diff --git a/common/platform_types.h b/common/platform_types.h
index 26c4bafa75..5225f4566f 100644
--- a/common/platform_types.h
+++ b/common/platform_types.h
@@ -108,6 +108,7 @@ typedef struct {
   sdu_size_t head_sdu_remaining_size_to_send; /*!< \brief remaining size of sdu: could be the total size or the remaining size of
                                                  already segmented sdu */
   bool head_sdu_is_segmented; /*!< \brief 0 if head SDU has not been segmented, 1 if already segmented */
+  uint64_t oldest_sdu_arrival_ms; /*!< \brief Timestamp (ms, RLC time) of oldest SDU in tx/retx queue, 0 if empty */
 } mac_rlc_status_resp_t;
 
 #define SDU_CONFIRM_NO false
diff --git a/openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_dlsch.c b/openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_dlsch.c
index 883b95d47e..613465e90c 100644
--- a/openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_dlsch.c
+++ b/openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_dlsch.c
@@ -442,6 +442,7 @@ static int collect_dl_candidates(gNB_MAC_INST *mac,
   int n = 0;
   const frame_structure_t *fs = &mac->frame_structure;
   const float dl_slots_per_s = (float)get_dl_slots_per_period(fs) / fs->numb_slots_period * fs->numb_slots_frame * 100;
+  const uint64_t now_ms = get_nr_rlc_current_time();
 
   UE_iterator (UE_list, UE) {
     if (n >= max_candidates)
@@ -527,6 +528,11 @@ static int collect_dl_candidates(gNB_MAC_INST *mac,
           .alloc_beam_idx = 0,
           .alloc_new_beam = false,
       };
+      nr_dl_candidate_t *c = &candidates[n - 1];
+      FOR_EACH_SEQ_ARR(const nr_lc_config_t *, lc, &sched_ctrl->lc_config) {
+        const uint64_t ts = sched_ctrl->rlc_status[lc->lcid].oldest_sdu_arrival_ms;
+        c->hol_delay_ms[lc->lcid] = (ts > 0 && ts <= now_ms) ? (now_ms - ts) : 0;
+      }
     } else {
       /* new transmission candidate */
       if (sched_ctrl->available_dl_harq.head < 0)
@@ -572,8 +578,11 @@ static int collect_dl_candidates(gNB_MAC_INST *mac,
           .alloc_new_beam = false,
       };
       nr_dl_candidate_t *c = &candidates[n - 1];
-      for (int lcid = 0; lcid < NR_MAX_NUM_LCID; lcid++)
-        c->pending_bytes_per_lcid[lcid] = sched_ctrl->rlc_status[lcid].bytes_in_buffer;
+      FOR_EACH_SEQ_ARR(const nr_lc_config_t *, lc, &sched_ctrl->lc_config) {
+        c->pending_bytes_per_lcid[lc->lcid] = sched_ctrl->rlc_status[lc->lcid].bytes_in_buffer;
+        const uint64_t ts = sched_ctrl->rlc_status[lc->lcid].oldest_sdu_arrival_ms;
+        c->hol_delay_ms[lc->lcid] = (ts > 0 && ts <= now_ms) ? (now_ms - ts) : 0;
+      }
     }
   }
 
diff --git a/openair2/LAYER2/NR_MAC_gNB/nr_mac_gNB.h b/openair2/LAYER2/NR_MAC_gNB/nr_mac_gNB.h
index ccd63fb5bf..244d992b6a 100644
--- a/openair2/LAYER2/NR_MAC_gNB/nr_mac_gNB.h
+++ b/openair2/LAYER2/NR_MAC_gNB/nr_mac_gNB.h
@@ -917,6 +917,7 @@ struct nr_dl_candidate {
   int retx_rbSize; ///< RBs needed for retx, 0 for new tx
   uint32_t pending_bytes; ///< total bytes waiting in RLC buffers
   uint32_t pending_bytes_per_lcid[NR_MAX_NUM_LCID]; ///< per-LCID bytes waiting in RLC buffers
+  uint64_t hol_delay_ms[NR_MAX_NUM_LCID]; ///< per-LCID head-of-line delay in milliseconds (age of oldest SDU)
   float avg_throughput; ///< EWMA goodput in bps (dl_thr_ue)
   float bler; ///< current BLER estimate
   int current_mcs; ///< current MCS state (retx: from HARQ, new tx: from BLER tracker)
diff --git a/openair2/LAYER2/nr_rlc/nr_rlc_entity.h b/openair2/LAYER2/nr_rlc/nr_rlc_entity.h
index cb9761aa2f..9fc9f3dd82 100644
--- a/openair2/LAYER2/nr_rlc/nr_rlc_entity.h
+++ b/openair2/LAYER2/nr_rlc/nr_rlc_entity.h
@@ -78,6 +78,7 @@ typedef struct {
   int status_size;
   int tx_size;
   int retx_size;
+  uint64_t oldest_sdu_arrival_ms; /* timestamp (ms, from sdu->arrival_ms) of oldest SDU in tx/retx queue, 0 if empty */
 } nr_rlc_entity_buffer_status_t;
 
 typedef struct nr_rlc_entity_s {
diff --git a/openair2/LAYER2/nr_rlc/nr_rlc_entity_am.c b/openair2/LAYER2/nr_rlc/nr_rlc_entity_am.c
index 62c1fa90c6..882a56a70f 100644
--- a/openair2/LAYER2/nr_rlc/nr_rlc_entity_am.c
+++ b/openair2/LAYER2/nr_rlc/nr_rlc_entity_am.c
@@ -1777,6 +1777,12 @@ nr_rlc_entity_buffer_status_t nr_rlc_entity_am_buffer_status(
   ret.tx_size = entity->common.bstatus.tx_size;
   ret.retx_size = entity->common.bstatus.retx_size;
 
+  ret.oldest_sdu_arrival_ms = 0;
+  if (entity->retransmit_list && entity->retransmit_list->sdu)
+    ret.oldest_sdu_arrival_ms = entity->retransmit_list->sdu->arrival_ms;
+  else if (entity->tx_list && entity->tx_list->sdu)
+    ret.oldest_sdu_arrival_ms = entity->tx_list->sdu->arrival_ms;
+
   return ret;
 }
 
@@ -1851,6 +1857,8 @@ void nr_rlc_entity_am_recv_sdu(nr_rlc_entity_t *_entity,
 
   if (entity->common.avg_time_is_on)
     sdu->sdu->time_of_arrival = time_average_now();
+
+  sdu->sdu->arrival_ms = entity->t_current;
 }
 
 /*************************************************************************/
diff --git a/openair2/LAYER2/nr_rlc/nr_rlc_entity_tm.c b/openair2/LAYER2/nr_rlc/nr_rlc_entity_tm.c
index 1729db8ebf..52f9f7daec 100644
--- a/openair2/LAYER2/nr_rlc/nr_rlc_entity_tm.c
+++ b/openair2/LAYER2/nr_rlc/nr_rlc_entity_tm.c
@@ -88,6 +88,10 @@ nr_rlc_entity_buffer_status_t nr_rlc_entity_tm_buffer_status(nr_rlc_entity_t *_e
   ret.tx_size = entity->common.bstatus.tx_size;
   ret.retx_size = 0;
 
+  ret.oldest_sdu_arrival_ms = 0;
+  if (entity->tx_list && entity->tx_list->sdu)
+    ret.oldest_sdu_arrival_ms = entity->tx_list->sdu->arrival_ms;
+
   return ret;
 }
 
@@ -147,6 +151,8 @@ void nr_rlc_entity_tm_recv_sdu(nr_rlc_entity_t *_entity,
 
   if (entity->common.avg_time_is_on)
     sdu->sdu->time_of_arrival = time_average_now();
+
+  sdu->sdu->arrival_ms = entity->t_current;
 }
 
 /*************************************************************************/
diff --git a/openair2/LAYER2/nr_rlc/nr_rlc_entity_um.c b/openair2/LAYER2/nr_rlc/nr_rlc_entity_um.c
index 4d47f78b7e..a25195a6d4 100644
--- a/openair2/LAYER2/nr_rlc/nr_rlc_entity_um.c
+++ b/openair2/LAYER2/nr_rlc/nr_rlc_entity_um.c
@@ -534,6 +534,10 @@ nr_rlc_entity_buffer_status_t nr_rlc_entity_um_buffer_status(nr_rlc_entity_t *_e
   ret.tx_size = entity->common.bstatus.tx_size;
   ret.retx_size = 0;
 
+  ret.oldest_sdu_arrival_ms = 0;
+  if (entity->tx_list && entity->tx_list->sdu)
+    ret.oldest_sdu_arrival_ms = entity->tx_list->sdu->arrival_ms;
+
   return ret;
 }
 
@@ -594,6 +598,8 @@ void nr_rlc_entity_um_recv_sdu(nr_rlc_entity_t *_entity,
 
   if (entity->common.avg_time_is_on)
     sdu->sdu->time_of_arrival = time_average_now();
+
+  sdu->sdu->arrival_ms = entity->t_current;
 }
 
 /*************************************************************************/
diff --git a/openair2/LAYER2/nr_rlc/nr_rlc_oai_api.c b/openair2/LAYER2/nr_rlc/nr_rlc_oai_api.c
index 348c489df1..b298c55519 100644
--- a/openair2/LAYER2/nr_rlc/nr_rlc_oai_api.c
+++ b/openair2/LAYER2/nr_rlc/nr_rlc_oai_api.c
@@ -47,7 +47,7 @@ void unlock_nr_rlc_current_time(void)
     AssertFatal(0, "error locking mutex");
 }
 
-static uint64_t get_nr_rlc_current_time(void)
+uint64_t get_nr_rlc_current_time(void)
 {
   lock_nr_rlc_current_time();
 
@@ -267,10 +267,12 @@ static mac_rlc_status_resp_t _nr_rlc_status_ind(nr_rlc_ue_t *ue, frame_t frame,
     // Fix me: temproary reduction meanwhile cpu cost of this computation is optimized
     buf_stat = rb->buffer_status(rb, 1000 * 1000);
     ret.bytes_in_buffer = buf_stat.status_size + buf_stat.retx_size + buf_stat.tx_size;
+    ret.oldest_sdu_arrival_ms = buf_stat.oldest_sdu_arrival_ms;
   } else {
     if (!(frame % 128) || channel_idP == 0) //to suppress this warning message
       LOG_W(RLC, "Radio Bearer (channel ID %d) is NULL for UE %d\n", channel_idP, ue->ue_id);
     ret.bytes_in_buffer = 0;
+    ret.oldest_sdu_arrival_ms = 0;
   }
 
   ret.pdus_in_buffer = 0;
diff --git a/openair2/LAYER2/nr_rlc/nr_rlc_oai_api.h b/openair2/LAYER2/nr_rlc/nr_rlc_oai_api.h
index 8fc7a3d3e0..554ea971d8 100644
--- a/openair2/LAYER2/nr_rlc/nr_rlc_oai_api.h
+++ b/openair2/LAYER2/nr_rlc/nr_rlc_oai_api.h
@@ -81,6 +81,8 @@ int nr_rlc_tx_list_occupancy(int ue_id, logical_chan_id_t lcid);
 
 void nr_rlc_activate_avg_time_to_tx(const int ue_id, const logical_chan_id_t channel_id, const bool is_on);
 
+uint64_t get_nr_rlc_current_time(void);
+
 void nr_rlc_srb_recv_sdu(const int ue_id, const logical_chan_id_t channel_id, unsigned char *buf, int size);
 
 bool nr_rlc_activate_srb0(int ue_id,
diff --git a/openair2/LAYER2/nr_rlc/nr_rlc_sdu.h b/openair2/LAYER2/nr_rlc/nr_rlc_sdu.h
index 03b5e46c88..df6fb3384e 100644
--- a/openair2/LAYER2/nr_rlc/nr_rlc_sdu.h
+++ b/openair2/LAYER2/nr_rlc/nr_rlc_sdu.h
@@ -25,6 +25,11 @@ typedef struct nr_rlc_sdu_t {
    * transmission is used for statistics
    */
   uint64_t time_of_arrival;  /* unit microsecond */
+
+  /* RLC time when the SDU was first received .Used for the HOL-delay
+   * in MAC. TODO: unify with time_of_arrival (feed E2AP/KPM in us) 
+   */
+  uint64_t arrival_ms;
 } nr_rlc_sdu_t;
 
 typedef struct nr_rlc_sdu_segment_t {