Ralph Martinez

A survey of MAC protocols proposed for wireless ATM

Wireless ATM (W-ATM) networks have been studied extensively. The extension of ATM network services to the wireless environment faces many interesting problems. The original ATM network was designed for high-speed noiseless, reliable channels. None of these characteristics are applicable to the wireless channel. One of the most critical aspects of a W-ATM network is the medium access control (MAC) protocol used by mobile terminals (MTs) to request service from the base station (BS), which has to consider the quality of service (QoS) of the specific application. In this article the authors analyze some MAC protocols, particularly those for TDMA systems, and discuss their advantages and disadvantages.

Internet Access via Baseband and Broadband ISDN Gateways

As the concept of digital super-highway being more widely perceived among the computer and communications professionals and users, one of the focuses of eflorts is to take the full advantage of new technologies, to provide users with mazimum Intemet connectivity. Among all, ISDN is one of today’s technology with the ability to transmit voice, data, and imaging simultaneously with declining communications costs. It is expected that the connectivity via baseband ISDN will be vital for home users and small to medium-size organizations, in order to match up the unprecedented amount of daily electronic information. And the broadband ISDN is believed to be the foundation of digital super-highway technology. The ISDN gateway project was motivated to design a gateway, utilizing the mature and widespreading Intemet technology, to provide ISDN users with the Internet connectivity and services. This paper describes the design, implementation of an ISDN to Internet gateway, using the TCP/IP protocol suite.

Evaluation of the ACR-NEMA standard for communications in digital radiology

An implementation and evaluation of a prototype multivendor communications system which complies with the American College of Radiology (ACR) and the National Electrical Manufacturers Association (NEMA) standard for communications in digital radiology is discussed. The system allows communications between interfaces from different manufacturers within a networked environment. The implementation includes network software compatible with the International Standards Organizations Open Systems Interconnect standard. The experience of the implementation effort and the evaluation of the system provide the basis for a critique of the ACR-NEMA standard. It is concluded that the ACR-NEMA standard is not well suited for application to the networked environment of picture archiving and communications systems. Two possible solutions are recommended for this problem. The first is a major revision of the existing standard. The second is the development of a family of network communications standards for digital radiology.

Remote consultation and diagnosis in a global PACS environment

A global PACS is a national network which interconnects several PACS networks at medical and hospital complexes using a national backbone network. A global PACS environment enables new and beneficial operations between radiologists and physicians, when they are located in different geographical locations. This paper presents three user scenarios which enable remote consultation and diagnosis between radiologists at a local PACS site and a remote PACS site. One scenario, called remote consultation, allows the radiologist to view the same image folder at both local and remote sites so that a diagnosis can be performed. We present performance date based on tests between these two sites and show the feasibility of the operation in a global PACS environment. Future improvements to the system will include real- time voice and interactive compressed video scenarios. This work is sponsored by the National Science Foundation and Toshiba Medical Systems Division.

Design, analysis, and implementation of a telemedicine remote consultation and diagnosis session playback using discrete event system specification

Telemedicine remote consultation and diagnosis (RCD) software is a complex and distributed system. RCD allows physicians to collaborate on radiology or pathology cases from distributed geographic locations. It is very important to simplify design, construction, and maintenance of such a system. Currently, object-oriented design methodology is used to design and develop a software system in a modular fashion. Object-oriented software is made of various objects that work together. From the design of the software system, we get information about object methods and inheritance. We also get information about which objects are contained in a particular object and which objects are used by another object. One important element that the traditional object-oriented design misses is time. We propose the use of discrete event system specification (DEVS) in the design and analysis of a software system, such as RCD. With DEVS, coupling between objects can be specified explicitly and an object behavior can be shown in time. We introduce DEVS, show the time-line analysis of Remote Consultation and Diagnosis session playback using DEVS, and then describe its implementation.

An architecture for Naval telemedicine

Navy fleets have a defined overall objective for mission readiness impacted by the health of personnel aboard the ships. Medical treatment facilities on the ships determines the degree of mission readiness. The paper describes the concepts and technologies necessary to establish a Naval telemedicine system, which can drastically improve health care delivery. It consists of various combinations of the following components: Fleet Naval Medical Consultation and Diagnostic Centers, Shipboard Naval Medical Consultation and Diagnostic Centers (hospital ship or combatant ships with medical specialists on board), and Remote Medical Referring Centers such as a ship, a small Naval station annex, or a field hospital. This Naval telemedicine architecture delivers clinical medicine and continuing medical education (CME) by means of computers, video-conferencing systems, or telephony to enhance the quality of care through improved access to research, medical and nonmedical imaging, remote consultations, patient clinical data, and multimedia medical education programs. It integrates the informatics infrastructure and provides a medical telepresence among participants.

Design of multimedia global PACS distributed computing environment

We present our approach to developing global picture archiving and communication system (global PACS) applications using the Open Software Foundation distributed computing environment (OSF DCE) services and toolkits. Designing distributed global PACS applications using the OSF DCE approach will feature an open architecture, heterogeneity, scalability, and technology independence for global PACS remote consultation and diagnosis applications, including synchronized image annotation, voice and video, system privacy and security. The applications can communicate through various transport services and communications networks. The paper presents the development of an initial global PACS DCE testbed in which the basic functions of remote consultation sessions have been implemented using DCE services. Further research and development work is summarized.<<ETX>>Telemedicine remote consultation and diagnosis (RCD) software is a complex and distributed system. RCD allows physicians to collaborate on radiology or pathology cases from distributed geographic locations. It is very important to simplify design, construction, and maintenance of such a system. Currently, an object-oriented design methodology is used to design and develop a software system in a modular fashion. Object-oriented software is made of various objects that work together. From the design of the software system, we get information about object methods and inheritance. We also get information about which objects are contained in a particular object and which objects are used by another object. One important element that the traditional object-oriented design misses is time. We propose the use of discrete event system specification (DEVS) in the design and analysis of a software system, such as RCD. With DEVS, coupling between objects can be specified explicitly and an object behavior can be shown in time. We introduce DEVS, show the time-line analysis of remote consultation and diagnosis session playback using DEVS, and then describe its implementation.

Performance evaluation of a picture archiving and communication network using stochastic activity networks

A fiber-optic star-based picture archiving and communication system (PACS) network that is based on a multiplexed passive star local area network with wavelength-division multiplexing (WDM) to provide separate logical channels for transfer of control and image data is discussed. The system consists of an image network (INET), for image transfer at a rate of 140 Mb/s, and a control network (CNET), operating at 10 Mb/s, for mediating the flow of image transfers. INET is a circuit switched network devoted solely to image transfer, while CNET employs the CSMA/CD protocol for bus arbitration. Stochastic activity networks were used to develop a detailed model of the command and image channels. The performance of the system was then evaluated under realistic workload conditions. In particular, a number of important performance variables, including the image response time, command channel delay, and queue length at each type of node and the network supervisor, are estimated. The results (1) show that stochastic activity networks are an appropriate model type for evaluating picture archiving and communication systems, (2) delineate the workload conditions under which PACS may effectively operate, and (3) show that even when these conditions are exceeded, the command channel load remains extremely light.

Design and Performance Evaluation of a High Speed Fiber Optic Integrated Computer Network for Picture Archiving and Communications System

Computer networks for Picture Archiving and Communications. Systems (PACS) have evolved over the last few years. Twisted pairs and coaxial cable networks have been used for image transfer at low data rates. Second generation PACS networks use fiber optic communications at speeds up to 140 Mbps. In this paper, the need for integrated voice, data, and image communications and network rates over 200 Mbps is presented. A high speed fiber optic network for integrated PACS services has been design and simulated in the Computer Engineering Research Laboratory at the University of Arizona. This paper summarizes the characteristics and protocols of this network. The network represents a high performance application for local PACS environments and its implementation is technically feasible now.

Hardware and software-in-the-loop techniques using the OPNET modeling tool for JTRS developmental testing

This paper describes the continuation of the hardware-in-the-loop (HITL) project started by the U.S. Army Information Systems Engineering Command (ISEC) in FY 2000. The paper describes the design and implementation of a hardware-in-the-loop (HITL) and software-in-the-loop (SITL) methods using the discrete-event modeling package, OPNET modeler. The project objective is to develop a capability to evaluate performance of large and complex army communications networks and network-centric systems by combining virtual models with real networks. HITL and SITL methods have been developed that allow virtual models to communicate real IP traffic with real applications in real networks. A generic reference model for HITL and SITL use has been proposed for use in DoD systems. This paper proposes use of the HITL and SITL techniques for developmental testing for JTRS Cluster 1. Potential DoD programs that require developmental testing may be JTRS clusters, WIN-T, and FCS. The U.S. Army Information Systems Engineering Command (ISEC), Technology Integration Center (TIC), Fort Huachuca, AZ, and BAE SYSTEMS, CNIR, Reston, VA sponsored this research in the Computer Engineering Research Laboratory (CERL) at the University of Arizona.