u-blox LARA-R2 series System Integration Manual page 21

When a GPRS connection is established, more than one slot can be used to transmit and/or more than one slot
can be used to receive. The transmitted power depends on network conditions, which set the peak current
consumption, but following the 3GPP specifications the maximum Tx RF power is reduced if more than one slot
is used to transmit, so the maximum peak of current is not as high as can be in case of a 2G single-slot call.
The multi-slot transmission power can be further reduced by configuring the actual Multi-Slot Power Reduction
profile with the dedicated AT command, AT+UDCONF=40 (see the u-blox AT Commands Manual [2]).
If the module transmits in GPRS class 12 in the 850 or 900 MHz bands, at the maximum RF power control level,
the current consumption can reach a quite high peak but lower than the one achievable in 2G single-slot mode.
This happens for 2.307 ms (width of the 4 transmit slots/bursts) with a periodicity of 4.615 ms (width of 1 frame
= 8 slots/bursts), so with a 1/2 duty cycle, according to 2G TDMA.
If the module is in GPRS connected mode in the 1800 or 1900 MHz bands, the current consumption figures are
quite less high than the one in the low bands, due to 3GPP transmitter output power specifications.
Figure 6 reports the current consumption profiles in GPRS class 12 connected mode, in the 850 or 900 MHz
bands, with 4 slots used to transmit and 1 slot used to receive.
Current [A]
2.0
1.5
1.0
0.5
0.0
RX unused TX TX
slot slot slot slot
GSM frame
4.615 ms
(1 frame = 8 slots)
Figure 6: VCC current consumption profile versus time during a 2G GPRS/EDGE multi-slot connection (4 TX slots, 1 RX slot)
In case of EDGE connections the VCC current consumption profile is very similar to the GPRS current profile, so
the image shown in Figure 6, representing the current consumption profile in GPRS class 12 connected mode, is
valid for the EDGE class 12 connected mode as well.
UBX-16010573 - R02
1600 mA
Peak current depends
on TX power and
actual antenna load
200mA
60-130mA
TX TX MON unused RX unused
slot slot slot slot slot slot
Objective Specification
LARA-R2 series - System Integration Manual
TX TX TX TX MON unused
slot slot slot slot slot slot
GSM frame
4.615 ms
(1 frame = 8 slots)
Time [ms]
System description
Page 21 of 148