LoRaWAN® Gateways: Radio Coexistence Issues and Solutions

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LoRa Alliance ® Whitepaper Page 5 of 49 LoRaWAN ® Gateways Radio Coexistence Issues and Solutions Copyright ©2021 LoRa Alliance, Inc. All rights reserved. www.lora-alliance.org Out-of-band blockers could be eliminated, or reduced, by using high-rejection filters (high-pass, low-pass, or band-pass, depending on the frequency range of the blockers) and high-linearity receivers (low-noise amplifier [LNA], switch). Out-of-band blockers close to the useful band are obviously more difficult to eliminate due to lower rejection of the RF filters. Examples of out-of-band blockers for LoRaWAN gateways include 2G/3G/4G base stations, TV transmitters, FM or digital audio broadcasting (DAB+) transmitters, radar transmitters, and others. 2.3 IN-BAND BLOCKERS In-band blockers are generally sources of low-level interference caused by other radio systems operating in the same band. As LoRaWAN operates in unlicensed bands, there are numerous radio systems operating in the band for specific or non-specific uses. Radio frequency identification (RFID) often operates in the same band and is always a source of in-band interference to be considered. In-band interference can occur on the same operating channel (co-channel), on adjacent channels, or on quite far channels, depending on the available bandwidth. The different interference may use different modulation techniques, such as narrow- band or wide-band, according to the local regulations. Here is an example of a spectrogram in the 902 – 928MHz band in North America: Figure 4: Example of in-band interference in the 902 – 928MHz band Blocking this interference is achieved by the channel filters integrated in the transceiver and demodulator. Linearity of the receiver is also important, but it has lower impact compared with out-of-band blockers. The impact on co-channels is obviously worse compared with the impact on adjacent channels and farther-removed channels.

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