Jerome R. Cox

AZTEC, a Preprocessing Program for Real-Time ECG Rhythm Analysis

A preprocessing program developed for real-time monitoring of the electrocardiogram by digital computer has proved useful for rhythm analysis. The program suppresses low amplitude signals, reduces the data rate by a factor of about 10, and codes the result in a form convenient for analysis.

Design of a large scale multimedia storage server

Abstract Large scale multimedia storage servers will be an integral part of the emerging distributed multimedia computing infrastructure. However, given the modest rate of improvements in storage transfer rates, designing servers that meet the demands of multimedia applications is a challenging task that needs significant architectural innovation. Our research project, called Massively-parallel And Real-time Storage ( mars ) architecture, is aimed at the design and prototype implementation of a large scale multimedia storage server. It uses some of the well-known techniques in parallel I/O, such as data striping and Redundant Arrays of Inexpensive Disks ( raid ) and an innovative atm based interconnect inside the server to achieve a scalable architecture that transparently connects storage devices to an atm -based broadband network. The atm interconnect within the server uses a custom asic called ATM Port Interconnect Controller ( apic ) currently being developed as a part of an arpa sponsored gigabit local atm testbed. Our architecture relies on innovative data striping and real-time scheduling to allow a large number of guaranteed concurrent accesses, and uses separation of metadata from real data to achieve a direct flow of the media streams between the storage devices and the network. This paper presents our system architecture; one that is scalable in terms of the number of supported users and the throughput.

The APIC approach to high performance network interface design: protected DMA and other techniques

We are building a high performance 1.2 Gb/s ATM network interface chip called the APIC (ATM Port Interconnect Controller). In addition to borrowing useful ideas from a number of research and commercial prototypes, the APIC design embraces several innovative features, and integrates all of these pieces into a coherent whole. Some of the novel ideas incorporated in the APIC design include: protected DMA and protected I/O, which allow applications to queue data for transmission or reception directly from user-space, effectively bypassing the kernel. This argues for moving the entire protocol stack including the interface device driver into the user-space, thereby yielding better latency and throughput performance than kernel-resident implementations. Pool DMA when used with packet splitting, is a technique that can be used to build true zero-copy kernel-resident protocol stack implementations, using a page-remapping technique. Finally, orchestrated interrupts and interrupt demultiplexing are mechanisms used to reduce the frequency of interrupts issued by the APIC. Although many of these ideas have been developed in the context of an ATM network interface, we believe they are also applicable in other contexts. In particular, protected DMA and I/O are promising techniques for improving the performance of several different types of I/O devices.

Design of the APIC: A high performance ATM host-network interface chip

We present the design of a high performance ATM host-network interface for multimedia workstations and servers. At Washington University, as part of an ARPA-sponsored gigabit local ATM testbed, we are building a prototype of this interface that can support a sustained aggregate bidirectional data rate of 2.4 Gbps. The centerpiece of our interface design is a custom chip called the APIC (ATM port interconnect controller). Multiple such chips can be interconnected to yield a desk-area network (DAN) which would serve as a high speed I/O interconnect for the host computer. This paper details the internal design of the APIC chip, and outlines some of its key features. Noteworthy among these are: connection caching, transmit pacing, cell batching, remote control, and support for AAL-0, AAL-5, multipoint, and loopback connections. We have chosen to defer to a later paper the details pertaining to several other features which provide support for zero-copy, improved interrupt handling, direct control of the chip from user-space, and efficient buffering and demultiplexing.

Project Zeus

The concept behind Zeus, an asynchronous transfer mode (ATM) network implemented on the campus of Washington University, is discussed. The first phase of the project, which demonstrated the feasibility of the core technology, provided a basis for a more complete design, and served as a testbed for application development, is reviewed. The switch architecture, network control software, application interfaces, and internetworking developed in the first phase are described.<<ETX>>

Progressive Coding and Transmission of Digital Diagnostic Pictures

In radiology, as a result of the increased utilization of digital imaging modalities, such as computed tomography (CT) and magnetic resonance imaging (MRI), over a third of the images produced in a typical radiology department are currently in digital form, and this percentage is steadily increasing. Image compression provides a means for the economical storage and efficient transmission of these diagnostic pictures. The level of coding distortion that can be accepted for clinical diagnosis purposes is not yet well-defined. In this paper we introduce some constraints on the design of existing transform codes in order to achieve progressive image transmission efficiently. The design constraints allow the image quality to be asymptotically improved such that the proper clinical diagnoses are always possible. The modified transform code outperforms simple spatial-domain codes by providing higher quality of the intermediately reconstructed images. The improvement is 10 dB for a compression factor of 256:1, and it is as high as 17.5 dB for a factor of 8:1. A novel progressive quantization scheme is developed for optimal progressive transmission of transformed diagnostic images. Combined with a discrete cosine transform, the new approach delivers intermediately reconstructed images of comparable quality twice as fast as the more usual zig-zag sampled approach. The quantization procedure is suitable for hardware implementation.

Study of a Distributed Picture Archiving and Communication System for Radiology

A preliminary design study has been carried out for a distributed picture archiving and communication system for the Mallinckrodt Institute of Radiology. The study develops design equations for three layers of a picture network and examines the estimated flow of digital images between a multiplicity of picture sources, picture archives and picture viewing stations. Application of these data to the design equations leads to some preliminary conclusions. One network architecture consistent with these conclusions is discussed.

Project Zeus: Design of a Broadband Network and its Application on a University Campus

This is a report of the results of the initial step in a plan for the design, deployment and operation of a high speed campus network at Washington University. The network is based on ATM switching technology that has been developed here during the last several years. This network will support ubiquitous multimedia workstations with high-resolution graphics and video capabilities, open up a wide range of new applications in research and education. It will support aggregate throughputs of hundreds of gigabits per second and will be designed to support port of 100 MB/s is now in operation. The next... Read complete abstract on page 2.

The Washington University multimedia system

The Washington University multimedia system (MMS) is a complete multimedia system capable of transmitting and receiving JPEG-compressed video, CD-quality audio, and high-resolution radiological images, in addition to normal network traffic, over the Washington University broadband ATM network. The MMS consists of an ATMizer and three multimedia subsystems. The ATMizer implements the host interface, the interface to the ATM network, and the interface to the three multimedia subsystems. This paper describes the architecture of the MMS, the software used with the system, and the applications which have been developed to demonstrate the capability and applicability of broadband ATM networks for multimedia applications.

Considerations in moving electronic radiography into routine use

Primary diagnosis plays a central role in the establishment of electronic radiography as a trusted technology. From this technology, other applications in radiology and medicine can easily flow. The fidelity of the electronic presentation of images, the ability of the radiologist to transfer film-based reading skills to a digitally based presentation, and the achievement of improvements in diagnostic efficiency are three important steps to building confidence in electronic methods in radiology. A discussion of these issues is presented as a prelude to the description of a plan for the use of broadband technology and multimedia in electronic radiography, both within and between hospitals. >