In this paper, some of the thoughts about 6G will be summarized as well as a discussion about possible impact on the area of EMC. The overall conclusion is that if present expected technical parameters for 6G will come true, this will lead to a need for a large development step within the EMC area.

From 5G and IoT towards 6G and IoE

Drivers for the need of 6G are expected to be both societal- and business related [1]. Examples of areas with driving needs are political, economic, social, technological, legal and environmental (PESTLE). A major driver may be a further development of a massive amount of connected devices within a large variety of applications. 5G has been seen as the technical enabler for Internet of Things (IoT) in a large scale and also the necessary enabler for the so called “Networked Society”. The full vision of IoT is sometimes referred to as Internet of Everything (IoE). However, it can already be seen that 5G will have limitations concerning IoE [2]. These limitations will exist even after the natural evolution of 5G-technologies. Therefore, the full vision of IoE will need a further technology step that is expected to be delivered by 6G [2]. This will require end-to-end co-design of communication, control and computing functionalities for IoE applications.

The requirements for the services expected by 6G will be characterized by massive ultra-reliable, low latency communications (mURLLC). It is also expected that 6G systems will integrate communications, computing, control, localization and sensing (3CLS) to deliver multi-purpose systems [2]. This in contrast to earlier generation of mobile systems that mainly have had one exclusive function – wireless communications. Integrated Terrestrial, Airborne and Satellite Networks are also expected in the current 6G visions.

 

Another expected evolution will be needs that require systems that combines Augmented Reality (AR), Virtual Reality (VR) and Mixed Reality (MR) into Extended Reality (XR). An increased use of devices such as VR glasses, body implants and different kinds of sensors could therefore be expected. The traditional technically performance measure Quality of Service (QoS) might be replaced by Quality of Physical-Experience (QoPE) [2]. QoS is typically expressed in measurable technical parameters. QoPE will be user oriented related to human senses, cognition and physiology. QoPE will therefore probably include parameters such as brain recognition, body physiology and gestures. Another driver for 6G systems might be Connected Robotics and Autonomous Systems (CRAS). Examples are drone-delivery systems, autonomous cars, autonomous drone swarms, vehicle platoons and autonomous robotics [2].

 

Another area discussed is to use so called electromagnetic smart surfaces (e.g. walls, roads, buildings) for wave propagation. By applying certain materials on such surfaces, wave-propagation properties that can increase the communication performance might be possible to exploit [2].

Key Performance Indicators for 6G

Some Key Performance Indicators (KPI) are already discussed for 6G. Examples of such indicators are summarized in Table 1 [1][2].

The considerable increase in frequency together with the high requirements on reliability creates a need for systems to have components for several largely different frequency bands installed. Transceivers with integrated microwave/mmWave/THz bands will be needed.

 

The co-location density of 100 devices per m³ corresponds to an average co-location distance in the order of 30 cm. Thus, this density will give considerable challenges with respect to EMC between devices. For 5G co-location densities in the order of 250 000 devices per km² are discussed [5]. This corresponds to an average co-location distance in the order of 2 meters. Thus, the co-location density is in the order of 10 times higher in 6G scenarios than for 5G scenarios.

 

For 6G, radio coverage is expected to be expressed not with respect to area but to coverage volume. This is to include even flying objects such as drones and highly located devices. As a comparison, measures for spectral performance and energy efficiency has been an evolution for every new generation of mobile standard, see Table 2.

Human exposure

For 6G, frequencies up to several hundreds of GHz up to the THz-region are discussed. Existing ICNIRP guidelines [3][4] for human exposure to electromagnetic fields covers frequencies up to 300 GHz. This means that further research within this matter has to be done in order to explore the higher frequency bands discussed for 6G.

Possible consequences for EMC

Some immediate consequences that will have an impact on EMC can be seen from the discussed KPIs and applications for 6G:

• Considerably higher densities of co-located wireless devices gives a more demanding electromagnetic environment.
• Dynamic unpredictable co-location scenarios, with an increased amount of autonomous and flying objects, means unpredictable interference for the devices,
• New frequency bands, with unknown immunity and radiated properties for the products. These properties have to be investigated and handled to achieve EMC.
• The considerable extension of frequency regions to several hundreds of GHz up to 1 THz, together with considerably larger operating bandwidths, requires further development of methodology and equipment for standard EMC emission- and immunity testing.
• Devices that integrate equipment for several different frequency bands require thorough EMC analyses from the very early design stage.
• An increase of other devices than smartphones for communication, e.g. VR glasses, body implants and different kinds of sensors gives EMC issues related to co-location.
• Integration of communications, computing, control, localization and sensing (3CLS) in the same system gives new EMC issues to handle, especially in smaller devices.
• Use of electromagnetic smart surfaces give new challenges with respect to e.g. wave propagation issues and electromagnetic properties for different surface coatings.

The co-location scenarios will be characterized by higher densities of devices per volume unit. This will lead to considerably more difficult challenges to achieve EMC between devices than we have seen so far. The resulting interference level will, amongst several parameters, depend on the operating frequency, transmit power, co-location density and duty cycle of the devices. New methods for analysing EMC in extremely dense co-location scenarios must be developed. Furthermore, high dynamics with respect to co-location density could be expected. Therefore, systems must be able to adapt the communication performance to both extremely dense and sparse co-location scenarios.

 

The increased amount of autonomous and flying devices will require new analysis methodology to achieve EMC in dynamic co-location scenarios.

 

The mass-increase of wireless products for IoE applications will make the unlicensed frequency bands occupied to a considerably larger extent than today.

Conclusion

The published visions for 6G will have large impact on the area of EMC. Considerably higher frequencies, bandwidths and co-location densities will automatically give new challenges with respect to EMC issues. Both analysis methods as well as testing equipment and methods will have to be further developed to cope with these challenges. The technical parameters and applications discussed in the present 6G visions indicates that the EMC area has to be developed by a large step, far beyond a more traditional evolution of methodology and equipment.

 

Peter Stenumgaard

Swedish Defence Research Agency (FOI)

 

References

[1] “Key Drivers and Research Challenges for 6G Ubiquitous Wireless intelligence”, University of Oulu, September 2019

[2] Walid Saad, Mehdi Bennis, Mingzhe Chen, “A Vision of 6G Wireless Systems: Applications, Trends, Technologies, and Open Research Problems”, Published in ArXiv 2019, DOI:10.1109/mnet.001.1900287.

[3] “ICNIRP Guidelines For Limiting Exposure To Time-Varying Electric, Magnetic And Electromagnetic Fields (UP TO 300 GHz)”, Published in: Health Physics 74 (4):494-522; 1998.

[4] “ICNIRP Statement On The “Guidelines For Limiting Exposure To Time‐Varying Electric, Magnetic, And Electromagnetic Fields (UP TO 300 GHz)”, Published in: Health Physics 97(3):257‐258; 2009.

[5] Wiklundh, K; Stenumgaard, P, “EMC Challenges for the Era of Massive Internet of Things”, IEEE Electromagnetic Compatibility Magazine, pp. 63-72, vol. 8, 2 July, 2019.