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