The time division multiple access, on the other hand, all the stations transmit at different times, but occupy the entire bandwidth, obviously when you talk of time, and different users have to do one after another, the problem of time synchronisation comes in, and this has to be solved, so users can be given different amount of bandwidths, that is one of the advantages of time division multiple access, mobile users can user their idle times to determine which is the base station through which they can take the service.
Another advantage is that they can switch off the power when not transmitting, reducing the overall interference in the system, but then the disadvantages I have already told requires synchronisation and, for that purpose, you require extra overrate bits. Then the time division multiple access also suffers from the multipath problems.
The frame because of the overrate bits required for the synchronisation is not 100% efficient and the efficiency goes down because of the overrate bits that we require for the synchronisation purposes. The numbers of slots per channel could be calculated for example in the GSM system, with 200 KHz bandwidth channel spacing, in 25 MHz spectrum bandwidth and 8 channels per 200 KHz, you find that these numbers come to the 1.000, which is more than the analogue systems.