Base Station type 1-C

Description

BS type 1-C is a 3GPP term defining a specific class of NR (New Radio) base station. According to the definition, it is an NR base station operating at FR1 (Frequency Range 1, i.e., sub-6 GHz) with a requirements set consisting only of conducted requirements defined at individual antenna connectors. This classification is part of the base station type framework introduced in Release 15 to address the diverse deployment scenarios and antenna configurations in 5G. The '1-C' designation indicates that the base station has conducted requirements only, meaning that its RF performance is assessed at the antenna connector rather than over the air. This is typical for base stations with external antennas or those where the antenna is not integrated, allowing conducted measurements to be performed.

The base station type framework in 3GPP TS 38.104 and related specifications defines several types: BS type 1-C, 1-H, 1-O, 2-O, etc. The '1' refers to FR1, while the letter indicates the requirement set: 'C' for conducted, 'H' for hybrid (both conducted and radiated), and 'O' for radiated (over-the-air). BS type 1-C is the simplest in terms of testing, as it only requires conducted measurements at the antenna connectors. This makes it suitable for traditional macro base stations where the antenna is connected via cables, and the RF characteristics can be measured directly. The conducted requirements include parameters like output power, frequency error, EVM, unwanted emissions, and blocking characteristics.

In contrast, BS type 1-O (radiated) is used for base stations with integrated antennas, such as massive MIMO or small cells, where over-the-air testing is necessary. BS type 1-H combines both conducted and radiated requirements, applicable to base stations that have some antenna connectors and some integrated antennas. The classification helps manufacturers, operators, and regulators apply the correct test methods and limits, ensuring that base stations comply with regional and international regulations.

The requirements for BS type 1-C are specified in 3GPP TS 38.104 (NR Base Station Radio Transmission and Reception) and TS 38.141-1 (Conducted conformance testing). These documents define the test procedures, measurement setups, and limits for conducted requirements. For example, the base station must meet certain output power limits, spectral emission masks, and receiver sensitivity levels when measured at the antenna connector. The conducted approach simplifies testing and reduces cost, as it does not require anechoic chambers or complex OTA measurement setups.

BS type 1-C is relevant for deployments where the base station is connected to external antennas, such as traditional macro cells in sub-6 GHz bands. It ensures that the base station's RF performance is compliant and interoperable with user equipment and other network elements. As 5G evolves, the base station type framework continues to be updated to accommodate new frequency ranges (FR2, mmWave) and advanced antenna systems, but BS type 1-C remains a foundational category for FR1 conducted testing.

Purpose & Motivation

The BS type 1-C classification exists to provide a clear and standardized way to define the radio requirements and testing methods for NR base stations operating in FR1 with conducted antenna connectors. Before 5G, base station requirements were often defined in a more monolithic way, but the introduction of advanced antenna systems (AAS) and massive MIMO created a need for differentiated requirements based on antenna configuration. BS type 1-C addresses the case where the base station has external antenna connectors, allowing conducted measurements to be performed directly at those connectors.

The motivation for this classification is regulatory and industry need for consistent testing. Conducted testing is well-established, cost-effective, and provides repeatable results. By defining BS type 1-C, 3GPP enables manufacturers to demonstrate compliance with conducted requirements, which are often mandated by regional regulators. It also allows operators to compare base station performance on a like-for-like basis. Without such a classification, there would be ambiguity in how to test base stations with different antenna architectures, leading to inconsistent compliance and potential interference issues.

Historically, the base station type framework was introduced in Release 15 as part of the first 5G NR specifications. It was a response to the complexity of 5G deployments, which include various frequency ranges, antenna configurations, and deployment scenarios. BS type 1-C is one of several types, and its definition has remained stable across releases, indicating its fundamental role in the ecosystem. As networks move towards 5G-Advanced and 6G, the framework will likely expand, but BS type 1-C will continue to be relevant for FR1 conducted testing.