In GSM cellular networks, the Abis channel that connects the Base Transceiver Station (BTS) and Base Station Controller (BSC) is an E1 link with several framing alternatives, all of which have a basic superframe duration of 20 milliseconds.
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TDMoIP was first developed in 1998 by RAD Data Communications (see U.S. patent number 6,731,649) and first deployed in Sweden in 1999 by Utfors (later acquired by Telenor).