Modem and AT commands, GSM data communication

Modem and AT commands

The T300/T302 contains a complete GSM/GPRS modem. This provides data and e-mail communication, as well as Internet/intranet access, for a connected PC, PDA or handheld device. Once the PC/PDA is connected to the phone using infrared, and the appropriate software is installed, the modem in the phone works in a similar way to a PC Card modem, or an external modem.

In the T300/T302, AT commands are used for:

•controlling the data communication between the PC and the remote service

•configuring and requesting settings and behaviours in the phone, from a connected PC or PDA

GSM data communication

The built-in data capability turns the phone into a modem when connected to a PC/PDA. The T300/ T302 offers the user data connection anytime, anywhere, unmatched by fixed telephone networks. Each GSM channel is divided into eight repeating time slots. A normal GSM voice or data call is circuit switched, and only one time slot is used for each call. The data speed is therefore limited to 9,600 bps. For more information, see

“Built-in GSM data modem technical data” on page 62.

High Speed Data gives a faster speed

High Speed Data (HSCSD) increases speeds for circuit switched data by allowing the phone to use a coding scheme with a high capacity, and to use two time slots for receiving data. The download speed is increased to up to 28,800 bps. The speed for sending data is limited to 14,400 bps. The data rate can be increased several times by the use of rate adaption, interworking with ISDN. This also provides additional features, such as quick call set-up capability.

T300/T302

White Paper, August 2002

GPRS enables constant connection and high speed

With GPRS, the connection is maintained “constantly”, and data is transmitted in packets. Pricing of GPRS can be dependent on the actual use of bandwidth, which means very low cost when no data is sent or received, while the phone remains connected. When transmitting large amounts of data, bandwidth can be increased automatically to allow faster transmission speed, up to 64,200 bps download speed.

AT commands support

This section outlines the AT commands supported by the T300/T302. The information here can be of use for advanced users, to indicate the possibilities they have to:

•develop new communications software

•add the T300/T302 to an application’s list of compatible modems

•adjust the settings of their mobile tele- phone and modem

The modem in the T300/T302 supports the V.25ter command set, which is the standard communication set used by modems.

The T300/T302 is compatible with industry de facto extensions, ETSI 07.05, 07.07 and 07.10.

Overview of AT command functions

AT commands are used to configure the mobile telephone, to request information about the current configuration or operational status of the mobile phone, and to test availability and request the range of valid parameters, when applicable, for an AT command.

The built-in modem can be set to any one of three modes of operation. These are:

Off-line command mode

The command mode for entry of AT commands, when the device is first turned on.

On-line data mode

Allows “normal” operation of the built-in modem, for exchanging data or facsimiles with a remote modem.

On-line command mode

For sending AT commands to the built-in modem while remaining connected to a remote modem.