afcd77108d
xran: fixes for FDD operation (#270) Two fixes in the xran fronthaul found while bringing up an FDD cell (Band n1, 10 MHz). Verified on a Band n1 FDD 10 MHz cell using Keysight RUsim/UEsim, End-to-end UE attach and traffic work. - Derive TTI from the configured numerology instead of a hardcoded 20 slots per frame: xran_fh_tx_send_slot() assumed 30 kHz SCS. Compute slots_per_frame as 10 << mu from the fronthaul config (mu_number[0] for K release, frame_conf.nNumerology for F release), so the TTI is correct for any numerology. With the original code, PRACH was not working properly. - Fix DL transmission in FDD mode: the TDD DL/guard slot check skipped every DL slot in FDD, where no TDD pattern exists and all slots carry DL. The check is now only applied when the frame duplex type is not FDD. Without this, no DL traffic was sent. Reviewed-by: Teodora Vladić <teodora.vladic@openairinterface.org> Reviewed-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()andoai_xran_fh_rx_prach_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()/
xran_fh_rx_prach_read_slot() that blocks and waits for the next slot.
This is done through a message queue which depends on xran calling the callbacks
oai_xran_fh_rx_callback()/oai_xran_fh_rx_prach_callback() as installed during
xran initialization.
Once unblocked, it reads first PUSCH data, then PRACH data, before returning to
OAI.