Understanding Resilience in Communication Networks
Resilient systems are those that are prepared to face challenges, withstand them, and prevent most from causing performance degradation. They can also absorb the impact of significant challenges, ensuring essential functionalities or a minimum service level. Moreover, resilient systems can recover, adapt, and evolve based on the experiences learned during this process.
Resilience is a critical requirement for communication networks, especially as they become increasingly integrated into various aspects of modern digital society, including smart cities, homes, healthcare, transportation, and factories. Any disruption to these digital services, whether due to human or technical failures, natural disasters, or terrorism, can significantly impact citizens’ daily lives. Hence, 6G networks need not only to provide high-performance services but also to be resilient in maintaining essential services in the face of potentially unknown challenges.
Resilience can be distinguished from related terms like availability, reliability, robustness, and security. While these terms may initially seem synonymous with resilience, there are significant differences. The primary distinction is that resilience encompasses all types of challenges and failures, even those that are rare or unforeseen, and aims to maintain a minimum service level, in contrast to robust systems that offer normal operation in the face of a failure or fully fail.
Enabling Resilience in Communication Networks
To realize a resilient communication system, certain capabilities are required, including the ability to:
- Protect: Incorporate mechanisms to inherently ensure protection against various types of challenges, such as security attacks, single points of failure, perturbations, and complex state management.
- Detect: Identify potential challenges and failures through local sensing, global monitoring, anomaly detection, prediction, and interpretation of the network’s state.
- Recover: Adapt the system’s operation based on its local state, the network’s global state, and application requirements, including the ability to quickly transition between available operational modes to absorb challenges and recover to normal operation.
These capabilities can be realized through three holistic enabling principles, which form the Resilience-by-Design (RBD) framework:
- Protective Design Measures (P1): Embed protective mechanisms into the early design stage of the network, such as secure protocols, single-point-of-failure-free architectures, and stateless designs.
- Self-Awareness Capability (P2): Equip the system with sensing, monitoring, anomaly detection, prediction, and interpretation capabilities to identify potential challenges and failures.
- Reconfiguration Capability (P3): Enable the system to dynamically transition between available operational modes to absorb challenges and recover to normal operation, including long-term adaptation through learning.
Applying Resilience-by-Design Across 6G Layers
To realize end-to-end resilience in 6G communication networks, the RBD principles must be applied across various system layers and perspectives, including:
Electronics
Ensure the robustness of electronic components, such as microprocessors and memories, against challenges like temperature fluctuations, power disruptions, and soft errors. Incorporate protective measures, state management, and redundancy to mitigate these threats.
Physical Channels
Implement strategies to enhance the resilience of physical communication channels, including protection against jamming, eavesdropping, and unfavorable channel conditions. Leverage techniques like channel hopping, spectrum spreading, coding, and intelligent reconfigurable surfaces.
Network Components and Functions
Design network components, including both hardware and software (e.g., virtual network functions), to be robust against failures, power outages, and security attacks. Implement measures such as state management, redundancy, and secure access control.
Networks
Ensure the resilience of network connectivity, including both control plane and data plane, by deploying diverse components, redundant links, and adaptive reconfiguration capabilities. Minimize the interdependence between network components to prevent cascading failures.
Services
Enhance the resilience of applications and services running over the 6G network, considering aspects like prioritization, adaptable service placement, and service-level resilience. Leverage machine learning techniques for automated adaptation and learning.
Cross-Layer and Cross-Infrastructure Considerations
Address the challenges posed by the complex interdependencies between different layers and the interactions between the 6G network and other critical infrastructures, such as the power distribution grid. Ensure the resilience of the control plane connectivity and maintain a zero-touch configuration to avoid single points of failure.
Balancing Resilience and Complexity/Cost
Designing resilient 6G communication systems involves trade-offs between resilience and complexity/cost. While using RBD principles can significantly enhance system resilience, they also increase the design complexity and cost. Therefore, an efficient RBD design aims to meet the required resilience requirements with minimum cost and complexity.
The degree of resilience needed may vary depending on the application requirements. For instance, remote surgery may demand a very high level of resilience, while a monitoring network can tolerate lower levels. Hence, it is crucial to characterize the impact of resilience enablers on the end-to-end resilience of the 6G system for a given service and application, guiding the system designer in choosing the right settings.
Additionally, managing the complexity of the entire communication network is a crucial challenge when implementing resilience strategies, as the higher the network complexity, the more susceptible it is to complex failures. Finding a balance between the system reconfigurability and complexity constitutes another challenging trade-off for the design of resilient 6G communication systems.
Resilience-by-Design in Action: 6G Use Cases
To illustrate the application of the RBD concept, let’s explore a few 6G use cases:
Distributed Cloud-based Monitoring
In a smart city scenario, numerous sensors are deployed to gather data, which is then transmitted to cloud-based processors for analysis and monitoring. The RBD principles can be applied to ensure resilience against various failure scenarios, such as sensor failures, link disruptions, processing failures, and control center malfunctions. For example, the system can leverage self-awareness capabilities to detect challenges, reconfigure operational modes to absorb the impact, and maintain a minimum level of visualization for end-users.
Autonomous Driving
6G will enable highly reliable and low-latency communication, supporting autonomous and remote-controlled driving applications. The RBD framework can be applied to ensure the resilience of this critical system, addressing challenges like sensor failures, link disruptions (including jamming), and processing failures. Strategies may include redundant sensors, diverse communication links, and autonomous decision-making capabilities to safely respond to disruptions.
Smart Factory Automation
Automated factories rely on 6G technology to enable real-time control of production processes, leveraging URLLC and mMTC capabilities. The RBD approach can be applied to maintain the resilience of the factory’s sensor network, communication links, and data processing, addressing challenges such as sensor failures, link disruptions, and control center malfunctions. Measures may include redundant sensors, backup communication links, and reconfigurable processing platforms.
Conclusion and Future Research Directions
This article has introduced a comprehensive framework for embedding resilience concepts into the design of 6G communication networks. By adopting the Resilience-by-Design (RBD) approach, which includes protective design measures, self-awareness capabilities, and reconfiguration capabilities, 6G systems can be better prepared to face and respond to a wide range of challenges, from security attacks to natural disasters.
As the development of 6G networks continues, several future research directions emerge, including:
- CAD tools for resilient electronic systems: Developing design tools that consider resilience requirements from the early design phases.
- Strategic threats and security services: Investigating the design and implementation of security services to protect against malicious interference in 6G’s increasingly open and distributed infrastructures.
- Anomaly detection in 6G: Exploring novel anomaly detection approaches that can adapt to the real-time requirements and highly dynamic conditions of 6G networks.
- Design of resilient operational modes: Determining how to design and evolve the necessary operational modes to address potential challenges and improve system resilience.
- Measuring end-to-end resilience: Establishing a set of relevant resilience metrics and methods to maximize these metrics for the entire 6G system.
- Long-term availability of network services: Addressing the challenge of optimal resource allocation and dynamic provisioning to ensure the long-term availability of 6G network services.
By addressing these research challenges, the resilience-by-design approach can be further refined and implemented to ensure that future 6G communication networks are prepared to withstand a wide range of threats and disruptions, maintaining essential services and safeguarding the digital society.