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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1997 - 19982

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Author: search.filters.author.Corson, M. ScottSubject: search.filters.subject.channel access

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    An Evolutionary-TDMA Scheduling Protocol (E-TDMA) for Mobile Ad Hoc Networks
    (1998) Zhu, C.; Corson, M. Scott; Corson, M. Scott; ISR; CSHCN
    A new single channel, time division multiple access (TDMA) schedulingprotocol, termed "Evolutionary-TDMA", is presented for mobile ad hocnetworks. The protocol allows nodes in an ad hoc network to reserveconflict-free TDMA slots for transmission to their neighbors. Two topology-dependent schedules are generated and maintained simultaneously. One is a broadcast schedule inwhich every node has one slot to transmit to all its neighbors. The other isa flexible schedule in which a node can reserve multiple slotsfor transmission of unicast, multicast and broadcast traffic. The schedules are reasonably bandwidth efficient and are frequently updated in an evolutionary manner to maintain conflict-free transmissions. The protocol executes across the entire network simultaneously in a fully distributed and parallel fashion. To react quickly to changing topology and bandwidth demands and to keep overhead low,participating nodes need only coordinate with their one-hop neighbors.Traffic prioritization and Quality of Service (QoS) can be supported with this protocol. Its performance, in terms of both scheduling quality and scheduling overhead, is insensitive to network size. Thus,it is a scalable protocol suitable for very large networks, and networks of varying size.
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    A Five-Phase Reservation Protocol (FPRP) for Mobile Ad Hoc Networks
    (1997) Zhu, Chenxi; Corson, M. Scott; ISR; CSHCN
    A new single channel, TDMA-based broadcast scheduling protocol, termed the Five-Phase Reservation Protocol (FPRP), is presented for mobile ad hoc networks. The protocol jointly and simultaneously performs the tasks of channel access and node broadcast scheduling. The protocol allows nodes to make reservations within TDMA broadcast schedules. It employs a contention-based mechanism with which nodes compete with each other to acquire the TDMA slots. The FPRP is free of the ``hidden terminal" problem, and is designed such that reservations can be made quickly and efficiently with minimal probability of conflict. It is fully distributed and parallel (a reservation is made through a localized conversation between nodes in a 2-hop neighborhood), and is thus arbitrarily scalable. A ``multihop ALOHA" policy is developed to support the FPRP. This policy uses a multihop, pseudo-Baysian algorithm to calculate contention probabilities and enable faster convergence of the reservation procedure. The performance of the protocol is studied via simulation, and the node coloring process is seen to be as effective as an existing centralized approach. Some future work and applications are also discussed.