Figure 8-2: Lora® Signal Bandwidth - Semtech LR1110 User Manual

nominal symbol rate and chip rate is the spreading factor and it represents the number of symbols sent per bit of
information.
Note that the spreading factor must be known in advance on both transmit and receive sides of the link as different
spreading factors are orthogonal to each other.
8.2.1.2 LoRa® Bandwidth (BWL)
The LoRa® modem operates at a programmable bandwidth (BWL) around a programmable central frequency fRF. The
LoRa® modem bandwidth always refers to the double side band (DSB), as shown in
An increase in signal bandwidth permits the use of a higher effective data rate, thus reducing transmission time at the
expense of reduced sensitivity.
Note: There are regulatory constraints in most countries on the permissible occupied bandwidth, therefore allowing usage
of only a subset of BWL.
8.2.1.3 Coding Rate (CR)
To further improve the robustness of the link, the LoRa® modem employs cyclic error coding to perform forward error
detection and correction. Such error coding incurs a transmission overhead.
8.2.1.4 Low Datarate Optimization (LDRO)
It increases the robustness of the LoRa® link at low effective data rates, improving the sensitivity level and increasing the
robustness towards frequency drift and Doppler events. Its use is mandated with spreading factors of 11 and 12 at 125 kHz
bandwidth, and SF12 at 250 kHz BW.
8.2.1.5 LoRa® Symbol Rate
With a knowledge of the key parameters that can be controlled by the user we define the LoRa® symbol rate as:
BWL
= ----------- -
Rs
2 SF
LR1110
User Manual Rev.1.0
UM.LR1110.W.APP March 2020
Figure 8-2: LoRa® Signal Bandwidth
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LoRa® Signal Bandwidth on page 52.
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