There are winners and losers among individual technologies, as well as enterprises and industry sectors, during the ongoing global Covid-19 coronavirus pandemic, and that is the case for IoT protocols. The 5G community may be delighted that Narrowband-IoT (NB-IoT) is emphatically among the winners since that protocol is one of their own, standardized by 3GPP and operating over cellular spectrum, possibly reducing the number they will have to support or interoperate with.
A recent surge in NB-IoT was noted by Rich Cockle, global head of IoT and big data at the GSMA, in a recent blog, radiating out from China almost like the virus itself. Cockle noted that NB-IoT passed 100m connections in January worldwide and although deployments of IoT devices have inevitably slackened during the pandemic, demand for NB-IoT has held up well. This reflects its rising adoption outside China, driven significantly by MNOs. In Europe for example, Deutsche Telekom has signed NB-IoT roaming agreements with Vodafone, Telia, and Swisscom among a few others. This made 18 European countries covered by NB-IoT mobile roaming.
Cockle highlighted how NB-IoT was closing the gap on the other cellular IoT option, LTE-M, which in any case has been most concentrated in North America. Then there are also two non-cellular options, LoRAWAN and Sigfox, in the mix, as well as the short-range (and venerable) IoT protocols, Zigbee, Z-wave and Bluetooth Low Energy (BLE), plus of course WiFi. Such a dizzying array of protocols has arisen over a period of 20 years at different times in each case, with their own pros and cons, to serve distinct if sometimes overlapping use cases.
Fortunately, not all of these will survive, or at any rate thrive, in the 5G era and can safely be ignored by operators. The two foremost candidates for slow extinction are Z-wave and Zigbee, despite the latter having once been tipped by Ethernet founder Bob Metcalfe as a protocol likely to make as big an impact as his own invention. He might have remembered that Ethernet originally saw off rivals such as IBM’s Token Ring in the LAN field, and similarly there were going to be winners in the IoT space, but not necessarily Zigbee. In the event, both Zigbee and Z-wave, as predominantly indoor protocols, have suffered from the failure of universal smart home hubs supporting multiple protocols to gain much traction.
This was not for lack of early drive from the major players with Amazon, Apple and Google emerging as a big three in the smart hub field supporting four radios, including Zigbee and Z-wave alongside WiFi and Bluetooth. However, they switched focus to smart speakers as the point of consolidation of home around voice and dropped Zigbee and Z-wave support to leave just WiFi and Bluetooth. Although still used by some IoT devices and services it looks like these will not be significant players under 5G. They will certainly never be supported on mainstream devices, including smartphones.
BLE and WiFi will of course maintain their perch in mainstream devices, the former for shorter range inter-device communication and services such as audio streaming from smartphones to speakers and contact tracing, the latter for ubiquitous high capacity coverage around the premise. But the question for operators concerns those other four IoT protocols that have emerged as contenders alongside WiFi in some cases for major and emerging IoT use cases, that is LoRAWAN, Sigfox, NB-IoT and LTE-M.
Taking the two non-cellular options first, Sigfox and LoRa became the main players in the LPWAN space around five years ago but the former has been struggling to hold its position since. Technically Sigfox has merits as an ultra-narrowband radio transmission system using binary phase-shift keying (BPSK), which encodes data by varying the phase of the carrier wave. This allows use of very inexpensive receivers at the endpoint, which only have to tune into a very small amount of spectrum, but requires a more sophisticated base station to mediate that process.
However, like LoRA, Sigfox has largely failed to penetrate the lucrative US market, partly because the frequency band it had to use there, around 900 MHz, often suffers from high levels of interference. Then more generally on the commercial front, Sigfox has failed to gain revenues because its business model relies on royalties from operators selling IoT services, which as we know have been slower to gain adoption than earlier enthusiasts had hoped.
This has led to Sigfox attempting to reinvent itself as a backup system for mobile IoT services, which it announced as 0G around October 2018. Essentially conceding the primary field to the cellular options, the hope was that a low power, low cost, low bit-rate, back-up complementary network would appeal to operators and their customers.
Sigfox identified low cost as the key to opening this door and developed a $0.20 reference design, while looking at energy harvesting to power remote connected devices and improve their longevity. This has at least kept the company in the game and although LoRAWAN is in a stronger position, these two LPWAN options will be around for a while yet.
LoRAWAN also combines range coverage with low power but spans a wider spectral band, which increases susceptibility to interference but the ability to encode more data means that can be mitigated by error correction given that low latency is not a goal. It scores by enabling the base station to be cheaper than for Sigfox, because the same radio can be used both ends. The cause of LoRAWAN has also been boosted by availability of multimode chips that also incorporate other radios (see Worth Noting).
The force does now though look to be with the two cellular options and just to make matters more confusing there are several variants of each. The main distinction is that LTE-M is better performing, offering both lower latency and higher throughput, but at the cost of greater energy consumption.
LTE-M has two main variants known as Cat-M1 and Cat-M2, with the latter having higher channel bandwidth and correspondingly greater downstream data rates of 4Mbps instead of 1Mbps, while keeping complexity as low as possible.
NB-IoT has three main variants, an in-band version using spectrum allocated to LTE, a guard-band version using either reserved or unused LTE spectrum, and a standalone version using dedicated spectrum. These variants then differ little technically with the main appeal is low cost and crucially being the most robust of all the options for indoor coverage. So while initially positioned largely for static sensor applications like smart metering, it has gained ground because of that indoor factor.