CC2431 Texas Advanced Optoelectronic Solutions, CC2431 Datasheet - Page 5

• Manufacturer Part Number: CC2431
• Description: System-on-Chip for 2.4 GHz ZigBee/ IEEE 802.15.4 with Location Engine
• Manufacturer: Texas Advanced Optoelectronic Solutions

2
The Location Engine is used to estimate the
position of nodes in an ad-hoc wireless
network. Reference nodes exist with known
coordinates, typically because they are part of
an installed infrastructure. Other nodes are
blind nodes, whose coordinates need to be
estimated. These blind nodes are often mobile
and attached to assets that need to be
tracked.
The Location Engine implements a distributed
computation algorithm that uses received
signal strength indicator (RSSI) values from
known reference nodes. Performing location
calculations at the node level reduces network
traffic and communication delays otherwise
present
approach.
The Location Engine has the following main
features:
2.1 Location Engine Operation
This
required to obtain location estimates from the
Location Engine.
The Location Engine requires a set of three to
16 reference coordinates to be input together
with a set of measured parameters. The output
from the Location Engine consists of a pair of
estimated location coordinates.
Before any input data is written, the Location
Engine must be enabled by writing a 1 to the
enable bit,
Location Engine
section
in
LOCENG.EN
a
describes
centralized
. When the Location
the
CC2431 Data Sheet (Rev. 2.01) SWRS034B
basic
computation
steps
To achieve the best possible accuracy one
should use antennas that have near-isotropic
radiation characteristics. The location error
depends on signal environment, deployment
pattern of reference nodes and the density of
reference nodes in a given area. In general,
having
improves
estimation.
Engine is not in use, writing a 0 to
LOCENG.EN
consumption of the CC2431 by gating off the
Engine’s clock signal.
Figure 1 shows the basic operation of the
Location Engine.
•
•
•
•
•
3 to 16 reference nodes can be used for
the location estimation algorithm
Location estimate with readout resolution
of 0.25 meters (note: The accuracy of the
location estimate will depend on several
factors described below).
Time to estimate node location is 50 µs to
13 ms
Location range 64 x 64 meters
Runs location estimation with minimum
CPU usage
more
the
will
reference
accuracy
reduce
of
nodes
CC2431
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the
the
available
location
power