Dear wisa, this is the best i can find in my documentation bout Dynamic HR Allocation, i know this is not answer your question, but maybe we can discuss bout this, what kinda switch/BSC do u use ? maybe we can find more things to discuss
Dynamic HR Allocation
This feature optimises the usage of capacity when the traffic load is high, whilst it offers the best possible speech quality when the traffic load is low. This is achieved by changing the channel rate of a connection in accordance with the traffic load in the cell. At high traffic load TCH/HR is allocated and at low traffic load TCH/FR is allocated.
The threshold for traffic load, parameter TLDTH, is defined by the operator. This parameter is defined as a percentage value, set per BSC, indicating the number of idle TCH/FR per total number of deblocked TCH/FR.
Depending on the traffic load condition the two following cases occur:
When the number of available TCH/FR in the cell is above the threshold value, FR resource types will have precedence over HR resource types at allocation.
When the number of available TCH/FR in the cell is below or equal the threshold value, HR resource types will have precedence over FR resource types at allocation.
At assignment, a change of priority order of preferred channel rate is only allowed if the MS has dual rate capability. At handover, a change of priority order of preferred channel rate is only allowed if the MS has dual rate capability and if the MSC allows changes between full rate and half rate also after the first channel allocation request.
Within the GSM 900 band, the number of idle full rate channels is determined based on the status of the parameter for available GSM 900 bands, ERBANDSINCLUDED. If the parameter is set to OFF, then only idle full rate P-channels are considered. If the parameter is set to ON, then all idle full rate channels in all available GSM 900 bands are considered.