Issue link: https://read.uberflip.com/i/1423190
LoRa Alliance ® Whitepaper Page 26 of 49 LoRaWAN ® Gateways Radio Coexistence Issues and Solutions Copyright ©2021 LoRa Alliance, Inc. All rights reserved. www.lora-alliance.org The level of the IM3 products depends on the level of the LTE BS signal at the input of the receiver, the attenuation of the LTE BS signal in the Rx chain, and the IIP3 of the receiver. According to the §3.4, an attenuation of 57dB (60dB) is expected from the RF filters to avoid desensitization of the LoRaWAN gateway due to LTE BS as an out-of-band blocker. Also, the maximum input power of LTE BS at the LoRaWAN gateway RF port is +3dBm, according to §3.3.6. To estimate the required IIP3 of the receiver, we can assume: • An LTE BS channel of 5MHz BW The power is therefore +3dBm -10*Log(5/0.1) = -14dBm in 100KHz BW. • IM3 products must be below -124dBm/100KHz to avoid desensitization. Considering the above assumptions, the IIP3 of the receiver must be better than - 43dBm. This calculation assumes that all the RF attenuation (57dB) is available at the antenna port, before any active part (single-pole X-throw SPxT , LNA, transceiver). Usually the RF attenuation is split in two RF filters, so the IIP3 of each active part and attenuation of each RF filter has to be carefully selected to minimize the IM3 products. If we consider no RF filtering, the required IIP3 of the receiver would be +42dBm minimum. 3.7 TRANSMIT INTERMODULATION In this section, only close LTE BS interferers are considered when mixing with a LoRaWAN transmitter. This is considered as a worst case due to the proximity with the LoRa band. Three regional use cases are detailed, depending on the LTE bands and LoRaWAN band available. Then, we are going consider and evaluate the transmit intermodulation products falling in: • LoRaWAN receive band, causing desensitization of any LPWAN gateway. The desensitization of its own LoRaWAN gateway is only possible in full- duplex configuration, as in half-duplex configuration, transmitter and receiver are not active simultaneously. • LTE UL band, causing desensitization of the colocated cellular base station • LTE DL band, causing desensitization of the LoRaWAN gateway cellular backhaul