Reduced Performance Group

Description

The Reduced Performance Group is a concept introduced in 3GPP Release 19 to characterize the performance of inter-frequency and inter-RAT measurements for User Equipment (UE) that support the feature known as "Increased UE carrier monitoring UTRA or E-UTRA". This feature allows a UE to monitor a larger number of carriers than it could otherwise handle, by dividing the monitored carriers into two groups: one group with better delay performance and another group with worse delay performance. The latter is referred to as the Reduced Performance Group. The group is defined per UE category and measurement type (e.g., UTRA or E-UTRA) and is specified in technical specifications such as 25.133 (Requirements for support of radio resource management for FDD) and 36.521 (E-UTRA UE conformance specification).

The primary motivation for dividing carriers into performance groups is to enable UEs with limited measurement capabilities to still monitor additional carriers without exceeding their processing capabilities, albeit with relaxed requirements for some carriers. By accepting a longer measurement delay on certain carriers, the UE can maintain connectivity and mobility performance on the more critical carriers while still gathering information on the additional carriers. This trade-off is particularly relevant in heterogeneous networks where multiple frequencies and radio access technologies coexist.

The Reduced Performance Group is determined based on the UE's measurement capability and the network configuration. It is not a fixed set of carriers but rather a classification that results from the UE's internal scheduling and prioritization of measurement tasks. The network can use this information to adjust mobility parameters or to decide whether to rely on measurements from the reduced performance group for handover decisions. In practice, the performance difference between the groups is defined by specific delay requirements in the 3GPP specifications, ensuring that even the reduced performance group meets a minimum level of responsiveness.

From an implementation perspective, the UE must support the increased carrier monitoring feature and be configured by the network to monitor a set of carriers that exceeds its baseline capability. The UE then signals its capability to the network, indicating which carriers it can monitor with full performance and which will be relegated to the reduced performance group. The network can then use this information for radio resource management (RRM) purposes. The grouping is dynamic and may change based on factors such as signal conditions, UE mobility, and network load.

In summary, the Reduced Performance Group is a tool for managing UE measurement resources efficiently. It allows networks to extract more value from UEs with limited capabilities while maintaining overall system performance. It is particularly relevant in the context of 5G and beyond, where the diversity of frequency bands and RATs continues to grow, and UE measurement requirements become increasingly challenging.

Purpose & Motivation

The Reduced Performance Group exists to address the challenge of limited UE measurement capabilities in multi-carrier, multi-RAT environments. Prior to its introduction, UEs could only monitor a limited number of carriers with full performance, which restricted network flexibility and mobility robustness. By allowing a subset of carriers to be monitored with relaxed delay requirements, the feature enables UEs to support a larger number of carriers without significant hardware upgrades. This is particularly important for legacy UEs and for cost-sensitive devices that cannot afford the complexity of full-performance monitoring on all carriers. The concept also helps networks manage inter-frequency and inter-RAT mobility more efficiently, as they can still obtain measurements from additional carriers, albeit with longer delays, to make informed handover decisions. The introduction in Rel-19 reflects the need to support the growing number of frequency layers in 5G deployments, including both NR and legacy RATs.