NC State University

Department of Computer Science Colloquia 2000-2001

Date: Monday, March 5, 2001
Time:   1:15 P.M. (Talk) <========= NOTE!!
Place: Withers 402-A, NCSU Historical Campus (click for courtesy parking request)

Speaker: David Thuente, Computer Science, Indiana University - Purdue University Fort Wayne

Modeling and Simulation of Data Link Layer Protocols for Radios

Abstract:  Modeling and simulation are critical tools for the design of communication systems and protocols.  MIL-STD-188-220B is an evolving family of data link layer protocols designed for narrow band radio communication. Type 2 services are connection oriented with decoupled acknowledgments based on HDLC protocols.  Type 4 services are connectionless with individual decoupled acknowledgments for every packet received. The two most visible and perhaps viable MAC algorithms from MIL-STD-188-220B are deterministic adaptable priority network access delay (DAP-NAD) and radio embedded network access delay (RE-NAD) and its extensions.  Comparative studies for Type 2 and Type 4 on data only networks were done using DAP-NAD and RE-NAD with the results indicating when Type 2 is most advantageous.  DAP-NAD was extended to include voice and the simulations were run comparing it with RE-NAD optimized for voice.  A number of extensions and modifications to DAP-NAD, including efficient integration of data and voice, are presented. The implicit token passing scheme is modified so that the token effectively jumps over stations that may have transmitted in the last period and allows heavily used nodes or "higher priority nodes" to have increased transmission opportunities. These modifications are shown to have markedly improved performance for the standard Tactical Internet Division and Below (TIDB) network used to compare other MAC algorithms as well as on 16 node randomly loaded networks. The modifications to DAP-NAD presented have further enhanced its ability to efficiently handle both data and voice which is recognized by calling the MAC algorithm: Data and Voice Network Access Delay (DAV-NAD).  Finally, some open research problems are discussed.

Host: A. Tharp, Computer Science, NCSU

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