1 Introduction

2 Technical Aspects of Femtocells

3 Business Aspects of Femtocells

4 Technical Challenges
4.1 Physical and Medium Access layers: Broadband Femtocells
4.2 Physical and Medium Access layers: Voice Femtocells
4.3 Network Infrastructure

5 Research Directions
5.1 Interference Management
5.2 MIMO Femtocells

6 Conclusions