First Method: Guard Channel Concept , whereby a fraction of the total available channels in a cell is reserved exclusively for handoff requests from ongoing calls which may be handed off into the cell.
Disadvantage : This method reduces the total carried traffic as fewer channels are allocated to originating calls.
Second Method: Queuing of Handoff requests is done during the time the received signal level drops below the handoff threshold and the time the call is terminated due to insufficient signal level.
Advantage : This method decreases the probability of forced termination of the call.
The umbrella cell configuration consists of one BTS with high transmission power and an antenna installed high above the ground that serves as an “umbrella” for a number of BTSs with low transmission power and small diameters
The use of both “Large” and “Small” cells for high speed moving users and for pedestrian or slow moving mobile users.