The 3GPP recently published Release 13 of the LTE standard, defining new narrowband categories of LTE for IoT: category M1, formerly known as eMTC, and category NB1, formerly known as NB-IoT. These new categories extend the market reach of LTE, enabling it to cost-effectively support lower data rate applications, including the extremely low power, sensing or monitoring devices envisioned to be everywhere in the IoT. The availability of these new LTE for IoT technologies immediately creates opportunities for IoT device makers, but the two technologies differ from each other in throughput, mobility, power, latency, and cost. What is the difference between them and which applications can each support?
Cat M1 defines a 1.4 MHz channel size and throughput of about 375 kbps uplink and 300 kbps downlink; Cat NB1 defines a very small channel size of 200 kHz and 10s of kbps of throughput. While certain applications, such as an IoT temperature sensor, will require only the smallest amount of throughput as available with Cat NB1, other applications, such a health or fitness wearable, transmitting a little more data, will need the higher throughput of Cat M1.
Connected mobility is determined by the ability of a technology to do handover between cells. Cat M1 supports handover (except in the coverage enhancement mode), but Cat NB1 does not. If your application is mobile, such as a health or fitness band or other wearable, Cat M1 is needed; if stationary, as in the case of an industrial sensor, then Cat NB1 will do.
For data transmissions above a certain level (hundreds of bytes) Cat NB1 will consume more power than Cat M1. The higher Cat M1 throughput allows devices to get to sleep faster between transmissions, thus saving power. This means that Cat NB1 is the best technology for simple sensor and metering applications, transmitting in short bursts, but that Cat M1 is the best fit for applications needing to transmit more than a few hundred bytes of data.
Can your application tolerate latency? With Cat M1 latency is similar to the latency in a typical Cat 1 deployment, approximately 10-15 milliseconds, but with Cat NB1, latency is greater and can range from 1.4 seconds to as much as 10 seconds in some deployment scenarios. For sensor and metering applications this is not an issue and Cat NB1 is suitable, but for latency intolerant applications such as warning or alarm systems, Cat M1 is needed.
Cat M1 supports VoLTE while Cat NB1 does not. Certain IoT applications benefit from VoLTE capability, including alarm panels and personal safety devices, indicating Cat M1 is required.
Cat M1 enables LTE module cost to equal today’s 2G module cost; Cat NB1 is expected to be approximately 10 percent less expensive than Cat M1.
The massive IoT will connect billions of objects with devices of every possible configuration and capability. The new LTE for IoT categories, M1 and NB1, along with the existing Cat 1 and higher technologies already deployed, ensure that there is an all-encompassing and cost-effective LTE platform for any deployment scenario. No other low power wide area technology offers the scalability, security, and longevity of LTE.