The DECT pages

The DECT protocol stack

How does it work? That is a simple question with a long answer. If you consider the DECT standard specification (EN 300 175) being in eight parts with an average size of a hundred pages, you can get an idea of the size of the answer. And that leaves out the parts about the various profiles, approval tests and additional applications of DECT.

But not to worry. Here is a selection of the most basic items which should give you an idea of the technical sophistication of DECT. Also this paper from the DECT forum is an excellent source of information.

The DECT protocol stack is based on the lower three layers of the OSI model. The exception to this is the Medium Access Control (MAC) layer, which handles the specifics of the ether and covers part of layer 1 and 2 of the OSI model. Also a Lower Layer Management Entity (LLME) is defined which has management interfaces to all the layers of the DECT protocol stack.

Click on any part of the stack to get more information on that particular layer or interface, or read the book.
Personal Wireless
Communication with DECT and PWT

The DECT stack


The DECT protocol stack presents a C(ontrol)-plane and a U(ser)-plane interface onto the stack. The C-plane is the interface to the control entity in the application, while the U-plane is designed for transport of data.

Control Plane

The Control Plane is the control interface for the application of the DECT handset and base system. Through this interface the network layer services can be used to eg. set-up calls and exchange end-to-end control information. In a handset this interface is used by the Control entity and User Interface entity in the handset which reads the keypad and controls the handsets display. Based on the users actions services on the C-plane are requested and indications from the C-plane are translated into information on the display. In a base system the C-plane is most likely used by an interworking unit to connect the DECT system to a (telephone)network (eg. ISDN). Remember that DECT is an access technology, it provides no network services like switching. The interworking unit will translate the signalling back and forth between the DECT stacks' network layer and the network protocol stack (eg. ISDN layer 3)

User Plane

The User Plane is the data interface for the application of the DECT handset and base system. In telephony applications this is used to transfer
ADPCM encoded speech with a rate of 32 kbps. In a handset this needs to be encoded/decoded and coupled to the audiosystem, ie. speaker and microphone. Also echo cancellation plays an important role.

In a base system the coupling is to the network, which can either be analog or digital. If, for instance, the coupling is to an ISDN the speech data needs to be transcoded into PCM (64 kbps) also taking echo cancellation into account.

Written by my own two hands and an ASCII editor. Problems? write me Last updated December 27, 2000 DECT home

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