Ultra-Reliable Low Latency Cellular Networks: Use Cases, Challenges and Approaches (1709.00560v2)

Abstract: The fifth-generation cellular mobile networks are expected to support mission critical ultra-reliable low latency communication (URLLC) services in addition to the enhanced mobile broadband applications. This article first introduces three emerging mission critical applications of URLLC and identifies their requirements on end-to-end latency and reliability. We then investigate the various sources of end-to-end delay of current wireless networks by taking the 4G Long Term Evolution (LTE) as an example. Subsequently, we propose and evaluate several techniques to reduce the end-to-end latency from the perspectives of error control coding, signal processing, and radio resource management. We also briefly discuss other network design approaches with the potential for further latency reduction.

• The paper provides a comprehensive analysis of latency sources in 4G and 5G networks that hinder URLLC performance.
• It introduces innovative techniques such as short error control codes and ultra-fast signal processing to reduce communication delays.
• The study illustrates the critical role of non-orthogonal multiple access and resource block slicing in enabling mission-critical applications.

Overview of "Ultra-Reliable Low Latency Cellular Networks: Use Cases, Challenges and Approaches"

The paper "Ultra-Reliable Low Latency Cellular Networks: Use Cases, Challenges and Approaches" addresses the demands and potential solutions for real-time, high-reliability communication over fifth-generation (5G) cellular networks. As 5G is poised to carry unprecedented data volumes, the focus shifts to supporting Ultra-Reliable Low Latency Communication (URLLC) for mission-critical applications. The authors He Chen, Rana Abbas, Peng Cheng, Mahyar Shirvanimoghaddam, Wibowo Hardjawana, Wei Bao, Yonghui Li, and Branka Vucetic from The University of Sydney have provided a comprehensive examination of the latency sources in current cellular systems and propose strategies to ameliorate them.

Key Elements

The paper delineates several critical applications requiring URLLC capabilities, among them tele-surgery, intelligent transportation, and industrial automation. These scenarios demand stringent reliability and latency—RTTs lower than 1 ms with block error rates as low as 10⁻⁹. For instance, in tele-surgery applications, the communication system must support highly reliable and instantaneous feedback, especially for haptic input critical to surgical operations.

Latency Sources and Challenges

Current 4G LTE networks exhibit several latency sources including scheduling requests, random access, signal processing, and the core network delay which aggregate latency levels inappropriate for URLLC needs. The authors systematically quantify these delays, illustrating a need to drastically reduce the combined latency factors from various network components.

Proposed Solutions

The paper proposes multiple approaches to reduce latency, primarily focusing on the physical and access layers of the network architecture.

1. Short Error Control Codes: The authors explore the benefits of self-adaptive and rateless codes, such as Analog Fountain Codes (AFC), capable of dynamic code rate adjustments over varying channel conditions, thus eliminating the channel state information (CSI) related overhead.
2. Ultra-Fast Signal Processing: Emphasis is placed on new signal processing techniques, such as parallel interference cancellation and enhanced channel estimation methodologies that significantly reduce computational latency while maintaining system throughput.
3. Non-Orthogonal Multiple Access (NOMA): The implementation of NOMA, particularly code-domain NOMA, is examined as it offers a system where multiple devices share resources grant-free, overcoming latency issues posed by traditional orthogonal methods in high-density networks.
4. Resource Block Slicing: Resource reservation via slicing allows for isolating services’ resource demands, reducing latency by minimizing cross-service interference and traffic overload problems.

Implications and Future Directions

The paper suggests that achieving URLLC will necessitate innovations across various layers of network architecture. Future exploration could involve cross-layer error control, device-to-device communication, and mobile edge computing, each requiring additional research and development. These components are vital for establishing communications that not only meet latency and reliability thresholds but also continue to evolve with emerging technological demands such as Internet-of-Things (IoT) applications.

Conclusion

By extensively analyzing latency sources in cellular networks, the authors present credible methods for latency reduction. While the necessity for ultra-reliable, low-latency communication is established, realizing URLLC in practice requires a multi-faceted approach as outlined. There is a potential in combining advances in coding strategies, signal processing, and resource management to address the challenges that lie ahead in evolving 5G infrastructure and beyond.