This section includes the agreed scenario and RRH parameters to be used in the investigated FR2 HST deployments. It captures the agreement and conclusions made during the work on FR2 HST deployment scenario and related aspects. Following Figure 5.1-1 illustrates the definition of the different used D-values.

General deployment parameters: RAN4 will at least consider the following general deployment for open-space scenarios:

• D_s and D_min: Take the 5 scenarios in Table 5.1-1 as basic assumption; and
• Scenario 1 and 4 shall be considered with high priority; and
• D_min for [5m, 20, 30 and 50 meters] if found to be necessary; and
• DR_{RH_height}: 15m as basic assumption, [10,20m] if found to be necessary; and
• D_{UE_height}: 5m.

RAN4 will at least consider the following assumptions for the deployment in the tunnel scenario:

• D_s and D_{UE_height} are considered similar as in open-space deployment in Scenario 2 and 4, i.e., Ds=700m and DUE_height =5m; and
• D_min and _{DRRH_height} are constrained by the tunnel (e.g, dimension, shape, etc), and shall be smaller than values for open space scenario;
• D_min: 1m; and
• D_{RRH_height}: 5.3m for one-track tunnel and 7.4m for two-track tunnel as the baseline assumption. The one-track tunnel shall be considered with higher priority.

Sub-Carrier Spacing (SCS): It is still open which SCS options to consider. The options are:

• Option-1: SCS = 120kHz; and
• Option-2: Consider both SCS = 120kHz and 60kHz.

Concerning the transmissions schemes following schemes were discussed in distinguished:

• JT: Joint Transmission scheme applied for all channel (SSB, TRS, PDCCH, PDSCH) - Full SFN; and
• DPS: Dynamic Point Selection based on the Rel-15 beam management (BM) principles; and
• Multi-DCI based Multi-TRP transmission based on the Rel-15 eMIMO principles.

Among these the following down selection has been agreed:

• For Rel-17 WI discussion, FR2 HST transmission schemes which are not compatible with Rel-15/16 NR are precluded; and
• For Rel-17 WI discussion, Joint transmission (JT) used for FR2 HST, only full SFN is considered; and
• For Rel-17 WI discussion, Multi-DCI based multi-TRP transmission is precluded.

RAN4 primarily consider HST FR2 deployment with

• One train moving over one railway track in one direction. RAN4 focuses on 1 direction 1 train. If this opposite direction is completely symmetric, the 1 direction study can apply directly; and
• RRHs are located on one side of the track.

Dedicated network for roof-mounted CPE:

• RAN4 to assume that in HST FR2 Scenario A, only high-speed CPEs installed on the roof of the train can be present in the network.

RAN4 did comparison between unidirectional and bi-directional RRH deployments for Scenario-A and concluded that from signal strength and beam coverage perspective the bi-directional deployment will not provide significant throughput improvement compared to unidirectional deployment. This conclusion is based on the deployment scenario analysis. RAN4 will only consider unidirectional deployments for Scenario-A. Bi-directional deployment can be considered if the feasibility issue of unidirectional deployment is identified. RAN4 assume that FR2 HST with CPEs is operated as dedicated network. Hence, assumption in RAN4 is that in HST FR2 Scenario A and B, only high-speed CPEs installed on the roof of the train can be present in the network. There is no need to differentiate roof-mounted CPE from other FR2 UEs in HST FR2 scenario. RAN4 will not consider curvature when defining the requirements. RAN4 assumed that uni-directional and bi-directional RRH deployments can be considered for tunnel scenario, in which single-panel reception UE and DPS transition scheme shall have higher priority. RAN4 also agreed that multi-panel reception may also be considered in the HST FR2 tunnel scenario to alleviate potential mobility issues that may occur inside the tunnel.

RAN4 will investigate both unidirectional and bidirectional deployment scenarios for FR2 HST. The exact understanding and definition of HST still needs further discussion based on the following interpretations:

• HST Interpretation-1: All RRHs under one BBU transmit the same signal (SFN).
  • Selected RRH(s) for TX, depending on DPS Tx mode is used or not.
• HST Interpretation-2: All RRHs under one BBU in the same cell ID, but for different TCI.
• Other interpretation is not precluded.

For full SFN JT and unidirectional RRH deployment, only consider following scenario:

• The setting with only one TCI state transmission.

The value of Ds_offset implicitly limit the RRH beam direction, so there is no need to introduce additional restriction on RRH beam's possible range of angle on azimuthal plane.