Description
The Statistical Spatial Channel Model (SSCM) is a comprehensive, geometry-based stochastic channel model (GSCM) standardized by 3GPP for the design, testing, and performance evaluation of New Radio (NR) air interface technologies, particularly those involving advanced multi-antenna systems. Defined in specifications like TR 38.900 and TR 38.901, it provides a mathematical framework to simulate the radio propagation channel between a transmitter (e.g., gNB) and a receiver (e.g., UE) in a statistically accurate manner. The model captures the spatial characteristics of the channel, which are paramount for technologies like Massive MIMO, beamforming, and multi-user MIMO.
The SSCM operates by modeling the propagation path as a combination of multiple clusters. Each cluster represents a group of multipath components with similar delay and angular properties. Key large-scale parameters (LSPs) such as delay spread, angular spread (azimuth and zenith at both arrival and departure), shadow fading, and pathloss are first drawn from statistical distributions that are specific to a defined scenario (e.g., Urban Microcell (UMi), Urban Macrocell (UMa), Rural Macrocell (RMa), Indoor Office). These LSPs are correlated with each other based on real-world measurements. Within each cluster, small-scale parameters like cluster delay, cluster power, and angles are generated. Finally, the channel impulse response (CIR) or channel matrix H is constructed by summing the contributions from all clusters and paths, incorporating antenna patterns and array geometries at both ends.
The model supports a wide frequency range from below 6 GHz up to millimeter-wave (mmWave) bands like 52.6 GHz and beyond. It includes essential features like line-of-sight (LOS) and non-line-of-sight (NLOS) conditions, blockage models for mmWave, and spatial consistency. Spatial consistency ensures that the channel characteristics for a moving UE evolve smoothly over time and space, which is critical for evaluating mobility performance and beam tracking algorithms. By providing a common, realistic reference model, the SSCM enables fair comparison of different antenna schemes, link-level and system-level simulations, and the derivation of key performance indicators (KPIs) for 5G NR systems.
Purpose & Motivation
The development of the SSCM was motivated by the limitations of previous channel models (like the SCM/SCME models for 3G/4G) in addressing the new challenges of 5G. Earlier models were not designed for the higher frequencies (mmWave), the extensive use of beamforming, or the massive scale of antenna arrays envisioned for 5G. There was a need for a unified model that could accurately capture spatial channel properties across a vast range of frequencies, bandwidths, and deployment scenarios.
Its primary purpose is to serve as a reliable tool for the standardization and development of 5G NR physical layer techniques. By using a common, agreed-upon channel model, different companies and researchers can simulate and compare the performance of proposed technologies (e.g., new coding schemes, reference signals, beam management procedures) under consistent and realistic conditions. This is crucial for reaching consensus during 3GPP standardization meetings. Furthermore, it helps network equipment vendors and mobile operators design and optimize their products and deployments by understanding how advanced features like Massive MIMO will perform in real-world environments like dense urban areas or indoor factories. The SSCM addresses the specific propagation challenges of mmWave, such high pathloss and sensitivity to blockages, which was a gap in prior models.
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (10 CRs across 4 releases). Complements the general historical overview above with the evidence-based evolution of this function.
Studied in Rel-14, normative work from Rel-15.
In Release 15, the SSCM function was extended to support frequencies above 6 GHz up to 100 GHz, introducing new supported scenarios including urban microcell street canyon, urban macrocell, indoor office, and rural macrocell. The model specifically added support for spatial consistency through the correlation of large scale and small scale parameters and for large antenna arrays based on a far-field assumption. Furthermore, it was designed to accommodate very large bandwidths, up to 10% of the center frequency but not exceeding 2 GHz.
- Addition of indoor industrial channel model – version created in error – withdrawn TS 38.901CR0023
In Release 16, the SSCM function was extended by the addition of an indoor industrial channel model. This specifically addressed the need for channel modeling in IIoT (Industrial Internet of Things) scenarios, culminating in the creation of a dedicated Release 16 report. The update also resolved remaining open issues for IIoT channel modelling within the standardized framework.
In Release 17, the SSCM function was updated with a correction to the scaling of angles for the Clustered Delay Line (CDL) model. This change also involved correcting a figure reference within the model documentation to ensure accuracy and consistency.
- CR correcting scaling of angles for CDL model and a figure reference TS 38.901CR0025
In Release 19, the SSCM function was enhanced with a new channel model for Integrated Sensing and Communication (ISAC) and introduced specific enhancements for the 7-24 GHz frequency range. The update also included improved modeling for handheld user terminal polarized antennas and incorporated aspects of uplink and downlink reciprocity modeling. These changes expanded the model's applicability for higher frequencies and advanced use cases like sensing.
- Introduction of Rel-19 7-24 GHz channel model enhancements TS 38.901CR0026
- CR to introduce channel model for ISAC TS 38.901CR0027
- Correction of channel modeling enhancements for 7 - 24 GHz TS 38.901CR0028
- CR on Handheld UT Polarized Antenna Model TS 38.901CR0032
- Correction of Rel-19 enhancements for channel modeling for 7-24 GHz TS 38.901CR0036
- CR on UL and DL reciprocity modelling TS 38.901CR0035
Explore further
Broader topics and technologies where SSCM plays a role.
Defining Specifications
3GPP specifications that define or reference SSCM, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TR 38.900 vf00 | Channel Model Study for >6 GHz | Rel-15 |
| TR 38.901 vj10 | Channel Model for 0.5-100 GHz | Rel-19 |