Institute for Systems Research
Permanent URI for this communityhttp://hdl.handle.net/1903/4375
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Item Enhanced Throughput for Satellite Multicasting(1999) Friedman, Daniel E.; Ephremides, Anthony; Ephremides, A.; ISR; CSHCNFaithful information delivery in satellite multicasting requires appropriate error control. If multicast automatic-repeat-request (ARQ)is employed, a retransmission does not benefit receivers which do notrequire it, and consequently the throughput suffers greatly as thenumber of receivers increases. This performance degradation might bealleviated substantially by conducting retransmissions through terrestrialpaths from the transmitter to each receiver instead of through themulticast satellite link. By sending a retransmission directly to thereceiver(s) which requires it, higher throughput can be provided in sucha hybrid network than in a pure-satellite network. In this work,we examine the throughput improvement provided by the hybrid network.The research and scientific content in this material hasbeen accepted for presentation at the International Mobile SatelliteConference, Ottawa, June 16-18, 1999. Item A Scheme to Improve Throughput for ARQ-Protected Satellite Communication(1997) Friedman, Daniel E.; Ephremides, Anthony; ISR; CSHCNAutomatic-repeat-request (ARQ) error control is often employed to assure high fidelity information transmission. However, ARQ error control can provide poor throughput for satellite multicasting. The throughput in such communication may be improved by the combination of a terrestrial network parallel to the satellite network and a judiciously modified ARQ protocol. In particular, retransmitted ARQ frames can be sent terrestrially in such a hybrid network, allowing higher throughput than in a pure- satellite network. This work presents analytic results to establish the potential for improving the throughput of satellite multicast communication employing ARQ error control by the adoption of such a hybrid network architecture.Item The Acts Experiments program at the Center for Satellite and Hybrid Communication Networks(1997) Friedman, Daniel E.; Gupta, Sonjai K.; Zhang, C.; Ephremides, Anthony; ISR; CSHCNThis paper describes experiments conducted over ACTS and the associated T1~VSAT terminal. The experiments were motivated by the commercial potential of low-cost receive-only satellite terminals that can operate in a hybrid network environment, and by the desire to demonstrate frame relay technology over satellite networks. The first experiment tested highly adaptive methods of satellite bandwidth allocation in an integrated voice- data service environment. The second involved comparison of FEC and ARQ methods of error control for satellite communication with emphasis on the advantage that a hybrid architecture provides, especially in the case of multicasts. Finally, the third experiment demonstrated hybrid access to databases through the use of Mosaic and compared the performance of internetworking protocols for interconnecting LANs via satellite. A custom unit termed Frame Relay Access Switch (FRACS) was developed by COMSAT Laboratories for these experiments; the preparation and conduct of these experiments involved a total of twenty people from the University of Maryland, the University of Colorado, and COMSAT Laboratories, from late 1992 through 1995.Item Experiments in Hybrid Networking with the Advanced Communications Technology Satellite(1996) Friedman, Daniel E.; Gupta, Sonjai K.; Zhang, C.; Ephremides, Anthony; ISR; CSHCNThis paper describes experiments conducted over ACTS that were motivated by the commercial potential of low-cost receive-only satellite terminals operating in a hybrid network environment. The first experiment tested highly adaptive methods of satellite bandwidth allocation in an integrated voice-data service environment. The second involved comparison of FEC and ARQ methods of error control for satellite communication with emphasis on the advantage that a hybrid architecture provides especially in the case of multicasts. Finally, the third experiment demonstrated hybrid access to databases through the use of Mosaic and compared the performance of internetworking protocols for interconnecting LANs via satellite.