Infrastructural Futures of 6G and 7G Cellular Networks
6G will be the “Killer App” of 5G
Its hype is largely about the potential 5G will provide society: lightning-fast downloads, near-zero latency, as well as technologies like virtual reality and self-driving cars. There is, however, one important point being overlooked in all the buzz-the fundamental technological advances of 5G. A wide variety of mobile technologies, including millimeter-waves, small cells, and massive MIMO (multiple input, multiple outputs) antenna systems, will shape wireless communications for decades to come. As we move into the era of cognitive computing and apps that are human-like, all of these technologies will enable wireless networks to advance. In less than 20 years, wireless networks will be able to transmit the information as fast as the human brain.
For a deeper understanding of the 5G revolution and its impact on the future of wireless technology, let’s first look back at the past 10 years. Data capacity and consumption on the global cellular network have increased at an unprecedented rate during that period. In the original formulation, engineer Martin Cooper predicted that cell phone technologies would double in strength about every 30 months (by 16 every decade).
Cooper’s law indicates that average download speeds have increased from a few megabits per second in 2010 to about 50 Mbps in 2020. From megabits per second to gigabits per second, peak data rates increased by more than a factor of 1,000 during the same period. CTIA, the trade group representing the wireless industry, recently revealed that the amount of data transferred over the U.S. cellular network increased 96 times between 2010 and 2019, with the average smartphone user downloading 9.2 gigabytes of data each month in 2019.
Consumers in the United States adopted smartphones in the past ten years, but there was only a 40 percent increase in spectrum available, so the nearly 100fold increase in carried capacity was still possible. A few days after the incident, the industry started using a five-gigabit millimeter wave spectrum, small cells, and MIMO antennas, enabling 5G. Several orders of magnitude more spectrum could be available to the U.S. alone in the decades to come, given the vast spectrum resources available above 100 GHz.
The three pillars of 5G will unleash an exponential development that will bring vastly increased capacity and use cases, just as Moore’s law brought millions of times more processing power over four decades. As a result of 5G-enabled speed increases for users and higher level traffic, industry metrics will certainly be 100 times higher than today’s levels in ten years from now – and, in truth, probably closer to two or three hundred times. In other words, the average smartphone user will consume more than a terabyte per month in 2031, and peak wireless download speeds will approach 1 terabyte per second in 2031, a significant increase over today’s nascent 5G networks.
It was clear the Federal Communications Commission (FCC) needed legislation to enable wireless carriers to rapidly densify their networks across the country. With its 2018 Small Cells Order, the Federal Communications Commission made small cells one of three technical pillars that will eventually facilitate wireless communications at terabits per second.
With its Spectrum Horizons order in 2019, the FCC also began releasing spectrum above 95 GHz, recognizing the need and potential of that spectrum. As was done by the FCC, the Office of Communications (Ofcom) in England followed suit in opening spectrum above 100GHz in 2020, as well as expanding spectrum availability in this sub-terahertz spectrum band.
Massive-MIMO is the third and final 5G technology pillar, changing the antenna array from a 2-by-2 element to a 16-by-16 element and eventually to a 64-by-64 array, enhancing greatly the capacity of a single base station. Massive-MIMO is already being deployed using time-division duplexing by many carriers around the world (which is how signals between base stations and customers share the same frequency but are separated in time so they do not collide). Soon, millimeter wave technology will be incorporated into wireless systems using sub-terahertz frequencies.
All of this matters because wideband data transfers perform better at millimeter-wave and terahertz frequencies than at the lower frequencies used for the first four generations of cellular technology. NYU Wireless has shown that, between sub-6 GHz and 140 GHz frequencies, propagation path loss for an urban radio channel doesn’t differ much at different frequencies, after accounting for the radiated signal’s first meter of travel.
Therefore, once a radio signal reaches what’s known as the “far-field” (beyond the first meter or two), the frequency has little effect on its attenuation as it travels through urban areas and indoor spaces. This is only applicable if there are no inclement atmospheric conditions such as rain, or if no molecules are likely to absorb the frequencies, such as oxygen. Therefore, the extensive work being done today to densify cell sites will pay huge dividends in future networks with frequencies above 100 GHz. Shortly, 5G networks won’t require further density, and today’s new tower sites can be used for decades to come without the need to build many more.
As a result, omnidirectional antennas have traditionally been considered the norm for wireless communications within the industry. However, beginning with 5G, wireless systems will use directional antennas with high antenna gains and narrow beamwidths on both the mobile and base station ends. In shifting from millimeter wave to sub-terahertz and eventually terahertz frequencies, we see greater signal strength to each user, not less.
A myth also holds that as we increase frequency above millimeters, radio energy in free space becomes lossier for a given distance traveled. It has been demonstrated that air has only a 10-decibel loss per kilometer up to 400 GHz.
In today’s market, a 5G small cell has a loss of only 1 decibel per 100 meters. For much of the spectrum up to 900 GHz, we found that it suffers from a loss of 100 decibels per kilometer or 10 decibels for a small cell. Antennas with directional patterns can compensate for the 10 dB loss at such high frequencies quite easily.
Even though rain and foliage can interfere with 5G transmissions, once the 5G cells are designed to reduce the effects of rain on transmissions up to 70 GHz, there is no further degradation beyond those frequencies up to 1 THz. As a result, it again demonstrates the benefits of 5G for decades to come. Snow is a different issue, but engineers must realize that directional antenna technologies will overcome the preconceived notion of greater losses at higher frequencies. These ideas come from a bygone era when omnidirectional antennas predominated.
6G Telecom Deployments
It is not likely that 6G will be launched simultaneously. Both LTE advanced pro and LTE advanced are expected to be launched in phases across the region in an incremental manner since they are incremental enhancements to LTE advanced. Most telecom organizations are looking to upgrade their network infrastructures with 5G network deployments and to upgrade their existing networks faster.
In the end, these 5G technologies provide more than enough link gain to more than compensate for any radio channel loss caused by site-specific deployments to avoid massive obstructions. At millimeter-wave frequencies and above, factors such as reflection increase, which increases the likelihood of signal paths being combined by directional antennas. In doing so, it improves both the radio frequency power budget and the channel signal-to-noise ratio, which then allows for the provision of much larger bandwidth channels than are currently available in wireless systems. Once we have moved up to higher carrier frequencies and wider bandwidth channels, the existing 5G tower infrastructure can support higher carrier frequencies and wider bandwidth channels. The competitive advantages offered by the three technical pillars of densification, wider bandwidth, and massive MIMO will enable engineering and deployment of 5G systems for decades to come as more spectrum in the subterahertz and terahertz bands become available. A decade ago, we were accurate with our predictions.
For 6G and 7G, the same cellular infrastructure will be used, as well as advances in radio circuitry and antenna technology that brought 5G to market. The next generation of cellular devices will, however, do so at much higher data rates, which will result in vast amounts of data capacity and new applications in the coming decades. The fact that 5G is coming sooner should be incentive enough for governments, funders, wireless carriers, and citizens. Moreover, government and industry should also be encouraged to develop new architectures like Open RAN and place a greater focus on security due to the great potential of 5G and beyond. With 5G networks, there will be many opportunities, whose benefits will remain for decades to come as these invisible waves become increasingly important to us.
Post resource: IEEE Spectrum
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