Small Cells are a critical tool in densifying the carrier networks. Power, Backhaul and Site Acquisition are essential to planning an effective deployment.
One major consideration is whether the application is indoor or outdoor. Wi Fi has solved data issues indoor but does not have a quality voice capability so mobile companies are deploying small cell technology to propagate their licensed frequencies.
Metro PCS provides a strong architectural overview below.
The issue of backhaul has been one of the more difficult aspects to deployment. Siklu has a strong offering. Their architecture creates collection or aggregation points linking the edge to transport and then back to the core.