Institute for Systems Research Technical Reports
Permanent URI for this collectionhttp://hdl.handle.net/1903/4376
This archive contains a collection of reports generated by the faculty and students of the Institute for Systems Research (ISR), a permanent, interdisciplinary research unit in the A. James Clark School of Engineering at the University of Maryland. ISR-based projects are conducted through partnerships with industry and government, bringing together faculty and students from multiple academic departments and colleges across the university.
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Item Integrating NASA Missions into the Internet using Commercial Satellite Constellations: Implementation of ATM-Based Cell-Relay Protocol Providing Support for Mission Integration(2000) Ramaswamy, Sreenivas; ISR; CSHCNNear-earth spacecraft are considered to be very LEO satellites. The commercial constellations to be tested range from high-density LEOs to GEOs. We have presently developed a complete baseline simulation model that uses basic algorithms for all of the test parameters. We are workingnow on developing individual test modules for each parameter, which will then be plugged onto the baseline model and evaluated for each satellitesystem. The baseline model itself will be reinforced with the Opnet ATMsuite to replace the current quasi-MAC protocol.Following the successful implementation of basic algorithms for each of these test cases (shortest path routing, hard handoff, beacon monitoring, file transfer, deterministic packet transmission, single-priority FIFO queueing), we are currently working on replacing the MAC protocol with the ATM suite. The advantages of this approach are two-fold: first, it allows usgreater flexibility in including multiple service classes, traffic types andpriority schemes. Also it creates a well-defined network/switching layer upon which TCP/IP and UDP/IP can be evaluated.
Item Delay Monitoring in ATM Networks(1999) Arora, Anubhav; Baras, John S.; Mykoniatis, George; Baras, John S.; ISR; CSHCNATM networks provide end-to-end QoS guarantees to connectionsfor their lifetime, in the form of bounds on delays, errors andlosses. Performance management involves measurement of theseparameters accurately and taking control measures if required, toimprove performance. This is very important for real time connectionsin which losses are irrecoverable and delays cause interruptions inservice. In this paper, we concentrate on delay monitoringmechanisms. After presenting the OAM standard for ATM and a fewsolutions in the literature, problems still remaining are formulatedand directions being pursued to obtain solutions are indicated.This paper was published in the Proceedings of the 3rd Annual Conferenceon Advanced Telecommunications and Information Distribution ResearchProgram (ATIRP), pp. 259-263, February 1-5, 1999, University of Maryland,University College, MD.
Item An End-to-End Measurement-Based Scheduling Architecture for ATM Networks(1999) Arora, Anubhav; Baras, John S.; Mykoniatis, George; ISR; CSHCNATM networks provide end-to-end QoS guarantees to connections for theirlifetime in the form of bounds on delay, error and/or loss. Theguarantees are important for real-time connections in which losses areirrecoverable and delays cause interruptions in service. Performancemanagement involves measurement of QoS parameters and applying controlmeasures, if required, to improve performance or resource utilization. Inthis paper, we propose a new hierarchical scheduling algorithm based ondynamic priorities which are adaptive to end-to-end QoS measurements madeon QoS sensitive (real-time) connections. This architecture can providebounds on average delay and delay variation with varying backgroundnetwork traffic.This paper has been submitted to INFOCOM 2000, Tel Aviv Israel, March 26-30, 2000.
Item Resource Allocation for Ka-Band Broadband Satellite Systems(1999) Birmani, Vineet; Baras, John S.; ISR; CSHCNForthcoming high data rate geostationary satellite systems, which are planned to work in rain affected Ka-band, would need effective resource management from a network management perspective. In this thesis we have looked at satellite power and bursting time-slots needed for the downlink channel, as satellite resources that need to be managed. Some solutions are proposed in order to tackle the above-mentioned problem.Item Architecture, Design, Simulation and Performance Evaluation for Implementing ALAX -- The ATM LAN Access Switch Integrating the IEEE 1355 Serial Bus(1997) Charleston, Giles C.; Makowski, A.; ISR; CSHCNIEEE 1355 is a serial bus standard for Heterogeneous Inter Connect (HIC) developed for "enabling high-performance, scalable, modular and parallel systems to be built with low system integration cost." However to date, few systems have been built around this standard specification. In this thesis, we propose ALAX -- an internetworking switching device based on IEEE 1355. The aim of the thesis is two-fold. First, we discuss and summarize research works leading to the architecture, design and simulation development for ALAX; we synthesize and analyze relevant data collected from the simulation experiments of the 4- port model of ALAX (i.e., 4-by-4 with four input and output queues) -- these activities were conducted during the 2-year length of the project. Secondly, we expand the original 4-by-4 size of the ALAX simulation model into 8-, 12- and 16-port models and present and interpret the outcomes. Thus, overall we establish a performance assessment of the ALAX switch, and also identify several critical design measurements to support the ALAX prototype implementation. We review progresses made in Local Area Networks (LANs) where traditional software-enabled bridges or routers are being replaced in many instances by hardware-enabled switches to enhance network performance. Within that context, ATM (Asynchronous Transfer Mode) technology emerges as an alternative for the next generation of high-speed LANs. Hence, ALAX incarnates our effective approach to build an ATM-LAN interface using a suitable switching platform. ALAX currently provides the capability to conveniently interconnect legacy Ethernet and ATM- based networks. Its distributed architecture features a multi- processor environment of T9000 transputers with parallel processing capability, a 32-by-32 way non-blocking crossbar fabric (C104 chipset) partitioned into Transport (i.e., Data) and Control planes, and many other modules interlaced with IEEE 1355- based connectors. It also employs existing and emerging protocols such as LANE (LAN Emulation), IEEE 802.3 and SNMP (Simple Network Management Protocol). We provide the component breakdown of the ALAX simulation model based on Optimized Network Engineering Tools (OPNET). The critical parameters for the study are acceptable processor speeds and queuing sizes of shared memory buffer at each switch port. The performance metric used is the end-to-end packet delay. Finally, we end the thesis with conclusive recommendations pertaining to performance and design measurement, and a brief summary of areas for further research study.Item Service Integration in Next Generation VSAT Networks(1997) Hadjitheodosiou, Michael H.; ISR; CSHCNVery Small Aperture Terminal (VSAT) satellite networks have so far been successful in the provision of specific communication services to geographically dispersed users. However, user demands are becoming more complex, and VSAT networks are expected to provide a much wider range of services (voice, data and multimedia). We investigate how this service integration could be achieved and show that performance improvements are possible if efficient multi-access protocols and speech compression with voice activity detection techniques are used. We also discuss the future role VSATs could play in the provision of access to the Integrated Broadband Communications Network to remote users. We discuss the possibility of using VSATs for ATM service provision. The need for careful consideration of the advantages and limitations of using VSAT networks for this type of service is discussed. Finally, we highlight a method for dynamic bandwidth allocation in a broadband satellite network.Item Medium Access Protocols for Interconnecting ATM and Wireless Networks(1997) Chan, Wai-Chung; Geraniotis, Evaggelos A.; ISR; CSHCNThe current trend in modern telecommunication is that most of the traffic (CBR, VBR and ABR, real-time and delay-insensitive) in the fixed broadband networks will be carried by fixed-length packets. It is desirable to extend the services to wireless networks as well. However, one major difficulty in wireless networks is the limited spectrum available. Another difficulty is that the bit error rate (BER) of the wireless channel is typically much higher than that of the channels of the wireline broadband networks. The latter problem is amplified for military wireless networks that experience substantial link interference (e.g., multipath fading, other-user interference jamming). Therefore, we can only expect that the same services are being carried in a similar fashion but with a lower source rate. In this paper, a medium access protocol for interconnecting ATM and wireless networks is discussed, followed by some alternatives, and other issues pertaining to guaranteeing low BER. This research was conducted in support of Task 1.1 of the ATIRP project during FY 96 and continues under Task 4.3 for FY 97.Item An Integrated Rapid Prototyping and Vacuum Casting System for Medical Applications(1997) Surana, Rena; ISREvaluation of products in the design stage has played a critical role in product development. Methods to build functional prototypes have been a deciding factor for designverification. As an emerging technology, rapid prototyping is revolutionizingthe process of building prototypes. However, material limitations and highcosts call for further expansion of this technology focusing on batch productionof prototypes with material options.Recognizing the challenge to produce multiple prototypes, this thesisresearch aims to integrate three state-of-the-art technologies: 3D solid modeling, rapid prototyping, and vacuum casting. A system architecture combining hardwareand computer software is designed and implemented.
The system utilizes computergraphics to construct a 3D model of an object through visualitzion. A softwaresystem, Maestro, processes a CAD file, generates support structures, and creates slice data to build prototypes by a stereolithography process. Thebuilt part serves as a master pattern for creation of a silicone rubber mold in a vacuum environment. This vacuum environment creates a material flow ratethat ensures replicas with superior quality in regards to surface finish anddimensional accuracy. This mold is then used to cast multiple replicas ofthe master pattern.
The unique contribution of this research is the application of thedeveloped system to meet a specific need in medical research - an effort torestore sight in blind individuals by implanting electordes in the visualcortex. Six replcas of a monkey skull are produced for surgeions to practicesurgical procedures. Image data obtained from CT scans of a mondkey head are successfully used to contruct a 3D solid model to fabricate a batch of six functional prototypes. The superior quality of these replicas hasoffered a unique opportunity for exploratory surgery in efforts to restoresight.
Item ATM in Hybrid Networks(1996) Baras, John S.; ISR; CSHCNA discussion of the extensions or modifications required to integrate ATM into hybrid networks, i.e. seamlessly interconnected terrestrial and space, wireline and wireless networks will be presented. In this context, the discussion will include: interoperability problems and issues, asymmetric channels, and various data rates. Several issues with proposed standards will also be addressed.A revised version of this technical report has been published in Proceedings of Design SuperCon 1996, Vol. Day One, pp. 1-1 thru 1-13, Santa Clara, CA, January 30-February 1, 1996.