Robert Schmidt
03096dd495
Use two queues for PRACH processing: - prach_ru_queue: pass jobs from TX thread (scheduler) to RU thread. For split 8, the RU thread itself handles PRACH processing; for split 7.2, it is the library that is responsible for handling PRACH messages (see oran_fh_if4p5_south_in()) - prach_l1rx_queue: after jobs have been handled in RU thread, use this queue to pass jobs to the RX thread. There, preamble detection is performed, and RACH.indication FAPI messages are filled if a preamble has been detected. Together, these queues replace a linear search in a global array that has been modified by three threads at the same time. The design ensures that access now is thread-safe, and with less overhead. Signed-off-by: Robert Schmidt <robert.schmidt@openairinterface.org>
This document describes the driver for the xran driver, implementing O-RAN FHI 7.2 interface. This is for developers; for user documentation, consider the O-RAN 7.2 tutorial instead.
The main source files and their purpose are as follows:
oaioran.c: definition of xran-specific callback functions.oran-config.c: reading of 7.2-specific configuration and preparing xran configration.oran-init.c: initialization of xran.oran_isolate.c: main entry point and definition of function pointers for OAI callbacks.
The entry point for the driver library is transport_init() in oran_isolate.c.
This function is concerned with setting necessary function pointers for OAI
integration, and prepares xran configuration through get_xran_config(). This
function reads 7.2 specific configuration and deduces some of the parameters
(e.g., frequency) from OAI-provided radio configuration in openair0_config_t.
Actual xran initialization happens in oai_oran_initialize() in oran-init.c.
It calls various helper function in the same file to set up DPDK memory buffer
(pools). Notably, these callbacks are installed:
oai_xran_fh_rx_callback()throughxran_5g_fronthault_config(): callback for PUSCH data; used to provide timing data.oai_xran_fh_rx_prach_callback()throughxran_5g_prach_req(): callback for PRACH data; not currently used and implemented in PUSCH data callback.oai_physide_dl_tti_call_back()throughxran_reg_physide_cb(): only used to unblock timing inoai_xran_fh_rx_callback()upon first xran call.
More detailed information about the xran callbacks can be taken from the xran documentation.
During normal operation, OAI calls into the driver through functions
oran_fh_if4p5_south_in() for PUSCH/PRACH and oran_fh_if4p5_south_out() for
PDSCH.
For PDSCH, oran_fh_if4p5_south_out() calls xran_fh_tx_send_slot() that
optionally compresses IQ data, then writes it into IQ buffers of xran.
For PUSCH/PRACH, oran_fh_if4p5_south_in() calls xran_fh_rx_read_slot() that
blocks and waits for the next slot. This is done through either a message
queue, or through polling, which in both cases depends on xran calling the
callback oai_xran_fh_rx_callback() as installed during xran initialization.
Once unblocked, it reads first PRACH data, then PUSCH data, before returning to
OAI.