AT86RF230_09 ATMEL [ATMEL Corporation], AT86RF230_09 Datasheet - Page 53

• Manufacturer Part Number: AT86RF230_09
• Description: Low Power 2.4 GHz Transceiver for ZigBee, IEEE 802.15.4, 6LoWPAN, RF4CE and ISM
• Manufacturer: ATMEL [ATMEL Corporation]

8.5 Link Quality Indication (LQI)
8.5.1 Overview
8.5.2 Request an LQI Measurement
5131E-MCU Wireless-02/09
The IEEE 802.15.4 standard defines the LQI measurement as a characterization of the
strength and/or quality of a received packet. The use of the LQI result by the network or
application layer is not specified in this standard. LQI values shall be an integer ranging
from 0 to 255. The minimum and maximum LQI values (0 and 255) should be
associated with the lowest and highest quality compliant signals, respectively, and LQI
values in between should be uniformly distributed between these two limits.
The AT86RF230 determines the link quality of a radio link. The radio transceiver uses
correlation results of multiple symbols within a frame to determine the LQI value. This is
done for each received frame. The minimum frame length for a valid LQI value is two
octets PSDU. LQI values are integers ranging from 0 to 255.
The LQI values can be associated with an expected packet error rate (PER). The PER
is the ratio of erroneous received frames to the total number of received frames. A PER
of zero indicates no frame error, whereas at a PER of one no frame was received
correctly.
As an example, Figure 8-3 shows the conditional packet error rate with associated LQI
values. The values are taken from received frames of length 20 octets PSDU on
transmission channels with low multipath delay spreads. Even if the transmission
channel characteristic has higher multipath delay spread than assumed for this
example, the dependency of PER to LQI values is not affected.
Since the packet error rate is a statistical value, the PER shown in Figure 8-3 is based
on a huge number of receptions.
Figure 8-3. Conditional Packet Error Rate versus LQI
The LQI byte can be obtained after a frame has been received by the radio transceiver.
One additional byte is attached to the received frame containing the LQI value. This
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100
LQI
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AT86RF230
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