diff --git a/doc/ORAN_FHI7.2_Tutorial.md b/doc/ORAN_FHI7.2_Tutorial.md
index 8e2058f5c1..c28f75a2cf 100644
--- a/doc/ORAN_FHI7.2_Tutorial.md
+++ b/doc/ORAN_FHI7.2_Tutorial.md
@@ -1059,10 +1059,10 @@ section](.#build-oai-gnb)) to see if it resolves the problem.
 # Operation with multiple RUs
 
 It is possible to connect up to 4 RUs to one DU at the same time and operate
-them as a (single) distributed antenna (array). This works since all RUs and
-the DU are synchronized onto a common clock using PTP. The assumed
-configuration is that with N RUs each having an M×M configuration, we
-effectively reach an (N×M)×(N×M) configuration.
+them either with a single antenna array or a distributed antenna array.  This
+works since all RUs and the DU are synchronized onto a common clock using PTP.
+The assumed configuration is that with N RUs each having an M×M configuration,
+we effectively reach an (N×M)×(N×M) configuration.
 
 Some caveats:
 - Since it's a distributed antenna, this implies that this setup will deploy a
diff --git a/doc/README.md b/doc/README.md
index 13028479cd..4786458a66 100644
--- a/doc/README.md
+++ b/doc/README.md
@@ -117,6 +117,7 @@ Some directories under `radio` contain READMEs:
 - [USRP](../radio/USRP/README.md)
 - [BladeRF](../radio/BLADERF/README)
 - [IQPlayer](../radio/iqplayer/DOC/iqrecordplayer_usage.md), and [general documentation](./iqrecordplayer_usage.md)
+- [fhi_72](../radio/fhi_72/README.md)
 
 The other SDRs (AW2S, LimeSDR, ...) have no READMEs.
 
diff --git a/radio/fhi_72/README.md b/radio/fhi_72/README.md
new file mode 100644
index 0000000000..2f72a9aa07
--- /dev/null
+++ b/radio/fhi_72/README.md
@@ -0,0 +1,46 @@
+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](../../doc/ORAN_FHI7.2_Tutorial.md). 
+
+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()` through `xran_5g_fronthault_config()`: callback
+  for PUSCH data; used to provide timing data.
+- `oai_xran_fh_rx_prach_callback()` through `xran_5g_prach_req()`: callback for
+  PRACH data; not currently used and implemented in PUSCH data callback. 
+- `oai_physide_dl_tti_call_back()` through `xran_reg_physide_cb()`: only used
+  to unblock timing in `oai_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.
diff --git a/radio/fhi_72/oaioran.c b/radio/fhi_72/oaioran.c
index 65839fd5a0..16dd2d85de 100644
--- a/radio/fhi_72/oaioran.c
+++ b/radio/fhi_72/oaioran.c
@@ -44,7 +44,7 @@
 #endif
 
 // Declare variable useful for the send buffer function
-volatile uint8_t first_call_set = 0;
+volatile bool first_call_set = false;
 
 int xran_is_prach_slot(uint8_t PortId, uint32_t subframe_id, uint32_t slot_id);
 #include "common/utils/LOG/log.h"
@@ -54,6 +54,12 @@ extern notifiedFIFO_t oran_sync_fifo;
 #else
 volatile oran_sync_info_t oran_sync_info = {0};
 #endif
+
+/** @details xran-specific callback, called when all packets for given CC and
+ * 1/4, 1/2, 3/4, all symbols of a slot arrived. Currently, only used to get
+ * timing information and unblock another thread in xran_fh_rx_read_slot()
+ * through either a message queue, or writing in global memory with polling, on
+ * a full slot boundary. */
 void oai_xran_fh_rx_callback(void *pCallbackTag, xran_status_t status)
 {
   struct xran_cb_tag *callback_tag = (struct xran_cb_tag *)pCallbackTag;
@@ -150,36 +156,23 @@ void oai_xran_fh_rx_callback(void *pCallbackTag, xran_status_t status)
     last_frame = frame;
   } // rx_sym == 7
 }
-void oai_xran_fh_srs_callback(void *pCallbackTag, xran_status_t status)
-{
-  rte_pause();
-}
-void oai_xran_fh_rx_prach_callback(void *pCallbackTag, xran_status_t status)
-{
-  rte_pause();
-}
 
+/** @details Only used to unblock timing in oai_xran_fh_rx_callback() on first
+ * call. */
 int oai_physide_dl_tti_call_back(void *param)
 {
   if (!first_call_set)
-    printf("first_call set from phy cb first_call_set=%p\n", &first_call_set);
-  first_call_set = 1;
+    LOG_I(HW, "first_call set from phy cb\n");
+  first_call_set = true;
   return 0;
 }
 
-int oai_physide_ul_half_slot_call_back(void *param)
-{
-  rte_pause();
-  return 0;
-}
-
-int oai_physide_ul_full_slot_call_back(void *param)
-{
-  rte_pause();
-  return 0;
-}
-
-int read_prach_data(ru_info_t *ru, int frame, int slot)
+/** @brief Reads PRACH data from xran buffers.
+ *
+ * @details Reads PRACH data from xran-specific buffers and, if I/Q compression
+ * (bitwidth < 16 bits) is configured, uncompresses the data. Places PRACH data
+ * in OAI buffer. */
+static int read_prach_data(ru_info_t *ru, int frame, int slot)
 {
   /* calculate tti and subframe_id from frame, slot num */
   int sym_idx = 0;
@@ -248,6 +241,11 @@ int read_prach_data(ru_info_t *ru, int frame, int slot)
   return (0);
 }
 
+/** @brief Check if symbol in slot is UL.
+ *
+ * @param frame_conf xran frame configuration
+ * @param slot the current (absolute) slot (number)
+ * @param sym_idx the current symbol index */
 static bool is_tdd_ul_symbol(const struct xran_frame_config *frame_conf, int slot, int sym_idx)
 {
   /* in FDD, every symbol is also UL */
@@ -259,11 +257,20 @@ static bool is_tdd_ul_symbol(const struct xran_frame_config *frame_conf, int slo
   return frame_conf->sSlotConfig[slot_in_period].nSymbolType[sym_idx] == 1 /* UL */;
 }
 
+/** @brief Check if current slot is DL or guard/mixed without UL (i.e., current
+ * slot is not UL). */
 static bool is_tdd_dl_guard_slot(const struct xran_frame_config *frame_conf, int slot)
 {
   return !is_tdd_ul_symbol(frame_conf, slot, XRAN_NUM_OF_SYMBOL_PER_SLOT - 1);
 }
 
+/** @details Read PRACH and PUSCH data from xran buffers.  If
+ * I/Q compression (bitwidth < 16 bits) is configured, deccompresses the data
+ * before writing. Prints ON TIME counters every 128 frames.
+ *
+ * Function is blocking and waits for next frame/slot combination. It is unblocked
+ * by oai_xran_fh_rx_callback(). It writes the current slot into parameters
+ * frame/slot. */
 int xran_fh_rx_read_slot(ru_info_t *ru, int *frame, int *slot)
 {
   void *ptr = NULL;
@@ -458,6 +465,9 @@ int xran_fh_rx_read_slot(ru_info_t *ru, int *frame, int *slot)
   return (0);
 }
 
+/** @details Write PDSCH IQ-data from OAI txdataF_BF buffer to xran buffers. If
+ * I/Q compression (bitwidth < 16 bits) is configured, compresses the data
+ * before writing. */
 int xran_fh_tx_send_slot(ru_info_t *ru, int frame, int slot, uint64_t timestamp)
 {
   int tti = /*frame*SUBFRAMES_PER_SYSTEMFRAME*SLOTNUM_PER_SUBFRAME+*/ 20 * frame
diff --git a/radio/fhi_72/oaioran.h b/radio/fhi_72/oaioran.h
index a20f6c80d3..e973ce2997 100644
--- a/radio/fhi_72/oaioran.h
+++ b/radio/fhi_72/oaioran.h
@@ -31,7 +31,9 @@ typedef struct {
   uint32_t f;
 } oran_sync_info_t;
 
+/** @brief xran callback for fronthaul RX, see xran_5g_fronthault_config(). */
 void oai_xran_fh_rx_callback(void *pCallbackTag, xran_status_t status);
+/** @brief xran callback for time alignment, see xran_reg_physide_cb(). */
 int oai_physide_dl_tti_call_back(void *param);
 
 #endif /* OAIORAN_H */
diff --git a/radio/fhi_72/oran-init.c b/radio/fhi_72/oran-init.c
index a5c620e995..97930a172b 100644
--- a/radio/fhi_72/oran-init.c
+++ b/radio/fhi_72/oran-init.c
@@ -443,7 +443,7 @@ int *oai_oran_initialize(struct xran_fh_init *xran_fh_init, struct xran_fh_confi
     pi->prach_tag = tag;
     pi->pusch_tag = tag;
 #ifdef E_RELEASE
-    LOG_W(PHY, "Please be aware that E release support will be removed by the end of January 2025. Instead, F release will be mandatory.\n");
+    LOG_W(PHY, "Please be aware that E release support will be removed in the future. Consider switching to F release.\n");
     oran_allocate_buffers(gxran_handle, o_xu_id, 1, pi, &xran_fh_config[o_xu_id]);
 #elif defined F_RELEASE
     oran_allocate_buffers(gxran_handle, o_xu_id, 1, pi, xran_fh_init->mtu, &xran_fh_config[o_xu_id]);
diff --git a/radio/fhi_72/oran_isolate.h b/radio/fhi_72/oran_isolate.h
index 7388f88f3b..174c1399a6 100644
--- a/radio/fhi_72/oran_isolate.h
+++ b/radio/fhi_72/oran_isolate.h
@@ -45,9 +45,13 @@ typedef struct ru_info_s {
   int16_t **prach_buf;
 } ru_info_t;
 
+/** @brief Reads RX data (PRACH/PUSCH) of next slot.
+ *
+ * @param ru pointer to structure keeping pointers to OAI data.
+ * @param frame output of the frame which has been read.
+ * @param slot output of the slot which has been read. */
 int xran_fh_rx_read_slot(ru_info_t *ru, int *frame, int *slot);
+/** @brief Writes TX data (PDSCH) of given slot. */
 int xran_fh_tx_send_slot(ru_info_t *ru, int frame, int slot, uint64_t timestamp);
 
-int compute_xran_statistics();
-
 #endif /* _ORAN_ISOLATE_H_ */