University of Pennsylvania 7/15/98 Asymmetric Bandwidth Channel (ABC) Architecture Insup Lee University of Pennsylvania July 25, 1998

University of Pennsylvania 7/25/98 Principal investigators Ruzena Bajcsy (PI), CIS David Farber, CIS/EE Vijay Kumar, MEAM/CIS Insup Lee, CIS Jonathan Smith, CIS/EE

University of Pennsylvania 7/25/98 The ABC Model Server Broadcast Clients A B C A is low latency and B/W, duplex B is high latency and B/W, simplex C is high latency and B/W, simplex A may be real-time

University of Pennsylvania 7/25/98 Motivation Common communication paradigm Becoming widely available: CATV, DBS, ADSL Cost advantage for multicast Applications –World-Wide Web (R/W>10) –Multiple robots –Shared virtual reality environment (a la “Snowcrash”) –Mobile computers

University of Pennsylvania 7/25/98 Outline (New Award) The ABC model Network resource management Programming paradigm and support Applications (robotics, virtual environment)

University of Pennsylvania 7/25/98 ABC Network Management Real-time/interactivity Integration with existing protocols (IP) –protocol boosters Routing algorithms Resource multiplexing Multicast as basic communication primitive Mobile computing Probabilistic real-time guarantees for wireless communication

University of Pennsylvania 7/25/98 The ABC Computation Model A client –makes a request and the server may reply by broadcasting the requested data –filters out the broadcasted data –needs to receive broadcasted data at predetermined time The server –determines whether to broadcast or not –clusters data and decide what to broadcast together –schedules the broadcast server, types of QoS attributes –adapts scheduling policy based on the system history –manages local storage at broadcast server –may be replicated for scalability

University of Pennsylvania 7/25/98 Multiple agent coordination A timed asynchronous system –distributed agents need to coordinate, under timing constraints, to perform the control task –performance failures –decisions should be consistent, valid and timely Approach –Timed synchronous communication –N-way timed synchronization –Timed atomic commitment –Majority timed atomic commitment

University of Pennsylvania 7/15/98 System Spec System Spec Requirement Spec Requirement Spec Formal verification Design System Implementation System Implementation Monitoring Script Monitoring Script Implementation Checker/ Corrector Checker/ Corrector System Filter Communication Run-time Check Run-time monitoring and checking Event Handler Event Handler Corrector Checker

University of Pennsylvania 7/25/98 Fundamental Issues on Monitoring How does a monitor gather information from a running system? How does the monitor relate to requirements? How do we integrate dynamic monitoring with static analysis? Can monitor be used to steer a system? What mathematical guarantees do monitors provide?

University of Pennsylvania 7/25/98 Coordinated Control of Robots Multiple robots with wireless communication Tradeoff between local computation and communication Scalable number of robots Simulation and implementation Apply hybrid systems modeling –Analyze the effectiveness of coordinated control –Determine the sensitivities of control parameters Computing/sensingCommunication Number of robots

University of Pennsylvania 7/25/98 Communication via wireless local area network –Proxim wireless LAN 1.4 Mbs (80 byte packages, 20 Hz) –IPX or TCP/IP protocol –Peer to peer network –Scalable to 10 robots, 8 Hz Experimental testbed Three heterogeneous robots –Robot 1 Nomad (omni directional) mobile platform fork-lift –Robot 2 Labmate (nonholonomic) mobile platform Actively controlled robot arm –Robot 3 Labmate (nonholonomic) mobile platform Passive arm Each robot is controlled by two IBM compatibles

University of Pennsylvania 7/25/98 Planning and Sensing Framework –One or more leaders in any formation –Leaders generate plans and broadcast plans to followers –Decentralized controllers Planning –Planner generates trajectories consistent with geometric, kinematics and dynamic constraints –Currently only one leader Sensing –Different robots have different sensors –Information from distributed sources is integrated centrally –Global map is broadcast

University of Pennsylvania 7/25/98 Reconstruction Goals and Mothod Goals –robot localization central control of agents central integration of data use of maps –local reconstruction dense depth information obstacle avoidance surface integration Method –self-calibration avoids prior calibration additional constraints specialized optimization accurate for all motions –stereo

University of Pennsylvania 7/25/98 Overview of VENUS Virtual Environment Network Using Satellite Satellite for high BW broadcast Allows global, consistent updates Cost of satellite amortized over all users Land-links for uni- or multicast Network Cloud

University of Pennsylvania 7/25/98 VENUS A virtual environment network using satellite An architecture to support large-scale, wide-area virtual reality client/server based –clients send lightweight update packets to server via low-BW links –server collates and broadcasts them using satellite high-BW link Advantages –broadcast allows all users to view the entire world –scalable since incremental cost per user is small –lower load on server since it only acts as coordinator