diff --git a/lib/include/srslte/common/common.h b/lib/include/srslte/common/common.h
index 5e2fa3cb4..34b07047f 100644
--- a/lib/include/srslte/common/common.h
+++ b/lib/include/srslte/common/common.h
@@ -46,13 +46,14 @@
 #define MSG3_DELAY_MS 2 // Delay added to TX_DELAY
 
 #define TTI_SUB(a, b) ((((a) + 10240) - (b)) % 10240)
+#define TTI_ADD(a, b)  (((a) + (b)) % 10240)
 
-#define TTI_TX(tti) ((tti + TX_DELAY) % 10240)
+#define TTI_TX(tti) TTI_ADD(tti, TX_DELAY)
 
 // Use only in FDD mode!!
 #define FDD_HARQ_DELAY_MS 4
-#define TTI_RX(tti) (TTI_SUB(tti, FDD_HARQ_DELAY_MS))
-#define TTI_RX_ACK(tti) ((tti + (2 * FDD_HARQ_DELAY_MS)) % 10240)
+#define TTI_RX(tti)      (TTI_SUB(tti, FDD_HARQ_DELAY_MS))
+#define TTI_RX_ACK(tti)  (TTI_ADD(tti, FDD_HARQ_DELAY_MS + TX_DELAY))
 
 #define TTIMOD_SZ 20
 #define TTIMOD(tti)     (tti%TTIMOD_SZ)
diff --git a/lib/include/srslte/interfaces/sched_interface.h b/lib/include/srslte/interfaces/sched_interface.h
index b21d8b341..5db6711c8 100644
--- a/lib/include/srslte/interfaces/sched_interface.h
+++ b/lib/include/srslte/interfaces/sched_interface.h
@@ -54,7 +54,8 @@ public:
     int pdsch_max_mcs; 
     int pusch_mcs; 
     int pusch_max_mcs; 
-    int nof_ctrl_symbols; 
+    int nof_ctrl_symbols;
+    int max_aggr_level;
   } sched_args_t; 
 
     
@@ -71,7 +72,8 @@ public:
     srslte_pusch_hopping_cfg_t pusch_hopping_cfg; 
     
     /* prach configuration */
-    uint32_t prach_config; 
+    uint32_t prach_config;
+    uint32_t prach_nof_preambles;
     uint32_t prach_freq_offset; 
     uint32_t prach_rar_window;
     uint32_t prach_contention_resolution_timer; 
@@ -154,9 +156,17 @@ public:
     uint32_t        tbs;
     srslte_dci_ul_t dci;
   } ul_sched_data_t;
-  
+
+  typedef struct {
+    uint32_t preamble_idx;
+    uint32_t ta_cmd;
+    uint16_t temp_crnti;
+    uint32_t msg3_size;
+    uint32_t prach_tti;
+  } dl_sched_rar_info_t;
+
   typedef struct {
-    uint32_t               ra_id;
+    dl_sched_rar_info_t    data;
     srslte_dci_rar_grant_t grant; 
   } dl_sched_rar_grant_t;
   
@@ -229,7 +239,7 @@ public:
     
   /* DL information */
   virtual int dl_ack_info(uint32_t tti, uint16_t rnti, uint32_t tb_idx, bool ack) = 0;
-  virtual int dl_rach_info(uint32_t tti, uint32_t ra_id, uint16_t rnti, uint32_t estimated_size) = 0; 
+  virtual int dl_rach_info(dl_sched_rar_info_t rar_info) = 0;
   virtual int dl_ri_info(uint32_t tti, uint16_t rnti, uint32_t ri_value) = 0; 
   virtual int dl_pmi_info(uint32_t tti, uint16_t rnti, uint32_t pmi_value) = 0;
   virtual int dl_cqi_info(uint32_t tti, uint16_t rnti, uint32_t cqi_value) = 0; 
diff --git a/lib/include/srslte/phy/phch/pusch_cfg.h b/lib/include/srslte/phy/phch/pusch_cfg.h
index af82505d3..b9f0672dd 100644
--- a/lib/include/srslte/phy/phch/pusch_cfg.h
+++ b/lib/include/srslte/phy/phch/pusch_cfg.h
@@ -43,7 +43,6 @@ typedef struct {
 
 typedef struct SRSLTE_API {
 
-  bool           is_from_rar;
   uint32_t       L_prb;
   uint32_t       n_prb[2];       // rb_start after frequency hopping
   uint32_t       n_prb_tilde[2]; // rb_start after frequency hopping per retx
diff --git a/lib/src/phy/channel/delay.c b/lib/src/phy/channel/delay.c
index c7c902db7..deafac27c 100644
--- a/lib/src/phy/channel/delay.c
+++ b/lib/src/phy/channel/delay.c
@@ -25,20 +25,24 @@
 
 static inline double calculate_delay_us(srslte_channel_delay_t* q, const srslte_timestamp_t* ts)
 {
-  // Convert period from seconds to samples
-  uint64_t period_nsamples = (uint64_t)roundf(q->period_s * q->srate_hz);
+  if (q->period_s) {
+    // Convert period from seconds to samples
+    uint64_t period_nsamples = (uint64_t)roundf(q->period_s * q->srate_hz);
 
-  // Convert timestamp to samples
-  uint64_t ts_nsamples = srslte_timestamp_uint64(ts, q->srate_hz) + (uint64_t)q->init_time_s * q->srate_hz;
+    // Convert timestamp to samples
+    uint64_t ts_nsamples = srslte_timestamp_uint64(ts, q->srate_hz) + (uint64_t)q->init_time_s * q->srate_hz;
 
-  // Calculate time modulus in period
-  uint64_t mod_t_nsamples = ts_nsamples - period_nsamples * (ts_nsamples / period_nsamples);
-  double   t              = (double)mod_t_nsamples / (double)q->srate_hz;
+    // Calculate time modulus in period
+    uint64_t mod_t_nsamples = ts_nsamples - period_nsamples * (ts_nsamples / period_nsamples);
+    double   t              = (double)mod_t_nsamples / (double)q->srate_hz;
 
-  double   arg      = 2.0 * M_PI * t / (double)q->period_s;
-  double   delay_us = q->delay_min_us + (q->delay_max_us - q->delay_min_us) * (1.0 + sin(arg)) / 2.0;
+    double   arg      = 2.0 * M_PI * t / (double)q->period_s;
+    double   delay_us = q->delay_min_us + (q->delay_max_us - q->delay_min_us) * (1.0 + sin(arg)) / 2.0;
 
-  return delay_us;
+    return delay_us;
+  } else {
+    return q->delay_max_us;
+  }
 }
 
 static inline uint32_t calculate_delay_nsamples(srslte_channel_delay_t* q)
diff --git a/lib/src/phy/dft/ofdm.c b/lib/src/phy/dft/ofdm.c
index 5c27e8faa..be55f8edb 100644
--- a/lib/src/phy/dft/ofdm.c
+++ b/lib/src/phy/dft/ofdm.c
@@ -455,12 +455,11 @@ void srslte_ofdm_rx_sf(srslte_ofdm_t *q) {
   if (q->freq_shift) {
     srslte_vec_prod_ccc(q->in_buffer, q->shift_buffer, q->in_buffer, 2*q->slot_sz);
   }
-  if(!q->mbsfn_subframe){
+  if (!q->mbsfn_subframe) {
     for (n=0;n<2;n++) {
       srslte_ofdm_rx_slot(q, n);
     }
-  }
-  else{
+  } else {
     srslte_ofdm_rx_slot_mbsfn(q, &q->in_buffer[0*q->slot_sz], &q->out_buffer[0*q->nof_re*q->nof_symbols]);
     srslte_ofdm_rx_slot(q, 1);
   }
@@ -469,14 +468,13 @@ void srslte_ofdm_rx_sf(srslte_ofdm_t *q) {
 void srslte_ofdm_rx_sf_ng(srslte_ofdm_t *q, cf_t *input, cf_t *output) {
   uint32_t n;
   if (q->freq_shift) {
-    srslte_vec_prod_ccc(q->in_buffer, q->shift_buffer, q->in_buffer, 2*q->slot_sz);
+    srslte_vec_prod_ccc(input, q->shift_buffer, input, 2*q->slot_sz);
   }
-  if(!q->mbsfn_subframe){
+  if (!q->mbsfn_subframe) {
     for (n=0;n<2;n++) {
       srslte_ofdm_rx_slot_ng(q, &input[n*q->slot_sz], &output[n*q->nof_re*q->nof_symbols]);
     }
-  }
-  else{
+  } else {
     srslte_ofdm_rx_slot_mbsfn(q, &q->in_buffer[0*q->slot_sz], &q->out_buffer[0*q->nof_re*q->nof_symbols]);
     srslte_ofdm_rx_slot(q, 1);
   }
diff --git a/srsenb/enb.conf.example b/srsenb/enb.conf.example
index 7f68829e9..62ada8f70 100644
--- a/srsenb/enb.conf.example
+++ b/srsenb/enb.conf.example
@@ -136,6 +136,7 @@ enable = false
 #####################################################################
 # Scheduler configuration options
 #
+# max_aggr_level:    Optional maximum aggregation level index (l=log2(L) can be 0, 1, 2 or 3)
 # pdsch_mcs:         Optional fixed PDSCH MCS (ignores reported CQIs if specified)
 # pdsch_max_mcs:     Optional PDSCH MCS limit 
 # pusch_mcs:         Optional fixed PUSCH MCS (ignores reported CQIs if specified)
@@ -144,6 +145,7 @@ enable = false
 #
 #####################################################################
 [scheduler]
+#max_aggr_level   = -1
 #pdsch_mcs        = -1
 #pdsch_max_mcs    = -1
 #pusch_mcs        = -1
@@ -162,6 +164,86 @@ nof_ctrl_symbols = 3
 #m1u_multiaddr = 239.255.0.1
 #m1u_if_addr = 127.0.1.201
 
+
+
+#####################################################################
+# Channel emulator options:
+# enable:            Enable/Disable internal Downlink/Uplink channel emulator
+#
+# -- Fading emulator
+# fading.enable:     Enable/disable fading simulator
+# fading.model:      Fading model + maximum doppler (E.g. none, epa5, eva70, etu300, etc)
+#
+# -- Delay Emulator     delay(t) = delay_min + (delay_max - delay_min) * (1 + sin(2pi*t/period)) / 2
+#                       Maximum speed [m/s]: (delay_max - delay_min) * pi * 300 / period
+# delay.enable:      Enable/disable delay simulator
+# delay.period_s:    Delay period in seconds.
+# delay.init_time_s: Delay initial time in seconds.
+# delay.maximum_us:  Maximum delay in microseconds
+# delay.minumum_us:  Minimum delay in microseconds
+#
+# -- Radio-Link Failure (RLF) Emulator
+# rlf.enable:        Enable/disable RLF simulator
+# rlf.t_on_ms:       Time for On state of the channel (ms)
+# rlf.t_off_ms:      Time for Off state of the channel (ms)
+#
+# -- High Speed Train Doppler model simulator
+# hst.enable:        Enable/Disable HST simulator
+# hst.period_s:      HST simulation period in seconds
+# hst.fd_hz:         Doppler frequency in Hz
+# hst.init_time_s:   Initial time in seconds
+#####################################################################
+[channel.dl]
+#enable        = false
+
+[channel.dl.fading]
+#enable        = false
+#model         = none
+
+[channel.dl.delay]
+#enable        = false
+#period_s      = 3600
+#init_time_s   = 0
+#maximum_us    = 100
+#minimum_us    = 10
+
+[channel.dl.rlf]
+#enable        = false
+#t_on_ms       = 10000
+#t_off_ms      = 2000
+
+[channel.dl.hst]
+#enable        = false
+#period_s      = 7.2
+#fd_hz         = 750.0
+#init_time_s   = 0.0
+
+[channel.ul]
+#enable        = false
+
+[channel.ul.fading]
+#enable        = false
+#model         = none
+
+[channel.ul.delay]
+#enable        = false
+#period_s      = 3600
+#init_time_s   = 0
+#maximum_us    = 100
+#minimum_us    = 10
+
+[channel.ul.rlf]
+#enable        = false
+#t_on_ms       = 10000
+#t_off_ms      = 2000
+
+[channel.ul.hst]
+#enable        = false
+#period_s      = 7.2
+#fd_hz         = -750.0
+#init_time_s   = 0.0
+
+
 #####################################################################
 # Expert configuration options
 #
diff --git a/srsenb/hdr/phy/phy_common.h b/srsenb/hdr/phy/phy_common.h
index 1c1ee89a0..b42fe7d43 100644
--- a/srsenb/hdr/phy/phy_common.h
+++ b/srsenb/hdr/phy/phy_common.h
@@ -27,6 +27,7 @@
 #include "srslte/common/log.h"
 #include "srslte/common/thread_pool.h"
 #include "srslte/common/threads.h"
+#include "srslte/phy/channel/channel.h"
 #include "srslte/interfaces/common_interfaces.h"
 #include "srslte/interfaces/enb_interfaces.h"
 #include "srslte/interfaces/enb_metrics_interface.h"
@@ -51,6 +52,9 @@ typedef struct {
   std::string equalizer_mode;
   float       estimator_fil_w;
   bool        pregenerate_signals;
+
+  srslte::channel::args_t dl_channel_args;
+  srslte::channel::args_t ul_channel_args;
 } phy_args_t;
 
 class phy_common
@@ -79,6 +83,7 @@ public:
 
   srslte::radio_interface_phy* radio = nullptr;
   stack_interface_phy_lte*     stack = nullptr;
+  srslte::channel_ptr          dl_channel = nullptr;
 
   // Common objects for schedulign grants
   stack_interface_phy_lte::ul_sched_t ul_grants[TTIMOD_SZ] = {};
diff --git a/srsenb/hdr/phy/sf_worker.h b/srsenb/hdr/phy/sf_worker.h
index 103adbd12..6394bc88b 100644
--- a/srsenb/hdr/phy/sf_worker.h
+++ b/srsenb/hdr/phy/sf_worker.h
@@ -75,6 +75,7 @@ private:
   std::vector<std::unique_ptr<cc_worker> > cc_workers;
 
   srslte_softbuffer_tx_t temp_mbsfn_softbuffer = {};
+
 };
 
 } // namespace srsenb
diff --git a/srsenb/hdr/phy/txrx.h b/srsenb/hdr/phy/txrx.h
index 5ef781eaf..ddd305449 100644
--- a/srsenb/hdr/phy/txrx.h
+++ b/srsenb/hdr/phy/txrx.h
@@ -28,6 +28,7 @@
 #include "srslte/common/thread_pool.h"
 #include "srslte/common/threads.h"
 #include "srslte/radio/radio.h"
+#include "srslte/phy/channel/channel.h"
 
 namespace srsenb {
     
@@ -53,6 +54,7 @@ private:
   srslte::thread_pool*         workers_pool = nullptr;
   prach_worker*                prach        = nullptr;
   phy_common*                  worker_com   = nullptr;
+  srslte::channel_ptr          ul_channel   = nullptr;
 
   // Main system TTI counter
   uint32_t tti = 0;
diff --git a/srsenb/hdr/stack/mac/mac.h b/srsenb/hdr/stack/mac/mac.h
index 9569f37ba..3bde027f8 100644
--- a/srsenb/hdr/stack/mac/mac.h
+++ b/srsenb/hdr/stack/mac/mac.h
@@ -136,8 +136,7 @@ private:
   srslte_cell_t cell; 
   mac_args_t    args; 
   
-  uint32_t      tti; 
-  bool          started; 
+  bool          started;
 
   /* Scheduler unit */
   sched            scheduler; 
@@ -153,23 +152,14 @@ private:
   std::map<uint16_t, ue*> ue_db;   
   uint16_t        last_rnti;   
   
-  uint8_t* assemble_rar(sched_interface::dl_sched_rar_grant_t *grants, uint32_t nof_grants, int rar_idx, uint32_t pdu_len);
+  uint8_t* assemble_rar(sched_interface::dl_sched_rar_grant_t *grants, uint32_t nof_grants, int rar_idx, uint32_t pdu_len, uint32_t tti);
   uint8_t* assemble_si(uint32_t index);
 
   const static int             rar_payload_len = 128;
   std::vector<srslte::rar_pdu> rar_pdu_msg;
   srslte::byte_buffer_t        rar_payload[sched_interface::MAX_RAR_LIST];
 
-  typedef struct {
-    uint32_t preamble_idx; 
-    uint32_t ta_cmd; 
-    uint16_t temp_crnti; 
-  } pending_rar_t; 
-
-  const static int MAX_PENDING_RARS = 64; 
-  pending_rar_t pending_rars[MAX_PENDING_RARS]; 
-  
-  const static int NOF_BCCH_DLSCH_MSG=sched_interface::MAX_SIBS; 
+  const static int NOF_BCCH_DLSCH_MSG=sched_interface::MAX_SIBS;
   uint8_t bcch_dlsch_payload[sched_interface::MAX_SIB_PAYLOAD_LEN];
   
   const static int pcch_payload_buffer_len = 1024;
@@ -199,13 +189,14 @@ private:
   /* Class to run upper-layer timers with normal priority */
   class timer_thread : public thread {
   public:
-    timer_thread(srslte::timers* t) : ttisync(10240), timers(t), running(false), thread("MAC_TIMER") { start(); }
+    timer_thread(mac* parent_, srslte::timers* t) : ttisync(10240), timers(t), running(false), parent(parent_), thread("MAC_TIMER") { start(); }
     void tti_clock();
     void stop();
   private:
     void run_thread();
     srslte::tti_sync_cv ttisync;
     srslte::timers     *timers;
+    mac                *parent;
     bool running; 
   };
   timer_thread   timers_thread;
diff --git a/srsenb/hdr/stack/mac/scheduler.h b/srsenb/hdr/stack/mac/scheduler.h
index 40abdc4e3..26483283c 100644
--- a/srsenb/hdr/stack/mac/scheduler.h
+++ b/srsenb/hdr/stack/mac/scheduler.h
@@ -30,6 +30,7 @@
 #include "srslte/interfaces/sched_interface.h"
 #include <map>
 #include <mutex>
+#include <queue>
 #include <pthread.h>
 
 namespace srsenb {
@@ -107,8 +108,9 @@ public:
 
   int ue_cfg(uint16_t rnti, ue_cfg_t *ue_cfg);
   int ue_rem(uint16_t rnti);
-  bool ue_exists(uint16_t rnti); 
-  
+  bool ue_exists(uint16_t rnti);
+  void ue_needs_ta_cmd(uint16_t rnti, uint32_t nof_ta_cmd);
+
   void phy_config_enabled(uint16_t rnti, bool enabled); 
   
   int bearer_ue_cfg(uint16_t rnti, uint32_t lc_id, ue_bearer_cfg_t *cfg); 
@@ -122,7 +124,7 @@ public:
 
   int dl_ant_info(uint16_t rnti, asn1::rrc::phys_cfg_ded_s::ant_info_c_* dedicated);
   int dl_ack_info(uint32_t tti, uint16_t rnti, uint32_t tb_idx, bool ack);
-  int dl_rach_info(uint32_t tti, uint32_t ra_id, uint16_t rnti, uint32_t estimated_size); 
+  int dl_rach_info(dl_sched_rar_info_t rar_info);
   int dl_ri_info(uint32_t tti, uint16_t rnti, uint32_t ri_value);
   int dl_pmi_info(uint32_t tti, uint16_t rnti, uint32_t pmi_value);
   int dl_cqi_info(uint32_t tti, uint16_t rnti, uint32_t cqi_value); 
@@ -167,13 +169,6 @@ protected:
   // This is for computing DCI locations
   srslte_regs_t regs;
 
-  typedef struct {
-    int buf_rar; 
-    uint16_t rnti; 
-    uint32_t ra_id; 
-    uint32_t rar_tti;    
-  } sched_rar_t; 
-  
   typedef struct {
     bool is_in_window;
     uint32_t window_start;
@@ -230,7 +225,7 @@ protected:
     void            new_tti(uint32_t tti_rx_, uint32_t start_cfi);
     alloc_outcome_t alloc_bc(uint32_t aggr_lvl, uint32_t sib_idx, uint32_t sib_ntx);
     alloc_outcome_t alloc_paging(uint32_t aggr_lvl, uint32_t paging_payload);
-    rar_code_t      alloc_rar(uint32_t aggr_lvl, const dl_sched_rar_t& rar_grant, uint32_t rar_tti, uint32_t buf_rar);
+    rar_code_t      alloc_rar(uint32_t aggr_lvl, const dl_sched_rar_t& rar_grant, uint32_t prach_tti, uint32_t buf_rar);
     void            generate_dcis();
     // dl_tti_sched itf
     alloc_outcome_t  alloc_dl_user(sched_ue* user, const rbgmask_t& user_mask, uint32_t pid) final;
@@ -305,11 +300,10 @@ protected:
     uint32_t L; 
     uint32_t n_prb; 
     uint32_t mcs; 
-  } pending_msg3_t; 
- 
-  const static int SCHED_MAX_PENDING_RAR = 8; 
-  sched_rar_t pending_rar[SCHED_MAX_PENDING_RAR];
-  pending_msg3_t pending_msg3[10]; 
+  } pending_msg3_t;
+
+  std::queue<dl_sched_rar_info_t> pending_rars;
+  pending_msg3_t pending_msg3[TTIMOD_SZ];
     
   // Allowed DCI locations for SIB and RAR per CFI
   sched_ue::sched_dci_cce_t common_locations[3];
diff --git a/srsenb/hdr/stack/mac/scheduler_ue.h b/srsenb/hdr/stack/mac/scheduler_ue.h
index 8f94294e0..b8d323c20 100644
--- a/srsenb/hdr/stack/mac/scheduler_ue.h
+++ b/srsenb/hdr/stack/mac/scheduler_ue.h
@@ -83,7 +83,7 @@ public:
   void tpc_inc(); 
   void tpc_dec();
 
-  void set_max_mcs(int mcs_ul, int mcs_dl);
+  void set_max_mcs(int mcs_ul, int mcs_dl, int max_aggr_level = -1);
   void set_fixed_mcs(int mcs_ul, int mcs_dl);
 
   dl_harq_proc* find_dl_harq(uint32_t tti);
@@ -117,6 +117,8 @@ public:
   void       set_sr();
   void       unset_sr();
 
+  void       set_needs_ta_cmd(uint32_t nof_ta_cmd);
+
   int generate_format1(
       dl_harq_proc* h, sched_interface::dl_sched_data_t* data, uint32_t tti, uint32_t cfi, const rbgmask_t& user_mask);
   int generate_format2a(
@@ -198,12 +200,15 @@ private:
   uint32_t ul_cqi_tti; 
   uint16_t rnti; 
   uint32_t max_mcs_dl;
+  uint32_t max_aggr_level;
   uint32_t max_mcs_ul;
   uint32_t max_msg3retx;
   int      fixed_mcs_ul; 
   int      fixed_mcs_dl;
   uint32_t P;
 
+  uint32_t nof_ta_cmd;
+
   int next_tpc_pusch;
   int next_tpc_pucch;
 
diff --git a/srsenb/hdr/stack/mac/ue.h b/srsenb/hdr/stack/mac/ue.h
index c97ec0192..28f7befe1 100644
--- a/srsenb/hdr/stack/mac/ue.h
+++ b/srsenb/hdr/stack/mac/ue.h
@@ -26,9 +26,11 @@
 #include "srslte/common/pdu.h"
 #include "srslte/common/mac_pcap.h"
 #include "srslte/common/pdu_queue.h"
+#include "srslte/common/block_queue.h"
 #include "srslte/interfaces/enb_interfaces.h"
 #include "srslte/interfaces/sched_interface.h"
 #include <pthread.h>
+#include <vector>
 #include "mac_metrics.h"
 
 namespace srsenb {
@@ -42,14 +44,18 @@ public:
      sched_interface*   sched,
      rrc_interface_mac* rrc_,
      rlc_interface_mac* rlc,
-     srslte::log*       log_);
+     srslte::log*       log_,
+     uint32_t           nof_rx_harq_proc = SRSLTE_FDD_NOF_HARQ,
+     uint32_t           nof_tx_harq_proc = SRSLTE_FDD_NOF_HARQ * SRSLTE_MAX_TB);
   virtual ~ue();
 
   void     reset();
   
   void     start_pcap(srslte::mac_pcap* pcap_);
 
-  void     set_tti(uint32_t tti); 
+  void     set_tti(uint32_t tti);
+
+  uint32_t set_ta(int ta);
   
   void     config(uint16_t rnti, uint32_t nof_prb, sched_interface *sched, rrc_interface_mac *rrc_, rlc_interface_mac *rlc, srslte::log *log_h);
   uint8_t* generate_pdu(uint32_t                        harq_pid,
@@ -108,12 +114,13 @@ private:
 
   uint32_t nof_failures = 0;
 
-  const static int       NOF_RX_HARQ_PROCESSES = SRSLTE_FDD_NOF_HARQ;
-  const static int       NOF_TX_HARQ_PROCESSES = SRSLTE_FDD_NOF_HARQ * SRSLTE_MAX_TB;
-  srslte_softbuffer_tx_t softbuffer_tx[NOF_TX_HARQ_PROCESSES];
-  srslte_softbuffer_rx_t softbuffer_rx[NOF_RX_HARQ_PROCESSES];
+  srslte::block_queue<uint32_t> pending_ta_commands;
 
-  uint8_t* pending_buffers[NOF_RX_HARQ_PROCESSES] = {nullptr};
+  int                                nof_rx_harq_proc = 0;
+  int                                nof_tx_harq_proc = 0;
+  std::vector<srslte_softbuffer_tx_t> softbuffer_tx;
+  std::vector<srslte_softbuffer_rx_t> softbuffer_rx;
+  std::vector<uint8_t*>               pending_buffers;
 
   // For DL there are two buffers, one for each Transport block
   srslte::byte_buffer_t tx_payload_buffer[SRSLTE_FDD_NOF_HARQ][SRSLTE_MAX_TB];
diff --git a/srsenb/src/main.cc b/srsenb/src/main.cc
index 664a0d66f..3ad70f3ac 100644
--- a/srsenb/src/main.cc
+++ b/srsenb/src/main.cc
@@ -130,9 +130,45 @@ void parse_args(all_args_t *args, int argc, char* argv[]) {
     ("scheduler.pdsch_max_mcs", bpo::value<int>(&args->stack.mac.sched.pdsch_max_mcs)->default_value(-1), "Optional PDSCH MCS limit")
     ("scheduler.pusch_mcs", bpo::value<int>(&args->stack.mac.sched.pusch_mcs)->default_value(-1), "Optional fixed PUSCH MCS (ignores reported CQIs if specified)")
     ("scheduler.pusch_max_mcs", bpo::value<int>(&args->stack.mac.sched.pusch_max_mcs)->default_value(-1), "Optional PUSCH MCS limit")
+    ("scheduler.max_aggr_level", bpo::value<int>(&args->stack.mac.sched.max_aggr_level)->default_value(-1), "Optional maximum aggregation level index (l=log2(L)) ")
     ("scheduler.nof_ctrl_symbols", bpo::value<int>(&args->stack.mac.sched.nof_ctrl_symbols)->default_value(3), "Number of control symbols")
 
-    /* Expert section */
+
+    /* Downlink Channel emulator section */
+    ("channel.dl.enable", bpo::value<bool>(&args->phy.dl_channel_args.enable)->default_value(false), "Enable/Disable internal Downlink channel emulator")
+    ("channel.dl.fading.enable", bpo::value<bool>(&args->phy.dl_channel_args.fading_enable)->default_value(false), "Enable/Disable Fading model")
+    ("channel.dl.fading.model", bpo::value<std::string>(&args->phy.dl_channel_args.fading_model)->default_value("none"), "Fading model + maximum doppler (E.g. none, epa5, eva70, etu300, etc)")
+    ("channel.dl.delay.enable", bpo::value<bool>(&args->phy.dl_channel_args.delay_enable)->default_value(false), "Enable/Disable Delay simulator")
+    ("channel.dl.delay.period_s", bpo::value<float>(&args->phy.dl_channel_args.delay_period_s)->default_value(3600), "Delay period in seconds (integer)")
+    ("channel.dl.delay.init_time_s", bpo::value<float>(&args->phy.dl_channel_args.delay_init_time_s)->default_value(0), "Initial time in seconds")
+    ("channel.dl.delay.maximum_us", bpo::value<float>(&args->phy.dl_channel_args.delay_max_us)->default_value(100.0f), "Maximum delay in microseconds")
+    ("channel.dl.delay.minimum_us", bpo::value<float>(&args->phy.dl_channel_args.delay_min_us)->default_value(10.0f), "Minimum delay in microseconds")
+    ("channel.dl.rlf.enable", bpo::value<bool>(&args->phy.dl_channel_args.rlf_enable)->default_value(false), "Enable/Disable Radio-Link Failure simulator")
+    ("channel.dl.rlf.t_on_ms", bpo::value<uint32_t >(&args->phy.dl_channel_args.rlf_t_on_ms)->default_value(10000), "Time for On state of the channel (ms)")
+    ("channel.dl.rlf.t_off_ms", bpo::value<uint32_t >(&args->phy.dl_channel_args.rlf_t_off_ms)->default_value(2000), "Time for Off state of the channel (ms)")
+    ("channel.dl.hst.enable", bpo::value<bool>(&args->phy.dl_channel_args.hst_enable)->default_value(false), "Enable/Disable HST simulator")
+    ("channel.dl.hst.period_s", bpo::value<float>(&args->phy.dl_channel_args.hst_period_s)->default_value(7.2f), "HST simulation period in seconds")
+    ("channel.dl.hst.fd_hz", bpo::value<float>(&args->phy.dl_channel_args.hst_fd_hz)->default_value(+750.0f), "Doppler frequency in Hz")
+    ("channel.dl.hst.init_time_s", bpo::value<float>(&args->phy.dl_channel_args.hst_init_time_s)->default_value(0), "Initial time in seconds")
+
+    /* Uplink Channel emulator section */
+    ("channel.ul.enable", bpo::value<bool>(&args->phy.ul_channel_args.enable)->default_value(false), "Enable/Disable internal Uplink channel emulator")
+    ("channel.ul.fading.enable", bpo::value<bool>(&args->phy.ul_channel_args.fading_enable)->default_value(false), "Enable/Disable Fading model")
+    ("channel.ul.fading.model", bpo::value<std::string>(&args->phy.ul_channel_args.fading_model)->default_value("none"), "Fading model + maximum doppler (E.g. none, epa5, eva70, etu300, etc)")
+    ("channel.ul.delay.enable", bpo::value<bool>(&args->phy.ul_channel_args.delay_enable)->default_value(false), "Enable/Disable Delay simulator")
+    ("channel.ul.delay.period_s", bpo::value<float>(&args->phy.ul_channel_args.delay_period_s)->default_value(3600), "Delay period in seconds (integer)")
+    ("channel.ul.delay.init_time_s", bpo::value<float>(&args->phy.ul_channel_args.delay_init_time_s)->default_value(0), "Initial time in seconds")
+    ("channel.ul.delay.maximum_us", bpo::value<float>(&args->phy.ul_channel_args.delay_max_us)->default_value(100.0f), "Maximum delay in microseconds")
+    ("channel.ul.delay.minimum_us", bpo::value<float>(&args->phy.ul_channel_args.delay_min_us)->default_value(10.0f), "Minimum delay in microseconds")
+    ("channel.ul.rlf.enable", bpo::value<bool>(&args->phy.ul_channel_args.rlf_enable)->default_value(false), "Enable/Disable Radio-Link Failure simulator")
+    ("channel.ul.rlf.t_on_ms", bpo::value<uint32_t >(&args->phy.ul_channel_args.rlf_t_on_ms)->default_value(10000), "Time for On state of the channel (ms)")
+    ("channel.ul.rlf.t_off_ms", bpo::value<uint32_t >(&args->phy.ul_channel_args.rlf_t_off_ms)->default_value(2000), "Time for Off state of the channel (ms)")
+    ("channel.ul.hst.enable", bpo::value<bool>(&args->phy.ul_channel_args.hst_enable)->default_value(false), "Enable/Disable HST simulator")
+    ("channel.ul.hst.period_s", bpo::value<float>(&args->phy.ul_channel_args.hst_period_s)->default_value(7.2f), "HST simulation period in seconds")
+    ("channel.ul.hst.fd_hz", bpo::value<float>(&args->phy.ul_channel_args.hst_fd_hz)->default_value(-750.0f), "Doppler frequency in Hz")
+    ("channel.ul.hst.init_time_s", bpo::value<float>(&args->phy.ul_channel_args.hst_init_time_s)->default_value(0), "Initial time in seconds")
+
+      /* Expert section */
     ("expert.metrics_period_secs", bpo::value<float>(&args->general.metrics_period_secs)->default_value(1.0), "Periodicity for metrics in seconds")
     ("expert.metrics_csv_enable",  bpo::value<bool>(&args->general.metrics_csv_enable)->default_value(false), "Write metrics to CSV file")
     ("expert.metrics_csv_filename", bpo::value<string>(&args->general.metrics_csv_filename)->default_value("/tmp/enb_metrics.csv"), "Metrics CSV filename")
diff --git a/srsenb/src/phy/cc_worker.cc b/srsenb/src/phy/cc_worker.cc
index 165b9c920..9761d5a87 100644
--- a/srsenb/src/phy/cc_worker.cc
+++ b/srsenb/src/phy/cc_worker.cc
@@ -481,7 +481,7 @@ int cc_worker::decode_pusch(stack_interface_phy_lte::ul_sched_grant_t* grants, u
         return SRSLTE_ERROR;
       }
 
-      uint32_t ul_pid = TTI_RX(tti_rx) % SRSLTE_FDD_NOF_HARQ;
+      uint32_t ul_pid = TTI_RX(ul_sf.tti) % SRSLTE_FDD_NOF_HARQ;
 
       // Handle Format0 adaptive retx
       // Use last TBS for this TB in case of mcs>28
@@ -492,11 +492,14 @@ int cc_worker::decode_pusch(stack_interface_phy_lte::ul_sched_grant_t* grants, u
       phy->ue_db_set_last_ul_tb(rnti, ul_pid, grant->tb);
 
       // Run PUSCH decoder
+      pusch_res = {};
       ue_db[rnti]->ul_cfg.pusch.softbuffers.rx = grants[i].softbuffer_rx;
       pusch_res.data                           = grants[i].data;
-      if (srslte_enb_ul_get_pusch(&enb_ul, &ul_sf, &ue_db[rnti]->ul_cfg.pusch, &pusch_res)) {
-        Error("Decoding PUSCH\n");
-        return SRSLTE_ERROR;
+      if (pusch_res.data) {
+        if (srslte_enb_ul_get_pusch(&enb_ul, &ul_sf, &ue_db[rnti]->ul_cfg.pusch, &pusch_res)) {
+          Error("Decoding PUSCH\n");
+          return SRSLTE_ERROR;
+        }
       }
 
       // Save PHICH scheduling for this user. Each user can have just 1 PUSCH dci per TTI
@@ -507,7 +510,7 @@ int cc_worker::decode_pusch(stack_interface_phy_lte::ul_sched_grant_t* grants, u
 
       // Notify MAC of RL status
       if (snr_db >= PUSCH_RL_SNR_DB_TH) {
-        phy->stack->snr_info(tti_rx, rnti, snr_db);
+        phy->stack->snr_info(ul_sf.tti, rnti, snr_db);
 
         if (grants[i].dci.tb.rv == 0) {
           if (!pusch_res.crc) {
@@ -519,19 +522,21 @@ int cc_worker::decode_pusch(stack_interface_phy_lte::ul_sched_grant_t* grants, u
         }
       }
 
-      // Notify MAC new received data and HARQ Indication value
-      phy->stack->crc_info(tti_rx, rnti, grant->tb.tbs / 8, pusch_res.crc);
-
       // Send UCI data to MAC
       send_uci_data(rnti, &ue_db[rnti]->ul_cfg.pusch.uci_cfg, &pusch_res.uci);
 
-      // Save metrics stats
-      ue_db[rnti]->metrics_ul(grants[i].dci.tb.mcs_idx, 0, snr_db, pusch_res.avg_iterations_block);
+      // Notify MAC new received data and HARQ Indication value
+      if (pusch_res.data) {
+        phy->stack->crc_info(tti_rx, rnti, grant->tb.tbs / 8, pusch_res.crc);
 
-      // Logging
-      char str[512];
-      srslte_pusch_rx_info(&ue_db[rnti]->ul_cfg.pusch, &pusch_res, str, 512);
-      Info("PUSCH: %s, snr=%.1f dB\n", str, snr_db);
+        // Save metrics stats
+        ue_db[rnti]->metrics_ul(grants[i].dci.tb.mcs_idx, 0, snr_db, pusch_res.avg_iterations_block);
+
+        // Logging
+        char str[512];
+        srslte_pusch_rx_info(&ue_db[rnti]->ul_cfg.pusch, &pusch_res, str, 512);
+        Info("PUSCH: %s, snr=%.1f dB\n", str, snr_db);
+      }
     }
   }
   return SRSLTE_SUCCESS;
diff --git a/srsenb/src/phy/phy_common.cc b/srsenb/src/phy/phy_common.cc
index 3464a93ea..f78fb2ddf 100644
--- a/srsenb/src/phy/phy_common.cc
+++ b/srsenb/src/phy/phy_common.cc
@@ -23,6 +23,7 @@
 #include "srslte/asn1/rrc_asn1.h"
 #include "srslte/common/log.h"
 #include "srslte/common/threads.h"
+#include "srslte/phy/channel/channel.h"
 #include <sstream>
 
 #include <assert.h>
@@ -39,7 +40,7 @@ namespace srsenb {
 
 phy_common::phy_common(uint32_t max_workers_) : tx_sem(max_workers_)
 {
-  nof_workers                = max_workers_;
+  nof_workers                = 0;
   params.max_prach_offset_us = 20;
   have_mtch_stop             = false;
   max_workers                = max_workers_;
@@ -79,6 +80,24 @@ bool phy_common::init(const srslte_cell_t&         cell_,
   pthread_mutex_init(&mtch_mutex, nullptr);
   pthread_cond_init(&mtch_cvar, nullptr);
 
+  // Instantiate UL channel emulator
+  if (params.ul_channel_args.enable) {
+    dl_channel =
+        srslte::channel_ptr(new srslte::channel(params.dl_channel_args, 1));
+
+    dl_channel->set_srate((uint32_t)srslte_sampling_freq_hz(cell.nof_prb));
+  }
+
+  is_first_tx = true;
+
+  // Instantiate UL channel emulator
+  if (params.ul_channel_args.enable) {
+    dl_channel =
+        srslte::channel_ptr(new srslte::channel(params.dl_channel_args, 1));
+
+    dl_channel->set_srate((uint32_t)srslte_sampling_freq_hz(cell.nof_prb));
+  }
+
   is_first_tx = true;
   reset();
   return true; 
@@ -115,6 +134,10 @@ void phy_common::worker_end(uint32_t           tti,
   // Wait for the green light to transmit in the current TTI
   sem_wait(&tx_sem[tti%nof_workers]);
 
+  if (dl_channel) {
+    dl_channel->run(buffer, buffer, nof_samples, tx_time);
+  }
+
   // always transmit on single radio
   radio->tx(0, buffer, nof_samples, tx_time);
 
diff --git a/srsenb/src/phy/txrx.cc b/srsenb/src/phy/txrx.cc
index a96e5edad..a1c6cbaa8 100644
--- a/srsenb/src/phy/txrx.cc
+++ b/srsenb/src/phy/txrx.cc
@@ -60,7 +60,11 @@ bool txrx::init(srslte::radio_interface_phy* radio_h_,
   
   nof_workers = workers_pool->get_nof_workers();
   worker_com->set_nof_workers(nof_workers);
-    
+
+  if (worker_com->params.dl_channel_args.enable) {
+    ul_channel = srslte::channel_ptr(new srslte::channel(worker_com->params.ul_channel_args, 1));
+  }
+
   start(prio_);
   return true; 
 }
@@ -86,6 +90,10 @@ void txrx::run_thread()
   radio_h->set_rx_srate(0, samp_rate);
   radio_h->set_tx_srate(0, samp_rate);
 
+  if (ul_channel) {
+    ul_channel->set_srate(samp_rate);
+  }
+
   log_h->info("Starting RX/TX thread nof_prb=%d, sf_len=%d\n", worker_com->cell.nof_prb, sf_len);
 
   // Set TTI so that first TX is at tti=0
@@ -104,6 +112,10 @@ void txrx::run_thread()
 
       radio_h->rx_now(0, buffer, sf_len, &rx_time);
 
+      if (ul_channel) {
+        ul_channel->run(buffer, buffer, sf_len, rx_time);
+      }
+
       /* Compute TX time: Any transmission happens in TTI+4 thus advance 4 ms the reception time */
       srslte_timestamp_copy(&tx_time, &rx_time);
       srslte_timestamp_add(&tx_time, 0, TX_DELAY * 1e-3);
diff --git a/srsenb/src/stack/mac/mac.cc b/srsenb/src/stack/mac/mac.cc
index c1ec75529..d1c11b31d 100644
--- a/srsenb/src/stack/mac/mac.cc
+++ b/srsenb/src/stack/mac/mac.cc
@@ -38,7 +38,7 @@ using namespace asn1::rrc;
 
 namespace srsenb {
 
-mac::mac() : timers_db(128), timers_thread(&timers_db), tti(0), last_rnti(0),
+mac::mac() : timers_db(128), timers_thread(this, &timers_db), last_rnti(0),
              rar_pdu_msg(sched_interface::MAX_RAR_LIST), rar_payload(),
              pdu_process_thread(this)
 {
@@ -52,7 +52,6 @@ mac::mac() : timers_db(128), timers_thread(&timers_db), tti(0), last_rnti(0),
   bzero(&locations, sizeof(locations));
   bzero(&cell, sizeof(cell));
   bzero(&args, sizeof(args));
-  bzero(&pending_rars, sizeof(pending_rars));
   bzero(&bcch_dlsch_payload, sizeof(bcch_dlsch_payload));
   bzero(&pcch_payload_buffer, sizeof(pcch_payload_buffer));
   bzero(&bcch_softbuffer_tx, sizeof(bcch_softbuffer_tx));
@@ -136,7 +135,6 @@ void mac::reset()
 
   timers_db.stop_all();
 
-  tti = 0;
   last_rnti = 70;
 
   /* Setup scheduler */
@@ -147,9 +145,8 @@ void mac::start_pcap(srslte::mac_pcap* pcap_)
 {
   pcap = pcap_;
   // Set pcap in all UEs for UL messages
-  for(std::map<uint16_t, ue*>::iterator iter=ue_db.begin(); iter!=ue_db.end(); ++iter) {
-    ue *u = iter->second;
-    u->start_pcap(pcap);
+  for (auto& u : ue_db) {
+    u.second->start_pcap(pcap);
   }
 }
 
@@ -282,10 +279,9 @@ void mac::get_metrics(mac_metrics_t metrics[ENB_METRICS_MAX_USERS])
 {
   pthread_rwlock_rdlock(&rwlock);
   int cnt=0;
-  for(std::map<uint16_t, ue*>::iterator iter=ue_db.begin(); iter!=ue_db.end(); ++iter) {
-    ue *u = iter->second;
-    if(iter->first != SRSLTE_MRNTI) {
-      u->metrics_read(&metrics[cnt]);
+  for (auto& u : ue_db) {
+    if(u.first != SRSLTE_MRNTI) {
+      u.second->metrics_read(&metrics[cnt]);
       cnt++;
     }
   }
@@ -372,8 +368,6 @@ int mac::crc_info(uint32_t tti, uint16_t rnti, uint32_t nof_bytes, bool crc)
 
 int mac::set_dl_ant_info(uint16_t rnti, phys_cfg_ded_s::ant_info_c_* dl_ant_info)
 {
-  log_h->step(tti);
-
   int ret = -1;
   pthread_rwlock_rdlock(&rwlock);
   if (ue_db.count(rnti)) {
@@ -470,60 +464,55 @@ int mac::rach_detected(uint32_t tti, uint32_t preamble_idx, uint32_t time_adv)
 {
   log_h->step(tti);
 
-  // Find empty slot for pending rars
-  uint32_t ra_id=0;
-  while(pending_rars[ra_id].temp_crnti && ra_id<MAX_PENDING_RARS-1) {
-    ra_id++;
-  }
-  if (ra_id == MAX_PENDING_RARS) {
-    Error("Maximum number of pending RARs exceeded (%d)\n", MAX_PENDING_RARS);
-    return -1;
-  }
-
   pthread_rwlock_rdlock(&rwlock);
 
+  uint32_t rnti = last_rnti;
+
   // Create new UE
-  ue_db[last_rnti] = new ue(last_rnti, cell.nof_prb, &scheduler, rrc_h, rlc_h, log_h);
+  if (!ue_db.count(rnti)) {
+    ue_db[rnti] = new ue(rnti, cell.nof_prb, &scheduler, rrc_h, rlc_h, log_h,
+        SRSLTE_FDD_NOF_HARQ);
+  }
 
   // Set PCAP if available
   if (pcap) {
-    ue_db[last_rnti]->start_pcap(pcap);
+    ue_db[rnti]->start_pcap(pcap);
   }
 
   pthread_rwlock_unlock(&rwlock);
 
-  // Save RA info
-  pending_rars[ra_id].preamble_idx = preamble_idx;
-  pending_rars[ra_id].ta_cmd       = time_adv;
-  pending_rars[ra_id].temp_crnti   = last_rnti;
+  // Generate RAR data
+  sched_interface::dl_sched_rar_info_t rar_info = {};
+  rar_info.preamble_idx = preamble_idx;
+  rar_info.ta_cmd       = time_adv;
+  rar_info.temp_crnti   = rnti;
+  rar_info.msg3_size    = 7;
+  rar_info.prach_tti       = tti;
 
   // Add new user to the scheduler so that it can RX/TX SRB0
   sched_interface::ue_cfg_t uecfg;
   bzero(&uecfg, sizeof(sched_interface::ue_cfg_t));
   uecfg.ue_bearers[0].direction = srsenb::sched_interface::ue_bearer_cfg_t::BOTH;
-  if (scheduler.ue_cfg(last_rnti, &uecfg)) {
-    // Release pending RAR
-    bzero(&pending_rars[ra_id], sizeof(pending_rar_t));
-    Error("Registering new user rnti=0x%x to SCHED\n", last_rnti);
+  if (scheduler.ue_cfg(rnti, &uecfg)) {
+    Error("Registering new user rnti=0x%x to SCHED\n", rnti);
     return -1;
   }
 
   // Register new user in RRC
-  rrc_h->add_user(last_rnti);
+  rrc_h->add_user(rnti);
 
   // Add temporal rnti to the PHY
-  if (phy_h->add_rnti(last_rnti, true)) {
-    Error("Registering temporal-rnti=0x%x to PHY\n", last_rnti);
+  if (phy_h->add_rnti(rnti, true)) {
+    Error("Registering temporal-rnti=0x%x to PHY\n", rnti);
   }
 
   // Trigger scheduler RACH
-  scheduler.dl_rach_info(tti, ra_id, last_rnti, 7);
+  scheduler.dl_rach_info(rar_info);
 
   log_h->info("RACH:  tti=%d, preamble=%d, offset=%d, temp_crnti=0x%x\n",
-                 tti, preamble_idx, time_adv, last_rnti);
+              tti, preamble_idx, time_adv, rnti);
   log_h->console("RACH:  tti=%d, preamble=%d, offset=%d, temp_crnti=0x%x\n",
-                 tti, preamble_idx, time_adv, last_rnti);
-
+                 tti, preamble_idx, time_adv, rnti);
   // Increase RNTI counter
   last_rnti++;
   if (last_rnti >= 60000) {
@@ -609,7 +598,7 @@ int mac::get_dl_sched(uint32_t tti, dl_sched_t *dl_sched_res)
 
     // Assemble PDU
     dl_sched_res->pdsch[n].data[0] =
-        assemble_rar(sched_result.rar[i].msg3_grant, sched_result.rar[i].nof_grants, i, sched_result.rar[i].tbs);
+        assemble_rar(sched_result.rar[i].msg3_grant, sched_result.rar[i].nof_grants, i, sched_result.rar[i].tbs, tti);
 
     if (pcap) {
       pcap->write_dl_ranti(
@@ -751,7 +740,7 @@ int mac::get_mch_sched(uint32_t tti, bool is_mcch, dl_sched_t* dl_sched_res)
  return SRSLTE_SUCCESS;
 }
 
-uint8_t* mac::assemble_rar(sched_interface::dl_sched_rar_grant_t* grants, uint32_t nof_grants, int rar_idx, uint32_t pdu_len)
+uint8_t* mac::assemble_rar(sched_interface::dl_sched_rar_grant_t* grants, uint32_t nof_grants, int rar_idx, uint32_t pdu_len, uint32_t tti)
 {
   uint8_t grant_buffer[64] = {};
   if (pdu_len < rar_payload_len) {
@@ -761,13 +750,10 @@ uint8_t* mac::assemble_rar(sched_interface::dl_sched_rar_grant_t* grants, uint32
     for (uint32_t i = 0; i < nof_grants; i++) {
       srslte_dci_rar_pack(&grants[i].grant, grant_buffer);
       if (pdu->new_subh()) {
-        /* Search pending RAR */
-        int idx = grants[i].ra_id;
-        pdu->get()->set_rapid(pending_rars[idx].preamble_idx);
-        pdu->get()->set_ta_cmd(pending_rars[idx].ta_cmd);
-        pdu->get()->set_temp_crnti(pending_rars[idx].temp_crnti);
+        pdu->get()->set_rapid(grants[i].data.preamble_idx);
+        pdu->get()->set_ta_cmd(grants[i].data.ta_cmd);
+        pdu->get()->set_temp_crnti(grants[i].data.temp_crnti);
         pdu->get()->set_sched_grant(grant_buffer);
-        bzero(&pending_rars[idx], sizeof(pending_rar_t));
       }
     }
     pdu->write_packet(rar_payload[rar_idx].msg);
@@ -830,7 +816,7 @@ int mac::get_ul_sched(uint32_t tti, ul_sched_t *ul_sched_res)
         ul_sched_res->nof_grants++;
         n++;
       } else {
-        Warning("Invalid DL scheduling result. User 0x%x does not exist\n", rnti);
+        Warning("Invalid UL scheduling result. User 0x%x does not exist\n", rnti);
       }
 
     } else {
@@ -884,7 +870,7 @@ srslte::timers::timer* mac::timer_get(uint32_t timer_id)
  *******************************************************/
 void mac::timer_thread::run_thread()
 {
-  running=true;
+  running = true;
   ttisync.set_producer_cntr(0);
   ttisync.resync();
   while(running) {
@@ -895,7 +881,7 @@ void mac::timer_thread::run_thread()
 
 void mac::timer_thread::stop()
 {
-  running=false;
+  running = false;
   ttisync.increase();
   wait_thread_finish();
 }
@@ -959,29 +945,27 @@ bool mac::process_pdus()
 {
   pthread_rwlock_rdlock(&rwlock);
   bool ret = false;
-  for(std::map<uint16_t, ue*>::iterator iter=ue_db.begin(); iter!=ue_db.end(); ++iter) {
-    ue *u         = iter->second;
-    uint16_t rnti = iter->first;
-    ret = ret | u->process_pdus();
+  for (auto& u : ue_db) {
+    ret = ret | u.second->process_pdus();
   }
   pthread_rwlock_unlock(&rwlock);
   return ret;
 }
 
-void mac::write_mcch(sib_type2_s* sib2, sib_type13_r9_s* sib13, mcch_msg_s* mcch)
+void mac::write_mcch(sib_type2_s* sib2_, sib_type13_r9_s* sib13_, mcch_msg_s* mcch_)
 {
-  this->mcch         = *mcch;
+  mcch         = *mcch_;
   mch.num_mtch_sched = this->mcch.msg.c1().mbsfn_area_cfg_r9().pmch_info_list_r9[0].mbms_session_info_list_r9.size();
   for (uint32_t i = 0; i < mch.num_mtch_sched; ++i) {
     mch.mtch_sched[i].lcid =
         this->mcch.msg.c1().mbsfn_area_cfg_r9().pmch_info_list_r9[0].mbms_session_info_list_r9[i].lc_ch_id_r9;
   }
-  this->sib2  = *sib2;
-  this->sib13 = *sib13;
+  sib2  = *sib2_;
+  sib13 = *sib13_;
 
   const int     rlc_header_len = 1;
   asn1::bit_ref bref(&mcch_payload_buffer[rlc_header_len], sizeof(mcch_payload_buffer) - rlc_header_len);
-  mcch->pack(bref);
+  mcch.pack(bref);
   current_mcch_length = bref.distance_bytes(&mcch_payload_buffer[1]);
   current_mcch_length =  current_mcch_length + rlc_header_len;
   ue_db[SRSLTE_MRNTI] = new ue(SRSLTE_MRNTI, cell.nof_prb, &scheduler, rrc_h, rlc_h, log_h);
diff --git a/srsenb/src/stack/mac/scheduler.cc b/srsenb/src/stack/mac/scheduler.cc
index 95a3bdbbb..68ed2b5ea 100644
--- a/srsenb/src/stack/mac/scheduler.cc
+++ b/srsenb/src/stack/mac/scheduler.cc
@@ -154,11 +154,14 @@ alloc_outcome_t sched::tti_sched_t::alloc_paging(uint32_t aggr_lvl, uint32_t pag
 }
 
 sched::tti_sched_t::rar_code_t
-sched::tti_sched_t::alloc_rar(uint32_t aggr_lvl, const dl_sched_rar_t& rar_grant, uint32_t rar_tti, uint32_t buf_rar)
+sched::tti_sched_t::alloc_rar(uint32_t aggr_lvl, const dl_sched_rar_t& rar_grant, uint32_t prach_tti, uint32_t buf_rar)
 {
-  uint16_t rar_sfidx = (uint16_t)((rar_tti + 1) % 10);
+  // RA-RNTI = 1 + t_id + f_id
+  // t_id = index of first subframe specified by PRACH (0<=t_id<10)
+  // f_id = index of the PRACH within subframe, in ascending order of freq domain (0<=f_id<6) (for FDD, f_id=0)
+  uint16_t ra_rnti = 1 + (uint16_t)(prach_tti % 10);
 
-  ctrl_code_t ret = alloc_dl_ctrl(aggr_lvl, buf_rar, rar_sfidx);
+  ctrl_code_t ret = alloc_dl_ctrl(aggr_lvl, buf_rar, ra_rnti);
   if (not ret.first) {
     Warning("SCHED: Could not allocate RAR for L=%d, cause=%s\n", aggr_lvl, ret.first.to_string());
     return {ret.first, NULL};
@@ -332,7 +335,7 @@ void sched::tti_sched_t::set_rar_sched_result(const pdcch_grid_t::alloc_result_t
     int         tbs =
         generate_format1a(prb_range.prb_start, prb_range.length(), rar_alloc.req_bytes, 0, rar_alloc.rnti, &rar->dci);
     if (tbs <= 0) {
-      log_h->warning("SCHED: Error RAR, ra_rnti_idx=%d, rbgs=(%d,%d), dci=(%d,%d)\n",
+      log_h->warning("SCHED: Error RAR, ra-rnti=%d, rbgs=(%d,%d), dci=(%d,%d)\n",
                      rar_alloc.rnti,
                      rar_alloc.rbg_range.rbg_start,
                      rar_alloc.rbg_range.rbg_end,
@@ -349,11 +352,10 @@ void sched::tti_sched_t::set_rar_sched_result(const pdcch_grid_t::alloc_result_t
     // Print RAR allocation result
     for (uint32_t i = 0; i < rar->nof_grants; ++i) {
       const auto& msg3_grant    = rar->msg3_grant[i];
-      uint32_t    pending_tti   = (get_tti_tx_dl() + MSG3_DELAY_MS + TX_DELAY) % 10;
+      uint32_t    pending_tti   = (get_tti_tx_dl() + MSG3_DELAY_MS + TX_DELAY) % TTIMOD_SZ;
       uint16_t    expected_rnti = parent->pending_msg3[pending_tti].rnti; // FIXME
-      log_h->info("SCHED: RAR, ra_id=%d, rnti=0x%x, rarnti_idx=%d, rbgs=(%d,%d), dci=(%d,%d), rar_grant_rba=%d, "
+      log_h->info("SCHED: RAR, temp_crnti=0x%x, ra-rnti=%d, rbgs=(%d,%d), dci=(%d,%d), rar_grant_rba=%d, "
                   "rar_grant_mcs=%d\n",
-                  msg3_grant.ra_id,
                   expected_rnti,
                   rar_alloc.rnti,
                   rar_alloc.rbg_range.rbg_start,
@@ -511,7 +513,7 @@ void sched::tti_sched_t::generate_dcis()
 
 uint32_t sched::tti_sched_t::get_nof_ctrl_symbols() const
 {
-  return tti_alloc.get_cfi() + (parent->cfg.cell.nof_prb <= 10) ? 1 : 0;
+  return tti_alloc.get_cfi() + ((parent->cfg.cell.nof_prb <= 10) ? 1 : 0);
 }
 
 int sched::tti_sched_t::generate_format1a(
@@ -602,6 +604,7 @@ void sched::init(rrc_interface_mac* rrc_, srslte::log* log)
   sched_cfg.pusch_max_mcs    = 28;
   sched_cfg.pusch_mcs        = -1;
   sched_cfg.nof_ctrl_symbols = 3;
+  sched_cfg.max_aggr_level   = 3;
   log_h                      = log;
   rrc                        = rrc_;
   reset();
@@ -609,9 +612,12 @@ void sched::init(rrc_interface_mac* rrc_, srslte::log* log)
 
 int sched::reset()
 {
-  bzero(pending_msg3, sizeof(pending_msg3_t) * 10);
-  bzero(pending_rar, sizeof(sched_rar_t) * SCHED_MAX_PENDING_RAR);
+  bzero(pending_msg3, sizeof(pending_msg3_t) * TTIMOD_SZ);
   bzero(pending_sibs, sizeof(sched_sib_t) * MAX_SIBS);
+  while (not pending_rars.empty()) {
+    pending_rars.pop();
+  }
+
   configured = false;
   pthread_rwlock_wrlock(&rwlock);
   ue_db.clear();
@@ -716,7 +722,7 @@ int sched::ue_cfg(uint16_t rnti, sched_interface::ue_cfg_t* ue_cfg)
   // Add or config user
   pthread_rwlock_rdlock(&rwlock);
   ue_db[rnti].set_cfg(rnti, ue_cfg, &cfg, &regs, log_h);
-  ue_db[rnti].set_max_mcs(sched_cfg.pusch_max_mcs, sched_cfg.pdsch_max_mcs);
+  ue_db[rnti].set_max_mcs(sched_cfg.pusch_max_mcs, sched_cfg.pdsch_max_mcs, sched_cfg.max_aggr_level);
   ue_db[rnti].set_fixed_mcs(sched_cfg.pusch_mcs, sched_cfg.pdsch_mcs);
   pthread_rwlock_unlock(&rwlock);
 
@@ -745,6 +751,16 @@ bool sched::ue_exists(uint16_t rnti)
   return ret;
 }
 
+void sched::ue_needs_ta_cmd(uint16_t rnti, uint32_t nof_ta_cmd) {
+  pthread_rwlock_rdlock(&rwlock);
+  if (ue_db.count(rnti)) {
+    ue_db[rnti].set_needs_ta_cmd(nof_ta_cmd);
+  } else {
+    Error("User rnti=0x%x not found\n", rnti);
+  }
+  pthread_rwlock_unlock(&rwlock);
+}
+
 void sched::phy_config_enabled(uint16_t rnti, bool enabled)
 {
   pthread_rwlock_rdlock(&rwlock);
@@ -756,12 +772,12 @@ void sched::phy_config_enabled(uint16_t rnti, bool enabled)
   pthread_rwlock_unlock(&rwlock);
 }
 
-int sched::bearer_ue_cfg(uint16_t rnti, uint32_t lc_id, sched_interface::ue_bearer_cfg_t* cfg)
+int sched::bearer_ue_cfg(uint16_t rnti, uint32_t lc_id, sched_interface::ue_bearer_cfg_t* cfg_)
 {
   int ret = 0;
   pthread_rwlock_rdlock(&rwlock);
   if (ue_db.count(rnti)) {
-    ue_db[rnti].set_bearer_cfg(lc_id, cfg);
+    ue_db[rnti].set_bearer_cfg(lc_id, cfg_);
   } else {
     Error("User rnti=0x%x not found\n", rnti);
     ret = -1;
@@ -922,19 +938,12 @@ int sched::dl_cqi_info(uint32_t tti, uint16_t rnti, uint32_t cqi_value)
   return ret;
 }
 
-int sched::dl_rach_info(uint32_t tti, uint32_t ra_id, uint16_t rnti, uint32_t estimated_size)
+int sched::dl_rach_info(dl_sched_rar_info_t rar_info)
 {
-  for (int i = 0; i < SCHED_MAX_PENDING_RAR; i++) {
-    if (!pending_rar[i].buf_rar) {
-      pending_rar[i].ra_id   = ra_id;
-      pending_rar[i].rnti    = rnti;
-      pending_rar[i].rar_tti = tti;
-      pending_rar[i].buf_rar = estimated_size;
-      return 0;
-    }
-  }
-  Warning("SCHED: New RACH discarted because maximum number of pending RAR exceeded (%d)\n", SCHED_MAX_PENDING_RAR);
-  return -1;
+  Info("SCHED: New RAR tti=%d, preamble=%d, temp_crnti=0x%x, ta_cmd=%d, msg3_size=%d\n",
+       rar_info.prach_tti, rar_info.preamble_idx, rar_info.temp_crnti, rar_info.ta_cmd, rar_info.msg3_size);
+  pending_rars.push(rar_info);
+  return 0;
 }
 
 int sched::ul_cqi_info(uint32_t tti, uint16_t rnti, uint32_t cqi, uint32_t ul_ch_code)
@@ -1046,7 +1055,7 @@ sched::tti_sched_t* sched::new_tti(uint32_t tti_rx)
 
   // if it is the first time tti is run, reset vars
   if (tti_rx != tti_sched->get_tti_rx()) {
-    uint32_t start_cfi = sched_cfg.nof_ctrl_symbols - ((cfg.cell.nof_prb >= 10) ? 0 : 1);
+    uint32_t start_cfi = sched_cfg.nof_ctrl_symbols;
     tti_sched->new_tti(tti_rx, start_cfi);
 
     // Protects access to pending_rar[], pending_msg3[], pending_sibs[], rlc buffers
@@ -1157,78 +1166,74 @@ bool is_in_tti_interval(uint32_t tti, uint32_t tti1, uint32_t tti2)
 }
 
 // Schedules RAR
+// On every call to this function, we schedule the oldest RAR which is still within the window. If outside the window we discard it.
 void sched::dl_sched_rar(tti_sched_t* tti_sched)
 {
-  for (uint32_t i = 0; i < SCHED_MAX_PENDING_RAR; i++) {
-    // check if the RAR is inactive or was already scheduled
-    if (pending_rar[i].buf_rar == 0) {
-      continue;
-    }
-    // Check if we are still within the RAR window, otherwise discard it
+  // Discard all RARs out of the window. The first one inside the window is scheduled, if we can't we exit
+  while (!pending_rars.empty()) {
+    dl_sched_rar_info_t rar = pending_rars.front();
     if (not is_in_tti_interval(tti_sched->get_tti_tx_dl(),
-                               pending_rar[i].rar_tti + 3,
-                               pending_rar[i].rar_tti + 3 + cfg.prach_rar_window)) {
-      log_h->console("SCHED: Could not transmit RAR within the window (RA TTI=%d, Window=%d, Now=%d)\n",
-                     pending_rar[i].rar_tti,
+                               rar.prach_tti + 3,
+                               rar.prach_tti + 3 + cfg.prach_rar_window))
+    {
+      if (tti_sched->get_tti_tx_dl() >= rar.prach_tti + 3 + cfg.prach_rar_window) {
+        log_h->console("SCHED: Could not transmit RAR within the window (RA TTI=%d, Window=%d, Now=%d)\n",
+                       rar.prach_tti,
+                       cfg.prach_rar_window,
+                       current_tti);
+        log_h->error("SCHED: Could not transmit RAR within the window (RA TTI=%d, Window=%d, Now=%d)\n",
+                     rar.prach_tti,
                      cfg.prach_rar_window,
                      current_tti);
-      log_h->error("SCHED: Could not transmit RAR within the window (RA TTI=%d, Window=%d, Now=%d)\n",
-                   pending_rar[i].rar_tti,
-                   cfg.prach_rar_window,
-                   current_tti);
-      pending_rar[i].buf_rar = 0;
-      pending_rar[i].rar_tti = 0;
-      continue;
+        // Remove from pending queue and get next one if window has passed already
+        pending_rars.pop();
+        continue;
+      }
+      // If window not yet started do not look for more pending RARs
+      return;
     }
 
-    /* Group pending RARs with same transmission TTI */
-    uint32_t       tti     = pending_rar[i].rar_tti;
-    uint32_t       buf_rar = 0;
+    /* Since we do a fixed Msg3 scheduling for all RAR, we can only allocate 1 RAR per TTI.
+     * If we have enough space in the window, every call to this function we'll allocate 1 pending RAR and associate a
+     * Msg3 transmission
+     */
     dl_sched_rar_t rar_grant;
-    uint32_t       L_prb = 3;
-    uint32_t       n_prb = 2;
+    uint32_t L_prb = 3;
+    uint32_t n_prb = cfg.nrb_pucch>0?cfg.nrb_pucch:2;
     bzero(&rar_grant, sizeof(rar_grant));
     uint32_t rba = srslte_ra_type2_to_riv(L_prb, n_prb, cfg.cell.nof_prb);
-    for (uint32_t j = i; j < SCHED_MAX_PENDING_RAR; ++j) {
-      if (pending_rar[j].rar_tti != pending_rar[i].rar_tti) {
-        continue;
-      }
-      if (rar_grant.nof_grants > 0) {
-        log_h->warning("Only 1 RA is responded at a time. Found %d for TTI=%d\n", rar_grant.nof_grants + 1, tti);
-        continue;
-      }
 
-      dl_sched_rar_grant_t* grant = &rar_grant.msg3_grant[rar_grant.nof_grants];
-      grant->grant.tpc_pusch      = 3;
-      grant->grant.trunc_mcs      = 0;
-      grant->grant.rba            = rba;
-      grant->ra_id                = pending_rar[j].ra_id;
-      buf_rar += pending_rar[j].buf_rar;
-      rar_grant.nof_grants++;
-    }
+    dl_sched_rar_grant_t *grant = &rar_grant.msg3_grant[0];
+    grant->grant.tpc_pusch = 3;
+    grant->grant.trunc_mcs = 0;
+    grant->grant.rba = rba;
+    grant->data = rar;
+    rar_grant.nof_grants++;
 
     // Try to schedule DCI + RBGs for RAR Grant
-    tti_sched_t::rar_code_t ret = tti_sched->alloc_rar(rar_aggr_level, rar_grant, pending_rar[i].rar_tti, buf_rar);
-    if (not ret.first) {
-      continue;
+    tti_sched_t::rar_code_t ret = tti_sched->alloc_rar(rar_aggr_level,
+                                                       rar_grant,
+                                                       rar.prach_tti,
+                                                       7 * rar_grant.nof_grants); //fixme: check RAR size
+
+    // If we can allocate, schedule Msg3 and remove from pending
+    if (!ret.first) {
+      return;
     }
 
-    // Schedule Msg3
-    uint32_t pending_tti              = (tti_sched->get_tti_tx_dl() + MSG3_DELAY_MS + TX_DELAY) % 10;
+    // Schedule Msg3 only if there is a requirement for Msg3 data
+    uint32_t pending_tti = (tti_sched->get_tti_tx_dl() + MSG3_DELAY_MS + TX_DELAY) % TTIMOD_SZ;
     pending_msg3[pending_tti].enabled = true;
-    pending_msg3[pending_tti].rnti    = pending_rar[i].rnti; // FIXME
-    pending_msg3[pending_tti].L       = L_prb;
-    pending_msg3[pending_tti].n_prb   = n_prb;
-    dl_sched_rar_grant_t* last_msg3   = &rar_grant.msg3_grant[rar_grant.nof_grants - 1];
-    pending_msg3[pending_tti].mcs     = last_msg3->grant.trunc_mcs;
-
-    // Reset allocated RARs
-    for (uint32_t j = i; j < SCHED_MAX_PENDING_RAR; ++j) {
-      if (pending_rar[j].rar_tti == pending_rar[i].rar_tti) {
-        pending_rar[j].buf_rar = 0;
-        pending_rar[j].rar_tti = 0;
-      }
-    }
+    pending_msg3[pending_tti].rnti = rar.temp_crnti; // FIXME
+    pending_msg3[pending_tti].L = L_prb;
+    pending_msg3[pending_tti].n_prb = n_prb;
+    dl_sched_rar_grant_t *last_msg3 = &rar_grant.msg3_grant[rar_grant.nof_grants - 1];
+    pending_msg3[pending_tti].mcs = last_msg3->grant.trunc_mcs;
+    Info("SCHED: Allocating Msg3 for rnti=%d at tti=%d\n", rar.temp_crnti, tti_sched->get_tti_tx_dl() + MSG3_DELAY_MS + TX_DELAY);
+
+    // Remove pending RAR and exit
+    pending_rars.pop();
+    return;
   }
 }
 
@@ -1236,7 +1241,7 @@ void sched::dl_sched_data(tti_sched_t* tti_sched)
 {
   // NOTE: In case of 6 PRBs, do not transmit if there is going to be a PRACH in the UL to avoid collisions
   uint32_t tti_rx_ack  = TTI_RX_ACK(tti_sched->get_tti_rx());
-  uint32_t pending_tti = tti_rx_ack % 10;
+  uint32_t pending_tti = tti_rx_ack % TTIMOD_SZ;
   if (cfg.cell.nof_prb == 6 and (srslte_prach_tti_opportunity_config_fdd(cfg.prach_config, tti_rx_ack, -1) or
                                  pending_msg3[pending_tti].enabled)) {
     tti_sched->get_dl_mask().fill(0, tti_sched->get_dl_mask().size());
@@ -1285,7 +1290,7 @@ void sched::generate_phich(tti_sched_t* tti_sched)
       tti_sched->ul_sched_result.phich[nof_phich_elems].rnti = rnti;
       log_h->debug("SCHED: Allocated PHICH for rnti=0x%x, value=%d\n",
                    rnti,
-                   tti_sched->ul_sched_result.phich[nof_phich_elems].phich);
+                   tti_sched->ul_sched_result.phich[nof_phich_elems].phich == ul_sched_phich_t::ACK);
       nof_phich_elems++;
     }
   }
@@ -1294,7 +1299,7 @@ void sched::generate_phich(tti_sched_t* tti_sched)
 
 void sched::ul_sched_msg3(tti_sched_t* tti_sched)
 {
-  uint32_t pending_tti = tti_sched->get_tti_tx_ul() % 10;
+  uint32_t pending_tti = tti_sched->get_tti_tx_ul() % TTIMOD_SZ;
   if (not pending_msg3[pending_tti].enabled) {
     return;
   }
diff --git a/srsenb/src/stack/mac/scheduler_ue.cc b/srsenb/src/stack/mac/scheduler_ue.cc
index 266ddb3c3..eaf720c3e 100644
--- a/srsenb/src/stack/mac/scheduler_ue.cc
+++ b/srsenb/src/stack/mac/scheduler_ue.cc
@@ -55,7 +55,8 @@ sched_ue::sched_ue() :
   max_mcs_ul(0),
   fixed_mcs_ul(0),
   fixed_mcs_dl(0),
-  phy_config_dedicated_enabled(false)
+  phy_config_dedicated_enabled(false),
+  nof_ta_cmd(0)
 {
   log_h = NULL;
 
@@ -86,6 +87,7 @@ void sched_ue::set_cfg(uint16_t                     rnti_,
 
     max_mcs_dl   = 28;
     max_mcs_ul   = 28;
+    max_aggr_level = 3;
     max_msg3retx = cell_cfg->maxharq_msg3tx;
 
     cfg = *cfg_;
@@ -153,7 +155,7 @@ void sched_ue::set_fixed_mcs(int mcs_ul, int mcs_dl) {
   fixed_mcs_dl = mcs_dl;
 }
 
-void sched_ue::set_max_mcs(int mcs_ul, int mcs_dl) {
+void sched_ue::set_max_mcs(int mcs_ul, int mcs_dl, int max_aggr_level_) {
   std::lock_guard<std::mutex> lock(mutex);
   if (mcs_ul < 0) {
     max_mcs_ul = 28;     
@@ -165,6 +167,11 @@ void sched_ue::set_max_mcs(int mcs_ul, int mcs_dl) {
   } else {
     max_mcs_dl = mcs_dl;     
   }
+  if (max_aggr_level_ < 0) {
+    max_aggr_level = 3;
+  } else {
+    max_aggr_level = max_aggr_level_;
+  }
 }
 
 
@@ -246,6 +253,11 @@ void sched_ue::unset_sr()
   sr = false; 
 }
 
+void sched_ue::set_needs_ta_cmd(uint32_t nof_ta_cmd_) {
+  nof_ta_cmd = nof_ta_cmd_;
+  Info("SCHED: rnti=0x%x needs %d TA CMD\n", rnti, nof_ta_cmd);
+}
+
 bool sched_ue::pucch_sr_collision(uint32_t current_tti, uint32_t n_cce)
 {
   if (!phy_config_dedicated_enabled) {
@@ -463,15 +475,26 @@ int sched_ue::generate_format1(
 
     h->new_tx(user_mask, 0, tti, mcs, tbs, data->dci.location.ncce);
 
+    int rem_tbs = tbs;
+    int x       = 0;
+
     // Allocate MAC ConRes CE
     if (need_conres_ce) {
-      data->pdu[0][0].lcid = srslte::sch_subh::CON_RES_ID;
+      data->pdu[0][data->nof_pdu_elems[0]].lcid = srslte::sch_subh::CON_RES_ID;
       data->nof_pdu_elems[0]++;
       Info("SCHED: Added MAC Contention Resolution CE for rnti=0x%x\n", rnti);
+    } else {
+      // Add TA CE. TODO: Common interface to add MAC CE
+      // FIXME: Can't put it in Msg4 because current srsUE doesn't read it
+      while(nof_ta_cmd > 0 && rem_tbs > 2) {
+        data->pdu[0][data->nof_pdu_elems[0]].lcid = srslte::sch_subh::TA_CMD;
+        data->nof_pdu_elems[0]++;
+        Info("SCHED: Added MAC TA CMD CE for rnti=0x%x\n", rnti);
+        nof_ta_cmd--;
+        rem_tbs -= 2;
+      }
     }
 
-    int rem_tbs = tbs;
-    int x       = 0;
     do {
       x = alloc_pdu(rem_tbs, &data->pdu[0][data->nof_pdu_elems[0]]);
       if (x) {
@@ -801,6 +824,9 @@ uint32_t sched_ue::get_pending_dl_new_data_unlocked(uint32_t tti)
       pending_data += lch[i].buf_retx + lch[i].buf_tx;
     }
   }
+  if (!is_first_dl_tx() && nof_ta_cmd) {
+    pending_data += nof_ta_cmd*2;
+  }
   return pending_data;
 }
 
@@ -1060,6 +1086,7 @@ uint32_t sched_ue::get_aggr_level(uint32_t nof_bits)
     factor = 1.0;
     l_max  = 2;
   }
+  l_max = SRSLTE_MIN(max_aggr_level, l_max);
   do {
     coderate = srslte_pdcch_coderate(nof_bits, l);
     l++;
diff --git a/srsenb/src/stack/mac/ue.cc b/srsenb/src/stack/mac/ue.cc
index 7afef5237..d7ce26c7d 100644
--- a/srsenb/src/stack/mac/ue.cc
+++ b/srsenb/src/stack/mac/ue.cc
@@ -38,29 +38,35 @@ ue::ue(uint16_t           rnti_,
        sched_interface*   sched_,
        rrc_interface_mac* rrc_,
        rlc_interface_mac* rlc_,
-       srslte::log*       log_) :
+       srslte::log*       log_,
+       uint32_t           nof_rx_harq_proc_,
+       uint32_t           nof_tx_harq_proc_) :
   rnti(rnti_),
   sched(sched_),
   rrc(rrc_),
   rlc(rlc_),
   log_h(log_),
-  mac_msg_dl(20, log_h),
-  mch_mac_msg_dl(10, log_h),
-  mac_msg_ul(20, log_h),
-  pdus(128)
+  mac_msg_dl(20, log_),
+  mch_mac_msg_dl(10, log_),  mac_msg_ul(20, log_),
+  pdus(128),
+  nof_rx_harq_proc(nof_rx_harq_proc_),
+  nof_tx_harq_proc(nof_tx_harq_proc_)
 {
   bzero(&metrics, sizeof(mac_metrics_t));
   bzero(&mutex, sizeof(pthread_mutex_t));
-  bzero(softbuffer_tx, sizeof(softbuffer_tx));
-  bzero(softbuffer_rx, sizeof(softbuffer_rx));
   pthread_mutex_init(&mutex, NULL);
 
   pdus.init(this, log_h);
 
-  for (int i = 0; i < NOF_RX_HARQ_PROCESSES; i++) {
+  softbuffer_tx.reserve(nof_tx_harq_proc);
+  softbuffer_rx.reserve(nof_rx_harq_proc);
+  pending_buffers.reserve(nof_rx_harq_proc);
+
+  for (int i = 0; i < nof_rx_harq_proc; i++) {
     srslte_softbuffer_rx_init(&softbuffer_rx[i], nof_prb);
+    pending_buffers[i] = nullptr;
   }
-  for (int i = 0; i < NOF_TX_HARQ_PROCESSES; i++) {
+  for (int i = 0; i < nof_tx_harq_proc; i++) {
     srslte_softbuffer_tx_init(&softbuffer_tx[i], nof_prb);
   }
   // don't need to reset because just initiated the buffers
@@ -72,10 +78,10 @@ ue::ue(uint16_t           rnti_,
 
 ue::~ue()
 {
-  for (int i = 0; i < NOF_RX_HARQ_PROCESSES; i++) {
+  for (int i = 0; i < nof_rx_harq_proc; i++) {
     srslte_softbuffer_rx_free(&softbuffer_rx[i]);
   }
-  for (int i = 0; i < NOF_TX_HARQ_PROCESSES; i++) {
+  for (int i = 0; i < nof_tx_harq_proc; i++) {
     srslte_softbuffer_tx_free(&softbuffer_tx[i]);
   }
   pthread_mutex_destroy(&mutex);
@@ -86,10 +92,10 @@ void ue::reset()
   bzero(&metrics, sizeof(mac_metrics_t));
 
   nof_failures = 0;
-  for (int i = 0; i < NOF_RX_HARQ_PROCESSES; i++) {
+  for (int i = 0; i < nof_rx_harq_proc; i++) {
     srslte_softbuffer_rx_reset(&softbuffer_rx[i]);
   }
-  for (int i = 0; i < NOF_TX_HARQ_PROCESSES; i++) {
+  for (int i = 0; i < nof_tx_harq_proc; i++) {
     srslte_softbuffer_tx_reset(&softbuffer_tx[i]);
   }
 }
@@ -121,24 +127,24 @@ void ue::set_lcg(uint32_t lcid, uint32_t lcg)
 
 srslte_softbuffer_rx_t* ue::get_rx_softbuffer(uint32_t tti)
 {
-  return &softbuffer_rx[tti % NOF_RX_HARQ_PROCESSES];
+  return &softbuffer_rx[tti % nof_rx_harq_proc];
 }
 
 srslte_softbuffer_tx_t* ue::get_tx_softbuffer(uint32_t harq_process, uint32_t tb_idx)
 {
-  return &softbuffer_tx[(harq_process * SRSLTE_MAX_TB + tb_idx) % NOF_TX_HARQ_PROCESSES];
+  return &softbuffer_tx[(harq_process * SRSLTE_MAX_TB + tb_idx) % nof_tx_harq_proc];
 }
 
 uint8_t* ue::request_buffer(uint32_t tti, uint32_t len)
 {
   uint8_t* ret = NULL;
   if (len > 0) {
-    if (!pending_buffers[tti % NOF_RX_HARQ_PROCESSES]) {
+    if (!pending_buffers[tti % nof_rx_harq_proc]) {
       ret                                          = pdus.request(len);
-      pending_buffers[tti % NOF_RX_HARQ_PROCESSES] = ret;
+      pending_buffers[tti % nof_rx_harq_proc] = ret;
     } else {
-      log_h->console("Error requesting buffer for pid %d, not pushed yet\n", tti % NOF_RX_HARQ_PROCESSES);
-      log_h->error("Requesting buffer for pid %d, not pushed yet\n", tti % NOF_RX_HARQ_PROCESSES);
+      log_h->console("Error requesting buffer for pid %d, not pushed yet\n", tti % nof_rx_harq_proc);
+      log_h->error("Requesting buffer for pid %d, not pushed yet\n", tti % nof_rx_harq_proc);
     }
   } else {
     log_h->warning("Requesting buffer for zero bytes\n");
@@ -155,6 +161,21 @@ void ue::set_tti(uint32_t tti) {
   last_tti = tti; 
 }
 
+uint32_t ue::set_ta(int ta_) {
+  int ta = ta_;
+  uint32_t nof_cmd = 0;
+  int ta_value = 0;
+  do {
+    ta_value    = SRSLTE_MAX(-31, SRSLTE_MIN(32, ta));
+    ta             -= ta_value;
+    uint32_t ta_cmd = (uint32_t) (ta_value + 31);
+    pending_ta_commands.try_push(ta_cmd);
+    nof_cmd++;
+    Info("Added TA CMD: rnti=0x%x, ta=%d, ta_value=%d, ta_cmd=%d\n", rnti, ta_, ta_value, ta_cmd);
+  } while (ta_value <= -31 || ta_value >= 32);
+  return nof_cmd;
+}
+
 #include <assert.h>
 
 void ue::process_pdu(uint8_t* pdu, uint32_t nof_bytes, srslte::pdu_queue::channel_t channel)
@@ -258,21 +279,21 @@ void ue::process_pdu(uint8_t* pdu, uint32_t nof_bytes, srslte::pdu_queue::channe
 
 void ue::deallocate_pdu(uint32_t tti)
 {
-  if (pending_buffers[tti % NOF_RX_HARQ_PROCESSES]) {
-    pdus.deallocate(pending_buffers[tti % NOF_RX_HARQ_PROCESSES]);
-    pending_buffers[tti % NOF_RX_HARQ_PROCESSES] = NULL;
+  if (pending_buffers[tti % nof_rx_harq_proc]) {
+    pdus.deallocate(pending_buffers[tti % nof_rx_harq_proc]);
+    pending_buffers[tti % nof_rx_harq_proc] = NULL;
   } else {
-    log_h->console("Error deallocating buffer for pid=%d. Not requested\n", tti % NOF_RX_HARQ_PROCESSES);
+    log_h->console("Error deallocating buffer for pid=%d. Not requested\n", tti % nof_rx_harq_proc);
   }
 }
 
 void ue::push_pdu(uint32_t tti, uint32_t len)
 {
-  if (pending_buffers[tti % NOF_RX_HARQ_PROCESSES]) {
-    pdus.push(pending_buffers[tti % NOF_RX_HARQ_PROCESSES], len);
-    pending_buffers[tti % NOF_RX_HARQ_PROCESSES] = NULL;
+  if (pending_buffers[tti % nof_rx_harq_proc]) {
+    pdus.push(pending_buffers[tti % nof_rx_harq_proc], len);
+    pending_buffers[tti % nof_rx_harq_proc] = NULL;
   } else {
-    log_h->console("Error pushing buffer for pid=%d. Not requested\n", tti % NOF_RX_HARQ_PROCESSES);
+    log_h->console("Error pushing buffer for pid=%d. Not requested\n", tti % nof_rx_harq_proc);
   }
 }
 
@@ -369,7 +390,20 @@ void ue::allocate_sdu(srslte::sch_pdu *pdu, uint32_t lcid, uint32_t total_sdu_le
 void ue::allocate_ce(srslte::sch_pdu *pdu, uint32_t lcid)
 {
   switch((srslte::sch_subh::cetype) lcid) {
-    case srslte::sch_subh::CON_RES_ID: 
+    case srslte::sch_subh::TA_CMD:
+      if (pdu->new_subh()) {
+        uint32_t ta_cmd = 31;
+        pending_ta_commands.try_pop(&ta_cmd);
+        if (pdu->get()->set_ta_cmd(ta_cmd)) {
+          Info("CE:    Added TA CMD=%d\n", ta_cmd);
+        } else {
+          Error("CE:    Setting TA CMD CE\n");
+        }
+      } else {
+        Error("CE:    Setting TA CMD CE. No space for a subheader\n");
+      }
+      break;
+    case srslte::sch_subh::CON_RES_ID:
       if (pdu->new_subh()) {
         if (pdu->get()->set_con_res_id(conres_id)) {
           Info("CE:    Added Contention Resolution ID=0x%lx\n", conres_id);
diff --git a/srsenb/src/stack/rrc/rrc.cc b/srsenb/src/stack/rrc/rrc.cc
index 63647d43e..ad18ca663 100644
--- a/srsenb/src/stack/rrc/rrc.cc
+++ b/srsenb/src/stack/rrc/rrc.cc
@@ -754,11 +754,13 @@ void rrc::config_mac()
       sched_cfg.sibs[i].period_rf = cfg.sib1.sched_info_list[i - 1].si_periodicity.to_number();
     }
   }
-  sched_cfg.si_window_ms = cfg.sib1.si_win_len.to_number();
-  sched_cfg.prach_rar_window =
+  sched_cfg.prach_config        = cfg.sibs[1].sib2().rr_cfg_common.prach_cfg.prach_cfg_info.prach_cfg_idx;
+  sched_cfg.prach_nof_preambles = cfg.sibs[1].sib2().rr_cfg_common.rach_cfg_common.preamb_info.nof_ra_preambs.to_number();
+  sched_cfg.si_window_ms        = cfg.sib1.si_win_len.to_number();
+  sched_cfg.prach_rar_window    =
       cfg.sibs[1].sib2().rr_cfg_common.rach_cfg_common.ra_supervision_info.ra_resp_win_size.to_number();
-  sched_cfg.prach_freq_offset = cfg.sibs[1].sib2().rr_cfg_common.prach_cfg.prach_cfg_info.prach_freq_offset;
-  sched_cfg.maxharq_msg3tx    = cfg.sibs[1].sib2().rr_cfg_common.rach_cfg_common.max_harq_msg3_tx;
+  sched_cfg.prach_freq_offset   = cfg.sibs[1].sib2().rr_cfg_common.prach_cfg.prach_cfg_info.prach_freq_offset;
+  sched_cfg.maxharq_msg3tx      = cfg.sibs[1].sib2().rr_cfg_common.rach_cfg_common.max_harq_msg3_tx;
 
   sched_cfg.nrb_pucch = SRSLTE_MAX(cfg.sr_cfg.nof_prb, cfg.cqi_cfg.nof_prb);
   rrc_log->info("Allocating %d PRBs for PUCCH\n", sched_cfg.nrb_pucch);
diff --git a/srsenb/test/mac/scheduler_test_rand.cc b/srsenb/test/mac/scheduler_test_rand.cc
index 5f498e30d..cf744de9d 100644
--- a/srsenb/test/mac/scheduler_test_rand.cc
+++ b/srsenb/test/mac/scheduler_test_rand.cc
@@ -173,7 +173,6 @@ struct sched_tester : public srsenb::sched {
   };
   struct ue_info {
     int                                      prach_tti, rar_tti, msg3_tti;
-    uint32_t                                 ra_id;
     srsenb::sched_interface::ue_bearer_cfg_t bearer_cfg;
     srsenb::sched_interface::ue_cfg_t        user_cfg;
     uint32_t                                 dl_data;
@@ -229,10 +228,8 @@ void sched_tester::add_user(uint16_t                                 rnti,
                             srsenb::sched_interface::ue_bearer_cfg_t bearer_cfg,
                             srsenb::sched_interface::ue_cfg_t        ue_cfg_)
 {
-  uint32_t ra_id = rand() % 5;
   ue_info  info;
   info.prach_tti  = tti_data.tti_rx;
-  info.ra_id      = ra_id;
   info.bearer_cfg = bearer_cfg;
   info.user_cfg   = ue_cfg_;
   tester_ues.insert(std::make_pair(rnti, info));
@@ -240,7 +237,11 @@ void sched_tester::add_user(uint16_t                                 rnti,
   if (ue_cfg(rnti, &ue_cfg_)) {
     TestError("[TESTER] Registering new user rnti=0x%x to SCHED\n", rnti);
   }
-  dl_rach_info(tti_data.tti_rx, ra_id, rnti, 7);
+  dl_sched_rar_info_t rar_info = {};
+  rar_info.prach_tti     = tti_data.tti_rx;
+  rar_info.temp_crnti = rnti;
+  rar_info.msg3_size  = 7;
+  dl_rach_info(rar_info);
 
   // setup bearers
   bearer_ue_cfg(rnti, 0, &bearer_cfg);
@@ -266,7 +267,7 @@ void sched_tester::new_test_tti(uint32_t tti_)
   } else {
     tti_data.ul_sf_idx = (tti_data.tti_tx_ul + 10240 - FDD_HARQ_DELAY_MS) % 10;
   }
-  tti_data.ul_pending_msg3 = pending_msg3[tti_data.tti_tx_ul % 10];
+  tti_data.ul_pending_msg3 = pending_msg3[tti_data.tti_tx_ul % TTIMOD_SZ];
   tti_data.current_cfi     = sched_cfg.nof_ctrl_symbols;
   tti_data.used_cce.resize(srslte_regs_pdcch_ncce(&regs, tti_data.current_cfi));
   tti_data.used_cce.reset();
@@ -413,7 +414,7 @@ void sched_tester::test_ra()
       if (tti_data.tti_tx_dl >= window[0]) {
         for (uint32_t i = 0; i < tti_data.sched_result_dl.nof_rar_elems; ++i) {
           for (uint32_t j = 0; j < tti_data.sched_result_dl.rar[i].nof_grants; ++j) {
-            if (tti_data.sched_result_dl.rar[i].msg3_grant[j].ra_id == userinfo.ra_id) {
+            if (tti_data.sched_result_dl.rar[i].msg3_grant[j].data.prach_tti == tti_data.tti_tx_dl) {
               userinfo.rar_tti = tti_data.tti_tx_dl;
             }
           }
@@ -532,7 +533,7 @@ void sched_tester::test_tti_result()
     CondError(rar.tbs == 0, "Allocated RAR process with invalid TBS=%d\n", rar.tbs);
     for (uint32_t j = 0; j < rar.nof_grants; ++j) {
       const auto& msg3_grant  = rar.msg3_grant[j];
-      uint32_t    pending_tti = (tti_sched->get_tti_tx_dl() + MSG3_DELAY_MS + TX_DELAY) % 10;
+      uint32_t    pending_tti = (tti_sched->get_tti_tx_dl() + MSG3_DELAY_MS + TX_DELAY) % TTIMOD_SZ;
       CondError(not pending_msg3[pending_tti].enabled, "Pending Msg3 should have been set\n");
       uint32_t rba =
           srslte_ra_type2_to_riv(pending_msg3[pending_tti].L, pending_msg3[pending_tti].n_prb, cfg.cell.nof_prb);
@@ -687,16 +688,17 @@ void sched_tester::test_harqs()
     to_ul_ack.insert(std::make_pair(ack_data.tti_tx_ul, ack_data));
   }
 
-  // Check whether some pids got old
-  for (auto& user : ue_db) {
-    for (int i = 0; i < 2 * FDD_HARQ_DELAY_MS; i++) {
-      if (not(user.second.get_dl_harq(i)->is_empty(0) and user.second.get_dl_harq(1))) {
-        if (srslte_tti_interval(tti_data.tti_tx_dl, user.second.get_dl_harq(i)->get_tti()) > 49) {
-          TestError("[TESTER] The pid=%d for rnti=0x%x got old.\n", user.second.get_dl_harq(i)->get_id(), user.first);
-        }
-      }
-    }
-  }
+  //  // Check whether some pids got old
+  //  for (auto& user : ue_db) {
+  //    for (int i = 0; i < 2 * FDD_HARQ_DELAY_MS; i++) {
+  //      if (not(user.second.get_dl_harq(i)->is_empty(0) and user.second.get_dl_harq(1))) {
+  //        if (srslte_tti_interval(tti_data.tti_tx_dl, user.second.get_dl_harq(i)->get_tti()) > 49) {
+  //          TestError("[TESTER] The pid=%d for rnti=0x%x got old.\n", user.second.get_dl_harq(i)->get_id(),
+  //          user.first);
+  //        }
+  //      }
+  //    }
+  //  }
 }
 
 void sched_tester::test_collisions()