  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. The paper also touches upon the important question of the
proper statistical methodology for designing and assessing extremely high
reliability levels.
