Call failure caused by wireless link fading

Call failure caused by wireless link fading
Typical case:
In the beginning of origination, MS forward and reverse signal are normal, but finally the call is failed;
In this period MS received signal fades greatly ( MS is in the corner of street or goes into subway).

Analyzing:
When MS is in the corner of the street or goes into subway, the radio environment will change greatly and signal fade very fast. Usually both forward and reverse link will fade at the same time. If MS starts access at this time, it is very possible to meet access failure for signal losing.
Note:
For the signal losing, MS and BTS sides will transmit again. If the fading time is short, access procedure can be continued; but if the fading time is too long, the retransmitted signal may be lost and the access will be failed.

Solution:
Optimize network topology structure and decrease the area where signal fades greatly.