Maximum Passband Output Power

Description

Maximum passband output power is a radio frequency (RF) performance metric introduced in 3GPP Release 19 for multi-band and multi-passband NR operation. It is defined as the mean power level measured per passband at the antenna connector, during the transmitter ON state in a specified reference condition. This parameter is specified in 3GPP TS 38.106 (NR repeater conformance testing) and TS 38.115 (NR repeater radio transmission and reception), indicating its relevance to repeater and multi-band base station deployments. The concept is part of the ongoing effort to support flexible spectrum usage and carrier aggregation across multiple passbands in 5G-Advanced networks.

In a multi-band transmitter, a passband is a contiguous range of frequencies that is processed by a common RF chain or filter. The maximum passband output power defines the upper limit of the mean power that can be transmitted within that passband, measured at the antenna connector. This is distinct from the total maximum output power of the transmitter, which may aggregate power across multiple passbands. The per-passband limit ensures that each passband complies with regulatory emission limits and does not cause excessive interference to other services or adjacent bands. The measurement is performed during the transmitter ON state, meaning the transmitter is actively transmitting a signal, and under specified reference conditions (e.g., specific modulation, bandwidth, and power settings).

The parameter is particularly important for repeaters and multi-band base stations that operate in non-contiguous spectrum. In such systems, the power amplifier (PA) may amplify multiple passbands simultaneously, and the power distribution among passbands must be controlled to avoid saturation and intermodulation distortion. The maximum passband output power provides a clear specification for testing and conformance, ensuring that the equipment meets the required performance. It also helps in network planning and interference coordination, as operators can predict the coverage and interference footprint of each passband.

Technically, the maximum passband output power is measured using a power meter or spectrum analyzer connected to the antenna connector. The measurement bandwidth is typically the passband bandwidth, and the power is averaged over the active period. The reference conditions include the operating band, the channel bandwidth, the modulation scheme, and the resource block allocation. The value is expressed in dBm and may vary depending on the frequency range (FR1 or FR2) and the passband configuration. 3GPP defines test cases to verify that the equipment does not exceed the maximum passband output power under various conditions, including extreme temperatures and voltages.

The concept is closely related to other RF parameters such as maximum output power, configured transmitted power, and power headroom. It is also relevant to the UE side, where similar per-passband power limits may apply for multi-band UE transmissions. However, the current definition in TS 38.106 and 38.115 is focused on repeaters and base stations. As networks evolve towards higher spectrum aggregation and multi-band operation, the maximum passband output power will become increasingly important for ensuring coexistence and efficient use of spectrum.

In summary, maximum passband output power is a key RF conformance parameter for multi-band NR transmitters. It ensures that each passband operates within its allocated power budget, preventing interference and ensuring reliable operation. It is part of the broader 3GPP framework for radio transmission and reception, which aims to guarantee interoperability and performance across diverse deployments.

Purpose & Motivation

The maximum passband output power parameter was introduced to address the challenges of multi-band and multi-passband operation in 5G-Advanced networks. As operators aggregate more spectrum across non-contiguous bands, transmitters must manage power distribution across multiple passbands to avoid nonlinear distortion and spectral regrowth. Traditional single-band power specifications were insufficient because they did not account for the per-passband power limits needed to protect adjacent bands and ensure regulatory compliance. The maximum passband output power provides a clear, measurable limit for each passband, enabling equipment vendors and operators to design and test multi-band systems effectively.

Before this parameter, multi-band transmitters were often specified with a total maximum output power, which could allow one passband to dominate and cause excessive interference in that band while starving others. The per-passband limit ensures fair power allocation and prevents any single passband from exceeding its allowed emission level. This is particularly important for repeaters, which amplify signals in multiple bands and must maintain linearity to avoid intermodulation products that could desensitize receivers.

The parameter also supports the evolution towards more flexible spectrum usage, including dynamic spectrum sharing and carrier aggregation across bands. By defining a standardized measurement method and reference conditions, 3GPP ensures that equipment from different vendors can be tested consistently, facilitating multi-vendor deployments and interoperability. The maximum passband output power is therefore a key enabler for efficient and reliable multi-band 5G networks.