In this paper, the authors present architecture to support Dynamic Spectrum Access (DSA) in general wireless networks. Their architecture advocates a new Spectrum Virtualization Layer (SVL), directly below the wireless physical layer (PHY or baseband processing). They call it Layer 0.5. SVL presents a virtual baseband to traditional wireless PHY, which is designed for a fixed contiguous spectrum band with fixed width. When spectrum allocation changes under DSA, SVL performs real-time reshaping of baseband signals so that the baseband of traditional wireless PHY maps to the current physical spectrum band allocation, which can be of different width, or even in separate non-contiguous bands.