Product manual

System description, DECT air interface
Technical Product Manual - DCT1800-GAP
TD 92093 (1/LZBNB 103 108 R4D) / 2006-03-09/ Ver.C
© 2006
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6.4 DECT & OSI
The DECT standard covers the lower three layers of the Open Systems Interchange (OSI) model. As
OSI takes no account of radio transmission uncertainties and handovers, DECT has re-defined these
layers into four layers and a management entity (see figure
30).
Physical Layer (PHL)
The physical layer defines the radio spectrum management. It creates (simplex) physical channels
with a fixed throughput. It mainly specifies radio-related characteristics such as: the 10 carrier
frequencies, the transmission power, the modulation method Gaussian filtered Frequency Shift Keying
(GFSK), the TDMA frame and the bit synchronization of packets transmitted in a time slot. For
information on characteristics of the physical layer refer to section ’Product specifications’.
Medium Access Control layer (MAC)
The Medium Access Control layer (MAC) allocates and releases radio resources. It dynamically selects
physical channels. To achieve a duplex service, the MAC layer uses two physical channels, e.g. a
channel in time slot 3 and one in time slot 15. The MAC layer also multiplexes Control (C) information
and User (U) information (i.e. speech or data information) onto the physical channels offered by the
physical layer (PHL). It guarantees the secure transmission of both signalling and user information by
appropriate error control (CRC). Bearer handovers are handled in this layer.
Data Link Control Layer (DLC)
The Data Link Control layer (DLC) provides reliable data links to the network layer. Once a data link
is set up by the DLC layer it has the task of maintaining this link, even if physical channels have to be
changed during the conversation.
Network Layer (NWK)
The NetWorK layer (NWK) which is the main signalling layer of the protocol, mainly supports the
establishment, maintenance and release of calls. It must be able to route calls to cordless phones
with a, possibly, constantly changing location within a cordless network.
In this layer the mobility management (location registration), security related functions (authentication,
ciphering) and the external handover procedure are located.
Lower Layer Management Entity (LLME)
The Lower Layer Management Entity (LLME) defines management procedures that concern more
than one layer. It contains the Dynamic Channel Selection (DCS), antenna diversity algorithms and
quality control synchronization.
Control (C) plane
The Control plane has a layered structure and contains those parts of the physical, medium access,
data link and network layer that are involved with call set-up, call maintenance and call release.
User (U) plane
The User plane has a layered structure and contains those parts of the physical, medium access and
data link layer that are involved with the exchange of user information (speech) in a DECT system.