mmWave is ISAC’s Achilles Heel, unless you’re paying attention

Last month, I penned a post on Integrated Sensing and Comms (ISAC), looking at the diverse reasons people are paying attention to the tech – beyond just the search for a truly novel 6G use case. To be honest, I was a little saddened that nobody remarked on my brilliant choice of bullet emojis (sensing + red balloons…where are my Nena fans?). But when the good folks at Telecom TV flagged the post last week, I was reminded that it was meant to be the first of a series. And, so, the show must go on.  

A key objective of my last post was to walk back the narrative that ISAC is “dead on arrival.” A big part of that narrative is based on the notion that ISAC requires the use of mmWave spectrum in order to be useful. 

The argument for mmWave as an ISAC pre-requisite is relatively straightforward; mmWave frequencies are big on bandwidth and short on wavelength, contributing to better high-resolution sensing. The view that a dependence on mmWave spectrum will hold ISAC back is just as straightforward; even where mmWave spectrum is available for 5G, deployments have been limited given the rollout costs vs. coverage constraints vs. the marginal (albeit growing) availability of mmWave-capable devices. 

None of this is up for debate. That said, it does ignore some important realities. 

• mmWave inevitability. Your circa 2026 5G phone might not support mmWave bands. That’s okay because your operator likely doesn’t support them…yet. As mobile traffic demands grow, however, this becomes increasingly untenable.
• mmWave necessity. Maybe you don’t think mobile traffic will continue its upward trajectory. Heck, you might even believe in Bigfoot and the Tooth Fairy. Again, it’s all okay. In many cases, low-resolution positioning will be fine. If not, you can take lower-resolution ISAC and pair it up with other sensors (EG cameras, LiDAR, inertial sensors) to get more useful info. To be fair, this won’t help with a belief in imaginary personalities, but there are support groups for that.  
• spot coverage middle ground. Let’s be honest, ubiquitous mmWave coverage isn’t likely coming to your town anytime soon. Luckily, many ISAC use cases won’t require ubiquity. If you need high-resolution sensing for a specific set of high-value assets or locations, broad mmWave coverage isn’t critical, is it? 

I said it before and I’m more than happy to repeat myself; there are times when it’s cool to be a doubter and reject the latest hype. Still, I can’t think of any times when you’re best to ignore opportunities and the value of innovation because you weren’t paying enough attention. There are plenty of reasons why ISAC may never amount to anything than marketing hype, but pegging it all on mmWave is rather lazy.