Reference Signal Received Path Power

Description

Reference Signal Received Path Power (RSRPP) is a key physical layer measurement introduced in 5G New Radio (NR) to support advanced antenna systems and multi-connectivity scenarios. Unlike traditional RSRP, which provides a wideband power measurement of reference signals, RSRPP is designed to measure the received power of a specific, identifiable signal path. This granularity is essential in environments where multiple Transmission and Reception Points (TRPs) or multiple beams from the same TRP are used simultaneously or in a coordinated fashion. The measurement is performed on specific reference signals, such as Channel State Information Reference Signals (CSI-RS) or Synchronization Signal Blocks (SSBs), that are configured for multi-TRP or multi-beam operations.

Architecturally, RSRPP measurement and reporting are managed by the UE's physical layer and Layer 2/3 protocols under network configuration. The gNB configures the UE via RRC signaling to measure specific CSI-RS resources or SSB resources associated with different TRPs or beams. The UE then measures the linear average power of the resource elements carrying these specific reference signals for the configured path. The measurement result, typically in dBm, is filtered and reported to the network, which uses this information for dynamic scheduling, beam management, and link adaptation decisions.

RSRPP's role is pivotal for enabling features like Non-Coherent Joint Transmission (NC-JT), where data is transmitted from multiple TRPs to a single UE, and for sophisticated beam management and recovery procedures. By understanding the received power on a per-path basis, the network can make intelligent decisions about which TRPs or beams to activate, how to balance power, and how to maintain robust connectivity in challenging radio conditions. It provides a foundational metric for the multi-connectivity and ultra-reliable low-latency communication (URLLC) use cases defined in 5G.

Purpose & Motivation

RSRPP was created to address the limitations of traditional RSRP in the context of 5G's advanced antenna technologies and multi-connectivity architectures. Prior to NR, LTE's RSRP provided an aggregate power measurement useful for cell selection and mobility, but it lacked the granularity needed to distinguish between multiple concurrent transmission paths from different TRPs or highly directional beams. As 5G introduced concepts like multi-TRP operation, integrated access and backhaul (IAB), and sophisticated beamforming, a new measurement was required to assess the quality of individual spatial paths.

The primary problem RSRPP solves is enabling the network to perform accurate link budget analysis and resource management for specific transmission paths. This is critical for maximizing the spectral efficiency and reliability gains promised by multi-antenna systems. For instance, in a coordinated multi-point (CoMP) scenario, the network needs to know the precise received power from each participating TRP to decide on power allocation and modulation and coding schemes (MCS) for each stream. RSRPP provides this essential data, facilitating features that improve cell-edge performance, increase network capacity, and enhance robustness against blockages—key requirements for 5G's enhanced Mobile Broadband (eMBB) and URLLC services.