Browsing by Author "Hsieh, Yi-Ling"

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A color-theory-based energy efficient routing algorithm for mobile wireless sensor networks
(2008-02-22)
Chang, Tai-Jung
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Wang, Kuochen
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Hsieh, Yi-Ling
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資訊工程學系
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Department of Computer Science
Wireless sensor networks (WSNs) with nodes spreading in a target area have abilities of sensing, computing, and communication. Since the GPS device is expensive, we used a small number of fixed anchor nodes that are aware of their locations to help estimate the locations of sensor nodes in WSNs. To efficiently route sensed data to the destination (the server), identifying the location of each sensor node can be of great help. We adopted a range-free color-theory based dynamic localization (CDL) [Shen-Hai Shee, Kuochen Wang, I.L. Hsieh, Color-theory-based dynamic localization in mobile wireless sensor networks, in: Proceedings of Workshop on Wireless, Ad Hoc, Sensor Networks, August 2005] approach, to help identify the location of each sensor node. Since sensor nodes are battery-powered, we propose an efficient color-theory-based energy efficient routing (CEER) algorithm to prolong the life time of each sensor node. The uniqueness of our approach is that by comparing the associated RGB values among neighboring nodes, we can efficiently choose a better routing path with energy awareness. Besides, the CEER has no topology hole problem. Simulation results have shown that our CEER algorithm can save up to 50-60% energy than ESDSR [Mohammed Tarique, Kemal E. Tepe, Mohammad Naserian, Energy saving dynamic source routing for ad hoc wireless networks, in: Proceedings of Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks, April 2005, pp. 305-310] in mobile wireless sensor networks. In addition, the latency per packet of CEER is 50% less than that of ESDSR. (c) 2007 Elsevier B.V. All rights reserved.
A Hierarchical Social Network-based P2P SIP System for Mobile Environments
(2010)
Li, Bo-Wei
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Wang, Kuochen
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Hsieh, Yi-Ling
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資訊工程學系
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Department of Computer Science
P2P SIP (peer to peer session initiation protocol) systems have emerged as a new trend in multimedia realm due to their abilities to overcome the shortcomings of conventional SIP systems. Most of P2P SIP systems were implemented using Chord, a Distributed Hash Table (DHT) based routing algorithm which can provide scalability and reliability. Previous studies on P2P SIP systems did not address node heterogeneity, location information and mobility issues all together. For node heterogeneity, nodes with different capabilities (processing power, storage and bandwidth) should be treated suitably. For location information, the signaling latency is correlated with the distance between end users. This will influence call setup latency greatly. As to mobility, the node churn property will involve additional messages to maintain a stable DHT-based network and increases call setup latency. To conquer these problems, we propose a hierarchical social network-based P2P SIP system. The social network property can increase routing efficiency when calling friends. In addition, the proposed hybrid (structured/unstructured) overlay is more resilient to cope with node churn. Simulation results show that our approach can improve 32% call setup latency with non-buddies and reduce 63% maintenance cost in comparison with the conventional Chord-based approach. In addition, we improve lookup efficiency from O(logN) to O(1) when making calls with buddies, where N is the number of nodes in a DHT-based network.
A Reliable Routing Scheme Based on Vehicle Moving Similarity for VANETs
(2011)
Wei, Min-Hsuan
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Wang, Kuochen
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Hsieh, Yi-Ling
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資訊工程學系
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Department of Computer Science
In this paper, we propose a reliable routing scheme based on vehicle moving similarity (RR-VMS), which focuses on stable rebroadcast nodes selection and route discovery to make inter-vehicle data transmissions more reliable. We select nearby vehicles having similar velocities with the source vehicle as rebroadcast nodes. We call these vehicles having moving similarity with the source vehicle. To reflect vehicle moving similarity, a vehicle persistence score (VPS) is derived. A vehicle with a high VPS, chosen as a rebroadcast node, will stay long enough in an inter-vehicle transmission path. Moreover, to reduce the number of rebroadcast nodes, we define a donut-like selection area to choose relay nodes in order to reduce the route hop count and network traffic. Simulation results show that in large speed range scenarios, the proposed RR-VMS increases (reduces) 8.3% (16%) and 8.3% (15%) of the delivery ratio (number of broken links) compared to AODV and PAODV, respectively. In addition, RR-VMS also reduces 30% and 13% routing overhead compared to AODV and PAODV respectively. The proposed method is simple and feasible to other ad hoc routing protocols as well that involve broadcast.
A Road-based QoS-aware Multipath Routing for Urban Vehicular Ad Hoc Networks
(2012)
Hsieh, Yi-Ling
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Wang, Kuochen
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資訊工程學系
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Department of Computer Science
Stable and efficient routing plays a key role for the success of VANETs. Road-based routing has been shown well-suited for urban VANETs, and multipath routing provides alternative routes once the current route fails. However, existing multipath routing protocols are node-based, which are not suitable for urban VANETs. In this paper, we propose a road-based QoS-aware multipath routing protocol for urban VANETs (RMRV). The proposed RMRV can find multiple paths and intelligently utilize them. We also propose a space-time planar graph approach to predict the connectivity of each road section (RS) in a path, and then derive the path's future lifetime and life periods. In this way, the source node may dynamically switch to use a path with the longest lifetime. The life periods of a path can further be utilized to estimate the packet delay for QoS routing. Simulation results show that comparing to RBVT-R, which is a single-path road-based routing protocol, the packet delivery ratio of the proposed RMRV (only one path used at a time) is 12.2% higher than that of RBVT-R, and the average end-to-end delay of RMRV is 11.5% lower than that of RBVT-R, on average. To the best of our knowledge, there is no existing road-based multipath routing protocol for VANETs.
Dynamic overlay multicast for live multimedia streaming in urban VANETs
(2012-11-14)
Hsieh, Yi-Ling
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Wang, Kuochen
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應用化學系
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資訊工程學系
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Department of Applied Chemistry
Infotainment service has been a foreseeing trend in VANETs (Vehicular Ad Hoc Networks), and multimedia streaming has a high potential in VANET infotainment service. This paper considers the scenario of live multimedia streaming multicast to vehicles of the same group using a dynamic application layer overlay. Due to the willingness for cooperation of non-group nodes, application layer overlay multicast is more feasible than other kinds of multicast such as network-coding-based multicast and network-layer multicast. To adapt to high mobility and full of obstacles in urban VANETs, we propose an effective dynamic overlay multicast scheme for multimedia streaming, called OMV (Overlay Multicast in VANETs). The proposed OMV enhances an overlay's stability with two strategies: (1) QoS-satisfied dynamic overlay and (2) mesh-structure overlay. The QoS-satisfied strategy to adjust the overlay selects potential new parents based on their streams' packet loss rates and end-to-end delays. The mesh-structure strategy allow; a child to have multiple parents. We evaluate the proposed OMV in urban VANETs with obstacles using two real video clips to demonstrate the feasibility of the OMV for real videos. Evaluation results show that comparing the proposed OMV to Qadri et al.'s work, which is a static mesh overlay and is the best method available in VANETs, the packet loss rate is reduced by 27.1% and the end-to-end delay is decreased by 11.7%, with a small control overhead of 2.1%, on average. Comparing the proposed OMV for tree overlays to ALMA, which is for dynamic tree multicast overlays and is also the best method available in MANETs, the packet loss rate is reduced by 7.1% and the end-to-end delay is decreased by 13.1%. In addition, to address the problem of obstacle-prone urban VANETs, we also derive feasible stream rates and overlay sizes for city maps with different road section sizes. To the best of our knowledge, how to organize and dynamically adjust an application layer multicast overlay for live multimedia streaming have not been studied in existing VANET literatures. In summary, to deal with highly dynamic topologies in urban VANETs. we propose a QoS-satisfied strategy for group nodes to switch to new parents that can offer better QoS. The proposed OMV is feasible for live multimedia streaming applications, such as emergency live video transmission and live video tour guides for passengers in different vehicles that belong to the same multicast group. (c) 2012 Elsevier B.V. All rights reserved.
Efficient Color-theory-based Dynamic Localization for Mobile Wireless Sensor Networks
(2011-07-01)
Shee, Shen-Hai
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Chang, Tzu-Chien
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Wang, Kuochen
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Hsieh, Yi-Ling
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資訊工程學系
Location information is critical to mobile wireless sensor networks (WSN) applications. With the help of location information, for example, routing can be performed more efficiently. In this paper, we propose a novel localization approach, Color-theory based Dynamic Localization (CDL), which is based on color theory to exploit localization in mobile WSNs. CDL makes use of the broadcast information, such as locations and RGB values, from all anchors (a small portion of nodes with GPS receivers attached), to help the server to create a location database and assist each sensor node to compute its RGB value. Then, the RGB values of all sensor nodes are sent to the server for localization of the sensor nodes. A unique feature of our color-theory based mechanism is that it can use one color to represent the distances of a sensor node to all anchors. Since CDL is easy to implement and is a centralized approach, it is very suitable for applications that need a centralized server to collect user (sensor) data and monitor user activities, such as community health-care systems and hospital monitoring systems. Evaluation results have shown that for mobile WSNs, the location accuracy of CDL (E-CDL, an enhanced version of CDL) is 40-50% (75-80%) better than that of MCL (Hu, L., & Evans, D. (2004). Localization for mobile sensor networks. In Proceedings of the 10th annual international conference on mobile computing and networking, pp. 45-57). In addition, we have implemented and validated our E-CDL algorithm on the MICAz Mote Developer's Kit.
Efficient localization in mobile wireless sensor networks
(2006)
Hsieh, Yi-Ling
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Wang, Kuochen
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資訊工程學系
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Department of Computer Science
The proposed DRL is a distributed range-free localization approach. In order to save communication cost in localization, DRL reduces information flooding among nodes by dynamically changing each seed's flooding-hop to limit seed flooding in a local area; however, it still maintains the whole coverage. In addition, DRL allows all the nodes mobile and moving freely, while there is only a limited fraction of nodes having self-positioning capability (called seeds). Moreover, DRL can adapt to low or high node density, because of its dynamic seed flooding and robust triangulation. Dynamic seed flooding is to change flooding coverage according to each seed's surrounding node density. Robust triangulation allows the cases of insufficiency of reference nodes. We have evaluated DRL and MCL [4]. Simulation results have shown that the location accuracy of DRL is 26% higher than that of MCL. With mobile positioning, DRL is suitable for applications, such as navigation systems using e-map and community health-care systems, in outdoor environments.
Efficient Push-Pull Based P2P Multi-streaming Using Application Level Multicast
(2010)
Liu, Chia-Yi
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Wang, Kuochen
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Hsieh, Yi-Ling
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資訊工程學系
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Department of Computer Science
P2P (peer-to-peer) streaming systems are getting more and more popular in recent years. P2P streaming architectures can be classified into tree-based and mesh-based. The tree-based architecture has low start-up delay, but is less resilient to node failures compared to the mesh-based architecture, and it would result in a low delivery ratio and unstable quality of received multimedia. In this paper, we propose an efficient P2P multi-streaming scheme called HyStream based on application level multicast to resolve these problems. First, we split video streaming data and build multiple trees to transfer streaming data. Second, we incorporate a forward error correction (FEC) algorithm to recover lost data. Finally, we integrate a pull-based method with the tree-based architecture, which is a push-based method. When encountering data loss, we use a pull-based data retransmission method to retrieve lost data. Simulation results show that the proposed HyStream has 11.7% improvement in delivery ratio against SplitStream under various node failure rates. The delivery ratio of HyStream is 2.2% higher than that of CoolStreaming in a peer churn environment. The start-up delay of 90th percentile nodes of HyStream is 35 seconds shorter than that of CoolStreaming. Note that our approach has small overhead of 6% redundant packets due to FEC, compared to SplitStream and CoolStreaming. In addition, HyStream has no more than 0.5% extra control overhead compared to SplitStream and CoolStreaming, even in a high peer churn environment.
Enhanced color-theory-based dynamic localization in mobile wireless sensor networks
(2007)
Chang, Tzu-Chien
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Wang, Kuochen
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Hsieh, Yi-Ling
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資訊工程學系
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Department of Computer Science
There are few localization schemes targeted at mobile wireless sensor networks. In this paper, we propose an Enhanced Color-theory-based Dynamic Localization (E-CDL) which is based on the CDL algorithm [1]. However, the location accuracy of this algorithm depends on the accuracy of the average hop distance derivation. Therefore, we present two novel schemes to estimate the average hop distance. We analyzed the behavior of sensor nodes communication, and computed the expected value of the average hop distance, which is 7r/9, where r is the radio range. In addition, since CDL is based on the DV-hop scheme, the derived shortest path length is usually larger than the corresponding Euclidean distance. With this observation, the derived shortest path length can be adjusted by the ratio of the Euclidean distance and the shortest path distance to further enhance the location accuracy. Finally, in mobile wireless sensor networks, sensor nodes may become isolated. By employing mobile anchor nodes, the isolation problem can be relieved and hence the location accuracy can be improved. Simulation results have shown that the location accuracy of E-CDL is 50% - 55% better than that of CDL, and 75% - 80% better than that of MCL (Monte Carlo Localization) [2]. In addition, we have implemented and verified our algorithm on the MICAz Mote Developer's Kit [3].