DECT is an access technology. This means that it has no switching functions, but only a way to access a network. This may be a telephone network, but can also be a computer network. In the later case the DECT handsets are dataterminals exchanging information with a host computer. Also the so called portable part can be a cordless terminal adapter (CTA) providing a 'wireless local loop' as the final link between the local telephone exchange and the fixed telephone at home.
The typical characteristics are as follows
|Frequency band||1880 MHz - 1900 MHz|
|Number of carriers||10|
|Transmit power||250 mW peak|
|Multiplex schema||Time Division Multiple Access|
|Multiplex frames||10 ms, devided into 24 slots|
|Duplexing||Time Division Duplex on same carrier|
|Bit rate||1152 kbps|
|Channel throughput||32 kbps user data (speech), 6.4 kbps control data|
A duplex connection is made by transmitting bursts of data evenly spaced in the defined time slots on the same carrier. The first twelve time slots are used by the fixed part, while the portable part transmits in the last twelve time slots. Based on ten carriers this provides for 120 possible circuits. Since a radio tranciever can work on one frequency at a time, this means that in a cell the fixed part tranceiver can handle up to twelve simultaneous calls.
The protocols are designed such that system installations in the same area proves no problem. Continuous Dynamic Channel Selection (CDCS), that is checking the quality of a physical channel before and during use, and secure exchange of identities provide for a peaceful co-existance of the systems.
Furthermore the DECT protocols provide for seamless hand-over of calls, both intracell (within the coverage area of one radio tranciever from one channel to another) and intercell (from a channel to one radio tranciever to a channel on another radio). In this way the portable part can, by using CDCS, ensure the quality of the connection and maintaining it while moving around.
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