Sub-optimal because the BCCH carrier will send some timeslots in GMSK (max power) and other timeslots in 8PSK (with a power which is a bit less than GMSK).
So neighbours MS will measure this particular with a level which is somewhat lower than reality. (measurements are performed on any timeslots of the BCCH carrier, not the TS0 only)
Usually, the delta between GMSK and 8PSK is less than 2dB... it's somewhat acceptable :)
Fahim - 30th November 2008 (04:36 GMT)
Lately I had been trying to find out more info about this issue.
In 3GPP TS 05.08 version 8.23.0, particulalry in section 7 it has been said that if 8PSK is used in BCCH carrier then cell selection, reselection and HO procedures invloving these cells will be somewhat sub-optimal.
If you have time could u plz check it out.
pix - 16th November 2008 (09:27 GMT)
it's a good setting to prefer the GPRS on BCCH. It means that the first PDCH are allocated on the BCCH TRX first, and then if more PDCH are needed, they'll be allocated on the other TRX.
The BCCH is better because of:
- better frequency planning (usually)
- no DL power control / no DL DTX
Fahim - 16th November 2008 (07:53 GMT)
Is there any drawbacks associated with enabling edge/gprs in the TRX which carries BCCH ?
In my Alcatel system all are so defined by default - any suggestion ?