updating config file for DAS

doc/ORAN_FHI7.2_Tutorial.md

@@ -1134,21 +1134,20 @@ Some caveats:
 For two RUs using a 8x8 configuration, i.e. a single antenna system, the reference DU configuration file is
 [`gnb-du.sa.band77.273prb.fhi72.8x8-benetel650_650.conf`](../targets/PROJECTS/GENERIC-NR-5GC/CONF/gnb-du.sa.band77.273prb.fhi72.8x8-benetel650_650.conf).
 
-For two RUs each using a 4x4 configuration, i.e. a distributed antenna system (DAS),
-we use the analog beamforming implementation. More details can be found in
-[this document](./analog_beamforming.md). It is important to note that
-the configuration file should be set as a 4x4 scenario and each RU would be given a
-different beam. The reference DU configuration file is [`gnb-du.sa.band77.273prb.fhi72.4x4-das-benetel650_650.conf`](../targets/PROJECTS/GENERIC-NR-5GC/CONF/gnb-du.sa.band77.273prb.fhi72.4x4-das-benetel650_650.conf).
+For two RUs each using a 4x4 configuration, i.e. a distributed antenna system (DAS), `enable_das` in `L1` section needs to be set to 1.
 
-DAS is enabled by setting to 1 the parameter `enable_das` in `L1` section.
-
-The following parameters shall be configured on the gNB in the `MACRLC` section:
+The current implementation relies on the **analog beamforming framework**. Therefore, when enabling DAS by setting `enable_das = 1` in the `L1` section, it is **also required** to enable analog beamforming by setting the following parameters on the gNB in the `MACRLC` section:
 - `set_analog_beamforming`
 - `beam_duration`
 - `beams_per_period`
 
-For guidance on how to set these parameters please refer to
-the [analog beamforming document](./analog_beamforming.md).
+* The `beam_weights` field in the **MACRLC** section can be **omitted**.
+* The number of beams per period is  `beams_per_period` must be set to the **number of configured SSBs**, which in turn should be equal to the **number of distributed antennas**.
+
+More details can be found in [this document](./analog_beamforming.md). 
+
+The reference DU configuration file is [`gnb-du.sa.band77.273prb.fhi72.4x4-das-benetel650_650.conf`](../targets/PROJECTS/GENERIC-NR-5GC/CONF/gnb-du.sa.band77.273prb.fhi72.4x4-das-benetel650_650.conf).
+
 
 Next, configure the `fhi_72` section as indicated below:
 

doc/analog_beamforming.md

@@ -26,6 +26,20 @@ Setting analog beamforming to 1 or 2 changes the way FAPI beam index is treated.
 
 DAS is enabled by setting to 1 the parameter `enable_das` in the L1 section of the configuration file. In case of DAS enabled, the field `beam_weights` in `MACRLC` section can be omitted and the number of beams per period equals the total number of beams.
 
+# Distributed Antenna Systems (DAS)
+
+A **Distributed Antenna System (DAS)** is an antenna deployment with multiple spatially separated radio units (RUs), for example with **two RUs each configured as 4×4**. 
+
+The current implementation relies on the **analog beamforming framework**. Therefore, when enabling DAS by setting:
+`enable_das = 1` it is **also required** to enable analog beamforming `analog_beamforming = 1`
+
+In this case:
+
+* The `beam_weights` field in the **MACRLC** section can be **omitted**.
+* The number of beams per period is  `beams_per_period` must be set to the **number of configured SSBs**, which in turn should be equal to the **number of distributed antennas (or RUs)**.
+
+
+
 # Implementation in OAI scheduler
 
 A new MAC structure `NR_beam_info_t` controls the behavior of the scheduler in presence of analog beamforming. Besides the already mentioned parameters `beam_duration` and `beams_per_period`, the structure also holds a matrix `beam_allocation[i][j]`, whose indices `i` and `j` stands respectively for the number of beams in the period and the slot index (the size of the latter depends on the frame characteristics).

targets/PROJECTS/GENERIC-NR-5GC/CONF/gnb-du.sa.band77.273prb.fhi72.4x4-das-benetel650_650.conf

@@ -118,7 +118,7 @@ gNBs =
         hoppingId                                                   = 0;
         p0_nominal                                                  = -96;
 
-      ssb_PositionsInBurst_Bitmap                                   = 0x1;
+      ssb_PositionsInBurst_Bitmap                                   = 0x3;
 
 # ssb_periodicityServingCell
 # 0 = ms5, 1=ms10, 2=ms20, 3=ms40, 4=ms80, 5=ms160, 6=spare2, 7=spare1