diff --git a/CMakeLists.txt b/CMakeLists.txt
index e49436d..90613cc 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -48,6 +48,8 @@ add_executable(skl_tunnel
     radio/src/radio_spi.c
     radio/src/radio_gpio.c
     radio/src/radio_hw_instance.cpp
+    radio/src/radio_protocol_frame.cpp
+    radio/src/radio_protocol.cpp
 
     app/src/app_board.cpp
     app/src/app_transparent_client.cpp
diff --git a/radio/include/radio_protocol.hpp b/radio/include/radio_protocol.hpp
new file mode 100644
index 0000000..d1e35d2
--- /dev/null
+++ b/radio/include/radio_protocol.hpp
@@ -0,0 +1,18 @@
+//
+// Created by erki on 28.07.22.
+//
+
+#ifndef SKL_TUNNEL_RADIO_PROTOCOL_HPP
+#define SKL_TUNNEL_RADIO_PROTOCOL_HPP
+
+#include "radio_protocol_frame.hpp"
+
+namespace radio::protocol
+{
+
+std::size_t composeFrameBuffer(const FrameStructure& frame);
+FrameStructure decomposeFrameBuffer(const std::uint8_t* data);
+
+}
+
+#endif //SKL_TUNNEL_RADIO_PROTOCOL_HPP
diff --git a/radio/include/radio_protocol_frame.hpp b/radio/include/radio_protocol_frame.hpp
new file mode 100644
index 0000000..0900db4
--- /dev/null
+++ b/radio/include/radio_protocol_frame.hpp
@@ -0,0 +1,135 @@
+//
+// Created by erki on 18.07.22.
+//
+
+#ifndef SKL_TUNNEL_RADIO_FRAME_HPP
+#define SKL_TUNNEL_RADIO_FRAME_HPP
+
+#include <array>
+#include <cstdint>
+#include <type_traits>
+#include <optional>
+#include <variant>
+
+#include <utility_assert.hpp>
+
+/**
+ * Reference section 37.1 of the SAMR21 datasheet for these structures.
+ */
+namespace radio::protocol
+{
+
+struct PhyHeader
+{
+  std::uint8_t frame_length : 7;
+  std::uint8_t reserved : 1;
+} __attribute__((packed));
+
+struct FrameControlField
+{
+  enum FrameType
+  {
+    FRAME_TYPE_BEACON = 0b000,
+    FRAME_TYPE_DATA = 0b001,
+    FRAME_TYPE_ACKNOWLEDGE = 0b010,
+    FRAME_TYPE_MAC_COMMAND = 0b011
+  };
+
+  enum AddressingMode
+  {
+    ADDRESSING_MODE_NOT_SPECIFIED = 0b00,
+    ADDRESSING_MODE_SHORT = 0b10,
+    ADDRESSING_MODE_LONG = 0b11
+  };
+
+  FrameType type : 3;
+  std::uint8_t security_enabled : 1;
+  std::uint8_t frame_pending : 1;
+  std::uint8_t ack_requested : 1;
+  std::uint8_t pan_id_compression : 1;
+  std::uint8_t : 3;
+  AddressingMode destination_addressing_mode : 2;
+  std::uint8_t frame_version : 2;
+  AddressingMode source_addressing_mode : 2;
+} __attribute__((packed));
+
+struct Address
+{
+  std::variant<std::uint16_t, std::uint64_t> mac = 0ull;
+  std::uint16_t pan_id = 0;
+
+  FrameControlField::AddressingMode getAddressingMode() const
+  {
+    if (std::holds_alternative<std::uint16_t>(mac))
+      return FrameControlField::ADDRESSING_MODE_SHORT;
+    else if (std::holds_alternative<std::uint64_t>(mac))
+      return FrameControlField::ADDRESSING_MODE_LONG;
+    else
+      return FrameControlField::ADDRESSING_MODE_NOT_SPECIFIED;
+  }
+
+  void setShortAddress(const std::uint16_t address)
+  {
+    mac = address;
+  }
+
+  void setLongAddress(const std::uint64_t address)
+  {
+    mac = address;
+  }
+
+  std::uint16_t getShortAddress() const
+  {
+    const std::uint16_t* addr = std::get_if<std::uint16_t>(&mac);
+    SKULLC_ASSERT_DEBUG(addr != nullptr);
+
+    return *addr;
+  }
+
+  std::uint64_t getLongAddress() const
+  {
+    const std::uint64_t* addr = std::get_if<std::uint64_t>(&mac);
+    SKULLC_ASSERT_DEBUG(addr != nullptr);
+
+    return *addr;
+  }
+};
+
+struct FrameStructure
+{
+  FrameControlField frame_control_field;
+  std::uint8_t sequence_number;
+  Address destination_address;
+  Address source_address;
+  std::uint16_t frame_checksum;
+
+  static constexpr std::size_t max_frame_size = 127;
+  static constexpr std::size_t max_payload_size
+          = max_frame_size - sizeof(FrameControlField) - sizeof(frame_checksum)
+            - sizeof(sequence_number) - (2 * (sizeof(std::uint16_t) + sizeof(std::uint64_t)));
+
+  std::uint8_t payload_length;
+  std::array<std::uint8_t, max_payload_size> payload;
+
+  FrameStructure();
+
+  static FrameStructure createDataFrame();
+
+  FrameStructure& setPayload(const std::uint8_t* data, const std::uint8_t length);
+  template<std::size_t N>
+  FrameStructure& setPayload(const std::array<std::uint8_t, N>& data)
+  {
+    static_assert(N <= max_payload_size, "Data length N exceeds max_payload_size.");
+    return setPayload(data.data(), std::uint8_t(N));
+  }
+
+  FrameStructure& setSourceAddress(const Address& addr);
+  FrameStructure& setDestinationAddress(const Address& addr);
+
+  std::uint8_t getTotalFrameLength() const;
+  std::uint8_t calculatePayloadLength(const std::uint8_t total_frame_length) const;
+};
+
+}
+
+#endif //SKL_TUNNEL_RADIO_FRAME_HPP
diff --git a/radio/src/radio_protocol.cpp b/radio/src/radio_protocol.cpp
new file mode 100644
index 0000000..1603d10
--- /dev/null
+++ b/radio/src/radio_protocol.cpp
@@ -0,0 +1,146 @@
+//
+// Created by erki on 28.07.22.
+//
+
+#include "radio_protocol.hpp"
+
+#include <cstring>
+
+namespace
+{
+
+using namespace radio::protocol;
+
+[[nodiscard]] std::uint8_t* serializeAddress(std::uint8_t* data, const Address& address)
+{
+  std::memmove(data, &address.pan_id, sizeof(address.pan_id));
+  data += sizeof(address.pan_id);
+
+  if (address.getAddressingMode() == FrameControlField::ADDRESSING_MODE_SHORT)
+  {
+    const std::uint16_t mac = address.getShortAddress();
+    std::memmove(data, &mac, sizeof(mac));
+    data += sizeof(mac);
+  }
+  else
+  {
+    const std::uint64_t mac = address.getLongAddress();
+    std::memmove(data, &mac, sizeof(mac));
+    data += sizeof(mac);
+  }
+
+  return data;
+}
+
+[[nodiscard]] std::uint8_t* serializePhyHeader(std::uint8_t* data, const PhyHeader& header)
+{
+  static_assert(sizeof(PhyHeader) == 1, "PHY Header must be 1 byte/octet.");
+  std::memmove(data, &header, sizeof(PhyHeader));
+  data += sizeof(PhyHeader);
+
+  return data;
+}
+
+[[nodiscard]] std::uint8_t* serializeMacProtocolDataUnit(std::uint8_t* data, const FrameStructure& frame)
+{
+  static_assert(sizeof(frame.frame_control_field) == 2, "FCF must be 2 bytes/octets.");
+  std::memmove(data, &frame.frame_control_field, sizeof(frame.frame_control_field));
+  data += sizeof(FrameControlField);
+
+  std::memmove(data, &frame.sequence_number, sizeof(frame.sequence_number));
+  data += sizeof(frame.sequence_number);
+
+  data = serializeAddress(data, frame.destination_address);
+  data = serializeAddress(data, frame.source_address);
+
+  std::memmove(data, frame.payload.data(), frame.payload_length);
+  data += frame.payload_length;
+
+  return data;
+}
+
+[[nodiscard]] const std::uint8_t* deserializeAddress(const std::uint8_t* data, const FrameControlField::AddressingMode& addressing_mode, Address& address)
+{
+  std::memmove(&address.pan_id, data, sizeof(address.pan_id));
+  data += sizeof(address.pan_id);
+
+  if (addressing_mode == FrameControlField::ADDRESSING_MODE_SHORT)
+  {
+    std::uint16_t mac = 0;
+    std::memmove(&mac, data, sizeof(mac));
+    data += sizeof(mac);
+
+    address.setShortAddress(mac);
+  }
+  else
+  {
+    std::uint64_t mac = 0;
+    std::memmove(&mac, data, sizeof(mac));
+    data += sizeof(mac);
+
+    address.setLongAddress(mac);
+  }
+
+  return data;
+}
+
+[[nodiscard]] const std::uint8_t* deserializePhyHeader(const std::uint8_t* data, PhyHeader& header)
+{
+  std::memmove(&header, data, sizeof(PhyHeader));
+  data += sizeof(PhyHeader);
+
+  return data;
+}
+
+[[nodiscard]] FrameStructure deserializeMacProtocolDataUnit(const std::uint8_t* data, const std::uint8_t total_frame_length)
+{
+  FrameStructure frame;
+  std::memmove(&frame.frame_control_field, data, sizeof(frame.frame_control_field));
+  data += sizeof(frame.frame_control_field);
+
+  std::memmove(&frame.sequence_number, data, sizeof(frame.sequence_number));
+  data += sizeof(frame.sequence_number);
+
+  data = deserializeAddress(data, frame.frame_control_field.destination_addressing_mode, frame.destination_address);
+  data = deserializeAddress(data, frame.frame_control_field.source_addressing_mode, frame.source_address);
+
+  frame.payload_length = frame.calculatePayloadLength(total_frame_length);
+  std::memmove(frame.payload.data(), data, frame.payload_length);
+  data += frame.payload_length;
+
+  std::memmove(&frame.frame_checksum, data, sizeof(frame.frame_checksum));
+
+  return frame;
+}
+
+}
+
+namespace radio::protocol
+{
+
+std::size_t composeFrameBuffer(std::uint8_t* data, const FrameStructure& frame)
+{
+  std::uint8_t* const data_start = data;
+
+  PhyHeader header;
+  std::memset(&header, 0, sizeof(PhyHeader));
+  header.frame_length = frame.getTotalFrameLength();
+  data = serializePhyHeader(data, header);
+
+  data = serializeMacProtocolDataUnit(data, frame);
+
+  return data - data_start;
+}
+
+FrameStructure decomposeFrameBuffer(const std::uint8_t* data)
+{
+  PhyHeader header;
+  data = deserializePhyHeader(data, header);
+
+  const std::uint8_t total_frame_length = header.frame_length;
+  const FrameStructure frame = deserializeMacProtocolDataUnit(data, total_frame_length);
+
+  return frame;
+}
+
+}
diff --git a/radio/src/radio_protocol_frame.cpp b/radio/src/radio_protocol_frame.cpp
new file mode 100644
index 0000000..9234e06
--- /dev/null
+++ b/radio/src/radio_protocol_frame.cpp
@@ -0,0 +1,99 @@
+//
+// Created by erki on 28.07.22.
+//
+
+#include "radio_protocol_frame.hpp"
+
+#include <cstring>
+
+namespace
+{
+
+using namespace radio::protocol;
+
+template<typename T>
+constexpr T zeroInitialized()
+{
+  static_assert(std::is_trivially_default_constructible<T>::value, "Struct is not trivially default constructible.");
+
+  T t;
+  std::memset(&t, 0, sizeof(T));
+
+  return t;
+}
+
+std::uint8_t get_address_size(const Address& address)
+{
+  std::uint8_t size = sizeof(address.pan_id);
+  if (address.getAddressingMode() == FrameControlField::ADDRESSING_MODE_SHORT)
+    size += sizeof(std::uint16_t);
+  else
+    size += sizeof(std::uint64_t);
+
+  return size;
+};
+
+}
+
+namespace radio::protocol
+{
+
+FrameStructure::FrameStructure()
+  : frame_control_field(zeroInitialized<FrameControlField>())
+  , sequence_number(0)
+  , frame_checksum(0)
+  , payload_length(0)
+{ }
+
+FrameStructure FrameStructure::createDataFrame()
+{
+  FrameStructure structure;
+  structure.frame_control_field.type = FrameControlField::FRAME_TYPE_DATA;
+  structure.frame_control_field.frame_version = 1;
+
+  return structure;
+}
+
+FrameStructure& FrameStructure::setPayload(const std::uint8_t* data, const std::uint8_t length)
+{
+  std::memmove(payload.data(), data, length);
+  return *this;
+}
+
+FrameStructure& FrameStructure::setSourceAddress(const Address& addr)
+{
+  source_address = addr;
+  frame_control_field.source_addressing_mode = addr.getAddressingMode();
+  return *this;
+}
+
+FrameStructure& FrameStructure::setDestinationAddress(const Address& addr)
+{
+  destination_address = addr;
+  frame_control_field.destination_addressing_mode = addr.getAddressingMode();
+  return *this;
+}
+
+std::uint8_t FrameStructure::getTotalFrameLength() const
+{
+  std::uint8_t size = sizeof(frame_control_field) + sizeof(sequence_number);
+
+  size += get_address_size(destination_address);
+  size += get_address_size(source_address);
+  size += payload_length;
+  size += sizeof(frame_checksum);
+
+  return size;
+}
+
+std::uint8_t FrameStructure::calculatePayloadLength(const std::uint8_t total_frame_length) const
+{
+  std::uint8_t payload_length = total_frame_length - sizeof(frame_control_field) - sizeof(sequence_number);
+  payload_length -= get_address_size(destination_address);
+  payload_length -= get_address_size(source_address);
+  payload_length -= sizeof(frame_checksum);
+
+  return payload_length;
+}
+
+}