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

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.There is a general consensus that the future of many industrial control, traffic safety, medical, and internet services depends on wireless connectivity with guaranteed consistent latencies of 1ms or less and exceedingly stringent reliability of BLERs as low as 10 -9 [3]. While the projected enormous capacity growth is achievable through conventional methods of moving to higher parts of the radio spectrum and network densifications, significant reductions in latency, while guaranteeing an ultra-high reliability, will involve a departure from the underlying theoretical principles of wireless communications. II. Emerging URLLC ApplicationsIn this section, we briefly introduce three emerging mission-critical applications, including telesurgery, intelligent transportation, and industry automation, whose latency and reliability requirements will be identified. Other possible applications of URLLC include Tactile Internet, augmented/virtual reality, fault detection, frequency and voltage control in smart grids, which are not elaborated here due to space limitation. A. Tele-surgeryThe application of URLLC in tele-surgery has two main use cases [4]: (1) remote surgical consultations, and (2) remote surgery. The remote surgical consultations can occur during complex life-saving procedures after serious accidents with patients having health emergency that cannot wait to be transported to a hospital. In such cases, first-responders at an accident venue may need to connect to surgeons in hospital to get advice and guidance to conduct complex medical operations. On the other hand, in a remote surgery scenario, the entire treatment procedure of patients is executed by a surgeon at a remote site, where hands are replaced by robotic arms. In these two use cases, the communication networks should be able to

Wireless Access in Ultra-Reliable Low-Latency Communication (URLLC)

“…A detailed description of URLLC use cases that are expected to play important roles in future 5G networks can be found in [6]; these include automotive, Industry 4.0, ITS and ad-hoc disaster and emergency relief. Another take on emerging mission-critical services in cellular networks, such as telesurgery, ITS and industrial automation, is given in [11]. Live audio production, another potential URLLC use case, is described in [49]; notably, this use case emphasizes isochronous communication that is not supported by 4G and the article elaborates the ways to achieve it in 5G networks.…”

Physical Layer Security for Ultra-Reliable and Low-Latency Communications

“…We note that this example demonstrates the importance of both the information confidentiality and message integrity, since the leaked random sequence leads to the fake misleading information being accepted (message integrity is not guaranteed). A brief discussion on the importance of message integrity in the context of URLLC can be found in [4] and in this work we focus on the information confidentiality. We also note that information confidentiality is widely addressed by cryptography algorithms in traditional communications.…”

On Performance Evaluation of Random Access Enhancements for 5G uRLLC

“…The third generation partnership project (3GPP) aims at realizing such uRLLC applications with ultra-low latency of 1 ms and 10 ms for user plane and control plane, respectively, and ultra-high reliability of more than 99.999% in terms of packet delivery performance [4]. However, the most critical source of latency in stateof-the-art long term evolution (LTE) radio access networks (RAN) is the initial link establishment using random access channel (RACH) procedure that can take several tens of milliseconds [5]. This becomes particularly problematic for FoF applications due to intermittent transmissions by uRLLC devices with small payloads contending for fixed number of preambles along with the massive, periodic and bursty nature of other applications.…”