The arrival of Long Term Evolution (LTE) has brought with it several options for IoT connectivity, thanks to the 4G protocol’s more efficient use of RF spectrum. The first to arrive was Cat-M, which supports 1Mb/s datarates for both the uplink and downlink using half-duplex communication. Cat-M also provide energy-saving enhancements. Compared to the core LTE protocol used by mobile phones, Cat-M can operate with fewer updates from the base station. The frequency of updates can be reduced to the point where the sensor node only has to wake up every ten minutes or so, which can greatly preserve battery life for devices that monitor slow-changing conditions, such as soil moisture.
Narrowband-IoT (NB-IoT) provides further enhancements to energy efficiency. NB-IoT uses a much narrower transmission band than full LTE:1.4 MHz rather than 20 MHz. This is accompanied by a reduction in transmit power to further improve battery life. In an ongoing process of enhancements, Release 14 of the LTE standard by 3GPP, has further improved efficiency by supporting techniques to allow nodes to disconnect rapidly after a transmission to reduce leakage power. Datarates of 50 kb/s on the downlink and 20 kb/s on the uplink are possible, extending to 50 kb/s if multi-tone signalling is employed for the uplink.
Thanks to the rich selection of protocols suitable for IoT use, whether operating in a short-range or wide-range scenario, developers and integrators can be sure to find one that fits the application. Independent module suppliers such as Murata can advise on which makes sense for each situation and provide solutions based on the best available silicon on the market.
About the Authors
Samir Hennaoui hold the title of Product Manager LPWA at Murata Europe and Rui Ramalho is the Product Manager for WLAN/BT at Murata Europe.