Most development of cellular communications technology has been focused on providing services to the wealthiest 20% of the world's population - the top of the economic pyramid. We discuss the motivation for serving the bottom of the pyramid (BoP), loosely defined as the 4 billion people earning less that US$2000/year. We consider the design requirements for a rural wireless telecommunications system for the BoP, and how they differ from traditional cellular system and WLL requirements. We discuss alternative technologies and architectures for meeting these requirements, ranging from satellite to WLAN systems. We then present our initial link analysis showing that cellular systems based on WCDMA or OFDM meet the requirements with small modifications. We end with some discussion of open problems and further work.