NextG: 6G

Let me get the déjà vu part behind us at the outset. 6G promises to revolutionize the way we live, work, and interact with our digital surroundings. As we adopt 5G in its complete glory, 6G offers the first tantalizing glimpse of its power. This focus on 6G may seem to be premature or predictable but it is, nevertheless, prominent at this juncture. While India has announced its 6G task force, the US has announced its Next-G alliance (I think the nomenclature itself ensures it continues to perpetuity!). It is noteworthy and interesting that the timelines are identical – 6G by 2030.

What will change?

Emanating from these parameters, the new-generation technology would bring forth several powerful changes and capabilities.

Let us discuss a couple of them.
Evolution to wide area cloud
The journey of integrating communication and compute has begun with 5G, and as they say well begun is half done, but it is poised to go further and deeper with the concept of 6G wide-area cloud (WAC). WAC is the integration of cloud concepts into the 3GPP network so as to make the mobile networks more efficient, reliable, and cost-effective, and also leveraging the mobile network to integrate the distributed computing resources for richer and more dynamic cloud services to applications, making them more powerful. The 6G WAC must provide a cloud framework that works in tandem with the 6G communication systems, enabling distributed applications to be deployed, using resources of multiple public, private, and hybrid clouds. I am aware that this is the bottom line here and now for 5G, but it is not true for 6G, ostensibly the next G, because it is set to evolve. Let us see how.

The convergence of mobile communications and cloud computing drove the definition of the service-based architecture (SBA) of the 5G Core (5GC), which in turn enabled network function virtualization (NFV) and cloud-native network function (CNF) as the cloudification of 5G mobile networks. This path of convergence is expected to continue to evolve in the 6G system (6GS), resulting in a 6G WAC. The 6G WAC is envisioned to be comprised of intelligent and ubiquitous computing, communication, and data services, spanning regional and metro area data centers, cell sites, on-premise equipment, and devices. Both the 6G system functions and applications can be supported as workloads by 6G WAC. In 4G and 5G, the network gained the ability to implement service chaining after the communication tunnel anchor point (e.g., the 4G PGW or 5G user plane function, UPF), potentially introducing functionality that can better serve the needs of the user plane.

The transition of 5G to 6G will advance this evolution by making network programmability accessible to network operations as well as customizable services. This transition lays the foundation for creating cloud-native environments to adopt cloud computing technologies and further enable the flexibility to introduce new functions and services, dynamically orchestrate network resources, and steer traffic to the desired path.

Mostly, broad principles are being set now and details will have to be filled up gradually, so let us bear the pain of slow stacking up of concepts and principles. The following aspects need to be borne in mind while defining the next generation of mobile technology.

First, to manage the interdependencies between computing- and data-related aspects and the mobile system, it would be necessary to define the service requirements, exchanging and leveraging special capabilities, and requesting transport for advanced services (e.g., chaining and pipelining) in computing and data. The computing management functions will interact directly or indirectly with the core network, radio access network (RAN) nodes, devices, and applications to enable communication-aware computing services. The 6G architecture shall have to reflect these interactions by way of new functions, information interchange, joint control, and optimized functionalities.

Second, ubiquitous computing requires disaggregation of the services provided as well as the capability of allocating and orchestrating the distributed resources for services based on various requirements and business models. To enable efficient deployment of applications, the WAC architecture must permit easy reservation and activation of services across multiple domains. 6G scalability requirements need to address challenges, including defining the relationships, such as between controlling orchestration requests (e.g., intent-based) for compute, communication, and data resources, the orchestration of selected resources, and choices between central versus distributed control. The computing and data services are planned to be widely distributed in 6G; disaggregated components would be placed along a chain of computing nodes from user devices to network sites to data centers. The 5G-based mechanisms of service discovery, capability exposure, transport management, and traffic steering may face scalability and efficiency issues. For example, service discovery may require finer grained approaches to find a service instance in the 6GS compared to current domain name system (DNS) queries. Protocol enhancements may be needed to traditional mobile protocols to provide sufficient routing flexibility. Also, the integration of mobile devices for computing and data services further requires modifications to the existing air interface functions and protocol stack.

The 3G/4G/5G protocol stack is oriented toward point-to-point communication for a service, where the upper sublayers provide a bearer construct between fixed termination points. As applications evolve toward a model requiring computing at different locations, this fixed-endpoint approach becomes more poorly matched to the needs of the underlying application. Although support for XR services in 5G is optimized from Release 18, these services are expected to develop significantly from 5G into 6G, becoming more widespread and more demanding in terms of the required network and compute capabilities. It is plausible for an XR service to have some computation performed at the local device (e.g., headset), some at a paired smartphone with better battery life, and more computational power than the form-constrained headset, some at the network edge, and some in an application server, accessed through the operator’s core network – all as part of a single service from the user’s perspective. Such multilocal distribution of computing should be expected as normal behavior from a service using the distributed cloud. The 6G protocol stack(s) should, therefore, naturally enable these use cases without increasing the complexity of the stack. Additional application classes can be expected to benefit from robust and native support of distributed computing, for example:

• AI/ML services involving multiple nodes, such as distributed federated learning, in which multiple peer nodes interact rather than relying on a single central server.
• Latency-sensitive transcoding of video formats to enable near-real-time display on a device that may have limited compute capability of its own.
• Secure multi-party computation, which may be important for 6G system security, and for applications that need to act on private data.

Tactile/haptic Internet
The tactile Internet is one of the most interesting advances that 6G promises to deliver and enable haptic interaction with visual feedback. Basically, human reaction time depends on the sensory stimulus and whether the human is prepared or unprepared for the situation. When reacting to a sudden, unforeseen incident, the time-lag for a human, sensing a stimulus and responding with a muscular reaction, is in the range of 1 second. Tactile/haptic Internet, thus, focusses upon way of transmission of information/feedback/interaction with the help of touch. The human auditory reaction time is about 100 milliseconds. To enable natural conversation, modern telephony is designed to ensure that voice is transmitted within 100 milliseconds. Higher latencies would disturb us. A typical human visual reaction time is in the range of 10 milliseconds. To allow for a seamless video experience, modern TV sets have a minimum picture-refresh rate of 100 Hertz, translating into a maximum inter-picture latency of 10 milliseconds. But if a human is expecting speed, such as when manually controlling a visual scene and issuing commands that anticipate rapid response, 1-millisecond reaction time is required. Examples are moving a mouse pointer over a screen and viewing a smooth path of the pointer over the screen or moving our heads while wearing virtual-reality (VR) goggles and expecting an immediate response from the visual display. The most challenging latency requirement for technical systems arises in tactile or haptic interaction – our sense of touch and the movement of our limbs interacting with visual or auditory feedback. Human body interactions with machines demand a strict latency requirement in the order of 1 millisecond. If the time-lag between (say) the virtual picture and human movement is above 1 millisecond, cybersickness may occur, with users becoming disoriented in an experience similar to the motion sickness sometimes suffered at sea, in the air, or on the road.

ITU has defined the following possible use cases of haptic Internet:

• Education and learning. With haptic interactions, difference between class room teaching and virtual teaching would become non-existent, thus vastly improving effectiveness and accessibility
• Healthcare. The amalgamated expertise of medical doctors connected via the tactile Internet during remote diagnosis and treatment, as well as through the combination of experienced surgeons’ tactile sense with the high spatial precision of robot-assisted operations, would make for a zero-error rendering of health services.
• Personal safety zones. A safe bubble can be created to interact with nearby objects, also connected to the tactile Internet. Applied to road traffic, in the long term, this safety zone will be able to protect drivers, passengers, and pedestrians. Vehicles will detect safety-critical situations and react instantly to avoid traffic accidents and warn other objects of impending danger. In production environments, occupational safety levels will improve as production machines or robots will detect and avoid the risk of harm to people in their vicinity.
• Traffic in a smart city will be optimized by heeding local safety constraints as well as parameters, such as the overall traffic density in a smart city. Guided autonomous driving or platoon driving will allow for a continuous traffic flow in which safety and energy efficiency will be significantly improved as compared to today’s situation.
• Energy. In decentralized electrical energy generation and distribution networks, the tactile Internet enables dynamic activation and deactivation of local power generation and consumption, potentially even considering the AC phase information to minimize the generation of unusable reactive power.

Haptic Internet would have the most significant impact on the virtual reality space. Haptic feedback is a prerequisite for high-fidelity interaction, allowing the user to perceive the objects in the VR not only audio-visually but also via the sense of touch. This allows for sensitive object manipulations as required in tele-surgery, micro-assembly, or related applications, demanding high levels of sensitivity and precision. When two users interact with the same object, a direct force coupling is brought into existence by the VR, and the users can feel one another’s actions. High-fidelity interaction is only possible if the communication latency between the users and the VR is in the order of a few milliseconds. During these few milliseconds, the movements of the users need to be transmitted to the VR server, where the physical simulation is computed and the result is returned to the users in the form of object status updates and haptic feedback. So, 6G would have to be designed to cater to these expectations.

The haptic Internet would be a big step toward inclusive society for people with disabilities. The tactile Internet would become their extended world, providing the sensory inputs, and taking them to the other side of the communication chain. Also, the support and assistance provided to people with disabilities by exoskeleton-based artificial limbs and power amplifiers will improve their mobility, ensuring them the ability to lead a self-determined life.

In the ever-evolving landscape of wireless communication, technological advancements continue to push the boundaries of what we once deemed possible. As we adapt to the rapid growth of smart devices and the Internet of Things (IoT), the world eagerly awaits the dawn of the next generation of wireless connectivity – 6G. In summary, the transition from 5G to 6G will bring faster speeds, reduced latency, seamless connectivity, advanced AI integration, and transformative applications across various sectors. Common people will experience a new level of convenience, efficiency, and connectivity, transforming the way they live, work, and interact with technology.

This article is authored by Alka Selot Asthana, Executive Director – Telecommunications Consultants India Ltd. Views expressed are personal.