LoRaWAN® Gateways: Radio Coexistence Issues and Solutions

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LoRa Alliance ® Whitepaper Page 32 of 49 LoRaWAN ® Gateways Radio Coexistence Issues and Solutions Copyright ©2021 LoRa Alliance, Inc. All rights reserved. www.lora-alliance.org Moreover, due to the very high power in the proximity (LTE BS or other) that could cause damage to the gateway, cavity filters are recommended to mitigate the risk. A cavity filter having about 40dB attenuation in the LTE UL band would ensure no damage of the gateway, even in case of poor installation. 4 COLOCATION WITH OTHER LPWAN GATEWAYS Nowadays, colocation of LPWAN gateways on a shared site is rare, but as massive Internet of Things (IoT) deployment is approaching, the probability is increasing significantly. LPWAN gateways could then share the same site or eventually could be installed on close rooftops, for instance. LPWAN gateways could be LoRaWAN gateways but also Sigfox gateways, Qowisio gateways, or any other LPWAN gateways sharing the same unlicensed band. The issue when colocating LPWAN on the same site or on a nearby site is that they use the same bands and, most of the time, the same channels. Therefore, RF filtering cannot be used to avoid interference. Of course, if gateways are configured in Rx mode only (no transmission), no issues are encountered. Issues are observed when a gateway emits on a dedicated channel, causing desensitization of the other gateways, as in-band blockers. It must be noted that in the case of colocated full-duplex LoRaWAN gateways (North America use case), there is no in-band blocking issue. This is because the US902 – 928MHz regional parameter (see [1]) defines separated bands for UL and DL frequencies as follows: • UL: 902 – 915MHz • DL: 923 – 928MHz The duplexer used to separate UL and DL bands prevents any desensitization of the receiver while transmitting. This is valid for full-duplex gateways and, therefore, for all the gateways located on the same site. However, transmit intermodulation may occur when two full-duplex gateways are transmitting at the same time. IM3 products may be generated in or outside the ISM band. According to CFR 47 FCC part 15.247, the IM3 product must be lower than - 30dBc. A 30dB isolation is therefore enough to meet this requirement. In the case of half-duplex gateways, the probability of issues is more significant. The transmitted gateway is considered as an in-band blocker for the other gateway's receivers. Different use cases must be considered depending on: • The gateway EIRP, according to the local regulation. It may vary from 16dBm EIRP to 36dBm EIRP. • The frequency separation between the DL (Tx) and the UL (Rx) channel frequencies. We may consider the following uses cases: co-channel, adjacent and alternate channels, and 2MHz offset. • The sensitivity and acceptable desensitization of the gateways. In the following table, we have considered the following typical performance:

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