Issue link: https://read.uberflip.com/i/1423190
LoRa Alliance ® Whitepaper Page 39 of 49 LoRaWAN ® Gateways Radio Coexistence Issues and Solutions Copyright ©2021 LoRa Alliance, Inc. All rights reserved. www.lora-alliance.org 6 LoRaWAN GATEWAY RADIO PERFORMANCE Knowledge of the LoRaWAN gateway performance is a prerequisite before colocating the gateway with other transmitters. The radio performance of the LoRaWAN gateway would help to understand the potential issues and the relevant solutions to prevent interference. Each gateway manufacturer may have its own proprietary architecture, but most of the architectures available in the LoRaWAN ecosystem are derived from the following Semtech Reference Designs: • Semtech Reference Design V1.0 based on SX1257 and SX1301 • Semtech Reference Design V1.5 based on SX1257, SX1301, and FPGA • Semtech Reference Design V2.0 based on AD9363, SX1301, FPGA, and DSP • Semtech SX1302CxxxGW1 – Corecell Reference Design for Gateway Applications Based on SX1302 and SX1250 The Reference Design architecture may be convenient for some installation sites, but it has some weaknesses in harsh environments, such as when colocated with high- power transmitters: • Close out-of-band signals may generate intermodulation products that could fall into the LoRaWAN unlicensed band. The level of the intermodulation products would obviously depend on the IIP3 of the receiver. • Close out-of-band signals may generate Tx intermodulation products that could fall into the LoRaWAN unlicensed band or in the LTE uplink bands, for instance, causing desensitization of the LoRaWAN gateway or cellular BS. • Tx noise generated by the PA has no, or very limited, out-of-band spurious rejection. Spurious emissions or noise could fall into the LTE uplink bands, for instance, causing desensitization of the cellular BS. • The gateway may be sensitive to lightning surges, which could damage the front-end chipsets. • Maximum input power may be limited. To fix potential issues regarding use of Semtech Reference Designs in harsh environments, a band-pass cavity filter shall be added at the antenna port. The cavity filter may be embedded in the gateway or connected outside the gateway. Also, when designing a LoRaWAN gateway, the choice of the band-pass RF filters must be carefully investigated. This is often a trade-off between contradictory requirements. The main specifications to be considered are: • Band-pass, driven by: o The usable unlicensed band according to the local regulation (country specific) o The LoRaWAN Regional Parameters that can be used for a LoRaWAN deployment in a dedicated country (see [8]) o The number of LoRaWAN channels that can be used or needed • The out-of-band rejection, driven by: o LTE UL and DL bands used in the dedicated country o Guard band between the LoRaWAN unlicensed band and LTE bands • The maximum input power, which is often neglected but must be chosen as high as possible to reinforce the robustness of the receiver