Cellular IoT Technologies – Connecting The World
While the world wide roll out of cellular 5G coverage continues to accelerate, many carriers are also experiencing tremendous growth and demand for their LTE-M and NB-IoT networks.
Both LTE-M and NB-Iot are low power, wide-area networks (LPWAN). They enable the deployment of low cost, industrial and consumer grade devices which primarily rely on network connectivity to function.
This blog post tries to explore the commonalities and differences between these two technology standards.
LTE-M (parts of which are sometimes also known as eMTC or Cat-M1) is designed for low power applications requiring medium bandwidth. The nominal throughput is 375 kbps downlink and 300 kbps uplink. On average ‘TCP/IP application throughput’ seems to come in at approximately 100 kbps.
This makes it suitable for typical TCP/TLS end-to-end secure connections. Mobility is supported, as LTE-M uses the same cell handover features as regular LTE. It is also possible to roam with LTE-M, making it suitable for applications that may operate across multiple regions.
The latency is in the millisecond range, offering the possibility of real time communication for time-critical applications. LTE-M is perfect for medium throughput applications requiring low power, low latency and/or mobility, like asset tracking, wearables, medical, POS and remote network surveillance/security applications.
NB-IoT (with a part of it also known as Cat-NB1) is a narrowband technology standard that does not use a traditional LTE physical layer.
Instead it is designed to operate in or around LTE bands and coexist with other LTE devices. It has a bandwidth of 200 kHz, giving it longer range and lower throughput compared to LTE-M and LTE. The throughput comes in at about 60 kbps for the downlink, and just 30 kbps for the uplink portion.
It is suitable for static, low power applications requiring low throughput like smart metering/agriculture/city and remote network alarming applications where the end node ‘chirps’ periodic updates to a central supervisory system.
Typically remotely deployed systems wake up at predetermined intervals (multiples of 2.048s), search for their ‘beacons’, upload any stored or collected data to the network, then remain ‘on-line’ for a short time window (8s or 20s) checking if the network might have any pending messages for the remote. If there are any pending messages, the node will download these. After downloading or the expiration of the time window (inactivity) the node will switch back to PSM (Power Saving Mode).
|Also known as||Cat-NB1||eMTC, Cat-M1|
|DOWN LINK Rate||60 kbps||375 kbps|
|UP LINK Rate||30 kbps||300 kbps|
|Max Data Rate*||250 kbps||1 Mbps|
|Bandwidth||200 kHz||1.4 GHz|
|Latency||1.5s to 10s||50ms to 150ms|
|Links||typically cyclic||typically on-demand|
|Duplex||Half Duplex||Full Duplex|
Remote Network Alarms
Remote Network Alarms
Remote Network Surveillance
* = theoretical
LTE-M and NB-IoT applications will continue to proliferate. As detailed above, we see that there are unique application spaces where each of these technologies can shine. The number of interconnected IoT nodes will continue to grow. And so will the demand for flexible cellular LPWAN connectivity options. Whenever there is a premium being placed on cost and power consumption, NB-IoT might be the better candidate, despite the lower throughput and higher latencies. If speed and real-time capabilities are required, LTE-M is the more suitable candidate.
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