LISA-U2 series - System Integration Manual
UBX-13001118 - R19
Early Production Information
Features description
Page 144 of 175
3.9
AssistNow clients and GNSS integration
For customers using u-blox GNSS receivers, LISA-U2 cellular modules feature embedded AssistNow clients.
AssistNow A-GPS provides better GNSS performance and faster Time-To-First-Fix. The clients can be enabled and
disabled with an AT command (see the
u-blox AT Commands Manual
LISA-U2 modules act as a stand-alone AssistNow client, making AssistNow available with no additional
requirements for resources or software integration on an external host micro controller. Full access to u-blox
GNSS receivers is available via the LISA-U2 series, through a dedicated DDC (I
2
C) interface, while the available
GPIOs can handle the positioning chipset / module power-on/off. This means that GSM/WCDMA and GNSS can
be controlled through a single serial port from any host processor.
3.10
Hybrid positioning and CellLocate
®
Although GNSS is a widespread technology, its reliance on the visibility of extremely weak GNSS satellite signals
means that positioning is not always possible. Especially difficult environments for GNSS are indoors, in enclosed
or underground parking garages, as well as in urban canyons where GNSS signals are blocked or jammed by
multipath interference. The situation can be improved by augmenting GNSS receiver data with cellular network
information to provide positioning information even when GNSS reception is degraded or absent. This additional
information can benefit numerous applications.
3.10.1
Positioning through cellular information: CellLocate
®
u-blox CellLocate
®
enables the estimation of device position based on the parameters of the mobile network cells
visible to the specific device. To estimate its position the u-blox cellular module sends the CellLocate
®
server the
parameters of network cells visible to it using a UDP connection. In return the server provides the estimated
position based on the CellLocate
®
database. The u-blox cellular module can either send the parameters of the
visible home network cells only (normal scan) or the parameters of all surrounding cells of all mobile operators
(deep scan).
Normal scan is only possible in 2G mode.
The CellLocate
®
database is compiled from the position of devices which observed, in the past, a specific cell or
set of cells (historical observations) as follows:
1.
Several devices reported their position to the CellLocate
®
server when observing a specific cell (the As in the
picture represent the position of the devices which observed the same cell A)