Browsing by Author "Chen, Lien-Wu"

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An Infrastructure-less Framework for Preventing Rear-End Collisions by Vehicular Sensor Networks
(2011-03-01)
Chen, Lien-Wu
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Peng, Yu-Hao
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Tseng, Yu-Chee
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資訊工程學系
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Department of Computer Science
We consider vehicular sensor networks (VSNs) consisting of a large number of sensor nodes deployed on vehicles to facilitate vehicular applications. We try to apply such VSNs to preventing rear-end collisions that are common accidents due to sharp stops. An infrastructure-less framework is proposed, which only relies on vehicles' onboard sensors to prevent such accidents. The proposed framework consists of a distributed warning protocol and a location-based backoff scheme. Vehicle-to- vehicle communications is used to form warning groups, where a warning group is a set of vehicles that drive along the same lane and every pair of adjacent cars is within a certain distance. Only single-hop transmissions are needed to join and leave a group, thus keeping the group maintenance overhead low. When a sudden brake event is detected in a warning group, the location-based backoff scheme can quickly propagate warning messages among its group members. Simulation results show that the proposed approach outperforms existing schemes.
Cooperative Sensing Data Collection and Distribution with Packet Collision Avoidance in Mobile Long-Thin Networks
(2018-10-01)
Chen, Lien-Wu
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Peng, Yu-Hao
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Tseng, Yu-Chee
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Tsai, Ming-Fong
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資訊工程學系
Mobile ad hoc networks (MANETs) have gained a lot of interests in research communities for the infrastructure-less self-organizing nature. A MANET with fleet cyclists using smartphones forms a two-tier mobile long-thin network (MLTN) along a common cycling route, where the high-tier network is composed of 3G/LTE interfaces and the low-tier network is composed of IEEE 802.11 interfaces. The low-tier network may consist of several path-like networks. This work investigates cooperative sensing data collection and distribution with packet collision avoidance in a two-tier MLTN. As numbers of cyclists upload their sensing data and download global fleet information frequently, serious bandwidth and latency problems may result if all members rely on their high-tier interfaces. We designed and analyzed a cooperative framework consisting of a distributed grouping mechanism, a group merging and splitting method, and a sensing data aggregation scheme. Through cooperation between the two tiers, the proposed framework outperforms existing works by significantly reducing the 3G/LTE data transmission and the number of 3G/LTE connections.
Cooperative Traffic Control With Green Wave Coordination for Multiple Intersections Based on the Internet of Vehicles
(2017-07-01)
Chen, Lien-Wu
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Chang, Chia-Chen
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資訊工程學系
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Department of Computer Science
Traffic congestion is a critical concern in most cities. Inefficient traffic control wastes time and fuel, and causes harmful carbon emissions, road accidents, and many economic problems. This paper proposes a cooperative traffic control framework for optimizing the global throughput and travel time for multiple intersections. Adjacent intersections are considered in analyzing their joint passing rates and attempting to maximize the number of vehicles traveling through a road network. The proposed framework provides fairness for each road segment and realizes the green wave concept for arterial roads. This paper extends previous studies by considering the passing rates of continuous road segments and coordinating traffic signals of multiple intersections. The simulation results show that the approach outperforms existing schemes in that it achieves a high global throughput, reduces the average waiting time, lowers the total travel time, and decreases average CO2 emissions. To verify the feasibility of the proposed framework, a wireless access in vehicular environments/dedicated short-range communications-based prototype for lane-level dynamic traffic control is designed and implemented.
Demo Abstract: A Vehicular Surveillance and Sensing System for Car Security and Tracking Applications
(2010-01-01)
Chen, Lien-Wu
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Syue, Kun-Ze
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Tseng, Yu-Chee
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資訊工程學系
;
Department of Computer Science
In this paper, we propose a Vehicular Surveillance and Sensing System (VS3), which targets at car security and tracking applications. VS3 can be triggered by events detected inside or outside a car, such as abnormal air quality, potential burglary, and identification of some target vehicles (such as stolen cars). Via a 3G module, a user can interact with VS3 via multimedia communications. For security applications, we show how VS3 detects an abnormal CO2 level or potential car burglary, notifies the vehicle owner, and then interacts with the owner. For tracking applications, we show how VS3 identifies potential stolen vehicles, transmits reports to the police department, and get neighboring cars involved to cooperatively track suspicious vehicles. This paper demonstrates our current prototype.
Demo Abstract: A Video-Based Metropolitan Positioning System with Centimeter-Grade Localization for VANETs
(2015)
Chen, Lien-Wu
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Ho, Yu-Fan
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Chang, Chia-Chen
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Tseng, Yu-Chee
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資訊工程學系
In this paper, we propose a video-based metropolitan positioning system (V-MPS) for providing centimeter-grade localization in vehicular networks. The V-MPS system integrates vehicular networks with installed roadside/intersection cameras to provide positioning information to vehicles on the road. V MPS can estimate the precise position of a vehicle and detect the located lane for each vehicle. To the best of our knowledge, V MPS is the first positioning system which provides the following features: 1) it achieves the centimeter-grade positioning accuracy for vehicular networks that can detect the located lanes of vehicles, 2) it employs existing roadside/intersection cameras that can keep additional construction cost low, and 3) it establishes an innovative infrastructure for applications of next-generation Intelligent Transportation System (ITS) that can make lane level traffic control, collision avoidance, and vehicle navigation possible. With vehicular networks, the estimated positions can be broadcast to nearby vehicles. With roadside/intersection cameras, the lane positions of vehicles can be detected even if GPS is not accurate enough to provide lane-level localization. In addition, the traffic condition can be continually monitored to optimize driving efficiency for next-generation ITS. This paper demonstrates our current prototype.
Design and analysis of contention-based request schemes for best-effort traffics in IEEE 802.16 networks
(2008-08-01)
Chen, Lien-Wu
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Tseng, Yu-Chee
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資訊工程學系
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Department of Computer Science
The IEEE 802.16 standard is designed to meet the need of metropolitan-area broadband wireless access. This work studies two collision-resolution requesting schemes for best-effort (BE) traffics in IEEE 802.16 networks. One is the exponential backoff scheme defined in the standard and the other is a piggyback mechanism enhanced by single-frame backoff, called the Request Piggyback (RPB) scheme. We analyze and compare their performance in terms of the request success probability and the packet delivery delay under Poisson traffic. The results show that the RPB scheme outperforms the exponential backoff scheme and can reduce request collision.
Distributed Emergency Guiding with Evacuation Time Optimization Based on Wireless Sensor Networks
(2016-02)
Chen, Lien-Wu
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Cheng, Jen-Hsiang
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Tseng, Yu-Chee
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資訊工程學系
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Department of Computer Science
This paper proposes a load-balancing framework for distributed emergency guiding based on wireless sensor networks. A load-balancing guiding scheme is designed and an analytical model is derived to reduce the total evacuation time of people indoors. The guiding scheme can provide the fastest path for people to reach an exit according to the evacuation time estimated using the analytical model. Based on thorough research, this is the first distributed solution in which corridor capacity and length, exit capacity, and the concurrent movement and distribution of people are considered in estimating the evacuation time and planning escape paths. Using the proposed framework, congestion in corridors and at exits can be eased to substantially reduce the total evacuation time. Analytical and simulation results show that this approach outperforms existing schemes and can prevent people from following local-optimal guiding directions that increase the evacuation time. A prototype called the Load-balancing Emergency Guiding System (LEGS) is implemented; this system can be used to compare the evacuation times and guiding directions provided by existing schemes and the proposed scheme for various distributions of people.
Dynamic Traffic Control with Fairness and Throughput Optimization Using Vehicular Communications
(2013-09-01)
Chen, Lien-Wu
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Sharma, Pranay
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Tseng, Yu-Chee
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資訊工程學系
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Department of Computer Science
Traffic congestion in modern cities seriously affects our living quality and environments. Inefficient traffic management leads to fuel wastage in volume of billion gallons per year. In this paper, we propose a dynamic traffic control framework using vehicular communications and fine-grained information, such as turning intentions and lane positions of vehicles, to maximize traffic flows and provide fairness among traffic flows. With vehicular communications, the traffic controller at an intersection can collect all fine-grained information before vehicles pass the intersection. Our proposed signal scheduling algorithm considers the flows at all lanes, allocates more durations of green signs to those flows with higher passing rates, and also gives turns to those with lower passing rates for fairness provision. Simulation results show that the proposed framework outperforms existing works by significantly increasing the number of vehicles passing an intersection while keeping average waiting time low for vehicles on non-arterial roads. In addition, we discuss our implementation of an Zigbee-based prototype and experiences.
Eco-Sign: A Load-Based Traffic Light Control System for Environmental Protection with Vehicular Communications
(2011-08-01)
Chen, Lien-Wu
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Sharma, Pranay
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Tseng, Yu-Chee
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資訊工程學系
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Department of Computer Science
The Eco-Sign system is a traffic light control system for minimizing greenhouse gases emitted by idling vehicles at intersections. Eco-Sign provides the following features: (i) it can notify vehicles to turn on/off their engines based on expected waiting time for green lights at intersections, (ii) it can dynamically adjust traffic light timing to minimize the number of vehicles stopping at an intersection based on vehicle arrival and departure rates, and (iii) it is a fully distributed system in the sense that each intersection can learn its local traffic condition and optimize its traffic sign setting to prevent congestions and thus traffic jams. Eco-Sign thus demonstrates a new traffic light control system for environmental protection.
Evacuation Time Analysis and Optimization for Distributed Emergency Guiding Based on Wireless Sensor Networks
(2012-01-01)
Chen, Lien-Wu
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Cheng, Jen-Hsiang
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Tseng, Yu-Chee
;
資訊工程學系
;
Department of Computer Science
This paper proposes a load-balancing framework for emergency guiding based on wireless sensor networks. We design a load-balancing guiding scheme and derive an analytical model in order to reduce the total evacuation time of indoor people. The guiding scheme can provide the fastest path to an exit for people based on the evacuation time estimated by the analytical model. This is the first distributed solution which takes the corridor capacity and length, exit capacity, concurrent move, and people distribution into consideration for estimating evacuation time and planning escape paths. Through the proposed framework, the congestion of certain corridors and exits can be released to significantly reduce the total evacuation time. Analytical and simulation results show that our approach outperforms existing works, which can prevent people from following the local optimal guiding direction with the longer evacuation time in total. We also implement a prototype, called Load-balancing Emergency Guiding System (LEGS), which can compare evacuation time and guiding directions of existing schemes and ours under different people distribution.
Exploiting spectral reuse in resource allocation, scheduling, and routing for IEEE 802.16 mesh networks
(2007)
Chen, Lien-Wu
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Tseng, Yu-Chee
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Wang, Da-Wei
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Wu, Jan-Jan
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資訊工程學系
The IEEE 802.16 standard for wireless metropolitan area networks (WMAN) has been created to meet the need of wide-range broadband wireless access at low cost. The objective of this paper is to study how to exploit spectral reuse in an IEEE 802.16 mesh network through timeslot allocation, bandwidth adaptation, hierarchical scheduling, and routing. To the best of our knowledge, this is the first work which formally quantifies spectral reuse in IEEE 802.16 mesh networks and which exploits spectral efficiency under an integrated framework. Simulation results show that the proposed spectral reuse scheduling and load-aware routing significantly enhance the network throughput performance in IEEE 802.16 mesh networks.
Exploiting Spectral Reuse in Routing, Resource Allocation, and Scheduling for IEEE 802.16 Mesh Networks
(2009-01-01)
Chen, Lien-Wu
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Tseng, Yu-Chee
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Wang, You-Chiun
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Wang, Da-Wei
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Wu, Jan-Jan
The IEEE 802.16 standard for wireless metropolitan area networks (WMANs) is defined to meet the need for wide-range broadband wireless access at low cost. The objective of this paper is to study how to exploit spectral reuse in resource allocation in an IEEE 802.16 mesh network, which includes routing tree construction (RTC), bandwidth allocation, time-slot assignment, and bandwidth guarantee of real-time flows. The proposed spectral reuse framework covers bandwidth allocation at the application layer, RTC and resource sharing at the medium access control: (MAC) layer, and channel reuse at the physical layer. To the best of our knowledge, this is the first paper that formally quantifies spectral reuse in IEEE 802.16 mesh networks and exploits spectral efficiency under an integrated framework. Simulation results show that the proposed schemes significantly improve the throughput of IEEE 802.16 mesh networks.
Optimal Path Planning With Spatial-Temporal Mobility Modeling for Individual-Based Emergency Guiding
(2015-12-01)
Chen, Lien-Wu
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Cheng, Jen-Hsiang
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Tseng, Yu-Chee
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資訊工程學系
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Department of Computer Science
This paper proposes an individual-based framework for emergency guiding. The spatial-temporal mobility of all people is modeled to determine a dedicated path that provides the shortest evacuation time for each person. According to our review of relevant research, this is the first optimal solution without using time-expanded graphs, and corridor capacities and lengths, exit capacities, concurrent motion, and distribution of people are considered to minimize evacuation time. We prove that the proposed path planning algorithm is optimal and analyze its time and space complexity. The proposed framework can be used to estimate the evacuation time for each person accurately and evenly distribute evacuation load among exits to achieve the most efficient load balance. In the proposed framework, the congestion in all corridors and exits can be alleviated to maximally reduce the total evacuation time. Simulation results show that our approach outperforms existing schemes, and can be used to determine an optimal escape path for each person and, thus, achieve the shortest total evacuation time.
Route Throughput Analysis with Spectral Reuse for Multi-Rate Mobile Ad Hoc Networks
(2009-09-01)
Chen, Lien-Wu
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Chu, WeiKuo
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Tseng, Yu-Chee
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Wu, Jan-Jan
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資訊工程學系
The mobile ad hoc networks (MANETs) have received a lot of attention for its flexible network architecture. While many routing protocols have been proposed for MANETs based on different criteria, few have considered the impact of multi-rate communication capability that is supported by many current WLAN products. Given a routing path, this paper provides an analytic tool to evaluate the expected throughput of the route with spectral reuse, assuming that hosts move following the discrete-time, random-walk model. The derived result can be added as another metric for route selection. Simulation results show that the proposed formulation can be used to evaluate path throughput accurately.
Surveillance on-the-road: Vehicular tracking and reporting by V2V communications
(2014-07-04)
Chen, Lien-Wu
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Tseng, Yu-Chee
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Syue, Kun-Ze
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資訊工程學系
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Department of Computer Science
Vehicular networks have attracted a lot of attention recently. One potential application of vehicular networks is to use video cameras embedded in vehicles to support video surveillance, which we call "surveillance on-the-road". Traditional surveillance systems only rely on fixed stations on the roads to monitor road conditions. With vehicular cameras, deeper and richer road conditions may be tracked. In this paper, we study the related communication issues to support such "on-the-road" surveillance scenarios. We use monitoring and tracking suspicious vehicles (such as stolen cars) on the road through license plate recognition (LPR) as an example (our results should be applicable to other scenarios as well). We show how vehicles can work cooperatively through vehicle-to-vehicle (V2V) communications to achieve this goal. With a tracking and a reporting modules, our solution does not rely on infrastructure networks. The tracking module allows handoff of a tracking job to neighboring vehicles as necessary and report of suspicious vehicles to nearby police cars. The reporting module can help guide message flows to avoid flooding the network. Simulation results verify the message efficiency of our approach. We also show how our framework can be applied to the developing WAVE/DSRC (Wireless Access in Vehicular Environments/Dedicated Short Range Communications) standards. (C) 2014 Elsevier B.V. All rights reserved.
VS(3): A Vehicular Surveillance and Sensing System for Security Applications
(2009)
Chen, Lien-Wu
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Syue, Kun-Ze
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Tseng, Yu-Chee
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資訊工程學系
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Department of Computer Science
The Vehicular Surveillance and Sensing System (VS(3)) is a 3G-based mobile device for car security applications. On the car side, it consists of a CO(2) sensor, a camera module, a 3G module, and a microprocessor. On the user side, only a 3G mobile phone is needed. VS(3) provides the following features: (i) it can be triggered by events detected on car, (ii) events can be abnormal air quality or potential burglary, and (iii) it supports text or multimedia interaction with users. Application scenarios include detecting an abnormal CO(2) level or potential car burglary, which triggers VS(3) to transmit SMS, MMS, or interactive video call to the vehicle owner, who can then monitor the car situation in return. VS(3) thus demonstrates a new car security and burglarproof prototype.