Other causes of delays are horizontal and
vertical handovers. Video chat can freeze or stall
the video during handover when the delay is not
within the limits. As the mobile moves, its associated
access point changes as per the current
location. The delay in such horizontal handover
is inevitable for 3G. As mentioned before, currently,
to solve the bandwidth constraints, mobile
carriers prefer video chat applications to use
available WiFi hotspots. Maintaining delay constraints
during such vertical handover is also a
key limitation [7].