Asymmetric Bandwidth Channel (ABC) Architecture

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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

Requirement

Spec

Formal verification

Design

System

Implementation

Monitoring

Script

Implementation

Checker/

Corrector

System


Filter

Communication

Run
-
time Check

Run
-
time monitoring and checking

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/sensing

Communication

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