PIONEERPOS AT Commands G24-LC - Manual (Page 294)

GPRS
3-230 G24-L AT Commands Reference Manual April 15, 2008
GPRS
GPRS Functionality
GSM 07.07 defines commands that a TE may use to control a GPRS ME via a non-multiplexed
character-stream interface. This places certain limitations on the functionality of the interface. For
example, it is not possible for the ME to send control information to the TE or for the TE to send
commands to the ME whilst the interface is in the online data state, unless the layer 2 protocol
itself supports this feature (GSM 07.60-12). However, G24-L-specific escape mechanism (DTR)
is provided to enable the TE to switch the G24-L into limited online command state.
The G24-L-specific escape mechanism use DTR as an escape signal (following &D parameters)
and designed for limited non network related commands. This specific mechanism purpose is to
give the user a way to retrieve the signal strength. The time limit of consecutive DTR toggles is a
minimum of 90 seconds. The G24-L-specific is not designed to support online command and data
states both at the same time, therefore any wrong or extreme usage can cause unexpected
behaviors. The basic GPRS concept is be “always connected” and there is no charge for being
connected (only per real data transferred).
GPRS Commands
This section defines commands that a terminal may use to control a GPRS ME. GPRS MTs vary
widely in functionality. A class A ME might support multiple PDP-types as well as
circuit-switched data, and use multiple external networks QoS profiles. At the other extreme, a
class C ME might support only a single PDP-type using a single external network, and rely on the
HLR to contain the PDP context definition. A comprehensive set of GPRS-specific commands is
defined below to provide the flexibility needed by the more complex ME. The commands are
designed to be expandable to accommodate new PDP types and interface protocols, merely by
defining new values for many of the parameters. Multiple contexts may be activated if the
interface link-layer protocol is able to support them. The commands use the extended information
and error message capabilities described in this specification. For MTs of intermediate
complexity, most commands have simplified forms where certain parameters may be omitted. For
the simplest MTs, and for backwards compatibility with existing communications software, it is
possible to control access to the GPRS using existing modem-compatible commands. This
"modem compatible" mode of operation is described below.