george,
each MS in a transfer is using one unique TFI in the TRX, in one direction.
For example, on TRX1:
TFI=1 is the UL TBF of MS2 and corresponds to the TS n°2 and n°3
TFI=2 is the UL TBF of MS3 and corresponds to the TS n°2
TFI=3 is the UL TBF of MS4 and corresponds to the TS n°2 & n°3
etc…
in DL
TFI=1 is the DL TBF of MS5 and corresponds to the TS n°1, 2 & 3
TFI=2 is the UL TBF of MS2 and corresponds to the TS n°2, 3, 4
TFI=3 is the UL TBF of MS6 and corresponds to the TS n°1, 2, 3
etc…
When the TBF is released (no more data to transmit -for ul tbf- or receive -for DL tbf-), the TFI can be reallocated to another MS.
Cheers
pix