Issue link: https://read.uberflip.com/i/1423190
LoRa Alliance ® Whitepaper Page 46 of 49 LoRaWAN ® Gateways Radio Coexistence Issues and Solutions Copyright ©2021 LoRa Alliance, Inc. All rights reserved. www.lora-alliance.org Distance between antennas is a key factor for antenna isolation. Obviously, this is less critical for an outdoor LoRaWAN gateway, because the gateways are generally based on large or medium-size enclosures. It is then naturally possible to optimize the antenna isolation when placing the antenna at a sufficient distance or even by deporting the antennas using coaxial cable and antenna brackets. However, even for outdoor LoRaWAN gateways, if no special care is taken during the design phase, isolation may be not enough. Moreover, the colocation of the LoRaWAN gateways and LTE BS may cause some coexistence issues in the LTE UE module receiver, such as: • High LTE BS power at backhaul RF port that may damage the cellular modem. RF power limiters may be recommended to mitigate this risk. • Blocking due to LTE BS transmitter • Intermodulation of LTE BS transmitter in the UE receive band It must be noted that the LTE BS classes define also the minimum coupling between the BS and the UE: • Wide-area BS: minimum coupling loss equal to 70dB • Medium-range BS: minimum coupling loss equal to 53dB • Local-area BS: minimum coupling loss equal to 45dB About 40 – 50dB isolation can be obtained between the LTE BS antenna port and LoRaWAN gateway LTE port. Therefore, adding an attenuator at the gateway LTE RF port is recommended to increase the coupling loss and mitigate desensitization. The recommended value of the attenuator is provided in this table: Attenuator to Be Added at Gateway LTE Port Wide-area Base Stations Medium-range Base Stations Local-area Base Stations N/A N/A N/A N/A N/A N/A 30dB 10dB or deported antenna None 30dB 10dB or deported antenna None 30dB 10dB or deported antenna None