An Investigation of Audio Communication Channel Propagation Models and Their Use in Distributed Simulation-Based Training Systems, 07-9377

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Principal Investigators
Kase J. Saylor
Gary L. Ragsdale
Jimmy R. Gaddy
Stephen R. Gray

Inclusive Dates: 01/01/03 - 12/31/03

Background - As the demand for simulation-based training systems increases, so does the demand for higher levels of realism. There are basically three different components of realism that constitute a high-quality simulation-based training system: visual realism, tactile realism, and aural realism. Many tools are available, i.e., software, computer hardware, switches, and lamps, that readily address the first two components very well, but there are only a few, expensive solutions that address the third component of realism. As a result, many simulators provide a simulated environment with a great "look and feel," but with a sub-par aural experience.

The tools that do address aural realism are generally expensive and utilize proprietary algorithms and specialized equipment. For each type of wired or wireless communication channel, a separate or modified model is utilized, and the addition of each model commonly raises the package price of the system. Furthermore, the use of proprietary equipment will "lock" a system to a certain vendor. There are some low-cost methods of providing audio communications in the simulated environment. For instance, the use of voice over IP (VoIP) is one method of providing a networked communication system. Unfortunately, VoIP does not, in and of itself, offer the robustness that is needed for aural realism. However, combining VoIP and well-designed, high-quality communication channel models offers such a solution. A tool that can create extensible communication channel models easily and uses inexpensive and nonproprietary hardware and software is an invaluable tool.

Approach - The purpose of this effort was to research and develop channel propagation models for both wired and wireless audio channels for application in simulation-based training systems. The models were designed with digital signal processing (DSP) techniques. The goal was to use commercial off-the-shelf (COTS) computer networking and audio peripherals to create an operator-in-the-loop audio system that uses high fidelity communication impairment models. The investigators have developed a design approach for constructing realistic communication channel models and implementing aural realism in a training simulator system.

Accomplishments - The project team has developed a prototype system that is capable of applying various propagation models to sampled data from multiple clients and then routing that data between clients. Routing decisions are based upon frequency subscriptions so that only clients subscribed to the same frequency can communicate with each other. The initial client software was designed in C++ in a Linux® environment, but a Java version has also been designed. The Java version allows a MS Windows® system to communicate over the audio network. The server software has been developed on a Linux system, and there are no immediate plans to port the server software to a different operating system.

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