I recently received a newsletter with the words “6G Is Coming …Are You Ready?” in the subject line. The newsletter was a promotion for a slide deck, “How can we shape the future of mobile connectivity with 6G?” written by two respected engineers. As often happens, those words in the subject line appeared nowhere in the newsletter itself.
The subject line begs the question, “Ready for what?” After several years of discussions, technical committees are just now deciding which capabilities might go into 6G. From what I’ve seen and heard, everyone agrees that 5G didn’t live up to expectations. Now, the wireless industry is betting on 6G to correct and deliver what 5G never did, much as 4G LTE did for 3G. Where does 6G stand from a physical layer perspective? That’s the question for which engineers need answers.
Figure 1 shows how 5G might evolve into 6G.
Having attended several 6G conferences, I’ve seen numerous changes in what 6G might become. While things such as the Metaverse have disappeared from the conversation, others have appeared along the way. Others have remained in place since the early days. One thing has become clear: 6G will be based on a standalone network core.
As you might expect, AI dominates the conversation. Many people claim we will see AI in radio functions such as coding and modulation, in the radio access network (RAN), and in the network core. AI in the network could improve spectral and energy efficiency, things that users might not see, but could reduce operating costs. AI could also potentially streamline network operations.
AI could enhance private networks, which are taking hold. For example, a factory floor could benefit in terms of predictive maintenance or logistics management, assuring that machines get serviced before they fail or that parts arrive at the proper workstation at the proper time.
What about mmWave, which promised blazingly fast download speeds? Unfortunately, short transmission distances and the inability to pierce walls and glass made mmWave radios too expensive to deploy in volume. That’s not to say that mmWave doesn’t have use cases. It’s making appearances in private networks, stadiums, race tracks, including the Kentucky Derby, and sports arenas. mmWave also serves fixed-wireless internet access (FWA).
When mmWave was still considered feasible, 6G discussions were looking beyond mmWave to include sub-THz frequencies (100 GHz to 300 GHz) as a way to achieve even faster download speeds. The sub-THz discussion has faded and is no longer discussed for 6G, nor is mmWave, for that matter. That said, research continues at universities, including Northeastern University.
Energy efficiency was also an early 6G topic at conferences. While by no means dead, energy efficiency simply hasn’t reappeared at the top. Why? Because it’s a money saver, but not something wireless operators can sell.
Integrated sensing and communication (ISAC), also called joint sensing and communication (JSAC), has so far stood the test of time. IEEE ComSoc defines ISAC as a “design paradigm and corresponding enabling technologies that combine sensing and communication systems to utilize resources efficiently and even to pursue mutual benefits.” It can potentially create a use case for cellular networks that operators can sell. With ISAC, the network can sense the location or position of a person, object, vehicle, or robot and use that data. As of the last 6G conference I attended in November 2025, waveforms that might be used for ISAC were still being investigated and proposed.
Will new waveforms mean new radios? That’s coming into focus, with the general answer being no. Carriers spent tons of money installing 5G radios, called 5G New Radio (5G NR).
You’ve probably heard a great deal about cellular-satellite communications. Indeed, carriers have begun boasting about how subscribers can communicate using satellites. Of course, the industry won’t wait for satellite communications to be standardized. Expect satellite communication to grow in importance and ultimately appear in a future 3GPP standards release. Once that happens, proprietary non-terrestrial network (NTN) technologies will likely fall by the wayside.
As 6G begins to take shape, engineers will need to take the lead in bringing new semiconductors, systems, networks, and test equipment to market. Test equipment will need to adapt to new frequencies that cellular networks might use. New frequencies could include the so-called Frequency Range 3 (FR3), which covers roughly 7 GHz to 15 GHz. The current cellular spectrum consists of FR1, roughly 600 MHz to 6 GHz, and FR2, which covers mmWave frequencies from 24 GHz to 71 GHz.
Without a modulation breakthrough, the only way to get a significant jump in data rates will be to add spectrum. New modulations won’t happen, though you can expect some upgrades to existing radios. Unfortunately, FR3 frequencies are currently in use by incumbents. The wireless industry will need to share spectrum with them, which will likely result in new spectrum-sharing techniques.
At a technical meeting held in June in Dalian, China, 3GPP moved the needle forward. What’s the status of the 6G study halfway through 3GPP Release 20?
To find out, I spoke with Mattias Frenne, Principal Researcher at Ericsson and Head of Ericsson 3GPP RAN 1 delegation. Frenne posted a video on LinkedIn where he summarized progress into the 6G radio physical layer (PHY). The RAN 1 working group studies the (PHY) and makes recommendations to 3GPP.
5G NR will continue in 6G, albeit with some modifications. Frenne noted that the signal, modulation, and channel coding will remain. The modifications will be software/firmware upgradable. Little or no 6G radio deployment need occur, at least not initially. According to Frenne, 6G will let operators reuse existing radios, though 5G NR radios may not provide the maximum performance increases. This gives operators the option of replacing 5G radios with 6G radios as traffic needs arise. Operators that have access to FR3 (7 GHz to 15 GHz) may deploy 6G radios earlier than those without access to FR3 frequencies.
While the radio waveform (Cyclic Prefix-Orthogonal Frequency Division Multiplexing (CP-OFDM) will not change for download and upload, Frenne reports that 6G will likely add Discrete Fourier Transform-Spread-Orthogonal Frequency Division Multiplexing DFT-S-OFDM to the upload to support more upload-heavy usage as people keep uploading videos to social media. DFT-S-OFDM should improve power-amplifier (PA) efficiency because DFT-S-OFDM supports multi-layer transmission. 5G currently supports single-layer transmission only. The result: transmission bandwidths of up to 400 MHz (DL) and 200 MHz (UL) will be possible in the 7 GHz band, as opposed to 100 MHz for 5G.
Regarding MIMO, RAN 1 is also investigating how to make it easier for 6G user equipment (UE) manufacturers to support two transmit antennas. Most devices use a single Tx antenna array with beamforming. Additionally, Frenne noted that participants in the RAN 1 delegation agreed to study Demodulation Reference Signal (DMRS)-based Channel State Information (CSI), high/low resolution CSI feedback, and UE/event-triggered CSI (on top of network-based trigger).
Even though 6G will keep 5G’s modulation, it still could take on changes to the constellation diagram distribution. Figure 2 shows a typical 64QAM constellation diagram with uniform symbol distribution. 6G could change that.
Other constellation possibilities include a circular distribution or a Probabilistic Constellation Shaping (PCS) distribution where the probabilities of occurrence of I/Q combinations are not equal. Figure 3 shows a 3D concept for 64QAM probabilistic distribution where the more likely combinations appear at the center, while edges are sparsely populated.
Another possibility is the Circular QAM constellation (Figure 4), which can achieve better peak-to-average power ratio (PAPR) performance than a rectangular constellation.
The RAN 1 delegates agreed to keep 5G’s rectangular, uniform, equally probable QAM, shown in Figure 2. They will, however, consider other forms. For example, a study of extended and enhanced modulation may cause RAN 1 to suggest moving to PCS or geometric shaping. There are tradeoffs in the choice of constellation, which depend on code rate. Thus, delegates have not yet agreed to change constellation patterns. They will reconsider the possibilities at the next RAN 1 meeting in September 2026.
Channel coding
As with the other topics, RAN 1 delegates chose to keep 5G channel coding for data (LDPC BG1/BG2, Low-density parity-check) and polar coding for control in the 6G physical layer, but looked into modifications such as adding third base graph (BG3) for user equipment. BG3 is aimed at “improving decoder area efficiency especially for high-data rates, while maintaining comparable performance.” This makes for more efficient code for data rates above 6 Gbit/s, which will use new coding. Data rates below 6 Gbit/s will continue to 5G NR coding.
Sensing beyond ISAC
6G could add a feature called sensing-assisted communication in addition to ISAC. This technology could aid signal quality by sensing the RF environment around base stations. For example, a base station could detect reflections that can cause weak signals or interference.
Freese also noted other network features that are under consideration for study. They include:
- Relaxing the need for tight coordination between schedulers (e.g., between multiple carriers, between DL and UL, etc.);
- Relaxing the need for rigid timelines, support separate CSI measurement/computation triggering/configuration and CSI reporting triggering/configuration;
- Simplification of UL channel collision/multiplexing/transmission (resource determination) involving Automatic Repeat request Acknowledgment (HARQ-ACK) or CSI;
- Better CSI timeline flexibility.
- Contention-based Physical Uplink Shared Channel (PUSCH), including buffer status report (BSR) to be evaluated together with multi-bit SR.
5G to 6G Ease of Integration
RAN1 delegates concluded that 6G-to-6G carrier aggregation can support non-collocated FR1-FR2 spectrum aggregation with imperfect backhaul.
For multi-radio access technology (multi-RAT) spectrum sharing, RAN1 agreed that 5G and 6G PDCCH (CORESETs) can overlap, which reduces the overhead in shared spectrum.
Then there’s AI
It appears that AI will play a role in DMRS overhead and beam management. The delegates will study DMRS overhead reduction, where an AI/ML-based receiver recovers the loss.
At the September 2026 RAN 1 meeting, delegates will further solidify the 6G PHY layer as 3GPP moves toward Release 21, expected in 2029.
Martin Rowe is an independent technical writer and former Senior Technical Editor of EEWorld. He holds a BSEE from Worcester Polytechnic Institute.