Poor infrastructure can lead to inadequate coverage, which leads to call drops; the existing towers themselves can get overloaded due to increase in customer base which ultimately causes the call drop problem.
With more and more building structures coming up in the urban areas, these structures can cause a disruption in the network coverage. Also, sometimes when a person talking on the mobile is himself mobile( moving from place to place) then a switch from one channel to another is required, and during such handover a call may drop especially when there is an overload.
Further, radio interference among subscribers is said to be another reason for it.
