The future connectivity landscape, and notably, the 5G wireless systems will feature Ultra-Reliable Low Latency Communication (URLLC). The coupling of high reliability and low latency requirements in URLLC use cases makes the wireless access design very challenging, in terms of both the protocol design and of the associated transmission techniques. This paper aims to provide a broad perspective on the fundamental tradeoffs in URLLC, as well as the principles used in building access protocols. Two specific technologies are considered in the context of URLLC: massive MIMO and multi-connectivity, also termed interface diversity . This paper also touches on the importance of the proper statistical methodology for designing and assessing extremely high-reliability levels.
Multiple antenna systems appear as a natural enabler for URLLC as multiple antenna communications provide high SNR and diversity links as well as spatial multiplexing capability. Those properties contribute to increasing the reliability or the latency or both. In spite of their obvious advantages, however, those mechanisms are still relatively unexplored. A statistical characterization of multiple-input, single-output systems under statistical delay constraints is investigated in @cite_32 , using the tools of stochastic network calculus. In @cite_28 , for the uplink of a single user massive MIMO system with 64 antennas at the base station, diverse multi-antenna schemes are tested: coherent and non-coherent transceivers, transceivers assuming that the channel is unknown at the transmitter and using space-time codes, where the preference is given to non-coherent transceivers. In @cite_41 , the accent is put on the processing delay caused by multiple antenna processing at a base station in a multi-user massive MIMO system. In @cite_68 , a multi-user massive MIMO system network is optimized under a probabilistic constraint on the queue size to satisfy URLLC requirements.
@cite_28 @cite_41 @cite_68 @cite_32
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Industrial automation and safety applications demand low latency and ultra reliable communication. Currently deployed wireless communication technologies are mostly developed for non-critical applications and hence, they are not suitable for these kind of applications. On the other hand, cable based communication is widely popular in industries, even though it has limitations towards cost of installment and is susceptible towards mechanical wear and tear. This paper reviews the feasibility of large antenna arrays at the receiver to achieve low latency and ultra reliable communication for up-link scenarios. The suitability of both coherent and non-coherent multiple input multiple output (MIMO) receivers are investigated. Non-coherent MIMO receiver is found to be a promising option as signal to noise power ratio (SNR) is fairly reasonable in achieving the desired reliability. The effect of antenna correlation at the transmitter and at receiver on reliability are also looked into. Its influence on the system performance is very nominal. Moreover, in certain scenarios, antenna correlation at the transmitter gives a significant improvement in system performance. Furthermore, having a single antenna at the sensors is found not to be a limiting factor in achieving the desired performance goal. Controlling robots in real-time over a wireless interface present fundamental challenges for forthcoming fifth generation wireless networks. Mission critical real-time applications such as telesurgery over the tactile Internet require a communication link that is both ultra-reliable and low-latency, and that simultaneously serving multiple devices and applications. Wireless performance requirements for these applications surpass the capabilities of current wireless cellular standards. The prevailing ambitions for the fifth generation wireless specifications go beyond higher throughput and embrace the wireless performance demands of mission critical real-time applications in robotics and the Internet of Things. To accommodate these demands, changes have to be made across all layers of the wireless infrastructure. The fifth generation wireless standards are far from finalized but massive Multiple-Input Multiple- Output has surfaced as a strong radio access technology candidate and has great potential to cope with all these stringent requirements. In this paper, we investigate how Ultra-Reliable and Low-Latency Communication with massive MIMO can be achieved for bilateral teleoperation, an integral part of the tactile Internet. We conclude through simulation what the performance bounds are for massive MIMO and thus how to configure such a system for near deterministic latency and what the inherit trade-offs are. Ultra-reliability and low latency are two key components in 5G networks. In this letter, we investigate the problem of ultra-reliable and low-latency communication in millimeter wave-enabled massive multiple-input multiple-output networks. The problem is cast as a network utility maximization subject to probabilistic latency and reliability constraints. To solve this problem, we resort to the Lyapunov technique, whereby a utility-delay control approach is proposed, which adapts to channel variations and queue dynamics. Numerical results demonstrate that our proposed approach ensures reliable communication with a guaranteed probability of 99.99 , and reduces latency by 28.41 and 77.11 as compared to baselines with and without probabilistic latency constraints, respectively.