ETSI
The present document will not provide the specification or operational detail for system implementations which include
but are not limited to trunking, roaming, network management, vocoder, security, data, subsystems interfaces and data
between private and public switched telephone networks. It describes only the appropriate access requirements
compatible with the Air Interface.
NOTE 2: The DMR standard consists of a multi-part deliverable, which will be referred to in the present document
if needed.
4.1 Protocol architecture
4.1.0 Protocol architecture - Introduction
The purpose of this clause is to provide a model where the different functions and processes are identified and allocated
to different layers in the DMR protocol stack.
The protocol stack in this clause and all other related clauses describe and specify the interfaces, but these stacks do not
imply or restrict any implementation.
The DMR protocol architecture which is defined herein follows the generic layered structure, which is accepted for
reference description and specification of layered communication architectures.
The DMR standard defines the protocols for the following 3 layered model as shown in figure 4.1.
The base of the protocol stack is the Physical Layer (PL) which is the layer 1.
The Data Link Layer (DLL), which is the layer 2, shall handle sharing of the medium by a number of users. At the
DLL, the protocol stack shall be divided vertically into two parts, the User plane (U-plane), for transporting information
without addressing capability (e.g. voice), and the Control plane (C-plane) for signalling information, both control and
data, with addressing capability, as illustrated by figure 4.1.
NOTE 1: It is appropriate to bear in mind the different requirements of C-plane and U-plane information. C-plane
information needs only a discrete (or non-continuous) physical link to pass information although it needs
a continuous virtual link to support the service. This may also be called signalling or packet mode service.
Acknowledgements may or may not be requested. U-plane information, on the other hand, requires a
regular physical link to be available so that a constant delay service can be supported. This may also be
called circuit mode service.
NOTE 2: The DLL identified in figure 4.1 may be further sub-divided in the air interface protocol to separate the
functionality of Medium Access Control (MAC) and Logical Link Control (LLC), which is often
performed in radio air interface protocols due to the specialized nature of these two tasks. Such separation
is not presented in the present document and is implementation specific. It is further implementation
specific if layer 2 at U-plane offers only MAC for the service.
The Call Control Layer (CCL), which is layer 3, lies in the C-plane and is responsible for control of the call (addressing,
facilities, etc.), provides the services supported by DMR, and supports Short Data and Packet Data service. U-plane
access at layer 2 (DLL) supports voice service which is available in DMR. The Control Layer and the facilities and
services offered by DMR are described in ETSI TS 102 361-2 [5]. The Short Data and Packet Data Protocol offered by
DMR are described in ETSI TS 102 361-3 [12].