Hi,

Ericsson document tell us:

In general the following cases occur:

If the MS and the cell support AMR HR and the number of idle FR TCH:s divided by the total number of de-blocked FR TCH:s is equal or above DTHAMR FR TCH:s will have precedence over HR TCH:s. If the number of idle FR TCH:s divided by the total number of de-blocked FR TCH:s is less than DTHAMR HR TCH:s will have precedence over FR TCH:s

If the MS or the cell do not support AMR HR and the number of idle FR TCH:s divided by the total number of de-blocked FR TCH:s is equal or above DTHNAMR FR TCH:s will have precedence over HR TCH:s. If the number of idle FR TCH:s divided by the total number of de-blocked FR TCH:s is less than DTHNAMR HR TCH:s will have precedence over FR TCH:s

so if your threshold for DTHNAMR be 70% so the traffic will start with FR channel.

example:

4 TRXs (1 BCCH & 2 SDCCHs & 29 TCHs)

%70 * 29 = 21

the BSC assigns FR channel in the begining until 8th channel assignment, for 9th MS assigning HR channel will be start.

Limitations:

1- some MSs can not support HR, so BSC assigns FR channel to them.

2- sometimes incoming HO parameters forces BSC to assign FR channel to MS.

Hi pix, Ericsson has only 1 threshold for Half Rate. Nokia has 2 threshold (FRL and FRU) for Half Rate (Hysteresis).