Cellular connectivity LPWA standards for IoT – debunking the myths
Arm’s mission to scale and grow the IoT ecosystem, by providing the secure architecture that underpins end-devices, puts us in a unique position in our industry as being broadly connectivity agnostic. After discussing cellular IoT at length across numerous continents and conferences with our ecosystem of partners, I’m sharing my thoughts on the most common assumptions that abound about cellular IoT today.
1) Cat-M1 and NB-IoT are struggling to gain traction and non-cellular LPWA technologies will ‘win’
Claims that Cat-M1 and NB-IoT are proving slow to be adopted, while non-cellular technologies such as Sigfox and LoRa are positioning themselves as the de facto LPWA deployment standard, require careful consideration as multiple elements are at play. Any LPWA technology – cellular-based or not, carrier deployed or enterprise deployed, must demonstrate that it can solve a real-world problem in a commercially viable manner.
The diverse nature of IoT applications imposes different demands on technology, and a ‘one technology fits all’ approach can’t deliver a cost-effective solution for all applications. The various LPWA technologies did not achieve specification maturity in unison, with NB-IoT only achieving 3GPP Release 13 specification stability in March 2017. LPWAN technologies are on different deployment and maturity cadences.
With few exceptions, the industry has invariably set overoptimistic expectations of how quickly wireless technologies are adopted, while under-forecasting the eventual volume shipments of those technologies. What has been a constant theme is that it is the open wireless standards that eventually reach commercial success, with Wi-Fi, Bluetooth and 3G tangible examples of open standards where the early hype was met with a resounding initial lack of actual commercial traction, but once the ecosystems developed and commercial uses cases became clearer, the respective successes now speak for themselves.
Whilst LoRa is enjoying early commercial traction, at GSMA’s MWC Shanghai it was clear that NB-IoT and Cat-M1 are firmly establishing themselves as key LPWA technologies. Globally, 40 carriers and 28 vendors are supporting cellular LPWA, and there are 56 active cellular LPWA pilots covering applications including meters, parking, bike sharing and security panels. There are now nine commercially live Cat-M1 or NB-IoT networks from seven major carriers globally.
2) NB-IoT is competing with Cat-M1
This is an industry example of ‘fake news’. While some commentators have been keen to create a VHS vs Betamax narrative, the two technologies possess attributes that address different use cases.
NB-IoT is suited to simple sensor node applications, where the connected ‘thing’ is typically stationary and the use case requires no more than a few 10s of bytes of data transferred intermittently throughout the day. Smart parking, smart utility meters, agricultural sensors and smart municipal lighting are use cases well suited to NB-IoT.
IoT applications requiring higher data rates, mobility or voice, such as digital signage, real-time asset tracking and alarm panels, are Cat-M1’s sweet spot. While there will always be use cases that fall into the gray area, these two technologies are complementary. To address the full spectrum of IoT applications, single mode and multimode cellular LPWA solutions together with non-cellular LPWA need to coexist.
3) Cellular LPWA solutions cannot run for 10 years on a battery
A 3GPP technical note (TR45.820) proposes a methodology to calculate battery life for Cat-M1 and NB-IoT. This makes some well-informed assumptions for receiver, transmitter standby and deep sleep power consumption for a given power amplifier and efficiency, and using a 5Whr battery.
The analysis considers the impact of three different coverage scenarios, which we can simplistically refer to as ‘Good’, ‘Typical’ and ‘Bad’ coverage, and examples of IoT applications requiring either infrequent (once daily or twice hourly) sensor data updates of 500 bytes or 200 bytes to the network. For example, a residential smart meter application would typically update the network once daily and with at most 100 bytes of data upload.
In ‘Good’ coverage and low sensor update rate use cases, the node does not need to frequently transmit, or retransmit, data. The battery life is dominated by standby and deep sleep power consumption. In these cases, a 5Whr battery life comfortably exceeding 10 years is theoretically possible for NB-IoT.
In a ‘Bad’ coverage scenario, e.g., deep indoors or at a cell edge, or if the application mandates sensor data updates every few minutes, the node’s receive and transmit power consumption will be the dominant contributors to battery life. Such repeated data transmissions may not allow for much greater than one year life of a 5Whr battery for NB-IoT.
Cellular LPWA technologies can enable battery life exceeding 10 years, but in deployment this will be a function of several variables, such as poor coverage or frequent sensor data update rates, which place similar constraints upon non-cellular technologies.
4) Cellular LPWA cannot enable sub-$5 modules
Given enough scale and volume, economies of scale can be utilized in the deployment of any technology and drive down costs. In the case of ‘traditional’ cellular M2M, 2G GPRS modules are now available for less than USD$5 – after a period of 25 years and several billion unit shipments of 2G chipsets for the silicon and module pricing to hit maturity.
However, the industry cannot wait another 25 years to start benefiting from the attributes of cellular LPWAN-connected ‘things’, so vertical integration of the LPWA module supply chain is required to deliver a revolutionary – and still profitable – step change in pricing sooner.
For the aggressive price targets for LPWAN, ‘stacking’ of silicon and module gross margins, the need for external SIM components and RF front-end passive components are all areas that the industry must collectively focus on to drive down cost. Visionaries need to step up to this challenge, and Arm is exploring how it can support innovators to achieve this goal.
IoT is about using the appropriate technology to enable viable commercial business models that solve real-world problems. There is no one-size-fits-all connectivity solution for IoT. PAN, local area network, WAN, licensed and unlicensed connectivity are complementary, so the “my connectivity technology is best” argument is not only false, it is misleading and confuses the end verticals our industry is trying to help, including utilities, agriculture, logistics, building management and insurance.
LPWA connectivity has a critical role to play in the wider context of IoT, and Arm will continue to ensure it provides secure, power-efficient processor and connectivity solutions to help enable the broader IoT ecosystem.