sched,bugfix: avoid using UL SNR average in tpc control loop

srsenb/hdr/stack/mac/sched_ue_ctrl/tpc.h

@@ -112,6 +112,7 @@ public:
       } else {
         ch_snr.acc_tpc_values = 0;
         ch_snr.snr_avg.push(ch_snr.pending_snr, ch_snr.last_snr_sample_count);
+        ch_snr.last_snr_sample       = ch_snr.pending_snr;
         ch_snr.last_snr_sample_count = 1;
       }
       ch_snr.pending_snr = null_snr;
@@ -166,7 +167,7 @@ private:
 
     float target_snr_dB = cc == PUSCH_CODE ? target_pusch_snr_dB : target_pucch_snr_dB;
     if (target_snr_dB < 0) {
-      // undefined target sinr case, or no more PHR
+      // undefined target SINR case
       return encode_tpc_delta(0);
     }
     if ((tti_count - ch_snr.last_tpc_tti_count) < min_tpc_tti_interval) {
@@ -176,12 +177,13 @@ private:
     if (cc == PUSCH_CODE and last_phr < 0 and not ch_snr.phr_flag) {
       // if negative PHR and PUSCH
       logger.info("TPC: rnti=0x%x, PUSCH command=0 due to PHR=%d<0", rnti, last_phr);
-      ch_snr.phr_flag = true;
+      ch_snr.phr_flag      = true;
-      return encode_tpc_delta(-1);
+      ch_snr.pending_delta = -1;
+      return encode_tpc_delta(ch_snr.pending_delta);
     }
 
     // target SINR is finite and there is power headroom
-    float diff = target_snr_dB - ch_snr.snr_avg.value();
+    float diff = target_snr_dB - ch_snr.last_snr_sample;
     diff -= ch_snr.win_tpc_values.value() + ch_snr.acc_tpc_values;
     if (diff >= 1) {
       ch_snr.pending_delta = diff > 3 ? 3 : 1;
@@ -194,6 +196,15 @@ private:
       ch_snr.pending_delta      = -1;
       ch_snr.last_tpc_tti_count = tti_count;
     }
+    if (ch_snr.pending_delta != 0) {
+      logger.debug("TPC: rnti=0x%x, %s command=%d, last SNR=%d, SNR average=%f, diff_acc=%f",
+                   rnti,
+                   cc == PUSCH_CODE ? "PUSCH" : "PUCCH",
+                   encode_tpc_delta(ch_snr.pending_delta),
+                   ch_snr.last_snr_sample,
+                   ch_snr.snr_avg.value(),
+                   diff);
+    }
     return encode_tpc_delta(ch_snr.pending_delta);
   }
 
@@ -221,6 +232,7 @@ private:
     // SNR average estimation with irregular sample spacing
     uint32_t                                  last_snr_sample_count = 1; // jump in spacing
     srsran::exp_average_irreg_sampling<float> snr_avg;
+    int                                       last_snr_sample;
     // Accumulation of past TPC commands
     srsran::sliding_sum<int> win_tpc_values;
     int8_t                   pending_delta      = 0;
@@ -228,7 +240,9 @@ private:
     uint32_t                 last_tpc_tti_count = 0;
 
     explicit ul_ch_snr_estim(float exp_avg_alpha, int initial_snr) :
-      snr_avg(exp_avg_alpha, initial_snr), win_tpc_values(FDD_HARQ_DELAY_UL_MS + FDD_HARQ_DELAY_DL_MS)
+      snr_avg(exp_avg_alpha, initial_snr),
+      win_tpc_values(FDD_HARQ_DELAY_UL_MS + FDD_HARQ_DELAY_DL_MS),
+      last_snr_sample(initial_snr)
     {}
   };
   std::array<ul_ch_snr_estim, nof_ul_ch_code> snr_estim_list;