scope:

The present document defines the Air Interface (AI) for the Terrestrial Trunked Radio (TETRA) system supporting Voice plus Data (V+D) and contains the specifications of the physical layer, the data link layer and the network layer according to the ISO model.
First, it establishes the TETRA radio aspects (layer 1):
- it defines and specifies the modulation;
- it defines and specifies the radio transmission and reception;
- it defines and specifies the synchronization;
- it defines and specifies the channel coding;
- it defines and specifies the channel multiplexing;
- it defines and specifies the control over the radio link.
Secondly, it establishes the services, messages and protocols used for voice and circuit mode data transfer, starting with the upper layers:
- it defines and specifies the services provided by the CC sub-entity;
- it defines and specifies the services provided by the SS sub-entity;
- it defines and specifies the services provided by the SDS sub-entity;
- it defines and specifies the protocol used by the Circuit Mode Control Entity (CMCE) to communicate across the air interface in order to offer the services of the Call Control (CC), Supplementary Service (SS) and Short Data Service (SDS) sub-entities;
- it defines and specifies the services and protocol used for the management of the users' mobility inside and across TETRA networks, namely the ones of the Mobility Management (MM) entity and the MLE;
- it defines and specifies the services and protocol used in the data link layer subdivided in two sub-entities, the Logical Link Control (LLC) and the Medium Access Control (MAC) entities.
Thirdly, it establishes the services, messages and protocols used for packet data transfer:
- it defines and specifies the services provided by the Sub-Network Specific Data Control Protocol (SNDCP) sub-entity;
- it defines and specifies the protocol used by Sub-Network Specific Data Control Protocol (SNDCP).
The normative annexes mainly specify the parameter values used in the protocol.
The informative annexes refer mainly to the description of more general layer 3 to layer 1 mechanism.