Browsing by Author "Wang, Jui-Tang"

Now showing 1 - 13 of 13

A Backbone-Aware Topology Formation (BATF) Scheme for ZigBee Wireless Sensor Networks
(2013-01-01)
Huang, Kuei-Li
;
Yen, Li-Hsing
;
Wang, Jui-Tang
;
Wu, Chao-Nan
;
Tseng, Chien-Chao
In a tree-structured ZigBee wireless sensor network, nodes close to the root of the tree (i.e., hot-spot nodes) may exhaust their power earlier than those distant from the root due to heavy loads on packet forwarding. This hot-spot problem is inherent in tree-structured networks and may demand extra energy to recover from failures of hot-spot nodes. In this paper, the backbone-aware topology formation (BATF) scheme is proposed to alleviate the hot-spot problem. BATF utilizes power-rich nodes to form a backbone tree that does not suffer from the hot-spot problem. Each power-rich node independently initiates a ZigBee tree network that attracts associations from ZigBee-compliant devices in order to distribute packet-forwarding loads over a larger set of nodes. Issues of BATF such as the partition of address space and ZigBee-compliant routing are discussed in detail. Simulation results confirm that BATF does alleviate the hot-spot problem as it improves network lifetime as well as data collection capability. Comparisons with native ZigBee protocols show that the improvement comes from our protocol design rather than simply introducing power-rich nodes.
A Bandwidth-sharing Reservation Scheme to Support QoS for Network Mobility
(2006-01-01)
Wang, Jui-Tang
;
Hsu, Yuan-Ying
;
Tseng, Chien-Chao
;
資訊工程學系
;
Department of Computer Science
A NEtwork that is MObile (NEMO) usually consists of at least one Mobile Router (MR) attached to the infrastructure to manage all external communication for this moving network. Users inside a NEMO might also require quality of services (QoS) guarantee while accessing the Internet via a mobile device. In this paper, we propose a Bandwidth-sharing Reservation (BSR) scheme so that a NEMO can support QoS services. The proposed BSR scheme establishes a bandwidth sharing reservation tunnel for all NEMO nodes to efficiently utilize external bandwidth of MR, and it makes advance reservations at neighboring networks to solve the mobility problem. Three reservation adjustment policies are designed to further improve bandwidth utilization. Both mathematical analysis and simulation results show that the proposed BSR scheme can significantly increase bandwidth utilization and decrease handoff blocking rate while providing QoS services to NEMO nodes in movement.
A Bandwidth-sharing Reservation Scheme to Support QoS for Network Mobility
(2006-01-01)
Wang, Jui-Tang
;
Hsu, Yuan-Ying
;
Tseng, Chien-Chao
;
資訊工程學系
;
Department of Computer Science
A NEtwork that is MObile (NEMO) usually consists of at least one Mobile Router (MR) attached to the infrastructure to manage all external communication for this moving network. Users inside a NEMO might also require quality of services (QoS) guarantee while accessing the Internet via a mobile device. In this paper, we propose a Bandwidth-sharing Reservation (BSR) scheme so that a NEMO can support QoS services. The proposed BSR scheme establishes a bandwidth sharing reservation tunnel for all NEMO nodes to efficiently utilize external bandwidth of MR, and it makes advance reservations at neighboring networks to solve the mobility problem. Three reservation adjustment policies are designed to further improve bandwidth utilization. Both mathematical analysis and simulation results show that the proposed BSR scheme can significantly increase bandwidth utilization and decrease handoff blocking rate while providing QoS services to NEMO nodes in movement.
A Fast Authentication Scheme for WiMAX-WLAN Vertical Handover
(2013-07-01)
Huang, Kuei-Li
;
Chi, Kuang-Hui
;
Wang, Jui-Tang
;
Tseng, Chien-Chao
;
資訊工程學系
In view that authentication has made a significant determinant in handover delay, this paper presents a fast authentication mechanism for mobile stations roaming within a WiMAX-WLAN interconnected environment. Incorporating a key reuse design that prevents repeated transactions at a remote server, our mechanism distributes security contexts ahead of handover to a local trusted key holder which manages several sites. A target site, upon receiving a mobile station, retrieves the contexts locally for authentication purpose and thus completes handover efficiently. While employing a target prediction algorithm as an option, our mechanism distributes the contexts to target candidates as dictated, which further improves handover performance if target prediction hits and maintains its advantage even in a miss. In addition, the handover optimization design specified in WiMAX is extended to support WiFi-to-WiMAX handovers. We reason that the proposed mechanism does not compromise the system in any sense as well. Analytical and simulation results show that, despite key pre-distribution misses, our mechanism leads to marked improvement over counterpart schemes in terms of handover delay and packet loss, meeting delay-sensitive application requirements.
A mobile bandwidth-aggregation reservation scheme for NEMOs
(2008-03-01)
Wang, Jui-Tang
;
Hsu, Yuan-Ying
;
Tseng, Chien-Chao
;
資訊工程學系
;
Department of Computer Science
A NEtwork that is MObile (NEMO) usually consists of at least one Mobile Router (MR) attached to the infrastructure to manage all external communication for of all nodes inside a NEMO. Because a NEMO moves as a whole, previous mobile ReSource reserVation Protocols have two problems in supporting quality of services (QoS) for NEMOs; that is, mobility unawareness and excessive signal overhead. In this paper, we first address these two problems and then propose a Mobile Bandwidth-Aggregation (MBA) reservation scheme to support QoS guaranteed services for NEMOs. In order to resolve these two problems, MBA makes an MR the proxy of all nodes insides a NEMO and has the MR aggregates and reserve the bandwidth required for all node inside a NEMO. Mathematical analysis and simulation results show that the proposed MBA scheme can significantly reduce the signal overhead for reservation maintenance. Furthermore we also present three hypothetic policies of tunnel reservations for NEMOs, and conduct simulation to evaluate these policies in terms of blocking probabilities and bandwidth utilizations.
Fast Handoff in Secure IEEE 802.11s Mesh Networks
(2011-01-01)
Chi, Kuang-Hui
;
Shih, Yung-Chien
;
Liu, Ho-Han
;
Wang, Jui-Tang
;
Tsao, Shiao-Li (Charles)
While mesh networking is gaining momentum with widespread application, we are concerned with fast handoff in a secure mesh environment. To this end, this paper presents a means in the context of IEEE 802.11s of letting a mesh portal act as an IEEE 802.1X authenticator to reduce costly IEEE 802.1X authentication processes during handoff. Our approach is developed for alignment with IEEE 802.11s and 802.11i, keeping protocols at the station side operable with no changes. As another strength, our design applies to generic multihop wireless networks. Both analytical and simulation modeling are conducted to evaluate our scheme as well. Performance results show that our approach reduces handoff delay by up to 268% or achieves comparable performance resulting from the counterpart IEEE 802.11i scheme with high likelihood of 70%-85% successful preauthentication. Moreover, our performance analysis suggests an optimal number of access points managed by one mesh portal in a network. Qualitative and quantitative discussions indicate that our approach is applicable in pragmatic settings.
GROUP AUTHENTICATION METHOD
(2009-02-26)
Chen, Yu-Wen
;
Wang, Jui-Tang
;
Tseng, Chien-Chao
A group authentication method adaptable to a communication system is disclosed. The communication system includes a user group, a serving network, and a home network. The user group includes at least one mobile station. The home network pre-distributes a group authentication key to itself and all the mobile stations in the same user group and generates a mobile station authentication key for each mobile station. The home network generates a group list for recording related information of the user group. The home network has a database for recording the group list. The serving network has a database for recording the group list and a group authentication data received from the home network. The group authentication method includes following steps. The serving network performs an identification action to a mobile station. The communication system performs a full authentication action or a local authentication action according to the result of the identification action.
Group-Based Authentication and Key Agreement
(2012-02-01)
Chen, Yu-Wen
;
Wang, Jui-Tang
;
Chi, Kuang-Hui
;
Tseng, Chien-Chao
;
資訊工程學系
This paper presents an authentication and key agreement protocol to streamline communication activities for a group of mobile stations (MSs) roaming from the same home network (HN) to a serving network (SN). In such a roaming scenario, conventional schemes require the SN to interact with the HN for authenticating respective MSs, at the cost of repeated message exchanges and communication delay. Instead, in our design, when the first MS of a group visits, the SN performs full authentication with the concerned HN and thereby obtains authentication information for the MS and other members. Thus when any other MS of the same group visits, the SN can authenticate locally without subsequent involvement of the HN, so as to simplify protocol operations. We will show that our scheme does not trade performance for security and robustness to the extent that security requirements are unduly weakened. Both qualitative and quantitative discussions indicate that our proposed scheme lends itself to pragmatic settings.
Hybrid address configuration for tree-based wireless sensor networks
(2008-06-01)
Wong, Yung-Chang
;
Wang, Jui-Tang
;
Chang, Nai-Hsin
;
Liu, Ho-Han
;
Tseng, Chien-Chao
This letter proposes a new scheme to alleviate the issue on address acquisition failure in wireless sensor networks (WSNs). The basic idea is to use a hierarchical address structure to make the proposed scheme less susceptible to physical distribution of WSN devices. Simulation results show that the new scheme significantly reduces the failure probability.
Performance Improvement of Delay-Based TCPs in Asymmetric Networks
(2011-03-01)
Ho, Cheng-Yuan
;
Ho, Cheng-Yun
;
Wang, Jui-Tang
;
資訊工程學系
;
Department of Computer Science
Delay-based TCPs detect network congestion in the early stage and successfully prevent periodic packet loss that usually occurs in loss-based TCPs. It has been demonstrated that delay-based algorithms outperform loss-based schemes in many aspects. However, a delay-based TCP may not prevent unnecessary throughput degradation in asymmetric networks and when the congestion occurs in the backward path over symmetric links. In this letter, we modify the mechanism of measuring RTT value for delay-based TCPs without clock synchronization. Based on the simulation results, we show the effectiveness and utilities.
POWER-EFFICIENT BACKBONE-ORIENTED WIRELESS SENSOR NETWORK, METHOD FOR CONSTRUCTING THE SAME AND METHOD FOR REPAIRING THE SAME
(2011-03-03)
Huang, Kuei-Li
;
Wu, Chao-Nan
;
Wang, Jui-Tang
;
Tseng, Chien-Chao
The present invention discloses a power-efficient backbone-oriented wireless sensor network, a method for constructing the same and a method for repairing the same, wherein energy-rich nodes are used to form backbones linking to a server, and wherein regular nodes having limited energy storage link to the backbones. When one energy-rich node malfunctions, the energy-rich node, which is posterior to the malfunctioning energy-rich node, searches for and links to a linkable neighboring energy-rich node on the backbone. If there is none linkable neighboring energy-rich node, the regular nodes are used to form a temporary tunnel until the malfunctioning energy-rich node has been repaired. The present invention can relieve the influence of hot spots, increase the robustness of the wireless sensor network, and prolong the service life of the wireless sensor network.
ROUTING METHOD AND ROUTING PATH RECOVERY MECHANISM IN WIRELESS SENSOR NETWORK ENVIRONMENT
(2010-10-14)
LAI, Jun-Yu
;
Huang, Kuei-Li
;
Wang, Jui-Tang
;
Tseng, Chien-Chao
;
Wu, Chao-Nan
The present invention discloses an asymmetric routing method and routing path recovery mechanism. The wireless sensor network environment includes at least a management unit, at least a gateway, and mobile nodes. When joining, each mobile node obtains an unique ID code and, additionally, a depth as the gradient to the management unit. Accordingly, a mobile node sends an uplink packet via a nearby node with lower depth to the management unit; while the management unit transmits a downlink packet to a mobile node by utilizing the source route method. When the parent node of a mobile node is damaged or moves to another position or said mobile node with its sub-tree descendants changes their position together, the uplink routing path is recovered via selecting a nearby node of the sub-tree as relay node and the downlink routing path is recovered via sending a control message to the management unit.
To Call or To Be Called Behind NATs is Sensitive in Solving the Direct Connection Problem
(2011-01-01)
Ho, Cheng-Yuan
;
Tseng, Chien-Chao
;
Wang, Fu-Yu
;
Wang, Jui-Tang
;
Lin, Ying-Dar
In this article, we first depict the call-role sensitivity problem in Network Address Translation (NAT) traversal, and then propose an approach to resolving the problem. The problem is whether a direct connection can be found between two peers across NATs mainly depends on the NAT type at the caller's side. We propose the extra-candidate connectivity check where both peers initiate a direct connectivity check to eliminate the effect of the call role. We have implemented the extra-candidate connectivity check and conducted experiments with 18 different NATs. Experimental results show that our approach can indeed resolve the call-role sensitivity problem, and maximize the direct connectivity rate (DCR) which is improved by 18.71% from the original scheme.