Browsing by Author "Sheu, JP"

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A fast video-on-demand broadcasting scheme for popular videos
(2004-06-01)
Sheu, JP
;
Wang, HL
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Chang, CH
;
Tseng, YC
;
資訊工程學系
Broadcasting is a prospective approach to support near video-on-demand services with light communication overhead. By letting clients share channels, such approaches involve partitioning a video into segments and repeatedly broadcasting these segments in multiple channels. An early paper proposed a broadcasting scheme called RFS (recursive frequency splitting), which can significantly reduce clients' waiting time. While efficient, RFS suffers from a high computational complexity of O (n log n), where n is the number of segments of the video, which is typically very large. This paper proposes an efficient segmentation scheme, which can significantly reduce the computational overhead by slightly sacrificing the number of segments that can be arranged as compared to RFS.
A multi-channel MAC protocol with power control for multi-hop mobile ad hoc networks
(2001)
Tseng, YC
;
Wu, SL
;
Lin, CY
;
Sheu, JP
;
資訊工程學系
In a mobile ad-hoc networks (MANET), one essential issue is Medium Access Control (MAC), which addresses how to utilize the radio spectrum efficiently and to resolve potential contention and collision among mobile hosts on rising the medium. Existing works have dedicated to using multiple channels [4, 6, 9. 10, 12, 18. 20] and power control [7, 13. 21] to improve the performance of MANET: III this paper.,ve investigate the possibility of bringing the concepts of power control a,ld multi-channel medium access together in the MAC design problem in a MANET: Existing protocols only address one of these issues independent): The proposed protocol is characterized by the following features: (i) it follows an "on-demand" style to assign, channels to mobile hosts. (ii) the number of channels required is independent of the network topology and degree, (iii) it flexibly adapts to host mobility: (iv) no form of clock synchronization is required, and(v) power control is used to exploit frequency reuse. Power control may also extend battery life and reduce signal interference. both of,which are important in wireless communication Through simulations, we demonstrate the advantage of our new protocol.
A multi-channel MAC protocol with power control for multi-hop mobile ad hoc networks
(2002)
Wu, SL
;
Tseng, YC
;
Lin, CY
;
Sheu, JP
;
資訊工程學系
In a mobile ad hoc network (MANET), one essential issue is Medium Access Control (MAC), which addresses how to utilize the radio spectrum efficiently and to resolve potential contention and collision among mobile hosts on using the medium. Existing works have been dedicated to using multiple channels and power control to improve the performance of MANET. In this paper, we investigate the possibility of bringing the concepts of power control and multi-channel medium access together in the MAC design problem in a MANET. Existing protocols only address one of these issues independently. The proposed protocol is characterized by the following features: (i) it follows an 'on-demand' style to assign channels to mobile hosts, (ii) the number of channels required is independent of the network topology and degree, (iii) it flexibly adapts to host mobility, (iv) no form of clock synchronization is required and (v) power control is used to exploit frequency reuse. Power control may also extend battery life and reduce signal interference, both of which are important in wireless communication. Through simulations, we demonstrate the advantage of our new protocol.
A multi-path QoS routing protocol in a wireless mobile ad hoc network
(2002)
Liao, WH
;
Wang, SL
;
Sheu, JP
;
Tseng, YC
;
資訊工程學系
A mobile ad hoc network (MANET) is one composed of a set of mobile hosts capable of communicating with each other without the assistance of base stations. This paper considers the QoS (quality-of-service) routing problem in a MANET, which is important for many real-time multimedia applications. We propose an on-demand protocol for searching for a multi-path QoS route from a source host to a destination host in a MANET, where a multi-path is a network with a source and a sink satisfying certain bandwidth requirement. Existing works all try to find a uni-path to the destination. The basic idea is to distribute a number of tickets from the source, which can be further partitioned into subtickets to search for a satisfactory multi-path. Through simulations, we justify that the value of our multi-path protocol is in its flexibility: (i) when the network bandwidth is very limited, it can offer a higher success rate to find a satisfactory QoS route than those protocols which try to find a uni-path, and (ii) when the network bandwidth is sufficient, it can perform almost the same as those protocols which try to find a uni-path (in both routing overhead and success rate).
A multi-path QoS routing protocol in a wireless mobile ad hoc network
(2001)
Liao, WH
;
Tseng, YC
;
Wang, SL
;
Sheu, JP
;
資訊工程學系
A mobile ad hoc network (MANET) is one consisting of a set of mobile hosts capable of communicating with each other without the assistance of base stations, This paper considers the QoS (quality-of-service) routing problem in a MANET. We propose an on-demand protocol for searching for a multi-path QoS route from a source host to a destination host in a MANET, where a multi-path is a network with a source and a sink satisfying certain bandwidth requirement. Existing works all try to find a uni-path to the destination. The basic idea is to distribute a number of tickets from the source, which can be further partitioned into sub-tickets to search for a satisfactory multi-path. Through simulations, we justify that the value of our multi-path protocol is on its flexibility: (i) when the network bandwidth is very limited, it can offer a higher success rate to find a satisfactory QoS route than those protocols which try to find a uni-path, and (ii) when the network bandwidth is sufficient, it can perform almost the same as those protocols which try to find a uni-path (in both routing overhead and success rate).
A priority MAC protocol to support real-time traffic in ad hoc networks
(2004-01-01)
Sheu, JP
;
Liu, CH
;
Wu, SL
;
Tseng, YC
;
資訊工程學系
Carrier sense multiple access and its variants have been widely used in mobile ad hoc networks. However, most existing access mechanisms cannot guarantee quality for real-time traffic. This paper presents a distributed medium access control protocol that provides multiple priority levels for stations to compete for the wireless channel. One common channel is assumed to be shared by all stations. Stations are assumed to be able to hear each other (i.e., the network is fully connected). The channel is accessed by stations according to their priorities, and for stations with the same priority, they send frames in a round robin manner. The channel access procedure is divided into three stages: priorities classification period, ID initialization period, and transmission period. Simulation results indicate that our protocol provides high channel utilization and bounded delays for real-time frames.
An on-demand, link-state, multi-path QoS routing in a wireless mobile ad-hoc network
(2004-01-01)
Chen, YS
;
Tseng, YC
;
Sheu, JP
;
Kuo, PH
;
資訊工程學系
The peer-to-peer multimedia applications have recently generated much interest in wireless network infrastructure with supporting the quality-of-service (QoS) communications. In this paper, we propose a new on-demand QoS routing, namely link-state multi-path QoS routing, protocol in a wireless mobile ad-hoc network (MANET). Our proposed scheme offers a bandwidth routing protocol for QoS support in a multihop mobile network. Our QoS routing protocol determines the end-to-end bandwidth calculation and bandwidth allocation at the destination. Our protocol collects link bandwidth information from source to destination in order to construct a network topology with the information of link bandwidth at the destination. To satisfy a given bandwidth requirement, the bandwidth calculation of the QoS route are determined at the destination to accurately determine the QoS uni-path or multi-path route depending on the status of network bandwidth. Our routing scheme may offer a multi-path route if a MANET with the insufficient network bandwidth, and provide a uni-path route if the network bandwidth is sufficient. The destination eventually determines the QoS multi-path routes and replies to the source host to perform the bandwidth reservation. Our routing scheme obviously improves the success rate of identifying a QoS route, and the simulation result demonstrates this improvement. (C) 2003 Elsevier B.V. All rights reserved.
Balancing traffic load for multi-node multicast in a wormhole 2-D torus/mesh
(2001)
Wang, SY
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Tseng, YC
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Shiu, CS
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Sheu, JP
;
資訊工程學系
This paper considers the multi-node multicast problem in a wormhole-routed 2-D torus/mesh, where an arbitrary number of source nodes each intends to multicast a message to an arbitrary set of destinations. To resolve the contention and the congestion problems, we propose to partition the network into subnetworks to distribute, and thus balance, the traffic load among all network links. Several ways to partition the network are explored. The network-partitioning idea was used in earlier works for single-node broadcast and single-node multicast. This paper contributes in extending its applicability to multi-node multicast and demonstrating its capability to balance load on torus/mesh. Simulation results show significant improvement over existing results for torus and mesh networks.
Channel-sharing strategies in two-tier cellular PCS systems
(2002-09-01)
Lin, KJ
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Tseng, YC
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Sheu, JP
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資訊工程學系
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Department of Computer Science
A two-tier cellular network is characterized by macrocells and microcells overlapping in the service area. This overlapping property provides an advantage that traffic loads can be shared by channels of the two tiers to increase the performance of the system. In this paper, we propose two channel-sharing strategies, namely vertical channel-sharing and vertical-horizontal channel-sharing, to better utilize channels of the network. The call loss probability of new calls and call dropping probability of handoff calls are developed through analyses and simulations. The results justify the advantage of our strategies over existing strategies. (C) 2002 Elsevier Science B.V. All rights reserved.
Circuit-switched broadcasting in multi-port multi-dimensional torus networks
(2001-11-01)
Wang, SY
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Tseng, YC
;
Ni, SY
;
Sheu, JP
;
資訊科學與工程研究所
The one-to-all broadcast is the most primary collective communication pattern in a multicomputer network. This paper studies this problem in a circuit-switched torus with alpha -port capability, where a node can simultaneously send and receive alpha messages at one time. This is a generalization of the one-port and all-port models. We show how to efficiently perform broadcast in tori of any dimension, any size, square or nonsquare, using near optimal numbers of steps. The main techniques used are: (i) a "span-by-dimension" approach, which makes our solution scalable to torus dimensions, and (ii) a "squeeze-then-expand" approach, which makes possible solving the difficult cases where tori are non-square. Existing results, as compared to ours, can only solve very restricted sizes or dimensions of tori, or use more numbers of steps.
Data broadcasting and seamless channel transition for highly demanded videos
(2001-05-01)
Tseng, YC
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Yang, MH
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Hsieh, CM
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Liao, WH
;
Sheu, JP
One way to broadcast a popular video is to use a number of dedicated channels, each responsible for broadcasting some portion of the video periodically in a predefined way. The stress on channels can be alleviated, and new viewers do not have to wait long to start their playback, Many approaches falling in this category have been proposed, One such scheme that interests us is the fast broadcasting (FB) scheme, which can broadcast a video using k channels by incurring at most O(D/2(k)) waiting time on new-coming viewers, where D is the length of the video. In this paper, we consider a set of videos, each being broadcast by the FB scheme, Since the levels of demands on these videos may change by time, it is sometimes inevitable to change the numbers of channels assigned to some videos. We propose a novel seamless channel transition enhancement on top of the FB scheme to dynamically change the number of channels assigned to a video on-the-fly. Clients currently viewing this video will not experience any disruption because of the transition. A channel allocation scheme is also proposed based on the arrival rates of videos to minimize the average waiting experienced by all viewers, From the system manager's point of view, the enhancement will make the FB scheme more attractive.
Design and implementation of a communication-efficient data-parallel program compiling system
(2001-09-01)
Shih, KP
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Lai, CY
;
Sheu, JP
;
Tseng, YC
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資訊工程學系
In this paper, we present the design and implementation of a data-parallel compiling system. The system has been implemented on a DEC Alpha 3000 workstation and incorporated into a parallel programming environment called UPPER (User-interactive Parallel Programming EnviRonment). Given an HPF program, the built-in compiler system can automatically analyze the access pattern of the HPF program, enumerate the computation and communication sets, and then generate the SPMD code for execution on nCUBE/2. Moreover, the user interface is designed to help the programmer to capture some information during the compilation and execution phases, including interprocessor communication, distribution of data elements onto processors, and execution results.
Dynamic channel allocation with location awareness for multi-hop mobile ad hoc networks
(2002-05-01)
Tseng, YC
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Chao, CM
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Wu, SL
;
Sheu, JP
;
資訊工程學系
The wireless mobile ad hoc network (MANET) has received a lot of attention recently. This paper considers the channel assignment problem in a MANET which has access to multiple channels. Although a MANET does not have the infrastructure of base stations, interestingly its channel assignment can be conducted efficiently in a way very similar to that in cellular systems (such as GSM). In this paper, we propose a new location-aware channel assignment protocol called GRID-B (read as GRID with Channel Borrowing), which is a sequel of our earlier GRID protocol [Location-aware channel assignment for a multi-channel mobile ad hoc network, Technical Report NCU-HSCCL-2000-02, 2000]. The protocol assigns channels to mobile hosts based on the location information of mobile hosts that might be available from the positioning device (such as GPS) attached to each host. According to our knowledge, no location-aware channel assignment protocol has been proposed before for MANETs. Several channel borrowing strategies are proposed to dynamically assign channels to mobile hosts so as to exploit channel reuse and resolve the unbalance of traffic loads among different areas (such as hot and cold spots). We then propose a multi-channel MAC protocol, which integrates GRID-B. Extensive simulation results are presented to show the advantage of the new GRID-B protocol. (C) 2002 Elsevier Science B.V. All rights reserved.
GRID: A fully location-aware routing protocol for mobile ad hoc networks
(2001)
Liao, WH
;
Sheu, JP
;
Tseng, YC
;
資訊工程學系
;
Department of Computer Science
A mobile ad hoc network (MANET) is one consisting of a set of mobile hosts capable of communicating with each other without the assistance of base stations. One prospective direction to assist routing in such an environment is to use location information provided by positioning devices such as global positioning systems (GPS). In this paper, we propose a new routing protocol called GRID. which tries to exploit location information in route discovery, packet relay, and route maintenance. Existing protocols, as compared to ours, are either not location-aware or partially location-aware in that location knowledge is not fully exploited in all these three aspects. One attractive feature of our protocol is its strong route maintenance capability - the intermediate hosts of a route can perform a "handoff" operation similar to that in cellular systems when it roams away to keep a route alive. This makes routes in the MANET more stable and insensitive to host mobility. Simulation results show that our GRID routing protocol can reduce the probability of route breakage, reduce the number of route discovery packets used, and lengthen routes' lifetime.
Increasing the throughput of multihop Packet Radio Networks with power adjustment
(2001)
Huang, CF
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Tseng, YC
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Wu, SL
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Sheu, JP
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資訊工程學系
The Packet Radio Network (PRN) is an attractive architecture to support mobile and wireless communication. Although the code assignment problem has been studied extensively on PRN, we observe in this paper that the power control problem has been ignored by most works, but may have significant impact on performance. By power control, we mean that the transmission ranges of stations are tunable. We show given a PRN in which each host already received a code, how to adjust the powers of stations to control/improve the topology of the PRN without violating the original code assignment. Several schemes are proposed. Through simulations, we demonstrate that although the code assignment problem is NP-complete and thus computationally very expensive, using our power adjustment schemes can easily improve the network performance by about 20% with polynomial costs.
Intelligent medium access for mobile ad hoc networks with busy tones and power control
(2000-09-01)
Wu, SL
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Tseng, YC
;
Sheu, JP
;
資訊工程學系
;
Department of Computer Science
In mobile ad hoc networks (MANETs), one essential issue is how to increase channel utilization while avoiding the hidden-terminal and the exposed-terminal problems. Several MAC protocols, such as RTS/CTS-based and busy-tone-based schemes, have been proposed to alleviate these problems. In this paper, we explore the possibility of combining the concept of power control with the RTS/CTS-based and busy-tone-based protocols to further increase channel utilization. A sender will use an appropriate power level to transmit its packets so as to increase the possibility of channel reuse. The possibility of using discrete, instead of continuous, power levels is also discussed. Through analyses and simulations, we demonstrate the advantage of our new MAC protocol. This, together with the extra benefits such as saving battery energy and reducing cochannel interference, does show a promising direction to enhance the performance of MANET's.
Special issue: Research in ad hoc networking, smart sensing, and pervasive computing
(2003-06-01)
Tseng, YC
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Sheu, JP
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Das, S
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Chang, RS
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交大名義發表
The broadcast storm problem in a mobile ad hoc network
(2002)
Tseng, YC
;
Ni, SY
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Chen, YS
;
Sheu, JP
;
資訊工程學系
Broadcasting is a common operation in a network to resolve many issues. In a mobile ad hoc network (MANET) in particular, due to host mobility, such operations are expected to be executed more frequently (such as finding a route to a particular host, paging a particular host, and sending an alarm signal). Because radio signals are likely to overlap with others in a geographical area, a straightforward broadcasting by flooding is usually very costly and will result in serious redundancy, contention, and collision, to which we call the broadcast storm problem. In this paper, we identify this problem by showing how serious it is through analyses and simulations. We propose several schemes to reduce redundant rebroadcasts and differentiate timing of rebroadcasts to alleviate this problem. Simulation results are presented, which show different levels of improvement over the basic flooding approach.