LoRaWAN® Gateways: Radio Coexistence Issues and Solutions

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LoRa Alliance ® Whitepaper Page 23 of 49 LoRaWAN ® Gateways Radio Coexistence Issues and Solutions Copyright ©2021 LoRa Alliance, Inc. All rights reserved. www.lora-alliance.org Figure 22: Example of Out-of-band emissions from a CDMA800 base station in India At 867MHz the noise is ~-90dBm/125KHz, which causes about 30dB desensitization. According to the above table, about 90dB isolation are required between the BS antenna and LoRaWAN antenna. The 2- or 3-meter separation provides only 60dB maximum isolation. There is therefore a lack of 30dB isolation, explaining the 30dB desensitization. 3.4 BLOCKING OF LTE EMITTERS LTE BS transmitters act as an out-of-band blocker for the LoRaWAN receiver. The output power of the LTE BS depends on the class of the BS, according to §3.3.2, but assuming 45dB isolation between LTE antenna and LoRa antenna, the maximum LTE DL power at the LoRa RF port is +3dBm, according to §3.3.6. Considering a LoRaWAN gateway sensitivity of -140dBm, therefore the LTE rejection must be better than +3dBm - (-140dBm) = 143dB. We will consider a requirement of 150dB minimum rejection for LTE band in this section. Rejection of the in-band blockers depends on the frequency offset from the LoRaWAN channels. These following typical values are used: • 75dB at +/- 0.2MHz • 93dB at +/- 2MHz • 100dB at +/- 5MHz • 105dB at +/- 10MHz The out-of-band rejection is completed by the RF filters of the LoRaWAN gateway receiver. The cumulated rejection of these RF filters, to achieve 150dB total attenuation, must be therefore as follows:

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