J.C.L. Liu

University of Florida, Gainesville, FL, United States

Are you J.C.L. Liu?

Claim your profile

Publications (24)13.94 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: With the advent of a consumer device such as a personal video recorder, recent advances in multimedia technologies have led to various enhanced services in the network area. In particular, a fiber channel arbitration loop-based network among PVRs has been presented to demonstrate the feasibility of high-quality content sharing. In addition, a multiple-loop architecture with shared disks, instead of expensive FC switches, has been devised in order to overcome the limit on the number of accommodable PVR users. Nevertheless, there arises the need for a practically constructible topology solution since the multiple-loop architecture is based on complete graph topology that requires the most connectivity for configuration. Therefore, we propose an innovative minimum spanning tree-based graph topology for multiple-loop topology organization. The MSG-based multiple-loop architecture can determine the constant average loop size and constant reject ratio, regardless of the number of deployed loops, and the acceptable total traffic with much less connectivity than CG, thereby effectively supporting high-quality live content sharing and distribution between PVRs.
    IEEE Communications Magazine 07/2010; · 3.66 Impact Factor
  • Source
    Sungwook Chung, Eunsam Kim, J.C.L. Liu
    [Show abstract] [Hide abstract]
    ABSTRACT: High-quality content can be distributed and shared efficiently in community networks by the advantages of the geographical coverage and the connected community members. Recently, we have proposed a Personal video recorder (PVR)-based community network employing the multiple-loop fiber channel arbitration loop (FC-AL) connection, which can provide the scalability without using expensive FC-AL switches. As a community network size grows, however, popular programs tend to be stored redundantly in many PVRs, thereby wasting the storage space that could otherwise be used to store additional TV programs. We therefore propose how to extend program storage hours in a community network by presenting storage saving algorithms for both PVRs and network disks. Through extensive simulations, we finally reveals that our schemes significantly extend program storage hours by an average of 69.7%.
    Global Telecommunications Conference, 2009. GLOBECOM 2009. IEEE; 01/2010
  • Sungwook Chung, Eunsam Kim, J.C.L. Liu
    [Show abstract] [Hide abstract]
    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.
    Consumer Communications and Networking Conference, 2009. CCNC 2009. 6th IEEE; 02/2009
  • Ju Wang, M. Masilela, J.C.L. Liu
    [Show abstract] [Hide abstract]
    ABSTRACT: In this paper, we investigate issues associated with the transporting of multimedia streams across wireless sensor networks. We developed a prototype wireless sensor device that is capable of streaming video data through its wireless interface. Our experiments results showed that wireless sensor networks perform poorly with existing networking stack for such applications due to long delivery path and small transmission buffer sizes on the relaying nodes. The effect of a poor link often propagates backwards upstream and causes unnecessary data retransmission. To overcome these problems, we proposed a pipelined transmission scheme with a novel flow control method that monitors local buffer levels. A secondary buffer scheme is also used to reduce the retransmission overhead caused by node failure. Simulation results show that the proposed scheme significantly increase the network efficiency. We also propose a novel stochastic route discovery algorithm for multiple video stream in wireless sensor networks. Our method uses a probing stage where possible routes are explored and their delivery performance recorded. The data collected during the probing stage are used to select the final routes.
    Multimedia, 2007. ISM 2007. Ninth IEEE International Symposium on; 01/2008
  • Eunsam Kim, J.C.L. Liu
    [Show abstract] [Hide abstract]
    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.
    IEEE Transactions on Consumer Electronics 06/2006; · 1.09 Impact Factor
  • Eunsam Kim, J.C.L. Liu
    [Show abstract] [Hide abstract]
    ABSTRACT: Not Available
    Consumer Communications and Networking Conference, 2006. CCNC 2006. 3rd IEEE; 02/2006
  • E. Kim, J.C.L. Liu
    [Show abstract] [Hide abstract]
    ABSTRACT: With the advent of personal video recorders (PVRs), the way people watch TV is rapidly changing. By recording or time-shifting live TV programs into the embedded-disk storage of a PVR, people can watch what they want independent of the broadcasting schedule. Furthermore, peer-to-peer networking technology provides an additional TV content distribution channel to unidirectional broadcasting. However, due to the current limited broadband bandwidth, it is difficult to support high-quality TV content streaming between PVRs on the Internet. In this article we propose novel integrated network/storage architecture to provide the streaming of high-quality broadcast TV contents over fast network connections. To take full advantage of our system resources, we also develop efficient sharing schemes such as matching of a communication pair and channel assignment for extensive time-shifting.
    IEEE Communications Magazine 10/2005; · 3.66 Impact Factor
  • Source
    J. Wang, J.C.L. Liu
    [Show abstract] [Hide abstract]
    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.
    Multimedia and Expo, 2005. ICME 2005. IEEE International Conference on; 08/2005
  • Source
    E. Kim, J.C.L. Liu
    [Show abstract] [Hide abstract]
    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
    Multimedia and Expo, 2005. ICME 2005. IEEE International Conference on; 08/2005
  • Source
    J. Wang, J.C.L. Liu
    [Show abstract] [Hide abstract]
    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).
    Multimedia and Expo, 2005. ICME 2005. IEEE International Conference on; 08/2005
  • E. Kim, J.C.L. Liu
    [Show abstract] [Hide abstract]
    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.
    Information Technology: Research and Education, 2005. ITRE 2005. 3rd International Conference on; 07/2005
  • Ju Wang, J.C.L. Liu
    [Show abstract] [Hide abstract]
    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.
    Software Engineering, Artificial Intelligence, Networking and Parallel/Distributed Computing, 2005 and First ACIS International Workshop on Self-Assembling Wireless Networks. SNPD/SAWN 2005. Sixth International Conference on; 06/2005
  • Source
    [Show abstract] [Hide abstract]
    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).
    Power Line Communications and Its Applications, 2005 International Symposium on; 05/2005
  • Source
    [Show abstract] [Hide abstract]
    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.
    Advanced Information Networking and Applications, 2005. AINA 2005. 19th International Conference on; 04/2005
  • Source
    J. Wang, A.R. Steele, J.C.L. Liu
    [Show abstract] [Hide abstract]
    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
    Multimedia and Expo, 2004. ICME '04. 2004 IEEE International Conference on; 07/2004
  • Source
    A.S. Abraham, Ju Wang, J.C.L. Liu
    [Show abstract] [Hide abstract]
    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.
    Multimedia and Expo, 2004. ICME '04. 2004 IEEE International Conference on; 07/2004
  • Ju Wang, J.C.L. Liu, Yuehao Cen
    [Show abstract] [Hide abstract]
    ABSTRACT: The undergoing third-generation wireless network needs to support the integration of voice and multimedia data services with varying quality-of-service (QoS) requirements. It is critical that the least bit-error rate (BER) for voice traffic, World Wide Web (WWW) traffic, and streaming video traffic be guaranteed at all time. In this paper, we discussed the integration of soft handoff and dynamic spreading factor in wideband code-division multiple-access system in supporting multimedia traffic. The contribution of our work is twofold. First, the processing time of the handoff request is analyzed. We found that intensive mobile handoff might consume significant amount of access channel time and increase the delay of handoff. We, therefore, proposed a batch mechanism such that multiple handoff requests could be processed simultaneously. The average delay is reduced from 1.12 s to 800 ms at heavy handoff rate. Our second contribution is a new resource allocation algorithm, where the spreading factor and transmission power for the handoff mobiles are jointly considered to maximize the throughput. The BER requirements for the handoff mobiles and the target cell are maintained during the handoff process. The original problem is formulated into a nonlinear programming format. We proposed a procedure to simplify it into a linear constraint problem, which is solved by a revised simplex method. Numerical results show a 25% increase in throughput for WWW traffic and a 26% improvement for the video traffic.
    IEEE Journal on Selected Areas in Communications 01/2004; · 3.12 Impact Factor
  • Source
    Ju Wang, J.C.L. Liu, Yishu He
    [Show abstract] [Hide abstract]
    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.
    Multimedia and Expo, 2003. ICME '03. Proceedings. 2003 International Conference on; 08/2003
  • Source
    N. Kamat, Ju Wang, J.C.L. Liu
    [Show abstract] [Hide abstract]
    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.
    Multimedia and Expo, 2003. ICME '03. Proceedings. 2003 International Conference on; 08/2003
  • Source
    J.C.L. Liu, D.H.C. Du
    [Show abstract] [Hide abstract]
    ABSTRACT: First Page of the Article
    Computer 10/2001; · 1.68 Impact Factor

Publication Stats

86 Citations
13.94 Total Impact Points

Institutions

  • 2001–2010
    • University of Florida
      • Department of Computer and Information Science and Engineering
      Gainesville, FL, United States
  • 2005–2008
    • Virginia Commonwealth University
      • Department of Computer Science
      Richmond, Virginia, United States
    • Charleston Southern University
      North Charleston, South Carolina, United States