Publications Articles

2002
Vernier FD, Lesh NB, Shen C. “Visualization Techniques for Circular Tabletop Interfaces”. Proceedings of AVI'2002. 2002 :257-263.Abstract
This paper presents visualization and layout schemes for a multi-person conversational setting.
visualization_techniques_for_circular_tabletop_interfaces.pdf
Gonzalez O, Ramamritham K, Shen C, Fohler G. Providing Real-Times Services for COTS Components. In: Building Reliable Component-Based Software Systems. Boston | London: Artech House Publishers ; 2002. pp. 281-298. Publisher's Version
Shen C, Lesh NB, Vernier FD, Forlines C, Frost J. Sharing and Building Digital Group Histories, in Proceedings of the 2002 ACM Conference on Computer Supported Cooperative Work (CSCW). New Orleans, LA ; 2002.Abstract
Organizations, families, institutions evolve a shared culture and history. In this work, we describe a system to facilitate conversation and storytelling about this collective past. Users explore digital archives of shared materials such as photographs, video, and text documents on a tabletop interface. Both the software and the interface encourage natural conversation and reflection. This work is an application of our ongoing research on systems for multiple, co-present users to explore digital collections. In this paper, we present a case study of our own group history along with the software extensions developed for this scenario. These extensions include methods for easily branching off from and returning to previous threads of the exploration, incorporating background contexts that support a variety of view points and flexible story sharing, and supporting the active and passive discovery of relevant information.
sharing_and_building.pdf
2001
Moghaddam B, Tian QN, Lesh NB, Shen C, Huang TS. Visualization and Layout for Personal Photo Libraries, in International Workshop on Content-Based Multimedia Indexing. Brescia, Italy: IEEE ; 2001.Abstract
In this paper, we present visualization and layout algorithms that can enhance informal storytelling using personal digital data such as photos in a face-to-face social setting. In order to build a more intuitive browser for retrieval, navigation and story-telling, we introduce a novel optimized layout technique for large image sets which respects (context sensitive) mutual similarities as visualized on a shared 2-D display (a table-top). The experimental results show a more perceptually intuitive and informative visualization of traditional CBIR-based retrievals, providing not only a better understanding of the query context but also aiding the user in forming new queries. A framework for user-modeling is also introduced and tested. This allows the system to adapt to the user's preferences and relevance feedback.
visualization_and_layout_for_personal_photo_libraries.pdf
Shen C, Lesh NB, Moghaddam B, Beardsley PA, Bardsley RS. “Personal Digital Historian: User Interface Design”. CHI '01 Design Expo, Extended Abstracts on Human Factors in Computing Systems. 2001.Abstract
Desktop computers are not designed for multi-person face-to-face conversation in a social setting. We describe the design of a novel user interface for multi-user interactive informal storytelling. Our design is guided by principles of experience sharing, the disappearing computer, visual navigation, and implicit query formulation.
personal_digital_historian_user_interface_design.pdf
Wang H, Shen C, Shin K. “Adaptive-Weighted Packet Scheduling for Premium Service”, in IEEE International Conference on Communications (ICC). Helsinki, Finland ; 2001.Abstract
This paper presents a new scheduling scheme to support premium service in the Differentiated Service (DiffServ) architecture. It is based on weighted packet scheduling policies such as weighted round robin or fair queuing. The key feature of the new scheduling scheme is to change the scheduling weights of Behavior Aggregates adaptively. By adaptively adjusting the weights according to the dynamics of the average queue size of premium service, the proposed scheme can achieve low loss rate, low delay and delay jitter for the premium service. Moreover, it requires neither rigid admission control nor accurate traffic conditioning to support premium service in the DiffServ architecture. This adaptive packet scheduling is shown to absorb the transient burstiness of the Expedited Forwarding (EF) aggregate — which is caused by the traffic distortion inside the network —without incurring packet loss or increasing the queuing delay.
adaptive-weighted_packet_scheduling_for_premium_service.pdf
2000
Chung S-T, Gonzalez O, Ramamritham K, Shen C. CReMeS: A CORBA Compliant Reflective Memory Based Real-Time Communication Service. Proceedings of the 21st IEEE Real-Time Systems Symposium (RTSS 2000). 2000 :47-56.Abstract
We present CReMeS, a CORBA-compliant design and implementation of a new real-time communication service. It provides for efficient, predictable, and scalable communication between information producers and consumers. The CReMeS architecture is based on MidART’s Real-Time Channel-based Reflective Memory (RT-CRM) abstraction. This architecture supports the separation of QoS specification between producer and consumer of data and employs a userlevel scheduling scheme for communicating real-time tasks. These help us achieve end-to-end predictability and allows our service to scale. The CReMeS architecture provides a CORBA interface to applications and demands no changes to the ORB layer and the language mapping layer. Thus, it can run on non real-time Off-The-Shelf ORBs and enables applications on these ORBs to have scalable and end-to-end predictable asynchronous communication facility. In addition, an application designer can select whether to use an out-of-band channel or the ORB GIOP/IIOP for data communication. This permits a trade-off between performance, predictability and reliability. Experimental results demonstrate that our architecture can achieve better performance and predictability than a real-time implementation of the CORBA Event Service when the out-of-band channel is employed for data communication; it delivers better predictability with comparable performance when the ORB GIOP/IIOP is used.
cremes_a_corba_compliant_reflective_memory_based_real-time_communication_service.pdf
Shen C, Mizunuma I. RT-CRM: Real-Time Channel-Based Reflective Memory. IEEE Transactions on Computers. 2000;49 (11) :1202-1214.Abstract
In this paper, we propose and present Real-Time Channel-based Reflective Memory (RT-CRM) – a new programming model and middleware communication service for constructing distributed real-time applications on commercially available open systems. RT-CRM provides remote realtime data reflection abstraction using a simple writer-push model. This writer-push approach enables us to easily decouple the QoS characteristics of the writers from that of the readers. This decoupling is crucial in supporting different kinds of remote data transfer and access needs that one often finds in distributed real-time systems. We will describe the design of RT-CRM, along with a set of easy-to-use API to access the RT-CRM service. We have implemented RT-CRM as part of a larger real-time middleware project, MidART.We address many of the important implementation issues including buffer management and QoS support. We demonstrate the feasibility of RT-CRM through a discussion of our application programming support and performance data.
rt-crm_real-time_channel-based_reflective_memory.pdf
1999
Shen C, Gonzalez O, Ramamritham K, Mizunuma I. User Level Scheduling of Communicating Real-Time Tasks. Proceedings of the Fifth IEEE Real-Time Technology and Applications Symposium (RTAS). 1999 :164-175.Abstract
Unique challenges are present when one tries to build distributed real-time applications using standard o-the-shelf systems which are in common use but are not necessarily designed specifically for real-time systems. In particular, to realize end-to-end predictability when, say, a process on one node sends data to a process on another node, several issues must be addressed: (1) mapping application real-time requirements into requirements imposed on the system schedulable entities (tasks), (2) ensuring predictable execution of the tasks in the face of possible priority inversions, limited OS level real-time scheduling support, and limited number of priorities, and (3) integrating real-time and non-real-time tasks in the same platform. In this paper, we propose solutions to these challenges. In particular, we present user-level scheduling schemes for communicating tasks. These solutions are practical and are based on simple primitives that can be found in most of today's commonly used operating systems. To validate our design and to examine the feasibility of user-level scheduling in actual systems, we have implemented our solutions in MidART running on PCs with Windows NT operating system over UDP/IP and Fast Ethernet LANs. This paper contributes to further our understanding of how to build real-time systems using commercially available o-the-shelf components.
user_level_scheduling_of_communicating_real-time_tasks.pdf
1998
Ackermann E, Bromley D, DeMaso DR, Gibson S, Gonzalez-Heydrich J, Marks J, Shen C, Umaschi M. Experience Journals: Using Computers to Share Personal Stories about Illness and Medical Intervention. Proceedings of MedInfo '98: 9th World Congress on Medical Informatics. 1998 :1325-1329.Abstract
Medical advances make it increasingly possible for children with previously fatal illness to live and thrive. However, a significant number still experience repeated operations, hospitalizations, and invasive procedures, or need special care at home. Many do so with little or no intervention to help them and their families cope with the emotional stresses involved. One significant source of emotional and cognitive support is the community of patients and families who have experienced similar medical procedures. However, in spite of a general willingness to share experiences, communication among patients and families is usually limited. To facilitate this process, we are investigating the use of computer technology to record, organize, and display stories about the experiences of families with children who have been treated for cardiac and neurological illness at Children’s Hospital, Boston. We are asking children and their families to record text and multimedia vignettes describing some aspect of their illness, coping strategies, or care that might be useful to others. These contributions will be available for browsing at a secure World-Wide-Web site. However, economic realities preclude reliance on a professional site administrator to organize and monitor what we hope to be a rapidly growing Web site with a large, distributed authorship. The need to make the Web site fully accessible to users who have varying familiarity with computers and Web browsing imposes further constraints. We are therefore developing software to automate the process of managing and organizing an easily accessed Web site that contains an “Experience Journal.” We describe this software, the rationale for its development, and our plans for its use in the coming year.
experience_journals_using_computers_to_share_personal_stories.pdf
Ramamritham K, Shen C, Gonzalez O, Sen S, Shirgurkar SB. Using Windows NT for Real-Time Applications: Experimental Observations and Recommendations. Proceedings of IEEE Real-Time Technology and Applications Symposium. 1998.Abstract
Windows NT was not designed as a real-time operating system, but market forces and the acceptance of NT in industrial applications have generated a need for achieving real-time functionality with NT. As its use for real-time applications proliferates, based on an experimental evaluation of NT, we quantitatively characterize the obstacles placed by NT. As a result of these observations, we provide a set of recommendations for users to consider while building real-time applications on NT. These are validated by the use of NT for a prototype application involving real-time control that includes multimedia information processing. The results of the above study should provide system designers with guidelines, as well as insight, into the design of an architecture based on NT for supporting applications with components having real-time constraints.
usingwindows_nt_for_real-time_applications.pdf
Shen C, Gonzalez O. Real-Time Communicating Tasks on COTS-Based Distributed Platforms: Task Models and End-to-End Scheduling. Proceedings of the 19th IEEE Real-Time Systems Symposium. 1998.Abstract
This paper describes our current work on scheduling communicating real-time tasks in a distributed environment. Unique challenges are presented when one tries to build distributed realtime applications using standard off-the-shelf systems which are in common use but are not necessarily designed for real-time systems. In particular, one must deal with (1) mapping application real-time requirements into system schedulable entities, (2) end-to-end scheduling in the face of possible priority inversion, (3) limited real-time scheduling support and limited number of priorities, and (4) integrating real-time and non-real-time tasks in the same platform. Due to space limitations, this paper focuses on solving the first two challenges. The complete solution will be presented in a forthcoming paper. We have implemented these solutions in our network middleware MidART running on PCs with Windows NT operating system over Ethernet LANs.
real-time_communicating_tasks_on_cots-based_distributed_platforms.pdf
1997
Gonzalez O, Shen C, Mizunuma I, Takegaki M. Implementation and Performance of MidART. Proceedings of IEEE Workshop on Middleware for Distributed Real-Time Systems and Services. 1997.Abstract
In this paper, we describe our experience in the implementation of MidART – Middleware and network Architecture for distributed Real-Time systems. Our MidART project addresses the problem of middleware design to support high speed network based distributed real-time applications. The uniqueness of MidART lies in the simplicity of services provided and the flexibility of data reflection models, compared with more general purpose but much more complicated middleware such as CORBA implementations. This simplicity leads to ease of understanding and ease of use by application builders, while its flexibility sufficiently serves the needs of the class of real-time applications MidART is designed for.
implementation_and_performance_of_midart.pdf
Sen S, Gonzalez O, Ramamritham K, Stankovic JA, Shen C, Takegaki M. Multimedia Capabilities in Distributed Real-Time Applications. In: Sang Son K-J, Bestavros A Real-Time Database Systems: Issues and Applications. New York, USA: Springer ; 1997. pp. 105-122. Publisher's Version
Shen C, Mizunuma I. RT-CRM: Real-Time Channel-Based Reflective Memory. Proceedings of the Third IEEE Real-Time Technology and Applications Symposium (RTAS). 1997 :239-251.Abstract
In this paper, we propose and present Real-Time Channel-based Reflective Memory (RT-CRM) – a useful programming model and middleware communication service for constructing distributed real-time industrial monitoring and control applications on commercially available open systems. RT-CRM provides remote real-time data reflection abstraction using a simple writer-push model. This writer-push approach enables us to easily decouple the QoS characteristics of the writers from that of the readers. This decoupling is crucial in supporting different kinds of remote data transfer and access needs that one often finds in distributed industrial systems. We will describe the design of RT-CRM, along with a set of easy-to-use API to access the RT-CRM service. We have implemented RT-CRM as part of a larger real-time middleware project, MidART. We address many of the important implementation issues including buffer management and QoS support. We demonstrate the feasiblity of RT-CRM through a discussion of our application programming support and preliminary performance data.
1997_rt-crm_real_time_channel-based_reflective_memory.pdf
1996
Goyal P, Vin HM, Shen C, Shenoy PJ. A Reliable, Adaptive Network Protocol For Video Transport. Proceedings of IEEE INFOCOM '96 [Internet]. 1996 :1080 - 1090. Publisher's VersionAbstract
We present an adaptive network layer protocol for VBR video transport. It: (1) minimizes the buffer requirement in the network while guaranteeing that packets of VBR encoded video flows will not be lost, and (2) minimizes the end-to-end delay and jitter of frames. To achieve the former objective, we utilize a receiver-oriented adaptive credit-based flow control algorithm, and derive the necessary and sufficient number of buffers that should be reserved for ensuring its reliability. To minimize the end-to-end delay and jitter for VBR encoded video streams, we: (1) present bandwidth estimation techniques which exploit the structure of the video traffic, and (2) define a new fairness criteria for buffer allocation and then present a fair buffer/bandwidth allocation algorithm. We experimentally evaluate this protocol for a wide range of parameters and many network configurations, and demonstrate its adaptability. We also compare the performance of the protocol with numerous other schemes and demonstrate its suitability for video transport.
a_reliable_adaptive_network_protocol_for_video_transport.pdf
Mizunuma I, Shen C, Takegaki M. Middleware for Distributed Industrial Real-Time Systems on ATM Networks. Proceedings of the 17th IEEE Real-Time Systems Symposium (RTSS '96). 1996 :32-38.Abstract
In this paper we address the problem of middleware design for constructing ATM LAN based distributed industrial plant monitoring and control systems. In particular, we present a real-time client-server programming model based on a uniform ATM network. This model is being realized in our middleware called MidART. The middleware provides a set of industrial application specic but network transparent programming abstractions and application programming interface (API) that support individual application QoS requirements. In order to achieve on-demand transmission of plant data, we have developed a concept called selective real-time channels to be supported by MidART. We present the design and protocols of selective real-time channels and describe how QoS requirements of applications are guaranteed.
middleware_for_distributed_industrial_real-time_systems.pdf
1995
Lauer HC, Shen C, Osborne R, Howard J, Zheng Q, Takegaki M, Shimakawa H, Mizunuma I. Digital Audio and Video in Industrial Systems, in NOSSDAV '95: The Fifth International Workshop on Network and Operating Systems Support for Digital Audio and Video. Durham, New Hampshire: IEEE ; 1995.Abstract
This is a position paper discussing the requirements of networks in industrial environments, especially with respect to digital audio and video. Topics include resource allocation, issues surrounding switching, scheduling, and priorities, end system interface requirements, and traffic characteristics and their implications on flow control.
digital_audio_and_video_in_industrial_systems.pdf
Anderson DB, Barrus JW, Howard JH, Rich C, Shen C, Waters RC. Building Multi-User Interactive Multimedia Environments at MERL. IEEE MultiMedia. 1995;2 (4) :77-82.Abstract
Building multi-user interactive multimedia environments at Mitsubishi Electric Research Laboratories (MERL) is a highly interdisciplinary activity, which involves the efforts of more than a dozen members of the laboratory. This report describes this research at three levels. At the bottom, supporting everything, are high-speed networks. On top of networks, we have built a piece of middleware called Spline. Finally, Diamond Park is an experimental environment we are building using Spline.
building_multi-user_interactive_multimedia_environments_at_merl.pdf
1993
Shen C, Ramamritham K, Stankovic JA. Resource Reclaiming in Multiprocessor Real-Time Systems. IEEE Transactions on Parallel and Distributed Systems [Internet]. 1993;4 (4) :382-397. Publisher's VersionAbstract
Most real-time scheduling algorithms schedule tasks with regard to their worst case computation times. Resources reclaiming refers to the problem of utilizing the resources left unused by a task when it executes in less than its worst case computation time, or when a task is deleted from the current schedule. Dynamic resource reclaiming algorithms that are effective, avoid any run time anomalies, and have bounded overhead costs that are independent of the number of tasks in the schedule are presented. Each task is assumed to have a worst case computation time, a deadline, and a set of resource requirements. The algorithms utilize the information given in a multiprocessor task schedule and perform online local optimization. The effectiveness of the algorithms is demonstrated through simulation studies.

Pages