Enhanced channel raster

Description

The enhanced channel raster is a physical layer concept introduced in 3GPP Release 19 for New Radio (NR). It defines a channel raster with a granularity of 10 kHz for frequency bands that normally have a 100 kHz channel raster. The channel raster determines the set of frequencies on which a carrier can be placed within a band. A finer raster allows for more precise positioning of carriers, which can improve spectrum efficiency, facilitate spectrum sharing, and enable better coexistence with other systems.

In traditional NR operation, the channel raster for many bands is 100 kHz, meaning that the center frequency of a carrier must be a multiple of 100 kHz. This coarse granularity can lead to inefficient use of spectrum, especially when trying to align with other technologies or when operating in fragmented spectrum. The enhanced channel raster reduces the granularity to 10 kHz, providing ten times more possible carrier positions. This is particularly beneficial for bands where operators need to avoid interference with adjacent carriers or where they want to maximize the use of available spectrum.

The enhanced channel raster is specified in 3GPP TS 38.101 (UE radio transmission and reception) and TS 38.104 (BS radio transmission and reception). It applies to specific bands, and the UE and gNB must support the finer raster to utilize it. The implementation involves additional signaling to indicate the exact carrier frequency, as the synchronization signals and broadcast channels must be placed accordingly. The finer raster may also impact the design of filters and oscillators, but modern radio technology can handle the increased flexibility.

One of the key use cases for the enhanced channel raster is in spectrum sharing scenarios, such as those involving dynamic spectrum access or coexistence with satellite systems. By allowing carriers to be placed with 10 kHz granularity, operators can better fit their channels into available spectrum, reducing guard bands and improving overall spectral efficiency. It also supports the deployment of narrowband carriers or supplementary uplink/downlink in fragmented spectrum.

The enhanced channel raster is part of the ongoing evolution of NR to support more diverse spectrum and deployment scenarios. As networks move towards 6G, finer raster granularity and more flexible spectrum usage will become increasingly important. The concept is expected to be further refined in future releases to support even more precise channel placement and dynamic spectrum adaptation.

Purpose & Motivation

The enhanced channel raster was introduced to address the limitations of the traditional 100 kHz channel raster in NR, which restricted the flexibility of carrier placement and could lead to inefficient spectrum utilization. In many bands, especially those with fragmented spectrum or shared with other services, a finer raster is needed to align carriers precisely and avoid interference. The 100 kHz raster often forced operators to leave unused guard bands or to place carriers suboptimally, reducing spectral efficiency.

Previous releases of NR used a fixed raster per band, which was sufficient for initial deployments but became inadequate as spectrum became more congested and sharing scenarios more common. The enhanced channel raster provides a standardized way to achieve finer granularity without requiring new band definitions. It enables operators to make the most of their spectrum assets, particularly in bands where coexistence with other technologies (e.g., LTE, satellite) is required.

The motivation also comes from the need to support new services and deployment models, such as private networks and localized spectrum access. By allowing 10 kHz granularity, the enhanced channel raster facilitates the deployment of carriers in spectrum chunks that are not aligned to 100 kHz boundaries, which is common in shared or unlicensed spectrum. This flexibility is essential for the efficient operation of 5G-Advanced and future 6G networks.