Connect the Dots: When in Doubt, Get Both NB-IoT and LTE-M

Create: 09/05/2017 - 14:53

Sometimes it’s hard to decide which way to go in your IoT deployments, especially when picking between Narrowband-IoT (NB-IoT) and LTE-M for a low-power wide area network (LPWAN). These decisions have long-term impact so it’s quite a risky business, which makes Sierra Wireless’s offering of a module that does both, while adding global navigation satellite system (GNSS) capability, so interesting.

NB-IoT (Cat-NB1) and LTE-M (Cat-M1) arrive in 3GPP’s Release 13 to help address the need for ultra-low-power, low-data-rate communications over relatively long ranges to enable fast, low-cost IoT deployments using already installed cellular networks. Due to bands of operation, LTE-M is U.S. centric, for now, while NB-IoT was initially more centered on Asia and Europe.

The two have many differences in respect to data rates, latency and bandwidth (Figure 1).

IoT connectivity options

Figure 1: NB-IoT and LTE-M differ in many respects, but what stands out here is LTE-M1’s full-duplex support, vs. NB-IoT’s half duplex. (Image source: Wikipedia, from data compiled from the 3GPP)

Additionally, there are two big differences to note. The first is sluggish support for NB-IoT: Deutsche Telecom is so far the only major operator to commit to it. The second difference may be part of the reason LTE-M has so much more support, and rightfully so. LTE-M supports two-way, simultaneous (full duplex) communication, NB-IoT is half duplex, so it communicates in one direction at a time.

For anyone who has deployed an IoT device or node, being able to send a critical update in a timely fashion, or have a node act quickly to a changing situation, can be important. Still, each standard has its place and relative advantages, which is why IoT solution providers may want to use chips that support both in their systems, just in case. The added cost of a dual-support integrated circuit (IC) is a lot less than ripping out a deployed node.

Sierra Wireless’s AirPrime WP Series Adds GNSS

Dual support of NB-IoT and LTE-M on the new Sierra Wireless AirPrime WP77 smart wireless modules is good, but Sierra Wireless also sweetened the deal with the inclusion of GNSS for tracking and location-based services (Figure 2). It also has Wi-Fi and Bluetooth connectivity support.

Sierra Wireless IoT deployments

Figure 2. The AirPrime WP Series supports both NB-IoT and LTE-M, with GNSS support. (Image source: Sierra Wireless)

Stepping back, the WP series is designed for secure telematics and gateway applications, so the added cost of an IC that supports both NB-IoT and LTE-M, while important, is not as much a factor as it would be on a deployed sensor node, so it makes sense to include the flexibility. This feature is critically important when a device is distributed globally: no one wants to support geo-specific system SKUs unless absolutely necessary.

The series has a dedicated CPU core running the Linux-based Legato application framework, measures 23 x 22 millimeters, supports various low-power modes and has a long list of interfaces to other sensors and companion chips.

The AirVantage IoT Platform (on top of Figure 2) is a complete deployment platform, supporting connectivity management, application enablement and device management.

Next Up: Four LPWAN Radios, Instead of Two?

While it’s exciting to see NB-IoT and LTE-M supported on a single chip, odds are high that the IC design began long before two trends became clear: support for NB-IoT was waning, and operators are hedging their bets by supporting licensed (cellular) and unlicensed options, such as LoRaWAN and Sigfox, for IoT deployments. For example, Orange and SK Telecom are using LTE-M and LoRaWAN.

Now we have a situation where it may be wise to ask IC vendors to support four radios, instead of two, or at least ask for a modular approach, to accommodate last-minute strategy tweaks.

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Patrick Mannion
Patrick Mannion is an independent writer and content consultant who has been working in, studying, and writing about engineering and technology for over 25 years.

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