1. intracell HO is usually due to
a- high RXLEV but poor RXQUAL
b- or, change of codec (AMR HR->FR or AMR FR->HR)
c- or, change of timeslots to make room for GPRS’s PDCH
d- or, change of zones in a concentric cell
e- or, other proprietaries causes of handovers (extended cells, TFO, etc)
The causes (a) and (d) are the most common, and they will normally lead to a change of TRX.
For cause (a), if there is no other TRX available, the TCH will be sent to another TS of the same TRX.
Other causes : the new TS can be in same TRX or other TRX, there is probably no rule there (depends on vendor)