An ultra narrowband receiver is highly selective and can reject noise and interference which may enter the receiver outside its narrow bandwidth, enabling an acceptable signal-to-noise ratio to be achieved with a relatively weak received signal. Consequently, transmitter power levels can be low and the effective range of transmissions may be greater than would typically be the case for technologies which do not provide such selectivity. Some other radio technologies, such as direct sequence spread spectrum and chirp spread spectrum, employ alternative approaches to selectively extract signals from interference and noise. Typical UNB systems operate with a bandwidth of a few 10s to a few 100s Hz and are used for the transmission and reception of digital signals.
The use of highly selective filters in UNB receivers can provide very effective rejection of UNB signals from other UNB devices on adjacent carrier frequencies, permitting the operation of many devices in a limited geographical area.
UNB technology is often used where links from very high numbers of devices are needed, with relatively small amounts of data being exchanged on each link. Some such applications can be found in the Internet of things, with UNB being one of the technologies that have been used to implement Low-Power Wide Area Networks. . Short, infrequent transmissions with low transmit power can enable long-life, battery-powered operation of UNB devices connected in a LPWAN. 
UNB LPWAN often operate on VHF or UHF frequencies where radio signal propagation characteristics are suited to typical UNB applications with ranges of 10km or greater..They may be deployed in a shared spectrum (ISM band) 
Typical properties of UNB devices operating in the UHF spectrum below 1 GHz have been described by ETSI; whilst specific UNB-based protocols for the implementation of LPWAN have also been standardised (alongside others) by ETSI.
- Thethingsnetwork.org, https://www.thethingsnetwork.org/forum/uploads/default/original/1X/3b1c1ae4a925e9aa897110ccde10ec61f3106b87.pdf
- Understanding Radio Receiver Selectivity | Electronics Notes, Website title: Electronics-notes.com, URL: https://www.electronics-notes.com/articles/radio/radio-receiver-selectivity/basics.php
- What is DSSS | Direct Sequence Spread Spectrum, https://www.electronics-notes.com/articles/radio/dsss/what-is-direct-sequence-spread-spectrum.php
- IEEE Computer Society, (August 31, 2007). IEEE Standard 802.15.4a-2007. New York, NY: IEEE, URL: https://ieeexplore.ieee.org/document/4299496
- Anteur, Mehdi; Deslandes, Vincent; Thomas, Nathalie; Beylot, Andre-Luc (December 2015). Ultra Narrow Band Technique for Low Power Wide Area Communications. IEEE Global Communications Conference (GLOBECOM). doi:10.1109/GLOCOM.2015.7417420, URL; https://ieeexplore.ieee.org/document/7417420
- ETSI TR103 435 System Reference document (SRdoc); Short Range Devices (SRD) Technical characteristics for Ultra Narrow Band (UNB) SRDs operating in the UHF spectrum below 1 GHz https://www.etsi.org/deliver/etsi_tr/103400_103499/103435/01.01.01_60/tr_103435v010101p.pdf
- Thonet, Gilles (July 2017). "Driving the internet of things through standardization". E-Tech.
- Low Power Wide Area Networks: An Overview, Published in 2015 IEEE Global Communications Conference (GLOBECOM) https://ieeexplore.ieee.org/document/7815384/
- Fenix.tecnico.ulisboa.pt, https://fenix.tecnico.ulisboa.pt/downloadFile/1689244997257704/extended_abst.pdf
- Sub 1GHz wireless LAN propagation path loss models for urban smart grid applications, https://ieeexplore.ieee.org/iel5/6163567/6167355/06167392.pdf
- ‘Short Range Devices; Low Throughput Networks (LTN); Protocols for radio interface A’, https://www.etsi.org/deliver/etsi_ts/103300_103399/103357/01.01.01_60/ts_103357v010101p.pdf
- Itu.int, https://www.itu.int/en/ITU-R/study-groups/workshops/RWP1B-SRD-UWB-14/Presentations/International,%20regional%20and%20national%20regulation%20of%20SRDs.pdf
- ETSI TR103 435 System Reference document (SRdoc); Short Range Devices (SRD) Technical characteristics for Ultra Narrow Band (UNB) SRDs operating in the UHF spectrum below 1 GHz , https://www.etsi.org/deliver/etsi_tr/103400_103499/103435/01.01.01_60/tr_103435v010101p.pdf
- ‘Short Range Devices; Low Throughput Networks (LTN); Protocols for radio interface A’ https://www.etsi.org/deliver/etsi_ts/103300_103399/103357/01.01.01_60/ts_103357v010101p.pdf
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