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2.4
E-OTD
2.4.1
Overview
Carriers and handset manufacturers recognize E-OTD as the most desirable method for providing location information for GSM
systems. E-OTD utilizes a TDMA-based infrastructure to determine the location of the caller. The difference in arrival times of
signals coming from multiple cell towers is measured and the location data is derived using triangulation.
2.4.2
Features and Benefits
In 1996 the FCC announced plans to require all E911 calls made from mobile phones to report Automatic Location Information
(ALI) for the purpose of locating the caller in case of emergency. Several methods have been identified to meet the FCC
requirements, each with advantages and disadvantages. Enhanced Observed Time Difference (E-OTD) is one of these methods.
E911 is a mandatory requirement in North America for voice handsets. It is not a mandatory requirement for data terminals.
The g20 supports the E-OTD method.
2.4.3
Technical Description
All measurements are made using hardware that already exists in the g20. There is no need for the terminal software to
implement anything. Mechanisms located in both the network and the g20 run measurements and calculation of the location.
2.5
MUX INTEGRATION
2.5.1
Overview
The g20 is supplied with an internal GSM 07.10 protocol stack, also referred to as a multiplexer or MUX.
The g20 with multiplexer support utility provides the following capabilities:
• Provides the terminal with two virtual channels on one physical RS-232 connection.
• Provides simultaneous data (CSD/GPRS) and command (AT command set) services. In this way, two applications can use
a single RS232 line via virtual channels. This enables a user to make network and phone service inquiries and maintain data
communication at the same time.
98-08901C68-O
Product Features
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