Written by: Svein-Egil Nielsen, CTO, Nordic Semiconductor
The market is looking strong for combined Bluetooth LE and cellular IoT (LTE-M/ NB-IoT) solutions.
A prime application bringing together short range technology using the license free ISM band with cellular using licensed spectrum is shipping containers. In that application, relatively inexpensive Bluetooth LE powered sensors could be used to monitor the condition of each item of cargo in a given container while a gateway using LTE-M (the version of cellular IoT best suited to mobile applications) could be used to track the container’s progress along the road.
Another application that would benefit from combining RF technologies is a multistorey parking lot whereby Bluetooth LE could be used to monitor spaces and guide drivers to vacant ones while a gateway using NB-IoT (the version of cellular IoT preferred where longer range and/or superior penetration of obstacles such as walls and ceilings is needed), aggregating data from many Bluetooth LE sensors could inform the remote lot owner about overall occupancy.
If the history of silicon technology teaches us anything it’s that solutions tend towards greater integration. That makes it likely that market driven demand will lead to a combined Bluetooth LE and NB- IoT/LTE-M integrated solution. It’s even possible that market pressure could lead to combined licensed/unlicensed RF spectrum LPWAN IoT wireless solutions - although I question the value of such a product. If unlicensed RF spectrum LPWAN technologies manage to survive the full scale roll-out of NB-IoT/LTE-M, there might be applications in remote parts of the world with no cellular infrastructure where it could be more commercially feasible to build an unlicensed LPWAN network. A combined LPWAN module could then typically use the cellular network but switch to unlicensed LPWAN when in that remote area. But it’s also possible the major cellular operators will build out infrastructure to even the most remote areas.
From an engineering perspective, combining cellular and unlicensed RF technology at the module level is not complicated. The bigger challenge is antenna design. Engineers can either use a single antenna (matching for multiple frequencies and sources) or use multiple antennas each dedicated to a tight range of operating frequencies. If multiple antennas are preferred, it’s important to ensure proper isolation between antenna systems to eliminate crosstalk.
Nordic has eased the challenges of combined product prototyping with the introduction of the Nordic Thingy:91. The product features Nordic’s cellular IoT solution, thenRF9160 SiP teamed with the nRF52840 short range wireless multiprotocol SoC. The nRF9160 SiP supports LTE-M and NB-IoT in the same compact package allowing designers to experiment with both versions of cellular IoT.