J.C.L. Liu

Charleston Southern University, North Charleston, South Carolina, United States

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Publications (23)4.63 Total impact

  • Sungwook Chung · Eunsam Kim · J.C.L. Liu
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    ABSTRACT: The feasibility of the residential area network architecture has been proposed, combined with personal video recorders (PVRs) and the fiber channel-arbitration loop (FC-AL) connection. However, the single-loop FC-AL-based architecture has the limitation on scalability. That is, the architecture only can allow 127 devices, thereby it cannot support the densely-populated apartments or buildings with thousands of users. Therefore, we propose the novel scalable multiple-loop topology-based architectures using shared disks instead of using expensive fiber channel switches. In order to provide the good scalability, we examine all feasible ring-based topology architectures, such as the ring topology, the complete graph topology, and the edge-added topology, initially from the linear topology. Based on our analyses, we have found that the complete graph topology can provide the most scalability with less use of shared disks. Finally, our experimental results based on our proposed network platform, reveals that the time-shift can be extended to almost 70 days.
    No preview · Conference Paper · Feb 2009
  • Eunsam Kim · J.C.L. Liu
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    ABSTRACT: Recent advances in storage and networking technology are rapidly changing users' TY viewing patterns. Personal video recorders (PVRs) enable people to watch what they want when they want by recording TV programs into local disks. In addition, PVRs can easily share TV contents over peer-to-peer networks once they are equipped with broadband connections. However, the current broadband bandwidth makes it difficult to support HD-quality TV content streaming on the Internet. In this paper, we propose a novel HD-quality streaming architecture for real-time broadcast content distribution. We develop two efficient scheduling schemes, matching a communication pair and switching/replication for system load-balancing, to further utilize network and disk bandwidth. We also evaluate buffer requirement to continue storing time-shifted programs without missing any broadcast data. By extensive simulation experiments, we show the effect of our proposed schemes and time-shifting policy.
    No preview · Article · Jun 2006 · IEEE Transactions on Consumer Electronics
  • Eunsam Kim · J.C.L. Liu
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    ABSTRACT: Recent advances in storage and networking technology are rapidly changing users' TV viewing patterns. PVRs enables people to watch what they want when they want independent of the broadcasting schedule by recording or time-shifting live TV programs into their local storages. Furthermore, Peer-to-Peer (P2P) networking technology provides an alternative TV content distribution channel to unidirectional broadcasting. However, due to the current limited broadband bandwidth, it is difficult to support HD-quality TV content streaming between PVRs on the Internet. In this paper, we propose a novel broadcast HD-quality streaming architecture for real-time content distribution over fast network connections. We describe two efficient scheduling schemes such as matching of a communication pair and switching/replication for system load-balancing to further utilize system resources such as networks and disks. By simulation experiments, we show the effect of our proposed schemes.
    No preview · Conference Paper · Feb 2006
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    Ju Wang · J.C.L. Liu
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    ABSTRACT: We present an efficient algorithm for power allocation and bit loading in multi-user OFDM system. We start with the close-form optimum power solution based on ideal channel coding and allowing negative transmission power. The solution is then revised by removing the subcarrier of negative power from the objective function and power constraints. The result of this procedure is proven to be the optimum power allocation in the continuous space. The continuing power/rate solution is then mapped to the feasible (non-continuous) rate space. Our algorithm is very efficient in computation (O(N)) and the resultant discrete space power/rate vector is very close to the optimum solution (less than 1% difference in the overall data rate).
    Preview · Conference Paper · Aug 2005
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    J. Wang · J.C.L. Liu
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    ABSTRACT: This paper presents a block-selection-based video watermarking scheme that is designed to be resilient against two dangerous attacks: cumulative attack and temporal attack. We use content-based block selection to counteract cumulative attack by spreading the locations of marked blocks. The block selection algorithm also leads to a novel frame synchronization method that can effectively re-synchronize suspected video frames to their original positions. Our scheme has low computation overhead and robust detection performance for moderately compressed video.
    Preview · Conference Paper · Aug 2005
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    Eunsam Kim · J.C.L. Liu
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    ABSTRACT: VOD services require the storage system support with multiple disks. SCSI-based systems are usual choices. However, disks can be attached directly to networks these days. Fiber channel arbitrated loop (FC-AL) is a leading network-accessible storage interface. As a residential service gateway, the FC-AL-based servers enable the stable delivery of high quality video to thousands of clients between external service providers and local clients. We have observed that, even though they performs better than conventional SCSI-based systems, all the disks in FC-AL-based VOD servers utilize only a small portion of their caches to a similar degree due to FC-AL fairness arbitration algorithm. In this paper, we analyze the impact of prefetching on the performance of the FC-AL-based systems according to disk block/cache size. Analysis is also focused on how to find the optimal number of blocks transmitted to the FC-AL from the disk cache per FC-AL arbitration among multiple disks. Finally, simulation results show that a 16-disk system provides over 800 concurrent video streams with quality guarantee, supporting our analytical model
    Preview · Conference Paper · Aug 2005
  • E. Kim · J.C.L. Liu
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    ABSTRACT: Modern storage systems become network-accessible. One of the leading network-attached storage systems is the Fiber Channel Arbitrated Loop (FC-AL). In order to further exploit the performance of the FC-AL-based video systems, we have built the end-to-end emulation by putting all system components together. The results showed that the system improved performance compared to conventional SCSI-based systems, but disk cache utilization among disks is similar but quite low. In this paper, in order to exploit the unused disk cache blocks, we employ prefetching. We describe how to determine FC-AL acquisition order and time among disks in advance. Then we propose a cache replacement policy to take full advantage of the sequential access pattern of video files and show how to estimate the maximum number of prefetched blocks. By analysis and simulations based on one-disk configuration, we show that the prefetching not only increases the total number of concurrent streams, but it also further utilizes the FC-AL.
    No preview · Conference Paper · Jul 2005
  • Ju Wang · J.C.L. Liu
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    ABSTRACT: We propose a hybrid uplink architecture that seamlessly integrates 802.11 WLAN (ad-hoc mode) and WCDMA interfaces. In our scheme, mobile stations can be dynamically appointed as a relaying mobile terminal (RMT) to forward uplink traffic. The RMT terminals significantly reduce the overall transmission activity and out-of-cell interference to the neighboring cells. To find the close approximation of the optimum RMT set, we propose a 2-approximation-based heuristic algorithm that is originally used to solve a minimum vertex set. The algorithm results in low out-of-cell interference, and the selected RMT terminals have good channel quality with the base stations.
    No preview · Conference Paper · Jun 2005
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    Yu-Ju Lin · H.A. Latchman · J.C.L. Liu · R. Newman
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    ABSTRACT: There is industrial intent to use powerline communication (PLC) networks in the home for delivery of multimedia data, with associated challenging quality of service (QoS) requirements. Existing protocols for PLC, for wireless networks, or even for wired networks cannot meet these challenges efficiently. This paper proposes and analyzes a new protocol designed to provide the high QoS needed for delivery of multiple multimedia streams in a PLC environment. The proposed protocol, periodic contention-free multiple access (PCF/MA), directly addresses the issues of asymmetric communication channel, hidden nodes and near-far effects. The proposed PCF/MA performance is analyzed theoretically and its performance is simulated. The results show that 85 Mbps MAC throughput is possible with 100 Mbps channel data rate, even when there are hidden nodes in the network. Through mathematical modeling and software simulation for tight bandwidth allocation, such a network can deliver up to 9 MPEG-2 video streams simultaneously without dropping any video frames, compared to 7 video streams using MCSMA/CA (Modified CSMA/CA).
    Full-text · Conference Paper · May 2005
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    Yu-Ju Lin · H.A. Latchman · J.C.L. Liu · R. Newman
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    ABSTRACT: There is industrial intent to use powerline communication (PLC) networks in the home for delivery of multimedia data, with associated challenging quality of service (QoS) requirements. Existing protocols for PLC, for wireless networks, or even for wired networks cannot meet these challenges efficiently. This paper proposes and analyzes a new protocol designed to provide the high QoS needed for delivery of multiple multimedia streams in a PLC environment. The proposed protocol, periodic contention-free multiple access (PCF/MA), directly addresses the issues of channel noise, hidden nodes and near-far effects. The proposed PCF/MA performance is analyzed theoretically and its performance is simulated. The results show that 85Mbps MAC throughput is possible with 100Mbps channel data rate, even when there are hidden nodes in the network.
    Full-text · Conference Paper · Apr 2005
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    J. Wang · A.R. Steele · J.C.L. Liu
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    ABSTRACT: This paper proposed a video watermarking scheme which embeds watermarking directly in the compressed domain, and thus can be deployed in a real-time scenario. Our method embeds a pseudo-random sequence to the qualified AC coefficients for a number of selected 8 by 8 DCT blocks. The effects of motion compensation introduced by the video compression is carefully considered to reduce the watermark-interference, phenomena which can significantly affect the detection performance if not taken care of. Our scheme shows a low computation overhead and compatible robustness under moderate video compression
    Preview · Conference Paper · Jul 2004
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    A.S. Abraham · Ju Wang · J.C.L. Liu
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    ABSTRACT: We proposed an adaptive MPEG-2/4 video encoding scheme suited for a dynamic networking environment. Conventional approaches use large quantization scales to reduce the transmission bit rate in low bandwidth situations. However, the larger quantization scale degrades the image quality severely. We believe not only that adaptive quantization should be used for bit allocation, but also that the image resolution should be jointly adjustable. Our goal is thus to investigate how image subsampling should be used in bandwidth fluctuations (e.g., 3/4G wireless networks). For this purpose, a rate-distortion model considering image subsampling is studied and implemented in the proposed encoder. Experiments show that, by choosing the right subsampling factor, a better image quality with considerably lower transmission bit rate can be obtained. A maximum gain in PSNR of 2 dB is observed with more than 50% reduction in quantization size.
    Preview · Conference Paper · Jul 2004
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    N. Kamat · Ju Wang · J.C.L. Liu
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    ABSTRACT: Routing the packet flows through the network is a very important function and if done efficiently, it can contribute appreciably towards ensuring the desired levels of voice over IP (VoIP) quality. Current limitations do not attempt to reconfigure the path of the flows in the case of loss of quality. We propose a dynamic rerouting scheme called BPAR scheme for voice traffic, in which the paths of packet voice flows are dynamically reconfigured, based on network probing and rerouting. We performed a series of emulations to evaluate the performance of the BPAR scheme. For GSM-compressed traffic, the dynamic reconfiguration proposed in this study shows an improvement of 12% reduction in average delay, and also a better connection acceptance (16% high) than other static methods under conditions of network congestion.
    Preview · Conference Paper · Aug 2003
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    Ju Wang · J.C.L. Liu · Yishu He
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    ABSTRACT: A high-quality MPEG-2 software decoder should support a good scalability performance for a wide range of video format, especially for the high-resolution MPEG-2 video (e.g., HDTV). However, it is found that the existing parallel decoder suffers significant performance degradation when decoding high-level MPEG-2 video with the full system configuration, due to inefficient management mechanism such that the memory space in the decoder. We propose an efficient buffer management mechanism such that the memory requirement is reduced by 50%. This is approached by two steps: first we use an ST scheme to minimize the transmission buffer in a slave node by allowing dynamic sharing between frames in one group of picture (GOP). Then we further reduce the buffer space by a dynamic buffer allocation according to image type. The revised parallel decode showed a satisfactory scale-up performance when decoding the high-resolution video formats.
    Preview · Conference Paper · Aug 2003
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    J.C.L. Liu · D.H.C. Du
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    ABSTRACT: First Page of the Article
    Preview · Article · Oct 2001 · Computer
  • Ju Wang · J.C.L. Liu
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    ABSTRACT: First Page of the Article
    No preview · Conference Paper · Sep 2001
  • R. Chow · Chung-Wei Lee · J.C.L. Liu
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    ABSTRACT: Traditional multimedia streaming techniques usually assume single-path (unicast) data delivery. But when the aggregate traffic between 2 nodes exceeds the bandwidth capacity of single link/path, a feasible solution is to appropriately disperse the aggregate traffic over multiple paths between these 2 nodes. In this paper we propose a set of multi-path streaming models for MPEG video traffic transmission. In addition to the attributes (such as load balancing and security) inherited from conventional data dispersion models, the proposed multimedia dispersion models are designed to achieve high error-free frame rate based on the characteristics of MPEG video structure. Our simulation results show that significant quality improvement can be observed if the proposed streaming models are employed appropriately
    No preview · Conference Paper · Feb 2001
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    M.A. Elicin · J. Wang · J.C.L. Liu
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    ABSTRACT: The emerging M-commerce needs more support in operating systems in order to be successful over a wireless environment. The system needs to support a seamless integration (i.e., transparent application switching) to support voice, audio and conventional data (e.g., e-mails, and ftp). It should also support many users with guaranteed quality. We investigate effective protocol design with dynamic spreading factors such that various QoS (i.e., BER) based on different traffic types can be provided. We further extend our protocol to guarantee a balanced support among different traffic types
    Preview · Conference Paper · Feb 2001
  • Chung-Wei Lee · J.C.L. Liu · R. Chow · R. Newman
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    ABSTRACT: QoS routing is crucial in supporting network-based multimedia applications. We identify the resource over-committing issue that exists in many proposed QoS routing algorithms. Over-committing network resource increases the possibility of blocking future requests. A novel QoS routing algorithm called friendliest routing algorithm is proposed to tackle this issue. In terms of blocking ratio, our evaluation shows that the proposed algorithm achieves 10% improvement in general and 30% in some circumstances
    No preview · Conference Paper · Feb 2001
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    Yuewei Wang · J.C.L. Liu · D.H.C. Du · JW Hsieh
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    ABSTRACT: A video-on-demand (VOD) server needs to store hundreds of movie titles and to support thousands of concurrent accesses. We define the `access profile' as the number of concurrent accesses to each movie title that should be supported by a VOD server. A current high-end magnetic disk array can only support tens of MPEG-2 concurrent accesses, and it is necessary to replicate and/or stripe the hot movie files over multiple disk arrays. How to replicate, stripe and place the movie files over a minimum number of magnetic disk arrays such that a given access profile can be supported is an important problem. In this paper, we formulate and solve this problem. The result of this study can be applied to the design of the storage subsystem of a VOD server to economically minimize the cost or to maximize the utilization of disk arrays
    Full-text · Conference Paper · Jul 1996

Publication Stats

142 Citations
4.63 Total Impact Points

Institutions

  • 2005
    • Charleston Southern University
      North Charleston, South Carolina, United States
    • Virginia Commonwealth University
      • Department of Computer Science
      Richmond, VA, United States
  • 2001-2005
    • University of Florida
      • • Department of Electrical and Computer Engineering
      • • Department of Computer and Information Science and Engineering
      Gainesville, FL, United States