What is eURLLC?

eURLLC stands for enhanced URLLC and is an enhancement to the URLLC (Ultra Reliable Low Latency Communication) characteristics of 5G which were introduced in Release 15 of the 3GPP specifications. eURLLC was introduced in Release 16 and is a subset of the 5G network architecture that supports highly important data transfer that requires low latency and high reliability for mission-critical applications.

The core technology of eURLLC is based on URLLC which demonstrates excellent reliability and low latency. To better understand the eURLLC technology, we must first evaluate the characteristics of URLLC. 

Key characteristics of URLLC (will get to eURLLC shortly)

• Less than 0.001% of 20-byte packets fail to be delivered after 1 ms. 
• Supports use cases that require high network reliability, more than 99.999%, and extremely low latency of approximately 1 millisecond for data transmission. 
• Uses network slicing, also known as software-defined networking or SDN technology, which enables each of the three 5G areas (mMTC, eMBB and URLLC) to operate separately within the 5G ecosystem. Each slice essentially acts as its own network, with its own provisioning, security, and quality of service requirements. So mMTC, which requires low security and bandwidth, is separated from URLLC, which provides high security and high reliability. Yet each of these slices exists within the same physical network infrastructure. 
• Uses technologies such as beamforming, network slicing and packet retransmission protocols to improve reliability and reduce latency. 
• A URLLC 5G system can also use grant-free uplink access, whereby base stations can reserve capacity for uplink transmissions. Hence, the user device does not need to wait for scheduling requests and grant access, which dramatically reduces end-to-end latency. As for downlink data, resources can be allocated from other network slices too. This is known as pre-empting and the device will be notified that the connection type has changed.

Enhancements in eURLLC

eURLLC from 3GPP Release 16 builds on this URLLC foundation established in Release 15 and enhances ultra-reliable, low-latency communication. 

The following are the changes introduced in eURLLC:

• Redundant transmission in the user plane
• Improvements during the handover procedure
• Session continuity
• Automated GBR service recovery 
• Division of E2E and PDB
• QOS monitoring
• Physical layer improvements

In order to address new vertical use cases such as factory automation, Release 16 is enhancing the 5G URLLC foundation to deliver even better link reliability (up to 99.9999%). For these use cases, simply increasing the number of retransmissions is insufficient, as there is usually also a stringent latency bound. Among others, one key technology to overcome this system challenge is coordinated multi-point (CoMP). It utilizes multi-TRP to introduce redundant communication paths with spatial diversity, so even when a path is temporarily blocked, the communication is uninterrupted by using the remaining paths.

Enhancements and Benefits of eURLLC

• Improved HARQ: Multiple HARQ feedbacks per slot for latency reduction
• Inter-device service multiplexing: Uplink cancellation indicator and power boosting
• Coordinated multi-point (CoMP): Multi-TRP (multiple transmission and reception points) for redundant communication paths with spatial diversity
• Intra-device channel prioritization: COncurrently supporting differentiated levels of service (for e.g. eMBB and mission-critical)
• Increased redundancy: Number of PDCP (packet data convergence protocol) packet duplicates increasing from 4 to 2
• More flexible scheduling: Multiple active SPS (semi-persistent scheduling) configurations and reduced periodicity, more efficient DL control monitoring and UL repetition with cross-slot boundaries
• Enhancements of session continuity
  • PSA relocation for Ethernet PDU Session.
  • Enhancements for ULCL relocation
  • Enhancements to AF-influenced traffic routing mechanism
• QoS Monitoring
• High-reliability redundant transmission in user plane
  • Dual-connectivity-based end-to-end redundant user plane paths
  • Support of redundant transmission on N3/N9 interfaces
  • Support of redundant transmission at transport layer

Applications of eURLLC

eURLLC is designed to support the same applications as URLLC but better. Autonomous driving is one of the main applications that would require a capable connection like eURLLC, as there is such a high risk involved. Autonomous driving has a whole host of benefits, from time-saving to improving safety by eliminating user error. However, it would need all vehicles to be connected to each other vehicle-to-vehicle, and to roadside systems, vehicle-to-infrastructure, such as traffic light systems, emergency services and road maintenance programs. Data would need to be shared in real-time, with minimal latency, as safety requirements demand ultra-reliable connections. Smart factories and Industry 4.0 also have similar requirements, where machinery and robotics need to interact with each other in real-time. They might also require real-time information from other sensors across the manufacturing facility. Low-latency systems allow these machine-operated systems to work safely and efficiently to enhance production lines. Other use cases can include remote and augmented reality healthcare, such as remote surgery, smart electricity distribution and cloud-based gaming and entertainment.