Partial Radiated Sensitivity

Description

Partial Radiated Sensitivity (PRS) is a receiver performance metric introduced in 3GPP Release 19 for over-the-air (OTA) testing of NR devices. It is defined as the minimum received radiated power level required by a device to maintain a specified communication quality — such as 95% of maximum throughput — averaged over a partial sphere surrounding the device. This metric is the receiver-side counterpart to Partial Radiated Power (PRP) and is designed to address the limitations of full-sphere sensitivity measurements, particularly for devices operating at higher frequency bands with directional antenna systems.

In traditional OTA testing, Total Radiated Sensitivity (TRS) measures the minimum power level needed to achieve a target communication quality when averaged over the entire sphere. However, for mmWave devices with beamforming arrays, the receiver sensitivity can vary significantly depending on the direction from which the signal arrives. A device may exhibit excellent sensitivity in the direction of its primary beam but poor sensitivity in other directions. Full-sphere averaging can mask these directional characteristics, leading to a metric that does not accurately reflect real-world performance in deployment scenarios where the signal arrives from a specific angular region.

PRS addresses this by allowing the sensitivity to be averaged over a defined partial sphere. The partial sphere is specified by a range of azimuth and elevation angles, and the sensitivity is measured at multiple points within that region. The averaging process accounts for the device's antenna gain pattern, beamforming configuration, and receiver processing capabilities. As with PRP, the value of PRS depends on the integration range: different partial spheres will yield different sensitivity metrics. This makes it essential to clearly specify the measurement conditions when reporting PRS values.

The measurement procedure for PRS involves establishing a communication link between the device under test and a test equipment (e.g., a base station emulator) at a known power level, then gradually reducing the power until the specified communication quality (e.g., 95% throughput) is no longer maintained. This process is repeated at multiple angular positions within the partial sphere, and the results are averaged to produce the PRS value. The test setup typically uses an anechoic chamber with a positioning system that can orient the device relative to the test antenna, or a multi-probe system that can synthesize signals from different directions.

PRS is specified in 3GPP TR 38.870 (Study on enhanced OTA testing for NR) and referenced in TS 38.161 (Terminal conformance specification for NR). These specifications define the test methodology, the coordinate system, the angular ranges, and the reporting requirements. The metric is particularly relevant for devices operating in FR2 and above, where directional antenna systems are mandatory and where full-sphere OTA testing is expensive and time-consuming. By focusing on the angular region relevant to the device's intended use, PRS provides a more efficient and meaningful assessment of receiver performance.

In the broader context of 5G-Advanced and 6G development, PRS represents a shift toward more application-specific and deployment-relevant testing methodologies. As devices become more complex and operate at higher frequencies, the ability to characterize performance in a targeted manner will be essential for ensuring interoperability, optimizing network performance, and reducing testing costs. PRS, alongside PRP, forms part of a new generation of OTA metrics designed to meet these challenges.

Purpose & Motivation

Partial Radiated Sensitivity exists to provide a more accurate and practical measure of receiver performance for NR devices, particularly those operating at FR2 and higher frequencies with directional antenna systems. Traditional Total Radiated Sensitivity (TRS) averages sensitivity over the entire sphere, which can obscure the directional characteristics of beamforming devices and may not reflect real-world performance where signals arrive from specific directions.

The motivation for PRS stems from the recognition that device sensitivity is not uniform across all directions. For a device with a phased array antenna, the receiver sensitivity is typically best in the direction of the main beam and worse in other directions. In many deployment scenarios — such as fixed wireless access, indoor hotspots, or satellite communication — the signal arrives from a known angular region. Measuring sensitivity over that region provides a more relevant and cost-effective assessment than full-sphere TRS.

Previous approaches to OTA sensitivity testing either required full-sphere measurements, which are expensive and time-consuming, or used simplified metrics that did not adequately capture directional performance. PRS fills this gap by providing a standardized, flexible framework for partial-sphere sensitivity measurement. It allows stakeholders to define the angular region of interest, perform consistent measurements, and compare results across devices and test labs. This is particularly important as the industry moves toward 5G-Advanced and 6G, where higher frequencies and more complex antenna systems will make efficient OTA testing even more critical.