Teodora
3a1fc2ef65
1. Closes #884 - increase the XRAN_MAX_FRAGMENT from 4 to 6 (sufficient for MTU 1500 with compression 8b) 2. Add new firmware version that supports jumbo frames 3. Update the config file to align with the new Liteon unit in our lab - center frequency, jumbo frames, compression and RU MAC address, as well as the max DL MIMO layers.
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.