Content for  TR 38.854  Word version:  17.1.0

The detailed RRH parameters are still under discussion in RAN4 and following options have been agreed for potential down selection: Number of RRH sites per BBU:

• [1 to 4] RRHs sites per BBU; and
• Other values are not precluded.

Number of Analog Beams per panel in RRH:

• [1,2,4] analogue beam(s) per panel in RRH; and
• Other values are not precluded.

SSB index to Beam Mapping. The impact of following options for SSB index to Beam mapping is FFS:

1. Option 1:
   1. All RRHs (connected to one BBU with fiber) share the same cell ID; and
   2. All RRHs under the same cell use the same set of SSB indexes, e.g., all RRHs use SSB-0 to SSB-3.
2. Option 2:
   1. All RRHs (connected to one BBU with fiber) share the same cell ID; and
   2. RRHs under the same cell use the different sets of SSB indexes, e.g., RRH-1 uses SSB-0 to SSB-3, RRH-2 uses SSB-4 to SSB-7.

When DPS is used as transmission scheme, SSB index to Beam Mapping used in the discussion for this WI is as follows: RRHs under the same cell use different sets of SSB indexes, e.g., RRH-1 uses SSB-0 to SSB-3, RRH-2 uses SSB-4 to SSB-7, etc. RAN4 discussed the aspect of potential handover problem due to sudden RX signal increase of the target cell. RAN4 thinks that this can be alleviated by DPS transmission scheme with carefully allocated SSB-index among neighboring cells to avoid inter-cell interference. Concerning RRH antenna array orientation the impact of following options for RRH antenna array orientation is FFS:

• Option 1: RRH panel boresight pointed to the railway in the middle point between 2 RRHs; or
• Option 2: RRH panel boresight pointed to the railway at the distance of Ds (projection of the neighbouring RRH on the railway); or
• Other option is not precluded.

Related to RRH/UE boresight direction of Antenna Panel and beam direction, RAN4 may not need to specify RRH/UE boresight direction of antenna panel and beam direction for deployment scenario study, but left for companies' choice:

• RRH/UE boresight direction of antenna panel and beam direction information can be provided by individual company to accompany their deployment scenario analysis result, which can be captured in TR.

The number of panels per CPE was open and for discussion. Concerning the number of panels per CPE following will be considered:

• 2 panels per CPE each for both for TX and RX. Each panel points in opposite directions.

For the bi-directional Operation for Two Panels in the CPE following is considered:

• Follow the Rel-15/16 principle of "only one active Rx/Tx panel at a time".

UE antenna panel(s) for forward and backward directions:

• RAN4 to consider CPE to be equipped with two panels pointed forward and backward along the track.

UE boresight direction of Antenna Panel and beam direction, RAN4 may not need to specify RRH/UE boresight direction of antenna panel and beam direction for deployment scenario study, but left for companies' choice:

• RRH/UE boresight direction of antenna panel and beam direction information can be provided by individual company to accompany their deployment scenario analysis result, which can be captured in TR.

Number of CPE devices per train/carriage:

• RAN4 requirement can be defined based on the baseline of 1 CPE device per train.