A carrier is 8 channels or 8 TS.
GSM channel = 8TS =4.615 ms frame duration = 200 KHz = 25 KHz per TS
1TS= 577 µ-s = 156.25 bits
A physical channel may be split into several (logical) channels:
Logical channel C1: every 4th slot;
Logical channel C2: every other slot