The need for software-defined radios raises a number of technical challenges, which play a significant role in the development of third-generation personal communications systems (PCS). Some of the most important technical challenges deal with analog-to-digital conversion and digital signal processing technologies, which, in many cases, cannot provide the advanced hardware needed to support the demanding PCS telecommunications services. We discuss these two technical challenges, focusing primarily on base station radio systems. We first identify the most important requirements for ADC and DSP technologies, and we then extensively discuss and/or propose enabling schemes that could relax these requirements and aid the implementation of software radio base stations. Furthermore, we discuss new structures that can support the development of physically distributed base stations.