3GPP has recently ratified the release 13 standard, bringing two mobile communications technologies to the market for the burgeoning Internet of Things. LTE-M (Cat-M1) and Narrowband IoT (Cat-NB1) are seen as key enablers for mass deployment of IoT devices when compared to their higher-rate predecessors such as Cat-0/1.
In order to take full advantage of these new standards, however, the approach to cellular chipset development must also change. Traditionally, cellular modem development with each new cellular standard begins with a relatively generic DSP platform, often from a previous product generation. From there, developers begin to modify existing software to support the new standard, releasing new features often and making tweaks along the way as new issues are discovered. While the status quo works well for silicon vendors, the resulting solution often fails to meet expectations, one possible reason that Cat-0 failed to be widely adopted.
Instead, chipset developers need to take cues from the short-range wireless chipsets that dominate the Internet of Things today. BLE chipset developers have long understood the need to optimize for the low cost and low power demanded by the market. There are a number of techniques used, but chief among them is a greater reliance on hardware rather than software. Modern BLE chips depend upon a Hardware Defined Radio (HDR) rather than the Software Defined Radio (SDR) traditionally used in cellular, an approach with a number of advantages that conserve energy while reducing cost. First, HDR requires less memory. Many cellular chips require large amounts of memory, often implemented as a separate DRAM chip encapsulated in the chip package. This increases both cost and power consumption. Second, a hardware-based modem can run with a much slower clock rate to get equivalent performance. By implementing the modem in hardware, system clock rates can be reduced four-fold thereby significantly reducing active power. Finally, avoiding software for the physical layer allows very fast startup and shutdown times compared to the traditional SDR approach. The ability to wake up and fall asleep quickly is key to extending battery life in embedded systems.
The new Cat-M1 and Cat-NB1 standards have a great deal to offer for the Internet of Things. But in order to fully deliver on the promise, silicon vendors need to further drive down cost and power consumption with optimized solutions using techniques from related wireless technologies.
