diff --git a/openair3/NAS/COMMON/IES/CMakeLists.txt b/openair3/NAS/COMMON/IES/CMakeLists.txt
index bf80586fbc..67cc9d782a 100644
--- a/openair3/NAS/COMMON/IES/CMakeLists.txt
+++ b/openair3/NAS/COMMON/IES/CMakeLists.txt
@@ -3,6 +3,4 @@ add_library(nas_common_ies_lib OBJECT
     NasKeySetIdentifier.c
 )
 
-target_include_directories(nas_common_ies_lib PRIVATE
-    ${CMAKE_CURRENT_SOURCE_DIR}
-)
+target_include_directories(nas_common_ies_lib PUBLIC .)
diff --git a/openair3/NAS/NR_UE/5GS/5GMM/IES/CMakeLists.txt b/openair3/NAS/NR_UE/5GS/5GMM/IES/CMakeLists.txt
index 0915eed19c..24ed3022a6 100644
--- a/openair3/NAS/NR_UE/5GS/5GMM/IES/CMakeLists.txt
+++ b/openair3/NAS/NR_UE/5GS/5GMM/IES/CMakeLists.txt
@@ -7,3 +7,7 @@ add_library(fgs_5gmm_ies_lib OBJECT
   FGCNasMessageContainer.c
   SORTransparentContainer.c
 )
+
+target_link_libraries(fgs_5gmm_ies_lib PUBLIC
+    nas_common_ies_lib
+)
diff --git a/openair3/NAS/NR_UE/5GS/5GMM/MSG/CMakeLists.txt b/openair3/NAS/NR_UE/5GS/5GMM/MSG/CMakeLists.txt
index 766106ee77..be84772da6 100644
--- a/openair3/NAS/NR_UE/5GS/5GMM/MSG/CMakeLists.txt
+++ b/openair3/NAS/NR_UE/5GS/5GMM/MSG/CMakeLists.txt
@@ -10,4 +10,6 @@ add_library(fgs_5gmm_lib OBJECT
     FGSDeregistrationRequestUEOriginating.c
 )
 
-target_include_directories(fgs_5gmm_lib PUBLIC . ../IES ../../)
+target_link_libraries(fgs_5gmm_lib PUBLIC fgs_5gmm_ies_lib)
+
+target_include_directories(fgs_5gmm_lib PRIVATE ../IES/ ../../)
diff --git a/openair3/NAS/NR_UE/5GS/5GMM/MSG/FGSDeregistrationRequestUEOriginating.c b/openair3/NAS/NR_UE/5GS/5GMM/MSG/FGSDeregistrationRequestUEOriginating.c
index b5fdc5591a..6e1c0f102e 100644
--- a/openair3/NAS/NR_UE/5GS/5GMM/MSG/FGSDeregistrationRequestUEOriginating.c
+++ b/openair3/NAS/NR_UE/5GS/5GMM/MSG/FGSDeregistrationRequestUEOriginating.c
@@ -28,9 +28,10 @@
  */
 
 #include "FGSDeregistrationRequestUEOriginating.h"
-#include "NR_NAS_defs.h"
 #include <stdint.h>
 
+#define IEI_NULL 0x00
+
 int encode_fgs_deregistration_request_ue_originating(fgs_deregistration_request_ue_originating_msg *drr,
                                                      uint8_t *buffer,
                                                      uint32_t len)
diff --git a/openair3/NAS/NR_UE/5GS/5GMM/MSG/RegistrationRequest.c b/openair3/NAS/NR_UE/5GS/5GMM/MSG/RegistrationRequest.c
index e2278c8988..dd08e61dba 100644
--- a/openair3/NAS/NR_UE/5GS/5GMM/MSG/RegistrationRequest.c
+++ b/openair3/NAS/NR_UE/5GS/5GMM/MSG/RegistrationRequest.c
@@ -28,11 +28,12 @@
  */
 
 #include "RegistrationRequest.h"
-#include "NR_NAS_defs.h"
 #include <stdint.h>
 #include "T.h"
 #include "nas_log.h"
 
+#define IEI_NULL 0x00
+
 int decode_registration_request(registration_request_msg *registration_request, uint8_t *buffer, uint32_t len)
 {
   uint32_t decoded = 0;
diff --git a/openair3/NAS/NR_UE/5GS/5GMM/MSG/fgs_service_request.c b/openair3/NAS/NR_UE/5GS/5GMM/MSG/fgs_service_request.c
index 85e67498a5..fa31e1e297 100644
--- a/openair3/NAS/NR_UE/5GS/5GMM/MSG/fgs_service_request.c
+++ b/openair3/NAS/NR_UE/5GS/5GMM/MSG/fgs_service_request.c
@@ -30,10 +30,10 @@
 #include "FGSMobileIdentity.h"
 #include "NasKeySetIdentifier.h"
 #include "ServiceType.h"
-#include "NR_NAS_defs.h"
 
 #define LEN_FGS_MOBILE_ID_CONTENTS_SIZE 2 // octets
 #define MIN_LEN_FGS_SERVICE_REQUEST 10 // octets
+#define IEI_NULL 0x00
 
 /**
  * @brief Encode 5GMM NAS Service Request message (8.2.16 of 3GPP TS 24.501)
diff --git a/openair3/NAS/NR_UE/5GS/5GSM/MSG/CMakeLists.txt b/openair3/NAS/NR_UE/5GS/5GSM/MSG/CMakeLists.txt
index 41498581c9..ca115451b3 100644
--- a/openair3/NAS/NR_UE/5GS/5GSM/MSG/CMakeLists.txt
+++ b/openair3/NAS/NR_UE/5GS/5GSM/MSG/CMakeLists.txt
@@ -1,3 +1,10 @@
 add_library(fgs_5gsm_lib OBJECT PduSessionEstablishRequest.c
                             PduSessionEstablishmentAccept.c)
-target_include_directories(fgs_5gsm_lib PUBLIC . ../../)
+
+target_link_libraries(fgs_5gsm_lib PUBLIC nas_common_ies_lib)
+
+target_include_directories(fgs_5gsm_lib PUBLIC .
+    ../../5GMM/MSG # NOTE: to be removed in a later commit
+    ../../5GMM/IES # NOTE: to be removed in a later commit
+    ../../
+)
diff --git a/openair3/NAS/NR_UE/5GS/5GSM/MSG/PduSessionEstablishmentAccept.h b/openair3/NAS/NR_UE/5GS/5GSM/MSG/PduSessionEstablishmentAccept.h
index 37dea829b0..69c9cde844 100644
--- a/openair3/NAS/NR_UE/5GS/5GSM/MSG/PduSessionEstablishmentAccept.h
+++ b/openair3/NAS/NR_UE/5GS/5GSM/MSG/PduSessionEstablishmentAccept.h
@@ -23,7 +23,8 @@
 #define PDU_SESSION_ESTABLISHMENT_ACCEPT_H_
 
 #include <stdint.h>
-#include "NR_NAS_defs.h"
+#include "fgs_nas_utils.h"
+#include "NR_NAS_defs.h" // TEMP: to be removed in later commit
 
 /* PDU Session Establish Accept Optional IE Identifiers - TS 24.501 Table 8.3.2.1.1 */
 
diff --git a/openair3/NAS/NR_UE/5GS/CMakeLists.txt b/openair3/NAS/NR_UE/5GS/CMakeLists.txt
index 4c0810b5f6..e04abb02db 100644
--- a/openair3/NAS/NR_UE/5GS/CMakeLists.txt
+++ b/openair3/NAS/NR_UE/5GS/CMakeLists.txt
@@ -5,3 +5,13 @@ add_subdirectory(5GSM/MSG)
 if(ENABLE_TESTS)
   add_subdirectory(tests)
 endif()
+add_library(fgs_lib fgs_nas_lib.c)
+
+target_link_libraries(fgs_lib PUBLIC
+    fgs_5gmm_lib
+    fgs_5gsm_lib
+    fgs_5gmm_ies_lib
+    nas_common_ies_lib
+)
+
+target_include_directories(fgs_lib PUBLIC . 5GMM/MSG 5GMM/IES)
diff --git a/openair3/NAS/NR_UE/5GS/NR_NAS_defs.h b/openair3/NAS/NR_UE/5GS/NR_NAS_defs.h
index 35b9793863..fd4fa2e1a8 100644
--- a/openair3/NAS/NR_UE/5GS/NR_NAS_defs.h
+++ b/openair3/NAS/NR_UE/5GS/NR_NAS_defs.h
@@ -24,15 +24,16 @@
 
 #include <stdint.h>
 #include "openair3/UICC/usim_interface.h"
-
-/* Map task id to printable name. */
-typedef struct {
-  int id;
-  char text[256];
-} text_info_t;
-
-#define TO_TEXT(LabEl, nUmID) {nUmID, #LabEl},
-#define TO_ENUM(LabEl, nUmID ) LabEl = nUmID,
+#include "fgs_nas_utils.h"
+#include "FGSAuthenticationResponse.h"
+#include "FGSDeregistrationRequestUEOriginating.h"
+#include "FGSIdentityResponse.h"
+#include "FGSMobileIdentity.h"
+#include "FGSNASSecurityModeComplete.h"
+#include "FGSUplinkNasTransport.h"
+#include "RegistrationComplete.h"
+#include "RegistrationRequest.h"
+#include "fgs_service_request.h"
 
 /* Message types defintions for:
    (a) 5GS Mobility Management (5GMM) (IDs 0x41 - 0x68)
@@ -220,9 +221,6 @@ typedef enum {
   FOREACH_CAUSE_SECU(TO_ENUM)
 } cause_secu_id_t;
 								
-// IEIs (Information Element Identifier)
-#define IEI_NULL 0x00
-
 /**
  * Security protected 5GS NAS message header (9.1.1 of 3GPP TS 24.501)
  * either 5GMM or 5GSM
@@ -239,6 +237,15 @@ typedef struct {
   uint8_t sequence_number;
 } __attribute__((packed)) fgs_nas_message_security_header_t;
 
+/// 5GS Protocol Discriminator identifiers
+
+typedef enum fgs_protocol_discriminator_e {
+  // 5GS Mobility Management
+  FGS_MOBILITY_MANAGEMENT_MESSAGE = 0x7E,
+  // 5GS Session Management
+  FGS_SESSION_MANAGEMENT_MESSAGE = 0x2E,
+} fgs_protocol_discriminator_t;
+
 /// 5GMM - 5GS mobility management
 
 /**
@@ -251,6 +258,46 @@ typedef struct {
   uint8_t message_type;
 } fgmm_msg_header_t;
 
+/// 5GS legacy defs
+
+typedef union {
+  fgmm_msg_header_t header;
+  registration_request_msg registration_request;
+  fgs_service_request_msg_t service_request;
+  fgs_identiy_response_msg fgs_identity_response;
+  fgs_authentication_response_msg fgs_auth_response;
+  fgs_deregistration_request_ue_originating_msg fgs_deregistration_request_ue_originating;
+  fgs_security_mode_complete_msg fgs_security_mode_complete;
+  registration_complete_msg registration_complete;
+  fgs_uplink_nas_transport_msg uplink_nas_transport;
+} MM_msg;
+
+typedef struct {
+  MM_msg mm_msg; /* 5GS Mobility Management messages */
+} fgs_nas_message_plain_t;
+
+typedef struct {
+  fgs_nas_message_security_header_t header;
+  fgs_nas_message_plain_t plain;
+} fgs_nas_message_security_protected_t;
+typedef union {
+  fgs_nas_message_security_header_t header;
+  fgs_nas_message_security_protected_t security_protected;
+  fgs_nas_message_plain_t plain;
+} fgs_nas_message_t;
+typedef struct {
+  union {
+    fgmm_msg_header_t plain_nas_msg_header;
+    struct security_protected_nas_msg_header_s {
+      uint8_t ex_protocol_discriminator;
+      uint8_t security_header_type;
+      uint16_t message_authentication_code1;
+      uint16_t message_authentication_code2;
+      uint8_t sequence_number;
+    } security_protected_nas_msg_header_t;
+  } choice;
+} nas_msg_header_t;
+
 /// 5GSM - 5GS session management
 
 /**
@@ -268,4 +315,10 @@ typedef struct {
   uint8_t message_type;
 } fgsm_msg_header_t;
 
+/// Function prototypes
+
+int mm_msg_encode(const MM_msg *mm_msg, uint8_t *buffer, uint32_t len);
+int nas_protected_security_header_encode(uint8_t *buffer, const fgs_nas_message_security_header_t *header, int length);
+int _nas_mm_msg_encode_header(const fgmm_msg_header_t *header, uint8_t *buffer, uint32_t len);
+
 #endif // NR_NAS_DEFS_H
diff --git a/openair3/NAS/NR_UE/5GS/fgs_nas_lib.c b/openair3/NAS/NR_UE/5GS/fgs_nas_lib.c
new file mode 100644
index 0000000000..8585e4ef70
--- /dev/null
+++ b/openair3/NAS/NR_UE/5GS/fgs_nas_lib.c
@@ -0,0 +1,134 @@
+/*
+ * Licensed to the OpenAirInterface (OAI) Software Alliance under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The OpenAirInterface Software Alliance licenses this file to You under
+ * the OAI Public License, Version 1.1  (the "License"); you may not use this file
+ * except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.openairinterface.org/?page_id=698
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *-------------------------------------------------------------------------------
+ * For more information about the OpenAirInterface (OAI) Software Alliance:
+ *      contact@openairinterface.org
+ */
+
+#include "NR_NAS_defs.h"
+#include "nas_log.h"
+#include "TLVEncoder.h"
+#include "fgs_nas_utils.h"
+
+int _nas_mm_msg_encode_header(const fgmm_msg_header_t *header, uint8_t *buffer, uint32_t len)
+{
+  int size = 0;
+
+  /* Check the buffer length */
+  if (len < sizeof(fgmm_msg_header_t)) {
+    return (TLV_ENCODE_BUFFER_TOO_SHORT);
+  }
+
+  /* Check the protocol discriminator */
+  if (header->ex_protocol_discriminator != FGS_MOBILITY_MANAGEMENT_MESSAGE) {
+    LOG_TRACE(ERROR, "Unexpected extened protocol discriminator: 0x%x", header->ex_protocol_discriminator);
+    return (TLV_ENCODE_PROTOCOL_NOT_SUPPORTED);
+  }
+
+  /* Encode the extendedprotocol discriminator */
+  ENCODE_U8(buffer + size, header->ex_protocol_discriminator, size);
+  /* Encode the security header type */
+  ENCODE_U8(buffer + size, (header->security_header_type & 0xf), size);
+  /* Encode the message type */
+  ENCODE_U8(buffer + size, header->message_type, size);
+  return (size);
+}
+
+int mm_msg_encode(const MM_msg *mm_msg, uint8_t *buffer, uint32_t len)
+{
+  LOG_FUNC_IN;
+  int header_result;
+  int encode_result;
+  uint8_t msg_type = mm_msg->header.message_type;
+
+  /* First encode the EMM message header */
+  header_result = _nas_mm_msg_encode_header(&mm_msg->header, buffer, len);
+
+  if (header_result < 0) {
+    LOG_TRACE(ERROR,
+              "Failed to encode 5GMM message header"
+              "(%d)",
+              header_result);
+    LOG_FUNC_RETURN(header_result);
+  }
+
+  buffer += header_result;
+  len -= header_result;
+
+  switch (msg_type) {
+    case FGS_REGISTRATION_REQUEST:
+      encode_result = encode_registration_request(&mm_msg->registration_request, buffer, len);
+      break;
+    case FGS_IDENTITY_RESPONSE:
+      encode_result = encode_identiy_response(&mm_msg->fgs_identity_response, buffer, len);
+      break;
+    case FGS_AUTHENTICATION_RESPONSE:
+      encode_result = encode_fgs_authentication_response(&mm_msg->fgs_auth_response, buffer, len);
+      break;
+    case FGS_SECURITY_MODE_COMPLETE:
+      encode_result = encode_fgs_security_mode_complete(&mm_msg->fgs_security_mode_complete, buffer, len);
+      break;
+    case FGS_UPLINK_NAS_TRANSPORT:
+      encode_result = encode_fgs_uplink_nas_transport(&mm_msg->uplink_nas_transport, buffer, len);
+      break;
+    case FGS_DEREGISTRATION_REQUEST_UE_ORIGINATING:
+      encode_result =
+          encode_fgs_deregistration_request_ue_originating(&mm_msg->fgs_deregistration_request_ue_originating, buffer, len);
+      break;
+    case FGS_SERVICE_REQUEST:
+      encode_result = encode_fgs_service_request(buffer, &mm_msg->service_request, len);
+      break;
+    default:
+      LOG_TRACE(ERROR, " Unexpected message type: 0x%x", mm_msg->header.message_type);
+      encode_result = TLV_ENCODE_WRONG_MESSAGE_TYPE;
+      break;
+      /* TODO: Handle not standard layer 3 messages: SERVICE_REQUEST */
+  }
+
+  if (encode_result < 0) {
+    LOG_TRACE(ERROR,
+              " Failed to encode L3 EMM message 0x%x "
+              "(%d)",
+              mm_msg->header.message_type,
+              encode_result);
+  }
+
+  if (encode_result < 0)
+    LOG_FUNC_RETURN(encode_result);
+
+  LOG_FUNC_RETURN(header_result + encode_result);
+}
+
+int nas_protected_security_header_encode(uint8_t *buffer, const fgs_nas_message_security_header_t *header, int length)
+{
+  LOG_FUNC_IN;
+
+  int size = 0;
+
+  /* Encode the protocol discriminator) */
+  ENCODE_U8(buffer, header->protocol_discriminator, size);
+
+  /* Encode the security header type */
+  ENCODE_U8(buffer + size, (header->security_header_type & 0xf), size);
+
+  /* Encode the message authentication code */
+  ENCODE_U32(buffer + size, header->message_authentication_code, size);
+  /* Encode the sequence number */
+  ENCODE_U8(buffer + size, header->sequence_number, size);
+
+  LOG_FUNC_RETURN(size);
+}
diff --git a/openair3/NAS/NR_UE/5GS/fgs_nas_utils.h b/openair3/NAS/NR_UE/5GS/fgs_nas_utils.h
new file mode 100644
index 0000000000..74f4d2ed7f
--- /dev/null
+++ b/openair3/NAS/NR_UE/5GS/fgs_nas_utils.h
@@ -0,0 +1,36 @@
+/*
+ * Licensed to the OpenAirInterface (OAI) Software Alliance under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The OpenAirInterface Software Alliance licenses this file to You under
+ * the OAI Public License, Version 1.1  (the "License"); you may not use this file
+ * except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.openairinterface.org/?page_id=698
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *-------------------------------------------------------------------------------
+ * For more information about the OpenAirInterface (OAI) Software Alliance:
+ *      contact@openairinterface.org
+ */
+
+#ifndef FGS_NAS_UTILS_H
+#define FGS_NAS_UTILS_H
+
+#include <stdint.h>
+
+/* Map task id to printable name. */
+typedef struct {
+  int id;
+  char text[256];
+} text_info_t;
+
+#define TO_TEXT(LabEl, nUmID) {nUmID, #LabEl},
+#define TO_ENUM(LabEl, nUmID ) LabEl = nUmID,
+
+#endif // FGS_NAS_UTILS_H
diff --git a/openair3/NAS/NR_UE/CMakeLists.txt b/openair3/NAS/NR_UE/CMakeLists.txt
index 8054d1cdd2..5e7d5da428 100644
--- a/openair3/NAS/NR_UE/CMakeLists.txt
+++ b/openair3/NAS/NR_UE/CMakeLists.txt
@@ -4,6 +4,7 @@ add_library(nr_nas STATIC nr_nas_msg.c)
 
 target_link_libraries(nr_nas PUBLIC asn1_lte_rrc_hdrs asn1_nr_rrc_hdrs)
 target_link_libraries(nr_nas PUBLIC
+    fgs_lib
     fgs_5gmm_lib
     fgs_5gsm_lib
     fgs_5gmm_ies_lib
@@ -11,7 +12,4 @@ target_link_libraries(nr_nas PUBLIC
     nas_utils
 )
 
-target_include_directories(nr_nas PRIVATE
-  ${CMAKE_CURRENT_SOURCE_DIR}
-  ${CMAKE_CURRENT_SOURCE_DIR}/5GS
-)
+target_include_directories(nr_nas PUBLIC . 5GS/)
diff --git a/openair3/NAS/NR_UE/nr_nas_msg.c b/openair3/NAS/NR_UE/nr_nas_msg.c
index 673bbfbb3d..33fabe8df0 100644
--- a/openair3/NAS/NR_UE/nr_nas_msg.c
+++ b/openair3/NAS/NR_UE/nr_nas_msg.c
@@ -20,7 +20,7 @@
  */
 
 /*! \file nr_nas_msg.c
- * \brief simulator for nr nas message
+ * \brief Definitions of handlers and callbacks for NR NAS UE task
  * \author Yoshio INOUE, Masayuki HARADA
  * \email yoshio.inoue@fujitsu.com,masayuki.harada@fujitsu.com
  * \date 2020
@@ -40,7 +40,6 @@
 #include "FGCNasMessageContainer.h"
 #include "FGSDeregistrationRequestUEOriginating.h"
 #include "FGSDeregistrationType.h"
-#include "LOG/log.h"
 #include "NasKeySetIdentifier.h"
 #include "NrUESecurityCapability.h"
 #include "OctetString.h"
@@ -158,50 +157,6 @@ static security_state_t nas_security_rx_process(nr_ue_nas_t *nas, uint8_t *pdu_b
   return NAS_SECURITY_INTEGRITY_PASSED;
 }
 
-static int nas_protected_security_header_encode(char *buffer, const fgs_nas_message_security_header_t *header, int length)
-{
-  LOG_FUNC_IN;
-
-  int size = 0;
-
-  /* Encode the protocol discriminator) */
-  ENCODE_U8(buffer, header->protocol_discriminator, size);
-
-  /* Encode the security header type */
-  ENCODE_U8(buffer + size, (header->security_header_type & 0xf), size);
-
-  /* Encode the message authentication code */
-  ENCODE_U32(buffer + size, header->message_authentication_code, size);
-  /* Encode the sequence number */
-  ENCODE_U8(buffer + size, header->sequence_number, size);
-
-  LOG_FUNC_RETURN(size);
-}
-
-static int _nas_mm_msg_encode_header(const fgmm_msg_header_t *header, uint8_t *buffer, uint32_t len)
-{
-  int size = 0;
-
-  /* Check the buffer length */
-  if (len < sizeof(fgmm_msg_header_t)) {
-    return (TLV_ENCODE_BUFFER_TOO_SHORT);
-  }
-
-  /* Check the protocol discriminator */
-  if (header->ex_protocol_discriminator != FGS_MOBILITY_MANAGEMENT_MESSAGE) {
-    LOG_TRACE(ERROR, "ESM-MSG   - Unexpected extened protocol discriminator: 0x%x", header->ex_protocol_discriminator);
-    return (TLV_ENCODE_PROTOCOL_NOT_SUPPORTED);
-  }
-
-  /* Encode the extendedprotocol discriminator */
-  ENCODE_U8(buffer + size, header->ex_protocol_discriminator, size);
-  /* Encode the security header type */
-  ENCODE_U8(buffer + size, (header->security_header_type & 0xf), size);
-  /* Encode the message type */
-  ENCODE_U8(buffer + size, header->message_type, size);
-  return (size);
-}
-
 static int fill_suci(FGSMobileIdentity *mi, const uicc_t *uicc)
 {
   mi->suci.typeofidentity = FGS_MOBILE_IDENTITY_SUCI;
@@ -259,71 +214,6 @@ static int fill_imeisv(FGSMobileIdentity *mi, const uicc_t *uicc)
   return 19;
 }
 
-int mm_msg_encode(MM_msg *mm_msg, uint8_t *buffer, uint32_t len)
-{
-  LOG_FUNC_IN;
-  int header_result;
-  int encode_result;
-  uint8_t msg_type = mm_msg->header.message_type;
-
-  /* First encode the EMM message header */
-  header_result = _nas_mm_msg_encode_header(&mm_msg->header, buffer, len);
-
-  if (header_result < 0) {
-    LOG_TRACE(ERROR,
-              "EMM-MSG   - Failed to encode EMM message header "
-              "(%d)",
-              header_result);
-    LOG_FUNC_RETURN(header_result);
-  }
-
-  buffer += header_result;
-  len -= header_result;
-
-  switch (msg_type) {
-    case FGS_REGISTRATION_REQUEST:
-      encode_result = encode_registration_request(&mm_msg->registration_request, buffer, len);
-      break;
-    case FGS_IDENTITY_RESPONSE:
-      encode_result = encode_identiy_response(&mm_msg->fgs_identity_response, buffer, len);
-      break;
-    case FGS_AUTHENTICATION_RESPONSE:
-      encode_result = encode_fgs_authentication_response(&mm_msg->fgs_auth_response, buffer, len);
-      break;
-    case FGS_SECURITY_MODE_COMPLETE:
-      encode_result = encode_fgs_security_mode_complete(&mm_msg->fgs_security_mode_complete, buffer, len);
-      break;
-    case FGS_UPLINK_NAS_TRANSPORT:
-      encode_result = encode_fgs_uplink_nas_transport(&mm_msg->uplink_nas_transport, buffer, len);
-      break;
-    case FGS_DEREGISTRATION_REQUEST_UE_ORIGINATING:
-      encode_result =
-          encode_fgs_deregistration_request_ue_originating(&mm_msg->fgs_deregistration_request_ue_originating, buffer, len);
-      break;
-    case FGS_SERVICE_REQUEST:
-      encode_result = encode_fgs_service_request(buffer, &mm_msg->service_request, len);
-      break;
-    default:
-      LOG_TRACE(ERROR, "EMM-MSG   - Unexpected message type: 0x%x", mm_msg->header.message_type);
-      encode_result = TLV_ENCODE_WRONG_MESSAGE_TYPE;
-      break;
-      /* TODO: Handle not standard layer 3 messages: SERVICE_REQUEST */
-  }
-
-  if (encode_result < 0) {
-    LOG_TRACE(ERROR,
-              "EMM-MSG   - Failed to encode L3 EMM message 0x%x "
-              "(%d)",
-              mm_msg->header.message_type,
-              encode_result);
-  }
-
-  if (encode_result < 0)
-    LOG_FUNC_RETURN(encode_result);
-
-  LOG_FUNC_RETURN(header_result + encode_result);
-}
-
 void transferRES(uint8_t ck[16], uint8_t ik[16], uint8_t *input, uint8_t rand[16], uint8_t *output, uicc_t *uicc)
 {
   uint8_t S[100] = {0};
@@ -786,7 +676,7 @@ static void generateSecurityModeComplete(nr_ue_nas_t *nas, as_nas_info_t *initia
   // encode the message
   initialNasMsg->nas_data = malloc_or_fail(size * sizeof(*initialNasMsg->nas_data));
 
-  int security_header_len = nas_protected_security_header_encode((char *)(initialNasMsg->nas_data), &(nas_msg.header), size);
+  int security_header_len = nas_protected_security_header_encode(initialNasMsg->nas_data, &nas_msg.header, size);
 
   initialNasMsg->length =
       security_header_len
@@ -1010,7 +900,7 @@ static void generateDeregistrationRequest(nr_ue_nas_t *nas, as_nas_info_t *initi
 
   // encode the message
   initialNasMsg->nas_data = calloc_or_fail(size, sizeof(*initialNasMsg->nas_data));
-  int security_header_len = nas_protected_security_header_encode((char *)(initialNasMsg->nas_data), &nas_msg.header, size);
+  int security_header_len = nas_protected_security_header_encode(initialNasMsg->nas_data, &nas_msg.header, size);
 
   initialNasMsg->length =
       security_header_len
@@ -1118,7 +1008,7 @@ static void generatePduSessionEstablishRequest(nr_ue_nas_t *nas, as_nas_info_t *
 
   // encode the message
   initialNasMsg->nas_data = malloc_or_fail(size * sizeof(*initialNasMsg->nas_data));
-  int security_header_len = nas_protected_security_header_encode((char *)(initialNasMsg->nas_data), &(nas_msg.header), size);
+  int security_header_len = nas_protected_security_header_encode(initialNasMsg->nas_data, &nas_msg.header, size);
 
   initialNasMsg->length =
       security_header_len
diff --git a/openair3/NAS/NR_UE/nr_nas_msg.h b/openair3/NAS/NR_UE/nr_nas_msg.h
index eb76ddcd51..d024a92c9c 100644
--- a/openair3/NAS/NR_UE/nr_nas_msg.h
+++ b/openair3/NAS/NR_UE/nr_nas_msg.h
@@ -35,15 +35,6 @@
 #include <openair3/UICC/usim_interface.h>
 #include <stdbool.h>
 #include <stdint.h>
-#include "FGSAuthenticationResponse.h"
-#include "FGSDeregistrationRequestUEOriginating.h"
-#include "FGSIdentityResponse.h"
-#include "FGSMobileIdentity.h"
-#include "FGSNASSecurityModeComplete.h"
-#include "FGSUplinkNasTransport.h"
-#include "RegistrationComplete.h"
-#include "RegistrationRequest.h"
-#include "fgs_service_request.h"
 #include "as_message.h"
 #include "NR_NAS_defs.h"
 #include "secu_defs.h"
@@ -92,54 +83,6 @@ typedef struct {
   instance_t UE_id;
 } nr_ue_nas_t;
 
-typedef enum fgs_protocol_discriminator_e {
-  /* Protocol discriminator identifier for 5GS Mobility Management */
-  FGS_MOBILITY_MANAGEMENT_MESSAGE = 0x7E,
-
-  /* Protocol discriminator identifier for 5GS Session Management */
-  FGS_SESSION_MANAGEMENT_MESSAGE = 0x2E,
-} fgs_protocol_discriminator_t;
-
-typedef union {
-  fgmm_msg_header_t header;
-  registration_request_msg registration_request;
-  fgs_service_request_msg_t service_request;
-  fgs_identiy_response_msg fgs_identity_response;
-  fgs_authentication_response_msg fgs_auth_response;
-  fgs_deregistration_request_ue_originating_msg fgs_deregistration_request_ue_originating;
-  fgs_security_mode_complete_msg fgs_security_mode_complete;
-  registration_complete_msg registration_complete;
-  fgs_uplink_nas_transport_msg uplink_nas_transport;
-} MM_msg;
-
-typedef struct {
-  MM_msg mm_msg; /* 5GS Mobility Management messages */
-} fgs_nas_message_plain_t;
-
-typedef struct {
-  fgs_nas_message_security_header_t header;
-  fgs_nas_message_plain_t plain;
-} fgs_nas_message_security_protected_t;
-
-typedef union {
-  fgs_nas_message_security_header_t header;
-  fgs_nas_message_security_protected_t security_protected;
-  fgs_nas_message_plain_t plain;
-} fgs_nas_message_t;
-
-typedef struct {
-  union {
-    fgmm_msg_header_t plain_nas_msg_header;
-    struct security_protected_nas_msg_header_s {
-      uint8_t ex_protocol_discriminator;
-      uint8_t security_header_type;
-      uint16_t message_authentication_code1;
-      uint16_t message_authentication_code2;
-      uint8_t sequence_number;
-    } security_protected_nas_msg_header_t;
-  } choice;
-} nas_msg_header_t;
-
 nr_ue_nas_t *get_ue_nas_info(module_id_t module_id);
 void generateRegistrationRequest(as_nas_info_t *initialNasMsg, nr_ue_nas_t *nas);
 void generateServiceRequest(as_nas_info_t *initialNasMsg, nr_ue_nas_t *nas);