SIM5218E Hardware Design
SIM5218E_ Hardware Design_V1.06
2012.09.21
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measurements and available network data back to the location server, the mobile calculates the
location on the handset and passes the result to the requesting entity.
In standalone (autonomous) mode, the handset demodulates the data directly from the GPS
satellites. This mode has some reduced cold-start sensitivity, and a longer time to first fix as
compared to the assisted modes. However, it requires no server interaction and works out of
network coverage.
This combination of GPS measurements and available network information provides:
■
High-sensitivity solution that works in all terrains: indoor, outdoor, urban, and rural
■
High availability that is enabled by using both satellite and network information
Therefore, while network solutions typically perform poorly in rural areas and areas of poor cell
geometry/density, and while unassisted, GPS-only solutions typically perform poorly indoors. The
SIM5218E GPS solution provides optimal time to fix, accuracy, sensitivity, availability, and
reduced network utilization in both of these environments, depending on the given condition.
The SIM5218E GPS solution in assisted modes provides cold-start GPS sensitivity that is an
approximately 20 to 30 dB improvement over unassisted, conventional GPS receivers.
Compared to network solutions that require equipment at each cell site, the SIM5218E GPS
solution integrates a complete GPS receiver in every module. This means that each handset is
capable of positioning location without requiring expensive cell site equipment. This solution not
only can be used to help operators address the FCC E911 mandate in the United States (and
mandates planned for other countries), but also provides a ubiquitous platform for location-based
applications, since SIM5218E GPS technologies will also enable consumer-priced,
position-capable handsets for location-based services worldwide.
3.18.2 Using GPS by NMEA port
SIM5218E uses GPS by NMEA port. User can select NMEA output over the UART or USB by
configuration. Output of NMEA sentences is automatic; no control via at commands is provided.
Supported NMEA sentences include GSV, GGA, RMC, GSA, and VTG.
Before using GPS, we should configure SIM5218E to be in properly operating type by AT
command. Please refer to related document for detailed information.
SIM5218E can get position location information through AT command directly, it’s unnecessary to
decode the NMEA code.
3.18.3 Technical data
Tracking sensitivity -156 dBm
Acquisition sensitivity -145 dBm
Accuracy <1.5m (CEP50)
TTFF (Open Sky) Hot start <1s
