasing control delay of passenger cars by TSP. We expect the result of this research to contribute to increasing the overall transit ridership in this country.

Transit Frequency Optimization with Variable Demand Considering Transfer Delay (환승지체 및 가변수요를 고려한 대중교통 운행빈도 모형 개발)

  • Yu, Gyeong-Sang;Kim, Dong-Gyu;Jeon, Gyeong-Su
    • Journal of Korean Society of Transportation
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    • v.27 no.6
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    • pp.147-156
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    • 2009
  • We present a methodology for modeling and solving the transit frequency design problem with variable demand. The problem is described as a bi-level model based on a non-cooperative Stackelberg game. The upper-level operator problem is formulated as a non-linear optimization model to minimize net cost, which includes operating cost, travel cost and revenue, with fleet size and frequency constraints. The lower-level user problem is formulated as a capacity-constrained stochastic user equilibrium assignment model with variable demand, considering transfer delay between transit lines. An efficient algorithm is also presented for solving the proposed model. The upper-level model is solved by a gradient projection method, and the lower-level model is solved by an existing iterative balancing method. An application of the proposed model and algorithm is presented using a small test network. The results of this application show that the proposed algorithm converges well to an optimal point. The methodology of this study is expected to contribute to form a theoretical basis for diagnosing the problems of current transit systems and for improving its operational efficiency to increase the demand as well as the level of service.

The Study for State of Construction and Improvement policy of Advanced Transit System of Korea (우리나라 경전철 도입 현황과 개선방안에 관한 연구)

  • Park Kwang-Bok;Han Kook Hawn
    • Proceedings of the KSR Conference
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    • 2003.10c
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    • pp.424-431
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    • 2003
  • This report was studied about the advanced transit system for operating in oversea country and state of construction in the domestic. And we suggested the improvement policy against the major problems due to delay to operation and construction of advanced transit system in each cities of local self Government.

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Clinical Evaluation of Radionuclide Esophageal Transit Studies using Liquid and Solid Foods (유동식 및 고형식을 이용한 동위원소 식도통과검사의 임상적 의의에 대한 연구)

  • Choe, Jae-Gol;Lee, Min-Jae;Song, Chi-Wook;Hyun, Jin-Hai;Suh, Won-Hyuck
    • The Korean Journal of Nuclear Medicine
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    • v.29 no.1
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    • pp.61-72
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    • 1995
  • The author performed radionuclide esophageal transit studies(RETS) with liquid and solid boluses using the same day protocol in 90 normal controls and 164 patients with various primary esophageal motility disorders who were diagnosed by manometric criteria and clinical courses. The authors calculated mean esophageal transit time(MTT) and mean residual retention(MRR) in each of the liquid and solid studies, and classified time-activity curve(TAC) patterns. The normal criteria of RETS with liquid bolus were MTT<24 sec, MRR<9%, and the TAC pattern that showed rapid declining slope and flat low residual(Type 1). The normal criteria of RETS with solid bolus were MTT<35 sec, MRR<9% and TAC of type 1. With these normal criteria, the sensitivity and the specificity of the liquid study were 62.2 % and 97.8%, respectively. The sensitivity increased to 75.4% with the solid study. The author also found that the RETS was highly reproducible. The achalasia typically showed no effective emptying of both liquid and solid boluses during the whole study period, and was well differentiated by its extremely long transit time and high retention from the other motility disorders. The diffuse esophageal spasm (DES) and nonspecific esophageal motility disorder(NEMD) showed intermediate delay in transit time and increased retention. In the groups of hypertensive lower esophageal sphincter(LES), hypotensive LES and nutcracker, there noted no significant difference with the normal control group in terms of MTT and MRR. The DES and NEMD could be more easily identified by solid studies that showed more marked delay in MTT and increased MRR as compared with the liquid study. In conclusion, esophageal scintigraphy is a safe, noninvasive and physiologic method for the evaluation of esophageal emptying.

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A Intra-media Synchronization Scheme using Media Scaling (서비스 품질 저하 기능의 미디어내 동기화 방안)

  • 배시규
    • Journal of Korea Society of Industrial Information Systems
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    • v.4 no.4
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    • pp.1-6
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    • 1999
  • When continuous media are transmitted over the communication networks, asynchrony which can not maintain temporal relationships among packets my occur due to a random transit delay. There exist two types of synchronization schemes ; for guaranteed or non-guaranteed resource networks. The former which applies a resource reservation technique maintains delay characteristics however, the latter supply a best-effort service. In this paper, I propose a intra-media synchronization scheme to transmit continuous media on general networks not guaranteeing a bounded delay time. The scheme controls transmission times of the packets by estimating next delay time with the delay distribution So, the arriving packets my be maintained within a limited delay boundary, and playout will be performed after buffering to smoothen small delay variations. To prevent network congestion and maintain minimum quality of service the transmitter performs media scaling-down by dropping the current packet when informed excessive delay from the receiver.

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Design of Zigbee Beacon Frame for High Efficiency Transmit in Home Network (홈 네트워크에서 고효율 전송을 위한 Zigbee Beacon Frame 설계)

  • Han, Kyoung-Heon;Han, Seung-Jo;Choi, Hyun-Yong
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.36 no.11B
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    • pp.1373-1382
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    • 2011
  • Zigbee is communication technology most ideal because Zigbee support low power communication and wide expansion in wireless home network. However, Zigbee is not popular, because of Zigbee always has Hidden Node Problem and Transit Delay Problem. We propose new Beacon Frame structure to solve the two problem in Zigbee. New Beacon Frame structure reduces a Super Frame Duration and add a same space of a Control Frame Duration. We expect to solved method of Hidden Node Problem that exchange terminal information to using RTS/CTS. Also, We expect to solved method of Transit Delay Problem that put Beacon between Control Frame Duration and Super Frame Duration for synchronization. We confirm new Beacon Frame to solved two problem in OPNET simulation at Zigbee QoS Parameters. We measure Delay(sec) for solution degree of Transit Delay Problem, and measure Throughput(bits/sec) and Load (bits/sec) for solution degree of Hidden Node Problem.

Evaluation of Bioavailability of Bioadhesive Microcapsules Containing Cephalexin (세팔렉신 함유 생체막점착성 마이크로캅셀의 생체이용율 평가)

  • Han, Kun;Kim, Jung-Hwan;Chung, Youn-Bok;Jee, Ung-Kil
    • Journal of Pharmaceutical Investigation
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    • v.24 no.3
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    • pp.177-186
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    • 1994
  • Bioadhesive microcapsules of cephalexin, using Eudragit RS/RL coated with polycarbophil or carbopol, were evaluated biopharmaceutically. The GI transit of microcapsules in rats was studied. Bioadhesive microcapsules coated with polycarbophil or carbopol were shown to have substantially longer GI transit time than Eudragit RS/RL microcapsule. The delay in transit time was due to bioadhesion of the polymer to the mucin-epithelial cell surface which was clearly observable on animal autopsy. Plasma drug levels in rabbits showed that bioadhesive microcapsules resulted in a longer duration of action and greater bioavailability than other microcapsule or drug powder. Thus, the principle of bioadhesion can significantly improve therapy, due to a reduced rate of gastric emptying, an increase in contact time, and the intimacy of contact of the drug with the absorbing membrane.

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Signal Timing Calculation Model of Transit Signal Priority using Shockwave Theory (충격파 이론을 이용한 대중교통 우선신호의 신호시간 산정모형)

  • Park, Sang Sup;Cho, Hye Rim;Kim, Youngchan;Jeong, Youngje
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.35 no.4
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    • pp.897-905
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    • 2015
  • This research suggested the traffic signal calculation model of active transit signal priority using a shockwave model. Using this signal priority timing optimization model, the shockwave area is computed under the condition of Early Green and Green Extension among active transit signal priority techniques. This study suggested the speed estimation method of backward shockwave using average travel time and intersection passing time. A shockwave area change is calculated according to signal timing change of transit signal priority. Moreover, this signal timing calculation model could determine the optimal signal priority timings to minimize intersection delay of general vehicles. A micro simulation analysis using VISSIM and its user application model ComInterface was applied. This study checked that this model could calculate the signal timings to minimize intersection delay considering saturation condition of traffic flow. In case studies using an isolated intersection, this study checked that this model could improve general vehicle delay of more over ten percentage as compared with equality reduction strategy of non-priority phases. Recently, transit priority facilities are spreading such as tram, BRT and median bus lane in Korea. This research has an important significance in that the proposed priority model is a new methodology that improve operation efficiency of signal intersection.