MINI-LINK BAS 5-14
Technical Description EN/LZB 111 0542 P2B
5.4 LLC Layer
The LLC is a sublevel of the data link layer and its main task is to
determine the structure of the information frame and provide a
transmission error control and a robustness of the transmission link in
part by a scrambling function.
5.4.1 TDMA/TDM Framing
TDMA technique which foresees the access to the shared medium is
done in different time intervals called timeslots.
TDMA refers to the uplink radio channel and TDM to the downlink
radio channel. In uplink direction the access has to be managed
because of the concurrent requests from terminals, whereas in the
downlink direction there is no contention that data streams come from
a backbone network.
Up and downlink are separated in frequency, according to the FDD. In
MINI-LINK BAS, the delay between transmission and reception can
be of few timeslots.
The MINI-LINK BAS is a FDD system with a full flexibility of
instantaneous capacity allocation in the up and downlink per AT and
connection.
5.4.1.1 Downlink TDM Frame
In the following figure the structure of the downlink TDM frame,
together with the slot format, is depicted.
2416 8 424 8
N
1
SLOT
FRAME
Permits CRC-P ATM cell CRC-8 FEC
FAW
480 bits/slot
TDM frame
Figure 5-6 Downlink TDM Frame
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