@@ -164,8 +164,6 @@ nr_schedule_ue_spec() is called
Calls nr_fill_nfapi_dl_pdu() to actually populate what should be done by the lower layers to make the Tx subframe
# RRC
RRC is a regular thread with itti loop on queue: TASK_RRC_GNB
it receives it's configuration in message NRRRC_CONFIGURATION_REQ, then real time mesages for all events: S1/NGAP events, X2AP messages and RRC_SUBFRAME_PROCESS
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@@ -176,14 +174,56 @@ how does it communicate to scheduler ?
# RLC
RLC code is new implementation, not using OAI mechanisms: it is implmented directly on pthreads, ignoring OAI common functions.
It runs a thread waiting incoming data, but it is mainly running inside calling thread.
It is a library, running in thread RRC (except on itti message: F1AP_UL_RRC_MESSAGE for F1).
RLC code is new implementation, not using OAI mechanisms: it is implemented directly on pthreads, ignoring OAI common functions.
It is a library, running in thread RRC but also in PHY layer threads and some bits in pdcp running thread or F1 interface threads.
# NGAP
NGAP would be a itti thread as is S1AP (+twin thread SCTP that is almost void processing)?
About all messages are exchanged with RRC thread
RLC data is isolated and encapsulated.
It is stored under a global var: nr_rlc_ue_manager
The init function rlc_module_init() populates this global variable.
A small effort could lead us to return the pointer to the caller of rlc_module_init() (internal type: nr_rlc_ue_manager_internal_t)
but it returns void.
It could return the initialized pointer (as FILE* fopen() for example), then the RLC layer could have multiple instances in one process.
Even, a future evolution could remove this global rlc layer: rlc can be only a library that we create a instance for each UE because it doesn't shareany data between UEs.
For DL (respectively from UL in UE), the scheduler need to know the quantity of data waitin to be sent: it calls mac_rlc_status_ind()
That "peek" the size of the waiting data for a UE.
The scheduler then push orders to lower layers. The transport layer will actually pull data from RLC with: mac_rlc_data_req()
the low layer push data into rlc by: mac_rlc_data_ind()
Still on DL (gNB side), PDCP push incoming data into RLC by calling: rlc_data_req()
For UL, the low layer push data into rlc by: mac_rlc_data_ind()
Then, rlc push it to pdcp by calling pdcp_data_ind() from a complex rlc internal call back (deliver_sdu())
When adding a UE, external code have to call nr_rrc_rlc_config_asn1_req(), to remove it: rrc_rlc_remove_ue()
Inside UE, channels called drd or srb can be created: ??? and deleted: rrc_rlc_config_req()
nr_rlc_tick() must be called periodically to manage the internal timers
successful_delivery() and max_retx_reached(): in ??? trigger, the RLC sends a itti message to RRC: RLC_SDU_INDICATION (neutralized by #if 0 right now)
#PDCP
The PDCP implementation is also protected through a general mutex.
The design is very similar to rlc layer. The pdcp data is isolated and encapsulated.
pdcp_layer_init(): same as rlc init
we have to call a second init function: pdcp_module_init()
At Tx side (DL in gNB), pdcp_data_req() is the entry function that the upper layer calls.
The upper layer can be GTP or a PDCP internal thread enb_tun_read_thread() that read directly from Linux socket in case we skip 3GPP core implementation.
PDCP internals for pdcp_data_req() is thread safe: inside pdcp_data_req_drb(), the pdcp manager protects with the mutex the access to the SDU receiving function of PDCP (recv_sdu() callback, corresponding to nr_pdcp_entity_drb_am_recv_sdu() for DRBs). When it needs, the pdcp layer push this data to rlc by calling : rlc_data_req()
Also, incoming downlink sdu can comme from internal RRC: in this case, pdcp_run() reads a itti queue, for message RRC_DCCH_DATA_REQ, to0 only call 'pdcp_data_req()'
At Rx side, pdcp_data_ind() is the entry point that receives the data from RLC.
- Inside pdcp_data_ind(), the pdcp manager mutex protects the access to the PDU receiving function of PDCP (recv_pdu() callback corresponding to nr_pdcp_entity_drb_am_recv_pdu() for DRBs)
- Then deliver_sdu_drb() function sends the received data to GTP thread through an ITTI message (GTPV1U_ENB_TUNNEL_DATA_REQ).
pdcp_config_set_security(): not yet developped
nr_DRB_preconfiguration(): the mac layer calls this for ???
nr_rrc_pdcp_config_asn1_req() adds a UE in pdcp, pdcp_remove_UE() removes it
# GTP
Gtp + UDP are two twin threads performing the data plane interface to the core network
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@@ -200,6 +240,10 @@ gtp thread calls directly pdcp_data_req(), so it runs inside it's context intern
## inside other threads
gtpv1u_create_s1u_tunnel(), delete tunnel, ... functions are called inside the other threads, without mutex.
# NGAP
NGAP would be a itti thread as is S1AP (+twin thread SCTP that is almost void processing)?
