DECT or Digital Enhanced (former European) Cordless Telecommunications is an ETSI standard for portable phones, commonly used for domestic or corporate use. DECT can also be used for wireless data transfers.
DECT is (like GSM) a cellular system. Comparing DECT against GSM shows one major difference: the cell radius (25..100 meters for DECT, 2..10 km with GSM).
British Telecom DECT cordless telephone (base unit and handset are shown)
Here are some another DECT properties:
- net bit rate: 32 kbits/s
- frequency: 1900 Mhz
- carriers: 10 (1880..1900 Mhz)
- timeslots: 2 x 12 (up and down stream)
- channel alocation: dynamic
- traffic density: 10000 Erlangss/kmē
- Frequency division multiple access (FDMA),
- Time division multiple access (TDMA) and
- Time division duplex (TDD)
DECT media access control layer is the layer which controls the physical layer and provides connection oriented, connectionless and broadcast services to the higher layers. It also provides encryption services.
DECT data link layer uses a variant of the ISDN data link protocol called LAPC. They are based on HDLC.
DECT network layer contains various protocol entities:
- Call Control (CC)
- Call Independent Supplementary Services (CISS)
- Connection Oriented Message Service (COMS)
- Connectionless Message Service (CLMS)
- Mobility Management (MM)
The call control protocol is derived from ISDN DSS1, which is a Q.931 derived protocol. Many DECT specific changes have been made.
Three application areas:
- Domestic DECTs are connected to a base (radio fixed parts) connected to the PSTN. A base can accept more DECT handsets.
- Business DECTs connected to PBX. Such a case, many radio fixed parts. The DECT handset dynamically connect to these (hand over feature)
- Public DECT connected to the PSTN (very rare). An high density alternative to GSM.
- Local loop (very rare). In this case, a DECT radio link replaces the normally wired connection between the final PSTN distribution point to the subscriber.