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Reply To: call drop due to expiry of T200 timer

#54386
Pan
Guest

Dear all! Pix, allow me to help you.
In 3GPP 44.006 any interested person can to find information about T200 equipment (it isn’t advertisment:).
T200 is data link (layer 2) timer. It is triggered on BSC side and on MS side (There is no Layer2 in BTS, only Layer1 – modulation and channel coding).
T200 supervises the acknowledged transfer of layer 3 messages (e.g. location updating, setup and many others) by data link layer. T200 expires when there is no acknowledgment from peer layer2 (BSC or MS) during T200 ms.
If T200 expired N200 times then layer2 indicates to layer3 about message transfer failure.
Values of T200 for different channel types (SDCCH, SACCH, FACCH) are implementation dependent and must be chosen according recommendations in 44.006.
Values of N200 (from 44.006):
– 5 for use on SACCH;
– 23 for use on SDCCH;
– 34 for use on FACCH/full rate;
– 48 for use on E FACCH/full rate;
– 29 for use on FACCH/half rate.