SARA-R4 series - System integration manual
UBX-16029218 - R20
System description
Page 23 of 128
C1-Public
1.5.1.2
VCC current consumption in LTE connected mode
During an LTE connection, the SARA-R4 series modules transmit and receive in half duplex mode.
The current consumption depends on output RF power, which is always regulated by the network (the
current base station) sending power control commands to the module. These power control
commands are logically divided into a slot of 0.5 ms (time length of one Resource Block), thus the rate
of power change can reach a maximum rate of 2 kHz.
shows an example of SARA-R4 series
modules’ current consumption profile versus time in
connected mode: transmission is enabled for one sub-frame (1 ms) according to LTE Category M1
half-duplex connected mode.
Detailed current consumption values can be found in the SARA-R4 series data sheet
Time
[ms]
Current [mA]
0
300
200
100
500
400
Current consumption value
depends on TX power and
actual antenna load
1 Slot
1 Resource Block
(0.5 ms)
1 LTE Radio Frame
(10 ms)
1 Slot
1 Resource Block
(0.5 ms)
1 LTE Radio Frame
(10 ms)
Figure 7: VCC current consumption profile versus time during LTE Cat M1 half-duplex connection
1.5.1.3
VCC current consumption in 2G connected mode
When a 2G call is established, the
VCC
consumption is determined by the current consumption profile
typical of the 2G transmitting and receiving bursts.
The current consumption peak during a transmission slot is strictly dependent on the transmitted
power, which is regulated by the network. The transmitted power in the transmit slot is also the more
relevant factor for determining the average current consumption.
If the module is transmitting in 2G single-slot mode in the 850 or 900 MHz bands at the maximum RF
power control level (approximately 2 W or 33 dBm in the Tx slot/burst), then the current consumption
can reach a high peak / pulse (see the SARA-R4 series data sheet
for 576.9
µ
s (width of the
transmit slot/burst) with a periodicity of 4.615 ms (width of 1 frame = 8 slots/burst), that is, with a
1/8 duty cycle according to GSM TDMA (Time Division Multiple Access).
If the module is transmitting in 2G single-slot mode in the 1800 or 1900 MHz bands, the current
consumption figures are much lower than during transmission in the low bands, due to the 3GPP
transmitter output power specifications.
During a 2G call, current consumption is not significantly high while receiving or in monitor bursts, and
it is low in the bursts unused to transmit / receive.
