LoRaWAN® Gateways: Radio Coexistence Issues and Solutions

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LoRa Alliance ® Whitepaper Page 40 of 49 LoRaWAN ® Gateways Radio Coexistence Issues and Solutions Copyright ©2021 LoRa Alliance, Inc. All rights reserved. www.lora-alliance.org Increasing RF filter bandwidth leads to lower rejection of the close LTE bands, and therefore the gateway's immunity is degraded. Increasing the RF filter rejection increases the insertion losses of the RF filters, and the bandwidth may be sacrificed to get the expected immunity. Cavity filters offer the best option for RF filters, as this is the ideal trade-off between maximum input power, out-of-band rejection, insertion losses, and largest bandwidth. See more details in [11]. 7 CAVITY FILTERS 7.1 MAIN REQUIREMENTS Previous chapters demonstrated that cavity filters are required when colocating LoRaWAN gateways with high-power emitters. Cavity filters improve performance of the LoRaWAN gateways regarding: • Out-of-band blockers • Transmit intermodulation • Intermodulation of LTE BS emitters in the LoRaWAN receiver • Out-of-band spurious emissions generated by the LoRaWAN transmitter • Out-of-band maximum input power However, cavity filters do not improve performance of the gateways regarding: • In-band blockers • Linearity of the receiver • In-band maximum input power • Out-of-band spurious emissions generated by other transmitters in the unlicensed band When selecting a cavity filter, the gateway manufacturer or must consider: - The usable unlicensed band for LoRaWAN - The Regional Parameters to be used for LoRaWAN - The cellular (LTE) bands colocated with the LoRaWAN gateway - Guard band between unlicensed band (LoRaWAN) and LTE DL bands - Attenuation of the main interfering bands (the colocation issues to be solved) - Outdoor or indoor (embedded) versions depending on the gateways - Typical insertion losses to evaluate impact on the budget link - Dimensions - Weight - Connectors type - Operating temperature range The following table summarizes the main common characteristics of cavity filters when using an unlicensed band in the 860 – 928MHz range (EMEA, North America, LATAM, and APAC zones):

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