That will probably happen in the 2030s. But even now, the foundations for the next generation of cellular wireless networks are being laid.
In a few years, 3GPP, the main standards body behind these networks, will begin defining what 6G will include.
Despite 5G facing commercial hurdles, the transition to 6G appears to be on track. At the 6G World Seminar on the roadmap to 6G in January, he pointed out that the adoption of some 5G standards has been slow. For example, very few carriers have deployed standalone 5G cores, according to Zahid Ghadialy, principal analyst at 3G4G. Instead, it has chosen to operate, at least for the time being, as a faster data rate front end to his existing 4G network.
Standalone 5G networks deliver low latency, which is one of the driving forces behind the features selected by the 3GPP standards body when defining how 5G will work. Another option promoted by 5G is the creation of private networks proposed to handle robotic systems in highly automated factories and warehouses.
In the middle of last year, market analyst IDC claimed that several factors were slowing down the adoption of private 5G, with 4G remaining the main option for those wanting private operation. One reason is his lack of 5G chipsets that support 3GPP Release 17 and Release 18 features, including protocol improvements for private networks. The same goes for high frequency operation. The short transmission range of millimeter waves, the need for operators, and the difficulty of handling mobile terminals make the busier lower frequencies a safer commercial option.
However, work continues towards higher frequencies for the next generation. Like its predecessor, 6G extends the frequency range of cellular communications even beyond its single-digit gigahertz range. While 5G has moved into the mmWave band, 6G is expected to extend beyond 100GHz. The World Radiocommunication Conference (WRC), which is held every four years, agreed late last year to a resolution to explore his five bands from 102 GHz to 275 GHz, with the top band having a total bandwidth of almost 25 GHz. We provide.
However, this does not mean that the carrier intends to focus on these higher bands. The sub-millimeter wave spectrum remains very attractive despite congestion and competition from other services. As Ghadialy points out, most of his 5G transmissions will use his C band between 4 and 8 GHz. “What’s different about 6G? It’s going to be sub-terahertz. But carriers still need low and mid-frequency bands. Otherwise, you have to open your car windows to receive the signal. I have to make a phone call.”
Ease of use and congestion
The tension between usability and congestion has led carriers and standards bodies to take a closer look at the area around 10GHz. In this region, the behavior is more radio-like compared to the more directional properties below terahertz. This is the range provisionally known as FR3.
“The industry is keen to find spectrum in the FR3 range,” Meik Kottkamp, radio technology manager at Rohde & Schwarz, said at the company’s Mobile Test Summit in the fall.
Still, research and development is underway in several groups to discover the best ways to implement and apply sub-THz communications. One of the benefits of moving into the sub-THz range is that waves make it easier to locate transmitters and track them as they move around. The directional nature of the beam means that the transceiver must closely track the other party to maintain communication. However, in the early days of sub-terahertz 6G, the focus will be on communication between objects that don’t move much.
In 2017, the IEEE published a 6G precursor standard for fixed wireless broadband installations and downloads from kiosks. As with millimeter waves, high levels of atmospheric absorption play a large role in how practical these frequencies are for long-distance links. Another issue is interference with passive RF applications such as radio astronomy and Earth observation that monitor wavelengths in this range. For these reasons, the focus, at least for now, has shifted to indoor applications.
Professor Thomas Kürner from the Technical University of Braunschweig, in parallel with the Heinrich Hertz Institute, is conducting experiments to determine how well these waves travel into indoor environments. One test was conducted on a Lufthansa Boeing 737 aircraft. This is a study of how often a signal needs to bounce around a plane to relay data to a receiver in the armrest for in-flight entertainment. It was also discovered that the windows needed a wave-blocking treatment to avoid interference with orbiting scientific instruments and ground-based telescopes. The natural attenuation of glass is only about 10dB.
early adopter
Data centers are likely to be early adopters. In early January, Microsoft applied to the U.S. Federal Communications Commission for a license to conduct indoor experiments at sub-terahertz frequencies envisioned for future 6G networks. Microsoft, working with Keysight, plans to conduct tests with carriers around 250GHz to supplement fiber-optic communications within data centers. The software giant said in its filing that it has tried free-space optical links in the past, but the beams were misaligned due to vibrations. By operating at much longer wavelengths than infrared, Microsoft says sub-THz transmission is less prone to these issues, while also offering the ability to form directional beams using multiple-input multiple-output (MIMO) arrays. I hope so.
While some experiments may consider moving closer to 1THz, the current generation of tests is focused on the region between 100GHz and 300GHz. Qualcomm has been conducting indoor and outdoor testing around 140GHz, and recently extended its license application to 151GHz, with a transmission bandwidth of about 10GHz.
ETSI has already begun work on standardizing how to simulate channel characteristics, but 3GPP’s standards proposal for sub-THz 6G is unlikely to arrive sometime after initial harvest, expected between 2025 and 2027. Sho. That will be in time for the next WRC to consider adding spectrum. About 7GHz. The research community is working on ways to implement transceivers that can operate efficiently above 100GHz, well above the comfort zone of today’s semiconductors. The cutoff frequency of silicon CMOS reaches approximately 450GHz, leaving little headroom.
A further problem is that in this region, the analog-to-digital data converters required to implement relatively simple modulation schemes are extremely power-hungry. In traditional CMOS, even a clock generator for a 6-bit, 50Gsample/s converter consumes more than 1.5W. The team at the University of California, Irvine calculated the carrier frequencies needed to support a total data rate of 50Gb/s using simple on-off he keying that does not require the use of his ADC in the receiver. did. Because 300 GHz of channel bandwidth is required, carriers may need to operate at 3 THz.
A team at the University of California, Irvine has developed several proposals that support quadrature amplitude modulation used in traditional protocols while avoiding the need to use data converters. This method revolves around the use of analog circuitry to implement relatively simple phase-shift keying combined in a phase- and amplitude-shifted array.
antenna array
Antenna arrays suitable for MIMO, despite having very short wavelengths and easy integration on-chip, present another major challenge. Irvine’s research demonstrated that integrated antennas have high losses and are only 16% efficient.
Efficiency is very important because high antenna gain is required to cope with large path losses and the 20-40dB losses associated with multipath reflections. Current off-chip designs appear to have efficiencies close to 90%. To enable a high degree of integration and maintain tight coupling, it can be connected to an interposer containing a transceiver chip.
Subterahertz communications may prove to be a highly specialized field for 6G well into the 2030s, with a focus on fixed wireless and indoor networks. However, experimentation with converter-free modulation schemes may prove that other channels also benefit from spin-offs as part of a way to save energy at high data rates.
