uRLLC

Ultra-Reliable Low-Latency Communications (URLLC) is a service category in 5G New Radio (NR) focused on delivering extremely dependable communications with very low end-to-end latency. It is designed to support time-critical applications where missed or delayed data can have serious consequences, such as safety, automation, or remote operation.

Key characteristics of URLLC include very low latency, typically in the single-digit to low tens of milliseconds depending on the use case and network conditions, and extremely high reliability, with target packet loss rates often in the range of 10^-5 to 10^-6. The design also emphasizes small or short payloads, deterministic or bounded latency, and mechanisms to reduce scheduling delays, jitter, and retransmissions. Techniques commonly employed include flexible numerology and short transmission time intervals, grant-free access for faster transmission, diversity across antennas and paths, and the use of edge computing to minimize backhaul hops.

Technical approaches combine network design and radio features with advanced resource management. Network slicing can allocate dedicated resources for URLLC flows, while edge computing brings processing closer to the user. Redundant transmissions, optimized HARQ procedures, and low-latency scheduling help meet strict timing constraints. Short packets and efficient coding reduce overhead and improve reliability.

Applications include industrial automation and robotics, autonomous or cooperative vehicles, teleoperation and remote surgery, and other mission-critical IoT scenarios. Realizing URLLC requires network densification, ultra-reliable backhaul, and careful traffic planning to balance latency, reliability, and capacity.