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Solid Design & Test Strategy Solves IoT Connectivity Challenges


Although the number one struggle for designers of IoT devices is connectivity, you can avoid many challenges by using an informed design and test strategy.


A recent survey of nearly 600 designers interested in IoT design showed that their number one struggle they have is with connectivity. That doesn’t mean security isn’t a concern, it just may not be as troublesome to implement, once they get around to it.


As the recent call-to-action by Arm Technology’s CEO Simon Segars indicates, security is in large part a matter of everyone agreeing to do it in the first place. This idea led to his introduction of a Security Manifesto and the concept of a Digital Social Contract to help align the industry toward a common good, for users and for the IoT to progress to 1 trillion devices.


Getting to an acceptable baseline level of security is necessary and hard, but doable, with some attention up front and the willingness to do it. So why do designers struggle with connectivity? And how can that struggle be mitigated? The answer is a better appreciation and understanding of RF design and test.


James Park, the founder of Fitbit, mentioned how the design of the original Fitbit got delayed for many months ecause the team determined they could design the RF portion themselves. They might have gotten it, eventually, but after three months, they gave in and asked for outside help. Apparently it boiled down to interference between the RF (Bluetooth) and digital circuitry that was solved with a revised layout. They got outside help, and the rest is history.


However, the problem remains: designing is fun, until testing begins, then the rubber hits the proverbial road. Software debug takes increasingly larger portions of design and development time, which puts pressure on test. However, giving short shrift to test, especially with respect to RF, can result in last-minute problems that can kill a production schedule.


Solving for connectivity design and test best practices


In his years at Rohde & Schwarz, Ak Emarievbe, co-founder and CEO of Belvor Technical Resources, has seen the problems designers get into on a daily basis. 


“The first thing designers need is to understand are the needs of the device and application ranging from power requirements, coverage, data rates, mobility, delay time and then choose carefully from the many wireless options.” 


These range from Bluetooth, Zigbee and Wi-Fi, to LoRaWAN and Sigfox for unlicensed-band wide-area coverage and NB-IoT and LTE Cat M1 for licensed-band operation, also for wide-area IoT coverage. 


The right radio access technology as well as RF design will ensure power consumption is minimized, and that there isn’t unnecessary RF power output, while ensuring the device is operable in all the target markets.


This latter point is critical, as many designers ultimately hope for high-volume, global market acceptance, and success. This affects not only the type of interface, but also how it designed in. The temptation may be to go with a chip-on-board design, especially where space is tight however it allows for flexibility with the design, but as Emarievbe points out, that slows down a design and increases overall cost of testing where a module might have been a better choice. Choosing which way to go requires analysis of the design’s form factor requirements, expected volumes and time to test. A module will invariably have been tested to the required standard (such as Bluetooth) and also in most cases might have been certified by regulatory agencies, such as FCC (the United States Federal Communications Commission) or ETSI (European Telecommunications Standards Institute), for regulatory compliance.


“Often that’s not enough,” said Emarievbe. “Designs need to meet carriers’ [wireless operators] network requirements too.”