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doc: Fix the formatting of gNB RACH Processing document

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- Organize into a main title and sub-headings
      - Put var/func as inline code
      - Add anchor links for the referenced step
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Shubhika Garg
2026-01-22 10:50:50 +01:00
parent 1aa13e4f23
commit 273b9fba4d
1 changed files with 22 additions and 18 deletions
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doc/rach_processing_in_gNB.md
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The gNB RACH processing
# The gNB RACH Processing
1. Collect I/Q samples
The gNB/ru main loop, in ru_thread()
## 1. Collect I/Q Samples
The gNB/ru main loop, in `ru_thread()`
If there is rach occasions in this slot
this main loop calls rx_nr_prach_ru() that stores the I/Q samples in the prach_item_t context
this main loop calls `rx_nr_prach_ru()` that stores the I/Q samples in the `prach_item_t` context.
2.process the samples
L1_rx_thread() has received slot indication by msg on queue resp_L1, it calls rx_func() => L1_nr_prach_procedures()
L1_nr_prach_procedures() fills nfapi_nr_rach_indication_t structure from result of rx_nr_prach() that process the content of rxsigF[prachOccasion][aa]
rx_func() sends the decoded rach to upper processing by call to NR_UL_indication() that calls handle_nr_rach() => nr_initiate_ra_proc()
## 2. Process the Samples
nr_initiate_ra_proc() creates a UE context if it needs, then sets UE.ra.ra_state to what it should do
`L1_rx_thread()` has received slot indication by msg on queue `resp_L1`, it calls `rx_func() => L1_nr_prach_procedures()`
`L1_nr_prach_procedures()` fills `nfapi_nr_rach_indication_t` structure from result of `rx_nr_prach()` that process the content of `rxsigF[prachOccasion][aa]`
`rx_func()` sends the decoded rach to upper processing by call to `NR_UL_indication()` that calls `handle_nr_rach() => nr_initiate_ra_proc()`.
3. send the RACH DL
tx_func() that is launched by L1_tx_thread() as it gets L1_tx_out msg (from main loop in 1.)
tx_func()=>run_scheduler_monolithic()=>gNB_dlsch_ulsch_scheduler()=>nr_scheduler_RA()
nr_scheduler_RA() process all existing UE contexts, to see it it has to schedule a RACH DL
`nr_initiate_ra_proc()` creates a UE context if it needs, then sets `UE.ra.ra_state` to what it should do.
4. global synchronisation
resp_L1 msg for (2.) is created in tx_func() that is launched by L1_tx_thread() (see3.) when it receives slot indication as it gets L1_tx_out msg
this msg is sent by the main loop (see 1.)
tx_func()=>run_scheduler_monolithic()=>nr_schedule_response ()=>nr_schedule_ul_tti_req ()=> nr_schedule_rx_prach()
writes in the triggering structure to (1.) that it will have to run rx_nr_prach_ru() in a given future slot
## 3. Send the RACH DL
`tx_func()` that is launched by `L1_tx_thread()` as it gets `L1_tx_out` msg (from main loop in [1.](#1-collect-iq-samples))
`tx_func()=>run_scheduler_monolithic()=>gNB_dlsch_ulsch_scheduler()=>nr_scheduler_RA()`
`nr_scheduler_RA()` process all existing UE contexts, to see it it has to schedule a RACH DL.
## 4. Global Synchronisation
`resp_L1` msg for ([2.](#2-process-the-samples)) is created in `tx_func()` that is launched by `L1_tx_thread()` (see [3.](#3-send-the-rach-dl)) when it receives slot indication as it gets `L1_tx_out` msg
this msg is sent by the main loop (see [1.](#1-collect-iq-samples))
`tx_func()=>run_scheduler_monolithic()=>nr_schedule_response ()=>nr_schedule_ul_tti_req ()=> nr_schedule_rx_prach()`
writes in the triggering structure to ([1.](#1-collect-iq-samples)) that it will have to run `rx_nr_prach_ru()` in a given future slot.