Lower sub-block edge

Description

The Lower sub-block edge is a fundamental frequency reference point defined in 3GPP specifications for radio transmission and reception. It represents the frequency at the lower edge of a sub-block, which is a contiguous portion of an operating band that is treated as a single entity for the purpose of defining transmitter and receiver requirements. Sub-blocks are used to divide an operating band into smaller segments, allowing for more granular and flexible definition of RF requirements, especially in multi-band and carrier aggregation scenarios.

In the context of 3GPP TS 25.104 (UTRA FDD), TS 36.104 (E-UTRA), and TS 38.104 (NR), the Lower sub-block edge serves as an anchor point for specifying out-of-band emissions, spurious emissions, and other RF parameters. For example, the lower sub-block edge may be used to define the boundary of the sub-block for the purpose of calculating the maximum output power or the adjacent channel leakage ratio (ACLR). It is also used in receiver requirements such as blocking and adjacent channel selectivity, where the sub-block edge helps define the frequency offsets for interferers.

The concept of sub-blocks was introduced to handle the increasing complexity of spectrum usage, particularly with the introduction of carrier aggregation and multiple operating bands. By defining sub-block edges, 3GPP can specify requirements that apply to a portion of the band rather than the entire band, which is essential when a UE or BS operates on multiple carriers within the same band. The Lower sub-block edge is paired with the Upper sub-block edge to fully define the sub-block boundaries.

In practice, the Lower sub-block edge is used in test specifications such as TS 25.141, TS 36.141, and TS 38.141 to verify that a device meets the required performance. Test equipment and measurement procedures reference this frequency to ensure that the device's transmitter and receiver characteristics are evaluated correctly. The exact value of the Lower sub-block edge depends on the operating band and the sub-block configuration, which is typically defined in the band-specific tables of the core specifications.

Overall, the Lower sub-block edge is a critical parameter for ensuring interoperability and efficient spectrum utilization in 3GPP networks. It enables flexible and scalable RF requirements that can adapt to various deployment scenarios, including those with multiple carriers and diverse band combinations.

Purpose & Motivation

The Lower sub-block edge exists to provide a precise frequency reference for defining RF requirements in a granular manner. Before its introduction, RF requirements were often defined for the entire operating band, which became impractical with the advent of carrier aggregation and the need to support multiple sub-blocks within a single band. The Lower sub-block edge allows 3GPP to specify transmitter and receiver requirements for a portion of the band, enabling more efficient and flexible spectrum usage.

This concept was motivated by the growing complexity of radio frequency (RF) front-ends and the need to ensure that devices can coexist and operate correctly in multi-carrier and multi-band scenarios. By defining sub-block edges, the specifications can address scenarios where different sub-blocks have different requirements, such as when a sub-block is used for a specific service or when it is adjacent to another operator's spectrum. This granularity helps in minimizing interference and optimizing performance.

Furthermore, the Lower sub-block edge facilitates testing and certification by providing a clear reference point for measurements. It allows test houses to verify compliance with 3GPP requirements in a consistent manner, regardless of the specific band or sub-block configuration. This has become increasingly important as the number of bands and band combinations has grown exponentially with each new release.