.Explain in brief what is FER.

Q:What do you understand by idle channel measurement?


Ans:

• When a new call is established or a handover is performed, the BSC selects the TRX and the time slot for the traffic channel based on the idle channel interference measurements. The frequency hopping has a significant effect on the idle channel interference measurement results.

When the frequency hopping is used, the frequency of a hopping logical channel is changed about 217 times in a second. The frequency of the idle time slots changes according to the same sequence.

In a case of the random hopping, this means that the measured idle channel interference is likely to be the same for all the TRXs that use the same MA-list. If the interference is averaged over more than one SACCH frame, the averaging effect is even stronger. However, normally the interferers are mobiles located in interfering cells. In this case, there are probably differences in the measured idle channel interferences between different time slots in the cell. This happens, because the interfering mobiles are only transmitting during the time slot that has been allocated to them. This is illustrated in Figure 7‑5.

If the cyclic hopping sequence is used, there might occur differences on the measured idle channel interference levels between the TRXs on the same time slot as explained in the following section.