In the past 20 years, mobile communications have evolved to the point where affordable broadband connectivity is widely available and plays a central role in today's information society. As mobile data rates are predicted to double annually in the next decade while the average revenue per user is likely to remain stagnate, the mobile communications industry is required to generate continuous innovation regarding extremely cost-efficient still ubiquitous wireless broadband access. In addition, new application fields, such as machine-to-machine (M2M) communication and cloud computing, will introduce novel and diverse requirements that have to be met. Potential technology options to address these aspects are advanced signal processing techniques, innovative spectrum usage concepts, and possibly a more flexible air interface numerology, encompassing the usage of more spectrum and significantly more and heterogeneous base stations.