•  Capacity of cellular system can be increased using additional cell sites but it is practically difficult to get a new physical site in urban areas.
• Defferent antenna heights and different power level can be used to provide small and largest cells located at single site.this technique is called as umbrella approaches.
•this approachis used to provide large area coverage to high speed user by small area coverage to low speed users. It also ensure additional macrocell channels for pedestrian users.


         Fig: Umbrella cell approach


•in microstation ambrella approach macrocell Earth from within a cell with individual station having low power transmitting antenna and less height base stations.
•large umbrella says maintaining high speed traffic f(example mobile in car on on vehicles).
•this approach is basically used to reduce the number of hand of high-speed users.