it is only based on what the BSC decides to do. and the BSC itself bases its decision on the outputs from the TCH allocation algorithm.
Usually, under a specific load threshol, the TCH is allocated in FR. Above this threhsold, the TCH is allocated in HR.
The load = the TCH load in that cell.
– increase of traffic on AterMux and A interfaces
– increase of traffic load in the BSC (might impact the BSC dimensioning)
– need to tune HR and AMR-R thresholds
– need to buy HR licenses in order to declare TRXs as HR-capable (same goes for AMR-HR)