TOBY-L2 and MPCI-L2 series - System Integration Manual
UBX-13004618 - R28
System description
Page 23 of 164
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
). This command is not supported by “00” and “60” product versions.
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.
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.
Time [ms]
RX
slot
unused
slot
TX
slot
TX
slot
TX
slot
TX
slot
MON
slot
unused
slot
RX
slot
unused
slot
TX
slot
TX
slot
TX
slot
TX
slot
MON
slot
unused
slot
GSM frame
4.615 ms
(1 frame = 8 slots)
Current [A]
200mA
60-130mA
Peak current depends
on TX power and
actual antenna load
GSM frame
4.615 ms
(1 frame = 8 slots)
1600 mA
0.0
1.5
1.0
0.5
2.0
2.5
Figure 6: VCC or 3.3Vaux current consumption profile 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
, representing the current consumption profile in GPRS class
12 connected mode, is valid for the EDGE class 12 connected mode as well.
