I have found a workaround for this issue, it does not completely solve the problem but improves the situation!!
if you set a short ringtone say which lasts for 10 seconds then your phone will behave like this on a incoming call:
vibration> 10 sec ringtone>vibration > 10 sec ringtone and so on....cyclically
so suppose your incoming call ringing is live for 35 seconds your phone will vibrate around 3 times before you have a missed call..............
the shorter your ringtone duration is the more time it will vibrate.
now how to shorten the length of ringtone: for that you can create a custom ringtone using Nokia's own "ringtone maker" or other free software app's available on net.