Coverage challenges have become more apparent with 3G and 4G networks for the following reasons:

• As the following chart shows, the maximum and shared data rates subscribers can expect drop dramatically as the user moves away from the cell site.

We can't fight physics. The further we move away from ideal conditions near the macrocell site, the fainter the signal, the greater the noise, the lower order modulation used and the lower the throughput. Unfortunately most subscribers are near the cell edge not near the macrocell site.

• With some notable exceptions, most of the spectrum that is used for 3G and 4G technologies are at higher frequency bands i.e. > 2 GHz. The challenge is that RF propagation is worse at higher frequencies.
  

• There are many RF obstructions that signals must overcome. Building walls, leaves, windows … all reflect, attenuate and disperse the RF signals. 
  

To reduce the number of 3G and 4G coverage holes, the operator can deploy large numbers of small cell sites / picocells at the 3G and 4G macrocell cell edges as the picture below shows:

This deployment strategy for picocells provides several benefits:

• The coverage holes perceived by the subscribers are reduced.

• 3G / 4G macrocell traffic is off loaded from the existing macrocells to the outdoor small cell site

• The overall capacity of the macrocell is increased since the macrocell does not have to use as many resources (low order modulation links) serving subscribers at the cell site edge.

Subscribers can experience 3G or 4G coverage holes in urban, suburban or rural areas. A flexible deployment of small cell sites / picocells with associated NLOS wireless backhaul will eliminate the coverage holes, increase overall access capacity and increase subscriber satisfaction.