TR38.901

Global coordinate system (GCS) and local coordinate system (LCS) are linked by a rotational matrix \(\mathbf{R}\), which can be decomposed as 3 successive primary rotations around Z/Y/X axes respectively. Accordingly, the composite rotational matrix \(\mathbf{R}\) can be expressed as the product of 3 Givens rotation matrices.

In SLS, large scale attenuation needs to be modelled. Coupling loss is defined as the combination of distance-dependent path loss, shadow fading, antenna gain at the transmitter and receiver, outdoor-to-indoor (O2I) penetration loss¹.

• Path loss is usually dependent on propagation types, i.e. line-of-sight (LOS) or non-line-of-sight (NLOS).
• Propagation type, LOS/NLOS, is per site².
• Location type, i.e. indoor or outdoor, is per user³.
• Shadow fading is per site⁴.
• O2I penetration loss is per user⁵.

In TR38.901, small-scale fading is generated as follows.

1. Network topology deployment, including BS and UE.
2. Determine propagation condition, i.e., LOS/NLOS, and indoor/outdoor.
3. Calculate pathloss.
4. Generate correlated LSP, i.e., DS, ASA/ASD/ZSA/ZSD, K, SF.
5. Generate exponentially distributed per-cluster delays.
6. Generate per-cluster power.
7. Generate per-ray angles, AoA/AoD/ZoA/ZoD.
8. Random coupling
9. Generate per-ray XPR.
10. Generate per-ray initial phase.
11. Generate per Tx-Rx pair CIR.
12. Apply pathloss and shadowing.

The procedure can be modelled as a 2D random process involving

• Cluster-specific parameters in steps 5-7, and
• Ray-specific parameters in steps 8-10.