Special Report: 5G in millimeter wave
In the run-up to 5G deployment, there was intense excitement about millimeter wave spectrum. The huge capacity in the frequency bands above 20 GHz would enable superfast speeds, enabling new applications and revenue streams; and it would accelerate moves towards flexible usage plans such as dynamic sharing because of the sheer amount of spectrum in play. That in turn could drive down the cost of spectrum, which is a key challenge to the 5G business model in markets, such as the USA and India, where the crucial midband airwaves have been auctioned at very high prices.
Most of the fervor about the transformative impact of mmWave spectrum has proved to be misplaced. It was certainly a key achievement of the 5G standards process to enable deployment in high frequency spectrum without the very specialized (and expensive) chips and equipment that have been needed for mmWave systems before, in markets such as military communications. There has also been important work done, by industry and regulatory bodies and by the ecosystem, on how high frequency spectrum might be allocated in order to drive new deployers and usage models.
But only the USA has really delivered at least some of the promise of 5G fixed wireless access (FWA) in mmWave, which was widely regarded as the leading use case. Verizon and, to a lesser extent AT&T, were forced to innovate in 26 GHz and 39 GHz because they held significant assets in these bands, but until the CBRS and C-band auctions of 2021, they lacked midband 5G airwaves. But in most markets where operators are deploying 5G FWA at any scale, they are using midband spectrum (as are the US operators now they have it). That may change as spectrum capacity gets filled up and FWA risks a hit on the quality of service for more lucrative mobile users, but for most operators, mmWave is either unavailable for now, or surplus to requirements.
The key problem with mmWave is the limitation on range and indoor penetration at high frequencies, which requires very dense networks to be built out to achieve anything close to wide area coverage (and as Verizon’s mmWave-based UltraBroadband service shows, even in a coverage area, access to the service is far from assured). This has seen hopes for mmWave shift to focus on small-area enterprise networks in scenarios such as factories or stadiums, and this is where many of the interesting shared spectrum or light licensing schemes are focused. For instance, UK regulator Ofcom has introduced a light licensing program that is designed to encourage alternative 5G deployers that may have a stronger business case than the MNOs to build enterprise and in-building small cell networks and so stimulate new use cases.
But for mmWave to be more than a niche asset in the national operator’s portfolio, the issue of range needs to be addressed. This has been a significant area of research for many ecosystem players – from innovative start-ups like Movandi and PivotalCommware, to giants like Samsung and Ericsson.
Real results are starting to be seen, as this week’s report highlights. Qualcomm has led development of new beamsteering techniques that can improve mmWave effectiveness even where line of sight is impossible (lack of LOS is a key factor reducing reach and penetration in high frequencies). And while Samsung has demonstrated a 10 kilometer link in mmWave spectrum, Ericsson has set out its own technical roadmap for extended range in these frequencies. Operators are active too – Verizon and Rakuten are among the MNOs working with Movandi, for instance, to improve indoor coverage and penetration and overall range.
These innovations will start to make mmWave spectrum more useful for an increasing range of applications, and should increase operators’ enthusiasm to buy it. However, it will remain inferior in range and coverage terms to midband or low-band spectrum, and will therefore always increase the cost of building out coverage. Most operators will wait until their midband spectrum is nearing capacity crunch before investing significantly in mmWave networks, and outside of a few dense city or enterprise hotspots, that may never happen for most.
The important challenge for the ecosystem is to focus on tools, devices and equipment that will enable mmWave to support a whole new variety of services and service providers, quite separate from the mainstream mobile operator use cases – ones that really do require unprecedented capacity and speed. Whether these are enterprise applications, or related to immersive experiences in the ‘metaverse’, the justification for all the R&D that is taking place in mmWave must be to extend the impact of 5G into areas that sub-20 GHz spectrum would not easily support.