Will 6G include a new waveform (for the first time since 3G)?

22nd June 2022
Sam Holland

While 5G networks are in the midst of being rolled out in many markets across the globe, conversations around 6G are already ramping up and large industry players are already speaking up. This article from Dr Ronny Hadani, Associate Professor at the University of Texas and Chief Scientific Officer at Cohere Technologies discusses the next stage after the fifth generation of telecommunications: 6G.

Nokia’s CEO believes that 6G networks will be in operation by 2030, as do senior executives at Ericsson. And AT&T recently asked the FCC for two, two-year experimental licences for 6G wireless systems.

However, what the industry can’t quite decide on yet is what will be needed to enable the development of the sixth generation of mobile connectivity. While some argue that it will require new technologies and standards, some attest that it will be based on the same waveform as 4G and 5G. There is no doubt that stakeholders from across the telecommunications industry will be vying to get their opinions on 6G heard in order to define the nature of tomorrow’s connectivity.

Room for improvement

4G and 5G are both based on a waveform called OFDM (orthogonal frequency division multiplexing). While OFDM is suitable for many use cases, its performance suffers in certain instances and signal degradation is a common issue at high mobility. As the IEEE puts it, “communications in high mobility scenarios suffer from severe channel Doppler spreads, which deteriorate the performance of the widely adopted Orthogonal Frequency Division Multiplexing modulation in the current fourth-generation and emerging fifth-generation networks.”

This is because OFDM is distorted when it travels through an environment that makes it harder for a device to interpret the signal – such as in high-mobility scenarios – resulting in a poor-quality connection. High-mobility use cases include things such as video streaming on the move, which is the type of critical application that 6G will be developed to enable. Therein lies the need for a new waveform to unlock the true value of 6G connectivity and ensure it lives up to its potential in ways that 5G has so far failed to do.

A part of the key for unlocking 6G might therefore be played by a new waveform: OTFS (orthogonal time frequency and space).

The next generation waveform

Unlike OFDM, OTFS provides a powerful two-dimension modulation format and is oblivious to the distortion that its peer suffers. In fact, OTFS is adaptive within complex channels of communication for a number of reasons. As well as its lack of distortion, it benefits from performance gains as it is resilient to high Doppler shifts, is able to exploit time-frequency (TF) diversity and responds well in fast-fading wireless channels.

Without distortion and with higher performance in more complex channels, OTFS enables a reliable, high-quality connection, regardless of how fast the user or device is moving. This is vital if 6G is to fully enable high-mobility use cases such as critical communications, robotics, augmented reality and the metaverse.

While the benefits of adopting OTFS as a waveform for 6G are clear, it is more likely that multiple waveforms will be adopted. OTFS is flexible so it can easily fuse with existing 4G and 5G technologies, such as OFDM. This will enable 6G to be rolled out faster – as it will simply be a case of integrating the OTFS waveform into existing infrastructure – which will be invaluable if 5G continues to fall short.

6G is going to the cloud

Let’s assume that 6G is in fact a new language and a new architecture. The existing infrastructure players will continue to keep the intelligence localised at the base station versus considering distributing the intelligence to the cloud. However, artificial intelligence wants high bandwidth at low latency; IoT wants a narrow pulse at low latency; automated vehicles need a medium bandwidth pulse at low latency that’s also connected to LIDAR and radar in a complimentary way because it ends up having a multipurpose control plane. All of those things are very complex and the only way to manage these networks as one is from the cloud.

Therefore, 6G is all about the cloud and is likely to be dominated by the large cloud players, such as Microsoft, IBM Red Hat, Rakuten,  Google and AWS, that are already making big investments in the telecoms sector. The cloud will create a new supply chain for the telecoms industry, and with it, new economics. The level of investment into cloud technology also outweighs investment into any other area of technology, so there’s no question that going to cloud will protect and probably enhance security and other key features.

Demonstrating the business case

As discussions progress around 5G, academics and researchers are already backing OTFS as an attractive candidate to enable 6G connectivity, due to its performance in challenging, high-mobility scenarios and the lack of distortion it shows within the channel. When integrated within cloud-based networks, consumers will benefit from enhanced performance and a wider range of use cases, and operators will be able to leverage their spectrum investments more efficiently.

The advantages of OTFS are clear to those involved, but the challenge that must be overcome is demonstrating the need for 6G itself, to both the wider industry and society in general. Only then will the investment needed to make it a reality be released.

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