LISA-U1 series - System Integration Manual
3G.G2-HW-10002-3
Preliminary
System description
Page 27 of 125
Time
[ms]
3G frame
10 ms
(1 frame = 15 slots)
Current [mA]
170 mA
Depends
on TX
power
1 slot
666 µs
670 mA
300
200
100
0
500
400
600
700
Figure 12: VCC current consumption profile versus time during a UMTS connection, with VCC=3.8 V
When a packet data connection is established, the actual current profile depends on the amount of transmitted
packets; there might be some periods of inactivity between allocated slots where current consumption drops
about 100 mA. Alternatively, at higher data rates the transmitted power is likely to increase due to the higher
quality signal required by the network to cope with enhanced data speed.
1.5.3.3
2G and 3G cyclic idle/active mode (power saving enabled)
The power saving configuration is by default disabled, but it can be enabled using the appropriate AT command
(refer to
u-blox AT Commands Manual
[2], AT+UPSV command). When power saving is enabled, the module
automatically enters idle-mode whenever possible.
When power saving is enabled, the module is registered or attached to a network and a voice or data call is not
enabled, the module automatically enters idle-mode whenever possible, but it must periodically monitor the
paging channel of the current base station (paging block reception), in accordance to GSM system requirements.
When the module monitors the paging channel, it wakes up to active mode, to enable the reception of paging
block. In between, the module switches to idle-mode. This is known as GSM discontinuous reception (DRX).
The module processor core is activated during the paging block reception, and automatically switches its
reference clock frequency from 32 kHz to the 26 MHz used in active-mode.
The time period between two paging block receptions is defined by the network (2G or 3G). This is the paging
period parameter, fixed by the base station through broadcast channel sent to all users on the same serving cell.
In case of 2G network, the time interval between two paging block receptions can be from 470.76 ms (DRX = 2,
i.e. width of 2 GSM multiframes = 2 x 51 GSM frames = 2 x 51 x 4.615 ms) up to 2118.42 ms (DRX = 9, i.e.
width of 9 GSM multiframes = 9 x 51 frames = 9 x 51 x 4.615 ms).
In case of 3G network, the principle is similar but time interval changes from 640 ms (DRX = 6, i.e. the width of
2
6
x 3G frames = 64 x 10 ms = 640 ms) up to 5120 ms (DRX = 9, i.e. width of 2
9
x 3G frames = 512 x 10 ms =
5120 ms).
An example of a module current consumption profile is shown in Figure 13: the module is registered with the
network (2G or 3G), automatically enters idle mode and periodically wakes up to active mode to monitor the
paging channel for paging block reception.
