6G work is dominated today by research, but the next two years will see the balance shift from research to actual development. The industry has aligned on the timing of the first implementable standard for 6G to be complete no earlier than March of 2029—so we have a way to go. The list of enabling technologies that got lots of attention a few years ago has gone through some degree of cultivation.

In a prior article, I wrote about technologies trending into 2025, that have a high probability of not being culled from the 6G enabling technologies list. They included 7-16GHz mobile terrestrial radio systems, machine learning—a form of AI, for the optimization of network performance, next-generation multiple in/multiple out (MIMO) for the management of multipath complexity, and open radio access Network (RAN) for base station networking.

The list of 6G enabling technologies that are getting plenty of attention now and are trending into 2025, but which have a higher commercialization risk, are as follows:

Millimeter-wave technology (from 5G days—24-71 GHz)

Frequency Range 2 (FR2), as the Third Generation Partnership Project (3GPP) refers to this band, is already in use in 5G, but the industry has struggled to make the services profitable. The technology remains expensive with no clear “killer app” to drive use and volume, and hence reduce the cost through economy of scale. There is also work necessary in standards and in implementation to improve the reliability of the radio links – especially smart beam management, which is something similar to MIMO in that it relies on accurate real-time channel state information and can also benefit from ML. However, the demand for capacity and spectrum is profound and the amount that will be freed up in the 7-17GHz range will not be enough. Hence FR2, much of which is allocated but still underutilised, can be a necessary part of this.

Integrated terrestrial & non-terrestrial networks

There has been much in the news of late, on integrating terrestrial and non-terrestrial wireless networks (NTN)—leveraging satellite and high-altitude platforms (HAPS—balloons, sub-orbital stratospheric aircraft, etc.). This is about better coverage and increased reliability—especially in the case of natural disasters or maritime distress. But the technologies are challenging:

*Transmit-to-receiver distances of hundreds of kilometers (not hundreds of meters)

*Managing data traffic between multiple disparate networks

*Managing interference given an added dimension to the transmission direction (almost no cell-phone towers point the signals straight up or straight down and all standardised radio channel models are two-dimensional only)

This is exciting territory, and while the business model for satellite companies may seem obvious (same infrastructure, more users), it is less clear for the terrestrial mobile operator.

Integrated Sensing and Communications (ISAC)

The opportunity to use communications signals to sense the environment is another area getting significant attention. Traffic management, drone management, crowd management, and myriad other applications are under consideration. The challenge is related to 1) the radio frequency, wavelength, and signal bandwidth and 2) capacity management. The frequency, wavelength, and bandwidth of the signals have a direct relationship with the physical and time precision of the sensing. Capacity is also critical; setting aside radio resources for sensing-only means that they cannot be used for communications.

However, signals that are ideal for communications are not necessarily ideal for sensing. Also, if sensing and communications can be done with the exact same signal, there is no guarantee that the desired direction of the sensing requirement will be the same as the direction in which the system must transmit the necessary radio signal. So, the technical work means juggling these multiple challenges in addition to addressing the complexities of interference in sensing from multiple base stations and mobile devices. The business models here are not obvious, so the ultimate utility of this technology remains to be seen.

The following topics are still getting research attention, but commercialization possibilities are even less clear:

Reflective Intelligent Surfaces (RIS):

Indoor propagation and outdoor-to-indoor propagation are problematic in many radio systems. For example, parking garages, large commercial buildings, shopping malls, and indoor stadiums are addressed by distributed antenna systems and radio repeaters—sometimes even by additional independent base stations. The theory is that less-expensive approaches using large wall-mounted “surfaces” that use intelligent reflection can make a large difference in indoor reception. They would be smart enough to adapt to changing conditions such as people, furniture changes, relocation of indoor machinery, etc. The challenges are how to make them inexpensive, reliable, and flexible as well as with ensuring performance. Plenty of work remains and the challenges, especially to make them inexpensive, are significant.

SubTHz technology (>100GHz)

The attraction of very wide bandwidths available at frequencies above 100GHz has been dampened by the lack of commercial success at the more modest FR2 bands described above. This is exacerbated by the fact that SubTHz is even more expensive and difficult to manage than 24-71GHz. Research remains significant in industry and in academia, but SubTHz is no longer under consideration for mainstream use as a 6G radio access technology. That said, there are significant and successful demonstrations of point-to-point “microwave” links using D-band technology (110-170GHz). The significant demand on backhaul data capacity may drive further investment in these ever-higher frequencies in this and in other niche applications. As expected, the technologies under investigation include semiconductors, antennas, beam management, high-speed DSP, and even in-band full duplex (double the data rate by Tx and Rx at the same time), and like all things, remains in the context of economic constraints.

By: DocMemory
Copyright © 2023 CST, Inc. All Rights Reserved