6G – When reliability meets performance

July 2022 | Muriel Medard

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Muriel Medard

Muriel Medard

MIT

Muriel Médard is the NEC Professor of Software Science and Engineering in the Department of Electrical Engineering and Computer Science at MIT. She is known for her work in reliable communications and networking, blending theoretical developments with practical implementations. She is a member of multiple learned academies and has received many awards for her research, her mentoring work and her service to the field of communications.

6G – When reliability meets performance

As 5G rolls out, conversations already are arising regarding 6G. Such considerations are not premature but indicate the forethought of the technical community. In effect, the successes, and the remaining challenges, of 5G are being incorporated into the thinking for 6G.

5G has shown that heterogeneity of user needs and of technologies is here to stay. For the former, enhancements on legacy applications require throughput increases, while growth of machine learning traffic generated by applications and by IoT creates a growing demand on network resources. Emerging applications, such as AR/VR, robotics and automotive, need rapid and guaranteed response times, particularly as they seek to become part of societal infrastructure.

Blending technologies

On the side of technological heterogeneity, besides legacy and new proximate bands at around 2 or 3GHz, 5G has introduced lower frequencies, such as those around 600MHZ, which are of particular value in rural areas, and far higher frequencies at around 28GHz, where abundant spectrum is available. These different frequencies have benefited from enhancements such as massive MIMO. Significantly, 5G for the first time also allows for non-standard technologies, WiFi being naturally chief among them. Satellite systems, previously operating as stand-alone entities, are being aggressively deployed, showing the possibility of blended terrestrial and satellite connections.

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That blending, which holds such promise, is currently absent in 5G but will be crucial in 6G. In effect, the rich variety of offerings in 5G has not been fully exploited. It is good to be able to select the best of an array of technologies to adapt to the needs of a user. It is far better to provide the aggregate benefit of those technologies, as in emerging multipath systems. For different connections to be used in an integrated fashion, it is essential to use network coding, which provides a fluid and tunable approach that can optimally avail itself of all resources in a real-time basis, with an optimal trade-off among throughput, latency and reliability.

Unlocking 6G’s efficiency

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Currently in 5G, there is an overlay of many quasi-sedimentary layers of successive legacies, from conventional suboptimal modulations, to interleaving over channels, to being limited to a small number of long-and low-rate physical layer codes such as LDPCs, to hybrid ARQ and ARQ repetition at the MAC and transport layers. 5G has often resorted to increasing bandwidth to mask the inefficiencies of these legacy issues by running systems in fast forward. Higher bandwidths are onerous, from monetary cost of leasing spectrum to attendant energy overhead of processing

Removing from standards unnecessary constraints will unlock massive efficiencies in 6G. MIT and Maynooth University have developed a universal decoder, that allows for optimal modulation and the bypassing of interleavers, while permitting use of an unlimited array of high-rate and low-length codes. Replacing traditional HARQ and ARQ with flexible approaches, particularly network-coded versions, will provide considerable increases in rate, reductions in latency and the sort of reliability that can truly instantiate URLLC.

The challenges of 6G security

Key to 6G is security, which has progressed from a specialist interest to an issue championed by the mainstream press. The confluence of multiple factors has made the topic increasingly complex.

  • First, the heterogeneity of manufacturers and of technologies, mentioned above, render a centrally orchestrated security solution impractical.

  • Second, the introduction of new technologies, particularly at very high frequencies, present new settings in terms of propagation and associated vulnerabilities.

  • Third, the erosion of traditional cryptographic schemes, such as RSA, by quantum computing, has been coupled with the rise of the possibility of such quantum computation.

  • Finally, the widespread use of federated learning entails that a highly connected, omnipresent wireless ecosystem also presents new and complex risks in terms of privacy.

When reliability meets performance Hexagon image

Many of the above apparent vulnerabilities can, when exploited well, enhance security. Through network coding, heterogeneous settings permit light-weight (in terms of computational and rate overhead) post-quantum secure operation without central coordination. Transmissions at high frequencies can be fashioned to obtain absolute security. Universal decoding provides the ability to incorporate encryption into error-correcting coding directly. Privacy management even in distributed, uncertain settings, can be enhanced by combining machine learning techniques with coding.

Creating a standard that provides flexibility for innovation, adaptability and performance enhancements, while maintaining the reliability and security needed for critical networks, will be the exciting challenge of 6G.

6G key technologies

Nokia Bell Labs has identified six key technologies that will be vital components of future 6G networks.

Explore our 6G technologies by clicking on the diagram or button below.

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