Maximum carrier Total Radiated Power

Description

Maximum carrier TRP (Total Radiated Power) is a key RF parameter for base stations equipped with advanced antenna systems (AAS), such as massive MIMO in 5G. It specifies the mean power level measured per radiated interface boundary (RIB) during the transmitter ON period for a specific carrier, under a specified reference condition. This parameter corresponds to the declared rated carrier TRP (Prated,c,TRP) and is used to characterize the radiated power of a carrier when the base station uses beamforming or multi-antenna transmission.

In traditional base stations, power is measured at the antenna connector, which is a conducted interface. However, with AAS, the antenna elements are integrated with the radio, and there is no accessible conducted interface. Therefore, TRP is used as a radiated metric, measured over the air. The maximum carrier TRP is defined in 3GPP specifications such as TS 37.145 and TS 38.141, which cover the RF requirements for AAS base stations. It is a critical parameter for ensuring that the base station complies with regulatory limits on radiated power and for network planning.

The measurement of maximum carrier TRP involves integrating the power radiated by the base station over the entire sphere surrounding the antenna. This is done using a test setup that captures the radiated power in different directions and calculates the total. The RIB is a conceptual boundary that separates the antenna from the rest of the base station, and the power is measured at this boundary. The transmitter ON period is the duration during which the base station is actively transmitting, excluding any guard periods or idle times.

The parameter is particularly important for 5G NR base stations operating in millimeter wave bands, where beamforming is essential to overcome high path loss. In such systems, the maximum carrier TRP determines the coverage and link budget. It also affects the interference levels in the network, as higher TRP can cause more interference to neighboring cells. Therefore, operators must carefully manage the TRP of each carrier to balance coverage and capacity.

The evolution of maximum carrier TRP reflects the shift from conducted to radiated testing in 3GPP. Introduced in Release 15, the term has been maintained with minor formatting changes. It is expected to remain relevant as 5G evolves towards higher frequencies and more advanced antenna systems.

Purpose & Motivation

Maximum carrier TRP was introduced to address the need for a radiated power metric for base stations with integrated antenna systems, where traditional conducted measurements at the antenna connector are not possible. It solves the problem of characterizing and limiting the radiated power of AAS base stations, ensuring compliance with regulatory requirements and enabling fair coexistence with other systems.

Before the advent of AAS, base station power was specified at the antenna connector, which provided a clear and repeatable measurement point. However, with AAS, the antenna is tightly integrated with the radio unit, and there is no physical connector. This necessitated a new approach based on over-the-air measurements. The maximum carrier TRP provides a standardized way to declare and verify the radiated power of a carrier, which is essential for type approval and network deployment.

The parameter also supports the implementation of beamforming, where the radiated power is concentrated in specific directions. By defining the maximum carrier TRP, 3GPP ensures that the total radiated power does not exceed limits, while allowing flexibility in beamforming gain. This is crucial for millimeter wave systems, where high gain is needed to overcome propagation losses, but excessive power can cause interference.