etworks. Thus DECT is not just capable of seizing a channel in less than 50ms. another cordless telephone peripheral to telephone networks, it also Although the above has been written in terms of DECT as a piece has the capability to become an access technology that is integrated of cordless terminal equipment, it was made plain during its devel- with the network. Proprietary Std messages Proprietary msgs. and elements protocols additions CI compatible message formatting Proprietary CI compatible DLC layer Proprietary protocols additions ESC header + Other header codes plus Proprietary proprietary standard messages additions messages CI compatible A- field header + CRC CI compatible physical layer Figure 49.8 Structures of escape routes within the Common Interface 49/10 Cordless telecommunications 49.4.1 DECT protocol architecture entities in support of, for example, establishment, maintenance and release of calls. Many additional messages support a range of The DECT protocol (ETSI, 1992b) is based on the principles of the independent capabilities and services. One group contains the OSI model. The complete common interface relevant to public necessary procedures that support cordless mobility which includes access applications is defined in terms of the three lowest layers FP and PP authentication and location registration. modified to account for the specific requirements of radio trans- The lower layer management entity is concerned with procedures mission and in-call handover. The structure is shown in Figure 49.9 that involve more than one layer and yet are often only of local where four DECT layers are identified. The OSI layers are indicated significance. Consequently they are only defined in general terms. for reference. The Physical Layer (PHL) has the task of modulation and demodulation, acquire bit and burst synchronisation, control 49.4.2 Interworking Units (IWU) synchronisation and independent burst collision detection and measure the received signal strengths. The transmission of information to end 