it is not possible that one user is using timeslots which are NOT consecutive and NOT on same TRX.
In other words, a user (= TBF DL/UL) will always get timselots which are consecutive AND on the same TRX.
Since several TBF can be multiplexed on the same timeslots, at the expense of lower throughput, it is necessary that timeslots are also available on other TRX. As a result, the system can shuffle different users on different timeslots, maximizing their throughput.
To sum up:
1/ define consecutive timeslots for EGPRS/GPRS on each TRX which is PS-capable.
2/ define as many TRX PS-capable as possible, without impacting speech capacity nor BSC PS-capacity.