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LoRaWAN® Gateways: Radio Coexistence Issues and Solutions

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LoRa Alliance ® Whitepaper Page 45 of 49 LoRaWAN ® Gateways Radio Coexistence Issues and Solutions Copyright ©2021 LoRa Alliance, Inc. All rights reserved. www.lora-alliance.org 1 2 3 4 Figure 30: Recommended GNSS active antenna block diagram 9 GATEWAY CELLULAR BACKHAUL The outdoor LoRaWAN gateways usually embed a cellular 3G or 4G modem for backhauling. The global market trend is a cellular modem to support a maximum of LTE bands to reach worldwide coverage. The performance of this cellular modem inside the gateway is obviously critical, as the backhauling must be reliable to ensure connectivity with the network server. The cellular modem is also subject to environmental interference. In case of colocation with LTE BS, the main causes of desensitization are: • The LoRaWAN transmitter of the gateway, which may: o Generate out-of-band spurious emissions in the LTE DL band o Act as an out-of-band blocker for the LTE UE receiver • The LTE BS transmitter (LTE BS DL), which may: o Generate out-of-band spurious emissions in the LTE DL band o Act as an out-of-band blocker for the LTE UE receiver o Generate intermodulation products in the LTE UE receiver • Any other high-power emitter (DVB-T/T2 or other), which may: o Generate out-of-band spurious emissions in the LTE DL band o Act as an out-of-band blocker for the LTE UE receiver The outdoor LoRaWAN gateways, therefore, embed at least two modems: a cellular modem and a LoRaWAN modem. Each one is connected to its own dedicated antenna. These antennas could be designed based on different technologies and are separated by a defined distance, leading to a certain isolation or mutual coupling between both antennas. Mutual desensitization may occur due to either out-of-band blocking effect or out-of- band spurious emissions generated in the receive bands. The blocking effects are usually not the major concern, as both the cellular receiver and the LoRaWAN receiver have enough out-of-band rejection for that purpose. The main concern is essentially out-of-band spurious emissions. Considering the out- of-band spurious emissions generated by a LoRaWAN gateway (see §3.5), about 40dB to 50dB isolation between antennas is required.

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