Requirement Set

Description

In 3GPP New Radio (NR) specifications, a Requirement Set is a collection of radio frequency (RF) requirements that apply to a specific base station type. The base station types are defined based on their architecture and operating characteristics: BS type 1-C (conducted, single-band), BS type 1-H (hybrid, single-band), BS type 1-O (over-the-air, single-band), and BS type 2-O (over-the-air, multi-band). Each requirement set includes parameters such as output power, frequency error, unwanted emissions, blocking characteristics, and receiver sensitivity. These requirements are essential for ensuring that base stations from different vendors can coexist and operate within the same network without causing harmful interference.

The requirement sets are specified in a series of 3GPP Technical Specifications (TS). TS 38.104 defines the base station RF requirements for NR, covering conducted and radiated requirements. TS 38.108 specifies requirements for satellite access nodes, TS 38.141 covers conformance testing for base stations, and TS 38.174 defines RF requirements for multi-band base stations. TS 36.108 provides similar requirements for LTE base stations. The requirement sets are structured to address different deployment scenarios, such as macro cells, small cells, and massive MIMO systems. They also account for different frequency ranges (FR1 and FR2) and bandwidths.

The concept of a requirement set is particularly important for over-the-air (OTA) testing, where the base station's performance is evaluated through radiated measurements rather than conducted connections. For BS type 1-O and 2-O, the requirements are defined in terms of Equivalent Isotropically Radiated Power (EIRP) and radiated spurious emissions. This is necessary because advanced antenna systems (AAS) integrate the antenna array with the radio unit, making conducted measurements impractical. The requirement sets for OTA testing are more complex and include additional parameters such as beam direction, beamwidth, and spatial characteristics.

Each requirement set is associated with a specific base station class or configuration. For example, a BS type 1-C requirement set might specify a maximum output power of 46 dBm per antenna port, while a BS type 1-O requirement set might specify a maximum EIRP of 65 dBm per beam. These values are chosen to balance coverage, capacity, and interference. The requirement sets also define test procedures and measurement uncertainties, ensuring that conformance testing is consistent across vendors and test labs.

The requirement set concept has evolved with each 3GPP release to accommodate new features and deployment scenarios. In Release 15, the initial NR specifications defined requirement sets for the basic base station types. Subsequent releases added requirements for new frequency bands, wider bandwidths, and advanced features like beamforming and multi-band operation. The requirement sets are continuously updated to reflect technological advancements and regulatory requirements. For engineers, understanding the requirement sets is crucial for designing, testing, and deploying NR base stations that comply with 3GPP standards and local regulations.

Purpose & Motivation

The Requirement Set concept exists to provide a clear and structured framework for defining RF performance requirements for NR base stations. Without such a framework, it would be difficult to ensure that base stations from different vendors can interoperate and coexist without causing interference. The requirement sets specify the minimum performance levels that a base station must meet, covering both transmitter and receiver characteristics. This enables operators to deploy multi-vendor networks with confidence and ensures that the radio spectrum is used efficiently.

Historically, RF requirements for base stations were defined in a more fragmented manner, often with separate specifications for different radio access technologies. With the introduction of NR in Release 15, 3GPP took the opportunity to create a more unified and flexible framework. The requirement sets were designed to address the challenges of new technologies such as massive MIMO and beamforming, which require OTA testing. They also needed to support a wide range of deployment scenarios, from traditional macro cells to small cells and indoor systems.

The requirement sets solve several problems. First, they provide a common language for specifying base station performance, making it easier for vendors to design products that meet global market needs. Second, they enable consistent testing and certification, reducing the time and cost of bringing new products to market. Third, they ensure that base stations comply with regulatory limits on emissions and interference, protecting other services and users. Finally, they facilitate spectrum sharing and coexistence between different operators and technologies. As NR continues to evolve, the requirement sets will be updated to support new features and bands, ensuring that the framework remains relevant and effective.