Which messages / traffic at gNB flows from MAC CE to other layers?

Hi all 5G Experts.

I’m trying to understand on high level which messages / traffic at gNB flows from MAC CE (L2) to MAC (L3) to PLCP (L3) messages (to other upper layers)?

For instance, of course, power messages. What else?

Mac CE are only at MAC layer, not at PDCP.

And what info is constitute aside to UE power info?

MAC CE for example is used for Carrier Aggregation activation and deactivation.

What also?

Meaning aside to Carrier Aggregation and Power info, what could we have in MAC CE?

I understand we can have Time Advance info in MAC CE.

Have a read here 5G_MAC_CE


From MAC CE (L2) to MAC (L3):

Control messages:

  • Scheduling information for downlink and uplink data

  • HARQ (Hybrid Automatic Repeat Request) feedback for retransmitting lost or corrupted data

  • Paging messages to initiate paging procedures for mobile devices

  • Handover triggers and information for seamless cell switching

  • Admission control decisions for new UE (User Equipment) connections

  • Resource allocation information for uplink and downlink channels

  • Measurements and reports from UEs on signal strength, channel quality, etc.

  • Mobility information like UE location updates

User plane data:

Encapsulated PDUs (Protocol Data Units) containing user data like voice, video, or internet traffic

Compressed and formatted data according to specific protocols (e.g., TCP/IP for internet data)

From MAC (L3) to PLCP (L3):

Downlink and uplink control signals:

  • Physical channel configuration parameters for different modulation and coding schemes

  • Grant signals indicating allocated resources for specific UEs

  • Paging signals for initiating UE searches

  • Synchronization signals for timing alignment

Modulated user plane data:

  • Encapsulated PDUs mapped to physical channels and modulated onto radio frequencies

  • Power control commands for adjusting UE transmission power

Specific examples:

  • Power messages: These are control messages from the MAC CE to the MAC that specify the desired transmission power for downlink and uplink data. The MAC then translates these values into appropriate power control commands for the PLCP.

  • Scheduling requests: UEs send scheduling requests through the MAC CE to the MAC to request resources for uplink data transmission. The MAC then processes these requests and sends resource allocation information back to the MAC CE for UEs.

Keep in mind that this is a simplified overview, and the actual message flow can be more complex depending on specific protocols, gNB configurations, and UE behaviors.