diff --git a/lib/test/upper/rlc_am_stress_test.cc b/lib/test/upper/rlc_am_stress_test.cc
index fb83e4cfd..52d4176de 100644
--- a/lib/test/upper/rlc_am_stress_test.cc
+++ b/lib/test/upper/rlc_am_stress_test.cc
@@ -30,10 +30,14 @@
 #include "srslte/common/log_filter.h"
 #include "srslte/common/logger_stdout.h"
 #include "srslte/common/threads.h"
+#include "srslte/common/rlc_pcap.h"
 #include "srslte/upper/rlc.h"
 #include <boost/program_options.hpp>
 #include <boost/program_options/parsers.hpp>
 #include <assert.h>
+#include <boost/thread.hpp>
+
+#define SDU_SIZE 1500
 
 using namespace std;
 using namespace srsue;
@@ -47,8 +51,13 @@ typedef struct {
   uint32_t pdu_tx_delay_usec;
   bool     reestablish;
   uint32_t log_level;
+  bool     single_tx;
+  bool     write_pcap;
+  float    opp_sdu_ratio;
 } stress_test_args_t;
 
+boost::mutex mutex;
+
 void parse_args(stress_test_args_t *args, int argc, char *argv[]) {
 
   // Command line only options
@@ -65,8 +74,11 @@ void parse_args(stress_test_args_t *args, int argc, char *argv[]) {
   ("sdu_gen_delay", bpo::value<uint32_t>(&args->sdu_gen_delay_usec)->default_value(10), "SDU generation delay (usec)")
   ("pdu_tx_delay",  bpo::value<uint32_t>(&args->pdu_tx_delay_usec)->default_value(10), "Delay in MAC for transfering PDU from tx'ing RLC to rx'ing RLC (usec)")
   ("error_rate",    bpo::value<float>(&args->error_rate)->default_value(0.1), "Rate at which RLC PDUs are dropped")
+  ("opp_sdu_ratio", bpo::value<float>(&args->opp_sdu_ratio)->default_value(0.0), "Ratio between MAC opportunity and SDU size (0==random)")
   ("reestablish",   bpo::value<bool>(&args->reestablish)->default_value(false), "Mimic RLC reestablish during execution")
-  ("loglevel",      bpo::value<uint32_t>(&args->log_level)->default_value(srslte::LOG_LEVEL_DEBUG), "Log level (1=Error,2=Warning,3=Info,4=Debug");
+  ("loglevel",      bpo::value<uint32_t>(&args->log_level)->default_value(srslte::LOG_LEVEL_DEBUG), "Log level (1=Error,2=Warning,3=Info,4=Debug)")
+  ("singletx",      bpo::value<bool>(&args->single_tx)->default_value(false), "If set to true, only one node is generating data")
+  ("pcap",          bpo::value<bool>(&args->write_pcap)->default_value(false), "Whether to write all RLC PDU to PCAP file");
 
   // these options are allowed on the command line
   bpo::options_description cmdline_options;
@@ -94,14 +106,17 @@ class mac_reader
     :public thread
 {
 public:
-  mac_reader(rlc_interface_mac *rlc1_, rlc_interface_mac *rlc2_, float fail_rate_, uint32_t pdu_tx_delay_usec_)
+  mac_reader(rlc_interface_mac *rlc1_, rlc_interface_mac *rlc2_, float fail_rate_, float opp_sdu_ratio_, uint32_t pdu_tx_delay_usec_, rlc_pcap *pcap_, bool is_dl_ = true)
   {
     rlc1 = rlc1_;
     rlc2 = rlc2_;
     fail_rate = fail_rate_;
+    opp_sdu_ratio = opp_sdu_ratio_;
     run_enable = true;
     running = false;
     pdu_tx_delay_usec = pdu_tx_delay_usec_;
+    pcap = pcap_;
+    is_dl = is_dl_;
   }
 
   void stop()
@@ -129,14 +144,25 @@ private:
     }
 
     while(run_enable) {
-      float r = (float)rand()/RAND_MAX;
-      int opp_size = r*1500;
-      rlc1->get_buffer_state(1);
-      int read = rlc1->read_pdu(1, pdu->msg, opp_size);
-      if(((float)rand()/RAND_MAX > fail_rate) && read>0) {
-        rlc2->write_pdu(1, pdu->msg, opp_size);
+      // generate MAC opportunities of random size or with fixed ratio
+      float r = opp_sdu_ratio ? opp_sdu_ratio : (float)rand()/RAND_MAX;
+      int opp_size = r*SDU_SIZE;
+      mutex.lock();
+      uint32_t buf_state = rlc1->get_buffer_state(1);
+      if (buf_state) {
+        int read = rlc1->read_pdu(1, pdu->msg, opp_size);
+        usleep(pdu_tx_delay_usec);
+        if(((float)rand()/RAND_MAX > fail_rate) && read>0) {
+          pdu->N_bytes = read;
+          rlc2->write_pdu(1, pdu->msg, pdu->N_bytes);
+          if (is_dl) {
+            pcap->write_dl_am_ccch(pdu->msg, pdu->N_bytes);
+          } else {
+            pcap->write_ul_am_ccch(pdu->msg, pdu->N_bytes);
+          }
+        }
       }
-      usleep(pdu_tx_delay_usec);
+      mutex.unlock();
     }
     running = false;
     byte_buffer_pool::get_instance()->deallocate(pdu);
@@ -145,7 +171,10 @@ private:
   rlc_interface_mac *rlc1;
   rlc_interface_mac *rlc2;
   float fail_rate;
+  float opp_sdu_ratio;
   uint32_t pdu_tx_delay_usec;
+  rlc_pcap *pcap;
+  bool is_dl;
 
   bool run_enable;
   bool running;
@@ -155,9 +184,9 @@ class mac_dummy
     :public srslte::mac_interface_timers
 {
 public:
-  mac_dummy(rlc_interface_mac *rlc1_, rlc_interface_mac *rlc2_, float fail_rate_, uint32_t pdu_tx_delay)
-    :r1(rlc1_, rlc2_, fail_rate_, pdu_tx_delay)
-    ,r2(rlc2_, rlc1_, fail_rate_, pdu_tx_delay)
+  mac_dummy(rlc_interface_mac *rlc1_, rlc_interface_mac *rlc2_, float fail_rate_, float opp_sdu_ratio_, int32_t pdu_tx_delay, rlc_pcap* pcap = NULL)
+    :r1(rlc1_, rlc2_, fail_rate_, opp_sdu_ratio_, pdu_tx_delay, pcap, true)
+    ,r2(rlc2_, rlc1_, fail_rate_, opp_sdu_ratio_, pdu_tx_delay, pcap, false)
   {
   }
 
@@ -222,6 +251,7 @@ public:
   void write_pdu(uint32_t lcid, byte_buffer_t *sdu)
   {
     assert(lcid == 1);
+    assert(sdu->N_bytes==SDU_SIZE);
     byte_buffer_pool::get_instance()->deallocate(sdu);
     std::cout << "rlc_am_tester " << name << " received " << rx_pdus++ << " PDUs" << std::endl;
   }
@@ -244,8 +274,11 @@ private:
         printf("Fatal Error: Could not allocate PDU in rlc_am_tester::run_thread\n");
         exit(-1);
       }
-      pdu->N_bytes = 1500;
-      pdu->msg[0]   = sn++;
+      for (uint32_t i = 0; i < SDU_SIZE; i++) {
+        pdu->msg[i] = sn;
+      }
+      sn++;
+      pdu->N_bytes = SDU_SIZE;
       rlc->write_sdu(1, pdu);
       usleep(sdu_gen_delay_usec);
     }
@@ -271,13 +304,18 @@ void stress_test(stress_test_args_t args)
   log2.set_level((LOG_LEVEL_ENUM)args.log_level);
   log1.set_hex_limit(-1);
   log2.set_hex_limit(-1);
+  rlc_pcap pcap;
+
+  if (args.write_pcap) {
+    pcap.open("rlc_stress_test.pcap", 0);
+  }
 
   rlc rlc1;
   rlc rlc2;
 
   rlc_am_tester tester1(&rlc1, "tester1", args.sdu_gen_delay_usec);
   rlc_am_tester tester2(&rlc2, "tester2", args.sdu_gen_delay_usec);
-  mac_dummy     mac(&rlc1, &rlc2, args.error_rate, args.pdu_tx_delay_usec);
+  mac_dummy     mac(&rlc1, &rlc2, args.error_rate, args.opp_sdu_ratio, args.pdu_tx_delay_usec, &pcap);
   ue_interface  ue;
 
   rlc1.init(&tester1, &tester1, &ue, &log1, &mac, 0);
@@ -298,14 +336,21 @@ void stress_test(stress_test_args_t args)
   rlc2.add_bearer(1, cnfg_);
 
   tester1.start(7);
-  tester2.start(7);
+  if (!args.single_tx) {
+    tester2.start(7);
+  }
   mac.start();
 
   for (uint32_t i = 0; i < args.test_duration_sec; i++) {
     // if enabled, mimic reestablishment every second
     if (args.reestablish) {
+      // lock mutex during reestablish to prevent a RLC PDU that is already been transmitted before
+      // resetting the tx'ing RLC entity, but not yet received before resetting the
+      // rx'ing RLC entity to screw the test
+      mutex.lock();
       rlc1.reestablish();
       rlc2.reestablish();
+      mutex.unlock();
     }
     usleep(1e6);
   }
@@ -313,6 +358,9 @@ void stress_test(stress_test_args_t args)
   tester1.stop();
   tester2.stop();
   mac.stop();
+  if (args.write_pcap) {
+    pcap.close();
+  }
 }