| Summary: | Communication protocols consists of a set of distributed algorithms which allow two or
more communicating entities to exchange information. Typically, these protocols represent one
of the seven layers in the Open Systems Interconnection (OSI) Reference Model. Traditionally,
protocols approved by international standards organizations, such as the ISO or CCITf, have
been defined by a combination of English prose, state tables, and state diagrams. These informal
methods, although useful, are imprecise and can lead to ambiguities. Using Estelle, a formal
description technique (FDT), protocol specifications can be made clear and free from any
ambiguities and provide a standardized manner in which to document protocol operations. Formal
methods also provide a foundation for performing protocol validation and implementation, and
evaluating protocol efficiency.
A brief summary of Estelle constructs and its application in modelling communication
protocol elements is presented, and a data link layer protocol, representing layer two of the
OSI model, is introduced. This protocol is based on a Type-IT Hybrid ARQ scheme and was
designed to provide reliable communications in a mobile radio environment. The mobile data
link protocol (MDLP) is formally specified using Estelle. In addition, the MDLP specification is
tested for conformance to the informal prose description. Finally, the operation of the MDLP is
simulated and a throughput evaluation is performed using a statistical channel model. Moreover,
for comparison purposes, throughput results are also obtained for a selective repeat ARQ scheme.
The protocol design, testing, and simulation was performed using the Estelle Development
Toolset (EDT). === Applied Science, Faculty of === Electrical and Computer Engineering, Department of === Graduate
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