Hwa-Chun Lin

National Tsing Hua University, Hsin-chu-hsien, Taiwan, Taiwan

Are you Hwa-Chun Lin?

Claim your profile

Publications (43)27.79 Total impact

  • Hwa-Chun Lin, Tsung-Ming Lin, Cheng-Feng Wu
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper considers the problem of disseminating messages from a source to multiple destinations in an overlay network in which nodal delays for processing messages are taken into account in addition to communication delays. The objective is to find a multicast tree to deliver a message from a source to multiple destinations in the minimum delay time. This problem is referred to as the minimum-delay multicast problem with nodal processing delays. This paper develops several heuristic algorithms that are based on the principle of iteratively selecting one of the destination nodes not yet on the current multicast tree and attaching the selected node to it until all destination nodes are on the multicast tree. A new delay measure called reception-and-processing delay is introduced in this paper as one of the delay measures used in selecting one of the destination nodes for attaching to the current multicast tree. This paper finds that the least-delay path from the current multicast tree to a destination node not yet on the tree may intersect or overlap with the current multicast tree if a commonly used method is employed to find the least-delay path. An efficient method is devised to avoid this undesirable phenomenon. The performances of the four heuristic algorithms and the effects of various characteristics of the overlay networks on the performances of the heuristic algorithms are studies via simulations.
    Information Sciences 09/2014; 279:433–445. · 3.89 Impact Factor
  • Hwa-Chun Lin, Hsiu-Ming Yang
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper studies the problem of constructing application-layer multicast trees for end-system based voice conferences in which voice mixing and replication are performed at end systems. This problem is formulated as a degree-constrained node-weighted Steiner tree problem with a degree-dependent cost associated with each node, which is a generalization of the degree-constrained node-weighted Steiner tree problem with a fixed cost associated with each node. This paper devises a novel technique to deal with degree-dependent nodal costs and develops a bicriteria approximation algorithm, with the degree of each node and the cost of the tree as two objectives, for this more general Steiner tree problem. The bound on the degree of each node and the bound on the cost of the tree constructed by the bicriteria approximation algorithm are derived. Two heuristic algorithms which construct multicast trees that obey the degree constraint on each node are obtained by modifying the bicriteria approximation algorithm. The performances of the two heuristic algorithms are studied via simulations.
    25th IEEE International Conference on Advanced Information Networking and Applications, AINA 2011, Biopolis, Singapore, March 22-25, 2011; 01/2011
  • [Show abstract] [Hide abstract]
    ABSTRACT: This paper considers the problem of constructing minimum-delay multicast trees for message dissemination in overlay networks in which nodal delays for processing messages are taken into account in addition to communication delays. The objective is to find a multicast tree to deliver a message from a source to multiple destinations in minimum delay time. This paper introduces a new delay measure called reception-and-processing delay that takes nodal processing delays into account for constructing multicast trees. In the process of constructing a multicast tree, the branches of the multicast tree may intersect or overlap with each other. An efficient method is devised to avoid this undesirable phenomenon. Several heuristic algorithms are developed for constructing multicast trees. The performances of the heuristic algorithms are studied via simulation. Our simulation results show that constructing the multicast tree by iteratively attaching the destination node with the smallest reception-and-processing delay to the current multicast tree yields the lowest average multicast delay among the heuristic algorithms studied in this paper.
    Parallel and Distributed Processing with Applications (ISPA), 2010 International Symposium on; 10/2010
  • Hwa-Chun Lin, Feng-Ju Li, Kai-Yang Wang
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper studies the problem of constructing maximum-lifetime data gathering trees in sensor networks in which the power levels of sensors are heterogeneous and adjustable. In-network data aggregation is also employed to aggregate sensor data while they are being forwarded toward the base station. For sensor networks in which sensors have fixed and the same transmission power level, Wu et al. has derived an upper bound on the lifetime of the optimal data gathering tree and developed an approximation algorithm for constructing data gathering trees. The model considered in this paper is more general than that considered by Wu et al. in that the transmission power levels of sensors are heterogeneous and adjustable. For this more general model, this paper derives an upper bound on the lifetime of the optimal data gathering tree. Given an initial tree, an algorithm is developed to construct a data gathering tree by iteratively rearranging the current tree and improving the lifetime of the current tree. The worst-case computational complexity of the algorithm is shown to be polynomial.
    Communications (ICC), 2010 IEEE International Conference on; 06/2010
  • Hwa-Chun Lin, Hsiu-Ming Yang
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper studies the problem of constructing a minimum-cost multicast tree (or Seiner tree) in which each node is associated with a cost that is dependent on the degree of the node on the multicast tree. The cost of a node may depend on its degree on the multicast tree due to a number of reasons. For example, a node may need to perform various processing for sending messages to each of its neighbors on the multicast tree. Thus, the overhead for processing the messages increases as the number of neighbors increases. This paper devises a novel technique to deal with the degree-dependent node costs and applies the technique to develop an approximation algorithm for the problem. The bound on the cost of the multicast tree constructed by the proposed approximation algorithm is derived.
    Proceedings of the Global Communications Conference, 2010. GLOBECOM 2010, 6-10 December 2010, Miami, Florida, USA; 01/2010
  • Hwa-Chun Lin, Chien-Yi Ho
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper proposes a distributed location management strategy called weighted sliding-frame strategy for wireless mobile networks in which the processing speeds of the location information databases (LIDs) are heterogeneous. In the proposed strategy, a number of consecutively numbered location information databases are arranged into a frame. A frame of location information databases overlaps with the next frame except one database. Each frame is assigned a weight which is used to distribute the location information of the mobile hosts among the frames. The number of mobile hosts whose location information are stored in a frame is proportional to the weight assigned the frame. A nonlinear convex programming problem is formulated and solved numerically in order to find the set of weights that minimize the average database response time. Our numerical results show that the proposed weighted sliding-frame strategy is able to properly distribute the location information of the mobile hosts among the frames such that the average database response time is significantly lower than that of the sliding-frame strategy proposed in our previous work.
    Proceedings of IEEE International Conference on Communications, ICC 2010, Cape Town, South Africa, 23-27 May 2010; 01/2010
  • [Show abstract] [Hide abstract]
    ABSTRACT: This paper proposes a new approach to designing alternate routing algorithms for all-optical wavelength-division multiplexing networks in order to reduce the connection blocking probability. The key idea is to try to route traffic in approximately the optimal way of splitting the traffic among the multiple routing paths between each source-destination pair. The optimal way of splitting the traffic among the multiple routing paths between each source–destination pair is obtained by solving a nonlinear multicommodity flow optimization problem. Two alternate routing algorithms, namely, traffic intensity based fixed-alternate routing algorithm and traffic intensity based dynamic-alternate routing algorithm, are proposed based on this approach. Simulations are performed to study the performances of the proposed alternate routing algorithms. Our simulation results show that the alternate routing algorithms designed according to the optimal way of splitting the traffic can effectively reduce the connection blocking probability.
    Journal of Lightwave Technology 11/2008; 22(26):3604-3616. · 2.86 Impact Factor
  • Hwa-Chun Lin, Chien-Yi Ho
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper proposes a distributed location management strategy for wireless mobile networks. In the proposed strategy, a number of consecutively numbered location information databases (LIDs) are arranged into a frame. A frame of LIDs overlaps with the next frame except one database. The location information of a mobile host is replicated and stored in the databases in the same frame. When the location area of a mobile host changes, the new location information is stored in the next frame of databases. Thus, the proposed strategy is referred to as the sliding-frame strategy. The average communication cost and average database response time of the proposed sliding-frame strategy are analyzed and shown to be always lower than or equal to those of the strategy proposed by Krishnamurthi et al.
    IEEE Transactions on Vehicular Technology 10/2008; · 2.64 Impact Factor
  • Hwa-Chun Lin, Sheng-Wei Wang, Meng-Lin Hung
    [Show abstract] [Hide abstract]
    ABSTRACT: An alternate routing algorithm requires a set of predetermined routing paths between each source-destination pair. To reduce the connection blocking probability, it is desirable that the predetermined routing paths between each source-destination pair be link-disjoint. The predetermined routing paths used in previous works on alternate routing are the -shortest link-disjoint paths in terms of hop count. The shared links among the -shortest link-disjoint paths between different source-destination pairs may cause high connection blocking probability. Thus, depending on the traffic requirements of all source-destination pairs, hop-count based -shortest link-disjoint paths may not be the best choice for the predetermined routing paths. This paper proposes a method to find a set of link-disjoint routing paths between each source-destination pair to be used by an alternate routing algorithm in order to reduce the connection blocking probability. The key idea is to find a set of link-disjoint routing paths based on the routing paths that are utilized by the optimal traffic pattern in the network. Then, for each source-destination pair, we select a set of link-disjoint routing paths from the routing paths that are utilized by the optimal traffic pattern such that the selected set of link-disjoint routing paths carries the most of the traffic between the source-destination pair. Simulations are performed to compare the performance of using the link-disjoint routing paths found by the proposed method as the predetermined routing paths and those of using the hop-count based -shortest link-disjoint paths and employing the routing paths found by the capacity-balanced alternate routing method proposed method by Ho and Mouftah (in 2002) as the predetermined routing paths. Our simulation results show that using the link-disjoint routing paths found by the proposed method yields significantly lower connection blocking probability than employing the hop-count based -shortest link-dis- joint paths and using the routing paths found by the capacity-balanced alternate routing method (Ho and Mouftah, 2002).
    Journal of Lightwave Technology 07/2008; 26(11):1432-1444. · 2.86 Impact Factor
  • Hwa-Chun Lin, Pei-Shin Liu
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper considers transceiver array-based single-hop wavelength division multiplexing (WDM) networks with reservation-based packet scheduling algorithms. In reservation-based packet scheduling algorithms for single-hop WDM networks, one or more of the wavelengths are used as control channels for transmitting reservation information. Time on a control channel is divided into control frames and each control frame is further divided into control slots. Each node is usually assigned a dedicated control slot in each control frame. Before transmitting a data packet, a node sends a control packet in a control slot to all other nodes to reserve a data slot. This paper proposes to adjust the lengths of the control frames dynamically according to the loads of the nodes by removing unused control slots. A dynamic control frame structure with variable number of control slots is proposed. A method is devised to enable the nodes in the network to dynamically acquire and release control slots depending on their loads such that the control frames include only necessary control slots for those nodes that have or potentially have data packets to send. Therefore, the delays for transmitting control packets and data packets can be reduced. Dynamically adjusting the lengths of the control frames is able to reduce the delays for transmitting control packets and data packets when the network load is light to medium or the traffic pattern is moderately or highly nonuniform; however, it introduces extra overhead in each control frame such that the length of the control frame may become larger than the size of the control frame in the fixed control frame structure resulting in higher mean packet delay when the load of the network is heavy and the traffic pattern is uniform or nearly uniform. Therefore, this paper further proposes a hybrid fixed and dynamic scheme that dynamically employs the fixed control frame scheme or the dynamic control frame scheme depending on the loads of the nodes- . The performance of the proposed hybrid scheme is studied via simulations. Our simulation results show that the hybrid scheme is able to dynamically choose the better of the fixed and dynamic control frame schemes such that it yields the lowest mean packet delay for the entire range of network loads and traffic patterns.
    Journal of Lightwave Technology 05/2008; 26(7):742-755. · 2.86 Impact Factor
  • Source
    Hwa-chun Lin, show-shiow Tzeng
    [Show abstract] [Hide abstract]
    ABSTRACT: In this paper, we consider cluster-based micro/picocellular networks with overlapped cell-clusters. Channel assignment and hand-off policies are essential and important policies in cellular wireless networks. The issue of how different channel assignment and hand-off policies in the overlapped areas affect the overall system performance has not yet been studied in the literature. This paper provides a thorough study and understanding of this issue. We propose two cluster channel assignment policies, namely, partitioned and shared cluster channel assignment policies, and two hand-off policies, namely, boundary and early hand-off policies. The proposed cluster channel assignment policies and hand-off policies are combined to obtain three different strategies, namely, partitioned-boundary, partitioned-early, and shared-boundary strategies. Extensive simulations are used to study the performance of the strategies. Our results show that the partitioned-early and shared-boundary strategies produce significantly lower hand-off dropping and forced termination probabilities than the partitioned-boundary strategy. The partitioned-early and shared-boundary strategies yield similar performance.
    Wireless Personal Communications 09/2007; 43(2):449-465. · 0.98 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper proposes a new fixed-alternate routing algorithm for all-optical WDM networks without wavelength conversion in order to reduce the connection blocking probability. The key idea in the proposed fixed-alternate routing algorithm is to try to route the traffics in approximately the optimal way. The multiple routing paths between each source-destination pair are arranged and used in descending order according to the traffic intensities obtained by solving a nonlinear multicommodity flow optimization problem. It is well known that finding the connection blocking probability is a very difficult task. Therefore, an objective function closely related to the connection probability is devised and used to formulate a nonlinear multicommodity flow optimization problem. Simulations are performed to study the performance of the proposed fixed-alternate routing algorithm. Our simulation results show that sorting the routing paths according to the optimally assigned traffic intensities in the proposed fixed-alternate routing algorithm can effectively reduce the connection blocking probability compared with sorting the routing paths according to hop counts in a typical fixed-alternate routing algorithm. In general, in all-optical WDM networks, a connection request that goes through a longer path experiences higher connection blocking probability than a connection request that goes through a shorter path. This is known as the fairness problem. Our simulation results show that the proposed algorithm yields better fairness than a typical fixed-alternate routing algorithm.
    Communications, 2006. ICC '06. IEEE International Conference on; 07/2006
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Link failure is one of the most critical network fault conditions. Relying solely on SNMP traps to detect and identify link failures is not a complete solution. To supplement the SNMP-trap mechanism, one or more detectors can be placed in the network to periodically poll the devices using the ping or traceroute utilities such that all links are under the surveillance of the detectors. The goal is to place the smallest number of detectors to have all of the links under surveillance such that the cost of placing detectors in the network is reduced. In this paper, this problem is formulated as a minimum set covering problem. A new heuristic algorithm is proposed for this problem. Simulations are performed to study the performance of the proposed heuristic algorithm.
    Communications, 2005. ICC 2005. 2005 IEEE International Conference on; 06/2005
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Efficient utilization of radio resource is one of the most important issues in wireless systems. In existing TDD based PRMA protocol and its variations, a mobile terminal is assigned on one of the frequency carriers after completing a registration procedure. Since mobile terminals enter and leave the system in an unpredictable fashion, some of the frequency carriers may become heavily loaded while other frequency carriers are underutilized. The frequency carriers can be utilized more efficiently by allowing the mobile terminals to switch among the frequency carriers. To enable the mobile terminals to switch among the frequency carriers efficiently, this paper proposes to arrange the frame boundaries on the frequency carriers in a slanted fashion. A scheme is proposed to enable a mobile terminal to switch among different frequency carriers such that shorter time is required to obtain a slot at the beginning of a talk spurt or a burst of data. Simulations are performed to compare the performance of the proposed scheme with a scheme that does not allow mobile terminals to switch among frequency carriers. Our simulation results show that the proposed slanted frame arrangement scheme yields significantly lower mean request waiting time and packet dropping ratio.
    International Journal of Wireless Information Networks 06/2005; 12(2):101-108.
  • Source
    Hwa-Chun Lin, Pei-Shin Liu
    [Show abstract] [Hide abstract]
    ABSTRACT: In reservation-based packet scheduling algorithms for single-hop WDM networks, one of the wavelengths is used as a control channel which is shared by all of the nodes for transmitting reservation information. Time on the control channel is divided into control frames of fixed length. Each of the control frames is further divided into a number of control slots. Before transmitting a data packet, a node sends a control packet in a control slot to inform all other nodes of its intention to send a data packet. The data packet can then be scheduled for transmission. Each of the nodes in the system is assigned a dedicated control slot. Free control slots in the control frames cannot be used by other nodes. The control packets generated by those nodes that have more data packets to send must be transmitted in the next or later control frames although there are a number of free control slots. The result of delaying the transmissions of control packets is increased packet delays. This effect has significant impact on packet delays under nonuniform traffics. To increase the utilization of the control slots and reduce the packet delays, we propose to adjust the lengths of the control frames dynamically according to the traffic patterns of the nodes. We propose a dynamic control frame structure with variable number of control slots. A scheme is devised to enable the nodes in the network to dynamically acquire and release control slots depending on their loads. Thus, the control frames will include only necessary control slots for those nodes that have or potentially have data packets to send. Therefore, the control slots on the control channel can be used efficiently and the packet delays can be reduced. Simulations are performed to study the performance of the proposed dynamic control frame structure. Our simulation results show that dynamically adjusting the lengths of the control frames can effectively increase the utilization of the control slots and reduce the mean packet - delay under nonuniform traffic compared with using fixed-length control frames
    Parallel Processing, 2003. Proceedings. 2003 International Conference on; 11/2003
  • Hwa-Chun Lin, Yung-Hua Chu
    Proceedings of the International Conference on Wireless Networks, ICWN '03, June 23 - 26, 2003, Las Vegas, Nevada, USA; 01/2003
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper studies the different arrangements of frames in the time division duplexing (TDD)-based packet reservation multiple access (PRMA) protocol on multiple frequency carriers. Two frame arrangements, namely, aligned and slanted arrangement, are investigated. In the aligned arrangement, frame boundaries are aligned on all frequency carriers, in the slanted arrangement, the frame boundaries are shifted by one slot from one frequency carrier to the next. With slanted frame arrangement, a scheme is proposed to enable a mobile terminal to switch among different frequency carriers such that shorter time is required to obtain a slot at the beginning of a talk spurt. Extensive simulations are performed to compare the performance of the two arrangements of frames. Simulation results show that the slanted frame arrangement yields significantly lower mean request waiting time and packet dropping ratio than the aligned frame arrangement.
    Telecommunications, 2003. ICT 2003. 10th International Conference on; 01/2003
  • Source
    Hwa-Chun Lin, Zhe-Hong Lin
    [Show abstract] [Hide abstract]
    ABSTRACT: A core based tree established by the core based tree multicast routing architecture (CBT), the protocol independent multicast-sparse mode (PIM-SM), or the core-manager based multicast routing (CMMR) is rooted at a center node called core or rendezvous point (RP). The routes from the core (or RP) to the members of the multicast group are shortest paths. The costs of the trees constructed based on the core and the packet delays are dependent on the location of the core. In existing core based multicast routing architectures (CBT, PIM-SM, and CMMR), the core for a multicast group is selected from a set of candidate cores. However, none of them suggests a method for selecting the set of candidate cores. We propose three methods for selecting the set of candidate cores. The three proposed methods are compared with a method which select the candidate cores randomly. Three performance measures, namely, tree cost, mean packet delay, and maximum packet delay are considered. Our results show that the three proposed methods produce lower tree cost and significantly lower mean packet delay and maximum packet delay than the method which selects the candidate cores randomly. One of the three proposed methods, namely, k-maximum path count method.
    Communications, 2002. ICC 2002. IEEE International Conference on; 02/2002
  • Source
    Hwa-Chun Lin, Chun-Hsin Wang
    [Show abstract] [Hide abstract]
    ABSTRACT: The problem of minimizing the number of transmissions for a multicast transmission under the condition that the packet delay is minimum in single-hop wavelength division multiplexing (WDM) networks is studied in this paper. This problem is proved to be NP-complete. A heuristic multicast scheduling algorithm is proposed for this problem. Extensive simulations are performed to compare the performance of the proposed heuristic algorithm with two other multicast scheduling algorithms, namely, the greedy and no-partition scheduling algorithms. The greedy algorithm schedules as many destination nodes as possible in the earliest data slot. The no-partition algorithm schedules the destination nodes of a multicast packet to receive the packet in the same data slot without partitioning the multicast transmission into multiple unicast or multicast transmissions. Our simulation results show that (i) an algorithm which partitions a multicast transmission into multiple unicast or multicast transmissions may not always produce lower mean packet delay than the no-partition algorithm when the number of data channels in the system is limited and (ii) the proposed heuristic algorithm always produces lower mean packet delay than the greedy and the no-partition algorithms because this algorithm not only partitions a multicast transmission into multiple unicast or multicast transmissions to keep the packet delay low but also reduces the number of transmissions to conserve resources.
    Photonic Network Communication 01/2002; 4(2):191-203. · 0.75 Impact Factor
  • Hwa-Chun Lin, Chun-Hsin Wang
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper shows that, for single-hop wavelength division multiplexing (WDM) networks, a multicast scheduling algorithm which always tries to partition a multicast transmission into multiple unicast or multicast transmissions may not always produce lower mean packet delay than a multicast scheduling algorithm that does not partition multicast transmissions. The performance of a multicast scheduling algorithm may depend on the traffic conditions and the availability of the channel resource in the network. A hybrid multicast scheduling algorithm that can be used in single-hop WDM networks
    Journal of Lightwave Technology 12/2001; 19(11):1654-1664. · 2.86 Impact Factor