Tools for Field Testing TTYs with Wireless Telephones – Version 1.2
DSPG Communication, April 5 2001
1
Overview
This document describes tools that were developed at DSPG Communications to support field
studies of TTY transmission over digital wireless telephones. They are being distributed to the
TTY Forum in the hope that they may be of some use to companies testing TTY over wireless
networks in field conditions.
The tools permit semi-automated data collection in mobile conditions. A laptop or notebook
computer is attached by USB cable to a model of TTY that consumers would typically use for
wireless telephone conversation.
Using the data collection software, Mobile TTY Test Software, the tester can launch bi-
directional scripts, which will alternate sides automatically after the GA characters. The text
passes via serial connection to the TTY and then via audio connection to the handset. Incoming
text is captured from the TTY by the laptop.
Data on call conditions can be entered into the data collection software, and these conditions
along with a time stamp are saved into a database format suitable for import to Excel or similar
software. The software separates the two sides of the conversation for separate scoring of each
side. This is done to assist in diagnosis of errors.
SCORE by Lober and Walsh (licensed for use by the TTY Forum in testing TTY over wireless
telecommunications), and CTM_SCORE (from 3GPP TS 26.231 CTM Minimum Performance
Specification) are supported; a utility program provided in the Gallaudet package runs both
scoring programs and integrates the output with data on call conditions supplied by the tester.
Wireless-to-wireline or wireless-to-wireless calls are supported, depending on the number of
modified TTYs available (two are needed for wireless-to-wireless calls).
Test scripts are provided. The scripts are intended to represent natural conversations of the type
consumers will have using TTY over wireless telephones.
The set-up is straightforward. The documentation is written in (excruciating) detail so that even
a non-engineer can do the set-up.
The most recent version of the TTY tools is available from ATIS at
http://www.atis.org/atis/atisinfo/ttsi/ttsitesting.htm. Note that this page is password protected.
Equipment
The basic set-up is depicted in the figures below.
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