Guest Post: A Reality Check on 6G Design Targets Part 2

June 12, 2023

Written by 6GWorld Contributor

By Heikki Almay, Co-Founder of Poutanet

As a continuation of my discussion with ChatGPT (which you can read about here) about 6G it proposed a few other interesting topics which supposedly should be key elements of 6G’s design:

  1. Artificial Intelligence
  2. Ubiquitous Coverage
  3. Spectrum Efficiency
  4. Interoperability
  5. Global Standardisation

No big surprises. This is what the language model found in its not-so-fresh training data. This is what we have been talking about.

1. Artificial intelligence (AI) integration: 6G networks should integrate AI technologies to enable intelligent network management and optimization, as well as support for AI-enabled applications. 

When AI proposes that there should be more AI in 6G you get the same feeling as when interviewing a job applicant who says he can do much more for you than you ever asked. Jokes aside – in many parts of the network machine learning may be the only way to handle the increasing complexity.

Within a base station efficient scheduling and beam steering are challenging tasks that can be optimized by using the large amount of real time data available from the radio interface. On this level AI could help improve capacity and reduce power consumption both in the base station and the user equipment. Distributed MIMO and cell-less network concepts that rely on distributed radio resources instead of traditional cells and individual base stations require enormous flexibility that is hard to capture by writing algorithms. What remains to be seen is if we will have a re-emergence of the RNC in the form of an AI-powered RIC. Those who remember the challenges posed by that earlier generation of radio network or base station controllers might prefer 6G to take an approach that distributes the intelligence.

Another interesting question that remains as to whether any of the above should be part of the 6G specifications. Topics like scheduling and beam steering have so far been the secret sauce of the RAN vendors.

When looking at a system level, AI-type solutions for network planning and (almost real-time) optimisation have a lot of potential. Perhaps 6G specifications should be extended to contain a digital twin of the network or at least the APIs that would allow firing up a digital equivalent of a network segment. Capacity and coverage optimisation, as well as detection and location of interference sources, are some of the low-hanging fruits.

Perhaps we could lean back and wait for generative design to specify and build 6G for us – but this is more likely a topic for 7G.

2. Ubiquitous coverage: 6G networks should provide seamless coverage across a wide range of environments.

Global coverage has been a key driver for the development of non-terrestrial networks (NTN). We have already seen the first handsets with satellite-based messaging – but from networking perspective there is zero integration. If we want satellite connections to become available to mainstream end-user devices, NTN needs to be pushed in 6G standardisation, but this may not be enough. Success will require alliances or mergers between mobile network operators and satellite operators. Satellite services come with a cost. Unless the satellite services are sold and billed as part of the mobile subscription (or in some other easy way) it is hard to imagine that those of us, who do not spend much time in the arctic or other remote places, would line up for an extra, low data-rate, connection. There are practical challenges as well – including the limited availability of suitable frequencies for satellite communication and the increasingly crowded low orbits. Satellite operators are not waiting for 6G but offer their proprietary broadband services already.

Apart from NTN it is hard to see topics that would significantly help to provide additional coverage. Yes, one more time the front line between broadcasters and mobile networks may move down by 100MHz or so – but the impact on coverage is limited. The business case for high masts in uninhabited areas does not improve a lot if you move from 700 MHz to 500 MHz. Improved indoor coverage and more capacity in rural areas – that is the most likely outcome. 

3. Spectrum efficiency: 6G networks should use spectrum more efficiently than 5G, through techniques such as dynamic spectrum sharing and advanced antenna technologies.

While spectral efficiency is a key topic, I am not at all convinced that dynamic spectrum sharing (DSS) is the way to go. DSS was implemented as a 4G to 5G migration solution for those operators who wanted to turn on 5G quickly, but did not have low- or mid-band FDD frequencies available for the purpose, or who did not want to invest in new RF and antennas. Essentially DSS means that you run 4G and 5G in parallel using the same frequencies. Claiming that DSS would increase spectral efficiency is a bit suspect, as DSS reduces the channel capacity when compared to running only 5G.

DSS is for smooth migration from 4G to 5G. The catch is that you should not hold your breath while waiting for the 4G users to go away – which means that operators are stuck with a complex and fairly vendor-specific feature set that ties together their 4G and 5G deployments. Like non-standalone 5G, DSS is a vehicle that allows service providers to lean back and enjoy the ride half-way to 5G – but that is where the journey ends.  

Advanced antenna technology is a better suggestion. Active antennas and massive MIMO have become common – but this is only the beginning. It would also be great to see new solutions for low frequencies which cannot be easily addressed with the current technologies.  

4. Interoperability: 6G networks should be designed to be interoperable with existing and future networks, to enable seamless roaming and connectivity.

Clearly there is a desire to have an incrementally improved version of 5G that will later allow smooth migration to 7G in the late 2030s. As the decisive difference between mobile network generations is the radio interface, the interoperability here should refer to user identification (SIM) and mobility (handovers and a mobility anchor point). Roaming means agreements between the operators. Obviously, the assumption is that telephone numbers, voice calls and SMS will follow us into 6G. Do we really need all of that – or is it just for maintaining the status quo of the industry? 5G has been around for half a decade now and voice over new radio is not widely deployed. Even voice over LTE still has limitations – like missing roaming arrangements. 

5. Global standardisation: 6G networks should be based on globally standardised specifications, to ensure compatibility and interoperability across different regions and countries.

Since 3G the mobile network generations have been fairly global and we have enjoyed life where our smartphones work wherever we go. Our SIM cards serve us globally too – aside from the sometimes astronomical roaming fees. For those carrying around something further away from the mainstream – for example a CAT-M or NB-IoT device – finding a network to connect to has been much more difficult. So far regional (or corporate) preferences have been included in the 3GPP specifications as options.

Unless miracles in world policy take place, 6G will be specified in an environment where the US is actively limiting collaboration with Chinese entities as well as the access of Chinese manufacturers to advanced silicon using US technology. The access of Chinese vendors to most of the Western mobile infrastructure markets has been blocked and, in turn, Western infrastructure vendors have had to retreat from the Chinese market.

Apart from the user equipment community it is hard to see why big players would bother or dare to reach across the front lines of the trade war to reach consensus, as this would typically also involve accepting that IPR of the other party is to be used. With some manoeuvring we may get a global standard – but the likelihood of strong regional options and reduced interoperability is higher than any time since 3GPP was established.

For those who did not read my first blog post on 6G design targets provided by ChatGPT a recap: Extremely high data rates, ultra-low latency, massive connectivity, energy efficiency and security/privacy were the first five topics provided by the AI – or rather, by the language model. In summary: the key 6G topics discussed in public suggest 6G will be formed around the same topics as 5G. This is a bit sad, as 5G has so far brought us mostly more capacity.

In future blogs I will try to focus on the topics that are holding back innovation and new services – which means more controversial ideas and approaches. 

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